Science.gov

Sample records for al ca na

  1. P- T- X controls on Ca and Na distribution between Mg-Al tourmaline and fluid

    NASA Astrophysics Data System (ADS)

    Berryman, Eleanor J.; Wunder, Bernd; Rhede, Dieter; Schettler, Georg; Franz, Gerhard; Heinrich, Wilhelm

    2016-04-01

    Ca-Na partitioning between tourmaline and a coexisting fluid is investigated in the system CaO-Na2O-B2O3-Al2O3-MgO-SiO2-H2O-Cl between 0.2-4.0 GPa and 500-700 °C. The synthesis experiments produced a mineral assemblage of tourmaline, coesite/quartz, and in some cases additional phases, typically comprising <1 wt% of the solid product. The synthesized tourmalines are solid solutions of dravite [NaMg3Al6Si6O18(BO3)3(OH)3(OH)], "oxy-uvite" (i.e. "Ca-Mg-O root name") [CaMg3Al6Si6O18(BO3)3(OH)3O], and magnesio-foitite [☐(Mg2Al)Al6Si6O18(BO3)3(OH)3(OH)]. Starting materials comprised a fluid of constant ionic strength (2.00 m) and an oxide mixture with a constant Mg/Al ratio. As a result, the number of vacancies at the X site and the Mg/Al ratio of tourmaline crystals synthesized at the same temperature vary only slightly. The major solid solution is Ca-Na exchange at the X site via the exchange vector X Ca W O[ X Na W (OH)]-1, with the exchange vector X (Ca☐)[ X Na2]-1 serving as a secondary Ca-incorporation mechanism. Tourmaline's X-site composition reflects the fluid composition, whereby the Ca (or Na) concentration in the fluid corresponds with the Ca (or Na) content in tourmaline at each pressure and temperature. At 0.2 GPa, 700 °C, Ca preferentially partitions into tourmaline, producing the most Ca-rich tourmaline crystals synthesized here. At pressures >1.0 GPa, Ca partitions preferentially into the fluid, resulting in Na-dominant tourmaline compositions. Temperature has a secondary effect on Ca-Na partitioning, with higher temperatures correlating with increased Ca incorporation in tourmaline. Based on the experimental findings, tourmaline is expected to have Ca-rich compositions when it forms in low pressure, high-temperature Ca-rich rocks, consistent with the current record of tourmaline occurrence. The bulk Mg/Al ratio and the pH of the tourmaline-forming system may also affect Ca incorporation in tourmaline, but remain to be investigated experimentally.

  2. Thermal transformation of quaternary compounds in NaF-CaF{sub 2}-AlF{sub 3} system

    SciTech Connect

    Zaitseva, Julia N.; Yakimov, Igor S.; Kirik, Sergei D.

    2009-08-15

    Details of quaternary compounds formation in the system NaF-CaF{sub 2}-AlF{sub 3} are specified. To achieve this aim, the samples of phases NaCaAlF{sub 6} and Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} have been obtained by high-temperature solid-phase synthesis. Their thermal behavior when heated up to 800 deg. C has been studied using the methods of high-temperature X-ray diffraction (XRD) and thermal analysis (TA). The system under consideration can be regarded as a quasibinary section CaF{sub 2}-NaAlF{sub 4}, where at T=745-750 deg. C invariant equilibrium is implemented with the phases CaF{sub 2}-NaCaAlF{sub 6}-Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}-(liquid melt)-(NaAlF{sub 4}). The peculiarity of the equilibrium is NaAlF{sub 4} metastability at normal pressure. Below the equilibrium temperature the quaternary phase Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} is stable and NaCaAlF{sub 6} above this temperature. The phase NaCaAlF{sub 6} fixed by rapid quenching from high temperatures and when heated up to 640 deg. C decomposes, yielding Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}. Further heating in vacuum at temperature up to 740 deg. C results in decomposition of Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} into CaF{sub 2} and Na{sub 3}AlF{sub 6}. The expected reverse transformation of Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14} into NaCaAlF{sub 6} has not been observed under experimental conditions. Transformations in bulk samples reveal direct and reverse transformation of quaternary phases. Synopsis: Thermal transformation of the quaternary compounds in system (NaF-CaF{sub 2}-AlF{sub 3}) was investigated using high-temperature X-ray diffraction (XRD) and thermal analysis (TA). In the system the invariant equilibrium is implemented with the phases CaF{sub 2}-NaCaAlF{sub 6}-Na{sub 2}Ca{sub 3}Al{sub 2}F{sub 14}-(liquid melt)-(NaAlF{sub 4}) at T=745-750 deg. C. - Graphical Abstract: The paper concerns of a small piece of the ternary system (NaF-CaF{sub 2}-AlF{sub 3}) which is very important for

  3. Early development of Al, Ca, and Na compositional gradients in labradorite leached in pH 2 HCl solutions

    NASA Astrophysics Data System (ADS)

    Nesbitt, H. W.; Skinner, W. M.

    2001-03-01

    Labradorite reacted with HCl solution (pH = 2.0) develops leached layers extending to about 500 Å depth after 12 h leaching, and to 1500 Å depth after 143 h leaching. Accurate Al, Ca, and Na compositional depth profiles were measured using x-ray photoelectron spectroscopy (XPS), with compositional accuracy of about 10% and depth resolution of about 50 Å. XPS analyses of pristine K-feldspar and labradorite surfaces yield Ca, Al, Si, and O analyses within about 5% of electron microprobe results. Alkali element analyses are inaccurate due to preferential sputtering or mobility induced by fracture. The accurate compositional depth profiles yield well constrained diffusion coefficients and moving boundary velocities for Ca and Al. Na, Ca, and Al compositional gradients change character after about 2 days of leaching, from a convex upward hyperboloid to a sigmoid shape. Thereafter, the feldspar diffusion front is clearly separated from the surface (where silica dissolution occurs), with the diffusion front migrating into the feldspar at about 4 × 10 -11 cm/s. Al diffuses down the compositional gradient at about 2.5 × 10 -17 cm 2/s and Ca diffuses almost twice as fast (4.0 × 10 -17 cm 2/s). The solution-solid interface and active leaching zone are separated (after 2 days) by a Si-rich zone virtually devoid of Na, Ca, and Al. Diffusion rates through this Si-rich overlayer may be very rapid and approach rates observed in aqueous solutions. Diffusive release of Ca and Al from labradorite cannot be modelled accurately with mathematical solutions where diffusion through homogeneous media is assumed. During leaching, Ca and Al apparently diffuse by "jumping" to, and residing on, previously vacated structural sites of the feldspar. The probability of Ca and Al migrating towards solution consequently is greater than their probability of migrating towards pristine plagioclase, primarily because there are many more "vacant" sites in the leached zone than in pristine

  4. Ag-Al-Ca

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 1 http://dx.doi.org/10.1007/97.etType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Ag-Al-Ca' with the content:

  5. Effects of CaO/SiO2 Ratio and Na2O Content on Melting Properties and Viscosity of SiO2-CaO-Al2O3-B2O3-Na2O Mold Fluxes

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Zhang, Chen; Cai, Dexiang; Zhang, Jianqiang; Sasaki, Yasushi; Ostrovski, Oleg

    2017-02-01

    This paper investigated the effects of CaO/SiO2 ratio (0.8 to 1.5) and Na2O concentration (6 to 9 wt pct) on melting properties and viscosity of SiO2-CaO-Al2O3-B2O3-Na2O mold fluxes with a fixed B2O3 content. Melting properties of fluxes (softening temperature T s, hemispherical temperature T h, and fluidity temperature T f) were determined by the hot-stage microscopy method. Viscosity was measured using rotating cylindrical viscometer, and structure of quenched fluxes was studied using Raman spectroscopy. Equilibrium phases in the SiO2-CaO-Al2O3-B2O3-Na2O system were calculated using FactSage. It was found that T h decreased with increasing CaO/SiO2 ratio from 0.8 to 1.0 and increased with a further increase in the CaO/SiO2 ratio to 1.5. The effect of Na2O content in the range of 6 to 9 wt pct on T h of the flux with a fixed CaO/SiO2 ratio at 1.3 was marginal. Increasing CaO/SiO2 ratio and Na2O content increased the break temperature and reduced the value of viscosity at 1673 K (1400 °C). Viscosity of liquid fluxes was discussed in the relationship with the flux structure. Melting properties and viscosity of boracic fluxes were compared with those of industrial fluorine-containing mold fluxes.

  6. An SEM, EDS and vibrational spectroscopic study of the silicate mineral meliphanite (Ca,Na)2Be[(Si,Al)2O6(F,OH)

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Theiss, Frederick L.; Romano, Antônio Wilson; Scholz, Ricardo

    2015-02-01

    The mineral meliphanite (Ca,Na)2Be[(Si,Al)2O6(F,OH)] is a crystalline sodium calcium beryllium silicate which has the potential to be used as piezoelectric material and for other ferroelectric applications. The mineral has been characterized by a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and vibrational spectroscopy. EDS analysis shows a material with high concentrations of Si and Ca and low amounts of Na, Al and F. Beryllium was not detected. Raman bands at 1016 and 1050 cm-1 are assigned to the SiO and AlOH stretching vibrations of three dimensional siloxane units. The infrared spectrum of meliphanite is very broad in comparison with the Raman spectrum. Raman bands at 472 and 510 cm-1 are assigned to OSiO bending modes. Raman spectroscopy identifies bands in the OH stretching region. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral meliphanite.

  7. Stability of Fluorine-Free CaO-SiO2-Al2O3-B2O3-Na2O Mold Fluxes

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Zhang, Jianqiang; Sasaki, Yasushi; Ostrovski, Oleg; Zhang, Chen; Cai, Dexiang

    2017-01-01

    B2O3 and Na2O are key components of fluorine-free mold fluxes for continuous casting, but both are highly volatile, which affects the flux stability. This paper investigated the evaporation of the SiO2-CaO-Al2O3-B2O3-Na2O fluxes (Na2O: 6 to 10 wt pct, CaO/SiO2 ratio: 0.8 to 1.3) in the temperatures ranging from 1573 K to 1673 K (1300 °C to 1400 °C) using thermogravimetric analysis. The weight loss as a result of the flux evaporation increased with the increasing temperature for all fluxes. The rate of evaporation was found to be very small for the Na2O-free flux but significantly increased with the addition of Na2O. The high evaporation rate of fluxes in the presence of B2O3 and Na2O was attributed to the formation of highly volatile NaBO2. Changing the ratio of CaO/SiO2, however, did not affect the rate of evaporation. Kinetic analysis of the evaporation processes demonstrated that external mass transfer contributed to the rate of evaporation.

  8. Stability of Fluorine-Free CaO-SiO2-Al2O3-B2O3-Na2O Mold Fluxes

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Zhang, Jianqiang; Sasaki, Yasushi; Ostrovski, Oleg; Zhang, Chen; Cai, Dexiang

    2017-04-01

    B2O3 and Na2O are key components of fluorine-free mold fluxes for continuous casting, but both are highly volatile, which affects the flux stability. This paper investigated the evaporation of the SiO2-CaO-Al2O3-B2O3-Na2O fluxes (Na2O: 6 to 10 wt pct, CaO/SiO2 ratio: 0.8 to 1.3) in the temperatures ranging from 1573 K to 1673 K (1300 °C to 1400 °C) using thermogravimetric analysis. The weight loss as a result of the flux evaporation increased with the increasing temperature for all fluxes. The rate of evaporation was found to be very small for the Na2O-free flux but significantly increased with the addition of Na2O. The high evaporation rate of fluxes in the presence of B2O3 and Na2O was attributed to the formation of highly volatile NaBO2. Changing the ratio of CaO/SiO2, however, did not affect the rate of evaporation. Kinetic analysis of the evaporation processes demonstrated that external mass transfer contributed to the rate of evaporation.

  9. Influences of Na2O and K2O Additions on Electrical Conductivity of CaO-MgO-Al2O3-SiO2 Melts

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Hua; Zheng, Wei-Wei; Chou, Kuo-Chih

    2017-01-01

    The present study investigated the influences of Na2O and K2O additions on electrical conductivity of blast furnace type CaO-MgO-Al2O3-SiO2 melts by the four-electrode method. Both the single addition of Na2O or K2O and the double additions of Na2O and K2O were studied. It was found that electrical conductivity monotonously increased as the amount of Na2O addition was gradually increased, whereas, when K2O was added, there was a continuous decrease of electrical conductivity. With melts containing both Na2O and K2O, electrical conductivity first decreased but then increased when Na2O was gradually substituted for K2O while keeping the molar fractions of other components constant. In other words, the mixed-alkali effect took place in CaO-Mg-Al2O3-SiO2-ΣR2O melts.

  10. Influences of Na2O and K2O Additions on Electrical Conductivity of CaO-MgO-Al2O3-SiO2 Melts

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Hua; Zheng, Wei-Wei; Chou, Kuo-Chih

    2017-04-01

    The present study investigated the influences of Na2O and K2O additions on electrical conductivity of blast furnace type CaO-MgO-Al2O3-SiO2 melts by the four-electrode method. Both the single addition of Na2O or K2O and the double additions of Na2O and K2O were studied. It was found that electrical conductivity monotonously increased as the amount of Na2O addition was gradually increased, whereas, when K2O was added, there was a continuous decrease of electrical conductivity. With melts containing both Na2O and K2O, electrical conductivity first decreased but then increased when Na2O was gradually substituted for K2O while keeping the molar fractions of other components constant. In other words, the mixed-alkali effect took place in CaO-Mg-Al2O3-SiO2-ΣR2O melts.

  11. Structure and microstructure of the glasses from NaCaPO4-SiO2 and NaCaPO4-SiO2-AlPO4 systems

    NASA Astrophysics Data System (ADS)

    Wajda, A.; Bułat, K.; Sitarz, M.

    2016-12-01

    Structure and microstructure of silico-phosphate glasses belong to NaXPO4-SiO2 and NaXPO4-SiO2-AlPO4 (where X = Ca or/and Mg) systems were investigated. Scanning electron microscopic studies combined with EDX were made it possible to show the occurrence of phase separation in the obtained materials. It was found that alumina has a homogenising effect on the microstructure of silico-phosphate glasses. Addition of a small amount of alumina (5 mol. % of AlPO4) causes the chemical compositions inversion of the matrix and the inclusions. Structural investigations of the obtained glasses as well as of the corresponding crystalline materials showed that the studied glasses exhibit domain composition. Structure of the domains is close to that of the corresponding crystalline phases. Spectroscopic investigations involving spectra decomposition into component bands were made it possible to establish the homogenising effect of aluminium on the structure of silicate-phosphate glasses. Presence of alumina leads to elimination of Pdbnd O bonds as well as replacement of Si-O-P by the Al-O-P ones.

  12. A clear effect of charge compensation through Na+ co-doping on the luminescence spectra and decay kinetics of Nd3+-doped CaAl4O7

    NASA Astrophysics Data System (ADS)

    Puchalska, M.; Watras, A.

    2016-06-01

    We present a detailed analysis of luminescence behavior of singly Nd3+ doped and Nd3+, Na+ co-doped calcium aluminates powders: Ca1-xNdxAl4O7 and Ca1-2xNdxNaxAl4O7 (x=0.001-0.1). Relatively intense Nd3+ luminescence in IR region corresponding to typical 4F3/2→4IJ (J=9/2-13/2) transitions with maximum located at about 1079 nm was obtained in all samples on direct excitation into f-f levels. The effect of dopant concentration and charge compensation by co-doping with Na+ ions on morphology and optical properties were studied. The results show that both, the Nd3+ concentration and the alkali metal co-doping affected the optical properties but had no influence on the powders morphology. The studies of luminescence spectra (298 and 77 K) in a function of dopant concentration showed an increasing distortion of the local symmetry of Nd3+with raising activator content due to certain defects created in the crystal lattice. On the other hand Na+ addition led to significant narrowing of absorption and luminescence bands and also a reduction of the number of their components, showing smaller disturbance of Nd3+ ions local symmetries. Consequently, charge compensated by Na+ co-doping materials showed significantly enhanced Nd3+ luminescence. The decrease of emission intensity and luminescence lifetimes with increase of activator concentration was attributed mainly to phonon-assisted cross-relaxation processes between Nd3+ ions. Analysis with Inokuti-Hirayama model indicated dipole-dipole mechanism of ion-ion interaction. Na+ addition led to much smaller concentration quenching due to smaller clustering of dopant ions in CaAl4O7 lattice.

  13. Genetic relationship between Na-rich chondrules and Ca,Al-rich inclusions? - Formation of Na-rich chondrules by melting of refractory and volatile precursors in the solar nebula

    NASA Astrophysics Data System (ADS)

    Ebert, Samuel; Bischoff, Addi

    2016-03-01

    Al-rich objects (Ca,Al-rich inclusions (CAIs), Al-rich chondrules, Al-rich fragments) occur in all chondrite classes. These objects can be centimeter-sized in CV3 carbonaceous chondrites, but they are generally much smaller in other chondrite groups and classes. Within the ordinary chondrites, most Al-rich objects are chondrules that vary from Ca- to Na-rich. Here, we have investigated the mineralogy and major element chemistry of 32 Na-rich chondrules and 3 Na-rich fragments from 15 different chondrites. Most objects (chondrules and chondrule fragments) are from ordinary chondrites (petrologic types 3.2-3.8), but two of the chondrules are from two CO3 chondrites, and three of the chondrules are from one Rumuruti (R)-chondrite. We found that these Na-rich objects have bulk Na2O-concentrations between 4.3 and 15.2 wt%. Texturally, they typically consist of euhedral to subhedral (often skeletal) mafic minerals (olivine and pyroxenes) embedded within a nepheline-normative, glassy mesostasis, which is brownish in transmitted light. In addition, some chondrules contain euhedral to subhedral spinel. Bulk chondrule compositions show group II, group III, and ultrarefractory rare earth element (REE) patterns similar to those found in CAIs. These results clearly demonstrate that the Na-rich chondrules must have been formed by melting of precursors containing an (ultra-)refractory element-rich component and Na-rich constituents. The Na-rich chondrules showed Sm and Eu anomalies, indicating that they must have formed at low oxygen fugacities. Based on the chemical composition of the Na-rich objects, we can rule out that they were formed as a result of planetary formation due to metasomatic processes or processes related to collisions between molten planetesimals.

  14. Thermodynamics of mixing in diopside jadeite, CaMgSi2O6 NaAlSi2O6, solid solution from static lattice energy calculations

    NASA Astrophysics Data System (ADS)

    Vinograd, Victor L.; Gale, Julian D.; Winkler, Björn

    2007-12-01

    Static lattice energy calculations (SLEC), based on empirical interatomic potentials, have been performed for a set of 800 different structures in a 2 × 2 × 4 supercell of C2/ c diopside with compositions between diopside and jadeite, and with different states of order of the exchangeable Na/Ca and Mg/Al cations. Excess static energies of these structures have been cluster expanded in a basis set of 37 pair-interaction parameters. These parameters have been used to constrain Monte Carlo simulations of temperature-dependent properties in the range of 273 2,023 K and to calculate a temperature composition phase diagram. The simulations predict the order disorder transition in omphacite at 1,150 ± 20°C in good agreement with the experimental data of Carpenter (Mineral Petrol 78:433 440, 1981). The stronger ordering of Mg/Al within the M1 site than of Ca/Na in the M2 site is attributed to the shorter M1 M1 nearest-neighbor distance, and, consequently, the stronger ordering force. The comparison of the simulated relationship between the order parameters corresponding to M1 and M2 sites with the X-ray refinement data on natural omphacites (Boffa Ballaran et al. in Am Mineral 83:419 433, 1998) suggests that the cation ordering becomes kinetically ineffective at about 600°C.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The effect of chlorine (Cl), fluorine (F) and water (H2O), alone and in combination, on the rheology and structure of synthetic peralkaline Na2O-CaO-Al2O3-SiO2 melts as an analog for highly evolved alkaline melts is investigated. We also investigated a peraluminous counterpart to study how the effect of Cl and F depends on the (Na+Ca)/Al ratio. The volatile-free melts were produced from oxide and carbonate powders at 1 atm and temperatures between 1200 and 1650 °C. Amounts of 0.5 to 1.3 mol% of Cl and 0.5 to 18 mol% F were added as NH4Cl, NH4F, NaCl, NaF, CaCl2 and CaF2. The composition of the samples was analysed by electron microprobe. The melts were hydrated with 0.5 to 4 wt% H2O. For the hydration of the peralkaline melts we used an internally heated pressure vessel at 1200 to 1250 °C and 1.5 to 3 kbar. Because of their high liquidus temperatures, the peraluminous melts were hydrated at 1600 to 1675°C and 5 kbar in a piston cylinder apparatus. Water contents were determined by Karl-Fischer-titration, thermogravimetry and IR-spectroscopy. The viscosities of the dry and hydrous peralkaline and peraluminous melts were measured with micropenetration and parallel plate techniques between 13 log10(Pa s) and 5.5 log10(Pa s). We found that the addition of 1.1 mol% Cl to peralkaline melts increased the viscosity by 0.8 log10(Pa s) while 1.9 mol% F decreased the viscosity by 1.2 log10(Pa s) relative to a viscosity of 12 log10(Pa s) of the halogen-free melt. In peralkaline melts containing equal amounts of both, Cl and F, the viscosity is 0.5 log10(Pa s) lower than the volatile-free melt, independent of the total amount of halogens. The effects of Cl and F seem to buffer each other. If there is twice as much F in the melt as Cl, the viscosity is reduced by 0.7 log10(Pa s). In peraluminous melts containing Cl and F the viscosity decreases with increasing volatile content independent of the ratio between the two volatiles. The addition of H2O decreases the viscosity of

  16. ITH33/IQM9.21 provides neuroprotection in a novel ALS model based on TDP-43 and Na(+)/Ca(2+) overload induced by VTD.

    PubMed

    Mouhid Al-Achbili, Lamia; Moreno-Ortega, Ana J; Matías-Guiu, Jorge; Cano-Abad, María F; Ruiz-Nuño, Ana

    2016-10-28

    Therapeutic options for amyotrophic lateral sclerosis (ALS) are scarce and controversial. Although the aetiology of neuronal vulnerability is unknown, growing evidence supports a complex network in which multiple toxicity pathways, rather than a single mechanism, are involved in the pathogenesis of ALS. However, most cellular models only explain single pathogenic mechanisms. The present study proposes the two main cytotoxic mechanisms: (1) veratridine (VTD), which induced Na(+) and Ca(2+) overload; and (2) the TARD DNA-binding protein 43 (TDP-43) in NSC-34 cell line as an in vitro model of ALS. The study was carried out by MTT as an indirect measurement of cell viability and by flow cytometry to determine cell death stages. The impact of Ca(2+) overload combined with TDP-43 overexpression increased early apoptosis of NSC-34 cells. Furthermore, we found that ITH33/IQM9.21 (ITH33) exerted a neuroprotective effect in this model by reducing activation of the apoptotic pathway. Therefore, treatment with VTD in TDP-43 overexpressing NSC-34 cells is a good in vitro ALS model that makes it possible to test new neuroprotective compounds such as ITH33.

  17. SEM, EDX and vibrational spectroscopic study of the mineral tunisite NaCa2Al4(CO3)4Cl(OH)8.

    PubMed

    Frost, Ray L; López, Andrés; Scholz, Ricardo; de Oliveira, Fernando A N

    2015-02-05

    The mineral tunisite has been studied by using a combination of scanning electron microscopy with energy dispersive X-ray fluorescence and vibrational spectroscopy. Chemical analysis shows the presence of Na, Ca, Al and Cl. SEM shows a pure single phase. An intense Raman band at 1127 cm(-1) is assigned to the carbonate ν1 symmetric stretching vibration and the Raman band at 1522 cm(-1) is assigned to the ν3 carbonate antisymmetric stretching vibration. Infrared bands are observed in similar positions. Multiple carbonate bending modes are found. Raman bands attributable to AlO stretching and bending vibrations are observed. Two Raman bands at 3419 and 3482 cm(-1) are assigned to the OH stretching vibrations of the OH units. Vibrational spectroscopy enables aspects of the molecular structure of the carbonate mineral tunisite to be assessed.

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

    PubMed

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

    2013-01-21

    Calcium phosphate based biomaterials are extensively used in the context of tissue engineering: small changes in composition can lead to significant changes in properties allowing their use in a wide range of applications. Samples of composition (Al(2)O(3))(x)(Na(2)O)(0.11-x)(CaO)(0.445)(P(2)O(5))(0.445), where x = 0, 0.03, 0.05, and 0.08, were prepared by melt quenching. The atomic-scale structure has been studied using neutron diffraction and solid state (27)Al MAS NMR, and these data have been rationalised with the determined density of the final glass product. With increasing aluminium concentration the density increases initially, but beyond about 3 mol. % Al(2)O(3) the density starts to decrease. Neutron diffraction data show a concomitant change in the aluminium speciation, which is confirmed by (27)Al MAS NMR studies. The NMR data reveal that aluminium is present in 4, 5, and 6-fold coordination and that the relative concentrations of these environments change with increasing aluminium concentration. Materials containing aluminium in 6-fold coordination tend to have higher densities than analogous materials with the aluminium found in 4-fold coordination. Thus, the density changes may readily be explained in terms of an increase in the relative concentration of 4-coordinated aluminium at the expense of 6-fold aluminium as the Al(2)O(3) content is increased beyond 3 mol. %.

  19. Hydrothermal synthesis and the crystal structure of borate cancrinite (Na,Ca){sub 2}[Na{sub 6}(AlSiO{sub 4}){sub 6}](BO{sub 3}) . 2H{sub 2}O

    SciTech Connect

    Shirinova, A. F. Khrustalev, V. N.; Samedov, H. R.; Chiragov, M. I.

    2006-01-15

    Transparent prismatic single crystals of borate cancrinite (Na,Ca){sub 2}[Na{sub 6}(AlSiO{sub 4}){sub 6}](BO{sub 3}) . 2H{sub 2}O are prepared through hydrothermal crystallization. The parameters of the hexagonal unit cell and intensities of 10806 reflections are measured on an Enraf-Nonius CAD4 automated diffractometer. The compound crystallizes in the hexagonal crystal system with the unit cell parameters a = 12.745(4) A, c = 5.180(2) A, V = 728.6(4) A{sup 3}, and space group P6{sub 3}. The structure is determined by direct methods and refined using the full-matrix least-squares procedure in the anisotropic approximation for the non-hydrogen atoms. The refinement of the structure is performed to the final discrepancy factor R{sub 1} = 0.027 for 2889 unique reflections with I > 2 {sigma} (I). In the structure of the borate cancrinite, the AlO{sub 4} and SiO{sub 4} tetrahedra form a zeolite-like framework in which twelve-membered hexagonal channels are occupied by sodium atoms and BO{sub 3} groups, whereas six-membered channels are filled with sodium and calcium atoms and water molecules. The mean interatomic distances are found to be as follows: (Si-O){sub mean} = 1.614 A and (Al-O){sub mean} = 1.741 A in the AlO{sub 4} and SiO{sub 4} tetrahedra, (Na-O){sub mean} = 2.542 A in the seven-vertex sodium polyhedra, and [(Na,Ca)-O]{sub mean} = 2.589 A in the ditrigonal bipyramids.

  20. Density functional investigation of metal encapsulated X@C 12Si 8 heterofullerene (X=Li +, Na +, K +, Be 2+, Mg 2+, Ca 2+, Al 3+, Ga 3+)

    NASA Astrophysics Data System (ADS)

    Shakib, F. A.; Momeni, M. R.

    2011-04-01

    The stability and the possible application of our recently reported SiC heterofullerenes inspire the investigation of their further stabilization through ion encapsulation. The endohedral complexes X@C 12Si 8, where X=Li +, Na +, K +, Be 2+, Mg 2+, Ca 2+, Al 3+, and Ga 3+, are probed at the MPWB1K/6-311G* and B3LYP/6-311G* levels of theory. The optimized geometries show the expanding or contracting capability of C 12Si 8 in order to accommodate metal ion guests. The inclusion energies indicate the stability of the complexes compared to the components. Meanwhile, the calculated binding energies show the stabilization of C 12Si 8 through the inclusion of Be 2+, Mg 2+, Al 3+, and Ga 3+. The host-guest interaction that is probed through NBO atomic charges supports the obtained results. This study refers to “metal ion encapsulation” as a strategy for stabilization of SiC heterofullerenes.

  1. Structural and electronic properties of AB- and AA-stacking bilayer-graphene intercalated by Li, Na, Ca, B, Al, Si, Ge, Ag, and Au atoms

    NASA Astrophysics Data System (ADS)

    Tayran, Ceren; Aydin, Sezgin; Çakmak, Mehmet; Ellialtıoğlu, Şinasi

    2016-04-01

    The structural and electronic properties of X (=Li, Na, Ca, B, Al, Si, Ge, Ag, and Au)-intercalated AB- and AA-stacking bilayer-graphene have been investigated by using ab initio density functional theory. It is shown that Boron (Lithium)-intercalated system is energetically more stable than the others for the AB (AA) stacking bilayer-graphene systems. The structural parameters, electronic band structures, and orbital nature of actual interactions are studied for the relaxed stable geometries. It is seen that the higher the binding energy, the smaller is the distance between the layers, in these systems. The electronic band structures for these systems show that different intercalated atoms can change the properties of bilayer-graphene differently. For qualitative description of the electronic properties, the metallicities of the systems are also calculated and compared with each other. The Mulliken analysis and electron density maps clearly indicate that the interactions inside a single layer (intralayer interactions) are strong and highly covalent, while the interactions between the two layers (interlayer interactions) are much weaker.

  2. A novel orange emitting Sm3+ ions doped NaCaAlPO4F3 phosphor: Optical and luminescence properties

    NASA Astrophysics Data System (ADS)

    Nagaraja, R.; Pushpa Manjari, V.; Sailaja, B.; Ravikumar, R. V. S. S. N.

    2017-02-01

    A novel orange light emitting Sm3+ ions doped NaCaAlPO4F3 phosphor was synthesized via solid state reaction. The prepared sample was characterized by powder X-ray diffraction (PXRD), Optical absorption, Photoluminescence (PL) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. From powder XRD data, the average crystallite size and structural parameters are estimated. Absorption spectra consist of ten absorption peaks corresponding to the transitions from the 6H5/2 ground state to various excited energy levels. Transition probabilities, branching ratios and radiative lifetime were evaluated by using Judd-Ofelt analysis. Photoluminescence spectrum show three prominent emission bands centered at 562, 597 and 643 nm corresponding to the 4G5/2 → 6HJ (J = 5/2, 7/2 and 9/2) transitions respectively. From the emission transitions, stimulated emission cross-section (σe) and gain bandwidth (GBW) were predicted. The decay profiles of the prepared phosphor reveals the single exponential nature and the experimental lifetime is calculated. The colorimetric parameters CIE coordinates, Correlated color temperature of the prepared phosphor are also evaluated. FT-IR spectrum demonstrates the characteristic vibration bands of the prepared phosphor material.

  3. Ca, Mg, Fe, Si, Al, and Na in the Massive, Metal-Rich, Dust-Enshrouded, DAZ White Dwarf GD 362

    NASA Astrophysics Data System (ADS)

    Melis, C.; Koester, D.; Zuckerman, B.; Rich, R. M.; Hansen, B.; Kalirai, J.

    2006-06-01

    GD362 presents the greatest number of atomic species ever documented in a hydrogen atmosphere white dwarf. Our spectroscopy with Keck I (LRIS; 4 Å red, 2 Å blue resolution) and KECK II (ESI, 0.5 Å resolution) covers the wavelengths 3100-7400 Å and 3850-11,000 Å , respectively; in these ranges we identify lines from H, Mg, Fe, Si, Al, Ca, and Na. Preliminary analysis of the spectra yields photospheric abundances for Mg, Fe, Si, and Al in about the solar ratio relative to each other and a few times below solar relative to hydrogen. Relative to the abundance of these four metals, the calcium (sodium) abundance is about a factor of 10 larger (smaller) in GD 362 than it is in the Sun. We do not detect oxygen in GD362. From this we derive a limit on its abundance by number at least 104 times below that of hydrogen. Tentatively, we derive from atmospheric models a surface gravity of log g ˜ 9.00 for GD362 (whose effective temperature is 9740 K). D1 and D2 sodium lines in the ESI spectrum are seen both from the stellar photosphere (broad and deep) and, probably, from the interstellar medium (narrow and weaker). However, GD362 emits mid-infrared flux in excess of its photospheric emission. The excess is due to a dusty disk located beyond ˜ 10 stellar radii. Thus, we cannot presently rule out circumstellar sodium as the carrier of the narrow feature. This research was supported in part by NASA's Astrobiology Institute and other NASA grants to UCLA.

  4. Tissintite, (Ca, Na,$${\\square}$$)AlSi2O6, a highly-defective, shock-induced, high-pressure clinopyroxene in the Tissint martian meteorite

    DOE PAGES

    Ma, Chi; Tschauner, Oliver; Beckett, John R.; ...

    2015-04-24

    Here, tissintite is a new vacancy-rich, high-pressure clinopyroxene, with a composition essentially equivalent to plagioclase. It was discovered in maskelynite (shocked plagioclase) and is commonly observed included within, or in contact with, shock-melt pockets in the Tissint meteorite, a depleted olivine-phyric shergottite fall from Mars. The simple composition of tissintite (An58-69) and its precursor plagioclase (An59-69) together with the limited occurrence, both spatially (only in maskelynite less than ~25 μm of a shock melt pocket) and in terms of bulk composition, make tissintite a "goldilocks" phase. It formed during a shock event severe enough to allow nucleation and growth of vacancy-rich clinopyroxene from a melt of not too calcic and not too sodic plagioclase composition that was neither too hot nor too cold. With experimental calibration, these limitations on occurrence can be used to place strong constraints on the thermal history of a shock event. The kinetics for nucleation and growth of tissintite are probably slower for more-sodic plagioclase precursors, so tissintite is most likely to occur in depleted olivinephyric shergottites like Tissint and other highly shocked meteorites and lunar and terrestrial rocks that consistently contained calcic plagioclase precursors in the appropriate compositional range for a shock of given intensity. Tissintite, (Ca0.45Na0.31more » $${\\square}$$ 0.24)(Al0.97Fe0.03Mg0.01)(Si1.80Al0.20)O6, is a C2/c clinopyroxene, containing 42-60 mol% of the Ca-Eskola component, by far the highest known. The cell parameters are a = 9.21 (17) Å, b = 9.09 (4) Å, c = 5.20 (2) Å, β = 109.6 (9)°, V = 410 (8) Å3, Z = 4. The density is 3.32 g/cm(3) and we estimate a cell volume for the Ca-Eskola end-member pyroxene of 411 ±13 Å3, which is consistent with a previous estimate and, therefore, supports the importance of this component in clinopyroxenes from ultra-high pressure metamorphic rocks from the Earth's upper mantle

  5. Tissintite, (Ca, Na, □)AlSi2O6, a highly-defective, shock-induced, high-pressure clinopyroxene in the Tissint martian meteorite

    NASA Astrophysics Data System (ADS)

    Ma, Chi; Tschauner, Oliver; Beckett, John R.; Liu, Yang; Rossman, George R.; Zhuravlev, Kirill; Prakapenka, Vitali; Dera, Przemyslaw; Taylor, Lawrence A.

    2015-07-01

    Tissintite is a new vacancy-rich, high-pressure clinopyroxene, with a composition essentially equivalent to plagioclase. It was discovered in maskelynite (shocked plagioclase) and is commonly observed included within, or in contact with, shock-melt pockets in the Tissint meteorite, a depleted olivine-phyric shergottite fall from Mars. The simple composition of tissintite (An58-69) and its precursor plagioclase (An59-69) together with the limited occurrence, both spatially (only in maskelynite less than ˜25 μm of a shock melt pocket) and in terms of bulk composition, make tissintite a "goldilocks" phase. It formed during a shock event severe enough to allow nucleation and growth of vacancy-rich clinopyroxene from a melt of not too calcic and not too sodic plagioclase composition that was neither too hot nor too cold. With experimental calibration, these limitations on occurrence can be used to place strong constraints on the thermal history of a shock event. The kinetics for nucleation and growth of tissintite are probably slower for more-sodic plagioclase precursors, so tissintite is most likely to occur in depleted olivine-phyric shergottites like Tissint and other highly shocked meteorites and lunar and terrestrial rocks that consistently contained calcic plagioclase precursors in the appropriate compositional range for a shock of given intensity. Tissintite, (Ca0.45Na0.31□0.24) (Al0.97Fe0.03Mg0.01) (Si1.80Al0.20)O6, is a C 2 / c clinopyroxene, containing 42-60 mol% of the Ca-Eskola component, by far the highest known. The cell parameters are a = 9.21 (17) Å, b = 9.09 (4) Å, c = 5.20 (2) Å, β = 109.6 (9)°, V = 410 (8) Å3, Z = 4. The density is 3.32 g/cm3 and we estimate a cell volume for the Ca-Eskola end-member pyroxene of 411 ± 13 Å3, which is consistent with a previous estimate and, therefore, supports the importance of this component in clinopyroxenes from ultra-high pressure metamorphic rocks from the Earth's upper mantle. At least in C 2 / c

  6. [Regulation of the Na/Ca exchanger].

    PubMed

    DiPolo, R; Rojas, H; Beaugé, L

    1993-01-01

    The introduction of the squid giant axon preparation to studies on Ca homeostasis has proven very useful in laying the foundations in the study of Ca regulation. In particular the Na/Ca exchange mechanism has been characterized in terms of its regulatory processes using the well define technique of intracellular dialysis and membrane potential control. The Na/Ca exchange countertransport system plays a critical role in physiological processes including cardiac contractility and photoreception. It has also been implicate in the etiology of essential hypertension, cardiac arrhythmias and cell death. The ability of the Na/Ca exchanger to regulate the intracellular ionized Ca concentration ([Ca2+i]) under physiological conditions, is determined by the direction (net Ca efflux or Ca influx), and magnitude of transport. The direction of Ca transport is decided by the chemical gradient of sodium and calcium. The magnitude of the exchange is regulated by kinetic factors. This kinetic factors are critical since they decide whether the exchanger will mediate a net Ca movement under certain conditions. Recently, a large effort has been put together to characterize the secondary modulation of the Na/Ca exchanger. In particular modulation by MgATP and intracellular Ca2+. In nerve cells we have discover that MgATP regulates the exchanger through as phosphorylation-dephosphorylation processes most probably relate to the action of a kinase-phosphatase system. The other important ligand that regulates the exchange activity is the level of [Ca2+i]. We have found the presence of a regulatory site in the cytoplasmic face of the exchanger different from the transport site and probably responsible for turning the carrier "on" or "off". In this article we will depict some of the processes involved in the metabolic and ionic regulation of the Na/Ca exchanger.

  7. Mixing Properties of CaMgSi2O6-KAlSi2O6-NaAlSi2O6 Clinopyroxenes Determined From Static Lattice Energy Minimization Calculations

    NASA Astrophysics Data System (ADS)

    Vinograd, V. L.; Safonov, O. G.; Winkler, B.

    2004-05-01

    Recent experimental studies (Chudinovskikh et al., 2001; Safonov et al., 2003) have shown that under pressures of 7-10 GPa clinopyroxen can contain up to 25 % of KAlSi2O6. This suggested that K-Cpx could be a major host of K in the upper mantle. Low K2O content of clinopyroxens of crustal origin could possibly be attributed to the instability of K-rich pyroxens with respect to other K-bearing phases. Thermodynamic calculations of phase equilibria in K-bearing systems require the knowledge of mixing properties of K-bearing pyroxens and standard properties of KAlSi2O6-Cpx. Here we report on our preliminary results of static lattice energy minimization calculations of the required thermodynamic parameters using the program GULP (Gale, 1997). We developed a new self-consistent set of interatomic potentials, which permitted us to accurately reproduce structural and elastic properties of major phases in the system K-Na-Ca-Mg-Al-Si-O and to predict the properties of the unknown KAlSi2O6 phase. It appears that the structural constants of this phase are close to those of diopside, while its elastic and thermodynamic properties are close to those of jadeite. The mixing properties of the disordered KAlSi2O6-CaMgSi2O6 solid solution we estimated using the supercell method: In the supercell of diopside containing 16 Ca and 16 Mg atoms we replaced randomly one Ca and one Mg with K and Al, respectively and calculated the increase in the lattice energy. Similar calculations have been done with the supercell containig 16 K and 16 Al atoms. These calculations permitted us to estimate Margules parameters of the subregular model of mixing (WK-cpx = 29.4, WDi = 26.5 kJ/mole) using the method of Sluiter and Kawazoe (2002). The analogous calculations for NaAlSi2O6-CaMgSi2O6 gave WJad = 41.85 and WDi = 39.86 kJ/mole. The latter numbers compare well with the Margules parameters derived by Wood et al. (1980) from calorimetric data. Thus, it appears that the KAlSi2O6 end member is able to

  8. Thermodynamic investigation of the CaO-Al[sub 2]O[sub 3]-CaCO[sub 3]-H[sub 2]O closed system at 25 C and the influence of Na[sub 2]O

    SciTech Connect

    Damidot, D.; Stronach, S.; Kindness, A.; Atkins, M.; Glasser, F.P. . Dept. of Chemistry)

    1994-01-01

    The solubilities of calcium hemicarboaluminate, calcium monocarboaluminate and calcium tricarboaluminate have been determined and the equilibrium phase diagram for the CaO-Al[sub 2]O[sub 3]-CaCO[sub 3]-H[sub 2]O closed system at 25 C has been calculated. Six isothermally invariant points have been located involving six stable hydrates: CH, C[sub 3]AH[sub 6], AH[sub 3], calcium hemicarboaluminate, calcium monocarboaluminate and calcite. Calcium tricarboaluminate, the carbonate analogue of ettringite, does not appear to be stable at 25 C. This study was part of a larger study on radioactive waste solidification.

  9. A clear effect of charge compensation through Na{sup +} co-doping on the luminescence spectra and decay kinetics of Nd{sup 3+}-doped CaAl{sub 4}O{sub 7}

    SciTech Connect

    Puchalska, M.; Watras, A.

    2016-06-15

    We present a detailed analysis of luminescence behavior of singly Nd{sup 3+} doped and Nd{sup 3+}, Na{sup +} co-doped calcium aluminates powders: Ca{sub 1−x}Nd{sub x}Al{sub 4}O{sub 7} and Ca{sub 1−2x}Nd{sub x}Na{sub x}Al{sub 4}O{sub 7} (x=0.001–0.1). Relatively intense Nd{sup 3+} luminescence in IR region corresponding to typical {sup 4}F{sub 3/2}→{sup 4}I{sub J} (J=9/2–13/2) transitions with maximum located at about 1079 nm was obtained in all samples on direct excitation into f–f levels. The effect of dopant concentration and charge compensation by co-doping with Na{sup +} ions on morphology and optical properties were studied. The results show that both, the Nd{sup 3+} concentration and the alkali metal co-doping affected the optical properties but had no influence on the powders morphology. The studies of luminescence spectra (298 and 77 K) in a function of dopant concentration showed an increasing distortion of the local symmetry of Nd{sup 3+}with raising activator content due to certain defects created in the crystal lattice. On the other hand Na{sup +} addition led to significant narrowing of absorption and luminescence bands and also a reduction of the number of their components, showing smaller disturbance of Nd{sup 3+} ions local symmetries. Consequently, charge compensated by Na{sup +} co-doping materials showed significantly enhanced Nd{sup 3+} luminescence. The decrease of emission intensity and luminescence lifetimes with increase of activator concentration was attributed mainly to phonon-assisted cross-relaxation processes between Nd{sup 3+} ions. Analysis with Inokuti–Hirayama model indicated dipole–dipole mechanism of ion-ion interaction. Na{sup +} addition led to much smaller concentration quenching due to smaller clustering of dopant ions in CaAl{sub 4}O{sub 7} lattice.

  10. Alloriite, Na5K1.5Ca(Si6Al6O24)(SO4)(OH)0.5 · H2O, a new mineral species of the cancrinite group

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Rastsvetaeva, R. K.; Pekov, I. V.; Zadov, A. E.

    2007-12-01

    Alloriite, a new mineral species, has been found in volcanic ejecta at Mt. Cavalluccio (Campagnano municipality, Roma province, Latium region, Italy) together with sanidine, biotite, andradite, and apatite. The mineral is named in honor of Roberto Allori (b. 1933), an amateur mineralogist and prominent mineral collector who carried out extensive and detailed field mineralogical investigations of volcanoes in the Latium region. Alloriite occurs as short prismatic and tabular crystals up to 1.5 × 2 mm in size. The mineral is colorless, transparent, with a white streak and vitreous luster. Alloriite is not fluorescent and brittle; the Mohs’ hardness is 5. The cleavage is imperfect parallel to {10overline 1 0}. The density measured with equilibration in heavy liquids is 2.35g/cm3 and calculated density ( D calc) is 2.358 g/cm3 (on the basis of X-ray single-crystal data) and 2.333 g/cm3 (from X-ray powder data). Alloriite is optically uniaxial, positive, ω = 1.497(2), and ɛ = 1.499(2). The infrared spectrum is given. The chemical composition (electron microprobe, H2O determined using the Penfield method, CO2, with selective sorption, wt %) is: 13.55 Na2O, 6.67 K2O, 6.23 CaO, 26.45 Al2O3, 34.64 SiO2, 8.92 SO3, 0.37 Cl, 2.1 H2O, 0.7 CO2, 0.08-O = Cl2, where the total is 99.55. The empirical formula ( Z = 1) is Na19.16K6.21Ca4.87(Si25.26Al22.74O96)(SO4)4.88(CO3)0.70Cl0.46(OH)0.76 · 4.73H2O. The simplified formula (taking into account the structural data, Z = 4) is: [Na(H2O)][Na4K1.5(SO4)] · [Ca(OH,Cl)0.5](Si6Al6O24). The crystal structure has been studied ( R = 0.052). Alloriite is trigonal, the space group is P31 c; the unit-cell dimensions are a = 12.892(3), c = 21.340(5) Å, and V = 3071.6(15) Å3. The crystal structure of alloriite is based on the same tetrahedral framework as that of afghanite. In contrast to afghanite containing clusters [Ca-Cl]+ and chains ...Ca-Cl-Ca-Cl..., the new mineral contains clusters [Na-H2O]+ and chains ...Na-H2O-Na-H2O.... The

  11. Crystal structure of the mineral (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4}: a triclinic representative of the amphibole family

    SciTech Connect

    Rastsvetaeva, R. K. Aksenov, S. M.

    2012-05-15

    A mineral belonging to the amphibole family found at the Rothenberg paleovolcano (Eifel, Germany) was studied by single-crystal X-ray diffraction. The triclinic pseudomonoclinic unit-cell parameters are a = 5.3113(1) Angstrom-Sign , b = 18.0457(3) Angstrom-Sign ; c = 9.8684(2) Angstrom-Sign , {alpha} = 90.016(2) Degree-Sign , {beta} = 105.543(4) Degree-Sign , {gamma} = 89.985(2) Degree-Sign . The structure was solved by direct methods in sp. gr. P1 and refined to the R factor of 2.7% based on 6432 reflections with |F| > 3{sigma}(F) taking into account twinning. The mineral with the idealized formula (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4} has some symmetry and structural features that distinguish it from other minerals of this family.

  12. Thermodynamic modeling of non-ideal mineral-fluid equilibria in the system Si-Al-Fe-Mg-Ca-Na-K-H-O-Cl at elevated temperatures and pressures: Implications for hydrothermal mass transfer in granitic rocks

    NASA Astrophysics Data System (ADS)

    Dolejš, David; Wagner, Thomas

    2008-01-01

    We present the results of thermodynamic modeling of fluid-rock interaction in the system Si-Al-Fe-Mg-Ca-Na-H-O-Cl using the GEM-Selektor Gibbs free energy minimization code. Combination of non-ideal mixing properties in solids with multicomponent aqueous fluids represents a substantial improvement and it provides increased accuracy over existing modeling strategies. Application to the 10-component system allows us to link fluid composition and speciation with whole-rock mineralogy, mass and volume changes. We have simulated granite-fluid interaction over a wide range of conditions (200-600 °C, 100 MPa, 0-5 m Cl and fluid/rock ratios of 10-2-104) in order to explore composition of magmatic fluids of variable salinity, temperature effects on fluid composition and speciation and to simulate several paths of alteration zoning. At low fluid/rock ratios (f/r) the fluid composition is buffered by the silicate-oxide assemblage and remains close to invariant. This behavior extends to a f/r of 0.1 which exceeds the amount of exsolved magmatic fluids controlled by water solubility in silicate melts. With increasing peraluminosity of the parental granite, the Na-, K- and Fe-bearing fluids become more acidic and the oxidation state increases as a consequence of hydrogen and ferrous iron transfer to the fluid. With decreasing temperature, saline fluids become more Ca- and Na-rich, change from weakly acidic to alkaline, and become significantly more oxidizing. Large variations in Ca/Fe and Ca/Mg ratios in the fluid are a potential geothermometer. The mineral assemblage changes from cordierite-biotite granites through two-mica granites to chlorite-, epidote- and zeolite-bearing rocks. We have carried out three rock-titration simulations: (1) reaction with the 2 m NaCl fluid leads to albitization, chloritization and desilication, reproducing essential features observed in episyenites, (2) infiltration of a high-temperature fluid into the granite at 400 °C leads to hydrolytic

  13. Esperanzaite, NaCa2Al2(As5+O4)2F4(OH)*2H2O, a new mineral species from the La Esperanza mine, Mexico: descriptive mineralogy and atomic arrangement

    USGS Publications Warehouse

    Foord, E.E.; Hughes, J.M.; Cureton, F.; Maxwell, C.H.; Falster, A.U.; Sommer, A.J.; Hlava, P.F.

    1999-01-01

    Esperanzaite, ideally NaCa2Al2(As5+O4)2F4(OH)??2H2O, Z = 2, is a new mineral species from the La Esperanza mine, Durango State, Mexico. The mineral occurs as blue-green botryoidal crystalline masses on rhyolite, with separate spheres up to 1.5 mm in diameter. The Mohs hardness is 4 1/2 , and the specific gravity, 3.24 (obs.) and 3.36(3) (calc.). Optical properties were measured in 589 nm light. Esperanzaite is biaxial (-), X = Y = Z = colorless, ?? 1.580(1), ?? 1.588(1), and ?? 1.593(1); 2V(obs) is 74(1)??and 2V(calc) is 76.3??. The dispersion is medium, r < v, and the optic axes are oriented according to a ?? Z = +50.5??, b = Y, c ?? X = +35??. The strongest five X-ray-diffraction maxima in the powder pattern [d in A??(I)(hkl)] are: 2.966(100)(131, 311, 031), 3.527(90)(220), 2.700(90)(221,002,040), 5.364(80)(001,020) and 4.796(80)(011). Esperanzaite is monoclinic, a 9.687(5), b 10.7379(6), c 5.5523(7) A??, ?? 105.32(1)??, space group P21/m. The atomic arrangement of esperanzaite was solved by direct methods and Fourier analysis (R = 0.032). The Fundamental Building Block (FBB) is formed of [001] stacks of heteropolyhedral tetramers; the tetramers are formed of two arsenate tetrahedra and two Al octahedra, corner-linked in four-member rings. The FBBs are linked by irregular Na??5 and Ca??8 polyhedra.

  14. Kinetics and stoichiometry of coupled Na efflux and Ca influx (Na/Ca exchange) in barnacle muscle cells

    PubMed Central

    1989-01-01

    Coupled Na+ exit/Ca2+ entry (Na/Ca exchange operating in the Ca2+ influx mode) was studied in giant barnacle muscle cells by measuring 22Na+ efflux and 45Ca2+ influx in internally perfused, ATP-fueled cells in which the Na+ pump was poisoned by 0.1 mM ouabain. Internal free Ca2+, [Ca2+]i, was controlled with a Ca-EGTA buffering system containing 8 mM EGTA and varying amounts of Ca2+. Ca2+ sequestration in internal stores was inhibited with caffeine and a mitochondrial uncoupler (FCCP). To maximize conditions for Ca2+ influx mode Na/Ca exchange, and to eliminate tracer Na/Na exchange, all of the external Na+ in the standard Na+ sea water (NaSW) was replaced by Tris or Li+ (Tris-SW or LiSW, respectively). In both Na-free solutions an external Ca2+ (Cao)-dependent Na+ efflux was observed when [Ca2+]i was increased above 10(-8) M; this efflux was half-maximally activated by [Ca2+]i = 0.3 microM (LiSW) to 0.7 microM (Tris-SW). The Cao-dependent Na+ efflux was half-maximally activated by [Ca2+]o = 2.0 mM in LiSW and 7.2 mM in Tris-SW; at saturating [Ca2+]o, [Ca2+]i, and [Na+]i the maximal (calculated) Cao-dependent Na+ efflux was approximately 75 pmol#cm2.s. This efflux was inhibited by external Na+ and La3+ with IC50's of approximately 125 and 0.4 mM, respectively. A Nai-dependent Ca2+ influx was also observed in Tris-SW. This Ca2+ influx also required [Ca2+]i greater than 10(-8) M. Internal Ca2+ activated a Nai-independent Ca2+ influx from LiSW (tracer Ca/Ca exchange), but in Tris-SW virtually all of the Cai-activated Ca2+ influx was Nai-dependent (Na/Ca exchange). Half-maximal activation was observed with [Na+]i = 30 mM. The fact that internal Ca2+ activates both a Cao-dependent Na+ efflux and a Nai- dependent Ca2+ influx in Tris-SW implies that these two fluxes are coupled; the activating (intracellular) Ca2+ does not appear to be transported by the exchanger. The maximal (calculated) Nai-dependent Ca2+ influx was -25 pmol/cm2.s. At various [Na+]i between 6 and 106 m

  15. Multicomponent diffusion in silicate melts: SiO2-TiO2-Al2O3-MgO-CaO-Na2O-K2O System

    NASA Astrophysics Data System (ADS)

    Guo, Chenghuan; Zhang, Youxue

    2016-12-01

    Nine successful diffusion couple experiments were carried out in a 7-component haplobasaltic silicate melt SiO2-TiO2-Al2O3-MgO-CaO-Na2O-K2O system to study multicomponent diffusion at ∼1500 °C and 1 GPa, typically with compositional gradients in only two components in each experiment. At least two concentration traverses were measured for each experiment. Effective binary diffusion coefficients (EBDC) for monotonic profiles were obtained by an error function fit, and the EBDC of a given component is dependent on its counter diffusing component, especially for SiO2. The EBDC's of SiO2 vary from 15.7 μm2/s when diffusing against Al2O3, to 102.9 μm2/s when diffusing against K2O. Furthermore, the multicomponent diffusion matrix was obtained by simultaneously fitting profiles of all oxides in all experiments. Most features in the diffusion profiles, for example uphill diffusion, are captured well by this 6 × 6 diffusion matrix. The slowest diffusing eigenvector is largely due to the exchange between Si and Al, and the fastest diffusing eigenvector is the exchange of Na with all other components. An anorthite dissolution experiment was also conducted to test whether the diffusion matrix can be applied to mineral dissolution experiments. The calculated diffusion profiles in the melt during anorthite dissolution roughly match the measured profiles, demonstrating the validity and utility of the diffusion matrix in this FeO-free aluminosilicate melt system.

  16. Vladimirivanovite, Na6Ca2[Al6Si6O24](SO4,S3,S2,Cl)2 · H2O, a new mineral of sodalite group

    NASA Astrophysics Data System (ADS)

    Sapozhnikov, A. N.; Kaneva, E. V.; Cherepanov, D. I.; Suvorova, L. F.; Levitsky, V. I.; Ivanova, L. A.; Reznitsky, L. Z.

    2012-12-01

    The results of an examination of vladimirivanovite, a new mineral of the sodalite group, found at the Tultui deposit in the Baikal region are discussed. The mineral occurs in the form of outer rims (0.01-3 mm thick) of lazurite, elongated segregations without faced crystals (0.2 to 3-4 mm in size; less frequently, 4 × 12-15 × 20 mm), and rare veinlets (up to 5 mm) hosted in calciphyre and marble. Vladimirivanovite is irregular and patchy dark blue. The mineral is brittle; on average, the microhardness VHN is 522-604, 575 kg/mm2; and the Mohs hardness is 5.0-5.5. The measured and calculated densities are 2.48(3) and 2.436 g/cm3, respectively. Vladimirivanovite is optically biaxial; 2 V meas = 63(±1)°, 2 V calc = 66.2°; the refractive indices are α = 1.502-1.507 (±0.002), N m = 1.509-1.514 (±0.002), and N g = 1.512-1.517 (±0.002). The chemical composition is as follows, wt %: 32.59 SiO2, 27.39 Al2O3, 7.66 CaO, 17.74 Na2O, 11.37 SO3, 1.94 S, 0.12 Cl, and 1.0 H2O; total is 99.62. The empirical formula calculated based on (Si + Al) = 12 with sulfide sulfur determined from the charge balance is Na6.36Ca1.52(Si6.03Al5.97)Σ12O23.99(SO4)1.58(S3)0.17(S2)0.08 · Cl0.04 · 0.62H2O; the idealized formula is Na6Ca2[Al6Si6O24](SO4,S3,S2,Cl)2 · H2O. The new mineral is orthorhombic, space group Pnaa; the unit-cell dimensions are a = 9.066, b = 12.851, c = 38.558 Å, V = 4492 Å3, and Z = 6. The strongest reflections in the X-ray powder diffraction pattern ( dÅ— I[ hkl]) are: 6.61-5[015], 6.43-11[020, 006], 3.71-100[119, 133], 2.623-30[20.12, 240], 2.273-6[04.12], 2.141-14[159, 13.15], 1.783-9[06.12, 04.18], and 1.606-6[080, 00.24]. The crystal structure has been solved with a single crystal. The mineral was named in memoriam of Vladimir Georgievich Ivanov (1947-2002), Russian mineralogist and geochemist. The type material of the mineral is deposited at the Mineralogical Museum of St. Petersburg State University, St. Petersburg, Russia.

  17. Conservation of Ca2+/Calmodulin Regulation across Na and Ca2+ channels

    PubMed Central

    Ben-Johny, Manu; Yang, Philemon S.; Niu, Jacqueline; Yang, Wanjun; Joshi-Mukherjee, Rosy; Yue, David T.

    2014-01-01

    SUMMARY Voltage-gated Na and Ca2+channels comprise distinct ion-channel superfamilies, yet the carboxy tails of these channels exhibit high homology hinting at a long-shared and purposeful module. For different Ca2+ channels, carboxyl-tail inter actions with calmodulin do elaborate robust and similar forms of Ca2+ regulation. However, Na channels have only shown subtler Ca2+modulation that differs among reports, challenging attempts at unified understanding. Here, by rapid Ca2+photoreleaseon to Na channels, we reset this view of Na channel regulation. For cardiac muscle channels (NaV1.5), reported effects from which most mechanistic proposals derive, we observe no Ca2+modulation. Conversely, for skeletal-muscle channels (NaV1.4), we uncover fast Ca2+ regulation eerily similar to that of Ca2+ channels. Channel opathic myotonia mutations halve NaV1.4 Ca2+ regulation, and transplanting the NaV1.4 carboxy tail onto Ca2+ channels recapitulates Ca2+ regulation. Thus we argue for the persistence and physiological relevance of an ancient Ca2+ regulatory module across Na and Ca2+ channels. PMID:24949975

  18. Biachellaite, (Na,Ca,K)8(Si6Al6O24)(SO4)2(OH)0.5 · H2O, a new mineral species of the cancrinite group

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Rastsvetaeva, R. K.; Pekov, I. V.; Zadov, A. E.; Allori, R.; Zubkova, N. V.; Giester, G.; Puscharovsky, D. Yu.; van, K. V.

    2009-12-01

    Biachellaite, a new mineral species of the cancrinite group, has been found in a volcanic ejecta in the Biachella Valley, Sacrofano Caldera, Latium region, Italy, as colorless isometric hexagonal bipyramidal-pinacoidal crystals up to 1 cm in size overgrowing the walls of cavities in a rock sample composed of sanidine, diopside, andradite, leucite and hauyne. The mineral is brittle, with perfect cleavage parallel to {10 bar 1 0} and imperfect cleavage or parting (?) parallel to {0001}. The Mohs hardness is 5. Dmeas = 2.51(1) g/cm3 (by equilibration with heavy liquids). The densities calculated from single-crystal X-ray data and from X-ray powder data are 2.515 g/cm3 and 2.520 g/cm3, respectively. The IR spectrum demonstrates the presence of SO{4/2-}, H2O, and absence of CO{3/2-}. Biachellaite is uniaxial, positive, ω = 1.512(1), ɛ = 1.514(1). The weight loss on ignition (vacuum, 800°C, 1 h) is 1.6(1)%. The chemical composition determined by electron microprobe is as follows, wt %: 10.06 Na2O, 5.85 K2O, 12.13 CaO, 26.17 Al2O3, 31.46 SiO2, 12.71 SO3, 0.45 Cl, 1.6 H2O (by TG data), -0.10 -O=Cl2, total is 100.33. The empirical formula ( Z = 15) is (Na3.76Ca2.50K1.44)Σ7.70(Si6.06Al5.94O24)(SO4)1.84Cl0.15(OH)0.43 · 0.81H2O. The simplified formula is as follows: (Na,Ca,K)8(Si6Al6O24)(SO4)2(OH)0.5 · H2O. Biachellaite is trigonal, space group P3, a =12.913(1), c = 79.605(5) Å; V = 11495(1) Å3. The crystal structure of biachellaite is characterized by the 30-layer stacking sequence ( ABCABCACACBACBACBCACBACBACBABC)∞. The tetrahedral framework contains three types of channels composed of cages of four varieties: cancrinite, sodalite, bystrite (losod) and liottite. The strongest lines of the X-ray powder diffraction pattern [ d, Å ( I, %) ( hkl)] are as follows: 11.07 (19) (100, 101), 6.45 (18) (110, 111), 3.720 (100) (2.1.10, 300, 301, 2.0.16, 302), 3.576 (18) (1.0.21, 2.0.17, 306), 3.300 (47) (1.0.23, 2.1.15), 3.220 (16) (2.1.16, 222). The type material of

  19. Study of OSL in NaF: Ca,Cu

    NASA Astrophysics Data System (ADS)

    More, Y. K.; Wankhede, S. P.; Moharil, S. V.

    2013-06-01

    Sodium Fluoride containing Cu+ ions was prepared by R.A.P. followed by melt-quenching technique. Results on photo, thermo and optically stimulated luminescence in NaF:Ca,Cu are reported. OSL sensitivity of NaF:Ca,Cu is approximately 2 times than that of standard phosphor LMP. The rate of OSL depletion for 90% decay for NaF:Ca,Cu is 0.3 times as that of OSL phosphor LMP. NaF:Ca,Cu thus deserves much more attention than it has received up till now.

  20. Role of Na+/Ca2+ exchanger in Ca2+ homeostasis in rat suprachiasmatic nucleus neurons

    PubMed Central

    Wang, Yi-Chi; Chen, Ya-Shuan; Cheng, Ruo-Ciao

    2015-01-01

    Intracellular Ca2+ is critical to the central clock of the suprachiasmatic nucleus (SCN). However, the role of Na+/Ca2+ exchanger (NCX) in intracellular Ca2+ concentration ([Ca2+]i) homeostasis in the SCN is unknown. Here we show that NCX is an important mechanism for somatic Ca2+ clearance in SCN neurons. In control conditions Na+-free solution lowered [Ca2+]i by inhibiting TTX-sensitive as well as nimodipine-sensitive Ca2+ influx. With use of the Na+ ionophore monensin to raise intracellular Na+ concentration ([Na+]i), Na+-free solution provoked rapid Ca2+ uptake via reverse NCX. The peak amplitude of 0 Na+-induced [Ca2+]i increase was larger during the day than at night, with no difference between dorsal and ventral SCN neurons. Ca2+ extrusion via forward NCX was studied by determining the effect of Na+ removal on Ca2+ clearance after high-K+-induced Ca2+ loads. The clearance of Ca2+ proceeded with two exponential decay phases, with the fast decay having total signal amplitude of ∼85% and a time constant of ∼7 s. Na+-free solution slowed the fast decay rate threefold, whereas mitochondrial protonophore prolonged mostly the slow decay. In contrast, blockade of plasmalemmal and sarco(endo)plasmic reticulum Ca2+ pumps had little effect on the kinetics of Ca2+ clearance. RT-PCR indicated the expression of NCX1 and NCX2 mRNAs. Immunohistochemical staining showed the presence of NCX1 immunoreactivity in the whole SCN but restricted distribution of NCX2 immunoreactivity in the ventrolateral SCN. Together our results demonstrate an important role of NCX, most likely NCX1, as well as mitochondrial Ca2+ uptake in clearing somatic Ca2+ after depolarization-induced Ca2+ influx in SCN neurons. PMID:25568156

  1. The effect of SiO2/Al2O3 ratio on the structure and microstructure of the glazes from SiO2-Al2O3-CaO-MgO-Na2O-K2O system

    NASA Astrophysics Data System (ADS)

    Partyka, Janusz; Sitarz, Maciej; Leśniak, Magdalena; Gasek, Katarzyna; Jeleń, Piotr

    2015-01-01

    Ceramic glazes are commonly used to covering of the facing surface of ceramics ware. A well-chosen oxide composition and firing conditions of glazes causes significant improvement of technical parameters of ceramic products. Modern glazes are classified as glass-ceramic composites with different crystalline phases arising during firing. The presence of crystals in the glass matrix is influenced by many factors, especially by oxides molar composition. A crucial role is played by the molar ratio of SiO2/Al2O3. In this work the six composition of glazes from SiO2-Al2O3-CaO-MgO-Na2O-K2O system were examined. The only variable is the ratio of the silicon oxideto alumina at a constant content of other components: MgO, CaO, K2O, Na2O, ZnO. In order to determine the real phase composition of the obtained glazes research on fluorescence spectrometer (XRF) were done. For structural studies X-ray diffraction (XRD) and spectroscopic in the middle infrared (MIR) were performed. In order to determine the state of the surface (microstructure) research on the scanning electron microscope (SEM) with EDX. The research allowed to determine the influence of SiO2/Al2O3 ratio on the structure and phase composition of glazes and the nature, and type of formed crystalline phases.

  2. LiCaAl/sub 6/:Cr/sup 3+/

    SciTech Connect

    Payne, S.A.; Chase, L.L.; Newkirk, H.W.; Smith, L.K.; Krupke, W.F. )

    1988-11-01

    The authors report the discovery of a new laser, LiCaAIF/sub 6/:Cr/sup 3/ (Cr/sup 3+/ :LiCAF). The intrinsic (extrapolated maximum) slope efficiency was found to be 67 percent. For comparison, they also measured the intrinsic slope efficiencies of BeAl/sub 2/O/sub 4/:Cr/sup 3+/ (alexandrite), Na/sub 3/Ga/sub 2/Li/sub 3/F/sub 12/:Cr/sup 3+/, and ScBO/sub 3/:Cr/sup 3+/, and obtained values of 65,28, and 26 percent, respectively. The tuning range of LiCaAIF/sub 6/:Cr/sup 3+/ was determined to be at least 720-840 nm. The conventional spectroscopic properties, such as the absorption, emission, and emission lifetimes as a function of temperature, are reported as well.

  3. Thermal Conductivity of Molten Silicate of Al2O3-CaO-Na2O-SiO2 Measured by Means of a Front Heating-Front Detection Laser Flash Method

    NASA Astrophysics Data System (ADS)

    Hasegawa, Hiroki; Kowatari, Takaya; Shiroki, Yasuhiro; Shibata, Hiroyuki; Ohta, Hiromichi; Waseda, Yoshio

    2012-12-01

    Thermal conductivity values have been systematically obtained for molten silicates containing Al2O3, CaO, Na2O, and SiO2 by means of a front heating-front detection laser flash method. The measurements were made for 13 samples in the temperature range between 1073 K and 1823 K (800 °C and 1550 °C), depending on the composition. Thermal conductivities of the silicate melts are found to be relatively insensitive to the variation of temperature, but they depend on the composition ratio, particularly the ratio of Non-Bridging Oxygen ions per Tetrahedrally coordinated cation—NBO/T. The thermal conductivity values decrease from 2.8 W/mK to 1.5 W/mK with the NBO/T value until it reaches about 1. Thermal conductivity values become constant for silicate melts with a higher value of NBO/T. It is known that the length of the silicate chain decreases with disconnection by the addition of alkaline earth cation or alkaline cation. The strong correlation between thermal conductivity and NBO/T is quite likely to suggest that silicate chain is a preferential path for heat transport in silicate melts.

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

    PubMed

    Partyka, Janusz; Leśniak, Magdalena

    2016-01-05

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

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

    NASA Astrophysics Data System (ADS)

    Partyka, Janusz; Leśniak, Magdalena

    2016-01-01

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

  6. Tissintite, (Ca, Na,${\\square}$)AlSi2O6, a highly-defective, shock-induced, high-pressure clinopyroxene in the Tissint martian meteorite

    SciTech Connect

    Ma, Chi; Tschauner, Oliver; Beckett, John R.; Liu, Yang; Rossman, George R.; Zhuravlev, Kirill; Prakapenka, Vitali; Dera, Przemyslaw; Taylor, Lawrence A.

    2015-04-24

    Here, tissintite is a new vacancy-rich, high-pressure clinopyroxene, with a composition essentially equivalent to plagioclase. It was discovered in maskelynite (shocked plagioclase) and is commonly observed included within, or in contact with, shock-melt pockets in the Tissint meteorite, a depleted olivine-phyric shergottite fall from Mars. The simple composition of tissintite (An58-69) and its precursor plagioclase (An59-69) together with the limited occurrence, both spatially (only in maskelynite less than ~25 μm of a shock melt pocket) and in terms of bulk composition, make tissintite a "goldilocks" phase. It formed during a shock event severe enough to allow nucleation and growth of vacancy-rich clinopyroxene from a melt of not too calcic and not too sodic plagioclase composition that was neither too hot nor too cold. With experimental calibration, these limitations on occurrence can be used to place strong constraints on the thermal history of a shock event. The kinetics for nucleation and growth of tissintite are probably slower for more-sodic plagioclase precursors, so tissintite is most likely to occur in depleted olivinephyric shergottites like Tissint and other highly shocked meteorites and lunar and terrestrial rocks that consistently contained calcic plagioclase precursors in the appropriate compositional range for a shock of given intensity. Tissintite, (Ca0.45Na0.31${\\square}$ 0.24)(Al0.97Fe0.03Mg0.01)(Si1.80Al0.20)O6, is a C2/c clinopyroxene, containing 42-60 mol% of the Ca-Eskola component, by far the highest known. The cell parameters are a = 9.21 (17) Å, b = 9.09 (4) Å, c = 5.20 (2) Å, β = 109.6 (9)°, V = 410 (8) Å3, Z = 4. The density is 3.32 g/cm(3) and we estimate a cell volume for the Ca-Eskola end-member pyroxene of 411 ±13 Å3, which is consistent with a previous estimate and, therefore, supports the importance

  7. Na+/Ca2+ exchangers: three mammalian gene families control Ca2+ transport.

    PubMed

    Lytton, Jonathan

    2007-09-15

    Mammalian Na+/Ca2+ exchangers are members of three branches of a much larger family of transport proteins [the CaCA (Ca2+/cation antiporter) superfamily] whose main role is to provide control of Ca2+ flux across the plasma membranes or intracellular compartments. Since cytosolic levels of Ca2+ are much lower than those found extracellularly or in sequestered stores, the major function of Na+/Ca2+ exchangers is to extrude Ca2+ from the cytoplasm. The exchangers are, however, fully reversible and thus, under special conditions of subcellular localization and compartmentalized ion gradients, Na+/Ca2+ exchangers may allow Ca2+ entry and may play more specialized roles in Ca2+ movement between compartments. The NCX (Na+/Ca2+ exchanger) [SLC (solute carrier) 8] branch of Na+/Ca2+ exchangers comprises three members: NCX1 has been most extensively studied, and is broadly expressed with particular abundance in heart, brain and kidney, NCX2 is expressed in brain, and NCX3 is expressed in brain and skeletal muscle. The NCX proteins subserve a variety of roles, depending upon the site of expression. These include cardiac excitation-contraction coupling, neuronal signalling and Ca2+ reabsorption in the kidney. The NCKX (Na2+/Ca2+-K+ exchanger) (SLC24) branch of Na+/Ca2+ exchangers transport K+ and Ca2+ in exchange for Na+, and comprises five members: NCKX1 is expressed in retinal rod photoreceptors, NCKX2 is expressed in cone photoreceptors and in neurons throughout the brain, NCKX3 and NCKX4 are abundant in brain, but have a broader tissue distribution, and NCKX5 is expressed in skin, retinal epithelium and brain. The NCKX proteins probably play a particularly prominent role in regulating Ca2+ flux in environments which experience wide and frequent fluctuations in Na+ concentration. Until recently, the range of functions that NCKX proteins play was generally underappreciated. This situation is now changing rapidly as evidence emerges for roles including photoreceptor

  8. Esperanzaite, NaCa(2)Al(2)(As(5+)O(4))[As(5+)O(3)(OH)](OH)(2)F(4)(H(2)O), A New Mineral From Mina La Esperanza, Mexico: Descriptive Mineralogy and Atomic Arrangement

    SciTech Connect

    Cureton, F.; Falster, A.U.; Foord, E.E.; Hlava, P.F.; Hughes, J.M.; Maxwell, C.H.

    1998-11-09

    Esperanzaite, ideally NaCazA12(As5+0.i)[As5+03 (OH)] (OH)2FJH20), Z =2, is a new mineral from the Mina h Esperarq Durango State, Mexico. The mineral occurs as blue-green botryoidal crystalline masses on rhyolite, with separate spheres up to 1.5 mm Y Deceased in diameter. Mobs hardness is 4.5, specific gravity 3.240h, and 3.36( 3)C.IC. Optical properties were measured in 589 nm light. Esperanzaite is biaxial (-), .Y= Y = Z= colorless, a 1.580(1), ~ 1.588( 1), and y 1.593(1 ); 2V0hs is 74(1 ~ and 2 }'CUIC is 76.3". Dispersion is medium, r < v, and optic axes are oriented as a A Z = +50.5o, b = Y, c P. X = +35". The five strongest X-ray diffraction maxima in the powder pattern are (~ /, hk~: 2.966,100, 13 i, 31 i, 031 ; 3.527,90, 220; 2.700,90,221,002, 040; 5.364>80, 001, 020; 4.796,80,011. Esperanzaite is monoclinic, u 9.687(5), b 10.7379(6), c 5.5523(7)& ~ 105.32( 1 )", space group P21/nz. The atomic arrangement of esperanzaite was solved by Direct Methods and Fourier analysis (R= 0.03 1). The Fundamental Building Block is formed of stacks of heteropolyhedral tetramers; the tetramers are formed of two arsenate tetrahedral and two Al octahedra, comer-linked in 4-member rings. The Fundamental Building Blocks are linked by irregular lda~j and Ca@ polyhedra.

  9. Extremely Na and Cl Rich Chondrule Al3509 from the Allende Meteorite

    NASA Astrophysics Data System (ADS)

    Wasserburg, G. J.; Hutcheon, I. D.; Aleon, J.; Ramon, E. C.; Krot, A. N.; Nagashima, K.; Brearley, A. J.

    2011-03-01

    This Ca-Al-rich chondrule is not a replacement product. It has ~10% Na and ~1% Cl. Large excesses of 36S were found uncorrelated with Cl and 26Al/27Al < 3 x 10^-6. It represents the fluid responsible for late alteration in volatile-rich outer layers prior to formation of Allende.

  10. Cathodic behavior of molten CaCl2-CaO and CaCl2-NaCl-CaO

    NASA Astrophysics Data System (ADS)

    Wang, Shu-Lan; Wang, Wei; Li, Shi-Chao; Cao, Shan-Hui

    2010-12-01

    The cathodic behavior of molten CaCl2, CaCl2-CaO and equimolar CaCl2-NaCl-CaO was studied by cyclic voltammograms and constant potential polarization at temperatures of 1123 to 1173 K on molybdenum and titanium electrodes. The diffusion coefficient of Ca2+ (CaO) in molten CaCl2-CaO was calculated from the linear relationship between the square root of scan rate and the peak current density. The deposition potentials and the potential temperature coefficient of CaO in molten CaCl2-0.5mol%CaO and CaCl2-NaCl-0.5mol%CaO were also obtained from their cyclic voltammograms. The result shows that CaO is more easily reduced than CaCl2. The addition of NaCl in molten CaCl2-CaO induces the underpotential electrodeposition of CaO.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  12. Na+/Ca2+ exchange and Na+/K+-ATPase in the heart

    PubMed Central

    Shattock, Michael J; Ottolia, Michela; Bers, Donald M; Blaustein, Mordecai P; Boguslavskyi, Andrii; Bossuyt, Julie; Bridge, John H B; Chen-Izu, Ye; Clancy, Colleen E; Edwards, Andrew; Goldhaber, Joshua; Kaplan, Jack; Lingrel, Jerry B; Pavlovic, Davor; Philipson, Kenneth; Sipido, Karin R; Xie, Zi-Jian

    2015-01-01

    This paper is the third in a series of reviews published in this issue resulting from the University of California Davis Cardiovascular Symposium 2014: Systems approach to understanding cardiac excitation–contraction coupling and arrhythmias: Na+ channel and Na+ transport. The goal of the symposium was to bring together experts in the field to discuss points of consensus and controversy on the topic of sodium in the heart. The present review focuses on cardiac Na+/Ca2+ exchange (NCX) and Na+/K+-ATPase (NKA). While the relevance of Ca2+ homeostasis in cardiac function has been extensively investigated, the role of Na+ regulation in shaping heart function is often overlooked. Small changes in the cytoplasmic Na+ content have multiple effects on the heart by influencing intracellular Ca2+ and pH levels thereby modulating heart contractility. Therefore it is essential for heart cells to maintain Na+ homeostasis. Among the proteins that accomplish this task are the Na+/Ca2+ exchanger (NCX) and the Na+/K+ pump (NKA). By transporting three Na+ ions into the cytoplasm in exchange for one Ca2+ moved out, NCX is one of the main Na+ influx mechanisms in cardiomyocytes. Acting in the opposite direction, NKA moves Na+ ions from the cytoplasm to the extracellular space against their gradient by utilizing the energy released from ATP hydrolysis. A fine balance between these two processes controls the net amount of intracellular Na+ and aberrations in either of these two systems can have a large impact on cardiac contractility. Due to the relevant role of these two proteins in Na+ homeostasis, the emphasis of this review is on recent developments regarding the cardiac Na+/Ca2+ exchanger (NCX1) and Na+/K+ pump and the controversies that still persist in the field. PMID:25772291

  13. X-Ray Data on Extraterrestrial CA Dialuminate (CaAl4O7)

    NASA Astrophysics Data System (ADS)

    Weber, D.; Ross, C. R., II; Bischoff, A.

    1993-07-01

    After the first discovery of Ca-dialuminate (CaAl4O7) in Allende [1], in recent years this phase has been found in several carbonaceous chondrites. Ca- dialuminate is a major phase in Ca,Al-rich inclusions from ALH85085 (e.g., [2]) and a dominating phase in CAIs from Acfer 182 ([3,4]). X-ray data on Ca-dialuminate are known from synthetic (e.g., [5-8]; cell constants) and terrestrial CaAl4O7 ([9]; only d-spacings), but are not available from extraterrestrial Ca-dialuminate. We report here the results of the first X-ray study of extraterrestrial Ca- dialuminate. The data (Table 1) were obtained by microdiffraction using a Rigaku PSPC microdiffractometer at the Bayerisches Geoinstitut. Ni-filtered Cr radiation was used with a direct beam diameter of about 50 micrometers. This powder diffraction method allows in situ measurement of polycrystalline Ca- dialuminate in a thin section. The CaAl4O7-rich inclusion 022/9 described in [4], consisting of a ~200-micrometer-sized core of Ca-dialuminate surrounded by layers of melilite and Ca-pyroxene, was chosen for analysis. The polycrystalline core contains only a small number of tiny inclusions (especially perovskite) and is therefore an excellent candidate for an X-ray study. For determination of the d-spacings of Ca-dialuminate an external standard (Ag6Ge10P12) was used for detector calibration. A large number of reflections could be indexed based upon comparison with the X-ray pattern of synthetic CaAl4O7 available in the JCPDS compilation [7]. The comparison was simplified because of the high purity of CaAl4O7 in inclusion 022/9 [4], and suggests the same structure for synthetic and extraterrestrial Ca-dialuminate. For determination of lattice parameters (cell constants, cell volume) refinement calculations were made based on 14 reflections (Table 1). The data for extraterrestrial CaAl4O7 shown in Table 1 indicate a close similarity to those obtained for synthetic CaAl4O7. The cell constants a, b, and therefore the cell

  14. NaAlF{sub 4}: Preparation, crystal structure and thermal stability

    SciTech Connect

    Kirik, Sergei D.; Zaitseva, Julia N.

    2010-02-15

    The compound NaAlF{sub 4} has been obtained in the form of thin fibrous crystals or fine colorless powder by condensation at 18 deg. C of vapors arising over chiolite Na{sub 5}Al{sub 3}F{sub 14} or NaCaAlF{sub 6}, heated up to 800 deg. C. Thermal stability has been investigated by the methods of thermal analysis and high temperature X-ray diffraction. When heated in air, NaAlF{sub 4} is stable up to 390-400 deg. C, then there is an exothermal solid state decay into Na{sub 5}Al{sub 3}F{sub 14}(s) and AlF{sub 3}(s). At higher temperature Na{sub 5}Al{sub 3}F{sub 14}(s) decays into Na{sub 3}AlF{sub 6}(s) and NaAlF{sub 4}(g). The crystal structure (space group Cmcm, a=3.6124(1) A, b=14.9469(7) A, c=5.2617(3) A, V=284.10 A{sup 3}) has been determined by X-ray powder diffraction method. In the crystal structure of NaAlF{sub 4} the octahedrons [AlF{sub 6}] are joined through vertices and form corrugated layers, sodium ion layers being located between them. The distances between the atoms of Al-F are in the range 1.791-1.814 A, and those for Na...F are in the range 2.297-2.439 A. In spite of limited thermal stability of the crystal form, the compound NaAlF{sub 4} is the main component of the gas mixture over solid and molten salts in the ternary system NaF-AlF{sub 3}-CaF{sub 2} and participates in chemical transformations between the phases at high temperature. - Graphical abstract: The compound NaAlF{sub 4} was for the first time described 55 years ago, but until now it was not properly studied. Meantime the phase is responsible for the most low-melting part of the NaF-AlF{sub 3} system, which is the great importance for the aluminum production. The lack of information about NaAlF{sub 4} is due to narrow interval of stability which is close to liquid part of the system.

  15. Regulation of cardiac myocyte contractility by phospholemman: Na+/Ca2+ exchange versus Na+ -K+ -ATPase.

    PubMed

    Song, Jianliang; Zhang, Xue-Qian; Wang, JuFang; Cheskis, Ellina; Chan, Tung O; Feldman, Arthur M; Tucker, Amy L; Cheung, Joseph Y

    2008-10-01

    Phospholemman (PLM) regulates cardiac Na(+)/Ca(2+) exchanger (NCX1) and Na(+)-K(+)-ATPase in cardiac myocytes. PLM, when phosphorylated at Ser(68), disinhibits Na(+)-K(+)-ATPase but inhibits NCX1. PLM regulates cardiac contractility by modulating Na(+)-K(+)-ATPase and/or NCX1. In this study, we first demonstrated that adult mouse cardiac myocytes cultured for 48 h had normal surface membrane areas, t-tubules, and NCX1 and sarco(endo)plasmic reticulum Ca(2+)-ATPase levels, and retained near normal contractility, but alpha(1)-subunit of Na(+)-K(+)-ATPase was slightly decreased. Differences in contractility between myocytes isolated from wild-type (WT) and PLM knockout (KO) hearts were preserved after 48 h of culture. Infection with adenovirus expressing green fluorescent protein (GFP) did not affect contractility at 48 h. When WT PLM was overexpressed in PLM KO myocytes, contractility and cytosolic Ca(2+) concentration ([Ca(2+)](i)) transients reverted back to those observed in cultured WT myocytes. Both Na(+)-K(+)-ATPase current (I(pump)) and Na(+)/Ca(2+) exchange current (I(NaCa)) in PLM KO myocytes rescued with WT PLM were depressed compared with PLM KO myocytes. Overexpressing the PLMS68E mutant (phosphomimetic) in PLM KO myocytes resulted in the suppression of I(NaCa) but had no effect on I(pump). Contractility, [Ca(2+)](i) transient amplitudes, and sarcoplasmic reticulum Ca(2+) contents in PLM KO myocytes overexpressing the PLMS68E mutant were depressed compared with PLM KO myocytes overexpressing GFP. Overexpressing the PLMS68A mutant (mimicking unphosphorylated PLM) in PLM KO myocytes had no effect on I(NaCa) but decreased I(pump). Contractility, [Ca(2+)](i) transient amplitudes, and sarcoplasmic reticulum Ca(2+) contents in PLM KO myocytes overexpressing the S68A mutant were similar to PLM KO myocytes overexpressing GFP. We conclude that at the single-myocyte level, PLM affects cardiac contractility and [Ca(2+)](i) homeostasis primarily by its direct

  16. Thermogynamics of Genesis of Ca-Al-Inclusions in Chrondrites

    NASA Astrophysics Data System (ADS)

    Shornikov, S. I.

    2013-09-01

    The semi-empirical model was used for thermodynamic calculations of composition changes in the Ca-Al-Inclusions in chondrites during their evaporation and condensation. The presented model discussed with the Grossman approaches.

  17. Selective Na+/Ca2+ exchanger inhibition prevents Ca2+ overload-induced triggered arrhythmias

    PubMed Central

    Nagy, Norbert; Kormos, Anita; Kohajda, Zsófia; Szebeni, Áron; Szepesi, Judit; Pollesello, Piero; Levijoki, Jouko; Acsai, Károly; Virág, László; Nánási, Péter P; Papp, Julius Gy; Varró, András; Tóth, András

    2014-01-01

    Background and Purpose Augmented Na+/Ca2+ exchanger (NCX) activity may play a crucial role in cardiac arrhythmogenesis; however, data regarding the anti-arrhythmic efficacy of NCX inhibition are debatable. Feasible explanations could be the unsatisfactory selectivity of NCX inhibitors and/or the dependence of the experimental model on the degree of Ca2+i overload. Hence, we used NCX inhibitors SEA0400 and the more selective ORM10103 to evaluate the efficacy of NCX inhibition against arrhythmogenic Ca2+i rise in conditions when [Ca2+]i was augmented via activation of the late sodium current (INaL) or inhibition of the Na+/K+ pump. Experimental Approach Action potentials (APs) were recorded from canine papillary muscles and Purkinje fibres by microelectrodes. NCX current (INCX) was determined in ventricular cardiomyocytes utilizing the whole-cell patch clamp technique. Ca2+i transients (CaTs) were monitored with a Ca2+-sensitive fluorescent dye, Fluo-4. Key Results Enhanced INaL increased the Ca2+ load and AP duration (APD). SEA0400 and ORM10103 suppressed INCX and prevented/reversed the anemone toxin II (ATX-II)-induced [Ca2+]i rise without influencing APD, CaT or cell shortening, or affecting the ATX-II-induced increased APD. ORM10103 significantly decreased the number of strophanthidin-induced spontaneous diastolic Ca2+ release events; however, SEA0400 failed to restrict the veratridine-induced augmentation in Purkinje-ventricle APD dispersion. Conclusions and Implications Selective NCX inhibition – presumably by blocking revINCX (reverse mode NCX current) – is effective against arrhythmogenesis caused by [Na+]i-induced [Ca2+]i elevation, without influencing the AP waveform. Therefore, selective INCX inhibition, by significantly reducing the arrhythmogenic trigger activity caused by the perturbed Ca2+i handling, should be considered as a promising anti-arrhythmic therapeutic strategy. PMID:25073832

  18. Observations of Al, Fe and Ca(+) in Mercury's Exosphere

    NASA Technical Reports Server (NTRS)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

    We report 5-(sigma) tangent column detections of Al and Fe, and strict 3-(sigma) tangent column upper limits for Ca(+) in Mercury's exosphere obtained using the HIRES spectrometer on the Keck I telescope. These are the first direct detections of Al and Fe in Mercury's exosphere. Our Ca(-) observation is consistent with that reported by The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft.

  19. Thermal conductivity of molten Na 2SiO 3 and CaNa 4Si 3O 9

    NASA Astrophysics Data System (ADS)

    Gier, Elizabeth J.; Carmichael, Ian S. E.

    1996-01-01

    we have measured the thermal conductivity of two molten silicates using the transient hot-wire method developed by Nieto de Castro et al. (1976) and adapted for high temperature measurement by Snyder et al. (1994). The results for Na 2SiO 3 and CaNa 4Si 3O 9 show the same strong temperature dependence as shown for CaMgSi 2O 6, with activation energies whose magnitudes are similar to those for viscous flow. As the effect of composition is comparable to that of temperature, we suggest that to model cooling of magmas, values of λ between 0.05 and 0.3 (W/mK) should be used.

  20. Na-Ca exchange and the trigger for sarcoplasmic reticulum Ca release: studies in adult rabbit ventricular myocytes.

    PubMed Central

    Litwin, S E; Li, J; Bridge, J H

    1998-01-01

    The importance of Na-Ca exchange as a trigger for sarcoplasmic reticulum (SR) Ca release remains controversial. Therefore, we measured whole-cell Ca currents (ICa), Na-Ca exchange currents (INaCa), cellular contractions, and intracellular Ca transients in adult rabbit cardiac myocytes. We found that changing pipette Na concentration markedly affected the relationship between cell shortening (or Ca transients) and voltage, but did not affect the Ca current-voltage relationship. We then inhibited Na-Ca exchange and varied SR content (by changing the number of conditioning pulses before each test pulse). Regardless of SR Ca content, the relationship between contraction and voltage was bell-shaped in the absence of Na-Ca exchange. Next, we rapidly and completely blocked ICa by applying nifedipine to cells. Cellular shortening was variably reduced in the presence of nifedipine. The component of shortening blocked by nifedipine had a bell-shaped relationship with voltage, whereas the "nifedipine-insensitive" component of contraction increased with voltage. With the SR disabled (ryanodine and thapsigargin pretreatment), ICa could initiate late-peaking contractions that were approximately 70% of control amplitude. In contrast, nifedipine-insensitive contractions could not be elicited in the presence of ryanodine and thapsigargin. Finally, we recorded reverse Na-Ca exchange currents that were activated by membrane depolarization. The estimated sarcolemmal Ca flux occurring by Na-Ca exchange (during voltage clamp steps to +30 mV) was approximately 10-fold less than that occurring by ICa. Therefore, Na-Ca exchange alone is unlikely to raise cytosolic Ca concentration enough to directly activate the myofilaments. We conclude that reverse Na-Ca exchange can trigger SR Ca release. Because of the sigmoidal relationship between the open probability of the SR Ca release channel and pCa, the effects of ICa and INaCa may not sum in a linear fashion. Rather, the two triggers may act

  1. Lanthanum and neodymium solubility in simplified SiO{sub 2}-B{sub 2}O{sub 3}-Na{sub 2}O-Al{sub 2}O{sub 3}-CaO high level waste glass

    SciTech Connect

    Kidari, Abdessamad; Bardez-Giboire, Isabelle

    2012-08-15

    Lanthanum and neodymium incorporation in simplified high level waste glasses has been investigated for SiO{sub 2}B{sub 2}O{sub 3}Na{sub 2}OAl{sub 2}O{sub 3}CaO compositions quenched from 1200 degrees C, for varying La /(La + Nd) (atomic) and increasing rare-earth oxides contents. In this system and beyond the solubility limit, rare-earths (RE) elements are reported to form apatite phases with the general formula Ca{sub 2}RE{sub 8}(SiO{sub 4}){sub 6}O{sub 2}. In the current study, speciation of these trivalent RE{sup 3+} cations in both amorphous network and crystal phases was determined from X-ray diffraction, scanning electron microscopy, optical absorption at 10 K, Raman spectroscopy, and electron probe microanalysis. It appeared that RE{sub 2}O{sub 3} solubility was higher for La -rich formulations than for Nd -rich ones and that an increase in the RE oxide content reduces the connectivity of the network building units through formation of non-bridging oxygens at the expense of the oxygen bridges. This depolymerization of the glass network did not affect neodymium environment which consisted in silicate tetrahedra. The composition of the apatite crystals was found to be affected by the La /(La + Nd) of the parent glass and deviation from the ideal composition (Ca{sub 2}RE{sub 8}(SiO{sub 4}){sub 6}O{sub 2}) occurred in the neodymium end of the system. It thus appears that both RE{sub 2}O{sub 3} solubility and crystal composition are strongly dependent on the type and crystal chemistry of the RE elements. (authors)

  2. The initial 41Ca/40Ca ratios in two type A Ca-Al-rich inclusions: Implications for the origin of short-lived 41Ca

    NASA Astrophysics Data System (ADS)

    Liu, Ming-Chang

    2017-03-01

    This paper reports new 41Ca-41K isotopic data for two Type A CAIs, NWA 3118 #1Nb (Compact Type A) and Vigarano 3138 F8 (Fluffy Type A), from reduced CV3 chondrites. The NWA CAI is found to have carried live 41Ca at the level of (4.6 ± 1.9) ×10-9 , consistent with the proposed Solar System initial 41Ca /40Ca = 4.2 ×10-9 by Liu et al. (2012a). On the other hand, the Vigarano CAI does not have resolvable radiogenic 41K excesses that can be attributed to the decay of 41Ca. Combined with the 26Al data that have been reported for these two CAIs, we infer that the 41Ca distribution was not homogeneous when 26Al was widespread at the canonical level of 26Al /27Al = 5.2 ×10-5 . Such a 41Ca heterogeneity can be understood under two astrophysical contexts: in situ charged particle irradiation by the protoSun in the solar nebula that had inherited some baseline 10Be abundance from the molecular cloud, and Solar System formation in a molecular cloud enriched in 26Al and 41Ca contaminated by massive star winds. That said, more high quality 41Ca data are still needed to better understand the origin of this radionuclide.

  3. Effect of alloying elements Al and Ca on corrosion resistance of plasma anodized Mg alloys

    NASA Astrophysics Data System (ADS)

    Anawati, Asoh, Hidetaka; Ono, Sachiko

    2016-04-01

    Plasma anodizing is a surface treatment used to form a ceramic-type oxide film on Mg alloys by the application of a high anodic voltage to create intense plasma near the metal surface. With proper selection of the process parameters, the technique can produce high quality oxide with superior adhesion, corrosion resistance, micro-hardness, wear resistance and strength. The effect of alloying element Al on plasma anodizing process of Mg alloys was studied by comparing the anodizing curves of pure Mg, AZ31, and AZ61 alloys while the effect of Ca were studied on AZ61 alloys containing 0, 1, and 2 wt% Ca. Anodizing was performed in 0.5 M Na3PO4 solution at a constant current density of 200 Am-2 at 25°C. Anodic oxide films with lava-like structure having mix composition of amorphous and crystal were formed on all of the alloys. The main crystal form of the oxide was Mg3(PO4)2 as analyzed by XRD. Alloying elements Al and Ca played role in modifying the plasma lifetime during anodization. Al tended to extend the strong plasma lifetime and therefore accelerated the film thickening. The effect of Ca on anodizing process was still unclear. The anodic film thickness and chemical composition were altered by the presence of Ca in the alloys. Electrochemical corrosion test in 0.9% NaCl solution showed that the corrosion behavior of the anodized specimens depend on the behavior of the substrate. Increasing Al and Ca content in the alloys tended to increase the corrosion resistance of the specimens. The corrosion resistance of the anodized specimens improved significantly about two orders of magnitude relative to the bare substrate.

  4. Ca2+ signaling evoked by activation of Na+ channels and Na+/Ca2+ exchangers is required for GABA-induced NG2 cell migration

    PubMed Central

    Tong, Xiao-ping; Li, Xiang-yao; Zhou, Bing; Shen, Wanhua; Zhang, Zhi-jun; Xu, Tian-le

    2009-01-01

    NG2 cells originate from various brain regions and migrate to their destinations during early development. These cells express voltage-gated Na+ channels but fail to produce typical action potentials. The physiological role of Na+ channels in these cells is unclear. We found that GABA induces membrane depolarization and Ca2+ elevation in NG2 cells, a process requiring activation of GABAA receptors, Na+ channels, and Na+/Ca2+ exchangers (NCXs), but not Ca2+ channels. We have identified a persistent Na+ current in these cells that may underlie the GABA-induced pathway of prolonged Na+ elevation, which in turn triggers Ca2+ influx via NCXs. This unique Ca2+ signaling pathway is further shown to be involved in the migration of NG2 cells. Thus, GABAergic signaling mediated by sequential activation of GABAA receptors, noninactivating Na+ channels, and NCXs may play an important role in the development and function of NG2 glial cells in the brain. PMID:19596850

  5. Aluminian Low-Ca Pyroxene in a Ca-Al-rich Chondrule from the Semarkona Meteorite

    NASA Technical Reports Server (NTRS)

    Rubin, Alan E.

    2006-01-01

    A Ca-AI-rich chondrule (labeled G7) from the Semarkona LL3.0 ordinary chondrite (OC) consists of 73 vol% glassy mesostasis, 22 vol% skeletal forsterite. 3 vol% fassaite (i.e., Al-Ti diopside), and 2 vol% Al-rich, low-Ca pyroxene. The latter phase, which contains up to 16.3 wt% A1203, is among the most AI-rich, low-Ca pyroxene grains ever reported. It is inferred that 20% of the tetrahedral sites and 13% of the octahedral sites in this grain are occupied by Al. Approximately parallel optical extinction implies that the Al-rich, low-Ca pyroxene grains are probably orthorhombic, consistent with literature data that show that A1203 stabilizes the orthoenstatite structure relative to protoenstatite at low pressure. The order of crystallization in the chondrule was forsterite, AI-rich low-Ca pyroxene, and fassaite; the residual liquid vitrified during chondrule quenching. Phase relationships indicate that, for a G7-composition liquid at equilibrium, spinel and anorthite should crystallize early and orthopyroxene should not crystallize at all. The presence of AI-rich orthopyroxene in G7 is due mainly to the kinetic failure of anorthite to crystallize; this failure was caused by quenching of the G7 precursor droplet. Aluminum preferentially enters the relatively large B tetrahedra of orthopyroxene; because only one tetrahedral size occurs in fassaite, this phase contains higher mean concentrations of Al2O3 than the Al-rich orthopyroxene (17.8 and 14.7 wt%, respectively). Chondrule G7 may have formed by remelting an amoeboid olivine inclusion that entered the OC region of the solar nebula during an episode of chondrule formation.

  6. Al-Ca and Al-Fe metal-metal composite strength, conductivity, and microstructure relationships

    SciTech Connect

    Kim, Hyong June

    2011-01-01

    Deformation processed metal-metal composites (DMMC’s) are composites formed by mechanical working (i.e., rolling, swaging, or wire drawing) of two-phase, ductile metal mixtures. Since both the matrix and reinforcing phase are ductile metals, the composites can be heavily deformed to reduce the thickness and spacing of the two phases. Recent studies have shown that heavily drawn DMMCs can achieve anomalously high strength and outstanding combinations of strength and conductivity. In this study, Al-Fe wire composite with 0.07, 0.1, and 0.2 volume fractions of Fe filaments and Al-Ca wire composite with 0.03, 0.06, and 0.09 volume fractions of Ca filaments were produced in situ, and their mechanical properties were measured as a function of deformation true strain. The Al-Fe composites displayed limited deformation of the Fe phase even at high true strains, resulting in little strengthening effect in those composites. Al-9vol%Ca wire was deformed to a deformation true strain of 13.76. The resulting Ca second-phase filaments were deformed to thicknesses on the order of one micrometer. The ultimate tensile strength increased exponentially with increasing deformation true strain, reaching a value of 197 MPa at a true strain of 13.76. This value is 2.5 times higher than the value predicted by the rule of mixtures. A quantitative relationship between UTS and deformation true strain was determined. X-ray diffraction data on transformation of Al + Ca microstructures to Al + various Al-Ca intermetallic compounds were obtained at the Advanced Photon Source at Argonne National Laboratory. Electrical conductivity was measured over a range of true strains and post-deformation heat treatment schedules.

  7. Effect of dronedarone on Na+, Ca2+ and HCN channels.

    PubMed

    Bogdan, Roman; Goegelein, Heinz; Ruetten, Hartmut

    2011-04-01

    Previous studies showed that amiodarone causes state-dependent inhibition of Na(+) channels thereby mediating an atrial-selective drug effect. The aim of the present study was to investigate the impact of the new antiarrhythmic compound dronedarone on Na(+), Ca(2+) and hyperpolarization-activated cyclic nucleotide-gated ion channels. Monophasic action potentials (MAP) and effective refractory period (ERP) were studied in arterially perfused left atria and ventricular wedge preparations of the pig. Fast Na(+) and Ca(2+) currents in isolated guinea pig ventricular myocytes as well as human HCN4 channels expressed in Chinese hamster ovary (CHO) cells were investigated with the patch-clamp technique. In left atrial epicardial tissue, dronedarone (3 μM) had no effect on the MAP duration, but the drug caused a significant prolongation of the ERP from 145 ± 9 to 184 ± 17 ms (n = 6; p < 0.05). In guinea pig ventricular myocytes, dronedarone exhibited a state-dependent inhibition of the fast Na(+) channel current with an IC(50) of 0.7 ± 0.1 μM, when the holding potential (V (hold)) was -80 mV. The maximal block at the highest concentration used was 77 ± 8%. In contrast, when V (hold) was -100 mV, inhibition with 10 μM dronedarone was only 9 ± 3% (n = 7). Dronedarone blocked Ca(2+) currents elicited by rectangular pulses at V (hold) = -40 mV with an IC(50) value of 0.4 ± 0.1 μM (maximal block by 10 μM dronedarone, 80 ± 6%), whereas at V (hold) = -80 mV, 10 μM dronedarone blocked only 20 ± 6% (n = 4) of the current. Applying an action potential clamp (V (hold) = -80 mV) yielded an IC(50) of 0.4 ± 0.3 μM. Human HCN4 channels expressed in CHO cells were blocked by dronedarone with an IC(50) of 1.0 ± 0.1 μM. Inhibition of fast Na(+) and Ca(2+) channels by dronedarone depends on the cell's resting membrane potential (state-dependent block) favouring an atrial-selective mode of

  8. Na3Al(AsO4)2

    PubMed Central

    Fakhar Bourguiba, Noura; Zid, Mohamed Faouzi; Driss, Ahmed

    2013-01-01

    The structure of the title compound tris­odium aluminium bis­(arsenate), Na3Al(AsO4)2, is built up from AlO4 and AsO4 corner-sharing tetra­hedra, forming an undulating two-dimensional framework parallel to (100). The layers are constituted of large Al6As6O36 rings made up from six AlO4 and AsO4 tetra­hedra in which two sodium cations are situated, the third sodium cation being located in the inter­layer space. The structural relationships between the title compound and Na3Fe(PO4)2, NaAlCo(PO4)2 and Al5Co3(PO4)8 are discussed. PMID:23424394

  9. Na+-Ca2+ exchanger contributes to Ca2+ extrusion in ATP-stimulated endothelium of intact rat aorta.

    PubMed

    Berra-Romani, Roberto; Raqeeb, Abdul; Guzman-Silva, Alejandro; Torres-Jácome, Julián; Tanzi, Franco; Moccia, Francesco

    2010-04-23

    The role of Na(+)-Ca(2+) exchanger (NCX) in vascular endothelium is still matter of debate. Depending on both the endothelial cell (EC) type and the extracellular ligand, NCX has been shown to operate in either the forward (Ca(2+) out)- or the reverse (Ca(2+) in)-mode. In particular, acetylcholine (Ach) has been shown to promote Ca(2+) inflow in the intact endothelium of excised rat aorta. Herein, we assessed the involvement of NCX into the Ca(2+) signals elicited by ATP in such preparation. Removal of extracellular Na(+) (0Na(+)) causes the NCX to switch into the reverse-mode and induced an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), which disappeared in the absence of extracellular Ca(2+), and in the presence of benzamil, which blocks both modes of NCX, and KB-R 7943, a selective inhibitor of the reverse-mode. ATP induced a transient Ca(2+) signal, whose decay was significantly prolonged by 0Na(+), benzamil, DCB, and monensin while it was unaffected by KB-R 7943. Notably, lowering extracellular Na(+) concentration increased the sensibility to lower doses of ATP. These date suggest that, unlike Ach-stimulated ECs, NCX promotes Ca(2+) extrusion when the stimulus is provided by ATP in intact endothelium of rat aorta. These data show that, within the same preparation, NCX operates in both modes, depending on the chemical nature of the extracellular stimulus.

  10. Coordinated regulation of cardiac Na(+)/Ca (2+) exchanger and Na (+)-K (+)-ATPase by phospholemman (FXYD1).

    PubMed

    Cheung, Joseph Y; Zhang, Xue-Qian; Song, Jianliang; Gao, Erhe; Chan, Tung O; Rabinowitz, Joseph E; Koch, Walter J; Feldman, Arthur M; Wang, JuFang

    2013-01-01

    Phospholemman (PLM) is the founding member of the FXYD family of regulators of ion transport. PLM is a 72-amino acid protein consisting of the signature PFXYD motif in the extracellular N terminus, a single transmembrane (TM) domain, and a C-terminal cytoplasmic tail containing three phosphorylation sites. In the heart, PLM co-localizes and co-immunoprecipitates with Na(+)-K(+)-ATPase, Na(+)/Ca(2+) exchanger, and L-type Ca(2+) channel. The TM domain of PLM interacts with TM9 of the α-subunit of Na(+)-K(+)-ATPase, while its cytoplasmic tail interacts with two small regions (spanning residues 248-252 and 300-304) of the proximal intracellular loop of Na(+)/Ca(2+) exchanger. Under stress, catecholamine stimulation phosphorylates PLM at serine(68), resulting in relief of inhibition of Na(+)-K(+)-ATPase by decreasing K(m) for Na(+) and increasing V(max), and simultaneous inhibition of Na(+)/Ca(2+) exchanger. Enhanced Na(+)-K(+)-ATPase activity lowers intracellular Na(+), thereby minimizing Ca(2+) overload and risks of arrhythmias. Inhibition of Na(+)/Ca(2+) exchanger reduces Ca(2+) efflux, thereby preserving contractility. Thus, the coordinated actions of PLM during stress serve to minimize arrhythmogenesis and maintain inotropy. In acute cardiac ischemia and chronic heart failure, either expression or phosphorylation of PLM or both are altered. PLM regulates important ion transporters in the heart and offers a tempting target for development of drugs to treat heart failure.

  11. The mitochondrial Na+/Ca2+ exchanger plays a key role in the control of cytosolic Ca2+ oscillations.

    PubMed

    Hernández-SanMiguel, Esther; Vay, Laura; Santo-Domingo, Jaime; Lobatón, Carmen D; Moreno, Alfredo; Montero, Mayte; Alvarez, Javier

    2006-07-01

    There is increasing evidence that mitochondria play an important role in the control of cytosolic Ca2+ signaling. We show here that the main mitochondrial Ca2+-exit pathway, the mitochondrial Na+/Ca2+ exchanger, controls the pattern of cytosolic Ca2+ oscillations in non-excitable cells. In HeLa cells, the inhibitor of the mitochondrial Na+/Ca2+ exchanger CGP37157 changed the pattern of the oscillations induced by histamine from a high-frequency irregular one to a lower frequency baseline spike type, surprisingly with little changes in the average Ca2+ values of a large cell population. In human fibroblasts, CGP37157 increased the frequency of the baseline oscillations in cells having spontaneous activity and induced the generation of oscillations in cells without spontaneous activity. This effect was dose-dependent, disappeared when the inhibitor was washed out and was not mimicked by mitochondrial depolarization. CGP37157 increased mitochondrial [Ca2+] and ATP production in histamine-stimulated HeLa cells, but the effect on ATP production was only transient. CGP37157 also activated histamine-induced Ca2+ release from the endoplasmic reticulum and increased the size of the cytosolic Ca2+ peak induced by histamine in HeLa cells. Our results suggest that the mitochondrial Na+/Ca2+ exchanger directly modulates inositol 1,4,5-trisphosphate-induced Ca2+ release and in that way controls cytosolic Ca2+ oscillations.

  12. Na(+)-Ca sup 2+ exchange in cultured rat hepatocytes: Evidence against a role in cytosolic Ca sup 2+ regulation or signaling

    SciTech Connect

    Lidofsky, S.D.; Xie, M.H.; Scharschmidt, B.F. )

    1990-07-01

    Plasma membrane Na(+)-Ca2+ exchange contributes importantly to the regulation of cytosolic Ca2+ concentration ((Ca2+)i) in excitable cells. Despite extensive study in excitable tissues, the role of this transporter in the regulation of (Ca2+)i in hepatocytes is unknown, and conflicting information has been reported regarding the presence of Na(+)-Ca2+ exchange in hepatocyte plasma membrane vesicles. We have therefore assessed the role of Na(+)-dependent Ca2+ transport in the regulation of (Ca2+)i in rat hepatocytes in primary culture under basal conditions and after exposure to vasopressin, a hormone that elevates (Ca2+)i. Ca2+ efflux, measured using 45Ca, did not differ in the presence or absence of extracellular Na+, either under basal conditions or in response to vasopressin. (Ca2+)i, measured using the Ca2(+)-sensitive dye fura-2, was not altered by transient or prolonged exposure to Na(+)-free media or by exposure to ouabain in concentrations sufficient to produce a five-fold elevation in intracellular Na+ concentration. The (Ca2+)i response to vasopressin was also unaffected by Na+ removal or ouabain. By contrast, in cultured rat cardiac myocytes, cells that possess Na(+)-Ca2+ exchange, transient or prolonged Na+ removal as well as ouabain exposure produced greater than fivefold increases in (Ca2+)i compared with controls. We conclude that Na(+)-Ca2+ exchange does not contribute to the regulation of (Ca2+)i in hepatocytes.

  13. Neutral carrier Na+- and Ca2+-selective microelectrodes for intracellular application.

    PubMed Central

    Dagostino, M; Lee, C O

    1982-01-01

    Na+- and Ca2+-selective microelectrodes were made with Simon's neutral carrier ETH 227 and ETH 1001, respectively, and their properties were studied for intracellular application. The kNaK (selectivity coefficient for Na+ with respect to K+) values of the Na+-selective microelectrodes were in the range of 0.01-0.02, which is comparable to those of recessed-tip Na+-selective glass microelectrodes. The kNaMg values of the microelectrodes were approximately 0.005 so that the interference by intracellular Mg2+ levels could be negligible. The kNaCa values were approximately 2 and the Na+-selective microelectrodes were more selective to Ca2+ than Na+. This indicates that their intracellular application requires special care to handle Ca2+ interference under certain conditions. The kNaK, kNaMg, and kNaCa values did not depend significantly on the methods used for their determination or on the ion activity levels tested. The Nicolsky equation described well the microelectrode potentials in the mixed solutions of NaCl (1-100 mM) and KCl. Potential and resistance of the microelectrodes were stable for a long period and their response time was fast. The results indicate that the Na+-selective microlectrodes are suitable for measurements of intracellular Na ion activities. Ca2+-selective microelectrode potentials at Ca2+ concentrations lower than 10(-4) M changed significantly for the first 2-3 h and then became fairly stable. The rate of the potential change was dependent on the column length of the Ca2+-selective liquid filled. Potentials of the microelectrodes varied from 10-20 mV for Ca2+ between 10(-7) and 10(-6) M concentrations, which may be the cytosolic free-Ca2+ range. With the Ca2+ concentrations greater than 10(-6) M, the microelectrodes had potential changes of approximately 30 mV or greater for a tenfold change in Ca2+ concentration. The kCaK and kCaNa values were in the ranges of 10(-5)-10(-6) and 10(-4)-10(-5), respectively. The kCaMg values were approximately

  14. Effect of reaction time and (Ca+Mg)/Al molar ratios on crystallinity of Ca-Mg-Al layered double Hydroxide

    NASA Astrophysics Data System (ADS)

    Heraldy, E.; Nugrahaningtyas, K. D.; Sanjaya, F. B.; Darojat, A. A.; Handayani, D. S.; Hidayat, Y.

    2016-02-01

    Ca-Mg-Al Layered Double Hydroxides (Ca-Mg-Al-LDH) compounds were successfully synthesized from brine water and AlCl3.6H2O as the starting materials by coprecipitation method. The product result was characterized by X-ray powder diffraction (XRD) and Fourier transform infrared (FT-IR). The effects of the reaction time and the molar ratios of the raw material on the crystallinity of Ca-Mg-Al-LDH were examining. Results show that increasing reaction time (30; 60 and 90 min.) could improve the crystallinity and monodispersity of layered double hydroxide compounds particles. The well-defined Ca-Mg- Al-LDH could be prepared with (Ca+Mg)/Al molar ratios 0.5.

  15. Synthetic gedrite: a stable phase in the system MgO-Al2O3-SiO2-H2O (MASH) at 800°C and 10kbar water pressure, and the influence of FeNaCa impurities

    NASA Astrophysics Data System (ADS)

    Fischer, H.; Schreyer, W.; Maresch, W. V.

    Seeded, solid-media piston-cylinder runs of unusually long duration up to 31 days indicate growth or persistence of synthetic gedrite of the composition □Mg6Al[AlSi7O22](OH)2(=6:1:7), prepared from the purest chemicals available, at 10kbar water pressure and 800°C. Conversely, breakdown was observed at 11kbar and 850°C to aluminous enstatite, Al2SiO5, and a melt of the composition MgO.Al2O3.8SiO2. Thus, pure gedrite free of iron, sodium, and calcium is likely to have only a small PT stability field in the MASH system, estimated as 10+/-1kbar, 800+/-20°C, even though metastable growth of gedrite can be observed over a larger PT range. A second starting material with the anhydrous composition 5MgO . 2Al2O3 . 6SiO2 also yielded gedrite of the composition 6:1:7, together with more aluminous phases such as kyanite, corundum or sapphirine, thus suggesting that the end-member gedrite defined as □Mg5Al2[Al2Si6O22](OH)2(=5:2:6) by the IMA Commission on New Minerals and Mineral Names probably does not exist. With the use of this second starting material, which contains FeNaCa impurities, growth of 6:1:7-gedrite was observed over a still wider PT-range. Seeded runs indicate that the true stability field of such slightly impure 6:1:7-gedrites may also be larger than that of the pure MASH phase and extend at least to 15kbar, 800°C. There is, thus, a remarkable stabilization effect on the orthoamphibole structure by impurities amounting only to a total of less than one weight percent of oxides in the starting material. The gedrites synthesized are structurally well ordered amphiboles nearly free of chain multiplicity faults, as revealed by HRTEM. The X-ray diffraction work on the gedrites synthesized yielded the smallest cell volume yet reported for this phase. The small stability field of the pure MASH gedrite is intersected by the upper pressure stability limit of hydrous cordierite for excess-H2O conditions, thus leading to complicated phase relations for both gedrite

  16. Sol formation ability of Ca/Na-montmorillonite at low ionic strength

    NASA Astrophysics Data System (ADS)

    Birgersson, Martin; Hedström, Magnus; Karnland, Ola

    Various colloidal phases of Wyoming type Ca/Na-montmorillonite have been investigated experimentally by sedimentation and swelling tests of originally pure Ca- or Na-montmorillonite in different CaCl 2/NaCl solutions of low ionic strength. Forces contributing to colloid (de)stability are discussed, and the experimental findings are compared with a theoretical sol formation zone in the [Ca 2+]-[Na +] diagram derived from simple assumptions regarding the forces. It is found that the sol formation ability drastically lowers when calcium ions are present in the system. This effect could be due to an explicit influence of these ions on edge face interactions.

  17. Ca(AlH4)2, CaAlH5, and CaH2+6LiBH4: Calculated dehydrogenation enthalpy, including zero point energy, and the structure of the phonon spectra.

    PubMed

    Marashdeh, Ali; Frankcombe, Terry J

    2008-06-21

    The dehydrogenation enthalpies of Ca(AlH(4))(2), CaAlH(5), and CaH(2)+6LiBH(4) have been calculated using density functional theory calculations at the generalized gradient approximation level. Harmonic phonon zero point energy (ZPE) corrections have been included using Parlinski's direct method. The dehydrogenation of Ca(AlH(4))(2) is exothermic, indicating a metastable hydride. Calculations for CaAlH(5) including ZPE effects indicate that it is not stable enough for a hydrogen storage system operating near ambient conditions. The destabilized combination of LiBH(4) with CaH(2) is a promising system after ZPE-corrected enthalpy calculations. The calculations confirm that including ZPE effects in the harmonic approximation for the dehydrogenation of Ca(AlH(4))(2), CaAlH(5), and CaH(2)+6LiBH(4) has a significant effect on the calculated reaction enthalpy. The contribution of ZPE to the dehydrogenation enthalpies of Ca(AlH(4))(2) and CaAlH(5) calculated by the direct method phonon analysis was compared to that calculated by the frozen-phonon method. The crystal structure of CaAlH(5) is presented in the more useful standard setting of P2(1)c symmetry and the phonon density of states of CaAlH(5), significantly different to other common complex metal hydrides, is rationalized.

  18. Geochemical modeling of leaching of Ca, Mg, Al, and Pb from cementitious waste forms

    SciTech Connect

    Martens, E.; Jacques, D.; Van Gerven, T.; Wang, L.; Mallants, D.

    2010-08-15

    Results from extraction tests on cement-waste samples were simulated with a thermodynamic equilibrium model using a consistent database, to which lead data were added. Subsequent diffusion tests were modeled by means of a 3D diffusive transport model combined with the geochemical model derived from the extraction tests. Modeling results of the leached major element concentrations for both uncarbonated and (partially) carbonated samples agreed well with the extraction test using the set of pure minerals and solid solutions present in the database. The observed decrease in Ca leaching with increasing carbonation level was qualitatively predicted. Simulations also revealed that Pb leaching is not controlled by dissolution/precipitation only. The addition of the calcite-cerrusite solid solution and adsorption reactions on amorphous Fe- and Al-oxides improved the predictions and are considered to control the Pb leaching during the extractions tests. The dynamic diffusive leaching tests were appropriately modeled for Na, K, Ca and Pb.

  19. Intracellular Na(+) modulates large conductance Ca(2+)-activated K (+) currents in human umbilical vein endothelial cells.

    PubMed

    Liang, Guo Hua; Kim, Moon Young; Park, Seonghee; Kim, Ji Aee; Choi, Shinkyu; Suh, Suk Hyo

    2008-10-01

    We studied the effects of Na(+) influx on large-conductance Ca(2+)-activated K(+) (BK(Ca)) channels in cultured human umbilical vein endothelial cells (HUVECs) by means of patch clamp and SBFI microfluorescence measurements. In current-clamped HUVECs, extracellular Na(+) replacement by NMDG(+) or mannitol hyperpolarized cells. In voltage-clamped HUVECs, changing membrane potential from 0 mV to negative potentials increased intracellular Na(+) concentration ([Na(+)](i)) and vice versa. In addition, extracellular Na(+) depletion decreased [Na(+)](i). In voltage-clamped cells, BK(Ca) currents were markedly increased by extracellular Na(+) depletion. In inside-out patches, increasing [Na(+)](i) from 0 to 20 or 40 mM reduced single channel conductance but not open probability (NPo) of BK(Ca) channels and decreasing intracellular K(+) concentration ([K(+)](i)) gradually from 140 to 70 mM reduced both single channel conductance and NPo. Furthermore, increasing [Na(+)](i) gradually from 0 to 70 mM, by replacing K(+), markedly reduced single channel conductance and NPo. The Na(+)-Ca(2+) exchange blocker Ni(2+) or KB-R7943 decreased [Na(+)](i) and increased BK(Ca) currents simultaneously, and the Na(+) ionophore monensin completely inhibited BK(Ca) currents. BK(Ca) currents were significantly augmented by increasing extracellular K(+) concentration ([K(+)](o)) from 6 to 12 mM and significantly reduced by decreasing [K(+)](o) from 12 or 6 to 0 mM or applying the Na(+)-K(+) pump inhibitor ouabain. These results suggest that intracellular Na(+) inhibit single channel conductance of BK(Ca) channels and that intracellular K(+) increases single channel conductance and NPo.

  20. Effect of exchangeable cations on apparent diffusion of Ca 2+ ions in Na- and Ca-montmorillonite mixtures

    NASA Astrophysics Data System (ADS)

    Kozaki, T.; Sawaguchi, T.; Fujishima, A.; Sato, S.

    Compacted Na-bentonite, of which the major mineral is montmorillonite, is a candidate buffer material for the geological disposal of high-level radioactive waste. A potential alteration of the bentonite in a repository is the partial replacement of the exchangeable cations of Na + with Ca 2+. The Ca 2+ cations could be released from cementitious materials and diffuse into the buffer material in the repository. In this study, to evaluate the alteration that could reduce the performance of the bentonite buffer, the apparent diffusion coefficients of HTO and Ca 2+ ions were determined from non-steady, one-dimensional diffusion experiments using Na- and Ca-montmorillonite mixtures with different ionic equivalent fractions of Ca 2+ ions. The apparent diffusion coefficient of HTO at a dry density of 1.0 Mg m -3 slightly increased with an increase in the ionic equivalent fraction of Ca 2+ ions. However, the apparent diffusion coefficient of Ca 2+ and the activation energy for diffusion at the same dry density were independent of the ionic equivalent fraction of Ca 2+ ions. These findings suggest that unlike HTO, which can be postulated to diffuse mainly in pore water, Ca 2+ ion diffusion could occur predominantly in interlayer spaces, of which the basal spacing was determined to be constant by the XRD technique.

  1. Elastic properties of NaXH4 (X = B, Al)

    NASA Astrophysics Data System (ADS)

    Zhang, Xiao-Dong; Jiang, Zhen-Yi; Hou, Yu-Qing; Li, Li-Sha

    2009-07-01

    Elastic properties of NaXH4 (X = B, Al) have been studied by first-principles calculations using a projected augmented plane-wave approach. The calculated elastic constants compare favorably with experimental values. Our calculations show that the theoretically calculated elastic constants and bulk moduli have small values compared with those of typical metals and intermetallic compounds, which indicates that NaXH4 (X = B, Al) are highly compressible. Comparison of bulk moduli B of different complex hydrides shows a correlation between B and the decomposition temperatures. Also, we calculated the elastic anisotropies and the Debye temperatures from the elastic constants.

  2. Actinide chemistry in Allende Ca-Al-rich inclusions

    NASA Technical Reports Server (NTRS)

    Murrell, M. T.; Burnett, D. S.

    1987-01-01

    Fission track radiography is used to investigate the U and Th microscale distribution in a set of Allende-meteorite Ca-Al-rich inclusions. In the Type B inclusions, the major phases melilite and fassaite are important actinide host phases, and on the rims of Type B inclusions and throughout all other inclusions studied, perovskite is the dominant actinide host phase. Results suggest that neither alteration nor loss or gain of an actinide-rich phase appears to have been an important Th/U fractionation mechanism, and that volatility differences may be the dominant factor. Th/U and rare earth element abundance patterns for the spinel and perovskite rim suggest rim formation by volatilization of interior material, and within the constraints of the brief time scale required for this heating, several mechanisms for spinel-perovskite rim formation are possible.

  3. Actinide chemistry in Allende Ca-Al-rich inclusions

    NASA Astrophysics Data System (ADS)

    Murrell, M. T.; Burnett, D. S.

    1987-04-01

    Fission track radiography is used to investigate the U and Th microscale distribution in a set of Allende-meteorite Ca-Al-rich inclusions. In the Type B inclusions, the major phases melilite and fassaite are important actinide host phases, and on the rims of Type B inclusions and throughout all other inclusions studied, perovskite is the dominant actinide host phase. Results suggest that neither alteration nor loss or gain of an actinide-rich phase appears to have been an important Th/U fractionation mechanism, and that volatility differences may be the dominant factor. Th/U and rare earth element abundance patterns for the spinel and perovskite rim suggest rim formation by volatilization of interior material, and within the constraints of the brief time scale required for this heating, several mechanisms for spinel-perovskite rim formation are possible.

  4. Hypoxia leads to Na,K-ATPase downregulation via Ca(2+) release-activated Ca(2+) channels and AMPK activation.

    PubMed

    Gusarova, Galina A; Trejo, Humberto E; Dada, Laura A; Briva, Arturo; Welch, Lynn C; Hamanaka, Robert B; Mutlu, Gökhan M; Chandel, Navdeep S; Prakriya, Murali; Sznajder, Jacob I

    2011-09-01

    To maintain cellular ATP levels, hypoxia leads to Na,K-ATPase inhibition in a process dependent on reactive oxygen species (ROS) and the activation of AMP-activated kinase α1 (AMPK-α1). We report here that during hypoxia AMPK activation does not require the liver kinase B1 (LKB1) but requires the release of Ca(2+) from the endoplasmic reticulum (ER) and redistribution of STIM1 to ER-plasma membrane junctions, leading to calcium entry via Ca(2+) release-activated Ca(2+) (CRAC) channels. This increase in intracellular Ca(2+) induces Ca(2+)/calmodulin-dependent kinase kinase β (CaMKKβ)-mediated AMPK activation and Na,K-ATPase downregulation. Also, in cells unable to generate mitochondrial ROS, hypoxia failed to increase intracellular Ca(2+) concentration while a STIM1 mutant rescued the AMPK activation, suggesting that ROS act upstream of Ca(2+) signaling. Furthermore, inhibition of CRAC channel function in rat lungs prevented the impairment of alveolar fluid reabsorption caused by hypoxia. These data suggest that during hypoxia, calcium entry via CRAC channels leads to AMPK activation, Na,K-ATPase downregulation, and alveolar epithelial dysfunction.

  5. A magnesium correction for the Na-K-Ca chemical geothermometer

    USGS Publications Warehouse

    Fournier, R.O.; Potter, Robert W.

    1978-01-01

    Graphs and equations have been devised to correct for the adverse effects of magnesium upon the Na-K-Ca geothermometer. Either the graphs or equations can be used to determine temperature corrections when given waters have Na-K-Ca calculated temperatures above 70? C and values of R less than 50, where R = {Mg/(Mg + Ca + K)} x 100 in equivalents. Waters with values of R greater than 50 probably come from relatively cool aquifers with temperatures about equal to the measured spring temperature, irrespective of much higher calculated Na-K-Ca temperatures.

  6. Enthalpies of formation of CaAl4O7 and CaAl12O19 (hibonite) by high temperature, alkali borate solution calorimetry

    NASA Technical Reports Server (NTRS)

    Geiger, C. A.; Kleppa, O. J.; Grossman, L.; Mysen, B. O.; Lattimer, J. M.

    1988-01-01

    Enthalpies of formation were determined for two calcium aluminate phases, CaAl4O7 and CaAl12O19, using high-temperature alkali borate solution calorimetry. The aluminates were synthesized by multiple-cycle heating and grinding stoichiometric mixtures of CaCO3 and Al2O3, and the products were characteized by X-ray diffraction and SEM microbeam analysis. The data on impurities (CaAl4O7 was found to be about 89.00 percent pure by weight and the CaAl12O19 samples about 91.48 percent pure) were used to correct the heat of solution values of the synthetic products. The enthalpies of formation, at 1063 K, from oxides, were found to be equal to -(25.6 + or - 4.7) kJ/g.f.w. for CaAl4O7 and -(33.0 + or - 9.7) kJ/g.f.w. for CaAl12O19; the respective standard enthalpies of formation from elements, at 298 K, were estimated to be -4007 + or - 5.2 kJ/g.f.w. and -10,722 + or - 12 kJ/g.f.w.

  7. Crystal structure of the NaCa(Fe{sup 2+}, Al, Mn){sub 5}[Si{sub 8}O{sub 19}(OH)](OH){sub 7} {center_dot} 5H{sub 2}O mineral: A new representative of the palygorskite group

    SciTech Connect

    Rastsvetaeva, R. K. Aksenov, S. M.; Verin, I. A.

    2012-01-15

    A specimen of a new representative of the palygorskite-sepiolite family from Aris phonolite (Namibia) is studied by single-crystal X-ray diffraction. The parameters of the triclinic (pseudomonoclinic) unit cell are as follows: a = 5.2527(2) Angstrom-Sign , b = 17.901(1) Angstrom-Sign , c = 13.727(1) Angstrom-Sign , {alpha} = 90.018(3) Degree-Sign , {beta} = 97.278(4) Degree-Sign , and {gamma} = 89.952(3) Degree-Sign . The structure is solved by the direct methods in space group P1-bar and refined to R = 5.5% for 4168 |F| > 7{sigma}(F) with consideration for twinning by the plane perpendicular to y (the ratio of the twin components is 0.52: 0.48). The crystal chemical formula (Z = 1) is (Na{sub 1.6}K{sub 0.2}Ca{sub 0.2})[Ca{sub 2}(Fe{sub 3.6}{sup 2+}Al{sub 1.6}Mn{sub 0.8})(OH){sub 9}(H{sub 2}O){sub 2}][(Fe{sub 3.9}{sup 2+}Ti{sub 0.1})(OH){sub 5} (H{sub 2}O){sub 2}][Si{sub 16}O{sub 38}(OH){sub 2}] {center_dot} 6H{sub 2}O, where the compositions of two ribbons of octahedra and a layer of Si tetrahedra are enclosed in brackets. A number of specific chemical, symmetrical, and structural features distinguish this mineral from other minerals of this family, in particular, from tuperssuatsiaite and kalifersite, which are iron-containing representatives with close unit cell parameters.

  8. Decomposition reactions for NaAl H4 , Na3 Al H6 , and NaH: First-principles study

    NASA Astrophysics Data System (ADS)

    Ke, Xuezhi; Tanaka, Isao

    2005-01-01

    The electronic properties and lattice dynamics of the sodium alanate phases have been studied by the density functional calculations. The phases include NaAlH4 (space group, I41/a ), Na3AlH6 (space group, P21/n ), and NaH (space group, Fm-3m ). The electronic properties are discussed on the basis of the electronic band structures, the atomic charges, the bond overlap population analysis, and the Born effective charges. The phonon dispersion relations and phonon density of states (DOS) of the phases are calculated by a direct force-constant method. Within the quasiharmonic approximation, the calculated thermodynamic functions including the heat capacity, the vibrational enthalpy, and the vibrational entropy are in good agreement with experimental values. Three decomposition reactions are studied based on the thermodynamic functions. The reactions are (1) NaAlH4→(1)/(3)Na3AlH6+(2)/(3)Al+H2 , (2) (1)/(3)Na3AlH6→NaH+(1)/(3)Al+(1)/(2)H2 , and (3) NaH→Na+(1)/(2)H2 . The reactions (1), (2), and (3) are predicted to take place at 285, 390, and 726K , respectively, which are in good agreement with the experiment (353, 423, and 698K , respectively). The individual contributions to the reactions including the enthalpy and entropy are investigated. We found that the enthalpy for the reaction is almost constant, and the net entropy contribution ( TΔS ) to the reaction is approximately equal to the entropy contribution of the H2 gas molecule (produced in that reaction).

  9. Cross sections for He and Ne isotopes in natural Mg, Al, and Si, He isotopes in CaF2, Ar isotopes in natural Ca, and radionuclides in natural Al, Si, Ti, Cr, and stainless steel induced by 12- to 45-MeV protons

    NASA Technical Reports Server (NTRS)

    Walton, J. R.; Heymann, D.; Yaniv, A.; Edgerley, D.; Rowe, M. W.

    1976-01-01

    Stacks of thin Mg, Al, Si, Ca, CaF2, Ti, and stainless steel foils were bombarded in twelve irradiations by a variable energy cyclotron. Cross sections are reported for He and Ne in natural Mg, Al, and Si, and for He in CaF2, and for Ar in natural Ca, as determined from mass spectrometer analysis of the inert gases. In addition, cross sections of Na-22 in natural Al and Si, of V-48 in natural Ti, and of Cr-51, Mn-52, and Co-57 in stainless steel are reported. From these were deduced Cr-51 and Mn-52 cross sections in natural Cr.

  10. Comparative NMR studies on Ca3LiRuO6 and Ca3NaRuO6

    NASA Astrophysics Data System (ADS)

    Chakrabarty, T.; Paulose, P. L.

    2016-06-01

    We report a comparative study of two ruthanate compounds, Ca3LiRuO6 and Ca3NaRuO6 by magnetic measurements, heat capacity and NMR. Ca3LiRuO6 is a weak ferromagnet with a magnetic ordering temperature of 115 K. The 7Li NMR linewidth of Ca3LiRuO6 displays a broad shoulder above the magnetic ordering temperature. Anomalous shoulder of this type is observed in the susceptibility data also. The origin of these phenomena is not clear but could possibly be attributed to low dimensional magnetism. A contrasting magnetic behavior is seen in Ca3NaRuO6, an antiferromagnet with a transition temperature at 87 K. The NMR study shows that the Knight shift is proportional to the magnetic susceptibility. Also, in Ca3NaRuO6, the Knight shift and the linewidth of the spectra change differently compared to Ca3LiRuO6. The heat capacity of both compounds show a λ-type anomaly at respective magnetic transition temperatures. However, in both the systems the entropy change (Δ S) is much less than that of an ordered S  =  3/2 system.

  11. Analysis of the Na+/Ca2+ exchanger gene family within the phylum Nematoda.

    PubMed

    He, Chao; O'Halloran, Damien M

    2014-01-01

    Na+/Ca2+ exchangers are low affinity, high capacity transporters that rapidly transport calcium at the plasma membrane, mitochondrion, endoplasmic (and sarcoplasmic) reticulum, and the nucleus. Na+/Ca2+ exchangers are widely expressed in diverse cell types where they contribute homeostatic balance to calcium levels. In animals, Na+/Ca2+ exchangers are divided into three groups based upon stoichiometry: Na+/Ca2+ exchangers (NCX), Na+/Ca2+/K+ exchangers (NCKX), and Ca2+/Cation exchangers (CCX). In mammals there are three NCX genes, five NCKX genes and one CCX (NCLX) gene. The genome of the nematode Caenorhabditis elegans contains ten Na+/Ca2+ exchanger genes: three NCX; five CCX; and two NCKX genes. Here we set out to characterize structural and taxonomic specializations within the family of Na+/Ca2+ exchangers across the phylum Nematoda. In this analysis we identify Na+/Ca2+ exchanger genes from twelve species of nematodes and reconstruct their phylogenetic and evolutionary relationships. The most notable feature of the resulting phylogenies was the heterogeneous evolution observed within exchanger subtypes. Specifically, in the case of the CCX exchangers we did not detect members of this class in three Clade III nematodes. Within the Caenorhabditis and Pristionchus lineages we identify between three and five CCX representatives, whereas in other Clade V and also Clade IV nematode taxa we only observed a single CCX gene in each species, and in the Clade III nematode taxa that we sampled we identify NCX and NCKX encoding genes but no evidence of CCX representatives using our mining approach. We also provided re-annotation for predicted CCX gene structures from Heterorhabditis bacteriophora and Caenorhabditis japonica by RT-PCR and sequencing. Together, these findings reveal a complex picture of Na+/Ca2+ transporters in nematodes that suggest an incongruent evolutionary history of proteins that provide central control of calcium dynamics.

  12. Analysis of the Na+/Ca2+ Exchanger Gene Family within the Phylum Nematoda

    PubMed Central

    He, Chao; O'Halloran, Damien M.

    2014-01-01

    Na+/Ca2+ exchangers are low affinity, high capacity transporters that rapidly transport calcium at the plasma membrane, mitochondrion, endoplasmic (and sarcoplasmic) reticulum, and the nucleus. Na+/Ca2+ exchangers are widely expressed in diverse cell types where they contribute homeostatic balance to calcium levels. In animals, Na+/Ca2+ exchangers are divided into three groups based upon stoichiometry: Na+/Ca2+ exchangers (NCX), Na+/Ca2+/K+ exchangers (NCKX), and Ca2+/Cation exchangers (CCX). In mammals there are three NCX genes, five NCKX genes and one CCX (NCLX) gene. The genome of the nematode Caenorhabditis elegans contains ten Na+/Ca2+ exchanger genes: three NCX; five CCX; and two NCKX genes. Here we set out to characterize structural and taxonomic specializations within the family of Na+/Ca2+ exchangers across the phylum Nematoda. In this analysis we identify Na+/Ca2+ exchanger genes from twelve species of nematodes and reconstruct their phylogenetic and evolutionary relationships. The most notable feature of the resulting phylogenies was the heterogeneous evolution observed within exchanger subtypes. Specifically, in the case of the CCX exchangers we did not detect members of this class in three Clade III nematodes. Within the Caenorhabditis and Pristionchus lineages we identify between three and five CCX representatives, whereas in other Clade V and also Clade IV nematode taxa we only observed a single CCX gene in each species, and in the Clade III nematode taxa that we sampled we identify NCX and NCKX encoding genes but no evidence of CCX representatives using our mining approach. We also provided re-annotation for predicted CCX gene structures from Heterorhabditis bacteriophora and Caenorhabditis japonica by RT-PCR and sequencing. Together, these findings reveal a complex picture of Na+/Ca2+ transporters in nematodes that suggest an incongruent evolutionary history of proteins that provide central control of calcium dynamics. PMID:25397810

  13. Energetics of Na(+)-Ca(2+) exchange in resting cardiac muscle.

    PubMed Central

    Ponce-Hornos, J E; Philipson, K D; Bonazzola, P; Langer, G A

    1999-01-01

    The energetic effect of extracellular Na(+) removal and readmission (in a nominally Ca(2+)-free perfusate) in Langendorff-perfused ventricles of transgenic mice (TM), which overexpress the sarcolemmal Na(+)-Ca(2+) exchanger; normal mice (NM); young (7-12 days old) rats (YR); and older (13-20 days old) rats (OR) was studied. In all heart muscles, extracellular Na(+) removal induced an increase in heat production (H(1)). Na(+) readmission further increased heat production to a peak value (H(2)) followed by a decrease toward initial values. These effects were more marked in the YR and TM as compared with the OR and NM groups, respectively. Caffeine (1 mM), ryanodine (0.2 microM), and verapamil (1 microM) decreased H(1) and H(2) in both rat groups. EGTA (1 mM) decreased H(1) and H(2) in the YR but not in the OR group. Thapsigargin (1 microM) decreased H(1) and H(2) in all four hearts preparations. A possible interpretation is that Na(+)-Ca(2+) exchange acts as an energy-saving mechanism to prevent Ca(2+) accumulation at the junctional sarcoplasmic reticulum zone (JSR) and thus prevents further release of Ca(2+). Extracellular Na(+) removal lead to Ca(2+) accumulation in the JSR inducing further SR-Ca(2+) release and increased energy release. Na(+) readmission removes the accumulated Ca(2+) at the JSR (cleft) zone by exchanging Ca(2+) with Na(+) producing a transitory increase in energy release due to Na(+)-K pump activation. PMID:10585954

  14. Na/beta-alumina/NaAlCl4, Cl2/C circulating cell

    NASA Astrophysics Data System (ADS)

    Cherng, Jing-Yih; Bennion, Douglas N.

    1987-09-01

    A study was made of a high specific energy battery based on a sodium negative electrode and a chlorine positive electrode with molten AlCl3-NaCl electrolyte and a solid beta alumina separator. The basic performance of a Na beta-alumina NaAlCl4, Cl2/C circulating cell at 200 C was demonstrated. This cell can be started at 150 C. The use of melting sodium chloroaluminate electrolyte overcomes some of the material problems associated with the high working temperatures of present molten salt systems, such as Na/S and LiAl/FeS, and retains the advantages of high energy density and relatively efficient electrode processes. Preliminary investigations were conducted on a sodium-chlorine static cell, material compability, electrode design, wetting, and theoretical calculations to assure a better chance of success before assembling a Na/Cl2 circulating cell. Mathematical models provide a theoretical explanation for the performance of the NaCl2 battery. The results of mathematical models match the experimental results very well. According to the result of the mathematical modeling, an output at 180 mA/sq cm and 3.2 V can be obtained with optimized cell design.

  15. Measurement of mitochondrial Ca2+ transport mediated by three transport proteins: VDAC1, the Na+/Ca2+ exchanger, and the Ca2+ uniporter.

    PubMed

    Ben-Hail, Danya; Palty, Raz; Shoshan-Barmatz, Varda

    2014-02-01

    Ca(2+) is a ubiquitous cellular signal, with changes in intracellular Ca(2+) concentration not only stimulating a number of intercellular events but also triggering cell death pathways, including apoptosis. Mitochondrial Ca(2+) uptake and release play pivotal roles in cellular physiology by regulating intracellular Ca(2+) signaling, energy metabolism and cell death. Ca(2+) transport across the inner and outer mitochondrial membranes is mediated by several proteins, including channels, antiporters, and a uniporter. In this article, we present the background to several methods now established for assaying mitochondrial Ca(2+) transport activity across both mitochondrial membranes. The first of these is Ca(2+) transport mediated by the outer mitochondrial protein, the voltage-dependent anion-selective channel protein 1 (VDAC1, also known as porin 1), both as a purified protein reconstituted into a planar lipid bilayer (PLB) or into liposomes and as a mitochondrial membrane-embedded protein. The second method involves isolated mitochondria for assaying the activity of an inner mitochondrial membrane transport protein, the mitochondrial Ca(2+) uniporter (MCU) that transports Ca(2+) and is powered by the steep mitochondrial membrane potential. In the event of Ca(2+) overload, this leads to opening of the mitochondrial permeability transition pore (MPTP) and cell death. The third method describes how Na(+)-dependent mitochondrial Ca(2+) efflux mediated by mitochondrial NCLX, a member of the Na(+)/Ca(2+) exchanger superfamily, can be assayed in digitonin-permeabilized HEK-293 cells. The Ca(2+)-transport assays can be performed under various conditions and in combination with inhibitors, allowing detailed characterization of the transport activity of interest.

  16. The elemental composition of the Sun. I. The intermediate mass elements Na to Ca

    NASA Astrophysics Data System (ADS)

    Scott, Pat; Grevesse, Nicolas; Asplund, Martin; Sauval, A. Jacques; Lind, Karin; Takeda, Yoichi; Collet, Remo; Trampedach, Regner; Hayek, Wolfgang

    2015-01-01

    The chemical composition of the Sun is an essential piece of reference data for astronomy, cosmology, astroparticle, space and geo-physics: elemental abundances of essentially all astronomical objects are referenced to the solar composition, and basically every process involving the Sun depends on its composition. This article, dealing with the intermediate-mass elements Na to Ca, is the first in a series describing the comprehensive re-determination of the solar composition. In this series we severely scrutinise all ingredients of the analysis across all elements, to obtain the most accurate, homogeneous and reliable results possible. We employ a highly realistic 3D hydrodynamic model of the solar photosphere, which has successfully passed an arsenal of observational diagnostics. For comparison, and to quantify remaining systematic errors, we repeat the analysis using three different 1D hydrostatic model atmospheres (marcs, miss and Holweger & Müller 1974, Sol. Phys., 39, 19) and a horizontally and temporally-averaged version of the 3D model (⟨ 3D ⟩). We account for departures from local thermodynamic equilibrium (LTE) wherever possible. We have scoured the literature for the best possible input data, carefully assessing transition probabilities, hyperfine splitting, partition functions and other data for inclusion in the analysis. We have put the lines we use through a very stringent quality check in terms of their observed profiles and atomic data, and discarded all that we suspect to be blended. Our final recommended 3D+NLTE abundances are: log ɛNa = 6.21 ± 0.04, log ɛMg = 7.59 ± 0.04, log ɛAl = 6.43 ± 0.04, log ɛSi = 7.51 ± 0.03, log ɛP = 5.41 ± 0.03, log ɛS = 7.13 ± 0.03, log ɛK = 5.04 ± 0.05 and log ɛCa = 6.32 ± 0.03. The uncertainties include both statistical and systematic errors. Our results are systematically smaller than most previous ones with the 1D semi-empirical Holweger & Müller model, whereas the ⟨ 3D ⟩ model returns

  17. Alcohol stimulates Na sup + /Ca sup 2+ exchange in brain mitochondria

    SciTech Connect

    Rottenberg, H.; Marbach, M. )

    1991-01-01

    Ethanol, at low concentrations, specifically stimulates the Na{sup +}-dependent Ca{sup 2+}-efflux in brain mitochondria. In addition, at higher concentrations, ethanol inhibits the Na{sup +}-independent Ca{sup 2+}-efflux. The electrogenic Ca{sup 2+}-uptake system is not affected by ethanol. The specific stimulation of Na{sup +}/Ca{sup 2+} exchange reaches a maximum of 60% stimulation, with half-maximal stimulation at 130 mM ethanol. The inhibition of the Na{sup +}-independent efflux is proportional to the ethanol concentration, becoming significant only above 200 mM, with 50% inhibition at 0.5 M. The inhibition of the Na{sup +}-independent efflux is, in large part, due to an inhibition of the activation of the Cyclosporin-sensitive pore. Long-term ethanol-feeding had no effect on the Ca{sup 2+} transport systems and their sensitivity to acute ethanol treatment. It is suggested that the stimulation of the Na{sup +}-dependent Ca{sup 2+}-efflux, which is the dominant Ca{sup 2+} efflux pathway in brain mitochondria, contributes to the intoxicating effects of ethanol.

  18. Thermoelectric properties of Al substituted misfit cobaltite Ca3(Co1- x Al x )4O9 at low temperature

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Chen, Hong-mei; Hu, Jin-lian; Tang, Xu-bing; Li, Hai-jin; Wang, Wei

    2014-07-01

    Thermoelectric properties of Al substituted compounds Ca3(Co1- x Al x )4O9 ( x = 0, 0.03, 0.05), prepared by a sol-gel process, have been investigated in the temperature range 305-20 K. The results indicate that after Al substitution for Co in Ca3(Co1- x Al x )4O9, the direct current electrical resistivity and thermopower increase due to the reduction of carrier concentration. Experiments show that Al substitution results in decreased lattice thermal conductivity. The figure of merit of temperature behavior suggests that Ca3(Co0.97Al0.03)4O9 would be a promising candidate thermoelectric material for high-temperature thermoelectric application.

  19. Residues Contributing to the Na+-binding Pocket of the SLC24 Na+/Ca2+-K+ Exchanger NCKX2*

    PubMed Central

    Altimimi, Haider F.; Fung, Eric H.; Winkfein, Robert J.; Schnetkamp, Paul P. M.

    2010-01-01

    Na+/Ca2+-K+ exchangers (NCKX; gene family SLC24) are plasma membrane Ca2+ transporters that mediate the extrusion of one Ca2+ ion and one K+ ion in exchange for four Na+ ions. NCKX is modeled to have two sets of five transmembrane segments separated by a large cytosolic loop; within each set of transmembrane segments are regions of internal symmetry termed α1 and α2 repeats. The central residues that are important for Ca2+ and K+ liganding and transport have been identified in NCKX2, and they comprise three central acidic residues, Glu188 in α1 and Asp548 and Asp575 in α2, as well as Ser/Thr residues one-helical turn away from these residues. In this study, we have scanned through more than 100 single-residue substitutions of NCKX2 for shifts in Na+ affinity using a fluorescence assay to monitor changes in free Ca2+ in HEK293 cells treated with gramicidin to control intracellular Na+. We have identified 31 residues that, when substituted, result in shifts in Na+ affinity, either toward higher or lower Km values when compared with wild type NCKX2 (Km for Na+ 58 mm). These residues include the central acidic residues Glu188, Asp548, and Asp575, and their neighboring residues in α1 and α2, in addition to a number of newly investigated residues in transmembrane segment 3. Our results relate the identification of residues important for Na+ transport in this study to those previously identified as important in the counter-transport of Ca2+ and K+, lending support to the alternating access model of transmembrane transport. PMID:20231282

  20. A Biophysically Based Mathematical Model for the Kinetics of Mitochondrial Na+-Ca2+ Antiporter

    PubMed Central

    Pradhan, Ranjan K.; Beard, Daniel A.; Dash, Ranjan K.

    2010-01-01

    Sodium-calcium antiporter is the primary efflux pathway for Ca2+ in respiring mitochondria, and hence plays an important role in mitochondrial Ca2+ homeostasis. Although experimental data on the kinetics of Na+-Ca2+ antiporter are available, the structure and composition of its functional unit and kinetic mechanisms associated with the Na+-Ca2+ exchange (including the stoichiometry) remains unclear. To gain a quantitative understanding of mitochondrial Ca2+ homeostasis, a biophysical model of Na+-Ca2+ antiporter is introduced that is thermodynamically balanced and satisfactorily describes a number of independent data sets under a variety of experimental conditions. The model is based on a multistate catalytic binding mechanism for carrier-mediated facilitated transport and Eyring's free energy barrier theory for interconversion and electrodiffusion. The model predicts the activating effect of membrane potential on the antiporter function for a 3Na+:1Ca2+ electrogenic exchange as well as the inhibitory effects of both high and low pH seen experimentally. The model is useful for further development of mechanistic integrated models of mitochondrial Ca2+ handling and bioenergetics to understand the mechanisms by which Ca2+ plays a role in mitochondrial signaling pathways and energy metabolism. PMID:20338843

  1. Ca(2+) and CaM are involved in Al(3+) pretreatment-promoted fluoride accumulation in tea plants (Camellia sinesis L.).

    PubMed

    Zhang, Xian-Chen; Gao, Hong-Jian; Wu, Hong-Hong; Yang, Tian-Yuan; Zhang, Zheng-Zhu; Mao, Jing-Dong; Wan, Xiao-Chun

    2015-11-01

    Tea plant (Camellia sinensis (L.) O. kuntze) is known to be a fluoride (F) and aluminum (Al(3+)) hyper-accumulator. Previous study showed that pre-treatment of Al(3+) caused a significant increase of F accumulation in tea plants. However, less is known about the intricate network of Al(3+) promoted F accumulation in tea plants. In this study, the involvement of endogenous Ca(2+) and CaM in Al(3+) pretreatment-promoted F accumulation in tea plants was investigated. Our results showed that Al(3+) induced the inverse change of intracellular Ca(2+) fluorescence intensity and stimulated Ca(2+) trans-membrane transport in the mature zone of tea root. Also, a link between internal Ca(2+) and CaM was found in tea roots under the presence of Al(3+). In order to investigate whether Ca(2+) and CaM were related to F accumulation promoted by Al(3+) pretreatment, Ca(2+) chelator EGTA and CaM antagonists CPZ and TFP were used. EGTA, CPZ, and TFP pretreatment inhibited Al(3+)-induced increase of Ca(2+) fluorescence intensity and CaM content in tea roots, and also significantly reduced Al(3+)-promoted F accumulation in tea plants. Taken together, our results suggested that the endogenous Ca(2+) and CaM are involved in Al(3+) pretreatment-promoted F accumulation in tea roots.

  2. Phase relations in the greenschist-blueschist-amphibolite-eclogite facies in the system Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O (NCFMASH), with application to metamorphic rocks from Samos, Greece

    NASA Astrophysics Data System (ADS)

    Will, Thomas; Okrusch, Martin; Schmädicke, Esther; Chen, Guoli

    Calculated phase equilibria among the minerals sodic amphibole, calcic amphibole, garnet, chloritoid, talc, chlorite, paragonite, margarite, omphacite, plagioclase, carpholite, zoisite/clinozoisite, lawsonite, pyrophyllite, kyanite, sillimanite, quartz and H2O are presented for the model system Na2O-CaO-FeO-MgO-Al2O3-SiO2-H2O (NCFMASH), which is relevant for many greenschist, blueschist, amphibolite and eclogite facies rocks. Using the activity-composition relationships for multicomponent amphiboles constrained by Will and Powell (1992), equilibria containing coexisting calcic and sodic amphiboles could be determined. The blueschist-greenschist transition reaction in the NCFMASH system, for example, is defined by the univariant reaction sodic amphibole + zoisite=calcic amphibole + chlorite + paragonite + plagioclase (+ quartz + H2O) occurring between approximately 420 and 450°C at 9.5 to 10kbar. The calculated petrogenetic grid is a valuable tool for reconstructing the PT-evolution of metabasic rocks. This is shown for rocks from the island of Samos, Greece. On the basis of mineral and whole rock analyses, PT-pseudosections were calculated and, together with the observed mineral assemblages and reaction textures, are used to reconstruct PT-paths. For rocks from northern Samos, pseudomorphs after lawsonite preserved in garnet, the assemblage sodic amphibole-garnet-paragonite-chlorite-zoisite-quartz and the retrograde appearance of albitic plagioclase and the formation of calcic amphibole around sodic amphibole constrain a clockwise PT-path that reaches its thermal maximum at some 520°C and 19kbar. The derived PT-trajectory indicates cooling during exhumation of the rocks and is similar to paths for rocks from the western part of the Attic-Cycladic crystalline complex. Rocks from eastern Samos indicate lower pressures and are probably related to high-pressure rocks from the Menderes Massif in western Turkey.

  3. External Na-independent Ca extrusion in cultured ventricular cells. Magnitude and functional significance

    PubMed Central

    1986-01-01

    The relative magnitudes and functional significance of Ca extrusion by Na-Ca exchange and by an Nao-independent mechanism were investigated in monolayer cultures of chick embryo ventricular cells. Abrupt exposure of cells in 0-Nao, nominally 0-Cao solution to 20 mM caffeine produced a large contracture (3.94 +/- 0.90 micron of cell shortening) that relaxed with a t1/2 of 8.60 +/- 1.22 s. An abrupt exposure to caffeine plus 140 mM Na resulted in a contracture that was smaller in amplitude (1.53 +/- 0.50 micron) and relaxed much more rapidly (t1/2 = 0.77 +/- 0.09 s). An abrupt exposure to caffeine in 0-Nao solutions produced an increase in 45Ca efflux that persisted for 20 s, and a net loss of Ca content, determined by atomic absorption spectroscopy (AAS), of approximately 4 nmol/mg protein, within 35 s. A comparable net loss of Ca was demonstrated in the presence of 100 microM [Ca]o. The abrupt exposure of cultured cells to 0 Nao in 1.8 mM Ca produced a Ca uptake, estimated with 45Ca, of 3.2 nmol/mg protein X 15 s, but produced no increase in cell Ca content (AAS). In cells in which a 30% increase in Nai was produced by 5 min exposure to 10(-6) M ouabain, the abrupt exposure to 0 Nao produced a Ca uptake of 6 nmol/mg protein X 15 s and an increase in Ca content (AAS) of 4 nmol/mg protein. We conclude that there is an Nao-independent mechanism for Ca extrusion in these cells, presumably a Ca-ATPase Ca pump, with a limited Ca transport capacity of no more than 2 nmol/mg protein X 15 s. This is five times smaller than the demonstrated maximum capacity of the Na-Ca exchanger in these cells. The relaxation of twitch tension in these cells seems to be dependent primarily on sarcoplasmic reticulum uptake of Ca, with a secondary role provided by the Na-Ca exchanger. The Ca pump appears to contribute little to beat-to-beat relaxation. PMID:3760814

  4. Inhibitory effect of YM-244769, a novel Na(+)/Ca(2+) exchanger inhibitor on Na(+)/Ca(2+) exchange current in guinea pig cardiac ventricular myocytes.

    PubMed

    Yamashita, Kanna; Watanabe, Yasuhide; Kita, Satomi; Iwamoto, Takahiro; Kimura, Junko

    2016-11-01

    Recently, YM-244769 (N-(3-aminobenzyl)-6-{4-[(3-fluorobenzyl)oxy]phenoxy} nicotinamide) has been reported as a new potent and selective Na(+)/Ca(2+) exchange (NCX) inhibitor by using various cells transfected with NCX using the (45)Ca(2+) fluorescent technique. However, the electrophysiological study of YM-244769 on NCX had not been performed in the mammalian heart. We examined the effects of YM-244769 on NCX current (INCX) in single cardiac ventricular myocytes of guinea pigs by using the whole-cell voltage clamp technique. YM-244769 suppressed the bidirectional INCX in a concentration-dependent manner. The IC50 values of YM-244769 for the bidirectional outward and inward INCX were both about 0.1 μM. YM-244769 suppressed the unidirectional outward INCX (Ca(2+) entry mode) with an IC50 value of 0.05 μM. The effect on the unidirectional inward INCX (Ca(2+) exit mode) was less potent, with 10 μM of YM-244769 resulting in the inhibition of only about 50 %. At 5 mM intracellular Na(+) concentration, YM-244769 suppressed INCX more potently than it did at 0 mM [Na(+)]i. Intracellular application of trypsin via the pipette solution did not change the blocking effect of YM-244769. In conclusion, YM-244769 inhibits the Ca(2+) entry mode of NCX more potently than the Ca(2+) exit mode, and inhibition by YM-244769 is [Na(+)]i-dependent and trypsin-insensitive. These characteristics are similar to those of other benzyloxyphenyl derivative NCX inhibitors such as KB-R7943, SEA0400, and SN-6. The potency of YM-244769 as an NCX1 inhibitor is higher than those of KB-R7943 and SN-6 and is similar to that of SEA0400.

  5. CaFeAl mixed oxide derived heterogeneous catalysts for transesterification of soybean oil to biodiesel.

    PubMed

    Lu, Yongsheng; Zhang, Zaiwu; Xu, Yunfeng; Liu, Qiang; Qian, Guangren

    2015-08-01

    CaAl layered double oxides (LDO) were prepared by co-precipitation and calcined at 750°C, and then applied to biodiesel production by transesterification reaction between methanol and soybean oil. Compared with characteristics of CaFe/LDO and CaAl/LDO, CaFeAl/LDO had the best performance based on prominent catalytic activity and stability, and achieved over 90% biodiesel yield, which stayed stable (over 85%) even after 8 cycles of reaction. The optimal catalytic reaction condition was 12:1M-ratio of methanol/oil, reaction temperatures of 60°C, 270rpm stirring rate, 60min reaction time, and 6% weight-ratio of catalyst/oil. In addition, the CaFeAl/LDO catalyst is insoluble in both methanol and methyl esters and can be easily separated for further reaction, turning it into an excellent alternative for biodiesel synthesis.

  6. Na+ Dysregulation Coupled with Ca2+ Entry through NCX1 Promotes Muscular Dystrophy in Mice

    PubMed Central

    Burr, Adam R.; Millay, Douglas P.; Goonasekera, Sanjeewa A.; Park, Ki Ho; Sargent, Michelle A.; Collins, James; Altamirano, Francisco; Philipson, Kenneth D.; Allen, Paul D.; Ma, Jianjie; López, José Rafael

    2014-01-01

    Unregulated Ca2+ entry is thought to underlie muscular dystrophy. Here, we generated skeletal-muscle-specific transgenic (TG) mice expressing the Na+-Ca2+ exchanger 1 (NCX1) to model its identified augmentation during muscular dystrophy. The NCX1 transgene induced dystrophy-like disease in all hind-limb musculature, as well as exacerbated the muscle disease phenotypes in δ-sarcoglycan (Sgcd−/−), Dysf−/−, and mdx mouse models of muscular dystrophy. Antithetically, muscle-specific deletion of the Slc8a1 (NCX1) gene diminished hind-limb pathology in Sgcd−/− mice. Measured increases in baseline Na+ and Ca2+ in dystrophic muscle fibers of the hind-limb musculature predicts a net Ca2+ influx state due to reverse-mode operation of NCX1, which mediates disease. However, the opposite effect is observed in the diaphragm, where NCX1 overexpression mildly protects from dystrophic disease through a predicted enhancement in forward-mode NCX1 operation that reduces Ca2+ levels. Indeed, Atp1a2+/− (encoding Na+-K+ ATPase α2) mice, which have reduced Na+ clearance rates that would favor NCX1 reverse-mode operation, showed exacerbated disease in the hind limbs of NCX1 TG mice, similar to treatment with the Na+-K+ ATPase inhibitor digoxin. Treatment of Sgcd−/− mice with ranolazine, a broadly acting Na+ channel inhibitor that should increase NCX1 forward-mode operation, reduced muscular pathology. PMID:24662047

  7. A role for the mitochondrial Na(+)-Ca2+ exchanger in the regulation of oxidative phosphorylation in isolated heart mitochondria.

    PubMed

    Cox, D A; Matlib, M A

    1993-01-15

    The role of the Na(+)-Ca2+ exchanger of heart mitochondria in cellular functioning is not yet clear. The objectives of this study were to investigate the effects of stimulation and inhibition of the Na(+)-Ca2+ exchanger on the matrix free Ca2+ concentration in isolated heart mitochondria and to determine the consequences of these changes on the rate of NADH production via Krebs cycle turnover and the oxidative phosphorylation rate (OPR) supported by alpha-ketoglutarate dehydrogenase, a Ca(2+)-regulated matrix enzyme. Activation of Na(+)-Ca2+ exchange by increasing extramitochondrial Na+ concentration was found to decrease the matrix free [Ca2+] in a concentration-dependent manner. Inhibitors of mitochondrial Na(+)-Ca2+ exchange activity inhibited the decrease in matrix free [Ca2+] mediated by Na+. Increasing concentrations of Na+ were also found to inhibit both the rate of NADH production and OPR. Inhibitors of mitochondrial Na(+)-Ca2+ exchange also blocked the effects of Na+ on the rate of NADH production and OPR in a similar concentration range. The results indicate that alterations in matrix free [Ca2+] induced by changes in mitochondrial Na(+)-Ca2+ exchange activity are translated into changes in the rate of NADH production and the overall rate of oxidative phosphorylation.

  8. Effects of SEA0400 and KB-R7943 on Na+/Ca2+ exchange current and L-type Ca2+ current in canine ventricular cardiomyocytes.

    PubMed

    Birinyi, Péter; Acsai, Károly; Bányász, Tamás; Tóth, András; Horváth, Balázs; Virág, László; Szentandrássy, Norbert; Magyar, János; Varró, András; Fülöp, Ferenc; Nánási, Péter P

    2005-07-01

    SEA0400 and KB-R7943 are compounds synthesised to block transsarcolemmal Na+/Ca2+ exchange current (I(Na/Ca)); however, they have also been shown to inhibit L-type Ca2+ current (I(Ca)). The potential value of these compounds depends critically on their relative selectivity for I(Na/Ca) over I(Ca). In the present work, therefore, the concentration-dependent effects of SEA0400 and KB-R7943 on I(Na/Ca) and I(Ca) were studied and compared in canine ventricular cardiomyocytes using the whole-cell configuration of the patch clamp technique. SEA0400 and KB-R7943 decreased I(Na/Ca) in a concentration-dependent manner, having EC50 values of 111+/-43 nM and 3.35+/-0.82 microM, when suppressing inward currents, while the respective EC50 values were estimated at 108+/-18 nM and 4.74+/-0.69 microM in the case of outward current block. SEA0400 and KB-R7943 also blocked I(Ca), having comparable EC50 values (3.6 microM and 3.2 microM, respectively). At higher concentrations (10 microM) both drugs accelerated inactivation of I(Ca), retarded recovery from inactivation and shifted the voltage dependence of inactivation towards more negative voltages. The voltage dependence of activation was slightly modified by SEA0400, but not by KB-R7943. Based on the relatively good selectivity of submicromolar concentrations of SEA0400--but not KB-R7943--for I(Na/Ca) over I(Ca), SEA0400 appears to be a suitable tool to study the role of I(Na/Ca) in Ca2+ handling in canine cardiac cells. At concentrations higher than 1 microM, however, I(Ca) is progressively suppressed by the compound.

  9. Ca(2+) clearance by plasmalemmal NCLX, Li(+)-permeable Na(+)/Ca(2+) exchanger, is required for the sustained exocytosis in rat insulinoma INS-1 cells.

    PubMed

    Han, Young-Eun; Ryu, Shin-Young; Park, Sun-Hyun; Lee, Kyu-Hee; Lee, Suk-Ho; Ho, Won-Kyung

    2015-12-01

    Na(+)/Ca(2+) exchangers are key players for Ca(2+) clearance in pancreatic β-cells, but their molecular determinants and roles in insulin secretion are not fully understood. In the present study, we newly discovered that the Li(+)-permeable Na(+)/Ca(2+) exchangers (NCLX), which were known as mitochondrial Na(+)/Ca(2+) exchangers, contributed to the Na(+)-dependent Ca(2+) movement across the plasma membrane in rat INS-1 insulinoma cells. Na(+)/Ca(2+) exchange activity by NCLX was comparable to that by the Na(+)/Ca(2+) exchanger, NCX. We also confirmed the presence of NCLX proteins on the plasma membrane using immunocytochemistry and cell surface biotinylation experiments. We further investigated the role of NCLX on exocytosis function by measuring the capacitance increase in response to repetitive depolarization. Small interfering (si)RNA-mediated downregulation of NCLX did not affect the initial exocytosis, but significantly suppressed sustained exocytosis and recovery of exocytosis. XIP (NCX inhibitory peptide) or Na(+) replacement for inhibiting Na(+)-dependent Ca(2+) clearance also selectively suppressed sustained exocytosis. Consistent with the idea that sustained exocytosis requires ATP-dependent vesicle recruitment, mitochondrial function, assessed by mitochondrial membrane potential (ΔΨ), was impaired by siNCLX or XIP. However, depolarization-induced exocytosis was hardly affected by changes in intracellular Na(+) concentration, suggesting a negligible contribution of mitochondrial Na(+)/Ca(2+) exchanger. Taken together, our data indicate that Na(+)/Ca(2+) exchanger-mediated Ca(2+) clearance mediated by NCLX and NCX is crucial for optimizing mitochondrial function, which in turn contributes to vesicle recruitment for sustained exocytosis in pancreatic β-cells.

  10. NaSrMn2F7, NaCaFe2F7, and NaSrFe2F7: novel single crystal pyrochlore antiferromagnets

    NASA Astrophysics Data System (ADS)

    Sanders, M. B.; Krizan, J. W.; Plumb, K. W.; McQueen, T. M.; Cava, R. J.

    2017-02-01

    The crystal structures and magnetic properties of three previously unreported A2B2F7 pyrochlore materials, NaSrMn2F7, NaCaFe2F7, and NaSrFe2F7 are presented. In these compounds, either S  =  2Fe2+ or S  =  5/2Mn2+ is on the B site, while nonmagnetic Na and Ca (Na and Sr) are disordered on the A site. The materials, which were grown as crystals via the floating zone method, display high effective magnetic moments and large Curie-Weiss thetas. Despite these characteristics, no ordering transition is detected. However, freezing of the magnetic spins, characterized by peaks in the susceptibility or specific heat, is observed at very low temperatures. The empirical frustration index, f  =  -θ CW/T f, for the materials are 36 (NaSrMn2F7), 27 (NaSrFe2F7), and 19 (NaCaFe2F7). AC susceptibility, DC susceptibility, and heat capacity measurements are used to characterize the observed spin glass behavior. The results suggest that the compounds are frustrated pyrochlore antiferromagnets with weak bond disorder. The magnetic phenomena that these fluoride pyrochlores exhibit, in addition to their availability as relatively large single crystals, make them promising candidates for the study of geometric magnetic frustration.

  11. Performance capabilities of middle-atmosphere temperature lidars: comparison of Na, Fe, K, Ca, Ca+, and Rayleigh systems.

    PubMed

    Gardner, Chester S

    2004-09-01

    The measurement accuracies of modern resonance fluorescence and Rayleigh temperature lidars are limited primarily by photon noise. The narrowband three-frequency fluorescence technique is shown to perform within a few decibels of the theoretical optimum at night for both temperature and wind observations. These systems also exhibit good performance during the day because the fluorescence wavelengths of Na, Fe, K, Ca, and Ca+ all correspond to strong solar Fraunhofer lines, where sky brightness is attenuated by a factor of 5 or more. Whereas Na systems achieve the highest signal-to-noise ratios for mesopause region observations (80-105 km), the three-frequency Fe system is attractive because it performs well as both a fluorescence and a Rayleigh lidar throughout the middle atmosphere at approximately 25-110 km.

  12. Calcium regulation in mouse mesencephalic neurons-Differential roles of Na(+)/Ca(2+) exchanger, mitochondria and endoplasmic reticulum.

    PubMed

    Wu, Pei-Chun; Kao, Lung-Sen

    2016-06-01

    Midbrain dopaminergic (DA) neurons are the key to finely tune the voluntary movement, habit and motivation. The progressive and selective degeneration of these neurons is a pathological hallmark of Parkinson's disease (PD). The susceptibility of DA neurons in the SNpc may result from differences in how Ca(2+) is handled. However, very little information is available about the mechanisms involved in the regulation of intracellular Ca(2+) concentration ([Ca(2+)]i) in DA neurons. In this study, the relative contributions of various Na(+)/Ca(2+) exchangers and their interplay with internal Ca(2+) stores, endoplasmic reticulum (ER) and the mitochondria, in the regulation of the [Ca(2+)]i of mouse mesencephalic neurons were characterized. Both the K(+)-dependent Na(+)/Ca(2+) exchanger (NCKX) and the K(+)-independent Na(+)/Ca(2+) exchanger (NCX) can be detected and are functional in DA and non-DA neurons. NCX accounts for the larger component of Na(+)/Ca(2+) exchange activity. Single-cell RT-PCR analysis showed each individual neuron expressed a distinct set of the Na(+)/Ca(2+) exchangers. Furthermore, the Na(+)/Ca(2+) exchangers play prominent roles in removing [Ca(2+)]i induced by glutamate but not [Ca(2+)]i induced by depolarization. The mitochondria serve as a major Ca(2+) sink and are functionally located close to NCX. In contrast, the ER is functionally located close to NCKX and acts primarily as a Ca(2+) source with marginal effects. This study reveals that the Na(+)/Ca(2+) exchangers, the ER and the mitochondria, which cooperate interactively, act similarly when regulating [Ca(2+)]i in mesencephalic DA and non-DA neurons. The heterogeneous expression of multiple types of Na(+)/Ca(2+) exchangers and the quantitative differences found in [Ca(2+)]i regulation, together with other risk factors specific to DA neurons such as dopamine oxidation resulting in oxidative stress, may drive these cells to undergo selective degeneration.

  13. Induced overexpression of Na+/Ca2+ exchanger transgene: altered myocyte contractility, [Ca2+]i transients, SR Ca2+ contents, and action potential duration.

    PubMed

    Wang, JuFang; Chan, Tung O; Zhang, Xue-Qian; Gao, Erhe; Song, Jianliang; Koch, Walter J; Feldman, Arthur M; Cheung, Joseph Y

    2009-08-01

    We have produced mice in which expression of the rat cardiac Na(+)/Ca(2+) exchanger (NCX1) transgene was switched on when doxycycline was removed from the feed at 5 wk. At 8 to 10 wk, NCX1 expression in induced (Ind) mouse hearts was 2.5-fold higher but protein levels of sarco(endo)plasmic reticulum Ca(2+)-ATPase, alpha(1)- and alpha(2)-subunits of Na(+)-K(+)-ATPase, phospholamban, ryanodine receptor, calsequestrin, and unphosphorylated and phosphorylated phospholemman were unchanged compared with wild-type (WT) or noninduced (non-Ind) hearts. There was no cellular hypertrophy since WT, non-Ind, and Ind myocytes had similar whole cell membrane capacitance. In Ind myocytes, NCX1 current amplitude was approximately 42% higher, L-type Ca(2+) current amplitude was unchanged, and action potential duration was prolonged compared with WT or non-Ind myocytes. Contraction and intracellular Ca(2+) concentration ([Ca(2+)](i)) transient amplitudes in Ind myocytes were lower at 0.6, not different at 1.8, and higher at 5.0 mM extracellular Ca(2+) concentration ([Ca(2+)](o)) compared with WT or non-Ind myocytes. Despite similar Ca(2+) current amplitude and sarcoplasmic reticulum (SR) Ca(2+) uptake, SR Ca(2+) content at 5.0 mM [Ca(2+)](o) was significantly higher in Ind compared with non-Ind myocytes, indicating that NCX1 directly contributed to SR Ca(2+) loading. Echocardiography demonstrated that heart rate, left ventricular mass, ejection fraction, stroke volume, and cardiac output were similar among the three groups of animals. In vivo close-chest catheterization demonstrated similar contractility and relaxation among the three groups of mice, both at baseline and after stimulation with isoproterenol. We conclude that induced expression of NCX1 transgene resulted in altered [Ca(2+)](i) homeostasis, myocyte contractility, and action potential morphology. In addition, heart failure did not occur 3 to 5 wk after NCX1 transgene was induced to be expressed at levels found in

  14. Age-dependent changes in diastolic Ca(2+) and Na(+) concentrations in dystrophic cardiomyopathy: Role of Ca(2+) entry and IP3.

    PubMed

    Mijares, Alfredo; Altamirano, Francisco; Kolster, Juan; Adams, José A; López, José R

    2014-10-03

    Duchenne muscular dystrophy (DMD) is a lethal X-inherited disease caused by dystrophin deficiency. Besides the relatively well characterized skeletal muscle degenerative processes, DMD is also associated with a dilated cardiomyopathy that leads to progressive heart failure at the end of the second decade. The aim of the present study was to characterize the diastolic Ca(2+) concentration ([Ca(2+)]d) and diastolic Na(+) concentration ([Na(+)]d) abnormalities in cardiomyocytes isolated from 3-, 6-, 9-, and 12-month old mdx mice using ion-selective microelectrodes. In addition, the contributions of gadolinium (Gd(3+))-sensitive Ca(2+) entry and inositol triphosphate (IP3) signaling pathways in abnormal [Ca(2+)]d and [Na(+)]d were investigated. Our results showed an age-dependent increase in both [Ca(2+)]d and [Na(+)]d in dystrophic cardiomyocytes compared to those isolated from age-matched wt mice. Gd(3+) treatment significantly reduced both [Ca(2+)]d and [Na(+)]d at all ages. In addition, blockade of the IP3-pathway with either U-73122 or xestospongin C significantly reduced ion concentrations in dystrophic cardiomyocytes. Co-treatment with U-73122 and Gd(3+) normalized both [Ca(2+)]d and [Na(+)]d at all ages in dystrophic cardiomyocytes. These data showed that loss of dystrophin in mdx cardiomyocytes produced an age-dependent intracellular Ca(2+) and Na(+) overload mediated at least in part by enhanced Ca(2+) entry through Gd(3+) sensitive transient receptor potential channels (TRPC), and by IP3 receptors.

  15. "JCE" Classroom Activity Connections: NaCl or CaCl[subscript 2], Smart Polymer Gel Tells More

    ERIC Educational Resources Information Center

    Chen, Yueh-Huey; Lin, Jia-Ying; Wang, Yu-Chen; Yaung, Jing-Fun

    2010-01-01

    This classroom activity connection demonstrates the differences between the effects of NaCl (a salt of monovalent metal ions) and CaCl[subscript 2] (a salt of polyvalent metal ions) on swollen superabsorbent polymer gels. Being ionic compounds, NaCl and CaCl[subscript 2] both collapse the swollen polymer gels. The gel contracted by NaCl reswells…

  16. Regulation of in vivo cardiac contractility by phospholemman: role of Na+/Ca2+ exchange.

    PubMed

    Wang, Jufang; Gao, Erhe; Rabinowitz, Joseph; Song, Jianliang; Zhang, Xue-Qian; Koch, Walter J; Tucker, Amy L; Chan, Tung O; Feldman, Arthur M; Cheung, Joseph Y

    2011-03-01

    Phospholemman (PLM), when phosphorylated at serine 68, relieves its inhibition on Na(+)-K(+)-ATPase but inhibits Na(+)/Ca(2+) exchanger 1 (NCX1) in cardiac myocytes. Under stress when catecholamine levels are high, enhanced Na(+)-K(+)-ATPase activity by phosphorylated PLM attenuates intracellular Na(+) concentration ([Na(+)](i)) overload. To evaluate the effects of PLM on NCX1 on in vivo cardiac contractility, we injected recombinant adeno-associated virus (serotype 9) expressing either the phosphomimetic PLM S68E mutant or green fluorescent protein (GFP) directly into left ventricles (LVs) of PLM-knockout (KO) mice. Five weeks after virus injection, ∼40% of isolated LV myocytes exhibited GFP fluorescence. Expression of S68E mutant was confirmed with PLM antibody. There were no differences in protein levels of α(1)- and α(2)-subunits of Na(+)-K(+)-ATPase, NCX1, and sarco(endo)plasmic reticulum Ca(2+)-ATPase between KO-GFP and KO-S68E LV homogenates. Compared with KO-GFP myocytes, Na(+)/Ca(2+) exchange current was suppressed, but resting [Na(+)](i), Na(+)-K(+)-ATPase current, and action potential amplitudes were similar in KO-S68E myocytes. Resting membrane potential was slightly lower and action potential duration at 90% repolarization (APD(90)) was shortened in KO-S68E myocytes. Isoproterenol (Iso; 1 μM) increased APD(90) in both groups of myocytes. After Iso, [Na(+)](i) increased monotonically in paced (2 Hz) KO-GFP but reached a plateau in KO-S68E myocytes. Both systolic and diastolic [Ca(2+)](i) were higher in Iso-stimulated KO-S68E myocytes paced at 2 Hz. Echocardiography demonstrated similar resting heart rate, ejection fraction, and LV mass between KO-GFP and KO-S68E mice. In vivo closed-chest catheterization demonstrated enhanced contractility in KO-S68E compared with KO-GFP hearts stimulated with Iso. We conclude that under catecholamine stress when [Na(+)](i) is high, PLM minimizes [Na(+)](i) overload by relieving its inhibition of Na

  17. Transplacental differences in Ca, Na, K, and electropotential in the guinea pig

    SciTech Connect

    Kelman, B.J.; Twardock, A.R.

    1983-07-01

    The fetal side of hemochorial placentas from guinea pigs between 58 and 62 days gestation were perfused in situ. Concurrent measurements were made of the clearances of radiocalcium and tritiated water from maternal to fetal circulation of the placenta, transplacental potential difference (TPD), maternal plasma and perfusate Ca, Na, and K concentrations, maternal blood pressure, gross permeability of albumin in the placenta, and net water movements. Movement of Ca from dam to fetus appeared to occur against an electrochemical gradient and was not associated with the movements of Na and K across the placenta. A negative correlation between perfusate Na and K concentrations, not dependent on maternal plasma Na and K concentrations and abolished by high concentrations of Ca in the fetal circulation of the placenta, strongly supports the concept of a Na-K exchange mechanism in the placenta directed so that K is moved against a concentration gradient towards the dam. There was no evidence that the TPD existed at the site of maternal-fetal exchange for Ca, Na, or K.

  18. First-principles investigation of point defect and atomic diffusion in Al2Ca

    NASA Astrophysics Data System (ADS)

    Tian, Xiao; Wang, Jia-Ning; Wang, Ya-Ping; Shi, Xue-Feng; Tang, Bi-Yu

    2017-04-01

    Point defects and atomic diffusion in Al2Ca have been studied from first-principles calculations within density functional framework. After formation energy and relative stability of point defects are investigated, several predominant diffusion processes in Al2Ca are studied, including sublattice one-step mechanism, 3-jump vacancy cycles and antistructure sublattice mechanism. The associated energy profiles are calculated with climbing image nudged elastic band (CI-NEB) method, then the saddle points and activation barriers during atomic diffusion are further determined. The resulted activation barriers show that both Al and Ca can diffuse mainly mediated by neighbor vacancy on their own sublattice. 3-jump cycle mechanism mediated by VCa may make some contribution to the overall Al diffusion. And antistructure (AS) sublattice mechanism can also play an important role in Ca atomic diffusion owing to the moderate activation barrier.

  19. Phospholemman regulates cardiac Na+/Ca2+ exchanger by interacting with the exchanger's proximal linker domain.

    PubMed

    Zhang, Xue-Qian; Wang, Jufang; Carl, Lois L; Song, Jianliang; Ahlers, Belinda A; Cheung, Joseph Y

    2009-04-01

    Phospholemman (PLM) belongs to the FXYD family of small ion transport regulators. When phosphorylated at Ser(68), PLM inhibits cardiac Na(+)/Ca(2+) exchanger (NCX1). We previously demonstrated that the cytoplasmic tail of PLM interacts with the proximal intracellular loop (residues 218-358), but not the transmembrane (residues 1-217 and 765-938) or Ca(2+)-binding (residues 371-508) domains, of NCX1. In this study, we used intact Na(+)/Ca(2+) exchanger with various deletions in the intracellular loop to map the interaction sites with PLM. We first demonstrated by Western blotting and confocal immunofluorescence microscopy that wild-type (WT) NCX1 and its deletion mutants were expressed in transfected HEK-293 cells. Cotransfection with PLM and NCX1 (or its deletion mutants) in HEK-293 cells did not decrease expression of NCX1 (or its deletion mutants). Coexpression of PLM with WT NCX1 inhibited NCX1 current (I(NaCa)). Deletion of residues 240-679, 265-373, 250-300, or 300-373 from WT NCX1 resulted in loss of inhibition of I(NaCa) by PLM. Inhibition of I(NaCa) by PLM was preserved when residues 229-237, 270-300, 328-330, or 330-373 were deleted from the intracellular loop of NCX1. These results suggest that PLM mediated inhibition of I(NaCa) by interacting with two distinct regions (residues 238-270 and 300-328) of NCX1. Indeed, I(NaCa) measured in mutants lacking residues 238-270, 300-328, or 238-270 + 300-328 was not affected by PLM. Glutathione S-transferase pull-down assays confirmed that PLM bound to fragments corresponding to residues 218-371, 218-320, 218-270, 238-371, and 300-373, but not to fragments encompassing residues 250-300 and 371-508 of NCX1, indicating that residues 218-270 and 300-373 physically associated with PLM. Finally, acute regulation of I(NaCa) by PLM phosphorylation observed with WT NCX1 was absent in 250-300 deletion mutant but preserved in 229-237 deletion mutant. We conclude that PLM mediates its inhibition of NCX1 by interacting with

  20. Na(+)-Ca2+ exchange function underlying contraction frequency inotropy in the cat myocardium.

    PubMed

    Vila Petroff, Martín G; Palomeque, Julieta; Mattiazzi, Alicia R

    2003-08-01

    In most mammalian species, an increase in stimulation frequency (ISF) produces an increase in contractility (treppe phenomenon), which results from larger Ca2+ transients at higher frequencies, due to an increase in sarcoplasmic reticulum Ca2+ load and release. The present study attempts to elucidate the contribution of the Na(+)-Ca2+ exchanger (NCX) to this phenomenon. Isolated cat ventricular myocytes, loaded with [Ca2+]i- and [Na+]i-sensitive probes, were used to determine whether the contribution of the NCX to the positive inotropic effect of ISF is due to an increase in Ca2+ influx (reverse mode) and/or a decrease in Ca2+ efflux (forward mode) via the NCX, due to frequency-induced [Na+]i elevation, or whether it was due to the reduced time for the NCX to extrude Ca2+. The results showed that the positive intropic effect produced by ISF was temporally dissociated from the increase in [Na+]i and was not modified by KB-R7943 (1 or 5 microM), a specific blocker of the reverse mode of the NCX. Whereas the ISF from 10 to 30 beats min(-1) (bpm) did not affect the forward mode of the NCX (assessed by the time to half-relaxation of the caffeine-induced Ca2+ transient), the ISF to 50 bpm produced a significant reduction of the activity of the forward mode of the NCX, which occurred in association with an increase in [Na+]i (from 4.33+/-0.40 to 7.25+/-0.50 mM). However, both changes became significant well after the maximal positive inotropic effect had been reached. In contrast, the positive inotropic effect produced by ISF from 10 to 50 bpm was associated with an increase in diastolic [Ca2+]i, which occurred in spite of a significant increase in the relaxation rate and at a time at which no increases in [Na+]i were detected. The contribution of the NCX to stimulus frequency inotropy would therefore depend on a decrease in NCX-mediated Ca2+ efflux due to the reduced diastolic interval between beats and not on [Na+]i-dependent mechanisms.

  1. Na+–Ca2+ Exchange Function Underlying Contraction Frequency Inotropy in the Cat Myocardium

    PubMed Central

    Vila Petroff, Martín G; Palomeque, Julieta; Mattiazzi, Alicia R

    2003-01-01

    In most mammalian species, an increase in stimulation frequency (ISF) produces an increase in contractility (treppe phenomenon), which results from larger Ca2+ transients at higher frequencies, due to an increase in sarcoplasmic reticulum Ca2+ load and release. The present study attempts to elucidate the contribution of the Na+–Ca2+ exchanger (NCX) to this phenomenon. Isolated cat ventricular myocytes, loaded with [Ca2+]i- and [Na+]i-sensitive probes, were used to determine whether the contribution of the NCX to the positive inotropic effect of ISF is due to an increase in Ca2+ influx (reverse mode) and/or a decrease in Ca2+ efflux (forward mode) via the NCX, due to frequency-induced [Na+]i elevation, or whether it was due to the reduced time for the NCX to extrude Ca2+. The results showed that the positive intropic effect produced by ISF was temporally dissociated from the increase in [Na+]i and was not modified by KB-R7943 (1 or 5 μm), a specific blocker of the reverse mode of the NCX. Whereas the ISF from 10 to 30 beats min−1 (bpm) did not affect the forward mode of the NCX (assessed by the time to half-relaxation of the caffeine-induced Ca2+ transient), the ISF to 50 bpm produced a significant reduction of the activity of the forward mode of the NCX, which occurred in association with an increase in [Na+]i (from 4.33 ± 0.40 to 7.25 ± 0.50 mm). However, both changes became significant well after the maximal positive inotropic effect had been reached. In contrast, the positive inotropic effect produced by ISF from 10 to 50 bpm was associated with an increase in diastolic [Ca2+]i, which occurred in spite of a significant increase in the relaxation rate and at a time at which no increases in [Na+]i were detected. The contribution of the NCX to stimulus frequency inotropy would therefore depend on a decrease in NCX-mediated Ca2+ efflux due to the reduced diastolic interval between beats and not on [Na+]i-dependent mechanisms. PMID:12938675

  2. Comparative studies of CdS, CdS:Al, CdS:Na and CdS:(Al-Na) thin films prepared by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Yılmaz, S.; Atasoy, Y.; Tomakin, M.; Bacaksız, E.

    2015-12-01

    In the present study, the spray pyrolysis technique was used to prepare pure CdS, 4 at.% Al-doped CdS, 4 at.% Na-doped CdS and (4 at.% Al, 4 at.% Na)-co-doped CdS thin films. It was found from X-ray diffraction data that all the specimens showed hexagonal wurtzite structure with the preferred orientation of (101). Scanning electron microscopy results indicated that 4 at.% Al-doping caused a grain growth in the morphology of CdS thin films whereas the 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping led to porous structure with small grains. The band gap value of CdS thin films increased to 2.42 eV after 4 at.% Al-doping. However, it reduced to 2.30 eV and 2.08 eV for 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping, respectively. The room temperature photoluminescence measurements illustrated that the peak intensity of CdS thin films enhanced with 4 at.% Al-doping while 4 at.% Na-doping and (4 at.% Al, 4 at.% Na)-co-doping caused a decline in the intensity. The maximum carrier concentration and minimum resistivity were obtained for 4 at.% Al-doped CdS thin films, which is associated with the grain growth. Furthermore, (4 at.% Al, 4 at.% Na)-co-doping gave rise to a slight reduction in the carrier concentration and a slight increment in the resistivity. As a result, it can be said that 4 at.% Al-doped CdS thin films exhibited the best electrical and optical properties, which is important for the opto-electronic applications.

  3. Atomistic Conversion Reaction Mechanism of WO3 in Secondary Ion Batteries of Li, Na, and Ca.

    PubMed

    He, Yang; Gu, Meng; Xiao, Haiyan; Luo, Langli; Shao, Yuyan; Gao, Fei; Du, Yingge; Mao, Scott X; Wang, Chongmin

    2016-05-17

    Intercalation and conversion are two fundamental chemical processes for battery materials in response to ion insertion. The interplay between these two chemical processes has never been directly seen and understood at atomic scale. Here, using in situ HRTEM, we captured the atomistic conversion reaction processes during Li, Na, Ca insertion into a WO3 single crystal model electrode. An intercalation step prior to conversion is explicitly revealed at atomic scale for the first time for Li, Na, Ca. Nanoscale diffraction and ab initio molecular dynamic simulations revealed that after intercalation, the inserted ion-oxygen bond formation destabilizes the transition-metal framework which gradually shrinks, distorts and finally collapses to an amorphous W and Mx O (M=Li, Na, Ca) composite structure. This study provides a full atomistic picture of the transition from intercalation to conversion, which is of essential importance for both secondary ion batteries and electrochromic devices.

  4. Insight into the Family of Na+/Ca2+ Exchangers of Caenorhabditis elegans

    PubMed Central

    Sharma, Vishal; He, Chao; Sacca-Schaeffer, Julian; Brzozowski, Eric; Martin-Herranz, Daniel E.; Mendelowitz, Zelda; Fitzpatrick, David A.; O’Halloran, Damien M.

    2013-01-01

    Here we provide the first genome-wide in vivo analysis of the Na+/Ca2+ exchanger family in the model system Caenorhabditis elegans. We source all members of this family within the Caenorhabditis genus and reconstruct their phylogeny across humans and Drosophila melanogaster. Next, we provide a description of the expression pattern for each exchanger gene in C. elegans, revealing a wide expression in a number of tissues and cell types including sensory neurons, interneurons, motor neurons, muscle cells, and intestinal tissue. Finally, we conduct a series of behavioral and functional analyses through mutant characterization in C. elegans. From these data we demonstrate that, similar to mammalian systems, the expression of Na+/Ca2+ exchangers in C. elegans is skewed toward excitable cells, and we propose that C. elegans may be an ideal model system for the study of Na+/Ca2+ exchangers. PMID:23893482

  5. AlF4- induces Ca2+ oscillations in guinea-pig ileal smooth muscle.

    PubMed

    Himpens, B; Missiaen, L; Droogmans, G; Casteels, R

    1991-02-01

    The effects of different compounds that inhibit the isolated plasma-membrane Ca2+/Mg2(+)-ATPase on the cytosolic free Ca2+ concentration ([Ca2+]i) and on the corresponding force development have been examined in smooth muscle of the longitudinal layer of the guinea-pig ileum. F-, in the presence of Al3+, induced an increase of the resting force and of the amplitude of the superimposed phasic contractions. The increase of resting force was associated with an increased level of basal [Ca2+]i while the phasic contractions were accompanied by concomitant oscillations in [Ca2+]i. Comparable contractions could be induced by vanadate and the calmodulin antagonist calmidazolium. The oscillations of [Ca2+]i and of force elicited by AlF4- were not modified by adrenergic or cholinergic blocking agents but were inhibited by verapamil. These phasic contractions were not affected by depleting the intracellular Ca2+ stores with ryanodine. This finding excludes a cytosolic origin of these oscillations. However, hyperpolarization and complete depolarization of the cells inhibited the oscillations. It is concluded that AlF4-, vanadate and calmidazolium induce cytoplasmic Ca2+ oscillations possibly by acting at the plasma membrane. Indeed all these substances affect by different mechanisms the isolated plasma-membrane Ca2+/Mg2(+)-ATPase. The generation of membrane-linked Ca2+ oscillations could therefore be related to an inhibition of the plasma-membrane Ca2+ pump resulting in an increase of [Ca2+]i. This change in [Ca2+]i could be responsible for the pronounced changes of the electrical and mechanical activity of this tissue.

  6. Functional differences of Na+/Ca2+ exchanger expression in Ca2+ transport system of smooth muscle of guinea pig stomach.

    PubMed

    Sakai, Yasushi; Kinoshita, Hiroki; Saitou, Keiichirou; Homma, Ikuo; Nobe, Koji; Iwamoto, Takahiro

    2005-01-01

    The plasma membrane ATP-dependent Ca2+ pump and the Na+/Ca2+ exchanger (NCX) are the major means of Ca2+ extrusion in smooth muscle. However, little is known regarding distribution and function of the NCX in guinea pig gastric smooth muscle. The expression pattern and distribution of NCX isoforms suggest a role as a regulator of Ca2+ transport in cells. Na+ pump inhibition and the consequent to removal of K+ caused gradual contraction in fundus. In contrast, the response was significantly less in antrum. Western blotting analysis revealed that NCX1 and NCX2 are the predominant NCX isoforms expressed in stomach, the former was expressed strongly in antrum, whereas the latter displayed greater expression in fundus. Isolated plasma membrane fractions derived from gastric fundus smooth muscle were also investigated to clarify the relationship between NCX protein expression and function. Na+-dependent Ca2+ uptake increased directly with Ca2+ concentration. Ca2+ uptake in Na+-loaded vesicles was markedly elevated in comparison with K+-loaded vesicles. Additionally, Ca2+ uptake by the Na+- or K+-loaded vesicles was substantially higher in the presence of A23187 than in its absence. The result can be explained based on the assumption that Na+ gradients facilitate downhill movement of Ca2+. Na+-dependent Ca2+ uptake was abolished by the monovalent cationic ionophore, monensin. NaCl enhanced Ca2+ efflux from vesicles, and this efflux was significantly inhibited by gramicidin. Results documented evidence that NCX2 isoform functionally contributes to Ca2+ extrusion and maintenance of contraction-relaxation cycle in gastric fundus smooth muscle.

  7. Close Association of Carbonic Anhydrase (CA2a and CA15a), Na+/H+ Exchanger (Nhe3b), and Ammonia Transporter Rhcg1 in Zebrafish Ionocytes Responsible for Na+ Uptake

    PubMed Central

    Ito, Yusuke; Kobayashi, Sayako; Nakamura, Nobuhiro; Miyagi, Hisako; Esaki, Masahiro; Hoshijima, Kazuyuki; Hirose, Shigehisa

    2013-01-01

    Freshwater (FW) fishes actively absorb salt from their environment to tolerate low salinities. We previously reported that vacuolar-type H+-ATPase/mitochondrion-rich cells (H-MRCs) on the skin epithelium of zebrafish larvae (Danio rerio) are primary sites for Na+ uptake. In this study, in an attempt to clarify the mechanism for the Na+ uptake, we performed a systematic analysis of gene expression patterns of zebrafish carbonic anhydrase (CA) isoforms and found that, of 12 CA isoforms, CA2a and CA15a are highly expressed in H-MRCs at larval stages. The ca2a and ca15a mRNA expression were salinity-dependent; they were upregulated in 0.03 mM Na+ water whereas ca15a but not ca2a was down-regulated in 70 mM Na+ water. Immunohistochemistry demonstrated cytoplasmic distribution of CA2a and apical membrane localization of CA15a. Furthermore, cell surface immunofluorescence staining revealed external surface localization of CA15a. Depletion of either CA2a or CA15a expression by Morpholino antisense oligonucleotides resulted in a significant decrease in Na+ accumulation in H-MRCs. An in situ proximity ligation assay demonstrated a very close association of CA2a, CA15a, Na+/H+ exchanger 3b (Nhe3b), and Rhcg1 ammonia transporter in H-MRC. Our findings suggest that CA2a, CA15a, and Rhcg1 play a key role in Na+uptake under FW conditions by forming a transport metabolon with Nhe3b. PMID:23565095

  8. Effect of the partial replacement of Ca by alkaline element Na on Tl-1223 superconductor

    NASA Astrophysics Data System (ADS)

    Awad, R.; Abou-Aly, A. I.; Isber, S.; Malaeb, W.

    2006-06-01

    We have investigated the effect of Na substitution at Ca sites on the lattice parameters, electrical resistivity, magnetic susceptibility and thermopower coefficient for TlBa2Ca2-xNaxCu3O9-δ with 0 <= x <= 0.4. The lattice parameters elongate with increasing the Na-content. A little enhancement in the superconducting transition temperature Tc has been observed as x increases from 0 to 0.05 and then it depresses gradually for x > 0.05. This observation was attributed to the fact that Na has converted the Tl- 1223 phase from over-doped regime to under-doped regime which is in conformity with the thermopower results, that found to change from negative (over-doped regime) to positive (under-doped regime). The inter-grain critical current density as function of Na has been also reported from ac magnetic susceptibility measurements.

  9. Removal of K+, Na+, Ca2+, and Mg2+ from saline-alkaline water using the microalga Scenedesmus obliquus

    NASA Astrophysics Data System (ADS)

    Yao, Zongli; Ying, Chengqi; Lu, Jianxue; Lai, Qifang; Zhou, Kai; Wang, Hui; Chen, Ling

    2013-11-01

    The capability of Scenedesmus obliquus to remove cations (K+, Na+, Ca2+, Mg2+) from saline-alkaline water was investigated at different salinities (0, 5, 10, 15, 20, 25) and carbonate alkalinities (0, 5, 10, 15, 20, 25, 30, 35 mmol/L). K+, Na+, Ca2+, and Mg2+ in saline-alkaline water were efficiently removed by S. obliquus. The maximum removal of the cations (29.37 mg for K+, 185.85 mg for Na+, 23.07 mg for Ca2+, 66.14 mg for Mg2+) occurred at salinity 25. The maximum removal of K+ (2.28 mg), Na+ (6.62 mg), Ca2+ (1.01 mg), and Mg2+ (0.62 mg) occurred at carbonate alkalinities of 25 mmol/L for K+, 35 mmol/L for Na+, 20 mmol/L for Ca2+, and 25 mmol/L for Mg2+, respectively. Under a salinity stress, the concentration of Na+ in S. obliquus increased significantly, while that of K+ decreased significantly. The concentrations of Ca2+ and Mg2+ decreased as well. The ratios of K+/Na+, Ca2+/Na+, and Mg2+/Na+ were significantly lower in all salinity treatments than those of the control. Under alkaline stress, the concentrations of Na+ and K+ in S. obliquus decreased significantly and the ratios of K+/Na+, Ca2+/Na+, and Mg2+/Na+ were significantly higher in all treatments than in the control. Moreover, the concentrations of Ca2+ and Mg2+ in S. obliquus at alkalinities of 5-10 mmol/L were significantly higher than those of the other treatments. The removal of Na+ by S. obliquus mainly occurs through biosorption, and Mg2+ and Ca2+ were removed through both biosorption and bioaccumulation.

  10. Calcium-Ca/AlCl4/2-thionyl chloride cell - Performance and safety

    NASA Astrophysics Data System (ADS)

    Meitav, A.; Peled, E.

    1982-03-01

    Tests to determine the effect of concentration and temperature on the conductivity of Ca(AlCl4)2-thionyl chloride solutions, to assess the discharge performance of the Ca/Ca(AlCl4)2-thionyl chloride cell at varying temperatures and electrolyte concentrations, and to study the safety of the cell during charging and reversal in comparison to a LiAlCl4 electrolyte-based cell are reported. Flat cells were examined for discharge and cylindrical cells with a reference electrode were used for electrodeposition experiments. Conductivity was found to increase when temperature decreased in the Ca(AlCl4)2 solutions, with a preferred concentration set at 0.7 M for low temperatures and 1.25 M in the range 10-60 C. No anodic disintegration was observed with lithium cathodes, although an explosion hazard remained. Finally, sandwich-like Ca/Ca(AlCl4)2-thionyl chloride cells possessed the energy density of the Li-SO2 cells, and were also impossible to charge or overdischarge, indicating a suitability for high rate multicell battery applications.

  11. Phosphate-sulfide assemblages and Al/Ca ratios in type-3 chondrites

    NASA Technical Reports Server (NTRS)

    Rubin, A. E.; Grossman, J. N.

    1985-01-01

    Electron microscopic examinations were carried out on various chondrites to re-examine previously reported anomalously high Al/Ca ratios. Polished thin sections of the three CV3, two CO3 and the Krymka LL3 chondrites were scanned to characterize the phosphate-sulfide inclusions. The formation of the assemblages was interpreted as proceeding in five steps, starting with the formation of metal grains with early nebular material and finishing with a reaction between schreibersite with Ca, O and Cl to form merrillite and chloropatite. The abundances of the observed assemblages were not high enough to imply Al/Ca ratios similar to whole-rocks. It is concluded that the specimens were originally examined with a broader electron beam than used to examine standard samples, and resulted in the anomalously high Al/Ca ratios.

  12. Neuroprotective profile of pyridothiazepines with blocking activity of the mitochondrial Na(+)/Ca(2+) exchanger.

    PubMed

    Martínez-Sanz, Francisco J; Lajarín-Cuesta, Rocío; González-Lafuente, Laura; Moreno-Ortega, Ana J; Punzón, Eva; Cano-Abad, María F; de los Ríos, Cristóbal

    2016-02-15

    The mitochondrial Na(+)/Ca(2+) exchanger plays an important role in the control of cytosolic Ca(2+) cycling in excitable cells, essential for the regulation of a plethora of Ca(2+)-dependent physio-pathological events, such as apoptosis in the presence of a Ca(2+) overload. There are very few pharmacological tools available to study both physiological and pathological implications of the mitochondrial Na(+)/Ca(2+) exchanger, where the benzothiazepine CGP37157 is the best-known ligand, used since the 1980s. However, it is not an efficient blocker and lacks of selectivity, as also blocks several other cellular Ca(2+) transporters. Moreover, CGP37157 is a very lipophilic drug, showing very poor water solubility, what has hindered its therapeutic use. Attempting to improve its pharmacokinetic profile as well as its potency and selectivity, we herein describe the synthesis of new CGP37157 analogs, where the benzene-fused ring has been replaced by a pyridine. On top of a better water solubility and lower log P value, some of these new pyridothiazepine derivatives also presented a higher capacity to regulate the mitochondrial Ca(2+) clearance, while keeping the neuroprotective properties presented in the head compound CGP37157.

  13. Ultrafast bulk diffusion of AlHx in high-entropy dehydrogenation intermediates of NaAlH4 [Highly mobile AlHx species and the dehydogenation kinetics of NaAlH4

    DOE PAGES

    Zhang, Feng; Wood, Brandon C.; Wang, Yan; ...

    2014-07-21

    Using first-principles molecular dynamics (FPMD) and total-energy calculations, we demonstrate low-barrier bulk diffusion of Al-bearing species in γ-NaAlH4, a recently proposed high-entropy polymorph of NaAlH4. For charged AlH4– and neutral AlH3 vacancies, the computed barriers for diffusion are <0.1 eV, and we directly observe the predicted diffusive pathways in FPMD simulations at picosecond time scales. In contrast, such diffusion in the α phase is inaccessible to FPMD, consistent with much higher barriers. The transport behavior of γ-NaAlH4, in addition to key dynamical and structural signatures, is consistent with experimental observations of high-mobility species, strongly supporting the idea that an intermediatemore » transition from the α phase to a high-entropy polymorph facilitates the hydrogen-releasing decomposition of NaAlH4. Lastly, our results provide an answer to longstanding questions regarding the responsible agent for the experimentally observed efficient Al transport during dehydrogenation and suggest that mass transport and phase transformation kinetics are coupled. Implications for understanding the (de)hydrogenation of undoped and catalyzed NaAlH4 are discussed.« less

  14. Pressure effects on the superconducting transition in nH-CaAlSi

    NASA Astrophysics Data System (ADS)

    Boeri, L.; Kim, J. S.; Giantomassi, M.; Razavi, F. S.; Kuroiwa, S.; Akimitsu, J.; Kremer, R. K.

    2008-04-01

    We present a combined experimental and theoretical study of the effects of pressure on Tc of the hexagonal layered superconductors nH-CaAlSi ( n=1 , 5, and 6), where nH denotes the different stacking variants that were recently discovered. Experimentally, the pressure dependence of Tc has been investigated by measuring the magnetic susceptibility of single crystals up to 10 kbars. In contrast to previous results on polycrystalline samples, single crystals with different stacking sequences display different pressure dependences of Tc . 1H-CaAlSi shows a decrease in Tc with pressure, whereas 5H - and 6H-CaAlSi exhibit an increase in Tc with pressure. Ab initio calculations for 1H -, 5H -, and 6H-CaAlSi reveal that an ultrasoft phonon branch associated with out-of-plane vibrations of the Al-Si layers softens with pressure, leading to a structural instability at high pressures. For 1H-CaAlSi , the softening is not sufficient to cause an increase in Tc , which is consistent with the present experiments but adverse to previous reports. For 5H and 6H , the softening provides the mechanism to understand the observed increase in Tc with pressure. Calculations for hypothetical 2H and 3H stacking variants reveal qualitative and quantitative differences.

  15. Effect of Ca addition on the damping capacity of Mg-Al-Zn casting alloys

    NASA Astrophysics Data System (ADS)

    Jun, Joong-Hwan; Moon, Jung-Hyun

    2015-07-01

    The influences of Ca addition on the microstructures and damping capacities of AZ91-(0˜2)%Ca casting alloys were investigated, on the basis of the results of X-ray diffractometry, optical microscopy, scanning electron microscopy and vibration tests in a single cantilever mode. The amount of intermetallic compounds decreased with increasing Ca content up to 0.5%, above which it increased; the average cell size showed the opposite tendency. All alloys exhibited similar damping levels in the strain-amplitude independent region. Considering the very low solubility of Ca in the matrix, and that most of the Ca elements are consumed by the formation of the Al2Ca phase and incorporation into the Mg17Al12 phase, this would be ascribed to the almost identical concentrations of Ca solutes distributed in the matrix. In the strain-amplitude dependent region, however, the AZ91-0.5%Ca alloy possessed the maximum damping capacity. From the viewpoint of microstructural evolution with Ca addition, the number density of compound particles is considered to be the principal factor affecting the damping behavior in the strain-amplitude dependent region.

  16. Formation Mechanism of CaS-Bearing Inclusions and the Rolling Deformation in Al-Killed, Low-Alloy Steel with Ca Treatment

    NASA Astrophysics Data System (ADS)

    Xu, Guang; Jiang, Zhouhua; Li, Yang

    2016-08-01

    The existing form of CaS inclusion in Ca-treated, Al-killed steel during secondary refining process was investigated with scanning electron microscopy and an energy-dispersive spectrometer (EDS). The results of 12 heats industrial tests showed that CaS has two kinds of precipitation forms. One form takes place by the direct reaction of Ca and S, and the other takes place by the reaction of CaO in calcium aluminates with dissolved Al and S in liquid steel. Thermodynamic research for different precipitation modes of CaS under different temperature was carried out. In particular, CaO-Al2O3-CaS isothermal section diagrams and component activities of calcium aluminates were calculated by the thermodynamic software FactSage. By thermodynamic calculation, a precipitation-area diagram of oxide-sulfide duplex inclusion was established by fixing the sulfur content. The quantity of CaS, which was precipitated in a reaction between [Al], [S] and (CaO), can be calculated and predicted based on the precipitation-area diagram of oxide-sulfide duplex inclusion. Electron probe microanalysis and EDS were used for observing rolling deformation of different types of CaS-bearing inclusions during the rolling process. Low modification of calcium aluminates wrapped by CaS has different degrees of harm to steel in the rolling process. A thick CaS layer can prevent some fragile calcium aluminates from being crushed during the rolling process. Some oxide-sulfide duplex inclusion contains little CaS performed better deformation during the rolling process, but when CaS in oxide-sulfide duplex inclusion becomes more, it will cause the whole inclusion to lose plastic yielding ability. The plastic deformation region of CaS-bearing inclusion in a CaO-Al2O3-CaS isothermal section diagram is confirmed.

  17. Triggering of sarcoplasmic reticulum Ca2+ release and contraction by reverse mode Na+/Ca2+ exchange in trout atrial myocytes.

    PubMed

    Hove-Madsen, Leif; Llach, Anna; Tibbits, Glen F; Tort, Lluis

    2003-05-01

    Whole cell patch clamp and intracellular Ca(2+) transients in trout atrial cardiomyocytes were used to quantify calcium release from the sarcoplasmic reticulum (SR) and examine its dependency on the Ca(2+) trigger source. Short depolarization pulses (2-20 ms) elicited large caffeine-sensitive tail currents. The Ca(2+) carried by the caffeine-sensitive tail current after a 2-ms depolarization was 0.56 amol Ca(2+)/pF, giving an SR Ca(2+) release rate of 279 amol Ca(2+). pF(-1). s(-1) or 4.3 mM/s. Depolarizing cells for 10 ms to different membrane potentials resulted in a local maximum of SR Ca(2+) release, intracellular Ca(2+) transient, and cell shortening at 10 mV. Although 100 microM CdCl(2) abolished this local maximum, it had no effect on SR Ca(2+) release elicited by a depolarization to 110 or 150 mV, and the SR Ca(2+) release was proportional to the membrane potential in the range -50 to 150 mV with 100 microM CdCl(2). Increasing the intracellular Na(+) concentration ([Na(+)]) from 10 to 16 mM enhanced SR Ca(2+) release but reduced cell shortening at all membrane potentials examined. In the absence of TTX, SR Ca(2+) release was potentiated with 16 mM but not 10 mM pipette [Na(+)]. Comparison of the total sarcolemmal Ca(2+) entry and the Ca(2+) released from the SR gave a gain factor of 18.6 +/- 7.7. Nifedipine (Nif) at 10 microM inhibited L-type Ca(2+) current (I(Ca)) and reduced the time integral of the tail current by 61%. The gain of the Nif-sensitive SR Ca(2+) release was 16.0 +/- 4.7. A 2-ms depolarization still elicited a contraction in the presence of Nif that was abolished by addition of 10 mM NiCl(2). The gain of the Nif-insensitive but NiCl(2)-sensitive SR Ca(2+) release was 14.8 +/- 7.1. Thus both reverse-mode Na(+)/Ca(2+) exchange (NCX) and I(Ca) can elicit Ca(2+) release from the SR, but I(Ca) is more efficient than reverse-mode NCX in activating contraction. This difference may be due to extrusion of a larger fraction of the Ca(2+) released from

  18. NiF2/NaF:CaF2/Ca Solid-State High-Temperature Battery Cells

    NASA Technical Reports Server (NTRS)

    West, William; Whitacre, Jay; DelCastillo, Linda

    2009-01-01

    Experiments and theoretical study have demonstrated the promise of all-solid-state, high-temperature electrochemical battery cells based on NiF2 as the active cathode material, CaF2 doped with NaF as the electrolyte material, and Ca as the active anode material. These and other all-solid-state cells have been investigated in a continuing effort to develop batteries for instruments that must operate in environments much hotter than can be withstood by ordinary commercially available batteries. Batteries of this type are needed for exploration of Venus (where the mean surface temperature is about 450 C), and could be used on Earth for such applications as measuring physical and chemical conditions in geothermal wells and oil wells. All-solid-state high-temperature power cells are sought as alternatives to other high-temperature power cells based, variously, on molten anodes and cathodes or molten eutectic salt electrolytes. Among the all-solid-state predecessors of the present NiF2/NaF:CaF2/Ca cells are those described in "Solid-State High-Temperature Power Cells" (NPO-44396), NASA Tech Briefs, Vol. 32, No. 5 (May 2008), page 40. In those cells, the active cathode material is FeS2, the electrolyte material is a crystalline solid solution of equimolar amounts of Li3PO4 and LiSiO4, and the active anode material is Li contained within an alloy that remains solid in the intended high operational temperature range.

  19. Effects of Al additives on growth of GaN polycrystals by the Na flux method

    NASA Astrophysics Data System (ADS)

    Imabayashi, Hiroki; Murakami, Kosuke; Matsuo, Daisuke; Honjo, Masatomo; Imanishi, Masayuki; Maruyama, Mihoko; Imade, Mamoru; Yoshimura, Masashi; Mori, Yusuke

    2017-03-01

    In this study, we investigated the growth of GaN polycrystals using the Al-added Na flux method. We studied the effects of Al on accelerating the nucleation and purity of GaN polycrystals. The yields of GaN crystals grown in Al-added Na flux were dramatically increased from those in Al-free Na flux, and the polycrystals grown by the Al-added Na flux method were highly transparent. As observed in secondary ion mass spectroscopy measurements, the Al content of the polycrystals was below the detection limit of 3 × 1016 atoms/cm3. From these results, the Al-added Na flux method is found to be appropriate for fabricating a large amount of GaN polycrystals without deteriorating the crystal quality.

  20. Ab initio calculation of half-metallic ferromagnetism in zinc-blende (CaN)1/(AlN)x and (CaN)x/(AlN)1 (x=2, 3) (001) superlattices

    NASA Astrophysics Data System (ADS)

    Song, Xiao-Sheng; Dong, Shengjie; Zhao, Hui

    2014-09-01

    Using first-principles density functional theory calculations, we investigated the electronic and magnetic properties of zinc-blende (CaN)1/(AlN)x and (CaN)x/(AlN)1 (x=2, 3) superlattices in the (001) direction. With a total magnetic moment of 1 μB for (CaN)1/(AlN)2, 2 μB for (CaN)2/(AlN)1, 1 μB for (CaN)1/(AlN)3, and 3 μB for (CaN)3/(AlN)1, these four superlattices show very stable half-metallic ferromagnetic behaviors. The analysis of the partial density of states reveals that the p-d hybridization of N and Ca is responsible for the magnetization. Besides, it is shown that the magnetic properties of these multilayer superlattices can be controlled by changing the ratio of the layer numbers of dissimilar materials.

  1. X-ray Diffraction Analysis on Post Treatment of Ca-Mg-Al-Layered Double Hydroxide Slurry

    NASA Astrophysics Data System (ADS)

    Heraldy, E.; Nugrahaningtyas, K. D.; Heriyanto

    2017-02-01

    This research objectives to study post treatment on Ca-Mg-Al-Layered Double Hydroxide (Ca-Mg-Al-LDH) slurry which was prepared from brine water by cooling treatment. The cooling rate was varied from 1 to 3 °C/min by using stirring and without stirring, and the cooling time was done at 0, 30 minutes and 24 hours. The quantitative X-ray diffraction (QXRD) was employed on Ca-Mg-Al-LDH using Le Bail refinement method. The refinement results found another Mg-Al-LDH and Ca-Al-LDH phases, such as Mg(OH)2, Al(OH)3 and CaCO3. The highest phase composition on material Ca-Mg-Al-LDH using Le Bail refinement was showed by Al(OH)3.

  2. A Ca substitution study of NaV2O4: High-pressure synthesis of the Na1-xCaxV2O4 solid solution

    SciTech Connect

    Varga, Tamas; Mitchell, John F.; Yamaura, Kazunari; Mandrus, David; Wang, Jun

    2009-01-01

    Ambient pressure CaV{sub 2}O{sub 4} and high-pressure NaV{sub 2}O{sub 4} crystallize in the CaFe{sub 2}O{sub 4} structure type containing double chains of edge-sharing VO{sub 6} octahedra. Recent measurements on NaV{sub 2}O{sub 4} reveal low-dimensional metallicity and evidence of half-metallic ferromagnetism. In contrast, CaV{sub 2}O{sub 4} is an antiferromagnetic insulator. To explore the evolution of these ground-state behaviors, we have prepared a series of Ca-doped NaV{sub 2}O{sub 4} compounds with the formula Na{sub 1-x}Ca{sub x}V{sub 2}O{sub 4} (x = 0-1) using high-pressure synthesis. Samples at the Na end (x = 0-0.07) show a broad antiferromagnetic transition in the 120-160 K range in accordance with earlier reports. Transport measurements show an insulator-metal transition at x {approx} 0.2. Samples with higher Ca concentrations (x = 0.4-0.7) exhibit a metal-insulator transition around 150 K. The results for the Na{sub 1-x}Ca{sub x}V{sub 2}O{sub 4} solid solution is discussed in comparison to existing studies at the Ca- and Na-rich ends.

  3. Mechanosensitivity of an epithelial Na+ channel in planar lipid bilayers: release from Ca2+ block.

    PubMed Central

    Ismailov, I I; Berdiev, B K; Shlyonsky, V G; Benos, D J

    1997-01-01

    A family of novel epithelial Na+ channels (ENaCs) have recently been cloned from several different tissues. Three homologous subunits (alpha, beta, gamma-ENaCs) from the core conductive unit of Na(+)-selective, amiloride-sensitive channels that are found in epithelia. We here report the results of a study assessing the regulation of alpha,beta,gamma-rENaC by Ca2+ in planar lipid bilayers. Buffering of the bilayer bathing solutions to [Ca2+] < 1 nM increased single-channel open probability by fivefold. Further investigation of this phenomenon revealed that Ca2+ ions produced a voltage-dependent block, affecting open probability but not the unitary conductance of ENaC. Imposing a hydrostatic pressure gradient across bilayers containing alpha,beta,gamma-rENaC markedly reduced the sensitivity of these channels to inhibition by [Ca2+]. Conversely, in the nominal absence of Ca2+, the channels lost their sensitivity to mechanical stimulation. These results suggest that the previously observed mechanical activation of ENaCs reflects a release of the channels from block by Ca2+. Images FIGURE 3 FIGURE 4 PMID:9138565

  4. Isoprenaline, Ca2+ and the Na(+)-K+ pump in guinea-pig ventricular myocytes.

    PubMed Central

    Gao, J; Mathias, R T; Cohen, I S; Baldo, G J

    1992-01-01

    1. The whole-cell patch clamp technique was employed to study the effects of the beta-agonist isoprenaline (ISO) on the Na(+)=K+ pump current, Ip, in acutely isolated ventricular myocytes from guinea-pig hearts. Propranolol, a beta-adrenergic antagonist, was used to demonstrate that all of the effects of ISO, stimulatory or inhibitory, are mediated by beta-receptors. 2. Below about 150 nM [Ca2+]i, we find that ISO reduces Ip, while above this [Ca2+]i ISO increases Ip. The stimulatory and inhibitory effects of ISO on Ip are independent of either intracellular sodium ([Na+]i) or extracellular potassium ([K+]o). These results suggest that the end-effect of ISO is directly on the maximum pump turnover rate (Vmax) rather than indirectly through changes in [Na+]i or [K+]o or modulatory effects on Na+ or K+ affinity. 3. The maximum effect of ISO increases Ip by 25% when [Ca2+] is buffered at 1.4 microM. A half-maximal effect is reached at roughly 10 nM-ISO and a near-maximal effect by 0.5 microM. 4. The permeabilized patch technique, using amphotericin B (Horn & Marty, 1988; Rae, Cooper, Gates & Watsky, 1991), was employed to minimize changes in the normal second messenger systems and calcium buffers. In these experiments, we used a high intracellular sodium solution (pipette sodium was 50 mM), thus sodium-calcium exchange was depressed and we expected [Ca2+]i to be above 150 nM. ISO increases Ip in these conditions as in the dialysed cells. 5. Our results suggest that beta-stimulation can increase Ip, but only if [Ca2+]i is above about 150 nM. In the beating heart [Ca2+]i rises well above this value during systole and the average [Ca2+]i, which depends on heart rate, is expected to normally be above this level. During beta-stimulation, the increase in Ip along with a concomitant increase in IK (Giles, Nakajima, Ono & Shibata, 1989; Duchatelle-Gourdon, Hartzell & Lagrutta, 1989) helps prevent action potential lengthening and allows an increase in heart rate even in the

  5. A Ca substitution study of NaV{sub 2}O{sub 4} : high-pressure synthesis of the Na{sub 1-x}Ca{sub x}V{sub 2}O{sub 4} slid solution.

    SciTech Connect

    Varga, T.; Mitchell, J. F.; Yamaura, K.; Mandrus, D. G.; Wang, J.; ORNL

    2009-01-01

    Ambient pressure CaV{sub 2}O{sub 4} and high-pressure NaV{sub 2}O{sub 4} crystallize in the CaFe{sub 2}O{sub 4} structure type containing double chains of edge-sharing VO{sub 6} octahedra. Recent measurements on NaV{sub 2}O{sub 4} reveal low-dimensional metallicity and evidence of half-metallic ferromagnetism. In contrast, CaV{sub 2}O{sub 4} is an antiferromagnetic insulator. To explore the evolution of these ground-state behaviors, we have prepared a series of Ca-doped NaV{sub 2}O{sub 4} compounds with the formula Na{sub 1-x}Ca{sub x}V{sub 2}O{sub 4} (x = 0-1) using high-pressure synthesis. Samples at the Na end (x = 0-0.07) show a broad antiferromagnetic transition in the 120-160 K range in accordance with earlier reports. Transport measurements show an insulator-metal transition at x {approx} 0.2. Samples with higher Ca concentrations (x = 0.4-0.7) exhibit a metal-insulator transition around 150 K. The results for the Na{sub 1-x}Ca{sub x}V{sub 2}O{sub 4} solid solution is discussed in comparison to existing studies at the Ca- and Na-rich ends.

  6. Characterization of single voltage-gated Na+ and Ca2+ channels in apical dendrites of rat CA1 pyramidal neurons.

    PubMed

    Magee, J C; Johnston, D

    1995-08-15

    1. We have used dendrite-attached patch-clamp techniques to record single Na+ and Ca2+ channel activity from the apical dendrites (up to 350 microns away from soma) of CA1 pyramidal neurons in rat hippocampal slices (ages: 2-8 weeks). 2. Na+ channels were found in every patch examined (range: 2 to > 20 channels per patch). Channel openings, which had a slope conductance of 15 +/- 0.3 pS (mean +/- S.E.M.), began with test commands to around -50 mV and consisted of both early transient channel activity and also later occurring prolonged openings of 5-15 ms. All Na+ channel activity was suppressed by inclusion of TTX (1 microM) in the recording pipette. 3. Ca2+ channel activity was recorded in about 80% of the patches examined (range: 1 to > 10 channels per patch). Several types of channel behaviour were observed in these patches. Single channel recordings in 110 mM BaCl2, revealed an approximately 10 pS channel of small unitary current amplitude (-0.5 pA at -20 mV). These channels began activating at relatively hyperpolarized potentials (-50 mV) and ensemble averages of this low voltage-activated (LVA) channel activity showed rapid inactivation. 4. A somewhat heterogeneous population of high voltage-activated, moderate conductance (HVAm; approximately 17 pS), Ca2+ channel activity was also encountered. These channels exhibited a relatively large unitary amplitude (-0.8 pA at 0 mV) and ensemble averages demonstrated moderate inactivation. The HVAm population of channels could be tentatively subdivided into two separate groups based upon mean channel open times. 5. Less frequently, HVA, large conductance (27 pS) Ca2+ channel activity (HVA1) was also observed. This large unitary amplitude (-1.5 pA at 0 mV) channel activity began with steps to approximately 0 mV and ensemble averages did not show any time-dependent inactivation. The dihydropyridine Ca2+ channel agonist Bay K 8644 (0.5 or 1 microM) was found to characteristically prolong these channel openings. 6. omega

  7. Characterization of single voltage-gated Na+ and Ca2+ channels in apical dendrites of rat CA1 pyramidal neurons.

    PubMed Central

    Magee, J C; Johnston, D

    1995-01-01

    1. We have used dendrite-attached patch-clamp techniques to record single Na+ and Ca2+ channel activity from the apical dendrites (up to 350 microns away from soma) of CA1 pyramidal neurons in rat hippocampal slices (ages: 2-8 weeks). 2. Na+ channels were found in every patch examined (range: 2 to > 20 channels per patch). Channel openings, which had a slope conductance of 15 +/- 0.3 pS (mean +/- S.E.M.), began with test commands to around -50 mV and consisted of both early transient channel activity and also later occurring prolonged openings of 5-15 ms. All Na+ channel activity was suppressed by inclusion of TTX (1 microM) in the recording pipette. 3. Ca2+ channel activity was recorded in about 80% of the patches examined (range: 1 to > 10 channels per patch). Several types of channel behaviour were observed in these patches. Single channel recordings in 110 mM BaCl2, revealed an approximately 10 pS channel of small unitary current amplitude (-0.5 pA at -20 mV). These channels began activating at relatively hyperpolarized potentials (-50 mV) and ensemble averages of this low voltage-activated (LVA) channel activity showed rapid inactivation. 4. A somewhat heterogeneous population of high voltage-activated, moderate conductance (HVAm; approximately 17 pS), Ca2+ channel activity was also encountered. These channels exhibited a relatively large unitary amplitude (-0.8 pA at 0 mV) and ensemble averages demonstrated moderate inactivation. The HVAm population of channels could be tentatively subdivided into two separate groups based upon mean channel open times. 5. Less frequently, HVA, large conductance (27 pS) Ca2+ channel activity (HVA1) was also observed. This large unitary amplitude (-1.5 pA at 0 mV) channel activity began with steps to approximately 0 mV and ensemble averages did not show any time-dependent inactivation. The dihydropyridine Ca2+ channel agonist Bay K 8644 (0.5 or 1 microM) was found to characteristically prolong these channel openings. 6. omega

  8. Origin of Na-Ca-Cl brines in Jurassic and Cretaceous reservoirs of Gulf Coast

    SciTech Connect

    Carpenter, A.B.

    1985-02-01

    Na-Ca-Cl brines in Jurassic and Cretaceous reservoirs in the Gulf Coast have been attributed to the diagenesis of concentrated Jurassic seawater related to Louann Salt deposition and alternatively to the diagenesis of brines produced by halie dissolution. These brines contain up to 35,000 mg/L Ca, up to 4000 mg/L, from 400 to 2400 mgL Br, and up to 13,000 mg/L K. Mutual relationships of Na, Cl, total divalent cations minus sulfate and bicarbonate, K, and Br are similar to those in seawater that has been evaporated past the initial stage of halite deposition, particularly when the K content of the brine exceeds 5000 mg/L. The concentrations of divalent cations and K increase, and the mutual relationships of all the dissolved salts become increasingly similar to those in seawater with increasing proximity to bedded salt. The abundance of authigenic K-feldspar in rocks above the salt beds explains the relatively rapid decrease in the K content of the brines upsection. The Ca and K contents of Jurassic Gulf Coast brines are similar to those in Na-Ca-Cl brines in feldspar-poor carbonate sequences in other basins.

  9. Trafficking of Na+/Ca2+ Exchanger to the Site of Persistent Inflammation in Nociceptive Afferents

    PubMed Central

    Scheff, Nicole N.

    2015-01-01

    Persistent inflammation results in an increase in the amplitude and duration of depolarization-evoked Ca2+ transients in putative nociceptive afferents. Previous data indicated that these changes were the result of neither increased neuronal excitability nor an increase in the amplitude of depolarization. Subsequent data also ruled out an increase in voltage-gated Ca2+ currents and recruitment of Ca2+-induced Ca2+ release. Parametric studies indicated that the inflammation-induced increase in the duration of the evoked Ca2+ transient required a relatively large and long-lasting increase in the concentration of intracellular Ca2+ implicating the Na+/Ca2+ exchanger (NCX), a major Ca2+ extrusion mechanism activated with high intracellular Ca2+ loads. The contribution of NCX to the inflammation-induced increase in the evoked Ca2+ transient in rat sensory neurons was tested using fura-2 AM imaging and electrophysiological recordings. Changes in NCX expression and protein were assessed with real-time PCR and Western blot analysis, respectively. An inflammation-induced decrease in NCX activity was observed in a subpopulation of putative nociceptive neurons innervating the site of inflammation. The time course of the decrease in NCX activity paralleled that of the inflammation-induced changes in nociceptive behavior. The change in NCX3 in the cell body was associated with a decrease in NCX3 protein in the ganglia, an increase in the peripheral nerve (sciatic) yet no change in the central root. This single response to inflammation is associated with changes in at least three different segments of the primary afferent, all of which are likely to contribute to the dynamic response to persistent inflammation. PMID:26041911

  10. Trafficking of Na+/Ca2+ exchanger to the site of persistent inflammation in nociceptive afferents.

    PubMed

    Scheff, Nicole N; Gold, Michael S

    2015-06-03

    Persistent inflammation results in an increase in the amplitude and duration of depolarization-evoked Ca(2+) transients in putative nociceptive afferents. Previous data indicated that these changes were the result of neither increased neuronal excitability nor an increase in the amplitude of depolarization. Subsequent data also ruled out an increase in voltage-gated Ca(2+) currents and recruitment of Ca(2+)-induced Ca(2+) release. Parametric studies indicated that the inflammation-induced increase in the duration of the evoked Ca(2+) transient required a relatively large and long-lasting increase in the concentration of intracellular Ca(2+) implicating the Na(+)/Ca(2+) exchanger (NCX), a major Ca(2+) extrusion mechanism activated with high intracellular Ca(2+) loads. The contribution of NCX to the inflammation-induced increase in the evoked Ca(2+) transient in rat sensory neurons was tested using fura-2 AM imaging and electrophysiological recordings. Changes in NCX expression and protein were assessed with real-time PCR and Western blot analysis, respectively. An inflammation-induced decrease in NCX activity was observed in a subpopulation of putative nociceptive neurons innervating the site of inflammation. The time course of the decrease in NCX activity paralleled that of the inflammation-induced changes in nociceptive behavior. The change in NCX3 in the cell body was associated with a decrease in NCX3 protein in the ganglia, an increase in the peripheral nerve (sciatic) yet no change in the central root. This single response to inflammation is associated with changes in at least three different segments of the primary afferent, all of which are likely to contribute to the dynamic response to persistent inflammation.

  11. The sodium pump modulates the influence of I(Na) on [Ca2+]i transients in mouse ventricular myocytes.

    PubMed Central

    Su, Z; Sugishita, K; Ritter, M; Li, F; Spitzer, K W; Barry, W H

    2001-01-01

    To investigate whether activity of the sarcolemmal Na pump modulates the influence of sodium current on excitation-contraction (E-C) coupling, we measured [Ca(2+)](i) transients (fluo-3) in single voltage-clamped mouse ventricular myocytes ([Na+](pip) = 15 or 0 mM) when the Na pump was activated (4.4 mM K(+)(o)) and during abrupt inhibition of the pump by exposure to 0 K with a rapid solution-switcher device. After induction of steady state [Ca2+](i) transients by conditioning voltage pulses (0.25 Hz), inhibition of the Na pump for 1.5 s immediately before and continuing during a voltage pulse (200 ms, -80 to 0 mV) caused a significant increase (15 +/- 2%; n = 16; p < 0.01) in peak systolic [Ca2+](i) when [Na+](pip) was 15 mM. In the absence of sodium current (I(Na), which was blocked by 60 microM tetrodotoxin (TTX)), inhibition of the Na pump immediately before and during a voltage pulse did not result in an increase in peak systolic [Ca2+](i). Abrupt blockade of I(Na) during a single test pulse with TTX caused a slight decrease in peak [Ca2+](i), whether the pump was active (9%) or inhibited (10%). With the reverse-mode Na/Ca exchange inhibited by KB-R 7943, inhibition of the Na pump failed to increase the magnitude of the peak systolic [Ca2+](i) (4 +/- 1%; p = NS) when [Na+](pip) was 15 mM. When [Na+](pip) was 0 mM, the amplitude of the peak systolic [Ca2+](i) was not altered by abrupt inhibition of the Na pump immediately before and during a voltage pulse. These findings in adult mouse ventricular myocytes indicate the Na pump can modulate the influence of I(Na) on E-C coupling in a single beat and provide additional evidence for the existence of Na fuzzy space, where [Na+] can significantly modulate Ca2+ influx via reverse Na/Ca exchange. PMID:11222287

  12. Electronic structure and unusual superconducting properties of of CaAlSi and SrAlSi

    NASA Astrophysics Data System (ADS)

    Mazin, Igor I.; Papaconstantopoulos, Dimitris

    2004-03-01

    We report full-potential LAPW calculations for CaAlSi and SrAlSi in ordered structures and in the virtual crystal approximation, at normal and elevated pressures. We also estimate the electron-phonon coupling using either frozen-phon calculations at the zone center, or the rigid muffin tin approximation. We conclude that there is no simple way to explain the recently reported qualitative disparity in the superconducting properties of the two compounds. An assumption of an ultrasoft phonon mode, on the other hand, allows to reconcile in a reasonable way the experimental findings with the theory.

  13. XPS and NMR analysis on 12CaO•7Al2O3

    NASA Astrophysics Data System (ADS)

    Pan, R. K.; Feng, S.; Tao, H. Z.

    2017-01-01

    12CaO·7Al2O3 (C12A7) glass was prepared by the melt quenching method. The glass transition temperature (T g) and the crystallization temperature (T c) of C12A7 glass are about 1050 K and 1194 K, respectively, measured by the differential scanning calorimetry (DSC). The structure of C12A7 glass was investigated by X-ray photoelectron spectroscopy (XPS) as well as magic angle spinning-nuclear magnetic resonance spectroscopy (MAS-NMR). Analysis shows that Al coordination number is about four in C12A7 glass, in which AlO4 tetrahedrons and bridging oxygens (BO) constitute the glass network. Ca2+ produces a few of non-bridging oxygens (NBO), which become neighbours of Al.

  14. Identification and apical membrane localization of an electrogenic Na+/Ca2+ exchanger NCX2a likely to be involved in renal Ca2+ excretion by seawater fish

    PubMed Central

    Islam, Zinia; Romero, Michael F.; Hirose, Shigehisa

    2011-01-01

    Seawater (SW) contains ∼10 mM Ca2+, yet marine fish must drink seawater as their major water source. Thus marine teleosts fish need to excrete Ca2+ to maintain whole body Ca2+ homeostasis. In the intestine, seawater Ca2+ interreacts with epithelial-secreted HCO3− by the intestinal epithelium, and the resulting CaCO3 precipitates, which is rectally excreted. Recently the transporters involved in intestinal HCO3− secretion were identified. Ca2+ is also excreted by the kidney, but the protein(s) involved in renal Ca2+ excretion have not been identified. Here we identified a candidate transporter by using SW pufferfish torafugu (Takifugu rubripes) and its closely related euryhaline species mefugu (Takifugu obscurus), which are becoming useful animal models for studying molecular mechanisms of seawater adaptation. RT-PCR analyses of Na+/Ca2+ exchanger (NCX) family members in various torafugu tissues demonstrated that only NCX2a is highly expressed in the kidney. Renal expression of NCX2a was markedly elevated when mefugu were transferred from freshwater to seawater. In situ hybridization and immunohistochemical analyses indicated that NCX2a is expressed in the proximal tubule at the apical membrane. NCX2a, expressed in Xenopus oocytes, conferred [Ca2+]out- and Na+-dependent currents. These results suggest that NCX2a mediates renal Ca2+ secretion at the apical membrane of renal proximal tubules and has an important role in whole body Ca2+ homeostasis of marine teleosts. PMID:21880864

  15. Preparation of Al-La Master Alloy by Thermite Reaction in NaF-NaCl-KCl Molten Salt

    NASA Astrophysics Data System (ADS)

    Jang, Poknam; Li, Hyonmo; Kim, Wenjae; Wang, Zhaowen; Liu, Fengguo

    2015-05-01

    A NaF-NaCl-KCl ternary system containing La2O3 was investigated for the preparation of Al-La master alloy by the thermite reaction method. The solubility of La2O3 in NaF-NaCl-KCl molten salt was determined by the method of isothermal solution saturation. Inductively coupled plasma-optical emission spectroscopy and x-ray diffraction (XRD) analyses were used to consider the content of La2O3 in molten salt and the supernatant composition of molten salt after dissolution of La2O3, respectively. The results showed that the content of NaF had a positive influence on the solubility of La2O3 in NaF-NaCl-KCl molten salts, and the solubility of La2O3 could reach 8.71 wt.% in molten salts of 50 wt.%NaF-50 wt.% (44 wt.%NaCl + 56 wt.%KCl). The XRD pattern of cooling molten salt indicated the formation of LaOF in molten salt, which was probably obtained by the reaction between NaF and La2O3. The kinetic study showed that the thermite reaction was in accord with a first-order reaction model. The main influence factors on La content in the Al-La master alloy product, including molten salt composition, amount of Al, concentration of La2O3, stirring, reduction time and temperature, were investigated by single-factor experimentation. The content of La in the Al-La master alloy could be reached to 10.1 wt.%.

  16. LiCaAlF6 scintillators in neutron and gamma radiation fields

    NASA Astrophysics Data System (ADS)

    Viererbl, L.; Klupák, V.; Vinš, M.; Koleška, M.; Šoltés, J.; Yoshikawa, A.; Nikl, M.

    2016-09-01

    Intentionally doped LiCaAlF6 (LiCAF) single crystals are prospective scintillators, especially for thermal neutron detection through the 6Li(n,t)4He nuclear reaction. Four different LiCAF scintillator samples were tested in various neutron and gamma fields. Two of the tested samples were LiCAF:Eu and LiCAF:Eu,Na single crystals, and another two samples were made of LiCAF:Eu micro crystals dispersed in transparent rubber, with different rubber dimensions. All LiCAF samples contain lithium enriched to6Li. A plutonium-beryllium source was used as a neutron source. The neutron spectrum was modified by moderator and filter to get different ratios between thermal, epithermal and fast neutron fluence rates. The MCNP code was used for calculations of the fluence rates for different configurations. Radionuclides 137Cs and 60Co were applied as gamma radiation sources. The light signal from the scintillator was evaluated with a photomultiplier and a multichannel analyzer. The purpose of this work was to study the characteristics of LiCAF scintillators, especially the ability to discriminate signals from neutron and gamma radiation, which is the basic scintillator condition for neutron detection in mixed neutron-gamma radiation fields. Generally, the discrimination can be done by the pulse height and/or the pulse shape of the evaluated signals. Both methods can be used for a LiCAF scintillator. However, only the pulse height discrimination method is discussed in this paper. The possibility of fast neutron detection with LiCAF scintillators was also tested.

  17. Ca-,Al-rich inclusions in the unique chondrite ALH85085 - Petrology, chemistry, and isotopic compositions

    NASA Astrophysics Data System (ADS)

    Kimura, M.; El Goresy, A.; Palme, H.; Zinner, E.

    1993-05-01

    A comprehensive study is performed for the Ca-,Al-rich inclusions (CAIs) in the unique chondrite ALH85085. The ALH85085 inclusions are smaller (5-80 microns) and more refractory than their counterparts in carbonaceous chondrites. The study includes 42 inclusions for petrography and mineralogy, 15 for bulk major and minor element chemical composition, six for Mg-Al isotopic systematics, 10 for Ca isotopes, nine for Ti isotopes, and six for trace element abundances. In addition, oxygen-isotopic compositions were determined in minerals from a single inclusion. No correlation is found between mineralogy, major element chemistry, and trace element abundances. It is further shown that the high-temperature geochemical behavior of ultrarefractory trace elements is decoupled from that of the major elements Ca and Ti (Ti is correlated with the relatively volatile elements Nb and Yb) implying that perovskite is of only minor importance as carrier of ultrarefractories.

  18. Quadruple-layered perovskite (CuCl)Ca2NaNb4O13

    NASA Astrophysics Data System (ADS)

    Kitada, A.; Tsujimoto, Y.; Yamamoto, T.; Kobayashi, Y.; Narumi, Y.; Kindo, K.; Aczel, A. A.; Luke, G. M.; Uemura, Y. J.; Kiuchi, Y.; Ueda, Y.; Yoshimura, K.; Ajiro, Y.; Kageyama, H.

    2012-01-01

    We will present the synthesis, structure and magnetic properties of a new quadruple-layered perovskite (CuCl)Ca2NaNb4O13. Through a topotactic ion-exchange reaction with CuCl2, the precursor RbCa2NaNb4O13 presumably having an incoherent octahederal tliting changes into (CuCl)Ca2NaNb4O13 with a 2ap×2ap×2cp superstructure (tetragonal; a=7.73232(5) Å, c=39.2156(4) Å). The well-defined superstructure for the ion-exchanged product should be stabilized by the inserted CuCl4O2 octahedral layers that firmly connect with neighboring perovskite layers. Magnetic studies show the absence of long-range magnetic ordering down to 2 K despite strong in-plane interactions. Aleksandrov‧s group theory and Rietveld refinement of synchrotron X-ray diffraction data suggest the structure to be of I4/mmm space group with in-phase tilting along the a and b axes, a two-tilt system (++0).

  19. The osmotic response of the isolated, unfixed mouse tectorial membrane to isosmotic solutions: effect of Na+, K+, and Ca2+ concentration.

    PubMed

    Shah, D M; Freeman, D M; Weiss, T F

    1995-07-01

    Changes in the size, shape, and structure of the isolated tectorial membrane (TM) of the mouse were measured in response to isosmotic changes in the ionic composition of the bathing solution. Substitution of artificial perilymph (AP) for artificial endolymph (AE) caused a small (approximately 1%) shrinkage of the TM's thickness. This substitution alters not only the predominate cation (from K+ to Na+) but also the Ca2+ concentration (from 20 mumol/l to 2 mmol/l). When the predominate cation was changed from K+ to Na+, while holding Ca2+ concentration constant, results depended on Ca2+ concentration: there was a small (approximately 1%) swelling for 20 mumol/l Ca2+, larger (approximately 14%) swelling for lower (< 7 mumol/l) concentrations of Ca2+, and little response for 2 mmol/l Ca2+ or for solutions containing the Ca2+ chelator EGTA. Addition of Ca2+ while holding the predominate cation constant caused shrinkage of the TM; both removal of Ca2+ and addition of the Ca2+ chelator EGTA caused swelling. Swelling responses were largely reversible if the magnitude of the swelling was small. Responses greater than a few percent were only partially reversible and caused long-lasting changes. Changes in ionic composition of the bath affected not only the thickness of the TM but also its other dimensions. Solution changes that increase TM thickness tend to cause radial shearing motions of the surfaces of the TM, which are accompanied by small decreases in width. Little change in length was observed. Although the responses were non-isotropic, increases in thickness were highly correlated with increases in volume. Swelling of the TM was also accompanied by a reduction in prominence of its radially oriented fibrillar structure. These results for the isolated TM of the mouse are qualitatively similar to those obtained previously for the isolated chick TM (Freeman et al., 1994) but different from those obtained for the in vitro mouse TM (Kronester-Frei, 1979a).

  20. Complexation of pectin with macro- and microelements. Antianemic activity of Na, Fe and Na, Ca, Fe complexes.

    PubMed

    Minzanova, S T; Mironov, V F; Vyshtakalyuk, A B; Tsepaeva, O V; Mironova, L G; Mindubaev, A Z; Nizameev, I R; Kholin, K V; Milyukov, V A

    2015-12-10

    New water-soluble pectin complexes with Ca(2+), Mg(2+), Co(2+), Cu(2+), Fe(2+), Mn(2+), Zn(2+) on the basis of pectin biopolymer have been synthesized and successfully tested on white rats. For a starting, we have obtained a sodium pectate to enhance solubility of target complexes as a whole. Shortly afterwards, running the reaction of ligand exchange of Nа(+) ions with corresponding s-, d- metal cations we were able to synthesize new pectin complexes. The ranges of s-, d-metals salts concentrations were detected experimentally, in which the selective formation of water-soluble complexes occurred. Antianemic effect of new pectin complexes with Na, Fe and Na, Ca, Fe was investigated on white rats with posthemorrhagic anemia. Under the effect of complexes, the improvement of animals and prevention of erythropoiesis disorders were observed. Antianemic effect of the complexes manifested itself in the doses equivalent to 25% or 50% of the iron daily rate, recommended in the treatment of iron-deficiency anemia with the drugs based on iron sulphate.

  1. Infrared and SEM analyses of polyethyleneglycol-400 adsorbed on zeolites NaA, CaA, NaX and NaY

    NASA Astrophysics Data System (ADS)

    Öztürk, Nuri; Ucun, Fatih; Didem Muhtar, A.; Bahçeli, Semiha

    2009-03-01

    The adsorption of polyethyleneglycol-400 (PEG-400) on zeolites NaA, CaA, NaX and NaY have been investigated by using FT-IR spectroscopy and scanning electron microscopic (SEM) analyses. The spectral data have indicated that the source of adsorption of the PEG-400 on the mentioned zeolites is the interaction between the (OH) group of the liquid adsorbent and the surface silanol groups of the zeolites by means of a hydrogen bond. Shortly, the PEG binds with the silanol groups through the hydrogen bonding where the ethereal oxygen acts as a hydrogen bond accepter. A part of the PEG molecule remains adsorbed on the surface and the rest part remains protruded. So, the most of the silanol groups on the zeolites are masked by the PEG-400.

  2. Hydrogen sorption behavior of CaAl1.5Li0.5

    NASA Astrophysics Data System (ADS)

    Bereznitsky, Matvey; Mogilyanski, Dmitry; Jacob, Isaac

    2016-04-01

    The hydrogen sorption properties of an alloy with nominal composition CaAl1.5Li0.5 have been investigated in a pursuit for hydrogen-absorbing Li-containing intermetallics. X-ray analysis of the original alloy indicated a coexistence of three closely related Laves phases. The maximum hydrogen capacity, recorded at about 6 MPa and 300 °C, was approximately 2.5 H atoms per formula unit (f.u.). Pressure-composition (p-c) isotherm measurements were taken in the temperature range between 350 and 450 °C up to pressures of 133 kPa. Thermodynamic parameters are derived for two plateau regions in the p-c isotherms. Analysis of these parameters and supporting evidence from X-ray patterns of hydrogenated and dehydrogenated samples suggest: (a) an initial irreversible disproportionation of the original alloy and (b) subsequent reversible hydrogenations, featuring reversible disproportionations of CaAl2 and LiAl intermetallic compounds. Attempts to form additional Li-containing intermetallics, namely CaAlLi, TiMn2- x Li x (x = 0.2, 0.3, 0.4, 0.6) and TiAl2- x Li x (x = 0.3, 0.5), and to hydrogenate them, are reported in brief.

  3. Optically pumped cerium-doped LiSrAlF{sub 6} and LiCaAlF{sub 6}

    DOEpatents

    Marshall, C.D.; Payne, S.A.; Krupke, W.F.

    1996-05-14

    Ce{sup 3+}-doped LiSrAlF{sub 6} crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF{sub 6} with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF{sub 6} crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF{sub 6} type of chemical formula, e.g. Ce-doped LiCaAlF{sub 6} and LiSrGaF{sub 6}, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF{sub 6} laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator. 10 figs.

  4. Optically pumped cerium-doped LiSrAlF.sub.6 and LiCaAlF.sub.6

    DOEpatents

    Marshall, Christopher D.; Payne, Stephen A.; Krupke, William F.

    1996-01-01

    Ce.sup.3+ -doped LiSrAlF.sub.6 crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF.sub.6 with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF.sub.6 type of chemical formula, e.g. Ce-doped LiCaAlF.sub.6 and LiSrGaF.sub.6, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator.

  5. Estimation of the solubility product of hydrocalumite-hydroxide, a layered double hydroxide with the formula of [Ca2Al(OH)6]OH·nH2O

    NASA Astrophysics Data System (ADS)

    Gácsi, Attila; Kutus, Bence; Kónya, Zoltán; Kukovecz, Ákos; Pálinkó, István; Sipos, Pál

    2016-11-01

    From aqueous NaOH/Ca(OH)2/NaAl(OH)4 mixtures, after allowing short reaction times we observed the precipitation of Ca(OH)2(s) at lower, and a mixture of Ca(OH)2(s) and a layered double hydroxide, hydrocalumite (HC) at higher aluminate concentrations. From the maximum aluminate concentration, at which the equilibrium solid phase is still portlandite (i.e., further increase in the aluminate concentration results in HC appearing in the precipitate beside the portlandite), the concentration based solubility products of two polymorphs of HC with the formula of [Ca2Al(OH)6]OH·nH2O (differing in n) has been estimated and was found to be log LHC=-11.4 at 25 °C and -12.1 at 75 °C, respectively (where LHC=[Ca2+]2[Al(OH)4-][OH-]3) and at constant ionic strength (I=1 M NaCl). To the best of our knowledge, this is the first published estimate for the solubility product of hydrocalumite. Additionally, from the composition obtained for NaOH/Ca(OH)2/NaAl(OH)4 mother liquors in equilibrium with Ca(OH)2(s), attempts were made to extract the formation constant of the ion pair CaAl(OH)4+. It was found, that the effects caused by the supposed formation of this solution species are too small to be reliably determined, which allowed an upper estimate for its formation constant, K, to be suggested in the temperature range of 25-75 °C (K<200 and 40 M-1 at 25 and 75 °C, respectively).

  6. The squid preparation as a general model for ionic and metabolic Na+/Ca2+ exchange interactions: physiopathological implications.

    PubMed

    DiPolo, R; Beaugé, L

    2007-03-01

    We propose an integrated kinetic model for the squid nerve Na+/Ca2+ exchanger based on experimental evidences obtained in dialyzed axons. This model satisfactorily explains the interrelationship between ionic (Na+(i)-H+(i)-Ca2+(i)) and metabolic (ATP, phosphoarginine (PA)) regulation of the exchanger. Data in dialyzed axons show that the Ca(i)-regulatory site located in the large intracellular loop plays a central role in the modulation by ATP by antagonizing the inhibitory Na+(i)-H+(i) synergism. We have used the Na(o)/Na(i) exchange mode to unequivocally measure the affinity of the Ca(i)-regulatory site. This allowed us to separate Ca(i)-regulatory from Ca(i)-transport sites and to estimate their respective affinities. In this work we show for the first time that under conditions of saturation of the Ca(i)-regulatory site (10 microM Ca2+(i), pH(i) 8.0), ATP have no effect on the Ca(i)-transport site. In addition, we have expanded our equilibrium kinetic model of ionic and metabolic interactions to a complete exchange cycle (circular model). This model, in which the Ca(i)-regulatory site plays a central role, accounts for the decrease in Na(i) inactivation, at high pH(i), high Ca2+(i,) and MgATP. Furthermore, the model also predicts the net Ca2+ movements across the exchanger based on the exchanger complexes redistribution both during physiological and pathological conditions (ischemia).

  7. NMR probe of pseudogap characteristics in CaAl2-xSi2+x

    NASA Astrophysics Data System (ADS)

    Lue, C. S.; Wang, S. Y.; Fang, C. P.

    2007-06-01

    We report the results of a Al27 nuclear magnetic resonance (NMR) study of CaAl2-xSi2+x , near the stoichiometric composition with x=0 . The low-temperature NMR relaxation rates for stoichiometric (x=0) and nonstoichiometric ( x=-0.1 and 0.1) compounds follow a Korringa law, associated with a finite density of carriers at the Fermi level. High-temperature relaxation rates for x⩾0 go over to a semiconductorlike activated form, providing information about the electronic structure near the Fermi energy. The results are consistent with pseudogap features identified by recent band-structure calculations. An analysis of the pseudogap change vs composition further points out that the band-filling picture is proper for the understanding of the NMR observations in CaAl2-xSi2+x .

  8. Involvement of Na+/Ca2+ exchanger in pentylenetetrazol-induced convulsion by use of Na+/Ca2+ exchanger knockout mice.

    PubMed

    Saito, Ryo; Kaneko, Erina; Tanaka, Yusuke; Honda, Kenji; Matsuda, Toshio; Baba, Akemichi; Komuro, Issei; Kita, Satomi; Iwamoto, Takahiro; Takano, Yukio

    2009-11-01

    Involvement of Na+/Ca2+ exchanger (NCX) in pentylenetetrazol (PTZ)-induced convulsion by use of NCX knockout mice and the selective ligand SEA0400 to NCX was examined. In the SEA0400-administered group, the latency to clonic convulsion was extended into 210 s, although the latency to clonic convulsion was observed until 100 s in control group. SEA0400 had little effect on bicuculline-induced clonic seizure nicotine-induced wild running and 4-aminopyridine-induced tonic flexion, respectively. Tonic flexion convulsion was occurred three fifth in the wild type mice group by administration of PTZ, but tonic flexion was not observed in NCX1 knockout mice groups. These results suggest that NCX is involved in inhibitory action in PTZ-induced convulsion.

  9. The Al-Rich Part of the System CaO-Al 2O 3-MgO . Part I. Phase Relationships

    NASA Astrophysics Data System (ADS)

    Göbbels, M.; Woermann, E.; Jung, J.

    1995-12-01

    In the Al-rich part of the ternary system CaO-Al 2O 3MgO two new ternary phases Ca 2Mg 2Al 28O 46 (CAM-I) and CaMg 2Al 16O 27 (CAM-II) with limited solid solution ranges were found. Due to the fact that the compositions of the Mg-rich end members of these solid solutions lie on the join between hibonite (CaAl 12O 19) and spinel (MgAl 2O 4), the model of the crystal structures of these phases can be constructed by a suitable combination of hibonite and spinel units. Both phases, CAM-I and CAM-II, exhibit solid solution ranges described by a substitution mechanism also found in the binary spinel phase, MgAl 2O 4: 3 Mg 2+ = 2 Al 3+ + □. Thus the ternary phases can be expressed by the chemical formulas. Ca 2Mg 2-3 xAl 28+2 x□ xO 46 for CAM-I with 0 ≤ x ≤ 0.30 and CaMg 2-3 yAl 16+2 y□ yO 27 for CAM-II with 0 ≤ y ≤ 0.2.

  10. Inhibitory effects of purified antibody against α-1 repeat (117-137) on Na(+)-Ca(2+) exchange and L-type Ca(2+) currents in rat cardiomyocytes.

    PubMed

    Feng, Qi-Long; Wu, Dong-Mei; Cui, Xiang-Li; Zhao, Hua-Chen; Lin, Yuan-Yuan; Zhao, Lu-Ying; Wu, Bo-Wei

    2010-10-25

    Considering that α-1 repeat region may be involved in the ion binding and translocation of Na(+)-Ca(2+) exchanger (NCX), it is possible that the antibodies against NCX α-1 repeat may have a crucial action on NCX activity. The aim of the present study is to investigate the effect of antibody against α-1 repeat (117-137), designated as α-1(117-137), on NCX activity. The antibody against the synthesized α-1(117-137) was prepared and affinity-purified. Whole-cell patch clamp technique was used to study the change of Na(+)-Ca(2+) exchange current (I(Na/Ca)) in adult rat cardiomyocytes. To evaluate the functional specificity of this antibody, its effects on L-type Ca(2+) current (I(Ca,L)), voltage-gated Na(+) current (I(Na)) and delayed rectifier K(+) current (I(K)) were also observed. The amino acid sequences of α-1(117-137) in NCX and residues 1 076-1 096 within L-type Ca(2+) channel were compared using EMBOSS Pairwise Alignment Algorithms. The results showed that outward and inward I(Na/Ca) were decreased by the antibody against α-1(117-137) dose-dependently in the concentration range from 10 to 160 nmol/L, with IC(50) values of 18.9 nmol/L and 22.4 nmol/L, respectively. Meanwhile, the antibody also decreased I(Ca,L) in a concentration-dependent manner with IC(50) of 22.7 nmol/L. No obvious effects of the antibody on I(Na) and I(K) were observed. Moreover, comparison of the amino acid sequences showed there was 23.8% sequence similarity between NCX α-1(117-137) and residues 1 076-1 096 within L-type Ca(2+) channel. These results suggest that antibody against α-1(117-137) is a blocking antibody to NCX and can also decrease I(Ca,L) in a concentration-dependent manner, while it does not have obvious effects on I(Na) and I(K).

  11. On the entropy of glaucophane Na2Mg3Al2Si8O22(OH)2

    USGS Publications Warehouse

    Robie, R.A.; Hemingway, B.S.; Gillet, P.; Reynard, B.

    1991-01-01

    The heat capacity of glaucophane from the Sesia-Lanza region of Italy having the approximate composition (Na1.93Ca0.05Fe0.02) (Mg2.60Fe0.41) (Al1.83Fe0.15Cr0.01) (Si7.92Al0.08)O22(OH)2 was measured by adiabatic calorimetry between 4.6 and 359.4 K. After correcting the Cp0data to values for ideal glaucophane, Na2Mg3Al2Si8O22(OH)2 the third-law entropy S2980-S00was calculated to be 541.2??3.0 J??mol-1??K-1. Our value for S2980-S00is 12.0 J??mol-1??K-1 (2.2%) smaller than the value of Likhoydov et al. (1982), 553.2??3.0, is within 6.2 J??mol-1??K-1 of the value estimated by Holland (1988), and agrees remarkably well with the value calculated by Gillet et al. (1989) from spectroscopic data, 539 J??mol-1??K-1. ?? 1991 Springer-Verlag.

  12. Removal of Ca2+ and Zn2+ from aqueous solutions by zeolites NaP and KP.

    PubMed

    Yusof, Alias Mohd; Malek, Nik Ahmad Nizam Nik; Kamaruzaman, Nurul Asyikin; Adil, Muhammad

    2010-01-01

    Zeolites P in sodium (NaP) and potassium (KP) forms were used as adsorbents for the removal of calcium (Ca2+) and zinc (Zn2+) cations from aqueous solutions. Zeolite KP was prepared by ion exchange of K+ with Na+ which neutralizes the negative charge of the zeolite P framework structure. The ion exchange capacity of K+ on zeolite NaP was determined through the Freundlich isotherm equilibrium study. Characterization of zeolite KP was determined using infrared spectroscopy and X-ray diffraction (XRD) techniques. From the characterization, the structure of zeolite KP was found to remain stable after the ion exchange process. Zeolites KP and NaP were used for the removal of Ca and Zn from solution. The amount of Ca2+ and Zn2+ in aqueous solution before and after the adsorption by zeolites was analysed using the flame atomic absorption spectroscopy method. The removal of Ca2+ and Zn2+ followed the Freundlich isotherm rather than the Langmuir isotherm model. This result also revealed that zeolite KP adsorbs Ca2+ and Zn2+ more than zeolite NaP and proved that modification of zeolite NaP with potassium leads to an increase in the adsorption efficiency of the zeolite. Therefore, the zeolites NaP and KP can be used for water softening (Ca removal) and reducing water pollution/toxicity (Zn removal).

  13. Improvement of CaFe/sub 2/O/sub 4/ photocathode by doping with Na and Mg

    SciTech Connect

    Matsumoto, Y.; Sugiyama, K.; Sato, E.

    1988-05-01

    The low conductivity of CaFe/sub 2/O/sub 4/ and the nonohmic contact in the CaFe/sub 2/O/sub 4//metal interface, which lead to only a small photocurrent, were improved by doping with Na and Mg. The oxides of the Ca/sub 1-x/Na/sub x/Fe/sub 2-y/Mg/sub y/O/sub 4/ system gave the high conductivity and the ohmic contact of the oxide/Pt-Pd interface, but very small photocurrent. It was judged from the measurement of the Seebeck coefficient that the hopping mechanism is dominant for the conduction of the oxides containing Na. The hopping level is presumed to bring about the ohmic contact and the very small photocurrent because of the small band bending. The CaFe/sub 2/O/sub 4//Na,Mg electrode, where one side of the surfaces was doped with Na and Mg and the interface of CaFe/sub 2/O/sub 4//Na,Mg/Pt-Pd was ohmic contact, gave a large photocurrent. Photoelectrochemical dissolution was observed for the CaFe/sub 2/O/sub 4//Na,Mg electrode in acidic solution but not in neutral solution. The mechanism of the dissolution is also discussed.

  14. Contribution of reverse Na+-Ca2+ exchange to spontaneous activity in interstitial cells of Cajal in the rabbit urethra.

    PubMed

    Bradley, E; Hollywood, M A; Johnston, L; Large, R J; Matsuda, T; Baba, A; McHale, N G; Thornbury, K D; Sergeant, Gerard P

    2006-08-01

    Interstitial cells of Cajal (ICC) isolated from the rabbit urethra exhibit regular Ca2+ oscillations that are associated with spontaneous transient inward currents (STICs) recorded under voltage clamp. Their frequency is known to be very sensitive to external Ca2+ concentration but the mechanism of this has yet to be elucidated. In the present study experiments were performed to assess the role of Na+-Ca2+ exchange (NCX) in this process. Membrane currents were recorded using the patch clamp technique and measurements of intracellular Ca2+ were made using fast confocal microscopy. When reverse mode NCX was enhanced by decreasing the external Na+ concentration [Na+]o from 130 to 13 mM, the frequency of global Ca2+ oscillations and STICs increased. Conversely, inhibition of reverse mode NCX by KB-R7943 and SEA0400 decreased the frequency of Ca2+ oscillations and STICs. Application of caffeine (10 mM) and noradrenaline (10 microM) induced transient Ca2+-activated chloride currents (I(ClCa)) at -60 mV due to release of Ca2+ from ryanodine- and inositol trisphosphate (IP3)-sensitive Ca2+ stores, respectively, but these responses were not blocked by KB-R7943 or SEA0400 suggesting that neither drug blocked Ca2+-activated chloride channels or Ca2+ release from stores. Intact strips of rabbit urethra smooth muscle develop spontaneous myogenic tone. This tone was relaxed by application of SEA0400 in a concentration-dependent fashion. Finally, single cell RT-PCR experiments revealed that isolated ICC from the rabbit urethra only express the type 3 isoform of the Na+-Ca2+ exchanger (NCX3). These results suggest that frequency of spontaneous activity in urethral ICC can be modulated by Ca2+ entry via reverse NCX.

  15. Function and regulation of the Na+-Ca2+ exchanger NCX3 splice variants in brain and skeletal muscle.

    PubMed

    Michel, Lauriane Y M; Verkaart, Sjoerd; Koopman, Werner J H; Willems, Peter H G M; Hoenderop, Joost G J; Bindels, René J M

    2014-04-18

    Isoform 3 of the Na(+)-Ca(2+) exchanger (NCX3) is crucial for maintaining intracellular calcium ([Ca(2+)]i) homeostasis in excitable tissues. In this sense NCX3 plays a key role in neuronal excitotoxicity and Ca(2+) extrusion during skeletal muscle relaxation. Alternative splicing generates two variants (NCX3-AC and NCX3-B). Here, we demonstrated that NCX3 variants display a tissue-specific distribution in mice, with NCX3-B as mostly expressed in brain and NCX-AC as predominant in skeletal muscle. Using Fura-2-based Ca(2+) imaging, we measured the capacity and regulation of the two variants during Ca(2+) extrusion and uptake in different conditions. Functional studies revealed that, although both variants are activated by intracellular sodium ([Na(+)]i), NCX3-AC has a higher [Na(+)]i sensitivity, as Ca(2+) influx is observed in the presence of extracellular Na(+). This effect could be partially mimicked for NCX3-B by mutating several glutamate residues in its cytoplasmic loop. In addition, NCX3-AC displayed a higher capacity of both Ca(2+) extrusion and uptake compared with NCX3-B, together with an increased sensitivity to intracellular Ca(2+). Strikingly, substitution of Glu(580) in NCX3-B with its NCX3-AC equivalent Lys(580) recapitulated the functional properties of NCX3-AC regarding Ca(2+) sensitivity, Lys(580) presumably acting through a structure stabilization of the Ca(2+) binding site. The higher Ca(2+) uptake capacity of NCX3-AC compared with NCX3-B is in line with the necessity to restore Ca(2+) levels in the sarcoplasmic reticulum during prolonged exercise. The latter result, consistent with the high expression in the slow-twitch muscle, suggests that this variant may contribute to the Ca(2+) handling beyond that of extruding Ca(2+).

  16. Magnetic and microstructural properties of Al substituted M-type Ca-Sr hexaferrites

    NASA Astrophysics Data System (ADS)

    Yang, Yujie; Wang, Fanhou; Liu, Xiansong; Shao, Juxiang; Huang, Duohui

    2017-01-01

    In the current study, Al substituted M-type Ca-Sr hexaferrites, with composition Ca0.6Sr0.1La0.3Fe12-xAlxO19 (0≤x≤1.4), have been prepared using the conventional ceramic techniques. The phase composition of the magnetic powders was characterized by X-ray diffraction (XRD). The XRD data show that the magnetic powders with Al content (x) from 0 to 0.8 show α-Fe2O3 as a second phase, while the magnetic powders with x from 1.0 to 1.4 consist of pure magnetoplumbite without any other impurity phases. A field emission scanning electron microscopy (FE-SEM) was used to observe the morphologies of the magnetic powders. FE-SEM images of the magnetic powders show the hexagonal platelet-like shape. The magnetic properties of the magnetic powders were measured by a physical property measurement system-vibrating sample magnetometer (PPMS-VSM). The saturation magnetization (Ms) linearly decreases with Al content (x) from 0 to 1.4. While the remanent magnetization (Mr) first increases with Al content (x) from 0 to 0.2 and then decreases when Al content (x)≥0.2. However, the coercivity (Hc) increases with Al content (x) from 0 to 1.4.

  17. Thermoelectric properties of the Ca(5)Al(2-x)In(x)Sb(6) solid solution.

    PubMed

    Zevalkink, Alex; Swallow, Jessica; Ohno, Saneyuki; Aydemir, Umut; Bux, Sabah; Snyder, G Jeffrey

    2014-11-14

    Zintl phases are attractive for thermoelectric applications due to their complex structures and bonding environments. The Zintl compounds Ca(5)Al(2)In(x)Sb(6)and Ca(5)Al(2)In(x)Sb(6) have both been shown to have promising thermoelectric properties, with zT values of 0.6 and 0.7, respectively, when doped to control the carrier concentration. Alloying can often be used to further improve thermoelectric materials in cases when the decrease in lattice thermal conductivity outweighs reductions to the electronic mobility. Here we present the high temperature thermoelectric properties of the Ca(5)Al(2-x)In(x)Sb(6)solid solution. Undoped and optimally Zn-doped samples were investigated. X-ray diffraction confirms that a full solid solution exists between the Al and In end-members. We find that the Al : In ratio does not greatly influence the carrier concentration or Seebeck effect. The primary effect of alloying is thus increased scattering of both charge carriers and phonons, leading to significantly reduced electronic mobility and lattice thermal conductivity at room temperature. Ultimately, the figure of merit is unaffected by alloying in this system, due to the competing effects of reduced mobility and lattice thermal conductivity.

  18. Changes in /sup 22/Na influx and outflux in Daphnia magna (Straus) as a function of elevated Al concentrations in soft water at low pH

    SciTech Connect

    Havas, M.; Likens, G.E.

    1985-11-01

    The effects of aluminum on sodium regulation by the freshwater crustacean Daphnia magna were determined. /sup 22/Na influx and outflux experiments were conducted in soft water adjusted to pH 4.5, 5.0, and 6.5 (reference pH) with either ambient (0.02 mg/liter) or high (1.02 mg/liter) concentrations of total Al. The results indicate that Al toxicity was pH dependent. Aluminum increased the rate of morbidity of D. magna at pH 6.5, had no additional effect to those of hydrogen ions (H/sup +/) at pH 5.0, and reduced the rate of morbidity at pH 4.5. Both H/sup +/ and total Al concentrations interfered with Na regulation, although it was possible to distinguish between their respective effects by using /sup 22/Na. At pH 6.5, Al decreased /sup 22/Na influx (by 46%) and increased /sup 22/Na outflux (by 25%), which led to a net loss of Na. At pH 5.0, Al reduced /sup 22/Na influx (by 58%) but had not additional effect to that of H/sup +/ on /sup 22/Na outflux. At pH 4.5, /sup 22/Na influx was significantly inhibited (by 73%) compared with the reference pH 6.5 treatment even in the absence of Al. Aluminum decreased /sup 22/Na outflux (by 31%) at pH 4.5, which reduced the net loss of Na and temporarily prolonged survival of the daphnids. These results indicate that Al affects both /sup 22/Na influx and outflux in D. magna. The lower rate of Na uptake may involve a denaturation of the enzyme responsible for the active uptake of Na. At pH 6.5, the increased outflux of /sup 22/Na may be due to either increased membrane permeability or increased renal losses (or both). At pH 4.5, the reduced outflux of /sup 22/Na resembles the amelioration that occurs in the presence of elevated Ca concentrations.

  19. Neuronal Na+ Channels Are Integral Components of Pro-arrhythmic Na+/Ca2+ Signaling Nanodomain That Promotes Cardiac Arrhythmias During β-adrenergic Stimulation

    PubMed Central

    Radwański, Przemysław B.; Ho, Hsiang-Ting; Veeraraghavan, Rengasayee; Brunello, Lucia; Liu, Bin; Belevych, Andriy E.; Unudurthi, Sathya D.; Makara, Michael A.; Priori, Silvia G.; Volpe, Pompeo; Armoundas, Antonis A.; Dillmann, Wolfgang H.; Knollmann, Bjorn C.; Mohler, Peter J.; Hund, Thomas J.; Györke, Sándor

    2016-01-01

    Background Cardiac arrhythmias are a leading cause of death in the US. Vast majority of these arrhythmias including catecholaminergic polymorphic ventricular tachycardia (CPVT) are associated with increased levels of circulating catecholamines and involve abnormal impulse formation secondary to aberrant Ca2+ and Na+ handling. However, the mechanistic link between β-AR stimulation and the subcellular/molecular arrhythmogenic trigger(s) remains elusive. Methods and Results We performed functional and structural studies to assess Ca2+ and Na+ signaling in ventricular myocyte as well as surface electrocardiograms in mouse models of cardiac calsequestrin (CASQ2)-associated CPVT. We demonstrate that a subpopulation of Na+ channels (neuronal Na+ channels; nNav) that colocalize with RyR2 and Na+/Ca2+ exchanger (NCX) are a part of the β-AR-mediated arrhythmogenic process. Specifically, augmented Na+ entry via nNav in the settings of genetic defects within the RyR2 complex and enhanced sarcoplasmic reticulum (SR) Ca2+-ATPase (SERCA)-mediated SR Ca2+ refill is both an essential and a necessary factor for the arrhythmogenesis. Furthermore, we show that augmentation of Na+ entry involves β-AR-mediated activation of CAMKII subsequently leading to nNav augmentation. Importantly, selective pharmacological inhibition as well as silencing of Nav1.6 inhibit myocyte arrhythmic potential and prevent arrhythmias in vivo. Conclusion These data suggest that the arrhythmogenic alteration in Na+/Ca2+ handling evidenced ruing β-AR stimulation results, at least in part, from enhanced Na+ influx through nNav. Therefore, selective inhibition of these channels and Nav1.6 in particular can serve as a potential antiarrhythmic therapy. PMID:27747307

  20. Emission red shift and unusual band narrowing of Mn2+ in NaCaPO4 phosphor.

    PubMed

    Shi, Liang; Huang, Yanlin; Seo, Hyo Jin

    2010-07-08

    Concentration dependence of Mn(2+) luminescence in NaCaPO(4)/Mn(2+) is investigated by structural analyses and optical and laser excitation spectroscopies in the temperature range 19-300 K. NaCaPO(4)/Mn(2+) forms solid solution over the Mn(2+) concentration range 1.0-22 mol %. We observe the red shift and unusual band narrowing of Mn(2+) emission by increasing Mn(2+) concentration in NaCaPO(4). The lifetime of Mn(2+) emission lengthens unexpectedly for higher Mn(2+) concentration. The results are discussed in relation with crystal structure, photon reabsorption, exchange interaction, and energy transfer and energy migration in NaCaPO(4)/Mn(2+).

  1. A rietveld refinement of NaCl-type Ca 5Y 4S 11

    NASA Astrophysics Data System (ADS)

    Thompson, John G.; Withers, Ray L.; Otero-Diaz, L. Carlos

    1995-10-01

    The crystal structure of Ca 5Y 4S 11 [a = 6.942(1) Å, α = 33.380(5)°, space group R3 m, No. 166, Z = {2}/{11}, Dx = 3.042 g cm -3] was determined using Rietveld refinement of X-ray powder diffraction data collected with Cu Kα 1 radiation using a Guiner-Hägg camera. Ca 5Y 4S 11 is one end-member composition ( x = {2}/{7}) of the solid-solution (1- x)CaS. xY 2S 3, which can be considered as a modulated NaCl-type structure with modulation wave-vector q = {1}/{2}(111)∗. The sulfur sublattice is fully occupied but the metal sublattice contains {2}/{11} vacancies on average. The refinement showed that the additional observed satellite reflections were almost entirely due to metal atom/vacancy ordering rather than sulfur atom displacement. Large anisotropic thermal parameters on both the sulfur and metal atoms were consistent with disordered displacement of these atoms by 0.2-0.4 Å normal to [111]. The chemical plausibility of the refined structure and the implication of this result for other substoichiometric NaCl-type solid solutions are discussed.

  2. Origin of Ca-Al-rich inclusions. II - Sputtering and collisions in the three-ph8se interstellar medium

    NASA Technical Reports Server (NTRS)

    Clayton, D. D.

    1981-01-01

    The theory put forward by Clayton (1977) for the formation of the Ca-Al-rich inclusions within C3 meteorites is extended to an evolutionary history in a three-phase interstellar medium. Widespread supersonic turbulence in the hot interstellar medium is maintained by supernova shock waves, giving rise to heavy sputtering of the refractory dust. Subsequent reaccumulation with varying dust/gas ratios or varying particle sizes produces isotopically fractionated Ca-Al-rich accumulates. It is thought that the Ca-Al-rich inclusions themselves are formed by the following sequence in the solar system: (1) cold accumulation of larger-than-average Ca-Al-rich particles containing supernova condensate cores into macroscopic (approximately 1 cm) Ca-Al-rich agglomerates, probably by sedimentation; and (2) fusion of the supernova condensates into macroscopic minerals by exothermic chemical reactions that begin when the accumulate has been warmed, thereby releasing energy from the unequilibrated forms accumulated from the interstellar medium.

  3. Results from Boiling Temperature Measurements for Saturated Solutions in the Systems NaCl + Ca(NO3)2 + H2O, NaNO3 + KNO3 + H2O, and NaCl + KNO3 + H2O, and Dry Out Temperatures for NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O

    SciTech Connect

    Rard, J A

    2005-11-29

    Boiling temperature measurements have been made for saturated ternary solutions of NaCl + KNO{sub 3} + H{sub 2}O and NaNO{sub 3} + KNO{sub 3} + H{sub 2}O at three selected salt ratios and for NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O over the full composition range. The maximum boiling temperature found for the NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O system is 164.7 {+-} 0.6 C, and the composition is estimated to occur at x(Ca(NO{sub 3}){sub 2}) {approx} 0.25. Experiments were also performed for the five component NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O mixtures with the molar ratio of NaCl:NaNO{sub 3}:KNO{sub 3} held essentially constant at 1:0.9780:1.1468 as the solute mole fraction of Ca(NO{sub 3}){sub 2}, x(Ca(NO{sub 3}){sub 2}), was varied between 0 and 0.25. The NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O system forms low melting mixtures and thus boiling temperatures for saturated were not determined. Instead, the temperatures corresponding to the cessation of boiling (i.e., dry out temperatures) of these liquid mixtures were determined. These dry out temperatures range from {approx} 300 C when x(Ca(NO{sub 3}){sub 2}) = 0 to {ge} 400 C when x(Ca(NO{sub 3}){sub 2}) = 0.20 and 0.25. The investigated mixture compositions correspond to some of the major mineral assemblages that are predicted to control the deliquescence relative humidity of salts formed by leaching dust samples from the proposed nuclear repository at Yucca Mountain, Nevada.

  4. Influence of (calcium-)uranyl-carbonate complexation on U(VI) sorption on Ca- and Na-bentonites.

    PubMed

    Meleshyn, A; Azeroual, M; Reeck, T; Houben, G; Riebe, B; Bunnenberg, C

    2009-07-01

    The influence of uranyl-carbonate and calcium-uranyl-carbonate complexations on the kinetics of U(VI) (approximately 3.4 x 10(-3) mol L(-1)) sorption from NaNO3 and Ca(NO3)2 solutions on Na- and Ca-bentonites at circumneutral ambient conditions was investigated. Complexation of U(VI) in Ca2UO2(CO3)3(aq) aqueous species, dominating the U(VI) speciation in Ca(NO3)2 solution, reduces its adsorption on bentonite by a factor of 2-3 in comparison with that in (UO2)2CO3(OH)3- species, dominating in NaNO3 solution, within the studied period of time (21 days). As a result of the dissolution of accessory calcite, Ca2UO2(CO3)3(aq) can be formed in the initially Ca-free solution in contact with either Na- or Ca-bentonite. U(VI) adsorption on Na-bentonite is a factor of approximately 2 higher than that on Ca-bentonite for solutions with the Ca2UO2(CO3)3(aq) complex dominating aqueous U(VI) speciation. This favors use of Na-bentonite over that of Ca-bentonite in final disposal of radioactive waste. Furthermore, the observed strong correlation between U(VI) adsorption and Mg release as a result of montmorillonite dissolution indicates in agreement with previous findings that under the applied conditions U(VI) is adsorbed on the edge surface of montmorillonite, which is a major mineral phase of the studied clays.

  5. Temperature-dependent polarized far-infrared optical properties of CaNdAlO 4 single crystal

    NASA Astrophysics Data System (ADS)

    Ma, J. Y.; Bi, C. Z.; Fang, X.; Kamran, M.; Zhao, H. Y.; Zhao, B. R.; Qiu, X. G.

    2008-10-01

    Polarized near-normal incident infrared reflectivity spectra of (1 0 0) CaNdAlO 4 single crystal along the ab plane and c-axis have been measured under different temperatures in the frequency region between 100 and 6000 cm -1. All the spectra are fitted with the factorized form of the dielectric function. Assignment of different phonon modes has been done in both crystalline directions. The dielectric property and optical conductivity of the CaNdAlO 4 crystal are analyzed. The differences between CaNbAlO 4 and SrLaAlO 4 are discussed with respect to vibration frequency and static optical permittivities.

  6. Dissolution of Al2TiO5 inclusions in CaO-SiO2-Al2O3 slags at 1823 K

    NASA Astrophysics Data System (ADS)

    Wang, De-Yong; Liu, Jun; Jiang, Mao-Fa; Tsukihashi, Fumitaka; Matsuura, Hiroyuki

    2011-12-01

    Al-Ti-O inclusions always clog submerged nozzles in Ti-bearing Al-killed steel. A typical synthesized Al2TiO5 inclusion was immersed in a CaO-SiO2-Al2O3 molten slag for different durations at 1823 K. The Al2TiO5 dissolution paths and mechanism were revealed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Decreased amounts of Ti and Al and increased amounts of Si and Ca at the dissolution boundary prove that inclusion dissolution and slag penetration simultaneously occur. SiO2 diffuses or penetrates the inclusion more quickly than CaO, as indicated by the w(CaO)/ w(SiO2) value in the reaction region. A liquid product (containing 0.7-1.2 w(CaO)/ w(SiO2), 15wt%-20wt% Al2O3, and 5wt%-15wt% TiO2) forms on the inclusion surface when Al2TiO5 is dissolved in the slag. Al2TiO5 initially dissolves faster than the diffusion rate of the liquid product toward the bulk slag. With increasing reaction time, the boundary reaches its largest distance, the Al2TiO5 dissolution rate equals the liquid product diffusion rate, and the dissolution process remains stable until the inclusion is completely dissolved.

  7. Preparation and properties of Eu doped CaAlSiN3 red phosphor

    NASA Astrophysics Data System (ADS)

    He, Pan; Zhang, Ning; Man, Shiqing

    2017-03-01

    The Eu2+ activated CaAlSiN3 phosphor was synthesized by solid-state reaction method under a nitrogen atmosphere at 1550°C for 6h. The phosphors structure was measured by X-ray diffraction (XRD); excitation spectra, emission spectra and decay lifetime were obtained by fluorescence spectrophotometer equipped. It showed a broad excitation band originating from the 4f7-4f65d transition of Eu2+ ion extending to 650nm and the peaking at 467nm; a strong emission band centering at 668nm, and the lifetime of Eu2+ in the CaAlSiN3 host is 1.4227 µs.

  8. Influence of Na(+) and Ca(2+) on flame retardancy, thermal degradation, and pyrolysis behavior of cellulose fibers.

    PubMed

    Shi, Ran; Tan, Liwen; Zong, Lu; Ji, Quan; Li, Ximei; Zhang, Keke; Cheng, Lingling; Xia, Yanzhi

    2017-02-10

    Flame-retardant cellulose-Na and cellulose-Ca fibers were successfully synthesized by grafting Na(+) and Ca(2+) onto cellulose fibers, and confirmed by FTIR. The combustion behavior of the fibers was assessed by the limiting oxygen index (LOI) and cone calorimeter (CONE). The maximum LOI values of cellulose-Na and cellulose-Ca fibers were 31 and 30, which are higher than that (19) of cellulose fibers. The CONE results showed that the values of heat-release rate and total heat release for cellulose-Na and cellulose-Ca fibers were significantly lower than those for cellulose fibers. The thermogravimetric analysis (TG) and differential thermogravimetric analysis (DTG) curves in the continuous and trigger modes showed that the cellulose-Na and cellulose-Ca fibers generated more residues than cellulose fibers. Thermogravimetric analysis-gas chromatography-mass spectrometry was used to detect the characteristic gases produced in the pyrolysis of cellulose-Na and cellulose-Ca fibers.

  9. Observations of the Minor Species Al, Fe and Ca(+) in Mercury's Exosphere

    NASA Technical Reports Server (NTRS)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

    We report the first detections of Al and Fe, and strict upper limits for Ca(+) in the exosphere of Mercury, using the HIRES spectrometer at the Keck I telescope. We report observed 4-sigma tangent columns of 1.5x10(exp 7) Al atoms per square centimeter at an altitude of 1220 km (1.5 Mercury radii (R(sub M)) from planet center), and that for Fe of 1.6 x 10 per square centimeter at an altitude of 950 km (1.4 R(sub M)). The observed 3-sigma Ca(+) column was 3.9x10(exp 6) ions per square centimeter at an altitude of 1630 km (1.67 R(sub M). A simple model for zenith column abundances of the neutral species were 9.5 x 10(exp 7) Al per square centimeter, and 3.0 x 10(exp 8) Fe per square centimeter. The observations appear to be consistent with production of these species by impact vaporization with a large fraction of the ejecta in molecular form. The scale height of the Al gas is consistent with a kinetic temperature of 3000 - 9000 K while that of Fe is 10500 K. The apparent high temperature of the Fe gas would suggest that it may be produced by dissociation of molecules. A large traction of both Al and Fe appear to condense in a vapor cloud at low altitudes.

  10. EXAFS Study of Refractory Cement Phases: CaAl2O{14}H{20}, Ca2Al2O{13}H{16}, and Ca3Al2O{12}H{12}

    NASA Astrophysics Data System (ADS)

    Richard, N.; Lequeux, N.; Boch, P.

    1995-11-01

    X-ray absorption spectroscopy (EXAFS and XANES) is used for the first time to characterize the local environment of aluminium and calcium in phases formed by hydration of high-alumina cements. Ca K-edge EXAFS spectrum confirms that C2AH8 is an AFm phase. A location is given for the interlayer aluminium cations, which are in a tetrahedrally coordinated hydrated site. Absorption measurements at the AI K-edge show a structural analogy between CAH{10} and gibbsite AH3. The structural model proposed for CAH{10} is based on two rings of six edge-sharing [ Al(OH)6] ^{3-} octahedra, with Ca^{2+} cations linking them together. High-alumina cements are commonly used for refractory applications. Changes in aluminium and calcium environments during CAH{10} dehydration is therefore investigated by X-ray absorption spectroscopy. Dehydration leads to a decrease in the Ca-O distance and reduces the number of oxygen neighbours in the first coordination shell around calcium. La spectroscopie d'absorption des rayons X est utilisée pour la première fois pour caractériser l'environnement local autour de l'aluminium et du calcium dans des phases formées par hydratation de ciments alumineux. Le spectre EXAFS au seuil K du calcium confirme que C2AH8 est une phase AFm. De plus, on indique une position pour les cations aluminium de l'intercouche, qui sont dans un site tétraédrique hydraté. Les expériences d'absorption au seuil K de l'aluminium révèlent une analogie entre la structure de CAH{10} et celle de la gibbsite AH3. Le modèle structural proposé pour CAH{10} est basé sur l'existence de deux anneaux formés chacun de six octaèdres [ Al(OH)6] ^{3-} liés par arêtes, les atomes de calcium assurant un lien entre ces anneaux. Les ciments alumineux sont couramment utilisés pour des applications réfractaires ; c'est pourquoi cette étude suit l'évolution de l'environnement autour du calcium et de l'aluminium au cours de la déshydratation de CAH{10}. Une diminution

  11. Phonons in the ordered c(2 × 2) phases of Na and Li on Al(001).

    PubMed

    Rusina, G G; Eremeev, S V; Borisova, S D; Sklyadneva, I Yu; Echenique, P M; Chulkov, E V

    2007-07-04

    The vibrational properties of the Al(001)-c(2 × 2)-Na (Li) ordered phases formed by alkali atoms (Na and Li) on the Al(001) surface at low and room temperatures are presented. The equilibrium structural characteristics, phonon dispersions and polarization of vibrational modes as well as the local density of phonon states are calculated using the embedded-atom method. The obtained structural parameters are in close agreement with experimental data.

  12. Phonons in the ordered c(2 × 2) phases of Na and Li on Al(001)

    NASA Astrophysics Data System (ADS)

    Rusina, G. G.; Eremeev, S. V.; Borisova, S. D.; Sklyadneva, I. Yu; Echenique, P. M.; Chulkov, E. V.

    2007-07-01

    The vibrational properties of the Al(001)-c(2 × 2)-Na (Li) ordered phases formed by alkali atoms (Na and Li) on the Al(001) surface at low and room temperatures are presented. The equilibrium structural characteristics, phonon dispersions and polarization of vibrational modes as well as the local density of phonon states are calculated using the embedded-atom method. The obtained structural parameters are in close agreement with experimental data.

  13. Effect of CaF2 on Interfacial Phenomena of High Alumina Refractories with Al Alloy

    NASA Astrophysics Data System (ADS)

    Koshy, Pramod; Gupta, Sushil; Sahajwalla, Veena; Edwards, Phil

    2008-08-01

    An experimental study was conducted to investigate the interfacial phenomena between Al-alloy and industrial grade high alumina refractories containing varying contents of CaF2 at 1250 °C. Interfacial reaction products and phases formed in the heat-treated refractory samples were characterized using electron probe microanalysis (EPMA) and X-ray diffraction (XRD), respectively, while interfacial phenomena including dynamic wetting behavior were analyzed using the sessile drop technique. Refractories containing less than 5 wt pct CaF2 showed good resistance to reactions with the molten alloy, due to the dominance of corundum, and the presence of anorthite at the interface. However, with a further increase in the additive content, a glassy matrix of anorthite with CaF2 was formed. Formation of this phase significantly increased the intensity of reactions resulting in the buildup of an interfacial layer. The study thus revealed the strong catalytic effect of CaF2 on reactions of high alumina refractories with Al-alloy.

  14. Sr isotopic fractionation in Ca-Al inclusions from the Allende meteorite

    USGS Publications Warehouse

    Patchett, P.J.

    1980-01-01

    True relative Sr isotopic compositions, determined by double spiking on Ca-Al inclusions from the Allende meteorite show up to 1.5??? per mass unit mass fractionation relative to the Earth and bulk chondrites. All abnormal inclusions are light-isotope enriched. A lack of isotopically heavy Sr in inclusions would place constraints on the time, place and mechanism of origin of these objects. ?? 1980 Nature Publishing Group.

  15. Angiotensin II-stimulated Ca2+ entry mechanisms in afferent arterioles: role of transient receptor potential canonical channels and reverse Na+/Ca2+ exchange.

    PubMed

    Fellner, Susan K; Arendshorst, William J

    2008-01-01

    In afferent arterioles, the signaling events that lead to an increase in cytosolic Ca(2+) concentration ([Ca(2+)](i)) and initiation of vascular contraction are increasingly being delineated. We have recently studied angiotensin II (ANG II)-mediated effects on sarcoplasmic reticulum (SR) mobilization of Ca(2+) and the role of superoxide and cyclic adenosine diphosphoribose in these processes. In the current study we investigated the participation of transient receptor potential canonical channels (TRPC) and a Na(+)/Ca(2+) exchanger (NCX) in Ca(2+) entry mechanisms. Afferent arterioles, isolated with the magnetized polystyrene bead method, were loaded with fura-2 to measure [Ca(2+)](i) ratiometrically. We observed that the Ca(2+)-dependent chloride channel blocker niflumic acid (10 and 50 microM) affects neither the peak nor plateau [Ca(2+)](i) response to ANG II. Arterioles were pretreated with ryanodine (100 microM) and TMB-8 to block SR mobilization via the ryanodine receptor and inositol trisphosphate receptor, respectively. The peak [Ca(2+)](i) response to ANG II was reduced by 40%. Addition of 2-aminoethoxydiphenyl borane to block TRPC-mediated Ca(2+) entry inhibited the peak [Ca(2+)](i) ANG II response by 80% and the plateau by 74%. Flufenamic acid (FFA; 50 microM), which stimulates TRPC6, caused a sustained increase of [Ca(2+)](i) of 146 nM. This response was unaffected by diltiazem or nifedipine. KB-R7943 (at the low concentration of 10 microM) inhibits reverse (but not forward) mode NCX. KB-R7943 decreased the peak [Ca(2+)](i) response to ANG II by 48% and to FFA by 38%. We conclude that TRPC6 and reverse-mode NCX may be important Ca(2+) entry pathways in afferent arterioles.

  16. Ultrafiltration behavior of major ions (Na, Ca, Mg, F, Cl, and SO4) in natural waters.

    PubMed

    Guo, L; Hunt, B J; Santschi, P H

    2001-04-01

    Aquatic colloids, including macromolecules and microparticles, with sizes ranging between 1 nm to 1 micron, play important roles in the mobility and bioavailability of heavy metals and other contaminants in natural waters. Cross-flow ultrafiltration has become one of the most commonly used techniques for isolating aquatic colloids. However, the ultrafiltration behavior of chemical species remains poorly understood. We report here the permeation behavior of major ions (Na, Ca, Mg, F, Cl, and SO4) in natural waters during ultrafiltration using an Amicon 1 kDa ultrafiltration membrane (S10N1). Water samples across a salinity gradient of 0-20@1000 were collected from the Trinity River and Galveston Bay. The permeation behavior of major ions was well predicted by a permeation model, resulting in a constant permeation coefficient for each ion. The value of the model-derived permeation coefficient (Pc) was 0.99 for Na, 0.97 for Cl, and 0.95 for F, respectively, in Trinity River waters. Values of Pc close to 1 indicate that retention of Na, Cl, and F by the 1 kDa membrane during ultrafiltration was indeed minimal (< 1-5%). In contrast, significant (14-36%) retention was observed for SO4, Ca, and Mg in Trinity River waters, with a Pc value of 0.64, 0.82, and 0.86 for SO4, Ca and Mg, respectively. However, these retained major ions can further permeate through the 1 kDa membrane during diafiltration with ultrapure water. The selective retention of major ions during ultrafiltration may have important implications for the measurement of chemical and physical speciation of trace elements when using cross-flow ultrafiltration membranes to separate colloidal species from natural waters. Our results also demonstrate that the percent retention of major ions during ultrafiltration decreases with increasing salinity or ionic strength. This retention is largely attributed to electrostatic repulsion by the negatively charged cartridge membrane.

  17. The plasma membrane Na+/Ca2+ exchange inhibitor KB-R7943 is also a potent inhibitor of the mitochondrial Ca2+ uniporter

    PubMed Central

    Santo-Domingo, J; Vay, L; Hernández-SanMiguel, E; Lobatón, C D; Moreno, A; Montero, M; Alvarez, J

    2007-01-01

    Background and purpose: The thiourea derivative KB-R7943, originally developed as inhibitor of the plasma membrane Na+/Ca2+ exchanger, has been shown to protect against myocardial ischemia-reperfusion injury. We have studied here its effects on mitochondrial Ca2+ fluxes. Experimental approach. [Ca2+] in cytosol, mitochondria and endoplasmic reticulum (ER), and mitochondrial membrane potential were monitored using both luminescent (targeted aequorins) and fluorescent (fura-2, tetramethylrhodamine ethyl ester) probes in HeLa cells. Key results: KB-R7943 was also a potent inhibitor of the mitochondrial Ca2+ uniporter (MCU). In permeabilized HeLa cells, KB-R7943 inhibited mitochondrial Ca2+ uptake with a Ki of 5.5±1.3 μM (mean±S.D.). In intact cells, 10μM KB-R7943 reduced by 80% the mitochondrial [Ca2+] peak induced by histamine. KB-R7943 did not modify the mitochondrial membrane potential and had no effect on the mitochondrial Na+/Ca2+ exchanger. KB-R7943 inhibited histamine-induced ER-Ca2+ release in intact cells, but not in cells loaded with a Ca2+-chelator to damp cytosolic [Ca2+] changes. Therefore, inhibition of ER-Ca2+-release by KB-R7943 was probably due to the increased feedback Ca2+-inhibition of inositol 1,4,5-trisphosphate receptors after MCU block. This mechanism also explains why KB-R7943 reversibly blocked histamine-induced cytosolic [Ca2+] oscillations in the same range of concentrations required to inhibit MCU. Conclusions and Implications: Inhibition of MCU by KB-R7943 may contribute to its cardioprotective activity by preventing mitochondrial Ca2+-overload during ischemia-reperfusion. In addition, the effects of KB-R7943 on Ca2+ homeostasis provide new evidence for the role of mitochondria modulating Ca2+-release and regenerative Ca2+-oscillations. Search for permeable and selective MCU inhibitors may yield useful pharmacological tools in the future. PMID:17471180

  18. Polymer Coated CaAl-Layered Double Hydroxide Nanomaterials for Potential Calcium Supplement

    PubMed Central

    Kim, Tae-Hyun; Lee, Jeong-A; Choi, Soo-Jin; Oh, Jae-Min

    2014-01-01

    We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 μg/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement. PMID:25490138

  19. Hibonite, Ca2/Al, Ti/24O38, from the Leoville and Allende chondritic meteorites.

    NASA Technical Reports Server (NTRS)

    Keil, K.; Fuchs, L. H.

    1971-01-01

    Hibonite was discovered in light-colored, Ca-Al-Ti-rich and Si-Fe-poor, achondritic inclusions of the Leoville and Allende HL-group chondrites. Two varieties of hibonite occur: one emits a bright red-orange luminescence under electron bombardment and has high amounts of Al2O3 (87.7; 87.9) and low amounts of MgO (0.65; 0.8) and TiO2 (0.68; 0.8). The other emits a bright blue luminescence and is low in Al2O3 (78.7; 79.2) and high in MgO (3.3; 3.7) and TiO2 (6.5; 7.9) (in wt. %). The oxide CaO is about the same in both varieties. It is suggested that the change in the color of the visible luminescence results from changes in composition. The origin of hibonite which occurs in complex mineral assemblages together with anorthite, gelhenite, wollastonite, aluminous diopside, andradite, Ca-pyroxene, perovskite, spinel, taenite, chromite, and pentlandite, and in close proximity to nodules containing calcite, whewellite, forsterite and many of the aforementioned phases, is discussed. The proposition that hibonite and associated phases originated by contact metamorphism and metasomatism of calcite-dolomite bearing assemblages cannot, at this time, be completely ruled out.

  20. Crystallization of Ca-Al-Rich Inclusions: Experimental Studies on the Effects of Repeated Heating Events

    NASA Technical Reports Server (NTRS)

    Paque, Julie M.; Lofgren, Gary E.; Le, Loan

    2000-01-01

    The observed textures and chemistry of Ca-Al-rich inclusions (CAIs) are presumed to be the culmination of a series of repeated heating and cooling events in the early history of the solar nebula. We have examined the effects of these heating/cooling cycles experimentally on a bulk composition representing an average Type B Ca-Al-rich inclusion composition. We have tested the effect of the nature of the starting material. Although the most recent and/or highest temperature event prior to incorporation into the parent body dominates the texture and chemistry of the CAI, prior events also affect the phase compositions and textures. We have determined that heating precursor grains to about 1275 C prior to the final melting event increases the likelihood of anorthite crystallization in subsequent higher temperature events and a prior high temperature even that produced dendritic melilite results in melilite that shows evidence of rapid crystallization in subsequent lower temperature events. Prior low temperature pre-crystallization events produce final ran products with pyroxene compositions similar to Type B Ca-Al-rich inclusions, and the glass (residual liquid) composition is more anorthitic than any other experiments to date. The addition of Pt powder to the starting material appears to enhance the ability of anorthite to nucleate from this composition.

  1. Polymer coated CaAl-layered double hydroxide nanomaterials for potential calcium supplement.

    PubMed

    Kim, Tae-Hyun; Lee, Jeong-A; Choi, Soo-Jin; Oh, Jae-Min

    2014-12-05

    We have successfully prepared layered double hydroxide (LDH) nanomaterials containing calcium and aluminum ions in the framework (CaAl-LDH). The surface of CaAl-LDH was coated with enteric polymer, Eudragit®L 100 in order to protect nanomaterials from fast dissolution under gastric condition of pH 1.2. The X-ray diffraction patterns, Fourier transform infrared spectroscopy, scanning electron and transmission electron microscopy revealed that the pristine LDH was well prepared having hydrocalumite structure, and that the polymer effectively coated the surface of LDH without disturbing structure. From thermal analysis, it was determined that only a small amount (less than 1%) of polymer was coated on the LDH surface. Metal dissolution from LDH nanomaterials was significantly reduced upon Eudragit®L 100 coating at pH 1.2, 6.8 and 7.4, which simulates gastric, enteric and plasma conditions, respectively, and the dissolution effect was the most suppressed at pH 1.2. The LDH nanomaterials did not exhibit any significant cytotoxicity up to 1000 μg/mL and intracellular calcium concentration significantly increased in LDH-treated human intestinal cells. Pharmacokinetic study demonstrated absorption efficiency of Eudragit®L 100 coated LDH following oral administration to rats. Moreover, the LDH nanomaterials did not cause acute toxic effect in vivo. All the results suggest the great potential of CaAl-LDH nanomaterials as a calcium supplement.

  2. Phase composition and elemental partitioning in glass-ceramics containing high-Na/Al high level waste

    NASA Astrophysics Data System (ADS)

    Stefanovsky, S. V.; Sorokaletova, A. N.; Nikonov, B. S.

    2012-05-01

    Mixtures of surrogates of high level waste with high sodium and aluminum contents and sodium-lithium borosilicate frit were melted in alumina crucibles in a resistive furnace followed by quenching of one portion of the melt and annealing of the residual material in a turned-off furnace. The annealed materials with waste loading of up to 45 wt.% contained minor spinel type phase and trace of nepheline (Na,K)AlSiO4. In the annealed materials contained waste oxides in amount of 50 wt.% and more nepheline and spinel were found to be major and minor phases, respectively. At high waste loadings two extra phases: Cs-aluminosilicate (CsAlSiO4) and mixed Na/Cs-aluminosilicate were found in amount of 3-5 vol.% each. The latter phase contains of up to ˜5.7 wt.% SO3 or 0.13 formula units S (Na0.75K0.05Cs0.29Ca0.02Sr0.02Al0.99Fe0.03Si0.76S0.13O4). Sulfur incorporation as S6+ or SO42- ions into crystal lattice may be facilitated in the presence of large-size Cs+ cations. Simplified suggested formula of this phase may be represented as Na0.8Cs0.3AlSi0.8S0.1O3.95. It was also synthesized by sintering of mixture of chemicals at 1300 °C and found to be instable at temperatures higher than 1300 °C.

  3. The effect of NaCl/g/ on the oxidation of NiAl

    NASA Technical Reports Server (NTRS)

    Smeggil, J. G.; Bornstein, N. S.

    1978-01-01

    NaCl is ingested into operating gas turbines. The effect of this salt on the high temperature surface stability properties of turbine hardware is not well understood. The involvement of gaseous NaCl in the high temperature oxidation of NiAl, a principal component in many high temperature environmental coatings, is herein examined. The results of this work indicate that gaseous NaCl present in an oxidizing atmosphere affects the formation of Al2O3 whiskers on a dense Al2O3 layer. Such whisker growth, attributed to vapor transport processes through an otherwise dense Al2O3 scale, increases the aluminum depletion of the NiAl substrate.

  4. Solid-State Reaction Between Fe-Al-Ca Alloy and Al2O3-CaO-FeO Oxide During Heat Treatment at 1473 K (1200 °C)

    NASA Astrophysics Data System (ADS)

    Liu, Chengsong; Yang, Shufeng; Li, Jingshe; Ni, Hongwei; Zhang, Xueliang

    2016-12-01

    The aim of this study was to control the physicochemical characteristics of inclusions in steel through appropriate heat treatment. Using a confocal scanning laser microscope (CSLM) and pipe furnace, the solid-state reactions between Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide during heat treatment at 1473 K (1200 °C) and the influence of these reactions on the compositions of and phases in the alloy and oxide were investigated by the diffusion couple method. Suitable pretreatment of the oxide using a CSLM and production of the diffusion couple of Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide gave good contact between the alloy and oxide. The diffusion couple was then sealed in a quartz tube with a piece of Ti foil to lower oxygen partial pressure and a block of Fe-Al-Ca alloy was introduced to conduct heat treatment experiments. Solid-state reactions between the alloy and oxide during heat treatment at 1473 K (1200 °C) were analyzed and discussed. A dynamic model to calculate the width of the particle precipitation zone based on the Wagner model of internal oxidation of metal was proposed. This model was helpful to understand the solid-state reaction mechanism between Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide.

  5. Solid-State Reaction Between Fe-Al-Ca Alloy and Al2O3-CaO-FeO Oxide During Heat Treatment at 1473 K (1200 °C)

    NASA Astrophysics Data System (ADS)

    Liu, Chengsong; Yang, Shufeng; Li, Jingshe; Ni, Hongwei; Zhang, Xueliang

    2017-04-01

    The aim of this study was to control the physicochemical characteristics of inclusions in steel through appropriate heat treatment. Using a confocal scanning laser microscope (CSLM) and pipe furnace, the solid-state reactions between Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide during heat treatment at 1473 K (1200 °C) and the influence of these reactions on the compositions of and phases in the alloy and oxide were investigated by the diffusion couple method. Suitable pretreatment of the oxide using a CSLM and production of the diffusion couple of Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide gave good contact between the alloy and oxide. The diffusion couple was then sealed in a quartz tube with a piece of Ti foil to lower oxygen partial pressure and a block of Fe-Al-Ca alloy was introduced to conduct heat treatment experiments. Solid-state reactions between the alloy and oxide during heat treatment at 1473 K (1200 °C) were analyzed and discussed. A dynamic model to calculate the width of the particle precipitation zone based on the Wagner model of internal oxidation of metal was proposed. This model was helpful to understand the solid-state reaction mechanism between Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide.

  6. Analysis of cardiac mitochondrial Na+–Ca2+ exchanger kinetics with a biophysical model of mitochondrial Ca2+ handing suggests a 3: 1 stoichiometry

    PubMed Central

    Dash, Ranjan K; Beard, Daniel A

    2008-01-01

    Calcium is a key ion and is known to mediate signalling pathways between cytosol and mitochondria and modulate mitochondrial energy metabolism. To gain a quantitative, biophysical understanding of mitochondrial Ca2+ regulation, we developed a thermodynamically balanced model of mitochondrial Ca2+ handling and bioenergetics by integrating kinetic models of mitochondrial Ca2+ uniporter (CU), Na+–Ca2+ exchanger (NCE), and Na+–H+ exchanger (NHE) into an existing computational model of mitochondrial oxidative phosphorylation. Kinetic flux expressions for the CU, NCE and NHE were developed and individually parameterized based on independent data sets on flux rates measured in purified mitochondria. While available data support a wide range of possible values for the overall activity of the CU in cardiac and liver mitochondria, even at the highest estimated values, the Ca2+ current through the CU does not have a significant effect on mitochondrial membrane potential. This integrated model was then used to analyse additional data on the dynamics and steady-states of mitochondrial Ca2+ governed by mitochondrial CU and NCE. Our analysis of the data on the time course of matrix free [Ca2+] in respiring mitochondria purified from rabbit heart with addition of different levels of Na+ to the external buffer medium (with the CU blocked) with two separate models – one with a 2: 1 stoichiometry and the other with a 3: 1 stoichiometry for the NCE – supports the hypothesis that the NCE is electrogenic with a stoichiometry of 3: 1. This hypothesis was further tested by simulating an additional independent data set on the steady-state variations of matrix free [Ca2+] with respect to the variations in external free [Ca2+] in purified respiring mitochondria from rat heart to show that only the 3: 1 stoichiometry model predictions are consistent with the data. Based on these analyses, it is concluded that the mitochondrial NCE is electrogenic with a stoichiometry of 3: 1. PMID

  7. Crystal structure of new synthetic Ca,Na carbonate-borate Ca{sub 2}Na(Na{sub x}Ca{sub 0.5-x})[B{sub 3}{sup t}B{sub 2}{sup {delta}}O{sub 8}(OH)(O{sub 1-x}OH{sub x})](CO{sub 3})

    SciTech Connect

    Yamnova, N. A. Borovikova, E. Yu.; Gurbanova, O. A.; Dimitrova, O. V.; Zubkova, N. V.

    2012-05-15

    New Ca,Na carbonate-borate Ca{sub 2}Na(Na{sub x}Ca{sub 0.5-x}) [B{sub 3}{sup t}B{sub 2}{sup {Delta}}O{sub 8}(OH)(O{sub 1-x}OH{sub x})](CO{sub 3}) crystals (x {approx} 0.4) have been synthesized by the hydrothermal method in the Ca(OH){sub 2}-H{sub 3}BO{sub 3}-Na{sub 2}CO{sub 3}-NaCl-system at t = 250 Degree-Sign C and P = 70-80 atm; the structure parameters are found to be a = 11.1848(3) Angstrom-Sign , b = 6.4727(2) Angstrom-Sign , c = 25.8181(7) Angstrom-Sign , {beta} = 96.364(3) Degree-Sign , V = 1857.60(9) Angstrom-Sign {sup 3}, sp. gr. C2/c, Z = 8, and {rho}{sub calcd} = 2.801 g/cm{sup 3} (Xcalibur S autodiffractometer (CCD), 2663 reflections with I > 2{sigma} (I), direct solution, refinement by the least-squares method in the anisotropic approximation of thermal atomic vibrations, hydrogen localization, R{sub 1} = 0.0387). The structure is based on boron-oxygen layers of pentaborate radicals 5(2{Delta} + 3T). Ca and Na polyhedra and CO{sub 3} triangles are located between the layers. A crystallochemical analysis of the new Ca,Na carbonate-borate has established its similarity to natural Na,Ca pentaborates (heidornite and tuzlaite) and synthetic Na,Ba-decaborate.

  8. Characterization of the Cation Binding Sites in the NCKX2 Na(+)/Ca(2+)-K(+) Exchanger.

    PubMed

    Zhekova, Hristina; Zhao, Chunfeng; Schnetkamp, Paul P M; Noskov, Sergei Yu

    2016-11-22

    NCKX1-5 are proteins involved in K(+)-dependent Na(+)/Ca(2+) exchange in various signal tissues. Here we present a homology model of NCKX2 based on the crystal structure of the NCX_Mj transporter found in Methanoccocus jannaschii. Molecular dynamics simulations were performed on the resultant wild-type NCKX2 model and two mutants (D548N and D575N) loaded with either four Na(+) ions or one Ca(2+) ion and one K(+) ion, in line with the experimentally observed transport stoichiometry. The selectivity of the active site in wild-type NCKX2 for Na(+), K(+), and Li(+) and the electrostatic interactions of the positive Na(+) ions in the negatively charged active site of wild-type NCKX2 and the two mutants were evaluated from free energy perturbation calculations. For validation of the homology model, our computational results were compared to available experimental data obtained from numerous prior functional studies. The NCKX2 homology model is in good agreement with the discussed experimental data and provides valuable insights into the structure of the active site, which is lined with acidic and polar residues. The binding of the potassium and calcium ions is accomplished via Asp 575 and 548, respectively. Mutation of these residues to Asn alters the functionality of NCKX2 because of the elimination of the favorable carboxylate-cation interactions. The knowledge obtained from the NCKX2 model can be transferred to other isoforms of the NCKX family: newly discovered pathological mutations in NCKX4 and NCKX5 affect residues that are involved in ion binding and/or transport according to our homology model.

  9. Neutron beam tests of CsI(Na) and CaF2(Eu) crystals for dark matter direct search

    NASA Astrophysics Data System (ADS)

    Guo, C.; Ma, X. H.; Wang, Z. M.; Bao, J.; Dai, C. J.; Guan, M. Y.; Liu, J. C.; Li, Z. H.; Ren, J.; Ruan, X. C.; Yang, C. G.; Yu, Z. Y.; Zhong, W. L.; Huerta, C.

    2016-05-01

    In recent decades, inorganic crystals have been widely used in dark matter direct search experiments. To contribute to the understanding of the capabilities of CsI(Na) and CaF2(Eu) crystals, a mono-energetic neutron beam is utilized to study the properties of nuclear recoils, which are expected to be similar to signals of dark matter direct detection. The quenching factor of nuclear recoils in CsI(Na) and CaF2Eu, as well as an improved discrimination factor between nuclear recoils and γ backgrounds in CsI(Na), are reported.

  10. Ca- and Sc-based ternary AlB2-like crystals: a first-principles study

    NASA Astrophysics Data System (ADS)

    Tsetseris, Leonidas

    2017-02-01

    The aluminum diboride (AlB2) crystal structure comprises intercalated metal atoms between honeycomb sheets. In addition to metal diborides, which represent the most common family of AlB2-like structures, many more materials are known to crystallize in this geometry. Here we use first-principles calculations to probe the structural and electronic properties of several such systems. Specifically, we investigate the stability of various polymorphs of CaAuAs, CaAuP, CaCuP, ScAuGe, ScAuSi, Ca2AgSi3 and Ca2AuGe3 and find lattice parameters in excellent agreement with available experimental data. The analysis of densities of states and band structure diagrams show that all materials are metallic. However, the details of band dispersion vary significantly, from typical metals such as CaAuP, to almost semi-metallic behaviour in CaCuP.

  11. The dynamics of mitochondrial Ca2+ fluxes.

    PubMed

    de la Fuente, Sergio; Montenegro, Pablo; Fonteriz, Rosalba I; Moreno, Alfredo; Lobatón, Carmen D; Montero, Mayte; Alvarez, Javier

    2010-10-01

    We have investigated the kinetics of mitochondrial Ca(2+) influx and efflux and their dependence on cytosolic [Ca(2+)] and [Na(+)] using low-Ca(2+)-affinity aequorin. The rate of Ca(2+) release from mitochondria increased linearly with mitochondrial [Ca(2+)] ([Ca(2+)](M)). Na(+)-dependent Ca(2+) release was predominant al low [Ca(2+)](M) but saturated at [Ca(2+)](M) around 400muM, while Na(+)-independent Ca(2+) release was very slow at [Ca(2+)](M) below 200muM, and then increased at higher [Ca(2+)](M), perhaps through the opening of a new pathway. Half-maximal activation of Na(+)-dependent Ca(2+) release occurred at 5-10mM [Na(+)], within the physiological range of cytosolic [Na(+)]. Ca(2+) entry rates were comparable in size to Ca(2+) exit rates at cytosolic [Ca(2+)] ([Ca(2+)](c)) below 7muM, but the rate of uptake was dramatically accelerated at higher [Ca(2+)](c). As a consequence, the presence of [Na(+)] considerably reduced the rate of [Ca(2+)](M) increase at [Ca(2+)](c) below 7muM, but its effect was hardly appreciable at 10muM [Ca(2+)](c). Exit rates were more dependent on the temperature than uptake rates, thus making the [Ca(2+)](M) transients to be much more prolonged at lower temperature. Our kinetic data suggest that mitochondria have little high affinity Ca(2+) buffering, and comparison of our results with data on total mitochondrial Ca(2+) fluxes indicate that the mitochondrial Ca(2+) bound/Ca(2+) free ratio is around 10- to 100-fold for most of the observed [Ca(2+)](M) range and suggest that massive phosphate precipitation can only occur when [Ca(2+)](M) reaches the millimolar range.

  12. New insights into transparent exopolymer particles (TEP) formation from precursor materials at various Na+/Ca2+ ratios

    NASA Astrophysics Data System (ADS)

    Meng, Shujuan; Liu, Yu

    2016-01-01

    Transparent exopolymer particles (TEP) are planktonic, organic microgels which play significant roles in cycling of carbon and trace elements, aggregation of particles, feeding and accommodating microbes as well as development of biofilms. However, few studies are available on the mechanism of TEP formation in various water environments. Here we investigate the formation of TEP with alginate blocks as precursors at various Na+/Ca2+ ratios to simulate the situations in different aquatic environments (e.g. freshwater and seawater). We found that the formation of TEP from precursor materials studied was essentially determined by the Ca2+ concentration at a fixed sodium concentration, while Na+ at high Na+/Ca2+ ratio out-competed Ca2+ for the binding sites on the precursor molecules, leading to a significantly decreased trend of TEP formation. Our results indicate that a more abundant TEP could be expected in freshwater than in seawater, and we also discuss the engineering implications of the findings.

  13. New insights into transparent exopolymer particles (TEP) formation from precursor materials at various Na+/Ca2+ ratios.

    PubMed

    Meng, Shujuan; Liu, Yu

    2016-01-21

    Transparent exopolymer particles (TEP) are planktonic, organic microgels which play significant roles in cycling of carbon and trace elements, aggregation of particles, feeding and accommodating microbes as well as development of biofilms. However, few studies are available on the mechanism of TEP formation in various water environments. Here we investigate the formation of TEP with alginate blocks as precursors at various Na(+)/Ca(2+) ratios to simulate the situations in different aquatic environments (e.g. freshwater and seawater). We found that the formation of TEP from precursor materials studied was essentially determined by the Ca(2+) concentration at a fixed sodium concentration, while Na(+) at high Na(+)/Ca(2+) ratio out-competed Ca(2+) for the binding sites on the precursor molecules, leading to a significantly decreased trend of TEP formation. Our results indicate that a more abundant TEP could be expected in freshwater than in seawater, and we also discuss the engineering implications of the findings.

  14. New insights into transparent exopolymer particles (TEP) formation from precursor materials at various Na+/Ca2+ ratios

    PubMed Central

    Meng, Shujuan; Liu, Yu

    2016-01-01

    Transparent exopolymer particles (TEP) are planktonic, organic microgels which play significant roles in cycling of carbon and trace elements, aggregation of particles, feeding and accommodating microbes as well as development of biofilms. However, few studies are available on the mechanism of TEP formation in various water environments. Here we investigate the formation of TEP with alginate blocks as precursors at various Na+/Ca2+ ratios to simulate the situations in different aquatic environments (e.g. freshwater and seawater). We found that the formation of TEP from precursor materials studied was essentially determined by the Ca2+ concentration at a fixed sodium concentration, while Na+ at high Na+/Ca2+ ratio out-competed Ca2+ for the binding sites on the precursor molecules, leading to a significantly decreased trend of TEP formation. Our results indicate that a more abundant TEP could be expected in freshwater than in seawater, and we also discuss the engineering implications of the findings. PMID:26790536

  15. Ca/Na selectivity coefficients from the Poisson-Boltzmann theory

    NASA Astrophysics Data System (ADS)

    Hedström, Magnus; Karnland, Ola

    As a model for ion equilibrium in montmorillonite, the Poisson-Boltzmann (PB) equation was solved for two parallel charged surfaces in contact with an external NaCl/CaCl 2 mixed solution. The ion concentration profiles in the montmorillonite interlayer were obtained from the PB equation and integration of those gave the occupancy of Na + and Ca 2+ in the clay. That information together with the composition of the external electrolyte were then used for the calculation of the Gaines-Thomas selectivity coefficient K GT. The predictions from the model were compared to experimental data from batch as well as compacted conditions, and the agreement was generally good. With a surface layer-charge density of one unit charge per 145 Å 2, which is close to the value for Wyoming-type montmorillonite, the calculated selectivity coefficients were found to vary from about 4 in batch to 8 in compacted montmorillonite with dry density ∼1700 kg/m 3. From the point of view of assessing the evolution, with regard to sodium-calcium ion exchange, of the bentonite buffer in a repository for spent nuclear fuel, these results justify the use of data obtained in batch experiments.

  16. Na+/Ca2+ exchanger contributes to stool transport in mice with experimental diarrhea

    PubMed Central

    NISHIYAMA, Kazuhiro; TANIOKA, Kohta; AZUMA, Yasu-Taka; HAYASHI, Satomi; FUJIMOTO, Yasuyuki; YOSHIDA, Natsuho; KITA, Satomi; SUZUKI, Sho; NAKAJIMA, Hidemitsu; IWAMOTO, Takahiro; TAKEUCHI, Tadayoshi

    2016-01-01

    The Na+/Ca2+ exchanger (NCX) is a bidirectional transporter that is controlled by membrane potential and transmembrane gradients of Na+ and Ca2+. To reveal the functional role of NCX on gastrointestinal motility, we have previously used NCX1 and NCX2 heterozygote knockout mice (HET). We found that NCX1 and NCX2 play important roles in the motility of the gastric fundus, ileum and distal colon. Therefore, we believed that NCX1 and NCX2 play an important role in transport of intestinal contents. Here, we investigated the role of NCX in a mouse model of drug-induced diarrhea. The fecal consistencies in NCX1 HET and NCX2 HET were assessed using a diarrhea induced by magnesium sulfate, 5-hydroxytryptamine (5-HT) and prostaglandin E2 (PGE2). NCX2 HET, but not NCX1 HET, exacerbated magnesium sulfate-induced diarrhea by increasing watery fecals. Likewise, 5-HT-induced diarrheas were exacerbated in NCX2 HET, but not NCX1 HET. However, NCX1 HET and NCX2 HET demonstrated PGE2 induced diarrhea similar to those of wild-type mice (WT). As well as the result of the distal colon shown previously, in the proximal and transverse colons of WT, the myenteric plexus layers and the longitudinal and circular muscle layers were strongly immunoreactive to NCX1 and NCX2. In this study, we demonstrate that NCX2 has important roles in development of diarrhea. PMID:27928109

  17. Precursor Routes to Complex Ternary Intermetallics: Single-Crystal and Microcrystalline Preparation of Clathrate-I Na8Al8Si38 from NaSi + NaAlSi.

    PubMed

    Dong, Yongkwan; Chai, Ping; Beekman, Matt; Zeng, Xiaoyu; Tritt, Terry M; Nolas, George S

    2015-06-01

    Single crystals of the ternary clathrate-I Na8Al8Si38 were synthesized by kinetically controlled thermal decomposition (KCTD), and microcrystalline Na8Al8Si38 was synthesized by spark plasma sintering (SPS) using a NaSi + NaAlSi mixture as the precursor. Na8AlxSi46-x compositions with x ≤ 8 were also synthesized by SPS from precursor mixtures of different ratios. The crystal structure of Na8Al8Si38 was investigated using both Rietveld and single-crystal refinements. Temperature-dependent transport and UV/vis measurements were employed in the characterization of Na8Al8Si38, with diffuse-reflectance measurement indicating an indirect optical gap of 0.64 eV. Our results indicate that, when more than one precursor is used, both SPS and KCTD are effective methods for the synthesis of multinary inorganic phases that are not easily accessible by traditional solid-state synthesis or crystal growth techniques.

  18. Enhanced Late Na and Ca Currents as Effective Antiarrhythmic Drug Targets

    PubMed Central

    Karagueuzian, Hrayr S.; Pezhouman, Arash; Angelini, Marina; Olcese, Riccardo

    2017-01-01

    While recent advances clarified the molecular and cellular modes of action of antiarrhythmic drugs (AADs), their link to suppression of dynamical arrhythmia mechanisms remains only partially understood. The current classifications of AADs (Classes I, III, and IV) rely on blocking peak Na, K and L-type calcium currents (ICa,L), with Class II with dominant beta receptor blocking activity and Class V including drugs with diverse classes of actions. The discovery that the calcium and redox sensor, cardiac Ca/calmodulin-dependent protein kinase II (CaMKII) enhances both the late Na (INa-L) and the late ICa,L in patients at high risk of VT/VF provided a new and a rational AAD target. Pathological rise of either or both of INa-L and late ICa,L are demonstrated to promote cellular early afterdepolarizations (EADs) and EAD-mediated triggered activity that can initiate VT/VF in remodeled hearts. Selective inhibition of the INa-L without affecting their peak transients with the highly specific prototype drug, GS-967 suppresses these EAD-mediated VT/VFs. As in the case of INa-L, selective inhibition of the late ICa,L without affecting its peak with the prototype drug, roscovitine suppressed oxidative EAD-mediated VT/VF. These findings indicate that specific blockers of the late inward currents without affecting their peaks (gating modifiers), offer a new and effective AAD class action i.e., “Class VI.” The development of safe drugs with selective Class VI actions provides a rational and effective approach to treat VT/VF particularly in cardiac conditions associated with enhanced CaMKII activity such as heart failure. PMID:28220073

  19. Removal of Tin and Copper from Liquid Iron by Al2O3-Saturated Ca-CaCl2 Slags at 1448 to 1648 K

    NASA Astrophysics Data System (ADS)

    Ghosh, Dinabandhu

    2009-08-01

    The removal of tin and copper from liquid iron by Al2O3-saturated Ca-CaCl2 slags was carried out in separate alumina crucibles at 1448 to 1648 K that showed small partition ratios of less than 1. The tin content of the liquid iron typically decreased from its initial value of 50 to 40 wt pct and the (gross) copper content of the iron-copper mixture from 50 to 45 wt pct, at equilibrium. The small refining efficiencies (37 pct, maximum) of the slags, the initial composition of which were, in most cases, Ca-50 wt pct CaCl2, may be attributed to the significant dissolution in them of alumina, up to 42.0 wt pct (29.6 mol pct), in experiments with Sn, and up to 54.4 wt pct (38.6 mol pct), in experiments with Cu. Treating Ca as the solvent, a number of interaction coefficients such as \\varepsilon_{{{text{Al}}_{ 2} {text{O}}_{ 3} }}^{{{text{Al}}_{ 2} {text{O}}_{ 3} }} , \\varepsilon_{{{text{Al}}_{ 2} {text{O}}_{ 3} }}^{{{text{CaCl}}_{ 2} }} , \\varepsilon_{{{text{Al}}_{ 2} {text{O}}_{ 3} }}^{text{Sn}} , \\varepsilon_{{{text{CaCl}}_{ 2} }}^{{{text{CaCl}}_{ 2} }} , \\varepsilon_{{{text{CaCl}}_{ 2} }}^{text{Sn}} , and \\varepsilon_{text{Sn}}^{text{Sn}} as well as the activity coefficient γ_{{{text{Al}}_{ 2} {text{O}}_{ 3} }}0 were all determined at 1448 K. The activity of Ca (relative to pure liquid Ca) was obtained as approximately 0.65 to 0.75 in the system. Further, the two partial molar mixing/excess properties of alumina bar{H}_{{{text{Al}}_{ 2} {text{O}}_{ 3} }}M and bar{S}_{{{text{Al}}_{ 2} {text{O}}_{ 3} }}^{XS} in the alumina-saturated Ca-17 pct CaCl2- 37 pct Al2O3 (molar basis) slag were evaluated and found to be -118.3(±10.8) kJ/mol and -0.062(±0.007) kJ/K·mol, respectively, at 1448 to 1648 K. In addition, in view of the reported success of CaC2 as a refining agent, some experiments were carried out with CaC2-CaF2 mixtures in alumina, magnesia, and graphite crucibles at 1873 K, to remove tin from liquid Fe-2 wt pct Sn. However, alumina and magnesia crucibles

  20. Crop residue effects on Ca, Mg, K and Na concentrations and loads in runoff water

    NASA Astrophysics Data System (ADS)

    Miras-Avalos, J. M.; Sande-Fouz, P.; Bertol, I.; Paz-Gonzalez, A.

    2009-04-01

    Soil organic matter constitutes and important source of macro and micronutrients for plants and microorganisms while improving some physical and chemical properties of the soil. In Galicia (NW Spain), cultivated soils developed on schists from the Ordenes series show a relatively high susceptibility to surface degradation, which tends to be increased when soil organic content decreases. Therefore, management systems providing a high protection to the soil and increasing its organic matter content should also improve its quality. However, tillage practices may reduce the organic matter content in soil surface horizons, causing crust formation. Degraded soil surface conditions favor surface runoff, thus enhancing nutrient losses. This study examined the effect of applying crop residues to the soil surface on main nutrient (Ca, Mg, K and Na) losses by runoff from a tilled soil with a relatively low organic matter content. Runoff and sediment yield were made over 1 m2 plots using a rainfall simulator with constant 65 mmh-1 intensity. Four successive rainfall applications were performed, the first three ones 25 mm each and the last one 65 mm. Added corn straw varied between 0 and 4 tha-1 in the five studied treatments. Total and dissolved concentrations of the studied elements showed a trend to decrease due to the effect of corn straw on soil losses. After 140 mm cumulative rainfall, total nutrient losses were as follows: Ca from 12.32 to 28.94 mg L-1, Mg from 20.81 to 148.90 mg L-1, K from 14.20 to 35.17 mg L-1 and Na from 14.99 to 23.41 mg L-1. The relative contribution of the dissolved fraction to the total nutrient content loss was highly variable, being up to 90% in the case of Na. The obtained results confirmed that corn residues applied to a degraded soil, with low structural stability, prevented macronutrient losses.

  1. Role of extracellular Na+, Ca2+-activated Cl- channels and BK channels in the contraction of Ca2+ store-depleted tracheal smooth muscle.

    PubMed

    Romero-Méndez, Catalina; Algara-Suárez, Paola; Sánchez-Armass, Sergio; Mandeville, Peter B; Meza, Ulises; Espinosa-Tanguma, Ricardo

    2009-07-01

    1. In the present study, we investigated the series of events involved in the contraction of tracheal smooth muscle induced by the re-addition of Ca(2+) in an in vitro experimental model in which Ca(2+) stores had been depleted and their refilling had been blocked by thapsigargin. 2. Mean (+/-SEM) contraction was diminished by: (i) inhibitors of store-operated calcium channels (SOCC), namely 100 micromol/L SKF-96365 and 100 micromol/L 1-(2-trifluoromethylphenyl) imidazole (to 66.3 +/- 4.4 and 41.3 +/- 5.2% of control, respectively); (ii) inhibitors of voltage-gated Ca(2+) channels Ca(V)1.2 channels, namely 1 micromol/L nifedipine and 10 micromol/L verapamil (to 86.2 +/- 3.4 and 76.9 +/- 5.9% of control, respectively); and (iii) 20 micromol/L niflumic acid, a non-selective inhibitor of Ca(2+)-dependent Cl(-) channels (to 41.1 +/- 9.8% of control). In contrast, contraction was increased 2.3-fold by 100 nmol/L iberiotoxin, a blocker of the large-conductance Ca(2+)-activated K(+) (BK) channels. 3. Furthermore, contraction was significantly inhibited when Na(+) in the bathing solution was replaced by N-methyl-D-glucamine (NMDG(+)) to 39.9 +/- 7.2% of control, but not when it was replaced by Li(+) (114.5 +/- 24.4% of control). In addition, when Na(+) had been replaced by NMDG(+), contractions were further inhibited by both nifedipine and niflumic acid (to 3.0 +/- 1.8 and 24.4 +/- 8.1% of control, respectively). Nifedipine also reduced contractions when Na(+) had been replaced by Li(+) (to 10.7 +/- 3.4% to control), the niflumic acid had no effect (116.0 +/- 4.5% of control). 4. In conclusion, the data of the present study demonstrate the roles of SOCC, BK channels and Ca(V)1.2 channels in the contractions induced by the re-addition of Ca(2+) to the solution bathing guinea-pig tracheal rings under conditions of Ca(2+)-depleted sarcoplasmic reticulum and inhibition of sarcoplasmic/endoplasmic reticulum calcium ATPase. The contractions were highly dependent on extracellular

  2. Network topology for the formation of solvated electrons in binary CaO-Al2O3 composition glasses.

    PubMed

    Akola, Jaakko; Kohara, Shinji; Ohara, Koji; Fujiwara, Akihiko; Watanabe, Yasuhiro; Masuno, Atsunobu; Usuki, Takeshi; Kubo, Takashi; Nakahira, Atsushi; Nitta, Kiyofumi; Uruga, Tomoya; Weber, J K Richard; Benmore, Chris J

    2013-06-18

    Glass formation in the CaO-Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO-Al2O3 glasses using combined density functional theory-reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O-Ca and O-Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al-O is stronger than that of Ca-O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71-74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass.

  3. Structure of human Na+/H+ exchanger NHE1 regulatory region in complex with calmodulin and Ca2+.

    PubMed

    Köster, Stefan; Pavkov-Keller, Tea; Kühlbrandt, Werner; Yildiz, Özkan

    2011-11-25

    The ubiquitous mammalian Na(+)/H(+) exchanger NHE1 has critical functions in regulating intracellular pH, salt concentration, and cellular volume. The regulatory C-terminal domain of NHE1 is linked to the ion-translocating N-terminal membrane domain and acts as a scaffold for signaling complexes. A major interaction partner is calmodulin (CaM), which binds to two neighboring regions of NHE1 in a strongly Ca(2+)-dependent manner. Upon CaM binding, NHE1 is activated by a shift in sensitivity toward alkaline intracellular pH. Here we report the 2.23 Å crystal structure of the NHE1 CaM binding region (NHE1(CaMBR)) in complex with CaM and Ca(2+). The C- and N-lobes of CaM bind the first and second helix of NHE1(CaMBR), respectively. Both the NHE1 helices and the Ca(2+)-bound CaM are elongated, as confirmed by small angle x-ray scattering analysis. Our x-ray structure sheds new light on the molecular mechanisms of the phosphorylation-dependent regulation of NHE1 and enables us to propose a model of how Ca(2+) regulates NHE1 activity.

  4. Petrography, mineralogy, and Mg isotope composition of VICTA: A vigarano CaAl4O7-bearing type A inclusion

    NASA Technical Reports Server (NTRS)

    Greenwood, R. C.; Morse, A.; Long, J. V. P.

    1993-01-01

    Thermodynamic calculations predict that Ca-dialuminate (CaAl4O7) condenses from a cooling gas of solar composition after hibonite and before melilite. Although Ca-dialuminate has now been recorded from Ca Al-rich inclusions (CAI's) in at least 9 meteorites, compared to hibonite it is a relatively rare phase. As pointed out by Michel-Levy et al., the absence of Ca-dialuminate from most hibonite-bearing inclusions poses a serious problem for the condensation model of CAI formation. Here we describe an inclusion which contains abundant CA-dialuminate partially altered to a hercynite-rich (FeAl2O4) assemblage. The evidence from VICTA indicates that compared to all other phases in type A inclusions, Ca-dialuminate is the most susceptible to secondary alteration; a feature which may explain its restricted occurrence. Unaltered Ca-dialuminate and melilite in VICTA display excess Mg-26 indicative of in situ decay of Al-26.

  5. Reactivity enhancement of oxide skins in reversible Ti-doped NaAlH{sub 4}

    SciTech Connect

    Delmelle, Renaud; Borgschulte, Andreas; Gehrig, Jeffrey C.; Züttel, Andreas

    2014-12-15

    The reversibility of hydrogen sorption in complex hydrides has only been shown unambiguously for NaAlH{sub 4} doped with transition metal compounds. Despite a multitude of investigations of the effect of the added catalyst on the hydrogen sorption kinetics of NaAlH{sub 4}, the mechanism of catalysis remains elusive so far. Following the decomposition of TiCl{sub 3}-doped NaAlH{sub 4} by in-situ X-ray photoelectron spectroscopy (XPS), we link the chemical state of the dopant with those of the hydride and decomposition products. Titanium and aluminium change their oxidation states during cycling. The change of the formal oxidation state of Al from III to zero is partly due to the chemical reaction from NaAlH{sub 4} to Al. Furthermore, aluminium oxide is formed (Al{sub 2}O{sub 3}), which coexists with titanium oxide (Ti{sub 2}O{sub 3}). The interplay of metallic and oxidized Ti with the oxide skin might explain the effectiveness of Ti and similar dopants (Ce, Zr…)

  6. CaMn2Al10: Itinerant Mn magnetism on the verge of magnetic order

    DOE PAGES

    Steinke, L.; Simonson, J. W.; Yin, W. -G.; ...

    2015-07-24

    We report the discovery of CaMn2Al10, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83μB/Mn, significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈ 9% of Rln2. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010]/χ[001] ≈ 3.5. A strong power-lawmore » divergence χ(T) ~ T–1.2 below 20 K implies incipient ferromagnetic order, an Arrott plot analysis of the magnetization suggests a vanishing low Curie temperature TC ~ 0. Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.« less

  7. CaMn2Al10 : Itinerant Mn magnetism on the verge of magnetic order

    NASA Astrophysics Data System (ADS)

    Steinke, L.; Simonson, J. W.; Yin, W.-G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-01

    We report the discovery of CaMn2Al10 , a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83 μB/Mn , significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈9 % of R ln 2 . These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010 ]/χ[001 ]≈3.5 . A strong power-law divergence χ (T ) ˜T-1.2 below 20 K implies incipient ferromagnetic order with a low Curie temperature TC<2 K . Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.

  8. 12CaO-7Al2O3 Electride Hollow Cathode

    NASA Technical Reports Server (NTRS)

    Rand, Lauren P. (Inventor); Williams, John D. (Inventor); Martinez, Rafael A. (Inventor)

    2017-01-01

    The use of the electride form of 12CaO-7Al2O3, or C12A7, as a low work function electron emitter in a hollow cathode discharge apparatus is described. No heater is required to initiate operation of the present cathode, as is necessary for traditional hollow cathode devices. Because C12A7 has a fully oxidized lattice structure, exposure to oxygen does not degrade the electride. The electride was surrounded by a graphite liner since it was found that the C12A7 electride converts to it's eutectic (CA+C3A) form when heated (through natural hollow cathode operation) in a metal tube.

  9. Chemical zoning and diffusion of Ca, Al, Mn, and Cr in olivine of springwater pallasite

    NASA Technical Reports Server (NTRS)

    Zhou, Y.; Steele, Ian M.

    1993-01-01

    The pallasites, consisting mainly of Fe-Ni metal and olivine, are thought to represent the interior of a planetary body which slowly cooled from high temperature. Although the olivines are nearly homogeneous, ion microprobe studies revealed variations of Ca, Ti, Co, Cr, and Ni near grain edges. These variations were thought to represent diffusion in response to falling temperature of the parent body. Pallasite cooling rates have been estimated based on kamacite taenite textures but results differ by x100. In principle elemental profiles in olivine can allow estimates of cooling rate if diffusion coefficients are known; in addition, given a cooling rate, diffusion coefficients could be derived. Data are presented which show that apparent diffusion profiles can be measured for Al, Ca, Cr, and Mn which qualitatively agree with expected diffusion rates and have the potential of providing independent estimates of pallasite cooling rates.

  10. Low-temperature heat capacities of CaAl2SiO6 glass and pyroxene and thermal expansion of CaAl2SiO6 pyroxene.

    USGS Publications Warehouse

    Haselton, H.T.; Hemingway, B.S.; Robie, R.A.

    1984-01-01

    Low-T heat capacities (5-380 K) have been measured by adiabatic calorimetry for synthetic CaAl2SiO6 glass and pyroxene. High-T unit cell parameters were measured for CaAl2SiO6 pyroxene by means of a Nonius Guinier-Lenne powder camera in order to determine the mean coefficient of thermal expansion in the T range 25-1200oC. -J.A.Z.

  11. Microstructural investigation of MX-80 bentonite and Na/Ca-montmorillonite using basal spacing determination

    NASA Astrophysics Data System (ADS)

    Holmboe, M.; Wold, S.

    2010-12-01

    Knowledge about the microstructure of saturated compacted bentonite is of fundamental importance in order to describe and predict diffusive transport through the bentonite barrier in a deep geological repository. If the mineral composition is well characterized, microstructural models of compacted bentonite on the nanoscale can be based on accurate information of the basal spacings and corresponding interlayer distances within the montmorillonite particles. From the average basal spacing, the interlayer and the so-called interparticle or free porosity can be calculated [1]. The basal spacings of the montmorillonite particles can be measured by neutron and X-ray small-angle scattering or diffraction. However, due to microstructural heterogeneity and interstratification of different hydration states, profile fitting through mixed layered modeling is necessary although challenging [2,3]. In this study, we have used low-angle XRD in reflection mode together with one-dimensional analysis of mixed layered clays [2] in order to compare both the relative layer distribution and average basal spacing of MX-80 bentonite and Na/Ca-montmorillonite samples. Two different methods for water saturation commonly used in the literature were compared, saturation by constant relative humidity (adsorption and desorption) and saturation under constant volume conditions, forming compacted clay with dry densities of 0.5-1.8 g/cm3. No significant difference in basal spacings was observed between highly compacted (< 4 H2O layers) homoionic montmorillonite and MX-80 bentonite samples saturated under volume constricted conditions, if the accessory minerals and lower smectite content was accounted for. This was however not the case for the samples saturated at constant RH%, which indicates mixing of the exchangeable cations in the interlayers. Interestingly, even if the total water content was the same water uptake restricted by water activity did not always result in the same magnitude of

  12. Partition coefficients for Al, Ca, Ti, Cr, and Ni in olivine obtained by melting experiment on an LL6 chondrite

    NASA Technical Reports Server (NTRS)

    Miyamoto, M.; Mikouchi, T.; Mckay, G. A.

    1994-01-01

    We report the partition coefficients for Ca, Al, Ti, Cr, and Ni in olivine obtained through a series of melting experiments on an LL6 chondrite under varying conditions of temperature and oxygen fugacity. It is necessary to examine the variation of partition coefficients up to extremely reducing conditions in order to study meteoritic olivines. For Ca, Al, and Cr, the partition coefficients tend to decrease as temperature increases, but do not change even under extremely reducing conditions.

  13. An Unusual Ca-Ti-Al Silicate in a Type A Allende Inclusion

    NASA Astrophysics Data System (ADS)

    Floss, C.; El Goresy, A.; Palme, H.; Spettel, B.; Zinner, E.

    1992-07-01

    During the investigation of a Type A inclusion from Allende, preparatory to experimental studies designed to address the role of volatilization in CAI formation, we noted an unusual Ca-Ti-Al silicate, previously observed only as rare tiny grains in several CAIs. Here we report the petrography and chemistry of inclusion A44 and preliminary data for this mineral. Petrography: A44 is a large, highly convoluted inclusion that is remarkably unaltered compared to most Allende CAIs. Except for several broken fragments and faulted regions, it is surrounded by a well-defined rim sequence ranging from 50 to 100 microns in width. The core of the inclusion consists of irregular to almost perfectly circular patches of spinel poikilitically enclosed by fassaite and melilite, which are separated by large regions of spinel-free melilite. Several of these spinel framboids surround voids containing wollastonite needles similar to those described by Allen et al. (1978). Minor perovskite is primarily associated with spinel, but is also found within melilite. Several grains of the Ca-Ti-Al silicate are present in the inclusion; their occurrences and chemistry are discussed below. Chemistry: Two fragments (A: 249.6 mg and E: 241.1 mg) were analyzed by INAA. Fragment A is uniformly enriched in refractory lithophiles and siderophiles to 13-20 x C1, except for depletions of W and Mo, due to the increased volatility of both elements under oxidizing conditions (Fegley and Palme, 1985). Fragment E shows a wider range of enrichment factors (14-30 x C1) with a Yb anomaly (Yb/Lu = 0.52 x C1) characteristic of Group III patterns. The presence of a Yb anomaly in E and its absence in A may indicate that the inclusion consists of fragments formed under different nebular conditions. Mg isotopic fractionations are +5.5 +- 2.0 for melilite and +5.0 +- 1.6 for spinel, values typical for Allende CAIs. Ca-Ti-Al Silicate: An unusually Ti- and Ca-rich mineral occurs in three distinct modes. Numerous grains

  14. The stability of sodalite in the system NaAlSiO sub 4 -NaCl

    SciTech Connect

    Sharp, Z.D. ); Helffrich, G.R. ); Bohlen, S.R. ); Essene, E.J. )

    1989-08-01

    The reaction sodalite = {beta}-nepheline + NaCl (s) was reversed in solid-medium apparatus and the reaction sodalite = carnegieite + NaCl (l) was reversed at 1 bar (1,649-1,652 K). The experimental reversals between 923 K and 973 K can be fit with a dP/dT of {minus}11 bar/K, suggesting that the excess entropy for sodalite is present only above 923 K. A phase diagram for the NaAlSiO{sub 4}-NaCl system that is consistent with the measured thermochemical data and the experiments between 973 and 1,650 K can be generated if the 61.7 J/mol{center dot}K entropy contribution is included in the S{sup 0}{sub 298} of sodalite. This entropy contribution must be removed below 973 K for the experiments to fit with calculations. Previously unreported thermodynamic data estimated in this study are {Delta}G{sup 0}{sub 298} for sodalite ({minus}12,697 kJ/mol) and carnegieite (NaAlSiO{sub 4}) ({minus}1,958 kJ/mol), S{sup 0}{sub 298} of carnegieite (129.6 J/mol{center dot}K) and compressibility of NaCl{sub liquid} (V{sup P}{sub 298} (cm{sup 3}) = 31.6{center dot}(1 - 24.7{center dot}10{sup {minus}3}{center dot}P + 800{center dot}10{sup {minus}6}{center dot}P{sup 2}))(T in K; P in kbar). Sodalite is a high-temperature, low-pressure phase, stable well above the solidus in sodic silica-undersaturated magmas enriched in NaCl, and its presence constrains NaCl activities in magmas. Estimates of minimum NaCl (l) activities in the Mont St-Hilaire sodalite syenites are 0.05 at 1,073 K and 0.13 at 1,273 K. Density calculations are consistent with the field observations that sodalite phenocrysts will float in a nepheline syenite liquid. This explains the enrichment of sodalite in the upper levels of the sodalite syenites at Mont St.Hilaire and elsewhere.

  15. In vitro Ca-45/++/ uptake and exchange by otoconial complexes in high and low K/+/Na/+/ fluids

    NASA Technical Reports Server (NTRS)

    Ross, M. D.; Pote, K. G.; Cloke, P. L.; Corson, C.

    1980-01-01

    Recently, data have been accumulating to indicate that saccular and utricular otoconial complexes of the gravity receptor organs are dynamic and interact constantly with their environment. This study investigates the possibility that the ionic composition of the surrounding fluid influences calcium ion binding and release, and explores the importance of the K(+)/Na(+) ratio. Two in-vitro methods were developed, the first of which employed artificial endolymph and perilymph while ionically balanced fluids in which only the K(+)/Na(+) was altered were used in the second. The ability of rat complexes to take up Ca-45(++) during incubation with these fluids was assessed using liquid scintillation spectrometry. In vitro uptake of Ca-45(++) was greater in fluids with a high K(+)/Na(+) ratio than in fluids in which the ratio was low. The ability of the complexes to take up Ca-45(++) appeared to decline with age.

  16. [Nitric oxide and electrogenic metals (Ca, Na, K) in epidermal cells].

    PubMed

    Petukhov, V I; Baumane, L K; Dmitriev, E V; Vanin, A F

    2015-01-01

    Using atomic emission spectrometry and EPR analysis metal-ligand homeostasis (MLH) has been studied in epidermal cells of 954 liquidators of the Chernobyl accident and 947 healthy individuals. A possible association of the redox status with the quantitative changes in the MLH, which could be used as discriminators of oxidative/nitrosative stress, attracts special interest. Characteristic features of oxidative stress mainly related to electrogenic metals (Ca, K, Na), were found not only among the liquidators examined, but also in some healthy individuals (18.1%); this suggests the presence of oxidative/nitrosative stress of non-radiation origin. Correlation between intracellular production of nitric oxide (NO) with quantitative changes in the electrogenic metals may indicate the possible involvement of NO in the generation of an electric potential of the cell.

  17. Na+/Ca2+ exchanger inhibitors inhibit neurite outgrowth in PC12 cells.

    PubMed

    Oda, Toru; Kume, Toshiaki; Izumi, Yasuhiko; Ishihara, Kumatoshi; Sugmimoto, Hachiro; Akaike, Akinori

    2011-01-01

    To elucidate the role of Na(+)/Ca(2+) exchanger (NCX) in neurite outgrowth, we investigated the effects of NCX inhibitors on neurite outgrowth in PC12 cells. KB-R7943 and 3',4'-dichlorobenzamil, NCX inhibitors, inhibited the neurite outgrowth caused by nerve growth factor (NGF). NCX inhibitors inhibited the neurite outgrowth caused by dibutylyl cAMP, which rapidly reorganizes the cytoskeleton. KB-R7943 inhibited the neurite outgrowth caused by Y-27632, an inhibitor of Rho kinase (ROCK) that regulates actin. However, NCX inhibitors did not inhibit NGF-induced phosphorylation of extracellular signal-regulated kinase. These results suggest that NCX inhibitor affects downstream of the Rho-ROCK signal transduction pathways in neurite outgrowth.

  18. Identical superconducting gap on different Fermi surfaces of Ca(Al0.5Si0.5)2 with the AlB2 structure

    NASA Astrophysics Data System (ADS)

    Tsuda, S.; Yokoya, T.; Shin, S.; Imai, M.; Hase, I.

    2004-03-01

    Angle-resolved photoemission spectroscopy of Ca(Al0.5Si0.5)2 (CaAlSi), which is a superconductor (transition temperature is 7.7 K) with the AlB2 structure, revealed that superconducting gaps on two Fermi surfaces (FSs) with three-dimensional character around Γ(A) and M(L) in the Brillouin zone provide essentially the same superconducting gap value (˜1.2 meV±0.2 meV). This is in contrast to the case of MgB2, in which different FSs exhibit different gap values. The reduced gap value 2Δ(0)/kBTc of ˜4.2±0.2 classifies CaAlSi as a moderately strong-coupling superconductor.

  19. Mitogen-activated protein kinase 6 controls root growth in Arabidopsis by modulating Ca2+ -based Na+ flux in root cell under salt stress.

    PubMed

    Han, Shuan; Wang, Chi-wen; Wang, Wen-le; Jiang, Jing

    2014-03-01

    Little is known about the role of mitogen-activated protein kinase 6 (MPK6) in Na(+) toxicity and inhibition of root growth in Arabidopsis under NaCl stress. In this study, we found that root elongation in seedlings of the loss-of-function mutants mpk6-2 and mpk6-3 was less sensitive to NaCl or Na-glutamate, but not to KCl or mannitol, as compared with that of wild-type (WT) seedlings. The less sensitive characteristic was eliminated by adding the Ca(2+) chelator EGTA or the Ca(2+) channel inhibitor LaCl3, but not the Ca(2+) ionophore A23187. This suggested that the tolerance of mpk6 to Na(+) toxicity was Ca(2+)-dependent. We measured plasma membrane (PM) Na(+)-conducted currents (NCCs) in root cells. Increased concentrations of NaCl increased the inward NCCs while decreased the outward NCCs in WT root cells, attended by a positive shift in membrane potential. In mpk6 root cells, NaCl significantly increased outward but not inward NCCs, accompanied by a negative shift in membrane potential. That is, mpk6 decreased NaCl-induced the Na(+) accumulation by modifying PM Na(+) flux in root cells. Observations of aequorin luminescence revealed a NaCl-induced increase of cytosolic Ca(2+) in mpk6 root cells, resulting from PM Ca(2+) influx. An increase of cytosolic Ca(2+) was required to alleviate the NaCl-increased Na(+) content and Na(+)/K(+) ratio in mpk6 roots. Together, these results show that mpk6 accumulated less Na(+) in response to NaCl because of the increased cytosolic Ca(2+) level in root cells; thus, its root elongation was less inhibited than that of WT by NaCl.

  20. Acid precipitation and food quality: Effects of dietary Al, Ca and P on bone and liver characteristics in American black ducks and mallards

    USGS Publications Warehouse

    Sparling, D.W.

    1991-01-01

    American black ducks (Anas rubripes) and mallards (A. platyrhynchos) were fed diets varying in concentrations of aluminum (Al). calcium (Ca), and phosphorus (P) for 10 weeks to identify toxic effects of Al under conditions representative of areas with acid precipitation. Femur and liver tissues were analyzed for Al. Ca, and P concentrations and structural characteristics. At two weeks of age, both species demonstrated pronounced differences in femur Al and P concentrations and femur mass from dietary Al and interaction between Ca:P regimen and Al:Low Ca:Low P enhanced Al storage and decreased P and mass in femurs. Femur Ca was lowest in the Low Ca:Low P regimen but was not affected by dietary Al. At 10 weeks, femur and liver Al continued to vary with dietary Al. Elevated Al and reduced Ca lowered modulus of elasticity. Femur P increased with elevated dietary P in black ducks. Elevated dietary P negated some of the effects of dietary A! on femur mass in black ducks. Reduced Ca concentrations weakened bones of both species and lowered both Ca and P. An array of clinical signs including lameness, discoloration of the upper mandible, complete and greenstick fractures, and death were responses to elevated Al and Ca:P regimen. Black ducks seemed to display these signs over a wider range of diets than mallards. Diets of 1,000 mg/kg Al had toxic effects on both species, particularly when combined with diets low in Ca and P.

  1. An ATP- and Ca/sup 2 +/-regulated Na/sup +/ channel in isolated intestinal epithelial cells

    SciTech Connect

    Kimmich, G.A.; Randles, J.

    1982-09-01

    When isolated intestinal epithelial cells are treated with 2 mM ATP, the undirectional influx of Na/sup +/ to those cells increases from values near 50 to rates over 200 nmol.min/sup -1/.mg protein/sup -1/. Calcium influx increases from 1 to 40 nmol.min/sup -1/.mg protein/sup -1/. Within 2 min, the total cell Na/sup +/ increases two- to threefold, and total Ca/sup +/ increases about fivefold. The cells lose a major part of their capability for accumulating sugars during this interval. About 2 min after the time of ATP addition the normal permeability for Na/sup +/ and Ca/sup 2 +/ is restored, at which time the previously accumulated ions are rapidly extruded on a net basis until control levels are attained and the cells regain their usual sugar transport capability. The ''repair'' process requires Ca/sup 2 +/ in the incubation medium and is dependent on cellular uptake of Ca/sup 2 +/. Chlorpromazine (0.5 mM) blocks the Ca/sup 2 +/ entry route and the restoration of normal Na/sup +/ permeability. The Na/sup +/ entry route is selectively blocked by 4-acetamido-4'-isocyanostilbene-2,2'-disulfonic acid. The data show that ATP induces the influx of Na/sup +/ and Ca/sup 2 +/ by two different routes, which can be selectively inhibited. These ion flux routes may be involved in the events that allow intestinal tissue to convert from an absorptive state to a state in which net ion secretion occurs.

  2. Network topology for the formation of solvated electrons in binary CaO–Al2O3 composition glasses

    PubMed Central

    Akola, Jaakko; Kohara, Shinji; Ohara, Koji; Fujiwara, Akihiko; Watanabe, Yasuhiro; Masuno, Atsunobu; Usuki, Takeshi; Kubo, Takashi; Nakahira, Atsushi; Nitta, Kiyofumi; Uruga, Tomoya; Weber, J. K. Richard; Benmore, Chris J.

    2013-01-01

    Glass formation in the CaO–Al2O3 system represents an important phenomenon because it does not contain typical network-forming cations. We have produced structural models of CaO–Al2O3 glasses using combined density functional theory–reverse Monte Carlo simulations and obtained structures that reproduce experiments (X-ray and neutron diffraction, extended X-ray absorption fine structure) and result in cohesive energies close to the crystalline ground states. The O–Ca and O–Al coordination numbers are similar in the eutectic 64 mol % CaO (64CaO) glass [comparable to 12CaO·7Al2O3 (C12A7)], and the glass structure comprises a topologically disordered cage network with large-sized rings. This topologically disordered network is the signature of the high glass-forming ability of 64CaO glass and high viscosity in the melt. Analysis of the electronic structure reveals that the atomic charges for Al are comparable to those for Ca, and the bond strength of Al–O is stronger than that of Ca–O, indicating that oxygen is more weakly bound by cations in CaO-rich glass. The analysis shows that the lowest unoccupied molecular orbitals occurs in cavity sites, suggesting that the C12A7 electride glass [Kim SW, Shimoyama T, Hosono H (2011) Science 333(6038):71–74] synthesized from a strongly reduced high-temperature melt can host solvated electrons and bipolarons. Calculations of 64CaO glass structures with few subtracted oxygen atoms (additional electrons) confirm this observation. The comparable atomic charges and coordination of the cations promote more efficient elemental mixing, and this is the origin of the extended cage structure and hosted solvated (trapped) electrons in the C12A7 glass. PMID:23723350

  3. Inhibition of mitochondrial Na+-dependent Ca²+ efflux by 17β-estradiol in the rat hippocampus.

    PubMed

    Petrović, S; Veličković, N; Stanojević, I; Milošević, M; Drakulić, D; Stanojlović, M; Horvat, A

    2011-09-29

    Our results, as well as those of others, have indicated that 17β-estradiol (E2) exerts its nongenomic effects in neuronal cells by affecting plasma membrane Ca(2+) flux. In neuronal cells mitochondria possess Ca(2+) buffering properties as they both sequester and release Ca(2+). The goal of this study was to examine the rapid non-genomic effect of E2 on mitochondrial Ca(2+) transport in hippocampal synaptosomes from ovariectomised rats. In addition, we aimed to determine if, and to what extent, E2 receptors participated in mitochondrial Ca(2+) transport modulation by E2 in vitro. E2-specific binding and Ca(2+) transport was monitored. At physiological E2 concentrations (0.1-1.5 nmol/L), specific E2 binding to mitochondria isolated from hippocampal synaptosomes was detected with a B(max.) and K(m) of 37.6±2.6 fmol/mg protein and 0.69±0.14 nmol/L of free E2, respectively. The main mitochondrial Ca(2+) influx mechanism is the Ruthenium Red-sensitive uniporter driven by mitochondrial membrane potential. Despite no effect of E2 on Ca(2+) influx, a physiological E2 concentration (0.5 nmol/L) protected mitochondrial membrane potential and consequently Ca(2+) influx from the uncoupling agent carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (1 μmol/L). In neuronal cells the predominant mitochondrial Ca(2+) efflux mechanism is the Na(+)/Ca(2+) exchanger. E2 caused Ca(2+) efflux inhibition (by 46%) coupled with increased affinity of the Na(+)/Ca(2+) exchanger for Na(+). Using E2 receptor (ERα and ERβ) antagonists and agonists, we confirmed ERβ's involvement in E2-induced mitochondrial membrane potential protection as well as Ca(2+) efflux inhibition. In summary, our results indicate that the non-genomic neuromodulatory role of E2 in rat hippocampus is achieved by affecting mitochondrial Ca(2+) transport via, in part, mitochondrial ERβ.

  4. Crystal growth and spectroscopic properties of Cr3+-doped CaGdAlO4

    NASA Astrophysics Data System (ADS)

    Zhang, Zhu; Huang, Yisheng; Zhang, Lizhen; Sun, Shijia; Yuan, Feifei; Lin, Zhoubin

    2017-04-01

    A Cr3+:CaGdAlO4 single crystal with dimensions of ∅21 × 33 mm3 was grown successfully by Czochralski method for the first time. Its spectral properties including polarized absorption spectra, polarized fluorescence spectra, excitation spectrum and fluorescence decay curves were investigated in detail. The absorption cross-sections at around 573 nm corresponding to the 4A2 → 4T2 transition of Cr3+ ions are 4.75 × 10-20 and 2.56 × 10-20 cm2 for σ- and π-polarizations, respectively. The excitation spectrum shows two broad and intense absorption bands at about 390 nm and 570 nm, which are associated with the 4A2 → 4T1 and 4A2 → 4T2 transitions of Cr3+ ions, respectively. The emission band with peak at around 744 nm is ascribed to the 2E → 4A2 transition of Cr3+ ions, with the emission cross-sections of 5.55 × 10-22 and 5.41 × 10-22 cm2 for σ- and π-polarizations, respectively. The fluorescence lifetime is 4.35 ms at room temperature. The Dq/B value is 2.72, which means that Cr3+ ions occupy the lattice sites with strong crystal field strength. The results show that Cr3+:CaGdAlO4 crystal can be regarded as a potential laser gain medium.

  5. Removal of Phosphorus in Silicon by the Formation of CaAl2Si2 Phase at the Solidification Interface

    NASA Astrophysics Data System (ADS)

    Sun, Liyuan; Wang, Zhi; Chen, Hang; Wang, Dong; Qian, Guoyu

    2017-02-01

    To fully understand the role of CaAl2Si2 phase in concentrating the non-metallic impurity phosphorus, an experiment of directional solidification of Al-70 at. pct Si alloy with extreme small lowering rate 0.05 mm min-1 was carried out. With good dynamic condition for the diffusion of impurity (Ca, Al, P) from silicon to the S/L interface, the CaAl2Si2 phase with 0.6-0.7 at. pct P was successfully observed by Electron Probe Micro Analyzer (EPMA), and its distribution character was originally presented. This impurity phase was widely detected in the refined sample but only at the interface of silicon crystal and Al-Si alloy which contributed to the deep removal of impurity P. The formation mechanism of CaAl2Si2-P phase was thus explored, in which the microsegregation and concentration of element P, Ca, Al in front of S/L interface were crucial. After acid leaching, the P content decreased from the original 23 ppm to below 5 ppm. Compared with normal solidification, a 16 pct higher removal efficiency of P was obtained in this study.

  6. CO₂ sorbents with scaffold-like Ca-Al layered double hydroxides as precursors for CO₂ capture at high temperatures.

    PubMed

    Chang, Po-Hsueh; Lee, Tai-Jung; Chang, Yen-Po; Chen, San-Yuan

    2013-06-01

    A highly stable high-temperature CO₂ sorbent consisting of scaffold-like Ca-rich oxides (Ca-Al-O) with rapid absorption kinetics and a high capacity is described. The Ca-rich oxides were prepared by annealing Ca-Al-NO₃ layered double hydroxide (LDH) precursors through a sol-gel process with Al(O(i)P)₃ and Ca(NO₃)₂ with Ca(2+)/Al(3+) ratios of 1:1, 2:1, 4:1, and 7:1. XRD indicated that only LDH powders were formed for Ca(2+)/Al(3+) ratios of 2:1. However, both LDH and Ca(OH)₂ phases were produced at higher ratios. Both TEM and SEM observations indicated that the Ca-Al-NO₃ LDHs displayed a scaffold-like porous structure morphology rather than platelet-like particles. Upon annealing at 600 °C, a highly stable porous network structure of the CaO-based Ca-Al-O mixed oxide (CAMO), composed of CaO and Ca₁₂Al₁₄O₃₃, was still present. The CAMO exhibited high specific surface areas (up to 191 m(2)g(-1)) and a pore size distribution of 3-6 nm, which allowed rapid diffusion of CO₂ into the interior of the material, inducing fast carbonation/calcination and enhancing the sintering-resistant nature over multiple carbonation/calcination cycles for CO₂ absorption at 700 °C. Thermogravimetric analysis results indicated that a CO₂ capture capacity of approximately 49 wt% could be obtained with rapid absorption from the porous 7:1 CAMO sorbents by carbonation at 700 °C for 5 min. Also, 94-98% of the initial CO₂ capture capability was retained after 50 cycles of multiple carbonation/calcination tests. Therefore, the CAMO framework is a good isolator for preventing the aggregation of CaO particles, and it is suitable for long-term cyclic operation in high-temperature environments.

  7. Post-translational modifications of the cardiac Na channel: contribution of CaMKII-dependent phosphorylation to acquired arrhythmias

    PubMed Central

    Herren, Anthony W.; Bers, Donald M.

    2013-01-01

    The voltage-gated Na channel isoform 1.5 (NaV1.5) is the pore forming α-subunit of the voltage-gated cardiac Na channel, which is responsible for the initiation and propagation of cardiac action potentials. Mutations in the SCN5A gene encoding NaV1.5 have been linked to changes in the Na current leading to a variety of arrhythmogenic phenotypes, and alterations in the NaV1.5 expression level, Na current density, and/or gating have been observed in acquired cardiac disorders, including heart failure. The precise mechanisms underlying these abnormalities have not been fully elucidated. However, several recent studies have made it clear that NaV1.5 forms a macromolecular complex with a number of proteins that modulate its expression levels, localization, and gating and is the target of extensive post-translational modifications, which may also influence all these properties. We review here the molecular aspects of cardiac Na channel regulation and their functional consequences. In particular, we focus on the molecular and functional aspects of Na channel phosphorylation by the Ca/calmodulin-dependent protein kinase II, which is hyperactive in heart failure and has been causally linked to cardiac arrhythmia. Understanding the mechanisms of altered NaV1.5 expression and function is crucial for gaining insight into arrhythmogenesis and developing novel therapeutic strategies. PMID:23771687

  8. Local Structures around Si, Al and Na in Hydrated Silicate Glasses

    SciTech Connect

    Farges, Francois; Wispelaere, Sidoine de; Rossano, Stephanie; Munos, Manuel; Wilke, Max; Flank, Anne-Marie; Lagarde, Pierre

    2007-02-02

    XANES spectra were collected at the Si-, Al-, and Na K-edge in hydrous silicate glasses to understand the effect of water on the local structure around these cations. Around network forming Si and Al, no drastic changes are observed. Around Na, the dissolution of water creates more ordered environments in Al-bearing glasses and less ordered environment in Al-free glasses. Ab-initio XANES calculations were undertaken to understand the structural origins for these features. Based on these results, a bond valence model was refined that considers not only the present XANES experiments and models but also NMR information. The double percolation model refined explains, among others, the explosive properties of water-bearing hydrous melts, at the origin of a number of cataclysmic eruptions in subduction zones.

  9. NaF-KF-AlF3 System: Phase Transition in K2NaAl3F12 Ternary Fluoride.

    PubMed

    Kirik, Sergei D; Zaitseva, Yulia N; Leshok, Darya Yu; Samoilo, Alexandr S; Dubinin, Petr S; Yakimov, Igor S; Simakov, Dmitry A; Gusev, Alexandr O

    2015-06-15

    Phase formation in the NaF-KF-AlF3 system, in the vicinity of the K2NaAl3F12 composition, has been studied. The samples have been prepared by melting the starting components at 650 °C. A new phase has been revealed, which appeared to be a low-temperature form of the well-known K2NaAl3F12 ternary fluoride obtained by the hydrothermal synthesis method. The high-temperature form melts at 598 °C and is stable in a narrow temperature region of about 15 deg below the melting point. Thermal analysis, high temperature X-ray diffraction, IR-spectroscopy, X-ray fluorescence, and X-ray powder diffraction crystal structure analysis have been applied to study the composition, crystal structure, and thermal properties of the low-temperature phase. The crystal structure consists of trigonal-hexagonal two-dimensional (2D) grids built from the [AlF6] octahedra connected via vertices. The 2D grids have a specific wave-like conformation with a wavelength of 11.88 Å and an amplitude of 0.46 Å. There is a shift of the adjacent grids relative to each other. Because of this shift, the space between the grids changes. The shift leads to the formation of pores adapted to potassium and sodium ions. The reasons for the wave-like structure of layers are discussed. It is shown that the two polymorphic forms differ in the order of cation occupations.

  10. Density-functional calculations of the surface tension of liquid Al and Na

    NASA Technical Reports Server (NTRS)

    Stroud, D.; Grimson, M. J.

    1984-01-01

    Calculations of the surface tensions of liquid Al and Na are described using the full ionic density functional formalism of Wood and Stroud (1983). Surface tensions are in good agreement with experiment in both cases, with results substantially better for Al than those found previously in the gradient approximation. Preliminary minimization with respect to surface profile leads to an oscillatory profile superimposed on a nearly steplike ionic density disribution; the oscillations have a wavellength of about a hardsphere diameter.

  11. Petrography and classification of Ca, Al-rich and olivine-rich inclusions in the Allende CV3 chondrite

    NASA Technical Reports Server (NTRS)

    Kormacki, A. S.; Wood, J. A.

    1984-01-01

    The results of a detailed, systematic petrographic survey of Ca, Al-rich and olivine-rich inclusions in the Allende CV3 chondrite are reported, and a new classification system based on clearly defined and readily applied petrographic criteria is presented. Most Allende inclusions are aggregates containing one or more of three distinct constituents: (1) rimmed concentric objects enriched in Al- and Ti-rich oxide minerals and various amounts of Ca-rich silicates; (2) porous, 'fine-grained' chaotic material enriched in Ca-rich silicates, especially clinopyroxenes and garnets; and (3) porous, 'fine-grained', mafic inclusion matrix, enriched in olivine, pyroxene, and feldspathoids. Two texturally distinct varieties of inclusions consist primarily of inclusion matrix: unrimmed olivine aggregates and rimmed olivine aggregates. Ca, Al-rich inclusions are classified on the basis of the size and abundance of their constituent concentric objects. Some fundamental relationships among Allende inclusions that previusly have not been emphasized are discussed.

  12. Control of mean ionic radius at Ca site by Sr co-doping for Ce doped LiCaAlF6 single crystals and the effects on optical and scintillation properties

    NASA Astrophysics Data System (ADS)

    Yokota, Yuui; Yamaji, Akihiro; Kurosawa, Shunsuke; Kamada, Kei; Yoshikawa, Akira

    2014-10-01

    Sr co-doped Ce:LiCaAlF6 [Ce:Li(Ca,Sr)AlF6] crystals with various Ca/Sr ratios were grown by a micro-pulling-down (μ-PD) method and effects of Sr co-doping on crystal structure, chemical composition, optical and scintillation properties for Ce:LiCaAlF6 crystals were investigated as a neutron scintillator. High transparent Ce2%:Li(Ca,Sr)AlF6 crystals with 2% and 5% Sr contents were obtained while Ce2%:Li(Ca,Sr)AlF6 crystals with 10% and 20% Sr contents included milky parts in the crystals. a- and c-axis lengths of Ce:Li(Ca,Sr)AlF6 phase systematically increased with an increase of Sr content. In addition to the emission at 284 and 308 nm from Ce3+ ion, emission peaks at 367 nm appeared by Sr co-doping.

  13. The reduction of chlorine on carbon in AlCl3-KCl-NaCl melts

    NASA Technical Reports Server (NTRS)

    Holleck, G. L.

    1971-01-01

    Using a rotating vitreous carbon disk electrode, the kinetic parameters for chlorine reduction in an AlCl3-KCl-NaCl (57.5-12.5-30 mol percent) melt were determined. It was found that the reduction of chlorine occurs according to two paths, with the first step probably being rate-determining.

  14. Profile of L-type Ca2+ current and Na+/Ca2+ exchange current during cardiac action potential in ventricular myocytes

    PubMed Central

    Banyasz, Tamas; Horvath, Balazs; Jian, Zhong; Izu, Leighton T.; Chen-Izu, Ye

    2011-01-01

    Objective The L-type Ca2+ current (ICa,L) and the Na+/Ca2+ exchange current (INCX) are major inward currents that shape the cardiac action potential (AP). Previously, the profile of these currents during AP was determined from voltage-clamp experiments that used Ca2+ buffer. In this study, we aimed to obtain direct experimental measurement of these currents during cardiac AP with Ca2+ cycling. Method A newly developed AP-clamp sequential dissection method was used to record ionic currents in guinea pig ventricular myocytes under a triad of conditions: using the cell’s own AP as the voltage command, using internal and external solutions that mimic the cell’s ionic composition and, importantly, no exogenous Ca2+ buffer was used. Results The nifedipine-sensitive current (INIFE), which is composed of ICa,L and INCX, revealed hitherto unreported features during AP with Ca2+ cycling in the cell. We identified two peaks in the current profile followed by a long residual current extending beyond the AP, coinciding with a residual depolarization. The second peak and the residual current become apparent only when Ca2+ is not buffered. Pharmacological dissection of INIFE using SEA0400 shows that ICa,L is dominant during phase-1&2 whereas INCX contributes significantly to the inward current at phase-3&4 of AP. Conclusion These data provide the first direct experimental visualization of ICa,L and INCX during cardiac AP and Ca2+ cycle. The residual current reported here can serve as a potential substrate for afterdepolarizations when increased under pathologic conditions. PMID:21884673

  15. An IR Study of Benzoyl Chloride Adsorbed on KA, NaA, and CaA Zeolites

    NASA Astrophysics Data System (ADS)

    Bardakçı, B.; Bahçeli, Semiha

    2005-09-01

    Infrared spectroscopy has been used to investigate the adsorption of liquid benzoyl chloride on A-type zeolites. The data show that at room temperature the Fermi resonance phenomenon occurs in the adsorption on KA, NaA and CaA zeolites which are little acidic aluminosilicates.

  16. Stability of Na-, K-, and Ca-montmorillonite at high temperatures and pressures: a Monte Carlo simulation.

    PubMed

    de Pablo, Liberto; Chávez, Maria L; de Pablo, Juan J

    2005-11-08

    Monte Carlo grand canonical molecular simulations on the hydration of Na-, K-, and Ca-montmorillonite show that between 333 and 533 K and 300-1300 bar Na-montmorillonite forms stable one-layer hydrates of d(001) spacings 12.64-12.38 Angstroms, K-montmorillonite of 12.78-12.59 Angstroms, and Ca-montmorillonite of 12.48-12.32 Angstroms. A two-layer hydrate of 14.80 Angstroms occurs for Na-montmorillonite at 533 K and 1300 bar, for K-montmorillonite of 15.32 Angstroms at 533 K and 1300 bar and of 14.74 Angstroms at 533 K and 2000 bar, and for Ca-montmorillonite of 13.83 Angstroms at 473 K and 1000 bar. Three-layer hydrates may possibly form within these same ranges. Outside of them, one-layer hydrates simulate as the only stable hydrates. In sedimentary basins, the two-layer hydrate of Ca-montmorillonite will locate at 6.7 km depth and those of Na- and K-montmorillonite at 8.7 km depth; above and below these depths, the one-layer hydrates are the stable phases.

  17. Diamide: positive inotropic effect in isolated atria and inhibition of Na+/Ca2+ exchange in cardiomyocytes.

    PubMed

    Antolini, M; Debetto, P; Trevisi, L; Luciani, S

    1991-02-01

    The influence of frequency of stimulation and external calcium on the positive inotropic response of guinea-pig left atria to diamide and the inhibitory action on Na+/Ca2+ exchange activity of rat cardiomyocytes by this oxidant of sulphhydryl groups have been investigated. Diamide (50-500 microM) induces a concentration-dependent positive inotropic effect which is more pronounced when atria are driven at 1.0 Hz rather than at 0.5 and 0.1 Hz, and are bathed in 2.72 mM rather than in 1.36 mM external calcium. A decrease in the positive inotropic effect at 35 degrees C with respect to 29 degrees C is also observed. In addition, diamide in positive inotropic concentrations (100-300 microM) significantly reduces Na+/Ca2+ exchange activity and cytoplasmic glutathione levels in adult rat cardiomyocytes. The thiol reducing agent dithiothreitol either reverses or prevents diamide effects both in isolated atria and cardiomyocytes, suggesting that the actions of diamide are correlated to its property to oxidize sulphhydryl groups to disulphides. In view of the functional importance of Na+/Ca2+ exchange in myocardial contractility, it is proposed that diamide may increase the heart force of contraction by an inhibition of the sarcolemmal Na+/Ca2+ exchange activity.

  18. Relationship between NaCl- and H2O2-Induced Cytosolic Ca2+ Increases in Response to Stress in Arabidopsis

    PubMed Central

    Ye, Rui; Xue, Yan; Chen, Amelia; An, Lizhe; Pei, Zhen-Ming

    2013-01-01

    Salinity is among the environmental factors that affect plant growth and development and constrain agricultural productivity. Salinity stress triggers increases in cytosolic free Ca2+ concentration ([Ca2+]i) via Ca2+ influx across the plasma membrane. Salinity stress, as well as other stresses, induces the production of reactive oxygen species (ROS). It is well established that ROS also triggers increases in [Ca2+]i. However, the relationship and interaction between salinity stress-induced [Ca2+]i increases and ROS-induced [Ca2+]i increases remain poorly understood. Using an aequorin-based Ca2+ imaging assay we have analyzed [Ca2+]i changes in response to NaCl and H2O2 treatments in Arabidopsis thaliana. We found that NaCl and H2O2 together induced larger increases in [Ca2+]i in Arabidopsis seedlings than either NaCl or H2O2 alone, suggesting an additive effect on [Ca2+]i increases. Following a pre-treatment with either NaCl or H2O2, the subsequent elevation of [Ca2+]i in response to a second treatment with either NaCl or H2O2 was significantly reduced. Furthermore, the NaCl pre-treatment suppressed the elevation of [Ca2+]i seen with a second NaCl treatment more than that seen with a second treatment of H2O2. A similar response was seen when the initial treatment was with H2O2; subsequent addition of H2O2 led to less of an increase in [Ca2+]i than did addition of NaCl. These results imply that NaCl-gated Ca2+ channels and H2O2-gated Ca2+ channels may differ, and also suggest that NaCl- and H2O2-evoked [Ca2+]i may reduce the potency of both NaCl and H2O2 in triggering [Ca2+]i increases, highlighting a feedback mechanism. Alternatively, NaCl and H2O2 may activate the same Ca2+ permeable channel, which is expressed in different types of cells and/or activated via different signaling pathways. PMID:24124535

  19. Refinement of Eutectic Si in High Purity Al-5Si Alloys with Combined Ca and P Additions

    NASA Astrophysics Data System (ADS)

    Ludwig, Thomas Hartmut; Li, Jiehua; Schaffer, Paul Louis; Schumacher, Peter; Arnberg, Lars

    2015-01-01

    The effects of combined additions of Ca and P on the eutectic Si in a series of high purity Al-5 wt pct Si alloys have been investigated with the entrained droplet technique and complementary sets of conventional castings. Differential scanning calorimetry (DSC) and thermal analysis were used to investigate the eutectic droplet undercooling and the recalescence undercooling, respectively. Optical microscopy, SEM, EPMA, and TEM were employed to characterize the resultant microstructures. It was found that 250 ppm Ca addition to Al-5Si wt pct alloys with higher P contents leads to a significant increase of the eutectic droplet undercooling. For low or moderate cooling rates, the TEM results underline that Ca additions do not promote Si twinning. Thus, a higher twin density cannot be expected in Ca containing Al-Si alloys after, e.g., sand casting. Consequently, a refinement of the eutectic Si from coarse flake-like to fine plate-like structure, rather than a modification of the eutectic Si to a fibrous morphology, was achieved. This strongly indicates that the main purpose of Ca additions is to counteract the coarsening effect of the eutectic Si imposed by higher P concentrations. Significant multiple Si twinning was observed in melt-spun condition; however, this can be attributed to the higher cooling rate. After DSC heating (slow cooling), most of Si twins disappeared. Thus, the well-accepted impurity-induced twinning mechanism may be not valid in the case of Ca addition. The possible refinement mechanisms were discussed in terms of nucleation and growth of eutectic Si. We propose that the pre-eutectic Al2Si2Ca phase and preferential formation of Ca3P2 deactivate impurity particles, most likely AlP, poisoning the nucleation sites for eutectic Si.

  20. Fluoride gastrointestinal absorption from Na2FPO3/CaCO3- and NaF/SiO2-based toothpastes.

    PubMed

    Falcão, A; Tenuta, L M A; Cury, J A

    2013-01-01

    Depending on toothpaste formulation, part of the fluoride is insoluble and would not be totally absorbable in the gastrointestinal tract, thus changing dental fluorosis risk estimation. This hypothesis was tested with formulations with either all fluoride in a soluble form (NaF/SiO2-based toothpaste, 1,100 µg F/g as labeled, 1,129.7 ± 49.4 µg F/g soluble fluoride as analyzed) or with around 20% of insoluble fluoride (Na2FPO3/CaCO3-based toothpaste, 1,450 µg F/g as labeled, 1,122.4 ± 76.4 µg F/g soluble fluoride as analyzed). Toothpastes were evaluated either fresh or after accelerated aging, which increased insoluble fluoride to 40% in the Na2FPO3/CaCO3-based toothpaste. In a blind, crossover clinical trial conducted in five legs, 20 adult volunteers ingested 49.5 µg of total fluoride/kg body weight from each formulation or purified water (control). Whole saliva and urine were collected as bioavailability indicators, and pharmacokinetics parameters calculated showed significantly (p < 0.05) lower fluoride bioavailability for Na2FPO3/CaCO3 toothpaste, which was reduced further after aging. A significant correlation between the amount of soluble fluoride ingested, but not total fluoride, and fluoride bioavailability was found (r = 0.57, p < 0.0001). The findings suggest that the estimated fluorosis risk as a result of ingestion of Na2FPO3/CaCO3-based toothpastes should be calculated based on the toothpaste's soluble rather than total fluoride concentration.

  1. Photoluminescence and thermoluminescence studies of CaAl2O4:Dy(3+) phosphor.

    PubMed

    Ziyauddin, Mohammad; Tigga, Shalinta; Brahme, Nameeta; Bisen, D P

    2016-02-01

    Calcium aluminate phosphors activated by Dy(3+) have been prepared by a combustion method at a temperature of 600°C. Photoluminescence (PL) and thermoluminescence (TL) properties of gamma-irradiated Dy-doped calcium aluminate were investigated. The PL spectrum shows a broad peak around 488 nm and 573 nm, under 347 nm excitation. Thermoluminescence studies were performed for different concentrations of Dy. Optimum intensity of photoluminescence was found for 0.02 mol% concentration of Dy. It was found that initially the peak TL intensity increases with increasing concentration of Dy in the CaAl2O4 host, attains a maximum value for 0.05 mol% concentration and decreases with further increase in the doping concentration due to concentration quenching.

  2. High Density Hydrogen Storage System Demonstration Using NaAlH4 Based Complex Compound Hydrides

    SciTech Connect

    Daniel A. Mosher; Xia Tang; Ronald J. Brown; Sarah Arsenault; Salvatore Saitta; Bruce L. Laube; Robert H. Dold; Donald L. Anton

    2007-07-27

    This final report describes the motivations, activities and results of the hydrogen storage independent project "High Density Hydrogen Storage System Demonstration Using NaAlH4 Based Complex Compound Hydrides" performed by the United Technologies Research Center under the Department of Energy Hydrogen Program, contract # DE-FC36-02AL67610. The objectives of the project were to identify and address the key systems technologies associated with applying complex hydride materials, particularly ones which differ from those for conventional metal hydride based storage. This involved the design, fabrication and testing of two prototype systems based on the hydrogen storage material NaAlH4. Safety testing, catalysis studies, heat exchanger optimization, reaction kinetics modeling, thermochemical finite element analysis, powder densification development and material neutralization were elements included in the effort.

  3. Experimental study of the astrophysically important 23Na(α ,p )26Mg and 23Na(α ,n )26Al reactions

    NASA Astrophysics Data System (ADS)

    Avila, M. L.; Rehm, K. E.; Almaraz-Calderon, S.; Ayangeakaa, A. D.; Dickerson, C.; Hoffman, C. R.; Jiang, C. L.; Kay, B. P.; Lai, J.; Nusair, O.; Pardo, R. C.; Santiago-Gonzalez, D.; Talwar, R.; Ugalde, C.

    2016-12-01

    The 23Na(α ,p )26Mg and 23Na(α ,n )26Al reactions are important for our understanding of the 26Al abundance in massive stars. The aim of this work is to report on a direct and simultaneous measurement of these astrophysically important reactions using an active target system. The reactions were investigated in inverse kinematics using 4He as the active target gas in the detector. We measured the excitation functions in the energy range of about 2 to 6 MeV in the center of mass. We have found that the cross sections of the 23Na(α ,p )26Mg and the 23Na(α ,n )26Al reactions are in good agreement with previous experiments and with statistical-model calculations. The astrophysical reaction rate of the 23Na(α ,n )26Al reaction has been reevaluated and it was found to be larger than the recommended rate.

  4. Praziquantel has no direct effect on (Na(+)+K+)-ATPases and (Ca2(+)-Mg2+)ATPases of Schistosoma mansoni.

    PubMed

    Cunha, V M; Noël, F

    1997-01-01

    Therapeutic concentrations of praziquantel produce a rapid and intense contraction of the human flatworm Schistosoma mansoni. As an action on ATPases responsible for calcium homeostasis arises as a possible explanation for the molecular mechanism of this effect, we tested here the effect of praziquantel on different preparations from male adult worms that were previously characterized for their content in (Na(+)+K+)-ATPase and (Ca2(+)-Mg2+)ATPase activities from different origins. Concentrations as high as 100 microM praziquantel did not inhibit (Na(+)+K+)-ATPase from tegument and carcass nor (Ca2(+)-Mg2+)ATPase from heterogeneous (P1) and microsomal (P4) fractions. As 100 microM praziquantel was also without effect on calcium permeability of microsomal vesicles actively loaded with 45Ca2+, the present results discard three hypotheses recently raised for the mechanism of praziquantel-induced contraction of S. mansoni.

  5. Metabolic regulation of the squid nerve Na(+)/Ca (2+) exchanger: recent developments.

    PubMed

    Beaugé, Luis; Dipolo, Reinaldo; Bollo, Mariana; Cousido, Alexandra; Berberián, Graciela; Podjarny, Alberto

    2013-01-01

    In squid nerves, MgATP modulation of the Na(+)/Ca(2+) exchanger requires the presence of a cytosolic protein which becomes phosphorylated during the process. This factor has been recently identified. Mass spectroscopy and Western blot analysis established that it is a member of the lipocalin superfamily of lipid-binding proteins (LBP or FABP) of 132 amino acids. We called it regulatory protein of squid nerve sodium/calcium exchanger (ReP1-NCXSQ, access to GenBank EU981897).ReP1-NCXSQ was cloned, expressed, and purified. Circular dichroism, far-UV, and infrared spectroscopy suggest a secondary structure, predominantly of beta-sheets. The tertiary structure prediction provides ten beta-sheets and two alpha-helices, characteristic of most of LPB. Functional experiments showed that, to be active, ReP1-NCXSQ must be phosphorylated by MgATP, through the action of a kinase present in the plasma membrane. Moreover, PO4-ReP1-NCXSQ can stimulate the exchanger in the absence of ATP. An additional crucial observation was that, in proteoliposomes containing only the purified Na(+)/Ca(2+) exchanger, PO4-ReP1-NCXSQ promotes activation; therefore, this upregulation has no other requirement than a lipid membrane and the incorporated exchanger protein.Recently, we solved the crystal structure of ReP1-NCXSQ which was as predicted: a "barrel" consisting of ten beta-sheets and two alpha-helices. Inside the barrel is the fatty acid coordinated by hydrogen bonds with Arg126 and Tyr128. Point mutations showed that neither Tyr20Ala, Arg58Val, Ser99Ala, nor Arg126Val is necessary for protein phosphorylation or activity. On the other hand, Tyr128 is essential for activity but not for phosphorylation. We can conclude that (1) for the first time, a role of an LBP is demonstrated in the metabolic regulation of an ion exchanger; (2) phosphorylation of this LBP can be separated from the activation capacity; and (3) Tyr128, a candidate to coordinate lipid binding inside the barrel, is essential

  6. New honeycomb iridium(V) oxides: NaIrO3 and Sr3CaIr2O9.

    PubMed

    Wallace, David C; McQueen, Tyrel M

    2015-12-21

    We report the structures and physical properties of two new iridates, NaIrO3 and Sr3CaIr2O9, both of which contain continuous two-dimensional honeycomb connectivity. NaIrO3 is produced by room temperature oxidative deintercalation of sodium from Na2IrO3, and contains edge-sharing IrO6 octahedra that form a planar honeycomb lattice. Sr3CaIr2O9, produced via conventional solid-state synthesis, hosts a buckled honeycomb lattice with novel corner-sharing connectivity between IrO6 octahedra. Both of these new compounds are comprised of Ir(5+) (5d(4)) and exhibit negligible magnetic susceptibility. They are thus platforms to investigate the origin of the nonmagnetic behavior exhibited by Ir(5+) oxides, and provide the first examples of a J = 0 state on a honeycomb lattice.

  7. Longitudinal distribution of Na+ and Ca2+ channels and beta-adrenoceptors on the sarcolemmal membrane of frog cardiomyocytes.

    PubMed Central

    Jurevicius, J; Fischmeister, R

    1997-01-01

    1. The distribution of L-type Ca2+ and tetrodotoxin-sensitive Na+ channels and of beta-adrenergic receptors was examined in frog ventricular myocytes using the whole-cell patch-clamp technique and a double capillary for extracellular microperfusion. 2. Rod-shaped cells (250-300 microns long) were sealed at both ends to two patch-clamp pipettes and positioned transversally at different positions between the mouths of two microcapillaries separated by a thin wall. A combination of nifedipine (1 microM) and tetrodotoxin (0.3 microM) (blocking solution) was added to one capillary in order to inhibit macroscopic Ca2+ and Na+ currents (Ica and INa, respectively) in the part of the cell exposed to this capillary. 3. Moving the cell in 10-20 microns steps from the control capillary to the capillary containing the blocking solution induced step decreases in Ica and INa amplitudes. Complete block of both currents occurred when the entire cell was exposed to the blocking solution. 4. Each step decrease in current was due to the loss of activity of the functional Ca2+ and Na+ channels present in the slice of sarcolemmal membrane newly exposed to the blocking solution. These step current changes allowed longitudinal mapping of current density for Ca2+ and Na+ channels on the sarcolemmal membrane. 5. Addition of a submaximal concentration of isoprenaline (10 nM) to the control capillary induced a local increase in Ica which enabled examination of the distribution of functional beta-adrenergic receptors as well. 6. Our results demonstrate that Ca2+ and Na+ channels and beta-adrenergic receptors are equally and essentially uniformly distributed on the sarcolemmal of frog ventricular myocytes. PMID:9379404

  8. Regulatory Effects of Ca2+ and H+ on the Rat Chorda Tympani Response to NaCl and KCl.

    PubMed

    DeSimone, John A; Phan, Tam-Hao T; Mummalaneni, Shobha; Rhyu, Mee-Ra; Heck, Gerard L; Lyall, Vijay

    2015-07-01

    Modulatory effects of pHi and [Ca(2+)]i on taste receptor cell (TRC) epithelial sodium channel (ENaC) were investigated by monitoring chorda tympani (CT) responses to NaCl and KCl at various lingual voltages, before and after lingual application of ionomycin and with 0-10mM CaCl2 in the stimulus and rinse solutions adjusted to pHo 2.0-9.7. 0.1 and 0.5M KCl responses varied continuously with voltage and were fitted to an apical ion channel kinetic model using the same parameters. ENaC-dependent NaCl CT response was fitted to the same channel model but with parameters characteristic of ENaC. A graded increase in TRC [Ca(2+)]i decreased the ENaC-dependent NaCl CT response, and inhibited and ultimately eliminated its pH sensitivity. CT responses to KCl were pHi- and [Ca(2+)]i-independent. Between ±60 mV applied lingual potential, the data were well described by a linear approximation to the nonlinear channel equation and yielded 2 parameters, the open-circuit response and the negative of the slope of the line in the CT response versus voltage plot, designated the response conductance. The ENaC-dependent NaCl CT response conductance was a linear function of the open-circuit response for all pHi-[Ca(2+)]i combinations examined. Analysis of these data shows that pHi and [Ca(2+)]i regulate TRC ENaC exclusively through modulation of the maximum CT response.

  9. Phase equilibria in the P(2)O(5)-CaO-CaF(2)-NaF-H(2)O quinary system and the formation of apatite

    NASA Astrophysics Data System (ADS)

    Martin, Roger Isaac

    incongruently with respect to CaFsb2. Therefore, treatment of dentin and tooth enamel with fluoride leads to the formation of fluorosis because the solution first becomes supersaturated with CaFsb2. Based on thermodynamics, the conversion of hydroxyapatite to fluoroapatite cannot be a single exchange of fluoride for hydroxl. CaHPOsb4 hydrolysis and equilibrium in sodium fluoride solutions at 37.4sp°C reveal the added effect of sodium on the system. Sodium phosphate species form and overcome CaHPOsb4 incongruency. At initial NaF concentrations greater than 150 mM, NaF species rise and may overcome fluoroapatite incongruency.

  10. Low-Mg(2+) treatment increases sensitivity of voltage-gated Na(+) channels to Ca(2+)/calmodulin-mediated modulation in cultured hippocampal neurons.

    PubMed

    Guo, Feng; Zhou, Pei-Dong; Gao, Qing-Hua; Gong, Jian; Feng, Rui; Xu, Xiao-Xue; Liu, Shu-Yuan; Hu, Hui-Yuan; Zhao, Mei-Mi; Adam, Hogan-Cann; Cai, Ji-Qun; Hao, Li-Ying

    2015-04-15

    Culture of hippocampal neurons in low-Mg(2+) medium (low-Mg(2+) neurons) results in induction of continuous seizure activity. However, the underlying mechanism of the contribution of low Mg(2+) to hyperexcitability of neurons has not been clarified. Our data, obtained using the patch-clamp technique, show that voltage-gated Na(+) channel (VGSC) activity, which is associated with a persistent, noninactivating Na(+) current (INa,P), was modulated by calmodulin (CaM) in a concentration-dependent manner in normal and low-Mg(2+) neurons, but the channel activity was more sensitive to Ca(2+)/CaM regulation in low-Mg(2+) than normal neurons. The increased sensitivity of VGSCs in low-Mg(2+) neurons was partially retained when CaM12 and CaM34, CaM mutants with disabled binding sites in the N or C lobe, were used but was diminished when CaM1234, a CaM mutant in which all four Ca(2+) sites are disabled, was used, indicating that functional Ca(2+)-binding sites from either lobe of CaM are required for modulation of VGSCs in low-Mg(2+) neurons. Furthermore, the number of neurons exhibiting colocalization of CaM with the VGSC subtypes NaV1.1, NaV1.2, and NaV1.3 was significantly higher in low- Mg(2+) than normal neurons, as shown by immunofluorescence. Our main finding is that low-Mg(2+) treatment increases sensitivity of VGSCs to Ca(2+)/CaM-mediated regulation. Our data reveal that CaM, as a core regulating factor, connects the functional roles of the three main intracellular ions, Na(+), Ca(2+), and Mg(2+), by modulating VGSCs and provides a possible explanation for the seizure discharge observed in low-Mg(2+) neurons.

  11. An XRD and Electron Diffraction Study of Cristobalite-Related Phases in the NaAlO 2-NaAlSiO 4System

    NASA Astrophysics Data System (ADS)

    Thompson, John G.; Melnitchenko, Alexandra; Palethorpe, Stephen R.; Withers, Ray L.

    1997-06-01

    A detailed study of the sodium aluminate-carnegieite system (Na2-xAl2-xSixO4, 0≤x≤1) at temperatures between 800 and 1300°C has revealed five previously unreported phases. All of the new phases can be described as modulated variants of an underlyingβ-cristobalite parent structure. Atx≈0.05 theγ-NaAlO2-type structure (P41212,a=1/2ap,c=cp) (p=parent) is stabilized to room-temperature; atx≈0.2-0.45 an orthorhombic (Pbca,a=2ap,b=2bp,c=1/2cp) KGaO2-type structure is obtained, except atx≈0.35 where a new tetragonal (P41212,a=2ap,c=cp) phase is observed; atx≈0.5-0.6 a new cubic (P213,a=2ap) phase is obtained; atx≈0.7-0.9 a new orthorhombic (Pc21b,a=2ap,b=2bp,c=2cp) phase is obtained. XRD and electron diffraction data, refined unit cell dimensions, and the phase relationships at 1300°C are presented. The proposed space group symmetries are based on observed extinction conditions and constraints provided by a modulated structure description of the new phases. The materials are prepared by gel synthesis followed by solid state reaction in air.

  12. Regulation of the rabbit ileal brush-border Na+/H+ exchanger by an ATP-requiring Ca++/calmodulin-mediated process.

    PubMed Central

    Rood, R P; Emmer, E; Wesolek, J; McCullen, J; Husain, Z; Cohen, M E; Braithwaite, R S; Murer, H; Sharp, G W; Donowitz, M

    1988-01-01

    Brush-border vesicles purified from rabbit ileal villus cells were used to evaluate how Ca++/calmodulin (CaM) regulates the neutral linked NaCl absorptive process, part of which is a Na+/H+ exchanger. After freezing and thawing to allow incorporation of macromolecules into the vesicles, the effect of Ca++/CaM on brush-border Na+ uptake with an acid inside pH gradient, and on Na+/H+ exchange was determined. Freezing and thawing vesicles with 0.85 microM free Ca++ plus 5 microM exogenous CaM failed to alter Na+/H+ exchange as did the addition of exogenous ATP plus an ATP regenerating system, which was sufficient to elevate intravesicular ATP to 47 microM from a basal level of 0.4 microM. However, the combination of Ca++/CaM plus ATP inhibited Na+ uptake in the presence of an acid inside pH gradient and inhibited Na+/H+ exchange, while Na+ uptake in the absence of a pH gradient was not altered. This effect required a hydrolyzable form of ATP, and did not occur when the nonhydrolyzable ATP analogue, AMP-PNP, replaced ATP. Under the identical intravesicular conditions used for the transport studies, Ca++ (0.85 microM) plus exogenous CaM (5 microM), in the presence of magnesium plus ATP, increased phosphorylation of five brush-border peptides. These data are consistent with Ca++/CaM acting via phosphorylation to regulate the ileal brush-border Na+/H+ exchanger. PMID:2843567

  13. Model of Silicon Refining During Tapping: Removal of Ca, Al, and Other Selected Element Groups

    NASA Astrophysics Data System (ADS)

    Olsen, Jan Erik; Kero, Ida T.; Engh, Thorvald A.; Tranell, Gabriella

    2016-12-01

    A mathematical model for industrial refining of silicon alloys has been developed for the so-called oxidative ladle refining process. It is a lumped (zero-dimensional) model, based on the mass balances of metal, slag, and gas in the ladle, developed to operate with relatively short computational times for the sake of industrial relevance. The model accounts for a semi-continuous process which includes both the tapping and post-tapping refining stages. It predicts the concentrations of Ca, Al, and trace elements, most notably the alkaline metals, alkaline earth metal, and rare earth metals. The predictive power of the model depends on the quality of the model coefficients, the kinetic coefficient, τ, and the equilibrium partition coefficient, L for a given element. A sensitivity analysis indicates that the model results are most sensitive to L. The model has been compared to industrial measurement data and found to be able to qualitatively, and to some extent quantitatively, predict the data. The model is very well suited for alkaline and alkaline earth metals which respond relatively fast to the refining process. The model is less well suited for elements such as the lanthanides and Al, which are refined more slowly. A major challenge for the prediction of the behavior of the rare earth metals is that reliable thermodynamic data for true equilibrium conditions relevant to the industrial process is not typically available in literature.

  14. Model of Silicon Refining During Tapping: Removal of Ca, Al, and Other Selected Element Groups

    NASA Astrophysics Data System (ADS)

    Olsen, Jan Erik; Kero, Ida T.; Engh, Thorvald A.; Tranell, Gabriella

    2017-04-01

    A mathematical model for industrial refining of silicon alloys has been developed for the so-called oxidative ladle refining process. It is a lumped (zero-dimensional) model, based on the mass balances of metal, slag, and gas in the ladle, developed to operate with relatively short computational times for the sake of industrial relevance. The model accounts for a semi-continuous process which includes both the tapping and post-tapping refining stages. It predicts the concentrations of Ca, Al, and trace elements, most notably the alkaline metals, alkaline earth metal, and rare earth metals. The predictive power of the model depends on the quality of the model coefficients, the kinetic coefficient, τ, and the equilibrium partition coefficient, L for a given element. A sensitivity analysis indicates that the model results are most sensitive to L. The model has been compared to industrial measurement data and found to be able to qualitatively, and to some extent quantitatively, predict the data. The model is very well suited for alkaline and alkaline earth metals which respond relatively fast to the refining process. The model is less well suited for elements such as the lanthanides and Al, which are refined more slowly. A major challenge for the prediction of the behavior of the rare earth metals is that reliable thermodynamic data for true equilibrium conditions relevant to the industrial process is not typically available in literature.

  15. Lead exchange into zeolite and clay minerals: A [sup 29]Si, [sub 27]Al, [sup 23]Na solid-state NMR study

    SciTech Connect

    Liang, J.J.; Sherriff, B.L. )

    1993-08-01

    Chabazite, vermiculite, montmorillonite, hectorite, and kaolinite were used to remove Pb, through ion exchange, from 0.01 M aqueous Pb(NO[sub 3])[sub 2] solutions. These minerals contained 27 (Na-chabazite), 16, 9, 9, and 0.5 wt % of Pb, respectively, after equilibration with the solutions. Ion exchange reached equilibrium within 24 h for Na-chabazite and vermiculite, but in less than 5 min for montmorillonite and hectorite. Na-chabazite took up more Pb than natural (Ca, Na)-chabazite (7 wt % Pb), whereas no such difference was observed in different cation forms of the clay minerals. Calcite impurities, associated with the clay minerals, effectively removed Pb from the aqueous solutions by the precipitation of cerussite (PbCO[sub 3]). [sup 29]Si, [sup 27]Al, and [sup 23]Na magic angle spinning (MAS) nuclear magnetic resonance (NMR), [sup 23]Na double rotation (DOR) NMR, and [sup 23]Na variable-temperature MAS NMR were used to study the ion exchange mechanisms. In Na-chabazite, cations in all three possible sites take part in the fast chemical exchange. The chemical exchange passes from the fast exchange regime to the slow regime at [minus]80 to [minus]100[degrees]C. One site contains a relatively low population of exchangeable cations. The other two more shielded sites contain most of the exchangeable cation. The exchangeable cations in chabazite and vermiculite were found to be close to the SiO[sub 4] and AlO[sub 4] tetrahedra, while those in the other clay minerals were more distant. Two sites (or groups of sites) for exchangeable cations were observed in hectorite. Lead tended to occupy the one which corresponds to the [minus]8 ppM peak on the [sup 23]Na MAS NMR spectrum. The behavior of the exchangeable cations in the interlayer sites was similar in all the clay minerals studied. 27 refs., 7 figs., 4 tabs.

  16. Effects of copper on the preparation and characterization of Na-Ca-P borate glasses.

    PubMed

    Shailajha, S; Geetha, K; Vasantharani, P; Sheik Abdul Kadhar, S P

    2015-03-05

    Glasses in the system Na2O-CaO-B2O3-P2O5: CuO have been prepared by melt quenching at 1200°C and rapidly cooling at room temperature. The structural, optical and thermal properties have been investigated using X-ray diffraction (XRD), ultraviolet-visible (UV-VIS) spectroscopy, thermogravimetric-differential thermal analysis (TG-DTA), Fourier transform infrared (FTIR) spectroscopy, high resolution scanning electron microscopy (HRSEM) with energy dispersive X-ray (EDX) spectroscopy and high resolution transmission electron microscope (HRTEM) with energy dispersive X-ray (EDAX). The amorphous and crystalline nature of these samples was verified by XRD. Glass transition, crystallization and thermal stability were determined by TG-DTA investigations. Direct optical energy band gaps before and after doping with different percents of copper oxide were evaluated from 4.81eV to 2.99eV indicated the role of copper in the glassy matrix by UV spectra. FTIR spectrum reveals characteristic absorption bands due to various groups of triangular and tetrahedral borate network. Due to the amorphous nature, the particles like agglomerates on the glass surface were investigated by the HRSEM analysis. The crystalline nature of the samples in XRD is confirmed by SAED pattern using HRTEM.

  17. Selectivity coefficient for Ca/Na ion exchange in highly compacted bentonite

    NASA Astrophysics Data System (ADS)

    Karnland, Ola; Birgersson, Martin; Hedström, Magnus

    Bentonite clay is proposed as buffer material around the waste canisters and as tunnel backfill material in several concepts for disposal of radioactive waste. The distribution of charge compensating cations in the bentonite is of interest for several reasons, one being possible release of colloid particles from the bentonite to groundwater with very low ionic strength. The cation distribution at equilibrium may be calculated for various relevant groundwater compositions by use of selectivity coefficients. However, present literature data generally concerns coefficients measured in batch experiments with high water-to-solid ratios. The basic aim with the present work was therefore to determine selectivity coefficients for sodium/calcium exchange in bentonite with low water-to-solid ratios, and thereby give a reliable base for calculating the cation distribution in a confined bentonite buffer with a relatively high density. In total, six tests with homo-ionic Na- and Ca-montmorillonite, prepared to three material densities, were equilibrated with test solutions of successively increasing concentration. The distribution of cations at equilibrium was measured by use of ion selective electrodes and ICP/AES, and selectivity coefficients were calculated according to the Gaines-Thomas convention. The obtained selectivity coefficient was found to be in the range of 3.8-7.8, which is similar to those previously reported for high water-to-solid ratios.

  18. Electronic structure, mechanical, and optical properties of CaO·Al2O3 system: a first principles approach

    NASA Astrophysics Data System (ADS)

    Hussain, A.; Mehmood, S.; Rasool, M. N.; Aryal, S.; Rulis, P.; Ching, W. Y.

    2016-08-01

    A comprehensive study of the structure, bonding, mechanical and optical properties of five stable phases within the calcium aluminate (Ca-Al-O) series with different CaO to Al2O3 proportions has been carried out using the density functional theory based orthogonalized linear combination of atomic orbitals (OLCAO) method. The phases are C3A, C12A7-crystal, CA, CA2, and CA6 and the oxygen deficient C12A7-electride phase. These five stable phases are wide band gap insulators with energy gap values ranging from 3.85 to 4.62 eV. The charge neutral C12A7-crystal has localized defective states in the gap whereas the C12A7-electride phase has a region of metallic bands of about 2 eV wide in the gap. Effective charge and bond order calculations reveal intimate details of electronic structure and bonding in relation to the aluminate contents in the series. It is shown that Al-O bonds dominate the Ca-O bonds in determining the crystal strength with CA6 having the highest and C12A7 having the lowest bond order density. Calculations of elastic coefficients and mechanical properties in these crystals show a high degree of diversity and anisotropic behavior consistent with the bond order calculations. The refractive index values from optical properties calculations are in good agreement with available literature. Other results furnish more insights for the Ca-Al-O series and provide the opportunity for further investigations on similar or more complicated quaternary systems with potential novel properties.

  19. Scintillation characteristics of LiCaAlF6-based single crystals under X-ray excitation

    NASA Astrophysics Data System (ADS)

    Nikl, M.; Bruza, P.; Panek, D.; Vrbova, M.; Mihokova, E.; Mares, J. A.; Beitlerova, A.; Kawaguchi, N.; Fukuda, K.; Yoshikawa, A.

    2013-04-01

    LiCaAlF6-based scintillators are studied under X- and soft gamma-ray excitations. Under nanosecond pulsed soft X-ray laser excitation the scintillation decay is measured with extremely high dynamical resolution and broad time scale. The undoped LiCaAlF6 shows complex temperature dependence of exciton luminescence and tunneling-driven energy transfer process in scintillation decay. In both the Ce and Eu-doped LiCaAlF6 the dominant part of measured scintillation decay is due to prompt recombination of electrons and holes at the doped emission centers. Nevertheless, the measured light yield value is considerably lower with respect to the derived upper limits. Possible origin of its deterioration is discussed.

  20. Role of Internal Potassium in Maintaining Growth of Cultured Citrus Cells on Increasing NaCl and CaCl2 Concentrations 1

    PubMed Central

    Ben-Hayyim, Gozal; Kafkafi, Uzi; Ganmore-Neumann, Ruth

    1987-01-01

    Shamouti orange (Citrus sinensis L. Osbeck) salt-tolerant cells were grown under low water potential conditions induced by polyethylene glycol (PEG), NaCl, and CaCl2. On the basis of equal osmotic potentials, PEG was the least inhibitory, NaCl next, and CaCl2 the most inhibitory. The relation between growth capacity and ion content can be summarized as follows. (a) Internal K+ concentration was a major factor which changed in the presence of PEG, NaCl, and CaCl2 and probably played a key role in determining growth capacity. (b) Internal concentrations of Na+, Ca2+, or Cl− could not be directly correlated with growth. (C) Internal Mg2+ concentration could be significant only in the presence of high external Ca2+ concentrations. (d) The contribution of nitrate and phosphate to the internal osmoticum was negligible. The ratio of external (Ca2+)/(Na+)2 concentration is crucial for growth. Ratios above 0.5 × 10−4 per millimolar gave maximal protection from adverse effects of NaCl. Growth capacity was found to be determined by the combination of (Ca2+)/(Na+)2 ratio and the absolute external concentration of NaCl. However, a correlation between internal K+ concentration and growth capacity seemed independent of external NaCl concentration. PMID:16665716

  1. 76 FR 78052 - Wells Fargo Bank, N.A., et al.; Notice of Application and Temporary Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-15

    ... COMMISSION Wells Fargo Bank, N.A., et al.; Notice of Application and Temporary Order December 9, 2011. AGENCY... respect to an injunction entered against Wells Fargo Bank, N.A. (``Wells Fargo Bank'') on December 9, 2011... is a national banking association. On March 20, 2010, Wachovia Bank, N.A. (``Wachovia Bank'')...

  2. 78 FR 48918 - Wells Fargo Bank, N.A., et al.; Notice of Application and Temporary Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-12

    ... COMMISSION Wells Fargo Bank, N.A., et al.; Notice of Application and Temporary Order August 6, 2013. AGENCY... injunction effective July 15, 2013, entered against Wells Fargo Bank, N.A. (``Wells Fargo Bank'') by the... 15, 2013, as the effective date of the Injunction. \\2\\ Gutierrez v. Wells Fargo Bank, N.A., Case...

  3. 77 FR 70193 - Wells Fargo Bank, N.A., et al.; Notice of Application and Temporary Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-23

    ... COMMISSION Wells Fargo Bank, N.A., et al.; Notice of Application and Temporary Order November 16, 2012... Act, with respect to an injunction entered against Wells Fargo Bank, N.A. (``Wells Fargo Bank'') on... adherence to fair lending practices. \\2\\ United States v. Wells Fargo Bank, N.A., No. 1:12-cv-01150...

  4. The compressibility of K2CO3-Na2CO3-Li2CO3-CaCO3 liquids derived from sound speed measurements: implications for the fusion curve of CaCO3

    NASA Astrophysics Data System (ADS)

    O'Leary, M. C.; Lange, R. A.; Ai, Y.

    2009-12-01

    Carbonate in the mantle is an important reservoir of carbon, which is released to the atmosphere as CO2 through volcanism. Therefore, it is of considerable interest to extend thermodynamic models of partial melting in the mantle at elevated pressures to carbonate-bearing lithologies. In order to achieve this, thermodynamic data on carbonate liquids are needed, including their density, thermal expansion and compressibility. In order to obtain information on the CaCO3 and MgCO3 liquid components, which are the most important carbonate components in the mantle, we’ve employed a strategy where the alkaline earth carbonates are mixed with the alkali carbonates in order to lower the liquidus temperatures of various sample liquids to values below the decomposition of carbonate liquids at one bar (~1300 K). This permits thermodynamic property measurements of the multi-component liquids to be made at one bar. If it can be shown that the volumetric properties of carbonate liquids mix ideally with respect to composition, then the partial molar volumetric properties of the CaCO3 and MgCO3 liquid components can be derived. In a previous study (Liu et al., 2003), the volume and thermal expansion of mixed K2CO3-Na2CO3-Li2CO3-CaCO3 liquids were reported and shown to behave ideally with respect to composition. In this study, sound speed measurements on mixed K2CO3-Na2CO3-Li2CO3-CaCO3 liquids at one bar, under a CO2 atmosphere from 725 to 1242 K (over 500 degrees) will be reported. Measurements are made with a frequency-sweep acoustic interferometer, where the liquids are held in Pt crucible, and the upper buffer rod is made of alumina. Our sound speed measurements on the pure end-member alkali carbonate liquids (e.g., Na2CO3-) are in excellent agreement with previous sound speed measurements on carbonate liquids reported in the literature (Zhu et al., 1991). The two data sets match within 0.4%, on average, which is within experimental error. The goal of this study is to test

  5. First-principles calculations on the structural and electronic properties of cubic KCaF3 and NaCaF3 (001) surfaces

    NASA Astrophysics Data System (ADS)

    Yang, Kun; He, Yanqing; Cheng, Yi; Che, Li; Yao, Li

    2017-03-01

    First-principles density functional theory (DFT) calculations have been used to investigate the structural and electronic properties of the cubic KCaF3 and NaCaF3 (001) surfaces with MF (M = K or Na) and CaF2 terminations. For both KCaF3 and NaCaF3 (001) surfaces, the MF termination has stronger surface rumpling than the CaF2 termination. All the computed band gaps for the KCaF3 and NaCaF3 (001) surfaces are smaller than those of the bulks. Furthermore, separated bands that originate from surface layer F p states are introduced at the top of the valance band of MF-terminated surfaces, indicating the emergence of the surface states. The calculated surface energies show that the MF-terminated surface is energetically more favorable than the CaF2-terminated surface.

  6. (H3O)2NaAl3F12, isostructural with A2NaAl3F12 (A = K(+), Rb(+), Cs(+)) fluorides having HTB-type sheets.

    PubMed

    Jouffret, Laurent; Lhoste, Jerome; Hemon-Ribaud, Annie; Leblanc, Marc; Maisonneuve, Vincent

    2014-05-01

    The title compound, (H3O)2NaAl3F12 [dihydronium sodium trialuminum(III) dodecafluoride], was obtained by solvothermal synthesis from the reaction of aluminium hydroxide, sodium hydroxide, 1,2,4-triazole and aqueous HF in ethanol at 463 K for 48 h. The structure consists of AlF6 octahedra organized in [AlF4(-)]n HTB-type sheets (HTB is hexagonal tungsten bronze) separated by H3O(+) and Na(+) cations.

  7. Signaling Mechanisms that Link Salt Retention to Hypertension: Endogenous Ouabain, the Na+ Pump, the Na+/Ca2+ Exchanger and TRPC Proteins

    PubMed Central

    Blaustein, Mordecai P.; Hamlyn, John M.

    2010-01-01

    Salt retention as a result of chronic, excessive dietary salt intake, is widely accepted as one of the most common causes of hypertension. In a small minority of cases, enhanced Na+ reabsorption by the kidney can be traced to specific genetic defects of salt transport, or pathological conditions of the kidney, adrenal cortex, or pituitary. Far more frequently, however, the salt retention may be the result of minor renal injury or small genetic variation in renal salt transport mechanisms. How the salt retention actually leads to the increase in peripheral vascular resistance (the hallmark of hypertension) and the elevation of blood pressure remain an enigma. Here we review the evidence that endogenous ouabain (an adrenocortical hormone), arterial smooth muscle α2 Na+ pumps, type-1 Na/Ca exchangers, and receptor- and store-operated Ca2+ channels play key roles in the pathway that links salt to hypertension. We discuss cardenolide structure-function relationships in an effort to understand why prolonged administration of ouabain, but not digoxin, induces hypertension, and why digoxin is actually anti-hypertensive. Finally, we summarize recent observations which indicate that ouabain upregulates arterial myocyte Ca2+ signaling mechanisms that promote vasoconstriction, while simultaneously downregulating endothelial vasodilator mechanisms. In sum, the reports reviewed here provide novel insight into the molecular mechanisms by which salt retention leads to hypertension. PMID:20211726

  8. Distinct interactions of Na{sup +} and Ca{sup 2+} ions with the selectivity filter of the bacterial sodium channel Na{sub V}Ab

    SciTech Connect

    Ke, Song; Zangerl, Eva-Maria; Stary-Weinzinger, Anna

    2013-01-25

    Highlights: ► Ca{sup 2+} translocates slowly in the filter, due to lack of “loose” knock-on mechanism. ► Identification of a high affinity binding site in Na{sub V}Ab selectivity filter. ► Changes of EEEE locus triggered by electrostatic interactions with Ca{sup 2+} ions. -- Abstract: Rapid and selective ion transport is essential for the generation and regulation of electrical signaling pathways in living organisms. In this study, we use molecular dynamics simulations and free energy calculations to investigate how the bacterial sodium channel Na{sub V}Ab (Arcobacter butzleri) differentiates between Na{sup +} and Ca{sup 2+} ions. Multiple nanosecond molecular dynamics simulations revealed distinct binding patterns for these two cations in the selectivity filter and suggested a high affinity calcium binding site formed by backbone atoms of residues Leu-176 and Thr-175 (S{sub CEN}) in the sodium channel selectivity filter.

  9. Ti₃C₂ MXene as a high capacity electrode material for metal (Li, Na, K, Ca) ion batteries.

    PubMed

    Er, Dequan; Li, Junwen; Naguib, Michael; Gogotsi, Yury; Shenoy, Vivek B

    2014-07-23

    Two-dimensional (2-D) materials are capable of handling high rates of charge in batteries since metal ions do not need to diffuse in a 3-D lattice structure. However, graphene, which is the most well-studied 2-D material, is known to have no Li capacity. Here, adsorption of Li, as well as Na, K, and Ca, on Ti3C2, one representative MXene, is predicted by first-principles density functional calculations. In our study, we observed that these alkali atoms exhibit different adsorption energies depending on the coverage. The adsorption energies of Na, K, and Ca decrease as coverage increases, while Li shows little sensitivity to variance in coverage. This observed relationship between adsorption energies and coverage of alkali ions on Ti3C2 can be explained by their effective ionic radii. A larger effective ionic radius increases interaction between alkali atoms, thus lower coverage is obtained. Our calculated capacities for Li, Na, K, and Ca on Ti3C2 are 447.8, 351.8, 191.8, and 319.8 mAh/g, respectively. Compared to materials currently used in high-rate Li and Na ion battery anodes, MXene shows promise in increasing overall battery performance.

  10. Incommensurately modulated twin structure of nyerereite Na1.64K0.36Ca(CO3)2.

    PubMed

    Bolotina, Nadezhda B; Gavryushkin, Pavel N; Korsakov, Andrey V; Rashchenko, Sergey V; Seryotkin, Yurii V; Golovin, Alexander V; Moine, Bertrand N; Zaitsev, Anatoly N; Litasov, Konstantin D

    2017-04-01

    The incommensurately modulated twin structure of nyerereite Na1.64K0.36Ca(CO3)2 has been first determined in the (3 + 1)-dimensional symmetry group Cmcm(α00)00s with modulation vector q = 0.383a*. Unit-cell values are a = 5.062 (1), b = 8.790 (1), c = 12.744 (1) Å. Three orthorhombic components are related by threefold rotation about [001]. Discontinuous crenel functions are used to describe the occupation modulation of Ca and some CO3 groups. The strong displacive modulation of the O atoms in vertexes of such CO3 groups is described using x-harmonics in crenel intervals. The Na, K atoms occupy mixed sites whose occupation modulation is described in two ways using either complementary harmonic functions or crenels. The nyerereite structure has been compared both with the commensurately modulated structure of K-free Na2Ca(CO3)2 and with the widely known incommensurately modulated structure of γ-Na2CO3.

  11. A method for Ca, Fe, Ga, Na, Si and Zn determination in alumina by inductively coupled plasma optical emission spectrometry after aluminum precipitation

    NASA Astrophysics Data System (ADS)

    Souza, Alexandre L.; Lemos, Sherlan G.; Oliveira, Pedro V.

    2011-05-01

    In this present work a method for the determination of Ca, Fe, Ga, Na, Si and Zn in alumina (Al 2O 3) by inductively coupled plasma optical emission spectrometry (ICP OES) with axial viewing is presented. Preliminary studies revealed intense aluminum spectral interference over the majority of elements and reaction between aluminum and quartz to form aluminosilicate, reducing drastically the lifetime of the torch. To overcome these problems alumina samples (250 mg) were dissolved with 5 mL HCl + 1.5 mL H 2SO 4 + 1.5 mL H 2O in a microwave oven. After complete dissolution the volume was completed to 20 mL and aluminum was precipitated as Al(OH) 3 with NH 3 (by bubbling NH 3 into the solution up to a pH ~ 8, for 10 min). The use of internal standards (Fe/Be, Ga/Dy, Zn/In and Na/Sc) was essential to obtain precise and accurate results. The reliability of the proposed method was checked by analysis of alumina certified reference material (Alumina Reduction Grade-699, NIST). The found concentrations (0.037% w w -1 CaO, 0.013% w w -1 Fe 2O 3, 0.012% w w -1 Ga 2O 3, 0.49% w w -1 Na 2O, 0.014% w w -1 SiO 2 and 0.013% w w -1 ZnO) presented no statistical differences compared to the certified values at a 95% confidence level.

  12. Effects of ABA and CaCl₂ on GABA accumulation in fava bean germinating under hypoxia-NaCl stress.

    PubMed

    Yang, Runqiang; Hui, Qianru; Gu, Zhenxin

    2016-01-01

    Effects of exogenous abscisic acid (ABA) and CaCl2 on γ-aminobutyric acid (GABA) accumulation of germinated fava bean under hypoxia-NaCl stress were investigated. Exogenous ABA resulted in the enhancement of glutamate decarboxylase (GAD) and diamine oxidase (DAO) activity as well as GABA content in cotyledon and shoot. CaCl2 increased both enzyme activities in shoot and GABA content in cotyledon and shoot. ABA downregulated GAD expression in cotyledon and radicle, while upregulated that in shoot; it also upregulated DAO expression in each organ. CaCl2 upregulated GAD expression in cotyledon, while downregulated that in radicle. However, it upregulated DAO expression in shoot, downregulated that in radicle. ABA inhibitor fluridon and ethylenediaminetetraacetic acid inhibited GAD and DAO activities significantly so that inhibited GABA accumulation through reducing ABA biosynthesis and chelating Ca(2+), respectively. However, they upregulated GAD and DAO expression in varying degrees. These results indicate that ABA and Ca(2+) participate in GABA biosynthesis in fava bean during germination under hypoxia-NaCl stress.

  13. On the existence of a high-temperature polymorph of Na2Ca6Si4O15—implications for the phase equilibria in the system Na2O-CaO-SiO2

    NASA Astrophysics Data System (ADS)

    Kahlenberg, Volker; Maier, Matthias

    2016-12-01

    Singe crystals of a new high-temperature polymorph of Na2Ca6Si4O15 have been obtained from solid state reactions performed at 1300 °C. The basic crystallographic data of this so-called β-phase at ambient conditions are as follows: space group P1 c1, a = 9.0112(5) Å, b = 7.3171(5) Å, c = 10.9723(6) Å, β = 107.720(14)°, V = 689.14(7) Å3, Z = 2. The crystals showed twinning by reticular merohedry (mimicking an orthorhombic C-centred unit cell) which was accounted for during data processing and structure solution. Structure determination was accomplished by direct methods. Least-squares refinements resulted in a residual of R(|F|) = 0.043 for 5811 observed reflections with I > 2σ(I). From a structural point of view β-Na2Ca6Si4O15 can be attributed to the group of mixed-anion silicates containing [Si2O7]-dimers as well as isolated [SiO4]-tetrahedra in the ratio 1:2, i.e. more precisely the formula can be written as Na2Ca6[SiO4]2[Si2O7]. The tetrahedral groups are arranged in layers parallel to (100). Sodium and calcium cations are located between the silicate anions for charge compensation and are coordinated by six to eight nearest oxygen ligands. Alternatively, the structure can be described as a mixed tetrahedral-octahedral framework based on kröhnkite-type [Ca(SiO4)2O2]-chains in which the CaO6-octahedra are corner-linked to bridging SiO4-tetrahedra. The infinite chains are running parallel to [001] and are concentrated in layers parallel to (010). Adjacent layers are shifted relative to each other by an amount of +δ or -δ along a*. Consequently, a …ABABAB… stacking sequence is created. A detailed comparison with related structures such as α-Na2Ca6Si4O15 and other A2B6Si4O15 representatives including topological as well as group theoretical aspects is presented. There are strong indications that monoclinic Na2Ca3Si2O8 mentioned in earlier studies is actually misinterpreted β-Na2Ca6Si4O15. In addition to the detailed crystallographic analysis of

  14. Effect of Ca(OH)2, NaCl, and Na2SO4 on the corrosion and electrochemical behavior of rebar

    NASA Astrophysics Data System (ADS)

    Jin, Zuquan; Zhao, Xia; Zhao, Tiejun; Hou, Baorong; Liu, Ying

    2016-06-01

    The corrosion of rebar in reinforced concrete in marine environments causes significant damage to structures built in ocean environments. Studies on the process and mechanism of corrosion of rebar in the presence of multiple ions may help to control damage and predict the service life of reinforced concrete structures in such environments. The effect of interactions between sulfate and chloride ions and calcium hydroxide on the electrochemical behavior of rebar are also important for evaluation of structure durability. In this work, electrochemical impedance spectroscopy (EIS) plots of rebar in Ca(OH)2 solution and cement grout, including NaCl and Na2SO4 as aggressive salts, were measured for diff erent immersion times. The results show that corrosion of rebar was controlled by the rate of charge transfer as the rebar was exposed to chloride solution. In the presence of high concentrations of sulfate ions in the electrolyte, generation and dissolution of the passive film proceeded simultaneously and corrosion was mainly controlled by the diff usion rate. When Na2SO4 and NaCl were added to Ca(OH)2 solution, the instantaneous corrosion rate decreased by a factor of 10 to 20 as a result of the higher pH of the corroding solution.

  15. Crystal structure of Rb-elpasolite Rb{sub 2}NaAlF{sub 6}

    SciTech Connect

    Yakubovich, O. V. Kiryukhina, G. V.; Dimitrova, O. V.

    2013-05-15

    Single crystals of Rb{sub 2}NaAlF{sub 6}, the Rb analogue of the mineral elpasolite, are obtained in the NaF-Rb{sub 2}CO{sub 3}-Al{sub 2}O{sub 3}-Rb{sub 3}PO{sub 4}-H{sub 2}O system under hydrothermal conditions, and their structure is determined by X-ray diffraction (R = 0.0188): a = 8.3087(1) A, space group Fm3bar m, Z = 4, and {rho}{sub calcd} = 3.88 g/cm{sup 3}. The hypothesis that Rb elpasolite exists in nature in late associations of pegmatites enriched in rubidium is proposed.

  16. Effect of Al2O3 Concentration on Density and Structure of (CaO-SiO2)-xAl2O3 Slag

    NASA Astrophysics Data System (ADS)

    Rajavaram, Ramaraghavulu; Kim, Hyelim; Lee, Chi-Hoon; Cho, Won-Seung; Lee, Chi-Hwan; Lee, Joonho

    2017-03-01

    The effect of Al2O3 concentration on the density and structure of CaO-SiO2-Al2O3 slag was investigated at multiple Al2O3 mole percentages and at a fixed CaO/SiO2 ratio of 1. The experiments were conducted in the temperature range of 2154 K to 2423 K (1881 °C to 2150 °C) using the aerodynamic levitation technique. In order to understand the relationship between density and structure, structural analysis of the silicate melts was carried out using Raman spectroscopy. The density of each slag sample investigated in this study decreased linearly with increasing temperature. When the Al2O3 content was less than 15 mole pct, density decreased with increasing Al2O3 content due to the coupling of Si (Al), whereas above 20 mole pct density of the slag increased due to the role of Al3+ ion as a network modifier.

  17. FT-IR Spectroscopic Study of 1,5-Pentanedithiol and 1,6-Hexanedithiol Adsorbed on NaA, CaA and NaY Zeolites

    NASA Astrophysics Data System (ADS)

    Öztürk, Nuri; Çırak, Çağrı; Bahçeli, Semiha

    2005-09-01

    The adsorption of 1,5-pentanedithiol (1,5-PDT) and 1,6-hexanedithiol (1,6-HDT) in liquid phases on NaA (or 4A-type), CaA (or 5A-type) and NaY zeolites has been studied by using infrared spectroscopy. From the IR spectra it is found that the peak positions of the symmetric as well as the antisymmetric modes of the methylene (CH2) groups are observed at almost the same band values for the title dithiolates adsorbed on the A-type and NaY zeolites. On the other hand, the weak SH stretching vibration, observed for all samples, can be attributed to the sulphure atoms of 1,5-PDT and 1,6-HDT coordinatively adsorbed on cationic sites of the zeolites.

  18. Effect of the Na:K Ratio on Melt Viscosity within the SiO2-NaAlSiO4-KAlSiO4 System

    NASA Astrophysics Data System (ADS)

    Smith, R. A.; Robert, G.; Guevarra, P.; Dreizler, M.

    2015-12-01

    We synthesized eight compositions in the SiO2-NaAlSiO4-KAlSiO4 system, four along the feldspathoid join, and four along the pyroxene join, to test the effects of the Na:K ratio on the viscosity and heat capacity of these melts. Na:K ratios include [100:0], [75:25], [50:50], and [25:75]. Synthesis of each composition involved weighing and mixing powdered SiO2, Al2O3, Na2(CO3) and K2(CO3), slow decarbonation of samples in a Lindberg oven, and melting between 1100°C and 1745°C in a high-temperature box furnace. We measured the heat capacity of each sample, from room temperature to 1500°C, using a Netzsch 404 F1 Pegasus differential scanning calorimeter. We measured the viscosities of three of the feldspathoid compositions, NaAlSiO4, Na0.75K0.25AlSiO4, and Na0.5K0.5AlSiO4, and one of the pyroxene compositions, Na0.5K0.5AlSi2O6, in a Brookfield rotating viscometer at temperatures ranging from 1400°C to 1580°C. NaAlSiO4 has a calorimetric glass transition temperature (Tg) of 833°C, and a viscosity of 101.58 Pa.s at 1557°C. Na0.75K0.25AlSiO4 has a Tg of 830°C, and a viscosity of 101.80 Pa.s at 1568°C. Na0.5K0.5AlSi04 has a Tg of 864°C, and a viscosity of 102.12 Pa.s at 1556°C. Na0.25K0.75AlSi04 has a Tg of 912°C. NaAlSi2O6 has a Tg of 834°C. Na0.75K0.25AlSi2O6 has a Tg of 834°C. Na0.5K0.5AlSi2O6 has a Tg of 845°C, and a viscosity of 103.11 Pa.s at 1553°C. Na0.25K0.75AlSi2O6 has a Tg of 899°C. Increase in potassium results in an increase in the calorimetric glass transition temperature, for both the feldspathoid and pyroxene compositions. K-rich pyroxene compositions have a slightly lower Tg than K-rich feldspathoid compositions. In the high-temperature range, however, the viscosity of feldspathoid is approximately one order of magnitude lower than that of pyroxene for the same Na:K ratio of 50:50. Additional experiments will be performed to determine the low-temperature viscosities of all samples using parallel-plate viscometry.

  19. Ca2+ and Zn2+ are transported by the electrogenic 2Na+/1H+ antiporter in echinoderm gastrointestinal epithelium

    PubMed

    Zhuang; Duerr; Ahearn

    1995-01-01

    45Ca2+ uptake by purified brush-border membrane vesicles of starfish (Pycnopodia helianthoides) pyloric ceca was stimulated by an outwardly directed H+ gradient and this stimulation was enhanced by the simultaneous presence of an induced membrane potential (inside negative; K+/valinomycin). External amiloride (competitive inhibitor; Ki=660 µmol l-1) and a monoclonal antibody raised against proteins associated with the lobster (Homarus americanus) electrogenic 2Na+/1H+ antiporter both inhibited approximately half of the proton-gradient-stimulated 45Ca2+ uptake. These results suggested that Ca2+ might be transported by the electrogenic antiporter and that the crustacean antibody was inhibitory to the exchange function in echinoderms, as was recently shown in crustacean epithelial brush-border membrane vesicles. Carrier-mediated 45Ca2+ influx by amiloride-sensitive and amiloride-insensitive systems displayed the following kinetic constants: (amiloride-sensitive) Kt=66±2 µmol l-1; Jmax=0.173±0.002 pmol µg-1 protein 8 s-1; (amiloride-insensitive) Kt=18±0.3 µmol l-1; Jmax=0.100±0.001 pmol µg-1 protein 8 s-1. Zn2+ was a mixed inhibitor of 45Ca2+ influx by carrier-mediated transport, displaying a Ki of 920 µmol l-1. Mn2+, Cu2+, Fe2+ and Mg2+ also inhibited 45Ca2+ uptake, but the mechanism(s) of inhibition by these other cations was not disclosed. An equilibrium shift experiment showed that both Na+ and Zn2+ were able to exchange with equilibrated 45Ca2+ in these vesicles, suggesting that both monovalent and divalent cations were able to enter pyloric cecal cells through a common carrier-mediated transport system. In addition, the echinoderm electrogenic system appeared to exhibit a molecular component recognized by the crustacean antibody that may imply a similar epitope in the two animals.

  20. Metal-Organic Frameworks As Templates for Nanoscale NaAlH 4

    SciTech Connect

    Bhakta, Raghunandan K.; Herberg, Julie L.; Jacobs, Benjamin; Highley, Aaron; Behrens, Richard; Ockwig, Nathan W.; Greathouse, Jeffery A.; Allendorf, Mark D.

    2009-09-01

    Metal-organic frameworks (MOFs) offer an attractive alternative to traditional hard and soft templates for nanocluster synthesis because their ordered crystalline lattice provides a highly controlled and inherently understandable environment. We demonstrate that MOFs are stable hosts for metal hydrides proposed for hydrogen storage and their reactive precursors, providing platform to test recent theoretical predictions that some of these materials can be destabilized with respect to hydrogen desorption by reducing their critical dimension to the nanoscale. With the MOF HKUST-1 as template, we show that NaAlH4 nanoclusters as small as eight formula units can be synthesized. The confinement of these clusters within the MOF pores dramatically accelerates the desorption kinetics, causing decomposition to occur at ~100 °C lower than bulk NaAlH4. However, using simultaneous thermogravimetric modulated beam mass spectrometry, we also show that the thermal decomposition mechanism of NaAlH4 is complex and may involve processes such as nucleation and growth in addition to the normally assumed two-step chemical decomposition reactions.

  1. Tululite, Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36: a new Ca zincate-aluminate from combustion metamorphic marbles, central Jordan

    NASA Astrophysics Data System (ADS)

    Khoury, Hani N.; Sokol, Ella V.; Kokh, Svetlana N.; Seryotkin, Yurii V.; Nigmatulina, Elena N.; Goryainov, Sergei V.; Belogub, Elena V.; Clark, Ian D.

    2016-02-01

    Tululite (Ca14(Fe3+,Al)(Al,Zn,Fe3+,Si,P,Mn,Mg)15O36 (the hypothetical end-member formula Ca14{Fe3+O6}[SiO4][Zn5Al9]O26) (IMA2014-065) is a new natural Ca zincate-aluminate, identified in medium-temperature (800-850 °C) combustion metamorphic (CM) spurrite-fluorellestadite marbles from central Jordan. The type locality (Tulul Al Hammam area) is situated in the northern part of the Siwaqa complex, the largest area of the "Mottled Zone" Formation in the Dead Sea region. The marbles originated from bitumen-rich chalky marine sediments of the Maastrichtian-Paleogene Muwaqqar Chalk Marl Formation, which have low clay content (and, consequently, low Al) and high Zn, Cd, and U enrichments. The bulk CM rocks derived from the low-Al protolith have unusually high (Zn + Cd)/Al ratios ( 0.2) and, as a result, a mineralogy with negligibly small percentages of Ca aluminates having low Ca:Al molar ratios (minerals of mayenite supergroup, Ca:Al = 6:7) common to most of calcareous CM rocks in the Mottled Zone. Instead, the mineral assemblage of the Zn-rich marbles contains tululite, with high Ca:Al = 2.55 molar ratios and Zn substituting for a large portion of Al (Zn:Al = 1.1). Tululite occurs in thin clusters as irregular grains with indented outlines (20-100 μm in size), having typical open-work textures associated with rock-forming calcite, fluorellestadite, spurrite, and accessory Zn-rich periclase, lime-monteponite solid solutions, calcium uranates, and zincite. Marbles also bear brownmillerite, dorrite, fluormayenite, high-fluorine Ca aluminate, and lakargiite. Secondary phases are brucite, gel-like calcium silicate hydrates and calcium silicate aluminate hydrates, including Zn- and U-bearing and Cd-rich compounds, Si-bearing hydrated compounds after calcium uranates, and basic Cd chlorides. The empirical formula of the holotype tululite (a mean of 32 analyses) is (Ca13.29Cd0.75)Σ14.04(Al5.46Zn5.20Fe3+ 2.23Si0.95Mn3+ 1.01Mg0.78P0.41)Σ16.04O36. Tululite is cubic, space

  2. A new role for follicle-stimulating hormone in the regulation of calcium flux in Sertoli cells: Inhibition of Na+/Ca++ exchange

    SciTech Connect

    Grasso, P.; Joseph, M.P.; Reichert, L.E. Jr. )

    1991-01-01

    Elucidation of mechanisms regulating intracellular calcium levels in steroidogenic tissues is important for understanding control of cellular function. We have previously described FSH receptor-mediated flux of 45Ca++ into cultured rat Sertoli cells and receptor-enriched proteoliposomes via voltage-sensitive and voltage-independent calcium channels. In the present study, we report heretofore unrecognized inhibitory effects of FSH on Na+/Ca++ exchange in these two systems. An outwardly directed Na+ gradient, developed by preincubating Sertoli cell monolayers in buffer made hypertonic with NaCl, resulted in uptake of 45Ca++ that was unaffected by calcium channel blocking agents, ruthenium red or methoxyverapamil, but was enhanced by ouabain, a specific inhibitor of Na+/K(+)-ATPase. Sodium-dependent 45Ca++ flux into Sertoli cells was inhibited in a concentration-related manner by increased extracellular Na+ (up to 135 mM). FSH consistently and reproducibly (28.9 +/- 3.8%, 10 separate assays) reduced sodium-dependent 45Ca++ influx in the absence or presence of ouabain. A lesser effect on Na+/Ca++ exchange was seen when Li+ replaced Na+ in the preincubation buffer, and a marked reduction occurred when Sertoli cells were incubated in buffer containing KCl, presumably due to membrane depolarization. FSH-sensitive Na+/45Ca++ exchange was also observed when using FSH receptor-enriched proteoliposomes. Our earlier calcium channel studies indicated that FSH affects Ca++ entry into Sertoli cells via a receptor-mediated process. The results reported here demonstrate that the interaction of FSH with its receptor is associated with changes in Na+/Ca++ exchange as well, and suggest that this activity may also be involved in regulating intracellular free Ca++ levels in the Sertoli cell.

  3. [Ca-dependent regulation by Na, K-pump of post-tetanic sensitization of extrasynaptic choline receptors in Helix lucorum neurons].

    PubMed

    Pivovarov, A S; Drozdova, E I

    2001-01-01

    Posttetanic potentiation (by orthodromic stimulation) of cholinosensitivity in LPa3 and RPa3 Helix lucorum neurons that are command in respect to withdrawal behavior was shown earlier (Pivovarov et al., 1999). Now we studied the regulatory role of the Na,K-pump and intracellular free Ga2+ in the posttetanic potentiation (PTP) of cholinosensitivity in command neurons. Semiintact Helix preparation "CNS-visceral bag" was used in experiments. Acetylcholine-induced inward currents were recorded using two-electrode voltage clamp technique. Acetylcholine was applied to somata of the identified LPa3 and RPa3 neurons with a 10-min interval before and after electrical tetanic stimulation of the n. intestinalis (10.5 mA; 0.1 s; 2/s; 2 min). Ouabain (extracellular application, 70 mcM) blocked the PTP. Intracellular injection of BAPTA (1 mM), chelator of Ca2+ ions, prevented the PTP. The PTP was absent after the ouabain application against the background of preliminary intracellular injection of BAPTA. A conclusion war drawn about Ca-dependent participation of Na,K-pump in posttetanic potentiation of cholinosensitivity in command Helix lucorum neurons of withdrawal behavior.

  4. (Ca,Na)(Zn,Mn){sub 2}As{sub 2}: A new spin and charge doping decoupled diluted ferromagnetic semiconductor

    SciTech Connect

    Zhao, K.; Chen, B. J.; Deng, Z.; Zhao, G. Q.; Zhu, J. L.; Liu, Q. Q.; Wang, X. C.; Han, W.; Frandsen, B.; Liu, L.; Cheung, S.; Uemura, Y. J.; Ning, F. L.; Munsie, T. J. S.; Medina, T.; Luke, G. M.; Carlo, J. P.; Munevar, J.; Zhang, G. M.; Jin, C. Q.

    2014-10-28

    Here, we report the successful synthesis of a spin- and charge-decoupled diluted magnetic semiconductor (DMS) (Ca,Na)(Zn,Mn){sub 2}As{sub 2}, crystallizing into the hexagonal CaAl{sub 2}Si{sub 2} structure. The compound shows a ferromagnetic transition with a Curie temperature up to 33 K with 10% Na doping, which gives rise to carrier density of n{sub p} ∼ 10{sup 20 }cm{sup −3}. The new DMS is a soft magnetic material with H{sub C} < 400 Oe. The anomalous Hall effect is observed below the ferromagnetic ordering temperature. With increasing Mn doping, ferromagnetic order is accompanied by an interaction between the local spin and mobile charge, giving rise to a minimum in resistivity at low temperatures and localizing the conduction electrons. The system provides an ideal platform for studying the interaction of the local spins and conduction electrons.

  5. Heat capacity measurements for cryolite (Na3AlF6) and reactions in the system NaFeAlSiOF

    USGS Publications Warehouse

    Anovitz, Lawrence M.; Hemingway, B.S.; Westrum, E.F.; Metz, G.W.; Essene, E.J.

    1987-01-01

    The heat capacity of cryolite (Na3AlF6) has been measured from 7 to 1000 K by low-temperature adiabatic and high-temperature differential scanning calorimetry. Low-temperature data were obtained on material from the same hand specimen in the calorimetric laboratories of the University of Michigan and U.S. Geological Survey. The results obtained are in good agreement, and yield average values for the entropy of cryolite of: S0298 = 238.5 J/mol KS0T-S0298 = 145.114 ln T+ 193.009*10-3T- 10.366* 105 T2- 872.89 J/mol K (273-836.5 K)??STrans = 9.9J/mol KS0T-S0298 =198.414 ln T+73.203* 10-3T-63.814* 105 T2-1113.11 J/mol K (836.5-1153 K) with the transition temperature between ??- and ??-cryolite taken at 836.5 K. These data have been combined with data in the literature to calculate phase equilibria for the system NaFeAlSiOF. The resultant phase diagrams allow constraints to be placed on the fO2, fF2, aSiO2 and T conditions of formation for assemblages in alkalic rocks. A sample application suggests that log fO2 is approximately -19.2, log fF2 is -31.9 to -33.2, and aSiO2 is -1.06 at assumed P T conditions of 1000 K, 1 bar for the villiaumite-bearing Ilimaussaq intrusion in southwestern Greenland. ?? 1987.

  6. The system Na2CO3-CaCO3-MgCO3 at 6 GPa and 900-1250°C and its relation to the partial melting of carbonated mantle

    NASA Astrophysics Data System (ADS)

    Shatskiy, Anton; Litasov, Konstantin D.; Sharygin, Igor S.; Egonin, Ilya A.; Mironov, Aleksandr M.; Palyanov, Yuri N.; Ohtani, Eiji

    2016-01-01

    In order to constrain the Na2CO3-CaCO3-MgCO3 T-X diagram at 6 GPa in addition to the binary and pseudo-binary systems we conducted experiments along the Na2CO3-Ca0.5Mg0.5CO3 join. At 900-1000°C, melting does not occur and isothermal sections are presented by one-, two- and three-phase regions containing Ca-bearing magnesite, aragonite, Na2CO3 (Na2) and Na2(Ca1-0.9Mg0-0.1)3-4(CO3)4-5 (Na2Ca3-4), Na4(Ca1-0.6Mg0-0.4)(CO3)3 (Na4Ca), Na2(Ca0-0.08Mg1-0.92)(CO3)2 (Na2Mg) phases with intermediate compositions. The minimum melting point locates between 1000°C and 1100°C. This point would resemble that of three eutectics: Mgs-Na2Ca3-Na2Mg, Na2Mg-Na2Ca3-Na4Ca or Na2Mg-Na4Ca-Na2, in the compositional interval of [45Na2CO3.55(Ca0.6Mg0.4)CO3]-[60Na2CO3.40Ca0.6Mg0.4CO3]. The liquidus projection has seven primary solidification phase regions for Mgs, Dol, Arg, Na2Ca3, Na4Ca, Na2 and Na2Mg. The results suggest that extraction of Na and Ca from silicate to carbonate components has to decrease minimum melting temperature of carbonated mantle rocks to 1000-1100°C at 6 GPa and yields Na-rich dolomitic melt with a Na# (Na2O/(Na2O + CaO + MgO)) ≥ 28 mol%.

  7. Low-threshold diode-pumped Yb3+,Na+:CaF2 self-Q-switched laser.

    PubMed

    Su, Liangbi; Xu, Jun; Xue, Yinghong; Wang, Chingyue; Chai, Lu; Xu, Xiaodong; Zhao, Guangjun

    2005-07-25

    For the first time to our knowledge, the laser performance of Yb3+, Na+-codoped CaF2 single crystals was demonstrated. Self-Q-switched laser operation at 1050nm was observed for 976 nm diode pumping at room temperature. On 5 W of incident power, the repetition rate and width of the self-Q-switched pulses reached 28 kHz and 1.5 micros, respectively. A maximal slope efficiency of 20.3% and minimal threshold absorbed pump power of 30 mW were respectively achieved with different output couplers, showing the promising application of Yb3+, Na+-codoped CaF2 crystals as compact and efficient solid-state lasers.

  8. Loparite, a rare-earth ore (Ce, Na, Sr, Ca)(Ti, Nb, Ta, Fe+3)O3

    USGS Publications Warehouse

    Hedrick, J.B.; Sinha, S.P.; Kosynkin, V.D.

    1997-01-01

    The mineral loparite (Ce, NA, Sr, Ca)(Ti, Nb, Ta, Fe+3)O3 is the principal ore of the light-group rare-earth elements (LREE) in Russia. The complex oxide has a perovskite (ABO3) structure with coupled substitutions, polymorphism, defect chemistry and a tendency to become metamict. The A site generally contains weakly bonded, easily exchanged cations of the LREE, Na and Ca. The B site generally contains smaller, highly charged cations of Ti, Nb or Fe+3. Mine production is from Russia's Kola Peninsula. Ore is beneficiated to produce a 95% loparite concentrate containing 30% rare-earth oxides. Loparite concentrate is refined by either a chlorination process or acid decomposition process to recover rare-earths, titanium, niobium and tantalum. Rare-earths are separated by solvent extraction and selective precipitation/dissolution. The concentrate is processed at plants in Russia, Estonia and Kazakstan.

  9. Ionic conductivity of single crystals of sodium aluminium germanate Na8Al6Ge6O24(OH)2

    NASA Astrophysics Data System (ADS)

    Sorokin, N. I.

    2015-09-01

    The electrical conductivity of single crystals of sodium aluminium germanate Na8Al6Ge6O24(OH)2 (cubic system, sp. gr. ), which is a germanium analog of sodalite, has been studied in the temperature range of 468‒758 K. Na8Al6Ge6O24(OH)2 crystals are obtained by hydrothermal synthesis (temperature in the dissolution zone 573‒673 K, temperature gradient ~1.5 K/cm). NaAlO2 and GeO2В oxides are used as starting reagents; NaOH hydroxide serves as a solvent. The ionic conductivity of Na8Al6Ge6O24(OH)2 crystals is 2 × 10-4 S/cm (at 758 K); the activation energy of ionic transfer is 0.46 ± 0.03 eV.

  10. Effect of Al and Ca co-doping, in the presence of Te, in superconducting YBCO whiskers growth.

    PubMed

    Pascale, Lise; Truccato, Marco; Operti, Lorenza; Agostino, Angelo

    2016-10-01

    High-Tc superconducting cuprates (HTSC) such as YBa2Cu3O7 - x (YBCO) are promising candidates for solid-state THz applications based on stacks of intrinsic Josephson junctions (IJJs) with atomic thickness. In view of future exploitation of IJJs, high-quality superconducting YBCO tape-like single crystals (whiskers) have been synthesized from Ca-Al-doped precursors in the presence of Te. The main aim of this paper is to determine the importance of the simultaneous use of Al, Te and Ca in promoting YBCO whiskers growth with good superconducting properties (Tc = 79-84 K). Further, single-crystal X-ray diffraction (SC-XRD) refinements of tetragonal YBCO whiskers (P4/mmm) are reported to fill the literature lack of YBCO structure investigations. All the as-grown whiskers have also been investigated by means of X-ray powder diffraction (XRPD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Our results demonstrate that the interplay of Ca, Te and Al elements is clearly necessary in order to obtain superconducting YBCO whiskers. The data obtained from SC-XRD analyses confirm the highly crystalline nature of the whiskers grown. Ca and Al enter the structure by replacing the Y and the octahedral coordinated Cu1 site, respectively, as in other similar orthorhombic compounds, while Te does not enter the structure of whiskers but its presence in the precursor is essential to the growth of the crystals.

  11. Luminescence properties of Eu 2+- and Ce 3+-doped CaAl 2S 4 and application in white LEDs

    NASA Astrophysics Data System (ADS)

    Yu, Ruijin; Wang, Jing; Zhang, Jianhui; Yuan, Haibin; Su, Qiang

    2008-03-01

    The Eu 2+- and Ce 3+-doped CaAl 2S 4 phosphors were comparatively synthesized by conventional solid-state reaction and the evacuated sealed quartz ampoule. The X-ray diffraction (XRD) patterns show that the sample with better crystalline quality was prepared by the evacuated sealed quartz ampoule, resulting in the enhancement of the emission intensity of Eu 2+ ion by a factor of 1.7. The intensive green LEDs were also fabricated by combining CaAl 2S 4:Eu 2+ with near-ultraviolet InGaN chips ( λem=395 nm). The dependence of as-fabricated green LEDs on forward-bias currents shows that it presents good chromaticity stability and luminance saturation, indicating that CaAl 2S 4:Eu 2+ is a promising green-emitting phosphor for a near-UV InGaN-based LED. In addition, the optical properties of CaAl 2S 4:Ce 3+ were systematically investigated by means of diffuse reflectance, photoluminescence excitation and emission, concentrating quenching and the decay curve.

  12. Flash-Heated Wild 2 Particles in the Stardust Aerogel: Anatomy of an Al-Ca-Mg Impact Melt

    NASA Astrophysics Data System (ADS)

    Leroux, H.; Roskosz, M.

    2014-09-01

    Using analytical TEM, chemical maps were recorded on an impact melt from the Stardust aerogel. We show that the impacting particle was a fine-grained refractory assemblage dominated by low and high-Ca pyroxenes and Mg-Al-spinel.

  13. Progress in the material development of LiCaAlF sub 6 :Cr sup 3+ laser crystals

    SciTech Connect

    Michelle D. Shinn.; Chase, L.L.; Caird, J.A.; Payne, S.A.; Atherton, L.J.; Kway, W.L.

    1990-03-01

    High Cr{sup 3+} doping levels, up to 8 mole percent, and low losses have been obtained with the tunable solid-state laser material LiCaAlF{sub 6}:Cr{sup 3+} (Cr:LiCAF). Measurements and calculations show that high pumping and extraction efficiencies are possible with the improved material. 13 refs., 4 figs., 1 tab.

  14. Mg, Al, Si, Ca, Ti, Fe, and Ni abundance for a sample of solar analogues

    NASA Astrophysics Data System (ADS)

    López-Valdivia, Ricardo; Bertone, Emanuele; Chávez, Miguel

    2017-01-01

    We report on the determination of chemical abundances of 38 solar analogues, including 11 objects previously identified as super metal-rich stars. We have measured the equivalent widths for 34 lines of 7 different chemical elements (Mg, Al, Si, Ca, Ti, Fe, and Ni) in high-resolution (R ˜ 80 000) spectroscopic images, obtained at the Observatorio Astrofísico Guillermo Haro (Sonora, Mexico), with the Cananea High-resolution Spectrograph. We derived chemical abundances using ATLAS12 model atmospheres and the Fortran code MOOG. We confirmed the super metallicity status of 6 solar analogues. Within our sample, BD+60 600 is the most metal-rich star ([Fe/H]=+0.35 dex), while for HD 166991 we obtained the lowest iron abundance ([Fe/H]=-0.53 dex). We also computed the so-called [Ref] index for 25 of our solar analogues, and we found, that BD+60 600 ([Ref]=+0.42) and BD+28 3198 ([Ref]=+0.34) are good targets for exoplanet search.

  15. Experimentally Produced Spinel Rims on Ca-Al-Rich Inclusion Bulk Compositions

    NASA Technical Reports Server (NTRS)

    Paque, Julie M.; Le, L.; Lofgren, G. E.

    1998-01-01

    Most Ca-Al-rich inclusions (CAls) from Allende are surrounded by a series of mineralogically distinct rim layers. Proposed modes of formation for these layers include flash heating, evaporation, and condensation. The innermost of these rim layers is generally spinel (SP), in some cases intergrown with perovskite (PV), and commonly containing varying amounts of secondary iron increasing towards the edge of the CAI. The SP or SP+PV rim is not always contiguous with the other rim layers, indicating that it is probably the result of a separate event. We have produced continuous SP rims on synthetic analogs representing Type A/B1, average Type B, and Type B2 bulk compositions by reheating a solid glass experimental charge to subliquidus crystallization temperatures. This experimental result is consistent with the formation of chondrules; and CAIs by more than one sequence of heating and cooling. Previous work indicated that prior crystallization events produced observable effects in the texture and chemistry of the final run product. Information on the nature of the heating/cooling cycles experienced by CAls and chondrules is important in modeling the environment of their formation. Additional information is contained in the original extended abstract.

  16. Remarkably improved hydrogen storage properties of NaAlH4 doped with 2D titanium carbide

    NASA Astrophysics Data System (ADS)

    Wu, Ruyan; Du, Hufei; Wang, Zeyi; Gao, Mingxia; Pan, Hongge; Liu, Yongfeng

    2016-09-01

    A 2D Ti3C2 MXene is introduced into NaAlH4 to improve its hydrogen storage properties for the first time. In the presence of Ti3C2, the operating temperatures for hydrogen storage in NaAlH4 are remarkably reduced, and the hydrogenation/dehydrogenation kinetics are significantly enhanced. The onset dehydrogenation temperature of the 7 wt% Ti3C2-containing NaAlH4 sample is reduced to 100 °C, and hydrogen recharging starts at 50 °C. Approximately 4.7 wt% hydrogen is released from the NaAlH4-7 wt% Ti3C2 sample within 100 min at 140 °C, and the dehydrogenated sample absorbs 4.6 wt% hydrogen within 60 min at 120 °C. However, pristine NaAlH4 only absorbs 0.4 wt% hydrogen under identical conditions. Further cycling measurements show significantly improved cycling stability for the Ti3C2-containing NaAlH4; the hydrogenation/dehydrogenation behaviour remains nearly constant after 10 cycles. XRD and XPS analyses reveal that the Ti3C2 reacts with NaAlH4 and is reduced to metallic Ti and Ti3+ species, which are responsible for the lowered operating temperatures and improved dehydrogenation/hydrogenation kinetics.

  17. Neuroprotective Effect of the Novel Compound ITH33/IQM9.21 Against Oxidative Stress and Na(+) and Ca(2+) Overload in Motor Neuron-like NSC-34 Cells.

    PubMed

    Moreno-Ortega, Ana J; Al-Achbili, Lamiaa Mouhid; Alonso, Elba; de Los Ríos, Cristóbal; García, Antonio G; Ruiz-Nuño, Ana; Cano-Abad, María F

    2016-10-01

    Alternatives for the treatment of amyotrophic lateral sclerosis (ALS) are scarce and controversial. The etiology of neuronal vulnerability in ALS is being studied in motor neuron-like NSC-34 cells to determine the underlying mechanisms leading to selective loss of motor neurons. One such mechanism is associated with mitochondrial oxidative stress, Ca(2+) overload, and low expression of Ca(2+)-buffering proteins. Therefore, in order to elicit neuronal death in ALS, NSC-34 cells were exposed to the following cytotoxic agents: (1) a mixture of oligomycin 10 µM and rotenone 30 µM (O/R), or (2) phenylarsine oxide 1 µM (PAO) (to mimic excess free radical production during mitochondrial dysfunction), and (3) veratridine 100 µM (VTD) (to induce overload of Na(+) and Ca(2+) and to alter distribution of Ca(2+)-buffering proteins [parvalbumin and calbindin-D28k]). Thus, the aim of the study was to test the novel neuroprotective compound ITH33/IQM9.21 (ITH33) and to compare it with riluzole on in vitro models of neurotoxicity. Cell viability measured with MTT showed that only ITH33 protected against O/R at 3 μM and PAO at 10 μM, but not riluzole. ITH33 and riluzole were neuroprotective against VTD, blocked the maximum peak and the number of [Ca(2+)]c oscillations per cell, and restored the effect on parvalbumin. However, only riluzole reversed the effect on calbindin-D28k levels. Therefore, ITH33 was neuroprotective against oxidative stress and Na(+)/Ca(2+) overload, both of which are involved in ALS.

  18. CaNa2EDTA chelation attenuates cell damage in workers exposed to lead--a pilot study.

    PubMed

    Čabarkapa, A; Borozan, S; Živković, L; Stojanović, S; Milanović-Čabarkapa, M; Bajić, V; Spremo-Potparević, B

    2015-12-05

    Lead induced oxidative cellular damage and long-term persistence of associated adverse effects increases risk of late-onset diseases. CaNa2EDTA chelation is known to remove contaminating metals and to reduce free radical production. The objective was to investigate the impact of chelation therapy on modulation of lead induced cellular damage, restoration of altered enzyme activities and lipid homeostasis in peripheral blood of workers exposed to lead, by comparing the selected biomarkers obtained prior and after five-day CaNa2EDTA chelation intervention. The group of smelting factory workers diagnosed with lead intoxication and current lead exposure 5.8 ± 1.2 years were administered five-day CaNa2EDTA chelation. Elevated baseline activity of antioxidant enzymes Cu, Zn-SOD and CAT as well as depleted thiols and increased protein degradation products-carbonyl groups and nitrites, pointing to Pb induced oxidative damage, were restored toward normal values following the treatment. Lead showed inhibitor potency on both RBC AChE and BChE in exposed workers, and chelation re-established the activity of BChE, while RBC AChE remained unaffected. Also, genotoxic effect of lead detected in peripheral blood lymphocytes was significantly decreased after therapy, exhibiting 18.9% DNA damage reduction. Administration of chelation reversed the depressed activity of serum PON 1 and significantly decreased lipid peroxidation detected by the post-chelation reduction of MDA levels. Lactate dehydrogenase LDH1-5 isoenzymes levels showed evident but no significant trend of restoring toward normal control values following chelation. CaNa2EDTA chelation ameliorates the alterations linked with Pb mediated oxidative stress, indicating possible benefits in reducing health risks associated with increased oxidative damage in lead exposed populations.

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

    PubMed

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

    2014-02-01

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

  20. Thermodynamics and kinetics of NaAlH4 nanocluster decomposition.

    PubMed

    Bhakta, Raghunandan K; Maharrey, Sean; Stavila, Vitalie; Highley, Aaron; Alam, Todd; Majzoub, Eric; Allendorf, Mark

    2012-06-14

    Reactive nanoparticles are of great interest for applications ranging from catalysis to energy storage. However, efforts to relate cluster size to thermodynamic stability and chemical reactivity are hampered by broad pore size distributions and poorly characterized chemical environments in many microporous templates. Metal hydrides are an important example of this problem. Theoretical calculations suggest that reducing their critical dimension to the nanoscale can in some cases considerably destabilize these materials and there is clear experimental evidence for accelerated kinetics, making hydrogen storage applications more attractive in some cases. However, quantitative measurements establishing the influence of size on thermodynamics are lacking, primarily because carbon aerogels often used as supports provide inadequate control over size and pore chemistry. Here, we employ the nanoporous metal-organic framework (MOF) Cu-BTC (also known as HKUST-1) as a template to synthesize and confine the complex hydride NaAlH(4). The well-defined crystalline structure and monodisperse pore dimensions of this MOF allow detailed, quantitative probing of the thermodynamics and kinetics of H(2) desorption from 1-nm NaAlH(4) clusters (NaAlH(4)@Cu-BTC) without the ambiguity associated with amorphous templates. Hydrogen evolution rates were measured as a function of time and temperature using the Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry method, in which sample mass changes are correlated with a complete analysis of evolved gases. NaAlH(4)@Cu-BTC undergoes a single-step dehydrogenation reaction in which the Na(3)AlH(6) intermediate formed during decomposition of the bulk hydride is not observed. Comparison of the thermodynamically controlled quasi-equilibrium reaction pathways in the bulk and nanoscale materials shows that the nanoclusters are slightly stabilized by confinement, having an H(2) desorption enthalpy that is 7 kJ (mol H(2))(-1) higher than the

  1. Pressure and temperature variation of octahedral Na and tetrahedral Al in amphiboles in metamafic rocks

    NASA Astrophysics Data System (ADS)

    Jenkins, D. M.; Lei, J.

    2013-12-01

    The sodium content in the M4 site of amphibole (BNa) was calibrated by Brown (1977, J Petrol, 18, 53-72) in a study that continues to be highly cited to this day. This study, based on empirical observations of amphibole compositional changes in the presence of the buffering assemblage plagioclase, chlorite, epidote, iron oxide, and water, demonstrated a systematic variation in the BNa and tetrahedral Al (TAl) content with pressure. Recent experimental work in this lab aimed at defining the extent of miscibility along the tremolite-glaucophane and hornblende-glaucophane joins in the Na2O-CaO-MgO-Al2O3-SiO2-H2O system has provided some additional information on the cation mixing along these joins. These joins also serve as the chemically-simplified framework of the BNa versus TAl correlation reported by Brown (1977). There are now sufficient, though still a bare minimum, of experimentally-confirmed mixing data for sodium-rich amphiboles to test this correlation and for quantifying the pressure-temperature (P-T) dependence of amphibole compositions in metamafic rocks relevant to subduction zones. From experimental results obtained over the range of 500-800°C, 1.5-2.0 GPa, and using a variety of amphibole synthesis and re-equilibration methods, the following set of asymmetric formalism (ASF) macroscopic interaction and mixing parameters have been derived that can be used with THERMOCALC dataset 55: Wtrgl = 70 kJ, Wglts = Wtrts =20 kJ, α(tr) = 1.0, α(ts) = 1.2, and α(gl) = 0.52. Using a fixed MORB bulk composition, the composition of amphiboles within the P-T stability field of the buffering assemblage were calculated for the above chemical system with FeO added (i.e., NCFMASH) over the range of 0.2 - 2.0 GPa and 400 - 700°C. The following main observations can be made. First, the empirical amphibole compositions at low TAl and high BNa contents are well modeled by the miscibility gap in the amphibole ternary sub-system tremolite

  2. Gel- to -crystallite conversion technique for the syntheses of M-{beta}/{beta}''-alumina (M = Li, Na, K, Rb, Ca or Eu)

    SciTech Connect

    Jayaraman, V. Periaswami, G.; Kutty, T.R.N.

    2008-10-02

    Various alkali and alkaline earths hydroxides are reacted with hydrated alumina gel Al{sub 2}O{sub 3}.nH{sub 2}O (80 < n < 120) in hydrophilic organic solvents to yield precursor(s) with metal cation entrapped in the matrix, with the general formula M{sub y}AlO{sub y}(OH){sub 3-y} (where M = Li, Na, K, Rb, Ca and Eu). Depending on the cation, the precursor crystallizes as metal-inserted gibbsite or boehmite structure. The nature of the precursor depends on the size of the cation, and its concentration, solvent used, solvent/water ratio, etc. These precursors yield M-{beta}/{beta}''-alumina phase on calcination at elevated temperatures in the case of sodium, potassium and rubidium. In the case of lithium, LiAl{sub 5}O{sub 8} (spinel) phase is obtained. While calcium and europium give rise to calcium hexaaluminate and EuAlO{sub 3} (perovskite), respectively, on calcination. The need of metal ion-inserted-{gamma}-alumina phase is emphasized in obtaining M-{beta}/{beta}''-alumina phase.

  3. Putative resolution of the EEEE selectivity paradox in L-type Ca2+ and bacterial Na+ biological ion channels

    NASA Astrophysics Data System (ADS)

    Kaufman, I. Kh; Luchinsky, D. G.; Gibby, W. A. T.; McClintock, P. V. E.; Eisenberg, R. S.

    2016-05-01

    The highly selective permeation of ions through biological ion channels can be described and explained in terms of fluctuational dynamics under the influence of powerful electrostatic forces. Hence valence selectivity, e.g. between Ca2+ and Na+ in calcium and sodium channels, can be described in terms of ionic Coulomb blockade, which gives rise to distinct conduction bands and stop-bands as the fixed negative charge Q f at the selectivity filter of the channel is varied. This picture accounts successfully for a wide range of conduction phenomena in a diversity of ion channels. A disturbing anomaly, however, is that what appears to be the same electrostatic charge and structure (the so-called EEEE motif) seems to select Na+ conduction in bacterial channels but Ca2+ conduction in mammalian channels. As a possible resolution of this paradox it is hypothesised that an additional charged protein residue on the permeation path of the mammalian channel increases |{{Q}f}| by e, thereby altering the selectivity from Na+ to Ca2+. Experiments are proposed that will enable the hypothesis to be tested.

  4. Effect of Na+ and Ca2+ ions on a lipid Langmuir monolayer: an atomistic description by molecular dynamics simulations.

    PubMed

    Giner Casares, Juan José; Camacho, Luis; Martín-Romero, Maria Teresa; López Cascales, José Javier

    2008-12-01

    Studying the effect of alkali and alkaline-earth metal cations on Langmuir monolayers is relevant from biophysical and nanotechnological points of view. In this work, the effect of Na(+) and Ca(2+) on a model of an anionic Langmuir lipid monolayer of dimyristoylphosphatidate (DMPA(-)) is studied by molecular dynamics simulations. The influence of the type of cation on lipid structure, lipid-lipid interactions, and lipid ordering is analyzed in terms of electrostatic interactions. It is found that for a lipid monolayer in its solid phase, the effect of the cations on the properties of the lipid monolayer can be neglected. The influence of the cations is enhanced for the lipid monolayer in its gas phase, where sodium ions show a high degree of dehydration compared with calcium ions. This loss of hydration shell is partly compensated by the formation of lipid-ion-lipid bridges. This difference is ascribed to the higher charge-to-radius ratio q/r for Ca(2+), which makes ion dehydration less favorable compared to Na(+). Owing to the different dehydration behavior of sodium and calcium ions, diminished lipid-lipid coordination, lipid-ion coordination, and lipid ordering are observed for Ca(2+) compared to Na(+). Furthermore, for both gas and solid phases of the lipid Langmuir monolayers, lipid conformation and ion dehydration across the lipid/water interface are studied.

  5. Microstructural and strength improvements through the use of Na{sub 2}CO{sub 3} in a cementless Ca(OH){sub 2}-activated Class F fly ash system

    SciTech Connect

    Jeon, Dongho; Jun, Yubin; Jeong, Yeonung; Oh, Jae Eun

    2015-01-15

    This study explores the beneficial effects of Na{sub 2}CO{sub 3} as an additive for microstructural and strength improvements in a Ca(OH){sub 2}-activated fly ash system. NaOH-activated fly ash samples were also tested to compare the effect of Na{sub 2}CO{sub 3}. Compressive strength testing, XRD, SEM/BSE/EDS, {sup 29}Si/{sup 27}Al MAS-NMR, MIP and TGA were performed. The testing results indicate that the use of Na{sub 2}CO{sub 3} for Ca(OH){sub 2}-activation led to a noticeable improvement in strength and microstructure, primarily due to (1) more dissolution of raw fly ash at an early age, (2) more formation of C–S–H [or C–S–H(I)], (3) porosity reduction, and (4) pore-size refinement. We also found that (1) an early high alkalinity from the NaOH formation was not a major cause of strength, (2) geopolymer was not formed despite the early NaOH formation, and (3) no visible pore-filling action of CaCO{sub 3} was observed. However, Na{sub 2}CO{sub 3} did not produce any improvement in strength for NaOH-activated fly ash. -- Highlights: •The use of Na{sub 2}CO{sub 3} significantly improved strength and microstructure. •The use of Na{sub 2}CO{sub 3} induced more dissolution of raw fly ash at early ages. •The use of Na{sub 2}CO{sub 3} promoted more C–S–H [or C–S–H(I)] formation. •The use of Na{sub 2}CO{sub 3} reduced total porosity and refined pore-size distribution. •The use of Na{sub 2}CO{sub 3} produced neither geopolymer formations nor pore-filling actions from CaCO{sub 3}.

  6. Ethylenediamine-Assisted Hydrothermal Synthesis of NaCaSiO3OH: Controlled Morphology, Mechanism, and Luminescence Properties by Doping Eu(3+)/Tb(3).

    PubMed

    Chen, Mingyue; Xia, Zhiguo; Liu, Quanlin

    2016-11-07

    This paper demonstrates a facile hydrothermal method using ethylenediamine (EDA) as a "shape modifier" for the controlled synthesis of rod bunch, decanedron, spindle, flakiness, and flowerlike NaCaSiO3OH microarchitectures. The set of experimental conditions is important to obtain adjustable shape and size of NaCaSiO3OH particles, as the change in either the amount of EDA/H2O or reaction time, or the amount of NaOH. Accordingly, the crystal growth mechanism during the synthesis process is proposed, and it is found that the EDA, acting as the chelating agent and shape modifier, plays a crucial role in fine-tuning the NaCaSiO3OH morphology. Morphology evolution process of flowerlike NaCaSiO3OH as a function of NaOH is also explained in detail. Eu(3+)/Tb(3+) doped NaCaSiO3OH samples exhibit strong red and green emission under ultraviolet excitation, corresponding to the characteristic electronic transitions of Eu(3+) and Tb(3+). These results imply that the morphology-tunable NaCaSiO3OH:Eu(3+)/Tb(3+) microarchitectures with tunable luminescence properties are expected to have promising applications for micro/nano optical functional devices.

  7. Different Densities of Na-Ca Exchange Current in T-Tubular and Surface Membranes and Their Impact on Cellular Activity in a Model of Rat Ventricular Cardiomyocyte

    PubMed Central

    2017-01-01

    The ratio of densities of Na-Ca exchanger current (INaCa) in the t-tubular and surface membranes (INaCa-ratio) computed from the values of INaCa and membrane capacitances (Cm) measured in adult rat ventricular cardiomyocytes before and after detubulation ranges between 1.7 and 25 (potentially even 40). Variations of action potential waveform and of calcium turnover within this span of the INaCa-ratio were simulated employing previously developed model of rat ventricular cell incorporating separate description of ion transport systems in the t-tubular and surface membranes. The increase of INaCa-ratio from 1.7 to 25 caused a prolongation of APD (duration of action potential at 90% repolarisation) by 12, 9, and 6% and an increase of peak intracellular Ca2+ transient by 45, 19, and 6% at 0.1, 1, and 5 Hz, respectively. The prolonged APD resulted from the increase of INaCa due to the exposure of a larger fraction of Na-Ca exchangers to higher Ca2+ transients under the t-tubular membrane. The accompanying rise of Ca2+ transient was a consequence of a higher Ca2+ load in sarcoplasmic reticulum induced by the increased Ca2+ cycling between the surface and t-tubular membranes. However, the reason for large differences in the INaCa-ratio assessed from measurements in adult rat cardiomyocytes remains to be explained. PMID:28321411

  8. Microstructure and Fatigue Behavior of Friction Stir-welded Noncombustive Mg-9Al-Zn-Ca Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, L.; Li, Z. Y.; Nakata, K.; Feng, J. C.; Huang, Y. X.; Liao, J. S.

    2016-06-01

    Microstructure and fatigue behavior of friction stir-welded noncombustive Mg-9Al-Zn-Ca magnesium alloy were investigated. The as-received hot-extruded material consisted of equiaxed α-Mg grains with β-Mg17Al12 and Al2Ca compounds distributed along the grain boundaries. Friction stir welding produced much refined α-Mg grains accompanied by the dissolution of the eutectic β-Mg17Al12 phase, while Al2Ca phase was dispersed homogenously into the Mg matrix. Friction stir welding produced slightly increased hardness and tensile strength in the defect-free welds compared with the base material due to microstructural refinement and uniform distribution of intermetallic compounds. The load-controlled uniaxial tensile high-cycle fatigue tests indicated that fatigue strength of 90 MPa was obtained for the friction stir-welded joint with fatigue crack initiated basically near the specimen's surface and at the retreating side of the joint. Crack propagation was characterized by cleavage and fatigue striations.

  9. Effect of alcoholic intoxication on water content and activity of Na,K-ATPase and Ca-ATPase in rat brain.

    PubMed

    Zamai, T N; Titova, N M; Zamai, A S; Usol'tseva, O S; Yulenkova, O V; Shumkova, D A

    2002-12-01

    We studied the effect of 2-week alcohol intoxication on water exchange and activity of Na,K-ATPase and Ca-ATPase in rat brain. Alcohol intoxication increased water content in the brain due to cell hyperhydration. It is assumed that hyperhydration results from increased Na+ content in cells due to inhibition Na,K-ATPase activity, which in turn is caused by activation of lipid peroxidation under the effect of ethanol. A possible mechanism of Na,K-ATPase inhibition.

  10. NaAlTi3O8, A Novel Anode Material for Sodium Ion Battery.

    PubMed

    Ma, Xuetian; An, Ke; Bai, Jianmin; Chen, Hailong

    2017-12-01

    Sodium ion batteries are being considered as an alternative to lithium ion batteries in large-scale energy storage applications owing to the low cost. A novel titanate compound, NaAlTi3O8, was successfully synthesized and tested as a promising anode material for sodium ion batteries. Powder X-ray Diffraction (XRD) and refinement were used to analyze the crystal structure. Electrochemical cycling tests under a C/10 rate between 0.01 - 2.5 V showed that ~83 mAh/g capacity could be achieved in the second cycle, with ~75% of which retained after 100 cycles, which corresponds to 0.75 Na(+) insertion and extraction. The influence of synthesis conditions on electrochemical performances was investigated and discussed. NaAlTi3O8 not only presents a new anode material with low average voltage of ~0.5 V, but also provides a new type of intercalation anode with a crystal structure that differentiates from the anodes that have been reported.

  11. Reversible hydrogen storage by NaAlH4 confined within a titanium-functionalized MOF-74(Mg) nanoreactor.

    PubMed

    Stavila, Vitalie; Bhakta, Raghunandan K; Alam, Todd M; Majzoub, Eric H; Allendorf, Mark D

    2012-11-27

    We demonstrate that NaAlH(4) confined within the nanopores of a titanium-functionalized metal-organic framework (MOF) template MOF-74(Mg) can reversibly store hydrogen with minimal loss of capacity. Hydride-infiltrated samples were synthesized by melt infiltration, achieving loadings up to 21 wt %. MOF-74(Mg) possesses one-dimensional, 12 Å channels lined with Mg atoms having open coordination sites, which can serve as sites for Ti catalyst stabilization. MOF-74(Mg) is stable under repeated hydrogen desorption and hydride regeneration cycles, allowing it to serve as a "nanoreactor". Confining NaAlH(4) within these pores alters the decomposition pathway by eliminating the stable intermediate Na(3)AlH(6) phase observed during bulk decomposition and proceeding directly to NaH, Al, and H(2), in agreement with theory. The onset of hydrogen desorption for both Ti-doped and undoped nano-NaAlH(4)@MOF-74(Mg) is ∼50 °C, nearly 100 °C lower than bulk NaAlH(4). However, the presence of titanium is not necessary for this increase in desorption kinetics but enables rehydriding to be almost fully reversible. Isothermal kinetic studies indicate that the activation energy for H(2) desorption is reduced from 79.5 kJ mol(-1) in bulk Ti-doped NaAlH(4) to 57.4 kJ mol(-1) for nanoconfined NaAlH(4). The structural properties of nano-NaAlH(4)@MOF-74(Mg) were probed using (23)Na and (27)Al solid-state MAS NMR, which indicates that the hydride is not decomposed during infiltration and that Al is present as tetrahedral AlH(4)(-) anions prior to desorption and as Al metal after desorption. Because of the highly ordered MOF structure and monodisperse pore dimensions, our results allow key template features to be identified to ensure reversible, low-temperature hydrogen storage.

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

    PubMed

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

    2004-05-01

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

  13. CaMKII Phosphorylation of Na(V)1.5: Novel in Vitro Sites Identified by Mass Spectrometry and Reduced S516 Phosphorylation in Human Heart Failure.

    PubMed

    Herren, Anthony W; Weber, Darren M; Rigor, Robert R; Margulies, Kenneth B; Phinney, Brett S; Bers, Donald M

    2015-05-01

    The cardiac voltage-gated sodium channel, Na(V)1.5, drives the upstroke of the cardiac action potential and is a critical determinant of myocyte excitability. Recently, calcium (Ca(2+))/calmodulin(CaM)-dependent protein kinase II (CaMKII) has emerged as a critical regulator of Na(V)1.5 function through phosphorylation of multiple residues including S516, T594, and S571, and these phosphorylation events may be important for the genesis of acquired arrhythmias, which occur in heart failure. However, phosphorylation of full-length human Na(V)1.5 has not been systematically analyzed and Na(V)1.5 phosphorylation in human heart failure is incompletely understood. In the present study, we used label-free mass spectrometry to assess phosphorylation of human Na(V)1.5 purified from HEK293 cells with full coverage of phosphorylatable sites and identified 23 sites that were phosphorylated by CaMKII in vitro. We confirmed phosphorylation of S516 and S571 by LC-MS/MS and found a decrease in S516 phosphorylation in human heart failure, using a novel phospho-specific antibody. This work furthers our understanding of the phosphorylation of Na(V)1.5 by CaMKII under normal and disease conditions, provides novel CaMKII target sites for functional validation, and provides the first phospho-proteomic map of full-length human Na(V)1.5.

  14. Contribution of reverse Na+–Ca2+ exchange to spontaneous activity in interstitial cells of Cajal in the rabbit urethra

    PubMed Central

    Bradley, E; Hollywood, M A; Johnston, L; Large, R J; Matsuda, T; Baba, A; McHale, N G; Thornbury, K D; Sergeant, Gerard P

    2006-01-01

    Interstitial cells of Cajal (ICC) isolated from the rabbit urethra exhibit regular Ca2+ oscillations that are associated with spontaneous transient inward currents (STICs) recorded under voltage clamp. Their frequency is known to be very sensitive to external Ca2+ concentration but the mechanism of this has yet to be elucidated. In the present study experiments were performed to assess the role of Na+–Ca2+ exchange (NCX) in this process. Membrane currents were recorded using the patch clamp technique and measurements of intracellular Ca2+ were made using fast confocal microscopy. When reverse mode NCX was enhanced by decreasing the external Na+ concentration [Na+]o from 130 to 13 mm, the frequency of global Ca2+ oscillations and STICs increased. Conversely, inhibition of reverse mode NCX by KB-R7943 and SEA0400 decreased the frequency of Ca2+ oscillations and STICs. Application of caffeine (10 mm) and noradrenaline (10 μm) induced transient Ca2+-activated chloride currents (IClCa) at −60 mV due to release of Ca2+ from ryanodine- and inositol trisphosphate (IP3)-sensitive Ca2+ stores, respectively, but these responses were not blocked by KB-R7943 or SEA0400 suggesting that neither drug blocked Ca2+-activated chloride channels or Ca2+ release from stores. Intact strips of rabbit urethra smooth muscle develop spontaneous myogenic tone. This tone was relaxed by application of SEA0400 in a concentration-dependent fashion. Finally, single cell RT-PCR experiments revealed that isolated ICC from the rabbit urethra only express the type 3 isoform of the Na+–Ca2+ exchanger (NCX3). These results suggest that frequency of spontaneous activity in urethral ICC can be modulated by Ca2+ entry via reverse NCX. PMID:16728449

  15. Solubilities of salts in the ternary systems NaCl + CaCl2 + H2O and KCl + CaCl2 + H2O at 75°C

    NASA Astrophysics Data System (ADS)

    Yang, Ji-Min; Liu, Xiao-Lin; Liang, Pei-Pei

    2011-07-01

    The solubility in the NaCl-CaCl2-H2O and KCl-CaCl2-H2O systems were determined at 75°C and the phase diagrams and the diagram of physicochemical property vs composition were plotted. One invariant point, two univariant curves, and two crystallization zones, corresponding to potassium chloride, dihydrate (CaCl2 · 2H2O) showed up in the phase diagrams of the ternary systems. The mixing parameters θM, Ca and ΨM, Ca, Cl (M = Na or K) and equilibrium constant K sp were evaluated in NaCl-CaCl2-H2O and KCl-CaCl2-H2O systems by least-squares optimization procedure, in which the single-salt Pitzer parameters of NaCl, KCl, and CaCl2 β(0), β(1), β(2), and C Φ were directly calculated from the literature. The results obtained were in good agreement with the experimental data.

  16. Effect of SiO2 on the Crystallization Behaviors and In-Mold Performance of CaF2-CaO-Al2O3 Slags for Drawing-Ingot-Type Electroslag Remelting

    NASA Astrophysics Data System (ADS)

    Shi, Cheng-Bin; Li, Jing; Cho, Jung-Wook; Jiang, Fang; Jung, In-Ho

    2015-10-01

    The crystallization characteristics of CaF2-CaO-Al2O3 slags with varying amounts of SiO2 were experimentally studied. The effects of slag crystallization behaviors on the horizontal heat transfer and lubrication performance in drawing-ingot-type electroslag remelting (ESR) were also evaluated in terms of as-cast ingots surface quality and drawing-ingot operation. The results show that increasing SiO2 addition from 0 to 6.8 mass pct strongly suppresses the crystallization of ESR type CaF2-CaO-Al2O3 slags. The crystallization temperature of the studied slags decreases with the increase in SiO2 addition. The liquidus temperatures of the slags also show a decreasing trend with increasing SiO2 content. In CaF2-CaO-Al2O3-(SiO2) slags, faceted 11CaO·7Al2O3·CaF2 crystals precipitate first during continuous cooling of the slag melts, followed by the formation of CaF2 at lower temperatures. 11CaO·7Al2O3·CaF2 was confirmed to be the dominant crystalline phase in the studied slags. CaF2-CaO-Al2O3 slags with a small amount of SiO2 addition are favorable for providing sound lubrication and horizontal heat transfer in mold for drawing-ingot-type ESR, which consequently bring the improvement in the surface quality of ESR ingot and drawing-ingot operating practice as demonstrated by plant trials.

  17. The effect of NaOH concentration on the steam-hydrothermally treated bioactive microarc oxidation coatings containing Ca, P, Si and Na on pure Ti surface.

    PubMed

    Zhou, Rui; Wei, Daqing; Cao, Jianyun; Feng, Wei; Cheng, Su; Du, Qing; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

    2015-04-01

    The microarc oxidation (MAO) coating covered pure Ti plates are steam-hydrothermally treated in autoclaves containing NaOH solutions with different concentrations of 0, 0.001, 0.01, 0.1 and 1mol·L(-1). Due to the composition of Ti, O, Ca, P, Si and Na elements in the MAO coating, anatase and hydroxyapatite (HA) crystals are generated from the previously amorphous MAO coating after the steam-hydrothermal treatment. Meanwhile, it is noticed that the amount of HA crystals increases but showing a decline trend in aspect ratio in morphologies with the increasing of NaOH concentration. Interestingly, the steam-hydrothermally treated MAO coatings exhibit better bonding strength with Ti substrate (up to 43.8±1.1MPa) than that of the untreated one (20.1±3.1MPa). In addition, benefiting from the corrosive attack of the dissolved NaOH in water vapor on the MAO coating, Ti-OH is also formed on the steam-hydrothermally treated MAO coating surface, which can trigger apatite nucleation. Thus, the steam-hydrothermally treated MAO coatings exhibit good apatite-inducing ability.

  18. Teaching the Modes of Ca[superscript 2+] Transport between the Plasma Membrane and Endoplasmic Reticulum Using a Classic Paper by Kwan et al.

    ERIC Educational Resources Information Center

    Liang, Willmann

    2009-01-01

    This teaching article uses the report by Kwan et al., "Effects of methacholine, thapsigargin, and La[superscript 3+] on plasmalemmal and intracellular Ca[superscript 2+] transport in lacrimal acinar cells," where the effects of Ca[superscript 2+]-mobilizing agents in regulating Ca[superscript 2+] fluxes were examined under various conditions.…

  19. Na channels and two types of Ca channels in rat pancreatic B cells identified with the reverse hemolytic plaque assay

    PubMed Central

    1988-01-01

    The reverse hemolytic plaque assay (RHPA) was used to study the secretory properties of single rat pancreatic B cells, and to identify insulin-secreting cells for patch-clamp experiments. In secretion studies using the RHPA, we find that the percentage of secreting B cells and the amount of insulin secreted per B cell increase as the glucose concentration is raised from 0 to 20 mM. Using the whole-cell variation of the patch-clamp technique, we find that identified B cells have three types of channels capable of carrying inward current: (a) tetrodotoxin-sensitive, voltage-dependent Na channels, which are nearly completely inactivated at -40 mV, (b) fast deactivating (FD) Ca channels, and (c) slowly deactivating (SD) Ca channels. We have shown that Na channels are functionally significant to the B cell, because tetrodotoxin partially inhibits glucose-induced insulin secretion. The properties of FD and SD Ca channels differ in several respects. FD channels deactivate at -80 mV, with a time constant of 129 microseconds, they are half-maximally activated near +15 mV, they do not inactivate during 100 ms, they conduct Ba2+ better than Ca2+, and they are very sensitive to washout during intracellular dialysis. SD channels, on the other hand, deactivate with a time constant of 2.8 ms, they are half-maximally activated near -5 mV, they inactivate rapidly, they conduct Ba2+ and Ca2+ equally well, and they are insensitive to washout. PMID:2458427

  20. Anodic Corrosion Behavior of NiFe2O4-Based Cermet in Na3AlF6-K3AlF6-AlF3 for Aluminum Electrolysis

    NASA Astrophysics Data System (ADS)

    Tian, Zhongliang; Lai, Yanqing; Yang, Shu; Li, Jie; Hwang, Jiann-Yang; Liu, Yexiang

    2015-03-01

    A (Cu,Ni)/(10NiO-NiFe2O4) cermet was tested as an inert anode for aluminum electrolysis in Na3AlF6-K3AlF6-AlF3 melt at 1173 K (900 °C), and its corrosion behavior was studied. The results show that the low-temperature Na3AlF6-K3AlF6-AlF3 bath is beneficial, improving the service conditions. With the combined effects of the electrolyte composition and the nascent oxygen during electrolysis, the metal phase (Cu,Ni) at the surface of anode will not be leached preferentially, but be transferred into the aluminates including FeAl2O4, NiAl2O4 and CuAl2O4. This is helpful for the anode to improve its corrosion resistance.

  1. Voronkovite, Na15(Na,Ca,Ce)3(Mn,Ca)3Fe3Zr3Si26O72(OH,O)4Cl · H2O, a new mineral species of the eudialyte group from the Lovozero alkaline pluton, Kola Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Khomyakov, A. P.; Nechelyustov, G. N.; Rastsvetaeva, R. K.

    2009-12-01

    This paper describes a new member of the eudialyte group named in honor of Alexander Alexandrovich Voronkov (1928-1982), the prominent Russian crystallographer. The new mineral has been found in the Shkatulka hyperalkaline pegmatite body at Mt. Alluaiv, Lovozero alkaline pluton, Kola Peninsula, Russia. The mineral is associated with microcline, sodalite, nepheline, aegirine, terskite, lomonosovite, vuonnemite, shkatulkalite, manganoneptunite, and sphalerite. Voronkovite occurs as rounded, poorly faced crystals up to 2-5 mm across. The new mineral is light brown, with vitreous luster and conchoidal fracture. The streak is white. Voronkovite is transparent and brittle; the Mohs hardness is 5; cleavage or parting is not observed. D(meas) = 2.97(2) g/cm3 (volumetric method); D(calc) = 2.95 g/cm3. The new mineral is uniaxial, positive, pleochroic from lemon yellow along X to brownish pink along Y, and is not luminescent in UV light. Voronkovite easily dissolves and gelates in acid at room temperature. The new mineral is trigonal, space group R3, a = 14.205(7), c = 30.265(15) Å, V = 5289(8) Å3, Z = 3. The strongest reflections in the X-ray diffraction pattern [ d, Å ( I)( hkl)] are 2.970(100)(315), 4.316(85)(205), 2.848(84)(404), 3.221(43)(208), 3.536(41)(027), 3.039(41)(119). The chemical composition (electron microprobe, H2O determined with chemical analysis) is as follows, wt %: 15.84 Na2O, 0.28 K2O, 3.08 CaO, 1.76 SrO, 4.65 MnO, 3.53 FeO, 0.93 La2O3, 1.36 Ce2O3, 0.68 Nd2O3, 0.15 Al2O3, 49.48 SiO2, 0.33 TiO2, 14.11 ZrO2, 0.23 HfO2, 0.91 Nb2O5, 0.44 Cl, 0.21 F, 1.56 H2O, 0.19 -O = (Cl,F)2; total is 99.34. The empirical formula calculated on the basis of Si + Al = 26 ( Z = 3) is as follows: (Na13.96Sr0.54K0.19)Σ14.69(Na1.64Ca0.92Ce0.26 La0.18)Σ3.00(Mn2.06Ca0.81Nd0.13)Σ3.00(F1.54Zr0.60Na0.48Nb0.21Ti0.13Hf0.04)Σ3.00Zr3.00(Si1.91Al0.09)Σ2.00(Si24O72)[(OH)2.98 O1.02]Σ4(Cl0.39F0.35)Σ0.74 · 1.23H2O. The simplified formula is Na15(Na,Ca,Ce)3(Mn,Ca)3Fe3Zr3Si26O72(OH

  2. [T-channels and Na+,Ca2+-exchangers as components of the Ca2+-system of the myocardial activity regulation of the frog Rana temporaria].

    PubMed

    Shemarova, I V; Kuznetsov, S V; Demina, I N; Nesterov, V P

    2009-01-01

    Earlier we have shown that regulation of rhythm and strength of the frog heart contractions, mediated by transmitters of the autonomic nervous system, is of the Ca2+-character. In the present work, we studied chrono- and inotropic effect of verapamil--an inhibitor of Ca2+-channels of the L-type, of nickel chloride--an inhibitor of Ca2+-channels of the T-type, and of Na+,Ca2+-exchangers as well as of adrenaline and acetylcholine (ACh) after nickel chloride. It has been found that the intracardially administered NiCl2 at a dose of 0.01 microg/kg produced a sharp fall of amplitude of action potential (AP) and an almost twofold deceleration of heart rate (HR). The intracardiac administration of NiCl2 (0.01 microg/kg) on the background of action of verapamil (6 mg/kg, i/m) led as soon as after 3 min to even more prominent HR deceleration and to further fall of the AP amplitude by more than 50% as compared with norm. The intracardiac administration of adrenaline (0.5 mg/kg) partly restored the cardiac activity. However, preservation of the myocardium electrical activity in such animals was brief and its duration did not exceed several minutes. Administration of Ni2+ on the background of acetylcholine (3.6 mg/kg) led to almost complete cessation of cardiac activity. As soon as after 3 min after injection of this agent the HR decreased to 2 contractions/min. On EG, the 10-fold fall of the AP amplitude was recorded. The elucidate role of extra- and intracellular Ca2+ in regulation of heart contractions, isometric contraction of myocardium preparations was studied in response to action of NiCl2 (10-200 microM), verapamil (70 microM), adrenaline (5 microM), and acetylcholine (0.2 microM) after NiCl2. It is found that Ni2+ caused a dose-dependent increase of the muscle contraction amplitude. Minimal change of the contraction amplitude (on average, by 14.9% as compared with control) was recorded at a Ni2+ concentration of 100 microM. An increase of Ni2+ in the sample to 200

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

    NASA Astrophysics Data System (ADS)

    Lambotte, Guillaume

    The main objective of this thesis is the thermodynamic modeling of liquid and solid solutions, the stoichiometric compounds and the gaseous phase of the chemical system which represent the species involved in the corrosion of the refractory lining of the electrolysis cell. This chemical system is the quaternary reciprocal system AlF3-NaF-SiF4-Al 2O3-Na2O-SiO2 with aluminum and carbon. The modeling of the entire reciprocal system has never been realized before and is very challenging due to the nature of the oxyfluoride solution. The thermodynamic modeling is based on Gibbs free energy functions coming from the theory of solutions. The central hypothesis of this project is that, if it is possible to reproduce the strong short-range ordering observed between the ions of the liquid solution, then reasonable results will be obtained for the phase equilibria involved in this chemical system. The thermodynamic model used in this thesis is the Modified Quasichemical Model in the Quadruplet Approximation (MQMQA) which takes into account the short-range ordering between first- and also second-nearest-neighbors, and is the best suited to model the oxyfluoride liquid solution. First, the reciprocal system with the most negative Gibbs free energy change for the exchange reaction between the end-members, NaF-SiF4-Na 2O-SiO2, was modeled, allowing thus the validation of the recent modifications of the MQMQA aimed at improving the modeling of the thermodynamic properties of reciprocal solutions presenting a strong short-range order among first-nearest neighbors as well as second-nearest neighbors. In order to model this system, an estimate of the thermodynamic properties of the hypothetical SiF4 liquid was necessary. The experimental data in the binary systems NaF-SiF4 and Na2O-SiO2 are reproduced within the experimental error limits. In the reciprocal system, a group of data in conflict with all others could not be reproduced. The data considered reliable are well reproduced. A

  4. Disappearance of superconductivity in the solid solution between (Ca4Al2O6)(Fe2As2) and (Ca4Al2O6)(Fe2P2) superconductors.

    PubMed

    Shirage, Parasharam M; Kihou, Kunihiro; Lee, Chul-Ho; Takeshita, Nao; Eisaki, Hiroshi; Iyo, Akira

    2012-09-19

    The effect of alloying the two perovskite-type iron-based superconductors (Ca(4)Al(2)O(6))(Fe(2)As(2)) and (Ca(4)Al(2)O(6))(Fe(2)P(2)) was examined. While the two stoichiometric compounds possess relatively high T(c)'s of 28 and 17 K, respectively, their solid solutions of the form (Ca(4)Al(2)O(6))(Fe(2)(As(1-x)P(x))(2)) do not show superconductivity over a wide range from x = 0.50 to 0.95. The resultant phase diagram is thus completely different from those of other typical iron-based superconductors such as BaFe(2)(As,P)(2) and LaFe(As,P)O, in which superconductivity shows up when P is substituted for As in the non-superconducting "parent" compounds. Notably, the solid solutions in the non-superconducting range exhibit resistivity anomalies at temperatures of 50-100 K. The behavior is reminiscent of the resistivity kink commonly observed in various non-superconducting parent compounds that signals the onset of antiferromagnetic/orthorhombic long-range order. The similarity suggests that the suppression of the superconductivity in the present case also has a magnetic and/or structural origin.

  5. Structural similarities of Na,K-ATPase and SERCA, the Ca(2+)-ATPase of the sarcoplasmic reticulum.

    PubMed Central

    Sweadner, K J; Donnet, C

    2001-01-01

    The crystal structure of SERCA1a (skeletal-muscle sarcoplasmic-reticulum/endoplasmic-reticulum Ca(2+)-ATPase) has recently been determined at 2.6 A (note 1 A = 0.1 nm) resolution [Toyoshima, Nakasako, Nomura and Ogawa (2000) Nature (London) 405, 647-655]. Other P-type ATPases are thought to share key features of the ATP hydrolysis site and a central core of transmembrane helices. Outside of these most-conserved segments, structural similarities are less certain, and predicted transmembrane topology differs between subclasses. In the present review the homologous regions of several representative P-type ATPases are aligned with the SERCA sequence and mapped on to the SERCA structure for comparison. Homology between SERCA and the Na,K-ATPase is more extensive than with any other ATPase, even PMCA, the Ca(2+)-ATPase of plasma membrane. Structural features of the Na,K-ATPase are projected on to the Ca(2+)-ATPase crystal structure to assess the likelihood that they share the same fold. Homology extends through all ten transmembrane spans, and most insertions and deletions are predicted to be at the surface. The locations of specific residues are examined, such as proteolytic cleavage sites, intramolecular cross-linking sites, and the binding sites of certain other proteins. On the whole, the similarity supports a shared fold, with some particular exceptions. PMID:11389677

  6. A potentially new type of nonchondritic interplanetary dust particle with hematite, organic carbon, amorphous Na,Ca-aluminosilicate, and FeO-spheres

    NASA Astrophysics Data System (ADS)

    Muñoz Caro, Guillermo M.; Rietmeijer, Frans J. M.; Souza-Egipsy, Virginia; Valles-González, Maria Pilar

    2012-02-01

    We used a combination of different analytical techniques to study particle W7190-D12 using microinfrared spectroscopy, micro-Raman spectroscopy, and field emission scanning electron microscopy (FESEM) energy dispersive X-ray spectroscopy (EDS). The particle consists mainly of hematite (α-Fe2O3) with considerable variations in structural disorder. It further contains amorphous (Na,K)-bearing Ca,Al-silicate and organic carbon. Iron-bearing spherules (<150 nm in diameter) cover the surface of this particle. At local sites of structural disorder at the hematite surface, the hematite spheres were reduced to FeO in the presence of organic carbons forming FeO-spheres. However, metallic Fe spheres cannot be excluded based on the available data. To the best of our knowledge, this particle is the first detection of such spherules at the surface of a stratospheric dust particle. Although there is no definitive evidence for an extraterrestrial origin of particle W7190-D12, we suggest that it could be an IDP that had moved away from the asteroid-forming region of the early solar system into the outer solar system of the accreting Kuiper Belt objects. After it was released from a Jupiter family comet, this particle became part of the zodiacal cloud. Atmospheric entry flash-heating caused (1) the formation of microenvironments of reduced iron oxide when indigenous carbon materials reacted with hematite covering its surface resulting in the formation of FeO-spheres and (2) Na-loss from Na,Al-plagioclase. The particle of this study, and other similar particles on this collector, may represent a potentially new type of nonchondritic IDPs associated with Jupiter family comets, although an origin in the asteroid belt cannot be ignored.

  7. Materials Data on NaCaAlSi2O7 (SG:19) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-07-09

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

  8. δ/ω-Plectoxin-Pt1a: An Excitatory Spider Toxin with Actions on both Ca2+ and Na+ Channels

    PubMed Central

    Zhou, Yi; Zhao, Mingli; Fields, Gregg B.; Wu, Chun-Fang; Branton, W. Dale

    2013-01-01

    The venom of spider Plectreurys tristis contains a variety of peptide toxins that selectively target neuronal ion channels. O-palmitoylation of a threonine or serine residue, along with a characteristic and highly constrained disulfide bond structure, are hallmarks of a family of toxins found in this venom. Here, we report the isolation and characterization of a new toxin, δ/ω-plectoxin-Pt1a, from this spider venom. It is a 40 amino acid peptide containing an O-palmitoylated Ser-39. Analysis of δ/ω-plectoxin-Pt1a cDNA reveals a small precursor containing a secretion signal sequence, a 14 amino acid N-terminal propeptide, and a C-terminal amidation signal. The biological activity of δ/ω-plectoxin-Pt1a is also unique. It preferentially blocks a subset of Ca2+ channels that is apparently not required for neurotransmitter release; decreases threshold for Na+ channel activation; and slows Na+ channel inactivation. As δ/ω-plectoxin-Pt1a enhances synaptic transmission by prolonging presynaptic release of neurotransmitter, its effects on Na+ and Ca2+ channels may act synergistically to sustain the terminal excitability. PMID:23691198

  9. Synthesis of Multicolor Core/Shell NaLuF₄:Yb(3+)/Ln(3+)@CaF₂ Upconversion Nanocrystals.

    PubMed

    Li, Hui; Hao, Shuwei; Yang, Chunhui; Chen, Guanying

    2017-02-07

    The ability to synthesize high-quality hierarchical core/shell nanocrystals from an efficient host lattice is important to realize efficacious photon upconversion for applications ranging from bioimaging to solar cells. Here, we describe a strategy to fabricate multicolor core @ shell α-NaLuF₄:Yb(3+)/Ln(3+)@CaF₂ (Ln = Er, Ho, Tm) upconversion nanocrystals (UCNCs) based on the newly established host lattice of sodium lutetium fluoride (NaLuF₄). We exploited the liquid-solid-solution method to synthesize the NaLuF₄ core of pure cubic phase and the thermal decomposition approach to expitaxially grow the calcium fluoride (CaF₂) shell onto the core UCNCs, yielding cubic core/shell nanocrystals with a size of 15.6 ± 1.2 nm (the core ~9 ± 0.9 nm, the shell ~3.3 ± 0.3 nm). We showed that those core/shell UCNCs could emit activator-defined multicolor emissions up to about 772 times more efficient than the core nanocrystals due to effective suppression of surface-related quenching effects. Our results provide a new paradigm on heterogeneous core/shell structure for enhanced multicolor upconversion photoluminescence from colloidal nanocrystals.

  10. Effect of plasma electrolytic oxidation in the solutions containing Ca, P, Si, Na on the properties of titanium.

    PubMed

    Krupa, Danuta; Baszkiewicz, Jacek; Zdunek, Joanna; Sobczak, Janusz W; Lisowski, Wojciech; Smolik, Jerzy; Słomka, Zbigniew

    2012-11-01

    The surface layers were formed on titanium by plasma electrolytic oxidation (PEO) in the solutions which contain various amounts of Na(2)SiO(3)x5H(2)O, Na(3)PO(4) x12H(2)O and Ca(CH(3)COO)(2) xH(2)O. The layers were characterized using a scanning electron microscope (SEM) coupled with an energy dispersive spectrometer (EDS) and an X-ray diffractometer (XRD). The titanium/oxide surface layer interface was analyzed by X-ray photoelectron spectroscopy (XPS). The adhesive strength of the oxide layers was evaluated by the scratch-test. The bioactivity of the surface was determined by soaking in a simulated body fluid (SBF) for 7 and 30 days. The corrosion resistance was determined by electrochemical methods after 13, 181, and 733 h exposure in SBF at a temperature of 37°C. The oxide layers obtained were rough and porous and enriched with Ca, P, Si, and Na and their properties depended on the concentration of the components of the electrolyte. The results of the electrochemical examinations, after a 13 h exposure in SBF, show that the surface modification by PEO improves the corrosion resistance of titanium and it is not degraded after a long-term exposure in SBF. The electrochemical impedance spectroscopy (EIS) results indicate that the surface layers have a complex structure.

  11. Age-dependent changes in diastolic Ca{sup 2+} and Na{sup +} concentrations in dystrophic cardiomyopathy: Role of Ca{sup 2+} entry and IP{sub 3}

    SciTech Connect

    Mijares, Alfredo; Altamirano, Francisco; Kolster, Juan; Adams, José A.; López, José R.

    2014-10-03

    Highlights: • Age-dependent increase in [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} in mdx cardiomyocytes. • Gadolinium significantly reduced both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} at all ages. • IP{sub 3}-pathway inhibition reduced cations concentrations in dystrophic cardiomyocytes. - Abstract: Duchenne muscular dystrophy (DMD) is a lethal X-inherited disease caused by dystrophin deficiency. Besides the relatively well characterized skeletal muscle degenerative processes, DMD is also associated with a dilated cardiomyopathy that leads to progressive heart failure at the end of the second decade. The aim of the present study was to characterize the diastolic Ca{sup 2+} concentration ([Ca{sup 2+}]{sub d}) and diastolic Na{sup +} concentration ([Na{sup +}]{sub d}) abnormalities in cardiomyocytes isolated from 3-, 6-, 9-, and 12-month old mdx mice using ion-selective microelectrodes. In addition, the contributions of gadolinium (Gd{sup 3+})-sensitive Ca{sup 2+} entry and inositol triphosphate (IP{sub 3}) signaling pathways in abnormal [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} were investigated. Our results showed an age-dependent increase in both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} in dystrophic cardiomyocytes compared to those isolated from age-matched wt mice. Gd{sup 3+} treatment significantly reduced both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} at all ages. In addition, blockade of the IP{sub 3}-pathway with either U-73122 or xestospongin C significantly reduced ion concentrations in dystrophic cardiomyocytes. Co-treatment with U-73122 and Gd{sup 3+} normalized both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} at all ages in dystrophic cardiomyocytes. These data showed that loss of dystrophin in mdx cardiomyocytes produced an age-dependent intracellular Ca{sup 2+} and Na{sup +} overload mediated at least in part by enhanced Ca{sup 2+} entry through Gd{sup 3+} sensitive transient receptor potential channels (TRPC), and by IP{sub 3} receptors.

  12. Removal of arsenic from water by Friedel's salt (FS: 3CaO·Al2O3·CaCl2·10H2O).

    PubMed

    Zhang, Danni; Jia, Yongfeng; Ma, Jiayu; Li, Zhibao

    2011-11-15

    Low levels of arsenic can be effectively removed from water by adsorption onto various materials and searching for low-cost, high-efficiency new adsorbents has been a hot topic in recent years. In the present study, the performance of Friedel's salt (FS: 3CaO·Al(2)O(3)·CaCl(2)·10H(2)O), a layered double hydroxide (LDHs), as an adsorbent for arsenic removal from aqueous solution was investigated. Friedel's salt was synthesized at lower temperature (50°C) compared to traditional autoclave methods by reaction of calcium chloride with sodium aluminate. Kinetic study revealed that adsorption of arsenate by Friedel's salt was fast in the first 12h and equilibrium was achieved within 48 h. The adsorption kinetics are well described by second-order Lageren equation. The adsorption capacity of the synthesized sorbent for arsenate at pH 4 and 7 calculated from Langmuir adsorption isotherms was 11.85 and 7.80 mg/g, respectively. Phosphate and silicate markedly decreased the removal of arsenate, especially at higher pH, but sulfate was found to suppress arsenate adsorption at lower pH and the adverse effect was disappeared at pH ≥ 6. Common metal cations (Ca(2+), Mg(2+)) enhanced arsenate adsorption. The results suggest that Friedel's salt is a potential cost-effective adsorbent for arsenate removal in water treatment.

  13. Blue upconversion luminescence in 12 CaO·7 Al 2O 3:Tm 3 + /Yb 3 + polycrystals

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Liu, Liang; Sun, Jinchao; Qian, Yannan; Zhang, Yushen; Xu, Yanling

    2012-03-01

    The effect of Yb 3 + concentration on the fluorescence of 12 CaO·7 Al 2O 3:Tm 3 + /Yb 3 + polycrystals is investigated. Under the excitation of 980 nm laser, the strong blue (477 nm) emission band is observed and attributed to 1G 4 → 3H 6 of Tm 3 + . The ratio of blue to red emission increases with the increasing of Yb 3 + and remains constant at 10 mol% Yb 3 + . The pump dependence and upconversion mechanisms show that the two-photon cooperative upconversion process is responsible for the enhancement of the blue upconversion emission. The Commission Internationale de l'eclairage chromaticity coordinates (x, y) illustrate that the 12 CaO·7 Al 2O 3:1 mol% Tm 3 + /10 mol% Yb 3 + can emit high-purity blue light.

  14. Experimental constraints on the monazite-fluorapatite-allanite and xenotime-(Y,HREE)-rich fluorapatite-(Y,HREE)-rich epidote phase relations as a function of pressure, temperature, and Ca vs. Na activity in the fluid

    NASA Astrophysics Data System (ADS)

    Budzyń, Bartosz; Harlov, Daniel E.; Majka, Jarosław; Kozub, Gabriela A.

    2014-05-01

    Stability relations of monazite-fluorapatite-allanite and xenotime-(Y,HREE)-rich fluorapatite-(Y,HREE)-rich epidote are strongly dependent on pressure, temperature and fluid composition. The increased Ca bulk content expands stability field of allanite relative to monazite towards higher temperatures (Spear, 2010, Chem Geol 279, 55-62). It was also reported from amphibolite facies Alpine metapelites, that both temperature and bulk CaO/Na2O ratio control relative stabilities of allanite, monazite and xenotime (Janots et al., 2008, J Metam Geol 26, 5, 509-526). This study experimentally defines influence of pressure, temperature, high activity of Ca vs. Na in the fluid, and high vs. moderate bulk CaO/Na2O ratio on the relative stabilities of monazite-fluorapatite-allanite/REE-rich epidote and xenotime-(Y,HREE)-rich fluorapatite-(Y,HREE)-rich epidote. This work expands previous experimental study on monazite (Budzyń et al., 2011, Am Min 96, 1547-1567) to wide pressure-temperature range of 2-10 kbar and 450-750°C, utilizing most reactive fluids used in previous experiments. Experiments were performed using cold-seal autoclaves on a hydrothermal line (2-4 kbar runs) and piston-cylinder apparatus (6-10 kbar runs) over 4-16 days. Four sets of experiments, two for monazite and two for xenotime, were performed with 2M Ca(OH)2 and Na2Si2O5 + H2O fluids. The starting materials included inclusion-free crystals of monazite (pegmatite, Burnet County, TX, USA) or xenotime (pegmatite, Northwest Frontier Province, Pakistan) mixed with (1) labradorite (Ab37An60Kfs3) + K-feldspar + biotite + muscovite ± garnet + SiO2 + CaF2 + 2M Ca(OH)2 or (2) albite (Ab100) + K-feldspar + biotite + muscovite ± garnet + SiO2 + CaF2 + Na2Si2O5 + H2O. 20-35 mg of solids and 5 mg of fluid were loaded into 3x15 mm Au capsules and arc welded shut. The monazite alteration is observed in all runs. Newly formed REE-rich fluorapatite and/or britholite are stable in all experimental P-T range in the

  15. Ultrafast bulk diffusion of AlHx in high-entropy dehydrogenation intermediates of NaAlH4 [Highly mobile AlHx species and the dehydogenation kinetics of NaAlH4

    SciTech Connect

    Zhang, Feng; Wood, Brandon C.; Wang, Yan; Wang, Cai -Zhuang; Ho, Kai -Ming; Chou, Mei -Yin

    2014-07-21

    Using first-principles molecular dynamics (FPMD) and total-energy calculations, we demonstrate low-barrier bulk diffusion of Al-bearing species in γ-NaAlH4, a recently proposed high-entropy polymorph of NaAlH4. For charged AlH4– and neutral AlH3 vacancies, the computed barriers for diffusion are <0.1 eV, and we directly observe the predicted diffusive pathways in FPMD simulations at picosecond time scales. In contrast, such diffusion in the α phase is inaccessible to FPMD, consistent with much higher barriers. The transport behavior of γ-NaAlH4, in addition to key dynamical and structural signatures, is consistent with experimental observations of high-mobility species, strongly supporting the idea that an intermediate transition from the α phase to a high-entropy polymorph facilitates the hydrogen-releasing decomposition of NaAlH4. Lastly, our results provide an answer to longstanding questions regarding the responsible agent for the experimentally observed efficient Al transport during dehydrogenation and suggest that mass transport and phase transformation kinetics are coupled. Implications for understanding the (de)hydrogenation of undoped and catalyzed NaAlH4 are discussed.

  16. Effects of neomycin on high-threshold Ca(2+) currents and tetrodotoxin-resistant Na(+) currents in rat dorsal root ganglion neuron.

    PubMed

    Zhou, Yu; Zhao, Zhi-Qi

    2002-08-16

    High-threshold Ca(2+) channels and tetrodotoxin-resistant Na(+) channels are highly expressed in small dorsal root ganglion neurons. In acutely isolated rat dorsal root ganglion neurons, the effects of neomycin, one of the aminoglycoside antibiotics, on high-threshold Ca(2+) currents and tetrodotoxin-resistant Na(+) currents were examined using whole-cell patch recording. We showed for the first time that neomycin dose-dependently inhibited peak high-threshold Ca(2+) currents and peak tetrodotoxin-resistant Na(+) currents with half-maximal inhibitory concentrations at 3.69 microM (n=20) and 1213.44 microM (n=25), respectively. Inactivation properties of high-threshold Ca(2+) currents and activation properties of tetrodotoxin-resistant Na(+) currents were also affected by neomycin with reduction of excitability of small dorsal root ganglion neurons. Half-maximal inactivation voltage of high-threshold Ca(2+) currents was -45.56 mV before and -50.46 mV after application of neomycin (n=10). Half-maximal activation voltage of tetrodotoxin-resistant Na(+) currents was -19.93 mV before and -11.19 mV after administration of neomycin (n=15). These results suggest that neomycin can inhibit high-threshold Ca(2+) currents and tetrodotoxin-resistant Na(+) currents in small dorsal root ganglion neurons, which may contribute to neomycin-induced peripheral and central analgesia.

  17. A facile and environmentally friendly NaCl nonaqueous ionic liquid route to prepare crystalline β-CaSiO3 nanowires.

    PubMed

    Wang, Wenzhong; Zhang, Suyun; Wang, Lijuan; Shi, Honglong

    2013-05-01

    We described an environmentally friendly and facile NaCl nonaqueous ionic liquid route for the first time to synthesize β-CaSiO3 nanowires. β-CaSiO3 nanowires were prepared by annealing precursor calcium silicate hydrate (CSH) nanostructures in NaCl nonaqueous ionic liquid, in which the precursor CSH nanostructures were first prepared by a facile one-step, solid state reaction, ground with both NaCl and surfactant nonyl phenyl ether (9) (NP-9), and heated at 850 °C for 2 h. β-CaSiO3 nanowires were characterized by XRD, TEM and HRTEM. The comparative experiments have been conducted systemically to investigate the growth mechanism of β-CaSiO3 nanowires, and the roles of salt NaCl nonaqueous ionic liquid and NP-9 on the formation of β-CaSiO3 nanowires. The results demonstrated that both salt NaCl nonaqueous ionic liquid and surfactant NP-9 played key roles on the formation of β-CaSiO3 nanowires. A rational growth mechanism of β-CaSiO3 nanowires has been proposed on the basis of experimental results.

  18. The properties, distribution and function of Na(+)-Ca(2+) exchanger isoforms in rat cutaneous sensory neurons.

    PubMed

    Scheff, N N; Yilmaz, E; Gold, M S

    2014-11-15

    The Na(+)-Ca(2+) exchanger (NCX) appears to play an important role in the regulation of the high K(+)-evoked Ca(2+) transient in putative nociceptive dorsal root ganglion (DRG) neurons. The purpose of the present study was to (1) characterize the properties of NCX activity in subpopulations of DRG neurons, (2) identify the isoform(s) underlying NCX activity, and (3) begin to assess the function of the isoform(s) in vivo. In retrogradely labelled neurons from the glabrous skin of adult male Sprague-Dawley rats, NCX activity, as assessed with fura-2-based microfluorimetry, was only detected in putative nociceptive IB4+ neurons. There were two modes of NCX activity: one was evoked in response to relatively large and long lasting (∼325 nm for >12 s) increases in the concentration of intracellular Ca(2+) ([Ca(2+)]i), and a second was active at resting [Ca(2+)]i > ∼150 nm. There also were two modes of evoked activity: one that decayed relatively rapidly (<5 min) and a second that persisted (>10 min). Whereas mRNA encoding all three NCX isoforms (NCX1-3) was detected in putative nociceptive cutaneous neurons with single cell PCR, pharmacological analysis and small interfering RNA (siRNA) knockdown of each isoform in vivo suggested that NCX2 and 3 were responsible for NCX activity. Western blot analyses suggested that NCX isoforms were differentially distributed within sensory neurons. Functional assays of excitability, action potential propagation, and nociceptive behaviour suggest NCX activity has little influence on excitability per se, but instead influences axonal conduction velocity, resting membrane potential, and nociceptive threshold. Together these results indicate that the function of NCX in the regulation of [Ca(2+)]i in putative nociceptive neurons may be unique relative to other cells in which these exchanger isoforms have been characterized and it has the potential to influence sensory neuron properties at multiple levels.

  19. Synthesis and hydration behavior of calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cement

    SciTech Connect

    Kang, Eun-Hee; Yoo, Jun-Sang; Kim, Bo-Hye; Choi, Sung-Woo; Hong, Seong-Hyeon

    2014-02-15

    Calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cements were prepared by solid state reaction and polymeric precursor methods, and their phase evolution, morphology, and hydration behavior were investigated. In polymeric precursor method, a nearly single phase Ca{sub 7}ZrAl{sub 6}O{sub 18} was obtained at relatively lower temperature (1200 °C) whereas in solid state reaction, a small amount of CaZrO{sub 3} coexisted with Ca{sub 7}ZrAl{sub 6}O{sub 18} even at higher temperature (1400 °C). Unexpectedly, Ca{sub 7}ZrAl{sub 6}O{sub 18} synthesized by polymeric precursor process was the large-sized and rough-shaped powder. The planetary ball milling was employed to control the particle size and shape. The hydration behavior of Ca{sub 7}ZrAl{sub 6}O{sub 18} was similar to that of Ca{sub 3}Al{sub 2}O{sub 6} (C3A), but the hydration products were Ca{sub 3}Al{sub 2}O{sub 6}·6H{sub 2}O (C3AH6) and several intermediate products. Thus, Zr (or ZrO{sub 2}) stabilized the intermediate hydration products of C3A.

  20. The Relative Nature of Perception: A Response to Cañal-Bruland and van der Kamp (2015)

    PubMed Central

    2015-01-01

    Cañal-Bruland and van der Kamp present an argument about the incommensurate relationship between affordance perception and spatial perception in a criticism of Proffitt and Linkenauger’s phenotypic approach to perception. Many of their criticisms are based on a difference in the interpretation of the core ideas underlying the phenotypic approach. The most important of these differences in interpretations concern fundamental assumptions about the nature of the perceptions of size and distance themselves. Extent perception must be relative to the organism; therefore, there can be no veridical perception of space. Also, we argue in the phenotypic approach that space perception is an emergent property of affordance perception; they are not different types of perceptions as Cañal-Bruland and van der Kamp presume. Third, affordance perception need not be perfectly accurate, just good enough. Additionally, affordance perception need not be dichotomous; this presumption likely originates in the methodology typically employed to study affordance perception. Finally, I agree with Cañal-Bruland and van der Kamp that joint research efforts will clarify and improve our understanding of these issues. PMID:27648215

  1. Strain-Induced Enhancement of Eu3+ Emission in Red Phosphor NaMgPO4:Eu3+, Al3+

    NASA Astrophysics Data System (ADS)

    Gao, Yong; Long, Qiwei; Nong, Rong; Wang, Tianman; Huang, Yingheng; Liao, Sen; Zhang, Huaxin

    2017-02-01

    A series of (NaMgPO4)0.98- x : {Eu}_{0.02}^{3 + }, {Al}x^{3 + } phosphors were prepared by the solid-state method. X-ray powder diffraction results confirm that the samples contain mixture phases of crystals. The doped effect of Al3+ on the photoluminescence properties of (NaMgPO4)0.98- x : {Eu}_{0.02}^{3 + }, {Al}x^{3 + } phosphors is discussed. The results indicate that two dependent curves of emission relative intensity and strain on Al3+ doping concentration are all Gaussian curves, and a high correlation is observed between emission relative intensity of Eu3+ and strain caused by Al3+. In other words, emission relative intensity of Eu3+ is enhanced with the increase of the strain. The enhanced mechanism of the strain is discussed. In addition, (NaMgPO4)0.98- x : {Eu}_{0.02}^{3 + }, {Al}x^{3 + } phosphors are electric dipole-dominated transition red phosphors. The optimal molar concentration of Al3+ for the samples is 9%, which (NaMgPO4)0.89: {Eu}_{0.02}^{3 + }, {Al}_{0.09}^{3 + } is a potential candidate as the red-emitting phosphor for ultraviolet-based white light-emitting diodes.

  2. Mechanism of capsaicin receptor TRPV1-mediated toxicity in pain-sensing neurons focusing on the effects of Na(+)/Ca(2+) fluxes and the Ca(2+)-binding protein calretinin.

    PubMed

    Pecze, László; Blum, Walter; Schwaller, Beat

    2013-07-01

    Transient receptor potential vanilloid subtype 1 (TRPV1) receptor is a pain-sensing, ligand-gated, non-selective cation channel expressed in peripheral sensory neurons. Prolonged activation of TRPV1 by capsaicin leads to cell swelling and formation of membrane blebs in rat dorsal root ganglion (DRG) neurons. Similar results were obtained in NIH3T3 fibroblast cells stably expressing TRPV1. Here, we assessed the contribution of Ca(2+) and Na(+) ions to TRPV1-mediated changes. Cell swelling was caused by a substantial influx of extracellular Na(+) via TRPV1 channels, causing concomitant transport of water. In the absence of extracellular Na(+), the membrane blebbing was completely inhibited, but Ca(2+) influx did not change under these conditions. Na(+) influx was modulated by the intracellular Ca(2+) concentration ([Ca(2+)]i). Elevation of [Ca(2+)]i by ionomycin sensitized/activated TRPV1 channels causing cell swelling in TRPV1-positive cells. In the absence of extracellular Ca(2+), capsaicin caused only little increase in [Ca(2+)]i indicating that the increase in [Ca(2+)]i observed after capsaicin application is derived essentially from extracellular Ca(2+) and not from internal Ca(2+) stores. In the absence of extracellular Ca(2+) also the process of cell swelling was considerably slower. Calretinin is a Ca(2+) buffer protein, which is expressed in a subset of TRPV1-positive neurons. Calretinin decreased the amplitude, but slowed down the decay of Ca(2+) signals evoked by ionomycin. Cells co-expressing TRPV1 and calretinin were less sensitive to TRPV1-mediated, capsaicin-induced volume increases. In TRPV1-expressing NIH3T3 cells, calretinin decreased the capsaicin-induced Ca(2+) and Na(+) influx. Swelling and formation of membrane blebs resulted in impaired plasma membrane integrity finally leading to cell death. Our results hint towards a mechanistic explanation for the apoptosis-independent capsaicin-evoked neuronal loss and additionally reveal a protective

  3. Dachiardite-K, (K2Ca)(Al4Si20O48) · 13H2O, a new zeolite from Eastern Rhodopes, Bulgaria

    NASA Astrophysics Data System (ADS)

    Chukanov, N. V.; Encheva, S.; Petrov, P.; Pekov, I. V.; Belakovskiy, D. I.; Britvin, S. N.; Aksenov, S. M.

    2016-12-01

    Dachiardite-K (IMA No. 2015-041), a new zeolite, is a K-dominant member of the dachiardite series with the idealized formula (K2Ca)(Al4Si20O48) · 13H2O. It occurs in the walls of opal-chalcedony veinlets cutting hydrothermally altered effusive rocks of the Zvezdel paleovolcanic complex near the village of Austa, Momchilgrad Municipality, Eastern Rhodopes, Bulgaria. Chalcedony, opal, dachiardite-Ca, dachiardite-Na, ferrierite-Mg, ferrierite-K, clinoptilolite-Ca, clinoptilolite-K, mordenite, smectite, celadonite, calcite, and barite are associated minerals. The mineral forms radiated aggregates up to 8 mm in diameter consisting of split acicular individuals. Dachiardite-K is white to colorless. Perfect cleavage is observed on (100). D meas = 2.18(2), D calc = 2.169 g/cm3. The IR spectrum is given. Dachiardite-K is biaxial (+), α = 1.477 (calc), β = 1.478(2), γ = 1.481(2), 2 V meas = 65(10)°. The chemical composition (electron microprobe, mean of six point analyses, H2O determined by gravimetric method) is as follows, wt %: 4.51 K2O, 3.27 CaO, 0.41 BaO, 10.36 A12O3, 67.90 SiO2, 13.2 H2O, total is 99.65. The empirical formula is H26.23K1.71Ca1.04Ba0.05Al3.64Si20.24O61. The strongest reflections in the powder X-ray diffraction pattern [ d, Å (I, %) (hkl)] are: 9.76 (24) (001), 8.85 (58) (200), 4.870 (59) (002), 3.807 (16) (202), 3.768 (20) (112, 020), 3.457 (100) (220), 2.966 (17) (602). Dachiardite-K is monoclinic, space gr. C2/m, Cm or C2; the unit cell parameters refined from the powder X-ray diffraction data are: a = 18.670(8), b = 7.511(3), c = 10.231(4) Å, β = 107.79(3)°, V= 1366(1) Å3, Z = 1. The type specimen has been deposited in the Earth and Man National Museum, Sofia, Bulgaria, with the registration number 23927.

  4. [Concentrations of Na, K, Ca, and P in serum from a representative sample of the Canary Islands population].

    PubMed

    Díaz Romero, C; Henríquez Sánchec, P; López Blanco, F; Rodríguez Rodríguez, E; Serra Majem, Ll

    2002-01-01

    As part of the nutritional survey of the Canary Islands (ENCA-1998), the concentrations in serum of Na, K, Ca and P were determined in 395 individuals representing the population of the Canary Islands. The concentrations were found to be within the reference intervals described for the healthy population. Differences were observed in the mean concentrations depending on the island of residence. Thus, individuals on the island of Tenerife showed higher levels of natremia and calcaemia (p < 0.05) than those on the other islands. The islanders of La Palma have the highest (p < 0.05) and lowest (p < 0.05) concentrations of K and Ca, respectively, whereas those living on the easternmost islands have the highest levels of phosphataemia. No differences were detected in the mineral levels by sex. Phosphataemia levels fall (p < 0.05) in line with socio-economic levels. Females under the age of 18 present lower levels of natremia (p < 0.05) than others while males over the age of 35 present higher levels of kalaemia (p < 0.05). No important age-related differences were found in calcaemia and individuals under the age of 18 had lower levels of phosphataemia (p < 0.05) than the remainder. Highly significant relationships were found between Na and K and between Ca and P, thus confirming existing physiological relationships. Smoking had no effect on the serum levels of the elements under study. Those individuals reporting an intake of more than seven beers and seven shots of spirit per week presented lower levels of calcaemia and natremia than the rest (p < 0.05). With wine consumption, an increase in kalaemia and a significant reduction (p < 0.05) in the Na/K ratio were detected. Individuals drinking only tap water had higher levels (p < 0.05) of natraemia and kalaemia, with lower levels (p < 0.05) of calcaemia and the Na/K ratio than those drinking bottled water. The Ca/P ratio was significantly reduced (p < 0.05) with physical exercise.

  5. Induced IR overtone and fundamental bands of isotopic H 2 molecules adsorbed in NaCaA zeolites

    NASA Astrophysics Data System (ADS)

    Förster, H.; Frede, W.

    1984-05-01

    NIR spectroscopy has been successfully applied to surface chemical problems, using the FT transmission technique. Vibrational spectra of H 2 and D 2, adsorbed in NaA and NaCaA zeolites, have been recorded in the fundamental regions of both adsorbates and, for the first time, in the overtone region of D 2. Useful information on the properties of the adsorbed molecules can be derived from the overtone spectra of D 2 and the fine structure of the H 2 fundamental. It turns out that the properties of the D 2 molecules, e.g. dissociation energy and anharmonicity, are hardly affected by adsorption. The fine structure of the H 2 fundamental, however, indicates the rotation to be strongly hindered. The ortho-para splitting is decreased with respect to the free molecule value and approaches that for planarly rotating molecules. Due to this hindrance, the corresponding D 2 splitting is not resolved.

  6. The effect of Na-bearing thermal solutions on Ca-Mg-bentonite sorption of Sr and Cs

    SciTech Connect

    Mukhamet-Galeyev, A.P.; Kudrin, A.V.; Nikonov, B.S.; Shikina, N.D.

    1995-12-31

    The sorption of Sr and Cs has been investigated on Ca-Mg-bentonite preliminary treated by 0.1--1.0 m NaCl solutions at 25, 170--250 C during 0.5--7 months. The bentonite remained stable in these conditions. Moreover, hydrothermal treatment has raised the sorption activity of the bentonite. The treated bentonite has shown a strong selectivity for Sr and less pronounced one for Cs. The sorption of the elements increased with temperature and decreased with NaCl content more significant for Sr, than for Cs. The distribution ratio R{sub d} was nearly independent on ion loading for Cs and strongly increased up to 10{sup 4.5} mL/g in 10{sup {minus}2.0}--10{sup {minus}0.5} meq/g ion loading interval for Sr, dropping sharply at more concentrations.

  7. Effect of Al2O3 on the Viscosity and Structure of CaO-SiO2-MgO-Al2O3-FetO Slags

    NASA Astrophysics Data System (ADS)

    Wang, Zhanjun; Sun, Yongqi; Sridhar, Seetharaman; Zhang, Mei; Guo, Min; Zhang, Zuotai

    2015-04-01

    The present paper provided a fundamental investigation on the effect of Al2O3 on the viscosity and structure of CaO-SiO2-MgO-Al2O3-FetO slags for the purpose of efficiently recycling the valuable elements from the steelmaking slags. The results show that the viscosity of CaO-SiO2-Al2O3-MgO-FetO slags slightly increases with increasing Al2O3 content. The degree of the polymerization (DOP) of quenched slags, determined from Raman spectra and magic angle spinning-nuclear magnetic resonance, is also found to increase with increasing Al2O3 content. It can be deduced that the increasing DOP can promote the formation of gehlenite phase (Ca2Al2SiO7), thus facilitating the formation of higher phosphorous (or vanadium) contained solid solution ( n'Ca2SiO4·Ca3((P or V)O4)2). As Al2O3 content increases up to a specific value, the charge compensating ions which present near [AlO4]-tetrahedra and [FeO4]-tetrahedra are not fully supplied due to the scarcity of Ca2+. In this case, the existing Fe3+ in the melt cannot completely form [FeO4]-tetrahedra and part of Fe3+ would form [FeO6]-octahedra to substitute Ca2+ to modify the slags.

  8. Internally consistent thermodynamic data for aqueous species in the system Na-K-Al-Si-O-H-Cl

    NASA Astrophysics Data System (ADS)

    Miron, George D.; Wagner, Thomas; Kulik, Dmitrii A.; Heinrich, Christoph A.

    2016-08-01

    their experimental uncertainties. The new dataset resolves the long-standing discrepancies between thermodynamic data of minerals and those of aqueous ions and complexes, by achieving an astonishing degree of consistency between a large number of fluid-mineral equilibrium data. All of this at the expense of changing the standard state properties of aqueous species, mainly the Gibbs energy of formation. Using the same strategy, the core dataset for the system Na-K-Al-Si-O-H-Cl can be extended with additional rock-forming elements such as Ca, Mg, Fe, Mn, Ti, S, C, B. In future, the standard-state properties of minerals and aqueous species should be simultaneously optimized, to create the next-generation of fully internally consistent data for fluid-mineral equilibria. Although we employ the widely used HKF equations for this study, the same computational approach can be readily applied to any other speciation-based equation of state for multicomponent aqueous solutions.

  9. The influence of Ca-Mg-Al hydrotalcite synthesized from brine water on thermal and mechanical properties of HTlc-EVA composite

    SciTech Connect

    Karina, Wiwiek Heraldy, Eddy Pramono, Edi; Heriyanto,; Astuti, Shanti

    2016-02-08

    Ca-Mg-Al hydrotalcite-like compound (Ca-Mg-Al HTlc) was prepared by co-precipitation method using brine water that is well known as the desalination process waste water. The structure of Ca-Mg-Al HTlc was determined by X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) analysis. Ca-Mg-Al HTlc was studied as a non-halogenated filler in ethylene vinyl acetate (EVA) matrix. Composites with different filler concentrations were prepared to evaluate the influence of Ca-Mg-Al HTlc on thermal and mechanical properties of EVA.The presence of Ca-Mg-Al HTlc in the composite has been confirmed by FTIR analysis. Thermal properties of composites show significant reduction of degradation temperature as well as the loading of HTlc in EVA. However, the total enthalpies combustion of composites with 1% and 5% HTlc loadings higher compared to neat EVA. Further, mechanical properties were determined by tensile test. The result shows that tensile strength and elongation at break of composites decrease relatively by Ca-Mg-Al HTlc addition.

  10. The influence of Ca-Mg-Al hydrotalcite synthesized from brine water on thermal and mechanical properties of HTlc-EVA composite

    NASA Astrophysics Data System (ADS)

    Karina, Wiwiek; Heraldy, Eddy; Pramono, Edi; Heriyanto, Astuti, Shanti

    2016-02-01

    Ca-Mg-Al hydrotalcite-like compound (Ca-Mg-Al HTlc) was prepared by co-precipitation method using brine water that is well known as the desalination process waste water. The structure of Ca-Mg-Al HTlc was determined by X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) analysis. Ca-Mg-Al HTlc was studied as a non-halogenated filler in ethylene vinyl acetate (EVA) matrix. Composites with different filler concentrations were prepared to evaluate the influence of Ca-Mg-Al HTlc on thermal and mechanical properties of EVA.The presence of Ca-Mg-Al HTlc in the composite has been confirmed by FTIR analysis. Thermal properties of composites show significant reduction of degradation temperature as well as the loading of HTlc in EVA. However, the total enthalpies combustion of composites with 1% and 5% HTlc loadings higher compared to neat EVA. Further, mechanical properties were determined by tensile test. The result shows that tensile strength and elongation at break of composites decrease relatively by Ca-Mg-Al HTlc addition.

  11. First principles study of Ca in BaTiO3 and Bi0.5Na0.5TiO3

    NASA Astrophysics Data System (ADS)

    Fongkaew, Ittipon; T-Thienprasert, Jiraroj; Limpijumnong, Sukit

    2015-11-01

    BaTiO3-Bi0.5Na0.5TiO3 is one of the promising candidates as a high-temperature relaxor with a high Curie temperature and several preferred dielectric characteristics. It has been found experimentally for a long time that adding calcium to BaTiO3-Bi0.5Na0.5TiO3 improves its temperature characteristic of the capacitance [J. Electron. Mater. 39, 2471]. In this study, Calcium (Ca) defects in perovskite BaTiO3 and Bi0.5Na0.5TiO3 have been studied based on first-principles calculations. In both BaTiO3 and Bi0.5Na0.5TiO3, our calculations showed that Ca atom energetically prefers to substitute for the cations, that is Ba, Bi, Na and Ti, depending on the growth conditions. In most cases, Ca predominantly substitutes on the A-site without providing additional electrical carriers (serve as either neutral defects or self-compensating defects). The growth conditions where Ca can be forced to substitute for B-site (with limited amount) and the conditions where Ca can be forced to serve as an acceptor are identified. Details of the local structures, formation energies and electronic properties of these Ca defects are reported.

  12. Boiling Temperature and Reversed Deliquescence Relative Humidity Measurements for Mineral Assemblages in the NaCl + NaNO3 + KNO3 + Ca(NO3)2 + H2O System

    SciTech Connect

    Rard, J A; Staggs, K J; Day, S D; Carroll, S A

    2005-12-01

    Boiling temperature measurements have been made at ambient pressure for saturated ternary solutions of NaCl + KNO{sub 3} + H{sub 2}O, NaNO{sub 3} + KNO{sub 3} + H{sub 2}O, and NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O over the full composition range, along with those of the single salt systems. Boiling temperatures were also measured for the four component NaCl + NaNO{sub 3} + KNO{sub 3} + H{sub 2}O and five component NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O mixtures, where the solute mole fraction of Ca(NO{sub 3}){sub 2}, x(Ca(NO{sub 3}){sub 2}), was varied between 0 and 0.25. The maximum boiling temperature found for the NaCl + KNO{sub 3} + H{sub 2}O system is {approx} 134.9 C; for the NaNO{sub 3} + KNO{sub 3} + H{sub 2}O system is {approx} 165.1 C at x(NaNO{sub 3}) {approx} 0.46 and x(KNO{sub 3}) {approx} 0.54; and for the NaCl + Ca(NO{sub 3}){sub 2} + H{sub 2}O system is 164.7 {+-} 0.6 C at x(NaCl) {approx} 0.25 and x(Ca(NO{sub 3}){sub 2}) {approx} 0.75. The NaCl + NaNO{sub 3} + KNO{sub 3} + Ca(NO{sub 3}){sub 2} + H{sub 2}O system forms molten salts below their maximum boiling temperatures, and the temperatures corresponding to the cessation of boiling (dry out temperatures) of these liquid mixtures were determined. These dry out temperatures range from {approx} 300 C when x(Ca(NO{sub 3}){sub 2}) = 0 to {ge} 400 C when x(Ca(NO{sub 3}){sub 2}) = 0.20 and 0.25. Mutual deliquescence/efflorescence relative humidity (MDRH/MERH) measurements were also made for the NaNO{sub 3} + KNO{sub 3} and NaCl + NaNO{sub 3} + KNO{sub 3} salt mixture from 120 to 180 C at ambient pressure. The NaNO{sub 3} and NaCl + NaNO{sub 3} + KNO{sub 3} salt mixture has a MDRH of 26.4% at 120 C and 20.0% at 150 C. This salt mixture also absorbs water at 180 C, which is higher than expected from the boiling temperature experiments. The NaCl + NaNO{sub 3} + KNO{sub 3} salt mixture was found to have a MDRH of 25.9% at 120 C and 10.5% at 180 C. The investigated mixture

  13. Evolution of Inclusions in Fe-13Cr Treated by CaO-SiO2-Al2O3-Based Top Slag

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Wang, Lijun; Zhai, Jun; Li, Jianmin; Chou, Kuo-Chih

    2017-02-01

    Experiments were carried out to determine the effect of Al2O3 in the slag of the CaO-SiO2-Al2O3-MgO-CaF2 system on the cleanness of Fe-13Cr stainless steel deoxidized by ferrosilicon. Increasing the Al2O3 content in basicity = 2.28 slag can reduce the usage of CaF2 and benefit the obtainment of a good kinetic condition for inclusion removal, but over 21 pct would lead to a higher total oxygen content in the melt and make the inclusion composition more complex. It is found that increasing basicity in 16 pct Al2O3 slag would have a good deoxidation ability and accelerate the transformation from high Al2O3 inclusions to low melting point CaO-Al2O3-SiO2-MgO system inclusions, but basicity over 2.58 would lead to high content of [Al] in liquid steel, which would promote the formation of MgO-Al2O3 inclusions. Therefore, it is not suitable to add a high content of Al2O3 into high-basicity slag. Adding Al2O3 into slag of 2.28 in basicity until a content of 16 pct could achieve inclusion plastication within 45 minutes without Ca treatment, which has potential application in industrial production.

  14. Davinciite, Na12K3Ca6Fe{3/2+}Zr3(Si26O73OH)Cl2, a New K,Na-Ordered mineral of the eudialyte group from the Khibiny Alkaline Pluton, Kola Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Khomyakov, A. P.; Nechelyustov, G. N.; Rastsvetaeva, R. K.; Rozenberg, K. A.

    2013-12-01

    This paper presents a description of a new zirconosilicate of the eudialyte group, which was named davinciite in honor of Leonardo da Vinci (1452-1519), a famous Italian scientist, painter, sculptor and architect. The new mineral has been found in hyperagpaitic pegmatite at the Rasvumchorr Mountain, Khibiny Pluton, Kola Peninsula, as relict inclusions, up to 1-2 mm in size in a rastsvetaevite matrix. It is associated with nepheline, sodalite, potassium feldspar, delhayelite, aegirine, shcherbakovite, villiaumite, nitrite, nacaphite, rasvumite, and djerfisherite. Davinciite is dark lavender and transparent, with a vitreous luster and white streak. The new mineral is brittle, with conchoidal fracture; the Mohs' hardness is 5. No indications of cleavage or parting were observed. The measured density is 2.82(2) g/cm3 (volumetric method); the calculated density is 2.848 g/cm3. Davinciite is optically uniaxial, positive; ω = 1.603(2), ɛ = 1.605(2). It is nonpleochroic and nonfluorescent in UV light. The new mineral slowly breaks down and gelates in 50% HCl and HNO3. It is trigonal, space group R3m. The unit-cell dimensions are a = 14.2956(2), c = 30.0228(5) Å, V=5313.6(2) Å3. The strongest reflections in the X-ray powder diffraction pattern [ d, Å ( I, %) ( hkl)] are as follows: 2.981(100)(315), 2.860(96)(404), 4.309(66)(205), 3.207(63)(208), 6.415(54)(104), 3.162(43)(217). The chemical composition (electron microprobe, H2O calculated from X-ray diffraction data) is as follows, wt %: 12.69 Na2O, 3.53 K2O, 11.02 CaO, 0.98 SrO, 0.15 BaO, 5.33 FeO, 0.37 MnO, 0.07 Al2O3, 51.20 SiO2, 0.39 TiO2, 11.33 ZrO2, 0.21HfO2, 0.09 Nb2O5, 1.89 Cl, 0.93H2O, -O = Cl2 0.43; total is 99.75. The empirical formula calculated on the basis of Si + Al + Zr + Hf + Ti + Nb = 29 ( Z = 3) is (Na1l.75Sr0.29Ba0.03)Σ12.07(K2.28Na0.72)Σ3Ca5.99(Fe2.26Mn0.16)Σ2.42(Zr2.80Ti0.15Hf0.03Nb0.02) Σ3(Si1.96Al0.04)Σ2[Si3O9]2 [Si9O27]2[(OH)1.42O0.58]Σ2[Cl1.62(H2O)0.38]Σ2 · 0.48H2O. The simplified

  15. A promising orange-red emitting nanocrystalline NaCaBO3:Sm3+ phosphor for solid state lightning

    NASA Astrophysics Data System (ADS)

    Bedyal, A. K.; Kumar, Vinay; Ntwaeaborwa, O. M.; Swart, H. C.

    2014-03-01

    Orange-red emitting NaCaBO3:Sm3+ nanophosphors were prepared by combustion method using metal nitrates and urea as initial materials. The phase of the product was identified by x-ray diffraction technique (XRD) and was found to be orthorhombic with a space group Pmmn and lattice parameters a = 16.12 Å, b = 10.25 Å, c = 3.52 Å and V = 581.60 Å3 calculated with the POWD program. The average particle size of the nanophosphor calculated from the XRD data and cross verified by TEM was 34 nm. The spectral properties of the NaCaBO3:Sm3+ nanophosphors were studied under near UV and electron excitation, which shows characteristic emission lines assigned to the transition (4G5/2 to the 6Hj, j = 5/2, 7/2, 9/2, 11/2) of the Sm3+ ion. The optimal Sm3+ ion concentration and its critical energy distance were determined as x = 2 mol% and 59.97 Å, respectively and the dipole-dipole interactions were responsible for concentration quenching in the present phosphor. The band gap of the phosphor was calculated to be 5.82 eV. The phosphorescence decay curve was also measured.

  16. On the structural basis for ionic selectivity among Na+, K+, and Ca2+ in the voltage-gated sodium channel.

    PubMed Central

    Favre, I; Moczydlowski, E; Schild, L

    1996-01-01

    Voltage-sensitive sodium channels and calcium channels are homologous proteins with distinctly different selectivity for permeation of inorganic cations. This difference in function is specified by amino acid residues located within P-region segments that link presumed transmembrane elements S5 and S6 in each of four repetitive Domains I, II, III, and IV. By analyzing the selective permeability of Na+, K+, and Ca2+ in various mutants of the mu 1 rat muscle sodium channel, the results in this paper support the concept that a conserved motif of four residues contributed by each of the Domains I-IV, termed the DEKA locus in sodium channels and the EEEE locus in calcium channels, determines the ionic selectivity of these channels. Furthermore, the results indicate that the Lys residue in Domain III of the sodium channel is the critical determinant that specifies both the impermeability of Ca2+ and the selective permeability of Na+ over K+. We propose that the alkylammonium ion of the Lys(III) residue acts as an endogenous cation within the ion binding site/selectivity filter of the sodium channel to tune the kinetics and affinity of inorganic cation binding within the pore in a manner analogous to ion-ion interactions that occur in the process of multi-ion channel conduction. PMID:8968582

  17. Structural studies of the NaCaPO 4-SiO 2 sol-gel derived materials

    NASA Astrophysics Data System (ADS)

    Sitarz, M.; Rokita, M.; Handke, M.; Galuskin, E.

    2003-06-01

    Structural studies of the NaCaPO 4-SiO 2 materials have been carried out. Amorphous materials from this system, after controlled crystallization process, can be used as potential nanomaterials. Structural studies of nanomaterials are of fundamental importance in view their future applications. Materials of different [PO 4] 3-/[SiO 4] 4- tetrahedra proportion have been prepared. Na + and Ca 2+ cations have compensated the negative charge of the lattice. Amorphous and crystalline materials have been obtained by sol-gel as well as conventional melting methods. The XRD phase identification has enabled amorphous and crystalline materials identification and suggests the separation of phosphorus and silicate crystalline phases. The obtained materials were examined using the electron scanning microscope and EDX spectrometer. Analysis of electron scanning microscope maps shows considerable inhomogeneity of crystalline samples. Fluctuations in ions distribution, in case of amorphous materials, have been noted too. DTA investigations have enabled to find the probable characteristic temperatures of glass crystallization. Detailed infrared spectroscopy measurements have been carried out. The spectra of obtained materials have been compared with the spectra of cristobalite. Spectroscopic studies confirm the inhomogeneity of materials.

  18. Fabrication of CaO-NaO-SiO(2)/TiO (2) scaffolds for surgical applications.

    PubMed

    Wren, A W; Coughlan, A; Smale, K E; Misture, S T; Mahon, B P; Clarkin, O M; Towler, M R

    2012-12-01

    A series of titanium (Ti) based glasses were formulated (0.62 SiO(2)-0.14 Na(2)O-0.24 CaO, with 0.05 mol% TiO(2) substitutions for SiO(2)) to develop glass/ceramic scaffolds for bone augmentation. Glasses were initially characterised using X-ray diffraction (XRD) and particle size analysis, where the starting materials were amorphous with 4.5 μm particles. Hot stage microscopy and high temperature XRD were used to determine the sintering temperature (~700 °C) and any crystalline phases present in this region (Na(2)Ca(3)Si(6)O(16), combeite and quartz). Hardness testing revealed that the Ti-free control (ScC-2.4 GPa) had a significantly lower hardness than the Ti-containing materials (Sc1 and Sc2 ~6.6 GPa). Optical microscopy determined pore sizes ranging from 544 to 955 μm. X-ray microtomography calculated porosity from 87 to 93 % and surface area measurements ranging from 2.5 to 3.3 SA/mm(3). Cytotoxicity testing (using mesenchymal stem cells) revealed that all materials encouraged cell proliferation, particularly the higher Ti-containing scaffolds over 24-72 h.

  19. Slowly inactivating component of Na+ current in peri-somatic region of hippocampal CA1 pyramidal neurons

    PubMed Central

    Park, Yul Young; Johnston, Daniel

    2013-01-01

    The properties of voltage-gated ion channels on the neuronal membrane shape electrical activity such as generation and backpropagation of action potentials, initiation of dendritic spikes, and integration of synaptic inputs. Subthreshold currents mediated by sodium channels are of interest because of their activation near rest, slow inactivation kinetics, and consequent effects on excitability. Modulation of these currents can also perturb physiological responses of a neuron that might underlie pathological states such as epilepsy. Using nucleated patches from the peri-somatic region of hippocampal CA1 neurons, we recorded a slowly inactivating component of the macroscopic Na+ current (which we have called INaS) that shared many biophysical properties with the persistent Na+ current, INaP, but showed distinctively faster inactivating kinetics. Ramp voltage commands with a velocity of 400 mV/s were found to elicit this component of Na+ current reliably. INaS also showed a more hyperpolarized I-V relationship and slower inactivation than those of the fast transient Na+ current (INaT) recorded in the same patches. The peak amplitude of INaS was proportional to the peak amplitude of INaT but was much smaller in amplitude. Hexanol, riluzole, and ranolazine, known Na+ channel blockers, were tested to compare their effects on both INaS and INaT. The peak conductance of INaS was preferentially blocked by hexanol and riluzole, but the shift of half-inactivation voltage (V1/2) was only observed in the presence of riluzole. Current-clamp measurements with hexanol suggested that INaS was involved in generation of an action potential and in upregulation of neuronal excitability. PMID:23236005

  20. Slowly inactivating component of Na+ current in peri-somatic region of hippocampal CA1 pyramidal neurons.

    PubMed

    Park, Yul Young; Johnston, Daniel; Gray, Richard

    2013-03-01

    The properties of voltage-gated ion channels on the neuronal membrane shape electrical activity such as generation and backpropagation of action potentials, initiation of dendritic spikes, and integration of synaptic inputs. Subthreshold currents mediated by sodium channels are of interest because of their activation near rest, slow inactivation kinetics, and consequent effects on excitability. Modulation of these currents can also perturb physiological responses of a neuron that might underlie pathological states such as epilepsy. Using nucleated patches from the peri-somatic region of hippocampal CA1 neurons, we recorded a slowly inactivating component of the macroscopic Na(+) current (which we have called INaS) that shared many biophysical properties with the persistent Na(+) current, INaP, but showed distinctively faster inactivating kinetics. Ramp voltage commands with a velocity of 400 mV/s were found to elicit this component of Na(+) current reliably. INaS also showed a more hyperpolarized I-V relationship and slower inactivation than those of the fast transient Na(+) current (INaT) recorded in the same patches. The peak amplitude of INaS was proportional to the peak amplitude of INaT but was much smaller in amplitude. Hexanol, riluzole, and ranolazine, known Na(+) channel blockers, were tested to compare their effects on both INaS and INaT. The peak conductance of INaS was preferentially blocked by hexanol and riluzole, but the shift of half-inactivation voltage (V1/2) was only observed in the presence of riluzole. Current-clamp measurements with hexanol suggested that INaS was involved in generation of an action potential and in upregulation of neuronal excitability.

  1. Extremely NA and CL Rich Chondrule AL3509 from the Allende Meteorite

    SciTech Connect

    Wasserburg, G J; Hutcheon, I D; Aleon, J; Ramon, E C; Krot, A N; Nagashima, K; Brearley, A J

    2011-04-07

    We report on the mineralogy, petrology, chemistry, oxygen isotopes, {sup 26}Al-{sup 26}Mg and {sup 36}Cl-{sup 36}S isotope systematics of the Allende chondrule Al3509 discovered and described by [1] and [2]. This spherical object ({approx}1cm {phi}) contains {approx}10% Na and 1% Cl, and nearly pure {sup 129}Xe [({sup 129}Xe/{sup 127}I) = 1.1 x 10{sup -4} (3)]. This high enrichment in halogens makes it of interest in searching for radiogenic {sup 36}S from {sup 36}Cl (t{sub 1/2} {approx} 0.3 Ma) decay. While there is strong evidence for the presence of {sup 36}Cl in sodalite and wadalite in CV CAIs [4,5], some sodalites show no evidence for excesses of {sup 36}S ({sup 36}S*). In contrast, high inferred initial {sup 36}Cl/{sup 35}Cl = 2 x 10{sup -5} has been found in wadalite from the Allende CAI AJEF [5]. The observed {sup 36}S excesses in sodalite are not correlated with radiogenic {sup 26}Mg, decay product of {sup 26}Al (t{sub 1/2} {approx} 0.72 Ma) [4]. From the inferred initial {sup 36}Cl/{sup 35}Cl ratios and consideration of both AGB and SNe stellar sources, {sup 36}Cl must be the product of charged particle irradiation within the early solar system. However, neither the specific nuclear production mechanism nor the irradiation site have been identified. Both sodalite and wadalite are found as late stage alteration products of CAIs together with grossular, monticellite, Al-rich pyroxene, wollastonite, nepheline, ferroan olivine, and ferroan pyroxenes. This late-stage alteration has been found to extensively change some CAIs in Allende, but clear residues of spinel, hibonite and Wark-Lovering rims are recognizable remnants of the original CAIs. The nature of the widespread volatile alteration process as well as that of the fluid phase remain controversial.

  2. The Synthesis of Infinite-Layer CaCuO2 and Hypothetical p-TYPE Doping with na Under High-Pressure

    NASA Astrophysics Data System (ADS)

    Qin, X. M.; Wang, F.; Yu, Y.; Li, F. Y.; Yu, R. C.; Jin, C. Q.

    The CaCuO2 with infinite-layer structure (IL CaCuO2) was synthesized under high-pressure. The p-type doped infinite layer compounds Ca1-xNaxCuO2 with the different carriers concentration (x=0.05, 0.1) were also prepared from high temperature and high-pressure technique. The lattice parameter a decreases with increasing Na content x in the p-type doped Ca1-xNaxCuO2, suggesting that the hole like carriers enter into the CuO2 plane, and Na is successfully doped into the infinite-layer CaCuO2. This was confirmed by the systematic evolution of resistance with increasing the doping level. However, no superconductivity was observed in the samples.

  3. Study of Np(V) Sorption by Ionic Exchange on Na, K, Ca and Mg-Montmorillonite

    NASA Astrophysics Data System (ADS)

    Benedicto, A.; Begg, J.; Zhao, P.; Kersting, A. B.; Zavarin, M.

    2012-12-01

    The transport behavior of actinides in soil and ground water are highly influenced by clay minerals due to their ubiquity in the environment, reactivity and colloidal properties. Neptunium(V) has been introduced in the environment as a result of nuclear weapons testing [e.g. 1, 2] and is a radionuclide of potential interest for safety assessment of high level radioactive waste disposal because its long half-life and high toxicity [3]. Surface complexation and ionic exchange have been identified as Np(V) sorption mechanisms onto montmorillonite. At pH below 5, Np(V) sorption is mainly attributed to ionic exchange. This study examines Np(V) ion exchange on Na, K, Ca and Mg forms of montmorillonite. Experiments were carried out using 237Np concentrations between 2 x 10-8 M and 5 x 10-6 M at three different ionic strengths 0.1, 0.01 and 0.001M. The pH was maintained at 4.5. Np(V) sorption to montmorillonite homoionized with monovalent cations (Na and K) demonstrated a markedly different behavior to that observed for montmorillonite homoionized with divalent cations (Ca and Mg). Np sorption to Na and K-montmorillonite was greater than Np sorption to Ca and Mg-montmorillonite. Isotherms with Na and K-montmorillonite showed a strong dependence on ionic strength: the percentage of Np adsorbed was near zero at 0.1M ionic strength, but increased to 30% at 0.001 M ionic strength. This suggests ionic exchange is the main Np adsorption mechanism under the experimental conditions investigated. Dependence on ionic strength was not observed in the Np sorption isotherms for Ca and Mg-montmorillonite indicating a low exchange capacity between Np and divalent cations. Modeling of the sorption experimental data will allow determination of the Na+↔NpO2+ and K+↔NpO2+ ionic exchange constants on montmorillonite. References: [1] A. R. Felmy; K. J. Cantrell; S. D. Conradson, Phys. Chem. Earth 2010, 35, 292-297 [2] D. K. Smith; D. L. Finnegan; S. M. Bowen, J. Environ. Radioact. 2003, 67

  4. The Abundances of Na, Mg, & Al in the Hyades: Giants, Dwarfs, and Mixing

    NASA Astrophysics Data System (ADS)

    Schuler, Simon C.; King, J. R.; The, L.

    2006-12-01

    The abundances of Na, Mg, and Al in three giants and four dwarfs in the Hyades open cluster have been derived from high-resolution, McDonald 2.7-m echelle spectra. These data are compared to the expected changes in surface composition of the giants as predicted by a stellar model generated with the Clemson-American University of Beirut stellar evolution code in order to investigate if the Hyades giants have undergone non-standard mixing. The preliminary results of our analysis are presented. This work is supported by the NOAO Leo Goldberg Fellowship to S.C.S.; NOAO is operated by AURA under cooperative agreement with the NSF. Additional support was provided by the NSF through grants AST 00-86576 and AST 02-39518 to J.R.K. and by the Charles Curry Foundation through a generous grant to Clemson University.

  5. Inhibiting Na+/K+ ATPase Can Impair Mitochondrial Energetics and Induce Abnormal Ca2+ Cycling and Automaticity in Guinea Pig Cardiomyocytes

    PubMed Central

    Li, Qince; Pogwizd, Steven M.; Prabhu, Sumanth D.; Zhou, Lufang

    2014-01-01

    Cardiac glycosides have been used for the treatment of heart failure because of their capabilities of inhibiting Na+/K+ ATPase (NKA), which raises [Na+]i and attenuates Ca2+ extrusion via the Na+/Ca2+ exchanger (NCX), causing [Ca2+]i elevation. The resulting [Ca2+]i accumulation further enhances Ca2+-induced Ca2+ release, generating the positive inotropic effect. However, cardiac glycosides have some toxic and side effects such as arrhythmogenesis, confining their extensive clinical applications. The mechanisms underlying the proarrhythmic effect of glycosides are not fully understood. Here we investigated the mechanisms by which glycosides could cause cardiac arrhythmias via impairing mitochondrial energetics using an integrative computational cardiomyocyte model. In the simulations, the effect of glycosides was mimicked by blocking NKA activity. Results showed that inhibiting NKA not only impaired mitochondrial Ca2+ retention (thus suppressed reactive oxygen species (ROS) scavenging) but also enhanced oxidative phosphorylation (thus increased ROS production) during the transition of increasing workload, causing oxidative stress. Moreover, concurrent blocking of mitochondrial Na+/Ca2+ exchanger, but not enhancing of Ca2+ uniporter, alleviated the adverse effects of NKA inhibition. Intriguingly, NKA inhibition elicited Ca2+ transient and action potential alternans under more stressed conditions such as severe ATP depletion, augmenting its proarrhythmic effect. This computational study provides new insights into the mechanisms underlying cardiac glycoside-induced arrhythmogenesis. The findings suggest that targeting both ion handling and mitochondria could be a very promising strategy to develop new glycoside-based therapies in the treatment of heart failure. PMID:24722410

  6. A solidification model for unmodified, Na-modified and Sr-modified Al-Si alloys

    NASA Astrophysics Data System (ADS)

    Tiedje, N. S.; Hattel, J.; Taylor, J. A.; Easton, M. A.

    2012-01-01

    An addition of small amounts of Na and Sr is commonly used in the industry to modify the eutectic in Al-Si alloys. Both Na and Sr suppress nucleation of the eutectic forcing nucleation and growth to take place at higher undercooling than in the unmodified material. Thus the scale of the eutectic and the shape of the Si crystals are modified to a fine fibrous form so that the ductility of the material is increased. In the present work a one-dimensional numerical model is proposed that describes nucleation and growth of both primary dendrites and eutectic grains as a function of cooling conditions and modification. The model assumes that dendrites nucleate easily when the liquidus temperature is reached and that they grow as heat is extracted by the mould. Nucleation of the eutectic grains depends on local undercooling and growth is governed by a balance between growth of the eutectic grains and the rate at which heat is extracted by the mould. Experimental data is used to determine constants in the nucleation function. It is shown how cooling conditions and mode of modification influence nucleation and growth conditions.

  7. Thermodynamics and Structure of CaO-Al2O3-3 Mass Pct B2O3 Slag at 1773 K (1500 °C)

    NASA Astrophysics Data System (ADS)

    Shu, Qifeng; Li, Pengfei; Zhang, Xiang; Chou, Kuochih

    2016-12-01

    Activity values of Al2O3 in CaO-Al2O3-B2O3 systems at 1773 K (1500 °C) were determined experimentally using a gas-copper-slag equilibrium technique. The oxygen partial pressure was controlled by C/CO equilibrium. A negative deviation from ideality was found in measured activity of Al2O3. The activity coefficient of Al2O3 decreases with the increase of CaO/Al2O3 ratio. To interpret the variation of Al2O3 activity with composition, structures of CaO-Al2O3-B2O3 glassy slag were investigated by using Raman spectroscopy. It was found that the number of bridging oxygen decreases with increasing CaO/Al2O3 ratio. With increase of CaO content, the aluminate network was gradually depolymerized, which corresponds to the decrease of the activity coefficient of Al2O3.

  8. CaMn2Al10: Itinerant Mn magnetism on the verge of magnetic order

    SciTech Connect

    Steinke, L.; Simonson, J. W.; Yin, W. -G.; Smith, G. J.; Kistner-Morris, J. J.; Zellman, S.; Puri, A.; Aronson, M. C.

    2015-07-24

    We report the discovery of CaMn2Al10, a metal with strong magnetic anisotropy and moderate electronic correlations. Magnetization measurements find a Curie-Weiss moment of 0.83μB/Mn, significantly reduced from the Hund's rule value, and the magnetic entropy obtained from specific heat measurements is correspondingly small, only ≈ 9% of Rln2. These results imply that the Mn magnetism is highly itinerant, a conclusion supported by density functional theory calculations that find strong Mn-Al hybridization. Consistent with the layered nature of the crystal structure, the magnetic susceptibility χ is anisotropic below 20 K, with a maximum ratio of χ[010][001] ≈ 3.5. A strong power-law divergence χ(T) ~ T–1.2 below 20 K implies incipient ferromagnetic order, an Arrott plot analysis of the magnetization suggests a vanishing low Curie temperature TC ~ 0. Our experiments indicate that CaMn2Al10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.

  9. Texture gradient evolution in Al-5%Ca-5%Zn sheet alloy after tensile deformation at high superplastic strain rate

    SciTech Connect

    Perez-Prado, M.T.; Cristina, M.C.; Torralba, M.; Ruano, O.A.; Gonzalez-Doncel, G.

    1996-12-15

    Texture inhomogeneities have been found in many materials. Given the significant influence of texture in industrial processes like superplastic forming of complex-shaped components, it is important to study the evolution of texture gradients under different testing conditions, particularly at high strain rates. Strong through-thickness texture-gradients have been observed in hot rolled Al alloys. As a consequence of the severe deformation during the hot rolling process, a well defined Brass texture-component (B-orientation) {l_brace}011{r_brace}<211> develops in the mid layer. The Al-5%Ca-5%Zn sheet alloy deforms superplastically when tested uniaxially at temperatures ranging from 350 to 450 C and at strain rates between 10{sup {minus}5}s{sup {minus}1} and 10{sup {minus}2}s{sup {minus}1}. The B-orientation, however, is not present in the texture of the as-rolled material, but it appears after straining in tension along the transverse direction under certain conditions of temperature and moderately high superplastic strain rates. In this work the evolution of the through-thickness texture-gradient in the Al-5%Ca-5% Zn sheet alloy when tested uniaxially in the transverse direction is investigated. Due to the importance of high strain rates in superplastic forming processes, tests at higher strain rates than those usually reported in the literature have been conducted. Current models which predict the appearance of the B-component are criticized on the light of these new findings.

  10. PLC-dependent intracellular Ca2+ release was associated with C6-ceramide-induced inhibition of Na+ current in rat granule cells.

    PubMed

    Liu, Zheng; Fei, Xiao-Wei; Fang, Yan-Jia; Shi, Wen-Jie; Zhang, Yu-Qiu; Mei, Yan-Ai

    2008-09-01

    In this report, the effects of C(6)-ceramide on the voltage-gated inward Na(+) currents (I(Na)), two types of main K(+) current [outward rectifier delayed K(+) current (I(K)) and outward transient K(+) current (I(A))], and cell death in cultured rat cerebellar granule cells were investigated. At concentrations of 0.01-100 microM, ceramide produced a dose-dependent and reversible inhibition of I(Na) without alteration of the steady-state activation and inactivation properties. Treatment with C(2)-ceramide caused a similar inhibitory effect on I(Na). However, dihydro-C(6)-ceramide failed to modulate I(Na). The effect of C(6)-ceramide on I(Na) was abolished by intracellular infusion of the Ca(2+)-chelating agent, 1,2-bis (2-aminophenoxy) ethane-N, N, N9, N9-tetraacetic acid, but was mimicked by application of caffeine. Blocking the release of Ca(2+) from the sarcoplasmic reticulum with ryanodine receptor blocker induced a gradual increase in I(Na) amplitude and eliminated the effect of ceramide on I(Na). In contrast, the blocker of the inositol 1,4,5-trisphosphate-sensitive Ca(2+) receptor did not affect the action of C(6)-ceramide. Intracellular application of GTPgammaS also induced a gradual decrease in I(Na) amplitude, while GDPbetaS eliminated the effect of C(6)-ceramide on I(Na). Furthermore, the C(6)-ceramide effect on I(Na) was abolished after application of the phospholipase C (PLC) blockers and was greatly reduced by the calmodulin inhibitors. Fluorescence staining showed that C(6)-ceramide decreased cell viability and blocking I(Na) by tetrodotoxin did not mimic the effect of C(6)-ceramide, and inhibiting intracellular Ca(2+) release by dantrolene could not decrease the C(6)-ceramide-induced cell death. We therefore suggest that increased PLC-dependent Ca(2+) release through the ryanodine-sensitive Ca(2+) receptor may be responsible for the C(6)-ceramide-induced inhibition of I(Na), which does not seem to be associated with C(6)-ceramide-induced granule

  11. The effects of sulfur intercalation on the optical properties of artificial `hackmanite', Na8[Al6Si6O24]Cl1.8S0.1; `sulfosodalite', Na8[Al6Si6O24]S; and natural tugtupite, Na8[Be2Al2Si8O24](Cl,S)2-δ

    NASA Astrophysics Data System (ADS)

    Warner, T. E.; Hutzen Andersen, J.

    2012-02-01

    The minerals `hackmanite' and tugtupite exhibit tenebrescence (reversible photochromism) and photoluminescence. These features are generally attributed to the presence of sulfide species within their structures. But how these optical properties might be affected by intercalating additional amounts of sulfur into their structures was until now unknown. Artificial `hackmanite', Na8[Al6Si6O24]Cl1.8S0.1, and `sulfosodalite', Na8[Al6Si6O24]S, were heated with sulfur in evacuated quartz-glass ampoules over the temperature range 450-1,050°C. This work has shown that sulfur intercalation into Na8[Al6Si6O24]Cl1.8S0.1 destroys the tenebrescence and induces a permanently pale blue and, at higher temperature, a pale green coloration. The effect on Na8[Al6Si6O24]S induced similar colorations but of a deeper hue. Annealing tugtupite, Na8[Be2Al2Si8O24](Cl,S)2-δ under a sulfur atmosphere over the range 600-700°C, destroyed the tenebrescence and resulted in a colorless tugtupite; but did not effect the photoluminescence. This suggests that the chemical species responsible for the tenebrescence in tugtupite is unlikely to be the same as that for the luminescence.

  12. Electrodeposition of Al-Ta alloys in NaCl-KCl-AlCl3 molten salt containing TaCl5

    NASA Astrophysics Data System (ADS)

    Sato, Kazuki; Matsushima, Hisayoshi; Ueda, Mikito

    2016-12-01

    To form Al-Ta alloys for high temperature oxidation resistance components, molten salt electrolysis was carried out in an AlCl3-NaCl-KCl melt containing TaCl5 at 423 K. The voltammogram showed two cathodic waves at 0.45 V and 0.7 V vs. Al/Al(III), which may correspond to reduction from Ta(V) to Ta(III) and from Ta(III) to tantalum metal, respectively. Electrodeposits of Al and Ta were obtained in the range from -0.05 to 0.3 V and the highest concentration of Ta in the electrodeposit was 72 at% at 0.3 V. With increasing Ta content in the alloy, the morphology of the electrodeposits became powdery and the particle size smaller.

  13. Interfacial Reactions of Zn-Al Alloys with Na Addition on Cu Substrate During Spreading Test and After Aging Treatments

    NASA Astrophysics Data System (ADS)

    Gancarz, Tomasz; Pstruś, Janusz; Berent, Katarzyna

    2016-08-01

    Spreading tests for Cu substrate with Zn-Al eutectic-based alloys with 0.2, 0.5, and 1.0 wt.% of Na were studied using the sessile drop method in the presence of QJ201 flux. Spreading tests were performed for 1, 3, 8, 15, 30, and 60 min of contact, at the temperatures of 475, 500, 525, and 550 °C. After cleaning the flux residue from solidified samples, the spreading area of Zn-Al + Na on Cu was determined in accordance with ISO 9455-10:2013-03. Selected, solidified solder-substrate couples were cross-sectioned and subjected to scanning electron microscopy of the interfacial microstructure. The experiment was designed to demonstrate the effect of Na addition on the kinetics of formation and growth of CuZn, Cu5Zn8, and CuZn4 phases, which were identified using x-ray diffraction and energy-dispersive spectroscopy analysis. The addition of Na to eutectic Zn-Al caused the spreading area to decrease and the thickness of intermetallic compound layers at the interface to reduce. Samples after the spreading test at 500 °C for 1 min were subjected to aging for 1, 10, and 30 days at 120,170, and 250 °C. The greater thicknesses of IMC layers were obtained for a temperature of 250 °C. With increasing Na content in Zn-Al + Na alloys, the thickness reduced, which correlates to the highest value of activation energy for Zn-Al with 1% Na.

  14. Sequential measurements of bone lead content by L X-ray fluorescence in CaNa sub 2 EDTA-treated lead-toxic children

    SciTech Connect

    Rosen, J.F.; Markowitz, M.E.; Bijur, P.E.; Jenks, S.T. ); Wielopolski, L. ); Kalef-Ezra, J.A. ); Slatkin, D.N. )

    1991-06-01

    With the development of L X-ray fluorescence (LXRF) to measure cortical bone lead directly, safely, rapidly, and noninvasively, the present study was undertaken to (a) evaluate LXRF as a possible replacement for the CaNa{sub 2}EDTA test; (b) quantify lead in tibial cortical bones of mildly to moderately lead-toxic children before treatment; and (c) quantify lead in tibial cortical bones of lead-toxic children sequentially following one to two courses of chelation therapy. The clinical research design was based upon a longitudinal assessment of 59 untreated lead-toxic children. Based upon a discriminant analysis, 90% of lead-toxic children were predicted correctly as being CaNa{sub 2}EDTA-positive or CaNa{sub 2}EDTA-negative. Using LXRF and PbB values to predict CaNa{sub 2}EDTA outcomes, the specificity and sensitivity of these two predictors were 86 and 93%, respectively. The data suggest that LXRF measurements of lead in tibial cortical bone have considerable promise to replace the CaNa{sub 2}EDTA test and to provide a more appropriate end point of chelation therapy than the conventional indices of PbB and EP. Moreover, markedly elevated bone lead values accumulated during early childhood may have an intergenerational impact, as maternal lead stores amassed during childhood cross the placenta and directly affect the developing fetus.

  15. Calmodulin-dependent binding to the NHE1 cytosolic tail mediates activation of the Na+/H+ exchanger by Ca2+ and endothelin.

    PubMed

    Li, Xiuju; Prins, Daniel; Michalak, Marek; Fliegel, Larry

    2013-12-01

    The mammalian Na(+)/H(+) exchanger isoform 1 (NHE1) is a ubiquitous plasma membrane protein that regulates intracellular pH by removing a single proton (H(+)) in exchange for one extracellular Na(+). The human protein contains a ∼500-amino acid membrane domain and a regulatory, ∼315-amino acid cytosolic domain. NHE1 is activated by a number of hormones including endothelin (ET) and by Ca(2+). The regulatory tail possesses an inhibitory calmodulin (CaM)-binding domain, and inhibition of NHE1 is relieved by binding of a Ca(2+)-CaM complex. We examined the dynamics of ET-1 and Ca(2+) regulation of binding to NHE1 in vivo. CFP was linked to the NHE1 protein cytoplasmic COOH terminus. This was stably transfected into AP-1 cells that are devoid of their own NHE1 protein. The protein was expressed and targeted properly and retained NHE1 activity comparable to the wild-type protein. We examined the in vivo coupling of NHE1 to CaM by Förster resonance energy transfer using CaM linked to the fluorescent protein Venus. CaM interaction with NHE1 was dynamic. Removal of serum reduced CaM interaction with NHE1. Addition of the Ca(2+) ionophore ionomycin increased the interaction between CaM and NHE1. We expressed an ET receptor in AP-1 cells and also found a time-dependent association of NHE1 with CaM in vivo that was dependent on ET treatment. The results are the first demonstration of the in vivo association of NHE1 and CaM through ET-dependent signaling pathways.

  16. Pressure induced elastic softening in framework aluminosilicate- albite (NaAlSi3O8)

    DOE PAGES

    Mookherjee, Mainak; Mainprice, David; Maheshwari, Ketan; ...

    2016-10-13

    Albite (NaAlSi3O8) is an aluminosilicate mineral. Its crystal structure consists of 3-D framework of Al and Si tetrahedral units. We have used Density Functional Theory to investigate the high-pressure behavior of the crystal structure and how it affects the elasticity of albite. Our results indicate elastic softening between 6–8 GPa. This is observed in all the individual elastic stiffness components. Our analysis indicates that the softening is due to the response of the three-dimensional tetrahedral framework, in particular by the pressure dependent changes in the tetrahedral tilts. At pressure <6 GPa, the PAW-GGA can be described by a Birch-Murnaghan equationmore » of state with VGGA0 = 687.4Å3, KGGA0 = 51.7 GPa, and GGGA0 = 4.7. The shear modulus and its pressure derivative are K⊕GGA0 = 33.7 GPa, and G⊕GGA0 = 2.9. At 1 bar, the azimuthal compressional and shear wave anisotropy AVGGAP = 42.8%, and AVGGAS = 50.1%. We also investigate the densification of albite to a mixture of jadeite and quartz. The transformation is likely to cause a discontinuity in density, compressional, and shear wave velocity across the crust and mantle. Furthermore, this could partially account for the Mohorovicic discontinuity in thickened continental crustal regions.« less

  17. Pressure induced elastic softening in framework aluminosilicate- albite (NaAlSi3O8)

    PubMed Central

    Mookherjee, Mainak; Mainprice, David; Maheshwari, Ketan; Heinonen, Olle; Patel, Dhenu; Hariharan, Anant

    2016-01-01

    Albite (NaAlSi3O8) is an aluminosilicate mineral. Its crystal structure consists of 3-D framework of Al and Si tetrahedral units. We have used Density Functional Theory to investigate the high-pressure behavior of the crystal structure and how it affects the elasticity of albite. Our results indicate elastic softening between 6–8 GPa. This is observed in all the individual elastic stiffness components. Our analysis indicates that the softening is due to the response of the three-dimensional tetrahedral framework, in particular by the pressure dependent changes in the tetrahedral tilts. At pressure <6 GPa, the PAW-GGA can be described by a Birch-Murnaghan equation of state with  = 687.4 Å3,  = 51.7 GPa, and  = 4.7. The shear modulus and its pressure derivative are  = 33.7 GPa, and  = 2.9. At 1 bar, the azimuthal compressional and shear wave anisotropy  = 42.8%, and  = 50.1%. We also investigate the densification of albite to a mixture of jadeite and quartz. The transformation is likely to cause a discontinuity in density, compressional, and shear wave velocity across the crust and mantle. This could partially account for the Mohorovicic discontinuity in thickened continental crustal regions. PMID:27734903

  18. Carbachol- and elevated Ca(2+)-induced translocation of functionally active protein kinase C to the brush border of rabbit ileal Na+ absorbing cells.

    PubMed Central

    Cohen, M E; Wesolek, J; McCullen, J; Rys-Sikora, K; Pandol, S; Rood, R P; Sharp, G W; Donowitz, M

    1991-01-01

    Protein kinase C is involved in mediating the effects of elevated Ca2+ in ileal villus Na+ absorbing cells to inhibit NaCl absorption. The present studies were undertaken to understand the mechanism by which this occurs. The effects of carbachol and the calcium ionophore A23187, agents which elevate intracellular Ca2+ and inhibit NaCl absorption in ileal villus cells, were studied. Carbachol treatment of villus cells caused a rapid decrease in protein kinase C activity in cytosol, with an accompanying increase in microvillus membrane C kinase. Exposure of the villus cells to calcium ionophore also caused a quantitatively similar decrease in cytosol C kinase and increase in C kinase activity in the microvillus membrane. This increase caused by carbachol and Ca2+ ionophore was specific for the microvillus membrane. In fact, 30 s and 10 min after exposure of the cells to carbachol, basolateral membrane protein kinase C decreased, in a time-dependent manner; whereas 10 min of Ca2+ ionophore exposure did not alter basolateral C kinase. Exposure of villus cells to Ca2+ ionophore or carbachol caused similar increases in microvillus membrane diacylglycerol content. As judged by the ability to inhibit Na+/H+ exchange measured in ileal villus cell brush border membrane vesicles, the protein kinase C which translocated to the microvillus membrane was functionally significant. Inhibition of Na+/H+ exchange required ATP and was reversed by the protein kinase C antagonist H-7. In conclusion, the effect of carbachol and Ca2+ ionophore in regulation of ileal NaCl absorption is associated with an increase in microvillus membrane diacylglycerol content and functionally active protein kinase C. The effects of both carbachol and Ca2+ ionophore are different on brush border and basolateral membrane distribution of protein kinase C. Images PMID:1885773

  19. Thermostimulated luminescence of Ca(Al x Ga1- x )2S4Eu2+ crystals

    NASA Astrophysics Data System (ADS)

    Asadov, E. G.; Kazimova, F. A.; Ibragimova, T. Sh.; Tagiev, K. O.

    2017-02-01

    Thermoluminescence of Ca(AlxGa1-x)2S4:Eu2+ ( x = 0.1-0.3) solid solutions upon UV irradiation has been studied in the course of linear heating. It is established that the observed thermostimulated emission bands are complex, consisting of several strongly overlapped partial maxima. The activation energies, capture cross sections, frequency factors, and concentrations of trap levels responsible for these peaks are determined. The emission intensity and number of components increase with growing aluminum content x.

  20. Thermal neutron imaging with rare-earth-ion-doped LiCaAlF 6 scintillators and a sealed 252Cf source

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Noriaki; Yanagida, Takayuki; Fujimoto, Yutaka; Yokota, Yuui; Kamada, Kei; Fukuda, Kentaro; Suyama, Toshihisa; Watanabe, Kenichi; Yamazaki, Atsushi; Chani, Valery; Yoshikawa, Akira

    2011-10-01

    Thermal neutron imaging with Ce-doped LiCaAlF 6 crystals has been performed. The prototype of the neutron imager using a Ce-doped LiCaAlF 6 scintillating crystal and a position sensitive photomultiplier tube (PSPMT) which had 64 multi-channel anode was developed. The Ce-doped LiCaAlF 6 single crystal was grown by the Czochralski method. A plate with dimensions of a diameter of 50×2 mm 2 was cut from the grown crystal, polished, and optically coupled to PSPMT by silicone grease. The 252Cf source (<1 MBq) was sealed with 43 mm of polyethylene for neutron thermalization. Alphabet-shaped Cd pieces with a thickness of 2 mm were used as a mask for the thermal neutrons. After corrections for the pedestals and gain of each pixel, we successfully obtained two-dimensional neutron images using Ce-doped LiCaAlF 6.

  1. Experimental determination of the effect of the ratio of B/Al on glass dissolution along the nepheline (NaAlSiO 4)-malinkoite (NaBSiO 4) join

    NASA Astrophysics Data System (ADS)

    Pierce, E. M.; Reed, L. R.; Shaw, W. J.; McGrail, B. P.; Icenhower, J. P.; Windisch, C. F.; Cordova, E. A.; Broady, J.

    2010-05-01

    The dissolution kinetics of five glasses along the NaAlSiO 4-NaBSiO 4 join were used to evaluate how the structural variations associated with boron-aluminum substitution affect the rate of dissolution. The composition of each glass varied inversely in mol% of Al 2O 3 (5-25 mol%) and B 2O 3 (20-0 mol%) with Na 2O (25 mol%) and SiO 2 (50 mol%) making up the remaining amount, in every case Na/(Al + B) = 1.0. Single-pass flow-through experiments (SPFT) were conducted under dilute conditions as a function of solution pH (from 7.0 to 12.0) and temperature (from 23 to 90 °C). Analysis of unreacted glass samples by 27Al and 29Si MAS-NMR suggests Al (˜98% [4]Al) and Si-atoms (˜100% [4]Si) occupy a tetrahedral coordination whereas, B-atoms occupy both tetrahedral ( [4]B) and trigonal ( [3]B) coordination. The distribution of [3]B fractionated between [3]B(ring) and [3]B(non-ring) moieties, with the [3]B(ring)/ [3]B(non-ring) ratio increases with an increase in the B/Al ratio. The MAS-NMR results also indicated an increase in the fraction of [4]B with an increase in the B/Al ratio. The 27Al peak maxima shift to lesser values with an increase in the B/Al ratio which suggests mixing between the [4]Al and [3]B sites, assuming avoidance between tetrahedral trivalent cations ( [4]Al-O- [4]B avoidance). Unlike the 27Al and 11B spectra, the 29Si spectra illustrate a subtle shift to more negative chemical shift (chemical shift range between -88 and -84 ppm) and increases in the spectral widths as the B/Al ratio increases. Raman spectroscopy of unreacted glass samples was also used to cross-check the results collected from MAS-NMR and suggested that NeB4 (the glass sample with the highest B content) may consist of B-Na enriched and Al-Si enriched micro-domains, which affected the measured dissolution rates. Results from SPFT experiments suggest a forward rate of reaction and pH power-law coefficients, η, that are independent of B/Al under these neutral to alkaline test conditions

  2. Crystal growth and optical properties of indium doped LiCaAlF6 scintillator single crystals

    NASA Astrophysics Data System (ADS)

    Tanaka, Chieko; Yokota, Yuui; Kurosawa, Shunsuke; Yamaji, Akihiro; Jary, Vitezslav; Babin, Vladimir; Pejchal, Jan; Ohashi, Yuji; Kamada, Kei; Nikl, Martin; Yoshikawa, Akira

    2017-03-01

    The In-doped LiCaAlF6 [In:LiCAF] single crystals were grown by the micro-pulling-down (μ-PD) method, and the phases, chemical compositions, transmittance and radioluminescence spectra were investigated. All the grown crystals showed high transparency and single phase of LiCAF without visible cracks and inclusions except for the end part of In2%:LiCAF crystal which included the impurity phase. In the radioluminescence spectra of the In:LiCAF crystals under X-ray irradiation, the emission peak around 750 nm was revealed.

  3. Composition and mineralogy of refractory-metal-rich assemblages from a Ca,Al-rich inclusion in the Allende meteorite

    NASA Astrophysics Data System (ADS)

    Bischoff, A.; Palme, H.

    1987-10-01

    Four refractory metal-rich samples (10-190 micrograms) were separated from a single Ca,Al inclusion of the Allende meteorite. Chemical analyses were carried out by INAA; mineral phases from six large fremdlinge and the surrounding inclusion were analyzed by EDS. It is found that three of the four separated samples have variable absolute but similar relative abundances of refractory metals. All six fremdlinge are made up of Ni-rich metal containing 2-9 percent Ir, surrounded by a fine-grained intergrowth of V-magnetite and FeS.

  4. Calcium aluminate silicate Ca2Al2SiO7 single crystal applicable to piezoelectric sensors at high temperature

    NASA Astrophysics Data System (ADS)

    Takeda, Hiroaki; Hagiwara, Manabu; Noguchi, Hiroaki; Hoshina, Takuya; Takahashi, Tomoko; Kodama, Nobuhiro; Tsurumi, Takaaki

    2013-06-01

    Ca2Al2SiO7 (CAS) bulk single crystals were grown by the Czochralski method. Material constants of the crystal were determined over the driving temperature range of a typical combustion pressure sensor. The electrical resistivity at 800 °C was found to be of the order of 108 Ωcm. We constructed a measurement system for the direct piezoelectric effect at high temperature, and characterized the crystals in a simulated engine cylinder combustion environment. Output charge signal against applied stress was detected at 700 °C. These observations suggest that CAS crystals are superior candidate materials for high temperature for stress sensing.

  5. Efficient Yb³⁺:CaGdAlO₄ bulk and femtosecond-laser-written waveguide lasers.

    PubMed

    Hasse, Kore; Calmano, Thomas; Deppe, Bastian; Liebald, Christoph; Kränkel, Christian

    2015-08-01

    We report on, to the best of our knowledge, the first fs-laser-written waveguide laser in Yb3+:CaGdAlO4 (Yb:CALGO). With Yb:CALGO crystals grown in our labs, we obtained a slope efficiency of 69% and up to 2.4 W of continuous wave (cw) output power in a waveguide-laser configuration. Moreover, bulk laser experiments with Yb:CALGO were performed, and slope efficiencies up to 73%, optical-to-optical efficiencies of 65%, and maximum cw output powers of 3.3 W were reached. These are the highest efficiencies in the laser configuration with Yb:CALGO.

  6. High-resolution continuum source electrothermal absorption spectrometry of AlBr and CaBr for the determination of bromine

    NASA Astrophysics Data System (ADS)

    Huang, Mao Dong; Becker-Ross, Helmut; Florek, Stefan; Heitmann, Uwe; Okruss, Michael

    2008-05-01

    Molecular absorption spectra of AlBr and CaBr, produced in a graphite furnace, were investigated using a high-resolution echelle spectrometer equipped with a xenon short-arc lamp as continuum source. The analytical usability of the spectra for the determination of bromine was studied. To this end, the molecular absorptions of AlBr at 278.914 nm and CaBr at 625.315 nm were evaluated. Apart from strong absorption bands of CaF around 625.3 nm, which disturb the use of CaBr, no spectral interferences were observed for both AlBr and CaBr. Regarding chemical interference with matrix substances, the molecular absorption of AlBr and CaBr is influenced in a different way. While the sensitivity of the CaBr absorption is susceptible to chloride, aluminum, potassium and sodium ions, there is no significant effect on the AlBr absorption. In contrast, the inorganic acids (nitric, phosphoric, and sulfuric) have an influence on AlBr, but not on the CaBr molecular absorption. Therefore, the two methods complement each other and each has its own application area. Regarding real samples, a salt sample from the death sea and an organic pharmaceutical were evaluated. The results were in good agreement with those derived from two independent methods and with an existing reference value. Relative standard deviations were found in the range of 5%. The limit of detection for bromine was about 2 ng for both AlBr and CaBr molecular absorption; the dynamic range was linear at least up to 250 ng Br.

  7. Ca(2+)-dependent heat production by rat skeletal muscle in hypertonic media depends on Na(+)-Cl- co-transport stimulation.

    PubMed Central

    Chinet, A

    1993-01-01

    1. The rate of energy dissipation (E) in isolated, superfused soleus muscles from young rats was continuously measured under normosmotic and 100-mosM hyperosmotic conditions. The substantial increase of E with respect to basal level in hyperosmolarity (excess E), which is entirely dependent on the presence of extracellular sodium, was largely prevented or inhibited by bumetanide, a potent inhibitor of Na(+)-Cl- co-transport system, or by the removal of chloride from the superfusate (isethionate substitution). Bumetanide or the removal of chloride also acutely decreased basal E, by about 7%. 2. Bumetanide almost entirely suppressed the major, Ca(2+)-dependent part of excess E in hyperosmolarity, as well as the concomitant increase of 45Ca2+ efflux and small increase in resting muscle tension; in contrast, the part of excess E associated with stimulation of Na(+)-H+ exchange in hyperosmolarity was left unmodified. 3. Reduction of 22Na+ influx by bumetanide was more marked in hyperosmolarity than under control conditions, although stimulation of total 22Na+ influx by a 100-mosM stress was not statistically significant. Inhibition of Ca2+ release into the sarcoplasm using dantrolene sodium did not prevent the stimulation of bumetanide-sensitive 22Na+ influx, but rather increased it about fourfold. 4. It is concluded that the largest part of excess E in hyperosmolarity, which is Ca(2+)-dependent energy expenditure, is suppressed when steady-state stimulation of a Na(+)-Cl- co-transport system is inhibited either directly by bumetanide or the removal of extracellular chloride, or indirectly by the blocking of active Na(+)-K+ transport. How the stimulation of Na(+)-Cl- co-transport, by as little as 1 nmol s-1 (g wet muscle weight)-1 during a 100-mosM stress, enhances Ca(2+)-dependent heat by as much as 2.5 mW (g wet muscle weight)-1 remains to be clarified. PMID:8394429

  8. Synthesis of a novel green fluorescent material Ca3Al2O6:Tb3+ based on a layered double hydroxide precursor

    NASA Astrophysics Data System (ADS)

    Gao, Xiaorui; Jiang, Kangle; Hao, Yongjing; Chang, Tao; Yin, Yaobing

    2015-08-01

    A novel green light emitting material, Ca3Al2O6:Tb3+ was synthesized by calcination of a terbium doped Ca/Al layered double hydroxide precursor at 1350°C. The precursor was prepared by coprecipitation from metal nitrates with sodium hydroxide. The material shows characteristic green emission at 543 nm when excited with 266 nm UV source. The photoluminescence intensity reaches its maximum at Tb3+ concentration of 0.5 mol %.

  9. Ubiquitous [Na+]i/[K+]i-Sensitive Transcriptome in Mammalian Cells: Evidence for Ca2+i-Independent Excitation-Transcription Coupling

    PubMed Central

    Koltsova, Svetlana V.; Trushina, Yulia; Haloui, Mounsif; Akimova, Olga A.; Tremblay, Johanne; Hamet, Pavel; Orlov, Sergei N.

    2012-01-01

    Stimulus-dependent elevation of intracellular Ca2+ ([Ca2+]i) affects the expression of numerous genes – a phenomenon known as excitation-transcription coupling. Recently, we found that increases in [Na+]i trigger c-Fos expression via a novel Ca2+i-independent pathway. In the present study, we identified ubiquitous and tissue-specific [Na+]i/[K+]i-sensitive transcriptomes by comparative analysis of differentially expressed genes in vascular smooth muscle cells from rat aorta (RVSMC), the human adenocarcinoma cell line HeLa, and human umbilical vein endothelial cells (HUVEC). To augment [Na+]i and reduce [K+]i, cells were treated for 3 hrs with the Na+,K+-ATPase inhibitor ouabain or placed for the same time in the K+-free medium. Employing Affymetrix-based technology, we detected changes in expression levels of 684, 737 and 1839 transcripts in HeLa, HUVEC and RVSMC, respectively, that were highly correlated between two treatments (p<0.0001; R2>0.62). Among these Na+i/K+i-sensitive genes, 80 transcripts were common for all three types of cells. To establish if changes in gene expression are dependent on increases in [Ca2+]i, we performed identical experiments in Ca2+-free media supplemented with extracellular and intracellular Ca2+ chelators. Surprisingly, this procedure elevated rather than decreased the number of ubiquitous and cell-type specific Na+i/K+i-sensitive genes. Among the ubiquitous Na+i/K+i-sensitive genes whose expression was regulated independently of the presence of Ca2+ chelators by more than 3-fold, we discovered several transcription factors (Fos, Jun, Hes1, Nfkbia), interleukin-6, protein phosphatase 1 regulatory subunit, dual specificity phosphatase (Dusp8), prostaglandin-endoperoxide synthase 2, cyclin L1, whereas expression of metallopeptidase Adamts1, adrenomedulin, Dups1, Dusp10 and Dusp16 was detected exclusively in Ca2+-depleted cells. Overall, our findings indicate that Ca2+i-independent mechanisms of excitation-transcription coupling are

  10. Ubiquitous [Na+]i/[K+]i-sensitive transcriptome in mammalian cells: evidence for Ca(2+)i-independent excitation-transcription coupling.

    PubMed

    Koltsova, Svetlana V; Trushina, Yulia; Haloui, Mounsif; Akimova, Olga A; Tremblay, Johanne; Hamet, Pavel; Orlov, Sergei N

    2012-01-01

    Stimulus-dependent elevation of intracellular Ca(2+) ([Ca(2+)](i)) affects the expression of numerous genes--a phenomenon known as excitation-transcription coupling. Recently, we found that increases in [Na(+)](i) trigger c-Fos expression via a novel Ca(2+) (i)-independent pathway. In the present study, we identified ubiquitous and tissue-specific [Na(+)](i)/[K(+)](i)-sensitive transcriptomes by comparative analysis of differentially expressed genes in vascular smooth muscle cells from rat aorta (RVSMC), the human adenocarcinoma cell line HeLa, and human umbilical vein endothelial cells (HUVEC). To augment [Na(+)](i) and reduce [K(+)](i), cells were treated for 3 hrs with the Na(+),K(+)-ATPase inhibitor ouabain or placed for the same time in the K(+)-free medium. Employing Affymetrix-based technology, we detected changes in expression levels of 684, 737 and 1839 transcripts in HeLa, HUVEC and RVSMC, respectively, that were highly correlated between two treatments (p<0.0001; R(2)>0.62). Among these Na(+) (i)/K(+) (i)-sensitive genes, 80 transcripts were common for all three types of cells. To establish if changes in gene expression are dependent on increases in [Ca(2+)](i), we performed identical experiments in Ca(2+)-free media supplemented with extracellular and intracellular Ca(2+) chelators. Surprisingly, this procedure elevated rather than decreased the number of ubiquitous and cell-type specific Na(+) (i)/K(+) (i)-sensitive genes. Among the ubiquitous Na(+) (i)/K(+) (i)-sensitive genes whose expression was regulated independently of the presence of Ca(2+) chelators by more than 3-fold, we discovered several transcription factors (Fos, Jun, Hes1, Nfkbia), interleukin-6, protein phosphatase 1 regulatory subunit, dual specificity phosphatase (Dusp8), prostaglandin-endoperoxide synthase 2, cyclin L1, whereas expression of metallopeptidase Adamts1, adrenomedulin, Dups1, Dusp10 and Dusp16 was detected exclusively in Ca(2+)-depleted cells. Overall, our findings

  11. Theoretical investigation on local structure and transport properties of NaFsbnd AlF3 molten salts under electric field environment

    NASA Astrophysics Data System (ADS)

    Lv, Xiaojun; Xu, Zhenming; Li, Jie; Chen, Jiangan; Liu, Qingsheng

    2016-08-01

    The effect of electric field and molecular ratio CR (NaF/AlF3) on basic structure and transport properties of NaFsbnd AlF3 molten salts were investigated by molecular dynamics simulations with the Buckingham potential model. The [AlF6]3- groups are the dominant specie in NaFsbnd AlF3 molten salts at CR ≥ 2.6, and followed by the [AlF5]2- groups, while CR ≤ 2.4, [AlF5]2- groups are the protagonists up to 40%. In NaFsbnd AlF3 system, with the increase of CR, the proportion of Fb decreases slightly and the percentage of Ff increases dramatically. The Alsbnd F bonds have ionic characters as well as partial covalently characters due to the hybridization of F-2p and Al-3s, 3p orbitals. The order of ion diffusion ability follows as Na+ > F- > Al3+. Adding more NaF can break some F bridges of structure networks and decrease the polymerization degree of NaFsbnd AlF3 molten salts, the viscosity reduces and ionic conductivity increases as a consequence. The calculated results of ionic conductivity are in agreement with the experimental results. Electric field has no significant impact on the local structure characters, while transport properties are not. The change of CR (NaF/AlF3) can significantly affect these characters of both the structure and transport.

  12. Persistent deNOx Ability of CaAl2O4:(Eu, Nd)/TiO2-xNy Luminescent Photocatalyst.

    PubMed

    Li, Huihui; Yin, Shu; Sato, Tsugio

    2010-08-20

    CaAl2O4:(Eu, Nd)/TiO2-xNy composite luminescent photocatalyst was successfully synthesized by a simple planetary ball milling process. Improvement of photocatalytic deNOx ability of TiO2-xNy, together with the persistent photocatalytic activity for the decomposition of NO after turning off the light were realized, by coupling TiO2-xNy with long afterglow phosphor, CaAl2O4:(Eu, Nd). The novel persistent photocatalytic behavior was related to the overlap between the absorption wavelength of TiO2-xNy and the emission wavelength of the CaAl2O4:(Eu, Nd). It was found that CaAl2O4:(Eu, Nd)/TiO2-xNy composites provided the luminescence to persist photocatalytic reaction for more than 3 h after turning off the light. GRAPHICAL CaAl2O4:(Eu, Nd)/TiO2-xNy composite luminescent photocatalyst with persistent deNOx activity after turning off the light was successfully synthesized by a simple planetary ball milling process. The novel persistent photocatalytic behavior was related to the overlap between the absorption wavelength of TiO2-xNy and the emission wavelength of the CaAl2O4:(Eu, Nd).

  13. Interfacial tension between CO 2 and brine (NaCl + CaCl 2) at elevated pressures and temperatures: The additive effect of different salts

    NASA Astrophysics Data System (ADS)

    Aggelopoulos, C. A.; Robin, M.; Vizika, O.

    2011-04-01

    An extensive laboratory study was conducted to measure the interfacial tension (IFT) between CO 2 and brine consisting in equal molal concentrations of NaCl and CaCl 2. The experiments were repeated at various pressures, temperatures and salinities that are representative of conditions prevailing during CO 2 storage in deep saline aquifers. The dependence of CO 2/brine IFT on pressure and temperature is similar to that previously reported for the systems: CO 2/NaCl solution and CO 2/CaCl 2 solution. CO 2/brine IFT increases linearly with water salinity and the magnitude of this increase was found equal to the sum of the individual CO 2/NaCl solution and CO 2/CaCl 2 solution IFT increments, indicating a strong additive effect on IFT when the brine is composed of various salts.

  14. A vibrational spectroscopic study of the silicate mineral pectolite - NaCa2Si3O8(OH)

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Theiss, Frederick L.; Romano, Antônio Wilson; Scholz, Ricardo

    2015-01-01

    The mineral pectolite NaCa2Si3O8(OH) is a crystalline sodium calcium silicate which has the potential to be used in plaster boards and in other industrial applications. Raman bands at 974 and 1026 cm-1 are assigned to the SiO stretching vibrations of linked units of Si3O8 units. Raman bands at 974 and 998 cm-1 serve to identify Si3O8 units. The broad Raman band at around 936 cm-1 is attributed to hydroxyl deformation modes. Intense Raman band at 653 cm-1 is assigned to OSiO bending vibration. Intense Raman bands in the 2700-3000 cm-1 spectral range are assigned to OH stretching vibrations of the OH units in pectolite. Infrared spectra are in harmony with the Raman spectra. Raman spectroscopy with complimentary infrared spectroscopy enables the characterisation of the silicate mineral pectolite.

  15. Hypotonic shock modulates Na(+) current via a Cl(-) and Ca(2+)/calmodulin dependent mechanism in alveolar epithelial cells.

    PubMed

    Dagenais, André; Tessier, Marie-Claude; Tatur, Sabina; Brochiero, Emmanuelle; Grygorczyk, Ryszard; Berthiaume, Yves

    2013-01-01

    Alveolar epithelial cells are involved in Na(+) absorption via the epithelial Na(+) channel (ENaC), an important process for maintaining an appropriate volume of liquid lining the respiratory epithelium and for lung oedema clearance. Here, we investigated how a 20% hypotonic shock modulates the ionic current in these cells. Polarized alveolar epithelial cells isolated from rat lungs were cultured on permeant filters and their electrophysiological properties recorded. A 20% bilateral hypotonic shock induced an immediate, but transient 52% rise in total transepithelial current and a 67% increase in the amiloride-sensitive current mediated by ENaC. Amiloride pre-treatment decreased the current rise after hypotonic shock, showing that ENaC current is involved in this response. Since Cl(-) transport is modulated by hypotonic shock, its contribution to the basal and hypotonic-induced transepithelial current was also assessed. Apical NPPB, a broad Cl(-) channel inhibitor and basolateral DIOA a potassium chloride co-transporter (KCC) inhibitor reduced the total and ENaC currents, showing that transcellular Cl(-) transport plays a major role in that process. During hypotonic shock, a basolateral Cl(-) influx, partly inhibited by NPPB is essential for the hypotonic-induced current rise. Hypotonic shock promoted apical ATP secretion and increased intracellular Ca(2+). While apyrase, an ATP scavenger, did not inhibit the hypotonic shock current response, W7 a calmodulin antagonist completely prevented the hypotonic current rise. These results indicate that a basolateral Cl(-) influx as well as Ca(2+)/calmodulin, but not ATP, are involved in the acute transepithelial current rise elicited by hypotonic shock.

  16. Zn, Ca and Na levels in the prostatic secretion of patients with prostatic adenoma.

    PubMed

    Romics, I; Bach, D

    1991-01-01

    Zinc, calcium and sodium levels of the prostatic secretions in patients with prostatic adenoma were studied. In a control group of 20 patients, two samples of the secretion, taken on the first and the seventh day, were compared and found to show no difference. In the treated group of 20 patients, where a 7-day therapy of ERU (extractum radix urticae) followed upon the first sampling, the 7th-day specimen presented a significant drop in the Zn level. Correlation was found to exist between the Zn and Ca levels. From literary data the inference was drawn that ERU is producing a derangement in the zinc-testosterone metabolism and diminishes the zinc secretion in adenomatous tissue.

  17. Propagation Properties of the Precipitation Band in an AlCl₃/NaOH System.

    PubMed

    Ban, Takahiko; Nagatsu, Yuichiro; Tokuyama, Hideaki

    2016-01-19

    When inherently immobile solid particles collectively form precipitates in a reaction-diffusion system involving a redissolution reaction, a propagation phenomenon may occur in which a dynamic pattern of precipitation bands forms. This propagating precipitation phenomenon has been studied by many researchers. However, two completely different processes-i.e., the reaction-diffusion of reactants and the crystal growth of products-progress simultaneously in the system, thereby rendering the phenomenon complex. There are no well-established experimental laws for this propagating precipitation phenomenon, such as the spacing, time, and width laws associated with the well-known Liesegang phenomenon, which is static in the sense that precipitation bands form and remain at the same position. In fact, it has not been clarified which of the processes controls the propagation phenomenon. Accordingly, we have investigated the apparent diffusion coefficient associated with the dynamics of propagating precipitation band in an AlCl3/NaOH system for the case in which a large excess of outer electrolytes (i.e., OH(-)) diffuses into gel in which inner electrolytes (i.e.,Al(3+)) are homogeneously distributed. An isolated precipitation band of Al(OH)3 was formed horizontally in a test tube and propagated vertically in proportion to the square root of time. In our experimental results, we found that the apparent diffusion coefficient, D(p), possesses an exponential dependence on the initial concentrations of the outer electrolyte, and the inner electrolyte; the measured relation was D(p) = D[Al(3+)](-0.6)[OH(-)](0.6), where D = (0.63 ± 0.04) × 10(5) cm(2)/s. From our model equations based on the prenucleation theory, which take into account a redissolution reaction, we found that the dynamics of the reaction front of the outer and the inner electrolytes was an important factor in controlling the propagation of the precipitation band. In our simulation results, we obtained a similar

  18. Single and combined effects of carbamazepine and vinpocetine on depolarization-induced changes in Na+, Ca2+ and glutamate release in hippocampal isolated nerve endings.

    PubMed

    Sitges, María; Chiu, Luz María; Nekrassov, Vladimir

    2006-07-01

    The single and combined effects of carbamazepine and vinpocetine on the release of the excitatory amino acid neurotransmitter glutamate, on the rise in internal Na+ (Na(i), as determined with SBFI), and on the rise in internal Ca2+ (Ca(i), as determined with fura-2) induced by an increased permeability of presynaptic Na+ channels, with veratridine, or by an increased permeability of presynaptic Ca2+ channels with high K+, were investigated in isolated hippocampal nerve endings. The present study shows that carbamazepine and vinpocetine, both inhibit dose dependently the release of preloaded [3H]Glu induced by veratridine. However, carbamazepine is two orders of magnitude less potent than vinpocetine. The calculated IC(50)'s for carbamazepine and vinpocetine to inhibit veratridine-induced [3H]Glu release are 200 and 2 microM, respectively. Consistently 150 microM carbamazepine and 1.5 microM vinpocetine reduce the veratridine-induced rise in Na(i) in a similar extent. The single effects of carbamazepine and of vinpocetine on the presynaptic Na+ channel mediated responses, namely the rise in Na(i) and the release of Glu induced by veratridine, are additive. Responses that depend on the entrance of external Ca2+ via presynaptic Ca2+ channels, such as the release of [3H]Glu and the rise in Ca(i) induced by high K+, are insensitive to 300 microM carbamazepine and slightly reduced by 5 microM vinpocetine. It is concluded that the additive effects of carbamazepine, which is one of the most common antiepileptic drugs, and vinpocetine that besides its known neuroprotective action and antiepileptic potential is a memory enhancer, may perhaps be advantageous in the treatment of epileptic patients.

  19. Precursor preparation for Ca-Al layered double hydroxide to remove hexavalent chromium coexisting with calcium and magnesium chlorides

    NASA Astrophysics Data System (ADS)

    Zhong, Lihua; He, Xiaoman; Qu, Jun; Li, Xuewei; Lei, Zhiwu; Zhang, Qiwu; Liu, Xinzhong

    2017-01-01

    Al(OH)3 and Ca(OH)2 powders are co-ground to prepare a precursor which hydrates into a layered double hydroxide (LDH) phase by agitation in aqueous solution with target hexavalent chromium (Cr(VI)) at room temperature, to achieve an obvious improvement in removal efficiency of Cr(VI) through an easy incorporation into the structure. Although the prepared precursor transforms into LDH phases also when agitated in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. The adsorption isotherm and kinetic studies show that the phenomena occurring on the Al-Ca precursor fit a pseudo-second-order kinetics with a Langmuir adsorption capacity of 59.45 mg/g. Besides, characterizations of the prepared precursor and the samples after adsorption are also performed by X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscope (TEM) to understand the reason of the preferential incorporation of Cr(VI) to the coexisting chloride salts during the LDH phase formation.

  20. Crustal structure of the Pannonian Basin: The AlCaPa and Tisza Terrains and the Mid-Hungarian Zone

    NASA Astrophysics Data System (ADS)

    Hetényi, György; Ren, Yong; Dando, Ben; Stuart, Graham W.; Hegedűs, Endre; Kovács, Attila Csaba; Houseman, Gregory A.

    2015-04-01

    The Pannonian Basin of Central Europe is one of the key examples of Miocene continental extension that is easily accessible to surface seismological investigation. It comprises two major crustal blocks: AlCaPa and Tisza which abut along a poorly understood structure referred to as the Mid-Hungarian Zone (MHZ), the whole being surrounded by the arc of the Carpathian Mountains, the Alps and the Dinarides. Using data from the CBP (Carpathian Basins Project) temporary broadband seismic array of 46 stations deployed across the western Pannonian Basin in 2006-2007, we calculated receiver functions that constrain the variation of crustal thickness across the basin and derive a map of Moho depth across a NW-SE oriented swath about 450 km long and 75 km wide. The measured Moho depths show no significant change in crustal thickness between AlCaPa and Tisza terrains, but the Moho is not or very weakly imaged along a ca. 40 km wide strip centred on the MHZ. Moho depths within the Pannonian Basin are typically in the range 25-30 km, and increase toward the periphery of the basin. Our measurements are generally consistent with earlier VP models from controlled-source seismic surveys and recent VS models determined by tomographic analysis of ambient noise signals. The lack of a sharp Moho image beneath the MHZ suggests that the crust-mantle boundary in that zone may consist of a gradual increase in velocity with depth. The relatively constant crustal thickness across the two domains of the Pannonian Basin suggests that thinning to the same final state is controlled thermally. This structural characteristic seems to be governed by a large-scale balance of gravitational potential energy that is insensitive to the separate prior histories of the two regions.

  1. Ca II AND Na I QUASAR ABSORPTION-LINE SYSTEMS IN AN EMISSION-SELECTED SAMPLE OF SDSS DR7 GALAXY/QUASAR PROJECTIONS. I. SAMPLE SELECTION

    SciTech Connect

    Cherinka, B.; Schulte-Ladbeck, R. E.

    2011-10-15

    The aim of this project is to identify low-redshift host galaxies of quasar absorption-line systems by selecting galaxies that are seen in projection onto quasar sightlines. To this end, we use the Seventh Data Release of the Sloan Digital Sky Survey to construct a parent sample of 97,489 galaxy/quasar projections at impact parameters of up to 100 kpc to the foreground galaxy. We then search the quasar spectra for absorption-line systems of Ca II and Na I within {+-}500 km s{sup -1} of the galaxy's velocity. This yields 92 Ca II and 16 Na I absorption systems. We find that most of the Ca II and Na I systems are sightlines through the Galactic disk, through high-velocity cloud complexes in our halo, or Virgo Cluster sightlines. Placing constraints on the absorption line rest equivalent width significance ({>=}3.0{sigma}), the local standard of rest velocity along the sightline ({>=}345 km s{sup -1}), and the ratio of the impact parameter to the galaxy optical radius ({<=}5.0), we identify four absorption-line systems that are associated with low-redshift galaxies at high confidence, consisting of two Ca II systems (one of which also shows Na I) and two Na I systems. These four systems arise in blue, {approx}L*{sub r} galaxies. Tables of the 108 absorption systems are provided to facilitate future follow-up.

  2. Dynamic Wetting of CaO-Al2O3-SiO2-MgO Liquid Oxide on MgAl2O4 Spinel

    NASA Astrophysics Data System (ADS)

    Abdeyazdan, Hamed; Dogan, Neslihan; Rhamdhani, M. Akbar; Chapman, Michael W.; Monaghan, Brian J.

    2015-02-01

    Inclusion type and content in steel is critical in steelmaking, affecting both productivity through clogging, and downstream physical properties of the steel. They are normally removed from steel by reacting with a slag (liquid oxide) phase. For efficient inclusion removal, the inclusions must attach/bond with this liquid phase. The strength of the attachment can be in part characterized by the wettability of the liquid oxide on the inclusions. In this study, the dynamic wetting of liquid oxides of the CaO-Al2O3-SiO2-MgO system on a solid spinel (MgAl2O4) substrate with low porosity of 1.9 pct was measured at 1773 K (1500 °C) using a modified sessile drop technique. The dynamic contact angle between the liquid and solid spinel was determined for different CaO/Al2O3 mass percent ratios ranging from 0.98 to 1.55. Characteristic curves of wettability ( θ) vs time showed a rapid decrease in wetting in the first 10 seconds tending to a plateau value at extended times. A mathematical model for spreading behavior of liquid oxides by Choi and Lee was adopted and shown to provide a reasonable representation of the spreading behavior with time. The chemical interaction at the interface between spinel (MgAl2O4) and slag was analyzed by carrying out detailed thermodynamic evaluation and characterization using scanning electron microscopy/energy dispersive spectroscopy. There is evidence of liquid penetrating the substrate via pores and along grain boundaries, forming a penetration layer in the substrate. The depth of the penetration layer was found to be a function of substrate porosity and sample cooling rate. It decreased from ~350 µm for 6.7 pct-porous substrate to ~190 µm for substrate with porosity of 1.9 pct and from ~190 µm to ~50 µm for a slow-cooled liquid oxide-spinel substrate sample in the furnace to a rapidly cooled liquid cooled-spinel substrate sample, respectively.

  3. The Effects of Individual Metal Contents on Isochrones for C, N, O, Na, Mg, Al, Si, and Fe

    NASA Astrophysics Data System (ADS)

    Beom, Minje; Na, Chongsam; Ferguson, Jason W.; Kim, Y.-C.

    2016-08-01

    The individual characteristics of C, N, O, Na, Mg, Al, Si, and Fe on isochrones have been investigated in this study. Stellar models have been constructed for various mixtures in which the content of each element is changed up to the extreme value reported in recent studies, and the changes in isochrone shape have been analyzed for the various mixtures. To express the abundance variation of different elements with a single parameter, we have focused on the relative changes in the total number of metal ions. A review of the shape changes revealed that Na, Mg, and Al work the same way in stellar models, similar to the well-known fact that C, N, and O have the same reactions in the stellar interior. In addition, it was found that in high-metallicity conditions the influence of Si and Fe on the red giant branch becomes smaller than that of Na, Mg, and Al closer to the tip. Furthermore, the influence of Fe on the main sequence is larger than that of Na, Mg, Al, and even Si.

  4. Improvement in dehydrogenation of MXH4 where M = Na, Li and X = Al, B confined in CNTs: a DFT investigation

    NASA Astrophysics Data System (ADS)

    Meenakshi; Agnihotri, Deepak; Jeet, Kiran; Sharma, Hitesh

    2016-11-01

    Nanoconfinement improves dehydrogenation kinetics of complex metal hydrides. The present paper reports effect of confinement of MXH4, where M = Na, Li and X = Al, B inside carbon nanotubes (CNTs) (n, 0) n = 9-11 chirality and diameter of 7.47 Å, 7.87 Å, 8.73 Å, respectively, using Density Functional calculations. The MXH4 interacts strongly with the surface atoms of CNT (11, 0) and is found to be the smallest stable system for confinement of MXH4 clusters. The Hydrogen release energy (E Hre) of NaAlH4 decreases sharply by 68.3 % , w.r.t. pure NaAlH4 cluster when confined inside CNT(11, 0). Similarly, in CNT (11, 0) E Hre decreases by 38.1 % for LiAlH4, 12.7 % for NaBH4 and 19.1 % for LiBH4. Thus, resulting confinement had a profound effect in improving the energetics of complex metal hydride nanoparticles without catalyst.

  5. Thermal Conductivity Investigation of {Ca}_{9} {RE}({VO}_{4})_{7} (RE = La, Nd, Gd) and {Ca}_{10}M(VO_{4})_{7} (M = Li, Na, K) Single Crystals

    NASA Astrophysics Data System (ADS)

    Popov, P. A.; Skrobov, S. A.; Matovnikov, A. V.; Kosmyna, M. B.; Puzikov, V. M.; Nazarenko, B. P.; Shekhovtsov, A. N.; Behrooz, A.; Paszkowicz, W.; Khodasevich, I. A.; Shereshovets, N. N.; Voitikov, S. V.; Orlovich, V. A.

    2017-01-01

    The {Ca}9{RE}({VO}4)7 (RE = La, Nd, Gd) and {Ca}_{10}{M}({VO}4)7 (M = Li, Na, K) single crystals have been grown by the Czochralski method. The binary vanadates are isostructural to "whitlockite" mineral (rhombohedral symmetry, R3 c space group). Their thermal conductivity has been investigated in the range 50 K-300 K parallel to the c axis. For {Ca}9{Gd}({VO}4)7 crystals, the thermal conductivity has been investigated in the range 300 K-550 K also. Additionally, for the {Ca}_{10}{M}({VO}4)7 (M = Li, Na, K) crystals the heat capacity has been studied in the temperature range 80 K-300 K. The character of the temperature dependence of thermal conductivity is close to that of glasses. The possible reasons of the observed features of the thermal conductivity have been analyzed. Raman spectra of {Ca}_{10}{M}({VO}4)7 (M = Li, Na, K) crystals have been measured and discussed. The spectral lines were broad and similar to polycrystalline or amorphous solids. These crystals are expected to be suitable for application as efficient nonlinear optic and laser materials.

  6. Thermodynamics of Complex Sulfide Inclusion Formation in Ca-Treated Al-Killed Structural Steel

    NASA Astrophysics Data System (ADS)

    Guo, Yin-tao; He, Sheng-ping; Chen, Gu-jun; Wang, Qian

    2016-08-01

    Controlling the morphology of the sulfide inclusion is of vital importance in enhancing the properties of structural steel. Long strip-shaped sulfides in hot-rolled steel can spherize when, instead of the inclusion of pure single-phase MnS, the guest is a complex sulfide, such as an oxide-sulfide duplex and a solid-solution sulfide particle. In this study, the inclusions in a commercial rolled structural steel were investigated. Spherical and elongated oxide-sulfide duplex as well as single-phase (Mn,Ca)S solid solution inclusions were observed in the steel. A thermodynamic equilibrium between the oxide and sulfide inclusions was proposed to understand the oxide-sulfide duplex inclusion formation. Based on the equilibrium solidification principle, thermodynamic discussions on inclusion precipitation during the solidification process were performed for both general and resulfurized structural steel. The predicted results of the present study agreed well with the experimental ones.

  7. The effect of composition on ion release from Ca-Sr-Na-Zn-Si glass bone grafts.

    PubMed

    Murphy, S; Boyd, D; Moane, S; Bennett, M

    2009-11-01

    Controlled delivery of active ions from biomaterials has become critical in bone regeneration. Some silica-based materials, in particular bioactive glasses, have received much attention due to the ability of their dissolution products to promote cell proliferation, cell differentiation and activate gene expression. However, many of these materials offer little therapeutic potential for diseased tissue. Incorporating trace elements, such as zinc and strontium, known to have beneficial and therapeutic effects on bone may provide a more viable bone graft option for those suffering from metabolic bone diseases such as osteoporosis. Rational compositional design may also allow for controlled release of these active ions at desirable dose levels in order to enhance therapeutic efficacy. In this study, six differing compositions of calcium-strontium-sodium-zinc-silicate (Ca-Sr-Na-Zn-Si) glass bone grafts were immersed in pH 7.4 and pH 3 solutions to study the effect of glass composition on zinc and strontium release in a normal and extreme physiological environment. The zinc release levels over 30 days for all zinc-containing glasses in the pH 7.4 solution were 3.0-7.65 ppm. In the more acidic pH 3 environment, the zinc levels were higher (89-750 ppm) than those reported to be beneficial and may produce cytotoxic or negative effects on bone tissue. Strontium levels released from all examined glasses in both pH environments similarly fell within apparent beneficial ranges--7.5-3500 ppm. Glass compositions with identical SrO content but lower ZnO:Na(2)O ratios, showed higher levels of Sr(2+) release. Whereas, zinc release from zinc-containing glasses appeared related to ZnO compositional content. Sustainable strontium and zinc release was seen in the pH 7.4 environment up to day 7. These results indicate that the examined Ca-Sr-Na-Zn-Si glass compositions show good potential as therapeutic bone grafts, and that the graft composition can be tailored to allow therapeutic

  8. High-pressure phase relations in the composition of albite NaAlSi3O8 constrained by an ab initio and quasi-harmonic Debye model, and their implications

    NASA Astrophysics Data System (ADS)

    Deng, L.; Liu, X.; Liu, H.; Dong, J.

    2010-12-01

    phase assemblage transforms into the CS phase assemblage at about 33.6 GPa at 0 K, and the Clayperon slope of this phase transition is about 0.014 GPa/K. This study implies that lingunite (Na-Holl), found in somemeteorites, is not possibly a thermodynamically stable high-P phase, and the Cf phase probably plays an important role in maintaining the sodium budget and hosting the large-ion lithophile elements in the deep interior of the Earth. References: Beck, P., Gillet, P., Gautron, L., Daniel, I., El Goresy, A., 2004. A new natural high-pressure (Na, Ca)-hexaluminosilicate [(CaxNa1-x)Al3+xSi3-xO11] in shocked Martian meteorites. Earth Planet. Sci. Lett. 219, 1-12. Liu, L., 1978. High-pressure phase transformations of albite, jadeite and nepheline. Earth Planet. Sci. Lett. 37, 438-444. Sekine, T., Ahrens, T.J., 1992. Shock-induced transformations in the system NaAlSi3O8-SiO2: a new interpretation. Phys. Chem. Mineral. 18, 359-364. Tutti, F., 2007. Formation of end-member NaAlSi3O8 hollandite-type structure (lingunite) in diamond anvil cell. Phys. Earth Planet. Inter. 161, 143-149.

  9. SEM, EDS and vibrational spectroscopic study of dawsonite NaAl(CO3)(OH)2

    NASA Astrophysics Data System (ADS)

    Frost, Ray L.; López, Andrés; Scholz, Ricardo; Sampaio, Ney Pinheiro; de Oliveira, Fernando A. N.

    2015-02-01

    In this work we have studied the mineral dawsonite by using a combination of scanning electron microscopy with EDS and vibrational spectroscopy. Single crystals show an acicular habitus forming aggregates with a rosette shape. The chemical analysis shows a phase composed of C, Al, and Na. Two distinct Raman bands at 1091 and 1068 cm-1 are assigned to the CO32- ν1 symmetric stretching mode. Multiple bands are observed in both the Raman and infrared spectra in the antisymmetric stretching and bending regions showing that the symmetry of the carbonate anion is reduced and in all probability the carbonate anions are not equivalent in the dawsonite structure. Multiple OH deformation vibrations centred upon 950 cm-1 in both the Raman and infrared spectra show that the OH units in the dawsonite structure are non-equivalent. Raman bands observed at 3250, 3283 and 3295 cm-1 are assigned to OH stretching vibrations. The position of these bands indicates strong hydrogen bonding of the OH units in the dawsonite structure. The formation of the mineral dawsonite has the potential to offer a mechanism for the geosequestration of greenhouse gases.

  10. Thermodynamics of open networks: Ordering and entropy in NaAlSiO4 glass, liquid, and polymorphs

    USGS Publications Warehouse

    Richet, P.; Robie, R.A.; Rogez, J.; Hemingway, B.S.; Courtial, P.; Tequi, C.

    1990-01-01

    The thermodynamic properties of carnegieite and NaAlSiO4 glass and liquid have been investigated through Cp determinations from 10 to 1800 K and solution-calorimetry measurements. The relative entropies S298-S0 of carnegieite and NaAlSiO4 glass are 118.7 and 124.8 J/mol K, respectively. The low-high carnegieite transition has been observed at 966 K with an enthalpy of transition of 8.1??0.3 kJ/mol, and the enthalpy of fusion of carnegieite at the congruent melting point of 1799 K is 21.7??3 kJ/mol. These results are consistent with the reported temperature of the nepheline-carnegieite transition and available thermodynamic data for nepheline. The entropy of quenched NaAlSiO4 glass at 0 K is 9.7??2 J/mol K and indicates considerable ordering among AlO4 and SiO4 tetrahedra. In the liquid state, progressive, temperature-induced Si, Al disordering could account for the high configurational heat capacity. Finally, the differences between the entropies and heat capacities of nepheline and carnegieite do not seem to conform to current polyhedral modeling of these properties ?? 1990 Springer-Verlag.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  12. Vitality and chemistry of roots of red spruce in forest floors of stands with a gradient of soil Al/Ca ratios in the northeastern United States

    USGS Publications Warehouse

    Wargo, P.M.; Vogt, K.; Vogt, D.; Holifield, Q.; Tilley, J.; Lawrence, G.; David, M.

    2003-01-01

    Number of living root tips per branch, percent dead roots, percent mycorrhizae and mycorrhizal morphotype, response of woody roots to wounding and colonization by fungi, and concentrations of starch, soluble sugars, phenols, percent C and N and C/N ratio, and Al Ca, Fe, K, Mg, Mn, and P were measured for 2 consecutive years in roots of red spruce (Picea rubens Sarg.) in stands in the northeastern United States (nine in 1993 and two additional in 1994) dominated by red spruce and with a gradient of forest floor exchangeable Al/Ca ratios. Root vitality was measured for nonwoody and coarse woody roots; chemical variables were measured for nonwoody (<1 mm), fine woody (1 to <2 mm), and coarse woody (2 to <5 mm) roots. There were significant differences among sites for all variables, particularly in 1993, although few were related to the Al/Ca ratio gradient. Percent mycorrhizae decreased, while some morphotypes increased or decreased as the Al/Ca ratio increased. In nonwoody roots, N increased as the Al/Ca ratio increased. Most sampled trees appeared to be in good or fair health, suggesting that an adverse response of these root variables to high Al concentrations may be apparent only after a significant change in crown health.

  13. Mechanical Properties and Fracture Behaviors of the As-Extruded Mg-5Al-3Ca Alloys Containing Yttrium at Elevated Temperature.

    PubMed

    Son, Hyeon-Taek; Kim, Yong-Ho; Kim, Taek-Soo; Lee, Seong-Hee

    2016-02-01

    Effects of yttrium (Y) addition on mechanical properties and fracture behaviors of the as-extruded Mg-Al-Ca based alloys at elevated temperature were investigated by a tensile test. After hot extrusion, the average grain size was refined by Y addition and eutectic phases were broken down into fine particles. Y addition to Mg-5Al-3Ca based alloy resulted in the improvement of strength and ductility at elevated temperature due to fine grain and suppression of grain growth by formation of thermally stable Al2Y intermetallic compound.

  14. Residues 248-252 and 300-304 of the cardiac Na+/Ca2+ exchanger are involved in its regulation by phospholemman.

    PubMed

    Zhang, Xue-Qian; Wang, JuFang; Song, Jianliang; Ji, Angi M; Chan, Tung O; Cheung, Joseph Y

    2011-10-01

    Using split cardiac Na(+)/Ca(2+) exchangers (NCX1), we previously demonstrated that phospholemman (PLM) regulates NCX1 by interacting with the proximal linker domain (residues 218-358) of the intracellular loop of NCX1. With the use of overlapping loop deletion mutants, interaction sites are localized to two regions spanning residues 238-270 and residues 300-328 of NCX1. In this study, we used alanine (Ala) linker scanning to pinpoint the residues in the proximal linker domain involved in regulation of NCX1 by PLM. Transfection of human embryonic kidney (HEK)293 cells with wild-type (WT) NCX1 or its Ala mutants but not empty vector resulted in NCX1 current (I(NaCa)). Coexpression of PLM with WT NCX1 inhibited I(NaCa). Mutating residues 248-252 (PASKT) or 300-304 (QKHPD) in WT NCX1 to Ala resulted in loss of inhibition of I(NaCa) by PLM. By contrast, inhibition of I(NaCa) by PLM was preserved when residues 238-242, 243-247, 253-257, 258-262, 263-267, 305-309, 310-314, 315-319, 320-324, or 325-329 were mutated to Ala. While mutating residue 301 to alanine completely abolished PLM inhibition, mutation of any single residue 250-252, 300, or 302-304 resulted in partial reduction in inhibition. Mutating residues 248-252 to Ala resulted in significantly weaker association with PLM. The NCX1-G503P mutant that lacks Ca(2+)-dependent activation retained its sensitivity to PLM. We conclude that residues 248-252 and 300-304 in the proximal linker domain of NCX1 were involved in its inhibition by PLM.

  15. An Internally Consistent Thermodynamic Model for the System CaO-MgO-Al2O3-SiO2 Derived Primarily from Phase Equilibrium Data.

    PubMed

    Gasparik

    2000-01-01

    An internally consistent thermodynamic model for the subsolidus system CaO-MgO-Al2O3-SiO2 (CMAS) was developed and refined using primarily data from phase equilibrium experiments. The solution properties of pyroxenes and garnet were approximated with an ionic model, with independent mixing on adjacent crystallographic sites. This approach simplified the calculation of phase relations by allowing sequential calculation of the site occupancies. Enthalpy, entropy, and volume differences, nominally at 970 K, were derived for all participating phases by matching as closely as possible the experimentally observed phase relations. Although thermochemical measurements were not used directly in the refinement, the results were continuously monitored and compared with the thermochemical data to achieve a close match. The new model can be used to calculate phase diagrams for the CMAS system and its subsystems in the whole pressure range of the upper mantle. Simple empirical corrections for the effects of Na, Fe, Cr, etc., could potentially be introduced to make the model applicable to the thermobarometry of chemically complex mantle materials. Application of the new model to garnet lherzolite xenoliths from northern Lesotho and garnet peridotites from Norway supports the proposals for higher temperatures of the continental lithosphere.

  16. An Essential Role for the K+-dependent Na+/Ca2+-exchanger, NCKX4, in Melanocortin-4-receptor-dependent Satiety*

    PubMed Central

    Li, Xiao-Fang; Lytton, Jonathan

    2014-01-01

    K+-dependent Na+/Ca2+-exchangers are broadly expressed in various tissues, and particularly enriched in neurons of the brain. The distinct physiological roles for the different members of this Ca2+ transporter family are, however, not well described. Here we show that gene-targeted mice lacking the K+-dependent Na+/Ca2+-exchanger, NCKX4 (gene slc24a4 or Nckx4), display a remarkable anorexia with severe hypophagia and weight loss. Feeding and satiety are coordinated centrally by melanocortin-4 receptors (MC4R) in neurons of the hypothalamic paraventricular nucleus (PVN). The hypophagic response of Nckx4 knock-out mice is accompanied by hyperactivation of neurons in the PVN, evidenced by high levels of c-Fos expression. The activation of PVN neurons in both fasted Nckx4 knock-out and glucose-injected wild-type animals is blocked by Ca2+ removal and MC4R antagonists. In cultured hypothalamic neurons, melanocyte stimulating hormone induces an MC4R-dependent and sustained Ca2+ signal, which requires phospholipase C activity and plasma membrane Ca2+ entry. The Ca2+ signal is enhanced in hypothalamic neurons from Nckx4 knock-out animals, and is depressed in cells in which NCKX4 is overexpressed. Finally, MC4R-dependent oxytocin expression in the PVN, a key essential step in satiety, is prevented by blocking phospholipase C activation or Ca2+ entry. These findings highlight an essential, and to our knowledge previously unknown, role for Ca2+ signaling in the MC4R pathway that leads to satiety, and a novel non-redundant role for NCKX4-mediated Ca2+ extrusion in controlling MC4R signaling and feeding behavior. Together, these findings highlight a novel pathway that potentially could be exploited to develop much needed new therapeutics to tackle eating disorders and obesity. PMID:25096581

  17. A comparative study of K-rich and Na/Ca-rich feldspar ice-nucleating particles in a nanoliter droplet freezing assay

    NASA Astrophysics Data System (ADS)

    Peckhaus, Andreas; Kiselev, Alexei; Hiron, Thibault; Ebert, Martin; Leisner, Thomas

    2016-09-01

    A recently designed droplet freezing assay was used to study the freezing of up to 1500 identical 0.2 nL water droplets containing suspensions of one Na/Ca-rich feldspar and three K-rich and one Na/Ca-rich feldspar particles. Three types of experiments have been conducted: cooling ramp, isothermal freezing at a constant temperature, and freeze-thaw cycles. The observed freezing behavior has been interpreted with the help of a model based on the classical nucleation theory (soccer ball model (SBM); Niedermeier et al., 2015). By applying the model to the different freezing experiments conducted with the same ice-nucleating material, the unique sets of model parameters for specific feldspar suspensions could be derived. The SBM was shown to adequately describe the observed cooling rate dependence, the ice-nucleating active sites (INAS) surface density ns(T) in a wide temperature range, and the shift of the freezing curves towards lower temperature with dilution. Moreover, the SBM was capable of reproducing the variation of INAS surface density ns(T) with concentration of ice-nucleating particles in the suspension droplets and correctly predicting the leveling-off of ns(T) at low temperature. The freeze-thaw experiments have clearly shown that the heterogeneous freezing induced even by very active ice-nucleating species still possesses a stochastic nature, with the degree of randomness increasing towards homogeneous nucleation. A population of the high-temperature INAS has been identified in one of the K-rich feldspar samples. The freezing of 0.8 wt % suspension droplets of this particular feldspar was observed already at -5 °C. These high-temperature active sites could be deactivated by treating the sample with hydrogen peroxide but survived heating up to 90 °C. Given a high mass concentration of these high-temperature active sites (2.9 × 108 g-1) and a very low value of contact angle (0.56 rad) the possibility of biological contamination of the sample was

  18. An x-ray photoemission electron microscopy study of the formation of Ti-Al phases in 4 mol% TiCl3 catalyzed NaAlH4 during high energy ball milling

    NASA Astrophysics Data System (ADS)

    Dobbins, Tabbetha; Abrecht, Mike; Uprety, Youaraj; Moore, Kristan

    2009-05-01

    This study reports reaction pathways to form TiAlx metallic complexes during the high energy ball milling of 4 mol% TiCl3 with NaAlH4 powders determined using local structure analysis of Tix+ and Alx+ species. Using x-ray photoemission electron microscopy (XPEEM) and x-ray diffraction (XRD), the oxidation state of Alx+ and Tix+ and the crystalline compounds existing in equilibrium with NaAlH4 were tracked for samples milled for times of 0 (i.e. mixing), 5, and 25 min. XPEEM analysis of the Al K edge after 5 min of milling reveals that Al remains in the 3+ oxidation state (i.e. in NaAlH4) around Ti0-rich regions of the sample. After 25 min of high energy milling, Ti0 has reacted with Al3+ (in nearby NaAlH4) to form TiAlx complexes. This study reports the pathway for TiAlx complex formation during milling of 4 mol% TiCl3 catalyzed NaAlH4 to be as follows: (1) Ti3+ reduces to Ti0 (with Al3+ near Ti0 regions) and (2) Ti0 reacts with Al3+ in NaAlH4 to form TiAlx complexes.

  19. Single-crystal Elasticity of Zoisite Ca2Al3Si3O12(OH) by Brillouin Scattering

    NASA Astrophysics Data System (ADS)

    Mao, Z.; Jiang, F.; Duffy, T. S.

    2005-12-01

    Zoisite, Ca 2Al3Si3O12(OH), is an important metamorphic mineral and one of the main H2O-containing phases minerals in subduction zones. Experiments in basaltic compositions have shown that zoisite can remain stable to pressures of ~3.1 GPa at 650°C (Forneris and Holloway, 2003), and it is stable to ~7 GPa and 1000°C in the calcium-aluminum-silicon-hydrogen system (Poli et al, 1998). The bulk modulus of zoisite was measured by X-ray diffraction in both multi-anvil apparatus and diamond anvil cells (Holland et al, 1996; Comodi et al, 1997; Pawley et al, 1998; Grevel et al, 2000). However, existing results show large discrepancies. That cannot be explained by presence of small amounts of Fe. In order to provide reliable elastic moduli, the single-crystal elastic constants of zoisite were determined by Brillouin spectroscopy. Three platelets were cut from a gem-quality zoisite sample. Single-crystal x-ray diffraction was performed at x17C of Brookhaven National Laboratory. The lattice parameters are a=16.207(5), b=5.540(5), c=10.056(2) Å with a calculated density 3.343(3)g/cm3. The Brillouin spectra were recorded in a forward scattering geometry at ambient conditions. Measurements were made in a total of 37 directions in each plane. The data were inverted for 9 elastic tensor components and 9 crystal orientation parameters. The single crystal elastic tensor constants C11, C12, C13, C22, C23, C33, C44, C55, C66 are 279.1(8), 95.1(18), 91.3(16), 249.3(8), 30.9(8), 216.5(8), 51.6(4), 80.2(4), 65.9(3)GPa respectively. The resulting bounds on the adiabatic bulk and shear moduli are 127.9(4) and 72.6(2)GPa respectively. Our results are generally consistent with previous static compression studies although we obtain higher c axis compressibility than some X-ray studies. Compared with the elastic moduli of lawsonite, zoisite has a similar bulk modulus (~125 GPa), but a 30% larger shear modulus than lawsonite (~52 GPa) (Sinogeikin et al, 2000). The VP/VS ratio is 1.76 for

  20. Nitric oxide regulates cardiac intracellular Na⁺ and Ca²⁺ by modulating Na/K ATPase via PKCε and phospholemman-dependent mechanism.

    PubMed

    Pavlovic, Davor; Hall, Andrew R; Kennington, Erika J; Aughton, Karen; Boguslavskyi, Andrii; Fuller, William; Despa, Sanda; Bers, Donald M; Shattock, Michael J

    2013-08-01

    In the heart, Na/K-ATPase regulates intracellular Na(+) and Ca(2+) (via NCX), thereby preventing Na(+) and Ca(2+) overload and arrhythmias. Here, we test the hypothesis that nitric oxide (NO) regulates cardiac intracellular Na(+) and Ca(2+) and investigate mechanisms and physiological consequences involved. Effects of both exogenous NO (via NO-donors) and endogenously synthesized NO (via field-stimulation of ventricular myocytes) were assessed in this study. Field stimulation of rat ventricular myocytes significantly increased endogenous NO (18 ± 2 μM), PKCε activation (82 ± 12%), phospholemman phosphorylation (at Ser-63 and Ser-68) and Na/K-ATPase activity (measured by DAF-FM dye, western-blotting and biochemical assay, respectively; p<0.05, n=6) and all were abolished by Ca(2+)-chelation (EGTA 10mM) or NOS inhibition l-NAME (1mM). Exogenously added NO (spermine-NONO-ate) stimulated Na/K-ATPase (EC50=3.8 μM; n=6/grp), via decrease in Km, in PLM(WT) but not PLM(KO) or PLM(3SA) myocytes (where phospholemman cannot be phosphorylated) as measured by whole-cell perforated-patch clamp. Field-stimulation with l-NAME or PKC-inhibitor (2 μM Bis) resulted in elevated intracellular Na(+) (22 ± 1.5 and 24 ± 2 respectively, vs. 14 ± 0.6mM in controls) in SBFI-AM-loaded rat myocytes. Arrhythmia incidence was significantly increased in rat hearts paced in the presence of l-NAME (and this was reversed by l-arginine), as well as in PLM(3SA) mouse hearts but not PLM(WT) and PLM(KO). We provide physiological and biochemical evidence for a novel regulatory pathway whereby NO activates Na/K-ATPase via phospholemman phosphorylation and thereby limits Na(+) and Ca(2+) overload and arrhythmias. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".

  1. Analysis of SO2 sorption capacity of rice husk ash (RHA)/CaO/NaOH sorbents using response surface methodology (RSM): untreated and pretreated RHA.

    PubMed

    Dahlan, Irvan; Lee, Keat Teong; Kamaruddin, Azlina Harun; Mohamed, Abdul Rahman

    2008-03-01

    The SO2 sorption capacity (SSC) of sorbents prepared from rice husk ash (RHA) with NaOH as additive was studied in a fixed-bed reactor. The sorbents were prepared using a water hydration method by slurrying RHA, CaO, and NaOH. Response surface methodology (RSM) based on four-variable central composite face centered design (CCFCD) was employed in the synthesis of the sorbents. The correlation between the sorbent SSC (as response) with four independent sorbent preparation variables, i.e. hydration period, RHA/CaO ratio, NaOH amount, and drying temperature, were presented as empirical mathematical models. Among all the variables studied, the amount of NaOH used was found to be the most significant variable affecting the SSC of the sorbents prepared. The SSC for sorbent prepared with the addition of NaOH was found to be significantly higher than sorbents prepared without NaOH. This is probably because NaOH is a deliquescent material, and its existence increases the amount of water collected on the surface of the sorbent, a condition required for sorbent-SO2 reaction to occur at low temperature. The effect of further treatment of RHA at 600 degrees C was also investigated. Although pretreated RHA sorbents demonstrated higher SSC as compared to untreated RHA sorbents, nevertheless, at optimum conditions, sorbents prepared from untreated RHA was found to be more favorable due to practical and economic concerns.

  2. Al-Cd Alloy Formation by Aluminum Underpotential Deposition from AlCl3+NaCl Melts on Cadmium Substrate

    NASA Astrophysics Data System (ADS)

    Jovićević, Niko; Cvetković, Vesna S.; Kamberović, Željko J.; Jovićević, Jovan N.

    2013-02-01

    Aluminum was incorporated into a polycrystalline cadmium electrode surface by underpotential deposition from equimolar AlCl3+ NaCl melt at 473 K, 523 K, and 573 K (200 °C, 250 °C, and 300 °C). The process was studied by linear sweep voltammetry and potentiostatic deposition/galvanostatic striping. The deposits were characterized X-ray diffraction (XRD), Auger electron spectroscopy (AES), and electron probe microanalyzer (EPMA). The electrochemical measurements showed evidence of Cd-Al alloys being formed but they could not be identified. The growth kinetics of the Cd-Al layers of various proportion and depths that depended on temperature and deposition time were described.

  3. Chelating efficacy of CaNa(2) EDTA on nickel-induced toxicity in Cirrhinus mrigala (Ham.) through its effects on glutathione peroxidase, reduced glutathione and lipid peroxidation.

    PubMed

    Gopal, Rengaswamy; Narmada, S; Vijayakumar, Remya; Jaleel, Cheruth Abdul

    2009-08-01

    In this age of modern biology, aquatic toxicological research has provided potential tools for ecotoxicologic investigations. Heavy metals primarily affect protein structures and induce a stress in the organisms. The present investigation was carried out to assess the effect of nickel chloride on the selected organs of the freshwater fish Cirrhinus mrigala and how CaNa(2) EDTA counters its effects as an antidote. Toxicity experiments were conducted for different exposure periods and also in certain tissues namely gill, liver, kidney and muscle. The total protein content, reduced glutathione, glutathione peroxidase and lipid peroxidation were found to be decreased in the nickel chloride treated tissues and the treatment with CaNa(2) EDTA+nickel chloride returned to near normal levels. Histopathological observations also revealed that after the administration of nickel chloride+CaNa(2) EDTA the chelator induced reduction in nickel toxicity. It has also contributed towards reduction in the pathological damage, thus enabling the organs to attain their near normal histological appearance. The present study shown that CaNa(2) EDTA is an effective chelating agent for the removal of nickel and it has proved efficient in restoring both the biochemical variables and pathological features immediately after a sub lethal exposure of nickel chloride in fish.

  4. The influence of Na(+) and Ca(2+) on the migration of colloids or/and ammonia nitrogen in an unsaturated zone medium.

    PubMed

    Li, HaiMing; Wei, JinBu; Ge, YaChao; Wang, ZhanQuan; Wang, Ye; Li, YingLong

    2016-11-01

    This experiment was conducted with an indoor sand-column device, the migration of colloids with the presence of Na(+) and Ca(2+) and the migration of ammonia nitrogen with the presence of Na(+), Ca(2+) or/and colloids was studied. The results showed that the migration of colloids was influenced by the ion valence state, different ions with different valence could block the migration of colloids. In addition, the blocking effect of bivalent ions was more obvious than that of monovalent ions. In the presence of Na(+) and Ca(2+), the Rd value of the ammonia-nitrogen migration process were 1.01 and 1.41, respectively, which indicated that bivalent ions have a greater blocking effect on ammonia-nitrogen migration than monovalent ions. Colloids could also block the ammonia-nitrogen migration, and Rd value in the ammonia-nitrogen migration process was 1.17. Moreover, the presence of Na(+)/colloids and Ca(2+)/colloids could enhance the blocking effect on the ammonia-nitrogen migration, and resulting the Rd values at 1.20 and 1.52, respectively. The cohesion of colloids caused by the compaction of its electric double layer with those ions added maybe the key causes of those blocking.

  5. In vitro growth and organogenesis of Prosopis farcta plantlets (Fabaceae, Mimosoideae) in culture medium supplemented with various concentrations of Ca++ and Na+.

    PubMed

    Stambouli, S; Bouzid, S; Dutuit, P; Harzallah-Skhiri, Fethia

    2012-03-01

    The objective of this study was to vary the mineral composition of the culture medium of Prosopis farcta seedlings per addition of Na+ and Ca++ ions with the aim to identify the culture media which support the growth and/or the expression of the in vitro plant organogenesis. The Na+ and Ca++ ions were added in the culture medium in various concentrations by taking the Gamborg medium, in which macroelements were diluted 10 times, as the basic one. After two months of culture, parameters relating to the vegetative development of plant seedlings and to the various expressions of organogenesis were measured. Weak concentrations in sodium and calcium ions as well as a weak concentration in Ca++ (0.1 mM) with 50 mM in Na+ support the best vegetative development of the plantlets. The most important percentage of plant seedlings presenting a bud initiation was obtained on a medium containing 0.1 mM of Na+ and 50 mM of Ca++. Our study defined several media likely to support in vitro development of Prosopis farcta plantlets allowing the selection of salt tolerant plants or cellular lines. Some other media were chosen for improving micropropagation of the species without adding growth substances.

  6. Salt exclusion and mycorrhizal symbiosis increase tolerance to NaCl and CaCl2 salinity in ‘Siam Queen’ basil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study was conducted to evaluate the effects of salinity on growth and nutrient uptake in basil (Ocimum basilicum L.). Plants were fertilized with a complete nutrient solution and exposed to no, low, or moderate levels of salinity from NaCl or CaCl2. Plants in the control and moderate salinity tre...

  7. Equilibrium aluminium hydroxo-oxalate phases during initial clay formation; H +-Al 3+-oxalic acid-Na + system

    NASA Astrophysics Data System (ADS)

    Bilinski, Halka; Horvath, Laszlo; Ingri, Nils; Sjöberg, Staffan

    1986-09-01

    The conditions necessary for initial clay formation have been studied in different model systems comprising different organic acids besides Si and Al. In the present paper the solid phases and the precipitation boundary characterizing the subsystem H +-Al 3+-oxalic acid (H 2L) are discussed. pH and tyndallometric measurements were performed in an ionic medium of 0.6 M Na(Cl) at 25 °C. The two phases Al 3(OH) 7(C 2O 4) · 3H 2O (phase I) and NaAl(OH) 2(C 2O 4) · 3H 2O (phase II) determine the precipitation boundary. The following formation constants for the two phases were deduced: lgβ1 = lg([ Al3+] -3[ H2C2O4] -1[ H+] 9 = -21.87 ± 0.08 and lgβ11 = lg([ Al3+] -1[ H2C2O4] -1[ H+] 4 = -5.61 ± 0.06. Phase I exists in the range [ Al] tot≥ 10 -4.4moldm-3,[ H2C2O4] tot ≥ 10 -4.9moldm-3 and at pH < 6.8, thus being a possible precipitate in oxalic-rich natural waters. The more soluble sodium phase is unlikely to exist in natural waters. The two phases are metastable relative to crystalline gibbsite and may be considered as the first precipitation step in the transition from aqueous Al oxalates down to stable Al hydroxide. Model calculations illustrating these competing hydrolysis-complexation reactions are discussed in terms of predominance and speciation diagrams. The solid phases have been characterized by X-ray analysis of powders, TGA and IR spectra, and tentative structures are proposed. Phase I seems to be an octahedral layer structure, in which 3/5 of the octahedral sites between two close packed oxygen sheets are occupied by Al 3+ and the oxalate ion acts as a bridge ligand between two aluminium atoms. Phase II forms a more open sheet structure and has ion exchange properties. Powder data for a phase crystallized from the studied solution after a year are also presented. This phase, Na 4Al 2(OH) 2(C 2O 4) 4 · 10H 2O, supports the results from the equilibrium analysis of recent solution data by SJöBERG and ÖHMAN (1985), who have found the dinuclear

  8. Diode-pumped Kerr-lens mode-locked Yb:CaGdAlO4 laser with tunable wavelength

    NASA Astrophysics Data System (ADS)

    Gao, Ziye; Zhu, Jiangfeng; Wang, Junli; Wang, Zhaohua; Wei, Zhiyi; Xu, Xiaodong; Zheng, Lihe; Su, Liangbi; Xu, Jun

    2016-01-01

    We experimentally demonstrated a wavelength tunable Kerr-lens mode-locked femtosecond laser based on an Yb:CaGdAlO4 (Yb:CGA) crystal. The Kerr-lens mode-locked wavelength tuning range was from 1043.5 to 1076 nm, as broad as 32.5 nm, by slightly tilting the end mirror. Pulses as short as 60 fs were generated at the central wavelength of 1043.8 nm with an average output power of 66 mW. By using an output coupler with 1.5% transmittance, the Kerr-lens mode-locked average output power reached 127 mW with a pulse duration of 81 fs at a central wavelength of 1049.5 nm.

  9. Thermochemistry and structure of glasses along the join NaAlSi 3O 8-NaBSi 3O 8

    NASA Astrophysics Data System (ADS)

    Geisinger, K. L.; Oestrike, R.; Navrotsky, A.; Turner, G. L.; Kirkpatrick, R. J.

    1988-10-01

    Glasses along the join NaAlSi 3O 8-NaBSi 3O 8 and the end-member crystalline phases albite and reedmergnerite were investigated using 11B, 23Na, 27Al and 29Si MAS NMR spectroscopy and oxide-melt solution calorimetry. The glasses have substantial positive enthalpies of mixing described by the equation ΔH mix (kcal · mol t¯1 ) = 4.4(±1.0)X(1 - X) , where X is the mole fraction Rd component. 11B MAS NMR spectra show that boron occurs in both trigonal and tetrahedral coordination in the glasses, with the percentage of B in trigonal coordination decreasing from about 60% at Rd 20Ab 80 to about 29% at Rd 100. Thus, the glasses are structurally more complex than the end-member crystals which are tetrahedral framework minerals. The NMR data suggest that all or most of the Si, Al and tetrahedral B occur in Q 4 (framework) sites. They are also consistent with the ideas that most of the tetrahedral B does not extensively copolymerize with trigonal boron, that at least some of the non-bridging oxygens formed by the presence of trigonal boron are located on SiO 4 tetrahedra, and that Si and trigonal B do not occur as next-nearest neighbors. Both the NMR and the ΔHmix results indicate the presence of clustering. Such clustering might involve separation into framework regions and regions dominated by trigonal boron and/or into B-rich and Al-rich framework regions.

  10. Photocatalytic characteristics for the nanocrystalline TiO2 on the Ag-doped CaAl2O4:(Eu,Nd) phosphor

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Sik; Sung, Hyun-Je; Kim, Bum-Joon

    2015-04-01

    This study investigated the photocatalytic behavior of nanocrystalline TiO2 deposited on