Enhancement of nitric oxide decomposition efficiency achieved with lanthanum-based perovskite-type catalyst.

PubMed

Pan, Kuan Lun; Chen, Mei Chung; Yu, Sheng Jen; Yan, Shaw Yi; Chang, Moo Been

2016-06-01

Direct decompositions of nitric oxide (NO) by La0.7Ce0.3SrNiO4, La0.4Ba0.4Ce0.2SrNiO4, and Pr0.4Ba0.4Ce0.2SrNiO4 are experimentally investigated, and the catalysts are tested with different operating parameters to evaluate their activities. Experimental results indicate that the physical and chemical properties of La0.7Ce0.3SrNiO4 are significantly improved by doping with Ba and partial substitution with Pr. NO decomposition efficiencies achieved with La0.4Ba0.4Ce0.2SrNiO4 and Pr0.4Ba0.4Ce0.2SrNiO4 are 32% and 68%, respectively, at 400 °C with He as carrier gas. As the temperature is increased to 600 °C, NO decomposition efficiencies achieved with La0.4Ba0.4Ce0.2SrNiO4 and Pr0.4Ba0.4Ce0.2SrNiO4, respectively, reach 100% with the inlet NO concentration of 1000 ppm while the space velocity is fixed at 8000 hr(-1). Effects of O2, H2O(g), and CO2 contents and space velocity on NO decomposition are also explored. The results indicate that NO decomposition efficiencies achieved with La0.4Ba0.4Ce0.2SrNiO4 and Pr0.4Ba0.4Ce0.2SrNiO4, respectively, are slightly reduced as space velocity is increased from 8000 to 20,000 hr(-1) at 500 °C. In addition, the activities of both catalysts (La0.4Ba0.4Ce0.2SrNiO4 and Pr0.4Ba0.4Ce0.2SrNiO4) for NO decomposition are slightly reduced in the presence of 5% O2, 5% CO2, or 5% H2O(g). For durability test, with the space velocity of 8000 hr(-1) and operating temperature of 600 °C, high N2 yield is maintained throughout the durability test of 60 hr, revealing the long-term stability of Pr0.4Ba0.4Ce0.2SrNiO4 for NO decomposition. Overall, Pr0.4Ba0.4Ce0.2SrNiO4 shows good catalytic activity for NO decomposition. Nitrous oxide (NO) not only causes adverse environmental effects such as acid rain, photochemical smog, and deterioration of visibility and water quality, but also harms human lungs and respiratory system. Pervoskite-type catalysts, including La0.7Ce0.3SrNiO4, La0.4Ba0.4Ce0.2SrNiO4, and Pr0.4Ba0.4Ce0.2SrNiO4, are applied for direct NO decomposition. The results show that NO decomposition can be enhanced as La0.7Ce0.3SrNiO4 is substituted with Ba and/or Pr. At 600 °C, NO decomposition efficiencies achieved with La0.4Ba0.4Ce0.2SrNiO4 and Pr0.4Ba0.4Ce0.2SrNiO4 reach 100%, demonstrating high activity and good potential for direct NO decomposition. Effects of O2, H2O(g), and CO2 contents on catalytic activities are also evaluated and discussed.

The occurrence and distribution of trace metals in the Mississippi River and its tributaries

USGS Publications Warehouse

Taylor, Howard E.; Garbarino, J.R.; Brinton, T.I.

1990-01-01

Quantitative and semiquantitative analyses of dissolved trace metals are reported for designated sampling sites on the Mississippi River and its main tributaries utilizing depth-integrated and width-integrated sampling technology to collect statistically representative samples. Data are reported for three sampling periods, including: July-August 1987, November-December 1987, and May-June 1988. Concentrations of Al, As, Ba, Be, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Pb, Sr, Tl, U, V, and Zn are reported quantitatively, with the remainder of the stable metals in the periodic table reported semiquantitatively. Correlations between As and V, Ba and U, Cu and Zn, Li and Ba, and Li and U are significant at the 99% confidence level for each of the sampling trips. Comparison of the results of this study for selected metals with other published data show generally good agreement for Cr, Cu, Fe, and Zn, moderate agreement for Mo, and poor agreement for Cd and V.

Trace element partitioning in fluvial tufa reveals variable portions of biologically influenced calcite precipitation

NASA Astrophysics Data System (ADS)

Ritter, Simon M.; Isenbeck-Schröter, Margot; Schröder-Ritzrau, Andrea; Scholz, Christian; Rheinberger, Stefan; Höfle, Bernhard; Frank, Norbert

2018-03-01

The formation of tufa is essentially influenced by biological processes and, in order to infer environmental information from tufa deposits, it has to be determined how the geochemistry of biologically influenced tufa deviates from equilibrium conditions between water and calcite precipitate. We investigated the evolution of the water and tufa geochemistry of consecutive tufa barrages in a small tufa-depositing creek in Southern Germany. High incorporation of divalent cations into tufa is ubiquitous, which is probably promoted by an influence of biofilms in the tufa element partitioning. The distribution coefficients for the incorporation of Mg, Sr and Ba into tufa at the Kaisinger creek D(Mg), D(Sr) and D(Ba) are 0.020-0.031, 0.13-0.18 and 0.26-0.43, respectively. This agrees with previous research suggesting that biofilm influenced tufa will be enriched in divalent cations over equilibrium values in the order of Mg < Sr < Ba. Furthermore, the incorporation of Mg, Sr and Ba into tufa of the Kaisinger creek decreases downstream, which can be attributed to changes of the relative portions of bio-influenced tufa formation with likely higher distribution coefficients and inorganically-driven tufa formation with likely lower distribution coefficients. Additionally, the distribution coefficients of metals in tufa of the Kaisinger creek D(Cd), D(Zn), D(Co) and D(Mn) show values of 11-22, 2.2-12, 0.7-4.9 and 30-57, respectively. These metals are highly enriched in upstream tufa deposits and their contents in tufa strongly decrease downstream. Such highly compatible elements could therefore be used to distinguish easily between different lateral sections in fluvial barrage-dam tufa depositional systems and could serve as a useful geochemical tool in studying ancient barrage-dam tufa depositional systems.

High-pressure synthesis of the cubic perovskite BaRuO3 and evolution of ferromagnetism in ARuO3 (A = Ca, Sr, Ba) ruthenates

PubMed Central

Jin, C.-Q.; Zhou, J.-S.; Goodenough, J. B.; Liu, Q. Q.; Zhao, J. G.; Yang, L. X.; Yu, Y.; Yu, R. C.; Katsura, T.; Shatskiy, A.; Ito, E.

2008-01-01

The cubic perovskite BaRuO3 has been synthesized under 18 GPa at 1,000°C. Rietveld refinement indicates that the new compound has a stretched Ru–O bond. The cubic perovskite BaRuO3 remains metallic to 4 K and exhibits a ferromagnetic transition at Tc = 60 K, which is significantly lower than the Tc ≈ 160 K for SrRuO3. The availability of cubic perovskite BaRuO3 not only makes it possible to map out the evolution of magnetism in the whole series of ARuO3 (A = Ca, Sr, Ba) as a function of the ionic size of the A-site rA, but also completes the polytypes of BaRuO3. Extension of the plot of Tc versus rA in perovskites ARuO3 (A = Ca, Sr, Ba) shows that Tc does not increase as the cubic structure is approached, but has a maximum for orthorhombic SrRuO3. Suppressing Tc by Ca and Ba doping in SrRuO3 is distinguished by sharply different magnetic susceptibilities χ(T) of the paramagnetic phase. This distinction has been interpreted in the context of a Griffiths' phase on the (Ca Sr)RuO3 side and bandwidth broadening on the (Sr,Ba)RuO3 side. PMID:18480262

Investigation of the Influence of Selected Soil and Plant Properties from Sakarya, Turkey, on the Bioavailability of Trace Elements by Applying an In Vitro Digestion Model.

PubMed

Altundag, Huseyin; Albayrak, Sinem; Dundar, Mustafa S; Tuzen, Mustafa; Soylak, Mustafa

2015-11-01

The main aim of this study was an investigation of the influence of selected soil and plant properties on the bioaccessibility of trace elements and hence their potential impacts on human health in urban environments. Two artificial digestion models were used to determine trace element levels passing from soil and plants to man for bioavailability study. Soil and plant samples were collected from various regions of the province of Sakarya, Turkey. Digestive process is started by addition of soil and plant samples to an artificial digestion model based on human physiology. Bioavailability % values are obtained from the ratio of the amount of element passing to human digestion to element content of soil and plants. According to bioavailability % results, element levels passing from soil samples to human digestion were B = Cr = Cu = Fe = Pb = Li < Al < Ni < Co < Ba < Mn < Sr < Cd < Na < Zn < Tl, while element levels passing from plant samples to human digestion were Cu = Fe = Ni = Pb = Tl = Na = Li < Co < Al < Sr < Ba < Mn < Cd < Cr < Zn < B. It was checked whether the results obtained reached harmful levels to human health by examining the literature.

Chemical Analysis of a Carbon-enhanced Very Metal-poor Star: CD-27 14351

NASA Astrophysics Data System (ADS)

Karinkuzhi, Drisya; Goswami, Aruna; Masseron, Thomas

2017-01-01

We present, for the first time, an abundance analysis of a very metal-poor carbon-enhanced star CD-27 14351 based on a high-resolution (R ˜ 48,000) FEROS spectrum. Our abundance analysis performed using local thermodynamic equilibrium model atmospheres shows that the object is a cool star with stellar atmospheric parameters, effective temperature Teff = 4335 K, surface gravity log g = 0.5, microturbulence ξ = 2.42 km s-1, and metallicity [Fe/H] = -2.6. The star exhibits high carbon and nitrogen abundances with [C/Fe] = 2.89 and [N/Fe] = 1.89. Overabundances of neutron-capture elements are evident in Ba, La, Ce, and Nd, with estimated [X/Fe] > 1, the largest enhancement being seen in Ce with [Ce/Fe] = 2.63. While the first peak s-process elements Sr and Y are found to be enhanced with respect to Fe, ([Sr/Fe] = 1.73 and [Y/Fe] = 1.91), the third peak s-process element Pb could not be detected in our spectrum at the given resolution. Europium, primarily an r-process element also shows an enhancement with [Eu/Fe] = 1.65. With [Ba/Eu] = 0.12, the object CD-27 14351 satisfies the classification criterion for a CEMP-r/s star. The elemental abundance distributions observed in this star are discussed in light of the chemical abundances observed in other CEMP stars in the literature.

Spectroscopic geochemical study of vanadiferous marine sediments of the Gibellini claims, southern Fish Creek Range, Eureka County, Nevada

USGS Publications Warehouse

Böhlke, J.K.; Radtke, A.S.; Heropoulos, Chris; Lamothe, P.J.

1981-01-01

Samples of cuttings from three drill holes in the Gibellini claims were analyzed by emission spectroscopic techniques for a large suite of major and trace elements. Unoxidized siliceous "black shale" from drill hole NGA 7 is strongly enriched in Cd, Mo, Sb, Se, V, and Zn, and also contains relatively high concentrations of As, Ba, Cu, Ni, and Tl compared with nonmetalliferous shales. Analyses of 103 samples plotted against depth in drill holes NGA, NG31, and NGA7, and selected XRD data, show the following: 1. Groups of elements with distinct distribution patterns define most of major mineralogic components of the rocks. The "normal shale" component, which includes several detrital and authigenic phases, is indicated by covariations among Ti, Al, Fe, Na, Mg, K, B, Be, Co, Cr, Ga, La, Sc, Sr, and Zr. The shale component is diluted by varying amounts of the following minerals (and associated elements): silica (Si); dolomite (Mg, Ca, Mn, Sr); apatite (Ca, Be, Cr, La, Sr, Y); barite (Ba, Sr); sphalerite (Zn, Cd, Fe?); smithsonite (Cd, Co, Mn, Ni, Zn); bianchite (Cd, Ni, Zn) ; and bokite (V). Pyrite, gypsum, and jarosite were also identified.2. The highly siliceous kerogenous metalliferous Gibellini facies is underlain by argillaceous and (or) dolomitic rocks. The transition zone deduced from the chemical data is not well defined in all instances, but probably represents the bottom of the black shale deposit. 3. Oxidation has reached to variable depths up to at least 150 ft, and has caused profound changes in the distributions of the enriched metals. Molybdenum, Se, and V have been partially removed from the upper parts of the sections and are concentrated near or slightly above the base of the Gibellini facies. Cadmium, Ni, and Zn have been strongly leached and now occur at or below the base of the Gibellini facies. The variable depth of oxidation, the redistribution and separation of the metals, and the complex mineralogy of the deposit may make development of the claim complicated.

Ionic‐Liquid‐Assisted Microwave Synthesis of Solid Solutions of Sr1−xBaxSnO3 Perovskite for Photocatalytic Applications

PubMed Central

Alammar, Tarek; Slowing, Igor I.; Anderegg, Jim

2017-01-01

Abstract Nanocrystalline Sr1−xBaxSnO3 (x=0, 0.2, 0.4, 0.8, 1) perovskite photocatalysts were prepared by microwave synthesis in an ionic liquid (IL) and subsequent heat‐treatment. The influence of the Sr/Ba substitution on the structure, crystallization, morphology, and photocatalytic efficiency was investigated and the samples were fully characterized. On the basis of X‐ray diffraction results, as the Ba content in the SrSnO3 lattice increases, a symmetry increase was observed from the orthorhombic perovskite structure for SrSnO3 to the cubic BaSnO3 structure. The analysis of the sample morphology by SEM reveals that the Sr1−xBaxSnO3 samples favor the formation of nanorods (500 nm–5 μm in diameter and several micrometers long). The photophysical properties were examined by UV/Vis diffuse reflectance spectroscopy. The band gap decreases from 3.85 to 3.19 eV with increasing Ba2+ content. Furthermore, the photocatalytic properties were evaluated for the hydroxylation of terephthalic acid (TA). The order of the activities for TA hydroxylation was Sr0.8Ba0.2SnO3>SrSnO3>BaSnO3>Sr0.6Ba0.4SnO3>Sr0.2Ba0.8SnO3. The highest photocatalytic activity was observed for Sr0.8Ba0.2SnO3, and this can be attributed to the synergistic impacts of the modification of the crystal structure and morphology, the relatively large surface area associated with the small crystallite size, and the suitable band gap and band‐edge position. PMID:28589568

High-pressure synthesis of the cubic perovskite BaRuO3 and evolution of ferromagnetism in ARuO3 (A = Ca, Sr, Ba) ruthenates.

PubMed

Jin, C-Q; Zhou, J-S; Goodenough, J B; Liu, Q Q; Zhao, J G; Yang, L X; Yu, Y; Yu, R C; Katsura, T; Shatskiy, A; Ito, E

2008-05-20

The cubic perovskite BaRuO(3) has been synthesized under 18 GPa at 1,000 degrees C. Rietveld refinement indicates that the new compound has a stretched Ru-O bond. The cubic perovskite BaRuO(3) remains metallic to 4 K and exhibits a ferromagnetic transition at T(c) = 60 K, which is significantly lower than the T(c) approximately = 160 K for SrRuO(3). The availability of cubic perovskite BaRuO(3) not only makes it possible to map out the evolution of magnetism in the whole series of ARuO(3) (A = Ca, Sr, Ba) as a function of the ionic size of the A-site r(A,) but also completes the polytypes of BaRuO(3). Extension of the plot of T(c) versus r(A) in perovskites ARuO(3) (A = Ca, Sr, Ba) shows that T(c) does not increase as the cubic structure is approached, but has a maximum for orthorhombic SrRuO(3). Suppressing T(c) by Ca and Ba doping in SrRuO(3) is distinguished by sharply different magnetic susceptibilities chi(T) of the paramagnetic phase. This distinction has been interpreted in the context of a Griffiths' phase on the (Ca Sr)RuO(3) side and bandwidth broadening on the (Sr,Ba)RuO(3) side.

Uniform-large Area BaSrTiO3 Growth and Novel Material Designs to Enable Fabrication of High Quality, Affordable, and Performance Consistent Phase Shifters for OTM Phased Array Antennas

DTIC Science & Technology

2012-07-11

molar flux of each precursor entering the reactor. The molar fluxes for Ba , Sr , and Ti are measured and computed in real-time, and these measured values...allows control of the relative amounts of Ba , Sr , and Ti, and the overall total mass flow in umole/min reaching the substrate. In all, there are three...is the Ba:Sr ratio with depth (from the top of the film). The ratio of Ba to Sr was controlled from 0.87 to 0.43. The total film thickness is 130 nm

Characterization of the slow calcium channel binding sites for ( sup 3 H)SR 33557 in rat heart sarcolemmal membranes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatelain, P.; Beaufort, P.; Meysmans, L.

1991-01-01

SR 33557 represents a new class of compounds (indolizine sulfone) that inhibit L-type Ca2+ channels. ({sup 3}H)SR 33557 has been shown to bind with high affinity (Kd congruent to 0.36 nM, calculated from saturation isotherms and association/dissociation kinetics) to a single class of sites in a purified preparation of rat cardiac sarcolemmal membranes. The binding was found to be saturable and reversible. The maximal binding capacity was in approximately 1:1 stoichiometry with that of other Ca2+ channel antagonists. Various divalent cations (Mg2+, Mn2+, Ca2+, Ba2+, and Cd2+) were shown to inhibit specific ({sup 3}H)SR 33557 binding, with Cd2+ being themore » most potent. Among several receptor or channel ligands (including omega-conotoxin and Na+ and K+ channel modulators), only the L-type Ca2+ channel antagonists were found to displace ({sup 3}H)SR 33557. However, dihydropyridines, phenylalkylamines, benzothiazepines, and diphenylbutylpiperidines were found to inhibit ({sup 3}H)SR 33557 in a noncompetitive manner as demonstrated by displacement and saturation experiments in addition to dissociation kinetics. From these results, we suggest that SR 33557 binds with high affinity to a unique site on the L-type Ca2+ channel found in rat cardiac sarcolemmal membranes.« less

[Application of ICP-MS to Identify the Botanic Source of Characteristic Honey in South Yunnan].

PubMed

Wei, Yue; Chen, Fang; Wang, Yong; Chen, Lan-zhen; Zhang, Xue-wen; Wang, Yan-hui; Wu, Li-ming; Zhou, Qun

2016-01-01

By adopting inductively coupled plasma mass spectrometry (ICP-MS) combined with chemometric analysis technology, 23 kinds of minerals in four kinds of characteristic honey derived from Yunnan province were analyzed. The result showed that 21 kinds of mineral elements, namely Na, Mg, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Sb, Ba, Tl and Pb, have significant differences among different varieties of honey. The results of principal component analysis (PCA) showed that the cumulative variance contribution rate of the first four main components reached 77.74%, seven kinds of elements (Mg, Ca, Mn, Co, Sr, Cd, Ba) from the first main component contained most of the honey information. Through the stepwise discriminant analysis, seven kinds of elements (Mg, K, Ca, Cr, Mn, Sr, Pb) were filtered. out and used to establish the discriminant function model, and the correct classification rates of the proposed model reached 90% and 86.7%, respectively, which showed elements contents could be effectively indicators to discriminate the four kinds characteristic honey in southern Yunnan Province. In view of all the honey samples were harvested from apiaries located at south Yunnan Province where have similar climate, soil and other environment conditions, the differences of the mineral elements contents for the honey samples mainly due to their corresponding nectariferous plant. Therefore, it is feasible to identify honey botanical source through the differences of mineral elements.

Distribution, source identification, and ecological risk assessment of heavy metals in wetland soils of a river-reservoir system.

PubMed

Jiang, Xiaoliang; Xiong, Ziqian; Liu, Hui; Liu, Guihua; Liu, Wenzhi

2017-01-01

The majority of rivers in the world have been dammed, and over 45,000 large reservoirs have been constructed for multiple purposes. Riparian and reservoir shorelines are the two most important wetland types in a dammed river. To date, few studies have concerned the heavy metal pollution in wetland soils of these river-reservoir systems. In this study, we measured the concentrations of ten heavy metals (Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, and Zn) in surface soils collected from riparian and reservoir shorelines along the Han River in different seasons. Our results found that the Co, Cu, and Ni concentrations in riparian wetlands were significantly lower than those in reservoir shorelines. In riparian wetlands, only soil Sr concentration significantly increased after summer and autumn submergence. Multivariate statistical analyses demonstrated that Ba and Cd might originate from industrial and mining sources, whereas Sr and Mn predominantly originated from natural rock weathering. The ecological risk assessment analysis indicated that both riparian and reservoir shorelines along the Han River in China exhibited a moderate ecological risk in soil heavy metals. The upper Han River basin is the water resource area of China's Middle Route of the South-to-North Water Transfer Project. Therefore, to control the contamination of heavy metals in wetland soils, more efforts should be focused on reducing the discharge of mining and industrial pollutants into the riparian and reservoir shorelines.

Effects of fertilization, crop year, variety, and provenance factors on mineral concentrations in onions.

PubMed

Ariyama, Kaoru; Nishida, Tadashi; Noda, Tomoaki; Kadokura, Masashi; Yasui, Akemi

2006-05-03

Mineral concentrations of onions (Allium cepa L.) grown under various conditions, including factors (fertilization, crop year, variety, and provenance), were investigated to clarify how much each factor contributes to the variation of their concentrations. This was because the mineral concentrations might be affected by various factors. The ultimate goal of this study was to develop a technique to determine the geographic origins of onions by mineral composition. Samples were onions grown under various conditions at 52 fields in 18 farms in Hokkaido, Japan. Twenty-six elements (Li, Na, Mg, Al, P, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Y, Mo, Cd, Cs, Ba, La, Ce, Nd, Gd, W, and Tl) in these samples were determined by inductively coupled plasma atomic emission spectrometry and inductively coupled plasma mass spectrometry. Fertilization conditions and crop years of onions caused variations of P, Ni, Cu, Rb, Sr, Mo, Cs, and Tl concentrations in onions; different onion varieties also showed variations in numerous element concentrations. However, the variations of mineral compositions of onions by these factors were smaller than the differences between production places with a few exceptions. Furthermore, Na, Rb, and Cs in group IA of the periodic table, Ca, Sr, and Ba in group IIA, and Zn and Cd in group IIB showed similar concentration patterns by group; this result demonstrated that elements in the same periodic groups behaved similarly in terms of their absorption in onions.

Allometric constraints on Sr/Ca and Ba/Ca partitioning in terrestrial mammalian trophic chains.

PubMed

Balter, Vincent

2004-03-01

In biological systems, strontium (Sr) and barium (Ba) are two non-essential elements, in comparison to calcium (Ca) which is essential. The Sr/Ca and Ba/Ca ratios tend to decrease in biochemical pathways which include Ca as an essential element, and these processes are termed biopurification of Ca. The quantitative pathway of the biopurification of Ca in relation to Sr and Ba between two biological reservoirs ( Rn and R(n -1)) is measured with an observed ratio (OR) expressed by the (Sr/Ca) Rn /(Sr/Ca)( Rn-1) and (Ba/Ca) Rn /(Ba/Ca)( Rn-1) ratios. For a mammalian organism, during the whole biopurification of Ca starting with the diet to the ultimate reservoir of Ca which is the bone, the mean values for ORSr and ORBa are 0.25 and 0.2, respectively. In this study, published Sr/Ca and Ba/Ca ratios are used for three sets of soils, plants, and bones of herbivorous and carnivorous mammals, each comprising a trophic chain, to illustrate the biopurification of Ca at the level of trophic chains. Calculated ORSr and ORBa of herbivore bones in relation to plants and of bones of carnivores in relation to bones of herbivores give ORSr=0.30+/-0.08 and ORBa=0.16+/-0.08, thus suggesting that trophic chains reflect the Sr/Ca and Ba/Ca fluxes that are prevalent at the level of a mammalian organism. The slopes of the three regression equations of log(Sr/Ca) vs. log(Ba/Ca) are similar, indicating that the process of biopurification of Ca with respect to Sr and Ba is due to biological processes and is independent of the geological settings. Modifications of the logarithmic expression of the Sr/Ca and Ba/Ca relationship allow a new formula of the biopurification process to be deduced, leading to the general equation ORBa=ORSr(1.79+/-0.33), where the allometric coefficient is the mean of the slopes of the three regression equations. Some recent examples are used to illustrate this new analysis of predator-prey relations between mammals. This opens up new possibilities for the utilization of Ba/Ca and Sr/Ca in addition to stable isotope ratios (delta13C and delta15N) for the determination of the relative contribution of different food sources to an animal's diet.

Ligand reprogramming in dinuclear helicate complexes: a consequence of allosteric or electrostatic effects?

PubMed

Jeffery, John C; Rice, Craig R; Harding, Lindsay P; Baylies, Christian J; Riis-Johannessen, Thomas

2007-01-01

The ditopic ligand 6,6'-bis(4-methylthiazol-2-yl)-3,3'-([18]crown-6)-2,2'-bipyridine (L(1)) contains both a potentially tetradentate pyridyl-thiazole (py-tz) N-donor chain and an additional "external" crown ether binding site which spans the central 2,2'-bipyridine unit. In polar solvents (MeCN, MeNO(2)) this ligand forms complexes with Zn(II), Cd(II), Hg(II) and Cu(I) ions via coordination of the N donors to the metal ion. Reaction with both Hg(II) and Cu(I) ions results in the self-assembly of dinuclear double-stranded helicate complexes. The ligands are partitioned by rotation about the central py--py bond, such that each can coordinate to both metals as a bis-bidentate donor ligand. With Zn(II) ions a single-stranded mononuclear species is formed in which one ligand coordinates the metal ion in a planar tetradentate fashion. Reaction with Cd(II) ions gives rise to an equilibrium between both the dinuclear double-stranded helicate and the mononuclear species. These complexes can further coordinate s-block metal cations via the remote crown ether O-donor domains; a consequence of which are some remarkable changes in the binding modes of the N-donor domains. Reaction of the Hg(II)- or Cd(II)-containing helicate with either Ba(2+) or Sr(2+) ions effectively reprogrammes the ligand to form only the single-stranded heterobinuclear complexes [MM'(L(1))](4+) (M=Hg(II), Cd(II); M'=Ba(2+), Sr(2+)), where the transition and s-block cations reside in the N- and O-donor sites, respectively. In contrast, the same ions have only a minor structural impact on the Zn(II) species, which already exists as a single-stranded mononuclear complex. Similar reactions with the Cd(II) system result in a shift in equilibrium towards the single-stranded species, the extent of which depends on the size and charge of the s-block cation in question. Reaction of the dicopper(I) double-stranded helicate with Ba(2+) shows that the dinuclear structure still remains intact but the pitch length is significantly increased.

Metals in bones of the middle-aged inhabitants of Sardinia island (Italy) to assess nutrition and environmental exposure.

PubMed

Bocca, Beatrice; Forte, Giovanni; Giuffra, Valentina; Serra, Rita Maria; Asara, Yolande; Farace, Cristiano; Milanese, Marco; Tognotti, Eugenia; Montella, Andrea; Bandiera, Pasquale; Madeddu, Roberto

2018-03-01

Metals in bones of 72 subjects lived between the twelfth and eighteenth century AC and collected in four Sardinian (Italian insular region) burial sites (Alghero, Bisarcio, Geridu, and Sassari) were determined and used as biomarkers to evaluate diet and potential social-environmental differences. Concentrations of Ba, Ca, Cd, Cu, Hg, Pb, Sr, and Zn were quantified in different types of compact bone (femur, fibula, humerus, radius, tibia, ulna) by sector field inductively coupled plasma mass spectrometry previous acidic digestion and differences among the various burial sites, centuries, types of bone, gender, and age were explored by univariate and multivariate analyses. Results indicated differences between sites in terms of diet: Bisarcio (inland village) had increased ratios of Ba/Ca and Zn/Ca due to higher incidence of vegetables, cereals, and animal foods in the diet; Geridu (coastal village) showed increased Sr/Ca ratio indicating foods of plant and marine origin that were predominant; Alghero (coastal site) and Sassari (inland site) displayed prevalently a mixed diet reflecting a higher economy and food imports. In addition, these latter sites showed increased levels of Hg/Ca (fish, drugs, cosmetics) and Pb/Ca (coins, utensils, pipeline for water). In conclusion, the elemental Ba/Ca, Sr/Ca, and Zn/Ca ratios were indicative of provenance and diet, while Hg/Ca and Pb/Ca ratios were associated to various forms of environmental exposure.

Synthesis, Crystal and Electronic Structures of the Pnictides AE 3TrPn 3 (AE = Sr, Ba; Tr = Al, Ga; Pn = P, As)

DOE PAGES

Stoyko, Stanislav; Voss, Leonard; He, Hua; ...

2015-09-24

New ternary arsenides AE 3TrAs 3 (AE = Sr, Ba; Tr = Al, Ga) and their phosphide analogs Sr 3GaP 3 and Ba 3AlP 3 have been prepared by reactions of the respective elements at high temperatures. Single-crystal X-ray diffraction studies reveal that Sr 3AlAs 3 and Ba 3AlAs 3 adopt the Ba 3AlSb 3-type structure (Pearson symbol oC56, space group Cmce, Z = 8). This structure is also realized for Sr 3GaP 3 and Ba 3AlP 3. Likewise, the compounds Sr 3GaAs 3 and Ba 3GaAs 3 crystallize with the Ba 3GaSb 3-type structure (Pearson symbol oP56, space groupmore » Pnma, Z = 8). Both structures are made up of isolated pairs of edge-shared AlPn 4 and GaPn 4 tetrahedra (Pn = pnictogen, i.e., P or As), separated by the alkaline-earth Sr 2+ and Ba 2+ cations. In both cases, there are no homoatomic bonds, hence, regardless of the slightly different atomic arrangements, both structures can be rationalized as valence-precise [AE 2+] 3[Tr 3+][Pn 3-] 3, or rather [AE 2+] 6[Tr 2Pn 6] 12-, i.e., as Zintl phases.« less

Influences of Indium Tin Oxide Layer on the Properties of RF Magnetron-Sputtered (BaSr)TiO3 Thin Films on Indium Tin Oxide-Coated Glass Substrate

NASA Astrophysics Data System (ADS)

Kim, Tae Song; Oh, Myung Hwan; Kim, Chong Hee

1993-06-01

Nearly stoichiometric ((Ba+Sr)/Ti=1.08-1.09) and optically transparent (BaSr)TiO3 thin films were deposited on an indium tin oxide (ITO)-coated glass substrate by means of rf magnetron sputtering for their application to the insulating layer of an electroluminescent flat panel display. The influence of the ITO layer on the properties of (BaSr)TiO3 thin films deposited on the ITO-coated substrate was investigated. The ITO layer did not affect the crystallographic orientation of (BaSr)TiO3 thin film, but enhanced the grain growth. Another effect of the ITO layer on (BaSr)TiO3 thin films was the interdiffusion phenomenon, which was studied by means of secondary ion mass spectrometry (SIMS). As the substrate temperature increased, interdiffusion intensified at the interface not only between the grown film and ITO layer but also between the ITO layer and base glass substrate. The refractive index (nf) of (BaSr)TiO3 thin film deposited on a bare glass substrate was 2.138-2.286, as a function of substrate temperature.

Composition-dependent surface chemistry of colloidal Ba xSr 1-xTiO 3 perovskite nanocrystals

DOE PAGES

Margossian, Tigran; Culver, Sean P.; Larmier, Kim; ...

2016-11-01

Ba xSr 1-xTiO 3 perovskite nanocrystals, prepared by the vapor diffusion sol-gel method and characterized by state of the art surface techniques, display significantly different O-H stretching frequencies and adsorption properties towards CO 2 as a function of the alkaline earth composition (Ba vs. Sr). Lastly, the difference of properties can be associated with the more basic nature of BaO-rich than SrO-rich surfaces.

Synthesis and effect of Sr substitution on fluorescence of new Ba 2-xSr xZnS 3: Eu 2+ red phosphor: Considerable enhancement of emission intensity

NASA Astrophysics Data System (ADS)

Lee, Chi-Woo; Petrykin, Valery; Kakihana, Masato

2009-01-01

A series of 0.5 mol% Eu 2+-activated Ba 2-xSr xZnS 3 phosphor materials were synthesized using precursors prepared by the polymerizable complex method and their fluorescent properties were studied for the first time. It was found that Sr substitution for Ba leads to the considerable improvement of internal quantum efficiency and emission intensity in these materials compared to Ba 2ZnS 3, while emission peak wavelength exhibits a blue shift from 680 to 660 nm. Rietveld refinement of crystal structure of sample with x=0.7 suggests that Sr ions preferentially occupy one of two Ba sites in this compound. Such a structural re-arrangement might be responsible for the observed quantum efficiency dependence on Sr concentration.

Determination of Heavy Metals in Almonds and Mistletoe as a Parasite Growing on the Almond Tree Using ICP-OES or ICP-MS.

PubMed

Kamar, Veysi; Dağalp, Rukiye; Taştekin, Mustafa

2017-12-28

In this study, the elements of Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Ni, Sr, Pb, Ti, and Zn were determined in the leaves, fruits, and branches of mistletoe, (Viscum albüm L.), used as a medicinal plant, and in the leaves, branches and barks of almond tree which mistletoe grows on. The aim of the study is to investigate whether the mistletoe are more absorbent than the almond tree in terms of the heavy metal contents and the determination of the amount of the elements penetrated into the mistletoe from the almond tree. ICP-MS (inductively coupled plasma-mass spectrometry) was used for the analysis of As, Cd, Mo, and Pb, whereas ICP-OES (inductively coupled plasma optical emission spectrometry) was used for the other elements. The results obtained were statistically evaluated at 95% confidence level. Within the results obtained in this study, it was determined whether there is a significant difference between metal elements in almond tree and mistletoe, or not. As a result, it was observed that there were higher contents of B, Ba, K, Mg, and Zn in the mistletoe than in the almond tree. K was found much higher than other elements in the mistletoe. On the other hand, Al, As, Ca, Cd, Cr, Cu, Fe, Mo, Ni, Sr, Pb, and Ti contents were determined to be more in almond tree than mistletoe.

Concentrations of trace elements in marine fish and its risk assessment in Malaysia.

PubMed

Agusa, Tetsuro; Kunito, Takashi; Yasunaga, Genta; Iwata, Hisato; Subramanian, Annamalai; Ismail, Ahmad; Tanabe, Shinsuke

2005-01-01

Concentrations of trace elements (V, Cr, Mn, Co, Cu, Zn, Ga, Se, Rb, Sr, Mo, Ag, Cd, Sn, Sb, Cs, Ba, Hg, Tl, Pb and Bi) were determined in muscle and liver of 12 species of marine fish collected from coastal areas in Malaysia. Levels of V, Cr, Mn, Co, Cu, Zn, Ga, Sr, Mo, Ag, Cd, Sn, Ba and Pb in liver were higher than those in muscle, whereas Rb and Cs concentrations showed the opposite trend. Positive correlations between concentrations in liver and muscle were observed for all the trace elements except Cu and Sn. Copper, Zn, Se, Ag, Cd, Cs and Hg concentrations in bigeye scads from the east coast of the Peninsular Malaysia were higher than those from the west, whereas V showed the opposite trend. The high concentration of V in the west coast might indicate oil contamination in the Strait of Malacca. To evaluate the health risk to Malaysian population through consumption of fish, intake rates of trace elements were estimated on the basis of the concentrations of trace elements in muscle of fish and daily fish consumption. Some specimens of the marine fish had Hg levels higher than the guideline value by US Environmental Protection Agency (EPA), indicating that consumption of these fish at the present rate may be hazardous to Malaysian people. To our knowledge, this is the first study on multielemental accumulation in marine fish from the Malaysian coast.

Terahertz dielectric response of ferroelectric Ba(x)Sr(1-x)TiO3 thin films.

PubMed

Kang, Seung Beom; Kwak, Min Hwan; Choi, Muhan; Kim, Sungil; Kim, Taeyong; Cha, Eun Jong; Kang, Kwang Yong

2011-11-01

Terahertz time-domain spectroscopy has been used to investigate the dielectric and optical properties of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films for nominal x-values of 0.4, 0.6, and 0.8 in the frequency range of 0.3 to 2.5 THz. The ferroelectric thin films were deposited at approximately 700 nm thickness on [001] MgO substrate by pulsed laser deposition. The measured complex dielectric and optical constants were compared with the Cole-Cole relaxation model. The results show that the Cole-Cole relaxation model fits well with the data throughout the frequency range and the dielectric relaxation behavior of ferroelectric Ba(x)Sr(1-x)TiO(3) thin films varies with the films compositions. Among the compositions of Ba(x)Sr(1-x)TiO(3) films with different Ba/Sr ratios, Ba(0.6)Sr(0.4)TiO(3) has the highest dielectric constants and the shortest dielectric relaxation time.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manaf, A., E-mail: azwar@ui.ac.id; Fahmi, Agam Aidil; Yustanti, Erlina

This paper describes the particle size characterization of mechanically alloyed Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} prepared with the aid of a high-power ultrasonic destruction. Analytical-grade BaCO{sub 3}, TiO{sub 2} and SrCO{sub 3} with a purity greater than 99 wt.% were used as precursors for Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3}. The mechanically powders were respectively sintered at 1200 °C for 3 hours to form crystalline powders. This work is aimed at studying the effect of diameter ratio between reactor and transducer of a high power sonicator on the Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} andmore » Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} nanoparticles formation. The presence of a single phase of the two materials was confirmed by X-Ray Diffraction (XRD). The concentration of the particles in demineralized water was 3.0 g / 100 mL which become the object of 3 hours ultrasonic destruction subjected to the application of transducer in which the ratio between the diameter of the reactor and the transducer (D/d) was fixed at 1.4, 1.6 and 1.8 respectively. It was found that the mean particle size before the ultrasonic destruction was 538 nm for Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and 480 nm for Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3}. With D/d of 1.8, the mean particle size of the two materials was found to decrease drastically to 38 nm and 24 nm, respectively. These mean particle sizes were respectively comparable with that of the crystallite size of the particles derived using the Whole Powder Pattern Modelling (WPPM) from which the mean crystallite size of 22 nm for Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and 14 nm for Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} were obtained. It is then confirmed single nanocrystallite Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} particles were already achieved. We can conclude that the ultrasonic destruction to mechanically milled crystalline particles would be one of an effective way to produce nanoparticles.« less

Biomonitoring of 33 Elements in Blood and Urine Samples from Coastal Populations in Sanmen County of Zhejiang Province.

PubMed

Zhang, Su-jing; Luo, Ru-xin; Ma, Dong; Zhuo, Xian-yi

2016-04-01

To determine the normal reference values of 33 elements, Ag, Al, As, Au, B, Ba, Be, Ca, Cd, Co, Cr, Cs, Cu, Fe, Ga, Hg, Li, Mg, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sr, Th, Ti, Tl, U, V, Zn and Zr, in the blood and urine samples from the general population in Sanmen County of Zhejiang province, a typical coastal area of eastern China. The 33 elements in 272 blood and 300 urine samples were determined by inductively coupled plasma-mass spectrometry (ICP-MS). The normality test of data was conducted using SPSS 17.0 Statistics. The data was compared with other reports. The normal reference values of the 33 elements in the blood and urine samples from the general population in Sanmen County were obtained, which of some elements were found to be similar with other reports, such as Co, Cu, Mn and Sr, while As, Cd, Hg and Pb were generally found to be higher than those previously reported. There was a wide variation between the reports from different countries in blood Ba. The normal reference values of the 33 elements in the blood and urine samples from the general population in Sanmen County are established, and successfully applied to two poisoning cases.

Comparison of dry, wet and microwave digestion methods for the multi element determination in some dried fruit samples by ICP-OES.

PubMed

Altundag, Huseyin; Tuzen, Mustafa

2011-11-01

The aim of this study was used to investigate the level of trace metals (Ba, Pb, Cd, Mn, Cr, Co, Ni, Cu, Mn, Zn, Sr and Fe) in some dried fruits (Prunus domestica L., Ficus carica L., Morus alba L., Vitis vinifera L., Prunus armeniaca L., and Malus domestica) samples from Turkey. Trace elements were determined by ICP-OES after dry, wet and microwave digestion methods in dried fruit samples. Validation of the proposed method was carried out by using a NIST-SRM 1515-Apple Leaves certified reference material. Element concentrations in dried fruit samples were 0.33-1.77 (Ba), 0.12-0.54 (Cd), 0.25-1.03 (Co), 0.45-2.30 (Cr), 0.43-2.74 (Cu), 0.56-4.87 (Mn), 0.61-2.54 (Ni), 0.40-2.14 (Pb), 2.16-6.54 (Zn), 0.83-12.02 (Al), 11.82-40.80 (Fe) and 0.16-6.34 (Sr) μg/g. The analytical parameters show that the microwave oven digestion procedure provided best results as compared to the wet and dry digestion procedures. The results were compared with the literature values. Copyright © 2011 Elsevier Ltd. All rights reserved.

Concentrations of strontium, barium, cadmium, copper, zinc, manganese, chromium, antimony, selenium, and lead in the liver and kidneys of dogs according to age, gender, and the occurrence of chronic kidney disease

PubMed Central

Mainzer, Barbara; Lahrssen-Wiederholt, Monika; Schafft, Helmut; Palavinskas, Richard; Breithaupt, Angele; Zentek, Jürgen

2015-01-01

This study was conducted to measure the concentrations of strontium (Sr), barium (Ba), cadmium (Cd), copper (Cu), zinc (Zn), manganese (Mn), chromium (Cr), antimony (Sb), selenium (Se), and lead (Pb) in canine liver, renal cortex, and renal medulla, and the association of these concentrations with age, gender, and occurrence of chronic kidney disease (CKD). Tissues from 50 dogs were analyzed using inductively coupled plasma mass spectrometry. Cu, Zn, and Mn levels were highest in the liver followed by the renal cortex and renal medulla. The highest Sr, Cd, and Se concentrations were measured in the renal cortex while lower levels were found in the renal medulla and liver. Female dogs had higher tissue concentrations of Sr (liver and renal medulla), Cd (liver), Zn (liver and renal cortex), Cr (liver, renal cortex, and renal medulla), and Pb (liver) than male animals. Except for Mn and Sb, age-dependent variations were observed for all element concentrations in the canine tissues. Hepatic Cd and Cr concentrations were higher in dogs with CKD. In conclusion, the present results provide new knowledge about the storage of specific elements in canine liver and kidneys, and can be considered important reference data for diagnostic methods and further investigations. PMID:25234328

On the substitution of Sr ions at Y sites in YB(suba2)Cu3O(sub7-d)

NASA Astrophysics Data System (ADS)

Siddiqi, S. A.; Sreedhar, K.; Drobac, D.; Infante, C.; Matacotta, F. C.; Ganguly, P.

1989-10-01

The effect of Sr substitution at the Ba sites in YBa2 Cu3 O sub 7-d has been studied; attempts to substitute Sr exclusively at Y sites have not been successful. We have been able to substitute Sr at Y sites only when the Ba ions are simultaneously substituted by Sr to give solid solutions of the type Y sub 1-x Sr sub x Ba sub 2-2x Sr sub 2x Cu3 O(sub 7-)x(sub /2-d). These examples show superconducting transitions higher than 78 K without significant deterioration in the magnitude of the ac susceptibility. The substitutions are best understood in terms of site constraints on the ions occupying the Y and Ba sites.

Improvement of electron mobility in La:BaSnO{sub 3} thin films by insertion of an atomically flat insulating (Sr,Ba)SnO{sub 3} buffer layer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shiogai, Junichi, E-mail: junichi.shiogai@imr.tohoku.ac.jp; Nishihara, Kazuki; Sato, Kazuhisa

One perovskite oxide, ASnO{sub 3} (A = Sr, Ba), is a candidate for use as a transparent conductive oxide with high electron mobility in single crystalline form. However, the electron mobility of films grown on SrTiO{sub 3} substrates does not reach the bulk value, probably because of dislocation scattering that originates from the large lattice mismatch. This study investigates the effect of insertion of bilayer BaSnO{sub 3} / (Sr,Ba)SnO{sub 3} for buffering this large lattice mismatch between La:BaSnO{sub 3} and SrTiO{sub 3} substrate. The insertion of 200-nm-thick BaSnO{sub 3} on (Sr,Ba)SnO{sub 3} bilayer buffer structures reduces the number of dislocationsmore » and improves surface smoothness of the films after annealing as proved respectively by scanning transmission electron microscopy and atomic force microscopy. A systematic investigation of BaSnO{sub 3} buffer layer thickness dependence on Hall mobility of the electron transport in La:BaSnO{sub 3} shows that the highest obtained value of mobility is 78 cm{sup 2}V{sup −1}s{sup −1} because of its fewer dislocations. High electron mobility films based on perovskite BaSnO{sub 3} can provide a good platform for transparent-conducting-oxide electronic devices and for creation of fascinating perovskite heterostructures.« less

Major, minor, trace and rare earth elements in sediments of the Bijagós archipelago, Guinea-Bissau.

PubMed

Carvalho, Lina; Figueira, Paula; Monteiro, Rui; Reis, Ana Teresa; Almeida, Joana; Catry, Teresa; Lourenço, Pedro Miguel; Catry, Paulo; Barbosa, Castro; Catry, Inês; Pereira, Eduarda; Granadeiro, José Pedro; Vale, Carlos

2018-04-01

Sixty sediment samples from four sites in the Bijagós archipelago were characterized for fine fraction, loss on ignition, major, minor and trace elemental composition (Al, Fe, Ca, Mg, Ti, P, Zr, Mn, Cr, Sr, Ba, B, V, Li, Zn, Ni, Pb, As, Co, U, Cu, Cs and Cd), and the elements of the La-Lu series. Element concentrations were largely explained by the Al content and the proportion of fine fraction content, with the exception of Ca and Sr. Sediments showed enhanced Ti, U, Cr, As and Cd concentrations with respect to estimated upper crust values, most likely mirroring a regional signature. Rare earth elements were in deficit relatively to the North American Shale Composite (NASC), mainly in coarser material. No pronounced Ce-anomaly was observed, while Eu-anomalies were positive in most analyzed sediments. Copyright © 2017 Elsevier Ltd. All rights reserved.

Toxic elements and bio-metals in Cantharellus mushrooms from Poland and China.

PubMed

Falandysz, Jerzy; Chudzińska, Maria; Barałkiewicz, Danuta; Drewnowska, Małgorzata; Hanć, Anetta

2017-04-01

Data on multi-trace element composition and content relationships have been obtained for Cantharellus cibarius, C. tubaeformis, and C. minor mushrooms from Poland and China by inductive coupled plasma-dynamic reaction cell-mass spectroscopy. There is no previous data published on As, Li, V, Tl, and U in chanterelles from Poland and on Ba, Co, Cr, Ni, Rb, and Sr in chanterelles from China. The results implied a role of the soil background geochemistry at the collection site with the occurrence of Ag, As, Ba, Cr, Cs, Li, Mn, Pb, Rb, Sr, U, and V in the fruiting bodies. Both geogenic Cd and anthropogenic Cd can contribute in load of this element in chanterelles from the Świetokrzyskie Mts. region in Poland, while geogenic source can be highly dominant in the background areas of Yunnan. An essentiality of Cu and Zn and effort by mushroom to maintain their physiological regulation could be reflected by data for Cantharellus mushrooms from both regions of the world, but its geogenic source (and possibly anthropogenic) can matter also in the region of the Świetokrzyskie Mountains in Poland. The elements Co, Ni, and Tl were at the same order of magnitude in contents in C. cibarius in Poland and Yunnan, China. C. tubaeformis differed from C. cibarius by a lower content of correlated Co, Ni, and Zn. Soil which is polymetallic and highly weathered in Yunnan can be suggested as a natural geogenic source of greater concentrations of As, Ba, Cr, Li, Pb, Sr, U, and V in the chanterelles there while lower of Mn and Rb, when related to chanterelles in Poland. A difference in Cs content between the sites can be attributed as an effect of the 137 Cs release from the Chernobyl accident, in which Poland was much more affected than Yunnan, where deposition was negligible.

Determination of mineral contents of wild Boletus edulis mushroom and its edible safety assessment.

PubMed

Su, Jiuyan; Zhang, Ji; Li, Jieqing; Li, Tao; Liu, Honggao; Wang, Yuanzhong

2018-04-06

This study aimed to determine the contents of main mineral elements of wild Boletus edulis and to assess its edible safety, which may provide scientific evidence for the utilization of this species. Fourteen mineral contents (Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, Ni, Sr, V and Zn) in the caps and stipes of B. edulis as well as the corresponding surface soils collected from nine different geographic regions in Yunnan Province, southwest China were determined. The analyses were performed using inductively coupled plasma atomic emission spectrometer (ICP-AES) after microwave digestion. Measurement data were analyzed using variance and Pearson correlation analysis. Edible safety was evaluated according to the provisionally tolerable weekly intake (PTWI) of heavy metals recommended by United Nations Food and Agriculture Organization and World Health Organization (FAO/WHO). Mineral contents were significantly different with the variance of collection areas. B. edulis showed relative abundant contents of Ca, Fe, Mg and Na, followed by Ba, Cr, Cu, Mn and Zn, and the elements with the lower content less were Cd, Co, Ni, Sr and V. The elements accumulation differed significantly in caps and stipes. Among them, Cd and Zn were bioconcentrated (BCF > 1) while others were bioexcluded (BCF < 1). The mineral contents in B. edulis and its surface soil were positively related, indicating that the elements accumulation level was related to soil background. In addition, from the perspective of food safety, if an adult (60 kg) eats 300 g fresh B. edulis per week, the intake of Cd in most of tested mushrooms were lower than PTWI value whereas the Cd intakes in some other samples were higher than this standard. The results indicated that the main mineral contents in B. edulis were significantly different with respect to geographical distribution, and the Cd intake in a few of regions was higher than the acceptable intakes with a potential risk.

Optical materials characterization final technical report february 1, 1978-september 30, 1978. Technical note

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feldman, A.; Horowitz, D.; Waxter, R.M.

1979-02-01

Data obtained as part of the Optical Materials Characterization Program are summarized in this report. Room temperature values of refractive index as a function of wavelength are presented for the following materials: commercially grown KCl, reactive atmosphere processed (RAP) KCl, KCl nominally doped with 1.5% KI, hot forged CaF2, fusion cast CaF2, CaF2 doped with Er (0.001% to 3% Er), SrF2, chemical vapor deposited (CVD) ZnSe (2 specimens), and ZnS (CVD, 2 specimens). Data for the thermo-optic constant (dn/dT) and the linear thermal expansion coefficient are given for the following materials over the temperature range -180 degrees C to 200more » degrees C: Al2O3, BaF2, CaF2, CdF2, KBr, KCl, LiF, MgF2, NaCl, NaF, SrF2, ZnS (CVD), and ZnSe (CVD). The piezo-optic constants of the following materials are presented: As2S3 glass, CaF2, BaF2, Ge, KCl, fused SiO2, SrF2, a chalcogenide glass (Ge 33%, As 12%, Se 55%) and ZnSe (CVD).« less

Les Néandertaliens étaient-ils essentiellement carnivores ? Résultats préliminaires sur les teneurs en Sr et en Ba de la paléobiocénose mammalienne de Saint-CésaireWere Neandertalians essentially carnivores? Sr and Ba preliminary results of the mammalian palaeobiocoenosis of Saint-Césaire

NASA Astrophysics Data System (ADS)

Balter, Vincent; Person, Alain; Labourdette, Nathalie; Drucker, Dorothée; Renard, Maurice; Vandermeersch, Bernard

2001-01-01

Strontium-calcium (Sr/Ca) and barium-calcium (Ba/Ca) ratios are reduced constantly between diet and bioapatite in mammal organisms. This phenomenon leads to a reduction in the Sr/Ca and Ba/Ca ratios at higher trophic level in predator-prey mammalian communities, and is applied here to the reconstruction of a castelperronian food web, which includes a Neanderthal specimen. Adapted chemical pretreatment allows to isolate bioapatite from diagenetic compounds for analysis of Ca, Sr and Ba. Sr/Ca and Ba/Ca results of the fauna are consistent with trophic predictions. Initial results for the Neandertal suggest that he was mostly carnivorous. Distribution of Ba/Ca values of bones of herbivorous taxa reveals that ruminant animals can be distinguished from non-ruminants. The biosegregation model predicts that the diet of the Neandertal was composed by about 97 % in weight of meat with a weak contribution of vegetable or fish, and that the association of fish and plant is excluded in any proportion.

Hair chemical element contents and influence factors of reproductive-age women in the West Ujimqin Banner, Inner Mongolia, China.

PubMed

Zhou, Shanshan; Yuan, Haodong; Ma, Xiaoling; Liu, Ying

2017-01-01

Women have an increased risk for chemical element deficiencies during reproductive age, particularly due to higher chemical element requirements and poor diets. Twenty-one chemical elements (Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Se, Si, Sn, Sr, Ti, V and Zn) in hair samples, which were collected from 71 non-pregnant and 236 pregnant women living in the West Ujimqin Banner, central Inner Mongolia, China, were measured, and the environment, dietary habits and ethnic group influence factors associated with the biomarker were analyzed. The results indicated that the average values of the chemical element contents from hair were greatly different compared to those from other areas, especially the Al, Cd, Pb, Ca and Sr contents. There was no significant difference among the three ethnicities for any element except Mn and Ti in non-pregnant women. Compared to non-pregnant women, in the first trimester group, the levels of nine chemical elements (Ba, Cd, Cu, Pb, Se, Si, Sn and Ti) decreased, while the others increased, and the contents of all of the chemical elements decreased in the second trimester group, while in the third trimester, there was a slight increase. Three chemical elements (Cu, Mn and Zn) displayed a synergistic correlation between each other in the third trimester group, which may protect the placenta from some oxidant damage. The high levels of Cd and Pb in hair likely originate from house renovations and traffic pollution. This study provided basic and useful information on the levels of chemical elements in reproductive-age women, and the results of this study are helpful to control the contents and improve the health of pregnant and non-pregnant women. Copyright © 2016 Elsevier Ltd. All rights reserved.

Trace element accumulation in hawksbill turtles (Eretmochelys imbricata) and green turtles (Chelonia mydas) from Yaeyama Islands, Japan.

PubMed

Anan, Y; Kunito, T; Watanabe, I; Sakai, H; Tanabe, S

2001-12-01

Concentrations of 18 trace elements (V, Cr, Mn, Co, Cu, Zn, Se, Rb, Sr, Zr, Mo, Ag, Cd, Sb, Ba, Hg, Tl, and Pb) were determined in the liver, kidney, and muscle of green turtles (Chelonia mydas) and hawksbill turtles (Eretmochelys imbricata) from Yaeyama Islands, Okinawa, Japan. Accumulation features of trace elements in the three tissues were similar between green and hawksbill turtles. No gender differences in trace element accumulation in liver and kidney were found for most of the elements. Significant growth-dependent variations were found in concentrations of some elements in tissues of green and hawksbill turtles. Significant negative correlations (p < 0.05) were found between standard carapace length (SCL) and the concentrations of Cu, Zn, and Se in the kidney and V in muscle of green turtles and Mn in the liver, Rb and Ag in kidney, and Hg in muscle of hawksbill turtles. Concentrations of Sr, Mo, Ag, Sb, and Tl in the liver, Sb in kidney, and Sb and Ba in muscle of green turtles and Se and Hg in the liver and Co, Se, and Hg in kidney of hawksbill turtles increased with an increase in SCL (p < 0.05). Green and hawksbill turtles accumulated extremely high concentrations of Cu in the liver and Cd in kidney, whereas the levels of Hg in liver were low in comparison with those of other higher-trophic-level marine animals. High accumulation of Ag in the liver of green turtles was also observed. To evaluate the trophic transfer of trace elements, concentrations of trace elements were determined in stomach contents of green and hawksbill turtles. A remarkably high trophic transfer coefficient was found for Ag and Cd in green turtles and for Cd and Hg in hawksbill turtles.

Luminescence properties of Eu2+ in M2MgSi2O7 (M=Ca, Sr, and Ba) phosphors

NASA Astrophysics Data System (ADS)

Kim, T.; Kim, Y.; Kang, S.

2012-03-01

The photoluminescence properties of alkali-earth magnesium silicates (M2MgSi2O7, M=Ca, Sr, and Ba) doped with Eu2+ were investigated. Solid solutions of Ba x Sr2- x Si2O7, Ca2MgSi2O7, and Sr2MgSi2O7 were prepared. Ba x Sr2- x Si2O7 retained a tetragonal crystal structure similar to the structure of the other compounds up to a stoichiometry of x=1.6, which enabled a systematic study of the common structure. Monoclinic Ba2MgSi2O7 was prepared, and the luminescence properties were compared with those of other samples. The emission and excitation spectra of tetragonal M2MgSi2O7 (M=Ca, Sr, and Ba) changed as a function of the covalency, site symmetry, and crystal field strength. The luminescence properties showed excellent agreement with theoretical predictions based on these factors. The Stokes shift differentiated the emission behaviors of the tetragonal and monoclinic structures.

Correlation of Structure, Tunable Colors, and Lifetimes of (Sr, Ca, Ba)Al₂O₄:Eu2+, Dy3+ Phosphors.

PubMed

Xie, Qidi; Li, Bowen; He, Xin; Zhang, Mei; Chen, Yan; Zeng, Qingguang

2017-10-18

(Sr, Ca, Ba)Al₂O₄:Eu 2+ , Dy 3+ phosphors were prepared via a high temperature solid-state reaction method. The correlation of phase structure, optical properties and lifetimes of the phosphors are investigated in this work. For the (Sr, Ca)Al₂O₄:Eu 2+ ,Dy 3+ phosphors, the different phase formation from monoclinic SrAl₂O₄ phase to hexagonal SrAl₂O₄ phase to monoclinic CaAl₂O₄ phase was observed when the Ca content increased. The emission color of SrAl₂O₄:Eu 2+ , Dy 3+ phosphors varied from green to blue. For the (Sr, Ba)Al₂O₄:Eu 2+ , Dy 3+ phosphors, different phase formation from the monoclinic SrAl₂O₄ phase to the hexagonal BaAl₂O₄ phase was observed, along with a shift of emission wavelength from 520 nm to 500 nm. More interestingly, the decay time of SrAl₂O₄:Eu 2+ , Dy 3+ changed due to the different phase formations. Lifetime can be dramatically shortened by the substitution of Sr 2+ with Ba 2+ cations, resulting in improving the performance of the alternating current light emitting diode (AC-LED). Finally, intense LEDs are successfully obtained by combining these phosphors with Ga(In)N near UV chips.

The Phase Transformation and Crystal Structure Studies of Strontium Substituted Barium Monoferrite

NASA Astrophysics Data System (ADS)

Mulyawan, A.; Adi, W. A.; Mustofa, S.; Fisli, A.

2017-03-01

Unlike other AFe2O4 ferrite materials, Barium Monoferrite (BaFe2O4) have an orthorhombic structure which is very interesting to further study the crystal structure and phase formation. In this study, Strontium substituted Barium Monoferrite in the form of Ba(1-x)Sr(x)Fe2O4 has successfully been synthesized through solid state reaction method which includes BaCO3, SrCO3, and Fe2O3 as starting materials. Ba(1-x)Sr(x)Fe2O4 was made by varying the dopant composition of Strontium (Sr2+) from x = 0, 0.1, 0.3, and 0.5. Each composition was assisted by ethanol and continued to the milling process for 5 hours then followed by sintering process at 900 °C for 5 hours. The phase transformation was studied by using X-ray diffractometer (XRD) and Rietveld refinement using General Structure Analysis System (GSAS) also 3D crystal visualization using VESTA. Referring to the refinement results, a single phase of BaFe2O4 was formed in x = 0 and 0.1. The composition has orthorhombic structure, space group B b21m, and lattice parameters of a = 19.0229, b = 5.3814 c = 8.4524 Å, α = β = γ = 90° and a = 18.9978, b = 5.3802 c = 8.4385 Å, α = β = γ = 90° respectively. In the composition of x = 0.3 it was found that the phase of BaSrFe4O8 begin to form due to the overload expansion of the Sr2+ occupancy which made the distortion of the initial lattice parameters and finally in the x = 0.5 composition the single phase of BaSrFe4O8 was clearly formed. Energy Dispersive Spectroscopy (EDS) was used to confirm the change of the material structure by measuring the elemental compound composition ratio. The result of EDS spectra clearly exhibited the dominant elements were Barium (Ba), Strontium (Sr), Iron (Fe), and Oxygen (O) with the compound ratio (Atomic percentage and mass percentage) correspond to the BaFe2O4 and BaSrFe4O8 phase.

Low temperature rf sputtering deposition of (Ba, Sr) TiO3 thin film with crystallization enhancement by rf power supplied to the substrate

NASA Astrophysics Data System (ADS)

Yoshimaru, Masaki; Takehiro, Shinobu; Abe, Kazuhide; Onoda, Hiroshi

2005-05-01

The (Ba, Sr) TiO3 thin film deposited by radio frequency (rf) sputtering requires a high deposition temperature near 500 °C to realize a high relative dielectric constant over of 300. For example, the film deposited at 330 °C contains an amorphous phase and shows a low relative dielectric constant of less than 100. We found that rf power supplied not only to the (Ba, Sr) TiO3 sputtering target, but also to the substrate during the initial step of film deposition, enhanced the crystallization of the (Ba, Sr) TiO3 film drastically and realized a high dielectric constant of the film even at low deposition temperatures near 300 °C. The 50-nm-thick film with only a 10 nm initial layer deposited with the substrate rf biasing is crystallized completely and shows a high relative dielectric constant of 380 at the deposition temperature of 330 °C. The (Ba, Sr) TiO3 film deposited at higher temperatures (upwards of 400 °C) shows <110> preferred orientation, while the film deposited at 330 °C with the 10 nm initial layer shows a <111> preferred orientation on a <001>-oriented ruthenium electrode. The unit cell of (Ba, Sr) TiO3 (111) plane is similar to that of ruthenium (001) plane. We conclude that the rf power supplied to the substrate causes ion bombardments on the (Ba, Sr) TiO3 film surface, which assists the quasiepitaxial growth of (Ba, Sr) TiO3 film on the ruthenium electrode at low temperatures of less than 400 °C.

Effect of Heat Treatment on The Crystal Structur, Electrical Conductivity and Surface of Ba1.5Sr0.5Fe2O5 Composite

NASA Astrophysics Data System (ADS)

Purwanto, P.; Adi, WA; Yunasfi

2017-05-01

The Composite of Ba1,5Sr0,5Fe2O5 has been synthesized by using powder metallurgy technique. The Ba1.5Sr0.5Fe2O5 were prepared from BaCO3, SrCO3 and Fe2O3 raw materials with a specific weight ratio. The three materials were synthesized by powder metallurgy under heat treatment at 800 °C, 900 °C, and 1000 °C for 5 hours. All the three samples were characterized by using X-ray Diffraction (XRD) to determine the crystal structure and crystal size, LCR meter to determine the conductivity, and Scanning Electron Microscope (SEM) to observe the morphological of the composites. The phase analysis result showed that the composite consists of several minor phases such as BaO2, SrO2, and Fe2O3. The Crystal size of composite Ba1.5Sr0.5Fe2O5 decreased while increases the strain of crystal with increasing of sintering temperature. The crystal size of the Ba1.5Sr0.5Fe2O5 composite is 3.55 nm to 7.23 nm and value of strain is 8.47% until 3.90%. Based on the conductivity measurement, it was obtained that the conductivity of the Ba1.5Sr0.5Fe2O5 composite decreased with increasing sintering temperature. It was also noticed that the conductivity increased with increasing of frequency. The conductivity ranged from 6.619×10-7 S/cm to 65.659×10-7 S/cm. The energy dispersive spectroscopy (EDS) analysis showed that several dominant elements were a good agreement with the phase analysis.

Growth and interface engineering in thin-film Ba0.6Sr0.4TiO3 /SrMoO3 heterostructures

NASA Astrophysics Data System (ADS)

Radetinac, Aldin; Ziegler, Jürgen; Vafaee, Mehran; Alff, Lambert; Komissinskiy, Philipp

2017-04-01

Epitaxial heterostructures of ferroelectric Ba0.6Sr0.4TiO3 and highly conducting SrMoO3 were grown by pulsed laser deposition on SrTiO3 (0 0 1) substrates. Surface oxidation of the SrMoO3 film is suppressed using a thin cap interlayer of Ba0.6Sr0.4TiO3-δ grown in reduced atmosphere. As shown by X-ray photoelectron spectroscopy, the Mo4+ valence state of the SrMoO3 films is stable upon annealing of the sample in oxygen up to 600 °C. The described oxygen interface engineering enables utilization of the highly conducting material SrMoO3 in multilayer oxide ferroelectric varactors.

Preparation of porous (Ba,Sr)TiO3 by adding corn-starch

NASA Astrophysics Data System (ADS)

Kim, J.-G.; Sim, J.-H.; Cho, W.-S.

2002-11-01

A new method of preparing porous (Ba,Sr)TiO3 ceramics has been introduced, using an ordinary ceramics processing technique. The effect of corn-starch on the positive temperature coefficient of resistivity characteristics and microstructure of the porous (Ba,Sr)TiO3 ceramics has been investigated. When the corn-starch addition was 1-20 wt%, the PTCR jump was over 106 and 1-2 orders higher than that of samples without corn-starch. Also, it was found that the (Ba,Sr)TiO3 ceramics had porous microstructure by the addition of corn-starch. The porosity of the ceramics with 20 wt% corn-starch was 44%. The electrical properties of the (Ba,Sr)TiO3 ceramics have been discussed, based on the microstructure, resistivity of grain boundaries, donor concentration of grains and the electrical potential barrier of grain boundaries.

Connectivity clues from short-term variability in settlement and geochemical tags of mytilid mussels

NASA Astrophysics Data System (ADS)

Fodrie, F. Joel; Becker, Bonnie J.; Levin, Lisa A.; Gruenthal, Kristen; McMillan, Pat A.

2011-01-01

The use of geochemical tags in calcified structures of fish and invertebrates is an exciting tool for investigating larval population connectivity. Tag evaluation over relatively short intervals (weeks) may detect environmental and ecological variability at a temporal scale highly relevant to larval transport and settlement. We collected newly settled mussels ( Mytilus californianus and M. galloprovincialis) weekly during winter/spring of 2002 along the coast of San Diego, CA, USA, at sites on the exposed coast (SIO) and in a protected coastal bay (HI), to investigate temporal patterns of geochemical tags in mussel shells. Analyses of post-settlement shell via LA-ICP-MS revealed statistically significant temporal variability for all elements we examined (Mg, Mn, Cu, Sr, Cd, Ba, Pb and U). Despite this, our ability to distinguish multielemental signatures between sites was largely conserved. Throughout our 13-week study, SIO and HI mussels could be chemically distinguished from one another in 78-87% of all cases. Settlement varied between 2 and 27 settlers gram-byssus -1 week -1 at SIO and HI, and both sites were characterized by 2-3 weeks with "high" settlement. Geochemical tags recorded in early larval shell of newly settled mussels differed between "high" and "low" settlement weeks at both sites (MANOVA), driven by Mg and Sr at SIO (p = 0.013) and Sr, Cd, Ba and Pb at HI (p < 0.001). These data imply that shifts in larval sources or transport corridors were responsible for observed settlement variation, rather than increased larval production. In particular, increased settlement at HI was observed concurrent with the appearance of geochemical tags (e.g., elevated Cd), suggesting that those larvae were retained in upwelled water near the mouth of the bay. Such shifts may reflect short-term changes in connectivity among sites due to altered transport corridors, and influence the demography of local populations.

Tuning the electrocaloric effect by varying Sr concentration in ferroelectric Ba1 -xSrxTiO3

NASA Astrophysics Data System (ADS)

Lisenkov, S.; Ponomareva, I.

2018-05-01

The electrocaloric effect is investigated systematically in Ba1 -xSrxTiO3 ferroelectrics using a semiclassical direct computational approach. The data are reported for the technologically important range of Sr concentrations of 0.0-0.6, electric fields up to 1000 kV/cm, and temperatures ranging from 5 to 600 K. A detailed comparison of computational data with experimental data from the literature reveals semiquantitative agreement and suggests the origin of discrepancies. The electrocaloric change in temperature Δ T shows strong dependence on Sr concentration which offers a way to tune electrocaloric response. In particular, the maximum electrocaloric Δ T is found to decrease with the increase in Sr concentration, whereas the location of the maximum shifts towards lower temperatures following the Curie point of the ferroelectric. Surprisingly, the width of the peak in the dependence of Δ T on the initial temperature is independent of the Sr concentration but shows a strong dependence on the applied electric field. Computational data are used to propose a compositionally graded ferroelectric Ba0.70Sr0.30TiO3/Ba0.55Sr0.45TiO3/Ba0.50Sr0.50TiO3/Ba0.45Sr0.55TiO3 whose Δ T shows almost no temperature dependence in the technologically important range of temperatures and electric fields. Such a desirable feature could potentially lead to the enhancement of relative cooling power.

Leaching characteristics of toxic constituents from coal fly ash mixed soils under the influence of pH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komonweeraket, Kanokwan; Cetin, Bora, E-mail: bora.cetin@sdsmt.edu; Benson, Craig H., E-mail: chbenson@wisc.edu

Highlights: • The impact of pH on the leaching of elements and metals from fly ash mixed soils. • Generally Ca, Cd, Mg, and Sr follows a cationic leaching pattern. • The leaching of As and Se shows an oxyanionic leaching pattern. • The leaching behavior of elements does not change based on material type. • Different fly ash types show different abilities in immobilizing trace elements. - Abstract: Leaching behaviors of Arsenic (As), Barium (Ba), Calcium (Ca), Cadmium (Cd), Magnesium (Mg), Selenium (Se), and Strontium (Sr) from soil alone, coal fly ash alone, and soil-coal fly ash mixtures, weremore » studied at a pH range of 2–14 via pH-dependent leaching tests. Seven different types of soils and coal fly ashes were tested. Results of this study indicated that Ca, Cd, Mg, and Sr showed cationic leaching pattern while As and Se generally follows an oxyanionic leaching pattern. On the other hand, leaching of Ba presented amphoteric-like leaching pattern but less pH-dependent. In spite of different types and composition of soil and coal fly ash investigated, the study reveals the similarity in leaching behavior as a function of pH for a given element from soil, coal fly ash, and soil-coal fly ash mixtures. The similarity is most likely due to similar controlling mechanisms (e.g., solubility, sorption, and solid-solution formation) and similar controlling factors (e.g., leachate pH and redox conditions). This offers the opportunity to transfer knowledge of coal fly ash that has been extensively characterized and studied to soil stabilized with coal fly ash. It is speculated that unburned carbon in off-specification coal fly ashes may provide sorption sites for Cd resulting in a reduction in concentration of these elements in leachate from soil-coal fly ash mixture. Class C fly ash provides sufficient CaO to initiate the pozzolanic reaction yielding hydrated cement products that oxyanions, including As and Se, can be incorporated into.« less

CHEMICAL ANALYSIS OF A CARBON-ENHANCED VERY METAL-POOR STAR: CD-27 14351

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karinkuzhi, Drisya; Goswami, Aruna; Masseron, Thomas

2017-01-01

We present, for the first time, an abundance analysis of a very metal-poor carbon-enhanced star CD-27 14351 based on a high-resolution ( R  ∼ 48,000) FEROS spectrum. Our abundance analysis performed using local thermodynamic equilibrium model atmospheres shows that the object is a cool star with stellar atmospheric parameters, effective temperature T {sub eff} = 4335 K, surface gravity log g  = 0.5, microturbulence ξ  = 2.42 km s{sup −1}, and metallicity [Fe/H] = −2.6. The star exhibits high carbon and nitrogen abundances with [C/Fe] = 2.89 and [N/Fe] = 1.89. Overabundances of neutron-capture elements are evident in Ba, La, Ce, and Nd, with estimated [X/Fe] > 1, the largest enhancementmore » being seen in Ce with [Ce/Fe] = 2.63. While the first peak s -process elements Sr and Y are found to be enhanced with respect to Fe, ([Sr/Fe] = 1.73 and [Y/Fe] = 1.91), the third peak s -process element Pb could not be detected in our spectrum at the given resolution. Europium, primarily an r -process element also shows an enhancement with [Eu/Fe] = 1.65. With [Ba/Eu] = 0.12, the object CD-27 14351 satisfies the classification criterion for a CEMP-r/s star. The elemental abundance distributions observed in this star are discussed in light of the chemical abundances observed in other CEMP stars in the literature.« less

Correlation of Structure, Tunable Colors, and Lifetimes of (Sr, Ca, Ba)Al2O4:Eu2+, Dy3+ Phosphors

PubMed Central

Xie, Qidi; Li, Bowen; He, Xin; Zhang, Mei; Chen, Yan; Zeng, Qingguang

2017-01-01

(Sr, Ca, Ba)Al2O4:Eu2+, Dy3+ phosphors were prepared via a high temperature solid-state reaction method. The correlation of phase structure, optical properties and lifetimes of the phosphors are investigated in this work. For the (Sr, Ca)Al2O4:Eu2+, Dy3+ phosphors, the different phase formation from monoclinic SrAl2O4 phase to hexagonal SrAl2O4 phase to monoclinic CaAl2O4 phase was observed when the Ca content increased. The emission color of SrAl2O4:Eu2+, Dy3+ phosphors varied from green to blue. For the (Sr, Ba)Al2O4:Eu2+, Dy3+ phosphors, different phase formation from the monoclinic SrAl2O4 phase to the hexagonal BaAl2O4 phase was observed, along with a shift of emission wavelength from 520 nm to 500 nm. More interestingly, the decay time of SrAl2O4:Eu2+, Dy3+ changed due to the different phase formations. Lifetime can be dramatically shortened by the substitution of Sr2+ with Ba2+ cations, resulting in improving the performance of the alternating current light emitting diode (AC-LED). Finally, intense LEDs are successfully obtained by combining these phosphors with Ga(In)N near UV chips. PMID:29057839

Magnetic and magnetocaloric properties of Ba and Ti co-doped SrRuO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sarkar, Babusona; Dalal, Biswajit; Dev Ashok, Vishal

2014-12-28

Temperature evolution of magnetic properties in Ba and Ti doped SrRuO{sub 3} has been investigated to observe the effects of larger ionic radius Ba at Sr site and isovalent nonmagnetic impurity Ti at Ru site. Ionic radius mismatch and different electronic configuration in comparison with Ru modify Sr(Ba)-O and Ru(Ti)-O bond lengths and Ru-O-Ru bond angle. The apical and basal Ru-O-Ru bond angles vary significantly with Ti doping. Ferromagnetic Curie temperature decreases from 161 K to 149 K monotonically with Ba (10%) and Ti (10%) substitutions at Sr and Ru sites. The zero field cooled (ZFC) magnetization reveals a prominent peak whichmore » shifts towards lower temperature with application of magnetic field. The substitution of tetravalent Ti with localized 3d{sup 0} orbitals for Ru with more delocalized 4d{sup 4} orbitals leads to a broad peak in ZFC magnetization. A spontaneous ZFC magnetization becomes negative below 160 K for all the compositions. The occurrence of both normal and inverse magnetocaloric effects in Ba and Ti co-doped SrRuO{sub 3} makes the system more interesting.« less

Superconductivity in the Sn-Ba-Sr-Y-Cu-O system

NASA Technical Reports Server (NTRS)

Aleksandrov, K. S.; Khrustalev, B. P.; Krivomazov, S. N.; Petrov, M. I.; Vasilyev, A. D.; Zwegintsev, S. A.

1991-01-01

After the discovery of high-T(sub c) superconductivity in the La-Ba-Cu-O compound, several families of superconducting oxides were synthesized. Here, researchers report the results of the search for superconductivity in the compounds based on tin which has a lone electron pair like Bi, Tl, and Pb. The following compounds were synthesized: Sn1Ba1Sr1Cu3O(sub x), Sn1Ba1Ca1Cu3O(sub x), Sn1Ba1Mg1Cu3O(sub x), Sn1Sr1Ca1Cu3O(sub x), Sn1Sr1Mg1Cu3O(sub x), and Sn1Ca1Mg1Cu3O(sub x). The initial components were oxides and carbonates of the appropriate elements. A standard firing-grinding procedure was used. Final heating was carried out at 960 C during 12 hours. Then the samples were cooled inside the furnace. All the synthesis cycles were carried out in air atmosphere. Among the synthesized compounds only Sn1Ba1Sr1Cu3O(sub x) showed remarkable conductivity. Other compounds were practically dielectrics. Presence of a possible superconductivity in Sn1Ba1Sr1Cu3O(sub x) was defined by using the Meissner effect. At low temperature a deviation from paramagnetic behavior is observed. The hysteresis loops obtained at lower temperature undoubtly testify to the presence of a superconductive phase in the sample. However, the part of the superconductive phase in the Sn1Ba1Sr1Cu3O(sub x) ceramic turned out to be small, less than 2 percent, which agrees with the estimation from magnetic data. In order to increase the content of the superconductive phase, two-valent cations Ba and Sr were partially substituted by univalent (K) and three-valent ones (Y).

Preparation and properties of Ba xSr 1- xCo yFe 1- yO 3- δ cathode material for intermediate temperature solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Zhao, Hailei; Shen, Wei; Zhu, Zhiming; Li, Xue; Wang, Zhifeng

Ba xSr 1- xCo yFe 1- yO 3- δ (BSCF) materials with perovskite structure were synthesized via solid-state reaction. Their structural characteristics, electrical-conduction behavior and cathode performance were investigated. Compared to A-site elements, B-site elements show a wide solid-solution range in BSCF. The electrical-conduction behavior of BSCF obeys the small polaron-hopping mechanism. An increase of Ba or Co content in the BSCF samples results in a decrease of electrical conductivity, which is mainly attributable to the preferential existence of B 3+ rather than B 4+ in Ba- or Co-rich samples. At the same time, this leads to increases in the lattice parameter a and the number of oxygen vacancies. BSCF samples with high Ba content show a high structural stability (high oxygen-loss temperature). Ba 0.6Sr 0.4Co 0.8Fe 0.2O 3- δ and Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3- δ materials present good thermal-cycling stability of the electrical conductivity. Compared with Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3- δ, Ba 0.6Sr 0.4Co 0.8Fe 0.2O 3- δ exhibits a better cathode performance in a Ce 0.8Gd 0.2O 2- δ (GDC)-supported half cell. The cell performance can be improved by introducing a certain amount of GDC electrolyte into the BSCF cathode material.

Analytical dependence of effective atomic number on the elemental composition of matter and radiation energy in the range 10-1000 keV

NASA Astrophysics Data System (ADS)

Eritenko, A. N.; Tsvetiansky, A. L.; Polev, A. A.

2018-01-01

In the present paper, a universal analytical dependence of effective atomic number on the composition of matter and radiation energy is proposed. This enables one to consider the case of a strong difference in the elemental composition with respect to their atomic numbers over a wide energy range. The contribution of photoelectric absorption and incoherent and coherent scattering during the interaction between radiation and matter is considered. For energy values over 40 keV, the contribution of coherent scattering does not exceed approximately 10% that can be neglected at a further consideration. The effective atomic numbers calculated on the basis of the proposed relationships are compared to the results of calculations based on other methods considered by different authors on the basis of experimental and tabulated data on mass and atomic attenuation coefficients. The examination is carried out for both single-element (e.g., 6C, 14Si, 28Cu, 56Ba, and 82Pb) and multi-element materials. Calculations are performed for W1-xCux alloys (x = 0.35; x = 0.4), PbO, ther moluminescent dosimetry compounds (56Ba, 48Cd, 41Sr, 20Ca, 12Mg, and 11Na), and SO4 in a wide energy range. A case with radiation energy between the K- and L1-absorption edges is considered for 82Pb, 74W, 56Ba, 48Cd, and 38Sr. This enables to substantially simplify the calculation of the atomic number and will be useful in technical and scientific fields related to the interaction between X-ray/gamma radiation and matter.

Structure, luminescence and thermal quenching properties of Eu doped Sr{sub 2−x}Ba{sub x}Si{sub 5}N{sub 8} red phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Y.H.; Chen, L.; Zhou, X.F.

Eu{sup 2+} doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} phosphors were synthesized at 1610 ℃ for 4 h via the solid-state reaction method. The XRD results confirm that the complete solid solutions are formed. With the increase of x, the emission spectra show an obvious blue-shift from 610 nm to 585 nm under the excitation of 460 nm. The color tone can be tuned from yellow to red. The corresponding mechanism for the blue-shift of peak-wavelength is studied in detail. The results of decomposed Gaussian spectra and fluorescence lifetime show that the local coordination structure surrounding activator ions changes with increasingmore » x value. It is found that the probability of Eu occupying Sr1 and Sr2 site is dependent on Ba/Sr ratio. The variation of thermal quenching properties and the corresponding mechanism is discussed in detail. The results indicate that Eu{sup 2+} doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} is a promising orange red-emitting phosphor for near UV or blue light-pumped white light-emitting-diodes (wLEDs). - Graphical abstract: Eu{sup 2+} doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} solid solutions were prepared by the solid-state reaction method. The structure, luminescence and thermal quenching properties with varying Ba/Sr ratio were investigated in detail. - Highlights: • The stucture and luminescence properties of Eu doped Sr{sub 2-x}Ba{sub x}Si{sub 5}N{sub 8} phosphors were investigated. • The samples with the intermediate compositions(x=1.0,1.5) show better stability than the end members of both Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+} and Ba{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+}. • The possible mechanism for the improvement of thermal quenching properties was proposed.« less

Method of Synthesizing a Novel Absorbent Titanosilicate Material (UPRM-5)

NASA Technical Reports Server (NTRS)

Hernandez-Maldonado, Arturo (Inventor); Primera-Pedrozo, Jose N (Inventor)

2013-01-01

A titanium silicate variant named UPRM-5 was prepared using tetraethylammonium hydroxide as a structure-directing agent (SDA). Successful detemplation was achieved via ion exchange with NH4Cl. Effective functionalization was obtained after ion exchanging the detemplated material using SrCl2 and BaCl2. Adsorption of CO2 at 25 deg C in Sr(-) and Ba-UPRM-5 materials activated at different temperatures. For low partial pressures, the observed CO2 adsorption capacities increased as follows: NH4-UPRM-5 less than Sr-UPRM-5 less than Ba-UPRM-5. Both the Sr(-) and Ba-UPRM-5 materials exhibited outstanding selectivity for CO2 over CH4, N2 and O2.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism.

PubMed

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-01-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 - x SrxFe y Mn1 - y O3 - δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ and the Fe-K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 - δ perovskite oxide.

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

NASA Astrophysics Data System (ADS)

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-10-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1-xSrxFeyMn1-yO3-d(0 ≤ x≤ 1, 0.2 ≤ y≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst with that of an industrial potassium promoted iron (Fe-K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed higher initial activity than the industrial Fe-K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe-K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d and the Fe-K catalysts in aH2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst while the Fe-K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3-d catalyst had higher potential for activating the steam than the Fe-K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3-d was superior to that of Fe-K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3-d perovskite oxide.

Synthesis of barium and strontium carbonate crystals with unusual morphologies using an organic additive

NASA Astrophysics Data System (ADS)

Chen, Long; Jiang, Jizhong; Bao, Zuben; Pan, Jian; Xu, Weibing; Zhou, Lili; Wu, Zhigang; Chen, Xu

2013-12-01

In this paper, strontium carbonate (SrCO3) and barium carbonate (BaCO3) crystals were synthesized in the presence of an organic additive-hexamethylenetetramine (HMT) using two CO2 sources. Scanning electron microscopy and X-ray powder diffractometry were used to characterize the products. The results showed that the morphologies of orthorhombic strontianite SrCO3 transformed from branch-like to flower-like, and to capsicum-like at last, while the morphologies of BaCO3 change from fiber-like to branchlike, and to rod-like finally with an increase of the molar ratio HMT/Sr2+ and HMT/Ba2+ from 0.2 to 10 using ammonium carbonate as CO2 source. When using diethyl carbonate instead of ammonium carbonate as CO2 source, SrCO3 flowers aggregated by rods and BaCO3 shuttles were formed. The possible formation mechanisms of SrCO3 and BaCO3 crystals obtained in different conditions were also discussed.

Dielectric and Energy Storage Properties of Ba0.65Sr0.35TiO3 Ceramics Modified by BiNbO4

NASA Astrophysics Data System (ADS)

Zheng, Yi; Zhang, Jihua; Wei, Meng; Dong, Xiangxiang; Huang, Jiapeng; Wu, Kaituo; Chen, Hongwei

2018-02-01

(1 - x) (Ba0.65Sr0.35TiO3)-xBiNbO4 (x = 0.0-0.15) ceramic were prepared by solid-state reaction method. The phase composition, microstructure, dielectric properties, polarization-electric field, breakdown strength and energy storage behaviors for the BiNbO4-modified Ba0.65Sr0.35TiO3 ceramics were investigated. With the addition of BiNbO4, the remnant polarization and saturation polarization decreased and the nonlinearity was suppressed. When x = 0.07, the maximum recoverable energy storage achieved was 0.5 J/cm3, 1.5 times that of un-doped Ba0.65Sr0.35TiO3 ceramics, with an efficiency of 96.89% and a breakdown electric field reaching 15.3 kV/mm. Therefore, BiNbO4 doping could improve the energy storage properties of Ba0.65Sr0.35TiO3 for high-energy pulse capacitor application.

Chemical Interaction between High-Tc Superconducting Oxides and Alkaline Earth Fluorides

NASA Astrophysics Data System (ADS)

Hashimoto, Takuya; Asakawa, Toshiaki; Shiraishi, Tadashi; Yoshida, Tsutomu; Yoshimoto, Mamoru; Koinuma, Hideomi

1989-07-01

Reactions of high-Tc superconductors and MF2 (M: Ca, Sr, Ba) were investigated by means of ac susceptibility, X-ray diffraction, and TG-DTA measurements. The superconducting transition temperature (Tconset) of Ba2YCu3O7-δ powder mixed with MF2 powder decreased as a result of heat treatment at 600°C in air, whereas it did not decrease by the heat treatment under carefully dried conditions. In contrast, neither of the heat-treatment conditions decreased the Tconset of Bi2Sr2CaCu2Ox mixed with MF2 powder. Heating with MF2 at temperatures higher than 700°C reduced volume fractions of these superconductors even in dry atmosphere and the reactivity increased in the order of BaF2

BaFe2As2/Fe Bilayers with [001]-tilt Grain Boundary on MgO and SrTiO3 Bicrystal Substrates

NASA Astrophysics Data System (ADS)

Iida, K.; Haindl, S.; Kurth, F.; Hänisch, J.; Schulz, L.; Holzapfel, B.

Co-doped BaFe2As2 (Ba-122) can be realized on both MgO and SrTiO3 bicrystal substrates with [001]-tilt grain boundary by employing Fe buffer layers. However, an additional spinel (i.e. MgAl2O4) buffer between Fe and SrTiO3 is necessary since an epitaxial, smooth surface of Fe layer can not be grown on bare SrTiO3. Both types of bicrystal films show good crystalline quality.

Microwave assisted extraction for trace element analysis of plant materials by ICP-AES.

PubMed

Borkowska-Burnecka, J

2000-11-01

Application of microwave assisted extraction for the decomposition and dissolution of plant samples for trace metal determination by ICP-AES was examined. Dried onion, leaves of spinach beet and three reference materials CTA-OTL-1, CTA-VTL-2 and CL-1 were analyzed. Water, EDTA and hydrochloric acid (0.01, 0.10 and 1.0 M, respectively) were used as leaching solutions. The extraction efficiency was investigated by comparison of the results with those obtained after microwave wet digestion. HCl was found to be very suitable for quantitative extraction of B, Ba, Cd, Cu, Mn, Ni, Pb, Sr and Zn from the samples. For reference materials, the measured concentrations are well consistent with the certified values. The use of EDTA led to a complete extraction of B, Cd, Ni, Pb, Sr and Zn. Water was found to be a good leaching solution for boron. For extraction with HCl and EDTA, the RSD values for the concentrations measured were below 8% for most of the elements.

Structural, optoelectronic, and thermoelectric properties of AZn13 (A=Na, K, Ca, Sr, Ba) compounds

NASA Astrophysics Data System (ADS)

Basit, Abdul; Murtaza, G.; Mahmood, Asif; Yar, Abdullah; Muhammad, S.

2016-08-01

We report the structural, electronic, optical, and thermoelectric properties of the five cubic alkali-earth transition-metals AZn13 (A-Na, K, Ca, Sr, Ba) using density functional theory. Structural properties, electronic structures and optical behaviors are calculated explicitly via highly accurate contemporary full potential-linearized augmented plane wave (FP-LAPW) method. The investigated ground state data of these materials is quite close to the experimental information. The modified Becke-Johnson (mBJ) predicts the intermetallic nature of AZn13 (A-Na, K, Ca, Sr, Ba) materials. The complex dielectric function of these intermetallic compounds has been calculated and the observed noticeable peaks are examined through mBJ. With the help of complex dielectric function, the other important optical parameters like reflectivities, conductivities and refractive indices of AZn13 (A-Na, K, Ca, Sr, Ba) have been calculated as a function of energy. The optical response suggests that AZn13 (A-Na, K, Ca, Sr, Ba) compounds can be used for the optoelectronic devices. Further, the thermoelectric properties have been calculated through BoltzTraP program, the calculated values for different thermoelectric parameters recommend that these AZn13 (A-Na, K, Ca, Sr, Ba) materials are the suitable candidates for thermoelectric applications.

Eu(2+)-Activated Alkaline-Earth Halophosphates, M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) for NUV-LEDs: Site-Selective Crystal Field Effect.

PubMed

Kim, Donghyeon; Kim, Sung-Chul; Bae, Jong-Seong; Kim, Sungyun; Kim, Seung-Joo; Park, Jung-Chul

2016-09-06

Eu(2+)-activated M5(PO4)3X (M = Ca, Sr, Ba; X = F, Cl, Br) compounds providing different alkaline-earth metal and halide ions were successfully synthesized and characterized. The emission peak maxima of the M5(PO4)3Cl:Eu(2+) (M = Ca, Sr, Ba) compounds were blue-shifted from Ca to Ba (454 nm for Ca, 444 nm for Sr, and 434 nm for Ba), and those of the Sr5(PO4)3X:Eu(2+) (X = F, Cl, Br) compounds were red-shifted along the series of halides, F → Cl → Br (437 nm for F, 444 nm for Cl, and 448 nm for Br). The site selectivity and occupancy of the activator ions (Eu(2+)) in the M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) crystal lattices were estimated based on theoretical calculation of the 5d → 4f transition energies of Eu(2+) using LCAO. In combination with the photoluminescence measurements and theoretical calculation, it was elucidated that the Eu(2+) ions preferably enter the fully oxygen-coordinated sites in the M5(PO4)3X:Eu(2+) (M = Ca, Sr, Ba; X = F, Cl, Br) compounds. This trend can be well explained by "Pauling's rules". These compounds may provide a platform for modeling a new phosphor and application in the solid-state lighting field.

Composition and phase analysis of nanocrystalline Ba{sub x}Sr{sub 1-x}Fe{sub 12}O{sub 19} (x = 1.0; 0.6; and 0.4) by using general structure analysis system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gunanto, Y. E., E-mail: yohanes.gunanto@uph.edu; Jobiliong, E., E-mail: eric.jobiliong@uph.edu; Adi, Wisnu Ari, E-mail: dwisnuaa@batan.go.id

2016-03-11

Single phase of nanocrystalline Ba{sub x}Sr{sub 1-x}Fe{sub 12}O{sub 19} (x = 1.0; 0.6; and 0.4) was successfully synthesized by mechanical milling method and thermal process. Stoichiometric quantities of analytical-grade SrCO{sub 3}, BaCO{sub 3}, and Fe{sub 2}O{sub 3}, were mixed and milled using a high-energy milling. The mixture of all precursors was sintered at a temperature of 1000 °C for 10 hours. The refinement of x-ray diffraction trace for all samples confirmed a single phase material with a hexagonal structure. The increase of the amount of strontium content in the barium atoms in the Ba{sub x}Sr{sub 1-x}Fe{sub 12}O{sub 19} system canmore » decrease the lattice parameter which have been successfully substituted into the barium atoms. The calculation result of cationic distribution showed that the Ba{sub x}Sr{sub 1-x}Fe{sub 12}O{sub 19} (x = 0.6) and (x = 0.4) samples have nominal composition of Ba{sub 0,61}Sr{sub 0,39}Fe{sub 12}O{sub 19} and Ba{sub 0,37}Sr{sub 0,63}Fe{sub 12}O{sub 19}, respectively. Results of the mean of crystallite size evaluation for respective powder materials showed that the Ba{sub x}Sr{sub 1-x}Fe{sub 12}O{sub 19} (x = 1.0; 0.6; and 0.4) samples have the crystallite size of 22 nm, 25 nm and 34 nm, respectively. We concluded that the cationic distribution of barium atoms was successfully substituted by strontium atoms approaching the nominal stoichiometric composition.« less

A new BaB{sub 2}Si{sub 2}O{sub 8}:Eu{sup 2+}/Eu{sup 3+}, Tb{sup 3+} phosphor - Synthesis and photoluminescence properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saradhi, M.P.; Department of Chemistry, Indian Institute of Technology Hyderabad, Yeddumailaram, Hyderabad - 502205; Laboratoire de Cristallographie et Sciences des Materiaux, ENSICAEN, Universite de Caen, CNRS, 6 Bd Marechal Juin, F-14050 Caen

2010-10-15

In the present work, we have synthesized maleevite mineral phase BaB{sub 2}Si{sub 2}O{sub 8} for the first time, which is isostructural with the pekovite mineral SrB{sub 2}Si{sub 2}O{sub 8}. In these europium doped host lattices, we observed the partial reduction of Eu{sup 3+} to Eu{sup 2+} at high temperature during the synthesis in air. Tb{sup 3+} co-doping in MB{sub 2}Si{sub 2}O{sub 8}:0.01(Eu{sup 3+}/Eu{sup 2+}) [M=Sr, Ba] improves the emission properties towards white light. The emission color varies from bluish white to greenish white under UV lamp excitation when the host cation changes from Sr to Ba. - Graphical abstract: Themore » figure shows structure refinement of both MB{sub 2}Si{sub 2}O{sub 8} [M=Sr, Ba]. The structure refinement of newly synthesized phase BaB{sub 2}Si{sub 2}O{sub 8} was carried out by taking SrB{sub 2}Si{sub 2}O{sub 8} as starting structure model. Inset in the figure shows the structure projection of BaB{sub 2}Si{sub 2}O{sub 8}. The Sr{sup 2+}/Ba{sup 2+} are embedded in polyanionic network formed by corner sharing BO{sub 4}{sup 5-} and SiO{sub 4}{sup 4-} tetrahedral that intern form interconnected layers of 4 and 8 membered rings perpendicular to b-axis.« less

A mid-twentieth century reduction in tropical upwelling inferred from coralline trace element proxies

NASA Astrophysics Data System (ADS)

Reuer, Matthew K.; Boyle, Edward A.; Cole, Julia E.

2003-05-01

The Cariaco Basin is an important archive of past climate variability given its response to inter- and extratropical climate forcing and the accumulation of annually laminated sediments within an anoxic water column. This study presents high-resolution surface coral trace element records ( Montastrea annularis and Siderastrea siderea) from Isla Tortuga, Venezuela, located within the upwelling center of this region. A two-fold reduction in Cd/Ca ratios (3.5-1.7 nmol/mol) is observed from 1946 to 1952 with no concurrent shift in Ba/Ca ratios. This reduction agrees with the hydrographic distribution of dissolved cadmium and barium and their expected response to upwelling. Significant anthropogenic variability is also observed from Pb/Ca analysis, observing three lead maxima since 1920. Kinetic control of trace element ratios is inferred from an interspecies comparison of Cd/Ca and Ba/Ca ratios (consistent with the Sr/Ca kinetic artifact), but these artifacts are smaller than the environmental signal and do not explain the Cd/Ca transition. The trace element records agree with historical climate data and differ from sedimentary faunal abundance records, suggesting a linear response to North Atlantic extratropical forcing cannot account for the observed historical variability in this region.

Vertical distribution of major, minor and trace elements in sediments from mud volcanoes of the Gulf of Cadiz: evidence of Cd, As and Ba fronts in upper layers

NASA Astrophysics Data System (ADS)

Carvalho, Lina; Monteiro, Rui; Figueira, Paula; Mieiro, Cláudia; Almeida, Joana; Pereira, Eduarda; Magalhães, Vítor; Pinheiro, Luís; Vale, Carlos

2018-01-01

Mud volcanoes are feature of the coastal margins where anaerobic oxidation of methane triggers geochemical signals. Elemental composition, percentage of fine particles and loss on ignition were determined in sediment layers of eleven gravity cores retrieved from four mud volcanoes (Sagres, Bonjardim, Soloviev and Porto) and three undefined structures located on the deep Portuguese margin of the Gulf of Cadiz. Calcium was positively correlated to Sr and inversely to Al as well as to most of the trace elements. Vertical profiles of Ba, Cd and As concentrations, and their ratios to Al, in Porto and Soloviev showed pronounced enhancements in the top 50-cm depth. Sub-surface enhancements were less pronounced in other mud volcanoes and were absent in sediments from the structures. These profiles were interpreted as diagenetic enrichments related to the anaerobic oxidation of methane originated from upward methane-rich fluxes. The observed barium fronts were most likely caused by the presence of barite which precipitated at the sulphate-methane transition zone. Cd and As enrichments have probably resulted from successive dissolution/precipitation of sulphides in response to vertical shifts of redox boundaries.

Geochemical signatures in fin rays provide a nonlethal method to distinguish the natal rearing streams of endangered juvenile Chinook Salmon Oncorhynchus tshawytscha in the Wenatchee River, Washington

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linley, Timothy J.; Krogstad, Eirik J.; Nims, Megan K.

Rebuilding fish populations that have undergone a major decline is a challenging task that can be made more complicated when estimates of abundance obtained from physical tags are biased or imprecise. Abundance estimates based on natural tags where each fish in the population is marked can help address these problems, but generally requires that the samples be obtained in a nonlethal manner. We evaluated the potential of using geochemical signatures in fin rays as a nonlethal method to determine the natal tributaries of endangered juvenile spring Chinook Salmon in the Wenatchee River, Washington. Archived samples of anal fin clips collectedmore » from yearling smolt in 2009, 2010 and 2011 were analyzed for Ba/Ca, Mn/Ba, Mg/Ca, Sr/Ca, Zn/Ca and 87Sr/86Sr by inductively coupled plasma mass spectrometry. Water samples collected from these same streams in 2012 were also quantified for geochemical composition. Fin ray and water Ba/Ca, Sr/Ca, and 87Sr/86Sr were highly correlated despite the samples having been collected in different years. Fin ray Ba/Ca, Mg/Ca, Sr/Ca, Zn/Ca and 87Sr/86Sr ratios differed significantly among the natal streams, but also among years within streams. A linear discriminant model that included Ba/Ca, Mg/Ca, Sr/Ca, and 87Sr/86Sr correctly classified 95% of the salmon to their natal stream. Our results suggest that fin ray geochemistry may provide an effective, nonlethal method to identify mixtures of Wenatchee River spring Chinook Salmon for recovery efforts when these involve the capture of juvenile fish to estimate population abundance.« less

Supercritical fluid route for synthesizing crystalline Barium Strontium Titanate nanoparticles.

PubMed

Reverón, H; Elissalde, C; Aymonier, C; Bidault, O; Maglione, M; Cansell, F

2005-10-01

Pure and well-crystallized Barium Strontium Titanate (BST) nanoparticles with controlled Ba/Sr ratio have been successfully synthesized under supercritical conditions using a continuous-flow reactor in the temperature range of 150-380 degrees C at 26 MPa. To synthesize the Ba0.6Sr0.4TiO3 composition, alkoxides, ethanol and water were used. The resulting nanopowder consists of fine particles with an average particle size of 23 nm. The results show that the Ba/Sr ratio of this powder can be accurately controlled from the composition of precursor. The characterization of the as-synthesized Ba0.6Sr0.4TiO3 solid-solution and the dielectric properties of the sintered ceramics are here reported.

Tuning the growth and strain relaxation of ferroelectric BaTiO3 thin films on SrRuO3 electrode: influence on electrical properties

NASA Astrophysics Data System (ADS)

Aidoud, Amina; Maroutian, Thomas; Matzen, Sylvia; Agnus, Guillaume; Amrani, Bouhalouane; Driss-Khodja, Kouider; Aubert, Pascal; Lecoeur, Philippe

2018-01-01

This study is focused on the link between the structural and electric properties of BaTiO3 thin films grown on SrRuO3-buffered (001) SrTiO3 substrates, SrRuO3 acting as bottom electrode. The growth regime and film structure are here tuned through the growth pressure for pulsed laser deposition in the 1-200 mTorr range. The dielectric, ferroelectric and leakage current properties are systematically measured for the different strain states of the BaTiO3 thin films on SrRuO3. The results are discussed with the help of ab initio calculations on the effects of Ba- and Ti-vacancies on BaTiO3 lattice parameters. A sharp increase of the dielectric constant is evidenced in the high pressure region, where the tetragonality of the BaTiO3 is decreasing rapidly with growth pressure. We interpret this divergence of the dielectric function as the signature of the vicinity of the phase boundary between the out-of-plane and in-plane orientations of the tetragonal BTO films.

The effect of strontium and barium doping on perovskite-structured energy materials for photovoltaic applications

NASA Astrophysics Data System (ADS)

Wu, Ming-Chung; Chen, Wei-Cheng; Chan, Shun-Hsiang; Su, Wei-Fang

2018-01-01

Perovskite solar cell is a novel photovoltaic technology with the superior progress in efficiency and the simple solution processes. Develop lead-free or lead-reduced perovskite materials is a significant concern for high-performance perovskite solar cell. Among the alkaline earth metals, the Sr2+ and Ba2+ are suitable for Pb2+ replacement in perovskite film due to fitting Goldschmidt's tolerance factor. In this study, we adopted Ba-doped and Sr-doped perovskite structured materials with different doping levels, including 1.0, 5.0, and 10.0 mol%, to prepare perovskite solar cells. Both Ba-doped and Sr-doped perovskite structured materials have a related tendency in absorption behavior and surface morphology. At 10.0 mol% doping level, the power conversion efficiency (PCE) of Sr-doped perovskite solar cells is only ∼0.5%, but the PCE of Ba-doped perovskite solar cells can be achieved to ∼9.7%. Ba-doped perovskite solar cells showed the acceptable photovoltaic characteristics than Sr-doped perovskite solar cells. Ba dopant can partially replace the amount of lead in the perovskite solar cells, and it could be a potential candidate in the field of lead-free or lead-reduced perovskite energy materials.

Dissolved metals and associated constituents in abandoned coal-mine discharges, Pennsylvania, USA. Part 2: Geochemical controls on constituent concentrations

USGS Publications Warehouse

Cravotta, C.A.

2008-01-01

Water-quality data for discharges from 140 abandoned mines in the Anthracite and Bituminous Coalfields of Pennsylvania reveal complex relations among the pH and dissolved solute concentrations that can be explained with geochemical equilibrium models. Observed values of pH ranged from 2.7 to 7.3 in the coal-mine discharges (CMD). Generally, flow rates were smaller and solute concentrations were greater for low-pH CMD samples; pH typically increased with flow rate. Although the frequency distribution of pH was similar for the anthracite and bituminous discharges, the bituminous discharges had smaller median flow rates; greater concentrations of SO4, Fe, Al, As, Cd, Cu, Ni and Sr; comparable concentrations of Mn, Cd, Zn and Se; and smaller concentrations of Ba and Pb than anthracite discharges with the same pH values. The observed relations between the pH and constituent concentrations can be attributed to (1) dilution of acidic water by near-neutral or alkaline ground water; (2) solubility control of Al, Fe, Mn, Ba and Sr by hydroxide, sulfate, and/or carbonate minerals; and (3) aqueous SO4-complexation and surface-complexation (adsorption) reactions. The formation of AlSO4+ and AlHSO42 + complexes adds to the total dissolved Al concentration at equilibrium with Al(OH)3 and/or Al hydroxysulfate phases and can account for 10-20 times greater concentrations of dissolved Al in SO4-laden bituminous discharges compared to anthracite discharges at pH of 5. Sulfate complexation can also account for 10-30 times greater concentrations of dissolved FeIII concentrations at equilibrium with Fe(OH)3 and/or schwertmannite (Fe8O8(OH)4.5(SO4)1.75) at pH of 3-5. In contrast, lower Ba concentrations in bituminous discharges indicate that elevated SO4 concentrations in these CMD sources could limit Ba concentrations by the precipitation of barite (BaSO4). Coprecipitation of Sr with barite could limit concentrations of this element. However, concentrations of dissolved Pb, Cu, Cd, Zn, and most other trace cations in CMD samples were orders of magnitude less than equilibrium with sulfate, carbonate, and/or hydroxide minerals. Surface complexation (adsorption) by hydrous ferric oxides (HFO) could account for the decreased concentrations of these divalent cations with increased pH. In contrast, increased concentrations of As and, to a lesser extent, Se with increased pH could result from the adsorption of these oxyanions by HFO at low pH and desorption at near-neutral pH. Hence, the solute concentrations in CMD and the purity of associated "ochres" formed in CMD settings are expected to vary with pH and aqueous SO4 concentration, with potential for elevated SO4, As and Se in ochres formed at low pH and elevated Cu, Cd, Pb and Zn in ochres formed at near-neutral pH. Elevated SO4 content of ochres could enhance the adsorption of cations at low pH, but decrease the adsorption of anions such as As. Such information on environmental processes that control element concentrations in aqueous samples and associated precipitates could be useful in the design of systems to reduce dissolved contaminant concentrations and/or to recover potentially valuable constituents in mine effluents.

Crystal growth and physical properties of SrCu2As2, SrCu2Sb2, and BaCu2Sb2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anand, V.K.; Perera, P. Kanchana; Pandey, Abhishek

2012-06-25

We report the growth of single crystals of SrCu2As2, SrCu2Sb2, SrCu2(As0.84Sb0.16)2, and BaCu2Sb2 using the self-flux technique and their structural, magnetic, thermal, and transport properties that were investigated by powder x-ray diffraction (XRD), magnetic susceptibility χ, specific heat Cp, and electrical resistivity ρ measurements versus temperature T from 1.8 to 350 K. Rietveld refinements of XRD patterns for crushed crystals confirm that SrCu2As2 crystallizes in the ThCr2Si2-type body-centered tetragonal structure (space group I4/mmm) and SrCu2Sb2 crystallizes in the CaBe2Ge2-type primitive tetragonal structure (space group P4/nmm). However, as reported previously, BaCu2Sb2 is found to have a large unit cell consisting ofmore » three blocks. Here a ThCr2Si2-type block is sandwiched between two CaBe2Ge2-type blocks along the c axis with an overall symmetry of I4/mmm, as reported, but likely with a monoclinic distortion. The χ data of all these compounds are diamagnetic and reveal nearly T-independent anisotropic behavior. The χ of SrCu2As2 is found to be larger in the ab plane than along the c axis, as also previously reported for pure and doped BaFe2As2, whereas the χ values of SrCu2Sb2 and BaCu2Sb2 are larger along the c axis. This difference in anisotropy appears to arise from the differences between the crystal structures. The finite values of the Sommerfeld linear specific heat coefficients γ and the T dependences of ρ reveal metallic character of all four compounds. The electronic and magnetic properties indicate that these compounds are sp metals with Cu in the nonmagnetic 3d10 electronic configuration corresponding to the oxidation state Cu+1, as previously predicted theoretically for SrCu2As2 by Singh [ Phys. Rev. B 79 153102 (2009)]. We present a brief review of theoretical and experimental work on the doping character of transition metals for Fe in BaFe2As2. The As–As covalent interlayer bond distances in the collapsed-tetragonal (Ca,Sr,Ba)Cu2As2 compounds are much shorter than the nonbonding As–As distances in BaFe2As2. Thus, the electronic character of the Cu and the strength of the As–As interlayer bonding are both expected to drastically change between weakly Cu-substituted BaFe2As2 and pure BaCu2As2, perhaps via a first-order lattice instability such as a miscibility gap in the Ba(Fe1−xCux)2As2 system.« less

Leaching characteristics of toxic constituents from coal fly ash mixed soils under the influence of pH.

PubMed

Komonweeraket, Kanokwan; Cetin, Bora; Benson, Craig H; Aydilek, Ahmet H; Edil, Tuncer B

2015-04-01

Leaching behaviors of Arsenic (As), Barium (Ba), Calcium (Ca), Cadmium (Cd), Magnesium (Mg), Selenium (Se), and Strontium (Sr) from soil alone, coal fly ash alone, and soil-coal fly ash mixtures, were studied at a pH range of 2-14 via pH-dependent leaching tests. Seven different types of soils and coal fly ashes were tested. Results of this study indicated that Ca, Cd, Mg, and Sr showed cationic leaching pattern while As and Se generally follows an oxyanionic leaching pattern. On the other hand, leaching of Ba presented amphoteric-like leaching pattern but less pH-dependent. In spite of different types and composition of soil and coal fly ash investigated, the study reveals the similarity in leaching behavior as a function of pH for a given element from soil, coal fly ash, and soil-coal fly ash mixtures. The similarity is most likely due to similar controlling mechanisms (e.g., solubility, sorption, and solid-solution formation) and similar controlling factors (e.g., leachate pH and redox conditions). This offers the opportunity to transfer knowledge of coal fly ash that has been extensively characterized and studied to soil stabilized with coal fly ash. It is speculated that unburned carbon in off-specification coal fly ashes may provide sorption sites for Cd resulting in a reduction in concentration of these elements in leachate from soil-coal fly ash mixture. Class C fly ash provides sufficient CaO to initiate the pozzolanic reaction yielding hydrated cement products that oxyanions, including As and Se, can be incorporated into. Copyright © 2014 Elsevier Ltd. All rights reserved.

Geochemical properties of topsoil around the coal mine and thermoelectric power plant.

PubMed

Stafilov, Trajče; Šajn, Robert; Arapčeska, Mila; Kungulovski, Ivan; Alijagić, Jasminka

2018-03-19

The results of the systematic study of the spatial distribution of trace metals in surface soil over the Bitola region, Republic of Macedonia, known for its coal mine and thermo-electrical power plant activities are reported. The investigated region (3200 km 2 ) is covered by a sparse sampling grid of 5 × 5 km, but in the urban zone and around the thermoelectric power plant the sampling grid is denser (1 × 1 km). In total, 229 soil samples from 149 locations were collected including top-soil (0-5 cm) and bottom-soil samples (20-30 cm and 0-30 cm). Inductively coupled plasma - atomic emission spectrometry (ICP-AES) was applied for the determinations of 21 elements (Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Na, Ni, P, Pb, Sr, V and Zn). Based on the results of factor analyses, three geogenic associations of elements have been defined: F1 (Fe, Ni, V, Co, Cr, Mn and Li), F2 (Zn, B, Cu, Cd, Na and K) and F3 (Ca, Sr, Mg, Ba and Al). Even typical trace metals such as As, Cd, Cu, Ni, P, Pb and Zn are not isolated into anthropogenic geochemical associations by multivariate statistical methods still show some trends of local anthropogenic enrichment. The distribution maps for each analyzed element is showing the higher content of these elements in soil samples collected around the thermoelectric power plants than their average content for the soil samples collected from the whole Bitola Region. It was found that this enrichment is a result of the pollution by fly ash from coal burning which deposited near the plant having a high content of these elements.

Chemical composition of modern and fossil hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation - Part 2: Alkaline earth elements as tracers of watershed hydrochemistry and provenance

NASA Astrophysics Data System (ADS)

Brügmann, G.; Krause, J.; Brachert, T. C.; Stoll, B.; Weis, U.; Kullmer, O.; Ssemmanda, I.; Mertz, D. F.

2012-11-01

This study demonstrates that alkaline earth elements in enamel of hippopotamids, in particular Ba and Sr, are tracers for water provenance and hydrochemistry in terrestrial settings. The studied specimens are permanent premolar and molar teeth found in modern and fossil lacustrine sediments of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by two orders of magnitude for Ba (120-9336 μg g-1) as well as for Sr (9-2150 μg g-1). The variations are partially induced during post-mortem alteration and during amelogenesis, but the major contribution originates ultimately from the variable water chemistry in the habitats of the hippopotamids which is controlled by the lithologies and weathering processes in the watershed areas. Amelogenesis causes a distinct distribution of MgO, Ba and Sr in modern and fossil enamel, in that element concentrations increase along profiles from the outer rim towards the enamel-dentin junction by a factor of 1.3-1.9. These elements are well correlated in single specimens, thus suggesting that their distribution is determined by a common, single process, which can be described by closed system Rayleigh crystallization of bioapatite in vivo. Enamel from most hippopotamid specimens has Sr/Ca and Ba/Ca which are typical for herbivores. However, Ba/Sr ranges from 0.1 to 3 and varies on spatial and temporal scales. Thus, Sr concentrations and Ba/Sr in enamel differentiate between habitats having basaltic mantle rocks or Archean crustal rocks as the ultimate sources of Sr and Ba. This provenance signal is modulated by climate change. In Miocene to Pleistocene enamel from the Lake Albert region, Ba/Sr decreases systematically with time from 2 to 0.5. This trend can be correlated with changes in climate from humid to arid, in vegetation from C3 to C4 biomass as well as with increasing evaporation of the lake water. The most plausible explanation is that Ba mobility decreased with increasing aridification due to preferential deposition with clay and Fe-oxide-hydroxide or barite on the watershed of Lake Albert.

Selectivity in biomineralization of barium and strontium.

PubMed

Krejci, Minna R; Wasserman, Brian; Finney, Lydia; McNulty, Ian; Legnini, Daniel; Vogt, Stefan; Joester, Derk

2011-11-01

The desmid green alga Closterium moniliferum belongs to a small number of organisms that form barite (BaSO(4)) or celestite (SrSO(4)) biominerals. The ability to sequester Sr in the presence of an excess of Ca is of considerable interest for the remediation of (90)Sr from the environment and nuclear waste. While most cells dynamically regulate the concentration of the second messenger Ca(2+) in the cytosol and various organelles, transport proteins rarely discriminate strongly between Ca, Sr, and Ba. Herein, we investigate how these ions are trafficked in C. moniliferum and how precipitation of (Ba,Sr)SO(4) crystals occurs in the terminal vacuoles. Towards this goal, we simultaneously visualize intracellular dynamics of multiple elements using X-ray fluorescence microscopy (XFM) of cryo-fixed/freeze-dried samples. We correlate the resulting elemental maps with ultrastructural information gleaned from freeze-fracture cryo-SEM of frozen-hydrated cells and use micro X-ray absorption near edge structure (micro-XANES) to determine sulfur speciation. We find that the kinetics of Sr uptake and efflux depend on external Ca concentrations, and Sr, Ba, and Ca show similar intracellular localization. A highly ion-selective cross-membrane transport step is not evident. Based on elevated levels of sulfate detected in the terminal vacuoles, we propose a "sulfate trap" model, where the presence of dissolved barium leads to preferential precipitation of (Ba,Sr)SO(4) due to its low solubility relative to SrSO(4) and CaSO(4). Engineering the sulfate concentration in the vacuole may thus be the most direct way to increase the Sr sequestered per cell, an important consideration in using desmids for phytoremediation of (90)Sr. Copyright © 2011 Elsevier Inc. All rights reserved.

Structure refinement of Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-d} as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFC)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zakaria, Nurhamidah, E-mail: nurhamidahzakaria@yahoo.com; Idris, Mohd Sobri, E-mail: sobri@unimap.edu.my; Osman, Rozana A. M., E-mail: rozana@unimap.edu.my

2016-07-19

Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-δ} was successfully prepared using modified solid-state synthesis routes. The lowest temperature to obtained single phase of Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-δ} is about 900°C for 15 hours. Longer period of time are required compared to only 5 hours at 950°C as established in literatures. The X-ray Diffraction (XRD) data confirmed that Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-δ} is formed a cubic perovskite with the space group of Pm-3m. The lattice parameters of Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-δ} are a = 3.990 (1) Å and unit cell volume is V = 63.5 (1)more » Å{sup 3}. The Rietveld refinement of XRD data revealed that the crystal structure of Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-δ} slightly changes as a function of temperature.« less

Lanthanoid-free perovskite oxide catalyst for dehydrogenation of ethylbenzene working with redox mechanism

PubMed Central

Watanabe, Ryo; Ikushima, Maiko; Mukawa, Kei; Sumomozawa, Fumitaka; Ogo, Shuhei; Sekine, Yasushi

2013-01-01

For the development of highly active and robust catalysts for dehydrogenation of ethylbenzene (EBDH) to produce styrene; an important monomer for polystyrene production, perovskite-type oxides were applied to the reaction. Controlling the mobility of lattice oxygen by changing the structure of Ba1 − xSrxFeyMn1 − yO3 − δ (0 ≤ x ≤ 1, 0.2 ≤ y ≤ 0.8), perovskite catalyst showed higher activity and stability on EBDH. The optimized Ba/Sr and Fe/Mn molar ratios were 0.4/0.6 and 0.6/0.4, respectively. Comparison of the dehydrogenation activity of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst with that of an industrial potassium promoted iron (Fe–K) catalyst revealed that the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed higher initial activity than the industrial Fe–K oxide catalyst. Additionally, the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst showed high activity and stability under severe conditions, even at temperatures as low as 783 K, or at the low steam/EB ratio of 2, while, the Fe–K catalyst showed low activity in such conditions. Comparing reduction profiles of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ and the Fe–K catalysts in a H2O/H2 atmosphere, reduction was suppressed by the presence of H2O over the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst while the Fe–K catalyst was reduced. In other words, Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ catalyst had higher potential for activating the steam than the Fe–K catalyst. The lattice oxygen in perovskite-structure was consumed by H2, subsequently the consumed lattice oxygen was regenerated by H2O. So the catalytic performance of Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ was superior to that of Fe–K catalyst thanks to the high redox property of the Ba0.4Sr0.6Fe0.6Mn0.4O3 − δ perovskite oxide. PMID:24790949

Nonstoichiometry in inorganic fluorides: I. Nonstoichiometry in MF m - RF n ( m < n ≤ 4) systems

NASA Astrophysics Data System (ADS)

Sobolev, B. P.

2012-05-01

The manifestation of gross nonstoichiometry in MF m - RF n systems ( m < n ≤ 4) has been studied. Fluorides of 34 elements, in the systems of which phases of practical interest are formed, are chosen. To search for new phases of complex composition, a program for studying the phase diagrams of the condensed state (˜200 systems) has been carried out at the Institute of Crystallography, Russian Academy of Sciences. The main products of high-temperature interactions of the fluorides of elements with different valences ( m ≠ n) are grossly nonstoichiometric phases of two structural types: fluorite (CaF2) and tysonite (LaF3). Systems of fluorides of 27 elements ( M 1+ = Na, K; M 2+ = Ca, Sr, Ba, Cd, Pb; R 3+ = Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; R 4+ = Zr, Hf, Th, U) are selected; nonstoichiometric M 1 - x R x F m(1 - x) + nx phases, which are of greatest practical interest, are formed in these systems. The gross nonstoichiometry in inorganic fluorides is most pronounced in 80 MF2 - RF3 systems ( M = Ca, Sr, Ba, Cd, Pb; R are rare earth elements). The problems related to the growth of single crystals of nonstoichiometric phases and basic fields of their application as new fluoride multicomponent materials, the properties of which are controlled by the defect structure, are considered.

A first principles study on newly proposed (Ca/Sr/Ba)Fe2Bi2 compounds with their parent compounds

NASA Astrophysics Data System (ADS)

Sundareswari, M.; Jayalakshmi, D. S.; Viswanathan, E.

2016-02-01

The structural, electronic, bonding and magnetic properties of newly proposed iron-based compounds viz., CaFe2Bi2, SrFe2Bi2, BaFe2Bi2 with their Fermi surface topology are reported here for the first time by means of first principles calculation. All these properties of newly proposed compounds are compared and analysed along with their respective parent compounds namely (Ca,Sr,Ba)Fe2As2.

Aluminum/alkaline earth metal composites and method for producing

DOEpatents

Russell, Alan M; Anderson, Iver E; Kim, Hyong J; Freichs, Andrew E

2014-02-11

A composite is provided having an electrically conducting Al matrix and elongated filaments comprising Ca and/or Sr and/or Ba disposed in the matrix and extending along a longitudinal axis of the composite. The filaments initially comprise Ca and/or Sr and/or Ba metal or allow and then may be reacted with the Al matrix to form a strengthening intermetallic compound comprising Al and Ca and/or Sr and/or Ba. The composite is useful as a long-distance, high voltage power transmission conductor.

Investigations of Ba{sub x}Sr{sub 1−x}TiO{sub 3} ceramics and powders prepared by direct current arc discharge technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Shuangbin; Wang, Xiaohan; University of Chinese Academy of Sciences, Beijing 100049

2014-09-01

Ba{sub x}Sr{sub 1−x}TiO{sub 3} ceramics with x ranging from 0 to 1 were prepared by direct current arc discharge technique and studied by means of x-ray diffraction (XRD) and Raman spectroscopy. The cubic-tetragonal ferroelectric phase transition in Ba{sub x}Sr{sub 1−x}TiO{sub 3} ceramics was found to occur at x ≈ 0.75. XRD investigation of as-grown BaTiO{sub 3} ceramics revealed co-existence of tetragonal and hexagonal modifications with a small amount of impurity phase BaTi{sub 4}O{sub 9}. No evidences of hexagonal phase were observed in Raman spectra of as-grown BaTiO{sub 3} ceramics, while Raman peaks related to hexagonal phase were clearly observed in the spectrummore » of fine-grain powders prepared from the same ceramics. A core-shell model for BaTiO{sub 3} ceramics prepared by direct current arc discharge technique is proposed. Absence of the hexagonal phase in any Ba{sub x}Sr{sub 1−x}TiO{sub 3} solid solution with x < 1 is discussed in the frame of specific atomic arrangement.« less

Antiferromagnetism in semiconducting SrMn2Sb2 and BaMn2Sb2 single crystals

NASA Astrophysics Data System (ADS)

Sangeetha, N. S.; Smetana, V.; Mudring, A.-V.; Johnston, D. C.

2018-01-01

Crystals of SrMn2Sb2 and BaMn2Sb2 were grown using Sn flux and characterized by powder and single-crystal x-ray diffraction, respectively, and by single-crystal electrical resistivity ρ , heat capacity Cp, and magnetic susceptibility χ measurements versus temperature T , and magnetization versus field M (H ) isotherm measurements. SrMn2Sb2 adopts the trigonal CaAl2Si2 -type structure, whereas BaMn2Sb2 crystallizes in the tetragonal ThCr2Si2 -type structure. The ρ (T ) data indicate semiconducting behaviors for both compounds with activation energies of ≳0.35 eV for SrMn2Sb2 and 0.16 eV for BaMn2Sb2 . The χ (T ) and Cp(T ) data reveal antiferromagnetic (AFM) ordering at TN = 110 K for SrMn2Sb2 and 450 K for BaMn2Sb2 . The anisotropic χ (T ≤TN) data also show that the ordered moments in SrMn2Sb2 are aligned in the hexagonal a b plane, whereas the ordered moments in BaMn2Sb2 are aligned collinearly along the tetragonal c axis. The a b -plane M (H ) data for SrMn2Sb2 exhibit a continuous metamagnetic transition at low fields 0

Soil pollution in Central district of Saint-Petersburg (Russia)

NASA Astrophysics Data System (ADS)

Terekhina, Natalia; Ufimtseva, Margarita

2015-04-01

Analysis of soil samples of upper horizon for the content of chemical elements (Fe, Mn, Cu, Zn, Pb, Ni, Cr, Co, Cd, Ba, Sr) was carried out by atomic emission with inductively coupled plasma. A relative indicator of soil contamination degree is a concentration coefficient, representing the ratio of metal content in tested soil samples to the local background value of the corresponding element. Total pollution index is calculated by the concentration coefficients, which are greater than 1, taking into account the hazard class of metals (1 class - Zn, Pb ,Cd; 2 - class Cr, Ni, Cu ,Со; 3 class - Fe, Mn, Sr, Ba). Analysis of trace element of urban soils demonstrated mosaic patterns of pollution for Central district. The method of correlation sets constructing and factor analysis revealed three groups of chemical elements having a strong and significant association with each other: Pb-Cu-Cd-Zn-Ba, Ni-Cr-Co, Fe-Mn. Elements of the first group are characterized by high values of concentration coefficient and are the main pollutants - their average content is 3-11 times higher than background values. Strontium does not have strong correlation with the other elements, and its lowest concentration coefficient indicates that the element can not be regarded as a pollutant. The spatial distribution of the total pollution index identified several sources of pollution, the origin of which may be different. The main reason is probably the impact of vehicle emissions, although local pollution of soil is possible (the soils, contaminated during reconstruction of lawns, dumping of construction materials, etc.). Differentiated assessment of database shows that 48% of samples refer to dangerous pollution category, 37% - to moderately dangerous category, 15% - to allowable category. Thus, almost half of the district is characterized as dangerous in terms of soil contamination. Solution of the problem of soil contamination is recommended in three ways: reducing the intensity of vehicular traffic through the historic center of the city, improving the quality of transport emissions, removal of contaminated soil layers in particularly polluted areas and the introduction of clean soil, optimization of verdurization of the urban environment, as a means of reducing the flow of atmospheric pollutants in soil.

Tungsten-doped thin film materials

DOEpatents

Xiang, Xiao-Dong; Chang, Hauyee; Gao, Chen; Takeuchi, Ichiro; Schultz, Peter G.

2003-12-09

A dielectric thin film material for high frequency use, including use as a capacitor, and having a low dielectric loss factor is provided, the film comprising a composition of tungsten-doped barium strontium titanate of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3, where X is between about 0.5 and about 1.0. Also provided is a method for making a dielectric thin film of the general formula (Ba.sub.x Sr.sub.1-x)TiO.sub.3 and doped with W, where X is between about 0.5 and about 1.0, a substrate is provided, TiO.sub.2, the W dopant, Ba, and optionally Sr are deposited on the substrate, and the substrate containing TiO.sub.2, the W dopant, Ba, and optionally Sr is heated to form a low loss dielectric thin film.

Dielectric properties of Ba0.6Sr0.4TiO3-La(B0.5Ti0.5)O3 (B=Mg, Zn) ceramics.

PubMed

Xu, Yebin; Liu, Ting; He, Yanyan; Yuan, Xiao

2009-11-01

Ba(0.6)Sr(0.4)TiO(3)-La(B(0.5)Ti(0.5))O(3) (B = Mg, Zn) ceramics were prepared by a solid-state reaction method, and their microwave dielectric characteristics and tunability were investigated. The ferroelectric-dielectric solid solutions with cubic perovskite structures were obtained for compositions of 10 to 60 mol% La(Mg(0.5)Ti(0.5))O(3) and 10 to 50 mol% La(Zn(0.5)Ti(0.5))O(3). With the increase of linear oxide dielectric content, the dielectric constant and tunability were decreased and Qf was increased. Ba(0.6)Sr(0.4)TiO(3)-La(Mg(0.5)Ti(0.5))O(3) has better dielectric properties than Ba(0.6)Sr(0.4)TiO(3)-La(Zn(0.5)Ti(0.5))O(3). 0.9Ba(0.6)Sr(0.4)TiO(3)-0.1La(Mg(0.5)Ti(0.5))O(3) has a dielectric constant epsilon = 338.2, Qf = 979 GHz and a tunability of was 3.7% at 100 kHz under 1.67 kV/mm. The Qf value of 0.5Ba(0.6)Sr(0.4)TiO(3)- 0.5La(Mg(0.5)Ti(0.5))O(3) reached 9367 GHz, but the tunable properties were lost.

Pressure-induced photoluminescence in Mn2+-doped BaF2 and SrF2 fluorites

NASA Astrophysics Data System (ADS)

Hernández, Ignacio; Rodríguez, Fernando

2003-01-01

This work reports an effective way for inducing room temperature photoluminescence (PL) in Mn2+-doped BaF2 and SrF2 using high-pressure techniques. The aim is to understand the surprising PL behavior exhibited by Mn2+ at the cubal site of the fluorite structure. While Mn2+-doped CaF2 shows a green PL with quantum yield close to 1 at room temperature, Mn2+-doped MF2 (M=Ba,Sr) is not PL either at room temperature (SrF2) or at any temperature (BaF2) at ambient pressure. We associate the loss of Mn2+ PL on passing from CaF2 to SrF2 or BaF2 with nonradiative multiphonon relaxation whose thermal activation energy decreases along the series CaF2→SrF2→BaF2. A salient feature of this work deals with the increase of activation energy induced by pressure. It leads to a quantum yield enhancement, which favors PL recovery. Furthermore, the activation energy mainly depends on the crystal volume per molecule irrespective of the crystal structure or the local symmetry around the impurity. In this way, the relevance of the fluorite-to-cotunnite phase transition is analyzed in connection with the PL properties of the investigated compounds. The PL spectrum and the corresponding lifetime are reported for both structural phases as a function of pressure.

Implications for food safety of the uptake by tomato of 25 trace-elements from a phosphogypsum amended soil from SW Spain.

PubMed

Enamorado, Santiago; Abril, José M; Delgado, Antonio; Más, José L; Polvillo, Oliva; Quintero, José M

2014-02-15

Phosphogypsum (PG) has been usually applied as Ca-amendment to reclaim sodic soils such as those in the marshland area of Lebrija (SW Spain). This work aimed at the effects of PG amendments on the uptake of trace-elements by tomato and its implications for food safety. A completely randomized experiment was performed using a representative soil from Lebrija in a greenhouse involving six replicates and four PG treatments equivalent to 0, 20, 60, and 200 Mg ha(-1). Soil-to-plant transfer factors (TFs) were determined for Be, B, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Ag, Cd, Sb, Cs, Ba, Tl, Pb, Th and U. The highest TF in shoots was observed for Cd (4.0; 1.5 in fruits), its concentration being increased with increasing PG doses due to its content in this metal (2.1 mg Cd kg(-1)PG). Phosphogypsum applying decreased the concentrations of Mn, Co and Cu in shoots; and of B, Cu, Sb, Cs, Ba, Tl and Th in fruits, however enhanced the accumulation of Se in fruits. Although Cd concentrations in tomato were below the maximum allowed levels in control pots (0 Mg PG ha(-1)), PG amendments above 60 Mg ha(-1) exceeded such limits. Copyright © 2013 Elsevier B.V. All rights reserved.

The effect of rare earth ions on structural, morphological and thermoelectric properties of nanostructured tin oxide based perovskite materials

NASA Astrophysics Data System (ADS)

Rajasekaran, P.; Alagar Nedunchezhian, A. S.; Yalini Devi, N.; Sidharth, D.; Arivanandhan, M.; Jayavel, R.

2017-11-01

Metal oxide based materials are promising for thermoelectric applications especially at elevated temperature due to their high thermal stability. Recently, perovskite based oxide materials have been focused as a novel thermoelectric material due to their tunable electrical conductivity. Thermoelectric properties of BaSnO3 has been extensively investigated. However, the effect of various rare earth doping on the thermoelectric properties of BaSnO3 is not studied in detail. In the present work, Ba1-x RE x SnO3 (RE  =  La and Sr) materials with x  =  0.05 were prepared by polymerization complex (PC) method in order to study the effect of RE incorporation on the structural, morphological and thermoelectric characteristics of BaSnO3. The structural and morphological properties of the synthesized materials were studied by XRD and TEM analysis. XRD analysis confirmed the mixed phases of the synthesized samples. The TEM images of Ba1-x Sr x SnO3 shows hexagonal and cubic morphology while, Ba1-x La x SnO3 exhibit rod like morphology. Various functional groups of the perovskite material were identified using FTIR analysis. Formation of the perovskite material was further confirmed by XPS analysis. The Seebeck coefficient of Ba0.95La0.05SnO3 was relatively higher than that of Ba0.95Sr0.05SnO3, especially at high temperature. The rod like morphology of Ba0.95La0.05SnO3 may facilitate fast electron transport which results high thermal power compared to Ba0.95Sr0.05SnO3 despite of its poor crystalline nature. The substitution of La3+ on the Ba2+ site could vary the carrier density which results high Seebeck coefficient of Ba0.95La0.05SnO3 compared to Ba0.95Sr0.05SnO3. From the experimental results, it is obvious that Ba0.95La0.05SnO3 could be a promising thermoelectric material for high temperature application.

Monolayer II-VI semiconductors: A first-principles prediction

NASA Astrophysics Data System (ADS)

Zheng, Hui; Chen, Nian-Ke; Zhang, S. B.; Li, Xian-Bin

A systematic study of 32 honeycomb monolayer II-VI semiconductors is carried out by first-principles methods. It appears that BeO, MgO, CaO, ZnO, CdO, CaS, SrS, SrSe, BaTe, and HgTe honeycomb monolayers have a good dynamic stability which is revealed by phonon calculations. In addition, from the molecular dynamic (MD) simulation of other unstable candidates, we also find two extra monolayers dynamically stable, which are tetragonal BaS and orthorhombic HgS. The honeycomb monolayers exist in form of either a planar perfect honeycomb or a low-buckled 2D layer, all of which possess a band gap and most of them are in the ultraviolet region. Interestingly, the dynamically stable SrSe has a gap near visible light, and displays exotic electronic properties with a flat top of the valence band, and hence has a strong spin polarization upon hole doping. The honeycomb HgTe has been reported to achieve a topological nontrivial phase under appropriate in-plane tensile strain and spin-orbital coupling (SOC). Some II-VI partners with less than 5% lattice mismatch may be used to design novel 2D heterojunction devices. If synthesized, potential applications of these 2D II-VI families could include optoelectronics, spintronics, and strong correlated electronics. Distinguished Student (DS) Program of APS FIP travel funds.

Chemical composition of modern and fossil Hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation - Part 2: Alkaline earth elements as tracers of watershed hydrochemistry and provenance

NASA Astrophysics Data System (ADS)

Brügmann, G.; Krause, J.; Brachert, T. C.; Stoll, B.; Weis, U.; Kullmer, O.; Ssemmanda, I.; Mertz, D. F.

2012-03-01

For reconstructing environmental change in terrestrial realms the geochemistry of fossil bioapatite in bones and teeth is among the most promising applications. This study demonstrates that alkaline earth elements in enamel of Hippopotamids, in particular Ba and Sr are tracers for water provenance and hydrochemistry. The studied specimens are molar teeth from Hippopotamids found in modern and fossil lacustrine settings of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by ca. two orders of magnitude for Ba (120-9336 μg g-1) as well as for Sr (9-2150 μg g-1). Concentration variations in enamel are partly induced during post-mortem alteration and during amelogenesis, but the major contribution originates from the variable water chemistry in the habitats of the Hippopotamids which is dominated by the lithologies and weathering processes in the watershed areas. Amelogenesis causes a distinct distribution of Ba and Sr in modern and fossil enamel, in that element concentrations increase along profiles from the outer rim towards the enamel-dentin junction by a factor of 1.3-1.5. These elements are well correlated with MgO and Na2O in single specimens, thus suggesting that their distribution is determined by a common, single process. Presuming that the shape of the tooth is established at the end of the secretion process and apatite composition is in equilibrium with the enamel fluid, the maturation process can be modeled by closed system Rayleigh crystallization. Enamel from many Hippopotamid specimens has Sr/Ca and Ba/Ca which are typical for herbivores, but the compositions extend well into the levels of plants and carnivores. Within enamel from single specimens these element ratios covary and provide a specific fingerprint of the Hippopotamid habitat. All specimens together, however, define subparallel trends with different Ba/Sr ranging from 0.1 to 3. This ratio varies on spatial and temporal scales and traces provenance signals as well as the fractionation of the elements in the hydrological cycle. Thus, Sr concentrations and Ba/Sr in enamel differentiate between habitats having basaltic or Archean crustal rocks as the ultimate sources of Sr and Ba. The provenance signal is modulated by climate change. In Miocene to Pleistocene enamel from the Lake Albert region, Ba/Sr decreases systematically with time from about 2 to 0.5. This trend can be correlated with changes in climate from humid to arid in vegetation from C3 to C4 biomass as well as with increasing evaporation of the lake water. The most plausible explanation is that with time, Ba mobility decreased relative to that of Sr. This can arise if preferential adsorption of Ba to clay and Fe-oxide-hydroxide is related to increasing aridification. Additionally, weathering solutions and lake water can become increasingly alkaline and barite becomes stable. In this case, Ba will be preferentially deposited on the watershed of Lake Albert and rivers with low Ba/Sr will feed the habitats of the Hippopotamids.

Removal of barium and strontium from aqueous solution using zeolite 4A.

PubMed

Araissi, Manel; Ayed, Imen; Elaloui, Elimame; Moussaoui, Younes

2016-01-01

The adsorption efficiency of Sr(2+) and Ba(2+) from aqueous solutions by zeolite 4A was investigated. Adsorption studies were carried out both in single and binary component systems. The single ion equilibrium adsorption data were fitted to three isotherm models: Langmuir, Freundlich and Dubinin-Radushkevich. The Langmuir model represents the equilibrium data better than the Freundlich model in the studied initial metal concentration (0.3-25 mmol L(-1)) in both the single and binary component systems. The obtained RL (separation factor or Langmuir parameter) values were in the range of 0-1 indicating that Sr(2+) and Ba(2+) sorption were favorable. The obtained mean free energy value for adsorption of Ba(2+) and Sr(2+) was 8.45 kJ mol(-1) and 9.12 kJ mol(-1), respectively, indicating that both ions were uptaken through an ion exchange process. The maximum adsorption capacities (Qmax) were 2.25 mmol g(-1) and 2.34 mmol g(-1) for Ba(2+) and Sr(2+) ions, respectively. Also, the study of the competitive sorption of ions in the binary system showed that zeolite 4A preferentially adsorbs cations in the following order: Ba(2+) < Sr(2+).

Electronic Structure of I-M8Ga16Sn30 (M = Ba, Sr, Yb) by First-Principles Calculation

NASA Astrophysics Data System (ADS)

Wang, Jin-song; Liu, Hong-xia; Deng, Shuping; Li, De-cong; Shen, Lan-xian; Cheng, Feng; Deng, Shu-kang

2017-05-01

Sn-based clathrates possess excellent thermoelectric properties ascribed to their higher Seebeck coefficient and lower thermal conductivity. Guest atoms significantly modulate the thermoelectric properties of Sn-based calculates because of their diverse atomic radius and interactions with framework atoms. Thus, we explored the electronic structure of I-M8Ga16Sn30 (M = Ba, Sr, Yb) by first-principles calculation. Results revealed significant differences between Yb8Ga16Sn30 and M8Ga16Sn30 (M = Ba, Sr,). In particular, the Yb-filled compound substitution possesses lowest formation energy and the off-center distance of the Yb atom is the largest compared with the other structures. I-M8Ga16Sn30 (M = Ba, Sr, Yb) is an indirect band gap semiconductor, and the enhanced hybridization effect between the guest and framework atoms' orbits exists because the Yb f orbit results in a decrease in band gap. Ba- and Sr-filled clathrates have similar valence bands but slightly different conduction bands; however, Yb8Ga16Sn30 possess the spiculate density of states near the Fermi level that reveals excellent thermoelectric properties.

Optimization of single crystals of solid electrolytes with tysonite-type structure (LaF3) for conductivity at 293 K: 2. Nonstoichiometric phases R 1- y M y F3- y ( R = La-Lu, Y; M = Sr, Ba)

NASA Astrophysics Data System (ADS)

Sorokin, N. I.; Sobolev, B. P.; Krivandina, E. A.; Zhmurova, Z. I.

2015-01-01

Single crystals of fluorine-conducting solid electrolytes R 1 - y Sr y F3 - y and R 1 - y Ba y F3 - y ( R = La-Lu, Y) with a tysonite-type structure (LaF3) have been optimized for room-temperature conductivity σ293 K. The optimization is based on high-temperature measurements of σ( T) in two-component nonstoichiometric phases R 1 - y M y F3 - y ( M = Sr, Ba) as a function of the MF2 content. Optimization for thermal stability is based on studying the phase diagrams of MF2- RF3 systems ( M = Sr, Ba) and the behavior of nonstoichiometric crystals upon heating when measuring temperature dependences σ( T). Single crystals of many studied R 1 - y Sr y F3 - y and R 1 - y Ba y F3 - y phases have σ293 K values large enough to use these materials in solid-state electrochemical devices (chemical sensors, fluorine-ion batteries, accumulators, etc.) operating at room temperature.

Magmatic evolution of lunar highland rocks estimated from trace elements in plagioclase: A new bulk silicate Moon model with sub-chondritic Ti/Ba, Sr/Ba, and Sr/Al ratios

NASA Astrophysics Data System (ADS)

Togashi, Shigeko; Kita, Noriko T.; Tomiya, Akihiko; Morishita, Yuichi

2017-08-01

The compositions of host magmas of ferroan anorthosites (FAN-host magmas) were estimated from secondary ion mass spectrometry analyses of plagioclase in lunar highland rocks. The evolution of the magmas was investigated by considering phase relations based on the MELTS algorithm and by re-examining partition coefficients for trace elements between plagioclase and melts. Data little affected by post-magmatic processes were selected by using plagioclase with relatively primitive Sc and Co contents. The FAN-host magma contained 90-174 ppm Sr, 40-119 ppm Ba and 0.5-1.3% TiO2, and had sub-chondritic Sr/Ba and Ti/Ba ratios. It is difficult to account for the formation of FAN-host magma on the basis of magma evolution processes of previously proposed bulk silicate Moon models with chondritic ratios for refractory elements at global scale. Therefore, the source of the FAN-host magma must have had primordial sub-chondritic Sr/Ba and Ti/Ba ratios. The FAN-host magmas were consistent in refractory elements with the estimated host mafic magma for feldspathic crust based on lunar meteorites, and some very-low-Ti mare rocks from lunar meteorites. Here, we propose an alternative bulk silicate Moon model (the cBSM model), which is enriched in crustal components of proto-bodies relative to the present whole Earth-Moon system.

Microstructure and dielectric parameters of epitaxial SrRuO3/BaTiO3/SrRuO3 heterostructures

NASA Astrophysics Data System (ADS)

Boikov, Yu. A.; Claeson, T.

2001-05-01

Epitaxial films of ferroelectric barium titanate are desirable in a number of applications but their properties are inferior to those of bulk material. Relations between microstructure and dielectric properties may give better understanding of limitations. Trilayer heterostructures SrRuO3/BaTiO3/SrRuO3 were grown by laser ablation on (100)LaAlO3 and (100)MgO substrates. The BaTiO3 layer was granular in structure. When grown on (100)SrRuO3/(100)LaAlO3, it was preferentially a-axis oriented due to tensile mechanical stress. Using (100)MgO as a substrate, on the other hand, produced a mixture of about equal value of a-axis and c-axis oriented grains of BaTiO3. The dielectric permittivity, ɛ, of the BaTiO3 layer was almost twice as large, at T>200 K and f=100 kHz, for the LaAlO3 substrate as compared to the MgO one. Its maximum value (ɛ/ɛ0≈6200) depended on temperature of growth, grain size, and electric field and compares well with optimal values commonly used for ceramic material. The maximum in the ɛ(T) shifted from about 370 to 320 K when the grain size in the BaTiO3 film decreased from 100 to 40 nm. At T<300 K, hysteresis loops in polarization versus electric field were roughly symmetric. The BaTiO3 films grown on (100)SrRuO3/(100)MgO exhibit the largest remnant polarizations and coercive fields in the temperature range 100-380 K.

Chemical Synthesis of Next Generation High Energy Product Hybrid SmCo Permanent Magnets for High Temperature Applications

DTIC Science & Technology

2010-08-01

among CoxC, AINiCo and Ba / Sr ferrite magnets. AINiCo is shown to exhibit high (BH)max, 35 kJmŗ, but a low intrinsic coercivity, mostly ə kOe...whereas Ba / Sr ferrite features high intrinsic coercivity, 3-4.5 kOe, but typical values of (BH)max below 25 kJm-3. However, the multiple...coercivity of cobalt carbide nanoparticles is compared with free powders of AINiCo and ceramic magnets of the Ba / Sr hexaferrite type. Curie temperatures near

Alkyl complexes of strontium and barium: synthesis and structural characterization of [(Me3Si)2(MeOMe2Si)C]2Sr(THF) and [(Me3Si)2(MeOMe2Si)C]2Ba(MeOCH2CH2OMe).

PubMed

Izod, Keith; Liddle, Stephen T; Clegg, William

2003-06-25

Metathesis between either SrI2 or BaI2 and 2 equiv of {(Me3Si)2(MeOMe2Si)C}K in THF yields the novel heavier alkali metal dialkyls {(Me3Si)2(MeOMe2Si)C}2M(L) [M(L) = Sr(THF) (2), Ba(DME) (3) (DME = 1,2-dimethoxyethane)] after recrystallization.

Multifunctional Oxide Films for Advanced Multifunction RF Systems

DTIC Science & Technology

2007-09-14

during the epitaxy runs. Effusion cells (SVT) provide perovskite and rocksalt matrix elements (Ti, Ba , Sr , Mg). An e-gun evaporator (MDC):can be used to...sample that best matched the targeted stoichiometry. 10 5 MgO Ba 0 . Sr 1.4 TiO3/MgO 10 000 BS I 102 3~) ;101 0~ 0 (a) RHiEED of BST rowthonM 0 105O... Ba 0. Sr .. iO3 /SrMO. 5 200 1Is V STO10 -STO 3 -10 _ 10 2 30S 15 10 100 10 20 30 40 50 60 70 80 90 20 (b) RHEED of BST growth on STO (c) XRD scan of

The Universality of the Rapid Neutron-capture Process Revealed by a Possible Disrupted Dwarf Galaxy Star

NASA Astrophysics Data System (ADS)

Casey, Andrew R.; Schlaufman, Kevin C.

2017-12-01

The rapid neutron-capture or r-process is thought to produce the majority of the heavy elements (Z> 30) in extremely metal-poor stars. The same process is also responsible for a significant fraction of the heavy elements in the Sun. This universality of the r-process is one of its characteristic features, as well as one of the most important clues to its astrophysical origin. We report the discovery of an extremely metal-poor field giant with [{Sr},{Ba}/{{H}}]≈ -6.0 and [{Sr},{Ba}/{Fe}]≈ -3.0, the lowest abundances of strontium and barium relative to iron ever observed. Despite its low abundances, the star 2MASS J151113.24-213003.0 has [{Sr}/{Ba}]=-0.11+/- 0.14, therefore its neutron-capture abundances are consistent with the main solar r-process pattern that has [{Sr}/{Ba}]=-0.25. It has been suggested that extremely low neutron-capture abundances are a characteristic of dwarf galaxies, and we find that this star is on a highly eccentric orbit with an apocenter ≳100 kpc that lies in the disk of satellites in the halo of the Milky Way. We show that other extremely metal-poor stars with low [Sr, Ba/H] and [Sr, Ba/Fe] plus solar [Sr/Ba] tend to have orbits with large apocenters, consistent with a dwarf galaxy origin for this class of object. The nucleosynthesis event that produced the neutron-capture elements in 2MASS J151113.24-213003.0 must produce both strontium and barium together in the solar ratio. We exclude contributions from the s-process in intermediate-mass asymptotic giant branch or fast-rotating massive metal-poor stars, pair-instability supernovae, the weak r-process, and neutron-star mergers. We argue that the event was a Pop III or extreme Pop II core-collapse supernova explosion. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Optimal formation and enhanced superconductivity of Tl-1212 phase (Tl0.6Pb0.4)(Ba,Sr)CaCu2O7

NASA Astrophysics Data System (ADS)

Ranjbar, M. G.; Ghoranneviss, Mahmood; Abd-Shukor, R.

2018-06-01

The effect of heating temperature on the formation of Tl-1212 phase with nominal starting composition (Tl0.6Pb0.4)(Ba,Sr)CaCu2O7 (Tl-1212) is reported. The Ba-bearing Tl-1212 phase is normally prepared at around 900 °C while with Sr-bearing sample is prepared at a much higher temperature of around 1000 °C. This work was conducted to determine the optimal temperature to synthesis the Tl-1212 phase when the sample contains Ba and Sr with 1:1 ratio. (Tl0.6Pb0.4)(Ba,Sr)CaCu2O7 samples were prepared using the solid-state reaction method via the precursor route. In the final preparation stage, the samples were heated at 850, 870, 900, 920, 950, 970 and 1000 °C in oxygen flow. X-Ray diffraction patterns showed that most samples consisted of a mixed (Tl0.6Pb0.4)(Ba,Sr)Ca2Cu3O9 (Tl-1223) and Tl-1212 phase except for the sample heated at 970 °C which showed a single Tl-1212 phase and the sample heated at 850 °C which showed the Tl-1223 phase. The transition temperature measured by four-probe method showed that the sample heated at 970 °C exhibited the highest onset temperature of 118 K and zero-resistance temperature of 100 K. This transition temperature is higher than the usually reported value for the Tl-1212 phase. AC susceptibility measurements also showed the 970 °C heated sample with the highest transition temperature T c χ' = 109 K. The interplay of ionic radius (Ba2+ and Sr2+) decreases of the unit cell volume and changes in the internal lattice strain enhanced the transition temperature and the formation of the Tl-1212 phase.

Synthesis of barium-strontium titanate hollow tubes using Kirkendall effect

NASA Astrophysics Data System (ADS)

Chen, Xuncai; Im, SangHyuk; Kim, Jinsoo; Kim, Woo-Sik

2018-02-01

(BaSr)TiO3 hexagonal hollow tubes was fabricated by a solid-state interfacial reaction including a Kirkendall diffusion. Using a co-precipitation and sol-gel process, a core@shell structure of (BaSr)CO3@TiO2 rods were prepared, and then converted to (BaSr)TiO3 hollow tubes at 750 °C. This was a first achievement of single-phase crystal hollow tube. Here, the inner diameter and wall thickness of hollow tube were about 700 nm and 130 nm, respectively. The fabrication of (BaSr)TiO3 hollow tubes was monitored with scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD) to investigate their formation mechanism. The present synthetic approach would provide a new insight into the design and fabrication of hollow architectures of many perovskite oxides.

Sr{sub 7}Ge{sub 6}, Ba{sub 7}Ge{sub 6} and Ba{sub 3}Sn{sub 2} -Three new binary compounds containing dumbbells and four-membered chains of tetrel atoms with considerable Ge-Ge {pi}-bonding character

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siggelkow, Lisa; Hlukhyy, Viktor; Faessler, Thomas F., E-mail: thomas.faessler@lrz.tum.de

2012-07-15

The germanides Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} as well as the stannide Ba{sub 3}Sn{sub 2} were prepared by arc melting and annealing in welded tantalum ampoules using induction as well as resistance furnaces. The compounds were investigated by powder and single crystal X-ray diffraction. Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} crystallize in the Ca{sub 7}Sn{sub 6} structure type (space group Pmna, Z=4: a=7.777(2) A, b=23.595(4) A, c=8.563(2) A, wR{sub 2}=0.081 (all data), 2175 independent reflections, 64 variable parameters for Sr{sub 7}Ge{sub 6} and a=8.0853(6) A, b=24.545(2) A, c=8.9782(8) A, wR{sub 2}=0.085 (all data), 2307 independent reflections, 64more » variable parameters for Ba{sub 7}Ge{sub 6}). Ba{sub 3}Sn{sub 2} crystallizes in an own structure type with the space group P4{sub 3}2{sub 1}2, Z=4, a=6.6854(2) A, c=17.842(2) A, wR{sub 2}=0.037 (all data), 1163 independent reflections, 25 variable parameters. In Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} the Ge atoms are arranged as Ge{sub 2} dumbbells and Ge{sub 4} four-membered atom chains. Their crystal structures cannot be rationalized according to the (8-N) rule. In contrast, Ba{sub 3}Sn{sub 2} presents Sn{sub 2} dumbbells as a main structural motif and thereby can be described as an electron precise Zintl phase. The chemical bonding situation in these structures is discussed on the basis of partial and total Density Of States (DOS) curves, band structures including fatbands, topological analysis of the Electron Localization Function (ELF) as well as Bader analysis of the bond critical points using the programs TB-LMTO-ASA and WIEN2K. While Ba{sub 3}Sn{sub 2} reveals semiconducting behaviour, all germanides Ae{sub 7}Ge{sub 6} (Ae=Ca, Sr, and Ba) show metallic properties and a considerable {pi}-bonding character between the Ge atoms of the four-membered chains and the dumbbells. The {pi}-bonding character of the germanides is best reflected by the resonance hybrid structures {l_brace}[Ge-Ge]{sup 6-}/[Ge-{sup ....}Ge-{sup ....}Ge-{sup ....}Ge]{sup 8-}{r_brace}{r_reversible}{l_brace}[Ge=Ge]{sup 4-}/[Ge-Ge-Ge-Ge]{sup 10-}{r_brace}. - Graphical abstract: The structure of Ba{sub 3}Sn{sub 2} contains Sn{sub 2} dumbbells as a main structural motif and thereby can be described as an electron precise Zintl phase. Ge{sub 2} dumbbells and Ge{sub 4} four-membered atom chains are the predominant features in Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6}. Their crystal structures cannot be rationalized according to the (8-N) rule. While Ba{sub 3}Sn{sub 2} reveals semiconducting behaviour, the germanides Ae{sub 7}Ge{sub 6} (Ae=Ca, Sr, and Ba) show metallic properties and a considerable {pi}-bonding character between the Ge atoms of the four-membered chains and the dumbbells. Highlights: Black-Right-Pointing-Pointer The germanides Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} as well as the stannide Ba{sub 3}Sn{sub 2} have been synthesized. Black-Right-Pointing-Pointer In Sr{sub 7}Ge{sub 6} and Ba{sub 7}Ge{sub 6} the Ge atoms are arranged as dumbbells and four-membered atom chains. Black-Right-Pointing-Pointer Ba{sub 3}Sn{sub 2} presents Sn{sub 2} dumbbells as a main structural motif. Black-Right-Pointing-Pointer The chemical bonding situation within these structures is discussed.« less

STABILIZATION OF SPIDER CRAB NERVE MEMBRANES BY ALKALINE EARTHS, AS MANIFESTED IN RESTING POTENTIAL MEASUREMENTS

PubMed Central

Guttman, Rita

1940-01-01

1. The alkaline earths, Ba, Sr, Ca, and Mg, in isotonic solutions of their chlorides, have, in general, no effect upon the resting potential of non-medullated spider crab nerve. 2. Ba, Sr, and Ca can, however, prevent the depressing action of K upon the resting potential. The order of effectiveness of these ions in this regard is the following: Ba > Sr > Ca. 3. Ba, Sr, Ca, and Mg oppose the depressing action of veratrine sulfate upon the resting potential. The order of effectiveness is Ba > Sr > Ca > Mg. The relation between drop in potential caused by veratrine sulfate and the logarithm of the veratrine sulfate concentration is a linear one. 4. The action of various other organic ions and molecules which depress the resting potential: saponin, amyl urethane, chloral hydrate, and Na salicylate is neutralized by Ba. 5. Hypertonic sea water solutions do not affect the resting potential. Also, preliminary experiments indicate that the nerves do not shrink in hypertonic solutions although they swell in hypotonic sea water. 6. The alkaline earths depress excitability reversibly. The various organic agents which depress the resting potential also depress excitability, in most cases, reversibly, but the concentrations necessary to depress excitability are much smaller than those necessary to depress the resting potential. 7. The relation of these findings to theories put forward as possible explanations of resting potential phenomena is considered. PMID:19873160

Concentrations and ratios of Sr, Ba and Ca along an estuarine river to the Gulf of Mexico - implication for sea level rise effects on trace metal distribution

NASA Astrophysics Data System (ADS)

He, S.; Xu, Y. J.

2015-11-01

Strontium and barium to calcium ratios are often used as proxies for tracking animal movement across salinity gradients. As sea level rise continues, many estuarine rivers in the world face saltwater intrusion, which may cause changes in mobility and distribution of these metals upstream. Despite intensive research on metal adsorption and desorption in marine systems, knowledge of the spatiotemporal distribution of these elements along estuarine rivers is still limited. In this study, we conducted an intensive monitoring of Sr and Ba dynamics along an 88 km long estuary, the Calcasieu River in South Louisiana, USA, which has been strongly affected by saltwater intrusion. Over the period from May 2013 to August 2015, we collected monthly water samples and performed in-situ water quality measurements at six sites from the upstream to the river mouth, with a salinity range from 0.02 to 29.50 ppt. Water samples were analyzed for Sr, Ba, and Ca concentrations. In-situ measurements were made on salinity, pH, water temperature, dissolved oxygen concentration, and specific conductance. We found that the Sr and Ca concentrations and the Sr / Ca ratio all increased significantly with increasing salinity. The average Sr concentration at the site closest to the Gulf of Mexico (site 6) was 46.21 μmol L-1, which was about 130 times higher than that of the site furthest upstream (site 1, 0.35 μmol L-1). The average Ca concentration at site 6 was 8.19 mmol L-1, which was about 60 times higher than that of site 1 (0.13 mmol L-1). The average Sr / Ca ratio at site 6 (8.41 mmol mol-1) was about 3 times the average Sr / Ca ratio at site 1 (2.89 mmol mol-1). However, the spatial variation in Ba concentration was marginal, varying from 0.36 μmol L-1 at site 6 to 0.47 at site 5. The average Ba / Ca ratio at site 1 (4.82 mmol mol-1) was about 54 times the average Ba / Ca ratio at site 6 (0.09 mmol mol-1), showing a clear negative relation between the Ba / Ca ratio and increasing salinity. All the elemental concentrations and ratios had considerable seasonal variations, with significant differences among sampling months for the Sr, Ba concentrations and the Ba / Ca ratio (p < 0.01). The results from this study suggest that concentrations of Sr and Ca in the world's estuaries will very likely increase in the future as sea level rise continues. For low-gradient estuarine rivers such as the Calcasieu River in South Louisiana, USA, water chemistry upstream would experience substantial Sr and Ca enrichment, which could affect aquatic environments and biological communities.

Ba(1-x)Sr(x)Zn2Si2O7--A new family of materials with negative and very high thermal expansion.

PubMed

Thieme, Christian; Görls, Helmar; Rüssel, Christian

2015-12-15

The compound BaZn2Si2O7 shows a high coefficient of thermal expansion up to a temperature of 280 °C, then a transition to a high temperature phase is observed. This high temperature phase exhibits negative thermal expansion. If Ba(2+) is successively replaced by Sr(2+), a new phase with a structure, similar to that of the high temperature phase of BaZn2Si2O7, forms. At the composition Ba0.8Sr0.2Zn2Si2O7, this new phase is completely stabilized. The crystal structure was determined with single crystal X-ray diffraction using the composition Ba0.6Sr0.4Zn2Si2O7, which crystallizes in the orthorhombic space group Cmcm. The negative thermal expansion is a result of motions and distortions inside the crystal lattice, especially inside the chains of ZnO4 tetrahedra. Dilatometry and high temperature X-ray powder diffraction were used to verify the negative thermal expansion. Coefficients of thermal expansion partially smaller than -10·10(-6) K(-1) were measured.

Electronic properties of high-temperature superconductors

NASA Astrophysics Data System (ADS)

Richert, Brent Armand

1989-08-01

A semiempirical tight-binding model was developed for the electronic energy bands, the local and total densities of states, and the atomic valences in the high temperature superconductors La(1.85)Sr(0.15)CuO4, YBaCu307, Bi2Sr2CuO6, Bi2CaSr2Cu2O8, Tl2Ba2CuO6, Tl2CaBa2Cu2O8, Tl2Ca2Ba2Cu3O10, TlCa3Ba2Cu4O11, BaPb(0.75)Bi(0.25)O3, and Ba(0.6)K(0.4)BiO3. Calculations of the changes in electronic properties associated with atomic substitutions in YBa2Cu3O7, Bi2CaSr2Cu2O8, and Tl2CaBa2Cu2O8 give results in agreement with expected chemical trends and consistent with observed changes in the superconducting properties. For example, substitution of Lead for Bismuth in BiMCaSr2Cu2O8 increases the concentration of hole carriers within the CuO2 planes. Similarly, doping with Mercury or Pb in TlMCaBa2Cu2O8 also affects the carrier concentration, with Hg creating holes and Pb destroying them. Oxygen vacancies in both La(1.85)Sr(0.15)CuO(4-y) and YBa2Cu3O(7-y) act as electron donors. This is consistent with the observations that oxygen vacancies degrade the superconductivity and metallic conductivity in these materials. Lanthanum vacancies in La2-xCuO4 donate holes, giving the same electronic effect as doping with divalent metal atoms or excess oxygen initially stoichiometric La2CuO4. A specific excitonic mechanism for high temperature superconductivity is proposed which requires insulating metal oxide layers adjacent to the superconducting planes.

Multielemental analysis of 20 mushroom species growing near a heavily trafficked road in Poland.

PubMed

Mleczek, M; Niedzielski, P; Kalač, P; Budka, A; Siwulski, M; Gąsecka, M; Rzymski, P; Magdziak, Z; Sobieralski, K

2016-08-01

The aim of this work was to compare 10 mostly edible aboveground and 10 wood-growing mushroom species collected near a heavily trafficked road (approximately 28,000 vehicles per 24 h) in Poland with regard to their capacity to accumulate 26 trace elements (Ag, Al, As, Au, B, Ba, Bi, Cd, Co, Cr, Cu, Fe, Ga, Ge, In, Li, Mn, Ni, Pb, Re, Sb, Se, Sr, Te, Tl, and Zn) in their fruit bodies in order to illustrate mushroom diversity in element accumulation. All analyses were performed using an inductively coupled plasma optical emission spectrometry (ICP-OES) spectrometer in synchronous dual view mode. The aboveground species had significantly higher levels of 12 elements, including Ag, As, Pb, and Se, compared to the wood-growing species. An opposite relationship was observed only for Au, Ba, and Sr. The results of principal component analysis (PCA) and hierarchical cluster analysis (HCA) implied some new relationships among the analyzed species and elements. Of the analyzed mushroom species, lead content in Macrolepiota procera would seem to pose a health risk; however, at present knowledge regarding lead bioaccessibility from mushrooms is quite limited.

Improvement of a sample preparation procedure for multi-elemental determination in Brazil nuts by ICP-OES.

PubMed

Welna, Maja; Szymczycha-Madeja, Anna

2014-04-01

Various sample preparation procedures, such as common wet digestions and alternatives based on solubilisation in aqua regia or tetramethyl ammonium hydroxide, were compared for the determination of the total Ba, Ca, Cr, Cd, Cu, Fe, Mg, Mn, Ni, P, Pb, Se, Sr and Zn contents in Brazil nuts using inductively coupled plasma optical emission spectrometry (ICP-OES). For measurement of Se, a hydride generation technique was used. The performance of these procedures was measured in terms of precision, accuracy and limits of detection of the elements. It was found that solubilisation in aqua regia gave the best results, i.e. limits of detection from 0.60 to 41.9 ng ml(-1), precision of 1.0-3.9% and accuracy better than 5%. External calibration with simple standard solutions could be applied for the analysis. The proposed procedure is simple, reduces sample handling, and minimises the time and reagent consumption. Thus, this can be a vital alternative to traditional sample treatment approaches based on the total digestion with concentrated reagents. A phenomenon resulting from levels of Ba, Se and Sr in Brazil nuts was also discussed.

Strontium, barium, and manganese metabolism in isolated presynaptic nerve terminals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rasgado-Flores, H.; Sanchez-Armass, S.; Blaustein, M.P.

1987-06-01

To gain insight into the mechanisms by which the divalent cations Sr, Ba, and Mn affect neurotransmitter release from presynaptic nerve terminals, the authors examined the sequestration of these cations, ion comparison to Ca, by mitochondrial and nonmitochondrial organelles and the extrusion of these cations from isolated nerve terminals. Sequestration was studied in synaptosomes made leaky to small ions by treatment with saponin; efflux was examined in intact synaptosomes that were preloaded with the divalent cations by incubation in depolarizing (K rich) media. The selectivity sequence for ATP-dependent mitochondrial uptake that they observed was Mn>>Ca>Sr>>Ba, whereas that for the SERmore » was Ca greater than or equal to Mn>Sr>>Ba. When synaptosomes that were preloaded with divalent cations were incubated in Na- and Ca-free media, there was little efflux of /sup 45/Ca, /sup 133/Ba, /sup 85/Sr, or /sup 54/Mn. When the incubation was carried out in media containing Na without Ca, there was substantial stimulation of Ca and Sr efflux, but only slight stimulation of Ba or Mn efflux. In Na-free media, the addition of 1 mM Ca promoted the efflux of all four divalent cations, probably via Ca-divalent cation exchange. In summary, the sequestration and extrusion data suggest that, with equal loads, Mn will be buffered to the greatest extent, whereas Ba will be least well buffered. These results may help to explain why Mn has a very long-lasting effect on transmitter release, while the effect of Sr is much briefer.« less

Antiferromagnetism in semiconducting SrMn 2 Sb 2 and BaMn 2 Sb 2 single crystals

DOE PAGES

Sangeetha, N. S.; Smetana, V.; Mudring, A. -V.; ...

2018-01-03

Here, crystals of SrMn 2Sb 2 and BaMn 2Sb 2 were grown using Sn flux and characterized by powder and single-crystal x-ray diffraction, respectively, and by single-crystal electrical resistivity ρ, heat capacity C p, and magnetic susceptibility χ measurements versus temperature T, and magnetization versus field M(H) isotherm measurements. SrMn 2Sb 2 adopts the trigonal CaAl 2Si 2-type structure, whereas BaMn 2Sb 2 crystallizes in the tetragonal ThCr 2Si 2-type structure. The ρ(T) data indicate semiconducting behaviors for both compounds with activation energies of ≳0.35 eV for SrMn 2Sb 2 and 0.16 eV for BaMn 2Sb 2. The χ(T) andmore » C p(T) data reveal antiferromagnetic (AFM) ordering at T N = 110 K for SrMn 2Sb 2 and 450 K for BaMn 2Sb 2. The anisotropic χ(T≤T N) data also show that the ordered moments in SrMn 2Sb 2 are aligned in the hexagonal ab plane, whereas the ordered moments in BaMn 2Sb 2 are aligned collinearly along the tetragonal c axis. The ab-plane M(H) data for SrMn 2Sb 2 exhibit a continuous metamagnetic transition at low fields 02Sb 2 exhibits no metamagnetic transitions up to 5.5 T. The χ(T) and C p(T) data for both SrMn 2Sb 2 and BaMn 2Sb 2 indicate strong dynamic short-range AFM correlations above their respective T N up to at least 900 K within a local-moment picture, corresponding to quasi-two-dimensional magnetic behavior. The present results and a survey of the literature for Mn pnictides with the CaAl 2Si 2 and ThCr 2Si 2 crystal structures show that the T N values for the CaAl 2Si 2-type compounds are much smaller than those for the ThCr 2Si 2-type materials.« less

Double-perovskites A 2FeMoO 6- δ (A = Ca, Sr, Ba) as anodes for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Zhang, Leilei; Zhou, Qingjun; He, Qiang; He, Tianmin

Double-perovskites A 2FeMoO 6- δ (A = Ca, Sr, Ba) have been investigated as potential anode materials for solid oxide fuel cells (SOFCs). At room temperature, A 2FeMoO 6- δ compounds crystallize in monoclinic, tetragonal, and cubic structures for A = Ca, Sr, and Ba, respectively. A weak peak observed at around 880 cm -1 in the Raman spectra can be attributed to traces of AMoO 4. XPS has confirmed the coexistence of Fe 2+-Mo 6+ and Fe 3+-Mo 5+ electronic configurations. Moreover, a systematic shift from Fe 2+/3+-Mo 6+/5+ to Fe 2+-Mo 6+ configuration is seen with increasing A-site cation size. A 2FeMoO 6- δ samples display distinct electrical properties in H 2, which can be attributed to different degrees of degeneracy of the Fe 2+-Mo 6+ and Fe 3+-Mo 5+ configurations. Ca 2FeMoO 6- δ is unstable in a nitrogen atmosphere, while Sr 2FeMoO 6- δ and Ba 2FeMoO 6- δ are stable up to 1200 °C. The thermal expansion coefficients of Sr 2FeMoO 6- δ and Ba 2FeMoO 6- δ are very close to that of La 0.9Sr 0.1Ga 0.8Mg 0.2O 3- δ (LSGM). The performances of cells with 300 μm thick LSGM electrolyte, double-perovskite SmBaCo 2O 5+ x cathodes, and A 2FeMoO 6- δ anodes follow the sequence Ca 2FeMoO 6- δ < Ba 2FeMoO 6- δ < Sr 2FeMoO 6- δ. The maximum power densities of a cell with an Sr 2FeMoO 6- δ anode reach 831 mW cm -2 in dry H 2 and 735 mW cm -2 in commercial city gas at 850 °C, respectively.

Description and validation of a new automated surveillance system for Clostridium difficile in Denmark.

PubMed

Chaine, M; Gubbels, S; Voldstedlund, M; Kristensen, B; Nielsen, J; Andersen, L P; Ellermann-Eriksen, S; Engberg, J; Holm, A; Olesen, B; Schønheyder, H C; Østergaard, C; Ethelberg, S; Mølbak, K

2017-09-01

The surveillance of Clostridium difficile (CD) in Denmark consists of laboratory based data from Departments of Clinical Microbiology (DCMs) sent to the National Registry of Enteric Pathogens (NREP). We validated a new surveillance system for CD based on the Danish Microbiology Database (MiBa). MiBa automatically collects microbiological test results from all Danish DCMs. We built an algorithm to identify positive test results for CD recorded in MiBa. A CD case was defined as a person with a positive culture for CD or PCR detection of toxin A and/or B and/or binary toxin. We compared CD cases identified through the MiBa-based surveillance with those reported to NREP and locally in five DCMs representing different Danish regions. During 2010-2014, NREP reported 13 896 CD cases, and the MiBa-based surveillance 21 252 CD cases. There was a 99·9% concordance between the local datasets and the MiBa-based surveillance. Surveillance based on MiBa was superior to the current surveillance system, and the findings show that the number of CD cases in Denmark hitherto has been under-reported. There were only minor differences between local data and the MiBa-based surveillance, showing the completeness and validity of CD data in MiBa. This nationwide electronic system can greatly strengthen surveillance and research in various applications.

c-Axis oriented epitaxial Ba 0.25Sr 0.75TiO 3 films display Curie-Weiss behavior

NASA Astrophysics Data System (ADS)

Boikov, Yu. A.; Claeson, T.

2002-02-01

Thin films of ferroelectrics have inferior dielectric properties, including microwave losses, compared to bulk material and generally do not display a proper Curie-Weiss behavior. This study shows that the film properties can be improved considerably, with a Curie-Weiss behavior, by choosing lattice matched electrodes and proper stoichiometry. A 700 nm thick Ba 0.25Sr 0.75TiO 3 layer was inserted, by laser ablation, between two epitaxial metallic oxide (200 nm) SrRuO 3 electrodes. Because of compressive stress in the plane of the substrate, the c-axis of the unit cell in the Ba 0.25Sr 0.75TiO 3 layer was normal to the substrate plane. Grains were of the order of 100-200 nm (with small misorientation angles in a× b plane) as determined by X-rays and AFM. The positions of pronounced maxima in the temperature dependence of the permittivity depended on external bias voltage applied between the SrRuO 3 electrodes to the dielectric film. The measured ε( T) curves agreed well with existing theoretical models at temperatures below and above the ferroelectric phase transition point. At T≈200 K, ε/ ε0 for the Ba 0.25Sr 0.75TiO 3 layer was suppressed up to 85% (from 4400 down to 560) when ±2.5 V bias voltage was applied to the metallic oxide electrodes. Well saturated polarization-vs.-voltage hysteresis loops were measured for the Ba 0.25Sr 0.75TiO 3 layer in the temperature interval 4.2-200 K. Because of depolarization effects, the polarization of the Ba 0.25Sr 0.75TiO 3 layer was suppressed at positive voltage applied between the electrodes, as compared with a negative one.

DEPENDENCE OF THE Sr-TO-Ba AND Sr-TO-Eu RATIO ON THE NUCLEAR EQUATION OF STATE IN METAL-POOR HALO STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Famiano, M. A.; Kajino, T.; Aoki, W.

A model is proposed in which the dependence on the equation of state (EOS) of the scatter of [Sr/Ba] in metal-poor stars is studied. Light r-process element enrichment in these stars has been explained via a truncated r-process, or “tr-process.” The truncation of the r-process from a generic core-collapse event followed by a collapse into an accretion-induced black hole is examined in the framework of a galactic chemical evolution model. The constraints on this model imposed by observations of extremely metal-poor stars are explained, and the upper limits in the [Sr/Ba] distributions are found to be related to the nuclearmore » EOS in a collapse scenario. The scatter in [Sr/Ba] and [Sr/Eu] as a function of metallicity has been found to be consistent with turbulent ejection in core-collapse supernovae. Adaptations of this model are evaluated to account for the scatter in isotopic observables. This is done by assuming mixing in ejecta in a supernova event. Stiff EOS are eliminated by this model.« less

Ca, Sr and Ba stable isotopes reveal the fate of soil nutrients along a tropical climosequence

USGS Publications Warehouse

Bullen, Thomas D.; Chadwick, Oliver A.

2016-01-01

Nutrient biolifting is an important pedogenic process in which plant roots obtain inorganic nutrients such as phosphorus (P) and calcium (Ca) from minerals at depth and concentrate those nutrients at the surface. Here we use soil chemistry and stable isotopes of the alkaline earth elements Ca, strontium (Sr) and barium (Ba) to test the hypothesis that biolifting of P has been an important pedogenic process across a soil climosequence developed on volcanic deposits at Kohala Mountain, Hawaii. The geochemical linkage between these elements is revealed as generally positive site-specific relationships in soil mass gains and losses, particularly for P, Ba and Ca, using the ratio of immobile elements titanium and niobium (Ti/Nb) to link individual soil samples to a restricted compositional range of the chemically and isotopically diverse volcanic parent materials. At sites where P is enriched in surface soils relative to abundances in deeper soils, the isotope compositions of exchangeable Ca, Sr and Ba in the shallowest soil horizons (< 10 cm depth) are lighter than those of the volcanic parent materials and trend toward those of plants growing on fresh volcanic deposits. In contrast the isotope composition of exchangeable Ba in deeper soil horizons (> 10 cm depth) at those sites is consistently heavier than the volcanic parent materials. The isotope compositions of exchangeable Ca and Sr trend toward heavier compositions with depth more gradually, reflecting increasing leakiness from these soils in the order Ba < Sr < Ca and downward transfer of light biocycled Ca and Sr to deeper exchange sites. Given the long-term stability of ecosystem properties at the sites where P is enriched in surface soils, a simple box model demonstrates that persistence of isotopically light exchangeable Ca, Sr and Ba in the shallowest soil horizons requires that the uptake flux to plants from those near-surface layers is less than the recycling flux returned to the surface as litterfall. This observation implicates an uptake flux from an additional source which we attribute to biolifting. We view the heavy exchangeable Ba relative to soil parent values in deeper soils at sites where P is enriched in surface soils, and indeed at all but the wettest site across the climosequence, to represent the complement of an isotopically light Ba fraction removed from these soils by plant roots consistent with the biolifting hypothesis. We further suggest that decreasing heaviness of depth-integrated exchangeable Ba in deeper soils with increasing median annual precipitation across the climosequence reflects greater reliance on shallow nutrient sources as site water balance increases. While the Ca, Sr and Ba isotopes considered together were useful in confirming an important role for nutrient biolifting across the climosequence, the Ba isotopes provided the most robust tracer of biolifting and have the greatest potential to find application as an isotopic proxy for P dynamics in soils.

Core-shell-shell heterostructures of α-NaLuF4:Yb/Er@NaLuF4:Yb@MF2 (M = Ca, Sr, Ba) with remarkably enhanced upconversion luminescence.

PubMed

Su, Yue; Liu, Xiuling; Lei, Pengpeng; Xu, Xia; Dong, Lile; Guo, Xianmin; Yan, Xingxu; Wang, Peng; Song, Shuyan; Feng, Jing; Zhang, Hongjie

2016-07-05

Core-shell-shell heterostructures of α-NaLuF4:Yb/Er@NaLuF4:Yb@MF2 (M = Ca, Sr, Ba) have been successfully fabricated via the thermal decomposition method. Upconversion nanoparticles (UCNPs) were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), upconversion luminescence (UCL) spectroscopy, etc. Under 980 nm excitation, the emission intensities of the UCNPs are remarkably enhanced after coating the MF2 (M = Ca, Sr, and Ba) shell. Among these samples, CaF2 coated UCNPs show the strongest overall emission, while BaF2 coated UCNPs exhibit the longest lifetime. These results demonstrate that alkaline earth metal fluorides are ideal materials to improve the UCL properties. Meanwhile, although the lattice mismatch between the ternary NaREF4 core and the binary MF2 (M = Sr and Ba) shell is relatively large, the successfully synthesized NaLuF4:Yb/Er@NaLuF4:Yb@MF2 indicates a new outlook on the fabrication of heterostructural core-shell UCNPs.

Structural studies of the rhombohedral and orthorhombic monouranates: CaUO{sub 4}, α-SrUO{sub 4}, β-SrUO{sub 4} and BaUO{sub 4}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murphy, Gabriel; Kennedy, Brendan J., E-mail: kennedyb@chem.usyd.edu.au; Johannessen, Bernt

The structures of some AUO{sub 4} (A=Ca, Sr, or Ba) oxides have been determined using a combination of neutron and synchrotron X-ray diffraction, supported by X-ray absorption spectroscopic measurements at the U L{sub 3}-edge. The smaller Ca cation favours a rhombohedral AUO{sub 4} structure with 8-coordinate UO{sub 8} moieties whilst an orthorhombic structure based on UO{sub 6} groups is found for BaUO{sub 4}. Both the rhombohedral and orthorhombic structures can be stabilised for SrUO{sub 4}. The structural studies suggest that the bonding requirements of the A site cation play a significant role in determining which structure is favoured. In themore » rhombohedral structure, Bond Valence Sums demonstrate the A site is invariably overbonded, which, in the case of rhombohedral α-SrUO{sub 4}, is compensated for by the formation of vacancies in the oxygen sub-lattice. The uranium cation, with its flexible oxidation state, is able to accommodate this by inducing vacancies along its equatorial coordination site as demonstrated by neutron powder diffraction. - Graphical abstract: Diffraction studies of AUO{sub 4} (A = Ca, Sr, or Ba) oxides reveal the importance of the bonding requirements of the A site cation in determining whether the structure is rhombohedral or orthorhombic. - Highlights: • Structures of AUO{sub 4} ( A = Ca Sr, Ba) refined against X-ray and Neutron diffraction. • The alkali cations size has a dramatic effect on the crystal structure. • Smaller cations favouring a rhombohedral structure. • Oxygen vacancies to stabilise the rhombohedral structure in SrUO{sub 4}.« less

Crystal structure and optical property of complex perovskite oxynitrides ALi0.2Nb0.8O2.8N0.2, ANa0.2Nb0.8O2.8N0.2, and AMg0.2Nb0.8O2.6N0.4 (A = Sr, Ba)

NASA Astrophysics Data System (ADS)

Moon, Keon Ho; Avdeev, Maxim; Kim, Young-Il

2017-10-01

Oxynitride type complex perovskites AM0.2Nb0.8O3-xNx (A = Sr, Ba; M = Li, Na, Mg) were newly synthesized by the solid state diffusion of Li+, Na+, or Mg2+ into the layered oxide, A5Nb4O15, with concurrent O/N substitution. Neutron and synchrotron X-ray Rietveld refinement showed that SrLi0.2Nb0.8O2.8N0.2, SrNa0.2Nb0.8O2.8N0.2, and SrMg0.2Nb0.8O2.6N0.4 had body-centered tetragonal symmetry (I4/mcm), while those with A = Ba had simple cubic symmetry (Pm 3 ̅ m). In the tetragonal Sr-compounds, the nitrogen atoms were localized on the c-axial 4a site. However, the octahedral cations, M/Nb (M = Li, Na, Mg) were distributed randomly in all six compounds. The lattice volume of AM0.2Nb0.8O3-xNx was dependent on various factors including the type of A and the electronegativity of M. Compared to the simple perovskites, ANbO2N (A = Sr, Ba), AM0.2Nb0.8O3-xNx had wider band gaps (1.76-2.15 eV for A = Sr and 1.65-2.10 eV for A = Ba), but significantly lower sub-gap absorption.

The effect of oxidant on resputtering of Bi from Bi-Sr-Ca-Cu-O films

NASA Astrophysics Data System (ADS)

Grace, J. M.; McDonald, D. B.; Reiten, M. T.; Olson, J.; Kampwirth, R. T.; Gray, K. E.

1991-09-01

The type and partial pressure of oxidant mixed with argon can affect the selective resputtering of Bi in composite-target, magnetron-sputtered Bi-Sr-Ca-Cu-O films. Comparative studies using oxygen and ozone show that ozone is a more potent oxidant, as well as a more potent source of resputterers, than is oxygen. Severe resputtering from ozone is significantly reduced by a -40 V potential on the sample block. We suggest that oxygen causes resputtering by forming O2(+)p , which interacts with the target to produce energetic O(-). In contrast, ozone may form lower-energy O(-) by electron impact in the dark space. Negative oxygen ions from the target itself may be responsible for a background resputtering effect. Our results and those found for Y-Ba-Cu-O by others are comparable. Bi in Bi-Sr-Ca-Cu-O behaves as Ba in Y-Ba-Cu-O, with regard to selective resputtering; furthermore, the response of Sr, Ca, and Cu to oxygen in sputtered Bi-Sr-Ca-Cu-O is similar to what is observed for Cu in Y-Ba-Cu-O.

Interplay between magnetism and relativistic fermions in Eu doped (Sr/Ba)MnSb2

NASA Astrophysics Data System (ADS)

Liu, Jinyu; Hu, Jin; Zhu, Yanglin; Chuang, Alyssa; Graf, David; Jaime, Marcelo; Balakirev, Fedor; Weickert, Franziska; Zhang, Qiang; Ditusa, John; Wu, Yan; Cao, Huibo; Mao, Zhiqiang

Layered compounds AMnBi2 (A =Ca, Sr, Ba, Eu, and Yb) have been established as Dirac materials with fascinating properties. In our previous work, we have demonstrated that Sr1-y Mn1-z Sb2 (y, z <0.1), isostructural to AMnBi2, not only host relativistic fermions, but also exhibit ferromagnetic properties, with its ferromagnetism being coupled to the relativistic fermions' transport. To gain further insight into the relativistic fermion-magnetism coupling, we have synthesized a series of Eu doped (Sr/Ba)MnSb2 single crystals and found Eu moments order antiferromagnetically. Through neutron scattering experiments, we determined the magnetic structures for Sr1-xEuxMnSb2 with x = 0.2, 0.5, and 0.8. From magnetotransport measurements, we find the Eu antiferromagnetism is also coupled to relativistic fermion transport. More importantly, we observed a novel quantum phase with saturated magnetoresistivity near the quantum limit for the 10% Eu doped BaMnSb2 sample. We will discuss possible mechanisms for this novel phase.

Optoelectronic Properties of Strontium and Barium Copper Sulfides Prepared by Combinatorial Sputtering

DOE PAGES

Han, Yanbing; Siol, Sebastian; Zhang, Qun; ...

2017-09-27

Optically transparent materials with p-type electrical conductivity can facilitate the development of transparent electronics and improve the efficiency of photovoltaic solar cells. Sulfide materials represent an interesting alternative to oxides for these applications due to better hole transport properties. We prepare transparent and conductive Ba-Cu-S thin films by combinatorial cosputtering and characterized for their composition, structure, and optoelectronic properties. The conductivity and transparency of these films are found to be strongly dependent on their chemical composition and the substrate temperature during growth. The conductivity of BaCu 2S 2 and BaCu 4S 3 can reach 53 S/cm (at 250 °C) andmore » 74 S/cm (at 200 degrees C), respectively, which is higher than their solution processed/bulk counterparts. The 90% reflectance corrected transmittance is achieved in the wavelength range 600-1000 nm for BaCu 2S 2 and 650-1000 nm for BaCu 4S 3 (at 250 °C). These electrical and optical properties are comparable with other recently presented transparent p-type conductors, while the 200-350 degrees C processing temperature is low enough to be used in semiconductor devices with limited thermal budgets. Some attempts have been made to synthesize the related Sr-Cu-S materials, following the theoretical suggestion of their potential as transparent p-type conductors, but these attempts resulted only in phase-separated SrS and CuxS phases. Alloying BaCu 2S 2 with Sr on the Ba site on the other hand increases the conductivity to >100 S/cm while only slightly compromising the transparency of the material. To explain the difference between the Ba and the Sr containing copper sulfides, the lower bounds on the SrCu 2S 2 and SrCu 4S 3 formation enthalpies are estimated. While the doping of the Ba-Cu-S materials presented here is too large for application in transparent electronics, it is promising for potential use as p-type contact layers in thin film solar cells.« less

Records of River Variation in the Shells of Freshwater Bivalves

NASA Astrophysics Data System (ADS)

Carroll, M.; Romanek, C.

2005-12-01

The skeletons of hard-shelled invertebrates such as corals and bivalves are commonly used in marine settings as archives of environmental information. They are less commonly used in freshwater settings where variability in water chemistry makes it more difficult to calibrate chemical proxies such as the Sr:Ca in a shell. Our objective is to evaluate whether trace element concentrations in freshwater bivalve shells contain information on environmental conditions. Multiple elements (Ba, Cu, Mn and Sr) were analyzed within the shells of modern bivalves from four streams on DOE's Savannah River Site in S.C. Laser Ablation ICP-MS was used to measure elemental concentrations across five aragonitic shells from each site. These elements were chosen because they are present in detectable concentrations (ppm) in the shell and they have been suggested as useful proxies for temperature, rainfall, productivity and pollution. Results were compared to historical monthly site records of water chemistry and chemical analyses of water samples collected from the streams where the clams were found. The average shell concentrations of Sr and Mn were significantly different between sites and increased proportionally to water concentration. This was not observed for Ba and Cu. For example, the Ba concentrations of shells collected at a site downstream of a lake were higher than those for shells from stream sites with significantly higher dissolved Ba concentrations. Copper was only detected at dark growth lines with the number of lines and shell material between them varying between shells within the same stream. Intrashell profiles of Ba, Sr and Mn concentrations exhibited cyclical variation. The magnitude of cyclical variation for Mn and Sr within a shell corresponds with the annual variation in monthly water sample concentrations. Again, this pattern was not observed for Ba, especially in shells from the site downstream of a lake. This supports suggestions that particulate organic matter, to which Ba preferentially partitions, plays a role in bivalve Ba uptake. Finally, variations in Ba, Cu, Mn and Sr profiles across shells are not in unison. The individual elemental responses to biological and physicochemical effects suggest that the elemental records in freshwater bivalve shells can be interpreted as environmental proxies.

Optoelectronic Properties of Strontium and Barium Copper Sulfides Prepared by Combinatorial Sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, Yanbing; Siol, Sebastian; Zhang, Qun

Optically transparent materials with p-type electrical conductivity can facilitate the development of transparent electronics and improve the efficiency of photovoltaic solar cells. Sulfide materials represent an interesting alternative to oxides for these applications due to better hole transport properties. We prepare transparent and conductive Ba-Cu-S thin films by combinatorial cosputtering and characterized for their composition, structure, and optoelectronic properties. The conductivity and transparency of these films are found to be strongly dependent on their chemical composition and the substrate temperature during growth. The conductivity of BaCu 2S 2 and BaCu 4S 3 can reach 53 S/cm (at 250 °C) andmore » 74 S/cm (at 200 degrees C), respectively, which is higher than their solution processed/bulk counterparts. The 90% reflectance corrected transmittance is achieved in the wavelength range 600-1000 nm for BaCu 2S 2 and 650-1000 nm for BaCu 4S 3 (at 250 °C). These electrical and optical properties are comparable with other recently presented transparent p-type conductors, while the 200-350 degrees C processing temperature is low enough to be used in semiconductor devices with limited thermal budgets. Some attempts have been made to synthesize the related Sr-Cu-S materials, following the theoretical suggestion of their potential as transparent p-type conductors, but these attempts resulted only in phase-separated SrS and CuxS phases. Alloying BaCu 2S 2 with Sr on the Ba site on the other hand increases the conductivity to >100 S/cm while only slightly compromising the transparency of the material. To explain the difference between the Ba and the Sr containing copper sulfides, the lower bounds on the SrCu 2S 2 and SrCu 4S 3 formation enthalpies are estimated. While the doping of the Ba-Cu-S materials presented here is too large for application in transparent electronics, it is promising for potential use as p-type contact layers in thin film solar cells.« less

Functionalized inorganic membranes for gas separation

DOEpatents

Ku, Anthony Yu-Chung [Rexford, NY; Ruud, James Anthony [Delmar, NY; Molaison, Jennifer Lynn [Marietta, GA; Schick, Louis Andrew ,; Ramaswamy, Vidya [Niskayuna, NY

2008-07-08

A porous membrane for separation of carbon dioxide from a fluid stream at a temperature higher than about 200.degree. C. with selectivity higher than Knudsen diffusion selectivity. The porous membrane comprises a porous support layer comprising alumina, silica, zirconia or stabilized zirconia; a porous separation layer comprising alumina, silica, zirconia or stabilized zirconia, and a functional layer comprising a ceramic oxide contactable with the fluid stream to preferentially transport carbon dioxide. In particular, the functional layer may be MgO, CaO, SrO, BaO, La.sub.2O.sub.3, CeO.sub.2, ATiO.sub.3, AZrO.sub.3, AAl.sub.2O.sub.4, A.sup.1FeO.sub.3, A.sup.1MnO.sub.3, A.sup.1CoO.sub.3, A.sup.1NiO.sub.3, A.sup.2HfO.sub.3, A.sup.3CeO.sub.3, Li.sub.2ZrO.sub.3, Li.sub.2SiO.sub.3, Li.sub.2TiO.sub.3 or a mixture thereof; wherein A is Mg, Ca, Sr or Ba; A.sup.1 is La, Ca, Sr or Ba; A.sup.2 is Ca, Sr or Ba; and A.sup.3 is Sr or Ba.

Physical and magnetic properties of (Ba/Sr) substituted magnesium nano ferrites

NASA Astrophysics Data System (ADS)

Ateia, Ebtesam E.; Takla, E.; Mohamed, Amira T.

2017-10-01

In the presented paper, strontium (Sr) and barium (Ba) nano ferrites were synthesized by citrate auto combustion method. The investigated samples are characterized by X-ray diffraction technique (XRD), field emission scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy. The structural properties of the obtained samples were examined by XRD analysis showing that the synthesized nanoparticles are in cubic spinel structure. The average crystallite sizes are in the range of 22.66 and 21.95 nm for Mg0.7Ba0.3Fe2O4 and Mg0.7 Sr0.3Fe2O4 respectively. The VSM analysis confirms the existence of ferromagnetic nature of Sr2+/Ba2+ substituted magnesium nano particles. Exchange interaction between hard (Sr/Ba) and soft (Mg) magnetic phases improves the structural and magnetic properties of nano ferrite particles. Rigidity modulus, longitudinal and shear wave velocities are predicted theoretically from Raman spectroscopy and structural data of the investigated spinel ferrite. The magnetic and structural properties of magnesium are enhanced by doping with barium and strontium nano particles. The saturation magnetization, remanent magnetization and coercivity reported on vibrating sample magnetometer curve illustrate the promising industrial and magnetic recording applications of the prepared samples.

Nonstoichiometry in inorganic fluorides: I. Nonstoichiometry in MF{sub m}-RF{sub n} (m < n {<=} 4) systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobolev, B. P., E-mail: sobolevb@yandex.ru

The manifestation of gross nonstoichiometry in MF{sub m}-RF{sub n} systems (m < n {<=} 4) has been studied. Fluorides of 34 elements, in the systems of which phases of practical interest are formed, are chosen. To search for new phases of complex composition, a program for studying the phase diagrams of the condensed state ({approx}200 systems) has been carried out at the Institute of Crystallography, Russian Academy of Sciences. The main products of high-temperature interactions of the fluorides of elements with different valences (m {ne} n) are grossly nonstoichiometric phases of two structural types: fluorite (CaF{sub 2}) and tysonite (LaF{submore » 3}). Systems of fluorides of 27 elements (M{sup 1+} = Na, K; M{sup 2+} = Ca, Sr, Ba, Cd, Pb; R{sup 3+} = Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; R{sup 4+} = Zr, Hf, Th, U) are selected; nonstoichiometric M{sub 1-x}R{sub x}F{sub m(1-x)+nx} phases, which are of greatest practical interest, are formed in these systems. The gross nonstoichiometry in inorganic fluorides is most pronounced in 80 MF{sub 2} - RF{sub 3} systems (M = Ca, Sr, Ba, Cd, Pb; R are rare earth elements). The problems related to the growth of single crystals of nonstoichiometric phases and basic fields of their application as new fluoride multicomponent materials, the properties of which are controlled by the defect structure, are considered.« less

Metal concentrations in aquatic environments of Puebla River basin, Mexico: natural and industrial influences.

PubMed

Morales-García, S S; Rodríguez-Espinosa, P F; Shruti, V C; Jonathan, M P; Martínez-Tavera, E

2017-01-01

The rapid urban expansion and presence of volcanoes in the premises of Puebla River basin in central Mexico exert significant influences over its aquatic environments. Twenty surface sediment samples from Puebla River basin consisting of R. Alseseca, R. Atoyac, and Valsequillo dam were collected during September 2009 and analyzed for major (Al, Fe, Mg, Ba, Ca, and K) and trace elements (As, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, V, and Zn) in order to identify the metal concentrations and their enrichment. R. Atoyac sediments presented higher concentrations of Ba (1193.8 μg g -1 ) and Pb (27.1 μg g -1 ) in comparison with the local reference sample values. All the metal concentrations except Sr for R. Alseseca sediments were within the range of local reference sample values indicating no significant external influence, whereas Valsequillo dam sediments had elevated concentrations of all the metals suggesting both natural and external influences in the study region. The magnitude of metal contamination was assessed using several indices such as geoaccumulation index (I geo ), enrichment factor (EF), degree of contamination (C d ), and pollution load index (PLI). The results suggest that As, Pb, and Zn were predominantly enriched in the Puebla River basin sediments. Comparing with sediment quality guidelines and ecotoxicological values, it is revealed that Cd, Cr, Cu, and Ni have possible harmful effects on the biological community. The present study provides an outlook of metal enrichment in Puebla River basin sediments, highlighting the necessity to conserve this river ecosystem for the near future.

Effect of divalent Ba cation substitution with Sr on coupled ‘multiglass’ state in the magnetoelectric multiferroic compound Ba3NbFe3Si2O14

PubMed Central

Rathore, Satyapal Singh; Vitta, Satish

2015-01-01

(Ba/Sr)3NbFe3Si2O14 is a magneto-electric multiferroic with an incommensurate antiferromagnetic spiral magnetic structure which induces electric polarization at 26 K. Structural studies show that both the compounds have similar crystal structure down to 6 K. They exhibit a transition, TN at 26 K and 25 K respectively, as indicated by heat capacity and magnetization, into an antiferromagnetic state. Although Ba and Sr are isovalent, they exhibit very different static and dynamic magnetic behaviors. The Ba-compound exhibits a glassy behavior with critical slowing dynamics with a freezing temperature of ~35 K and a critical exponent of 3.9, a value close to the 3-D Ising model above TN, in addition to the invariant transition into an antiferromagnetic state. The Sr-compound however does not exhibit any dispersive behavior except for the invariant transition at TN. The dielectric constant reflects magnetic behavior of the two compounds: the Ba-compound has two distinct dispersive peaks while the Sr-compound has a single dispersive peak. Thus the compounds exhibit coupled ‘multiglass’ behavior. The difference in magnetic properties between the two compounds is found to be due to modifications to super exchange path angle and length as well as anti-site defects which stabilize either ferromagnetic or antiferromagnetic interactions. PMID:25988657

Chemical composition and some trace element contents in coals and coal ash from Tamnava-Zapadno Polje Coal Field, Serbia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vukasinovic-Pesic, V.; Rajakovic, L.J.

2009-07-01

The chemical compositions and trace element contents (Zn, Cu, Co, Cr, Ni, Pb, Cd, As, B, Hg, Sr, Se, Be, Ba, Mn, Th, V, U) in coal and coal ash samples from Tamnava-Zapadno Polje coal field in Serbia were studied. The coal from this field belongs to lignite. This high volatility coal has high moisture and low S contents, moderate ash yield, and high calorific value. The coal ash is abundant in alumosilicates. Many trace elements such as Ni > Cd > Cr > B > As > Cu > Co > Pb > V > Zn > Mn inmore » the coal and Ni > Cr > As > B > Cu > Co = Pb > V > Zn > Mn in the coal ash are enriched in comparison with Clarke concentrations.« less

Structural trends for celestite (SrSO[subscript 4]), anglesite (PbSO[subscript 4]), and barite (BaSO[subscript 4]): Confirmation of expected variations within the SO[subscript 4] groups

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antao, Sytle M.

2012-05-10

The crystal structures of the isostructural orthorhombic sulfates celestite (SrSO{sub 4}), anglesite (PbSO{sub 4}), and barite (BaSO{sub 4}) were refined by Rietveld methods using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. Their structural model was refined in space group Pbnm. The unit-cell parameters are a = 6.87032(3), b = 8.36030(5), c = 5.34732(1) {angstrom}, and V = 307.139(3) {angstrom}{sup 3} for SrSO{sub 4}; a = 6.95802(1), b = 8.48024(3), c = 5.39754(1) {angstrom}, and V = 318.486(1) {angstrom}{sup 3} for PbSO{sub 4}; and a = 7.15505(1), b = 8.88101(3), c = 5.45447(1) {angstrom}, and V = 346.599(1) {angstrom}{sup 3} formore » BaSO{sub 4}. The average [12] distances are 2.827(1), 2.865(1), and 2.953(1) {angstrom} for SrSO{sub 4}, PbSO{sub 4}, and BaSO{sub 4}, respectively, and their corresponding average [4] distances are 1.480(1), 1.477(3), and 1.471(1) {angstrom}. The geometrical features of the SO{sub 4} and MO{sub 12} polyhedra become more symmetrical from SrSO{sub 4} to BaSO{sub 4}. Across the series, the a, b, and c parameters vary non-linearly with increasing V. The radii of the M{sup 2+} cations, rM, [12], and [4] distances vary linearly with V. These structural trends arise from the effective size of the M{sup 2+} cation (rM: Sr < Pb < Ba) that is coordinated to 12 O atoms.« less

Dissolved Strontium and Barium in Fresh and Saltwater: a 2-year Study in the Calcasieu River to the Gulf of Mexico

NASA Astrophysics Data System (ADS)

He, S.; Xu, Y. J.

2016-02-01

Strontium and barium to calcium ratios are often used as proxies for tracking animal movement across salinity gradients. As sea level rise continues, many estuarine rivers face saltwater intrusion, which may cause changes in mobility and distribution of these metals upstream. Despite intensive research on metal adsorption and desorption in marine systems, knowledge of the spatiotemporal distribution of these elements along estuarine rivers is still limited. In this study, we conducted an intensive monitoring of Sr and Ba dynamics along an 88-km long estuary, the Calcasieu River, which has been strongly affected by saltwater intrusion. Over the period from May 2013 to July 2015, we collected monthly water samples and performed in-situ water quality measurements at six sites from the upstream to the river mouth. Water samples were analyzed for dissolved Sr, Ba, and Ca concentrations. In-situ measurements of salinity, pH, water temperature, dissolved oxygen concentration, and specific conductance were taken. Our preliminary data showed that the Sr and Ca concentrations and the Sr/Ca ratio all increased significantly with decreasing distance to the Gulf of Mexico, while the Ba/Ca ratio decreased with decreasing distance to the Gulf. The spatial variation in Ba concentration was marginal. The Sr and Ca concentrations and ratios were positively related to salinity, while Ba/Ca was negatively related to salinity. All the elemental concentrations and ratios had considerable seasonal and interannual variations. There were significant differences among sampling months for all the elemental concentrations and ratios (p<0.05), and there were significant differences among sampling years for the Sr and Ca concentrations and the Ba/Ca ratio (p<0.05).

Theoretical and experimental studies on wide-band-gap p-type conductive BaCuSeF and related compounds

NASA Astrophysics Data System (ADS)

Sakakima, Hiroshi; Nishitani, Mikihiko; Yamamoto, Koichi; Wada, Takahiro

2015-08-01

BaCuSeF and related compounds, MCuQF (M = Ba, Sr; Q = Se, S), are known to show p-type conduction. The formation energies of the Cu vacancy ΔH[VCu] in a MCuQF system were computed by first-principles calculation with a generalized gradient approximation (GGA) of the Perdew-Burke-Ernzerhof (PBE) functional as an electron exchange and correlation functional. The density of states (DOS) of BaCuSeF was calculated with the hybrid functional of Heyd-Scuseria-Ernzerhof (HSE) 06. ΔH[VCu] was found to be very small under both the Cu- and Q-rich conditions, which probably contributes to p-type conduction. The electronic structure of BaCuSeF was studied by X-ray photoelectron spectroscopy (XPS) with UV photoelectron yield spectroscopy (UVPYS) and photoemission yield spectroscopy (PYS). The determined depth of the top of the valence band relative to the vacuum level was about 4.9 eV. This value is desirable for applications in compound semiconductor thin-film tandem solar cells since the absorbers of polycrystalline thin-film solar cells, such as CdTe and Cu(In,Ga)Se2, are p-type semiconductors. The DOS of BaCuSeF calculated with the HSE06 functional was almost consistent with the XPS spectrum.

Splicing factor SR34b mutation reduces cadmium tolerance in Arabidopsis by regulating iron-regulated transporter 1 gene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Wentao; Du, Bojing; Liu, Di

Highlights: • Arabidopsis splicing factor SR34b gene is cadmium-inducible. • SR34b T-DNA insertion mutant is sensitive to cadmium due to high cadmium uptake. • SR34b is a regulator of cadmium transporter IRT1 at the posttranscription level. • These results highlight the roles of splicing factors in cadmium tolerance of plant. - Abstract: Serine/arginine-rich (SR) proteins are important splicing factors. However, the biological functions of plant SR proteins remain unclear especially in abiotic stresses. Cadmium (Cd) is a non-essential element that negatively affects plant growth and development. In this study, we provided clear evidence for SR gene involved in Cd tolerancemore » in planta. Systemic expression analysis of 17 Arabidopsis SR genes revealed that SR34b is the only SR gene upregulated by Cd, suggesting its potential roles in Arabidopsis Cd tolerance. Consistent with this, a SR34b T-DNA insertion mutant (sr34b) was moderately sensitive to Cd, which had higher Cd{sup 2+} uptake rate and accumulated Cd in greater amounts than wild-type. This was due to the altered expression of iron-regulated transporter 1 (IRT1) gene in sr34b mutant. Under normal growth conditions, IRT1 mRNAs highly accumulated in sr34b mutant, which was a result of increased stability of IRT1 mRNA. Under Cd stress, however, sr34b mutant plants had a splicing defect in IRT1 gene, thus reducing the IRT1 mRNA accumulation. Despite of this, sr34b mutant plants still constitutively expressed IRT1 proteins under Cd stress, thereby resulting in Cd stress-sensitive phenotype. We therefore propose the essential roles of SR34b in posttranscriptional regulation of IRT1 expression and identify it as a regulator of Arabidopsis Cd tolerance.« less

Dielectric Properties of Sol-Gel Derived Barium Strontium Titanate and Microwave Sintering of Ceramics

NASA Astrophysics Data System (ADS)

Selmi, Fathi A.

This thesis consists of two areas of research: (1) sol-gel processing of Ba_{rm 1-x}Sr_{rm x} TiO_3 ceramics and their dielectric properties measurement; and (2) microwave versus conventional sintering of ceramics such as Al_2 O_3, Ba_{ rm 1-x}Sr_{rm x}TiO_3, Sb-doped SnO _2 and YBa_2Cu _3O_7. Sol-gel powders of BaTiO_3, SrTiO_3, and their solid solutions were synthesized by the hydrolysis of titanium isopropoxide and Ba and Sr methoxyethoxides. The loss tangent and dielectric constant of both sol-gel and conventionally prepared and sintered Ba_{rm 1-x}Sr _{rm x}TiO _3 ceramics were investigated at high frequencies. The sol-gel prepared ceramics showed higher dielectric constant and lower loss compared to those prepared conventionally. Ba _{rm 1-x}Sr _{rm x}TiO_3 ceramics were tunable with applied bias, indicating the potential use of this material for phase shifter applications. Porous Ba_{0.65}Sr _{0.35}TiO_3 was also investigated to lower the dielectric constant. Microwave sintering of alpha -Al_2O_3 and SrTiO_3 was investigated using an ordinary kitchen microwave oven (2.45 GHz; 600 Watts). The use of microwaves with good insulation of alpha -Al_2O_3 and SrTiO_3 samples resulted in their rapid sintering with good final densities of 96 and 98% of the theoretical density, respectively. A comparison of grain size for conventionally and microwave sintered SrTiO_3 samples did not show a noticeable difference. However, the grain size of microwave sintered alpha-Al_2O _3 was found to be larger than that of conventionally sintered sample. These results show that rapid sintering of ceramics can be achieved by using microwave radiation. The sintering behavior of coprecipitated Sb-doped SnO_2 was investigated using microwave power absorption. With microwave power, samples were sintered at 1450^circC for 20 minutes and showed a density as high as 99.9% of theoretical. However, samples fired in a conventional electric furnace at the same temperature for 4 hours showed only 60% of theoretical density. Microwave sintering also led to improvement in terms of uniform structure and electrical properties. Ba_{0.65}Sr _{0.35}TiO_3 was sintered using the microwave power at 1300 ^circC for 10 minutes. A density of 99% was achieved with small and uniform grain size. Superconducting powders have been successfully prepared by the sol-gel process and sintered and annealed using microwave power. Sintering and densification was achieved in a shorter time with microwave heating than with conventional heating and microwave heating appears to result in refined microstructure.

Non-linear second harmonic generation (SHG) studies of BaTiO3/SrTiO3 superlattices

NASA Astrophysics Data System (ADS)

Vlahos, Eftihia; Lee, Che-Hui; Wu, Pingping; Wung Bark, Chung; Jang, Ho Won; Folkman, Chad; Hyub Baek, Seung; Park, J. W.; Biegalski, Mike; Tenne, Dmitri; Schlom, Darrell; Chen, Long-Qing; Eom, Chang-Beom; Gopalan, Venkatraman

2010-03-01

Theoretical phase-field simulations predict that certain types of superlattices consisting of alternating (BaTiO3)n/(SrTiO3)n layers have novel vortex domain wall configurations which give rise to exceptionally high polarization tunability combined with negligible polarization hysteresis. Optical second harmonic generation (SHG) was used to probe the phase and transition temperatures of multilayer (BaTiO3)m/(SrTiO3)n superlattices, as a function of epitaxial strain. In addition, in-plane electro-optic measurements were carried out. The experimental results are in excellent agreement both with theoretical predictions, as well as the temperature-strain phase diagram obtained experimentally from UV Raman studies. The ferroelectric, in-plane SHG signal, from the tensile strained SrTiO3 layers reveals an mm2 point group symmetry, whereas the point group symmetry of the compressively strained BaTiO3 layers, was determined to be 4mm.

Absorption spectroscopy of heavy alkaline earth metals Ba and Sr in rare gas matrices—CCSD(T) calculations and atomic site occupancies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, Barry M.; McCaffrey, John G., E-mail: john.mccaffrey@nuim.ie

2016-01-28

Isolation of the heavier alkaline earth metals Ba and Sr in the solid rare gases (RGs) Ar, Kr, and Xe is analysed with absorption spectroscopy and interpreted partly with the assistance of ab initio calculations of the diatomic M ⋅ RG ground state interaction potentials. The y{sup 1}P←a{sup 1}S resonance transitions in the visible spectral region are used to compare the isolation conditions of these two metal atom systems and calcium. Complex absorption bands were recorded in all three metal atom systems even after extensive sample annealing. Coupled cluster calculations conducted on the ground states of the nine M ⋅more » RG diatomics (M = Ca, Sr, and Ba; RG = Ar, Kr, and Xe) at the coupled cluster single, double, and non-iterative triple level of theory revealed long bond lengths (>5 Å) and shallow bound regions (<130 cm{sup −1}). All of the M ⋅ RG diatomics have bond lengths considerably longer than those of the rare gas dimers, with the consequence that isolation of these metal atoms in a single substitutional site of the solid rare gas is unlikely, with the possible exception of Ca/Xe. The luminescence of metal dimer bands has been recorded for Ba and Sr revealing very different behaviours. Resonance fluorescence with a lifetime of 15 ns is observed for the lowest energy transition of Sr{sub 2} while this transition is quenched in Ba{sub 2}. This behaviour is consistent with the absence of vibrational structure on the dimer absorption band in Ba{sub 2} indicating lifetime broadening arising from efficient relaxation to low-lying molecular states. More extensive 2D excitation-emission data recorded for the complex site structures present on the absorption bands of the atomic Ba and Sr systems will be presented in future publications.« less

Method of forming a dielectric thin film having low loss composition of Ba.sub.x Sr.sub.y Ca.sub.1-x-y TiO.sub.3 : Ba.sub.0.12-0.25 Sr.sub.0.35-0.47 Ca.sub.0.32-0.53 TiO.sub.3

DOEpatents

Xiang, Xiao-Dong; Chang, Hauyee; Takeuchi, Ichiro

2000-01-01

A dielectric thin-film material for microwave applications, including use as a capacitor, the thin-film comprising a composition of barium strontium calcium and titanium of perovskite type (Ba.sub.x Sr.sub.y Ca.sub.1-x-y)TiO.sub.3. Also provided is a method for making a dielectric thin film of that formula over a wide compositional range through a single deposition process.

Multi-elemental analysis of Lentinula edodes mushrooms available in trade.

PubMed

Mleczek, Mirosław; Siwulski, Marek; Rzymski, Piotr; Niedzielski, Przemysław; Gąsecka, Monika; Jasińska, Agnieszka; Budzyńska, Sylwia; Budka, Anna

2017-03-04

The present study investigated the content of 62 elements in the fruiting bodies of Lentinula edodes (Shiitake mushroom) cultivated commercially in Poland on various substrates from 2007-2015. The general mean content (mg kg -1 dry weight (DW)) of the studied elements ranked in the following order: K (26,335) > P (11,015) > Mg (2,284) > Ca (607) > Na (131) > Zn (112) > Fe (69) > Mn (33) > B (32) > Rb (17) > Cu (14.5) > Al (11.2) > Te (2.9) > As (1.80) > Cd (1.76) > Ag (1.73) > Nd (1.70) > Sr (1.46) > Se (1.41) > U (1.11) > Pt (0.90) > Ce (0.80) > Ba (0.61) > Co (0.59) > Tl (0.58) > Er (0.50) > Pb (0.42) > Li (0.40) > Pr (0.39) > Ir (0.37) > In (0.35) > Mo (0.31) > Cr (0.29) > Ni (0.28) > Sb (0.26) > Re (0.24) > Ti (0.19) > Bi (0.18) > Th (0.12) > La (0.10) = Pd (0.10) > Os (0.09) = Zr (0.09) > Rh (0.08) > Ho (0.07) > Ru (0.06) > Sm (0.04) = Eu (0.04) = Tm (0.04) > Gd (0.03) > Sc (0.02) = Y (0.02) > Lu (0.01) = Yb (0.01) = V (0.01). The contents of Au, Be, Dy, Ga, Ge, Hf, and Tb were below the limits of detection (0.02, 0.02, 0.01, 0.01, 0.01, 0.01, 0.02 mg kg -1 respectively). The concentrations of Al, As, B, Ba, Ca, Cd, Cr, Er, Fe, In, Lu, Mn, Nd, Sr, Ti, Tm, and Zr were comparable over the period the mushrooms were cultivated. The study revealed that Lentinula edodes contained As and Cd at levels potentially adverse to human health. This highlights the need to monitor these elements in food products obtained from this mushroom species and ensure that only low levels of these elements are present in cultivation substrates.

The circumvention of the natural biopurification of calcium along nutrient pathways by atmospheric inputs of industrial lead

NASA Astrophysics Data System (ADS)

Elias, Robert W.; Hirao, Yoshimitsu; Patterson, Clair C.

1982-12-01

Biopurification factors for Ca with respect to Sr, Ba, and natural, uncontaminated Pb were measured for different nutrient-consumer pairs in a remote subalpine ecosystem. The factor for Sr is expressed as: (nutrient Sr/Ca) ÷ (consumer Sr/Ca). Similar expressions were used for Ba/Ca and Pb/Ca. It was found that Ca was biopurified of Sr 3-fold, of Ba 16-fold, and of Pb 100-fold in going from rock to sedge leaves. In going from sedge leaf to vole, Ca was biopurified of Sr 4-fold, of Ba 8-fold, and of Pb 16-fold. In going from meadow vole to pine marten, Ca was biopurified of Sr 6-fold, of Ba 7-fold, and of Pb 1.1-fold. Similar ranges of values for these factors were obtained for detrital and amphibian food chains. Fluxes of industrial lead entering the ecosystem as precipitation and dry deposition were measured and it was found that 40% of the lead in soil humus and soil moisture, 82% of the lead in sedge leaves, 92% of the lead in vole, and 97% of the lead in marten was industrial. The natural skeletal Pb/Ca ratio in carnivores (4 × 10 -8) was determined by means of corrections for inputs of industrial lead, food chain relationships, and measured biopurification factors for the ecosystem studied. This represents a 1700-fold reduction of the average Pb/Ca ratio in igneous rocks at the earth's surface (6.4 × 10 -5) by the compounding of successive Pb biopurification factors in transferring Ca from rock to carnivore. The natural ratio is similar to the value of 6 × 10 -8 observed for Pb/Ca in the bones of Peruvians who lived 2000 years ago but is 1/900th of the value of about 3.5 × 10 -5 for the skeletal Pb/Ca ratio found in present day Americans. This study shows experimentally how the Ba/Ca ratio in average surface igneous rock (3 × 10 -3) has been reduced 800-fold through compounding of successive biopurification steps to provide the skeletal Ba/Ca ratio of about 4 × 10 -6 observed in humans. It also provides biopurification factors for Sr and Ba among a number of nutrient-consumer pairs which anthropologists can use to delineate degrees of herbivory in diets of hominids within the last 10,000 years.

Explaining the Ba, Y, Sr, and Eu abundance scatter in metal-poor halo stars: constraints to the r-process

NASA Astrophysics Data System (ADS)

Cescutti, G.; Chiappini, C.

2014-05-01

Context. Thanks to the heroic observational campaigns carried out in recent years we now have large samples of metal-poor stars for which measurements of detailed abundances exist. In particular, large samples of stars with metallicities -5 < [Fe/H] <-1 and measured abundances of Sr, Ba, Y, and Eu are now available. These data hold important clues on the nature of the contribution of the first stellar generations to the enrichment of our Galaxy. Aims: We aim to explain the scatter in Sr, Ba, Y, and Eu abundance ratio diagrams unveiled by the metal-poor halo stars. Methods: We computed inhomogeneous chemical evolution models for the Galactic halo assuming different scenarios for the r-process site: the electron-capture (EC) supernovae and the magnetorotationally driven (MRD) supernovae scenarios. We also considered models with and without the contribution of fast-rotating massive stars (spinstars) to an early enrichment by the s-process. A detailed comparison with the now large sample of stars with measured abundances of Sr, Ba, Y, Eu, and Fe is provided (both in terms of scatter plots and number distributions for several abundance ratios). Results: The scatter observed in these abundance ratios of the very metal-poor stars (with [Fe/H] <-2.5) can be explained by combining the s-process production in spinstars, and the r-process contribution coming from massive stars. For the r-process we have developed models for both the EC and the MRD scenarios that match the observations. Conclusions: With the present observational and theoretical constraints we cannot distinguish between the EC and the MRD scenarios in the Galactic halo. Independently of the r-process scenarios adopted, the production of elements by an s-process in spinstars is needed to reproduce the spread in abundances of the light neutron capture elements (Sr and Y) over heavy neutron capture elements (Ba and Eu). We provide a way to test our suggestions by means of the distribution of the Ba isotopic ratios in a [Ba/Fe] or [Sr/Ba] vs. [Fe/H] diagram. Appendix A is available in electronic form at http://www.aanda.org

On the photo-luminescence properties of sol–gel derived undoped and Dy{sup 3+} ion doped nanocrystalline Scheelite type AMoO{sub 4} (A = Ca, Sr and Ba)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jena, Paramananda; Gupta, Santosh K., E-mail: santufrnd@gmail.com; Natarajan, V.

2015-04-15

Nanocrystalline Scheelite type Dy doped AMoO{sub 4} [where A = Ba, Sr and Ca] samples were prepared by acrylamide assisted sol–gel process and characterized by XRD, FT-Raman, FTIR, SEM and photoluminescence (PL). PL of undoped sample shows blue/green emission in CaMoO{sub 4} and SrMoO{sub 4} but multicolour visible emission leading to near white light in BaMoO{sub 4} nanoparticles; the origin of which is explained. It was observed that on doping 0.5 mol% of Dy{sup 3+} in molybdate samples complete energy transfer takes place in case of SrMoO{sub 4} and BaMoO{sub 4}, but host contributed substantially in Dy doped BaMoO{sub 4}more » sample, resulting in biexponential decay. It was also observed that symmetry around Dy{sup 3+} decreases as the size of alkaline earth ion increases. Due to combined blue, yellow and red colour emission in dysprosium doped sample; all samples showed near white light emission under UV and near UV excitation.« less

Ae2Sb2X4F2 (Ae = Sr, Ba): new members of the homologous series Ae2M(1+n)X(3+n)F2 designed from rock salt and fluorite 2D building blocks.

PubMed

Kabbour, Houria; Cario, Laurent

2006-03-20

We have designed new compounds within the homologous series Ae2F2M(1+n)X(3+n) (Ae = Sr, Ba; M = main group metal; n = integer) built up from the stacking of 2D building blocks of rock salt and fluorite types. By incrementally increasing the size of the rock salt 2D building blocks, we have obtained two new n = 1 members of this homologous series, namely, Sr2F2Sb2Se4 and Ba2F2Sb2Se4. We then succeeded in synthesizing these compounds using a high-temperature ceramic method. The structure refinements from the powder or single-crystal X-ray diffraction data confirmed presence of the expected alternating stacking of fluorite [Ae2F2] (Ae = Sr, Ba) and rock salt [Sb2Se4] 2D building blocks. However the Ba derivative shows a strong distortion of the [Sb2Se4] block and a concomitant change of the Sb atom coordination likely related to the lone-pair activity.

Preferential Eu Site Occupation and Its Consequences in the Ternary Luminescent Halides AB 2 I 5 : Eu 2 + ( A = Li – Cs ; B = Sr , Ba)

DOE PAGES

Fang, C.  M.; Biswas, Koushik

2015-07-22

Several rare-earth-doped, heavy-metal halides have recently been identified as potential next-generation luminescent materials with high efficiency at low cost. AB 2I 5:Eu 2+ (A=Li–Cs; B=Sr, Ba) is one such family of halides. Its members, such as CsBa 2I 5:Eu 2+ and KSr 2I 5:Eu 2+, are currently being investigated as high-performance scintillators with improved sensitivity, light yield, and energy resolution less than 3% at 662 keV. Within the AB 2I 5 family, our first-principles-based calculations reveal two remarkably different trends in Eu site occupation. The substitutional Eu ions occupy both eightfold-coordinated B1(VIII) and the sevenfold-coordinated B2(VII) sites in the Sr-containingmore » compounds. However, in the Ba-containing crystals, Eu ions strongly prefer the B2(VII)sites. This random versus preferential distribution of Eu affects their electronic properties. The calculations also suggest that in the Ba-containing compounds one can expect the formation of Eu-rich domains. These results provide atomistic insight into recent experimental observations about the concentration and temperature effects in Eu-doped CsBa 2I 5. We discuss the implications of our results with respect to luminescent properties and applications. We also hypothesize Sr, Ba-mixed quaternary iodides ABa VIIISr VIII 5:Eu as scintillators having enhanced homogeneity and electronic properties.« less

(Ba1- x Bi0.33 x Sr0.67 x )(Ti1- x Bi0.67 x V0.33 x )O3 and (Ba1- x Bi0.5 x Sr0.5 x )(Ti1- x Bi0.5 x Ti0.5 x )O3 solid solutions: phase evolution, microstructure, dielectric properties and impedance analysis

NASA Astrophysics Data System (ADS)

Chen, Xiuli; Li, Xiaoxia; Yan, Xiao; Liu, Gaofeng; Zhou, Huanfu

2018-06-01

Perovskite solid solution ceramics of (Ba1- x Bi0.33 x Sr0.67 x )(Ti1- x Bi0.67 x V0.33 x )O3 and (Ba1- x Bi0.5 x Sr0.5 x )(Ti1- x Bi0.5 x Ti0.5 x )O3 (BBSTBV, BBSTBT, 0.02 ≤ x ≤ 0.2) were prepared by the traditional solid state reaction technique. The phase evolution, microstructure and dielectric properties of BBSTBV and BBSTBT ceramics were researched. X-Ray diffraction results illustrated that both BBSTBV and BBSTBT could form a homogenous solid solution which has a similar structure with BaTiO3. The optimized properties of (Ba0.8Bi0.1Sr0.1)(Ti0.8Bi0.1Ti0.1)O3 ceramics with stable ɛ r ( 1769-2293), small Δ ɛ/ ɛ 25 °C values (± 15%) over a broad temperature range from - 58 to 151 °C and low tan δ ≤ 0.03 from - 11 to 131 °C were obtained. In the high-temperature region, the relaxation and conduction process are attributed to the thermal activation and the oxygen vacancies may be the ionic charge carriers in perovskite ferroelectrics.

Isotopic and Chemical Evidence for Primitive Aqueous Alteration in the Tagish Lake Meteorite

NASA Astrophysics Data System (ADS)

Sakuma, Keisuke; Hidaka, Hiroshi; Yoneda, Shigekazu

2018-01-01

Aqueous alteration is one of the primitive activities that occurred on meteorite parent bodies in the early solar system. The Tagish Lake meteorite is known to show an intense parent body aqueous alteration signature. In this study, quantitative analyses of the alkaline elements and isotopic analyses of Sr and Ba from acid leachates of TL (C2-ungrouped) were performed to investigate effects of aqueous alteration. The main purpose of this study is to search for isotopic evidence of extinct 135Cs from the Ba isotopic analyses in the chemical separates from the Tagish Lake meteorite. Barium isotopic data from the leachates show variable 135Ba isotopic anomalies (ε = ‑2.6 ∼ +3.6) which correlatewith 137Ba and 138Ba suggesting a heterogeneous distribution of s- and r-rich nucleosynthetic components in the early solar system. The 87Rb–87Sr and 135Cs–135Ba decay systems on TL in this study do not provide any chronological information. The disturbance of the TL chronometers is likely a reflection of the selective dissolution of Cs and Rb given the relatively higher mobility of Cs and Rb compared to Ba and Sr, respectively, during fluid mineral interactions.

Co-precipitation of radium with barium and strontium sulfate and its impact on the fate of radium during treatment of produced water from unconventional gas extraction.

PubMed

Zhang, Tieyuan; Gregory, Kelvin; Hammack, Richard W; Vidic, Radisav D

2014-04-15

Radium occurs in flowback and produced waters from hydraulic fracturing for unconventional gas extraction along with high concentrations of barium and strontium and elevated salinity. Radium is often removed from this wastewater by co-precipitation with barium or other alkaline earth metals. The distribution equation for Ra in the precipitate is derived from the equilibrium of the lattice replacement reaction (inclusion) between the Ra(2+) ion and the carrier ions (e.g., Ba(2+) and Sr(2+)) in aqueous and solid phases and is often applied to describe the fate of radium in these systems. Although the theoretical distribution coefficient for Ra-SrSO4 (Kd = 237) is much larger than that for Ra-BaSO4 (Kd = 1.54), previous studies have focused on Ra-BaSO4 equilibrium. This study evaluates the equilibria and kinetics of co-precipitation reactions in Ra-Ba-SO4 and Ra-Sr-SO4 binary systems and the Ra-Ba-Sr-SO4 ternary system under varying ionic strength (IS) conditions that are representative of brines generated during unconventional gas extraction. Results show that radium removal generally follows the theoretical distribution law in binary systems and is enhanced in the Ra-Ba-SO4 system and restrained in the Ra-Sr-SO4 system by high IS. However, the experimental distribution coefficient (Kd') varies widely and cannot be accurately described by the distribution equation, which depends on IS, kinetics of carrier precipitation and does not account for radium removal by adsorption. Radium removal in the ternary system is controlled by the co-precipitation of Ra-Ba-SO4, which is attributed to the rapid BaSO4 nucleation rate and closer ionic radii of Ra(2+) with Ba(2+) than with Sr(2+). Carrier (i.e., barite) recycling during water treatment was shown to be effective in enhancing radium removal even after co-precipitation was completed. Calculations based on experimental results show that Ra levels in the precipitate generated in centralized waste treatment facilities far exceed regulatory limits for disposal in municipal sanitary landfills and require careful monitoring of allowed source term loading (ASTL) for technically enhanced naturally occurring materials (TENORM) in these landfills. Several alternatives for sustainable management of TENORM are discussed.

A study on the thermal conversion of scheelite-type ABO4 into perovskite-type AB(O,N)3.

PubMed

Li, Wenjie; Li, Duan; Gao, Xin; Gurlo, Aleksander; Zander, Stefan; Jones, Philip; Navrotsky, Alexandra; Shen, Zhijian; Riedel, Ralf; Ionescu, Emanuel

2015-05-07

Phase-pure scheelite AMoO4 and AWO4 (A = Ba, Sr, Ca) were thermally treated under an ammonia atmosphere at 400 to 900 °C. SrMoO4 and SrWO4 were shown to convert into cubic perovskite SrMoO2N and SrWO1.5N1.5, at 700 °C and 900 °C respectively, and to form metastable intermediate phases (scheelite SrMoO4-xNx and SrWO4-xNx), as revealed by X-ray diffraction (XRD), elemental analysis and FTIR spectroscopy. High-temperature oxide melt solution calorimetry reveals that the enthalpy of formation for SrM(O,N)3 (M = Mo, W) perovskites is less negative than that of the corresponding scheelite oxides, though the conversion of the scheelite oxides into perovskite oxynitrides is thermodynamically favorable at moderate temperatures. The reaction of BaMO4 with ammonia leads to the formation of rhombohedral Ba3M2(O,N)8 and the corresponding binary metal nitrides Mo3N2 and W4.6N4; similar behavior was observed for CaMO4, which converted upon ammonolysis into individual oxides and nitrides. Thus, BaMO4 and CaMO4 were shown to not provide access to perovskite oxynitrides. The influence of the starting scheelite oxide precursor, the structure distortion and the degree of covalency of the B-site-N bond are discussed within the context of the formability of perovskite oxynitrides.

An Industry-Scale Mass Marking Technique for Tracing Farmed Fish Escapees

PubMed Central

Warren-Myers, Fletcher; Dempster, Tim; Fjelldal, Per Gunnar; Hansen, Tom; Swearer, Stephen E.

2015-01-01

Farmed fish escape and enter the environment with subsequent effects on wild populations. Reducing escapes requires the ability to trace individuals back to the point of escape, so that escape causes can be identified and technical standards improved. Here, we tested if stable isotope otolith fingerprint marks delivered during routine vaccination could be an accurate, feasible and cost effective marking method, suitable for industrial-scale application. We tested seven stable isotopes, 134Ba, 135Ba, 136Ba, 137Ba, 86Sr, 87Sr and 26Mg, on farmed Atlantic salmon reared in freshwater, in experimental conditions designed to reflect commercial practice. Marking was 100% successful with individual Ba isotopes at concentrations as low as 0.001 µg. g-1 fish and for Sr isotopes at 1 µg. g-1 fish. Our results suggest that 63 unique fingerprint marks can be made at low cost using Ba (0.0002 – 0.02 $US per mark) and Sr (0.46 – 0.82 $US per mark) isotopes. Stable isotope fingerprinting during vaccination is feasible for commercial application if applied at a company level within the world’s largest salmon producing nations. Introducing a mass marking scheme would enable tracing of escapees back to point of origin, which could drive greater compliance, better farm design and improved management practices to reduce escapes. PMID:25738955

Electrical transport across nanometric SrTiO3 and BaTiO3 barriers in conducting/insulator/conducting junctions

NASA Astrophysics Data System (ADS)

Navarro, H.; Sirena, M.; González Sutter, J.; Troiani, H. E.; del Corro, P. G.; Granell, P.; Golmar, F.; Haberkorn, N.

2018-01-01

We report the electrical transport properties of conducting/insulator/conducting heterostructures by studying current-voltage IV curves at room temperature. The measurements were obtained on tunnel junctions with different areas (900, 400 and 100 μm2) using a conducting atomic force microscope. Trilayers with GdBa2Cu3O7 (GBCO) as the bottom electrode, SrTiO3 or BaTiO3 (thicknesses between 1.6 and 4 nm) as the insulator barrier, and GBCO or Nb as the top electrode were grown by DC sputtering on (100) SrTiO3 substrates For SrTiO3 and BaTiO3 barriers, asymmetric IV curves at positive and negative polarization can be obtained using electrodes with different work function. In addition, hysteretic IV curves are obtained for BaTiO3 barriers, which can be ascribed to a combined effect of the FE reversal switching polarization and an oxygen vacancy migration. For GBCO/BaTiO3/GBCO heterostructures, the IV curves correspond to that expected for asymmetric interfaces, which indicates that the disorder affects differently the properties at the bottom and top interfaces. Our results show the role of the interface disorder on the electrical transport of conducting/insulator/conduction heterostructures, which is relevant for different applications, going from resistive switching memories (at room temperature) to Josephson junctions (at low temperatures).

A simplified soil extraction sequence to monitor the main and trace element speciation in soil after compost and mineral fertilizer additions upon the composition of wheat grains

NASA Astrophysics Data System (ADS)

Sager, Manfred; Erhart, Eva

2016-04-01

High quality biological waste treatment aims at producing compost in order to maintain a clean environment and to sustain soil organic carbon levels. Fertilization with compost as a source of organic carbon, nutrients, and accessory elements, as well as fertilization with mineral N- and PK fertilizer have been tested in a field experiment on a calcaric Fluvisol in the Danube wetlands, at 4 levels each. Yields of wheat were recorded, and grains and soils were sampled from each treatment, and analyzed for main and trace element composition. The corresponding soils were characterized by mobile phases, obtained by leaching with 0,16M acetic acid to cover exchangeables plus carbonates, and subsequently by 0,1M oxalate buffer pH 3 to dissolve the pedogenic oxides. Total amounts were obtained from digests with perchloric- nitric-hydrofluoric acid. For quasi-total amounts, aqua regia was replaced by pressure decomposition with KClO3 in dilute nitric acid. The proposed extraction sequence permits to analyze and interpret soil for main elements, trace elements, nutrients and anions simultaneously. Factor analyses of soil extracts obtained from dilute acetic acid revealed Ba-Be-Cd-Cu-Li-S (traces), Ca-Mg-Mn (main carbonates), Al-Fe-B, Y, and P-K (nutrients) as chemically feasible principal components. Subsequent soil extracts from oxalate contained Al-B-Co-K-Na-Pb-Si-V-S (maybe acid silicate weathering), Cr-Li-Ni-Sr-Ti (maybe basic silicate weathering), Be-Cu-Fe-P, Co-Mg-Mn-Zn (Mn-oxides) and Ba-Sc as principal components. Factor analyses of total element data distinguished the principal components Ce-La-Li-Sc-Y-P (rare earths), Al-Ca-Fe-K-Mg-Na-P (main elements), Cd-Co-Cr-Cu-Ni-Zn (trace elements), As-Pb (contaminants), Ba-Mn-Sr, and Ti, which looks chemically feasible also. Factor analyses of those soil fractions which presumably form the main fractions of exchangeables, carbonates, pedogenic oxides and silicates, showed no cross connections, except for P. Oxalate-soluble Fe together with P and S was independent from oxalate-soluble Al-Mn-Si. In the crops, all element levels were within a non-contaminated and non-deficient range, therefore correlations with concentrations as well as loads in the wheat grains where largely not pronounced. Maximum correlations between plant and soil data were obtained with Li and Be. The load data (concentration times yield, given in g/ha) were much more intercorrelated than the concentrations. Regarding the same element, correlation coefficients between loads and respective concentrations were larger than 0,800 for Al, Ba, Cd, Co, Cr, Li, Mo, Na, Ni, Se, and Sr, which means the transfer remained independent from the load. In case of Ca, Mg, P, S, Zn, however, correlation coefficients between loads and concentrations were < 0,500, thus the transfer was not constant because of obvious metabolic influences. The proposed method of soil characterization was applied at a field trial here for the first time, and offers new possibilities of intercorrelations between plant uptake and geochemical soil fractions.

Synthesis, structural and optical properties of (ALa)(FeMn)O6 (A = Ba and Sr) double perovskites

NASA Astrophysics Data System (ADS)

Kumar, Dinesh; Sudarshan, V.; Singh, Akhilesh Kumar

2018-05-01

Here, we report structural and optical properties of ALaFeMnO6 (A = Ba and Sr) double perovskite synthesized via auto-combustion followed by calcinations process. Rietveld refinement of structure using x-ray diffraction data reveals that BaLaFeMnO6 crystallizes into cubic crystal structure with space group Pm-3m while SrLaFeMnO6 crystallizes into rhombohedral crystal structure having space group R-3c. The absorption spectrum measurement using UV-Vis spectroscopy reveals that these samples are prefect insulator having energy band gap between conduction and valence band of the order of 6 eV.

Effects of glyphosate on the mineral content of glyphosate-resistant soybeans (Glycine max).

PubMed

Duke, Stephen O; Reddy, Krishna N; Bu, Kaixuan; Cizdziel, James V

2012-07-11

There are conflicting claims as to whether treatment with glyphosate adversely affects mineral nutrition of glyphosate-resistant (GR) crops. Those who have made claims of adverse effects have argued links between reduced Mn and diseases in these crops. This article describes experiments designed to determine the effects of a recommended rate (0.86 kg ha(-1)) of glyphosate applied once or twice on the mineral content of young and mature leaves, as well as in seeds produced by GR soybeans (Glycine max) in both the greenhouse and field using inductively coupled plasma mass spectrometry (ICP-MS). In the greenhouse, there were no effects of either one application (at 3 weeks after planting, WAP) or two applications (at 3 and 6 WAP) of glyphosate on Ca, Mg, Mn, Zn, Fe, Cu, Sr, Ba, Al, Cd, Cr, Co, or Ni content of young or old leaves sampled at 6, 9, and 12 WAP and in harvested seed. Se concentrations were too low for accurate detection in leaves, but there was also no effect of glyphosate applications on Se in the seeds. In the field study, there were no effects of two applications (at 3 and 6 WAP) of glyphosate on Ca, Mg, Mn, Zn, Fe, Cu, Sr, Ba, Al, Cd, Cr, Co, or Ni content of young or old leaves at either 9 or 12 WAP. There was also no effect on Se in the seeds. There was no difference in yield between control and glyphosate-treated GR soybeans in the field. The results indicate that glyphosate does not influence mineral nutrition of GR soybean at recommended rates for weed management in the field. Furthermore, the field studies confirm the results of greenhouse studies.

Relationships between magnetic susceptibility and heavy metals in urban topsoils in the arid region of Isfahan, central Iran

NASA Astrophysics Data System (ADS)

Karimi, Rezvan; Ayoubi, Shamsollah; Jalalian, Ahmad; Sheikh-Hosseini, Ahmad Reza; Afyuni, Majid

2011-05-01

Recently methods dealing with magnetometry have been proposed as a proper proxy for assessing the heavy metal pollution of soils. A total of 113 topsoil samples were collected from public parks and green strips along the rim of roads with high-density traffic within the city of Isfahan, central Iran. The magnetic susceptibility (χ) of the collected soil samples was measured at both low and high frequency (χlf and χhf) using the Bartington MS2 dual frequency sensor. As, Cd, Cr, Ba, Cu, Mn, Pb, Zn, Sr and V concentrations were measured in the all collected soil samples. Significant correlations were found between Zn and Cu (0.85) and between Zn and Pb (0.84). The χfd value of urban topsoil varied from 0.45% to 7.7%. Low mean value of χfd indicated that the magnetic properties of the samples are predominately contributed by multi-domain grains, rather than by super-paramagnetic particles. Lead, Cu, Zn, and Ba showed positive significant correlations with magnetic susceptibility, but As, Sr, Cd, Mn, Cr and V, had no significant correlation with the magnetic susceptibility. There was a significant correlation between pollution load index (PLI) and χlf. PLI was computed to evaluate the soil environmental quality of selected heavy metals. Moreover, the results of multiple regression analysis between χlf and heavy metal concentrations indicated the LnPb, V and LnCu could explain approximately 54% of the total variability of χlf in the study area. These results indicate the potential of the magnetometric methods to evaluate the heavy metal pollution of soils.

Simultaneous quantification of 17 trace elements in blood by dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS) equipped with a high-efficiency sample introduction system.

PubMed

D'Ilio, S; Violante, N; Di Gregorio, M; Senofonte, O; Petrucci, F

2006-10-10

A quadrupole inductively coupled plasma mass spectrometer (Q-ICP-MS) equipped with a dynamic reaction cell (DRC) and coupled with a desolvating nebulization system (APEX-IR) was employed to determine 17 elements (Al, As, Ba, Cd, Co, Cr, Li, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, V, and Zr) in blood samples. Ammonia (for Al, Cr, Mn, and V) and O2 (for As and Se) were used as reacting gases. Selection of the best flow rate of the gases and optimization of the quadrupole dynamic bandpass tuning parameter (RPq) were carried out, using digested blood diluted 1+9 with deionized water and spiked with 1 microg L(-1) of Al, Cr, Mn, V and 5 microgL(-1) of As and Se. Detection limits were determined in digested blood using the 3sigma criterion. The desolvating system allowed a sufficient sensitivity to be achieved to determine elements at levels of ng L(-1) without detriment of signal stability. The accuracy of the method was tested with the whole blood certified reference material (CRM), certified for Al, As, Cd, Co, Cr, Mn, Mo, Ni, Pb, Sb, Se, and V, and with indicative values for Ba, Li, Sn, Sr, and Zr. The addition calibration approach was chosen for analysis. In order to confirm the DRC data, samples were also analyzed by means of sector field inductively coupled plasma mass spectrometry (SF-ICP-MS), operating in medium (m/Deltam=4000) and high (m/Deltam=10,000) resolution mode and achieving a good agreement between the two techniques.

Thin film dielectric composite materials

DOEpatents

Jia, Quanxi; Gibbons, Brady J.; Findikoglu, Alp T.; Park, Bae Ho

2002-01-01

A dielectric composite material comprising at least two crystal phases of different components with TiO.sub.2 as a first component and a material selected from the group consisting of Ba.sub.1-x Sr.sub.x TiO.sub.3 where x is from 0.3 to 0.7, Pb.sub.1-x Ca.sub.x TiO.sub.3 where x is from 0.4 to 0.7, Sr.sub.1-x Pb.sub.x TiO.sub.3 where x is from 0.2 to 0.4, Ba.sub.1-x Cd.sub.x TiO.sub.3 where x is from 0.02 to 0.1, BaTi.sub.1-x Zr.sub.x O.sub.3 where x is from 0.2 to 0.3, BaTi.sub.1-x Sn.sub.x O.sub.3 where x is from 0.15 to 0.3, BaTi.sub.1-x Hf.sub.x O.sub.3 where x is from 0.24 to 0.3, Pb.sub.1-1.3x La.sub.x TiO.sub.3+0.2x where x is from 0.23 to 0.3, (BaTiO.sub.3).sub.x (PbFeo.sub.0.5 Nb.sub.0.5 O.sub.3).sub.1-x where x is from 0.75 to 0.9, (PbTiO.sub.3).sub.- (PbCo.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.1 to 0.45, (PbTiO.sub.3).sub.x (PbMg.sub.0.5 W.sub.0.5 O.sub.3).sub.1-x where x is from 0.2 to 0.4, and (PbTiO.sub.3).sub.x (PbFe.sub.0.5 Ta.sub.0.5 O.sub.3).sub.1-x where x is from 0 to 0.2, as the second component is described. The dielectric composite material can be formed as a thin film upon suitable substrates.

Atmospheric dust deposition on soils around an abandoned fluorite mine (Hammam Zriba, NE Tunisia).

PubMed

Djebbi, Chaima; Chaabani, Fredj; Font, Oriol; Queralt, Ignasi; Querol, Xavier

2017-10-01

The present study focuses on the eolian dispersion and dust deposition, of major and trace elements in soils in a semi-arid climate, around an old fluorite (CaF 2 ) and barite (BaSO 4 ) mine, located in Hammam Zriba in Northern Tunisia. Ore deposits from this site contain a high amount of metal sulphides constituting heavy metal pollution in the surrounding environment. Samples of waste from the surface of mine tailings and agricultural topsoil samples in the vicinity of the mine were collected. The soil samples and a control sample from unpolluted area, were taken in the direction of prevailing northwest and west winds. Chemical analysis of these solids was performed using both X-ray fluorescence and X-ray diffraction. To determine the transfer from mine wastes to the soils, soluble fraction was performed by inductively coupled plasma and ionic chromatography. The fine grained size fraction of the un-restored tailings, still contained significant levels of barium, strontium, sulphur, fluorine, zinc and lead with mean percentages (wt%) of 30 (calculated as BaO), 13 (as SrO), 10 (as SO 3 ), 4 (F), 2 (Zn) and 1.2 (Pb). Also, high concentrations of cadmium (Cd), arsenic (As) and mercury (Hg) were found with an averages of 36, 24 and 1.2mgkg -1 , respectively. As a result of the eolian erosion of the tailings and their subsequent wind transport, the concentrations of Ba, Sr, S, F, Zn and Pb were extremely high in the soils near to the tailings dumps, with 5%, 4%, 7%, 1%, 0.8% and 0.2%, respectively. Concentration of major pollutants decreases with distance, but they were high even in the farthest samples. Same spatial distribution was observed for Cd, As and Hg. While, the other elements follow different spatial patterns. The leaching test revealed that most elements in the mining wastes, except for the anions, had a low solubility despite their high bulk concentrations. According the 2003/33/CE Decision Threshold, some of these tailings samples were considered as hazardous. Furthermore, other waste samples, considered non hazardous, were not inert. In contrast, the SO 4 2- , Ba, Pb and Sb leachable contents measured in most of the soil samples were relatively high, exceeding the inert threshold for landfill disposal of wastes. Copyright © 2017 Elsevier Inc. All rights reserved.

Microstructural and thermal properties of pure BaFe{sub 12}O{sub 19} and Sr doped barium ferrite (Ba{sub 0.9}Sr{sub 0.1}Fe{sub 12}O{sub 19}) synthesized by auto combustion method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taufeeq, Saba, E-mail: sabataufeeq23@gmail.com; Parveen, Azra; Agrawal, Shraddha

2016-05-23

Nanoparticles (NPs) of Pure BaFe{sub 12}O{sub 19} and Strontium doped Barium Ferrite (Ba{sub 0.9}Sr{sub 0.1}Fe{sub 12}O{sub 19}) have been successfully synthesized by Auto combustion method using citric acid as a chelating agent and calcined at 450°C for 3 hrs and 850°C for 4 hrs. Microstructural studies were carried by XRD and SEM techniques. Structural studies suggest that the crystal system remains hexagonal even with the doping of Strontium. The XRD analysis confirms the formation of the structures in the nanometer regime and the peaks are the evidence of the crystalline phase. The SEM images shows the morphology of surface ofmore » the samples. The thermal property studied by TGA shows the weight loss which is with varying the temperature and weight loss also varies with Sr doping. The TGA analysis exhibits the loss of weight at different temperatures.« less

Modification of energy band alignment and electric properties of Pt/Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}/Pt thin-film ferroelectric varactors by Ag impurities at interfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirsch, S.; Komissinskiy, P., E-mail: komissinskiy@oxide.tu-darmstadt.de; Flege, S.

2014-06-28

We report on the effects of Ag impurities at interfaces of parallel-plate Pt/Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}/Pt thin film ferroelectric varactors. Ag impurities occur at the interfaces due to diffusion of Ag from colloidal silver paint used to attach the varactor samples with their back side to the plate heated at 600–750 °C during deposition of Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}. X-ray photoelectron spectroscopy and secondary ion mass spectrometry suggest that amount and distribution of Ag adsorbed at the interfaces depend strongly on the adsorbent surface layer. In particular, Ag preferentially accumulates on top of the Pt bottom electrode. The presence of Agmore » significantly reduces the barrier height between Pt and Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3} leading to an increased leakage current density and, thus, to a severe degradation of the varactor performance.« less

Band-gap tuning and magnetic properties of heterovalent ions (Ba, Sr and Ca) substituted BiFeO{sub 3} nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chauhan, Sunil, E-mail: sunilchauhanjiit@gmail.com; Kumar, Manoj; Katyal, S. C.

2016-05-23

A Comparative study of heterovalent Ba, Sr and Ca ions substitution on the structural, vibrational, optical and magnetic properties of BiFeO{sub 3} nanoparticles was carried out. The distorted rhombohedral structure was confirmed from both X-ray diffraction and Raman spectroscopy techniques in pure BiFeO{sub 3} and Bi{sub 0.85}A{sub 0.15}FeO{sub 3} (A= Ba, Sr and Ca) samples. UV-Visible spectroscopy results show that the band-gap of BiFeO{sub 3} nanoparticles can be tuned by heterovalent ions substitution from 2.12 eV for BiFeO{sub 3} to 2.10, 2.06 and 2.03 eV for Ca, Sr and Ba substituted BiFeO{sub 3} nanoparticles respectively. The magnetic measurements indicate enhancementmore » in magnetization for heterovalent A{sup 2+} substituted BiFeO{sub 3} samples and the magnetization increases with increase of ionic radius of the substituted ions.« less

Influence of MO/MF2 modifiers (M = Ca, Sr, Ba) on spectroscopic properties of Eu3+ ions in germanate and borate glasses

NASA Astrophysics Data System (ADS)

Zur, Lidia; Janek, Joanna; Pietrasik, Ewa; Sołtys, Marta; Pisarska, Joanna; Pisarski, Wojciech A.

2016-11-01

Series of Eu3+-doped lead-free germanate and borate glasses were synthesized. The MO glass modifiers (M = Ca, Sr or Ba) were partially or totally substituted by MF2 in chemical composition. In contrast to samples modified by CaO/CaF2 or SrO/SrF2, the germanate glass samples containing BaO and/or BaF2 are fully amorphous, while the lead-free borate glasses are fully amorphous, independently from glass modifiers. Effect of glass modifiers on spectroscopic properties of Eu3+ were systematically investigated. For that reason, excitation and emission spectra of Eu3+ ions in examined systems were registered. Based on the emission spectra, ratio of integrated luminescence intensity of the 5D0 → 7F2 transition to that of the 5D0 → 7F1 transition (R factor) was calculated. Moreover, the luminescence decay curves were collected and the luminescence lifetimes of the 5D0 excited state of Eu3+ ions were determined in function of MF2 concentration.

Growth, improved thermal stability and spectral properties of Yb3+-ions doped high temperature phase α-Ba3Gd(BO3)3 crystals co-doped by Sr2+, Ca2+ and La3+ ions

NASA Astrophysics Data System (ADS)

Pan, Shangke; Zhang, Jianyu; Pan, Jianguo

2018-02-01

To investigate the cause of the thermal instability of Yb3+-ions doped Ba3Gd(BO3)3 crystal grown from Czochralski technique, the low temperature phase β-Ba3Gd(BO3)3 powder was synthesized at the temperature of 800 °C. To inhibit the phase transition of high temperature phase Yb:α-Ba3Gd(BO3)3 during the crystal growth process, co-doping ions Sr2+, Ca2+ and La3+ ions were introduced in Yb:α-Ba3Gd(BO3)3 crystal. The melting point increased and the thermal stability of Yb:α-Ba3Gd(BO3)3 crystal was improved by co-doping ions. The absorption peaks of co-doped crystals centered at 976 nm with FWHM of 11, 11 and 12 nm and the absorption cross sections were 3.40 × 10-21 cm2, 4.00 × 10-21 cm2 and 2.66 × 10-21 cm2, respectively. The emission cross sections at 1040 nm were 2.19 × 10-21 cm2, 2.53 × 10-21 cm2 and 1.93 × 10-21 cm2, respectively. The fluorescence times of co-doped by Sr2+, Ca2+ and La3+ ions were shorter than that of Yb:α-Ba3Gd(BO3)3 crystal. So Yb:α-Ba3Gd(BO3)3 crystals co-doped by Sr2+, Ca2+ and La3+ ions will be more suitable for LD-pumping laser.

Sputter Deposition of Yttrium-Barium Superconductor and Strontium Titanium Oxide Barrier Layer Thin Films

NASA Astrophysics Data System (ADS)

Truman, James Kelly

1992-01-01

The commercial application of superconducting rm YBa_2Cu_3O_{7 -x} thin films requires the development of deposition methods which can be used to reproducibly deposit films with good superconducting properties on insulating and semiconducting substrates. Sputter deposition is the most popular method to fabricate Y-Ba-Cu-O superconductor thin films, but when used in the standard configuration suffers from a deviation between the compositions of the Y-Ba-Cu-O sputter target and deposited films, which is thought to be primarily due to resputtering of the film by negative ions sputtered from the target. In this study, the negative ions were explicitly identified and were found to consist predominantly O^-. The sputter yield of O^- was found to depend on the Ba compound used in the fabrication of Y -Ba-Cu-O targets and was related to the electronegativity difference between the components. An unreacted mixture of rm Y_2O_3, CuO, and BaF_2 was found to have the lowest O^- yield among targets with Y:Ba:Cu = 1:2:3. The high yield of O^- from rm YBa_2Cu_3O _{7-x} was found to depend on the target temperature and be due to the excess oxygen present. The SIMS negative ion data supported the composition data for sputter-deposited Y-Ba-Cu-O films. Targets using BaF _2 were found to improve the Ba deficiency, the run-to-run irreproducibility and the nonuniformity of the film composition typically found in sputtered Y -Ba-Cu-O films. Superconducting Y-Ba-Cu-O films were formed on SrTiO_3 substrates by post-deposition heat treatment of Y-Ba-Cu-O-F films in humid oxygen. The growth of superconducting rm YBa_2Cu_3O_{7-x}, thin films on common substrates such as sapphire or silicon requires the use of a barrier layer to prevent the deleterious interaction which occurs between Y-Ba-Cu-O films and these substrates. Barrier layers of SrTiO_3 were studied and found to exhibit textured growth with a preferred (111) orientation on (100) Si substrates. However, SrTiO_3 was found to be unsuitable as a barrier layer for the growth of rm YBa _2Cu_3O_{7-x}, on Si since Ba reacted with the si after migrating through the SrTiO_3 layer. For sapphire, no textured growth of SrTiO_3 was observed but it was found to be a suitable barrier layer since it prevented any interaction between Y-Ba-Cu-O films and sapphire substrates.

Luminescence Properties of Self-Activated Mm(VO4)2 (M = Mg, Ca, Sr, and Ba) Phosphors Synthesized by Solid-State Reaction Method.

PubMed

Min, Xin; Huang, Zhaohui; Fang, Minghao; Liu, Yan'gai; Tang, Chao; Wu, Xiaowen

2016-04-01

In this paper, M3(VO4)2 (M = Mg, Ca, Sr, and Ba) self-activated phosphors were prepared by a solid-state reaction method at 1,000 °C for 5 h. The phase formation and micrographs were analyzed by X-ray diffraction and scanning electron microscopy. The Ca3(VO4)2 phosphor does not show any emission peaks under excitation with ultraviolet (UV) light. However, the M3(VO4)2 (M = Mg, Sr, and Ba) samples are effectively excited by UV light chips ranging from 200 nm to 400 nm and exhibit broad emission bands due to the charge transfer from the oxygen 2p orbital to the vacant 3d orbital of the vanadium in the VO4. The color of these phosphors changes from yellow to light blue via blue-green with increasing ionic radius from Mg to Sr to Ba. The luminescence lifetimes and quantum yield decrease with the increasing unit cell volume and V-V distance, in the order of Mg3(VO4)2 to Sr3(VO4)2 to Ba3(VO4)2. The emission intensity decreases with the increase of temperatures, but presents no color shift. This confirms that these self-activated M3(VO4)2 phosphors can be suggested as candidates of the single-phase phosphors for light using UV light emitting diodes (LEDs).

Magneto-optical properties of BaTiO3/La0.76Sr0.24MnO3/BaTiO3 heterostructures

NASA Astrophysics Data System (ADS)

Moog, M.; Singamaneni, S. R.; Prater, J. T.; Biegalski, M. D.; Tsui, F.

2018-05-01

The magnetic properties of epitaxial BaTiO3/La0.76Sr0.24MnO3/BaTiO3 (BTO/LSMO/BTO) heterostructures have been studied using magneto-optic Kerr effect (MOKE) technique. Both longitudinal and polar MOKE were probed as a function of magnetic field and temperature (in the range between 80 and 320 K) for epitaxial films of BTO/LSMO/BTO and LSMO grown on TiO2-terminated SrTiO3 (001) substrates by pulsed laser deposition technique. The LSMO film without the BTO layers exhibits nearly square field-dependent MOKE hysteresis loops with low saturation fields below a bulk-like Curie temperature (TC) of ˜ 350K. In contrast, the film with the BTO layers exhibits a significantly suppressed TC of 155 K, accompanied by significantly enhanced coercive fields and perpendicular magnetic anisotropy.

Dissipation of available benzo[a]pyrene in aging soil co-contaminated with cadmium and pyrene.

PubMed

Wang, Kai; Chen, Xin-xin; Zhu, Zhi-qiang; Huang, Hua-gang; Li, Ting-qiang; Yang, Xiao-e

2014-01-01

A microcosm experiment was conducted to investigate the dissipation of available benzo[a]pyrene (BaP) in soils co-contaminated with cadmium (Cd) and pyrene (PYR) during aging process. The available residue of BaP in soil was separated into desorbing and non-desorbing fractions. The desorbing fraction contributed more to the dissipation of available BaP than the non-desorbing fraction did. The concentration of bound-residue fraction of BaP was quite low across all treatments. Within the duration of this study (250 days), transformation of BaP from available fractions to bound-residue fraction was not observed. Microbial degradation was the dominant mechanism of the dissipation of available BaP in the soil. The dissipation of available BaP was significantly inhibited with the increment in Cd level in the soil. The addition of PYR (250 mg kg(-1)) remarkably promoted the dissipation of available BaP without reducing Cd availability in the soil. The calculated half-life of available BaP in the soil prolonged with the increment in Cd level; however, the addition of PYR shortened the half-life of available BaP by 13.1, 12.7, and 32.8% in 0.44, 2.56, and 22 mg Cd kg(-1) soils, respectively. These results demonstrated that the inhibiting effect of Cd and the promoting effect of PYR on the dissipation of available BaP were competitive. Therefore, this study shows that the bioremediation process of BaP can be more complicated in co-contaminated soils.

Photoemission study of absorption mechanisms in Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ, BaBiO3, and Nd1.85Ce0.15CuO4

NASA Astrophysics Data System (ADS)

Lindberg, P. A. P.; Shen, Z.-X.; Wells, B. O.; Dessau, D. S.; Ellis, W. P.; Borg, A.; Kang, J.-S.; Mitzi, D. B.; Lindau, I.; Spicer, W. E.; Kapitulnik, A.

1989-11-01

Photoemission measurements in the constant-final-state (absorption) mode were performed on three different classes of high-temperature superconductors Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ, BaBiO3, and Nd1.85Ce0.15CuO4 using synchrotron radiation from 20 to 200 eV. Absorption signals from all elements but Ce are identified. The results firmly show that the Bi 6s electrons are more delocalized in BaBiO3 than in Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ, in agreement with the results of band-structure calculations. Differences in the absorption signals due to O and Bi excitations between BaBiO3 and Bi2.0Sr1.8Ca0.8La0.3Cu2.1O8+δ are discussed. Delayed absorption onsets attributed to giant resonances (Ba 4d-->4f, La 4d-->4f, and Nd 4d-->4f transitions) are also reported.

Electronic structure and bonding interactions in Ba1- x Sr x Zr0.1Ti0.9O3 ceramics

NASA Astrophysics Data System (ADS)

Mangaiyarkkarasi, Jegannathan; Sasikumar, Subramanian; Saravanan, Olai Vasu; Saravanan, Ramachandran

2017-06-01

An investigation on the precise electronic structure and bonding interactions has been carried out on Ba1- x Sr x Zr0.1Ti0.9O3 (short for BSZT, x = 0, 0.05, 0.07 and 0.14) ceramic systems prepared via high-temperature solid state reaction technique. The influence of Sr doping on the BSZT structure has been examined by characterizing the prepared samples using PXRD, UV-visible spectrophotometry, SEM and EDS. Powder profile refinement of X-ray data confirms that all the synthesized samples have been crystallized in cubic perovskite structure with single phase. Charge density distribution of the BSZT systems has been completely analyzed by the maximum entropy method (MEM). Co-substitution of Sr at the Ba site and Zr at the Ti site into the BaTiO3 structure presents the ionic nature between Ba and O ions and the covalent nature between Ti and O ions, revealed from MEM calculations. Optical band gap values have been evaluated from UV-visible absorption spectra. Particles with irregular shapes and well defined grain boundaries are clearly visualized from SEM images. The phase purity of the prepared samples is further confirmed by EDS qualitative spectral analysis.

Multivariate characterization of elements accumulated in King Bolete Boletus edulis mushroom at lowland and high mountain regions.

PubMed

Falandysz, J; Kunito, T; Kubota, R; Bielawski, L; Frankowska, A; Falandysz, Justyna J; Tanabe, S

2008-12-01

Based on ICP-MS, ICP-OES, HG-AAS, CV-AAS and elementary instrumental analysis of King Bolete collected from four sites of different soil bedrock geochemistry considered could be as mushroom abundant in certain elements. King's Bolete fruiting bodies are very rich in K (> 20 mg/g dry weight), rich in Ca, Mg, Na, Rb and Zn (> 100 microg/g dw), and relatively also rich in Ag, Cd, Cs, Cu, Fe, Mn and Se (> 10 microg/g dw). The caps of King Bolete when compared to stipes around two-to three-fold more abundant are in Ag, Cd, Cs, Cu, Hg, K, Mg, Mo, N, Rb, Se and Zn. King Bolete collected at the lowland and mountain sites showed Ag, Ba, Co, Cr, Hg, K, Mg, Mn, Mo and Na in caps in comparable concentrations, and specimens from the mountain areas accumulated more Cd and Sb. Elements such as Al, Pb and Rb occurred at relatively elevated concentration in King Bolete picked up at the metal ores-rich region of the Sudety Mountains. Because of high bioconcentration potential King Bolete at the background sites accumulate in fruiting bodies great concentrations of problematic elements such as Cd, Pb and Hg, i.e. up to nearly 20, 3 and 5 microg/g dw, on the average, respectively. The interdependence among determined mineral elements examined were using the principal components analysis (PCA) method. The PCA explained 56% of the total variance. The metals tend to cluster together (Ba, Cd, Cs, Cr, Ga, Rb, Se, Sr and V; K and Mg; Cu and Mo). The results provided useful environmental and nutritional background level information on 26 minerals as the composition of King Bolete from the sites of different bedrock soil geochemistry.

Electrical characterization of Mn doped-(Ba{sub 0.3}Sr{sub 0.7})Mn{sub x}(Ti{sub 0.9}Zr{sub 0.1}){sub 1-x}O{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahmood, A.; Materials Research Laboratory, Institute of Physics & Electronics, University of Peshawar, 25120; Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD

2015-12-15

Highlights: • Solid state processing of the (Ba{sub 0.3}Sr{sub 0.7})Mn{sub x}(Ti{sub 0.9}Zr{sub 0.1}){sub 1−x}O{sub 3} ceramics. • Mn incorporated on the Ti-site into the host lattice of (Ba{sub 0.3}Sr{sub 0.7})Mn{sub x}(Ti{sub 0.9}Zr{sub 0.1}){sub 1−x}O{sub 3}. • NTCR behavior was observed in the sintered samples. - Abstract: (Ba{sub 0.3}Sr{sub 0.7})Mn{sub x}(Ti{sub 0.9}Zr{sub 0.1}){sub 1-x}O{sub 3} (x = 0.00, 0.013, 0.015 and 0.05) ceramics were prepared by solid state sintering route at the 1500 °C for 6 h in air. Effect of Mn substitution on the structure of Ba{sub 0.3}Sr{sub 0.7}(Ti0{sub .9}Zr{sub 0.1}){sub 1−x}O{sub 3} perovskite was investigated systematically. Dielectric and impedancemore » spectroscopic studies were conducted to understand the electronic microstructure of the Ba{sub 0.3}Sr{sub 0.7}(Ti0{sub .9}Zr{sub 0.1}){sub 1−x}O{sub 3} ceramics. Sample with x = 0.05 showed the highest dielectric constant (ϵ{sub r} = 1826) and low dielectric loss (tanδ = 0.001) at 10 kHz, around the room temperature, while the sample with x = 0.00 showed good microwave (MW) dielectric properties (Qf{sub o} = 838 and ϵ{sub r} = 550). The impedance spectroscopic analysis confirmed the electrical homogeneity of the samples with x = 0.013, 0.015 and 0.05, where grain boundaries dominated the conduction mechanism. Similarly, the sample with x = 0.00 was found to possess both grain boundary and bulk resistive contributions.« less

Trace elements and radon in groundwater across the United States, 1992-2003

USGS Publications Warehouse

Ayotte, Joseph D.; Gronberg, Jo Ann M.; Apodaca, Lori E.

2011-01-01

Trace-element concentrations in groundwater were evaluated for samples collected between 1992 and 2003 from aquifers across the United States as part of the U.S. Geological Survey National Water-Quality Assessment Program. This study describes the first comprehensive analysis of those data by assessing occurrence (concentrations above analytical reporting levels) and by comparing concentrations to human-health benchmarks (HHBs). Data from 5,183 monitoring and drinking-water wells representing more than 40 principal and other aquifers in humid and dry regions and in various land-use settings were used in the analysis. Trace elements measured include aluminum (Al), antimony (Sb), arsenic (As), barium (Ba), beryllium (Be), boron (B), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), lithium (Li), manganese (Mn), molybdenum (Mo), nickel (Ni), selenium (Se), silver (Ag), strontium (Sr), thallium (Tl), uranium (U), vanadium (V), and zinc (Zn). Radon (Rn) gas also was measured and is included in the data analysis. Climate influenced the occurrence and distribution of trace elements in groundwater whereby more trace elements occurred and were found at greater concentrations in wells in drier regions of the United States than in humid regions. In particular, the concentrations of As, Ba, B, Cr, Cu, Mo, Ni, Se, Sr, U, V, and Zn were greater in the drier regions, where processes such as chemical evolution, ion complexation, evaporative concentration, and redox (oxidation-reduction) controls act to varying degrees to mobilize these elements. Al, Co, Fe, Pb, and Mn concentrations in groundwater were greater in humid regions of the United States than in dry regions, partly in response to lower groundwater pH and (or) more frequent anoxic conditions. In groundwater from humid regions, concentrations of Cu, Pb, Rn, and Zn were significantly greater in drinking-water wells than in monitoring wells. Samples from drinking-water wells in dry regions had greater concentrations of As, Ba, Pb, Li, Sr, V, and Zn, than samples from monitoring wells. In humid regions, however, concentrations of most trace elements were greater in monitoring wells than in drinking-water wells; the exceptions were Cu, Pb, Zn, and Rn. Cu, Pb, and Zn are common trace elements in pumps and pipes used in the construction of drinking-water wells, and contamination from these sources may have contributed to their concentrations. Al, Sb, Ba, B, Cr, Co, Fe, Mn, Mo, Ni, Se, Sr, and U concentrations were all greater in monitoring wells than in drinking-water wells in humid regions. Groundwater from wells in agricultural settings had greater concentrations of As, Mo, and U than groundwater from wells in urban settings, possibly owing to greater pH in the agricultural wells. Significantly greater concentrations of B, Cr, Se, Ag, Sr, and V also were found in agricultural wells in dry regions. Groundwater from dry-region urban wells had greater concentrations of Co, Fe, Pb, Li, Mn, and specific conductance than groundwater from agricultural wells. The geologic composition of aquifers and aquifer geochemistry are among the major factors affecting trace-element occurrence. Trace-element concentrations in groundwater were characterized in aquifers from eight major groups based on geologic material, including (1) unconsolidated sand and gravel; (2) glacial unconsolidated sand and gravel; (3) semiconsolidated sand; (4) sandstone; (5) sandstone and carbonate rock; (6) carbonate rock; (7) basaltic and other volcanic rock; and (8) crystalline rock. The majority of groundwater samples and the largest percentages of exceedences of HHBs were in the glacial and nonglacial unconsolidated sand and gravel aquifers; in these aquifers, As, Mn, and U are the most common trace elements exceeding HHBs. Overall, 19 percent of wells (962 of 5,097) exceeded an HHB for at least one trace element. The trace elements with HHBs included in this summary were Sb, As, Ba, Be, B, Cd, Cr,

Profile and bioconcentration of minerals by King Bolete (Boletus edulis) from the Płocka Dale in Poland.

PubMed

Frankowska, Aneta; Ziółkowska, Joanna; Bielawski, Leszek; Falandysz, Jerzy

2010-01-01

This study aimed to provide basic data on the composition of metallic elements, including toxicologically important Cd and Hg, in popular and prized wild King Bolete mushrooms. We investigated the importance of soil substratum as a source of these metals. ICP-OES and CV-AAS were applied to determine the profile of Al, Ba, Ca, Cd, Cu, Fe, Hg, K, Mg, Mn, Na, Sr and Zn in caps and stipes of King Bolete mushroom and in the surface layer of soil (0-10 cm) from the Płocka Dale area of Poland. Hg, Cu, Cd, Zn, Mg and K exhibited bioconcentration factors (BCF) > 1. Specifically, Hg, Cu and Cd (mean BCFs for caps were 110, 19 and 16, respectively) were efficiently bioconcentrated by King Bolete, while other elements were bioexcluded (BCF < 1). Cadmium was present in the caps at mean levels of 5.5 ± 2.4 mg kg(-1) dry weight (dw) and mercury at levels of 4.9 ± 1.4 mg kg(-1) dw, both occurring at elevated concentrations in those King Bolete mushrooms surveyed.

Pre-Steady-State Kinetics of Ba-Ca Exchange Reveals a Second Electrogenic Step Involved in Ca2+ Translocation by the Na-Ca Exchanger

PubMed Central

Haase, Andreas; Hartung, Klaus

2009-01-01

Kinetic properties of the Na-Ca exchanger (guinea pig NCX1) expressed in Xenopus oocytes were investigated with excised membrane patches in the inside-out configuration and photolytic Ca2+ concentration jumps with either 5 mM extracellular Sr2+ or Ba2+. After a Ca2+ concentration jump on the cytoplasmic side, the exchanger performed Sr-Ca or Ba-Ca exchange. In the Sr-Ca mode, currents are transient and decay in a monoexponential manner similar to that of currents in the Ca-Ca exchange mode described before. Currents recorded in the Ba-Ca mode are also transient, but the decay is biphasic. In the Sr-Ca mode the amount of charge translocated increases at negative potentials in agreement with experiments performed in the Ca-Ca mode. In the Ba-Ca mode the total amount of charge translocated after a Ca2+ concentration jump is ∼4 to 5 times that in Ca-Ca or Sr-Ca mode. In the Ba-Ca mode the voltage dependence of charge translocation depends on the Ca2+ concentration on the cytosolic side before the Ca2+ concentration jump. At low initial Ca2+ levels (∼0.5 μM), charge translocation is voltage independent. At a higher initial concentration (1 μM Ca2+), the amount of charge translocated increases at positive potentials. Biphasic relaxation of the current was also observed in the Ca-Ca mode if the external Ca2+ concentration was reduced to ≤0.5 mM. The results reported here and in previous publications can be described by using a 6-state model with two voltage-dependent conformational transitions. PMID:19486679

Structure evolution upon chemical and physical pressure in (Sr{sub 1−x}Ba{sub x}){sub 2}FeSbO{sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tiittanen, T.; Karppinen, M., E-mail: maarit.karppinen@aalto.fi

Here we demonstrate the gradual structural transformation from the monoclinic I2/m to tetragonal I4/m, cubic Fm-3m and hexagonal P6{sub 3}/mmc structure upon the isovalent larger-for-smaller A-site cation substitution in the B-site ordered double-perovskite system (Sr{sub 1−x}Ba{sub x}){sub 2}FeSbO{sub 6}. This is the same transformation sequence previously observed up to Fm-3m upon heating the parent Sr{sub 2}FeSbO{sub 6} phase to high temperatures. High-pressure treatment, on the other hand, transforms the hexagonal P6{sub 3}/mmc structure of the other end member Ba{sub 2}FeSbO{sub 6} back to the cubic Fm-3m structure. Hence we may conclude that chemical pressure, physical pressure and decreasing temperature allmore » work towards the same direction in the (Sr{sub 1−x}Ba{sub x}){sub 2}FeSbO{sub 6} system. Also shown is that with increasing Ba-for-Sr substitution level, i.e. with decreasing chemical pressure effect, the degree-of-order among the B-site cations, Fe and Sb, decreases. - Graphical abstract: In the (Sr{sub 1−x}Ba{sub x}){sub 2}FeSbO{sub 6} double-perovskite system the gradual structural transformation from the monoclinic I2/m to tetragonal I4/m, cubic Fm-3m and hexagonal P6{sub 3}/mmc structure is seen upon the isovalent larger-for-smaller A-site cation substitution. High-pressure treatment under 4 GPa extends stability of the cubic Fm-3m structure within a wider substitution range of x. - Highlights: • Gradual structural transitions upon A-cation substitution in (Sr{sub 1−x}Ba{sub x}){sub 2}FeSbO{sub 6.} • With increasing x structure changes from I2/m to I4/m, Fm-3m and P6{sub 3}/mmc. • Degree of B-site order decreases with increasing x and A-site cation radius. • High-pressure treatment extends cubic Fm-3m phase stability for wider x range. • High-pressure treatment affects bond lengths mostly around the A-cation.« less

Second harmonic generation response of the cubic chalcogenides Ba( 6-x)Sr x[Ag( 4-y)Sn( y/4)](SnS 4) 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haynes, Alyssa S.; Liu, Te-Kun; Frazer, Laszlo

We synthesized the barium/strontium solid solution sequence Ba 6-xSr x[Ag( 4-y)Sn( y/4)](SnS 4) 4 for nonlinear optical (NLO) applications in the infrared (IR) via a flux synthesis route. All title compounds are isotypic, crystallizing in the cubic space group Imore » $$\\bar{_4}$$ 3d and are composed of a three-dimensional (3D) anionic framework of alternating corner-sharing SnS 4 and AgS 4 tetrahedra charge balanced by Ba and Sr. The shrinkage of Ba/Sr-S bond lengths causes the tetrahedra in the anionic framework to become more distorted, which results in a tunable band gap from 1.58 to 1.38 eV with increasing x values. The performance of the barium limit (x=0) is also superior to that of Sr (x=6), but surprisingly second harmonic generation (SHG) of the solid solution remains strong and is insensitive to the value of x over the range 0-3.8. Results show that the non-type-I phase-matched SHG produced by these cubic chalcogenides display intensities higher than the benchmark AgGaSe 2 from 600 to 1000 nm.« less

Effect of Sr doping on structural and magnetic behavior of SmBa1-xSrxCo2O5+δ (x = 0 and 1)

NASA Astrophysics Data System (ADS)

Kumari, Archana; Dhanasekhar, C.; Das, A. K.

2018-05-01

Layered double perovskite, SmBa1-xSrxCo2O5+δ (x = 0, δ = 0.5 and x = 1, δ = 1) samples were prepared by solid state reaction method. X-ray diffraction studies show that the SmBaCo2O5.5 sample crystallizes in the orthorhombic crystal structure with Pmmm space group, whereas SmSrCo2O6 sample crystallizes in the orthorhombic crystal structure with Pnma space group. The temperature dependent magnetization of the SmBaCo2O5.5 sample shows a paramagnetic (PM)-ferromagnetic (FM) and a FM-antiferromagnetic (AFM) transitions at TC = 267 K and TN = 221 K, respectively. In contrast, the SmSrCo2O6 sample shows a PM-FM transition at TC = 175 K. According to Goodenough-Kanamori-Anderson rules, the ferromagnetic behavior in SmSrCo2O6 can be understood from the super exchange interaction between the intermediate spin Co3+ and low spin Co4+ via O2- (IS Co3+ -O2- - LS Co4+). The change in magnetic entropy (ΔSMmax) is found to be maximum for the SmSrCo2O6 sample.

Increased Curie Temperature Induced by Orbital Ordering in La0.67Sr0.33MnO3/BaTiO3 Superlattices.

PubMed

Zhang, Fei; Wu, Biao; Zhou, Guowei; Quan, Zhi-Yong; Xu, Xiao-Hong

2018-01-17

Recent theoretical studies indicated that the Curie temperature of perovskite manganite thin films can be increased by more than an order of magnitude by applying appropriate interfacial strain to control orbital ordering. In this work, we demonstrate that the regular intercalation of BaTiO 3 layers between La 0.67 Sr 0.33 MnO 3 layers effectively enhances ferromagnetic order and increases the Curie temperature of La 0.67 Sr 0.33 MnO 3 /BaTiO 3 superlattices. The preferential orbital occupancy of e g (x 2 -y 2 ) in La 0.67 Sr 0.33 MnO 3 layers induced by the tensile strain of BaTiO 3 layers is identified by X-ray linear dichroism measurements. Our results reveal that controlling orbital ordering can effectively improve the Curie temperature of La 0.67 Sr 0.33 MnO 3 films and that in-plane orbital occupancy is beneficial to the double exchange ferromagnetic coupling of thin-film samples. These findings create new opportunities for the design and control of magnetism in artificial structures and pave the way to a variety of novel magnetoelectronic applications that operate far above room temperature.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sangeetha, N. S.; Smetana, V.; Mudring, A. -V.

Here, crystals of SrMn 2Sb 2 and BaMn 2Sb 2 were grown using Sn flux and characterized by powder and single-crystal x-ray diffraction, respectively, and by single-crystal electrical resistivity ρ, heat capacity C p, and magnetic susceptibility χ measurements versus temperature T, and magnetization versus field M(H) isotherm measurements. SrMn 2Sb 2 adopts the trigonal CaAl 2Si 2-type structure, whereas BaMn 2Sb 2 crystallizes in the tetragonal ThCr 2Si 2-type structure. The ρ(T) data indicate semiconducting behaviors for both compounds with activation energies of ≳0.35 eV for SrMn 2Sb 2 and 0.16 eV for BaMn 2Sb 2. The χ(T) andmore » C p(T) data reveal antiferromagnetic (AFM) ordering at T N = 110 K for SrMn 2Sb 2 and 450 K for BaMn 2Sb 2. The anisotropic χ(T≤T N) data also show that the ordered moments in SrMn 2Sb 2 are aligned in the hexagonal ab plane, whereas the ordered moments in BaMn 2Sb 2 are aligned collinearly along the tetragonal c axis. The ab-plane M(H) data for SrMn 2Sb 2 exhibit a continuous metamagnetic transition at low fields 02Sb 2 exhibits no metamagnetic transitions up to 5.5 T. The χ(T) and C p(T) data for both SrMn 2Sb 2 and BaMn 2Sb 2 indicate strong dynamic short-range AFM correlations above their respective T N up to at least 900 K within a local-moment picture, corresponding to quasi-two-dimensional magnetic behavior. The present results and a survey of the literature for Mn pnictides with the CaAl 2Si 2 and ThCr 2Si 2 crystal structures show that the T N values for the CaAl 2Si 2-type compounds are much smaller than those for the ThCr 2Si 2-type materials.« less

Versatile fluoride substrates for Fe-based superconducting thin films

NASA Astrophysics Data System (ADS)

Kurth, F.; Reich, E.; Hänisch, J.; Ichinose, A.; Tsukada, I.; Hühne, R.; Trommler, S.; Engelmann, J.; Schultz, L.; Holzapfel, B.; Iida, K.

2013-04-01

We demonstrate the growth of Co-doped BaFe2As2 (Ba-122) thin films on CaF2 (001), SrF2 (001), and BaF2 (001) single crystal substrates using pulsed laser deposition. All films are grown epitaxially despite of a large misfit of -10.6% for BaF2 substrate. For all films, a reaction layer is formed at the interface confirmed by X-ray diffraction and for the films grown on CaF2 and BaF2 additionally by transmission electron microscopy. The superconducting transition temperature of the film on CaF2 is around 27 K, whereas the corresponding values of the films on SrF2 and BaF2 are around 22 K and 21 K, respectively. The Ba-122 on CaF2 shows almost identical crystalline quality and superconducting properties as films on Fe-buffered MgO.

Synchrotron X-ray studies of epitaxial ferroelectric thin films and nanostructures

NASA Astrophysics Data System (ADS)

Klug, Jeffrey A.

The study of ferroelectric thin films is a field of considerable scientific and technological interest. In this dissertation synchrotron x-ray techniques were applied to examine the effects of lateral confinement and epitaxial strain in ferroelectric thin films and nanostructures. Three materials systems were investigated: laterally confined epitaxial BiFeO3 nanostructures on SrTiO3 (001), ultra-thin commensurate SrTiO 3 films on Si (001), and coherently strained films of BaTiO3 on DyScO3 (110). Epitaxial films of BiFeO3 were deposited by radio frequency magnetron sputtering on SrRuO3 coated SrTiO 3 (001) substrates. Laterally confined nanostructures were fabricated using focused ion-beam processing and subsequently characterized with focused beam x-ray nanodiffraction measurements with unprecedented spatial resolution. Results from a series of rectangular nanostructures with lateral dimensions between 500 nm and 1 mum and a comparably-sized region of the unpatterned BiFeO3 film revealed qualitatively similar distributions of local strain and lattice rotation with a 2-3 times larger magnitude of variation observed in those of the nanostructures compared to the unpatterned film. This indicates that lateral confinement leads to enhanced variation in the local strain and lattice rotation fields in epitaxial BiFeO3 nanostructures. A commensurate 2 nm thick film of SrTiO3 on Si was characterized by the x-ray standing wave (XSW) technique to determine the Sr and Ti cation positions in the strained unit cell in order to verify strain-induced ferroelectricity in SrTiO3/Si. A Si (004) XSW measurement at 10°C indicated that the average Ti displacement from the midpoint between Sr planes was consistent in magnitude to that predicted by a density functional theory (DFT) calculated ferroelectric structure. The Ti displacement determined from a 35°C measurement better matched a DFT-predicted nonpolar structure. The thin film extension of the XSW technique was employed to measure the polar displacement of the Ba cations in a 50 nm thick coherently strained BaTiO3 film on DyScO3 (110). An analysis assuming a bulk-like ratio between the Ti and Ba displacements found that the polar shift of Ba cations was larger than in bulk BaTiO3, which was consistent with strain-induced enhancement of ferroelectric polarization in BaTiO3/DyScO3 (110).

Metal (Ca, Ba, Sr, Pb) heptafluorotantalates(V): Synthesis, Raman spectra and crystal structures

NASA Astrophysics Data System (ADS)

Bunič, Tina; Tramšek, Melita; Goreshnik, Evgeny; Žemva, Boris

2007-01-01

MTaF 7 (M = Ca, Sr, Ba, Pb) were prepared by the reaction of MF 2 + Ta + F 2 (Ca, Sr, Ba) or MF 2 + TaF 5 in anhydrous HF. CaTaF 7 crystallizes in a monoclinic P2 1/ a space group, a = 9.793(3) Å, b = 11.608(3) Å, c = 13.359(4) Å, β = 90.539(13)°, V = 1518.5(7) Å 3. All Ta atoms possess distorted pentagonal-bipyramidal environment with Ta-F distances of 1.878(14)-2.044(13) Å. Three crystallographically independent Ca atoms have coordination number 8. Ca-F distances lie in the range of 2.239(16)-2.836(17) Å. Each Ca 2+ and TaF 72- moiety is bonded to 6 counter-ions. BaTaF 7 crystallizes in a cubic system, space group Pa3¯,a = 9.9009(3)Å, V = 970.56(5) Å 3. Coordination sphere around Ta atom is mono-capped trigonal prism with a Ta-F distance of 1.916(5)-2.004(5) Å. Two crystallographically independent barium atoms have different coordination numbers: for Ba1 C.N. is 12 with Ba1-F distances of 6 × 2.761(5) Å and 6 × 2.858(5) Å, for Ba2 C.N. is 14 with Ba2-F bond lengths 6 × 2.718(5), 2 × 2.814(8) and 6 × 3.236(5) Å. Ba 2+ and TaF 72- moieties are bonded to 8 neighbors. Isostructural PbTaF 7 and SrTaF 7 appear to be monoclinic, space group P2 1/ m, a = 4.8657(11) Å, b = 7.2298(16) Å, c = 6.7370(16) Å, β = 93.932(13)°, V = 236.44(9) Å 3 for PbTaF 7, and a = 4.875(3) Å, b = 7.196(4) Å, c = 6.7218(13) Å, β = 94.265(10), V = 235.2(2) Å for SrTaF 7. Tantalum coordination polyhedron may be described as a distorted mono-capped trigonal prism with the capping atom located on one of the rectangular faces with Ta-F distances of 1.868(3)-1.982(3) Å (PbTaF 7) and 1.908(16)-2.019(12) Å (SrTaF 7). Lead (or strontium) atoms are 9-coordinated and may be viewed as strongly distorted tri-capped trigonal prism, Pb-F 2.438(4)-2.669(3) Å, Sr-F 2.501(19)-2.860(19) Å. Each cation is connected to 8 anions.

Growth and Characterization of Reduced Dimensionality Superconductor-Related Phases by Molecular Beam Epitaxy

DTIC Science & Technology

1998-02-01

BaTiO3 Ferromagnets M., = 1.4 g SrRuO3 Colossal Magnetoresistance AR/RH > 104~ (6 T) (La,Sr)MnO 3 3 submitted to JOM B4Ti 3O12 PbUiO 3 (Ba,K)BiO3 YBa2C...films, perhaps as a result of those films being closer to the correct Ba/Ti stoichiometric ratio. This is seen in Fig. 5, where data for the permittivity ...as a function of temperature is shown for a 60 nm thick BaTiO 3 film (Note Permittivity BSS-12 -- Ls BSS12 that as explained earlier, this film

Metal-halide mixtures for latent heat energy storage

NASA Technical Reports Server (NTRS)

Chen, K.; Manvi, R.

1981-01-01

Alkali metal and alkali halide mixtures are identified which may be suitable for thermal energy storage at temperatures above 600 C. The use of metal-halides is appropriate because of their tendency to form two immiscible melts with a density difference, which reduces scale formation and solidification on heat transfer surfaces. Also, the accumulation of phase change material along the melt interface is avoided by the self-dispersing characteristic of some metal-halides, in particular Sr-SrCl2, Ba-BaCl2, and Ba-BaBr2 mixtures. Further advantages lie in their high thermal conductivities, ability to cope with thermal shock, corrosion inhibition, and possibly higher energy densities.

Point contact Andreev reflection spectroscopic (PCARS) studies on 122-type iron-based superconductors

NASA Astrophysics Data System (ADS)

Lu, Xin; Park, W. K.; Greene, L. H.; Yuan, H. Q.; Chen, G. F.; Luo, G. L.; Wang, N. L.; Sefat, A. S.; McGuire, M. A.; Jin, R.; Sales, B. C.; Mandrus, D.; Gillett, J.; Sebastian, S. E.

2010-03-01

PCARS is applied to investigate the superconducting gap in iron pnictide single crystal superconductors of the AFe2As2 (A=Ba, Sr) family with two categories of G(V) curves observed [1]: one where Andreev reflection (AR) is present for (Ba0.6K0.4)Fe2As2 and Ba(Fe0.9Co0.1)2As2, and the other without AR but a V^2/3 shape for Sr0.6Na0.4Fe2As2 and Sr(Fe0.9Co0.1)2As2. The latter is also observed in the nonsuperconducting parent compound BaFe2As2. Mesoscopic phase-separated coexistence of magnetic and superconducting orders is considered to explain distinct behaviors. A gap size ˜3.0-4.0 meV with 2δ0/kBTc˜2.0-2.6 is observed for PCARS on Ba0.6K0.4Fe2As2. For the Ba(Fe0.9Co0.1)2As2, G(V) curves typically display a zero-bias conductance peak, sometimes with a V-shape background. [1] Xin Lu et al., arXiv:0910.4230

Application of ICP-OES for evaluating energy extraction and production wastewater discharge impacts on surface waters in Western Pennsylvania.

PubMed

Pancras, Joseph Patrick; Norris, Gary A; Landis, Matthew S; Kovalcik, Kasey D; McGee, John K; Kamal, Ali S

2015-10-01

Oil and gas extraction and coal-fired electrical power generating stations produce wastewaters that are treated and discharged to rivers in Western Pennsylvania with public drinking water system (PDWS) intakes. Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to quantify inorganic species in wastewater and river samples using a method based on EPA Method 200.7 rev4.4. A total of 53 emission lines from 30 elements (Al, As, B, Ba, Ca, Cd, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, Tl, V, and Zn) were investigated. Samples were prepared by microwave-assisted acid digestion using a mixture of 2% HNO3 and 0.5% HCl. Lower interferences and better detection characteristics resulted in selection of alternative wavelengths for Al, As, Sb, Mg, Mo, and Na. Radial view measurements offered accurate determinations of Al, Ba, K, Li, Na, and Sr in high-brine samples. Spike recovery studies and analyses of reference materials showed 80-105% recoveries for most analytes. This method was used to quantify species in samples with high to low brine concentrations with method detection limits a factor of 2 below the maximum contaminant limit concentrations of national drinking water standards. Elements B, Ca, K, Li, Mg, Na, and Sr were identified as potential tracers for the sources impacting PDWS intakes. Usability of the ICP-OES derived data for factor analytic model applications was also demonstrated. Published by Elsevier B.V.

p-tert-Butylcalix[6]arene hexacarboxylic acid as host for Pb(ii), Sr(ii) and Ba(ii)†

PubMed Central

Adhikari, Birendra Babu; Zhao, Xiang; Derakhshan, Shahab

2015-01-01

p-tert-Butylcalixarene hexacarboxylic acid initially binds with low symmetry, to later adopt a highly symmetric up-down alternating conformation in the presence of Pb, Sr or Ba. The conformational dynamics for the three ions are distinct, from 15 hours, to 20 days, to 38 days, respectively. PMID:25198172

Theoretical investigation on thermoelectric properties of (Ca,Sr,Ba)Fe2(As/Bi)2 compounds under temperature

NASA Astrophysics Data System (ADS)

Jayalakshmi, D. S.; Sundareswari, M.; Viswanathan, E.; Das, Abhijeet

2018-04-01

The electrical conductivity, resistivity and Seebeck coefficient, Pauli magnetic susceptibility and power factor are computed under temperature (100 K - 800 K) in steps of 100 K for the theoretically designed compounds namely (Ca,Sr,Ba)Fe2Bi2 and their parent compounds namely (Ca,Sr,Ba)Fe2As2 by using Boltzmann transport theory interfaced to the Wien2k program. The Bulk modulus, electron phonon coupling constant, thermoelectric figure of merit (ZT) and transition temperature are calculated for the optimized anti ferromagnetic phase of the proposed compounds. The results are discussed for the novel compounds in view of their superconductivity existence and compared with their parent unconventional superconducting compounds.

Enhance D. C. resistivity of Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} ceramic by acceptor (Mn) doping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Hakikat, E-mail: sharmahakikat@yahoo.in; Arya, G. S.; Pramar, Kusum

2015-05-15

In the present work, we prepared Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} and Mn (2 and 3 at % on Ti site) doped Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} ceramic by sol- gel method. The samples were characterized by X-ray diffraction (XRD). The XRD patterns reveled that Mn ions did not change the perovskite structure of BST (70/30). The dielectric measurements proved that dielectric constant decreased with Mn doping. The dc resistivity was studied by using I-V measurements. The dc resistivity of the BST increased with Mn doping, which suppressed the leakage current.

Multi-proxy Reconstructions of the Eastern Equatorial Pacific: Measuring Sr/Ca, Ba/Ca, and Li/Mg in Modern Corals Using ICP-OES

NASA Astrophysics Data System (ADS)

Cheung, A. H.; Cole, J. E.; Vetter, L.; Jimenez, G.; Thompson, D. M.; Tudhope, A. W.

2017-12-01

Sea surface temperature (SST) in the Eastern Equatorial Pacific (EEP) exhibits large variability on multiple timescales. These variations are often related to modes of climate variability that exert significant influence on global climate, such as the El Niño Southern Oscillation. However, the short length and sparsity of instrumental data in the EEP limits our ability to discern changes in this region. Geochemical signals in corals can help extend instrumental data further back in time. While δ18O and Sr/Ca are the most commonly analyzed geochemical tracers of SST in corals, they often have site-specific complications. Several alternatives (e.g., Li/Mg) have been proposed to overcome these challenges, but have yet to be applied to long climate records, in part due to the cost and time required to measure these elements. Here, we develop a new method that uses Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) to analyze Li/Mg, Sr/Ca, and Ba/Ca ratios in coral aragonite. We apply this method to two Porites spp. corals collected from the northern Galapagos archipelago (Wolf and Darwin Islands). We specifically assess the fidelity of Li/Mg and Sr/Ca to reconstruct SST, and Ba/Ca to reconstruct upwelling conditions. Our results confirm that both Li/Mg and Sr/Ca track SST. We show that despite analytical noise, downcore reconstructions of Li/Mg have the potential to provide additional information about SST that is not present in reconstructions generated from Sr/Ca alone. Skeletal Ba/Ca shows little relationship with upwelling, perhaps because of the distance of our sites from the center of upwelling in the southern Galapagos. These results demonstrate the potential for analyzing Sr, Li, Ba, Mg simultaneously in corals with a cost- and time- efficient method, which may be applied to coral paleoclimate sites worldwide.

PbF2-based single crystals and phase diagrams of PbF2-MF2 systems (M = Mg, Ca, Sr, Ba, Cd)

NASA Astrophysics Data System (ADS)

Buchinskaya, I. I.; Fedorov, Pavel P.; Sobolev, B. P.

1997-07-01

Optical grade single crystals of Pb0.67Cd0.33F2 and Pb1-xCaxF2 (x less than 0.05) were grown by the Bridgman technique in graphite crucibles under fluorinating atmosphere of teflon pyrolysis products. For determinations of concentration areas of solid solutions, suitable for crystal growth, the phase interactions in the systems PbF2 with fluorides of alkaline-earth elements and Cd were studied by DTA and x-ray powder diffraction techniques. Phase diagrams were described by corresponding thermodynamic models. Transition from pure PbF2 to two- component Pb0.67Cd0.33F2 crystal is accompanied by some increase in radiation hardness of the latter and positive changes of mechanical characteristics (the Pb0.67Cd0.33F2 composition microhardness is 147 plus or minus 5 kg/mm2 that is 5 times that of a pure lead fluoride, 28 plus or minus 4 kg/mm2). These solid solutions have a cubic Fm3m fluorite-type lattice as a high-temperature modification of PbF2.

Carbonate-coordinated metal complexes precede the formation of liquid amorphous mineral emulsions of divalent metal carbonates†

PubMed Central

Wolf, Stephan E.; Müller, Lars; Barrea, Raul; Kampf, Christopher J.; Leiterer, Jork; Panne, Ulrich; Hoffmann, Thorsten

2011-01-01

During the mineralisation of metal carbonates MCO3 (M = Ca, Sr, Ba, Mn, Cd, Pb) liquid-like amorphous intermediates emerge. These intermediates that form via a liquid/liquid phase separation behave like a classical emulsion and are stabilized electrostatically. The occurrence of these intermediates is attributed to the formation of highly hydrated networks whose stability is mainly based on weak interactions and the variability of the metal-containing pre-critical clusters. Their existence and compositional freedom are evidenced by electrospray ionization mass spectrometry (ESI-MS). Liquid intermediates in non-classical crystallisation pathways seem to be more common than assumed. PMID:21218241

Composition and Elution Behavior of Various Elements from Printed Circuit Boards, Cathode-ray Tube Glass, and Liquid-crystal Displays in Waste Consumer Electronics.

PubMed

Inaba, Kazuho; Murata, Tomoyoshi; Yamamura, Shigeki; Nagano, Masaaki; Iwasaki, Kazuhiro; Nakajima, Daisuke; Takigami, Hidetaka

2018-01-01

The contents and elution behavior of metals in consumer electronics parts were determined so as to understand their maximum environmental risk. Elements contained most in printed-circuit boards were Cu, Si, Br, Ca, Al, Sn, Pb, Sb, Ba, Fe, Ni, Ti, and Zn; in cathode-ray tube glass were Si, Pb, Ba, Sr, Zn, Zr, Ca, and Sb; in arsenic contained liquid-crystal displays were Si, Ca, Sr, Ba, As, and Fe; and in antimony contained liquid-crystal displays were Si, Ba, Ca, Sb, Sr, Fe, and Sn. The elements eluted most from printed-circuit boards were Zn, Pb, and Cu; from cathode-ray tube glass were Pb, Zn, B, Ba, and Si; and from liquid-crystal displays were B and Si, and the toxic As and Sb. The amount eluted was greatest at acidic pH. It was revealed that officially recommended 6-h-shaking with a pure water test was insufficient to understand the real environmental risk of waste electronics.

Interface Control of Ferroelectricity in an SrRuO3 /BaTiO3 /SrRuO3 Capacitor and its Critical Thickness.

PubMed

Shin, Yeong Jae; Kim, Yoonkoo; Kang, Sung-Jin; Nahm, Ho-Hyun; Murugavel, Pattukkannu; Kim, Jeong Rae; Cho, Myung Rae; Wang, Lingfei; Yang, Sang Mo; Yoon, Jong-Gul; Chung, Jin-Seok; Kim, Miyoung; Zhou, Hua; Chang, Seo Hyoung; Noh, Tae Won

2017-05-01

The atomic-scale synthesis of artificial oxide heterostructures offers new opportunities to create novel states that do not occur in nature. The main challenge related to synthesizing these structures is obtaining atomically sharp interfaces with designed termination sequences. In this study, it is demonstrated that the oxygen pressure (PO2) during growth plays an important role in controlling the interfacial terminations of SrRuO 3 /BaTiO 3 /SrRuO 3 (SRO/BTO/SRO) ferroelectric (FE) capacitors. The SRO/BTO/SRO heterostructures are grown by a pulsed laser deposition method. The top SRO/BTO interface, grown at high PO2 (around 150 mTorr), usually exhibits a mixture of RuO 2 -BaO and SrO-TiO 2 terminations. By reducing PO2, the authors obtain atomically sharp SRO/BTO top interfaces with uniform SrO-TiO 2 termination. Using capacitor devices with symmetric and uniform interfacial termination, it is demonstrated for the first time that the FE critical thickness can reach the theoretical limit of 3.5 unit cells. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Interface Control of Ferroelectricity in an SrRuO 3/BaTiO 3/SrRuO 3 Capacitor and its Critical Thickness

DOE PAGES

Shin, Yeong Jae; Kim, Yoonkoo; Kang, Sung -Jin; ...

2017-03-03

Here, the atomic-scale synthesis of artificial oxide heterostructures offers new opportunities to create novel states that do not occur in nature. The main challenge related to synthesizing these structures is obtaining atomically sharp interfaces with designed termination sequences. In this study, it is demonstrated that the oxygen pressure (P O2) during growth plays an important role in controlling the interfacial terminations of SrRuO 3/BaTiO 3/SrRuO 3 (SRO/BTO/SRO) ferroelectric (FE) capacitors. The SRO/BTO/SRO heterostructures are grown by a pulsed laser deposition method. The top SRO/BTO interface, grown at high P O2 (around 150 mTorr), usually exhibits a mixture of RuO 2-BaOmore » and SrO-TiO 2 terminations. By reducing P O2, the authors obtain atomically sharp SRO/BTO top interfaces with uniform SrO-TiO 2 termination. Using capacitor devices with symmetric and uniform interfacial termination, it is demonstrated for the first time that the FE critical thickness can reach the theoretical limit of 3.5 unit cells.« less

Ionomic profiling of Nicotiana langsdorffii wild-type and mutant genotypes exposed to abiotic stresses.

PubMed

Ardini, Francisco; Soggia, Francesco; Abelmoschi, Maria Luisa; Magi, Emanuele; Grotti, Marco

2013-01-01

To provide a new insight into the response of plants to abiotic stresses, the ionomic profiles of Nicotiana langsdorffii specimens have been determined before and after exposure to toxic metals (chromium) or drought conditions. The plants were genetically transformed with the rat glucocorticoid receptor (GR) or the gene for Agrobacterium rhizogenes rolC, because these modifications are known to produce an imbalance in phytohormone equilibria and a significant change in the defence response of the plant. Elemental profiles were obtained by developing and applying analytical procedures based on inductively coupled plasma atomic emission and mass spectrometry (ICP-AES/MS). In particular, the removal of isobaric interferences affecting the determination of Cr and V by ICP-MS was accomplished by use of a dynamic reaction cell, after optimization of the relevant conditions. The combined use of ICP atomic emission and mass spectrometry enabled the determination of 29 major and trace elements (Ba, Bi, Ca, Cd, Co, Cr, Cu, Eu, Fe, Ga, K, Li, Mg, Mn, Mo, Na, P, Pb, Pt, Rb, S, Sb, Sn, Sr, Te, V, W, Y, and Zn) in different parts of the plants (roots, stems, and leaves), with high accuracy and precision. Multivariate data processing and study of element distribution patterns provided new information about the ionomic response of the target organism to chemical treatment or water stress. Genetic modification mainly affected the distribution of Bi, Cr, Mo, Na, and S, indicating that these elements were involved in biochemical processes controlled by the GR or rolC genes. Chemical stress strongly affected accumulation of several elements (Ba, Ca, Fe, Ga, K, Li, Mn, Mo, Na, P, Pb, Rb, S, Sn, Te, V, and Zn) in different ways; for Ca, Fe, K, Mn, Na, and P the effect was quite similar to that observed in other studies after treatment with other transition elements, for example Cu and Cd. The effect of water deficit was less evident, mainly consisting in a decrease of Ba, Cr, Na, and Sr in roots.

Exposure of children to metals via tap water ingestion at home: Contamination and exposure data from a nationwide survey in France.

PubMed

Le Bot, Barbara; Lucas, Jean-Paul; Lacroix, Françoise; Glorennec, Philippe

2016-09-01

29 inorganic compounds (Al, As, B, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, Gd, K, Mg, Mn, Mo, Na, Nd, Ni, Pb, Sb, Se, Sr, Tl, U, V and Zn) were measured in the tap water of 484 representative homes of children aged 6months to 6years in metropolitan France in 2008-2009. Parents were asked whether their children consumed tap water. Sampling design and sampling weights were taken into account to estimate element concentrations in tap water supplied to the 3,581,991 homes of 4,923,058 children aged 6months to 6years. Median and 95th percentiles of concentrations in tap water were in μg/L: Al: <10, 48.3, As: 0.2, 2.1; B: <100, 100; Ba: 30.7, 149.4; Ca: 85,000, 121,700; Cd: <0.5, <0.5; Ce: <0.5, <0.5; Co: <0.5, 0.8; Cr: <5, <5; Cu: 70, 720; K: 2210, 6740; Fe: <20, 46; Mn: <5, <5; Mo: <0.5, 1.5; Na: 14,500, 66,800; Ni: <2, 10.2; Mg: 6500, 21,200; Pb: <1, 5.4; Sb: <0.5, <0.5; Se: <1, 6.7; Sr: 256.9, 1004; Tl: <0.5, <0.5; U: <0.5, 2.4; V: <1, 1; Zn: 53, 208. Of the 2,977,123 young children drinking tap water in France, some were drinking water having concentrations above the 2011 World Health Organization drinking-water quality guidelines: respectively 498 (CI 95%: 0-1484) over 700μg/L of Ba; 121,581 (CI 95%: 7091-236,070) over 50mg/L of Na; 2044 (CI 95%: 0-6132) over 70μg/L of Ni, and 78,466 (17,171-139,761) over 10μg/L of Pb. Since it is representative, this tap water contamination data can be used for integrated exposure assessment, in conjunction with diet and environmental (dust and soil) exposure data. Copyright © 2016 Elsevier Ltd. All rights reserved.

Metallic elements and metalloids in Boletus luridus, B. magnificus and B. tomentipes mushrooms from polymetallic soils from SW China.

PubMed

Falandysz, Jerzy; Zhang, Ji; Wiejak, Anna; Barałkiewicz, Danuta; Hanć, Anetta

2017-08-01

Yunnan Province in China is known for its high biodiversity of mushrooms and a diverse geochemistry of soil bedrock and polymetallic soils, but our knowledge of mineral compositions of mushrooms from Yunnan is scarce. The metallic trace elements, Ag, Ba, Co, Cd, Cs, Cu, Cr, Hg, Li, Mn, Ni, Pb, Rb, Sr, V, Tl, U and Zn, and the metalloids, As and Sb, have been investigated using validated methods with a dynamic reactive cell by mass spectroscopy - inductive coupled plasma and cold vapour - atomic absorption spectroscopy on three popular species of Boletus mushrooms from Southwestern China. The trace mineral profiles in caps and stipes of B. luridus (24 individuals), B. magnificus (29 individuals) and B. tomentipes (38 individuals) have been evaluated. The interspecific differences in the content of several trace elements could be attributed to known differences in the geochemistry of soils in Yunnan, but for copper a difference was observed within species. The mean values of concentrations in composite samples of caps for B. luridus, B. magnificus and B. tomentipes from three to four locations were at the ranges (mgkg -1 dry biomass): Ag (1.3-3.7), As (0.79-53), Ba (4.0-12), Co (0.68-1.2), Cd (0.79-2.2), Cs (0.67-55), Cu (37-77), Cr (5.0-7.6), Hg (2.1-5.4), Li (0.15-0.61), Mn (13-28), Ni (0.86-4.6), Pb (0.59-1.8), Rb (90-120), Sb (0.014-0.088), Sr (0.63-1.6), V (1.4-2.2), Tl (0.017-0.054), U (0.029-0.065) and Zn (130-180). Caps of Boletus mushrooms were richer in Ag, Cu, Hg and Zn than stipes, while other elements were distributed roughly equally between both morphological parts. B. luridus, B. magnificus and B. tomentipes grew in certain sites in Yunnan contained Ag, As, Ba, Cr, Hg, Ni, Sr or V at elevated concentration. A specific geochemistry of the soils type (latosols, lateritic red earths, and red and yellow earths in the Circum-Pacific Mercuriferous Belt of Southwestern China) can explain occurrence of some minerals at greater or elevated amount in mushrooms in Yunnan, while number of available research and data on mineral composition of mushrooms due to geochemical anomalies of soil parent material is so far little. Copyright © 2017 Elsevier Inc. All rights reserved.

Interfacial dislocations in (111) oriented (Ba 0.7Sr 0.3)TiO 3 films on SrTiO 3 single crystal

DOE PAGES

Shen, Xuan; Yamada, Tomoaki; Lin, Ruoqian; ...

2015-10-08

In this study, we have investigated the interfacial structure of epitaxial (Ba,Sr)TiO 3 films grown on (111)-oriented SrTiO 3 single-crystal substrates using transmission electron microscopy (TEM) techniques. Compared with the (100) epitaxial perovskite films, we observe dominant dislocation half-loop with Burgers vectors of a<110> comprised of a misfit dislocation along <112>, and threading dislocations along <110> or <100>. The misfit dislocation with Burgers vector of a <110> can dissociate into two ½ a <110> partial dislocations and one stacking fault. We found the dislocation reactions occur not only between misfit dislocations, but also between threading dislocations. Via three-dimensional electron tomography,more » we retrieved the configurations of the threading dislocation reactions. The reactions between threading dislocations lead to a more efficient strain relaxation than do the misfit dislocations alone in the near-interface region of the (111)-oriented (Ba 0.7Sr 0.3)TiO 3 films.« less

Synchrotron X-ray diffraction study of the Ba{sub 1−x}SrSnO{sub 3} solid solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prodjosantoso, Anti K., E-mail: Prodjosantoso@yahoo.com; Zhou, Qingdi; Kennedy, Brendan J.

At room temperature the sequence of phases with increasing amounts of strontium in the stannate perovskite system Ba{sub 1−x}SrSnO{sub 3} has been established from high resolution synchrotron X-ray powder diffraction. The observed sequence orthorhombic (Pbnm), orthorhombic (Ibmm), tetragonal (I4/mcm), and cubic (Pm3-bar m) is a consequence of the sequential introduction of cooperative tilting of the corner sharing SnO{sub 6} octahedra. The cell volume changes smoothly across the series with no obvious discontinuities associated with the phase transitions. - Graphical abstract: Portions of the synchrotron X-ray diffraction profiles (λ=0.82453 Å) from selected Ba{sub 1−x}Sr{sub x}SnO{sub 3} samples together with the resultsmore » of fitting by the Rietveld method. Highlights: ► Structures of the stannate perovskites Ba{sub 1−x}SrSnO{sub 3} refined from synchrotron XRD. ► The sequence Pm3-bar m→I4/mcm→Ibmm→Pbnm results from tilting of the octahedra. ► The tilting maintains optimal bonding of the cations seen from the BVS analysis.« less

Computational study of Ca, Sr and Ba under pressure

NASA Astrophysics Data System (ADS)

Jona, F.; Marcus, P. M.

2006-05-01

A first-principles procedure for the calculation of equilibrium properties of crystals under hydrostatic pressure is applied to Ca, Sr and Ba. The procedure is based on minimizing the Gibbs free energy G (at zero temperature) with respect to the structure at a given pressure p, and hence does not require the equation of state to fix the pressure. The calculated lattice constants of Ca, Sr and Ba are shown to be generally closer to measured values than previous calculations using other procedures. In particular for Ba, where careful and extensive pressure data are available, the calculated lattice parameters fit measurements to about 1% in three different phases, both cubic and hexagonal. Rigid-lattice transition pressures between phases which come directly from the crossing of G(p) curves are not close to measured transition pressures. One reason is the need to include zero-point energy (ZPE) of vibration in G. The ZPE of cubic phases is calculated with a generalized Debye approximation and applied to Ca and Sr, where it produces significant shifts in transition pressures. An extensive tabulation is given of structural parameters and elastic constants from the literature, including both theoretical and experimental results.

Synthesis of MSnO{sub 3} (M = Ba, Sr) nanoparticles by reverse micelle method and particle size distribution analysis by whole powder pattern modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmed, Jahangeer; Blakely, Colin K.; Bruno, Shaun R.

2012-09-15

Highlights: ► BaSnO{sub 3} and SrSnO{sub 3} nanoparticles synthesized using the reverse micelle method. ► Particle size and size distribution studied by whole powder pattern modeling. ► Nanoparticles are of optimal size for investigation in dye-sensitized solar cells. -- Abstract: Light-to-electricity conversion efficiency in dye-sensitized solar cells critically depends not only on the dye molecule, semiconducting material and redox shuttle selection but also on the particle size and particle size distribution of the semiconducting photoanode. In this study, nanocrystalline BaSnO{sub 3} and SrSnO{sub 3} particles have been synthesized using the microemulsion method. Particle size distribution was studied by whole powdermore » pattern modeling which confirmed narrow particle size distribution with an average size of 18.4 ± 8.3 nm for SrSnO{sub 3} and 15.8 ± 4.2 nm for BaSnO{sub 3}. These values are in close agreement with results of transmission electron microscopy. The prepared materials have optimal microstructure for successive investigation in dye-sensitized solar cells.« less

Mechanochemical synthesis of MgF2 - MF2 composite systems (M = Ca, Sr, Ba)

NASA Astrophysics Data System (ADS)

Scholz, G.; Breitfeld, S.; Krahl, T.; Düvel, A.; Heitjans, P.; Kemnitz, E.

2015-12-01

The capability of mechanochemical synthesis for the formation of MgF2-MF2 (M: Ca, Sr, Ba) composites, solid solutions or well-defined compounds was tested applying a fluorination of different fluorine-free metal sources with NH4F directly at milling. No evidence was found for a substitution of Mg2+ with Ca2+ (Sr2+, Ba2+) ions, or vice versa, in rutile or fluorite structure. However, an equimolar ratio of Mg2+ to the second cation allows the mechanochemical synthesis of tetrafluoromagnesates, MMgF4, which is more and more hampered the smaller the radius of the cation M2+ is. BaMgF4 is formed even phase pure from the acetates, SrMgF4 can only be observed in a mixture accompanied by the binary fluorides. In addition, 19F MAS NMR spectra along with calculations of 19F isotropic chemical shift values according to the superposition model point to the formation of a metastable phase of CaMgF4, which disappears at thermal treatment and decomposes into the binary fluorides CaF2 and MgF2.

Integrated elemental and Sr-Nd-Pb-Hf isotopic studies of Mesozoic mafic dykes from the eastern North China Craton: implications for the dramatic transformation of lithospheric mantle

NASA Astrophysics Data System (ADS)

Liu, Shen; Feng, Caixia; Santosh, M.; Feng, Guangying; Coulson, Ian M.; Xu, Mengjing; Guo, Zhuang; Guo, Xiaolei; Peng, Hao; Feng, Qiang

2018-02-01

Evolution of the lithospheric mantle beneath the North China Craton (NCC) from its Precambrian cratonic architecture until Paleozoic, and the transformation to an oceanic realm during Mesozoic, with implications on the destruction of cratonic root have attracted global attention. Here we present geochemical and isotopic data on a suite of newly identified Mesozoic mafic dyke swarms from the Longwangmiao, Weijiazhuang, Mengjiazhuang, Jiayou, Huangmi, and Xiahonghe areas (Qianhuai Block) along the eastern NCC with an attempt to gain further insights on the lithospheric evolution of the region. The Longwangmiao dykes are alkaline with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 4.3) and EM1-like Sr-Nd-Pb-Hf isotopic signature ((87Sr/86Sr) i > 0.706; ε Nd (t) < -6.3, (206Pb/204Pb) i > 16.6, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.8, ε Hf (t) < -22.4). The Weijiazhuang dykes are sub-alkaline with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 3.7), and display similar EM1-like isotopic features ((87Sr/86Sr) i > 0.706; ε Nd (t) < -7.0, (206Pb/204Pb) i > 16.7, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.9, ε Hf (t) < -23.3). The Mengjiazhuang dykes are also sub-alkaline with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 2.4) and EM1-like isotopic features((87Sr/86Sr) i > 0.706; ε Nd (t) < -18.4, (206Pb/204Pb) i > 16.7, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.9, ε Hf (t) < -8.6). The Jiayou dykes also display sub-alkaline affinity with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 3.7) and EM1-like Sr-Nd-Pb-Hf isotopic features ((87Sr/86Sr) i > 0.706; ε Nd(t) < -15.3, (206Pb/204Pb) i > 16.7, (207Pb/204Pb) i > 15.4, (208Pb/204Pb) i > 36.9, ε Hf (t) < -18.4). The Huangmi dykes are alkaline (with Na2O + K2O ranging to more than 5.9 wt.%)) with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N > 9.3) and EM1-like isotopic composition ((87Sr/86Sr) i > 0.705; ε Nd (t) < -15.1, (206Pb/204Pb) i > 16.9, (207Pb/204Pb) i > 15.5, (208Pb/204Pb) i > 36.9, ε Hf (t) < -12.2). The Xiahonghe dykes are alkaline with LILE (Ba and K)- and LREE-enrichment ((La/Yb) N = 2.12-2.84) and similar EM1-like Sr-Nd-Pb-Hf isotopic signature ((87Sr/86Sr) i > 0.705; ε Nd (t)<-18.0, (206Pb/204Pb) i > 16.9, (207Pb/204Pb) i > 15.5, (208Pb/204Pb) i > 36.9, ε Hf (t) < -8.6). Our data from the various mafic dyke suites suggest that the magmas were derived from EM1-like lithospheric mantle, corresponding to lithospheric mantle modified by the previously foundered lower crust beneath the eastern NCC. Our results suggest contrasting lithospheric evolution from Triassic (212 Ma) to Cretaceous (123 Ma) beneath the NCC. These mafic dykes mark an important phase of lithospheric thinning in the eastern North China Craton.

High ferroelectric polarization in c-oriented BaTiO 3 epitaxial thin films on SrTiO 3/Si(001)

DOE PAGES

Scigaj, M.; Chao, C. H.; Gázquez, J.; ...

2016-09-21

The integration of epitaxial BaTiO 3 films on silicon, combining c-orientation, surface flatness, and high ferroelectric polarization is of main interest towards its use in memory devices. This combination of properties has been only achieved so far by using yttria-stabilized zirconia buffer layers. Here, the all-perovskite BaTiO 3/LaNiO 3/SrTiO 3 heterostructure is grown monolithically on Si(001). The BaTiO 3 films are epitaxial and c-oriented and present low surface roughness and high remnant ferroelectric polarization around 6 μC/cm 2. Lastly, this result paves the way towards the fabrication of lead-free BaTiO 3 ferroelectric memories on silicon platforms.

First-Principles Prediction of Two-Dimensional Electron Gas Driven by Polarization Discontinuity in Nonpolar/Nonpolar AHfO3/SrTiO3 (A=Ca, Sr, and Ba) Heterostructures

NASA Astrophysics Data System (ADS)

Cheng, Jianli; Nazir, Safdar; Yang, Kesong

By using first-principles electronic structure calculations, we explored the possibility of producing two-dimensional electron gas (2DEG) in nonpolar/nonpolar AHfO3/SrTiO3 (A = Ca, Sr, and Ba) heterostructures (HS). Two types of interfaces, AO/TiO2 and HfO2/SrO, each with AO and HfO2 surface terminations, are modeled, respectively. The polarization domain and resulting interfacial electronic property are found to be more sensitive to the surface termination of the film rather than the interface model. As film thickness increases, an insulator-to-metal transition (IMT) is found in all the HS with HfO2 surface termination: for AO/TiO2 interfaces, predicted critical film thickness for an IMT is about 7, 6, and 3 unit cells for CaHfO3/SrTiO3, SrHfO3/SrTiO3, and BaHfO3/SrTiO3, respectively; for HfO2/SrO interfaces, the critical film thickness is about 7.5, 5.5, and 4.5 unit cells, respectively. In contrast, for the HS with AO surface termination, only CaHfO3/SrTiO3 exhibits an IMT with a much larger critical film thickness about 11 - 12 unit cells. This work is expected to stimulate further experimental investigation to the interfacial conductivity in the nonpolar/nonpolar AHfO3/SrTiO3 HS. National Science Foundation and Department of Defense National Security Science and Engineering Faculty Fellowship.

Synthesis and coordination chemistry of TpC*MI complexes where M=Mg, Ca, Sr, Ba and Zn and TpC*=tris[3-(2-methoxy-1,1-dimethyl)pyrazolyl]hydroborate.

PubMed

Chisholm, Malcolm H; Gallucci, Judith C; Yaman, Gulsah

2009-01-14

Reactions involving MI2 where M=Mg, Ca, Sr, Ba or Zn and M'TpC* where M'=Na or Tl and TpC*=tris[3-methoxy-1,1-dimethyl)pyrazolyl]hydroborate in tetrahydrofuran are described leading to the isolation and characterization of the complexes TpC*MgI, , TpC*CaI, , TpC*SrI, , TpC*SrI(THF), , TpC*BaI, , TpC*BaI(pz*H), , where pz*H=3-(2-methoxyl-1,1-dimethyl)pyrazole, TpC*BaI.1/2toluene, and TpC*ZnI, . The compounds , , , , and have been characterized by single-crystal X-ray crystallography. Compounds and are isostructural and are salt-like containing kappa6-TpM+ cations and I- anions. In all other structures, the iodide is bound to the metal and TpC* is kappa6 bonded to the group 2 M(2+) ions. Reactions involving TpC*CaI, , and sodium or lithium alkoxides or amides failed to yield the amide or alkoxide calcium TpC* derivative, though related reactions involving TpC*ZnI, , and KOSiMe3 proceeded quantitatively to yield kappa3TpC*ZnOSiMe3, , which was also structurally characterized and shown to have the kappa3-TpC* bound ligand.

Air quality in urban parking garages (PM10, major and trace elements, PAHs): Instrumental measurements vs. active moss biomonitoring

NASA Astrophysics Data System (ADS)

Vuković, Gordana; Aničić Urošević, Mira; Razumenić, Ivana; Kuzmanoski, Maja; Pergal, Miodrag; Škrivanj, Sandra; Popović, Aleksandar

2014-03-01

This study was performed in four parking garages in downtown of Belgrade with the aim to provide multi-pollutant assessment. Concentrations of 16 US EPA priority PAHs and Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr and Zn were determined in PM10 samples. The carcinogenic health risk of employees' occupational exposure to heavy metals (Cd, Cr, Ni and Pb) and PAHs (B[a]A, Cry, B[b]F, B[k]F, B[a]P and DB[ah]A) was estimated. A possibility of using Sphagnum girgensohnii moss bags for monitoring of trace element air pollution in semi-enclosed spaces was evaluated as well. The results showed that concentrations of PM10, Cd, Ni and B[a]P exceeded the EU Directive target values. Concentration of Zn, Ba and Cu were two orders of magnitude higher than those measured at different urban sites in European cities. Cumulative cancer risk obtained for heavy metals and PAHs was 4.51 × 10-5 and 3.75 × 10-5 in M and PP, respectively; upper limit of the acceptable US EPA range is 10-4. In the moss, higher post-exposure than pre-exposure (background) element concentrations was observed. In comparison with instrumental monitoring data, similar order of abundances of the most elements in PM10 and moss samples was found. However, using of the S. girgensohnii moss bag technique in indoor environments needs further justification.

PIXE and ICP-MS Analysis of Andrographis Paniculata Medicinal Plant

NASA Astrophysics Data System (ADS)

Chandrasekhar Rao, J.; Naidu, B. G.; Sarita, P.; Srikanth, S.; Naga Raju, G. J.

2017-08-01

The concentrations of elements Li, Be, Al, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Ag, Cd, Ba, Pb and U in Andrographis Paniculata medicinal plant used in the treatment of Diabetes Mellitus were determined by using Particle Induced X-ray Emission (PIXE) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) techniques. This plant was collected from four different geographical locations in Andhra Pradesh, India in order to assess the regional variation of elemental concentrations. Appreciable levels of K, Ca, Cr, Mn, Cu and Zn determined in this plant can be correlated to the antidiabetic property of Andrographis Paniculata since these elements are known to regulate and potentiate insulin action. Presence of toxic elements As, Cd and Pb necessitates the adoption of precautionary measures while prescribing dosage of the herbal medicine prepared from this plant for the treatment diabetes mellitus.

Investigation on gamma and neutron radiation shielding parameters for BaO/SrO‒Bi2O3‒B2O3 glasses

NASA Astrophysics Data System (ADS)

Sayyed, M. I.; Lakshminarayana, G.; Dong, M. G.; Ersundu, M. Çelikbilek; Ersundu, A. E.; Kityk, I. V.

2018-04-01

In this work, mass attenuation coefficients (μ/ρ), effective atomic number (Zeff), electron density (Ne), mean free path (MFP), and half-value layer (HVL) of 20 BaO/SrO‒(x) Bi2O3‒(80‒x) B2O3 glasses (where x=10, 20, 30, 40, 50 and 60 mol%) were calculated using WinXCom program and MCNP5 code. The obtained (μ/ρ) results using both MCNP5 code and WinXCom program were in good agreement. It is found that the addition of Bi2O3 leads to increase the Zeff values in both BaO/SrO‒Bi2O3‒B2O3 glass systems. However, the Zeff values of the BaO‒Bi2O3‒B2O3 glass system are higher than those of the SrO‒Bi2O3‒B2O3 glasses. The fast neutrons effective removal cross sections (ΣR) for 20 SrO‒40 Bi2O3‒40 B2O3 glass is the highest among all studied glasses. The calculated half-value layer values were compared with different glass systems and it was found that the shielding properties of the selected glasses are comparable or even better than other glass systems such as phosphate glasses.

Electronic, optical properties and chemical bonding in six novel 1111-like chalcogenide fluorides AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) from first principles calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bannikov, V.V.; Shein, I.R.; Ivanovskii, A.L., E-mail: ivanovskii@ihim.uran.ru

2012-12-15

Employing first-principles band structure calculations, we have examined the electronic, optical properties and the peculiarities of the chemical bonding for six newly synthesized layered quaternary 1111-like chalcogenide fluorides SrAgSF, SrAgSeF, SrAgTeF, BaAgSF, BaAgSeF, and SrCuTeF, which are discussed in comparison with some isostructural 1111-like chalcogenide oxides. We found that all of the studied phases AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) are semiconductors for which the fitted 'experimental' gaps lie in the interval from 2.23 eV (for SrAgSeF) to 3.07 eV (for SrCuTeF). The near-Fermi states of AMChF are formed exclusively by the valence orbitals of the atomsmore » from the blocks (MCh); thus, these phases belong to the layered materials with 'natural multiple quantum wells'. The bonding in these new AMChF phases is described as a high-anisotropic mixture of ionic and covalent contributions, where ionic M-Ch bonds together with covalent M-Ch and Ch-Ch bonds take place inside blocks (MCh), while inside blocks (AF) and between the adjacent blocks (MCh)/(AF) mainly ionic bonds emerge. - Graphical Abstract: Isoelectronic surface for SrAgSeF and atomic-resolved densities of states for SrAgTeF, and SrCuTeF. Highlights: Black-Right-Pointing-Pointer Very recently six new layered 1111-like chalcogenide fluorides AMChF were synthesized. Black-Right-Pointing-Pointer Electronic, optical properties for AMChF phases were examined from first principles. Black-Right-Pointing-Pointer All these materials are characterized as non-magnetic semiconductors. Black-Right-Pointing-Pointer Bonding is highly anisotropic and includes ionic and covalent contributions. Black-Right-Pointing-Pointer Introduction of magnetic ions in AMChF is proposed for search of novel magnetic materials.« less

Interdiffusion effect on strained La0.8Ba0.2MnO3 thin films by off-axis sputtering on SrTiO3 (100) substrates

NASA Astrophysics Data System (ADS)

Chou, Hsiung; Hsu, S. G.; Lin, C. B.; Wu, C. B.

2007-02-01

Strained La0.8Ba0.2MnO3 thin films on SrTiO3 (100) substrate are grown by an off-axis sputtering technique. It is found that the ferromagnetic temperature TC increases for thinner films. Secondary ion mass spectroscopy indicates that Sr diffuses partially into the film, making it structurally nonuniform. The region close to the film/substrate interface acts as La1-x(SryBa1-y)xMnO3 with a near negligible y for the as grown film and a non-negligible amount of y for the high-temperature postannealed film. The enhancement of TC is attributed to the combination of the strain and interdiffusion effects.

Photon mass attenuation coefficients, effective atomic numbers and electron densities of some thermoluminescent dosimetric compounds

NASA Astrophysics Data System (ADS)

Gowda, Shivalinge; Krishnaveni, S.; Yashoda, T.; Umesh, T. K.; Gowda, Ramakrishna

2004-09-01

Photon mass attenuation coefficients of some thermoluminescent dosimetric (TLD) compounds, such as LiF, CaCO_3, CaSO_4, CaSO_4\\cdot2H_2O, SrSO_4, CdSO_4, BaSO_4, C_4H_6BaO_4 and 3CdSO_4\\cdot8H_2O were determined at 279.2, 320.07, 514.0, 661.6, 1115.5, 1173.2 and 1332.5 keV in a well-collimated narrow beam good geometry set-up using a high resolution, hyper pure germanium detector. The attenuation coefficient data were then used to compute the effective atomic number and the electron density of TLD compounds. The interpolation of total attenuation cross-sections of photons of energy E in elements of atomic number Z was performed using the logarithmic regression analysis of the data measured by the authors and reported earlier. The best-fit coefficients so obtained in the photon energy range of 279.2 to 320.07 keV, 514.0 to 661.6 keV and 1115.5 to 1332.5 keV by a piece-wise interpolation method were then used to find the effective atomic number and electron density of the compounds. These values are found to be in agreement with other available published values.

Natural and anthropic effects on hydrochemistry and major and trace elements in the water mass of a Spanish Pyrenean glacial lake set.

PubMed

Santolaria, Zoe; Arruebo, Tomás; Pardo, Alfonso; Rodríguez-Casals, Carlos; Matesanz, José María; Lanaja, Francisco Javier; Urieta, José Santiago

2017-07-01

This study presents the key hydrochemical characteristics and concentration levels of major (Ca, Mg, Na, Si, K, Sr, Fe) and trace (Ba, Sc, Cr, Mn, Al, As, Li, Co, Cu, U, Pb, Hg, Au, Sn, Zn, Cd, Ag, Ni) elements in the water mass of four selected Pyrenean cirque glacial lakes (Sabocos, Baños, Truchas and Escalar tarns) with different catchment features, between 2010 and 2013. Resulting data set is statistically analyzed to discriminate between the natural or anthropic origin of the elements. Analyses indicate that in all cases, the main source of most major and trace elements is geological weathering, being thus individual bedrock composition the main driver of differences between lakes. Several anthropogenic sources of airborne Cu, Sc, Co, and Cr must be also considered. The shallowness of the lake is also a factor that may influence element cycling and concentration levels in its water mass. Concentrations of anthropogenic elements were low, comparable to those reported in other glacial lakes, way below the WHO, US EPA, EC, and Spanish legal limits for drinking water quality, indicating the absence of serious pollution. Toxic heavy metals Cd, Pb, Hg, and Zn were not detected in any of the tarns.

Dissolved trace elements in a nitrogen-polluted river near to the Liaodong Bay in Northeast China.

PubMed

Bu, Hongmei; Song, Xianfang; Guo, Fen

2017-01-15

Dissolved trace element concentrations (Ba, Fe, Mn, Si, Sr, and Zn) were investigated in the Haicheng River near to the Liaodong Bay in Northeast China during 2010. Dissolved Ba, Fe, Mn, and Sr showed significant spatial variation, whereas dissolved Fe, Mn, and Zn displayed seasonal variations. Conditions such as water temperature, pH, and dissolved oxygen were found to have an important impact on redox reactions involving dissolved Ba, Fe, and Zn. Dissolved Fe and Mn concentrations were regulated by adsorption or desorption of Fe/Mn oxyhydroxides and the effects of organic carbon complexation on dissolved Ba and Sr were found to be significant. The sources of dissolved trace elements were found to be mainly from domestic sewage, industrial waste, agricultural surface runoff, and natural origin, with estimated seasonal and annual river fluxes established as important inputs of dissolved trace elements from the Haicheng River into the Liaodong Bay or Bohai Sea. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interaction of ultra-depleted MORBs with plagioclase: implications for CO2/Ba ratios

NASA Astrophysics Data System (ADS)

Shimizu, K.; Hauri, E.; Saal, A. E.; Perfit, M. R.; Hekinian, R.

2017-12-01

Carbon in Earth's upper mantle can significantly reduce its solidus temperature, which in turn can affect other physical properties through generation of partial melt. Carbon content in the depleted upper mantle can be estimated using ultra-depleted mid-ocean ridge basalt (UD-MORB) glasses and melt inclusions that are undersaturated in CO2. CO2 has been shown to behave as a highly incompatible element during mantle melting both through natural samples and experiments. Given its highly incompatible behavior, CO2/Ba and CO2/Nb ratios in CO2 undersaturated UD-MORBs have been used to estimate the CO2/Ba and CO2/Nb ratios and carbon content in Earth's upper mantle. A potential issue with part of this approach is the effect of melt-plagioclase chemical interaction on the CO2/Ba ratios in UD-MORBs. Plagioclase is ubiquitous in the oceanic crust and is enriched in Ba relative to other phases. Chemical interactions (assimilation and/or diffusion) between MORB melts and plagioclase bearing rocks have been shown to affect the Ba (and Sr and Eu) concentrations in MORBs, implying that such processes may also affect their CO2/Ba ratio. Hence, understanding the effect of chemical interaction between plagioclase and UD-MORBs is important for having better constraints on CO2/Ba ratio and carbon content in Earth's upper mantle. In this study, we report on the compositions of olivine-hosted melt inclusions and glasses from the Siqueiros and Garrett transform faults. A subset of melt inclusions in lavas from both transform faults show potential signatures of chemical interaction with plagioclase such as low CO2/Ba, Nb/Ba, and Nd/Sr. CO2 degassing cannot explain the low CO2/Ba ratio in the samples as they are undersaturated in CO2. To better understand the effect of chemical interaction with plagioclase on the composition of UD-MORBs, we model end-member scenarios, which are (1) assimilation of plagioclase and (2) diffusion of elements from plagioclase into the UD-MORBs. In general, the trends produced by these end-member scenarios bracket those observed in the samples (trends between CO2/Ba, Nb/Ba, and Nd/Sr as well as between Al2O3, FeO, and MgO). Hence, chemical interaction with plagioclase may affect the CO2/Ba ratio in UD-MORBs, and care should be taken to evaluate this effect using Nd/Sr and Nb/Ba ratios.

Processing effects on the microstructure and dielectric properties of hydrothermal barium titanate and (barium,strontium)titanate thin films

NASA Astrophysics Data System (ADS)

McCormick, Mark Alan

The goal of this work was to produce BaTiO3 and BaxSr (1-x)TiO3 (BST) thin films with high dielectric constants, using a low-temperature (<100°C) hydrothermal synthesis route. To accomplish this, titanium metal-organic precursor films were spin-cast onto metal-coated glass substrates and converted to polycrystalline BaTiO3 or BST upon reacting in aqueous solutions of Ba(OH)2 or Ba(OH)2 and Sr(OH)2. The influences of solution molarity, processing temperature, and reaction time on thin film reaction kinetics, microstructure, and dielectric properties were examined for BaTiO3 films. Post-deposition annealing at temperatures as low as 200°C substantially affected the lattice parameter, dielectric constant, and dielectric loss. This behavior is explained in terms of hydroxyl defect incorporation during film formation. Current-voltage (I-V) measurements were performed to determine the dominant conduction mechanism(s) during application of a do field, and to extract the metal/ceramic barrier height. In particular, Schottky barrier-limited conduction and Poole-Frenkel conduction were investigated as potential leakage mechanisms. For BST thin films, film stoichiometry deviated from the initial solution composition, with a preferred incorporation of Sr2+ into the perovskite lattice. The dielectric constant of the BST films was measured as a function of composition (Ba:Sr ratio) and temperature over the range 25--150°C. Finally, capacitance-voltage (C-V) measurements were made for BST films to determine the influence of film composition on dielectric tunability.

Crystal structures of the double perovskites Ba{sub 2}Sr{sub 1-} {sub x} Ca {sub x} WO{sub 6}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, W.T.; Akerboom, S.; IJdo, D.J.W.

2007-05-15

Structures of the double perovskites Ba{sub 2}Sr{sub 1-} {sub x} Ca {sub x} WO{sub 6} have been studied by the profile analysis of X-ray diffraction data. The end members, Ba{sub 2}SrWO{sub 6} and Ba{sub 2}CaWO{sub 6}, have the space group I2/m (tilt system a {sup 0} b {sup -} b {sup -}) and Fm3-barm (tilt system a {sup 0} a {sup 0} a {sup 0}), respectively. By increasing the Ca concentration, the monoclinic structure transforms to the cubic one via the rhombohedral R3-bar phase (tilt system a {sup -} a {sup -} a {sup -}) instead of the tetragonal I4/mmore » phase (tilt system a {sup 0} a {sup 0} c {sup -}). This observation supports the idea that the rhombohedral structure is favoured by increasing the covalency of the octahedral cations in Ba{sub 2} MM'O{sub 6}-type double perovskites, and disagrees with a recent proposal that the formation of the {pi}-bonding, e.g., d {sup 0}-ion, determines the tetragonal symmetry in preference to the rhombohedral one. - Graphical abstract: Enlarged sections showing the evolution of the basic (222) and (400) reflections in Ba{sub 2}Sr{sub 1-} {sub x} Ca {sub x} WO{sub 6}. Tick marks below are the positions of Bragg's reflections calculated using the space groups I2/m (x=0), R3-bar (x=0.25, 0.5 and 0.75) and Fm3-barm (x=1), respectively.« less

Assessment of the Coral Temperature Proxies for Orbicella faveolata in the Southwestern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Vara, M. A.; DeLong, K. L.; Herrmann, A. D.; Ouellette, G., Jr.; Richey, J. N.

2017-12-01

Coral Sr/Ca is a robust proxy of sea surface temperature (SST); however, discrepancies in the Sr/Ca-SST relationship among colonies of the same species may reduce confidence in absolute temperature reconstructions. Furthermore, terrestrial carbonate weathering can provide local sources of Sr and/or Ca to coastal waters that may disrupt the temperature-based coral Sr/Ca signal. Thus other trace metal SST proxies have been suggested to circumvent these issues (Li/Ca, Li/Mg, and Sr-U). Coral Ba/Ca has been used as a proxy for runoff and coastal upwelling, and therefore may be used to identify intervals when these processes overprint the Sr/Ca-SST signal. This study tests multiple coral SST proxies using reproducibility assessments to determine the best performing SST proxy. We conduct these assessments with cores recovered in 1991 by the U.S. Geological Survey from five Orbicella faveolata colonies from three reefs offshore of Veracruz, Mexico (19.06°N, 96.93°W) in water depths varying from 3 to 12 m. Previous studies found micromilling the complex skeletal structure of O. faveolata challenging and that monthly resolution may not recover full seasonal cycles. We use a laser ablation inductively coupled plasma mass spectrometer to simultaneously sample this coral's structure at weekly intervals spanning 8 years for Li/Ca, Li/Mg, Sr-U, Sr/Ca, and Ba/Ca. Here we found coral Li/Ca means and seasonal variations are similar among colonies thus this proxy may capture absolute temperature and SST variability. Similar to previous research with Porites corals, Li/Ca in these O. faveolata corals decreases with increases in SST with similar slopes and intercepts. During the last 10 years of these corals' lives, coral Sr/Ca analysis reveals a mean shift among colonies suggesting an external source could have disrupted the Sr/Ca signal, possibly seasonal runoff and/or winter upwelling common to Veracruz waters. Coral Ba/Ca analyses reveals elevated values in winters that coincide with increases in coral Sr/Ca in the deeper colony suggesting upwelling is occurring at that location. However, the coral Ba/Ca does not coincide with increase coral Sr/Ca in the shallower coral indicating no direct influence from runoff. Coral Li/Mg and Sr-U do not show substantial seasonal variations as expected with a coral-SST proxy.

Raman spectroscopy of DNA-metal complexes. II. The thermal denaturation of DNA in the presence of Sr2+, Ba2+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, and Cd2+.

PubMed

Duguid, J G; Bloomfield, V A; Benevides, J M; Thomas, G J

1995-12-01

Differential scanning calorimetry, laser Raman spectroscopy, optical densitometry, and pH potentiometry have been used to investigate DNA melting profiles in the presence of the chloride salts of Ba2+, Sr2+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, and Cd2+. Metal-DNA interactions have been observed for the molar ratio [M2+]/[PO2-] = 0.6 in aqueous solutions containing 5% by weight of 160 bp mononucleosomal calf thymus DNA. All of the alkaline earth metals, plus Mn2+, elevate the melting temperature of DNA (Tm > 75.5 degrees C), whereas the transition metals Co2+, Ni2+, and Cd2+ lower Tm. Calorimetric (delta Hcal) and van't Hoff (delta HVH) enthalpies of melting range from 6.2-8.7 kcal/mol bp and 75.6-188.6 kcal/mol cooperative unit, respectively, and entropies from 17.5 to 24.7 cal/K mol bp. The average number of base pairs in a cooperative melting unit () varied from 11.3 to 28.1. No dichotomy was observed between alkaline earth and transition DNA-metal complexes for any of the thermodynamic parameters other than their effects on Tm. These results complement Raman difference spectra, which reveal decreases in backbone order, base unstacking, distortion of glycosyl torsion angles, and rupture of hydrogen bonds, which occur after thermal denaturation. Raman difference spectroscopy shows that transition metals interact with the N7 atom of guanine in duplex DNA. A broader range of interaction sites with single-stranded DNA includes ionic phosphates, the N1 and N7 atoms of purines, and the N3 atom of pyrimidines. For alkaline earth metals, very little interaction was observed with duplex DNA, whereas spectra of single-stranded complexes are very similar to those of melted DNA without metal. However, difference spectra reveal some metal-specific perturbations at 1092 cm-1 (nPO2-), 1258 cm-1 (dC, dA), and 1668 cm-1 (nC==O, dNH2 dT, dG, dC). Increased spectral intensity could also be observed near 1335 cm-1 (dA, dG) for CaDNA. Optical densitometry, employed to detect DNA aggregation, reveals increased turbidity during the melting transition for all divalent DNA-metal complexes, except SrDNA and BaDNA. Turbidity was not observed for DNA in the absence of metal. A correlation was made between DNA melting, aggregation, and the ratio of Raman intensities I1335/I1374. At room temperature, DNA-metal interactions result in a pH drop of 1.2-2.2 units for alkaline earths and more than 2.5 units for transition metals. Sr2+, Ba2+, and Mg2+ cause protonated sites on the DNA to become thermally labile. These results lead to a model that describes DNA aggregation and denaturation during heating in the presence of divalent metal cations; 1) The cations initially interact with the DNA at phosphate and/or base sites, resulting in proton displacement. 2) A combination of metal-base interactions and heating disrupts the base pairing within the DNA duplex. This allows divalent metals and protons to bind to additional sites on the DNA bases during the aggregation/melting process. 3) Strands whose bases have swung open upon disruption are linked to neighboring strands by metal ion bridges. 4) Near the midpoint of the melting transition, thermal energy breaks up the aggregate. We have no evidence to indicate whether metal ion cross-bridges or direct base-base interactions rupture first. 5) Finally, all cross-links break, resulting in single-stranded DNA complexed with metal ions.

Encapsulation of boswellic acid with β- and hydroxypropyl-β-cyclodextrin: Synthesis, characterization, in vitro drug release and molecular modelling studies

NASA Astrophysics Data System (ADS)

Tambe, Amruta; Pandita, Nancy; Kharkar, Prashant; Sahu, Niteshkumar

2018-02-01

Boswellic acids (BAs) are a group of pentacyclic triterpenes present in gum-resin of Boswellia serrata. They are well known for their anti-inflammatory, hypolipidemic, immunomodulatory and anti-tumor activity, but they have poor aqueous solubility and limited bioavailability. In order to enhance their aqueous solubility, inclusion complexes of BAs with β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) were synthesized and their drug release profiles were studied. Molecular associations of β-CD and HP-β-CD with BAs were investigated by phase solubility studies. The stability constants were found to be 380.2 and 145.9 M-1 for BA: β-CD and BA: HP-β-CD inclusion complexes, respectively with AN- type curve. BA: β-CD and BA: HP-β-CD inclusion complexes were synthesized using kneading (KN), co-precipitation (CP) and solvent evaporation (SE) methods in 1:1 as well as 1:2 ratios. Further these were characterized by Fourier transform infrared (FTIR) spectrophotometry, Powder X-ray Diffraction (P-XRD) and Differential scanning calorimetric (DSC) analysis. FTIR analysis showed shifting of frequencies in complexes as compared to CDs and BAs. P-XRD data obtained for BA: β-CD complexes synthesized by CP and SE methods showed amorphous pattern. Also, DSC analysis showed a change in thermal behaviour for synthesized complexes. In vitro drug release studies of BA: β-CD complexes showed enhanced release with 1:2 complexes than 1:1 complexes at pH 1.2 and pH 6.8. Similarly, drug release enhancement was observed more with BA: HP-β-CD complexes in 1:2 ratio than 1:1. To understand the interaction of BAs with CD cavity molecular modelling studies were performed which favored 1:2 complex formation over 1:1 complexes. The study thus highlights that CDs can be used for solubility and dissolution enhancement of BAs.

Film growth and structure design in the barium oxide-strontium oxide-titanium dioxide system

NASA Astrophysics Data System (ADS)

Fisher, Patrick J.

This thesis describes the growth and characterization of thin films in the SrO-BaO-TiO2 system. The films are grown by molecular beam cpitaxy (MBE) and pulsed laser deposition (PLD) on ceramic substrates, and characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), reflection-high energy electron diffraction (RHEED), and transmission electron microscopy (TEM). Films are grown with varied global and initial local stoichiometries, with the goal of determining the stability of specific cation organizations. Simple oxides, TiO2 (anatase) and SrO (rock salt) were grown on oxide substrates using MBE. Growth conditions, including substrate material, substrate temperature, O3 flux, and metal flux, are varied in each case. It is observed that the growth morphology of anatase is highly dependent on the ozone flux, with fluxes of 1.00 sccm and greater resulting in flat anatase surfaces. Increased roughness at higher substrate was determined to be a result of rutile inclusions. Growth oscillations are observed in the RHEED intensity for both TiO2 and SrO in overlapping regions of growth space, indicating 2D growth modes. Varied shuttering sequences were used during MBE growth of perovskites: globally non-stoichiometric films, as well as locally non-stoichiometric but globally stoichiometric perovskite. Films were grown within a (SrO) m(TiO2)n framework, where growth cycles involved m monolayers of SrO followed by n monolayers of TiO2. XRD results indicate that Ruddlesden-Popper defects, that is, rock salt double layers, enable incorporation of all levels of Sr excess, whereas excess Ti is observed to incorporate into the perovskite structure only at extreme excesses. A series of films with m equal to n were grown; that is, multiple monolayers of SrO deposited followed by multiple monolayers of TiO2. These initially locally non-stoichiometric arrangements interreact to form highly crystalline perovskite, even with layer thicknesses of up to 33 monolayers. The Ba0.6Sr0.4TiO3 films were characterized for their microwave dielectric properties, and were found to have high dielectric constants (epsilonr ˜1300 in each case, implying high tunabilities) but high tan delta values as well. The mechanisms by which the perovskite structure incorporates cation excesses is discussed, and it is argued that two probable mechanisms, one involving plane-sharing of Ti and Sr cations and the other involving rock salt multilayers, also enable the observed transport necessary for multilayer reaction. Working under the argument that these mechanisms involve low-energy architectures, a novel homologous series of phases based on rock salt multilayers is grown using monotayer control: the SrmTiO2+ m series, with each TiO2 monolayer followed by m SrO monolayers (m = 1-5). The phases in this series were characterized structurally, and an in-plane contraction was observed between the m = 2 and m = 3 phases, which is argued to be a relaxation of the SrO monolayers. Considering Ti-excess organizations, the BaTi2O5 structure is grown and observed to nucleate over a narrow window of growth conditions and substrates. LaAlO 3(100) promotes the nucleation of anatasc and ejection of perovskite; SrTiO3(100) promotes the nucleation of perovskite and ejection of TiO2; importantly, MgO(100) promotes the nucleation (010)-oriented BaTi2O5 growing with multiple domains. A BaTi2 O5 buffer layer was then used to promote the inclusion of Sr into (Ba,SOTi205 epilayers. Sr incorporation into a perovskite-related structure was observed to occur over the full range of (Ba,Sr)Ti2O 5 compositions.

Melting and Vaporization of the 1223 Phase in the System (Tl-Pb-Ba-Sr-Ca-Cu-O)

PubMed Central

Cook, L. P.; Wong-Ng, W.; Paranthaman, P.

1996-01-01

The melting and vaporization of the 1223 [(Tl,Pb):(Ba,Sr):Ca:Cu] oxide phase in the system (Tl-Pb-Ba-Sr-Ca-Cu-O) have been investigated using a combination of dynamic methods (differential thermal analysis, thermogravimetry, effusion) and post-quenching characterization techniques (powder x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectrometry). Vaporization rates, thermal events, and melt compositions were followed as a function of thallia loss from a 1223 stoichiometry. Melting and vaporization equilibria of the 1223 phase are complex, with as many as seven phases participating simultaneously. At a total pressure of 0.1 MPa the 1223 phase was found to melt completely at (980 ± 5) °C in oxygen, at a thallia partial pressure (pTl2O) of (4.6 ± 0.5) kPa, where the quoted uncertainties are standard uncertainties, i.e., 1 estimated standard deviation. The melting reaction involves five other solids and a liquid, nominally as follows: 1223→1212+(Ca,Sr)2CuO3+(Sr,Ca)CuO2+BaPbO3+(Ca,Sr)O+Liquid Stoichiometries of the participating phases have been determined from microchemical analysis, and substantial elemental substitution on the 1212 and 1223 crystallographic sites is indicated. The 1223 phase occurs in equilibrium with liquids from its melting point down to at least 935 °C. The composition of the lowest melting liquid detected for the bulk compositions of this study has been measured using microchemical analysis. Applications to the processing of superconducting wires and tapes are discussed. PMID:27805086

Solid-state (127)I NMR and GIPAW DFT study of metal iodides and their hydrates: structure, symmetry, and higher-order quadrupole-induced effects.

PubMed

Widdifield, Cory M; Bryce, David L

2010-10-14

Central-transition (127)I solid-state nuclear magnetic resonance (SSNMR) spectra are presented for several anhydrous group 2 metal iodides (MgI(2), CaI(2), SrI(2), and BaI(2)), hydrates (BaI(2)·2H(2)O and SrI(2)·6H(2)O), and CdI(2) (4H polytype). Variable offset cumulative spectrum data acquisition coupled with echo pulse sequences and an 'ultrahigh' applied field of 21.1 T were usually suitable to acquire high-quality spectra. Spectral analysis revealed iodine-127 nuclear quadrupole coupling constants (C(Q)((127)I)) ranging in magnitude from 43.5 (CaI(2)) to 214 MHz (one site in SrI(2)). For very large C(Q), analytical second-order perturbation theory could not be used to reliably extract chemical shifts and a treatment which includes quadrupolar effects exactly was required (Bain, A. D. Mol. Phys. 2003, 101, 3163). Differences between second-order and exact modeling allowed us to observe 'higher-order' quadrupole-induced effects for the first time. This finding will have implications for the interpretation of SSNMR spectra of quadrupolar nuclei with large quadrupole moments. In favorable situations (i.e., C(Q)((127)I) < 120 MHz), measurements were also performed at 11.75 T which when combined with the 21.1 T data allowed us to measure iodine chemical shift (CS) tensor spans in the range from 60 (BaI(2)·2H(2)O) to 300 ppm (one site in BaI(2)). These measurements represent the first complete characterizations (i.e., electric field gradient and CS tensors as well as their relative orientation) of noncubic iodide sites using (127)I SSNMR. In select cases, the SSNMR data are supported with (127)I NQR measurements. We also summarize a variety of trends in the halogen SSNMR parameters for group 2 metal halides. Gauge-including projector-augmented wave DFT computations are employed to complement the experimental observations, to predict potential structures for the two hydrates, and to highlight the sensitivity of C(Q)((127)I) to minute structural changes, which has potential applications in NMR crystallography.

Practical and quality-control aspects of multi-element analysis with quadrupole ICP-MS with special attention to urine and whole blood.

PubMed

De Boer, Jan L M; Ritsema, Rob; Piso, Sjoerd; Van Staden, Hans; Van Den Beld, Wilbert

2004-07-01

Two screening methods were developed for rapid analysis of a great number of urine and blood samples within the framework of an exposure check of the population after a firework explosion. A total of 56 elements was measured including major elements. Sample preparation consisted of simple dilution. Extensive quality controls were applied including element addition and the use of certified reference materials. Relevant results at levels similar to those found in the literature were obtained for Co, Ni, Cu, Zn, Sr, Cd, Sn, Sb, Ba, Tl, and Pb in urine and for the same elements except Ni, Sn, Sb, and Ba in blood. However, quadrupole ICP-MS has limitations, mainly related to spectral interferences, for the analysis of urine and blood, and these cause higher detection limits. The general aspects discussed in the paper give it wider applicability than just for analysis of blood and urine-it can for example be used in environmental analysis.

Toxic trace elements in solid airborne particles and ecological risk assessment in the vicinity of local boiler house plants

NASA Astrophysics Data System (ADS)

Talovskaya, Anna V.; Osipova, Nina A.; Yazikov, Egor G.; Shakhova, Tatyana S.

2017-11-01

The article deals with assessment of anthropogenic pollution in vicinity of local boilers using the data on microelement composition of solid airborne particles deposited in snow. The anthropogenic feature of elevated accumulation levels of solid airborne particles deposited in snow in the vicinity of coal-fired boiler house is revealed in elevated concentrations (3-25 higher than background) of Cd, Sb, Mo, Pb, Sr, Ba, Ni, Mo, Zn and Co. In the vicinity oil-fired boiler house the specific elements as parts of solid airborne particles deposited in snow are V, Ni and Sb, as their content exceeds the background from 3 to 8 times. It is determined that the maximum shares in non-carcinogenic human health risk from chronic inhalation of trace elements to the human body in the vicinity of coal-fired boiler house belong to Al, Mn, Cu, Ba, Co, Pb, whereas in the vicinity of oil-fired boiler house - Al, Mn, Cu, Ni, V.

Origin discrimination of defatted pork via trace elements profiling, stable isotope ratios analysis, and multivariate statistical techniques.

PubMed

Park, Yu Min; Lee, Cheong Mi; Hong, Joon Ho; Jamila, Nargis; Khan, Naeem; Jung, Jong-Hyun; Jung, Young-Chul; Kim, Kyong Su

2018-09-01

This study verified the origin of 346 defatted Korean and non-Korean pork samples via trace elements profiling, and C and N stable isotope ratios analysis. The analyzed elements were 6 Li, 7 Li, 10 B, 11 B, 51 V , 50 Cr, 52 Cr, 53 Cr, 55 Mn, 58 Ni, 60 Ni, 59 Co, 63 Cu, 65 Cu, 64 Zn, 66 Zn, 69 Ga, 71 Ga, 75 As, 82 Se, 84 Sr, 86 Sr, 87 Sr, 88 Sr, 85 Rb, 94 Mo, 95 Mo, 97 Mo, 107 Ag, 109 Ag, 110 Cd, 111 Cd, 113 Cd, 112 Cd, 114 Cd, 116 Cd, 133 Cs, 206 Pb, 207 Pb, and 208 Pb. Content (mg/kg) of 51 V (0.012), 50 Cr (0.882), 75 As (0.017), 85 Rb (57.7), and 87 Sr (46.3) were high in Korean pork samples whereas 6 Li, 7 Li, 59 Co, 55 Mn, 58 Ni, 84 Sr, 86 Sr, 88 Sr, 111 Cd, and 133 Cs were found higher in non-Korean samples. The results of discriminant analysis showed that the trace elements content and stable isotope ratios were significant for the discrimination of geographical origins with a perfect discrimination rate of 100%. Copyright © 2018 Elsevier Ltd. All rights reserved.

Transfer of volatiles and metals from mafic to felsic magmas in composite magma chambers: An experimental study

NASA Astrophysics Data System (ADS)

Guo, Haihao; Audétat, Andreas

2017-02-01

In order to determine the behavior of metals and volatiles during intrusion of mafic magma into the base of silicic, upper crustal magma chambers, fluid-rock partition coefficients (Dfluid/rock) of Li, B, Na, S, Cl, K, Mn, Fe, Rb, Sr, Ba, Ce, Cu, Zn, Ag, Cd, Mo, As, Se, Sb, Te, W, Tl, Pb and Bi were determined experimentally at 2 kbar and 850 °C close to the solidus of mafic magma. In a first step, volatile-bearing mafic glasses were prepared by melting a natural basaltic trachyandesite in the presence of volatile-bearing fluids at 1200 °C/10 kbar in piston cylinder presses. The hydrous glasses were then equilibrated in subsequent experiments at 850 °C/2 kbar in cold-seal pressure vessels, which caused 80-90% of the melt to crystallize. After 0.5-2.0 days of equilibration, the exsolved fluid was trapped by means of in-situ fracturing in the form of synthetic fluid inclusions in quartz. Both the mafic rock residue and the fluid inclusions were subsequently analyzed by laser-ablation ICP-MS for major and trace elements. Reverse experiments were conducted by equilibrating metal-bearing aqueous solutions with rock powder and then trapping the fluid. In two additional experiments, information on relative element mobilities were obtained by reacting fluids that exsolved from crystallizing mafic magma with overlying silicic melts. The combined results suggest that under the studied conditions S, Cl, Cu, Se, Br, Cd and Te are most volatile (Dfluid/rock >10), followed by Li, B, Zn, As, Ag, Sb, Cs, W, Tl, Pb and Bi (Dfluid/rock = 1-10). Less volatile are Na, Mg, K, Ca, Mn, Fe, Rb, Sr, Mo and Rb (Dfluid/rock 0.1-1), and the least fluid-mobile elements are Al, Si, Ti, Zr, Ba and Ce (Dfluid/rock <0.1). This trend is broadly consistent with relative element volatilities determined on natural high-temperature fumarole gases, although some differences exist. Based on the volatility data and measured mineral-melt and sulfide-melt partition coefficients, volatile fluxing in felsic natural samples may be identified by Cu, Se, Te and Cd-enrichment in magmatic sulfides, and by As, Se, Cd and Bi-enrichment in magmatic apatite.

Dielectric properties and microstructure of nano-MgO dispersed Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} thin films prepared by sputter deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, S.-F.; Chu, Jinn P.; Lin, C.C.

2005-07-01

In this study, thin films prepared from the targets of Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} (BST), BST/5 mol % MgO, BST/10 mol % MgO, and BST/20 mol % MgO composites, using radio frequency magnetron sputtering, have been reported. As-deposited films were found to be amorphous and began to crystallize after annealing at temperatures of 650 deg. C and above. The addition of MgO in the BST films resulted in the hindrance of crystallization and inhibition of grain growth. MgO was substituted into the BST lattices to a certain degree. High-resolution transmission electron microscopy results revealed some MgO dispersed in the BSTmore » matrix. The MgO dispersed in the dense BST matrix was found to be around 25 nm in size. The dielectric constant was estimated to be 90 for the pure BST film annealed at 700 deg. C, and observed to be slightly reduced with the MgO addition. The dielectric losses of the Ba{sub 0.3}Sr{sub 0.7}TiO{sub 3} (0.006) and BST/MgO films (0.002-0.004) were much less than those of the Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}(0.013) and Ba{sub 0.7}Sr{sub 0.3}TiO{sub 3} films (0.11-0.13). The leakage current was smaller for the BST/10 mol % MgO film compared to the pure BST film and this low leakage current may be attributed to the substitution of Mg in the B sites of BST lattices which might have behaved as an electron acceptors.« less

Elemental signatures in otoliths of hatchery rainbow trout (Oncorhynchus mykiss): Distinctiveness and utility fo detecting origins and movement

USGS Publications Warehouse

Gibson-Reinemer, D. K.; Johnson, B.M.; Martinez, P.J.; Winkelman, D.L.; Koenig, A.E.; Woodhead, J.D.

2009-01-01

Otolith chemistry in freshwater has considerable potential to reveal patterns of origin and movement, which would benefit traditional fisheries management and provide a valuable tool to curb the spread of invasive and illicitly stocked species. We evaluated the relationship between otolith and water chemistry for five markers (Ba/Ca, Mn/Ca, Sr/ Ca, Zn/Ca, and 87Sr/86Sr) in rainbow trout (Oncorhynchus mykiss) using the existing hatchery system in Colorado and Wyoming, USA, to provide controlled, seminatural conditions. Otolith Ba/Ca, Sr/Ca, and 87Sr/86Sr reflected ambient levels, whereas Mn/Ca and Zn/Ca did not. Using only the markers correlated with water chemistry, we classified fish to their hatchery of origin with up to 96% accuracy when element and isotope data were used together. Large changes in 87Sr/Sr were evident in otolith transects, although subtler changes in Sr/Ca were also detectable. Our results suggest the relatively few otolith markers that reflect ambient chemistry can discriminate among locations and track movements well enough to provide valuable insight in a variety of applied contexts.

Electronic structure of the gold/Bi2Sr2CaCu2O8 and gold/EuBa2Cu3O7 - delta interfaces as studied by photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Dessau, D. S.; Shen, Z.-X.; Wells, B. O.; Spicer, W. E.; List, R. S.; Arko, A. J.; Bartlett, R. J.; Fisk, Z.; Cheong, S.-W.; Mitzi, D. B.; Kapitulnik, A.; Schirber, J. E.

1990-07-01

High-resolution photoemission has been used to probe the electronic structure of the gold/Bi2Sr2CaCu2O8 and gold/EuBa2Cu3O7-δ interface formed by a low-temperature (20 K) gold evaporation on cleaved high quality single crystals. We find that the metallicity of the EuBa2Cu3O7-δ substrate in the near surface region (˜5 Å) is essentially destroyed by the gold deposition, while the near surface region of Bi2Sr2CaCu2O8 remains metallic. This has potentially wide ranging consequences for the applicability of the different types of superconductors in real devices.

MOCVD (Ba{sub x}Sr{sub 1-x})Ti{sub 1+y}O{sub 3+z} (BST) thin films for high frequency tunable devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baumann, P. K.; Kaufman, D. Y.; Im, J.

2001-01-01

We have investigated the structural and electrical characteristics of (Ba{sub x}Sr{sub 1-x})Ti{sub 1+y}O{sub 3+z} (BST) thin films synthesized at 650{sup o}C on Pt/SiO{sub 2}/Si substrates using a large area, vertical metalorganic chemical vapor deposition (MOCVD) reactor equipped with a liquid delivery system. Films with a Ba/Sr ratio of 70/30 were studied, as determined using X-ray fluorescence spectroscopy (XRF) and Rutherford backscattering spectrometry (RBS). A substantial reduction of the dielectric loss was achieved when annealing the entire capacitor structure in air at 700{sup o}C. Dielectric tunability as high as 2.3:1 was measured for BST capacitors with the currently optimized processing conditions.

Sr and Nd isotopic and trace element compositions of Quaternary volcanic centers of the Southern Andes

USGS Publications Warehouse

Futa, K.; Stern, C.R.

1988-01-01

Isotopic compositions of samples from six Quaternary volcanoes located in the northern and southern extremities of the Southern Volcanic Zone (SVZ, 33-46??S) of the Andes and from four centers in the Austral Volcanic Zone (AVZ, 49-54??S) range for 87Sr 86Sr from 0.70280 to 0.70591 and for 143Nd 144Nd from 0.51314 to 0.51255. The ranges are significantly greater than previously reported from the southern Andes but are different from the isotopic compositions of volcanoes in the central and northern Andes. Basalts and basaltic andesites from three centers just north of the Chile Rise-Trench triple junction have 87Sr 86Sr, 143Nd 144Nd, La Yb, Ba La, and Hf Lu that lie within the relatively restricted ranges of the basic magmas erupted from the volcanic centers as far north as 35??S in the SVZ of the Andes. The trace element and Sr and Nd isotopic characteristics of these magmas may be explained by source region contamination of subarc asthenosphere, with contaminants derived from subducted pelagic sediments and seawater-altered basalts by dehydration of subducted oceanic lithosphere. In the northern extremity of the SVZ between 33?? and 34??S, basaltic andesites and andesites have higher 87Sr 86Sr, Rb Cs, and Hf Lu, and lower 143Nd 144Nd than basalts and basaltic andesites erupted farther south in the SVZ, which suggests involvement of components derived from the continental crust. In the AVZ, the most primitive sample, high-Mg andesite from the southernmost volcanic center in the Andes (54??S) has Sr and Nd isotopic compositions and K Rb and Ba La similar to MORB. The high La Yb of this sample suggests formation by small degrees of partial melting of subducted MORB with garnet as a residue. Samples from centers farther north in the AVZ show a regionally regular northward increase in SiO2, K2O, Rb, Ba, Ba La, and 87Sr 86Sr and decrease in MgO, Sr, K Rb, Rb Cs, and 143Nd 144Nd, suggesting increasingly greater degrees of fractional crystallization and associated intra-crustal contamination. ?? 1988.

Crystal Chemical Substitutions of YBa2Cu3O7-d to Enhance Flux Pinning (Postprint)

DTIC Science & Technology

2012-02-01

ionic radii (1.42 A for 8-fold coordination), specifically including larger RE ions La, Pr, and Nd and Ca 2+ and Sr +2. Note also that Pm is normal1y...ng is especially critical for the larger RE ions or mixtures with these ions , which pre vents partial substitution of these RE io ns for Ba ...similar 123 phase can be formed with th e composition ThSr2Cu2•7Meo 30?. This 123 p hase can be formed by substituting Sr for Ba an d a small amount of

Crystallization and properties of Sr-Ba aluminosilicate glass-ceramic matrices

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Hyatt, Mark J.; Drummond, Charles H., III

1991-01-01

Powders of roller quenched (Sr,Ba)O-Al2O3-2SiO2 glasses of various compositions were uniaxially pressed into bars and hot isostatically pressed at 1350 C for 4 hours or cold isostatically pressed and sintered at different temperatures between 800 to 1500 C for 10 or 20 hours. Densities, flexural strengths, and linear thermal expansion were measured for three compositions. The glass transition and crystallization temperatures were determined by Differential Scanning Calorimetry (DSC). The liquidus and crystallization temperature from the melt were measured using high temperature Differential Thermal Analysis (DTA). Crystalline phases formed on heat treatment of the glasses were identified by powder X ray diffraction. In Sr containing glasses, the monoclinic celsian phase always crystallized at temperatures above 1000 C. At lower temperatures, the hexagonal analog formed. The temperature for orthorhombic to hexagonal structural transformation increased monotonically with SrO content, from 327 C for BaO-Al2O3-2SiO2 to 758 C for SrO-Al2O3-2SiO2. These glass powders can be sintered to almost full densities and monoclinic celsian phase at a relatively low temperature of 1100 C.

On the persistence of polar domains in ultrathin ferroelectric capacitors.

PubMed

Zubko, Pavlo; Lu, Haidong; Bark, Chung-Wung; Martí, Xavi; Santiso, José; Eom, Chang-Beom; Catalan, Gustau; Gruverman, Alexei

2017-07-19

The instability of ferroelectric ordering in ultra-thin films is one of the most important fundamental issues pertaining realization of a number of electronic devices with enhanced functionality, such as ferroelectric and multiferroic tunnel junctions or ferroelectric field effect transistors. In this paper, we investigate the polarization state of archetypal ultrathin (several nanometres) ferroelectric heterostructures: epitaxial single-crystalline BaTiO 3 films sandwiched between the most habitual perovskite electrodes, SrRuO 3 , on top of the most used perovskite substrate, SrTiO 3 . We use a combination of piezoresponse force microscopy, dielectric measurements and structural characterization to provide conclusive evidence for the ferroelectric nature of the relaxed polarization state in ultrathin BaTiO 3 capacitors. We show that even the high screening efficiency of SrRuO 3 electrodes is still insufficient to stabilize polarization in SrRuO 3 /BaTiO 3 /SrRuO 3 heterostructures at room temperature. We identify the key role of domain wall motion in determining the macroscopic electrical properties of ultrathin capacitors and discuss their dielectric response in the light of the recent interest in negative capacitance behaviour.

Inclusion property of Cs, Sr, and Ba impurities in LiCl crystal formed by layer-melt crystallization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Jung-Hoon; Cho, Yung-Zun; Lee, Tae-Kyo

Pyroprocessing is one of the promising technologies enabling the recycling of spent nuclear fuels from a commercial light water reactor (LWR). In general, pyroprocessing uses dry molten salts as electrolytes. In particular, LiCl waste salt after pyroprocessing contains highly radioactive I/II group fission products mainly composed of Cs, Sr, and Ba impurities. Therefore, it is beneficial to reuse LiCl salt in the pyroprocessing as an electrolyte for economic and environmental issues. Herein, to understand the inclusion property of impurities within LiCl crystal, the physical properties such as lattice parameter change, bulk modulus, and substitution enthalpy of a LiCl crystal havingmore » 0-6 at% Cs{sup +} or Ba{sup 2+} impurities under existence of 1 at% Sr{sup 2+} impurity were calculated via the first-principles density functional theory. The substitution enthalpy of LiCl crystals having 1 at% Sr{sup 2+} showed slightly decreased value than those without Sr{sup 2+} impurity. Therefore, through the substitution enthalpy calculation, it is expected that impurities will be incorporated within LiCl crystal as co-existed form rather than as a single component form. (authors)« less

Crystallization and properties of Sr-Ba aluminosilicate glass-ceramic matrices

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.; Hyatt, Mark J.; Drummond, Charles H., III

1991-01-01

Powders of roller quenched (Sr,Ba)O-Al2O3-2SiO2 glasses of various compositions were uniaxially pressed into bars and hot isostatically pressed at 1350 C for 4 hours or cold isostatically pressed and sintered at different temperatures between 800 to 1500 C for 10 or 20 hours. Densities, flexural strengths, and linear thermal expansion were measured for three compositions. The glasss transition and crystallization temperatures were determined by Differential Scanning Calorimetry (DSC). The liquidus and crystallization temperature from the melt were measured using high temperature Differential Thermal Analysis (DTA). Crystalline phases formed on heat treatment of the glasses were identified by powder x ray diffraction. In Sr containing glasses, the monoclinic celsian phase always crystallized at temperatures above 1000 C. At lower temperatures, the hexagonal analog formed. The temperature for orthorhombic to hexagonal structure transformation increased monotonically with SrO content, from 327 C for BaO-Al2O3-2SiO2 to 758 C for SrO-Al2O3-2SiO2. These glass powders can be sintered to almost full densities and monoclinic celsian phase at a relatively low temperature of 1100 C.

Simplified multi-element analysis of ground and instant coffees by ICP-OES and FAAS.

PubMed

Szymczycha-Madeja, Anna; Welna, Maja; Pohl, Pawel

2015-01-01

A simplified alternative to the wet digestion sample preparation procedure for roasted ground and instant coffees has been developed and validated for the determination of different elements by inductively coupled plasma optical emission spectrometry (ICP-OES) (Al, Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, Zn) and flame atomic absorption spectrometry (FAAS) (Ca, Fe, K, Mg, Na). The proposed procedure, i.e. the ultrasound-assisted solubilisation in aqua regia, is quite fast and simple, requires minimal use of reagents, and demonstrated good analytical performance, i.e. accuracy from -4.7% to 1.9%, precision within 0.5-8.6% and recovery in the range 93.5-103%. Detection limits of elements were from 0.086 ng ml(-1) (Sr) to 40 ng ml(-1) (Fe). A preliminary classification of 18 samples of ground and instant coffees was successfully made based on concentrations of selected elements and using principal component analysis and hierarchic cluster analysis.

Multielement analysis of Canadian wines by inductively coupled plasma mass spectrometry (ICP-MS) and multivariate statistics.

PubMed

Taylor, Vivien F; Longerich, Henry P; Greenough, John D

2003-02-12

Trace element fingerprints were deciphered for wines from Canada's two major wine-producing regions, the Okanagan Valley and the Niagara Peninsula, for the purpose of examining differences in wine element composition with region of origin and identifying elements important to determining provenance. Analysis by ICP-MS allowed simultaneous determination of 34 trace elements in wine (Li, Be, Mg, Al, P, Cl, Ca, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Mo, Ag, Cd, Sb, I, Cs, Ba, La, Ce, Tl, Pb, Bi, Th, and U) at low levels of detection, and patterns in trace element concentrations were deciphered by multivariate statistical analysis. The two regions were discriminated with 100% accuracy using 10 of these elements. Differences in soil chemistry between the Niagara and Okanagan vineyards were evident, without a good correlation between soil and wine composition. The element Sr was found to be a good indicator of provenance and has been reported in fingerprinting studies of other regions.

Incorporation of Mg, Sr, Ba, U, and B in High-Mg Calcite Benthic Foraminifers Cultured Under Controlled pCO2

NASA Astrophysics Data System (ADS)

Not, C.; Thibodeau, B.; Yokoyama, Y.

2018-01-01

Measurement of elemental ratios (E/Ca) has been performed in two symbiont-bearing species of high-Mg calcite benthic foraminifers (hyaline, Baculogypsina sphaerulata and porcelaneous, Amphisorus hemprichii), cultured under five pCO2 levels, representing preindustrial, modern, and three predicted future values. E/Ca ratios were analyzed by Laser Ablation coupled with Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS). We measured several E/Ca, such as Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, and B/Ca simultaneously. We observed that high-Mg calcite benthic foraminifers possess higher E/Ca than low-Mg calcite foraminifers, irrespective of their calcification mode (hyaline or porcelaneous). In both modes of calcification, Mg, Sr, Ba, U, and B incorporation could be controlled by Rayleigh fractionation. However, more data are needed to validate and quantify the relative importance of this process and closely investigate the presence/absence of other mechanism. Therefore, it highlights the need for a multielemental approach when looking at trace element incorporation. Finally, no significant relationship was observed between the different ratios and the pCO2 of the water, suggesting that none of the Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, and B/Ca is sensitive to bottom water pCO2 or pH for these species.

Effects of crystallization on structural and dielectric properties of thin amorphous films of (1 - x)BaTiO3-xSrTiO3 (x=0-0.5, 1.0)

NASA Astrophysics Data System (ADS)

Kawano, H.; Morii, K.; Nakayama, Y.

1993-05-01

The possibilities for fabricating solid solutions of (Ba1-x,Srx)TiO3 (x≤0.5,1.0) by crystallization of amorphous films and for improving their dielectric properties by adjusting the Sr content were investigated. Thin amorphous films were prepared from powder targets consisting of mixtures of BaTiO3 and SrTiO3 by sputtering with a neutralized Ar-ion beam. The amorphous films crystallized into (Ba1-x, Srx)TiO3 solid solutions with a cubic perovskite-type structure after annealing in air at 923 K for more than 1 h. The Debye-type dielectric relaxation was observed for the amorphous films, whereas the crystallized films showed paraelectric behavior. The relative dielectric constants were of the order of 20 for the amorphous samples, but increased greatly after crystallization to about 60-200, depending on the composition; a larger increase in the dielectric constant was observed in the higher Sr content films, in the range x≤0.5, which could be correlated with an increase in the grain size of the crystallites. The crystallization processes responsible for the difference in the grain size are discussed based on the microstructural observations.

Diffusion of Zr, Ru, Ce, Y, La, Sr and Ba fission products in UO 2

DOE PAGES

Perriot, R.; Liu, X. -Y.; Stanek, C. R.; ...

2015-01-08

The diffusivity of the solid fission products (FP) Zr (Zr 4+), Ru (Ru 4+, Ru 3+), Ce (Ce 4+), Y (Y 3+), La (La 3+), Sr (Sr 2+) and Ba (Ba 2+) by a vacancy mechanism has been calculated, using a combination of density functional theory (DFT) and empirical potential (EP) calculations. The activation energies for the solid fission products are compared to the activation energy for Xe fission gas atoms calculated previously. Apart from Ru, the solid fission products all exhibit higher activation energy than Xe. Furthermore, for all solid FPs except Y 3+, the migration of the FPmore » has lower barrier than the migration of a neighboring U atom, making the latter the rate limiting step for direct migration. An indirect mechanism, consisting of two successive migrations around the FP, is also investigated. The calculated diffusivities show that most solid fission products diffuse with rates similar to U self-diffusion. But, Ru, Ba and Sr exhibit faster diffusion than the other solid FPs, with Ru 3+ and Ru 4+ diffusing even faster than Xe for T < 1200 K. The diffusivities correlate with the observed fission product solubility in UO 2, and the tendency to form metallic and oxide second phase inclusions.« less

Selenium and 17 other largely essential and toxic metals in muscle and organ meats of Red Deer (Cervus elaphus)--consequences to human health.

PubMed

Jarzyńska, Grażyna; Falandysz, Jerzy

2011-07-01

Concentrations, composition and interrelationships of selenium and metallic elements (Ag, Ba, Cd, Co, Cr, Cs, Cu, Ga, Mn, Mo, Pb, Rb, Sb, Sr, Tl, V and Zn) have been examined in muscle and organ meats of Red Deer hunted in Poland. The analytical data obtained were also discussed in terms of Se supplementation and deficit to Deer as well as the benefits and risk to humans associated with the essential and toxic metals intake resulting from consumption of Deer meat and products. These elements were determined in 20 adult animals of both sexes that were obtained in the 2000/2001 hunting season from Warmia and Mazury in the north-eastern part of Poland. The whole kidneys contained Ba, Cd, Cr, Ga, Pb, Se, Sr and Tl at statistically greater concentrations than liver or muscle tissue from the same animal. Liver showed statistically greater concentrations of Ag, Co, Cu, Mn and Mo than kidneys or muscle tissue, and muscle tissue was richer in Zn, when compared to the kidneys or liver. Cs and Rb were similarly distributed between all three tissue types, while V was less abundant in liver than kidneys or muscle tissue. There were significant associations between some metallic elements retained in Red Deer demonstrated by Principal Component Analysis (PCA) of the data set. In organ and muscle meats (kidneys, liver and muscle tissue considered together) the first principal component (PC1) was strongly influenced by positively correlated variables describing Se, Ba and Cd and negatively correlated variables describing Ag, Co, Cs, Mn, Pb, Tl and V; PC2, respectively, by Cu, Mn and Mo (+) and Zn (-); PC3 by Ga (+) and PC4 by Sb (+). Selenium occurred in muscle tissue, liver and kidneys at median concentrations of 0.13, 0.19 and 4.0mg/g dry weight, respectively. These values can be defined as marginally deficient (< 0.6mg Se/kg liver dw) or satisfactory (≤ 3.0mg Se/kg kidneys dw) for the amount required to maintain the Deer's body condition and health, depending on the criterion for supplementation used. In terms of human nutritional needs, a relatively high selenium content of kidneys can be beneficial. The muscle meat, liver and kidneys of Red Deer can be considered as a very good source of essential Co, Cr, Cu, Mo, Mn, Se and Zn in the human diet. Lead is generally considered as toxic, and the concentrations found in Red Deer (via the food chain intake) were well below the European Union tolerance limit. Pb from the lead bullets can always create food hygienic problem, if not well recognized during sanitary inspection, and this was noted for one muscle meat sample in this study (5% surveyed). There is no tolerance limit of Cd in game animal meats. The median values of Cd noted in fresh muscle tissue, liver and whole kidneys were 0.07, 0.18, and 3.3mg/kg wet weight, respectively. Cd exists as a chemical element present at trace levels in plants and mushrooms in Deer's food chain in background (uncontaminated) areas. When these are consumed by the Deer, the amount of Cd sequestered with metallothioneins and retained in the organ and muscle meat in this study is low enough to be considered safe for human consumption. Copyright © 2011 Elsevier Ltd. All rights reserved.

Artificially layered films of CuBa{sub 2} (Ca{sub 1{minus}x}Sr{sub x}){sub n{minus}1}Cu{sub n}O{sub y} grown using pulsed laser deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aruta, C.; Balestrino, G.; Martellucci, S.

We have shown that the pulsed laser deposition technique (PLD) can be successfully used to grow artificially layered films of the CuBa{sub 2}(Ca{sub 1{minus}x}Sr{sub x}){sub n{minus}1}Cu{sub n}O{sub y} compound using only two targets having nominal composition BaCuO{sub y} and (Ca{sub 1{minus}x}Sr{sub x})CuO{sub y}, respectively. n was varied between 2 and 5. We have demonstrated, by a kinematic analysis of the x-ray diffraction spectra that the average random discrete thickness fluctuations which affect both the BaCuO{sub y} and (Ca{sub 1{minus}x}Sr{sub x})CuO{sub y} layers are much smaller than one atomic layer. Such features are confirmed by the appearance of sharp peaks evenmore » for the n=2 artificially layered structure where only one (Ca{sub 1{minus}x}Sr{sub x})CuO{sub y} cell is deposited in the stacking sequence. These results show that truly new structures can be obtained by a layer by layer deposition technique with a low interfacial disorder and give strong support to the idea of synthesizing new artificial high T{sub c} structures by the PLD technique.{copyright} {ital 1997 American Institute of Physics.}« less

Sintering of BaCe(sub 0.85)Y(sub 0.15)O(sub 3-delta) with/without SrTiO3 Dopant

NASA Technical Reports Server (NTRS)

Dynys, F.; Sayir, A.; Heimann, P. J.

2004-01-01

The perovskite composition, BaCe(sub 0.85)Y(sub 0.15)O(sub 3-delta), displays excellent protonic conduction at high temperatures making it a desirable candidate for hydrogen separation membranes. This paper reports on the sintering behavior of BaCe(sub 0.85)Y(sub 0.15)O(sub 3-delta) powders doped with SrTiO3. Two methods were used to synthesize BaCe(sub 0.85)Y(sub 0.15)O(sub 3-delta) powders: (1) solid state reaction and (2) wet chemical co-precipitation. Co-precipitated powder crystallized into the perovskite phase at 1000 C for 4 hrs. Complete reaction and crystallization of the perovskite phase by solid state was achieved by calcining at 1200 C for 24 hrs. Solid state synthesis produced a coarser powder with an average particle size of 1.3 microns and surface area of 0.74 sq m/g. Co-precipitation produced a finer powder with a average particle size of 65 nm and surface area of 14.9 sq m/g. Powders were doped with 1, 2, 5, and 10 mole % SrTiO3. Samples were sintered at 1450 C, 1550 C and 1650 C. SrTiO3 enhances sintering, optimal dopant level is different for powders synthesized by solid state and co-precipitation. Both powders exhibit similar grain growth behavior. Dopant levels of 5 and 10 mole % SrTiO3 significantly enhances the grain size.

New observations on the pressure dependence of luminescence from Eu2+-doped MF2 (M = Ca, Sr, Ba) fluorides.

PubMed

Su, Fu Hai; Chen, Wei; Ding, Kun; Li, Guo Hua

2008-05-29

The luminescence from Eu(2+) ions in MF2 (M = Ca, Sr, Ba) fluorides has been investigated under the pressure range of 0-8 GPa. The emission band originating from the 4f(6)5d(1) --> 4f(7) transition of Eu(2+) ions in CaF2 and SrF2 shows the red-shift as increasing pressure with pressure coefficients of -17 meV/GPa for CaF2 and -18 meV/GPa for SrF2. At atmospheric pressure, the emission spectrum of BaF2:Eu(2+) comprises two peaks at 2.20 and 2.75 eV from the impurity trapped exciton (ITE) and the self-trapped exciton (STE), respectively. As the pressure is increased, both emission peaks shift to higher energies, and the shifting rate is slowed by the phase transition from the cubic to orthorhombic phase at 4 GPa. Due to the phase transition at 4-5 GPa pressure, the ITE emission disappears gradually, and the STE emission is gradually replaced by the 4f(6)5d(1) --> 4f(7) transition of Eu(2+). Above 5 GPa, the pressure behavior of the 4f(6)5d(1) --> 4f(7) transition of Eu(2+) in BaF2:Eu(2+) is the same as the normal emission of Eu(2+) in CaF2 and SrF2 phosphors.

Transmittance of optical materials from 0.17 micro to 3.0 micro.

PubMed

McCarthy, D E

1967-11-01

The transmittance of thirty-one optical materials is given from 0.17, micro to 3.0 micro. Included are NaCl, KBr, CsBr, CsI, CaF(2), BaF(2), NaF, TlBr, TICL, KRS-5, KRS-6, T-12, KC, CuC, T O(2), ADP, KDP, SrTiO(3), GaP, CaCO(3), CdSe, As(2)S(3), ruby, Al(2)O(3), Irtran 1-6, and quartz. All are synthetic with the exception of CaCO(3). In many cases, the short wavelength cutoff of the synthetic materials is less than that which has been reported for naturally occurring materials.

[Determination of twenty one elements in lithium hexafluorophosphate by ICP-AES].

PubMed

Fang, Yi-wen; Hao, Zhi-feng; Song, Yi-bing; Sun, Chang-yong; Yu, Jian; Yu, Lin

2005-02-01

One gram (+/- 0.0001 g) of lithium hexafluorophosphate was weighed exactly under dry atmosphere and was dissolved with an adequate amount of dimethyl carbonate (DMC). After the sample solution was pretreated with a series of methods, Be, Cu, Pb, Ca, Zr, Co, Mg, V, Ti, Mo, Ni, Mn, Sr, Zn, K, Al, Ba, Cd, Fe, Cr and Na were determined by ICP-AES. The results show that the recoveries of standard addition were 93.3%-102.1%, and the relative standard deviations (n = 11) were 0%-3.56%. The method is efficient, accurate and easy to operate. It has been applied to the determination of lithium hexafluorophosphate products with satisfactory results.

Study of non-stoichiometric BaSrTiFeO3 oxide dedicated to semiconductor gas sensors

NASA Astrophysics Data System (ADS)

Fasquelle, D.; Verbrugghe, N.; Deputier, S.

2016-11-01

Developing instrumentation systems compatible with the European RoHS directive (restriction of hazardous substances) to monitor our environment is of great interest for our society. Our research therefore aims at developing innovating integrated systems of detection dedicated to the characterization of various environmental exposures. These systems, which integrate new gas sensors containing lead-free oxides, are dedicated to the detection of flammable and toxic gases. We have firstly chosen to study semiconductor gas sensors implemented with lead-free oxides in view to develop RoHS devices. Therefore thick films deposited by spin-coating and screen-printing have been chosen for their robustness, ease to realize and ease to finally obtain cost-effective sensors. As crystalline defects and ionic vacancies are of great interest for gas detection, we have decided to study a non-stoichiometric composition of the BaSrTiFeO3 sensible oxide. Nonstoichiometric BaSrTiFeO3 lead-free oxide thick films were deposited by screen-printing on polycrystalline AFO3 substrates covered by a layer of Ag-Pd acting as bottom electrode. The physical characterizations have revealed a crystalline structure mainly composed of BaTiO3 pseudo-cubic phase and Ba4Ti12O27 monoclinic phase for the powder, and a porous microstructure for the thick films. When compared to a BSTF thick film with a stoichiometric composition, a notable increase in the BSTF dielectric constant value was observed when taking into account of a similar microstructure and grain size. The loss tangent mean value varies more softly for the non-stoichiometric BaSrTiFeO3 films than for the perovskite BSTF film as tanδ decreases from 0.45 to 0.04 when the frequency increases from 100 Hz to 1 MHz.

Effect of SiO2/B2O3 Ratio on the Crystallization Behavior and Dielectric Properties of Barium Strontium Titanate Glass-Ceramics Prepared by Sol-Gel Process

NASA Astrophysics Data System (ADS)

Chen, Yongzhou; Zhang, Yong; Song, Xiaozhen; Shen, Ziqin; Zhang, Tianyuan

2018-05-01

Ferroelectric glass-ceramics, with a basic composition 90 wt.% (Ba0.65Sr0.35)TiO3-10 wt.% (B2O3-nSiO2) (n = 0.5, 1, 3, 5) were synthesized by the sol-gel method and their phase development and dielectric properties were investigated by differential thermal analysis, x-ray diffraction, field emission scanning electron microscopy, dielectric temperature curves and impedance spectroscopy. From the differential thermal analysis, glass transition and crystallization behavior can be observed. From the x-ray diffraction study, two crystalline phases (Ba,Sr)TiO3 and Ba2TiSi2O8 were formed over the entire composition range of the glass-ceramics. In addition, the main crystal phase has undergone a transformation from (Ba,Sr)TiO3 to Ba2TiSi2O8 with the increase of n. A typical structure in which the crystal phase was surrounded by a glassy matrix has been observed in the scanning electron microscope images. As a result of temperature dependent dielectric property measurements, the dielectric constant increased obviously with the increase of n from 0.5 to 1. Further increasing n led to a reduction of the dielectric constant, which is in coincidence with the variation of the intensity of (Ba,Sr)TiO3 phase with n. According to the impedance spectroscopy analysis and the activation energy calculation, the relaxation peak in both Z″ and M″ data should be attributed to the crystal-glass interface, and the change of conduction mechanism with the increase of SiO2/B2O3 ratio may be attributed to the corresponding transition of the main crystal phase.

Trace element concentrations in livers of polar bears from two populations in Northern and Western Alaska.

PubMed

Kannan, Kurunthachalam; Agusa, Tetsuro; Evans, Thomas J; Tanabe, Shinsuke

2007-10-01

Concentrations of 20 trace elements (V, Cr, Mn, Co, Cu, Zn, Rb, Sr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, Hg, Tl, Pb, and Bi) were measured in livers of polar bears (Ursus maritimus) collected from Northern and Western Alaska from 1993 to 2002 to examine differences in the profiles of trace metals between the Beaufort Sea (Northern Alaska) and the Chukchi Sea (Western Alaska) subpopulations in Alaska. Among the trace elements analyzed, concentrations of Cu (50-290 microg/g, dry wt) in polar bear livers were in the higher range of values that have been reported for marine mammals. Concentrations of Hg in polar bears varied widely, from 3.5 to 99 microg/g dry wt, and the mean concentrations in polar bears were comparable to concentrations reported previously for several other species of marine mammals. Mean concentrations of Pb and Cd were 0.67 and 1.0 microg/g dry wt, respectively; these concentrations were lower than levels reported elsewhere for polar bears from Greenland and Canada. Age- and gender-related variations in the concentrations of trace elements in our polar bears were minimal. Concentrations of Hg decreased slowly in samples collected during 1993-2002, whereas Cd and Pb concentrations were found to be stable or slowly increasing, in the livers of Alaskan polar bears. Concentrations of Ag, Bi, Ba, Cu, and Sn were significantly higher in the Chukchi Sea subpopulation than in the Beaufort Sea subpopulation. Concentrations of Hg were significantly higher in the Beaufort Sea subpopulation than in the Chukchi Sea subpopulation. Differences in the profiles and concentrations of Hg, Ag, Bi, Ba, Cu, and Sn suggest that the sources of exposure to these trace elements between Western and Northern Alaskan polar bears are different, in agreement with findings reported earlier for several organic contaminants.

Crystal-chemical controls on the partitioning of Sr and Ba between plagioclase feldspar, silicate melts, and hydrothermal solutions

NASA Astrophysics Data System (ADS)

Blundy, Jonathan D.; Wood, Bernard J.

1991-01-01

The isothermal (750°C) experiments of LAGACHE and DUJON (1987) reveal that the partitioning of Sr between plagioclase feldspar and hydrothermal solutions is a funtion of the anorthite (An) content of the plagioclase, indicating that crystal chemistry may exert a powerful influence on trace element partitioning. In order to compare these results with those on trace element partitioning between plagioclase and silicate melts we have compiled from the literature a large dataset of experimental and volcanic distribution coefficients ( D's) for Sr (and Ba). These data, which span a compositional range from lunar basalt to high silica rhyolite and a temperature range of over 650°C, show a relationship between DSr (and DBa) and mole fraction An ( XAn) which is similar to that exhibited by the hydrothermal results obtained at constant temperature. Plots of In DSr and In DBa versus XAn are linear with negative slope, indicating that both elements are more compatible in albite than anorthite. In terms of molar distribution coefficients ( D Sr∗) the hydrothermal and silicate melt data display an identical linear relationship between RT In D Sr∗ (where T is the absolute temperature in K and R is the gas constant, 8.314 JK -1 mol -1) and XAn. We conclude therefore that crystal chemistry provides the dominant control on partitioning of Sr and Ba into plagioclase and that the effects of temperature, pressure, and fluid composition are minor. Apparent relationships between DSr (and DBa) and the reciprocal temperature (1/ T) are artefacts of the linear relationships between XAn and 1/ T in the experimental studies. By defining a Henry's law standard state for the silicate melts and hydrothermal solutions, and considering plagioclases to be ternary regular solutions, we are able to relate the observed relationships between RT In D i∗ (where i is Ba or Sr) and XAn to the excess free energies of the trace element partitioning reactions between plagioclase and melt or hydrothermal solution. The interaction parameters are consistent with simple models in which the larger Ba or Sr cations are accommodated by lattice strain in the host plagioclase lattice, which is assumed to be perfectly elastic and isotropic. Thus D i∗ is a function of the Young's modulus of the host crystal and the size mismatch between trace and host cations. The greater elasticity of albite relative to anorthite accounts for the observed preference of Sr and Ba for sodic plagioclases over calcic plagioclases. For geochemical purposes the weight fraction partition coefficient Di is of more value than its molar counterpart. Regression of the Di data versus XAn yields the semi-empirical relationships RTIn DSr = 26,800 - 26,700 · XAnRTIn DBa = 10,200 - 38,200 · XAn. Thus measurement of the An and trace element (Ba, Sr) contents of a magmatic plagioclase enables calculation of the Ba and Sr contents of the coexisting liquid, which can be extremely important in the deciphering of igneous processes. By reference to plagioclase fractionation in the simple An-Ab binary we show that failure to take into account the compositional dependence of DSr can result in erroneous interpretations of geochemical trends. We also consider applications to three natural igneous suites: the Aden Volcanics; the layered Kiglapait Intrusion, Labrador; and the southern Actamello Massif, Italy.

Trace-element and Sr, Nd, Pb, and O isotopic composition of Pliocene and Quaternary alkali basalts of the Patagonian Plateau lavas of southernmost South America

USGS Publications Warehouse

Stern, C.R.; Frey, F.A.; Futa, K.; Zartman, R.E.; Peng, Z.; Kurtis, Kyser T.

1990-01-01

The Pliocene and Quaternary Patagonian alkali basalts of southernmost South America can be divided into two groups. The "cratonic" basalts erupted in areas of Cenozoic plateau volcanism and continental sedimentation and show considerable variation in 87Sr/86Sr (0.70316 to 0.70512), 143Nd/144Nd (e{open}Nd) and 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios (18.26 to 19.38, 15.53 to 15.68, and 38.30 to 39.23, respectively). These isotopic values are within the range of oceanic island basalts, as are the Ba/La, Ba/Nb, La/Nb, K/Rb, and Cs/Rb ratios of the "cratonic" basalts. In contrast, the "transitional" basalts, erupted along the western edge of the outcrop belt of the Pliocene and Quaternary plateau lavas in areas that were the locus of earlier Cenozoic Andean orogenic arc colcanism, have a much more restricted range of isotopic composition which can be approximated by 87Sr/86Sr=0.7039??0.0004, e{open}Nd, 206Pb/204Pb=18.60??0.08, 207Pb/204Pb=15.60??0.01, and 208Pb/204Pb=38.50??0.10. These isotopic values are similar to those of Andean orogenic are basalts and, compared to the "cratonic" basalts, are displaced to higher 87Sr/86Sr at a given 143Nd/144Nd and to higher 207Pb/204Pb at a given 208Pb/204Pb. The "transitional" basalts also have Ba/La, Ba/Nb, La/Nb, and Cs/Rb ratios higher than the "cratonic" and oceanic island basalts, although not as high as Andean orogenic are basalts. In contrast to the radiogenic isotopes, ??18O values for both groups of the Patagonian alkali basalts are indistinguishable and are more restricted than the range reported for Andean orogenic are basalts. Whole rock ??18O values calculated from mineral separates for both groups range from 5.3 to 6.5, while measured whole rock ??18O values range from 5.1 to 7.8. The trace element and isotopic data suggest that decreasing degrees of partial melting in association with lessened significance of subducted slabderived components are fundamental factors in the west to east transition from arc to back-arc volcanism in southern South America. The "cratonic" basalts do not contain the slab-derived components that impart the higher Ba/La, Ba/Nb, La/Nb, Cs/Rb, 87Sr/86Sr at a given 143Nd/144Nd, 207Pb/204Pb at a given 208Pb/204Pb, and ??18O to Andean orogenic arc basalts. Instead, these basalts are formed by relatively low degrees of partial melting of heterogeneous lower continental lithosphere and/or asthenosphere, probably due to thermal and mechanical pertubation of the mantle in response to subduction of oceanic lithosphere below the western margin of the continent. The "transitional" basalts do contain components added to their source region by either (1) active input of slab-derived components in amounts smaller than the contribution to the mantle below the arc and/or with lower Ba/La, Ba/Nb, La/Nb, and Cs/Rb ratios than below the arc due to progressive downdip dehydration of the subducted slab; or (2) subarc source region contamination processes which affected the mantle source of the "transitional" basalts earlier in the Cenozoic. ?? 1990 Springer-Verlag.

Thermoelectric properties of doped BaHfO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixit, Chandra Kr., E-mail: ckparadise@gmail.com, E-mail: sharmarameshfgiet@gmail.com; Bhamu, K. C.; Sharma, Ramesh, E-mail: ckparadise@gmail.com, E-mail: sharmarameshfgiet@gmail.com

2016-05-06

We have studied the structural stability, electronic structure, optical properties and thermoelectric properties of doped BaHfO{sub 3} by full potential linearized augmented plane wave (FP-LAPW) method. The electronic structure of BaHfO{sub 3} doped with Sr shows enhances the indirect band gaps of 3.53 eV, 3.58 eV. The charge density plots show strong ionic bonding in Ba-Hf, and ionic and covalent bonding between Hf and O. Calculations of the optical spectra, viz., the dielectric function, refractive index and extinction coefficient are performed for the energy range are calculated and analyzed. Thermoelectric properties of semi conducting are also reported first time. Themore » doped BaHfO{sub 3} is approximately wide band gap semiconductor with the large p-type Seebeck coefficient. The power factor of BaHfO{sub 3} is increased with Sr doping, decreases because of low electrical resistivity and thermal conductivity.« less

Determination of the Extent of Trace Metals Pollution in Soils, Sediments and Human Hair at e-Waste Recycling Site in Ghana.

PubMed

Tokumaru, Takashi; Ozaki, Hirokazu; Onwona-Agyeman, Siaw; Ofosu-Anim, John; Watanabe, Izumi

2017-10-01

The concentrations of trace elements (Mg, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Y, Mo, Cd, In, Sn, Sb, Cs, Ba, Tl, Pb, and Bi) in soils, sediment, human hair, and foodstuff collected around the electronic waste (e-waste) recycling sites in Accra, Ghana were detected using inductively coupled plasma-mass spectrometry (ICP-MS). High levels of Cu, Zn, Mo, Cd, In, Sn, Sb, and Pb were observed in soils collected from the e-waste recycling sites. Four sequential extraction procedures were used to evaluate the mobility and bioavailability of metals (Cu, Zn, Cd, Sb, and Pb). Especially, the results showed that Cd and Zn in soils were mostly recovered in exchangeable fraction (respectively 58.9 and 62.8%). Sediment collected from around the site had enrichment of Zn, Sn, Sb, Mo, In, Pb, and Bi. The concentrations of Cu, Mo, Cd, Sb, and Pb in human hair were significantly higher than those collected from the control site (p < 0.01). Additionally, hierarchical cluster analysis reviewed that these elements were derived from e-waste activities. The results of Pb isotopic ratios in the samples indicate that Pb in human hair possibly originated from contaminated soils, fish, and foodstuff.

Structure and optical band gaps of (Ba,Sr)SnO{sub 3} films grown by molecular beam epitaxy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schumann, Timo; Raghavan, Santosh; Ahadi, Kaveh

2016-09-15

Epitaxial growth of (Ba{sub x}Sr{sub 1−x})SnO{sub 3} films with 0 ≤ x ≤ 1 using molecular beam epitaxy is reported. It is shown that SrSnO{sub 3} films can be grown coherently strained on closely lattice and symmetry matched PrScO{sub 3} substrates. The evolution of the optical band gap as a function of composition is determined by spectroscopic ellipsometry. The direct band gap monotonously decreases with x from to 4.46 eV (x = 0) to 3.36 eV (x = 1). A large Burnstein-Moss shift is observed with La-doping of BaSnO{sub 3} films. The shift corresponds approximately to the increase in Fermi level and is consistent with the low conduction band mass.

Numerical solutions of anharmonic vibration of BaO and SrO molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pramudito, Sidikrubadi; Sanjaya, Nugraha Wanda; Sumaryada, Tony, E-mail: tsumaryada@ipb.ac.id

2016-03-11

The Morse potential is a potential model that is used to describe the anharmonic behavior of molecular vibration between atoms. The BaO and SrO molecules, which are two almost similar diatomic molecules, were investigated in this research. Some of their properties like the value of the dissociation energy, the energy eigenvalues of each energy level, and the profile of the wavefunctions in their correspondence vibrational states were presented in this paper. Calculation of the energy eigenvalues and plotting the wave function’s profiles were performed using Numerov method combined with the shooting method. In general we concluded that the Morse potentialmore » solved with numerical methods could accurately produce the vibrational properties and the wavefunction behavior of BaO and SrO molecules from the ground state to the higher states close to the dissociation level.« less

Development of Solid State Laser Materials for Application in Lasers for Atmospheric Ozone and Water Vapor Sensing

NASA Technical Reports Server (NTRS)

Noginov, Makhail A.; Loutts, G. B.

2002-01-01

We have grown neodymium doped mixed apatite crystals, (Sr(x)Ba(l-x)5(PO4)3F, Sr5(P(1-x)V(x)O4)3F, and Ba5(P(1-x)V(x)O4)3F, and spectroscopically studied them as potential gain media for a laser source for atmospheric water sensing operating at 944.11 nm0. We conclude that an appropriate apatite host material for a 944.11 nm laser should be a mixture of Sr5(PO4)3F with a small fraction of Ba5(PO4)3F. The precise wavelength tuning around 944.11 nm can be accomplished by varying the host composition, temperature, and threshold population inversion. In apatite crystals of mixed composition, the Amplified Spontaneous Emission (ASE) loss at 1.06 microns is predicted to be significantly smaller than that in the end members.

Protonic Conduction of BaCe0.85YO. 1503 Doped with SrTiO3

NASA Technical Reports Server (NTRS)

Dynys, Frederick W.; Sayir, Ali

2005-01-01

Reformers based on ceramic membrane technology potentially offer hydrogen production that is comparable to the cost of fossil fuels. Protonic conducting ceramic with the chemical formula AB03 offers the promise of highly selective hydrogen separation at intermediate temperature (400-800 C). Among different perovskite-type oxides, BaCe03 and SrCe03 based compositions show high protonic conductivities but strong resistance to densification. X-ray diffraction studies on sintered specimens of BaCe0.85Y0.1503-6 show multi-phase formation which was found to show dependence upon powder synthesis method. Doping with SrTiO3 suppresses multi-phase formation and enhances grain growth. Conductivity measurements in temperature range of 200 to 1000 C were performed by ac impedance spectroscopy under dry and wet conditions. Sintering behavior, phase formation and conductivity results will be reported.

A comparative study on the magnetic and electrical properties of MFe12O19 (M=Ba and Sr)/BiFeO3 nanocomposites

NASA Astrophysics Data System (ADS)

Ahmed, M. A.; Mansour, S. F.; Ismael, H.

2015-03-01

M-type hexaferrite (MFe12O19), M=Ba or Sr nanoparticles with hexagonal crystal structure have been successfully synthesized by a citrate auto-combustion method. BiFeO3 (BFO) was prepared by the flash auto-combustion technique. Different nanocomposites were prepared according to the formula [(1-X) MFe12O19+XBiFeO3; M=Ba or Sr, X=0.3, 0.4, 0.5 and 0.6]. The structure and morphology of the obtained nanocomposites have been determined by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). From the results, it is observed that the value of saturation magnetization decreases with increasing BFO content, which was mainly due to the contribution of the volume of the weak-magnetic BFO to the total sample volume.

Fluorine Kα X-Ray Emission Spectra of MgF2, CaF2, SrF2 and BaF2

NASA Astrophysics Data System (ADS)

Sugiura, Chikara; Konishi, Wataru; Shoji, Shizuko; Kojima, Shinjiro

1990-11-01

The fluorine Kα emission spectra in fluorescence from a series of alkaline-earth fluorides MF2 (M=Mg, Ca, Sr and Ba) are measured with a high-resolution two-crystal vacuum spectrometer. An anomalously low intensity of the K1L1 satellite peak arising from 1s-1(2s2p)-1 initial states is observed for SrF2. The measured emission spectra are presented along with the UPS spectra of the F- 2p valence bands obtained by Poole et al. and the fluorine K absorption-edge spectra by Oizumi et al. By using these spectra, the first peak or shoulder in the fluorine K absorption-edge spectra is identified as being due to a core exciton which is formed below the bottom of the conduction band. The binding energy of the exciton is estimated to be 1.3(± 0.3), 1.1(± 0.2), 1.0(± 0.2) and 1.7(± 0.2) eV for MgF2, CaF2, SrF2 and BaF2, respectively.

The isotopic and chemical evolution of Mount St. Helens

USGS Publications Warehouse

Halliday, A.N.; Fallick, A.E.; Dickin, A.P.; Mackenzie, A.B.; Stephens, W.E.; Hildreth, W.

1983-01-01

Isotopic and major and trace element analysis of nine samples of eruptive products spanning the history of the Mt. St. Helens volcano suggest three different episodes; (1) 40,000-2500 years ago: eruptions of dacite with ??{lunate}Nd = +5, ??{lunate}Sr = -10, variable ??18O, 206Pb/204Pb ??? 18.76, Ca/Sr ??? 60, Rb/Ba ??? 0.1, La/Yb ??? 18, (2) 2500-1000 years ago: eruptions of basalt, andesite and dacite with ??{lunate}Nd = +4 to +8, ??{lunate}Sr = -7 to -22, variable ??18O (thought to represent melting of differing mantle-crust reservoirs), 206Pb/204Pb = 18.81-18.87, variable Ca/Sr, Rb/Ba, La/Yb and high Zr, (3) 1000 years ago to present day: eruptions of andesite and dacite with ??{lunate}Nd = +6, ??{lunate}Sr = -13, ??18O ???6???, variable 206Pb/204Pb, Ca/Sr ??? 77, Rb/Ba = 0.1, La/Yb ??? 11. None of the products exhibit Eu anomalies and all are LREE enriched. There is a strong correlation between 87Sr/86Sr and differentiation indices. These data are interpreted in terms of a mantle heat source melting young crust bearing zircon and garnet, but not feldspar, followed by intrusion of this crustal reservoir by mantle-derived magma which caused further crustal melting and contaminated the crustal magma system with mafic components. Since 1000 years ago all the eruptions have been from the same reservoir which has displayed a much more gradual re-equilibration of Pb isotopic compositions than other components suggesting that Pb is being transported via a fluid phase. The Nd and Sr isotopic compositions lie along the mantle array and suggest that the mantle underneath Mt. St. Helens is not as depleted as MORB sources. There is no indication of seawater involvement in the source region. ?? 1983.

Giant piezoelectric property of (110) oriented BaxSr1-xTiO3 films

NASA Astrophysics Data System (ADS)

Chen, Z. H.; Chen, Z.; Qiu, J. H.; Yuan, N. Y.; Ding, J. N.

2017-10-01

A phenomenological Landau-Devonshire theory is applied to investigate the phase diagrams and physical properties of (110) oriented BaxSr1-xTiO3 films. New ferroelectric phases, such as the tetragonal a1 phase and the orthorhombic a2 c phase, appear in the ;misfit strain-temperature; phase diagrams for (110) oriented films compared with that of (001) oriented films. Moreover, the orthorhombic a2 c phase, and the tetragonal c phase and the triclinic γ phase are stable at low temperature for x = 0.5 and x = 0.7 , respectively. The ferroelectric, dielectric, and piezoelectric properties strongly depend on the misfit strain and electric field. (110) oriented Ba0.7Sr0.3TiO3 film has the larger ferroelectric polarization and piezoelectric coefficient than that of Ba0.5Sr0.5TiO3 film. The giant piezoelectric coefficient of 340 pm / V is obtained at the electric field of 50 KV / cm in (110) oriented Ba0.7Sr0.3TiO3 film, which is comparable with the values of Pb (Zr1-xTix)O3 and (1 - x) Pb (Mg1/3Nb2/3)O3 -xPbTiO3 films. It makes (110) oriented BaxSr1-xTiO3 films suitable for applications in electromechanical devices.

[Distribution of rubidium, cesium, beryllium, strontium, and barium in blood and urine in general Chinese population].

PubMed

Ding, Chunguang; Pan, Yajuan; Zhang, Aihua; Zhu, Chun; Liu, Deye; Xu, Guang; Zheng, Yuxin; Yan, Huifang

2015-12-01

To investigate the distribution of rubidium (Rb), cesium (Cs), beryllium (Be), strontium (Sr), and barium (Ba) in blood and urine in general Chinese population. A total of 18 120 subjects aged 6~60 years were enrolled from 24 regions in 8 provinces in Eastern, Central, and Western China from 2009 to 2010 based on the method of cluster random sampling. Questionnaire survey was conducted to collect the data on living environment and health status. Blood and urine samples were collected from these subjects, and the levels of Rb, Cs, Be, Sr, and Ba in these samples were determined by inductively coupled plasma mass spectrometry. The distribution of these elements in blood and urine in male or female subjects living in different regions was analyzed statistically. In the general Chinese population, the concentration of Be in the whole blood was below the detection limit (0.06 μg/L); the geometric mean (GM) of Ba in the whole blood was below the detection limit (0.45 μg/L), with the 95th percentile (P95)of 1.37 μg/L; the GMs (95% CI)of Rb, Cs, and Sr in the whole blood were 2 374(2 357~2 392) μg/L, 2.01 (1.98~2.05) μg/L, and 23.5 (23.3~23.7) μg/L, respectively; in males and females, the GMs (95%CI)of blood Rb, Cs, and Sr were 2 506 (2 478~2 533) μg/L and 2 248 (2 227~2 270) μg/L, 1.88 (1.83~1.94) μg/L and 2.16 (2.11~2.20) μg/L, and 23.4 (23.1~23.7) μg/L and 23.6 (23.3~23.9) μg/L, respectively(P<0.01, P>0.05, and P>0.05). In the general Chinese population, the GM of urine Be was below the detection limit (0.06 μg/L), while the GMs (95%CI)of urine Rb, Cs, Sr, and Ba were 854 (836~873) μg/L, 3.65 (3.56~3.74) μg/L, 39.5 (38.4~40.6) μg/L, and 1.10 (1.07~1.12) μg/L, respectively; in males and females, the GMs (95%CI)of urine Rb, Cs, Sr, and Ba were 876 (849~904) μg/L and 832 (807~858) μg/L, 3.83 (3.70~3.96) μg/L and 3.47 (3.35~3.60) μg/L, 42.5 (40.9~44.2) μg/L and 36.6 (35.1~38.0) μg/L, and 1.15 (1.12~1.19) μg/L and 1.04 (1.01~1.07) μg/L, respectively (all P< 0.01). Correlation analyses showed that there were weak correlations between blood Rb and urine Rb (r=0.197)and between blood Sr and urine Sr (r=0.180), but a good correlation between blood Cs and urine Cs (r=0.487). The levels of Rb, Cs, Be, Sr, and Ba in the general Chinese population are similar to those reported in other countries, and there is a significant difference in the concentration of each element among the populations living in different regions, as well as significant differences in blood Rb, urine Rb, urine Cs, urine Sr, and urine Ba between males and females.

The formation of the Milky Way halo and its dwarf satellites; a NLTE-1D abundance analysis. II. Early chemical enrichment

NASA Astrophysics Data System (ADS)

Mashonkina, L.; Jablonka, P.; Sitnova, T.; Pakhomov, Yu.; North, P.

2017-12-01

We present the non-local thermodynamic equilibrium (NLTE) abundances of up to 10 chemical species in a sample of 59 very metal-poor (VMP, -4 ≤ [Fe/H] ≾-2) stars in seven dwarf spheroidal galaxies (dSphs) and in the Milky Way (MW) halo. Our results are based on high-resolution spectroscopic datasets and homogeneous and accurate atmospheric parameters determined in Paper I. We show that once the NLTE effects are properly taken into account, all massive galaxies in our sample, that is, the MW halo and the classical dSphs Sculptor, Ursa Minor, Sextans, and Fornax, reveal a similar plateau at [α/Fe] ≃ 0.3 for each of the α-process elements: Mg, Ca, and Ti. We put on a firm ground the evidence for a decline in α/Fe with increasing metallicity in the Boötes I ultra-faint dwarf galaxy (UFD), that is most probably due to the ejecta of type Ia supernovae. For Na/Fe, Na/Mg, and Al/Mg, the MW halo and all dSphs reveal indistinguishable trends with metallicity, suggesting that the processes of Na and Al synthesis are identical in all systems, independent of their mass. The dichotomy in the [Sr/Ba] versus [Ba/H] diagram is observed in the classical dSphs, similarly to the MW halo, calling for two different nucleosynthesis channels for Sr. We show that Sr in the massive galaxies is well correlated with Mg suggesting a strong link to massive stars and that its origin is essentially independent of Ba, for most of the [Ba/H] range. Our three UFDs, that is Boötes I, UMa II, and Leo IV, are depleted in Sr and Ba relative to Fe and Mg, with very similar ratios of [Sr/Mg] ≃-1.3 and [Ba/Mg] ≃-1 on the entire range of their Mg abundances. The subsolar Sr/Ba ratios of Boötes I and UMa II indicate a common r-process origin of their neutron-capture elements. Sculptor remains the classical dSph, in which the evidence for inhomogeneous mixing in the early evolution stage, at [Fe/H] <-2, is the strongest. Full Tables 3 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/608/A89

Flow-Through Leaching of Marine Barite: New Insights on its Composition and Diagenesis

NASA Astrophysics Data System (ADS)

Hsieh, C.; Torres, M. E.; Ungerer, A.; Klinkhammer, G. P.

2007-12-01

The distribution of stable mineral barite (BaSO4) in marine sediments has long been studied as a proxy for paleoproductivity. It is important to investigate the variation in Sr/Ba ratios of crystal barite, as it has a great influence on barite solubility and its early diagenetic processes. In addition, the role of alternative barium carriers to the sediments (e.g. aluminum silicates and oxyhydroxides) and their contributions to overall barium budget and burial efficiency need to be resolved. The techniques currently used to describe and quantify barium phases are all based on batch leaching techniques that define barium phases operationally, not chemically. Because during batch analyses each phase is characterized by a single-point measurement, variations due to phase heterogeneities cannot be resolved; nor can the results of these experiments be related in any systematic way to what happens in nature. To overcome this problem, we are developing a flow-through method that makes use of automated chromatographic techniques, which allows complete monitoring of the dissolution of barite samples with time-resolved analysis (TRA) as each phase is sequentially leached using different reagents. We have analyzed a barite sample recovered from seeps along the San Clemente escarpment, and show that we can attain complete dissolution of the sample (>85%) in 2 hours, using DTPA at 80°C. Approximately 100 μg of barite are first leached with distilled water (pH 5) for 30 minutes. During this step ~2% of the barite is removed. This highly soluble phase has Sr/Ba ratios that range from 30 to 120 mmol/mol. Acid leaching of the samples with 10 mM HNO3 removes an additional 4~8% of the barite, and this phase has Sr/Ba ratios ranging from 13 to 35 mmol/mol. Higher acid concentration (100 mM HNO3) dissolves up to 40% of the barite. These results are consistent with electron microprobe data that show clear oscillatory zoning of the (Ba,Sr)SO4. Unlike the barite sample, sediment samples collected at the base of the escarpment did not show a Ba release in the water leach. We might speculate that the highly susceptible Sr-rich barium phase present in the barite sample, dissolved during transport from a seep site leaving a barite with a lower Sr/Ba ratio, as found in the sediment samples. Our analytical approach has the potential to further address a variety of outstanding questions on the complex geochemical cycle of barium and its applications to climate change, upper ocean fertility and ocean circulation through time.

Strong polarization enhancement in asymmetric three-component ferroelectric superlattices

NASA Astrophysics Data System (ADS)

Lee, Ho Nyung; Christen, Hans M.; Chisholm, Matthew F.; Rouleau, Christopher M.; Lowndes, Douglas H.

2005-01-01

Theoretical predictions-motivated by recent advances in epitaxial engineering-indicate a wealth of complex behaviour arising in superlattices of perovskite-type metal oxides. These include the enhancement of polarization by strain and the possibility of asymmetric properties in three-component superlattices. Here we fabricate superlattices consisting of barium titanate (BaTiO3), strontium titanate (SrTiO3) and calcium titanate (CaTiO3) with atomic-scale control by high-pressure pulsed laser deposition on conducting, atomically flat strontium ruthenate (SrRuO3) layers. The strain in BaTiO3 layers is fully maintained as long as the BaTiO3 thickness does not exceed the combined thicknesses of the CaTiO3 and SrTiO3 layers. By preserving full strain and combining heterointerfacial couplings, we find an overall 50% enhancement of the superlattice global polarization with respect to similarly grown pure BaTiO3, despite the fact that half the layers in the superlattice are nominally non-ferroelectric. We further show that even superlattices containing only single-unit-cell layers of BaTiO3 in a paraelectric matrix remain ferroelectric. Our data reveal that the specific interface structure and local asymmetries play an unexpected role in the polarization enhancement.

Structures, phase transitions and microwave dielectric properties of the 6H perovskites Ba 3BSb 2O 9, B=Mg, Ca, Sr, Ba

NASA Astrophysics Data System (ADS)

Ling, Chris D.; Rowda, Budwy; Avdeev, Maxim; Pullar, Robert

2009-03-01

We present a complete temperature-composition phase diagram for Ba 3BSb 2O 9, B=Mg, Ca, Sr, Ba, along with their electrical behavior as a function of B. These compounds have long been recognized as 6H-type perovskites, but (with the exception of B=Mg) their exact structures and properties were unknown due to their low symmetries, temperature-dependent phase transitions, and difficulties in synthesizing pure samples. The full range of possible space group symmetries is observed, from ideal hexagonal P6 3/ mmc to monoclinic C2/ c to triclinic P1¯. Direct second-order transitions between these phases are plausible according to group theory, and no evidence was seen for any further intermediate phases. The phase diagram with respect to temperature and the effective ionic radius of B is remarkably symmetrical for B=Mg, Ca, and Sr. For B=Ba, a first-order phase transition to a locally distorted phase allows a metastable hexagonal phase to persist to lower temperatures than expected before decomposing around 600 K. Electrical measurements revealed that dielectric permittivity corrected for porosity does not change significantly as a function of B and is in a good agreement with the values predicted by the Clausius-Mossotti equation.

Baseline element concentrations in soils and plants, Wattenmeer National Park, North and East Frisian Islands, Federal Republic of Germany

USGS Publications Warehouse

Severson, R.C.; Gough, L.P.; van den Boom, G.

1992-01-01

Baseline element concentrations are given for dune grass (Ammophilia arenaria), willow (Salix repens), moss (Hylocomium splendens) and associated surface soils. Baseline and variability data for pH, ash, Al, As, Ba, C, Ca, Cd, Ce, Co, Cr, Cu, Fe, Hg, K, La, Li, Mg, Mn, Na, Nb, Nd, Ni, P, Pb, S, Sc, Se, Sr, Th, Ti, V, Y, Yb, and Zn are reported; however, not all variables are reported for all media because, in some media, certain elements were below the analytical detection limit. Spatial variation in element concentration between five Frisian Islands are given for each of the sample media. In general, only a few elements in each media showed statistically significant differences between the islands sampled. The measured concentrations in all sample media exhibited ranges that cannot be attributed to anthropogenic additions of trace elements, with the possible exception of Hg and Pb in surface soils.Baseline element concentrations are given for dune grass (Ammophilia arenaria), willow (Salix repens), moss (Hylocomium splendens) and associated surface soils. Baseline and variability data for pH, ash, Al, As, Ba, C, Ca, Cd, Ce, Co, Cr, Cu, Fe, Hg, K, La, Li, Mg, Mn, Na, Nb, Nd, Ni, P, Pb, S, Sc, Se, Sr, Th, Ti, V, Y, Yb, and Zn are reported; however, not all variables are reported for all media because, in some media, certain elements were below the analytical detection limit. Spatial variation in element concentration between five Frisian Islands are given for each of the sample media. In general, only a few elements in each media showed statistically significant differences between the islands sampled. The measured concentrations in all sample media exhibited ranges that cannot be attributed to anthropogenic additions of trace elements, with the possible exception of Hg and Pb in surface soils.

Reference levels of trace elements in hair samples from children and adolescents in Madrid, Spain.

PubMed

Llorente Ballesteros, María Teresa; Navarro Serrano, Irene; Izquierdo Álvarez, Silvia

2017-09-01

Hair samples are used as a tool to evaluate environmental exposure to contaminants and metabolic status in the individual. However, the use of human hair is controversial, mainly because of the lack of well-defined reference levels. In the case of Spain, very few biomonitoring studies have investigated these issues in infants, children or adolescents. To establish reference levels for trace elements in children and teenagers in Madrid, Spain. Inductively coupled plasma mass spectrometry (ICP-MS) was used to measure Al, As, Ag, Ba, Bi, Cd, Cr, Co, Cu, Fe, Mn, Mo, Ni, Pb, Se, Sr, Tl and Zn levels in hair samples from 648 healthy children and adolescents (253 boys and 395 girls) between April 2008 and December 2009. Median levels were as follows: Al 18.5μg/g, As 0.07μg/g, Ag 196ng/g, Ba 0.5μg/g, Bi 0.01μg/g, Cd 18.3ng/g, Cr 0.4μg/g, Co 14.5ng/g, Cu 25.7μg/g, Fe 15.5μg/g, Mn 328ng/g, Mo 0.04μg/g, Ni 0.5μg/g, Pb 0.70μg/g, Se 0.5μg/g, Sr 1.29μg/g, Tl 0.28ng/g and Zn 121μg/g. The values of trace elements here described could be considered as possible reference ranges for hair samples from children and adolescents aged 0-18 years living in the Madrid region (central Spain). These values could also be selected as a preliminary screening tool to assess exposure sources and to generate information needed to develop prevention strategies and likewise could be a complement to other diagnostic procedures. Copyright © 2016 Elsevier GmbH. All rights reserved.

[Distribution Characteristics and Source Analysis of Dustfall Trace Elements During Winter in Beijing].

PubMed

Xiong, Qiu-lin; Zhao, Wen-ji; Guo, Xiao-yu; Chen, Fan-tao; Shu, Tong-tong; Zheng, Xiao-xia; Zhao, Wen-hui

2015-08-01

The dustfall content is one of the evaluation indexes of atmospheric pollution. Trace elements especially heavy metals in dustfall can lead to risks to ecological environment and human health. In order to study the distribution characteristics of trace elements, heavy metals pollution and their sources in winter atmospheric dust, 49 dustfall samples were collected in Beijing City and nearby during November 2013 to March 2014. Then the contents (mass percentages) of 40 trace elements were measured by Elan DRC It type inductively coupled plasma mass (ICP-MS). Test results showed that more than half of the trace elements in the dust were less than 10 mg x kg(-1); about a quarter were between 10-100 mg x kg-1); while 7 elements (Pb, Zr, Cr, Cu, Zn, Sr and Ba) were more than 100 mg x kg(-1). The contents of Pb, Cu, Zn, Bi, Cd and Mo of winter dustfall in Beijing city.were respectively 4.18, 4.66, 5.35, 6.31, 6.62, and 8.62 times as high as those of corresponding elements in the surface soil in the same period, which went beyond the soil background values by more than 300% . The contribution of human activities to dustfall trace heavy metals content in Beijing city was larger than that in the surrounding region. Then sources analysis of dustfall and its 20 main trace elements (Cd, Mo, Nb, Ga, Co, Y, Nd, Li, La, Ni, Rb, V, Ce, Pb, Zr, Cr, Cu, Zn, Sr, Ba) was conducted through a multi-method analysis, including Pearson correlation analysis, Kendall correlation coefficient analysis and principal component analysis. Research results indicated that sources of winter dustfall in Beijing city were mainly composed of the earth's crust sources (including road dust, construction dust and remote transmission of dust) and the burning of fossil fuels (vehicle emissions, coal combustion, biomass combustion and industrial processes).

Slurry micro-sampling technique for use in argon-helium microwave induced plasma optical emission spectrometry.

PubMed

Ślachciński, Mariusz

2016-12-01

The Flow Focusing Pneumatic Nebulizer (FFPN) working at low liquid flow rates was evaluated for the elemental analysis in slurried samples by argon-helium microwave induced plasma optical emission spectrometry (MIP-OES). The obtained results achieved were compared with commercially available V-groove Babington type nebulizer (VBPN). A univariate approach and the simplex optimization procedure were used to achieve optimized conditions and derive analytical figures of merit. Analytical performance of the micro nebulization system was characterized by a determination of the limits of detection (LODs), the precision (RSDs) and the wash-out times for Ba, Ca, Cd, Cu, Fe, Mg, Mn, Pb and Sr. The experimental concentration detection limits for simultaneous determination, calculated as the concentration giving a signal equal to three times of the standard deviation of the blank (LOD, 3σ blank criterion, peak height) were 0.9, 0.2, 0.3, 0.2, 0.3, 0.1, 0.2, 0.4, 0.4 and 0.3ngmL -1 for Ba, Ca, Cd, Cu, Fe, Mg, Mn, Pb and Sr, respectively. The method offers relatively good precision (RSD ranged from 5% to 8%) for micro-slurry sampling analysis. Analyses of the certified reference materials (NRCC DOLT-2, GBW 07302 and SRM 2710) were performed in order to determine the accuracy available with the presented nebulization systems. The measured contents of elements in the reference materials were in satisfactory agreement with the certified values. In addition, these elements were determined in two real samples. Slurry concentration up to 3% m/v (particles <20μm), prepared in 10% m/v HCl through the application of ultrasonic agitation, was used with calibration by the standard addition technique. An ultrasonic probe was used to homogenize the slurry in the polypropylene bottle just before its introduction into the nebulizer. The nebulizers exhibited no clogging problems. Copyright © 2016 Elsevier B.V. All rights reserved.

Chemical partitioning of fine particle-bound metals on haze-fog and non-haze-fog days in Nanjing, China and its contribution to human health risks

NASA Astrophysics Data System (ADS)

Li, Huiming; Wu, Hongfei; Wang, Qin'geng; Yang, Meng; Li, Fengying; Sun, Yixuan; Qian, Xin; Wang, Jinhua; Wang, Cheng

2017-01-01

Information on chemical partitioning and associated risk of airborne metals, particularly during a haze-fog episode, is limited. Fine particulate matter (PM2.5) was collected during a severe haze-fog event in winter and non-haze-fog periods in summer and fall from an urban region of a typical Chinese mega-city, Nanjing. The particulate-bound metals (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, Pb, Sr, Ti, V, and Zn) were chemically fractionated in a four-step sequential extraction procedure and human health risk was assessed. During the haze-fog episode, PM2.5 was extremely elevated with a mean concentration of 281 μg/m3 (range: 77-431 μg/m3), whereas the mean PM2.5 concentrations in summer and fall periods were 86 μg/m3 (range: 66-111 μg/m3) and 77 μg/m3 (range: 42-131 μg/m3), respectively. All elements had significantly higher concentrations and many metals exceeded relevant limits on haze-fog days. K, Na, Sr, Zn, Mo, Ca, Cd, Mg, Mn, Cu, Ba, Cr and As all showed relatively high proportions of the soluble and exchangeable fraction and strong bio-accessible potential. High temperature and humidity may increase the bio-accessible fraction of many airborne metals. The hazard index for potential toxic metals was 0.115, which was lower than the safe limit (1). However, the combined carcinogenic risk was 1.32 × 10- 6 for children and 5.29 × 10- 6 for adults, with both values being higher than the precautionary criterion (10- 6). Results of this study provide information for the behavior and risk mitigation of airborne metals.

Membranes for separation of carbon dioxide

DOEpatents

Ku, Anthony Yu-Chung [Rexford, NY; Ruud, James Anthony [Delmar, NY; Ramaswamy, Vidya [Niskayuna, NY; Willson, Patrick Daniel [Latham, NY; Gao, Yan [Niskayuna, NY

2011-03-01

Methods for separating carbon dioxide from a fluid stream at a temperature higher than about 200.degree. C. with selectivity higher than Knudsen diffusion selectivity include contacting a porous membrane with the fluid stream to preferentially transport carbon dioxide. The porous membrane includes a porous support and a continuous porous separation layer disposed on a surface of the porous support and extending between the fluid stream and the porous support layer. The porous support comprises alumina, silica, zirconia, stabilized zirconia, stainless steel, titanium, nickel-based alloys, aluminum-based alloys, zirconium-based alloys or a combination thereof. Median pore size of the porous separation layer is less than about 10 nm, and the porous separation layer comprises titania, MgO, CaO, SrO, BaO, La.sub.2O.sub.3, CeO.sub.2, HfO.sub.2, Y.sub.2O.sub.3, VO.sub.z, NbO.sub.z, TaO.sub.z, ATiO.sub.3, AZrO.sub.3, AAl.sub.2O.sub.4, A.sup.1FeO.sub.3, A.sup.1MnO.sub.3, A.sup.1CoO.sub.3, A.sup.1NiO.sub.3, A.sup.2HfO.sub.3, A.sup.3 CeO.sub.3, Li.sub.2ZrO.sub.3, Li.sub.2SiO.sub.3, Li.sub.2TiO.sub.3, Li.sub.2HfO.sub.3, A.sup.4N.sup.1.sub.yO.sub.z, Y.sub.xN.sup.1.sub.yO.sub.z, La.sub.xN.sup.1.sub.yO.sub.z, HfN.sup.2.sub.yO.sub.z, or a combination thereof; wherein A is La, Mg, Ca, Sr or Ba; A.sup.1 is La, Ca, Sr or Ba; A.sup.2 is Ca, Sr or Ba; A.sup.3 is Sr or Ba; A.sup.4 is Mg, Ca, Sr, Ba, Ti or Zr; N.sup.1 is V, Nb, Ta, Cr, Mo, W, Mn, Si or Ge; N.sup.2 is V, Mo, W or Si; x is 1 or 2; y ranges from 1 to 3; and z ranges from 2 to 7.

Heterobimetallic Complexes with MIII-(μ-OH)-MII Cores (MIII = Fe, Mn, Ga; MII = Ca, Sr, and Ba): Structural, Kinetic, and Redox Properties

PubMed Central

Park, Young Jun; Cook, Sarah A.; Sickerman, Nathaniel S.; Sano, Yohei; Ziller, Joseph W.

2013-01-01

The effects of redox-inactive metal ions on dioxygen activation were explored using a new FeII complex containing a tripodal ligand with 3 sulfonamido groups. This iron complex exhibited a faster initial rate for the reduction of O2 than its MnII analog. Increases in initial rates were also observed in the presence of group 2 metal ions for both the FeII and MnII complexes, which followed the trend NMe4+ < BaII < CaII = SrII. These studies led to the isolation of heterobimetallic complexes containing FeIII-(μ-OH)-MII cores (MII = Ca, Sr, and Ba) and one with a [SrII(OH)MnIII]+ motif. The analogous [CaII(OH)GaIII]+ complex was also prepared and its solid state molecular structure is nearly identical to that of the [CaII(OH)FeIII]+ system. Nuclear magnetic resonance studies indicated that the diamagnetic [CaII(OH)GaIII]+ complex retained its structure in solution. Electrochemical measurements on the heterobimetallic systems revealed similar one-electron reduction potentials for the [CaII(OH)FeIII]+ and [SrII(OH)FeIII]+ complexes, which were more positive than the potential observed for [BaII(OH)FeIII]+. Similar results were obtained for the heterobimetallic MnII complexes. These findings suggest that Lewis acidity is not the only factor to consider when evaluating the effects of group 2 ions on redox processes, including those within the oxygen-evolving complex of Photosystem II. PMID:24058726

Heterobimetallic Complexes with MIII-(μ-OH)-MII Cores (MIII = Fe, Mn, Ga; MII = Ca, Sr, and Ba): Structural, Kinetic, and Redox Properties.

PubMed

Park, Young Jun; Cook, Sarah A; Sickerman, Nathaniel S; Sano, Yohei; Ziller, Joseph W; Borovik, A S

2013-02-01

The effects of redox-inactive metal ions on dioxygen activation were explored using a new Fe II complex containing a tripodal ligand with 3 sulfonamido groups. This iron complex exhibited a faster initial rate for the reduction of O 2 than its Mn II analog. Increases in initial rates were also observed in the presence of group 2 metal ions for both the Fe II and Mn II complexes, which followed the trend NMe 4 + < Ba II < Ca II = Sr II . These studies led to the isolation of heterobimetallic complexes containing Fe III -( μ -OH)-M II cores (M II = Ca, Sr, and Ba) and one with a [Sr II (OH)Mn III ] + motif. The analogous [Ca II (OH)Ga III ] + complex was also prepared and its solid state molecular structure is nearly identical to that of the [Ca II (OH)Fe III ] + system. Nuclear magnetic resonance studies indicated that the diamagnetic [Ca II (OH)Ga III ] + complex retained its structure in solution. Electrochemical measurements on the heterobimetallic systems revealed similar one-electron reduction potentials for the [Ca II (OH)Fe III ] + and [Sr II (OH)Fe III ] + complexes, which were more positive than the potential observed for [Ba II (OH)Fe III ] + . Similar results were obtained for the heterobimetallic Mn II complexes. These findings suggest that Lewis acidity is not the only factor to consider when evaluating the effects of group 2 ions on redox processes, including those within the oxygen-evolving complex of Photosystem II.

Plasmons in cuprate superconductors

NASA Astrophysics Data System (ADS)

Bozovic, Ivan

1990-08-01

The customary way of determining the complex dielectric constant from the measured reflectance spectra suffers from large uncertainties because of the extrapolations required for the Kramers-Kronig transformation. To avoid these, a method is introduced in which reflectance and ellipsometric data on single crystals and epitaxial films are combined. Utilizing this approach, the spectral functions of YBa2Cu3O7 (Y-Ba-Cu-O) and Bi2Sr2CaCu2O8 (Bi-Sr-Ca-Cu-O) are determined with substantially improved accuracy. This enables the unambiguous identification of optic plasmons at 1.4 eV in Y-Ba-Cu-O and at 1.1 eV in Bi-Sr-Ca-Cu-O. No other low-lying optic plasmons are detected, which likely rules out most plasmon-mediated superconductivity models. Next, the bare plasma frequency is found to be ħωp=3.2+/-0.3 eV in Y-Ba-Cu-O and ħωp=2.4+/-0.3 eV in Bi-Sr-Ca-Cu-O. These values support ascribing the strong infrared absorption to charge carriers which, however, are not free-electron-like, but rather show characteristic polaronic behavior. Finally, in both Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O, it is found that Im(-1/ɛ)=βω2 for small ω, and this law is conjectured to be universal for all layered cuprate superconductors. It is again not Drude-like; it may be compatible with the layered electron-gas model. The latter implies existence of a broad band of acoustic plasmon branches.

Composition-control of magnetron-sputter-deposited (BaxSr1-x)Ti1+yO3+z thin films for voltage tunable devices

NASA Astrophysics Data System (ADS)

Im, Jaemo; Auciello, O.; Baumann, P. K.; Streiffer, S. K.; Kaufman, D. Y.; Krauss, A. R.

2000-01-01

Precise control of composition and microstructure is critical for the production of (BaxSr1-x)Ti1+yO3+z (BST) dielectric thin films with the large dependence of permittivity on electric field, low losses, and high electrical breakdown fields that are required for successful integration of BST into tunable high-frequency devices. Here, we present results on composition-microstructure-electrical property relationships for polycrystalline BST films produced by magnetron-sputter deposition, that are appropriate for microwave and millimeter-wave applications such as varactors and frequency triplers. Films with controlled compositions were grown from a stoichiometric Ba0.5Sr0.5TiO3 target by control of the background processing gas pressure. It was determined that the (Ba+Sr)/Ti ratios of these BST films could be adjusted from 0.73 to 0.98 by changing the total (Ar+O2) process pressure, while the O2/Ar ratio did not strongly affect the metal ion composition. Film crystalline structure and dielectric properties as a function of the (Ba+Sr)/Ti ratio are discussed. Optimized BST films yielded capacitors with low dielectric losses (0.0047), among the best reported for sputtered BST, while still maintaining tunabilities suitable for device applications.

Influences of alkaline earth metal substitution on the crystal structure and physical properties of magnetic RuSr1.9A0.1GdCu2O8 (A = Ca, Sr, and Ba) superconductors.

PubMed

Hur, Su Gil; Park, Dae Hoon; Hwang, Seong-Ju; Kim, Seung Joo; Lee, J H; Lee, Sang Young

2005-11-24

We have investigated the effect of alkaline earth metal substitution on the crystal structure and physical properties of magnetic superconductors RuSr(1.9)A(0.1)GdCu(2)O(8) (A = Ca, Sr, and Ba) in order to probe an interaction between the magnetic coupling of the RuO(2) layer and the superconductivity of the CuO(2) layer. X-ray diffraction and X-ray absorption spectroscopic analyses demonstrate that the isovalent substitution of Sr ions with Ca or Ba ions makes it possible to tune the interlayer distance between the CuO(2) and the RuO(2) layers. From the measurements of electrical resistance and magnetic susceptibility, it was found that, in contrast to negligible change of magnetization, both of the alkaline earth metal substitutions lead to a notable depression of zero-resistance temperature T(c) (DeltaT(c) approximately 17-19 K). On the basis of the absence of a systematic correlation between the T(c) and the interlayer distance/magnetization, we have concluded that the internal magnetic field of the RuO(2) layer has insignificant influence on the superconducting property of the CuO(2) layer in the ruthenocuprate.

AC conductivity studies of La doped Ba0.5Sr0.5TiO3

NASA Astrophysics Data System (ADS)

D'Souza, Slavia Deeksha; Rohith, Kotla Surya; Bhatnagar, Anil K.; Kumar, A. Sendil

2017-05-01

Ferroelectric material with high dielectric constant of Ba0.5Sr0.5TiO3 is synthesized through Solid State Reaction and fraction of Lanthanum is substituted to introduce hole concentration. XRay Diffraction shows all the samples are stabilized in cubic crystal structure. With La doped samples the Cole-Cole plot is modified and AC conductivity increases at higher temperatures as well as higher frequencies compared to undoped sample.

Theoretical Studies of the Spin Hamiltonian Parameters and Local Distortions for Cu2+ in Alkaline Earth Lead Zinc Phosphate Glasses

NASA Astrophysics Data System (ADS)

Wang, Bo-Kun; Wu, Shao-Yi; Yuan, Zi-Yi; Liu, Zi-Xuan; Jiang, Shi-Xin; Liu, Zheng; Yao, Zi-Jian; Teng, Bao-Hua; Wu, Ming-He

2016-08-01

The spin Hamiltonian parameters and local structures are theoretically studied for Cu2+-doped alkaline earth lead zinc phosphate (RPPZ, R=Mg, Ca, Sr, and Ba) glasses based on the high-order perturbation calculations for a tetragonally elongated octahedral 3d9 cluster. The relative elongation ratios are found to be ρ≈3.2%, 4.4%, 4.6%, and 3.3% for R=Mg, Ca, Sr, and Ba, respectively, because of the Jahn-Teller effect. The whole decreasing crystal-field strength Dq and orbital reduction factor k from Mg to Sr are ascribed to the weakening electrostatic coulombic interactions and the increasing probability of productivity of nonbridge oxygen (and hence increasing Cu2+-O2- electron cloud admixtures) under PbO addition, respectively, with increasing alkali earth ionic radius. The anomalies (the largest Dq and the next highest k among the systems) for R=Ba are attributed to the cross linkage of this large cation in the network. The overall increasing order (Mg≤Ba

Study on Dy0.45Ba0.05Sr0.5Co0.8Fe0.2O3-δ-Ce0.85Gd0.15O1.95 composite cathode material for intermediate temperature solid oxide fuel cell

NASA Astrophysics Data System (ADS)

Kautkar, Pranay R.; Acharya, Smita A.

2018-05-01

xDy0.45Ba0.05Sr0.5Co0.8Fe0.2O3-δ - xCe0.85Gd0.15O1.95 (x = 50 %) composite cathode supported on Ce0.85Gd0.15O1.95 (GDC15) electrolyte are studied for applications in IT-SOFCs. Results attribute that Dy0.45Ba0.05Sr0.5Co0.8Fe0.2O3-δ material is chemically compatible with Ce0.85Gd0.15O1.95 (GDC15). Rietveld refined X-ray diffraction patterns notify orthorhombic (space group:Pbnm) symmetry for Dy0.45 Ba0.05Sr0.5Co0.8Fe0.2O3-δ and fluorite type structure (space group: Fm-3m) symmetry for GDC15. The polarization resistance (Rp) of composite cathode reduces to the minimum value of 1.35 Ω cm2 at 650 °C in air. Area specific resistance (ASR) of composite cathode has found 0.67 Ω.cm2 at 650°C respectively. Result shows that the surface diffusion of the dissociative adsorbed oxygen at electrode/electrolyte interface on the composite cathode.

The Electronic Structures and Optical Properties of Alkaline-Earth Metals Doped Anatase TiO2: A Comparative Study of Screened Hybrid Functional and Generalized Gradient Approximation

PubMed Central

Ma, Jin-Gang; Zhang, Cai-Rong; Gong, Ji-Jun; Wu, You-Zhi; Kou, Sheng-Zhong; Yang, Hua; Chen, Yu-Hong; Liu, Zi-Jiang; Chen, Hong-Shan

2015-01-01

Alkaline-earth metallic dopant can improve the performance of anatase TiO2 in photocatalysis and solar cells. Aiming to understand doping mechanisms, the dopant formation energies, electronic structures, and optical properties for Be, Mg, Ca, Sr, and Ba doped anatase TiO2 are investigated by using density functional theory calculations with the HSE06 and PBE functionals. By combining our results with those of previous studies, the HSE06 functional provides a better description of electronic structures. The calculated formation energies indicate that the substitution of a lattice Ti with an AEM atom is energetically favorable under O-rich growth conditions. The electronic structures suggest that, AEM dopants shift the valence bands (VBs) to higher energy, and the dopant-state energies for the cases of Ca, Sr, and Ba are quite higher than Fermi levels, while the Be and Mg dopants result into the spin polarized gap states near the top of VBs. The components of VBs and dopant-states support that the AEM dopants are active in inter-band transitions with lower energy excitations. As to optical properties, Ca/Sr/Ba are more effective than Be/Mg to enhance absorbance in visible region, but the Be/Mg are superior to Ca/Sr/Ba for the absorbance improvement in near-IR region. PMID:28793520

The Electronic Structures and Optical Properties of Alkaline-Earth Metals Doped Anatase TiO2: A Comparative Study of Screened Hybrid Functional and Generalized Gradient Approximation.

PubMed

Ma, Jin-Gang; Zhang, Cai-Rong; Gong, Ji-Jun; Wu, You-Zhi; Kou, Sheng-Zhong; Yang, Hua; Chen, Yu-Hong; Liu, Zi-Jiang; Chen, Hong-Shan

2015-08-24

Alkaline-earth metallic dopant can improve the performance of anatase TiO2 in photocatalysis and solar cells. Aiming to understand doping mechanisms, the dopant formation energies, electronic structures, and optical properties for Be, Mg, Ca, Sr, and Ba doped anatase TiO2 are investigated by using density functional theory calculations with the HSE06 and PBE functionals. By combining our results with those of previous studies, the HSE06 functional provides a better description of electronic structures. The calculated formation energies indicate that the substitution of a lattice Ti with an AEM atom is energetically favorable under O-rich growth conditions. The electronic structures suggest that, AEM dopants shift the valence bands (VBs) to higher energy, and the dopant-state energies for the cases of Ca, Sr, and Ba are quite higher than Fermi levels, while the Be and Mg dopants result into the spin polarized gap states near the top of VBs. The components of VBs and dopant-states support that the AEM dopants are active in inter-band transitions with lower energy excitations. As to optical properties, Ca/Sr/Ba are more effective than Be/Mg to enhance absorbance in visible region, but the Be/Mg are superior to Ca/Sr/Ba for the absorbance improvement in near-IR region.

Trace elements in farmed fish (Cyprinus carpio, Ctenopharyngodon idella and Oncorhynchus mykiss) from Beijing: implication from feed.

PubMed

Jiang, Haifeng; Qin, Dongli; Mou, Zhenbo; Zhao, Jiwei; Tang, Shizhan; Wu, Song; Gao, Lei

2016-06-01

Concentrations of 30 trace elements, Li, V, Cr, Mn, Fe, Ni, Cu, Mo, Zn, Se, Sr, Co, Al, Ti, As, Cs, Sc, Te, Ba, Ga, Pb, Sn, Cd, Sb, Ag, Tm, TI, Be, Hg and U in major cultured freshwater fish species (common carp-Cyprinus carpio, grass carp-Ctenopharyngodon idella and rainbow trout-Oncorhynchus mykiss) with the corresponding feed from 23 fish farms in Beijing, China, were investigated. The results revealed that Fe, Zn, Cu, Mn, Sr, Se were the major accumulated essential elements and Al, Ti were the major accumulated non-essential elements, while Mo, Co, Ga, Sn, Cd, Sb, Ag, Tm, U, TI, Be, Te, Pb and Hg were hardly detectable. Contents of investigated trace elements were close to or much lower than those in fish from other areas in China. Correlation analysis suggested that the elemental concentrations in those fish species were relatively constant and did not vary much with the fish feed. In comparison with the limits for aquafeeds and fish established by Chinese legislation, Cd in 37.5% of rainbow trout feeds and As in 20% of rainbow trout samples exceeded the maximum limit, assuming that inorganic As accounts for 10% of total As. Further health risk assessment showed that fish consumption would not pose risks to consumers as far as non-essential element contaminants are concerned. However, the carcinogenic risk of As in rainbow trout for the inhabitants in Beijing exceeded the acceptable level of 10(-)(4), to which more attention should be paid.

Raman spectroscopy of DNA-metal complexes. I. Interactions and conformational effects of the divalent cations: Mg, Ca, Sr, Ba, Mn, Co, Ni, Cu, Pd, and Cd.

PubMed

Duguid, J; Bloomfield, V A; Benevides, J; Thomas, G J

1993-11-01

Interactions of divalent metal cations (Mg2+, Ca2+, Ba2+, Sr2+, Mn2+, Co2+, Ni2+, Cu2+, Pd2+, and Cd2+) with DNA have been investigated by laser Raman spectroscopy. Both genomic calf-thymus DNA (> 23 kilobase pairs) and mononucleosomal fragments (160 base pairs) were employed as targets of metal interaction in solutions containing 5 weight-% DNA and metal:phosphate molar ratios of 0.6:1. Raman difference spectra reveal that transition metal cations (Mn2+, Co2+, Ni2+, Cu2+, Pd2+, and Cd2+) induce the greatest structural changes in B-DNA. The Raman (vibrational) band differences are extensive and indicate partial disordering of the B-form backbone, reduction in base stacking, reduction in base pairing, and specific metal interaction with acceptor sites on the purine (N7) and pyrimidine (N3) rings. Many of the observed spectral changes parallel those accompanying thermal denaturation of B-DNA and suggest that the metals link the bases of denatured DNA. While exocyclic carbonyls of dT, dG, and dC may stabilize metal ligation, correlation plots show that perturbations of the carbonyls are mainly a consequence of metal-induced denaturation of the double helix. Transition metal interactions with the DNA phosphates are weak in comparison to interactions with the bases, except in the case of Cu2+, which strongly perturbs both base and phosphate group vibrations. On the other hand, the Raman signature of B-DNA is largely unperturbed by Mg2+, Ca2+, Sr2+, and Ba2+, suggesting much weaker interactions of the alkaline earth metals with both base and phosphate sites. A notable exception is a moderate perturbation by alkaline earths of purine N7 sites in 160-base pair DNA, with Ca2+ causing the greatest effect. Correlation plots demonstrate a strong interrelationship between perturbations of Raman bands assigned to ring vibrations of the bases and those of bands assigned to exocyclic carbonyls and backbone phosphodiester groups. However, strong correlations do not occur between the Raman phosphodioxy band (centered near 1092 cm-1) and other Raman bands, suggesting that the former is not highly sensitive to the structural changes induced by divalent metal cations. The structural perturbations induced by divalent cations are much greater for > 23-kilobase pair DNA than for 160-base pair DNA, as evidenced by both the Raman difference spectra and the tendency toward the formation of insoluble aggregates. In the presence of transition metals, aggregation of high-molecular-weight DNA is evident at temperatures as low as 11 degrees C. A relationship between DNA melting and aggregation is proposed in which initial metal binding at major groove sites locally destabilizes the B-DNA double helix, causing displacement of the bases away from one another and exposing additional metal binding sites. Metal cation linkage of two displaced bases would allow separate DNA strands to crosslink. Aggregation is proposed to result from the formation of an extended network of these crosslinks.

A Compilation of Metals and Trace Elements Extracted from Materials Relevant to Pharmaceutical Applications such as Packaging Systems and Devices.

PubMed

Jenke, Dennis; Rivera, Christine; Mortensen, Tammy; Amin, Parul; Chacko, Molly; Tran, Thang; Chum, James

2013-01-01

Nearly 100 individual test articles, representative of materials used in pharmaceutical applications such as packaging and devices, were extracted under exaggerated conditions and the levels of 32 metals and trace elements (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ge, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, V, Zn, and Zr) were measured in the extracts. The extracting solvents included aqueous mixtures at low and high pH and an organic solvent mixture (40/60 ethanol water). The sealed vessel extractions were performed by placing an appropriate portion of the test articles and an appropriate volume of extracting solution in inert extraction vessels and exposing the extraction units (and associated extraction blanks) to defined conditions of temperature and duration. The levels of extracted target elements were measured by inductively coupled plasma atomic emission spectroscopy. The overall reporting threshold for most of the targeted elements was 0.05 μg/mL, which corresponds to 0.5 μg/g for the most commonly utilized extraction stoichiometry (1 g of material per 10 mL of extracting solvent). The targeted elements could be classified into four major groups depending on the frequency with which they were present in the over 250 extractions reported in this study. Thirteen elements (Ag, As, Be, Cd, Co, Ge, Li, Mo, Ni, Sn, Ti, V, and Zr) were not extracted in reportable quantities from any of the test articles under any of the extraction conditions. Eight additional elements (Bi, Cr, Cu, Mn, Pb, Sb, Se, and Sr) were rarely extracted from the test articles at reportable levels, and three other elements (Ba, Fe, and P) were infrequently extracted from the test articles at reportable levels. The remaining eight elements (Al, B, Ca, Mg, Na, S, Si, and Zn) were more frequently present in the extracts in reportable quantities. These general trends in accumulation behavior were compared to compiled lists of elements of concern as impurities in pharmaceutical products. Nearly 100 individual test articles, representative of materials used in pharmaceutical applications such as packaging and devices, were extracted under exaggerated conditions, and the levels of thirty-two metals and trace elements (Ag, Al, As, B, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ge, Li, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Se, Si, Sn, Sr, Ti, V, Zn, and Zr) were measured in the extracts. The targeted elements could be classified into four major groups depending on the frequency with which they were present in the extractions reported in this study: those elements that were not extracted in reportable quantities from any of the test articles under any of the extraction conditions, those elements that were rarely extracted from the test articles at reportable levels, those elements that were infrequently extracted from the test articles at reportable levels, and those elements that were more frequently present in the extracts in reportable quantities.

High mobility La-doped BaSnO3 on non-perovskite MgO substrate

NASA Astrophysics Data System (ADS)

Kim, Youjung; Shin, Juyeon; Kim, Young Mo; Char, Kookrin

(Ba,La)SnO3 is a transparent perovskite oxide with high electron mobility and excellent oxygen stability. Field effect device with (Ba,La)SnO3 channel was reported to show good output characteristics on STO substrate. Here, we fabricated (Ba,La)SnO3\\ films and field effect devices with (Ba,La)SnO3 channel on non-perovskite MgO substrates, which are available in large size wafers. X-ray diffraction and transmission electron microscope (TEM) images of (Ba,La)SnO3\\ films on MgO substrates show that the films are epitaxial with many threading dislocations. (Ba,La)SnO3 exhibits the high mobility with 97.2 cm2/Vs at 2 % La doping on top of 150 nm thick BaSnO3 buffer layer. Excellent carrier modulation was observed in field effect devices. FET performances on MgO substrates are slightly better than those on SrTiO3 substrates in spite of the higher dislocation density on MgO than on SrTiO3 substrates. These high mobility BaSnO3 thin films and transistors on MgO substrates will accelerate development for applications in high temperature and high power electronics. Samsung Science and Technology Foundation.

Synthesis and characterisation of the n = 2 Ruddlesden–Popper phases Ln{sub 2}Sr(Ba)Fe{sub 2}O{sub 7} (Ln = La, Nd, Eu)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gurusinghe, Nicola N.M.; Figuera, Juand de la; Marco, José F.

2013-09-01

Graphical abstract: - Highlights: • Some Ruddlesden–Popper phases have been characterised. • Substitution on the A site influences cationic order. • The magnetic moment redirects with temperature - Abstract: A series of n = 2 Ruddlesden–Popper phases A{sub 2}B{sub 2}O{sub 7} of composition Ln{sub 2}Sr(Ba)Fe{sub 2}O{sub 7} (Ln = La, Nd, Eu) have been prepared. La{sub 2}SrFe{sub 2}O{sub 7} and La{sub 2}BaFe{sub 2}O{sub 7} crystallise in the tetragonal space group I4/mmm. The structures of Eu{sub 2}SrFe{sub 2}O{sub 7} and Nd{sub 2}SrFe{sub 2}O{sub 7} are best described in space group P4{sub 2}/mnm. Substitution on the A site with smaller lanthanide- andmore » larger alkaline metal- ions leads to enhanced cationic order in these phases and reflects increasing differences in cationic radii. All the compounds are antiferromagnetically ordered between 298 and 2 K. In La{sub 2}SrFe{sub 2}O{sub 7} the magnetic moment lies along [1 1 0] at all temperatures between 298 and 2 K whereas in La{sub 2}BaFe{sub 2}O{sub 7} the magnetic moment at 298 K lies along the crystallographic x-axis but redirects from the [1 0 0] to the [1 1 0] direction between 210 and 190 K and is retained in this direction until 2 K. In Nd{sub 2}SrFe{sub 2}O{sub 7} the magnetic moment at 298 K lies along [1 1 0] but rotates from [1 1 0] to [0 0 1] between 17 and 9 K. A series of {sup 57}Fe Mössbauer spectra recorded from La{sub 2}SrFe{sub 2}O{sub 7} between 290 and 600 K indicate a magnetic ordering temperature of T{sub N} ≥ 535 K.« less

Structural and electronic properties of Sr{sub x}Ba{sub 1-x}SnO{sub 3} from first principles calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moreira, E.; Henriques, J.M.; Azevedo, D.L.

2012-03-15

Neutron diffraction data for Sr{sub x}Ba{sub 1-x}SnO{sub 3} (x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) solid solutions were used as inputs to obtain optimized geometries and electronic properties using the density functional theory (DFT) formalism considering both the local density and generalized gradient approximations, LDA and GGA, respectively. The crystal structures and SnO{sub 6} octahedra tilting angles found after total energy minimization agree well with experiment, specially for the GGA data. Elastic constants were also obtained and compared with theoretical and experimental results for cubic BaSnO{sub 3}. While the alloys with cubic unit cell have an indirect band gap, tetragonalmore » and orthorhombic alloys exhibit direct band gaps (exception made to x=1.0). The Kohn-Sham minimum electronic band gap oscillates from 1.52 eV (cubic x=0.0, LDA) to 2.61 eV (orthorhombic x=1.0, LDA), and from 0.74 eV (cubic BaSnO{sub 3}, GGA) to 1.97 eV (orthorhombic SrSnO{sub 3}, GGA). Parabolic interpolation of bands has allowed us to estimate the effective masses for charge carriers, which are shown to be anisotropic and larger for holes. - Graphical Abstract: Highlights: Black-Right-Pointing-Pointer DFT calculations were performed on Sr{sub x}Ba{sub 1-x}SnO{sub 3} solid solutions. Black-Right-Pointing-Pointer Calculated crystal structures agree well with experiment. Black-Right-Pointing-Pointer Alloys have direct or indirect gaps depending on the Sr molar fraction. Black-Right-Pointing-Pointer The Kohn-Sham gap variation from x=0.0 to x=1.0 is close to the experimental value. Black-Right-Pointing-Pointer Carrier effective masses are very anisotropic, specially for holes.« less

Diet and behavior of the Saint-Césaire Neanderthal inferred from biogeochemical data inversion.

PubMed

Balter, Vincent; Simon, Laurent

2006-10-01

Biogeochemistry is a powerful tool for dietary reconstruction, and mixing equations can be used to quantify the contribution of multiple sources to an individual's diet. The goals of this paper are: 1) to generalize the inverse method to dietary mixtures; and 2) to reconstruct the diet of the Saint-Césaire Neanderthal using Sr/Ca and Ba/Ca data of the mineral fraction of bone (hydroxylapatite), and with published delta13C and delta15N data of the associated organic fraction of bone (collagen). A new method is proposed to calculate the maximum diagenetic contribution of the Sr/Ba ratio, assuming that the soil soluble fraction is the diagenetic end-member and, for a given fraction of diagenesis, allows the restoration of the original Sr/Ba ratio. Considering the Saint-Césaire Châtelperronian mammalian assemblage as the meat source, and on the basis of available Sr, Ba, and Ca contents of plants, the results indicate that the percentage of plants in the Neanderthal's diet must have been close to zero for realistic Sr and Ba impoverishment between diet and hydroxylapatite. Contrary to previous studies, it is shown that fish could constitute a significant proportion (30%) of the diet of the Saint-Césaire Neanderthal. However, this mass balance solution is not supported by the zooarchaeological data. When the entire faunal assemblage is considered as the dietary source, the calculation shows that bovids (except reindeer) represent the greatest percentage of consumed meat (58%), followed by horses/rhinoceros (22%), reindeer (13%), and mammoths (7%). These respective percentages are in close accordance with zooarchaeological records, suggesting that the faunal assemblage associated with the Neanderthal of Saint-Césaire reliably reflects what he ate during the last few years of his life. In behavioral terms, this result supports the hypothesis that this Neanderthal carried the foodstuffs back to the Saint-Césaire shelter before their consumption.

Hydration energies and structures of alkaline earth metal ions, M2+(H2O)n, n = 5-7, M = Mg, Ca, Sr, and Ba.

PubMed

Rodriguez-Cruz, S E; Jockusch, R A; Williams, E R

1999-09-29

The evaporation of water from hydrated alkaline earth metal ions, produced by electrospray ionization, was studied in a Fourier transform mass spectrometer. Zero-pressure-limit dissociation rate constants for loss of a single water molecule from the hydrated divalent metal ions, M(2+)(H(2)O)(n) (M = Mg, Ca, and Sr for n = 5-7, and M = Ba for n = 4-7), are measured as a function of temperature using blackbody infrared radiative dissociation. From these values, zero-pressure-limit Arrhenius parameters are obtained. By modeling the dissociation kinetics using a master equation formalism, threshold dissociation energies (E(o)) are determined. These reactions should have a negligible reverse activation barrier; therefore, E(o) values should be approximately equal to the binding energy or hydration enthalpy at 0 K. For the hepta- and hexahydrated ions at low temperature, binding energies follow the trend expected on the basis of ionic radii: Mg > Ca > Sr > Ba. For the hexahydrated ions at high temperature, binding energies follow the order Ca > Mg > Sr > Ba. The same order is observed for the pentahydrated ions. Collisional dissociation experiments on the tetrahydrated species result in relative dissociation rates that directly correlate with the size of the metals. These results indicate the presence of two isomers for hexahydrated magnesium ions: a low-temperature isomer in which the six water molecules are located in the first solvation shell, and a high-temperature isomer with the most likely structure corresponding to four water molecules in the inner shell and two water molecules in the second shell. These results also indicate that the pentahydrated magnesium ions have a structure with four water molecules in the first solvation shell and one in the outer shell. The dissociation kinetics for the hexa- and pentahydrated clusters of Ca(2+), Sr(2+), and Ba(2+) are consistent with structures in which all the water molecules are located in the first solvation shell.

Modulation of Cardiac Ryanodine Receptor Channels by Alkaline Earth Cations

PubMed Central

Diaz-Sylvester, Paula L.; Porta, Maura; Copello, Julio A.

2011-01-01

Cardiac ryanodine receptor (RyR2) function is modulated by Ca2+ and Mg2+. To better characterize Ca2+ and Mg2+ binding sites involved in RyR2 regulation, the effects of cytosolic and luminal earth alkaline divalent cations (M2+: Mg2+, Ca2+, Sr2+, Ba2+) were studied on RyR2 from pig ventricle reconstituted in bilayers. RyR2 were activated by M2+ binding to high affinity activating sites at the cytosolic channel surface, specific for Ca2+ or Sr2+. This activation was interfered by Mg2+ and Ba2+ acting at low affinity M2+-unspecific binding sites. When testing the effects of luminal M2+ as current carriers, all M2+ increased maximal RyR2 open probability (compared to Cs+), suggesting the existence of low affinity activating M2+-unspecific sites at the luminal surface. Responses to M2+ vary from channel to channel (heterogeneity). However, with luminal Ba2+or Mg2+, RyR2 were less sensitive to cytosolic Ca2+ and caffeine-mediated activation, openings were shorter and voltage-dependence was more marked (compared to RyR2 with luminal Ca2+or Sr2+). Kinetics of RyR2 with mixtures of luminal Ba2+/Ca2+ and additive action of luminal plus cytosolic Ba2+ or Mg2+ suggest luminal M2+ differentially act on luminal sites rather than accessing cytosolic sites through the pore. This suggests the presence of additional luminal activating Ca2+/Sr2+-specific sites, which stabilize high Po mode (less voltage-dependent) and increase RyR2 sensitivity to cytosolic Ca2+ activation. In summary, RyR2 luminal and cytosolic surfaces have at least two sets of M2+ binding sites (specific for Ca2+ and unspecific for Ca2+/Mg2+) that dynamically modulate channel activity and gating status, depending on SR voltage. PMID:22039534

The role of the seagrass Posidonia oceanica in the cycling of trace elements

NASA Astrophysics Data System (ADS)

Sanz-Lázaro, C.; Malea, P.; Apostolaki, E. T.; Kalantzi, I.; Marín, A.; Karakassis, I.

2012-03-01

The aim of this work was to study the role of the seagrass Posidonia oceanica on the cycling of a wide set of trace elements (Ag, As, Ba, Bi, Cd, Co, Cr, Cs, Cu, Fe, Ga, Li, Mn, Ni, Pb, Rb, Sr, Tl, V and Zn). We measured the concentration of these trace elements in the different compartments of P. oceanica (leaves, rhizomes, roots and epibiota) in a non-polluted seagrass meadow representative of the Mediterranean and calculated the annual budget from a mass balance. We provide novel data on accumulation dynamics of many trace elements in P. oceanica compartments and demonstrate that trace element accumulation patterns are mainly determined by plant compartment rather than by temporal variability. Epibiota was the compartment which showed the greatest concentrations for most trace elements. Thus, they constitute a key compartment when estimating trace element transfer to higher trophic levels by P. oceanica. For most trace elements, translocation seemed to be low and acropetal. Zn, Cd, Sr and Rb were the trace elements that showed the highest release rate through decomposition of plant detritus, while Cs, Tl and Bi the lowest. P. oceanica acts as a sink of potentially toxic trace elements (Ni, Cr, As and Ag), which can be sequestered, decreasing their bioavailability. P. oceanica may have a relevant role in the cycling of trace elements in the Mediterranean.

The role of the seagrass Posidonia oceanica in the cycling of trace elements

NASA Astrophysics Data System (ADS)

Sanz-Lázaro, C.; Malea, P.; Apostolaki, E. T.; Kalantzi, I.; Marín, A.; Karakassis, I.

2012-07-01

The aim of this study was to investigate the role of the seagrass Posidonia oceanica on the cycling of a wide set of trace elements (Ag, As, Ba, Bi, Cd, Co, Cr, Cs, Cu, Fe, Ga, Li, Mn, Ni, Pb, Rb, Sr, Tl, V and Zn). We measured the concentration of these trace elements in different compartments of P. oceanica (leaves, rhizomes, roots and epiphytes) in a non-polluted seagrass meadow representative of the Mediterranean and calculated the annual budget from a mass balance. We provide novel data on accumulation dynamics of many trace elements in P. oceanica compartments and demonstrate that trace element accumulation patterns are mainly determined by plant compartment rather than by temporal variability. Epiphytes were the compartment, which showed the greatest concentrations for most trace elements. Thus, they constitute a key compartment when estimating trace element transfer to higher trophic levels by P. oceanica. Trace element translocation in P. oceanica seemed to be low and acropetal in most cases. Zn, Cd, Sr and Rb were the trace elements that showed the highest release rate through decomposition of plant detritus, while Cs, Tl and Bi showed the lowest. P. oceanica acts as a sink of potentially toxic trace elements (Ni, Cr, As and Ag), which can be sequestered, decreasing their bioavailability. P. oceanica may have a relevant role in the cycling of trace elements in the Mediterranean.

Decoupling of magnetism and electric transport in single-crystal (Sr1‑x A x )2IrO4 (A  =  Ca or Ba)

NASA Astrophysics Data System (ADS)

Zhao, H. D.; Terzic, J.; Zheng, H.; Ni, Y. F.; Zhang, Y.; Ye, Feng; Schlottmann, P.; Cao, G.

2018-06-01

We report a systematical structural, transport and magnetic study of Ca or Ba doped Sr2IrO4 single crystals. Isoelectronically substituting Ca2+ (up to 15%) or Ba2+ (up to 4%) ion for the Sr2+ ion provides no additional charge carriers but effectively changes the lattice parameters in Sr2IrO4. In particular, 15% Ca doping considerably reduces the c-axis and the unit cell by nearly 0.45% and 1.00%, respectively. These significant, anisotropic compressions in the lattice parameters conspicuously cause no change in the Néel temperature which remains at 240 K, but drastically reduces the electrical resistivity by up to five orders of magnitude or even precipitates a sharp insulator-to-metal transition at lower temperatures, i.e. the vanishing insulating state accompanies an unchanged Néel temperature in (Sr1‑x A x )2IrO4. This observation brings to light an intriguing difference between chemical pressure and applied pressure, the latter of which does suppress the long-range magnetic order in Sr2IrO4. This difference reveals the importance of the Ir1–O2–Ir1 bond angle and homogenous volume compression in determining the magnetic ground state. All results, along with a comparison drawn with results of Tb and La doped Sr2IrO4, underscore that the magnetic transition plays a nonessential role in the formation of the charge gap in the spin–orbit-tuned iridate.

Pollution Assessment of Toxic and Potentially Toxic Elements in Agricultural Soils of the City Addis Ababa, Ethiopia.

PubMed

Aschale, Minbale; Sileshi, Yilma; Kelly-Quinn, Mary; Hailu, Dereje

2017-02-01

Due to the significantly fast urban expansion and increased industrial activities, the soils in the farms in Addis Ababa are contaminated by some toxic and potentially toxic elements (As, V, Cr, Fe, Co, Ni, Cu, B, Ba, Sr, Zn, Mn, Pb and Cd) in varying degrees. The mean concentrations of Cr, Ni, As and B in most of the soil farms were found to be higher than the maximum recommended limits. The mean concentrations of Cd, Cu, Pb, Co, Ni and Mn were found to be higher than the background soil concentrations given for uncontaminated soils. Multivariate analyses coupled with correlation analysis were used to identify possible sources. The geo-accumulation index values for Cr, Mn and Pb indicated that the farm soils were unpolluted to moderately polluted as a result of anthropogenic activities. A comprehensive environmental management strategy should be formulated by the government to measure further pollution of the farmland soil.

Pb, Sr and Ba calix[6]arene hexacarboxylic acid octahedral complexation: a dramatic effect of dealkylation

PubMed Central

Adhikari, Birendra Babu; To, Cuong-Alexander; Iwasawa, Tetsuo; Schramm, Michael P.

2015-01-01

Calix[6]arene hexacarboxylic acid binds instantly and with low symmetry to Pb, Sr and Ba. Later a highly symmetric up-down alternating conformation emerges. The solution structures are identical to their p-tert-butylcalix[6]arene hexacarboxylic acid counterparts. With either receptor an octahedral cage is formed around the metal. The transformation from low to high symmetry however proceeds at significantly faster rates for the de-t-butylated host. PMID:26752941

Relationships between water, otolith, and scale chemistries of westslope cutthroat trout from the Coeur d'Alene River, Idaho: the potential application of hard-part chemistry to describe movements in freshwater

Treesearch

Brian K. Wells; Bruce E. Rieman; James L. Clayton; Donna L. Horan; Cynthia M. Jones

2003-01-01

We quantified Mg:Ca, Mn:Ca, Sr:Ca, and Ba:Ca molar ratios from an area representing the summer 2000 growth season on otoliths and scales from 1-year-old westslope cutthroat trout Oncorhyncus clarki lewisi collected from three streams in the Coeur d'Alene River, Idaho, system. We also quantified Mg:Ca, Sr:Ca, and Ba:Ca molar ratios in the water...

Growth of Nanoscale BaTiO3/SrTiO3 Superlattices by Molecular-Beam Epitaxy

DTIC Science & Technology

2008-05-01

also of interest for novel acous- tic phonon devices including mirrors, filters, and cavities for coherent acoustic phonon generation and control...phonon “laser”).4 The structure of these devices is de- termined by the acoustic phonon wavelength, which is typically in the range of a few nanometers...nanoscale [(BaTiO3)n /(SrTiO3)m]p superlattices with atomically abrupt interfaces that are vital for the perfor- mance of acoustic phonon devices as

Trace element concentrations in needles and bark of Larix Sibirica within the Mo-W ore field (Buryat Republic, Russia)

NASA Astrophysics Data System (ADS)

Timofeev, Ivan; Kosheleva, Natalia

2016-04-01

The present study aims to assess the changes in the trace element (TE) composition of Larix Sibirica species growing in the impact area of Dzhida Mo-W plant in the Zakamensk city. The objectives of the study were: (1) to reveal the biogeochemical background features and changes in the TE composition of larch needles and bark in the mining region; (2) to determine patterns of spatial distribution of TE content in larch organs; (3) to assess the ecological state of larch plantation in different land-use zones of the city. A landscape-geochemical survey of the territory was carried out in summer of 2013. Total of 21 mixed (taken from 3-5 trees) samples of needles and bark were collected in undisturbed and different land-use areas. The bulk contents of TEs in dry plant samples were analyzed by mass spectrometry with induced coupled plasma. Sixteen priority pollutants were selected for thorough analysis, including elements of hazard classes I (Zn, As, Pb, Cd), II (Cr, Co, Ni, Cu, Mo, Sb), III (V, Sr, Ba, W), and some others (Sn, Bi). Concentrations of TEs (C_b) in background trees were compared with the global clarks (C_g) for annual increment of terrestrial vegetation (Dobrovol'skii 2003) via calculating the global enrichment EF_g=C_b/Cg and dispersion factors DF_g=C_g/C_b}. The concentrations of the elements in the urban samples Ci were grouped depending on the type of land use and compared with the background (C_b) via calculating the local enrichment EF_l=C_i/Cb and dispersion factors DF_l=C_b/C_i. The ecological state of the urban plants was diagnosed using three TE ratios. The Fe/Mn ratio represents photosynthetic activity with optimum value 1.5-2.5. The Pb/Mn ratio characterizes balance between technogenic and biophilic elements, its value for unpolluted terrestrial plants is 0.006. The Cu/Zn ratio determines the proportionality in the provision of enzyme synthesis with these metals, its optimum value is 0.27. TE composition of needles of background larch is characterized by increased concentrations of ?? ? Mn (EF_g=2.9) ? Sr (1.5), and reduced ones for Ni, Co, Pb, Mo, Sn, V (DF_l=5.1-22.1), that of Cd, Cu, Zn are close to global clarks. Ba, Pb, Cd (EF_g=3.5-2.3) are accumulated in the bark, Cu, Zn, Co, Cr, Ni, Sn dissipate (DF_g=2.1-3.7), and the content of Mn, Sr, Mo, V, As is close to Cg. In the city larch needles accumulate Cr (EF_l=37.8), W (18.9), V, Pb, Bi (8.6-11.4), Sb, Ni, Cd, Sn (6.6-2.5); Mn (DF_l=3.1) is among scattered. Changes in the TE composition of larch bark is most clearly evident in the industrial area, where high concentrations of W, Sn (EF_l=5.4-6.6), Sb, Pb, As (2.8-3.4), Mo, Cd, V, Bi, Zn (1.5-2.0) and low ones -- of Cr, Ni, Co, Ba (DF_l=4.6-2.1) are observed. As an indicator of long-term pollution, bark displays that vegetation of industrial zone has been subject previously to most intense anthropogenic impact, so, Pb/Mn=0.06 was there the highest. After plant closing residential area experiences the greatest impact according to Fe/Mn=4.7; Pb/Mn=0.04 values in the needles. This is caused by the active transport of aeolian dry material of tailings. 1. Dobrovol'skii VV (2003) Basics of biogeochemistry: the textbook for students of higher educational institutions. Moscow, "Academia" Publ., 400 p.

Testing Room-Temperature Ionic Liquid Solutions for Depot Repair of Aluminum Coatings

DTIC Science & Technology

2011-05-01

Ne 3 Na Mg IIIB IVB VB VIB VIIB ------ VIIIB ------ IB IIB Al Si P S Cl Ar 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 5 Rb Sr Y Zr Nb Mo Tc...Ru Rh Pd Ag Cd In Sn Sb Te I Xe 6 Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 7 Fr Ra Ac Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Th Pa U Np...Electroplating Bath Lid Arrangement ;:::::::::::=== Thermometer Purge gas vent Anode lead Cathode lead (Extractable from the lid) Purge feed gas

Stable isotope dilution analysis of hydrologic samples by inductively coupled plasma mass spectrometry

USGS Publications Warehouse

Garbarino, John R.; Taylor, Howard E.

1987-01-01

Inductively coupled plasma mass spectrometry is employed in the determination of Ni, Cu, Sr, Cd, Ba, Ti, and Pb in nonsaline, natural water samples by stable isotope dilution analysis. Hydrologic samples were directly analyzed without any unusual pretreatment. Interference effects related to overlapping isobars, formation of metal oxide and multiply charged ions, and matrix composition were identified and suitable methods of correction evaluated. A comparability study snowed that single-element isotope dilution analysis was only marginally better than sequential multielement isotope dilution analysis. Accuracy and precision of the single-element method were determined on the basis of results obtained for standard reference materials. The instrumental technique was shown to be ideally suited for programs associated with certification of standard reference materials.

Lattice distortions and local compressibility around trivalent rare-earth impurities in fluorites

NASA Astrophysics Data System (ADS)

Tovar, M.; Ramos, C. A.; Fainstein, C.

1983-10-01

We have calculated the lattice distortions around trivalent rare-earth dilute impurities, occupying substitutionally metal sites in fluorites. Explicit results are given for the equilibrium positions of the nearest fluorine ligands, R, the induced electric dipole moments, and the local hydrostatic strains for MF2 (M=Cd, Ca, Sr, Pb, and Ba). These results are used to study the impurity-ligand distance dependence of the fourth-order cubic-crystal-field parameter, b4, for Gd3+ and the isoelectronic ion Eu2+. Comparison is made with the change of b4 with hydrostatic stress using the calculated local compressibility of the lattice. A consistent description of the experimental data is obtained assuming b4~R-m with m~10.

Luminescence of BaBrI and SrBrI single crystals doped with Eu2+

NASA Astrophysics Data System (ADS)

Shalaev, A. A.; Shendrik, R.; Myasnikova, A. S.; Bogdanov, A.; Rusakov, A.; Vasilkovskyi, A.

2018-05-01

The crystal growth procedure and luminescence properties of pure and Eu2+-doped BaBrI and SrBrI crystals are reported. Emission and excitation spectra were recorded under ultraviolet and vacuum ultraviolet excitations. The energy of the first Eu2+ 4f-5d transition and SrBrI band gap are obtained. The electronic structure calculations were performed within GW approximation as implemented in the Vienna Ab Initio Simulation Package. The energy between lowest Eu2+ 5d state and the bottom of conduction band are found based on luminescence quenching parameters. The vacuum referred binding energy diagram of lanthanide levels was constructed using the chemical shift model.

Epitaxial Ba2IrO4 thin-films grown on SrTiO3 substrates by pulsed laser deposition

NASA Astrophysics Data System (ADS)

Nichols, J.; Korneta, O. B.; Terzic, J.; Cao, G.; Brill, J. W.; Seo, S. S. A.

2014-03-01

We have synthesized epitaxial Ba2IrO4 (BIO) thin-films on SrTiO3 (001) substrates by pulsed laser deposition and studied their electronic structure by dc-transport and optical spectroscopic experiments. We have observed that BIO thin-films are insulating but close to the metal-insulator transition boundary with significantly smaller transport and optical gap energies than its sister compound, Sr2IrO4. Moreover, BIO thin-films have both an enhanced electronic bandwidth and electronic-correlation energy. Our results suggest that BIO thin-films have great potential for realizing the interesting physical properties predicted in layered iridates.

Orientation effect on microwave dielectric properties of Si-integrated Ba0.6Sr0.4TiO3 thin films for frequency agile devices

NASA Astrophysics Data System (ADS)

Kim, Hyun-Suk; Hyun, Tae-Seon; Kim, Ho-Gi; Kim, Il-Doo; Yun, Tae-Soon; Lee, Jong-Chul

2006-07-01

The effect of texture with (100) and (110) preferred orientations on dielectric properties of Ba0.6Sr0.4TiO3 (BST) thin films grown on SrO (9nm) and CeO2 (70nm ) buffered Si substrates, respectively, was investigated. The coplanar waveguide (CPW) phase shifter using (100) oriented BST films on SrO buffered Si exhibited a much-enhanced figure of merit of 24.7°/dB, as compared to that (10.2°/dB) of a CPW phase shifter using (110) oriented BST films on CeO2 buffered Si at 12GHz. This work demonstrates that the microwave properties of the Si-integrated BST thin films are highly correlated with crystal orientation.

Synthesis and Characterization of Polyether Adducts of Barium and Strontium Carboxylates and Their Use in the Formation of MTiO(3) Films.

PubMed

Wojtczak, William A.; Atanassova, Paolina; Hampden-Smith, Mark J.; Duesler, Eileen

1996-11-20

The synthesis, characterization, and reactivity of new polyether adducts of strontium and barium carboxylates of general composition M(O(2)CCF(3))(n)()(L) (M = Ba, L = 15-crown-5, (1); M = Ba (2), Sr (3), respectively, with L = tetraglyme are reported. The compounds were synthesized by reaction of BaCO(3) or MH(2) (M = Sr or Ba) with organic acids in the presence of the polyether ligands. These compounds have been characterized by IR and (13)C and (1)H NMR spectroscopies, elemental analyses, and thermogravimetric analysis. The species Ba(2)(O(2)CCF(3))(4)(15-crown-5)(2) (1) and [Ba(2)(O(2)CCF(3))(4)(tetraglyme)](infinity) (2), were also characterized by single-crystal X-ray diffraction. Ba(2)(O(2)CCF(3))(4)(15-crown-5)(2) (1) crystallizes in the orthorhombic space group Cccm with cell dimensions of a = 13.949(1) Å, b = 19.376(2) Å, c = 16.029(1) Å, and Z = 8. [Ba(2)(O(2)CCF(3))(4)(tetraglyme)](infinity) (2) crystallizes in the monoclinic space group C2/c with cell dimensions of a = 12.8673(12) Å, b = 16.6981(13) Å, c = 15.1191(12) Å, beta = 99.049(8) degrees, and Z = 4. Compounds 1-3 thermally decompose at high temperatures in the solid state to give MF(2). However, solutions of compounds 1-3 dissolved in ethanol with Ti(O-i-Pr)(4) give crystalline perovskite phase MTiO(3) films, or in the case of mixtures of 2 and 3, Ba(1)(-)(x)()Sr(x)()TiO(3) films below 600 degrees C when spin coated onto silicon substrates and thermally treated. The crystallinity, purity, and elemental composition of the films was determined by glancing angle X-ray diffraction and Auger electron spectroscopy.

Quasi-2D silicon structures based on ultrathin Me2Si (Me = Mg, Ca, Sr, Ba) films

NASA Astrophysics Data System (ADS)

Migas, D. B.; Bogorodz, V. O.; Filonov, A. B.; Borisenko, V. E.; Skorodumova, N. V.

2018-04-01

By means of ab initio calculations with hybrid functionals we show a possibility for quasi-2D silicon structures originated from semiconducting Mg2Si, Ca2Si, Sr2Si and Ba2Si silicides to exist. Such a 2D structure is similar to the one of transition metal chalcogenides where silicon atoms form a layer in between of metal atoms aligned in surface layers. These metal surface atoms act as pseudo passivation species stabilizing crystal structure and providing semiconducting properties. Considered 2D Mg2Si, Ca2Si, Sr2Si and Ba2Si have band gaps of 1.14 eV, 0.69 eV, 0.33 eV and 0.19 eV, respectively, while the former one is also characterized by a direct transition with appreciable oscillator strength. Electronic states of the surface atoms are found to suppress an influence of the quantum confinement on the band gaps. Additionally, we report Sr2Si bulk in the cubic structure to have a direct band gap of 0.85 eV as well as sizable oscillator strength of the first direct transition.

Octonary resistance states in La 0.7Sr 0.3MnO 3/BaTiO 3/La 0.7Sr 0.3MnO 3 multiferroic tunnel junctions

DOE PAGES

Yue -Wei Yin; Tao, Jing; Huang, Wei -Chuan; ...

2015-10-06

General drawbacks of current electronic/spintronic devices are high power consumption and low density storage. A multiferroic tunnel junction (MFTJ), employing a ferroelectric barrier layer sandwiched between two ferromagnetic layers, presents four resistance states in a single device and therefore provides an alternative way to achieve high density memories. Here, an MFTJ device with eight nonvolatile resistance states by further integrating the design of noncollinear magnetization alignments between the ferromagnetic layers is demonstrated. Through the angle-resolved tunneling magnetoresistance investigations on La 0.7Sr 0.3MnO 3/BaTiO 3/La 0.7Sr 0.3MnO 3 junctions, it is found that, besides collinear parallel/antiparallel magnetic configurations, the MFTJ showsmore » at least two other stable noncollinear (45° and 90°) magnetic configurations. As a result, combining the tunneling electroresistance effect caused by the ferroelectricity reversal of the BaTiO 3 barrier, an octonary memory device is obtained, representing potential applications in high density nonvolatile storage in the future.« less

On the novel double perovskites A2Fe(Mn0.5W0.5)O6 (A= Ca, Sr, Ba). Structural evolution and magnetism from neutron diffraction data

NASA Astrophysics Data System (ADS)

García-Ramos, Crisanto A.; Larrégola, Sebastián; Retuerto, María; Fernández-Díaz, María Teresa; Krezhov, Kiril; Alonso, José Antonio

2018-06-01

New A2Fe(Mn0.5W0.5)O6 (A = Ca, Sr, Ba) double perovskite oxides have been prepared by ceramic techniques. X-ray diffraction (XRD) complemented with neutron powder diffraction (NPD) indicate a structural evolution from monoclinic (space group P21/n) for A = Ca to cubic (Fm-3m) for A = Sr and finally to hexagonal (P63/mmc) for A = Ba as the perovskite tolerance factor increases with the A2+ ionic size. The three oxides present different tilting schemes of the FeO6 and (Mn,W)O6 octahedra. NPD data also show evidence in all cases of a considerable anti-site disordering, involving the partial occupancy of Fe positions by Mn atoms, and vice-versa. Magnetic susceptibility data show magnetic transitions below 50 K characterized by a strong irreversibility between ZFC and FC susceptibility curves. The A = Ca perovskite shows a G-type magnetic structure, with weak ordered magnetic moments due to the mentioned antisite disordering. Interesting magnetostrictive effects are observed for the Sr perovskite below 10 K.

Chemical Substitution-Induced and Competitive Formation of 6H and 3C Perovskite Structures in Ba3-xSrxZnSb2O9: The Coexistence of Two Perovskites in 0.3 ≤ x ≤ 1.0.

PubMed

Li, Jing; Jiang, Pengfei; Gao, Wenliang; Cong, Rihong; Yang, Tao

2017-11-20

6H and 3C perovskites are important prototype structures in materials science. We systemically studied the structural evolution induced by the Sr 2+ -to-Ba 2+ substitution to the parent 6H perovskite Ba 3 ZnSb 2 O 9 . The 6H perovskite is only stable in the narrow range of x ≤ 0.2, which attributes to the impressibility of [Sb 2 O 9 ]. The preference of 90° Sb-O-Sb connection and the strong Sb 5+ -Sb 5+ electrostatic repulsion in [Sb 2 O 9 ] are competitive factors to stabilize or destabilize the 6H structure when chemical pressure was introduced by Sr 2+ incorporation. Therefore, in the following, a wide two-phase region containing 1:2 ordered 6H-Ba 2.8 Sr 0.2 ZnSb 2 O 9 and rock-salt ordered 3C-Ba 2 SrZnSb 2 O 9 was observed (0.3 ≤ x ≤ 1.0). In the final, the successive symmetry descending was established from cubic (Fm3̅m, 1.3 ≤ x ≤ 1.8) to tetragonal (I4/m, 2.0 ≤ x ≤ 2.4), and finally to monoclinic (I2/m, 2.6 ≤ x ≤ 3.0). Here we proved that the electronic configurations of B-site cations, with either empty, partially, or fully filled d-shell, would also affect the structure stabilization, through the orientation preference of the B-O covalent bonding. Our investigation gives a deeper understanding of the factors to the competitive formation of perovskite structures, facilitating the fine manipulation on their physical properties.

Structural, electronic, optical and thermoelectric investigations of antiperovskites A3SnO (A = Ca, Sr, Ba) using density functional theory

NASA Astrophysics Data System (ADS)

Hassan, M.; Shahid, A.; Mahmood, Q.

2018-02-01

Density functional theory study of the structural, electrical, optical and thermoelectric behaviors of very less investigated anti-perovskites A3SnO (A = Ca, Sr, Ba) is performed with FP-LAPW technique. The A3SnO exhibit narrow direct band gap, in contrast to the wide indirect band gap of the respective perovskites. Hence, indirect to direct band gap transformation can be realized by the structural transition from perovskite to anti-perovskite. The p-p hybridization between A and O states result in the covalent bonding. The transparency and maximum reflectivity to the certain energies, and the verification of the Penn's model indicate potential optical device applications. Thermoelectric behaviors computed within 200-800 K depict that Ca3SnO exhibits good thermoelectric performance than Ba3SnO and Sr3SnO, and all three operate at their best at 800 K suggesting high temperature thermoelectric device applications.

Study on possible correlation of superconductivity with defects and superparamagnetism in undoped AFe2As2 with A =Ca, Sr and Ba

NASA Astrophysics Data System (ADS)

Zhao, Kui; Lv, Bing; Deng, Liangzi; Xue, Yuyi; Chu, Paul; High pressure low temperature lab Team

2014-03-01

Extensive studies have been carried out on the induction of bulk superconductivity in the Fe-pnictide 122 system with a Tc up to 38 K through doping and/or pressure. However, non-bulk superconductivity has also been detected unexpectedly in undoped AFe2As2 where A = Ca, Sr, and Ba with Tc = ~12K, ~22K and ~23K, respectively. The reason for the observation remains unknown. Recently, systematic investigation shows that highly anisotropic superconductivity with a Tc up to 49 K and superparamagnetism occur in rare-earth doped Ca122. Further examination reveals slight deviation from the 1:2:2 stoichiometry which correlates closely with the occurrence of non-bulk superconductivity and superparamagnetism in these samples. We have therefore decided to investigate systematically the stoichiometry, defects, magnetism and superconductivity in undoped AFe2As2 single crystals under different synthesis conditions where A = Ca, Sr, and Ba. Results will be presented and discussed.

Alkaline earth lead and tin compounds Ae2Pb, Ae2Sn, Ae = Ca, Sr, Ba, as thermoelectric materials

PubMed Central

Parker, David; Singh, David J

2013-01-01

We present a detailed theoretical study of three alkaline earth compounds Ca2Pb, Sr2Pb and Ba2Pb, which have undergone little previous study, calculating electronic band structures and Boltzmann transport and bulk moduli using density functional theory. We also study the corresponding tin compounds Ca2Sn, Sr2Sn and Ba2Sn. We find that these are all narrow band gap semiconductors with an electronic structure favorable for thermoelectric performance, with substantial thermopowers for the lead compounds at temperature ranges from 300 to 800 K. For the lead compounds, we further find very low calculated bulk moduli—roughly half of the values for the lead chalcogenides, suggestive of soft phonons and hence low lattice thermal conductivity. All these facts indicate that these materials merit experimental investigation as potential high performance thermoelectrics. We find good potential for thermoelectric performance in the environmentally friendly stannide materials, particularly at high temperature. PMID:27877610

Epitaxial Ferroelectric Ba(0.5)Sr(0.5)TiO3 Thin Films for Room-Temperature High-Frequency Tunable Element Applications

NASA Technical Reports Server (NTRS)

Chen, C. L.; Feng, H. H.; Zhang, Z.; Brazdeikis, A.; Miranda, F. A.; VanKeuls, F. W.; Romanofsky, R. R.; Huang, Z. J.; Liou, Y.; Chu, W. K.;

Current Status of Thin Film (Ba,Sr) TiO3 Tunable Microwave Components for RF Communications

NASA Technical Reports Server (NTRS)

VanKeuls, F. W.; Romananofsky, R. R.; Mueller, C. H.; Warner, J. D.; Canedy, C. L.; Ramesh, R.; Miranda, F. A.

2000-01-01

The performance of proof-of-concept ferroelectric microwave devices has been moving steadily closer to the level needed for satellite and other rf communications applications. This paper will review recent progress at NASA Glenn in developing thin film Ba(x)Sr(1-x)TiO3 tunable microwave components for these applications. Phase shifters for phased array antennas, tunable filters and tunable oscillators employing microstrip and coupled microstrip configurations will be presented. Tunabilities, maximum dielectric constants, and phase shifter parameters will be discussed (e.g., coupled microstrip phase shifters with phase shift over 200 deg. at 18 GHz and a figure of merit of 74.3 deg./dB). Issues of postannealing, Mn-doping and Ba(x)Sr(1-x)TiO3 growth on sapphire and alumina substrates will be covered. The challenges of incorporating these devices into larger systems, such as yield, variability in phase shift and insertion loss, and protective coatings will also be addressed.

Current Status of Thin Film (Ba,Sr)TiO3 Tunable Microwave Components for RF Communications

NASA Technical Reports Server (NTRS)

VanKeuls, F. W.; Romanofsky, R. R.; Mueller, C. H.; Warner, J. D.; Canedy, C. L.; Ramesh, R.; Miranda, F. A.

2000-01-01

The performance of proof-of-concept ferroelectric microwave devices has been moving steadily closer to the level needed for satellite and other rf communications applications. This paper will review recent progress at NASA Glenn in developing thin film Ba(x)Sr(1-x)TiO3 tunable micro-wave components for these applications. Phase shifters for phased array antennas, tunable filters and tunable oscillators employing microstrip and coupled microstrip configurations will be presented. Tunabilities, maximum dielectric constants, and phase shifter parameters will be discussed (e.g., coupled microstrip phase shifters with phase shift over 200 deg at 18 GHz and a figure of merit of 74.3 deg/dB). Issues of post-annealing, Mn-doping and Ba(x)Sr(1-x) TiO3 growth on sapphire and alumina substrates will be covered. The challenges of incorporating these devices into larger systems, such as yield, variability in phase shift and insertion loss, and protective coatings will also be addressed.

Studies of local structural distortions in strained ultrathin BaTiO3 films using scanning transmission electron microscopy.

PubMed

Park, Daesung; Herpers, Anja; Menke, Tobias; Heidelmann, Markus; Houben, Lothar; Dittmann, Regina; Mayer, Joachim

2014-06-01

Ultrathin ferroelectric heterostructures (SrTiO3/BaTiO3/BaRuO3/SrRuO3) were studied by scanning transmission electron microscopy (STEM) in terms of structural distortions and atomic displacements. The TiO2-termination at the top interface of the BaTiO3 layer was changed into a BaO-termination by adding an additional BaRuO3 layer. High-angle annular dark-field (HAADF) imaging by aberration-corrected STEM revealed that an artificially introduced BaO-termination can be achieved by this interface engineering. By using fast sequential imaging and frame-by-frame drift correction, the effect of the specimen drift was significantly reduced and the signal-to-noise ratio of the HAADF images was improved. Thus, a quantitative analysis of the HAADF images was feasible, and an in-plane and out-of-plane lattice spacing of the BaTiO3 layer of 3.90 and 4.22 Å were determined. A 25 pm shift of the Ti columns from the center of the unit cell of BaTiO3 along the c-axis was observed. By spatially resolved electron energy-loss spectroscopy studies, a reduction of the crystal field splitting (CFS, ΔL3=1.93 eV) and an asymmetric broadening of the eg peak were observed in the BaTiO3 film. These results verify the presence of a ferroelectric polarization in the ultrathin BaTiO3 film.

Analysis of Sr{sub 5{minus}x}Ba{sub x}(PO{sub 4}){sub 3}F:Yb{sup 3+} crystals for improved laser performance with diode-pumping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schaffers, K.I.; Bayramian, A.J.; Marshall, C.D.

Crystals of Yb{sup 3+}:Sr{sub 1-x}Ba{sub x}(PO{sub 4}){sub 3}F (0 < x < 5) have been investigated as a means to obtain broader absorption bands than are currently available with Yb{sup 3+}:S-FAP [Yb{sup 3+}: Sr{sub 5}(PO{sub 4}){sub 3}F], thereby improving diode-pumping efficiency for high peak power applications. Large diode-arrays have a FWHM pump band of >5 nm while the FWHM of the 900 nm absorption band for Yb:S-FAP is 5.5 nm; therefore, a significant amount of pump power can be wasted due to the nonideal overlap. Spectroscopic analysis of Yb:Sr{sub 5-x}Ba{sub x}-FAP crystals indicates that adding barium to the lattice increasesmore » the pump band to 13-16 run which more than compensates for the diode-array pump source without a detrimental reduction in absorption cross section. However, the emission cross section decreases by approximately half with relatively no effect on the emission lifetime. The small signal gain has also been measured and compared to the parent material Yb:S-FAP and emission cross sections have been determined by the method of reciprocity, the Filchtbauer-Ladenburg method, and small signal gain. Overall, Yb{sup 3+}:Sr{sub 5-x}Ba{sub x}(PO{sub 4}){sub 3}F crystals appear to achieve the goal of nearly matching the favorable thermal and laser performance properties of Yb:S-FAP while having a broader absorption band to better accommodate diode pumping.« less

Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron pnictide single crystals

NASA Astrophysics Data System (ADS)

Lu, Xin; Park, W. K.; Yuan, H. Q.; Chen, G. F.; Luo, G. L.; Wang, N. L.; Sefat, A. S.; McGuire, M. A.; Jin, R.; Sales, B. C.; Mandrus, D.; Gillett, J.; Sebastian, Suchitra E.; Greene, L. H.

2010-05-01

Point-contact Andreev reflection spectroscopy is applied to investigate the gap structure in iron pnictide single-crystal superconductors of the AFe2As2 (A = Ba, Sr) family ('Fe-122'). The observed point-contact junction conductance curves, G(V), can be divided into two categories: one where Andreev reflection is present for both (Ba0.6K0.4)Fe2As2 and Ba(Fe0.9Co0.1)2As2, and the other with a V2/3 background conductance universally observed, extending even up to 100 meV for Sr0.6Na0.4Fe2As2 and Sr(Fe0.9Co0.1)2As2. The latter is also observed in point-contact junctions on the nonsuperconducting parent compound BaFe2As2 and superconducting (Ba0.6K0.4)Fe2As2 crystals. Mesoscopic phase-separated coexistence of magnetic and superconducting orders is considered to explain distinct behaviors in the superconducting samples. For Ba0.6K0.4Fe2As2, double peaks due to Andreev reflection with a strongly sloping background are frequently observed for point contacts on freshly cleaved c-axis surfaces. If normalized using a background baseline and analyzed using the Blonder-Tinkham-Klapwijk model, the data show a gap size of ~ 3.0-4.0 meV with 2Δ0/kBTc ~ 2.0-2.6, consistent with the smaller gap size reported for the LnFeAsO family ('Fe-1111'). For the Ba(Fe0.9Co0.1)2As2, the G(V) curves typically display a zero-bias conductance peak.

Tracing subduction zone fluid-rock interactions using trace element and Mg-Sr-Nd isotopes

NASA Astrophysics Data System (ADS)

Wang, Shui-Jiong; Teng, Fang-Zhen; Li, Shu-Guang; Zhang, Li-Fei; Du, Jin-Xue; He, Yong-Sheng; Niu, Yaoling

2017-10-01

Slab-derived fluids play a key role in mass transfer and elemental/isotopic exchanges in subduction zones. The exhumation of deeply subducted crust is achieved via a subduction channel where fluids from various sources are abundant, and thus the chemical/isotopic compositions of these rocks could have been modified by subduction-zone fluid-rock interactions. Here, we investigate the Mg isotopic systematics of eclogites from southwestern Tianshan, in conjunction with major/trace element and Sr-Nd isotopes, to characterize the source and nature of fluids and to decipher how fluid-rock interactions in subduction channel might influence the Mg isotopic systematics of exhumed eclogites. The eclogites have high LILEs (especially Ba) and Pb, high initial 87Sr/86Sr (up to 0.7117; higher than that of coeval seawater), and varying Ni and Co (mostly lower than those of oceanic basalts), suggesting that these eclogites have interacted with metamorphic fluids mainly released from subducted sediments, with minor contributions from altered oceanic crust or altered abyssal peridotites. The positive correlation between 87Sr/86Sr and Pb* (an index of Pb enrichment; Pb* = 2*PbN/[CeN + PrN]), and the decoupling relationships and bidirectional patterns in 87Sr/86Sr-Rb/Sr, Pb*-Rb/Sr and Pb*-Ba/Pb spaces imply the presence of two compositionally different components for the fluids: one enriched in LILEs, and the other enriched in Pb and 87Sr/86Sr. The systematically heavier Mg isotopic compositions (δ26Mg = - 0.37 to + 0.26) relative to oceanic basalts (- 0.25 ± 0.07) and the roughly negative correlation of δ26Mg with MgO for the southwestern Tianshan eclogites, cannot be explained by inheritance of Mg isotopic signatures from ancient seafloor alteration or prograde metamorphism. Instead, the signatures are most likely produced by fluid-rock interactions during the exhumation of eclogites. The high Rb/Sr and Ba/Pb but low Pb* eclogites generally have high bulk-rock δ26Mg values, whereas high Pb* and 87Sr/86Sr eclogites have mantle-like δ26Mg values, suggesting that the two fluid components have diverse influences on the Mg isotopic systematics of these eclogites. The LILE-rich fluid component, possibly derived from mica-group minerals, contains a considerable amount of isotopically heavy Mg that has shifted the δ26Mg of the eclogites towards higher values. By contrast, the 87Sr/86Sr- and Pb-rich fluid component, most likely released from epidote-group minerals in metasediments, has little Mg so as not to modify the Mg isotopic composition of the eclogites. In addition, the influence of talc-derived fluid might be evident in a very few eclogites that have low Rb/Sr and Ba/Pb but slightly heavier Mg isotopic compositions. These findings represent an important step toward a broad understanding of the Mg isotope geochemistry in subduction zones, and contributing to understanding why island arc basalts have averagely heavier Mg isotopic compositions than the normal mantle.

Microfabrication of SrRuO3 thin films on various oxide substrates using LaAlO3/BaOx sacrificial bilayers

NASA Astrophysics Data System (ADS)

Harada, Takayuki; Tsukazaki, Atsushi

2018-02-01

Oxides provide various fascinating physical properties that could find use in future device applications. However, the physical properties of oxides are often affected by formation of oxygen vacancies during device fabrication processes. In this study, to develop a damage-free patterning process for oxides, we focus on a lift-off process using a sacrificial template layer, by which we can pattern oxide thin films without severe chemical treatment or plasma bombardment. As oxides need high thin-film growth temperature, a sacrificial template needs to be made of thermally stable and easily etchable materials. To meet these requirements, we develop a sacrificial template with a carefully designed bilayer structure. Combining a thermally and chemically stable LaAlO3 and a water-soluble BaOx, we fabricated a LaAlO3/BaOx sacrificial bilayer. The patterned LaAlO3/BaOx sacrificial bilayers were prepared on oxide substrates by room-temperature pulsed laser deposition and standard photolithography process. The structure of the sacrificial bilayer can be maintained even in rather tough conditions needed for oxide thin film growth: several hundred degrees Celsius under high oxygen pressure. Indeed, the LaAlO3/BaOx bilayer is easily removable by sonication in water. We applied the lift-off method using the LaAlO3/BaOx sacrificial bilayer to a representative oxide conductor SrRuO3 and fabricated micron-scale Hall-bar devices. The SrRuO3 channels with the narrowest line width of 5 μm exhibit an almost identical transport property to that of the pristine film, evidencing that the developed process is beneficial for patterning oxides. We show that the LaAlO3/BaOx lift-off process is applicable to various oxide substrates: SrTiO3, MgO, and Al2O3. The new versatile patterning process will expand the range of application of oxide thin films in electronic and photonic devices.

Enhanced Mixed Electronic-Ionic Conductors through Cation Ordering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobson, Allan J.; Morgan, Dane; Grey, Clare

2014-08-31

The performance of many energy conversion and storage devices depend on the properties of mixed ionic-electronic conducting (miec) materials. Mixed or ambipolar conductors simultaneously transport ions and electrons and provide the critical interface between chemical and electrical energy in devices such as fuel cells, ion transport membranes, and batteries. Enhancements in storage capacity, reversibility, power density and device lifetime all require new materials and a better understanding of the fundamentals of ambipolar conductivity and surface reactivity.The high temperature properties of the ordered perovksites AA’B 2O 5+x, where A = rare earth ion, Y and B = Ba, Sr were studied.more » The work was motivated by the high oxygen transport and surface exchange rates observed for members of this class of mixed ionic and electronic conductors. A combined experimental and computational approach, including structural, electrochemical, and transport characterization and modeling was used. The approach attacks the problem simultaneously at global (e.g., neutron diffraction and impedance spectroscopy), local (e.g., pair distribution function, nuclear magnetic resonance) and molecular (ab initio thermokinetic modeling) length scales. The objectives of the work were to understand how the cation and associated anion order lead to exceptional ionic and electronic transport properties and surface reactivity in AA’B2O5+x perovskites. A variety of compounds were studied by X-ray and neutron diffraction, measurements of thermodynamics and transport and theoretically. These included PrBaCo 2O 5+x and NdBaCo 2O 5+x, PrBaCo 2-xFexO 6- δ (x = 0, 0.5, 1.0, 1.5 and 2) and LnBaCoFeO 6- δ (Ln = La, Pr, Nd, Sm, Eu and Gd), Sr 3YCo 4O 10.5, YBaMn 2O 5+x. A 0.5A’ 0.5BO 3 (where A=Y, Sc, La, Ce, Pr, Nd, Pm, Sm; A’= Sr, Ba; and B= Fe, Co, Mn, Ni), Ba 2In 2O 5, and La 1 xSr xCoO 3-δ /(La 1-ySry) 2CoO 4±δ interfaces.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Du, Mao -Hua; Singh, David J.; Zhang, Lijun

Oxides with good p-type conductivity have been long sought after to achieve high performance all-oxide optoelectronic devices. Divalent Sn(II) based oxides are promising candidates because of their rather dispersive upper valence bands caused by the Sn-5s/O-2p anti-bonding hybridization. There are so far few known Sn(II) oxides being p-type conductive suitable for device applications. Here, we present via first-principles global optimization structure searches a material design study for a hitherto unexplored Sn(II)-based system, ternary alkaline-earth metal Sn(II) oxides in the stoichiometry of MSn 2O 3 (M = Mg, Ca, Sr, Ba). We identify two stable compounds of SrSn 2O 3 andmore » BaSn 2O 3, which can be stabilized by Sn-rich conditions in phase stability diagrams. Their structures follow the Zintl behaviour and consist of basic structural motifs of SnO 3 tetrahedra. Unexpectedly they show distinct electronic properties with band gaps ranging from 1.90 (BaSn 2O 3) to 3.15 (SrSn 2O 3) eV, and hole effective masses ranging from 0.87 (BaSn 2O 3) to above 6.0 (SrSn 2O 3) m0. Further exploration of metastable phases indicates a wide tunability of electronic properties controlled by the details of the bonding between the basic structural motifs. Lastly, this suggests further exploration of alkaline-earth metal Sn(II) oxides for potential applications requiring good p-type conductivity such as transparent conductors and photovoltaic absorbers.« less

Extraction of heavy metal (Ba, Sr) and high silica glass powder synthesis from waste CRT panel glasses by phase separation.

PubMed

Xing, Mingfei; Wang, Jingyu; Fu, Zegang; Zhang, Donghui; Wang, Yaping; Zhang, Zhiyuan

2018-04-05

In this study, a novel process for the extraction of heavy metal Ba and Sr from waste CRT panel glass and synchronous preparation of high silica glass powder was developed by glass phase separation. CRT panel glass was first remelted with B 2 O 3 under air atmosphere to produce alkali borosilicate glass. During the phase separation process, the glass separated into two interconnected phases which were B 2 O 3 -rich phase and SiO 2 -rich phase. Most of BaO, SrO and other metal oxides including Na 2 O, K 2 O, Al 2 O 3 and CaO were mainly concentrated in the B 2 O 3 -rich phase. The interconnected B 2 O 3 -rich phase can be completely leached out by 5mol/L HNO 3 at 90 ℃. The remaining SiO 2 -rich phase was porous glasses consisting almost entirely of silica. The maximum Ba and Sr removal rates were 98.84% and 99.38% and high silica glass powder (SiO 2 purity > 90 wt%) was obtained by setting the temperature, B 2 O 3 added amount and holding time at 1000-1100 ℃, 20-30% and 30 min, respectively. Thus this study developed an potential economical process for detoxification and reclamation of waste heavy metal glasses. Copyright © 2017 Elsevier B.V. All rights reserved.

Apoptosis of haematopoietic cells upon thymidylate synthase inhibition is independent of p53 accumulation and CD95-CD95 ligand interaction.

PubMed Central

Muñoz-Pinedo, C; Oliver, F J; López-Rivas, A

2001-01-01

Treatment of haematopoietic BA/F3 cells with the thymidylate synthase inhibitor 5-fluoro-2'-deoxyuridine (FUdR) activated apoptosis through a mechanism that required continuous protein synthesis and was inhibited by Bcl-2 over-expression. Analysis of p53 levels in cells treated with FUdR indicated a marked accumulation of this protein. Accumulation of p53 was also observed in cells over-expressing Bcl-2. In BA/F3 cells transfected with a cDNA coding for the human papilloma virus protein E6, p53 accumulation after FUdR treatment was inhibited markedly. However, apoptosis was induced in both control and E6 cells to a similar extent. The role of the CD95/CD95 ligand (CD95L) system in FUdR-induced apoptosis was also assessed. As determined by reverse transcriptase PCR, BA/F3 expressed a low constitutive level of CD95L mRNA, which decreased following FUdR treatment. Moreover, blocking CD95-CD95L interactions with antagonistic CD95 monoclonal antibody did not prevent drug-induced apoptosis. Furthermore, analysis of caspase involvement showed important differences in apoptosis induced by CD95-triggering or FUdR treatment. In summary, these results suggest that apoptosis induced by thymineless stress in haematopoietic BA/F3 cells occurs by a mechanism that does not require accumulation of p53 and which is independent of CD95-CD95L interactions. PMID:11115403

Photoluminescence of A- and B-site Eu{sup 3+}-substituted (Sr{sub x}Ba{sub 1−x}){sub 2}CaW{sub y}Mo{sub 1−y}O{sub 6} phosphors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sletnes, M.; Lindgren, M.; Valmalette, J.C.

The photoluminescence of two series of A- and B-site Eu{sup 3+} substituted (Sr{sub x}Ba{sub 1−x}){sub 2}CaW{sub y}Mo{sub 1−y}O{sub 6} double perovskite phosphor materials, (Sr{sub x}Ba{sub 1−x}){sub 1.96}Eu{sub 0.02}K{sub 0.02}CaW{sub y}Mo{sub 1−y}O{sub 6} and (Sr{sub x}Ba{sub 1−x}){sub 2}Ca{sub 0.96}Eu{sub 0.02}Li{sub 0.02}W{sub y}Mo{sub 1−y}O{sub 6} (x and y=0, 0.25, 0.50, 0.75, and 1), were studied systematically as a function of stoichiometry and crystal structure. The Eu{sup 3+} lattice sites controlled by co-doping with either K or Li were confirmed by Raman spectroscopy. The variation in integrated emission intensity and emission colour over the experimental matrix was examined using statistical tools, and themore » observed trends were rationalized based on the physical and electronic structure of the phosphors. Phosphors with Eu on B-site with maximum Sr content had remarkably higher emission intensities than all other materials, but the emission was more orange than red due to domination of the {sup 5}D{sub 0}–{sup 7}F{sub 1} (595 nm) transition of Eu{sup 3+}. The relative intensities of the {sup 5}D{sub 0}–{sup 7}F{sub 2} (615 nm) and {sup 5}D{sub 0}–{sup 7}F{sub 1} transitions of Eu{sup 3+}, and thus the red-shift of the emission, decreased linearly with increasing Sr content in the A-site Eu-substituted phosphors, and reached a maximum for Sr{sub 1.96}Eu{sub 0.02}K{sub 0.02}CaW{sub 0.25}Mo{sub 0.75}O{sub 6}. A maximum external quantum efficiency of 17% was obtained for the phosphor Sr{sub 2}Ca{sub 0.7}Eu{sub 0.15}Li{sub 0.15}W{sub 0.5}Mo{sub 0.5}O{sub 6} with Eu on B-site. - Highlights: • Systematic study of the photoluminescence of Eu{sup 3+}-doped (Sr{sub x}Ba{sub 1−x}){sub 2}CaW{sub y}Mo{sub 1−y}O{sub 6}. • The Eu{sup 3+} lattice sites were confirmed by Raman spectroscopy. • A large parameter space was investigated using statistical tools. • A maximum external QE of 17% was obtained for Sr{sub 2}Ca{sub 0.7}Eu{sub 0.15}Li{sub 0.15}W{sub 0.5}Mo{sub 0.5}O{sub 6}.« less

A New Probe to Change Curie Temperature of PbTiO3 Sensors

NASA Technical Reports Server (NTRS)

Katiyar, R. S.; Jinfang, Meng

1997-01-01

High temperature Raman spectra of nanocrystalline Pb(0.8)Ba(0.2)TiO3, Pb(0.8)Sr(0.2) TiO3, Pb(0.8)La(0.2)TiO3 and Pb(0.8)Ba(0.2)TiO3, have been measured, as a function of particle size. There appears respectively a distinct temperature-induced soft mode phase transition in every sample whose Curie temperature can be determined from the mean-field theory. The detailed Curie temperature shift in modified PbTi03 ceramics by Ba, Sr, La, and Zr, has also been investigated as a function of particle size. This study will favor preparations of high efficiency PbTi03 sensors with an adjustable Curie temperature.

Development and evaluation of geochemical methods for the sourcing of archaeological maize

USGS Publications Warehouse

Benson, L.V.; Taylor, Howard E.; Peterson, K.A.; Shattuck, B.D.; Ramotnik, C.A.; Stein, J.R.

2008-01-01

Strontium (Sr)-isotope values on bone from deer mice pairs from 12 field sites in the Chaco Canyon area, New Mexico, were compared with isotope values of synthetic soil waters from the same fields. The data indicate that mice obtain Sr from near-surface sources and that soil samples collected at depths ranging from 25 to 95 cm contain Sr that is more accessible to the deep roots of maize; thus, synthetic soil solutions provide better data for the sourcing of archaeological maize. However, the Sr-isotope composition of mice may be more valuable in sourcing archaeological remains of animals such as rabbit, turkey, and deer. In a separate study, five Native American maize (Zea mays L. ssp. mays) accessions grown out at New Mexico State University Agricultural Science Center, Farmington, New Mexico were used to determine if soil-water metal pairs partition systematically into cobs and kernels. The sampled maize included landraces from three Native American groups (Acoma, Hopi, Zuni) that still occupy the Four Corners area. Two cobs each were picked from 10 plants of each landrace. Partitioning of the Ba/Mn, Ba/Sr, Ca/Sr, and K/Rb metal pairs from the soil water to the cob appears to behave in a systematic fashion. In addition, 51 rare earth element (REE) pairs also appear to systematically partition from the soil water into cobs; however, the ratios of the REE dissolved in the soil waters are relatively invariant; therefore, the distribution coefficients that describe the partitioning of REE from the soil water to the cob may not apply to archeological cobs grown under chemically heterogeneous conditions. Partitioning of Ba/Rb, Ba/Sr, Mg/P, and Mn/P metal pairs from the soil water to kernels also behaves in a systematic fashion. Given that modern Native American landraces were grown under optimal environmental conditions that may not have been duplicated by prehistoric Native Americans, the distribution coefficients obtained in this study should be used with caution. ?? 2007 Elsevier Ltd. All rights reserved.

Trace elements in urban and suburban rainfall, Mersin, Northeastern Mediterranean

NASA Astrophysics Data System (ADS)

Özsoy, Türkan; Örnektekin, Sermin

2009-10-01

Spatial/temporal variabilities of rainwater constituents are examined based on soluble/insoluble trace elements, pH and electrical conductivity measurements in rainfall sampled during December 2003-May 2005 at two urban and two suburban sites in Mersin, an industrialized city of 850,000 inhabitants on the southern coast of Turkey. In the analyses, backward air mass trajectories for rainy days were used in addition to factor analyses, enrichment factors, phase distributions and correlations between trace elements. The pH varied from 4.8 to 8.5 with an average value of 6.2, reflecting a mainly alkaline regime. Mean concentrations of trace elements collected from urban and suburban sites are spatially variable. Based on the overall data, total concentrations of trace elements were ordered as Ca > Na > Fe > Al > Mg > K > Zn > Mn > Sr > Pb > Ni > Cr > Ba > Cu > Co > Cd. Mainly terrigeneous (Ca, Fe, Al) and, to a lesser extent, sea salt particles (Na, Mg) were shown to be the major source of trace elements. Excluding major cations, the solubilities of trace elements were found to be ordered as Sr > Zn > Ba > Mn > Cu > Ni > Cr > Fe > Al, confirming the lower solubility of crustal elements. Cd, Co and Pb were excluded from the above evaluation because of the low numbers of soluble samples allowing quantitative measurements. The solubilities of Al, Fe, Mn and particularly of Ni were found to be considerably lower than those reported for various sites around the world, most likely due to the effect of pH. During the entire sampling period, a total of 28 dust transport episodes associated with 31 red rain events were identified. Extremely high mean concentration ratios of Al (8.2), Fe (14.4) and Mn (13.1) were observed in red rain, compared to normal rain. The degree of this enhancement displayed a decrease from crustal to anthropogenic origin elements and the lowest enhancements were found for anthropogenic origin elements of Zn and Cd (both having a ratio of 1.1). Aerosol dust was found to be the main source of almost all analyzed elements in Mersin precipitation, regardless that they are crustal or anthropic derived elements. The magnitude of crustal source contribution to trace element budget of precipitation was at its highest levels for crustal originated elements, most probably due to much higher scavenging ratios of crustal elements compared to anthropogenic ones.

Chemical characteristics and source of size-fractionated atmospheric particle in haze episode in Beijing

NASA Astrophysics Data System (ADS)

Tan, Jihua; Duan, Jingchun; Zhen, Naijia; He, Kebin; Hao, Jiming

2016-01-01

The abundance, behavior, and source of chemical species in size-fractionated atmospheric particle were studied with a 13-stage low pressure impactor (ELPI) during high polluted winter episode in Beijing. Thirty three elements (Al, Ca, Fe, K, Mg, Na, Si, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Zr, Mo, Ag, Cd, In, Sn, Sb, Cs, Ba, Hg, Tl, and Pb) and eight water soluble ions (Cl-, NO3-, SO42 -, NH4+, Na+, K+, Ca2 +, and Mg2 +) were determined by ICP/MS and IC, respectively. The size distribution of TC (OC + EC) was reconstructed. Averagely, 51.5 ± 5.3% and 74.1 ± 3.7% of the total aerosol mass was distributed in the sub-micron (PM1) and fine particle (PM2.5), respectively. A significant shift to larger fractions during heavy pollution episode was observed for aerosol mass, NH4+, SO42 -, NO3-, K, Fe, Cu, Zn, Cd, and Pb. The mass size distributions of NH4+, SO42 -, NO3-, and K were dominated by accumulation mode. Size distributions of elements were classified into four main types: (I) elements were enriched within the accumulation mode (< 1 μm, Ge, Se, Ag, Sn, Sb, Cs, Hg, Ti, and Pb); (II) those mass (K, Cr, Mn, Cu, Zn, As, Mo, and Cd) was resided mainly within the accumulation mode, ranged from 1 to 2 μm; (III) Na, V, Co, Ni, and Ga were distributed among fine, intermediate, and coarse modes; and (IV) those which were mainly found within particles larger than 2.7 μm (Al, Mg, Si, Ca, Sc, Tl, Fe, Sr, Zr, and Ba). [H+]cor showed an accumulation mode at 600-700 nm and the role of Ca2 + should be fully considered in the estimation of acidity. The acidity in accumulation mode particles suggested that generally gaseous NH3 was not enough to neutralize sulfate completely. PMF method was applied for source apportionment of elements combined with water soluble ions. Dust, vehicle, aged coal combustion, and sea salt were identified, and the size resolved source apportionments were discussed. Aged coal combustion was the important source of fine particles and dust contributed most to coarse particle.

Elastic properties of iron-based superconductor SrFe2(As1-xPx)2

NASA Astrophysics Data System (ADS)

Horikoshi, Keita; Imai, Jo; Nakanishi, Yoshiki; Nakamura, Mitsuteru; Kobayashi, Tatsuya; Adachi, Toru; Miyasaka, Shigeki; Tajima, Setsuko; Yoshizawa, Masahito

2018-05-01

We have measured the transverse elastic constants C44 and C66 of iron-based superconductor SrFe2(As1-xPx)2 (Sr122) single crystals as a function of temperature. Under-doped samples show elastic anomalies towards the structural/magnetic transition temperature. Optimal sample shows an upturn at the superconducting transition temperature in both C44 and C66. These behavior is similar to Ba122, while only C66 shows anomaly for Ba122. The elastic anomalies were analyzed by Jahn-Teller formula, and it was found that the Jahn-Teller energy of C44 is much larger than that of C66. This indicates that monoclinic structural fluctuations exist inherently in Sr122 in addition to the known tetragonal fluctuations. Co-existence of these diverse fluctuations and their cooperation are a key to investigate the mechanism and properties of superconductivity in iron based superconductors.

JNK1 Mediates Lipopolysaccharide-Induced CD14 and SR-AI Expression and Macrophage Foam Cell Formation.

PubMed

An, Dong; Hao, Feng; Hu, Chen; Kong, Wei; Xu, Xuemin; Cui, Mei-Zhen

2017-01-01

Foam cell formation is the key process in the development of atherosclerosis. The uptake of oxidized low-density lipoprotein (oxLDL) converts macrophages into foam cells. We recently reported that lipopolysaccharide (LPS)-induced foam cell formation is regulated by CD14 and scavenger receptor AI (SR-AI). In this study, we employed pharmaceutical and gene knockdown approaches to determine the upstream molecular mediators, which control LPS-induced foam cell formation. Our results demonstrated that the specific c-Jun N-terminal kinase (JNK) pathway inhibitor, SP600125, but neither the specific inhibitor of extracellular signaling-regulated kinase (ERK) kinase MEK1/2, U0126, nor the specific inhibitor of p38 MAPK, SB203580, significantly blocks LPS-induced oxLDL uptake, suggesting that the JNK pathway is the upstream mediator of LPS-induced oxLDL uptake/foam cell formation. To address whether JNK pathway mediates LPS-induced oxLDL uptake is due to JNK pathway-regulated CD14 and SR-AI expression, we assessed whether the pharmaceutical inhibitor of JNK influences LPS-induced expression of CD14 and SR-AI. Our results indicate that JNK pathway mediates LPS-induced CD14 and SR-AI expression. To conclusively address the isoform role of JNK family, we depleted JNK isoforms using the JNK isoform-specific siRNA. Our data showed that the depletion of JNK1, but not JNK2 blocked LPS-induced CD14/SR-AI expression and foam cell formation. Taken together, our results reveal for the first time that JNK1 is the key mediator of LPS-induced CD14 and SR-AI expression in macrophages, leading to LPS-induced oxLDL uptake/foam cell formation. We conclude that the novel JNK1/CD14/SR-AI pathway controls macrophage oxLDL uptake/foam cell formation.

Single crystals of the fluorite nonstoichiometric phase Eu{0.916/2+}Eu{0.084/3+}F2.084 (conductivity, transmission, and hardness)

NASA Astrophysics Data System (ADS)

Sobolev, B. P.; Turkina, T. M.; Sorokin, N. I.; Karimov, D. N.; Komar'kova, O. N.; Sulyanova, E. A.

2010-07-01

The nonstoichiometric phase EuF2+ x has been obtained via the partial reduction of EuF3 by elementary Si at 900-1100°C. Eu{0.916/2+}Eu{0.084/3+}F2.084 (EuF2.084) single crystals have been grown from melt by the Bridgman method in a fluorinating atmosphere. These crystals belong to the CaF2 structure type (sp. gr. Fm bar 3 m) with the cubic lattice parameter a = 5.8287(2) Å, are transparent in the spectral range of 0.5-11.3 μm, and have microhardness H μ = 3.12 ± 0.13 GPa and ionic conductivity σ = 1.4 × 10-5 S/cm at 400°C with the ion transport activation energy E a = 1.10 ± 0.05 eV. The physicochemical characteristics of the fluorite phases in the EuF2 - EuF3 systems are similar to those of the phases in the SrF2 - EuF3 and SrF2 - GdF3 systems due to the similar lattice parameters of the EuF2 and SrF2 components. Europium difluoride supplements the list of fluorite components MF2 ( M = Ca, Sr, Ba, Cd, Pb), which are crystal matrices for nonstoichiometric (nanostructured) fluoride materials M 1 - x R x F2 + x ( R are rare earth elements).

Low loss composition of BaxSryCa1-x-yTiO3: Ba0.12-0.25Sr0.35-0.47Ca0.32-0.53TiO3

DOEpatents

Xiang, Xiao-Dong; Chang, Hauyee; Takeuchi, Ichiro

2001-01-01

A dielectric thin-film material for microwave applications, including use as a capacitor, the thin-film comprising a composition of barium strontium calcium and titanium of perovskite type (Ba.sub.x Sr.sub.y Ca.sub.1-x-y)TiO.sub.3. Also provided is a method for making a dielectric thin film of that formula over a wide compositional range through a single deposition process.

Split-Ring Resonator Loaded Miniaturised Slot for the Slotted Waveguide Antenna Stiffened Structure

DTIC Science & Technology

2011-03-01

explains the material analysis of BST varactors using the new sputterer so the varactors can be fabricated at RMIT university and utilised for the SRR...44-0093 (*) - Barium Strontium Titanium Oxide - Ba0.77Sr0.23TiO3 - Y: 0.10 % - d x by: 1. - WL: 1.5406 - Tetragonal - Operations: Import D:\\Sensors...unknown unknown BST on sapphire - 2 44-0093 (*) - Barium Strontium Titanium Oxide - Ba0.77Sr0.23TiO3 - Y: 0.10 % - d x by: 1. - WL: 1.5406 - 0

Investigation of Ba, BaO, Sr and SrO Pulsed Laser-Induced Vapor Plumes in N2, O2, Microwave Discharged O2, and Vacuum at Low Laser Fluence.

DTIC Science & Technology

1996-12-01

Physics and chemistry of the upper atmosphere. Great Britain: Cambridge University Press, 1989. Serway , Raymond A . Physics for Scientists and Engineers...Results ... ......... .69 4.2 Summary of the Spectral Data ..... ........... 70 4.3 Recommendations for Future Study ... ......... .71 Appendix A ...calibration curve to correlate the laser energy setting with the actual output pulse energy. A linear regression resulted in the relation "output" = 1.77 x

Electrolytes comprising metal amide and metal chlorides for multivalent battery

DOEpatents

Liao, Chen; Zhang, Zhengcheng; Burrell, Anthony; Vaughey, John T.

2017-03-21

An electrolyte includes compounds of formula M.sup.1X.sub.n and M.sup.2Z.sub.m; and a solvent wherein M.sup.1 is Mg, Ca, Sr, Ba, Sc, Ti, Al, or Zn; M.sup.2 is Mg, Ca, Sr, Ba, Sc, Ti, Al, or Zn; X is a group forming a covalent bond with M.sup.1; Z is a halogen or pseudo-halogen; n is 1, 2, 3, 4, 5, or 6; and m is 1, 2, 3, 4, 5, or 6.

Spectroscopic and Thermodynamic Characterization of the Metal-Binding Sites in the LH1-RC Complex from Thermophilic Photosynthetic Bacterium Thermochromatium tepidum.

PubMed

Kimura, Yukihiro; Yura, Yuki; Hayashi, Yusuke; Li, Yong; Onoda, Moe; Yu, Long-Jiang; Wang-Otomo, Zheng-Yu; Ohno, Takashi

2016-12-15

The light-harvesting 1 reaction center (LH1-RC) complex from thermophilic photosynthetic bacterium Thermochromatium (Tch.) tepidum exhibits enhanced thermostability and an unusual LH1 Q y transition, both induced by Ca 2+ binding. In this study, metal-binding sites and metal-protein interactions in the LH1-RC complexes from wild-type (B915) and biosynthetically Sr 2+ -substituted (B888) Tch. tepidum were investigated by isothermal titration calorimetry (ITC), atomic absorption (AA), and attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopies. The ITC measurements revealed stoichiometric ratios of approximately 1:1 for binding of Ca 2+ , Sr 2+ , or Ba 2+ to the LH1 αβ-subunit, indicating the presence of 16 binding sites in both B915 and B888. The AA analysis provided direct evidence for Ca 2+ and Sr 2+ binding to B915 and B888, respectively, in their purified states. Metal-binding experiments supported that Ca 2+ and Sr 2+ (or Ba 2+ ) competitively associate with the binding sites in both species. The ATR-FTIR difference spectra upon Ca 2+ depletion and Sr 2+ substitution demonstrated that dissociation and binding of Ca 2+ are predominantly responsible for metal-dependent conformational changes of B915 and B888. The present results are largely compatible with the recent structural evidence that another binding site for Sr 2+ (or Ba 2+ ) exists in the vicinity of the Ca 2+ -binding site, a part of which is shared in both metal-binding sites.

Activation by divalent cations of a Ca2+-activated K+ channel from skeletal muscle membrane.

PubMed

Oberhauser, A; Alvarez, O; Latorre, R

1988-07-01

Several divalent cations were studied as agonists of a Ca2+-activated K+ channel obtained from rat muscle membranes and incorporated into planar lipid bilayers. The effect of these agonists on single-channel currents was tested in the absence and in the presence of Ca2+. Among the divalent cations that activate the channel, Ca2+ is the most effective, followed by Cd2+, Sr2+, Mn2+, Fe2+, and Co2+. Mg2+, Ni2+, Ba2+, Cu2+, Zn2+, Hg2+, and Sn2+ are ineffective. The voltage dependence of channel activation is the same for all the divalent cations. The time-averaged probability of the open state is a sigmoidal function of the divalent cation concentration. The sigmoidal curves are described by a dissociation constant K and a Hill coefficient N. The values of these parameters, measured at 80 mV are: N = 2.1, K = 4 X 10(-7) mMN for Ca2+; N = 3.0, K = 0.02 mMN for Cd2+; N = 1.45, K = 0.63 mMN for Sr2+; N = 1.7, K = 0.94 mMN for Mn2+; N = 1.1, K = 3.0 mMN for Fe2+; and N = 1.1 K = 4.35 mMN for Co2+. In the presence of Ca2+, the divalent cations Cd2+, Co2+, Mn2+, Ni2+, and Mg2+ are able to increase the apparent affinity of the channel for Ca2+ and they increase the Hill coefficient in a concentration-dependent fashion. These divalent cations are only effective when added to the cytoplasmic side of the channel. We suggest that these divalent cations can bind to the channel, unmasking new Ca2+ sites.

How does the spin-state of Co ions affect the insulator-metal transition in Bi2A2Co2O8 (A = Ca, Sr, Ba)?

PubMed Central

Huang, Xiaokun; Zhang, Weiyi

2016-01-01

The misfit layered Bi2A2Co2O8 (A = Ca, Sr, Ba) compounds experience an insulator to metal transition as A’s ionic radius increases. This feature is contradictory to the conventional wisdom that larger lattice constant favors insulating rather than metallic state, and is also difficult to be reconciled using the Anderson weak localization theory. In this paper, we show from the first-principles calculation that an insulator-metal transition takes place from a nonmagnetic low-spin state of Co3+ ions to a hexagonally arranged intermediate-spin low-spin mixed-state in CoO2 plane when ionic radius increases from Ca to Ba. The predicted low-spin state of Bi2Ca2Co2O8 and Bi2Sr2Co2O8 and intermediate-spin low-spin mixed-state of Bi2Ba2Co2O8 are consistent not only with their measured transport properties, but also with the magnetic-field suppressed specific-heat peak observed at the transition temperature. In agreement with experiments, strong electronic correlation is required to stabilize the low-spin insulator and intermediate-spin low-spin metal. PMID:27901119

High pressure low temperature studies on 1-2-2 iron-based superconductors using designer diamond cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uhoya, Walter O.; Tsoi, Georgiy M.; Vohra, Yogesh K.

In this study, high pressure low temperature electrical resistance measurements were carried out on a series of 122 iron-based superconductors using a designer diamond anvil cell. These studies were complemented by image plate x-ray diffraction measurements under high pressures and low temperatures at beamline 16-BM-D, HPCAT, Advanced Photon Source. A common feature of the 1-2-2 iron-based materials is the observation of anomalous compressibility effects under pressure and a Tetragonal (T) to Collapsed Tetragonal (CT) phase transition under high pressures. Specific studies on antiferromagnetic spin-density-wave Ba 0.5Sr 0.5Fe 2As 2 and Ba(Fe 0.9Ru 0.1) 2As 2 samples are presented to 10more » K and 41 GPa. The collapsed tetragonal phase was observed at a pressure of 14 GPa in Ba 0.5Sr 0.5Fe 2As 2 at ambient temperature. The highest superconducting transition temperature in Ba 0.5Sr 0.5Fe 2As 2 was observed to be at 32 K at a pressure of 4.7 GPa. The superconductivity was observed to be suppressed on transformation to the CT phase in 122 materials.« less

How does the spin-state of Co ions affect the insulator-metal transition in Bi2A2Co2O8 (A = Ca, Sr, Ba)?

PubMed

Huang, Xiaokun; Zhang, Weiyi

2016-11-30

The misfit layered Bi 2 A 2 Co 2 O 8 (A = Ca, Sr, Ba) compounds experience an insulator to metal transition as A's ionic radius increases. This feature is contradictory to the conventional wisdom that larger lattice constant favors insulating rather than metallic state, and is also difficult to be reconciled using the Anderson weak localization theory. In this paper, we show from the first-principles calculation that an insulator-metal transition takes place from a nonmagnetic low-spin state of Co 3+ ions to a hexagonally arranged intermediate-spin low-spin mixed-state in CoO 2 plane when ionic radius increases from Ca to Ba. The predicted low-spin state of Bi 2 Ca 2 Co 2 O 8 and Bi 2 Sr 2 Co 2 O 8 and intermediate-spin low-spin mixed-state of Bi 2 Ba 2 Co 2 O 8 are consistent not only with their measured transport properties, but also with the magnetic-field suppressed specific-heat peak observed at the transition temperature. In agreement with experiments, strong electronic correlation is required to stabilize the low-spin insulator and intermediate-spin low-spin metal.

White HDPE bottles as source of serious contamination of water samples with Ba and Zn.

PubMed

Reimann, Clemens; Grimstvedt, Andreas; Frengstad, Bjørn; Finne, Tor Erik

2007-03-15

During a recent study of surface water quality factory new white high-density polyethylene (HDPE) bottles were used for collecting the water samples. According to the established field protocol of the Geological Survey of Norway the bottles were twice carefully rinsed with water in the field prior to sampling. Several blank samples using milli-Q (ELGA) water (>18.2 MOmega) were also prepared. On checking the analytical results the blanks returned values of Ag, Ba, Sr, V, Zn and Zr. For Ba and Zn the values (c. 300 microg/l and 95 microg/l) were about 10 times above the concentrations that can be expected in natural waters. A laboratory test of the bottles demonstrated that the bottles contaminate the samples with significant amounts of Ba and Zn and some Sr. Simple acid washing of the bottles prior to use did not solve the contamination problem for Ba and Zn. The results suggest that there may exist "clean" and "dirty" HDPE bottles depending on manufacturer/production process. When collecting water samples it is mandatory to check bottles regularly as a possible source of contamination.

BA71ΔCD2: a New Recombinant Live Attenuated African Swine Fever Virus with Cross-Protective Capabilities.

PubMed

Monteagudo, Paula L; Lacasta, Anna; López, Elisabeth; Bosch, Laia; Collado, Javier; Pina-Pedrero, Sonia; Correa-Fiz, Florencia; Accensi, Francesc; Navas, María Jesús; Vidal, Enric; Bustos, María J; Rodríguez, Javier M; Gallei, Andreas; Nikolin, Veljko; Salas, María L; Rodríguez, Fernando

2017-11-01

African swine fever is a highly contagious viral disease of mandatory declaration to the World Organization for Animal Health (OIE). The lack of available vaccines makes its control difficult; thus, African swine fever virus (ASFV) represents a major threat to the swine industry. Inactivated vaccines do not confer solid protection against ASFV. Conversely, live attenuated viruses (LAV), either naturally isolated or obtained by genetic manipulation, have demonstrated reliable protection against homologous ASFV strains, although little or no protection has been demonstrated against heterologous viruses. Safety concerns are a major issue for the use of ASFV attenuated vaccine candidates and have hampered their implementation in the field so far. While trying to develop safer and efficient ASFV vaccines, we found that the deletion of the viral CD2v (EP402R) gene highly attenuated the virulent BA71 strain in vivo Inoculation of pigs with the deletion mutant virus BA71ΔCD2 conferred protection not only against lethal challenge with the parental BA71 but also against the heterologous E75 (both genotype I strains). The protection induced was dose dependent, and the cross-protection observed in vivo correlated with the ability of BA71ΔCD2 to induce specific CD8 + T cells capable of recognizing both BA71 and E75 viruses in vitro Interestingly, 100% of the pigs immunized with BA71ΔCD2 also survived lethal challenge with Georgia 2007/1, the genotype II strain of ASFV currently circulating in continental Europe. These results open new avenues to design ASFV cross-protective vaccines, essential to fight ASFV in areas where the virus is endemic and where multiple viruses are circulating. IMPORTANCE African swine fever virus (ASFV) remains enzootic in most countries of Sub-Saharan Africa, today representing a major threat for the development of their swine industry. The uncontrolled presence of ASFV has favored its periodic exportation to other countries, the last event being in Georgia in 2007. Since then, ASFV has spread toward neighboring countries, reaching the European Union's east border in 2014. The lack of available vaccines against ASFV makes its control difficult; so far, only live attenuated viruses have demonstrated solid protection against homologous experimental challenges, but they have failed at inducing solid cross-protective immunity against heterologous viruses. Here we describe a new LAV candidate with unique cross-protective abilities: BA71ΔCD2. Inoculation of BA71ΔCD2 protected pigs not only against experimental challenge with BA71, the virulent parental strain, but also against heterologous viruses, including Georgia 2007/1, the genotype II strain of ASFV currently circulating in Eastern Europe. Copyright © 2017 Monteagudo et al.

BA71ΔCD2: a New Recombinant Live Attenuated African Swine Fever Virus with Cross-Protective Capabilities

PubMed Central

Monteagudo, Paula L.; Lacasta, Anna; López, Elisabeth; Bosch, Laia; Collado, Javier; Pina-Pedrero, Sonia; Correa-Fiz, Florencia; Accensi, Francesc; Navas, María Jesús; Vidal, Enric; Bustos, María J.; Rodríguez, Javier M.; Gallei, Andreas; Nikolin, Veljko; Salas, María L.

2017-01-01

ABSTRACT African swine fever is a highly contagious viral disease of mandatory declaration to the World Organization for Animal Health (OIE). The lack of available vaccines makes its control difficult; thus, African swine fever virus (ASFV) represents a major threat to the swine industry. Inactivated vaccines do not confer solid protection against ASFV. Conversely, live attenuated viruses (LAV), either naturally isolated or obtained by genetic manipulation, have demonstrated reliable protection against homologous ASFV strains, although little or no protection has been demonstrated against heterologous viruses. Safety concerns are a major issue for the use of ASFV attenuated vaccine candidates and have hampered their implementation in the field so far. While trying to develop safer and efficient ASFV vaccines, we found that the deletion of the viral CD2v (EP402R) gene highly attenuated the virulent BA71 strain in vivo. Inoculation of pigs with the deletion mutant virus BA71ΔCD2 conferred protection not only against lethal challenge with the parental BA71 but also against the heterologous E75 (both genotype I strains). The protection induced was dose dependent, and the cross-protection observed in vivo correlated with the ability of BA71ΔCD2 to induce specific CD8+ T cells capable of recognizing both BA71 and E75 viruses in vitro. Interestingly, 100% of the pigs immunized with BA71ΔCD2 also survived lethal challenge with Georgia 2007/1, the genotype II strain of ASFV currently circulating in continental Europe. These results open new avenues to design ASFV cross-protective vaccines, essential to fight ASFV in areas where the virus is endemic and where multiple viruses are circulating. IMPORTANCE African swine fever virus (ASFV) remains enzootic in most countries of Sub-Saharan Africa, today representing a major threat for the development of their swine industry. The uncontrolled presence of ASFV has favored its periodic exportation to other countries, the last event being in Georgia in 2007. Since then, ASFV has spread toward neighboring countries, reaching the European Union's east border in 2014. The lack of available vaccines against ASFV makes its control difficult; so far, only live attenuated viruses have demonstrated solid protection against homologous experimental challenges, but they have failed at inducing solid cross-protective immunity against heterologous viruses. Here we describe a new LAV candidate with unique cross-protective abilities: BA71ΔCD2. Inoculation of BA71ΔCD2 protected pigs not only against experimental challenge with BA71, the virulent parental strain, but also against heterologous viruses, including Georgia 2007/1, the genotype II strain of ASFV currently circulating in Eastern Europe. PMID:28814514

Contraction produced by intracellular injection of calcium, strontium, and barium in the single crayfish muscle fibers.

PubMed

Matsumura, M; Mashima, H

1976-01-01

Ca ions were ionophoretically injected through an intracellular microelectrode into the single muscle fiber of a crayfish, and the resulting contraction sphere was observed under a microscope and photographed with a movie camera. The minimum contraction produced by the threshold current involved usually three or four, sometimes two, sarcomers on both sides of the injecting pipette but contraction involving only one sarcomere was not observered. The rheobase of the Ca-injecting current was 3.2 X 10(-9) A. The strength-duration curves were determined for Ca-, Sr-, and Ba-injecting currents; all fitted a similar hyperbolic equation. The threshold amount of Ca above rheobasic injection was 2.1 X 10(-15)mol, and the ratios between threshold amounts were Ca: Sr: Ba=1: 1.9: 3.0. The effects of Ca and Sr were additive for the contraction. More current was required for the Ca-injection to produce the contraction in the K-depolarized-or 15mM-procaine-treated muscle, although less current was sufficient for the muscle treated with 0.5-1.0 mM of caffeine. The participation of the Ca-induced Ca release mechanism in the contraction produced by Ca injection and the role of Sr or Ba as a substitute for Ca were discussed.

Hydration Energies and Structures of Alkaline Earth Metal Ions, M2+ (H2O)n, n = 5–7, M = Mg, Ca, Sr, and Ba

PubMed Central

Rodriguez-Cruz, Sandra E.; Jockusch, Rebecca A.

2005-01-01

The evaporation of water from hydrated alkaline earth metal ions, produced by electrospray ionization, was studied in a Fourier transform mass spectrometer. Zero-pressure-limit dissociation rate constants for loss of a single water molecule from the hydrated divalent metal ions, M2+(H2O)n (M = Mg, Ca, and Sr for n = 5–7, and M = Ba for n = 4–7), are measured as a function of temperature using blackbody infrared radiative dissociation. From these values, zero-pressure-limit Arrhenius parameters are obtained. By modeling the dissociation kinetics using a master equation formalism, threshold dissociation energies (Eo) are determined. These reactions should have a negligible reverse activation barrier; therefore, Eo values should be approximately equal to the binding energy or hydration enthalpy at 0 K. For the hepta- and hexahydrated ions at low temperature, binding energies follow the trend expected on the basis of ionic radii: Mg > Ca > Sr > Ba. For the hexahydrated ions at high temperature, binding energies follow the order Ca > Mg > Sr > Ba. The same order is observed for the pentahydrated ions. Collisional dissociation experiments on the tetrahydrated species result in relative dissociation rates that directly correlate with the size of the metals. These results indicate the presence of two isomers for hexahydrated magnesium ions: a low-temperature isomer in which the six water molecules are located in the first solvation shell, and a high-temperature isomer with the most likely structure corresponding to four water molecules in the inner shell and two water molecules in the second shell. These results also indicate that the pentahydrated magnesium ions have a structure with four water molecules in the first solvation shell and one in the outer shell. The dissociation kinetics for the hexa- and pentahydrated clusters of Ca2+, Sr2+, and Ba2+ are consistent with structures in which all the water molecules are located in the first solvation shell. PMID:16429612

Early chemical enrichment of the Galactic dwarf satellites from a homogeneous and NLTE abundance analysis

NASA Astrophysics Data System (ADS)

Mashonkina, Lyudmila; Jablonka, Pascale; Sitnova, Tatyana; Pakhomov, Yuri; North, Pierre

2018-06-01

We review recent abundance results for very metal-poor (VMP, -4 ≤ [Fe/H] ≤ -2) stars in seven dwarf spheroidal galaxies (dSphs) and in the Milky Way (MW) halo comparison sample that were obtained based on high-resolution spectroscopic datasets, homogeneous and accurate atmospheric parameters, and the non-local thermodynamic equilibrium (NLTE) line formation for 10 chemical species. A remarkable gain of using such an approach is the reduction, compared to a simple compilation of the literature data, of the spread in abundance ratios at given metallicity within each galaxy and from one to the other. We show that all massive galaxies in our sample, that is, the MW halo and the classical dSphs Sculptor, Ursa Minor, Sextans, and Fornax, reveal a similar plateau at [α/Fe] \\simeq 0.3 for each of the α-process elements: Mg, Ca, and Ti. We put on a firm ground the evidence for a decline in α/Fe with increasing metallicity in the Boötes I ultra-faint dwarf galaxy (UFD), that is most probably due to the ejecta of type Ia supernovae. In our classical dSphs, we observe the dichotomy in the [Sr/Ba] versus [Ba/H] diagram, similarly to the MW halo, calling for two different nucleosynthesis channels for Sr at the earliest evolution stages of these galaxies. Our three UFDs, that is Boötes I, UMa II, and Leo IV, are depleted in Sr and Ba relative to Fe and Mg, with very similar ratios of [Sr/Mg] ≈ -1.3 and [Ba/Mg] ≈ -1 on the entire range of their Mg abundances. The subsolar Sr/Ba ratios of Boötes I and UMa II indicate a common r-process origin of their neutron-capture elements. For Na/Fe, Na/Mg, and Al/Mg, the MW halo and all dSphs reveal indistinguishable trends with metallicity, suggesting that the processes of Na and Al synthesis are identical in all systems, independent of their mass. Sculptor remains the classical dSph, in which the evidence for inhomogeneous mixing in the early evolution stage, at [Fe/H] < -2, is the strongest.

Earthworm Activity and the Potential for Enhanced Leaching of Inorganic Elements in Soils

NASA Astrophysics Data System (ADS)

Gruau, G.; Ablain, F.; Cluzeau, D.

2002-12-01

The potential influence of earthworms on the mobility of soil inorganic constituents was experimentally investigated. Six 20 cm long and 15 cm i.d. columns were packed with soil (loamy material, Paris basin, France). Three earthworm specimens - Lombricus terrestris - were introduced into 3 of the 6 columns (earthworm treatment or ET), the remaing 3 being used to study changes in water composition and solute fluxes without earthworms (control treatment or CT). The 6 columns were operated for 8 weeks and were subjected to 100 ml addition of distilled water at 1, 8, 15, 22, 29, 36, 43 and 50 days. Effluents were collected weekly, filtered and analysed for their Dissolved Organic Carbon (DOC) as well as Si, Na, K, Mg, Ca, Fe, Mn, Al, Sr, Ba, Cu, Zn, Cr, Cd, REE and U concentrations. Replicates yielded extremely consistent results, with standard deviations generally lower than 10%. Effluent volumes were greatest during ET simulations (28% difference on a cumulative basis), which can be attributed to the construction by Lombricus terrestris of permanent vertical burrows into the soil columns. Different temporal chemical trends were observed depending on whether earthworms were present or not. During ET simulations, a washout phenomenon occurred for DOC, Ca, Mg, Fe, Ba, Sr, Cu and U during the startup outflow period (week 2). This washout was followed by a period of apparent equilibrium with concentrations in ET effluents remaining roughly constant for all solutes except REE, Zn and to a lesser extent Mn. No such washout nor equilibrium period was observed during CT simulations. Instead, concentrations in Ca, Mg, Fe, Ba, Sr, Cr and Cu decreased from week 2 to week 8, while those in other solutes increased from week 2 to week 5, then declining untill week 8. For many elements (not all), final (equilibrium?) concentrations (8 weeks simulation) were highest in ET effluents (e.g. 17% higher for Ca and Na; 30% higher for Zn), despite the enhanced infiltration rate (and thus the likely shorter soil-water interaction time). Although preliminary, these results suggest that earthworm activities can potentialy increase the leaching of a wide variety of inorganic elements in soils. This increase could occur through the ability of earthworms to change the biogeochemical conditions in the soil along their burrows (so-called drilosphere).

Solvo-thermal synthesis of a unique alkaline earth-transition Ba-Cd micro-porous coordination framework as hetero-metallic luminescent sensor for Cu2+ and real-time detection of benzaldehyde

NASA Astrophysics Data System (ADS)

Ding, Bin; Ma, Dian Xue; Zhang, Hui Min; Meng, Xin; Qiu, Rong Rong; Ren, Rong; Wu, Jie; Wu, Xiang Xia; Huo, Jian Zhong; Liu, Yuan Yuan; Shi, Xue Fang

2018-06-01

In this work a unique hetero-metallic alkaline earth-transition Ba-Cd luminescent micro-porous metal-organic framework {[BaCd(μ6-tp)1.5(μ2-Cl)(H2O) (DMF)2]·0.75H2O}n (H2tp = terephthalic acid) (1) has been prepared under solvo-thermal conditions. In 1 infinite 1D {Ba-X-Cd} (X = O, Cl) inorganic chains are linked via these full de-pronated tp2- ligands forming a unique 3D I1O2 type micro-porous coordination framework. PXRD patterns of 1 have been determined confirming pure phases of 1. Luminescence investigations suggested that 1 exhibits highly selective and sensitive sensing for trace amounts of benzaldehyde in ethanol, which provides a facile method for real-time detection of benzaldehyde. Meanwhile 1 also exhibits highly selective and sensitive sensing for Cu2+ over other cations with high quenching efficiency Ksv value 1.15 × 104 L·mol-1. As far as we know, 1 represents the first example of alkaline earth-transition hetero-metallic Ba-Cd micro-porous coordination framework as bi-functional luminescent probes for Cu2+ and benzaldehyde.

Solvo-thermal synthesis of a unique alkaline earth-transition Ba-Cd micro-porous coordination framework as hetero-metallic luminescent sensor for Cu2+ and real-time detection of benzaldehyde.

PubMed

Ding, Bin; Ma, Dian Xue; Zhang, Hui Min; Meng, Xin; Qiu, Rong Rong; Ren, Rong; Wu, Jie; Wu, Xiang Xia; Huo, Jian Zhong; Liu, Yuan Yuan; Shi, Xue Fang

2018-06-15

In this work a unique hetero-metallic alkaline earth-transition Ba-Cd luminescent micro-porous metal-organic framework {[BaCd(μ 6 -tp) 1.5 (μ 2 -Cl)(H 2 O) (DMF) 2 ]·0.75H 2 O} n (H 2 tp=terephthalic acid) (1) has been prepared under solvo-thermal conditions. In 1 infinite 1D {Ba-X-Cd} (X=O, Cl) inorganic chains are linked via these full de-pronated tp 2- ligands forming a unique 3D I 1 O 2 type micro-porous coordination framework. PXRD patterns of 1 have been determined confirming pure phases of 1. Luminescence investigations suggested that 1 exhibits highly selective and sensitive sensing for trace amounts of benzaldehyde in ethanol, which provides a facile method for real-time detection of benzaldehyde. Meanwhile 1 also exhibits highly selective and sensitive sensing for Cu 2+ over other cations with high quenching efficiency K sv value 1.15×10 4 L·mol -1 . As far as we know, 1 represents the first example of alkaline earth-transition hetero-metallic Ba-Cd micro-porous coordination framework as bi-functional luminescent probes for Cu 2+ and benzaldehyde. Copyright © 2018 Elsevier B.V. All rights reserved.

Adsorption preference for divalent metal ions by Lactobacillus casei JCM1134.

PubMed

Endo, Rin; Aoyagi, Hideki

2018-05-09

The removal of harmful metals from the intestinal environment can be inhibited by various ions which can interfere with the adsorption of target metal ions. Therefore, it is important to understand the ion selectivity and adsorption mechanism of the adsorbent. In this study, we estimated the adsorption properties of Lactobacillus casei JCM1134 by analyzing the correlation between its maximum adsorption level (q max ) for seven metals and their ion characteristics. Some metal ions showed altered adsorption levels by L. casei JCM1134 as culture growth time increased. Although it was impossible to identify specific adsorption components, adsorption of Sr and Ba may depend on capsular polysaccharide levels. The maximum adsorption of L. casei JCM1134 (9 h of growth in culture) for divalent metal ions was in the following order: Cu 2+  > Ba 2+  > Sr 2+  > Cd 2+  > Co 2+  > Mg 2+  > Ni 2+ . The q max showed a high positive correlation with the ionic radius. Because this tendency is similar to adsorption occurring through an ion exchange mechanism, it was inferred that an ion exchange mechanism contributed greatly to adsorption by L. casei JCM1134. Because the decrease in the amount of adsorption due to prolonged culture time was remarkable for metals with a large ion radius, it is likely that the adsorption components involved in the ion exchange mechanism decomposed over time. These results and analytical concept may be helpful for designing means to remove harmful metals from the intestinal tract.

Radical bonding: structure and stability of bis(phenalenyl) complexes of divalent metals from across the periodic table.

PubMed

Craciun, Smaranda; Donald, Kelling J

2009-07-06

We examine the bonding possibilities of the bis(phenalenyl) MP(2) sandwich complexes of the divalent metals M = Be, Mg, Ca, Sr, Ba, Zn, Cd, and Hg, at the B3LYP level of theory. The outcome is an extraordinarily diverse class of low symmetry bis(phenalenyl)metal complexes in which bonding preferences and binding enthalpies differ dramatically. The lowest energy group 2 metal MP(2) complexes include an intriguing eta(1),eta(3) BeP(2) structure, and bent eta(6),eta(6) systems for M = Ca, Sr, and Ba. The group 12 bis(phenalenyl) complexes are thermodynamically unstable eta(1),eta(1) slip-sandwich structures. To better understand changes in the structural preferences going from the (eta(6),eta(6)) group 2 to the (eta(1),eta(1)) group 12 complexes, we explored the bonding in the bis(phenalenyl) complexes of transition metals with stable +2 oxidations states between Ca and Zn in period 4. The computed binding enthalpies are large and negative for nearly all of the minimum energy bis(phenalenyl) complexes of the group 2 and the transition metals; they are tiny for MgP(2), and are quite positive for the group 12 systems. The structural preferences and stability of the complexes is a subtle negotiation of several influences: the (un)availability of (n - 1)d and np, orbitals for bonding, the cost of the rehybridization at carbon sites in the phenalenyl rings in preparation for bonding to the metals, and the (P---P) interaction between the phenalenyl radicals.

Assessment of the analytical capabilities of inductively coupled plasma-mass spectrometry

USGS Publications Warehouse

Taylor, Howard E.; Garbarino, John R.

1988-01-01

A thorough assessment of the analytical capabilities of inductively coupled plasma-mass spectrometry was conducted for selected analytes of importance in water quality applications and hydrologic research. A multielement calibration curve technique was designed to produce accurate and precise results in analysis times of approximately one minute. The suite of elements included Al, As, B, Ba, Be, Cd, Co, Cr, Cu, Hg, Li, Mn, Mo, Ni, Pb, Se, Sr, V, and Zn. The effects of sample matrix composition on the accuracy of the determinations showed that matrix elements (such as Na, Ca, Mg, and K) that may be present in natural water samples at concentration levels greater than 50 mg/L resulted in as much as a 10% suppression in ion current for analyte elements. Operational detection limits are presented.

[Age and gender characteristics of the content of macro- and trace elements in the organisms of the children from the European North].

PubMed

Soroko, S I; Maksimova, I A; Protasova, O V

2014-01-01

By means of the nuclear-emission spectral analysis with inductively connected argon plasma were studied the contents of 28 macro- and trace elements (Al, Ag, Li, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, In, K, Mg, Mn, Na, Ni, Mo, P, Zn, Se, Tl, Pb, Sr, S, Si) in the hair of children and teenagers living in the European North of the Russian Federation (Arkhangelsk region). There were revealed both: decrease and increase of some elements' contents. Also were revealed the dynamics of mentioned elements contents in the hair of the same children in different years. Significant individual variability of the macro and trace elements' status of children-northerners and some gender dependence were revealed.

Concentration of stable elements in food products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montford, M.A.; Shank, K.E.; Hendricks, C.

1980-01-01

Food samples were taken from commercial markets and analyzed for stable element content. The concentrations of most stable elements (Ag, Al, As, Au, Ba, Br, Ca, Ce, Cl, Co, Cr, Cs, Cu, Fe, Hf, I, K, La, Mg, Mn, Mo, Na, Rb, Sb, Sc, Se, Sr, Ta, Th, Ti, V, Zn, Zr) were determined using multiple-element neutron activation analysis, while the concentrations of other elements (Cd, Hg, Ni, Pb) were determined using atomic absorption. The relevance of the concentrations found are noted in relation to other literature values. An earlier study was extended to include the determination of the concentrationmore » of stable elements in home-grown products in the vicinity of the Oak Ridge National Laboratory. Comparisons between the commercial and local food-stuff values are discussed.« less

Ternary oxide nanostructures and methods of making same

DOEpatents

Wong, Stanislaus S [Stony Brook, NY; Park, Tae-Jin [Port Jefferson, NY

2009-09-08

A single crystalline ternary nanostructure having the formula A.sub.xB.sub.yO.sub.z, wherein x ranges from 0.25 to 24, and y ranges from 1.5 to 40, and wherein A and B are independently selected from the group consisting of Ag, Al, As, Au, B, Ba, Br, Ca, Cd, Ce, Cl, Cm, Co, Cr, Cs, Cu, Dy, Er, Eu, F, Fe, Ga, Gd, Ge, Hf, Ho, I, In, Ir, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, Os, P, Pb, Pd, Pr, Pt, Rb, Re, Rh, Ru, S, Sb, Sc, Se, Si, Sm, Sn, Sr, Ta, Tb, Tc, Te, Ti, Tl, Tm, U, V, W, Y, Yb, and Zn, wherein the nanostructure is at least 95% free of defects and/or dislocations.

Refractory Materials of Zirconate. Part 2: Synthesis and some properties of strontium, zirconate, calcium zirconate and barium zirconate

NASA Technical Reports Server (NTRS)

Okubo, Tsutomo; Yonemochi, Osamu; Nakamura, Kazuo; Maeda, Minoru

1988-01-01

Chemical compounds SrZrO3, CaZrO3, and BaZrO3 were synthesized by solid reaction and arc fusion, and their properties examined. Results were as follows: (1) in the synthesis of CaZrO3 by solid reaction, ZrO2 solid solution with cubic form was produced, which then changed into CaZrO3; (2) the BaZrO3 was a cubic form and did not show any transformation, while SrZrO3 and CaZrO3 with an orthorhombic form transformed to a cubic form at high temperature; and (3) the solubility of BaZrO3 in acid and its vaporization rate at a high temperature were greater than those of zirconates.

Strain induced enhancement of magnetization in Ba{sub 2}FeMoO{sub 6} based heterostructure with (Ba{sub x}Sr{sub 1-x})TiO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Kyeong-Won; Norton, David P.; Ghosh, Siddhartha, E-mail: ghoshsid@gmail.com

2016-05-14

High quality epitaxial Ba{sub 2}FeMoO{sub 6} thin films and Ba{sub 2}FeMoO{sub 6}–(Ba{sub x}Sr{sub 1−x})TiO{sub 3} bi-layer (BL) and superlattice (SL) structures were grown via pulsed laser deposition under low oxygen pressure, and their structural, magnetic, and magneto-transport properties were examined. Superlattice and bi-layer structures were confirmed by X-ray diffraction patterns. Low temperature magnetic measurement shows that the saturation magnetization (M{sub S}) is significantly higher for SLs and almost similar or lower for BLs, when compared to phase pure Ba{sub 2}FeMoO{sub 6} thin films. The variation of the coercive field (H{sub C}) follows exact opposite trend, where BL samples have highermore » H{sub C} and SL samples have lower H{sub C} than pure Ba{sub 2}FeMoO{sub 6} thin films. Also, a significant decrease of the Curie temperature is found in both BL and SL structures compared to pure Ba{sub 2}FeMoO{sub 6} thin films. Negative magneto-resistance is seen in all the BL and SL structures as well as in pure Ba{sub 2}FeMoO{sub 6} thin films. In contrast to the magnetic properties, the magneto-transport properties do not show much variation with induced strain.« less

Heteroepitaxial growth of Ba1 - xSrxTiO3/YBa2Cu3O7 - x by plasma-enhanced metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Chern, C. S.; Liang, S.; Shi, Z. Q.; Yoon, S.; Safari, A.; Lu, P.; Kear, B. H.; Goodreau, B. H.; Marks, T. J.; Hou, S. Y.

1994-06-01

Epitaxial Ba1-xSrxTiO3(BST)/YBa2Cu3O7-x heterostructures with superior electrical and dielectric properties have been fabricated by plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD). Data of x-ray diffraction and high resolution transmission electron microscopy showed that <100> oriented Ba1-xSrxTiO3 layers were epitaxially deposited on epitaxial (001) YBa2Cu3O7-x layers. The leakage current density through the Ba1-xSrxTiO3 films was about 10-7 A/cm2 at 2 V (about 2×105 V/cm) operation. Moreover, the results of capacitance-temperature measurements showed that the PE-MOCVD Ba1-xSrxTiO3 films had Curie temperatures of about 30 °C and a peak dielectric constant of 600 at zero bias voltage. The Rutherford backscattering spectrometry and x-ray diffraction results showed that the BST film composition was controlled between Ba0.75Sr0.25TiO3 and Ba0.8Sr0.2TiO3. The structural and electrical properties of the Ba1-xSrxTiO3/YBa2Cu3O7-x heterostructure indicated that conductive oxide materials with close lattice to Ba1-xSrxTiO3 can be good candidates for the bottom electrode.

Defect Structures of La1 - y Sr y F3 - y , La1 - y Ba y F3 - y , and Nd1 - y Ca y F3 - y ( y = 0.05, 0.10) Nonstoichiometric Tysonite Phases

NASA Astrophysics Data System (ADS)

Chernaya, T. S.; Verin, I. A.; Khrykina, O. N.; Bolotina, N. B.

2018-01-01

Characteristic features of defect structures of La1 - y Sr y F3 - y , La1 - y Ba y F3 - y , and Nd1 - y Ca y F3 - y ( y = 0.05, 0.10) nonstoichiometric phases of different compositions are determined from X-ray diffraction data. Interest in subtle details of their structure is determined by the possibility of ion transport over fluorine vacancies and by a strong compositional dependence of the ionic conductivity. The La0.95Sr0.05F2.95, La0.95Ba0.05F2.95, and Nd0.95Ca0.05F2.95 phases, as well as the La0.9Ba0.1F2.9 phase, crystallize as β-LaF3 (sp. gr. P3̅c1, Z = 6). The La0.9Sr0.1F2.9 and Nd0.9Ca0.1F2.9 phases lose their superstructure and are described by a cell whose volume is three times smaller (sp. gr. P63/ mmc, Z = 2). Defects of crystal structure R1 - y M y F3 - y are not exhausted by vacancies in fluorine positions. All crystals with a "large" cell are twinned according to the merohedral twin law. The majority of atomic positions in models with a "small" cell are split by group symmetry elements and are occupied statistically.

Design of ternary alkaline-earth metal Sn(II) oxides with potential good p-type conductivity

DOE PAGES

Du, Mao -Hua; Singh, David J.; Zhang, Lijun; ...

2016-04-19

Oxides with good p-type conductivity have been long sought after to achieve high performance all-oxide optoelectronic devices. Divalent Sn(II) based oxides are promising candidates because of their rather dispersive upper valence bands caused by the Sn-5s/O-2p anti-bonding hybridization. There are so far few known Sn(II) oxides being p-type conductive suitable for device applications. Here, we present via first-principles global optimization structure searches a material design study for a hitherto unexplored Sn(II)-based system, ternary alkaline-earth metal Sn(II) oxides in the stoichiometry of MSn 2O 3 (M = Mg, Ca, Sr, Ba). We identify two stable compounds of SrSn 2O 3 andmore » BaSn 2O 3, which can be stabilized by Sn-rich conditions in phase stability diagrams. Their structures follow the Zintl behaviour and consist of basic structural motifs of SnO 3 tetrahedra. Unexpectedly they show distinct electronic properties with band gaps ranging from 1.90 (BaSn 2O 3) to 3.15 (SrSn 2O 3) eV, and hole effective masses ranging from 0.87 (BaSn 2O 3) to above 6.0 (SrSn 2O 3) m0. Further exploration of metastable phases indicates a wide tunability of electronic properties controlled by the details of the bonding between the basic structural motifs. Lastly, this suggests further exploration of alkaline-earth metal Sn(II) oxides for potential applications requiring good p-type conductivity such as transparent conductors and photovoltaic absorbers.« less

CD14 is a key mediator of both lysophosphatidic acid and lipopolysaccharide induction of foam cell formation.

PubMed

An, Dong; Hao, Feng; Zhang, Fuqiang; Kong, Wei; Chun, Jerold; Xu, Xuemin; Cui, Mei-Zhen

2017-09-01

Macrophage uptake of oxidized low-density lipoprotein (oxLDL) plays an important role in foam cell formation and the pathogenesis of atherosclerosis. We report here that lysophosphatidic acid (LPA) enhances lipopolysaccharide (LPS)-induced oxLDL uptake in macrophages. Our data revealed that both LPA and LPS highly induce the CD14 expression at messenger RNA and protein levels in macrophages. The role of CD14, one component of the LPS receptor cluster, in LPA-induced biological functions has been unknown. We took several steps to examine the role of CD14 in LPA signaling pathways. Knockdown of CD14 expression nearly completely blocked LPA/LPS-induced oxLDL uptake in macrophages, demonstrating for the first time that CD14 is a key mediator responsible for both LPA- and LPS-induced oxLDL uptake/foam cell formation. To determine the molecular mechanism mediating CD14 function, we demonstrated that both LPA and LPS significantly induce the expression of scavenger receptor class A type I (SR-AI), which has been implicated in lipid uptake process, and depletion of CD14 levels blocked LPA/LPS-induced SR-AI expression. We further showed that the SR-AI-specific antibody, which quenches SR-AI function, blocked LPA- and LPS-induced foam cell formation. Thus, SR-AI is the downstream mediator of CD14 in regulating LPA-, LPS-, and LPA/LPS-induced foam cell formation. Taken together, our results provide the first experimental evidence that CD14 is a novel connecting molecule linking both LPA and LPS pathways and is a key mediator responsible for LPA/LPS-induced foam cell formation. The LPA/LPS-CD14-SR-AI nexus might be the new convergent pathway, contributing to the worsening of atherosclerosis. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Potential ecotoxicological significance of elevated concentrations of strontium in eggshells of passerine birds

USGS Publications Warehouse

Mora, Miguel A.; Taylor, Robert J.; Brattin, Bryan L.

2007-01-01

We investigated the occurrence and potential ecotoxicological significance of elevated concentrations of strontium (Sr) in eggshells of nine passerine birds from four regions in Arizona. Concentrations of Sr in eggshells ranged from 70 to 1360 µg g−1 dry weight (overall mean  =  684 ± 345 SD µg g−1 dw) for the four regions. 23% of the eggshells had Sr concentrations greater than 1000 µg g−1 dw. To our knowledge, these are among the highest levels of Sr that have been reported in bird eggshells in North America. Of the nine species, Brown-headed Cowbirds (Molothrus ater) had the greatest concentrations of Sr. There was a significant positive correlation between Sr and calcium (Ca), and between barium (Ba) and Ca. Ca, Sr, and Ba interact with each other and can exert similar chemical and pharmacological effects. Mean (n ≥ 3) eggshell∶egg ratios for Sr varied with species and ranged from 6.1∶1 to 40.2∶1; ratios for individual eggs reached 92.7∶1. Mean Sr/Ca values ranged from 1.3 × 10−3 to 3.0 × 10−3 and mean eggshell thickness ranged from 83 ± 6 to 120 ± 9 µm for all species. Eggshell thickness was not significantly correlated with Sr for any species but tended to increase with Sr concentrations. We postulate that high concentrations of Sr in the shell could affect later-stage embryos by possible interference with Ca metabolism and bone growth, resulting in reduced hatching success and potential minor beak deformities.

Superconductivity at different T{sub c} in CdBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balchev, N.; Lovchinov, V.; Gattef, E.

1995-06-01

A Cd analogue of the Tl and Hg n=3 series with nominal composition CdBa{sub 2}Ca{sub 2}Cu{sub 3}O{sub y} has been synthesized. The samples were superconducting according to magnetic susceptibility measurements. The critical temperature was 103 or 107 K depending on the preparation conditions. The EDX analysis revealed the presence of Cd-1111, Cd-1121, and Cd-2333 as minor phases. The observed diamagnetic effects were attributed to the different T{sub c} of these phases.

Diamagnetism to ferromagnetism in Sr-substituted epitaxial BaTiO{sub 3} thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singamaneni, Srinivasa Rao, E-mail: ssingam@ncsu.edu; Prater, John T.; Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695

2016-04-04

We report on the ferromagnetic-like behavior in otherwise diamagnetic BaTiO{sub 3} (BTO) thin films upon doping with non-magnetic element Sr having the composition Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} (BST). The epitaxial integration of BST (∼800 nm) thick films on Si (100) substrate was achieved using MgO (40 nm) and TiN (20 nm) as buffer layers to prepare BST/MgO/TiN/Si (100) heterostructure by pulsed laser deposition. The c-axis oriented and cube-on-cube epitaxial BST is formed on Si (100) as evidenced by the in-plane and out-of-plane X-ray diffraction. All the deposited films are relaxed through domain matching epitaxy paradigm as observed from X-ray diffraction pattern and A{submore » 1}TO{sub 3} mode (at 521.27 cm{sup −1}) of Raman spectra. As-deposited BST thin films reveal ferromagnetic-like properties, which persist up to 400 K. The magnetization decreases two-fold upon oxygen annealing. In contrast, as-deposited un-doped BTO films show diamagnetism. Electron spin resonance measurements reveal no evidence of external magnetic impurities. XRD and X-ray photoelectron spectroscopy spectra show significant changes influenced by Sr doping in BTO. The ferromagnetic-like behavior in BST could be due to the trapped electron donors from oxygen vacancies resulting from Sr-doping.« less

Structural, spectroscopic and electronic properties of hydrogen-bonded water molecules in crystals. Ab initio calculations and experimental data of MC1 2· n(H,D) 2O, M = Sr or Ba

NASA Astrophysics Data System (ADS)

Möller, H.; Niu, J. E.; Lutz, H. D.; Schwarz, W. H. E.

1997-12-01

Structural, spectroscopic and electronic properties of (more or less deuterated) water molecules in the crystal fields of SrCl 2·2H 2O, SrCl 2·H 2O and BaCl 2·H 2O, previously investigated by experimental techniques, were calculated by ab initio SCF-MP methods. The H 2O molecules of each compound are asymmetrically surrounded by three adjacent chloride ions, one hydrogen atom being attached to a nearby Cl -, the other less perturbed hydrogen atom bridging the two less near Cl -. The diversity of structural and spectroscopic features found experimentally, for instance the trends from free H 2O to H 2O in BaCl 2·H 2OSrCl 2·H 2OSrCl 2·2H 2O, are well reproduced by the model calculations, which provide the correct assignment and physical interpretation. The differences between the compounds and the asymmetry of the hydrate water molecules can be rationalized with the help of crystal fields. The crystal environment expands the internuclear distances of H 2O by up to 3 pm. The change of vibrational frequencies can be explained qualitatively by only taking the coupling and anharmonicity of the free water molecule and its modified structure in the crystals into account. The infra-red intensities, however, are strongly influenced by the electronic polarization.

Charge-separated and molecular heterobimetallic rare earth-rare earth and alkaline earth-rare earth aryloxo complexes featuring intramolecular metal-pi-arene interactions.

PubMed

Deacon, Glen B; Junk, Peter C; Moxey, Graeme J; Ruhlandt-Senge, Karin; St Prix, Courtney; Zuniga, Maria F

2009-01-01

Treatment of a rare earth metal (Ln) and a potential divalent rare earth metal (Ln') or an alkaline earth metal (Ae) with 2,6-diphenylphenol (HOdpp) at elevated temperatures (200-250 degrees C) afforded heterobimetallic aryloxo complexes, which were structurally characterised. A charge-separated species [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] was obtained for a range of metals, demonstrating the similarities between the chemistry of the divalent rare earth metals and the alkaline earth metals. The [(Ln'/Ae)(2)(Odpp)(3)](+) cation in the heterobimetallic structures is unusual in that it consists solely of bridging aryloxide ligands. A molecular heterobimetallic species [AeEu(Odpp)(4)] (Ae = Ca, Sr, Ba) was obtained by treating an alkaline earth metal and Eu metal with HOdpp at elevated temperatures. Similarly, [BaSr(Odpp)(4)] was prepared by treating Ba metal and Sr metal with HOdpp. Treatment of [Ba(2)(Odpp)(4)] with [Mg(Odpp)(2)(thf)(2)] in toluene afforded [Ba(2)(Odpp)(3)][Mg(Odpp)(3)(thf)]. Analogous solution-based syntheses were not possible for [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] complexes, for which the free-metal route was essential. As a result of the absence of additional donor ligands, the crystal structures of the heterobimetallic complexes feature extensive pi-Ph-metal interactions involving the pendant phenyl groups of the Odpp ligands, thus enabling the large electropositive metal atoms to attain coordination saturation. The charge-separated heterobimetallic species were purified by extraction with toluene/thf mixtures at ambient temperature (Ba-containing compounds) or by extraction with toluene under pressure above the boiling point of the solvent (other products). In donor solvents, heterobimetallic complexes other than those containing barium were found to fragment into homometallic species.

Characterization of ZrO2 buffer layers for sequentially evaporated Y-Ba-CuO on Si and Al2O3 substrates

NASA Technical Reports Server (NTRS)

Valco, George J.; Rohrer, Norman J.; Pouch, John J.; Warner, Joseph D.; Bhasin, Kul B.

1988-01-01

Thin film high temperature superconductors have the potential to change the microwave technology for space communications systems. For such applications it is desirable that the films be formed on substrates such as Al2O3 which have good microwave properties. The use of ZrO2 buffer layers between Y-Ba-Cu-O and the substrate has been investigated. These superconducting films have been formed by multilayer sequential electron beam evaporation of Cu, BaF2 and Y with subsequent annealing. The three layer sequence of Y/BaF2/Cu is repeated four times for a total of twelve layers. Such a multilayer film, approximately 1 micron thick, deposited directly on SrTiO3 and annealed at 900 C for 45 min produces a film with a superconducting onset of 93 K and critical temperature of 85 K. Auger electron spectroscopy in conjunction with argon ion sputtering was used to obtain the distribution of each element as a function of depth for an unannealed film, the annealed film on SrTiO3 and annealed films on ZrO2 buffer layers. The individual layers were apparent. After annealing, the bulk of the film on SrTiO3 is observed to be fairly uniform while films on the substrates with buffer layers are less uniform. The Y-Ba-Cu-O/ZrO2 interface is broad with a long Ba tail into the ZrO2, suggesting interaction between the film and the buffer layer. The underlying ZrO2/Si interface is sharper. The detailed Auger results are presented and compared with samples annealed at different temperatures and durations.

ICP-AES determination of minor- and major elements in apples after microwave assisted digestion.

PubMed

Juranović Cindrić, Iva; Krizman, Ivona; Zeiner, Michaela; Kampić, Štefica; Medunić, Gordana; Stingeder, Gerhard

2012-12-15

The aim of this paper was to determine the content of minor and major elements in apples by inductively coupled plasma atomic emission spectrometry (ICP-AES). Prior to ICP-AES measurement, dried apples were digested in a microwave assisted digestion system. The differences in the measured element concentrations after application of open and closed microwave system as sample preparation procedures are discussed. In whole apples, flesh and peel Ag, Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Sr and Zn were analysed after optimisation and validating the analytical method using ICP-AES. The accuracy of the method determined by spiking experiments was very good (recoveries 88-115%) and the limits of detection of elements of interest were from 0.01 up to 14.7 μg g(-1). The reference ranges determined in all apple samples are 39-47 mg g(-1) for K, 9-14 mg g(-1) for Na, 3-7 mg g(-1) for Mg, 3-7 μg g(-1) for Zn, 0.7-2.8 μg g(-1) for Sr. The range of Mn in peel 4-6 μg g(-1) is higher compared to whole apple from 0.7 to 1.7 μg g(-1). Cd is found only in peel, in the concentration range of 0.4-1.1 μg g(-1). Copyright © 2012 Elsevier Ltd. All rights reserved.

Processing of La(1.8)Sr(0.2)CuO4 and YBa2Cu3O7 superconducting thin films by dual-ion-beam sputtering

NASA Astrophysics Data System (ADS)

Madakson, P.; Cuomo, J. J.; Yee, D. S.; Roy, R. A.; Scilla, G.

1988-03-01

High-quality La(1.8)Sr(0.2)CuO4 and YBa2Cu3O7 superconducting thin films, with zero resistance at 88 K, have been made by dual-ion-beam sputtering of metal and oxide targets at elevated temperatures. The films are about 1.0 micron thick and are single phase after annealing. The substrates investigated are Nd-YAP, MgO, SrF2, Si, CaF2, ZrO2-(9 pct)Y2O3, BaF2, Al2O3, and SrTiO3. Characterization of the films was carried out using Rutherford backscattering spectroscopy, resistivity measurements, TEM, X-ray diffraction, and SIMS. Substrate/film interaction was observed in every case. This generally involves diffusion of the substrate into the film, which is accompanied by, for example, the replacement of Ba by Sr in the YBa2Cu2O7 structure, in the case of SrTiO3 substrate. The best substrates were those that did not significantly diffuse into the film and which did not react chemically with the film.

Inclusion behavior of Cs, Sr, and Ba impurities in LiCl crystal formed by layer-melt crystallization: Combined first-principles calculation and experimental study

NASA Astrophysics Data System (ADS)

Choi, Jung-Hoon; Cho, Yung-Zun; Lee, Tae-Kyo; Eun, Hee-Chul; Kim, Jun-Hong; Kim, In-Tae; Park, Geun-Il; Kang, Jeung-Ku

2013-05-01

The pyroprocessing which uses a dry method to recycle spent oxide fuel generates a waste LiCl salt containing radioactive elements. To reuse LiCl salt, the radioactive impurities has to be separated by the purification process such as layer-melt crystallization. To enhance impurity separation efficiency, it is important to understand the inclusion mechanism of impurities within the LiCl crystal. Herein, we report the inclusion properties of impurities in LiCl crystals. First of all, the substitution enthalpies of Cs+, Sr2+, and Ba2+ impurities with 0-6 at% in LiCl crystal were evaluated via first-principles calculations. Also, the molten LiCl containing 1 mol of Cs+, Sr2+, and Ba2+ impurities was crystallized through the experimental layer-melt crystallization method. These substitution enthalpy and experiment clarify that a high substitution enthalpy should result in the high separation efficiency for an impurity. Furthermore, we find that the electron density map gives a clue to the mechanism for inclusion of impurities into LiCl crystal.

Dual spectra band emissive Eu2+/Mn2+ co-activated alkaline earth phosphates for indoor plant growth novel phosphor converted-LEDs.

PubMed

Yun, Young Jun; Kim, Jin Kyu; Ju, Ji Young; Choi, Seul Ki; Park, Woon Ik; Suh, Jae Yong; Jung, Ha-Kyun; Kim, Yongseon; Choi, Sungho

2017-05-10

This paper reports designing a novel single composition blue/red color illuminating phosphor followed by fabricating "smart" agricultural/horticultural LED lighting. Color-tunable Eu 2+ /Mn 2+ co-activated alkaline earth phosphates, Na(Sr,Ba)PO 4 and Ca 3 Mg 3 (PO 4 ) 4 , are considered, and the stable doping sites for the corresponding activators are identified by using first-principle DFT calculations. We can realize the designated color purity with stable thermal quenching preserved luminescence behavior is induced by the Eu 2+ center positioned at different coordination states with intermixed Sr 2+ /Ba 2+ sites in Na(Sr,Ba)PO 4 hosts. Moreover, we demonstrate that the resultant LED lighting adopting the proposed novel phosphor composition stimulates the enhanced photosynthesis reaction for indoor hydroponics plants, such as oats and onions, which is superior to the narrow line emission band induced by the mixture of conventional red/green/blue LEDs. Thus, using the color-tunable single composition luminescent material may produce an innovative energy-efficient artificial lighting for indoor plant growth.

Strain evolution of each type of grains in poly-crystalline (Ba,Sr)TiO3 thin films grown by sputtering

PubMed Central

Park, Woo Young; Park, Min Hyuk; Lee, Jong Ho; Yoon, Jung Ho; Han, Jeong Hwan; Choi, Jung-Hae; Hwang, Cheol Seong

2012-01-01

The strain states of [111]-, [110]-, and [002]-oriented grains in poly-crystalline sputtered (Ba,Sr)TiO3 thin films on highly [111]-oriented Pt electrode/Si substrates were carefully examined by X-ray diffraction techniques. Remarkably, [002]-oriented grains respond more while [110]- and [111]-oriented grains do less than the theoretically estimated responses, which is understandable from the arrangement of the TiO6 octahedra with respect to the stress direction. Furthermore, such mechanical responses are completely independent of the degree of crystallization and film thickness. The transition growth temperature between the positive and negative strains was also different depending on the grain orientation. The unstrained lattice parameter for each type of grain was different suggesting that the oxygen vacancy concentration for each type of grain is different, too. The results reveal that polycrystalline (Ba,Sr)TiO3 thin films are not an aggregation of differently oriented grains which simply follow the mechanical behavior of single crystal with different orientations. PMID:23230505

Electrical properties of Ba doped LSGM for electrolyte material of solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Raghvendra, Singh, Prabhakar; Singh, Rajesh Kumar

2013-02-01

We report our investigations on Lanthanum Strontium Magnesium Gallate, LSGM, La0.8Sr0.2Ga0.8Mg0.2O3-δ doped with Barium at Strontium site having composition La0.8(Sr0.1Ba0.1)Ga0.8Mg0.2O3-δ (LSBGM). The pure cubic phase along with some additional phase was confirmed by XRD pattern. Electrical properties of the Composition LSBGM [La0.8(Sr0.1Ba0.1)Ga0.8Mg0.2O3-δ] prepared by solid state route, was studied employing impedance spectroscopy in the temperature range 573 K-993 K and frequency range 20 Hz-1MHz. The total ionic conductivity of the composition was found to be 0.072 S.cm-1 at 953 K and the activation energy from Arrhenius plot was found to be 1.16 eV in the measured temperature range. This confirms oxygen ion conductivity in the system. SEM micrograph shows the uniform densed particle morphology with gains of average size 200 nm.

Method for preparing spherical ferrite beads and use thereof

DOEpatents

Lauf, Robert J.; Anderson, Kimberly K.; Montgomery, Frederick C.; Collins, Jack L.

2002-01-01

The invention allows the fabrication of small, dense, highly polished spherical beads of hexagonal ferrites with selected compositions for use in nonreciprocal microwave and mm-wave devices as well as in microwave absorbent or reflective coatings, composites, and the like. A porous, generally spherical bead of hydrous iron oxide is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead is washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) under conditions of elevated temperature and pressure to convert the bead into a mixed hydrous iron-alkaline earth oxide while retaining the generally spherical shape. This mixed oxide bead is then washed, dried, and calcined to produce the desired (BaFe.sub.12 O.sub.19 or SrFe.sub.12 O.sub.19) crystal structure. The calcined bead is then sintered to form a dense bead of the BaFe.sub.12 O.sub.19 and SrFe.sub.12 O.sub.19 phase suitable for polishing and incorporation into various microwave devices and components.

Synthesis, spectroscopic characterization, thermal analysis and electrical conductivity studies of Mg(II), Ca(II), Sr(II) and Ba(II) vitamin B2 complexes

NASA Astrophysics Data System (ADS)

Refat, Moamen S.; Moussa, Mohamed A. A.; Mohamed, Soha F.

2011-05-01

Riboflavin (RF) complexes of Mg(II), Ca(II), Sr(II) and Ba(II) were successfully synthesized. Structures of metal complexes obtained were confirmed and characterized by elemental analysis, molar conductance, and infrared spectra. DC electrical conductivity measurements indicated that the alkaline earth metal (II) complexes of RF ligand are non-electrolytes. Elemental analysis of chelates suggest that the metal(II) ligand ratio is 1:2 with structure formula as [M(RF) 2( X) 2]· nH 2O. Infrared assignments clearly show that RF ligand coordinated as a bidentate feature through azomethine nitrogen of pyrazine ring and C dbnd O of pyrimidine-2,4-dione. Thermal analyses of Mg(II), Ca(II), Sr(II) and Ba(II) complexes were investigated using (TG/DSC) under atmospheric nitrogen between 30 and 800 °C. The surface morphology of the complexes was studied by SEM. The electrical conductivities of RF and its metal complexes were also measured with DC electrical conductivity in the temperature range from room to 483 K.

Theoretical Investigation of Half-Metallic Oxides XFeO3 (X = Sr, Ba) via Modified Becke-Johnson Potential Scheme

NASA Astrophysics Data System (ADS)

Maqsood, Saba; Rashid, Muhammad; Din, Fasih Ud; Saddique, M. Bilal; Laref, A.

2018-03-01

The cubic XFeO3 (X = Sr, Ba) perovskite oxides are studied for their thermodynamic stability in the ferromagnetic phase by using density functional theory calculations. We also explore the elastic properties of these compounds in terms of elastic constants C ij, bulk modulus B, shear modulus G, anisotropy factor A, Poisson's ratio ν and the B/ G ratio. The electronic properties are examined to elucidate the magnetic order, and the thermoelectric properties of XFeO3 (X = Sr, Ba) materials are also presented. The modified Becke-Johnson local density approximation scheme has been used to compute the electronic band structure and density of states, which show that these materials are half-metallic ferromagnetic. We study the magnetic properties by computing the crystal field energy (ΔCF), John-Teller energy (ΔJT) and the exchange splitting energies Δx( d) and Δx( pd). Our results indicate that strong hybridization causes a decrease in the magnetic moment of Fe, which then produces permanent magnetic moments in the nonmagnetic sites.

Average and local structure of the Pb-free ferroelectric perovskites ( Sr , Sn ) TiO 3 and ( Ba , Ca , Sn ) TiO 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laurita, Geneva; Page, Katharine; Suzuki, Shoichiro

2015-12-16

The characteristic structural off -centering of Pb 2+ in oxides, associated with its 6s 2 lone pair, allows it to play a dominant role in polar materials, and makes it a somewhat ubiquitous component of ferroelectrics. In this work, we examine the compounds Sr 0.9Sn 0.1TiO 3 and Ba 0.79Ca 0.16Sn 0.05TiO 3 using neutron total scattering techniques with data acquired at di erent temperatures. In these compounds, previously reported as ferroelectrics, Sn 2+ appears to display some of the characteristics of Pb 2+. We compare the local and long-range structures of the Sn2+-substituted compositions to the unsubstituted parent compoundsmore » SrTiO 3 and BaTiO 3. Lastly, we find that even at these small substitution levels, the Sn 2+ lone pairs drive the local ordering behavior, with the local structure of both compounds more similar to the structure of PbTiO 3 rather than the parent compounds.« less

Solvothermal synthesis of well-dispersed MF2 (M = Ca,Sr,Ba) nanocrystals and their optical properties

NASA Astrophysics Data System (ADS)

Zhang, Xiaoming; Quan, Zewei; Yang, Jun; Yang, Piaoping; Lian, Hongzhou; Lin, Jun

2008-02-01

MF2 (M = Ca,Sr,Ba) nanocrystals (NCs) were synthesized via a solvothermal process in the presence of oleic acid and characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectra, UV/vis absorption spectra, photoluminescence (PL) excitation and emission spectra, and lifetimes, respectively. In the synthetic process, oleic acid as a surfactant played a crucial role in confining the growth and solubility of the MF2 NCs. The as-prepared CaF2, SrF2 and BaF2 NCs present morphologies of truncated octahedron, cube and sheet in a narrow distribution, respectively. Possible growth mechanisms were proposed to explain these results. The as-prepared NCs are highly crystalline and can be well dispersed in cyclohexane to form stable and clear colloidal solutions, which demonstrate strong emission bands centred at 400 nm in photoluminescence (PL) spectra compared with the cyclohexane solvent. The PL properties of the colloidal solutions of the as-prepared NCs can be ascribed to the trap states of surface defects.

Effect of bottom electrode on dielectric property of sputtered-(Ba,Sr)TiO{sub 3} films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ito, Shinichi; Yamada, Tomoaki; Takahashi, Kenji

2009-03-15

(Ba{sub 0.5}Sr{sub 0.5})TiO{sub 3} (BST) films were deposited on (111)Pt/TiO{sub 2}/SiO{sub 2}/Al{sub 2}O{sub 3} substrates by rf sputtering. By inserting a thin layer of SrRuO{sub 3} in between BST film and (111)Pt electrode, the BST films grew fully (111)-oriented without any other orientations. In addition, it enables us to reduce the growth temperature of BST films while keeping the dielectric constant and tunability as high as those of BST films directly deposited on Pt at higher temperatures. The dielectric loss of the films on SrRuO{sub 3}-top substrates was comparable to that on Pt-top substrates for the same level of dielectricmore » constant. The results suggest that the SrRuO{sub 3} thin layer on (111)Pt electrode is an effective approach to growing highly crystalline BST films with (111) orientation at lower deposition temperatures.« less

The effect of plant growth-promoting rhizobacteria on the phytoextraction of Cd and Zn by Brassica napus L.

PubMed

Dąbrowska, G; Hrynkiewicz, K; Trejgell, A; Baum, C

2017-07-03

The test strains Bacteroidetes bacterium (Ba), Pseudomonas fluorescens (Pf) and Variovorax sp. (Va) were selected in advance for their in vitro capability for growth promotion of rapeseed in the presence of increased concentrations of Cd, Cu, Pb and Zn in the medium. In the pot experiment, the strains were used for single Ba, Pf, Va or combined Ba + Pf, Ba + Va, Pf + Va, and Ba + Pf + Va inoculation of B. napus growing in contaminated soil from alluvial deposits. The positive effect of bacterial strains on plant growth was observed in vitro, but was not confirmed in situ in the contaminated soil, where the tested strains inhibited biomass production, rather than stimulating it. However, single inoculation with Ba significantly increased the chlorophyll content and K + concentration in the leaves. The inoculation of rapeseed with Ba and Va strains was indicated to be the most promising combination for phytoextraction of Cd and Zn from contaminated soil. Combined inoculation with Pf+Va and Pf + Ba+Va significantly decreased the concentration of heavy metals in the roots of rapeseed. We conclude that suitable combinations of PGPR can control the metal uptake of B. napus, selectively increasing either metal extraction or metal stabilization in the rhizosphere and offering promising applications in soil remediation.

High stability of electro-transport and magnetism against the A-site cation disorder in SrRuO3

PubMed Central

Wang, Y. L.; Liu, M. F.; Liu, R.; Xie, Y. L.; Li, X.; Yan, Z. B.; Liu, J.-M.

2016-01-01

It is known that the electro-transport and magnetism of perovskite alkaline-earth ruthenate oxides are sensitive to the lattice distortion associated with the A-site cation size. Orthorhombic CaRuO3 and cubic BaRuO3 exhibit distinctly different electro-transport and magnetic properties from orthorhombic SrRuO3. It has been suggested that SrRuO3 can be robust against some intrinsic/external perturbations but fragile against some others in terms of electro-transport and magnetism, and it is our motivation to explore such stability against the local site cation disorder. In this work, we prepare a set of SrRuO3-based samples with identical averaged A-site size but different A-site cation disorder (size mismatch) by Ca and Ba co-substitution of Sr. It is revealed that the electro-transport and magnetism of SrRuO3 demonstrate relatively high stability against this A-site cation disorder, characterized by the relatively invariable electrical and magnetic properties in comparison with those of SrRuO3 itself. A simple electro-transport network model is proposed to explain quantitatively the measured behaviors. The present work suggests that SrRuO3 as an itinerant electron ferromagnetic metal possesses relatively high robustness against local lattice distortion and cation occupation disorder. PMID:27297396

[Immunological balance of CD8+CD28+/CD8+CD28- T lymphocytes can predict gastrointestinal hemorrhage in patients with inflammatory bowel disease].

PubMed

Dai, Shi-Xue; Gu, Hong-Xiang; Wu, Gang; Zhong, Tao; Jian, Hong-Jian; Zhan, Yong-le; Zhang, Min-Hai; Gao, Yong; Xu, Jun; Chen, Dong-Sheng; Liao, Guang-Jie; Feng, Yan-Ling; Liu, Hong-Bo; Zou, Ying; Chi, Hong-Gang

2016-12-20

To evaluate the sensitivity and specificity of CD8 + CD28 + /CD8 + CD28 - T lymphocyte balance in predicting the gastrointestinal hemorrhage (GH) in patients with inflammatory bowel disease (IBD). Forty-nine IBD patients, including 30 with ulcerous colitis (UC) and 19 with Crohn's disease (CD), were enrolled to test peripheral blood CD8 + CD28 + and CD8 + CD28 - T cells using flow cytometry. All the patients were followed up for one year. The receiver-operating characteristic (ROC) curves were used to test the efficiency of CD8 + CD28 + /CD8 + CD28 - T lymphocyte balance to predict GH. The differences in lasting time of remission (LTR) under different factors were compared using Kaplan-Meier survival analysis, and the correlation between CD8 + T lymphocytes and the factors were analyzed. The utilization rates of immunosuppressant, steroids, and biological agent (BA) were significantly higher in CD patients than in UC patients (P=0.003, 0.043 and 0.002, respectively). The frequencies of CD8 + CD28 + T cells were obviously higher in UC patients than those in CD patients (t=3.022, P=0.004). CD8 + CD28 + T cells, CD8 + CD28 - T cells, and especially CD8 + CD28 + /CD8 + CD28 - ratio (area under curve of 0.977, P=0.000; cut-off value of 1.14 [13.95%/12.24%] with a sensitivity of 93.3% and a specificity of 91.2%) showed good efficiencies in predicting GH (P<0.01). The mean and median of LTR of IBD patients who did not receive BA or surgical treatment were significantly longer (Χ 2 =9.730, P=0.002; Χ 2 =15.981, P=0.000). CD8 + CD28 + /CD8 + CD28 - ratio was significantly related to both BA (P=0.009) and surgery (P=0.038). Both decreased CD8 + CD28 + T cells and elevated CD8 + CD28 - T cells are closely correlated with GH, and their ratio can predict the occurrence of GH with a high sensitivity and specificity and is correlated with BA and surgery at the cut-off value of 1.14.

Non-Debye domain-wall-induced dielectric response in Sr0.61-xCexBa0.39Nb2O6

NASA Astrophysics Data System (ADS)

Kleemann, W.; Dec, J.; Miga, S.; Woike, Th.; Pankrath, R.

2002-06-01

Two different non-Debye dielectric spectra are observed in a polydomain relaxor-ferroelectric Sr0.61-xBa0.39Nb2O6:Ce3+x single crystal in the vicinity of its transition temperature, Tc~320 K. At infralow frequencies the susceptibility varies as χ*~ω-β, β~0.2, and is attributed to an irreversible creep-like viscous motion of domain walls, while logarithmic dispersion due to reversible wall relaxation [T. Nattermann, Y. Shapir, and I. Vilfan, Phys. Rev. B 42, 8577 (1990)] occurs at larger ω.

Microwave properties of film Ba x Sr1 - x TiO3 ferroelectric variconds with a magnesium-containing additive

NASA Astrophysics Data System (ADS)

Tumarkin, A. V.; Tepina, E. R.; Nenasheva, E. A.; Kartenko, N. F.; Kozyrev, A. B.

2012-06-01

The electrophysical properties of bulk ceramics based on Ba x Sr1 - x TiO3 solid solutions with a Mg-containing additive and planar variconds based on ferroelectric films obtained by the ion-plasma sputtering of targets with different elemental compositions are studied. Controllability n( U) = C(0)/ C( U) and the dielectric loss tangent (tanδ) of ferroelectric variconds are measured as functions of the elemental composition of the ferroelectric. The figure of merit of the variconds is estimated, and the film composition providing the best electrophysical parameters is determined.

An easy access to nanocrystalline alkaline earth metal fluorides - just by shaking

NASA Astrophysics Data System (ADS)

Dreger, M.; Scholz, G.; Kemnitz, E.

2012-04-01

High energy ball milling as fast, direct and solvent free method allows an easy access to nanocrystalline alkaline earth metal fluorides MF2 (M: Mg, Ca, Sr, Ba). Comparable metal sources (acetates, carbonates, hydroxides, alkoxides) were used for the reaction with NH4F as fluorinating agent. Even very simple manual shaking experiments between NH4F and the corresponding hydroxides in the stoichiometric ratio (M:F = 1:2, M: Ca, Sr, Ba) give phase pure fluorides. Moreover, comparable classical thermal reactions in closed crucibles at higher temperatures provide phase pure crystalline fluorides in nearly all cases as well.

Immune Cell Subsets Evaluation as a Predictive Tool for Hepatitis B Infection Outcome and Treatment Responsiveness.

PubMed

Kandilarova, Snezhina M; Georgieva, Atanaska I; Mihaylova, Anastasiya P; Baleva, Marta P; Atanasova, Valentina K; Petrova, Diana V; Popov, Georgi T; Naumova, Elissaveta J

2017-03-01

The patient's immune response is one of the major factors influencing HBV eradication or chronification, and it is thought to be responsible for the treatment success. Our study aimed to investigate whether cellular defense mechanisms are associated with the course of HBV infection (spontaneous recovery [SR] or chronification [CHB]) and with the therapeutic approach. A total of 139 patients (118 with CHB, 21 SR) and 29 healthy individuals (HI) were immunophenotyped by flowcytometry. Fifty-six patients were treatment-naïve, 20 were treated with interferons and 42 with nucleoside/ nucleotide analogues. Deficiency of T lymphocytes, helper-inducer (CD3+CD4+), suppressorcytotoxic (CD8+CD3+) and cytotoxic (CD8+CD11b-, CD8+CD28+) subsets, activated T cells (CD3+HLA-DR+, CD8+CD38+) and increased CD57+CD8- cells, elevated percentages of B lymphocytes and NKT cells were observed in CHB patients compared with HI. In SR patients, elevated CD8+CD11b+, NKT and activated T cells were found in comparison with controls. The higher values of T cells and their subsets in SR patients than in CHB patients reflect a recovery of cellular immunity in resolved HBV infection individuals. In both groups of treated patients, reduced T lymphocytes, CD3+CD4+ and CD8+CD38+ subsets were found in comparison with HI. Higher proportions of cytotoxic subsets were observed in treated patients compared with treatment-naïve CHB patients, more pronounced in the group with interferon therapy. Our data demonstrate that cellular immune profiles may be of prognostic value in predicting the clinical course of HBV infection, and the determination of the therapeutic response.

[Characterization of structural change of ascorbate peroxidase from Chinese kale during denaturation by circular dichroism].

PubMed

Xi, Jia-Fu; Tang, Lei; Zhang, Jian-Hua; Zhang, Hong-Jian; Chen, Xu-Sheng; Mao, Zhong-Gui

2014-11-01

Circular dichroism (CD) is a special absorption spectrum. The secondary structure of protein such as α-helix, β-sheet and β-turn in the far ultraviolet region (190-250 nm) has a characteristic CD spectrum. In order to understand the activity and structural changes of ascorbate peroxidase from Chinese kale (BaAPX) during denaturation, specific activity and percentage of secondary structure of BaAPX under different time, temperature and concentration were analyzed by CD dynamically. In addition, the percentage of four secondary structures in BaAPX was calculated by CD analysis software Dichroweb. The results show that BaAPX is a full α-type enzyme whose specific activity is positively related to the percentage of α-helix. During denaturation of BaAPX, three kinds of structural changes were proposed: the one-step structural change from initial state (N state) to minimum state of α-helix (R state) under low concentration and low temperature; the one-step structural change from N state to equilibrium state (T state) under high concentration and low temperature; the two-step structural changes from N state through R state to final T state under heat treatment and low temperature renaturation.

Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron-pnictide single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Xin; Park, W.K.; Yuan, H.Q.

2010-04-23

Point-contact Andreev reflection spectroscopy is applied to investigate the gap structure in iron pnictide single-crystal superconductors of the AFe{sub 2}As{sub 2} (A = Ba, Sr) family ('Fe-122'). The observed point-contact junction conductance curves, G(V), can be divided into two categories: one where Andreev reflection is present for both (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} and Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, and the other with a V{sup 2/3} background conductance universally observed, extending even up to 100 meV for Sr{sub 0.6}Na{sub 0.4}Fe{sub 2}As{sub 2} and Sr(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}. The latter is also observed in point-contact junctions on the nonsuperconducting parentmore » compound BaFe{sub 2}As{sub 2} and superconducting (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} crystals. Mesoscopic phase-separated coexistence of magnetic and superconducting orders is considered to explain distinct behaviors in the superconducting samples. For Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2}, double peaks due to Andreev reflection with a strongly sloping background are frequently observed for point contacts on freshly cleaved c-axis surfaces. If normalized using a background baseline and analyzed using the Blonder–Tinkham–Klapwijk model, the data show a gap size of ~ 3.0–4.0 meV with 2Δ{sub 0}/k{sub B}T{sub c} ~ 2.0–2.6, consistent with the smaller gap size reported for the LnFeAsO family ('Fe-1111'). For the Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, the G(V) curves typically display a zero-bias conductance peak.« less

Point-contact spectroscopic studies on normal and superconducting AFe2As2-type iron pnictide single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Xin; Park, W. K.; Yuan, H. Q.

2010-01-01

Point-contact Andreev reflection spectroscopy is applied to investigate the gap structure in iron pnictide single-crystal superconductors of the AFe{sub 2}As{sub 2} (A = Ba, Sr) family (Fe-122). The observed point-contact junction conductance curves, G(V), can be divided into two categories: one where Andreev reflection is present for both (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} and Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, and the other with a V{sup 2/3} background conductance universally observed, extending even up to 100 meV for Sr{sub 0.6}Na{sub 0.4}Fe{sub 2}As{sub 2} and Sr(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}. The latter is also observed in point-contact junctions on the nonsuperconducting parentmore » compound BaFe{sub 2}As{sub 2} and superconducting (Ba{sub 0.6}K{sub 0.4})Fe{sub 2}As{sub 2} crystals. Mesoscopic phase-separated coexistence of magnetic and superconducting orders is considered to explain distinct behaviors in the superconducting samples. For Ba{sub 0.6}K{sub 0.4}Fe{sub 2}As{sub 2}, double peaks due to Andreev reflection with a strongly sloping background are frequently observed for point contacts on freshly cleaved c-axis surfaces. If normalized using a background baseline and analyzed using the Blonder-Tinkham-Klapwijk model, the data show a gap size of {approx} 3.0-4.0 meV with 2{Delta}{sub 0}/k{sub B}T{sub c} {approx} 2.0-2.6, consistent with the smaller gap size reported for the LnFeAsO family (Fe-1111). For the Ba(Fe{sub 0.9}Co{sub 0.1}){sub 2}As{sub 2}, the G(V) curves typically display a zero-bias conductance peak.« less

Crystal residence times from trace element zoning in plagioclase reveal changes in magma transfer dynamics at Mt. Etna during the last 400 years

NASA Astrophysics Data System (ADS)

Viccaro, Marco; Barca, Donatella; Bohrson, Wendy A.; D'Oriano, Claudia; Giuffrida, Marisa; Nicotra, Eugenio; Pitcher, Bradley W.

2016-04-01

Trace element zoning in plagioclase of selected alkaline lavas from the historic (1607-1892 AD) and recent (1983-2013 AD) activity of Mt. Etna volcano has been used to explore the possible role that volcano-tectonics exert on magma transfer dynamics. The observed textural characteristics of crystals include near-equilibrium textures (i.e., oscillatory zoning) and textures with variable extent of disequilibrium (patchy zoning, coarse sieve textures and dissolved cores). Historic crystals exhibit lower K concentrations at lower anorthite contents, a feature in agreement with the general more potassic character of the recent lavas if compared to the historic products. Historic plagioclases have statistically higher Ba and lower Sr concentrations than the recent crystals, which result in different Sr/Ba ratios for the two suites of plagioclase. Variations in the anorthite content along core-to-rim profiles obtained on crystals with different types of textures for both the historic and recent eruptive periods were evaluated particularly versus Sr/Ba. At comparable average An contents, crystals characterized by oscillatory zoning, which are representative of near-equilibrium crystallization from the magma, display distinct Sr/Ba ratios. We suggest that these features are primarily related to recharge of a new, geochemically-distinct magma into the storage and transport system of the volcano. In addition to distinct trace element and textural characteristics of plagioclase, Sr diffusion modeling for plagioclase suggests that residence times are generally shorter for crystals found in recently erupted lavas (25-77 years, average 43 years) compared to those of the historic products (43-163 years, average 99 years). Shorter residences times correlate with gradual increases in eruption volume and eruption frequency rates through time. We attribute these features to an increasing influence, since the 17th century, of extensional tectonic structures within the upper 10 km of the Etnean crust, which have promoted shorter residence times and higher eruption frequency.

Spatial Distribution, Sources Apportionment and Health Risk of Metals in Topsoil in Beijing, China.

PubMed

Sun, Chunyuan; Zhao, Wenji; Zhang, Qianzhong; Yu, Xue; Zheng, Xiaoxia; Zhao, Jiayin; Lv, Ming

2016-07-20

In order to acquire the pollution feature and regularities of distribution of metals in the topsoil within the sixth ring road in Beijing, a total of 46 soil samples were collected, and the concentrations of twelve elements (Nickel, Ni, Lithium, Li, Vanadium, V, Cobalt, Co, Barium, Ba, Strontium, Sr, Chrome, Cr, Molybdenum, Mo, Copper, Cu, Cadmium, Cd, Zinc, Zn, Lead, Pb) were analyzed. Geostatistics and multivariate statistics were conducted to identify spatial distribution characteristics and sources. In addition, the health risk of the analyzed heavy metals to humans (adult) was evaluated by an U.S. Environmental Protection Agency health risk assessment model. The results indicate that these metals have notable variation in spatial scale. The concentration of Cr was high in the west and low in the east, while that of Mo was high in the north and low in the south. High concentrations of Cu, Cd, Zn, and Pb were found in the central part of the city. The average enrichment degree of Cd is 5.94, reaching the standard of significant enrichment. The accumulation of Cr, Mo, Cu, Cd, Zn, and Pb is influenced by anthropogenic activity, including vehicle exhaustion, coal burning, and industrial processes. Health risk assessment shows that both non-carcinogenic and carcinogenic risks of selected heavy metals are within the safety standard and the rank of the carcinogenic risk of the four heavy metals is Cr > Co > Ni > Cd.

Spatial Distribution, Sources Apportionment and Health Risk of Metals in Topsoil in Beijing, China

PubMed Central

Sun, Chunyuan; Zhao, Wenji; Zhang, Qianzhong; Yu, Xue; Zheng, Xiaoxia; Zhao, Jiayin; Lv, Ming

2016-01-01

In order to acquire the pollution feature and regularities of distribution of metals in the topsoil within the sixth ring road in Beijing, a total of 46 soil samples were collected, and the concentrations of twelve elements (Nickel, Ni, Lithium, Li, Vanadium, V, Cobalt, Co, Barium, Ba, Strontium, Sr, Chrome, Cr, Molybdenum, Mo, Copper, Cu, Cadmium, Cd, Zinc, Zn, Lead, Pb) were analyzed. Geostatistics and multivariate statistics were conducted to identify spatial distribution characteristics and sources. In addition, the health risk of the analyzed heavy metals to humans (adult) was evaluated by an U.S. Environmental Protection Agency health risk assessment model. The results indicate that these metals have notable variation in spatial scale. The concentration of Cr was high in the west and low in the east, while that of Mo was high in the north and low in the south. High concentrations of Cu, Cd, Zn, and Pb were found in the central part of the city. The average enrichment degree of Cd is 5.94, reaching the standard of significant enrichment. The accumulation of Cr, Mo, Cu, Cd, Zn, and Pb is influenced by anthropogenic activity, including vehicle exhaustion, coal burning, and industrial processes. Health risk assessment shows that both non-carcinogenic and carcinogenic risks of selected heavy metals are within the safety standard and the rank of the carcinogenic risk of the four heavy metals is Cr > Co > Ni > Cd. PMID:27447657

Source apportionment studies on particulate matter (PM10 and PM2.5) in ambient air of urban Mangalore, India.

PubMed

Kalaiarasan, Gopinath; Balakrishnan, Raj Mohan; Sethunath, Neethu Anitha; Manoharan, Sivamoorthy

2018-07-01

Particulate matter (PM 10 and PM 2.5 ) samples were collected from six sites in urban Mangalore and the mass concentrations for PM 10 and PM 2.5 were measured using gravimetric technique. The measurements were found to exceed the national ambient air quality standards (NAAQS) limits, with the highest concentration of 231.5 μg/m 3 for PM 10 particles at Town hall and 120.3 μg/m 3 for PM 2.5 particles at KMC Attavar. The elemental analysis using inductively coupled plasma optical emission spectrophotometer (ICPOES) revealed twelve different elements (As, Ba, Cd, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Sr and Zn) for PM 10 particles and nine different elements (Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sr and Zn) for PM 2.5 particles. Similarly, ionic composition of these samples measured by ion chromatography (IC) divulged nine different ions (F - , Cl - , NO 3 - , PO 4 3- , SO 4 2- , Na + , K + , Mg 2+ and Ca 2+ ) for PM 10 particles and ten different ions (F - , Cl - , NO 3 - , PO 4 3- , SO 4 2- , Na + , NH 4 + , K + , Mg 2+ and Ca 2+ ) for PM 2.5 particles. The source apportionment study of PM 10 and PM 2.5 for urban Mangalore in accordance with these six sample sites using chemical mass balance model (CMBv8.2) revealed nine and twelve predominant contributors for both PM 10 and PM 2.5 , respectively. The highest contributor of PM 10 was found to be paved road dust followed by diesel and gasoline vehicle emissions. Correspondingly, PM 2.5 was found to be contributed mainly from two-wheeler vehicle emissions followed by four-wheeler and heavy vehicle emissions (diesel vehicles). The current study depicts that the PM 10 and PM 2.5 in ambient air of Mangalore region has 70% of its contribution from vehicular emissions (both exhaust and non-exhaust). Copyright © 2018 Elsevier Ltd. All rights reserved.

Major ions, nutrients, and trace elements in the Mississippi River near Thebes, Illinois, July through September 1993

USGS Publications Warehouse

Taylor, Howard E.; Antweiler, Ronald C.; Brinton, Terry I.; Roth, David A.; Moody, John A.

1994-01-01

Extensive flooding in the upper Mississippi River Basin during summer 1993 had a significant effect on the water quality of the Mississippi River. To evaluate the change in temporal distribution and transport of dissolved constituents in the Mississippi River, six water samples were collected by a discharge-weighted method from July through September 1993 near Thebes, Illinois. Sampling at this location provided water-quality information from the upper Mississippi, the Missouri, and the Illinois River Basins. Dissolved major constituents that were analyzed in each of the samples included bicarbonate, calcium (Ca), carbonate (C03), chloride (Cl), dissolved organic carbon, magnesium (Mg), potassium (K), silica NOD, sodium (Na), and sulfate (S04). Dissolved nutrients included ammonium ion (NH4), nitrate (N03), nitrite (N02), and orthophosphate (P04) . Dissolved trace elements included aluminum (Al), arsenic (As), barium (Ba), boron (B), beryllium (Be), bromide (Br), cadmium (Cd), chromium (Cr), cobalt, (Co), copper (Cu), fluoride (F), iron (Fe), lead, lithium (Li), manganese (Mn), mercury (Hg), molybdenum (Mo), nickel (Ni), strontium (Sr), thallium, uranium (U), vanadium (V), and zinc (Zn). Other physical properties of water that were measured included specific conductance, pH and suspended-sediment concentration (particle size, less than 63 micrometers). Results of this study indicated that large quantities of dissolved constituents were transported through the river system. Generally, pH, alkalinity, and specific conductance and the concentrations of B, Br, Ca, Cl, Cr, K, Li, Mg, Mo, Na, S04, Sr, U, and V increased as water discharge decreased, while concentrations of F, Hg, and suspended sediment sharply decreased as water discharge decreased after the crest of the flood. Concentrations of other constituents, such as Al, As, Ba, Be, Co, Cu, Ni, N03, N02, NH4, P04, and Si02, varied with time as discharge decreased after the crest of the flood. For most constituents, the load transported during floods generally is much greater than that transported during low-flow conditions. How ever, for Cd, Cr, Fe, Mn, V, and Zn, loads increased substantially as water discharge decreased after the crest of the flood.

Dissolved organic matter degradation by sunlight coagulates organo-mineral colloids and produces low-molecular weight fraction of metals in boreal humic waters

NASA Astrophysics Data System (ADS)

Oleinikova, Olga V.; Drozdova, Olga Yu.; Lapitskiy, Sergey A.; Demin, Vladimir V.; Bychkov, Andrey Yu.; Pokrovsky, Oleg S.

2017-08-01

Photochemical degradation of dissolved organic matter (DOM) is recognized as the major driver of CO2 emission to the atmosphere from the inland waters of high latitudes. In contrast to numerous studies of photo-induced DOM transformation, the behavior of trace element (TE) during photodegradation of boreal DOM remains virtually unknown. Towards a better understanding of concentration, size fractionation and speciation change of DOM and TE in boreal waters subjected to solar radiation, we conducted on-site photo-degradation experiments in stream and bog water collected from a pristine zone of the Northern Karelia (Russian subarctic). The removal of Fe and Al occurred only in the bog water (90% and 50% respectively, over 5 days of reaction), whereas no detectable decrease of dissolved (<0.22 μm) Al and Fe concentration was observed in the boreal stream. A number of low-soluble TE linked to Fe-rich organo-mineral colloids followed the behavior of Fe during bog water exposure to sunlight: Al, P, Ti, V, Cr, As, Y, Zr, REEs, Hf, Th, Pb and U. The second group of elements (Li, B, Mg, Ca, Sr, Ba, Na, K, Rb, Si, Mn, Ni, Cu, Co, Cd, Sb) was indifferent to photodegradation of DOM and exhibited a non-systematic variation (±10-15% from the control) of <0.22 μm fraction in the course of sunlight exposure. The bog water insolation yielded a factor of 3 ± 1 increase of low molecular weight (LMW < 1 kDa) fraction of organic carbon, Al, Fe, U, Mg, Ca, Mn, Co, Ni, Sr, Cd and Ba after 200 h of sunlight exposure compared to the dark control. The LMW< 1 kDa fraction was preferentially enriched in Fe, Al, Ca, Mg and other divalent metals relative to Corg. The climate warming leading to water temperature rise in the boreal zone will intensify the Fe and Al hydroxide coagulation while increasing the production of LMW organic ligands and free metals and metal - organic complexes.

In Vitro Investigations of Human Bioaccessibility from Reference Materials Using Simulated Lung Fluids

PubMed Central

Pelfrêne, Aurélie; Cave, Mark R.; Wragg, Joanna; Douay, Francis

2017-01-01

An investigation for assessing pulmonary bioaccessibility of metals from reference materials is presented using simulated lung fluids. The objective of this paper was to contribute to an enhanced understanding of airborne particulate matter and its toxic potential following inhalation. A large set of metallic elements (Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, and Zn) was investigated using three lung fluids (phosphate-buffered saline, Gamble’s solution and artificial lysosomal fluid) on three standard reference materials representing different types of particle sources. Composition of the leaching solution and four solid-to-liquid (S/L) ratios were tested. The results showed that bioaccessibility was speciation- (i.e., distribution) and element-dependent, with percentages varying from 0.04% for Pb to 86.0% for Cd. The higher extraction of metallic elements was obtained with the artificial lysosomal fluid, in which a relative stability of bioaccessibility was observed in a large range of S/L ratios from 1/1000 to 1/10,000. For further investigations, it is suggested that this method be used to assess lung bioaccessibility of metals from smelter-impacted dusts. PMID:28125027

Effect of high-energy electron irradiation in an electron microscope column on fluorides of alkaline earth elements (CaF2, SrF2, and BaF2)

NASA Astrophysics Data System (ADS)

Nikolaichik, V. I.; Sobolev, B. P.; Zaporozhets, M. A.; Avilov, A. S.

2012-03-01

The effect of high-energy (150 eV) electron irradiation in an electron microscope column on crystals of fluorides of alkaline earth elements CaF2, SrF2, and BaF2 is studied. During structural investigations by electron diffraction and electron microscopy, the electron irradiation causes chemical changes in MF2 crystals such as the desorption of fluorine and the accumulation of oxygen in the irradiated area with the formation of oxide MO. The fluorine desorption rate increases significantly when the electron-beam density exceeds the threshold value of ˜2 × 103 pA/cm2). In BaF2 samples, the transformation of BaO into Ba(OH)2 was observed when irradiation stopped. The renewal of irradiation is accompanied by the inverse transformation of Ba(OH)2 into BaO. In the initial stage of irradiation of all MF2 compounds, the oxide phase is in the single-crystal state with a lattice highly matched with the MF2 matrix. When the irradiation dose is increased, the oxide phase passes to the polycrystalline phase. Gaseous products of MF2 destruction (in the form of bubbles several nanometers in diameter) form a rectangular array with a period of ˜20 nm in the sample.

Interfacial charge-mediated non-volatile magnetoelectric coupling in Co 0.3Fe 0.7/Ba 0.6Sr 0.4TiO 3/Nb:SrTiO 3 multiferroic heterostructures

DOE PAGES

Zhou, Ziyao; Howe, Brandon M.; Liu, Ming; ...

2015-01-13

The central challenge in realizing non-volatile, E-field manipulation of magnetism lies in finding an energy efficient means to switch between the distinct magnetic states in a stable and reversible manner. In this work, we demonstrate using electrical polarization-induced charge screening to change the ground state of magnetic ordering in order to non-volatilely tune magnetic properties in ultra-thin Co 0.3Fe 0.7/Ba 0.6Sr 0.4TiO 3/Nb:SrTiO 3 (001) multiferroic heterostructures. A robust, voltage-induced, non-volatile manipulation of out-of-plane magnetic anisotropy up to 40 Oe is demonstrated and confirmed by ferromagnetic resonance measurements. This discovery provides a framework for realizing charge-sensitive order parameter tuning inmore » ultra-thin multiferroic heterostructures, demonstrating great potential for delivering compact, lightweight, reconfigurable, and energy-efficient electronic devices.« less

Internal residual stress studies and enhanced dielectric properties in La0.7Sr0.3CoO3 buffered (Ba,Sr)TiO3 thin films

NASA Astrophysics Data System (ADS)

Lu, Shengbo; Xu, Zhengkui

2009-09-01

Ba0.6Sr0.4TiO3 (BST) thin films were deposited on La0.7Sr0.3CoO3 (LSCO) buffered and unbuffered Pt (111)/Ti/SiO2/Si substrates by pulsed laser deposition. The former exhibits a (100) preferred orientation and the latter a random orientation, respectively. Grazing incident x-ray diffraction study revealed that the tensile residual stress observed in the latter is markedly reduced in the former. As a result, the dielectric property of the LSCO buffered BST thin film is greatly improved, which shows a larger dielectric constant and tunability, smaller loss tangent, and lower leakage current than those of the unbuffered BST thin film. The relaxation of the larger tensile residual stress is attributed to the larger grain size in the buffered BST thin film and to a closer match of thermal expansion coefficient between the BST and the LSCO buffer layer.

Superconducting Sr 2- xAxCuO 2F 2+ δ( A=Ca, Ba): Synthetic Pathways and Associated Structural Rearrangements

NASA Astrophysics Data System (ADS)

Francesconi, M. G.; Slater, P. R.; Hodges, J. P.; Greaves, C.; Edwards, P. P.; Al-Mamouri, M.; Slaski, M.

1998-01-01

The low-temperature fluorination of a range of insulating alkaline earth cuprates Sr2-xAxCuO3(A=Ca (0≤x≤2);A=Ba (0≤x≤0.6)) can result in superconducting oxide fluorides Sr2-xAxCuO2F2+δ. In contrast, conventional high-temperature solid-state reactions produce thermodynamically more stable mixtures of oxides and fluorides. Various soft-chemistry fluorination pathways (utilizing F2gas, NH4F,MF2[M=Cu, Zn, Ni, Ag]) are compared with respect to their efficacy and mechanisms. Attention is also focused on the structural features of the mixed-oxide precursor and the final-oxide fluorides to highlight the remarkable structural rearrangements that occur during the low-temperature fluorination. The effects of fluorination of other Sr-Cu-O systems are used to identify the structural requirements of the precursor oxide in order to achieve such transformations.

Crystallographic orientation of epitaxial BaTiO3 films: The role of thermal-expansion mismatch with the substrate

NASA Astrophysics Data System (ADS)

Srikant, V.; Tarsa, E. J.; Clarke, D. R.; Speck, J. S.

1995-02-01

Expitaxial ferroelectric BaTiO3 thin films have been grown on (001) MgO and MgO-buffered (001) GaAs substrates by pulsed laser deposition to explore the effect of substrate lattice parameter. X-ray-diffraction studies showed that the BaTiO3 films on both MgO single-crystal substrates and MgO-buffered (001) GaAs substrates have a cube-on-cube epitaxy; however, for the BaTiO3 films grown on MgO the spacing of the planes parallel to the substrate was close to the c-axis dimension of the unconstrained tetragonal phase, whereas the BaTiO3 films on MgO/GaAs exhibited a spacing closer to the a-axis dimension of the unconstrained tetragonal phase. The cube-on-cube epitaxy was maintained through the heterostructures even when thin epitaxial intermediate buffer layers of SrTiO3 and La(0.5)Sr(0.5)CoO3 were used. The intermediate layers had no effect on the position of the BaTiO3 peak in theta - 2 theta scans. Together, these observations indicate that, for the materials combinations studied, it is the thermal-expansion mismatch between the film and the underlying substrate that determines the crystallographic orientation of the BaTiO3 film. Preliminary measurements indicate that the BaTiO3 films are 'weakly' ferroelectric.

Associations of semen quality with non-essential heavy metals in blood and seminal fluid: data from the Environment and Male Infertility (EMI) study in Lebanon.

PubMed

Sukhn, Carol; Awwad, Johnny; Ghantous, Akram; Zaatari, Ghazi

2018-06-21

Human exposure to environmental pollutants is widespread. It was suggested that exposure to non-essential heavy metals may adversely affect semen development in men. To evaluate associations between non-essential heavy metals in blood and seminal fluid and semen quality parameters in men. Male partners of heterosexual couples were included. The following elements were measured in blood and seminal fluid: lead (Pb), cadmium (Cd), arsenic (As), barium (Ba), mercury (Hg), and uranium (U) using ion-coupled plasma-mass spectrometry. The fertility clinic at the American University of Beirut Medical Center. Semen quality parameters (volume, concentration, total count, progressive motility, viability, and normal morphology). We found that participants with low-quality semen had significantly higher Cd and Ba concentrations in the seminal fluid than participants with normal-quality semen. We also observed significant associations between low sperm viability and higher blood Cd and Ba, as well as higher seminal Pb, Cd, Ba, and U. Furthermore, U concentrations in the seminal fluid were associated with increased odds ratios for below-reference progressive sperm motility and normal morphology. Environmental exposures to Pb, Cd, Ba, and U appear to adversely influence sperm development in men. In non-occupationally exposed men, measurements of heavy metals in the seminal fluid may be more predictive of below-reference sperm quality parameters than in blood.

The 1201 superconductors Hg1-y(VO4)y(Ba, Sr)2CuO4-2y+δ: evidence for VO4 tetrahedra

NASA Astrophysics Data System (ADS)

Malo, S.; Hervieu, M.; Maignan, A.; Knížek, K.; Raveau, B.; Michel, C.

1997-02-01

A series of mercury based cuprates with nominal composition Hg1-yV(y)Ba2-xSrxCuO4+2y+δ has been prepared for x = 0, 0.25, 0.5, 0.75, 1 and 1.25. The actual solid solution limit from the EDS measurement is x = 1.1, y ranges from 0.2 to 0.35. The single crystal study coupled with high resolution electron microscopy shows for the first time the presence of VO4 tetrahedra replacing partly the mercury atoms according to the formulation Hg1-y(VO4)y(Ba,Sr)2 CuO4-2y+δ. The role of vanadium for the stabilisation of the structure and as a doping agent in the superconducting properties is discussed.

Effects of applied electric field during postannealing on the tunable properties of (Ba,Sr)TiO3 thin films

NASA Astrophysics Data System (ADS)

Xia, Yidong; Cheng, Jinbo; Pan, Bai; Wu, Di; Meng, Xiangkang; Liu, Zhiguo

2005-08-01

The impact of postannealing in electric field on the structure, tunability, and dielectric behavior of rf magnetron sputtering derived (Ba,Sr)TiO3 films has been studied. It has been demonstrated that postannealing in the proper electric field can increase the dielectric constant and the tunability remarkably and destroy the symmetry of capacitance-voltage characteristics of the films. The increased out-of-plane lattice constant and the appearance of the hysteresis loops in the electric-annealed films indicated the formation of small polar regions with tetragonal structure, which are responsible for the increased dielectric constant and tunability. It was proposed that the segregation of Ti3+ ions caused by electric annealing could induce the formation of BaTiO3-like regions, which are ferroelectric at room temperature.

Charge transport mechanism analysis of Al/CdS:Sr{sup 2+}/ITO device under dark and light

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datta, Joydeep; Das, Mrinmay; Dey, Arka

2016-05-06

In this study, we have synthesized CdS:Sr{sup 2+} by hydrothermal technique. Material property has been studied by X-ray diffraction (XRD), Scanning electron microscope (SEM) and UV-vis absorption spectroscopy. XRD data revealed that there are mixed phases of CdS and SrS in the synthesized sample. The optical band gap of the material was estimated as 3.15 eV from UV-vis data. The synthesized material has been applied in metal-semiconductor device and transport properties have been analyzed by measuring current–voltage characteristics under dark and light conditions at room temperature. Variation in different device parameters like ideality factor, barrier height and series resistance ofmore » Al/CdS:Sr{sup 2+}/ITO device were analyzed by using Cheung’s function.« less

ApoA-II modulates the association of HDL with class B scavenger receptors SR-BI and CD36.

PubMed

de Beer, Maria C; Castellani, Lawrence W; Cai, Lei; Stromberg, Arnold J; de Beer, Frederick C; van der Westhuyzen, Deneys R

2004-04-01

The class B scavenger receptors SR-BI and CD36 exhibit a broad ligand binding specificity. SR-BI is well characterized as a HDL receptor that mediates selective cholesteryl ester uptake from HDL. CD36, a receptor for oxidized LDL, also binds HDL and mediates selective cholesteryl ester uptake, although much less efficiently than SR-BI. Apolipoprotein A-II (apoA-II), the second most abundant HDL protein, is considered to be proatherogenic, but the underlying mechanisms are unclear. We previously showed that apoA-II modulates SR-BI-dependent binding and selective uptake of cholesteryl ester from reconstituted HDL. To investigate the effect of apoA-II in naturally occurring HDL on these processes, we compared HDL without apoA-II (from apoA-II null mice) with HDLs containing differing amounts of apoA-II (from C57BL/6 mice and transgenic mice expressing a mouse apoA-II transgene). The level of apoA-II in HDL was inversely correlated with HDL binding and selective cholesteryl ester uptake by both scavenger receptors, particularly CD36. Interestingly, for HDL lacking apoA-II, the efficiency with which CD36 mediated selective uptake reached a level similar to that of SR-BI. These results demonstrate that apoA-II exerts a marked effect on HDL binding and selective lipid uptake by the class B scavenger receptors and establishes a potentially important relationship between apoA-II and CD36.

Electric-field control of electronic transport properties and enhanced magnetoresistance in La0.7Sr0.3MnO3/0.5BaZr0.2Ti0.8O3-0.5Ba0.7Ca0.3TiO3 lead-free multiferroic structures

NASA Astrophysics Data System (ADS)

Yan, Jian-Min; Gao, Guan-Yin; Liu, Yu-Kuai; Wang, Fei-Fei; Zheng, Ren-Kui

2017-10-01

We report the fabrication of lead-free multiferroic structures by depositing ferromagnetic La0.7Sr0.3MnO3 (LSMO) polycrystalline films on polished 0.5BaZr0.2Ti0.8O3-0.5Ba0.7Ca0.3TiO3 (BZT-BCT) piezoelectric ceramic substrates. By applying electric fields to the BZT-BCT along the thickness direction, the resistivity of LSMO films can be effectively manipulated via the piezoelectric strain of the BZT-BCT. Moreover, the LSMO polycrystalline films exhibit almost temperature independent and significantly enhanced magnetoresistance (MR) below TC. At T = 2 K and H = 8 T, the MR of polycrystalline films is approximately two orders of magnitude higher than that of LSMO epitaxial films grown on (LaAlO3)0.3(SrAl1/2Ta1/2O3)0.7 single-crystal substrates. The enhanced MR mainly results from the spin-polarized tunneling of charge carriers across grain boundaries. The LSMO/BZT-BCT structures with electric-field controllable modulation of resistivity and enhanced MR effect may have potential applications in low-energy consumption and environmentally friendly electronic devices.

Strontium and barium in aqueous solution and a potassium channel binding site

NASA Astrophysics Data System (ADS)

Chaudhari, Mangesh I.; Rempe, Susan B.

2018-06-01

Ion hydration structure and free energy establish criteria for understanding selective ion binding in potassium (K+) ion channels and may be significant to understanding blocking mechanisms as well. Recently, we investigated the hydration properties of Ba2+, the most potent blocker of K+ channels among the simple metal ions. Here, we use a similar method of combining ab initio molecular dynamics simulations, statistical mechanical theory, and electronic structure calculations to probe the fundamental hydration properties of Sr2+, which does not block bacterial K+ channels. The radial distribution of water around Sr2+ suggests a stable 8-fold geometry in the local hydration environment, similar to Ba2+. While the predicted hydration free energy of -331.8 kcal/mol is comparable with the experimental result of -334 kcal/mol, the value is significantly more favorable than the -305 kcal/mol hydration free energy of Ba2+. When placed in the innermost K+ channel blocking site, the solvation free energies and lowest energy structures of both Sr2+ and Ba2+ are nearly unchanged compared with their respective hydration properties. This result suggests that the block is not attributable to ion trapping due to +2 charge, and differences in blocking behavior arise due to free energies associated with the exchange of water ligands for channel ligands instead of free energies of transfer from water to the binding site.

New insights into organic-inorganic hybrid perovskite CH₃NH₃PbI₃ nanoparticles. An experimental and theoretical study of doping in Pb²⁺ sites with Sn²⁺, Sr²⁺, Cd²⁺ and Ca²⁺.

PubMed

Navas, Javier; Sánchez-Coronilla, Antonio; Gallardo, Juan Jesús; Hernández, Norge Cruz; Piñero, Jose Carlos; Alcántara, Rodrigo; Fernández-Lorenzo, Concha; De los Santos, Desireé M; Aguilar, Teresa; Martín-Calleja, Joaquín

2015-04-14

This paper presents the synthesis of the organic-inorganic hybrid perovskite, CH3NH3PbI3, doped in the Pb(2+) position with Sn(2+), Sr(2+), Cd(2+) and Ca(2+). The incorporation of the dopants into the crystalline structure was analysed, observing how the characteristics of the dopant affected properties such as the crystalline phase, emission and optical properties. XRD showed how doping with Sn(2+), Sr(2+) and Cd(2+) did not modify the normal tetragonal phase. When doping with Ca(2+), the cubic phase was obtained. Moreover, DR-UV-Vis spectroscopy showed how the band gap decreased with the dopants, the values following the trend Sr(2+) < Cd(2+) < Ca(2+) < CH3NH3PbI3 ≈ Sn(2+). The biggest decrease was generated by Sr(2+), which reduced the CH3NH3PbI3 value by 4.5%. In turn, cathodoluminescence (CL) measurements confirmed the band gap obtained. Periodic-DFT calculations were performed to understand the experimental structures. The DOS analysis confirmed the experimental results obtained using UV-Vis spectroscopy, with the values calculated following the trend Sn(2+) ≈ Pb(2+) > Cd(2+) > Sr(2+) for the tetragonal structure and Pb(2+) > Ca(2+) for the cubic phase. The electron localization function (ELF) analysis showed similar electron localizations for undoped and Sn(2+)-doped tetragonal structures, which were different from those doped with Sr(2+) and Cd(2+). Furthermore, when Cd(2+) was incorporated, the Cd-I interaction was strengthened. For Ca(2+) doping, the Ca-I interaction had a greater ionic nature than Cd-I. Finally, an analysis based on the non-covalent interaction (NCI) index is presented to determine the weak-type interactions of the CH3NH3 groups with the dopant and I atoms. To our knowledge, this kind of analysis with these hybrid systems has not been performed previously.

Synthesis, structure, and bonding of BaTl4. Size effects on encapsulation of cations in electron-poor metal networks.

PubMed

Dai, Jing-Cao; Gupta, Shalabh; Corbett, John D

2011-01-03

The synthesis, structure, and bonding of BaTl(4) are described [C2/m, Z = 4, a = 12.408(3), b = 5.351(1), c = 10.383(2) Å, β = 116.00(3)°]. Pairs of edge-sharing Tl pentagons are condensed to generate a network of pentagonal biprisms along b that encapsulate Ba atoms. Alternating levels of prisms along c afford six more bifunctional Tl atoms about the waists of the biprisms, giving Ba a coordination number of 16. Each Tl atom is bonded to five to seven other Tl atoms and to three to five Ba atoms. There is also strong evidence that Hg substitutes preferentially in the shared edges of the Tl biprisms in BaHg(0.80)Tl(3.20) to generate more strongly bound Hg(2) dimers. Cations that are too small relative to the dimensions of the surrounding polyanionic network make this BaTl(4) structure (and for SrIn(4) and perhaps EuIn(4) as well) one stable alternative to tetragonal BaAl(4)-type structures in which cations are bound in larger hexagon-faced nets, as for BaIn(4) and SrGa(4). Characteristic condensation and augmentation of cation-centered prismatic units is common among many relatively cation- and electron-poor, polar derivatives of Zintl phases gain stability. At the other extreme, the large family of Frank-Kasper phases in which the elements exhibit larger numbers of bonded neighbors are sometimes referred to as orbitally rich.

Hydrothermal synthesis of barium strontium titanate and bismuth titanate materials

NASA Astrophysics Data System (ADS)

Xu, Huiwen

Hydrothermal processing facilitates the synthesis of crystalline ceramic materials of varying composition or complex crystal structure. The present work can be divided into two parts. First is to study the low temperature hydrothermal synthesis of bismuth titanate. Second is to study both thermodynamic and kinetic aspects of the hydrothermally synthesized barium strontium titanate. A chelating agent was used to form a Bi-Ti gel precursor. By hydrothermally treating the Bi-Ti gel, crystalline bismuth titanate has been synthesized at 160°C for the first time. Microstructural evolution during the low temperature synthesis of bismuth titanate can be divided into two stages, including condensation of Bi-Ti gel particles and crystallization of bismuth titanate. Crystallization of bismuth titanate occurred by an in situ transformation mechanism at an early stage followed by a dissolution-reprecipitation mechanism. Phase separation was observed in hydrothermally synthesized barium strontium titanate (BST). By hydrothermally treating BST powders between 250°C--300°C, an asymmetrical miscibility gap was found in the BaTiO3-SrTiO 3 system at low temperatures (T ≤ 320°C). A subregular solid solution model was applied to calculate the equilibrium compositions and the Gibbs free energy of formation of BST solid solution at low temperatures (T ≤ 320°C). The Gibbs free energy of formation of Sr-rich BST phase is larger than that of Ba-rich BST phase. Kinetic studies of single phase BST solid solution at 80°C show that, compared to the BaTiO3 or Ba-rich BST, SrTiO3 and Sr-rich BST powders form at lower reaction rates.

[Study on Hydrothermal Preparation and Luminescence Properties of Luminescent Material BaSrMg(PO₄)₂:Eu³⁺].

PubMed

Hu, Qing-song; Zhu, Cheng-jing; Xia, Yue-yi; Wang, Li-li; Liu, Wen-han; Pan, Zai-fa

2016-02-01

Eu³⁺ doped BaSrMg (PO₄)₂ were prepared by a hydrothermal method. The crystal structure and morphology of BaSrMg(PO₄)₂:Eu³⁺ phosphor were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM). The effects of different pH values (5, 6, 7 and 8) and different reaction temperatures (120, 140, 160, 180 and 200 °C) on the crystal structure and morphology of BaSrMg(PO₄)₂:Eu³⁺ phosphor were studied in this paper. The results of XRD indicate that diffraction peaks are sharp and strong only when pH value is 6, meanwhile the FESEM shows the morphology is regular-shaped. The XRD patterns show amorphous halos superimposed with several weak sharp peaks for the samples preparing under the pH values of 5, 7 and 8. It indicates that these three samples are solid solution or mixed phases, which are in accord with the results of FESEM. From the fluorescence spectra, the peaks in the excitation spectra were assigned to the transition from ⁷F₀ to ⁵D₄, ⁵L₈, ⁵L₆ and ⁵D₂, while the peaks of emission spectra corresponding to the transition of ⁵D₁ --> ⁷F₁ and ⁵D₀-->⁷Fj (J = 0, 1, 2, 3 and 4). The strongest emission peak of the optimized phosphor located at 613 nm (⁵D0--> ⁷F₂), excited by the main excitation peak with wavelength of 394 nm. The splitting of the emission peaks changes depends on pH values and temperatures, which indicating that luminescence properties is closely related to the crystal structure and morphology of particles.

Morphologically well-defined Gd0.1Ce0.9O1.95 embedded Ba0.5Sr0.5Co0.8Fe0.2O3-δ nanofiber with an enhanced triple phase boundary as cathode for low-temperature solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Kim, Chanho; Park, Hyunjung; Jang, Inyoung; Kim, Sungmin; Kim, Kijung; Yoon, Heesung; Paik, Ungyu

2018-02-01

Controlling triple phase boundary (TPB), an intersection of the ionic conductor, electronic conductor and gas phase as a major reaction site, is a key to improve cell performances for low-temperature solid oxide fuel cells. We report a synthesis of morphologically well-defined Gd0.1Ce0.9O1.95 (GDC) embedded Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) nanofibers and their electrochemical performances as a cathode. Electrospun fibers prepared with a polymeric solution that contains crystalline Ba0.5Sr0.5Co0.8Fe0.2O3-δ particles in ∼200 nm size and Gd(NO3)3/Ce(NO3)3 precursors in an optimized weight ratio of 3 to 2 result in one dimensional structure without severe agglomeration and morphological collapse even after a high calcination at 1000 °C. As-prepared nanofibers have fast electron pathways along the axial direction of fibers, a higher surface area of 7.5 m2 g-1, and more oxygen reaction sites at TPBs than those of GDC/BSCF composite particles and core-shell nanofibers. As a result, the Gd0.1Ce0.9O1.95 embedded Ba0.5Sr0.5Co0.8Fe0.2O3-δ nanofiber cell shows excellent performances of the maximum power density of 0.65 W cm-2 at 550 °C and 1.02 W cm-2 at 600 °C, respectively.

Luminescence properties of Sm3+-doped alkaline earth ortho-stannates

NASA Astrophysics Data System (ADS)

Stanulis, Andrius; Katelnikovas, Artūras; Enseling, David; Dutczak, Danuta; Šakirzanovas, Simas; Bael, Marlies Van; Hardy, An; Kareiva, Aivaras; Jüstel, Thomas

2014-05-01

A series of Sm3+ doped M2SnO4 (M = Ca, Sr and Ba) samples were prepared by a conventional high temperature solid-state reaction route. All samples were characterized by powder X-ray diffraction (XRD) analysis, photoluminescence (PL), photoluminescence thermal quenching (TQ) and fluorescence lifetime (FL) measurements. The morphology of synthesized phosphor powders was examined by scanning electron microscopy (SEM). Moreover, luminous efficacies (LE) and color points of the CIE 1931 color space diagram were calculated and discussed. Synthesized powders showed bright orange-red emission under UV excitation. Based on the results obtained we demonstrate that Sm3+ ions occupy Ca and Sr sites in the Ca2SnO4 and Sr2SnO4 ortho-stannate structures, respectively. In contrast, Sm3+ substitutes Sn in the barium ortho-stannate Ba2SnO4 structure.

Synthesis, structural and electrical studies of Ba1-xSrxCe0.65Zr0.25Pr0.1O3-δ electrolyte materials for solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Madhuri Sailaja, J.; Murali, N.; Margarette, S. J.; Mammo, Tulu Wegayehu; Veeraiah, V.

2018-03-01

This paper is discussed Sr doping effect on the microstructure, chemical stability and conductivity of Ba1-xSrxCe0.65Zr0.25Pr0.1O3-δ (0 ≤ x ≤ 0.2) electrolyte prepared by sol-gel method. The lattice constants and unit cell volumes are found to decrease as Sr atomic percentage increased in accordance with the Vegard law, confirming the formation of solid solution with orthorhombic structure. Among them all the synthesized samples are showed a conductivity with different atmosphere values at 500 °C. Ba0.92Sr0.08Ce0.65Zr0.25Pr0.1O3-δ recorded highest conductivity with a value of 3.3 × 10-6 S/cm (dry air) & 3.41 × 10-6 S/cm (wet air with 3% relative humidity) at 500 °C due to its smaller lattice volume, larger grain size and lower activation energy that led to excessive increase in conductivity. All pellets exhibited good chemical stability when exposed to air and H2O atmospheres. This study elucidates that the composition will be a promising electrolyte material for use as SOFC at intermediate temperatures if Sr doping is limited to small amounts.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brgoch, Jakoah; Klob, Simon D.; Denault, Kristin A.

The preparation of Eu 2+-substituted barium aluminum silicates is achieved using a rapid microwave-assisted preparation. The phase evolution of two BaAl 2Si 2O 8:Eu 2+ polymorphs, the higher temperature hexagonal phase (hexacelsian), and the lower temperature monoclinic phase (celsian), is explored by varying the ramp time and soak time. This preparation method significantly reduces the reaction time needed to form these phases compared to conventional solid state routes. The luminescent properties of the two phases are identified under UV excitation with the hexagonal phase emitting in the UV region (λ em = 372 nm) and the monoclinic phase emitting inmore » the blue region (λ em = 438 nm). The differences in optical properties of the two polymorphs are correlated to the coordination number and arrangement of the alkali earth site. The optical properties of the monoclinic phase can be further tuned through the substitution of Sr 2+, forming the solid solution (Ba 1–xSr x)Al 2Si 2O 8:Eu 2+. Changes in the crystal structure due to Sr 2+ substitution produce a surprising blue-shift in the emission spectrum, which is explained by a greater dispersion of bond lengths in the (Ba/Sr)–O polyhedra. The entire monoclinic solid solution exhibits excellent quantum yields of nearly 90 %, owing to the structural rigidity provided by the highly connected tetrahedral network.« less

Accumulation of alkaline earth metals by the green macroalga Bryopsis maxima.

PubMed

Takahashi, Shigekazu; Aizawa, Kyoko; Nakamura, Saki; Nakayama, Katsumi; Fujisaki, Shingo; Watanabe, Soichiro; Satoh, Hiroyuki

2015-04-01

Twenty-five days after the disaster at the Fukushima Daiichi nuclear power plant in 2011, we collected samples of the green macroalga Bryopsis maxima from the Pacific coast of Japan. Bryopsis maxima is a unicellular, multinuclear, siphonous green macroalga. Radiation analysis revealed that B. maxima emitted remarkably high gamma radiation of (131)I, (134)Cs, (137)Cs, and (140)Ba as fission products of (235)U. Interestingly, B. maxima contained naturally occurring radionuclides derived from (226)Ra and (228)Ra. Analysis of element content revealed that B. maxima accumulates many ocean elements, especially high quantities of the alkaline earth metals Sr (15.9 g per dry-kg) and Ba (3.79 g per dry-kg), whereas Ca content (12.5 g per dry-kg) was lower than that of Sr and only 61 % of the mean content of 70 Japanese seaweed species. Time-course analysis determined the rate of radioactive (85)Sr incorporation into thalli to be approximately 0.13 g Sr per dry-kg of thallus per day. Subcellular fractionation of B. maxima cells showed that most of the (85)Sr was localized in the soluble fraction, predominantly in the vacuole or cytosol. Given that (85)Sr radioactivity was permeable through a dialysis membrane, the (85)Sr was considered to be a form of inorganic ion and/or bound with a small molecule. Precipitation analysis with sodium sulfate showed that more than 70% of the Sr did not precipitate as SrSO4, indicating that a proportion of the Sr may bind with small molecules in B. maxima.

Induction of acute hepatic injury by endotoxin in mice.

PubMed

Xie, Guo-Qi; Jiang, Jian-Xin; Chen, Yong-Hua; Liu, Da-Wei; Zhu, Pei-Fang; Wang, Zheng-Guo

2002-11-01

To investigate the changes of scavenger receptor (SR) and CD14 in Kupffer cells in endotoxemia in order to uncover the mechanism of the liver to turn a defense organ into effector one in sepsis. Mouse models of endotoxemia of different severity were reproduced by injection of different doses of lipopolysaccharide (LPS) via the tail vein. The expression of SR and CD14 in the liver was assayed by immunohistochemistry and was subsequently analyzed with an image analysis system. The levels of TNF-alpha and IL-6 in liver tissue were determined with ELISA. The expression of SR in the liver in the high-dose group was markedly decreased one hour after injection of LPS, and also in the low-dose group at 3 hours. The expression of SR in the liver in the two groups was shown to be progressively decreased with the time prolonged. There was significant difference in average optical density (OD) values of SR between the two groups. The expression of CD14 in the two groups was shown to be significantly increased one hour after injection of LPS, and more significantly with the time prolonged. But there was no significant difference in OD values of CD14 between the two groups. The contents of intrahepatic proinflammatory mediators TNF-alpha, IL-6, ALT and TBIL were significantly increased after injection of LPS. Correlation analysis revealed that the changes of TNF-alpha, IL-6, ALT, and TBIL were negatively correlated with the expression of SR, and positively with the expression of CD14. The up-regulation of CD14 expression and down-regulation of SR expression on Kupffer cells might be one of the important mechanisms for the conversion of Kupffer cells from immune defensive to inflammatory response cells in acute hepatic injury.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prakash, Abhinav, E-mail: praka019@umn.edu; Dewey, John; Yun, Hwanhui

Owing to its high room-temperature electron mobility and wide bandgap, BaSnO{sub 3} has recently become of significant interest for potential room-temperature oxide electronics. A hybrid molecular beam epitaxy (MBE) approach for the growth of high-quality BaSnO{sub 3} films is developed in this work. This approach employs hexamethylditin as a chemical precursor for tin, an effusion cell for barium, and a radio frequency plasma source for oxygen. BaSnO{sub 3} films were thus grown on SrTiO{sub 3} (001) and LaAlO{sub 3} (001) substrates. Growth conditions for stoichiometric BaSnO{sub 3} were identified. Reflection high-energy electron diffraction (RHEED) intensity oscillations, characteristic of a layer-by-layermore » growth mode were observed. A critical thickness of ∼1 nm for strain relaxation was determined for films grown on SrTiO{sub 3} using in situ RHEED. Scanning transmission electron microscopy combined with electron energy-loss spectroscopy and energy dispersive x-ray spectroscopy confirmed the cube-on-cube epitaxy and composition. The importance of precursor chemistry is discussed in the context of the MBE growth of BaSnO{sub 3}.« less

Thermoelectric properties of AMg 2X 2, AZn 2Sb 2 (A = Ca, Sr, Ba; X = Sb, Bi), and Ba 2ZnX 2 (X = Sb, Bi) Zintl compounds

DOE PAGES

Sun, Jifeng; Singh, David J.

2017-04-03

In this paper, we report a theoretical investigation of the electronic structure and transport properties of eleven Zintl compounds including nine 122 phases (AMg 2X 2, AZn 2Sb 2 (A = Ca, Sr, Ba; X = Sb, Bi)) and two 212 phases (Ba 2ZnX 2 (X = Sb, Bi)). The electronic structures and electrical transport properties are studied using ab initio calculations and semi-classical Boltzmann theory within the constant relaxation time approximation. All the compounds are semiconducting. We find that the n-type 122 phases with the CaAl 2Si 2 structure type show better performance than p-type materials due to themore » multi-valley degeneracy with anisotropic carrier pockets at and near the conduction band minimum. The pocket anisotropy is beneficial in achieving high conductivity and Seebeck coefficient simultaneously. This mechanism yields substantial improvement in the power factor. Finally, the general performance of 212 phases is inferior to that of the 122 phases, with the Ba 2ZnSb 2 compound showing better performance.« less

Novel and easy access to highly luminescent Eu and Tb doped ultra-small CaF2, SrF2 and BaF2 nanoparticles - structure and luminescence.

PubMed

Ritter, Benjamin; Haida, Philipp; Fink, Friedrich; Krahl, Thoralf; Gawlitza, Kornelia; Rurack, Knut; Scholz, Gudrun; Kemnitz, Erhard

2017-02-28

A universal fast and easy access at room temperature to transparent sols of nanoscopic Eu 3+ and Tb 3+ doped CaF 2 , SrF 2 and BaF 2 particles via the fluorolytic sol-gel synthesis route is presented. Monodisperse quasi-spherical nanoparticles with sizes of 3-20 nm are obtained with up to 40% rare earth doping showing red or green luminescence. In the beginning luminescence quenching effects are only observed for the highest content, which demonstrates the unique and outstanding properties of these materials. From CaF 2 :Eu10 via SrF 2 :Eu10 to BaF 2 :Eu10 a steady increase of the luminescence intensity and lifetime occurs by a factor of ≈2; the photoluminescence quantum yield increases by 29 to 35% due to the lower phonon energy of the matrix. The fast formation process of the particles within fractions of seconds is clearly visualized by exploiting appropriate luminescence processes during the synthesis. Multiply doped particles are also available by this method. Fine tuning of the luminescence properties is achieved by variation of the Ca-to-Sr ratio. Co-doping with Ce 3+ and Tb 3+ results in a huge increase (>50 times) of the green luminescence intensity due to energy transfer Ce 3+ → Tb 3+ . In this case, the luminescence intensity is higher for CaF 2 than for SrF 2 , due to a lower spatial distance of the rare earth ions.

Validity and limitations of the superexchange model for the magnetic properties of Sr2IrO4 and Ba2IrO4 mediated by the strong spin-orbit coupling

NASA Astrophysics Data System (ADS)

Solovyev, I. V.; Mazurenko, V. V.; Katanin, A. A.

2015-12-01

Layered perovskites Sr2IrO4 and Ba2IrO4 are regarded as the key materials for understanding the properties of magnetic relativistic insulators, mediated by the strong spin-orbit (SO) coupling. One of the most fundamental issues is to which extent these properties can be described by the superexchange (SE) model, formulated in the limit of the large Coulomb repulsion for some appropriately selected pseudospin states, and whether these materials themselves can be classified as Mott insulators. In this work, we address these issues by deriving the relevant models and extracting parameters of these models from the electronic-structure calculations with the SO coupling, based on the density functional theory. First, we construct the effective Hubbard-type model for the magnetically active t2 g bands, by recasting the problem in the language of localized Wannier orbitals. Then, we map the obtained electron model onto the pseudospin model by applying the theory of SE interactions, which is based on the second-order perturbation theory with respect to the transfer integrals. We discuss the microscopic origin of anisotropic SE interactions, inherent to the compass Heisenberg model, and the appearance of the antisymmetric Dzyaloshinskii-Moriya term, associated with the additional rotation of the IrO6 octahedra in Sr2IrO4 . In order to solve the pseudospin Hamiltonian problem and evaluate the Néel temperature (TN), we employ the nonlinear sigma model. We have found that, while for Sr2IrO4 our value of TN agrees with the experimental data, for Ba2IrO4 it is overestimated by a factor of 2. We argue that this discrepancy is related to limitations of the SE model: while for more localized t2 g states in Sr2IrO4 it works reasonably well, the higher-order terms in the perturbation theory expansion play a more important role in the more "itinerant" Ba2IrO4 , giving rise to the new type of isotropic and anisotropic exchange interactions, which are not captured by the SE model. This conclusion is supported by unrestricted Hartree-Fock calculations for the same electron model, where in the case of Ba2IrO4 , already on the mean-field level, we were able to reproduce the experimentally observed magnetic ground state, while for Sr2IrO4 the main results are essentially the same as in the SE model.

Hydrogeochemical and Isotopic Indicators of Hydraulic Fracturing Flowback Fluids in Shallow Groundwater and Stream Water, derived from Dameigou Shale Gas Extraction in the Northern Qaidam Basin.

PubMed

Zheng, Zhaoxian; Zhang, Hongda; Chen, Zongyu; Li, Xufeng; Zhu, Pucheng; Cui, Xiaoshun

2017-06-06

Most of the shale gas production in northwest China is from continental shale. Identifying hydrogeochemical and isotopic indicators of toxic hydraulic fracturing flowback fluids (HFFF) has great significance in assessing the safety of drinking water from shallow groundwater and streamwater. Hydrogeochemical and isotopic data for HFFF from the Dameigou shale formations (Cl/Br ratio (1.81 × 10 -4 -6.52 × 10 -4 ), Ba/Sr (>0.2), δ 11 B (-10-1‰), and ε SW Sr (56-65, where ε SW Sr is the deviation of the 87 Sr/ 86 Sr ratio from that of seawater in parts per 10 4 )) were distinct from data for the background saline shallow groundwater and streamwater before fracturing. Mixing models indicated that inorganic elemental signatures (Br/Cl, Ba/Sr) and isotopic fingerprints (δ 11 B, ε SW Sr ) can be used to distinguish between HFFF and conventional oil-field brine in shallow groundwater and streamwater. These diagnostic indicators were applied to identify potential releases of HFFF into shallow groundwater and streamwater during fracturing, flowback and storage. The monitored time series data for shallow groundwater and streamwater exhibit no clear trends along mixing curves toward the HFFF end member, indicating that there is no detectable release occurring at present.

Bean Metal-Responsive Element-Binding Transcription Factor Confers Cadmium Resistance in Tobacco1

PubMed Central

Sun, Na; Liu, Meng; Zhang, Wentao; Yang, Wanning; Bei, Xiujuan; Ma, Hui; Qiao, Fan; Qi, Xiaoting

2015-01-01

Cadmium (Cd) is highly toxic to plants. Modulation of Cd-responsive transcription is an important way for Cd detoxification in plants. Metal-responsive element (MRE) is originally described in animal metallothionein genes. Although functional MREs also exist in Cd-regulated plant genes, specific transcription factors that bind MRE to regulate Cd tolerance have not been identified. Previously, we showed that Cd-inducible bean (Phaseolus vulgaris) stress-related gene2 (PvSR2) produces a short (S) PvSR2 transcript (S-PvSR2) driven by an intronic promoter. Here, we demonstrate that S-PvSR2 encodes a bean MRE-binding transcription factor1 (PvMTF-1) that confers Cd tolerance in tobacco (Nicotiana tabacum). PvMTF-1 expression was up-regulated by Cd at the levels of RNA and protein. Importantly, expression of PvMTF-1 in tobacco enhanced Cd tolerance, indicating its role in regulating Cd resistance in planta. This was achieved through direct regulation of a feedback-insensitive Anthranilate Synthase α-2 chain gene (ASA2), which catalyzes the first step for tryptophan biosynthesis. In vitro and in vivo DNA-protein interaction studies further revealed that PvMTF-1 directly binds to the MRE in the ASA2 promoter, and this binding depends on the zinc finger-like motif of PvMTF-1. Through modulating ASA2 up-regulation by Cd, PvMTF-1 increased free tryptophan level and subsequently reduced Cd accumulation, thereby enhancing Cd tolerance of transgenic tobacco plants. Consistent with this observation, tobacco transiently overexpressing ASA2 also exhibited increased tolerance to Cd. We conclude that PvMTF-1 is a zinc finger-like transcription factor that links MRE to Cd resistance in transgenic tobacco through activation of tryptophan biosynthesis. PMID:25624396

Interaction of angiogenically stimulated intermediate CD163+ monocytes/macrophages with soft hydrophobic poly(n-butyl acrylate) networks with elastic moduli matched to that of human arteries.

PubMed

Mayer, Anke; Kratz, Karl; Hiebl, Bernhard; Lendlein, Andreas; Jung, Friedrich

2012-03-01

The cell population of peripheral blood monocytes/macrophages (MO) is heterogeneous: The majority of the MO are CD14++ CD16- and named "classical" (= MO1). Furthermore, two other subpopulations were described: CD14++ CD16+ ("intermediate" = MO2) and CD14+ CD16++ ("non-classical" = MO3). It is reported that MO2 possess anti-inflammatory properties and express the MO lineage marker CD163. On a hydrophilic neutrally charged acrylamide-based hydrogel human intermediate (CD14++ CD16+ ), angiogenically stimulated CD163++ monocytes/macrophages (aMO2) maintained a proangiogenic and noninflammatory status for at least 14 days. Here, we explored whether this aMO2 subset adhered to hydrophobic poly(n-butyl acrylate) networks (cPnBA) and also remained in its proangiogenic and noninflammatory status. Because substrate elasticity can impact adherence, morphology, and function of cells, cPnBAs with different Young's modulus (250 and 1100 kPa) were investigated, whereby their elasticity was tailored by variation of the cross-linker content and matched to the elasticity of human arteries. The cPnBAs exhibited similar surface properties (e.g., surface roughness), which were maintained after ethylene oxide sterilization and exposure in serum-free cell culture medium for 18 h at 37°C. aMO2 were seeded on cPnBA samples (1.7 × 10(5) cells/1.33 cm(2) ) in Dulbecco's modified Eagle medium (DMEM high glucose) supplemented with vascular endothelial growth factor 165 (VEGF-A(165) , 10 ng/mL) and fetal calf serum (10 vol%) for 3 and 72 h. On both polymeric samples (n = 3 each), the numbers of adherent cells per unit area were significantly higher (P < 0.01; cPnBA0250: 3 h 13 ± 5 cells/mm(2) , 72 h 234 ± 106 cells/mm(2) ; cPnBA1100: 3 h 14 ± 3 cells/mm(2) , 72 h 198 ± 113 cells/mm(2) ) compared to control cultures (glass, 3 h: 6 ± 3 cells/mm(2) , 72 h: 130 ± 83 cells/mm(2) ) and showed a typically spread morphology. The mRNA expression profile of the aMO2 was not influenced by the substrate elasticity. In the supernatant of aMO2 on cPnBA0250, significantly less VEGF-A(165) product was found than expected based on the mRNA level measured (P < 0.01). Tests with recombinant VEGF-A(165) then demonstrated that significantly more VEGF-A(165) was adhered on cPnBA0250 than on cPnBA1100 (P < 0.01). Seeded on cPnBA, aMO2-unaffected by the elastic moduli of both substrates-seemed to remain in their subset status and secreted VEGF-A(165) without release of proinflammatory cytokines. These in vitro results might indicate that this MO subset can be used as cellular delivery system for proangiogenic and noninflammatory mediators to support the endothelialization of cPnBA. © 2012, Copyright the Authors. Artificial Organs © 2012, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Extended Abstracts. International Symposium on Halide Glasses (2nd), Rensselaer Polytechnic Institute, Troy, New York, USA, 2-5 August 1983.

DTIC Science & Technology

1983-08-02

Research and Development in ’" T. Miyashita and i.. . nabe 34 "Environmental Effects on the Strength of Fluoride Glass Fibers" A. Nakata, J. Lau, and J...continuous optical window. Ujnfortunately YVP3 ony permit’s thin samiples (1 mm) to be synthesized. Vitrco&us domnain ina the ternary sys ~tem TIT "Zni - YbF 4...synthesis methods, quenched glasses have been obtained in the CdF2-ZnF 2-BaF2 and CdF2-MnF2-BaF 2 ternary sys - tems. Binary glasses (Cd0 .5Ba0 .5 )F2 have

Radionuclide transfer to reptiles.

PubMed

Wood, Michael D; Beresford, Nicholas A; Semenov, Dmitry V; Yankovich, Tamara L; Copplestone, David

2010-11-01

Reptiles are an important, and often protected, component of many ecosystems but have rarely been fully considered within ecological risk assessments (ERA) due to a paucity of data on contaminant uptake and effects. This paper presents a meta-analysis of literature-derived environmental media (soil and water) to whole-body concentration ratios (CRs) for predicting the transfer of 35 elements (Am, As, B, Ba, Ca, Cd, Ce, Cm, Co, Cr, Cs, Cu, Fe, Hg, K, La, Mg, Mn, Mo, Na, Ni, Pb, Po, Pu, Ra, Rb, Sb, Se, Sr, Th, U, V, Y, Zn, Zr) to reptiles in freshwater ecosystems and 15 elements (Am, C, Cs, Cu, K, Mn, Ni, Pb, Po, Pu, Sr, Tc, Th, U, Zn) to reptiles in terrestrial ecosystems. These reptile CRs are compared with CRs for other vertebrate groups. Tissue distribution data are also presented along with data on the fractional mass of bone, kidney, liver and muscle in reptiles. Although the data were originally collected for use in radiation dose assessments, many of the CR data presented in this paper will also be useful for chemical ERA and for the assessments of dietary transfer in humans for whom reptiles constitute an important component of the diet, such as in Australian aboriginal communities.

Oxygen isotope fractionation in divalent metal carbonates

USGS Publications Warehouse

O'Neil, J.R.; Clayton, R.N.; Mayeda, T.K.

1969-01-01

Equilibrium fractionation factors for the distribution of 18O between alkaline-earth carbonates and water have been measured over the temperature range 0-500??C. The fractionation factors ?? can be represented by the equations CaCO3-H2O, 1000 ln??=2.78(106 T-2)-3.39, SrCO3-H 2O, 1000 ln??=2.69(106 T-2)-3.74, BaCO3-H2O, 1000 ln??=2.57(106 T -2)-4.73. Measurements on MnCO3, CdCO3, and PbCO3 were made at isolated temperatures. A statistical-mechanical calculation of the isotopic partition function ratios gives reasonably good agreement with experiment. Both cationic size and mass are important in isotopic fractionation, the former predominantly in its effect on the internal vibrations of the anion, the latter in its effect on the lattice vibrations.

Age-specific inhalation radiation dose commitment factors for selected radionuclides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strenge, D.L.; Peloquin, R.A.; Baker, D.A.

Inhalation dose commitment factors are presented for selected radionuclides for exposure of individuals in four age groups: infant, child, teen and adult. Radionuclides considered are /sup 35/S, /sup 36/Cl, /sup 45/Ca, /sup 67/Ga, /sup 75/Se, /sup 85/Sr, /sup 109/Cd, /sup 113/Sn, /sup 125/I, /sup 133/Ba, /sup 170/Tm, /sup 169/Yb, /sup 182/Ta, /sup 192/Ir, /sup 198/Au, /sup 201/Tl, /sup 204/Tl, and /sup 236/Pu. The calculational method is based on the human metabolic model of ICRP as defined in Publication 2 (ICRP 1959) and as used in previous age-specific dose factor calculations by Hoenes and Soldat (1977). Dose commitment factors are presentedmore » for the following organs of reference: total body, bone, liver, kidney, thyroid, lung and lower large intestine.« less

The use of decision trees and naïve Bayes algorithms and trace element patterns for controlling the authenticity of free-range-pastured hens' eggs.

PubMed

Barbosa, Rommel Melgaço; Nacano, Letícia Ramos; Freitas, Rodolfo; Batista, Bruno Lemos; Barbosa, Fernando

2014-09-01

This article aims to evaluate 2 machine learning algorithms, decision trees and naïve Bayes (NB), for egg classification (free-range eggs compared with battery eggs). The database used for the study consisted of 15 chemical elements (As, Ba, Cd, Co, Cs, Cu, Fe, Mg, Mn, Mo, Pb, Se, Sr, V, and Zn) determined in 52 eggs samples (20 free-range and 32 battery eggs) by inductively coupled plasma mass spectrometry. Our results demonstrated that decision trees and NB associated with the mineral contents of eggs provide a high level of accuracy (above 80% and 90%, respectively) for classification between free-range and battery eggs and can be used as an alternative method for adulteration evaluation. © 2014 Institute of Food Technologists®

Anode materials for lithium ion batteries

DOEpatents

Abouimrane, Ali; Amine, Khalil

2015-06-09

A composite material has general Formula (1-x)J-(x)Q wherein: J is a metal carbon alloy of formula Sn.sub.zSi.sub.z'Met.sub.wMet'.sub.w'C.sub.t; Q is a metal oxide of formula A.sub..gamma.M.sub..alpha.M'.sub..alpha.'O.sub..beta.; A is Li, Na, or K; M, M', Met, and Met' are individually Ge, Mo, Al, Ga, As, Sb, Te, Ti, Ta, Zr, Ca, Mg, Sr, Ba, Li, Na, K, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Rt, Ru or Cd; 0

Scavenger receptor function of mouse Fcγ receptor III contributes to progression of atherosclerosis in apolipoprotein E hyperlipidemic mice.

PubMed

Zhu, Xinmei; Ng, Hang Pong; Lai, Yen-Chun; Craigo, Jodi K; Nagilla, Pruthvi S; Raghani, Pooja; Nagarajan, Shanmugam

2014-09-01

Recent studies showed loss of CD36 or scavenger receptor-AI/II (SR-A) does not ameliorate atherosclerosis in a hyperlipidemic mouse model, suggesting receptors other than CD36 and SR-A may also contribute to atherosclerosis. In this report, we show that apolipoprotein E (apoE)-CD16 double knockout (DKO; apoE-CD16 DKO) mice have reduced atherosclerotic lesions compared with apoE knockout mice. In vivo and in vitro foam cell analyses showed apoE-CD16 DKO macrophages accumulated less neutral lipids. Reduced foam cell formation in apoE-CD16 DKO mice is not due to change in expression of CD36, SR-A, and LOX-1. This led to a hypothesis that CD16 may have scavenger receptor activity. We presented evidence that a soluble form of recombinant mouse CD16 (sCD16) bound to malondialdehyde-modified low-density lipoprotein (MDALDL), and this binding is blocked by molar excess of MDA- modified BSA and anti-MDA mAbs, suggesting CD16 specifically recognizes MDA epitopes. Interestingly, sCD16 inhibited MDALDL binding to macrophage cell line, as well as soluble forms of recombinant mouse CD36, SR-A, and LOX-1, indicating CD16 can cross-block MDALDL binding to other scavenger receptors. Anti-CD16 mAb inhibited immune complex binding to sCD16, whereas it partially inhibited MDALDL binding to sCD16, suggesting MDALDL binding site may be in close proximity to the immune complex binding site in CD16. Loss of CD16 expression resulted in reduced levels of MDALDL-induced proinflammatory cytokine expression. Finally, CD16-deficient macrophages showed reduced MDALDL-induced Syk phosphorylation. Collectively, our findings suggest scavenger receptor activity of CD16 may, in part, contribute to the progression of atherosclerosis. Copyright © 2014 by The American Association of Immunologists, Inc.

Trace elements in native and improved paddy rice from different climatic regions of Sri Lanka: implications for public health.

PubMed

Diyabalanage, Saranga; Navarathna, Thamara; Abeysundara, Hemalika T K; Rajapakse, Sanath; Chandrajith, Rohana

2016-01-01

Samples of 226 new improved and 21 indigenous rice ( Oryza sativa L.) varieties were collected from the rice fields in three climatic zones of Sri Lanka and concentrations of 18 trace elements (Li, B, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Ba, Pb and Bi) were measured giving particular emphasis on Se, Cd and As using ICP-MS. The two way multivariate analysis of variance (MANOVA) method was employed to identify the differences in composition among rice from different climatic zones. The mean values obtained for both white and red rice were Se (36; 25 µg/kg), As (42; 45 µg/kg) and Cd (70; 123 µg/kg) on dry weight basis. However mean content of Se, As and Cd of native rice varieties were 69, 74 and 33 µg/kg, respectively. Statistical interpretations showed that in the majority of cases, there was a significant difference in Cd content among climatic zones whereas Se and Pb show differences between white and red rice varieties. Arsenic did not indicate any significant difference either between rice types or among climatic regions. Notably Se and As contents in indigenous rice were higher than that of improved rice types. To assess the safety of dietary of intake, daily intake of Se, Cd and As by rice were calculated. Non-gender specific Estimated Daily Intake (EDI) of Se, Cd and As consuming improved rice are 9.31, 24.1 and 12.2 µg day -1 , respectively. Since over 50 % of daily meals of people contain rice or rice based products, Se intake is expected to be deficient among the Sri Lankan population.

Structural studies of zirconium doped Ba{sub 0.70}Sr{sub 0.30}TiO{sub 3} lead free ferroelectric thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Sarita, E-mail: sss.sharmasarita@gmail.com; Ram, Mast; Thakur, Shilpa

2016-05-06

Ba{sub 0.7}Sr{sub 0.3}(Zr{sub x}Ti{sub 1-x})O{sub 3}(BSZT, x=0,0.05,0.10,0.15,0.20) thin films were prepared by using sol gel method. Structural and microstructural properties were studied by using XRD, Raman Spectroscopy and atomic force microscopy (AFM) respectively. XRD and Raman Spectroscopy show the presence of tetragonal phase in multilayer BSZT thin film. The experimental results demonstrate that structural and microstructural properties of BSZT thin film were significantly dependent on variation of Zr content.

Rare gases and Ca, Sr, and Ba in Apollo 17 drill-core fines

NASA Technical Reports Server (NTRS)

Pepin, R. O.; Dragon, J. C.; Johnson, N. L.; Bates, A.; Coscio, M. R., Jr.; Murthy, V. R.

1975-01-01

Trapped gas isotopic compositions and spallation gas concentrations as functions of depth in the Apollo 17 drill core were determined from mass spectrometer studies by means of correlation techniques. The distribution of He, Ne, Ar, Kr, and Xe as well as Ca, Sr, and Ba was investigated, and rare-gas spallation and neutron capture profiles are compared with attention to proposed depositional models for the Taurus-Littrow regolith. The data exclude a sedimentation pattern similar to that found at the Apollo 15 site but are possibly compatible with long-term continuous accretion models or models of very recent rapid accumulation of regolith.

Anomalies in the thermomechanical behavior of Ba0.5Sr0.5Co0.8Fe0.2O3-δ ceramic oxygen conductive membranes at intermediate temperatures

NASA Astrophysics Data System (ADS)

Huang, B. X.; Malzbender, J.; Steinbrech, R. W.; Grychtol, P.; Schneider, C. M.; Singheiser, L.

2009-08-01

The thermomechanical properties of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) were measured using ring-on-ring tests and depth-sensitive microindentation. The cubic BSCF material exhibits an anomaly in mechanical properties between 200 and 400 °C. The observed anomaly is attributed to the transition of Co3+ spin states which is experimentally confirmed by susceptibility measurements. Furthermore, slip lines were observed around the impression when indentation tests were carried out above 260 °C.

Imaging and engineering the nanoscale-domain structure of a Sr0.61Ba0.39Nb2O6 crystal using a scanning force microscope

NASA Astrophysics Data System (ADS)

Terabe, K.; Takekawa, S.; Nakamura, M.; Kitamura, K.; Higuchi, S.; Gotoh, Y.; Gruverman, A.

2002-09-01

We have investigated the ferroelectric domain structure formed in a Sr0.61Ba0.39Nb2O6 single crystal by cooling the crystal through the Curie point. Imaging the etched surface structure using a scanning force microscope (SFM) in both the topographic mode and the piezoresponse mode revealed that a multidomain structure of nanoscale islandlike domains was formed. The islandlike domains could be inverted by applying an appropriate voltage using a conductive SFM tip. Furthermore, a nanoscale periodically inverted-domain structure was artificially fabricated using the crystal which underwent poling treatment.

Impedance and magnetoelectric characteristics of (1 - x)BaTiO3- xLa0.7Sr0.3MnO3 ( x = 0.1 and 0.3) nano-composites

NASA Astrophysics Data System (ADS)

Nayek, C.; Murugavel, P.; Dinesh Kumar, S.; Subramanian, V.

2015-08-01

We have synthesized the phase-pure (1 - x)BaTiO3- xLa0.7Sr0.3MnO3 ( x = 0.1 and 0.3) magnetoelectric composites without interdiffusion among the existing phases. The magnetic measurements revealed an anomaly at the ferroelectric Curie temperature (393 K) of BaTiO3, and the dielectric data revealed an anomaly at the ferromagnetic transition temperature (360 K) of La0.7Sr0.3MnO3 ascertaining the magnetoelectric coupling in the composite. Impedance analysis indicated dipolar polarization contributions to the dielectric spectrum with two non-Debye-type relaxations. Both the grain and grain boundary contributions were present in the system with dominant grain boundary effect in all the composites. The composites show semiconducting behavior with the barrier hopping-type conducting mechanism. To avoid the free charge carrier and the space charge contributions, the magnetoelectric response was measured at high frequency range. The maximum values of magnetoelectric voltage coefficient measured at 100 kHz were 221 and 219 mV/Oe-cm for x = 0.1 and 0.3 samples, respectively.

Dielectric properties of calicum and barium-doped strontium titanate

NASA Astrophysics Data System (ADS)

Tung, Li-Chun

Dielectric properties of high quality polycrystalline Ca- and Ba-doped SrTiO3 perovskites are studied by means of dielectric constant, dielectric loss and ferroelectric hysteresis measurements. Low frequency dispersion of the dielectric constant is found to be very small and a simple relaxor model may not be able to explain its dielectric behavior. Relaxation modes are found in these samples, and they are all interpreted as thermally activated Bipolar re-orientation across energy barriers. In Sr1- xCaxTiO3 (x = 0--0.3), two modes are found associated with different relaxation processes, and the concentration dependence implies a competition between these processes. In Sr1-xBa xTiO3 (x = 0--0.25), relaxation modes are found to be related to the structural transitions, and the relaxation modes persist at low doping levels (x < 0.1), where structural ordering is not observed by previous neutron scattering studies. The validity of well-accepted Barret formula is discussed and two of the well-accepted models, anharmonic oscillator model and transverse Ising model, are found to be equivalent. Both of the Ca and Ba systems can be understood qualitatively within the concept of transverse Ising model.

Magnetic and structural transitions in La1-xAxCoO3 ( A=Ca , Sr, and Ba)

NASA Astrophysics Data System (ADS)

Kriener, M.; Braden, M.; Kierspel, H.; Senff, D.; Zabara, O.; Zobel, C.; Lorenz, T.

2009-06-01

We report thermal-expansion, lattice-constant, and specific-heat data of the series La1-xAxCoO3 for 0≤x≤0.30 with A=Ca , Sr, and Ba. For the undoped compound LaCoO3 , the thermal-expansion coefficient α(T) exhibits a pronounced maximum around T=50K caused by a temperature-driven spin-state transition from a low-spin state of the Co3+ ions at low temperatures toward a higher spin state at higher temperatures. The partial substitution of the La3+ ions by divalent Ca2+ , Sr2+ , or Ba2+ ions causes drastic changes in the macroscopic properties of LaCoO3 . The large maximum in α(T) is suppressed and completely vanishes for x≳0.125 . For A=Ca three different anomalies develop in α(T) with further increasing x , which are visible in specific-heat data as well. Together with temperature-dependent x-ray data, we identify several phase transitions as a function of the doping concentration x and temperature. From these data we propose an extended phase diagram for La1-xCaxCoO3 .

Methods of reforming hydrocarbon fuels using hexaaluminate catalysts

DOEpatents

Gardner, Todd H [Morgantown, WV; Berry, David A [Morgantown, WV; Shekhawat, Dushyant [Morgantown, WV

2012-03-27

A metal substituted hexaaluminate catalyst for reforming hydrocarbon fuels to synthesis gas of the general formula AB.sub.yAl.sub.12-yO.sub.19-.delta., A being selected from alkali metals, alkaline earth metals and lanthanide metals or mixtures thereof. A dopant or surface modifier selected from a transitions metal, a spinel of an oxygen-ion conductor is incorporated. The dopant may be Ca, Cs, K, La, Sr, Ba, Li, Mg, Ce, Co, Fe, Ir, Rh, Ni, Ru, Cu, Pe, Os, Pd, Cr, Mn, W, Re, Sn, Gd, V, Ti, Ag, Au, and mixtures thereof. The oxygen-ion conductor may be a perovskite selected from M'RhO.sub.3, M'PtO.sub.3, M'PdO.sub.3, M'IrO.sub.3, M'RuO.sub.3 wherein M'=Mg, Sr, Ba, La, Ca; a spinel selected from MRh.sub.2O.sub.4, MPt.sub.2O.sub.4, MPd.sub.2O.sub.4, MIr.sub.2O.sub.4, MRu.sub.2O.sub.4 wherein M=Mg, Sr, Ba, La, Ca and mixtures thereof; a florite is selected from M''O.sub.2.

Research on The Removal of Scale Ions from Circulating Cooling Wastewater by Chemical Coagulation Process

NASA Astrophysics Data System (ADS)

Du, Song; Jin, Wenbiao; Duan, Feng

2018-06-01

In this paper, the circulating cooling wastewater was treated by chemical coagulation process through adding NaOH/Na2CO3.The effect of NaOH and Na2CO3 dose on removal of scale ions, such as Ca2+, Mg2+, Ba2+, Sr2+, SiO2, was studied and the removal mechanism was discussed. The results showed that the increase of NaOH dose was beneficial to the removal of above-mentioned scale ions. When NaOH was only added, the removal efficiency of Ca2+, Mg2+, Ba2+, Sr2+, SiO2 was 86.3%, 91.6%, 86.5%, 58.1%, 84.2%, respectively. When 680 mg/L of NaOH and 300 mg/L of Na2CO3 were added, and the effluent pH was above 11.2, the removal efficiency of Ca2+, Mg2+ was 95.8% and 89.4%, respectively, and the concentration of Ca2+and Mg2+ was below 20 mg/L, which met the target of wastewater treatment. Finally the possible removal mechanism of Ca2+, Mg2+, Ba2+, Sr2+and SiO2 was discussed.

Structure and magnetic properties of oxychalcogenides A2F2Fe2OQ2 (A = Sr, Ba; Q = S, Se) with Fe2O square planar layers representing an antiferromagnetic checkerboard spin lattice.

PubMed

Kabbour, Houria; Janod, Etienne; Corraze, Benoît; Danot, Michel; Lee, Changhoon; Whangbo, Myung-Hwan; Cario, Laurent

2008-07-02

The oxychalcogenides A2F2Fe2OQ2 (A = Sr, Ba; Q = S, Se), which contain Fe2O square planar layers of the anti-CuO2 type, were predicted using a modular assembly of layered secondary building units and subsequently synthesized. The physical properties of these compounds were characterized using magnetic susceptibility, electrical resistivity, specific heat, (57)Fe Mossbauer, and powder neutron diffraction measurements and also by estimating their exchange interactions on the basis of first-principles density functional theory electronic structure calculations. These compounds are magnetic semiconductors that undergo a long-range antiferromagnetic ordering below 83.6-106.2 K, and their magnetic properties are well-described by a two-dimensional Ising model. The dominant antiferromagnetic spin exchange interaction between S = 2 Fe(2+) ions occurs through corner-sharing Fe-O-Fe bridges. Moreover, the calculated spin exchange interactions show that the A2F2Fe2OQ2 (A = Sr, Ba; Q = S, Se) compounds represent a rare example of a frustrated antiferromagnetic checkerboard lattice.

Structures and unimolecular chemistry of M(Pro2-H)(+) (M = Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu, Zn) by IRMPD spectroscopy, SORI-CID, and theoretical studies.

PubMed

Jami-Alahmadi, Yasaman; Fridgen, Travis D

2016-01-21

M(Pro2-H)(+) complexes were electrosprayed and isolated in an FTICR cell where their unimolecular chemistries and structures were explored using SORI-CID and IRMPD spectroscopy. These experiments were augmented by computational methods such as electronic structure, simulated annealing, and atoms in molecules (AIM) calculations. The unimolecular chemistries of the larger metal cation (Ca(2+), Sr(2+) and Ba(2+)) complexes predominantly involve loss of neutral proline whereas the complexes involving the smaller Mg(2+) and transition metal dications tend to lose small neutral molecules such as water and carbon dioxide. Interestingly, all complexes involving transition metal dications except for Cu(Pro2-H)(+) lose H2 upon collisional or IRMPD activation. IRMPD spectroscopy shows that the intact proline in the transition metal complexes and Cu(Pro2-H)(+) is predominantly canonical (charge solvated) while for the Ca(2+), Sr(2+), and Ba(2+) complexes, proline is in its zwitterionic form. The IRMPD spectra for both Mg(Pro2-H)(+) and Mn(Pro2-H)(+) are concluded to have contributions from both charge-solvated and canonical structures.

Physical characteristics and magnetic properties of BaFe{sub 12}O{sub 19}/SrTiO{sub 3} based composites derived from mechanical alloying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Widodo, Rahmat Doni, E-mail: rahmat-doni@yahoo.com; Manaf, Azwar

2016-04-19

A composite system BaFe{sub 12}O{sub 19}/SrTiO{sub 3} with ferrimagnetic BaFe{sub 12}O{sub 19} phase (BHF) and ferroelectric SrTiO{sub 3} phase (STO) have been prepared by mechanical alloying and subsequent heat treatment. The composite powders were studied by Particle Size Analyze, X-ray diffraction and magnetic measurement. It was found that the particle size of composite powders initially increased due to laminated layers formation of a composite and then decreased to an asymptotic value of ∼8 µm as the milling time extended even to a relatively longer time. However, based on results of line broadening analysis the mean grain size of the particles wasmore » found in the nanometer scale. We thus believed that mechanical blending and milling of mixture components for the composite materials has promoted heterogeneous nucleation and only after successive sintering at 1100°C the milled powder transformed into particles of nanograin. In this report, microstructure as well as magnetic properties for the composite is also briefly discussed.« less

Effect of Mn and Ti substitution on the reflection loss characteristic of Ba{sub 0.6}Sr{sub 0.4}Fe{sub 11-z}MnTi{sub z}O{sub 19} (z = 0, 1, 2 and 3)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gunanto, Y. E., E-mail: yohanes.gunanto@uph.edu; Cahyadi, L., E-mail: lina.cahyadi@uph.edu; Adi, W. Ari, E-mail: dwisnuaa@batan.go.id

2016-04-19

The synthesis and characterization of composition Ba{sub 0.6}Sr{sub 0.4}Fe{sub 11-z}MnTi{sub z}O{sub 19} (z = 0; 1; 2 and 3) compound by solid state reaction using mechanical milling have been performed. The raw materials were BaCO{sub 3}, SrCO{sub 3}, Fe{sub 2}O{sub 3}, MnCO{sub 3}, and TiO{sub 2}. The mixed powder was compacted and sintered at 1000°C for 5 hours. X-ray diffraction studies indicate expansion of hexagonal unit cell and compression of atomic density with substitution of Mn{sup 2+} and Ti{sup 4+} ions. Effect of substitution upon magnetic properties revealed that total magnetization, remanence, and coercivity changed with substitution due to preferentialmore » site occupancy of substituted Mn{sup 2+} and Ti{sup 4+} ions. Since the coercivity and total magnetization may be controlled by substitution while maintaining resistive properties, this material is useful for microwave absorber.« less

Electrical Characteristics and Preparation of (Ba0.5Sr0.5)TiO3 Films by Spray Pyrolysis and Rapid Thermal Annealing

NASA Astrophysics Data System (ADS)

Koo, Horng-Show; Chen, Mi; Ku, Hong-Kou; Kawai, Tomoji

2007-04-01

Functional films of (Ba0.5Sr0.5)TiO3 on Pt (1000 Å)/Ti (100 Å)/SiO2 (2000 Å)/Si substrates are prepared by spray pyrolysis and subsequently rapid thermal annealing. Barium nitrate, strontium nitrate and titanium isopropoxide are used as starting materials with ethylene glycol as solvent. For (Ba0.5Sr0.5)TiO3 functional thin film, thermal characteristics of the precursor powder scratched from as-sprayed films show a remarkable peak around 300-400 °C and 57.7% weight loss up to 1000 °C. The as-sprayed precursor film with coffee-like color and amorphous-like phase is transformed into the resultant film with white, crystalline perovskite phase and characteristic peaks (110) and (100). The resultant films show correspondent increases of dielectric constant, leakage current and dissipation factor with increasing annealing temperatures. The dielectric constant is 264 and tangent loss is 0.21 in the resultant films annealed at 750 °C for 5 min while leakage current density is 1.5× 10-6 A/cm2 in the film annealed at 550 °C for 5 min.

Energy storage properties of Dy3+ doped Sr0.5Ba0.5Nb2O6 thick film with nano-size grains

NASA Astrophysics Data System (ADS)

Yang, Daeyeol; Kang, Soo-Bin; Lim, Ji-Ho; Yoon, Songhyeon; Ryu, Jungho; Choi, Jong-Jin; Velayutham, Thamil Selvi; Kim, Hyungsun; Jeong, Dae-Yong

2017-09-01

We studied the temperature stable high-energy storage capacitors. Sr0.5Ba0.5Nb2O6 (SBN) is the lead-free ferroelectric solid solution between BaNb2O6 and SrNb2O6. By doping Dy into SBN, the Curie temperature was lowered and dielectric constant was increased. To improve the breakdown behavior of Dy-doped SBN, the aerosoldeposition(AD) was applied to fabricate the dense films with nano-sized grains. These nano-grain give a large number of grain boundaries, suppressing the electron conduction in ceramics. The dielectric constant and breakdown electric field of the AD films annealed at 650 °C were measured as 2307 and 9.9 MV/m, while bulk were 1080 and 4 MV/m. Energy density and efficiency of the AD films annealed at 650 °C were also enhanced as 0.65 J/cc and 90.2% and bulk were 0.08 J/cc and 72.1%, respectively. In addition, the dielectric constant of AD film annealed at 550 °C and 650 °C were quite stable up to 150 °C.

Structural, electrical and multiferroic characteristics of thermo-mechanically fabricated BiFeO3-(BaSr)TiO3 solid solutions

NASA Astrophysics Data System (ADS)

Behera, C.; Choudhary, R. N. P.; Das, Piyush R.

2018-05-01

A solid solution consisting of two perovskite compounds (BiFeO3 and (BaSr)TiO3) of chemical composition (Bi1/2Ba1/4Sr1/4)(Fe1/2Ti1/2)O3 has been fabricated in the low dimensional regime by thermo-mechanical (ball milling and heating) approach. The effect of particle size on the structural, micro-structural, relative permittivity, switching (ferroelectric and magnetic) and conduction phenomena of the material has been studied using various experimental techniques such as x-rays diffraction, transmission and scanning electron microscopy, ferroelectric and magnetic hysteresis, dynamic magneto-electric coupling measurement and impedance spectroscopy techniques. All the above extracted properties are found to be particle size dependent. The first order magneto-electric coupling constant is found to be 2.56, 6.6 and 8.7 mV cm‑1.Oe for 30, 60 and 90 h milled calcined (hmc) sample respectively. As the above micro/nano-material with different particle size, has a high relative dielectric constant and low tangent loss, it can be used for some multifunctional devices including capacity energy storage device in nano-electronics.

Effects of solvent and alkaline earth metals on the heat-induced precipitation process of sodium caseinate.

PubMed

Lopez, Francesco; Cuomo, Francesca; Nostro, Pierandrea Lo; Ceglie, Andrea

2013-01-01

The precipitation temperatures of sodium caseinate in H(2)O and D(2)O in the presence of Mg(2+), Ca(2+), Sr(2+) and Ba(2+) were investigated through fluorescence, turbidity and conductivity experiments. As for the ability of the divalent cations (1-17.5mM) to induce the precipitation process in H(2)O, the sequence Ba(2+) ≥ Ca(2+)>Mg(2+)>Sr(2+) was found. Remarkably, while at low salt concentrations (<10mM) precipitation temperatures (T(Ps)) were found to change significantly depending on the specific cation, at higher concentrations (>10mM) the differences among the different cations were greatly reduced. By fitting these results with a modified Jones-Dole equation, we confirmed that the less hydrated ions possess a greater capacity to induce precipitation. In D(2)O, the order of ion ability to induce caseinate precipitation was Ba(2+)>Ca(2+)>Sr(2+)>Mg(2+). The different hydrophobicity between D(2)O and H(2)O was shown to affect significantly the T(Ps) of caseinate in the presence of calcium, strontium and barium. Copyright © 2012 Elsevier Ltd. All rights reserved.

The first-principle study of the electronic, optical and thermoelectric properties of XTiO3 (X = Ca, Sr and Ba) compounds

NASA Astrophysics Data System (ADS)

Mubarak, A. A.

2016-07-01

The FP-LAPW method is utilized to investigate the elastic, optoelectronic and thermoelectric properties of XTiO3 (X = Ca, Sr and Ba) within the GGA. The calculated lattice constants and bulk modulus are found in agreement with previous studies. The present oxide-perovskite compounds are characterized as elastically stable and anisotropic. CaTiO3 and SrTiO3 are categorized as ductile compounds, whereas the BaTiO3 compound is in the critical region between ductile and brittle. The DOS and the band structure calculations reveal indirect (M-Γ) energy bandgap for the present compounds. The hydrostatic pressure increases the energy bandgap and the width of the valence band. The character of the band structure does not change due to this pressure. The optical parameters are calculated in different radiation regions. Beneficial optics applications are predicted as revealed from the optical spectra. The transport properties are applied as a function of the variable temperatures or carrier concentration. It is found that the compounds under study are classified as a p-type semiconductor. The majority charge carriers responsible for conduction in these calculated compounds are holes rather than electrons.

Strong anisotropy of electric field effects on uniaxial relaxor ferroelectric Sr0.75Ba0.25Nb2O6 crystals proved by acoustic emission

NASA Astrophysics Data System (ADS)

Dul'kin, E.; Kojima, S.; Roth, M.

2018-01-01

[001] oriented Sr0.75Ba0.25Nb2O6 uniaxial relaxor ferroelectric crystals have been studied by acoustic emission in the temperature range of 20÷200 °C and under an external electric field up to 1 kV/cm. Under the application of an electric field the temperature of a dielectric maximum exhibits a nontrivial behavior: it remains constant at first, secondly steep decreases down to some threshold field, and thirdly starts to increase as a field enhances, whereas the same temperature of a dielectric maximum under a bias electric field to [100] oriented Sr0.75Ba0.25Nb2O6 crystals exhibits a smoothed minimum before the start to increase as a field enhances (E. Dul'kin et al., J. Appl. Phys. 110, 044106 (2011)). Such a difference of electric field effects in c- and a-cut crystals is discussed from the viewpoint of random-bond-random-field model of relaxor ferroelectrics. By the comparison between experimental and theoretical data, a dipole moment of the PNR was estimated to be 0.1 (C cm).

The Density and Compressibility of BaCO3-SrCO3-CaCO3-K2CO3-Na2CO3-Li2CO3 Liquids: New Measurements and a Systematic Trend with Cation Field Strength

NASA Astrophysics Data System (ADS)

Hurt, S. M.; Lange, R. A.; Ai, Y.

2015-12-01

The volumetric properties of multi-component carbonate liquids are required to extend thermodynamic models that describe partial melting of the deep mantle (e.g. pMELTS; Ghiorso et al., 2003) to carbonate-bearing lithologies. Carbonate in the mantle is an important reservoir of carbon, which is released to the atmosphere as CO2 through volcanism, and thus contributes to the carbon cycle. Although MgCO3 is the most important carbonate component in the mantle, it is not possible to directly measure the 1-bar density and compressibility of MgCO3 liquid because, like other alkaline-earth carbonates, it decomposes at a temperature lower than its melting temperature. Despite this challenge, Liu and Lange (2003) and O'Leary et al. (2015) showed that the one bar molar volume, thermal expansion and compressibility of the CaCO3 liquid component could be obtained by measuring the density and sound speeds of stable liquids in the CaCO3-Li2CO3-Na2CO3-K2CO3 quaternary system at one bar. In this study, this same strategy is employed on SrCO3- and BaCO3-bearing alkali carbonate liquids. The density and sound speed of seven liquids in the SrCO3-Li2CO3-Na2CO3-K2CO3 quaternary and three liquids in the BaCO3-Li2CO3-Na2CO3-K2CO3 quaternary were measured from 739-1367K, with SrCO3 and BaCO3 concentrations ranging from 10-50 mol%. The density measurements were made using the double-bob Archimedean method and sound speeds were obtained with a frequency-sweep acoustic interferometer. The molar volume and sound speed measurements were used to calculate the isothermal compressibility of each liquid, and the results show the volumetric properties mix ideally with composition. The partial molar volume and compressibility of the SrCO3 and BaCO3 components are compared to those obtained for the CaCO3 component as a function of cation field strength. The results reveal a systematic trend that allows the partial molar volume and compressibility of the MgCO3 liquid component to be estimated.

Strain-mediated magnetic response in La0.67Sr0.33MnO3/SrTiO3/La0.67Sr0.33MnO3/BaTiO3 structure

NASA Astrophysics Data System (ADS)

Swain, Anupama; Komatsu, Katsuyoshi; Itoh, Mitsuru; Taniyama, Tomoyasu; Gorige, Venkataiah

2018-05-01

Electric field controlled magnetism is an exciting area of condensed matter physics to explore the device applications at ultra-low power consumption compared to the conventional current controlled or magnetic field controlled devices. In this study, an attempt was made to demonstrate electric field controlled magnetoresistance (MR) in a tri-layer structure consisting of La0.67Sr0.33MnO3 (LSMO) (40 nm)/SrTiO3 (10 nm)/LSMO (10 nm) grown on a 500-μm-thick BaTiO3 (001) (BTO) single crystal substrate by pulsed laser deposition technique. Epitaxial growth of the trilayer structure was confirmed by x-ray diffraction measurements. Jumps observed in the temperature-dependent magnetization curve at around the structural phase transitions of BTO ensure the strain-mediated magnetoelectric coupling between LSMO and BTO layers. A significant change in MR of this structure in applied electric fields does not show any polarity dependence. The findings are related to the lattice strain-mediated magnetoelectric coupling in ferromagnetic LSMO/ferroelectric BTO heterostructures.

Fabrication of barium titanate doped strontium using co-precipitation method

NASA Astrophysics Data System (ADS)

Iriani, Y.; Yasin, M. A.; Suryana, R.

2018-03-01

Fabrication of barium titanate (BaTiO3/BT) doped strontium (Sr) using co-precipitation method has been successfully conducted. The research aim is to get the best of mole variation of Sr doping to ferroelectric material properties. Doping Sr was varied at 1%, 2%, 3%, 4% and 5% in BaTiO3. Each sample was sintered at temperature of 1100°C with holding time for 6 h and temperature rate at 10°C/min. They were then characterized by XRD instrument to investigate the crystal structure, LCR meter to measure the dielectric constant, and Sawyer Tower circuit to reveal the hysteresis curve. The peaks of XRD shift towards larger angle when mole doping Sr increase. The crystallinity of all samples is above 90% and the crystallite size is in the range of 27 nm to 34 nm. Hysteresis curve from Sawyer Tower testing confirms that all samples are ferroelectric material. The RLC measurement results reveal that the less frequency leads to the higher dielectric constant while the highest dielectric constant belongs to the BT doped 3% of Sr. Therefore, it is the best variation obtained in this research.

Determining baseline element composition of lichens. I. Parmelia sulcata at Theodore Roosevelt national park, North Dakota

USGS Publications Warehouse

Gough, L.P.; Severson, R.C.; Jackson, L.L.

1988-01-01

Element-concentration baselines are given for Parmelia sulcata and associated soils. Parmelia chlorochroa was found sporadically and therefore only representative concentration ranges are reported for this species. Element data include (1) for lichens; Al, As, Ba, B, Ca, Cr, Cu, Fe, Hg, Mn, Ni, P, Sr, S, Ti, V, Y, and Zn; and (2) for soils: Al, Ba, Be, Ca, Cs, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Nb, P, Pb, Sr, S, Ti, V, Y, and Zn. Very little (usually 7.2 km); thus, P sulcata is, in general, chemically similar throughout the park. This same uniformity was found for soil geochemistry. Numerous samples collected at close intervals would be required, therefore, to produce detailed element-concentration maps for P. sulcata and soils. No instances of elemental phytotoxic conditions were found; however, P. sulcata apparently possesses large concentrations of Ba, Cu, Fe, Pb, S, V, and possibly Zn.

Characteristics of growth of complex ferroelectric oxide films by plasma-ion sputtering

NASA Astrophysics Data System (ADS)

Mukhortov, V. M.; Golovko, Yu. I.; Mukhortov, Vl. M.; Dudkevich, V. P.

1981-02-01

An experimental investigation was made of the process of growth of a complex oxide film, such as BaTiO3 or (Ba, Sr)TiO3, by plasma-ion sputtering. It was found that ion bombardment of a ceramic target knocked out neutral excited atoms. These atoms lost energy away from the target by collisions and at a certain critical distance hcr they were capable of oxidation to produce BaO, TiO, TiO2, and SrO. Therefore, depending on the distance between the cathode and the substrate, the “construction” material arrived in the form of atoms or molecules of simple oxides. These two (atomic and molecular) deposition mechanisms corresponded to two mechanisms of synthesis and crystallization differing in respect of the dependences of the growth rate, unit cell parameters, and other structural properties on the deposition temperature. The role of re-evaporation and of oxidation-reduction processes was analyzed.

Synthesis and molecular structures of phenylamides of magnesium, calcium, strontium, and barium--from molecular to polymeric structures.

PubMed

Gärtner, Martin; Görls, Helmar; Westerhausen, Matthias

2007-09-03

Several preparative procedures for the synthesis of the THF complexes of the alkaline earth metal bis(phenylamides) of Mg (1), Ca (2), Sr (3), and Ba (4) are presented such as metalation of aniline with strontium and barium, metathesis reactions of MI2 with KN(H)Ph, and metalation of aniline with arylcalcium compounds or dialkylmagnesium. The THF content of these compounds is rather low and an increasing aggregation is observed with the size of the metal atom. Thus, tetrameric [(THF)2Ca{mu-N(H)Ph}2]4 (2) and polymeric [(THF)2Sr{mu-N(H)Ph}2]infinity and {[(THF)2Ba{mu-N(H)Ph}2]2[(THF)Ba{mu-N(H)Ph}2]2}infinity show six-coordinate metal atoms with increasing interactions to the pi systems of the phenyl groups with increasing the radius of the alkaline earth metal atom.

Crystallization studies and dielectric properties of (Ba0.7Sr0.3)TiO3 in bariumaluminosilicate glass

NASA Astrophysics Data System (ADS)

Divya, P. V.; Vignesh, G.; Kumar, V.

2007-12-01

Ferroelectric glass-ceramics with a basic composition (1 - y)(Ba0.70Sr0.30)TiO3 : y(BaO : Al2O3 : 2SiO2) have been synthesized by the sol-gel method. The major crystalline phase is the perovskite. The crystallization of the ferroelectric phase in the glass matrix have been studied using differential thermal analysis and x-ray diffraction and the kinetic parameters characterizing the crystallization have been determined using an Arrhenius model. Glass contents <= 5 mol% promoted liquid phase sintering, which reduced the sintering temperature to 1250 °C. The dielectric permittivity of the glass-ceramic samples decreased and the ferroelectric-paraelectric phase transition became more diffuse with increasing glass content. The dielectric connectivity of the ferroelectric phase in the composite have also been investigated and are reported.

Metals detected by ICP/MS in wound tissue of war injuries without fragments in Gaza

PubMed Central

2010-01-01

Background The amount and identity of metals incorporated into "weapons without fragments" remain undisclosed to health personnel. This poses a long-term risk of assumption and contributes to additional hazards for victims because of increased difficulties with clinical management. We assessed if there was evidence that metals are embedded in "wounds without fragments" of victims of the Israeli military operations in Gaza in 2006 and 2009. Methods Biopsies of "wounds without fragments" from clinically classified injuries, amputation (A), charred (C), burns (B), multiple piercing wounds by White Phosphorus (WP) (M), were analyzed by ICP/MS for content in 32 metals. Results Toxic and carcinogenic metals were detected in folds over control tissues in wound tissues from all injuries: in A and C wounds (Al, Ti, Cu, Sr, Ba, Co, Hg, V, Cs and Sn), in M wounds (Al, Ti, Cu, Sr, Ba, Co and Hg) and in B wounds (Co, Hg, Cs, and Sn); Pb and U in wounds of all classes; B, As, Mn, Rb, Cd, Cr, Zn in wounds of all classes, but M; Ni was in wounds of class A. Kind and amounts of metals correlate with clinical classification of injuries, exposing a specific metal signature, similar for 2006 and 2009 samples. Conclusions The presence of toxic and carcinogenic metals in wound tissue is indicative of the presence in weapon inducing the injury. Metal contamination of wounds carries unknown long term risks for survivors, and can imply effects on populations from environmental contamination. We discuss remediation strategies, and believe that these data suggest the need for epidemiological and environmental surveys. PMID:20579349

Impact of Ficoll density gradient centrifugation on major and trace element concentrations in erythrocytes and blood plasma.

PubMed

Lu, Ying; Ahmed, Sultan; Harari, Florencia; Vahter, Marie

2015-01-01

Ficoll density gradient centrifugation is widely used to separate cellular components of human blood. We evaluated the suitability to use erythrocytes and blood plasma obtained from Ficoll centrifugation for assessment of elemental concentrations. We determined 22 elements (from Li to U) in erythrocytes and blood plasma separated by direct or Ficoll density gradient centrifugation, using inductively coupled plasma mass spectrometry. Compared with erythrocytes and blood plasma separated by direct centrifugation, those separated by Ficoll had highly elevated iodine and Ba concentration, due to the contamination from the Ficoll-Paque medium, and about twice as high concentrations of Sr and Mo in erythrocytes. On the other hand, the concentrations of Ca in erythrocytes and plasma were markedly reduced by the Ficoll separation, to some extent also Li, Co, Cu, and U. The reduced concentrations were probably due to EDTA, a chelator present in the Ficoll medium. Arsenic concentrations seemed to be lowered by Ficoll, probably in a species-specific manner. The concentrations of Mg, P, S, K, Fe, Zn, Se, Rb, and Cs were not affected in the erythrocytes, but decreased in plasma. Concentrations of Mn, Cd, and Pb were not affected in erythrocytes, but in plasma affected by EDTA and/or pre-analytical contamination. Ficoll separation changed the concentrations of Li, Ca, Co, Cu, As, Mo, I, Ba, and U in erythrocytes and blood plasma, Sr in erythrocytes, and Mg, P, S, K, Fe, Zn, Se, Rb and Cs in blood plasma, to an extent that will invalidate evaluation of deficiencies or excess intakes. Copyright © 2014 Elsevier GmbH. All rights reserved.

The 1 Repetition Maximum Mechanics of a High-Handle Hexagonal Bar Deadlift Compared With a Conventional Deadlift as Measured by a Linear Position Transducer.

PubMed

Lockie, Robert G; Moreno, Matthew R; Lazar, Adrina; Risso, Fabrice G; Liu, Tricia M; Stage, Alyssa A; Birmingham-Babauta, Samantha A; Torne, Ibett A; Stokes, John J; Giuliano, Dominic V; Davis, DeShaun L; Orjalo, Ashley J; Callaghan, Samuel J

2018-01-01

Lockie, RG, Moreno, MR, Lazar, A, Risso, FG, Liu, TM, Stage, AA, Birmingham-Babauta, SA, Torne, IA, Stokes, JJ, Giuliano, DV, Davis, DL, Orjalo, AJ, and Callaghan, SJ. The 1 repetition maximum mechanics of a high-handle hexagonal bar deadlift compared with a conventional deadlift as measured by a linear position transducer. J Strength Cond Res 32(1): 150-161, 2018-The high-handle hexagonal bar deadlift (HHBD), a variation of the conventional deadlift (CD), is said to reduce the lift range of motion, which may change the mechanics of the lift. However, no research has investigated this. This study compared the mechanics between a 1 repetition maximum (1RM) CD and HHBD. Thirty-one strength-trained subjects (21 men, 10 women) completed a 1RM CD and HHBD. A linear position transducer measured lift distance, duration, and work; and peak and mean power, velocity, and force. The presence of a sticking region (SR) was determined for each lift. A repeated-measures analysis of variance (ANOVA) calculated differences between 1RM CD and HHBD mechanics. A one-way ANOVA compared the mechanics of each lift between subjects who exhibited an SR or not, and the SR between the CD and HHBD. Significance was set at p < 0.01. Subjects lifted a greater load in the HHBD (154.50 ± 45.29 kg) compared with the CD (134.72 ± 40.63 kg). Lift distance and duration were 22 and 25% shorter during the 1RM HHBD, respectively. The HHBD featured greater peak power and velocity, and peak and mean force; more work was done in the CD. Most subjects did not exhibit a CD (68%) or HHBD (77%) SR. There were no differences in CD or HHBD mechanics between subjects with or without an SR, and no differences in SR region distance or duration between the CD and HHBD. Greater force can be generated in the HHBD, which could have implications for strength-training adaptations over time.

Bias polarization study of steam electrolysis by composite oxygen electrode Ba0.5Sr0.5Co0.8Fe0.2O3-δ/BaCe0.4Zr0.4Y0.2O3-δ

NASA Astrophysics Data System (ADS)

Yang, Tao; Shaula, Aliaksandr; Pukazhselvan, D.; Ramasamy, Devaraj; Deng, Jiguang; da Silva, E. L.; Duarte, Ricardo; Saraiva, Jorge A.

2017-12-01

The polarization behavior of Ba0.5Sr0.5Co0.8Fe0.2O3-δ-BaCe0.4Zr0.4Y0.2O3-δ (BSCF-BCZY) electrode under steam electrolysis conditions was studied in detail. The composite oxygen electrode supported by BCZY electrolyzer has been assessed as a function of temperature (T), water vapor partial pressures (pH2O), and bias polarization voltage for electrodes of comparable microstructure. The Electrochemical impedance spectra show two depressed arcs in general without bias polarization. And the electrode resistance became smaller with the increase of the bias polarization under the same water vapor partial pressures. The total resistance of the electrode was shown to be significantly affected by temperature, with the same level of pH2O and bias polarization voltage. This result highlights BSCF-BCZY as an effective oxygen electrode under moderate polarization and pH2O conditions.

Chemistry and superconductivity in thallium-based cuprates. Technical report No. 56, 1 June 1989-30 May 1990

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenblatt, M.; Li, S.; McMills, L.E.

1990-06-01

Following the discoveries of high temperature superconductivity in the rare-earth copper oxide systems at 40K bY Bednorz and Muller in 1986 and at 90K by other researchers in 1987, Sheng and Hermann, in 1988, discovered superconductivity in the thallium-alkaline-earth copper oxide systems with critical temperatures as high as 120K. All of the Tl-based compounds can be described by the general formula, TlmA2Can-1CuO2n+m+2, where m=1 or 2; n=5; A=Ba, Sr. For convenience, the names of these compounds are abbreviated as 2223 for TlBa2Ca2Cu3O10, where each number denotes the number of Tl, Ba(Sr), Ca and Cu ions per formula, respectively. The compoundsmore » with m=1 and m=2 are usually referred to as single and double T1-O layered compounds, respectively. The highest superconducting transition temperature known so far was found in Tl2BaCa2Cu3O10 at 125K.« less

Electronic Phase Separation in the Slightly Underdoped Iron Pnictide Superconductor Ba{sub 1-x}K{sub x}Fe{sub 2}As{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, J. T.; Inosov, D. S.; Sun, G. L.

2009-03-20

Here we present a combined study of the slightly underdoped novel pnictide superconductor Ba{sub 1-x}K{sub x}Fe{sub 2}As{sub 2} by means of x-ray powder diffraction, neutron scattering, muon-spin rotation ({mu}SR), and magnetic force microscopy (MFM). Static antiferromagnetic order sets in below T{sub m}{approx_equal}70 K as inferred from the neutron scattering and zero-field-{mu}SR data. Transverse-field {mu}SR below T{sub c} shows a coexistence of magnetically ordered and nonmagnetic states, which is also confirmed by MFM imaging. We explain such coexistence by electronic phase separation into antiferromagnetic and superconducting- or normal-state regions on a lateral scale of several tens of nanometers. Our findings indicatemore » that such mesoscopic phase separation can be considered an intrinsic property of some iron pnictide superconductors.« less

Sol-gel auto-combustion synthesis and properties of Co2Z-type hexagonal ferrite ultrafine powders

NASA Astrophysics Data System (ADS)

Liu, Junliang; Yang, Min; Wang, Shengyun; Lv, Jingqing; Li, Yuqing; Zhang, Ming

2018-05-01

Z-type hexagonal ferrite ultrafine powders with chemical formulations of (BaxSr1-x)3Co2Fe24O41 (x varied from 0.0 to 1.0) have been synthesized by a sol-gel auto-combustion technique. The average particle sizes of the synthesized powders ranged from 2 to 5 μm. The partial substitution of Ba2+ by Sr2+ led to the shrinkage of the crystal lattices and resulted in changes in the magnetic sub-lattices, which tailored the static and dynamic magnetic properties of the as-synthesized powders. As the substitution ratio of Ba2+ by Sr2+, the saturation magnetization of the synthesized powders almost consistently increased from 43.3 to 56.1 emu/g, while the real part of permeability approached to a relatively high value about 2.2 owing to the balance of the saturation magnetization and magnetic anisotropy field.

Expression of CXCR6 on CD8(+) T cells was up-regulated in allograft rejection.

PubMed

Jiang, Xiaofeng; Sun, Wenyu; Zhu, Lei; Guo, Dawei; Jiang, Honglei; Ma, Dongyan; Jin, Junzhe; Zhao, Yu; Liang, Jian

2010-02-01

CXCL16/SR-PSOX is a novel transmembrane-type chemokine, which was also identified as a novel scavenger receptor for oxidized low density lipoprotein. Its receptor CXCR6 expresses on activated CD8(+) T cells, type 1-polarized CD4(+), and constitutively expresses on NKT cells. Moreover, it has been shown that CXCL16 accumulated activated CD8(+) T cells to sites of inflammation. To date, the effect of CXCL16 (SR-PSOX)/CXCR6 on CD8(+) T cells and its role in allograft rejection/acceptance are not well understood. In the current study, we show that rejected allografts showed higher expressions of CXCR6 and CXCL16. More importantly, expression of CXCR6 on CD8(+) T cells was also up-regulated by rejection. However, the blockade of CXCL16(SR-PSOX)/CXCR6 interaction could not inhibit cytotoxic activity of CD8(+) T cells, and therefore, could not prolong the cardiac graft survival time. Copyright 2009 Elsevier B.V. All rights reserved.

The crystal structure of tin sulphate, SnSO[subscript 4], and comparison with isostructural SrSO[subscript 4], PbSO[subscript 4], and BaSO[subscript 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antao, Sytle M.

2012-10-23

The crystal structure of tin (II) sulphate, SnSO{sub 4}, was obtained by Rietveld refinement using synchrotron high-resolution powder X-ray diffraction (HRPXRD) data. The structure was refined in space group Pbnm. The unit-cell parameters for SnSO{sub 4} are a = 7.12322(1), b = 8.81041(1), c = 5.32809(1) {angstrom}, and V = 334.383(1) {angstrom}{sup 3}. The average [12] distance is 2.9391(4) {angstrom}. However, the Sn{sup 2+} cation has a pyramidal [3]-coordination to O atoms and the average [3] = 2.271(1) {angstrom}. If Sn is considered as [12]-coordinated, SnSO{sub 4} has a structure similar to barite, BaSO{sub 4}, and its structuralmore » parameters are intermediate between those of BaSO{sub 4} and PbSO{sub 4}. The tetrahedral SO{sub 4} group has an average [4] = 1.472(1) {angstrom} in SnSO{sub 4}. Comparing SnSO{sub 4} with the isostructural SrSO{sub 4}, PbSO{sub 4}, and BaSO{sub 4}, several well-defined trends are observed. The radii, rM, of the M{sup 2+}(=Sr, Pb, Sn, and Ba) cations and average distances vary linearly with V because of the effective size of the M{sup 2+} cation. Based on the trend for the isostructural sulphates, the average [12] distance is slightly longer than expected because of the lone pair of electrons on the Sn{sup 2+} cation.« less

Selenium and other elements in juvenile striped bass from the San Joaquin Valley and San Francisco Estuary, California

USGS Publications Warehouse

Saiki, Michael K.; Palawski, Donald U.

1990-01-01

Concentrations of selenium and other trace elements were determined in 55 whole body samples of juvenile anadromous striped bass (Morone saxatilis) from the San Joaquin Valley and San Francisco Estuary, California. The fish (≤1 yr old—the predominant life stage in the San Joaquin Valley) were collected in September–December 1986 from 19 sites in the Valley and 3 sites in the Estuary, and analyzed for the following elements: aluminum (Al), arsenic (As), boron (B), barium (Ba), beryllium (Be), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), magnesium (Mg), molybdenum (Mo), nickel (Ni), lead (Pb), selenium (Se), strontium (Sr), vanadium (V), and zinc (Zn). When compared to concentrations in whole freshwater fish measured by surveys from other waters, a few samples contained higher levels, of As, Cd, Cu, Pb, and Se. The median concentrations of Al, As, Cu, Fe, Mg, Se, and Sr also differed significantly (P⩽0.05) among sites. However, only Se concentrations were highest (up to 7.9 μg/g dry weight) in samples from Valley sites exposed to agricultural subsurface (tile) drainwater; concentrations were lower in samples collected elsewhere. Water quality variables—especially those strongly influenced by tile drainwater (conductivity, total dissolved solids, total alkalinity, and total hardness)—were also significantly correlated (P⩽0.05) with Se concentrations in fish. Selenium concentrations in striped bass from the Estuary were only one-fourth to one-half the concentrations measured in the most contaminated fish from the San Joaquin River.

Syntheses, topological analyses, and NLO-active properties of new Cd(II)/M(II) (M = Ca, Sr) metal-organic frameworks based on R-isophthalic acids (R = H, OH, and t-Bu).

PubMed

Lin, Jian-Di; Wu, Shu-Ting; Li, Zhi-Hua; Du, Shao-Wu

2010-11-28

Solvothermal syntheses of Cd(NO(3))(2)·4H(2)O and R-isophthalic acids (R = H, OH and t-Bu) in the presence of Ca(II) or Sr(II) lead to four new three-dimensional Cd(II)/Ca(II) or Cd(II)/Sr(II) heterometallic frameworks: [CdCa(m-BDC)(2)(DMF)(2)] (1), [CdSr(2)(m-BDC)(2)(NO(3))(2)(DMF)(4)] (2), [CdCa(OH-m-BDC)(2)(H(2)O)(2)]·2Me(2)NH (3), and (Me(2)NH(2))(2)[Cd(2)Ca(Bu(t)-m-BDC)(4)] (4) (m-H(2)BDC = isophthalate, OH-m-H(2)BDC = 5-hydroxyisophthalate and Bu(t)-m-H(2)BDC = 5-butylisophthalate). All of these compounds except for 4 crystallize in acentric (or chiral) space groups and the bulk materials for 1 and 3 display strong powder SHG efficiencies, approximately 1.54 and 2.31 times than that of a potassium dihydrogen phosphate (KDP) powder. Topological analyses show that 1 and 2 have structures with sxb and dia topologies, respectively, while both 3 and 4 exhibit pcu topological nets when the metal carboxylate clusters are viewed as nodes. The fluorescence properties and thermal stabilities for these compounds are also investigated.

XES studies of density of states of high temperature superconductors

NASA Technical Reports Server (NTRS)

Jasiolek, Gabriel

1990-01-01

X-ray emission spectroscopic studies concerning the superconducting crystals, thin films and ceramics of the Y-Ba-Cu-O, Tm-Ba-Cu-O, Bi-Sr-Ca-Cu-O, Bi-Pb-Sr-Ca-Cu-O and T1-Ba-Ca-Cu-O types are presented. The contributions of the 13d(9)L, 13d(10)L, 13d(10)LL and 13d(10)L(2) configurations, where L denotes a ligand hole at the oxygen orbitals in the spectroscopic pattern of these superconductors are discussed. An attempt to connect the x-ray 'as registered' Cu L emission spectra with the density of states close to the Fermi level, considering an influence of the CuL3 absorption edge, is presented. The corrected intensity distributions below the Fermi level are found to correspond to the theoretical density of states. Furthermore, an approach to the average valence of copper based on the account of the self-absorption and fluorescence effects and on the configurations listed above is shown. The average valence of copper in the materials investigated is estimated to lie in the range of +2.10 to 2.32 when the formal trivalent copper is considered as that characterized by the 13d(9)L configuration. The density of states at the Fermi level was estimated to be 2.4 states/eV-cell for a Bi-Sr-Ca-Cu-O crystal and 3.6 states/eV-cell for a Tl-Ba-Ca-Cu-O ceramic.

Bandgap behavior and singularity of the domain-induced light scattering through the pressure-induced ferroelectric transition in relaxor ferroelectric AxBa1-xNb2O6 (A: Sr,Ca)

NASA Astrophysics Data System (ADS)

Ruiz-Fuertes, J.; Gomis, O.; Segura, A.; Bettinelli, M.; Burianek, M.; Mühlberg, M.

2018-01-01

In this letter, we have investigated the electronic structure of AxBa1-xNb2O6 relaxor ferroelectrics on the basis of optical absorption spectroscopy in unpoled single crystals with A = Sr and Ca under high pressure. The direct character of the fundamental transition could be established by fitting Urbach's rule to the photon energy dependence of the absorption edge yielding bandgaps of 3.44(1) eV and 3.57(1) eV for A = Sr and Ca, respectively. The light scattering by ferroelectric domains in the pre-edge spectral range has been studied as a function of composition and pressure. After confirming with x-ray diffraction the occurrence of the previously observed ferroelectric to paraelelectric phase transition at 4 GPa, the light scattering produced by micro- and nano-ferroelectric domains at 3.3 eV in Ca0.28Ba0.72Nb2O6 has been probed. The direct bandgap remains virtually constant under compression with a drop of only 0.01 eV around the phase transition. Interestingly, we have also found that light scattering by the polar nanoregions in the paraelectric phase is comparable to the dispersion due to ferroelectric microdomains in the ferroelectric state. Finally, we have obtained that the bulk modulus of the ferroelectric phase of Ca0.28Ba0.72Nb2O6 is B0 = 222(9) GPa.

XES studies of density of states of high temperature superconductors

NASA Technical Reports Server (NTRS)

Jasiolek, Gabriel

1991-01-01

X-ray emission spectroscopic studies concerning the superconducting crystals, thin films, and ceramics of the Y-Ba-Cu-O, Tm-Ba-Cu-O, Bi-Sr-Ca-Cu-O, Bi-Pb-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O types are presented. The contributions of the 13d(9)L, 13d(10)L, 13d(10)LL, and 13d(10)L(2) configurations, where L denotes a ligand hole at the oxygen orbitals in the spectroscopic pattern of these superconductors are discussed. An attempt to connect the x-ray 'as registered' Cu L(alpha) emission spectra with the density of states close to the Fermi level, considering an influence of the CuL3 absorption edge, is presented. The corrected intensity distributions below the Fermi level are found to correspond to the theoretical density of states. Furthermore, an approach to the average valence of copper basing on the account of the self-absorption and fluorescence effects and on the configurations listed above is shown. The average valence of copper in the materials investigated is estimated to lie in the range of +2.10 to 2.32 when the formal trivalent copper is considered as that characterized by the 13d(9)L configuration. The density of states at the Fermi level was estimated to be 2.4 states/eV-cell for a Bi-Sr-Ca-Cu-O crystal and 3.6 states/eV-cell for a Tl-Ba-Ca-CU-O ceramic.

Dielectric maximum temperature non-monotonic behavior in unaxial Sr0.75Ba0.25Nb2O6 relaxor seen via acoustic emission

NASA Astrophysics Data System (ADS)

Dul'kin, E.; Kojima, S.; Roth, M.

2011-08-01

[100] oriented Sr0.75Ba0.25Nb2O6 relaxor crystals have been studied by means of acoustic emission (AE) over a wide 20-400 °C temperature range. Both the Burns temperature, Td = 350 °C, and the intermediate temperature, T* = 183°C, and the susceptibility maximum temperature, Tm (59 °C on heating and 47 °C on cooling), have been successfully detected. Dependent upon the external electric field, the Tm exhibits a local minimum near 0.25 kV/cm accompanied by pronounced AE maximum in a manner which had recently been detected in Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 by Dul'kin et al. [Appl. Phys. Lett. 94, 252904 (2009)] and in Pb(Sc1/2Ta1/2)O3 by Dul'kin et al. [Phys. Rev. B 82, 180101(R) (2010)], whereas the T* increases monotonically, similar to that which had recently been revealed in BaTiO3 by Dul'kin et al. [Appl. Phys. Lett. 97, 032903 (2010)] with a rate of 7.5 K cm/kV. An observed Tm behavior is discussed from the point of view of the existence of the random electric field components along the [100] direction in Sr0.75Ba0.25Nb2O6 crystals.