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.

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.

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

NASA Astrophysics Data System (ADS)

Marashdeh, Ali; Frankcombe, Terry J.

2008-06-01

The dehydrogenation enthalpies of Ca(AlH4)2, CaAlH5, and CaH2+6LiBH4 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(AlH4)2 is exothermic, indicating a metastable hydride. Calculations for CaAlH5 including ZPE effects indicate that it is not stable enough for a hydrogen storage system operating near ambient conditions. The destabilized combination of LiBH4 with CaH2 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(AlH4)2, CaAlH5, and CaH2+6LiBH4 has a significant effect on the calculated reaction enthalpy. The contribution of ZPE to the dehydrogenation enthalpies of Ca(AlH4)2 and CaAlH5 calculated by the direct method phonon analysis was compared to that calculated by the frozen-phonon method. The crystal structure of CaAlH5 is presented in the more useful standard setting of P21/c symmetry and the phonon density of states of CaAlH5, significantly different to other common complex metal hydrides, is rationalized.

Structural analyses of Ca2+/CaM interaction with NaV channel C-termini reveal mechanisms of calcium-dependent regulation

PubMed Central

Wang, Chaojian; Chung, Ben C.; Yan, Haidun; Wang, Hong-Gang; Lee, Seok-Yong; Pitt, Geoffrey S.

2014-01-01

Ca2+ regulates voltage-gated Na+ (NaV) channels and perturbed Ca2+ regulation of NaV function is associated with epilepsy syndromes, autism, and cardiac arrhythmias. Understanding the disease mechanisms, however, has been hindered by a lack of structural information and competing models for how Ca2+ affects NaV channel function. Here, we report the crystal structures of two ternary complexes of a human NaV cytosolic C-terminal domain (CTD), a fibroblast growth factor homologous factor, and Ca2+/calmodulin (Ca2+/CaM). These structures rule out direct binding of Ca2+ to the NaV CTD, and uncover new contacts between CaM and the NaV CTD. Probing these new contacts with biochemical and functional experiments allows us to propose a mechanism by which Ca2+ could regulate NaV channels. Further, our model provides hints towards understanding the molecular basis of the neurologic disorders and cardiac arrhythmias caused by NaV channel mutations. PMID:25232683

Na+ channel regulation by Ca2+/calmodulin and Ca2+/calmodulin-dependent protein kinase II in guinea-pig ventricular myocytes†

PubMed Central

Aiba, Takeshi; Hesketh, Geoffrey G.; Liu, Ting; Carlisle, Rachael; Villa-Abrille, Maria Celeste; O'Rourke, Brian; Akar, Fadi G.; Tomaselli, Gordon F.

2010-01-01

Aims Calmodulin (CaM) regulates Na+ channel gating through binding to an IQ-like motif in the C-terminus. Ca2+/CaM-dependent protein kinase II (CaMKII) regulates Ca2+ handling, and chronic overactivity of CaMKII is associated with left ventricular hypertrophy and dysfunction and lethal arrhythmias. However, the acute effects of Ca2+/CaM and CaMKII on cardiac Na+ channels are not fully understood. Methods and results Purified NaV1.5–glutathione-S-transferase fusion peptides were phosphorylated in vitro by CaMKII predominantly on the I–II linker. Whole-cell voltage-clamp was used to measure Na+ current (INa) in isolated guinea-pig ventricular myocytes in the absence or presence of CaM or CaMKII in the pipette solution. CaMKII shifted the voltage dependence of Na+ channel availability by ≈+5 mV, hastened recovery from inactivation, decreased entry into intermediate or slow inactivation, and increased persistent (late) current, but did not change INa decay. These CaMKII-induced changes of Na+ channel gating were completely abolished by a specific CaMKII inhibitor, autocamtide-2-related inhibitory peptide (AIP). Ca2+/CaM alone reproduced the CaMKII-induced changes of INa availability and the fraction of channels undergoing slow inactivation, but did not alter recovery from inactivation or the magnitude of the late current. Furthermore, the CaM-induced changes were also completely abolished by AIP. On the other hand, cAMP-dependent protein kinase A inhibitors did not abolish the CaM/CaMKII-induced alterations of INa function. Conclusion Ca2+/CaM and CaMKII have distinct effects on the inactivation phenotype of cardiac Na+ channels. The differences are consistent with CaM-independent effects of CaMKII on cardiac Na+ channel gating. PMID:19797425

The role of Na-Ca exchange current in the cardiac action potential.

PubMed

Janvier, N C; Boyett, M R

1996-07-01

Since 1981, when Mullins published his provocative book proposing that the Na-Ca exchanger is electrogenic, it has been shown, first by computer simulation by Noble and later by experiment by various investigators, that inward iNaCa triggered by the Ca2+ transient is responsible for the low plateau of the atrial action potential and contributes to the high plateau of the ventricular action potential. Reduction or complete block of inward iNaCa by buffering intracellular Ca2+ with EGTA or BAPTA, by blocking SR Ca2+ release or by substituting extracellular Na+ with Li+ can result in a shortening of the action potential. The effect of block of outward iNaCa or complete block of both inward and outward iNaCa on the action potential has not been investigated experimentally, because of the lack of a suitable blocker, and remains a goal for the future. An increase in the intracellular Na+ concentration (after the application of cardiac glycoside or an increase in heart rate) or an increase in extracellular Ca2+ are believed to lead to an outward shift in iNaCa at plateau potentials and a shortening of the action potential. Changes in the Ca2+ transient are expected to result in changes in inward iNaCa and thus the action potential. This may explain the shortening of the premature action potential as well as the prolongation of the action potential when a muscle is allowed to shorten during the action potential. Inward iNaCa may play an important role in both normal and abnormal pacemaker activity in the heart.

Role of Na+/Ca2+ Exchangers in Therapy Resistance of Medulloblastoma Cells.

PubMed

Pelzl, Lisann; Hosseinzadeh, Zohreh; Al-Maghout, Tamer; Singh, Yogesh; Sahu, Itishri; Bissinger, Rosi; Schmidt, Sebastian; Alkahtani, Saad; Stournaras, Christos; Toulany, Mahmoud; Lang, Florian

2017-01-01

Alterations of cytosolic Ca2+-activity ([Ca2+]i) are decisive in the regulation of tumor cell proliferation, migration and survival. Transport processes participating in the regulation of [Ca2+]i include Ca2+ extrusion through K+-independent (NCX) and/or K+-dependent (NCKX) Na+/Ca2+-exchangers. The present study thus explored whether medulloblastoma cells express Na+/Ca2+-exchangers, whether expression differs between therapy sensitive D283 and therapy resistant UW228-3 medulloblastoma cells, and whether Na+/Ca2+-exchangers participate in the regulation of cell survival. In therapy sensitive D283 and therapy resistant UW228-3 medulloblastoma cells transcript levels were estimated by RT-PCR, protein abundance by Western blotting, cytosolic Ca2+-activity ([Ca2+]i) from Fura-2-fluorescence, Na+/ Ca2+-exchanger activity from the increase of [Ca2+]i (Δ[Ca2+]i) and from whole cell current (Ica) following abrupt replacement of Na+ containing (130 mM) and Ca2+ free by Na+ free and Ca2+ containing (2 mM) extracellular perfusate as well as cell death from PI -staining and annexin-V binding in flow cytometry. The transcript levels of NCX3, NCKX2, and NCKX5, protein abundance of NCX3, slope and peak of Δ[Ca2+]i as well as Ica were significantly lower in therapy sensitive D283 than in therapy resistant UW228-3 medulloblastoma cells. The Na+/Ca2+-exchanger inhibitor KB-R7943 (10 µM) significantly blunted Δ[Ca2+]i, and augmented the ionizing radiation-induced apoptosis but did not significantly modify clonogenicity of medulloblastoma cells. Apoptosis was further enhanced by NCX3 silencing. Na+/Ca2+-exchanger activity significantly counteracts apoptosis but does not significantly affect clonogenicity after radiation of medulloblastoma cells. © 2017 The Author(s). Published by S. Karger AG, Basel.

Ehimeite, NaCa2Mg4CrSi6Al2O22(OH)2: The first Cr-dominant amphibole from the Akaishi Mine, Higashi-Akaishi Mountain, Ehime Prefecture, Japan

NASA Astrophysics Data System (ADS)

Nishio-Hamane, Daisuke; Ohnishi, Masayuki; Minakawa, Tetsuo; Yamaura, Jun-Ichi; Saito, Shohei; Kadota, Ryo

The first Cr-dominant amphibole, ehimeite, ideally NaCa2Mg4CrSi6Al2O22(OH)2, has been found in a chromitite deposit in the Akaishi Mine, Higashi-Akaishi Mountain, Ehime Prefecture, Japan. Ehimeite occurs as prismatic crystals of up to 1.5 cm in length and 0.5 cm in width and is found in association with chromite, kämmererite (Cr-rich clinochlore), Cr-poor clinochlore, phlogopite, and uvarovite. It is transparent, emerald green to pale green in color with pale green streaks, and has a vitreous luster. Optically, it is biaxial positive with α = 1.644(2), β = 1.647(2), γ = 1.659(2), and 2Vcalc. = 53°. It has a Mohs’ hardness of 6 and densities of 3.08(3) g/cm3 (measured using heavy liquids) and 3.121 g/cm3 (calculated from powder diffraction data and the empirical formula). The empirical formula is (Na0.88K0.07)Σ0.95(Ca1.89Na0.02Mg0.09)Σ2.00(Mg4.03Cr0.62Al0.19Fe3+0.07Fe2+0.07Ti0.03)Σ5.00(Si6.14Al1.86)Σ8.00O22(OH)2 on the basis of O = 22 and OH = 2, and ehimeite mainly forms a solid solution, NaCa2Mg4(Cr, Al)Si6Al2O22(OH)2, with pargasite. It has a monoclinic unit cell with a = 9.9176(14) Å, b = 18.0009(12) Å, c = 5.2850(7) Å, β = 105.400(7)°, V = 909.6 (17) Å3, and Z = 2, and it belongs to the space group C2/m, as refined from powder XRD data. The eight strongest lines in the powder XRD pattern [d (Å), I/I0, hkl] are (3.370, 58, 150), (2.932, 43, 221), (2.697, 81, 151), (2.585, 50, 061), (2.546, 100, 202), (2.346, 42, 351), (2.156, 35, 261), and (1.514, 55, 263). The crystal structure has been refined to R1 = 0.0488 using single-crystal XRD data. It has been concluded that ehimeite in the Akaishi Mine was formed by the reaction of chromitite and the metamorphic fluid in the retrograde stage of serpentinization during the Sanbagawa metamorphism.

The existence and stability of the anions matching the MFk+2- formula (M = Li, Na, K, Be, Mg, Ca, B, Al, Ga)

NASA Astrophysics Data System (ADS)

Marchaj, Marzena; Freza, Sylwia; Skurski, Piotr

2013-02-01

The electronic stabilities of the MFk+2- anions (where M = Li, Na, K, Be, Mg, Ca, B, Al, Ga; and k is the maximal formal valence of atom M) were investigated at the OVGF/6-311 + G(3df) level. The vertical electron detachment energies (VDE) of the anions examined were found to be large (7.1-10.1 eV) albeit not significantly exceeding those for the corresponding MFk+1- superhalogen anions. Even though all the MFk+2- species studied were predicted to be both geometrically and electronically stable, some of them turned out to be thermodynamically unstable (i.e., susceptible to the F atom loss).

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.

Synthesis of Nanoscale CaO-Al2O3-SiO2-H2O and Na2O-Al2O3-SiO2-H2O Using the Hydrothermal Method and Their Characterization

PubMed Central

Yang, Jingbin; Li, Dongxu; Fang, Yuan

2017-01-01

C-A-S-H (CaO-Al2O3-SiO2-H2O) and N-A-S-H (Na2O-Al2O3-SiO2-H2O) have a wide range of chemical compositions and structures and are difficult to separate from alkali-activated materials. Therefore, it is difficult to analyze their microscopic properties directly. This paper reports research on the synthesis of C-A-S-H and N-A-S-H particles with an average particle size smaller than 300 nm by applying the hydrothermal method. The composition and microstructure of the products with different CaO(Na2O)/SiO2 ratios and curing conditions were characterized using XRD, the RIR method, FTIR, SEM, TEM, and laser particle size analysis. The results showed that the C-A-S-H system products with a low CaO/SiO2 ratio were mainly amorphous C-A-S-H gels. With an increase in the CaO/SiO2 ratio, an excess of Ca(OH)2 was observed at room temperature, while in a high-temperature reaction system, katoite, C4AcH11, and other crystallized products were observed. The katoite content was related to the curing temperature and the content of Ca(OH)2 and it tended to form at a high-temperature and high-calcium environment, and an increase in the temperature renders the C-A-S-H gels more compact. The main products of the N-A-S-H system at room temperature were amorphous N-A-S-H gels and a small amount of sodalite. An increase in the curing temperature promoted the formation of the crystalline products faujasite and zeolite-P. The crystallization products consisted of only zeolite-P in the high-temperature N-A-S-H system and its content were stable above 70%. An increase in the Na2O/SiO2 ratio resulted in more non-bridging oxygen and the TO4 was more isolated in the N-A-S-H structure. The composition and microstructure of the C-A-S-H and N-A-S-H system products synthesized by the hydrothermal method were closely related to the ratio of the raw materials and the curing conditions. The results of this study increase our understanding of the hydration products of alkali-activated materials. PMID

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

Synthesis of Al₂Ca Dispersoids by Powder Metallurgy Using a Mg-Al Alloy and CaO Particles.

PubMed

Fujita, Junji; Umeda, Junko; Kondoh, Katsuyoshi

2017-06-28

The elemental mixture of Mg-6 wt %Al-1 wt %Zn-0.3 wt %Mn (AZ61B) alloy powder and CaO particles was consolidated by an equal-channel angular bulk mechanical alloying (ECABMA) process to form a composite precursor. Subsequently, the precursor was subjected to a heat treatment to synthesize fine Al₂Ca particles via a solid-state reaction between the Mg-Al matrix and CaO additives. Scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) and electron probe micro-analysis on the precursor indicated that 4.7-at % Al atoms formed a supersaturated solid solution in the α-Mg matrix. Transmission electron microscopy-EDS and X-ray diffraction analyses on the AZ61B composite precursor with 10-vol % CaO particles obtained by heat treatment confirmed that CaO additives were thermally decomposed in the Mg-Al alloy, and the solid-soluted Ca atoms diffused along the α-Mg grain boundaries. Al atoms also diffused to the grain boundaries because of attraction to the Ca atoms resulting from a strong reactivity between Al and Ca. As a result, needle-like (Mg,Al)₂Ca intermetallics were formed as intermediate precipitates in the initial reaction stage during the heat treatment. Finally, the precipitates were transformed into spherical Al₂Ca particles by the substitution of Al atoms for Mg atoms in (Mg,Al)₂Ca after a long heat treatment.

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.

Removing Al and regenerating caustic soda from the spent washing liquor of Al etching

NASA Astrophysics Data System (ADS)

Barakat, M. A.; El-Sheikh, S. M.; Farghly, F. E.

2005-08-01

Spent liquor from washing of aluminum section materials after etching with caustic soda (NaOH) has been treated. Aluminum was removed from the liquor and caustic soda was regenerated by adding precipitating agents to hydrolyze sodium aluminate (Na2AlO2), separating the aluminumprecipitate, and concentrating free NaOH in the resulting solution for reuse in the etching process. Four systems were investigated: hydrated lime [Ca(OH)2], hydrogen peroxide (H2O2), H2O2/Ca(OH)2 mixture, and dry lime (CaO). Results revealed that CaO was more efficient in the removal of aluminum from the spent liquor with a higher hydrolyzing rate of Na2AlO2 than Ca(OH)2, H2O2, or their mixture.

Experimental and first-principles study of photoluminescent and optical properties of Na-doped CuAlO2: the role of the NaAl-2Na i complex

NASA Astrophysics Data System (ADS)

Liu, Ruijian; Li, Yongfeng; Yao, Bin; Ding, Zhanhui; Deng, Rui; Zhang, Ligong; Zhao, Haifeng; Liu, Lei

2015-08-01

We report that a band-tail emission at 3.08 eV, lower than near-band-edge energy, is observed in photoluminescence measurements of bulk Na-doped CuAlO2. The band-tail emission is attributed to Na-related defects. Electronic structure calculations based on the first-principles method demonstrate that the donor-acceptor compensated complex of NaAl-2Na i in Na-doped CuAlO2 plays a key role in leading to the band-tail emission and bandgap narrowing. Furthermore, Hall effect measurements indicates that the hole concentration in CuAlO2 is independent on Na doping, which is well understood by the donor-acceptor compensation effect of NaAl-2Na i complex.

Nanoscale modulations in (KLa)(CaW)O-6 and (NaLa)(CaW)O-6

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

Licurse, Mark; Borisevich, Albina Y; Davies, Peter

2012-01-01

Complex nanoscale modulations are identified in two new A-site ordered perovskites, (KLa)(CaW)O{sub 6} and (NaLa)(CaW)O{sub 6}. In (KLa)(CaW)O{sub 6}, selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) show an incommensurate nanocheckerboard modulation with {approx}9.4 x 9.4 a{sub p} periodicity (a{sub p} {approx} 4 {angstrom} for the cubic perovskite aristotype). For (NaLa)(CaW)O{sub 6} a one-dimensional modulation is observed with a {approx}16(1 1 0)a{sub p} repeat; the <1 1 0> orientation of the nanostripes is different from the <1 0 0> stripes observed in other mixed A-site systems. Studies using high temperature x-ray diffraction suggest the formation of the complexmore » modulations is associated with small deviations from the ideal 1:1:1:1 stoichiometry of the (A{sup +}La{sup 3+})(CaW)O{sub 6} phases. Z-contrast images acquired on an aberration-corrected microscope provide evidence for deviations from stoichiometry with a {approx}1:15 periodic arrangement of La{sub 4/3}(CaW)O{sub 6}:(NaLa)(CaW)O{sub 6} nano-phases.« less

Modulation of contraction by intracellular Na+ via Na(+)-Ca2+ exchange in single shark (Squalus acanthias) ventricular myocytes.

PubMed Central

Näbauer, M; Morad, M

1992-01-01

1. The effect of direct alteration of intracellular Na+ concentration on contractile properties of whole-cell clamped shark ventricular myocytes was studied using an array of 256 photodiodes to monitor the length of the isolated myocytes. 2. In myocytes dialysed with Na(+)-free solution, the voltage dependence of Ca2+ current (ICa) and contraction were similar and bell shaped. Contractions activated at all voltages were completely suppressed by nifedipine (5 microM), and failed to show significant tonic components, suggesting dependence of the contraction on Ca2+ influx through the L-type Ca2+ channel. 3. In myocytes dialysed with 60 mM Na+, a ICa-dependent and a ICa-independent component of contraction could be identified. The Ca2+ current-dependent component was prominent in voltages between -30 to +10 mV. The ICa-independent contractions were maintained for the duration of depolarization, increased with increasing depolarization between +10 to +100 mV, and were insensitive to nifedipine. 4. In such myocytes, repolarization produced slowly decaying inward tail currents closely related to the time course of relaxation and the degree of shortening prior to repolarization. 5. With 60 mM Na+ in the pipette solution, positive clamp potentials activated decaying outward currents which correlated to the size of contraction. These outward currents appeared to be generated by the Na(+)-Ca(2+)-exchanger since they depended on the presence of intracellular Na+, and were neither suppressed by nifedipine nor by K+ channel blockers. 6. The results suggest that in shark (Squalus acanthias) ventricular myocytes, which lack functionally relevant Ca2+ release pools, both Ca2+ channel and the Na(+)-Ca2+ exchanger deliver sufficient Ca2+ to activate contraction, though the effectiveness of the latter mechanism was highly dependent on the [Na+]i. PMID:1338467

Transmembrane Na+ and Ca2+ electrochemical gradients in cardiac muscle and their relationship to force development

PubMed Central

1982-01-01

Na+- and CA2+-sensitive microelectrodes were used to measure intracellular Na+ and Ca2+ activities (alpha iCa) of sheep ventricular muscle and Purkinje strands to study the interrelationship between Na+ and Ca2+ electrochemical gradients (delta muNa and delta muCa) under various conditions. In ventricular muscle, alpha iNa was 6.4 +/- 1.2 mM and alpha iCa was 87 +/- 20 nM ([Ca/+] = 272 nM). A graded decrease of external Na+ activity (alpha oNa) resulted in decrease of alpha iNa, and increase of alpha iCa. There was increase of twitch tension in low- alpha oNa solutions, and occasional increase of resting tension in 40% alpha oNa. Increase of external Ca2+ (alpha oCa) resulted in increase of alpha iCa and decrease of alpha iNa. Decrease of alpha oCa resulted in decrease of alpha iCa and increase of alpha iNa. The apparent resting Na-Ca energy ratio (delta muCa/delta muNa) was between 2.43 and 2.63. When the membrane potential (Vm) was depolarized by 50 mM K+ in ventricular muscle, Vm depolarized by 50 mV, alpha iNa decreased, and alpha iCa increased, with the development of a contracture. The apparent energy coupling ratio did not change with depolarization. 5 x 10(-6) M ouabain induced a large increase in alpha iNa ad alpha iCa, accompanied by an increase in twitch and resting tension. Under the conditions we have studied, delta muNa and delta muCa appeared to be coupled and n was nearly constant at 2.5, as would be expected if the Na-Ca exchange system was able to set the steady level of alpha iCa. Tension threshold was about 230 nM alpha iCa. The magnitude of twitch tension was directly related to alpha iCa. PMID:6292328

[Effect of NaHCO3 stress on uptake and transportation of Na+, K+ and Ca2+ in three shrub species].

PubMed

Mao, Gui-Lian; Li, Guo-Qi; Xu, Xing; Zhang, Xin-Xue

2014-03-01

We detected absorption and transportation of ions in the leaves of Atriplex nummularia, Atriplex canescens and Lycium barbarum under NaHCO3 stress (300 mmol x L(-1)) by using atomic absorption spectrophotometry and non-invasive ion flux measurement. The results showed that leaves of the A. nummularia, A. canescens and L. barbarum exhibited a high capacity to induce the Na+ accumulation when compared with that of control. The higher the concentration of NaHCO3 treatment, the more Na+ accumulated in the leaves of the three plants under experimental condition. L. barbarum showed a higher Na+ efflux in the mesophyll cells, whereas A. nummularia and A. canescens showed a relative lower efflux. A lower K+ content and a higher Na+/K+ ratio were detected in leaves of A. nummularia and L. barbarum. However, a higher K+ content and a lower Na+/K+ ratio were seen in leaves of A. canescens. Due to induction of Ca2+ efflux under the NaHCO3 treatment, a lower Ca2+ content and a higher Na+/Ca2+ ratio were observed in L. barbarum. On the contrary, a higher Ca2+ influx was observed in A. nummularia and A. canescens. These results suggested that the three shrubs species had different Na+ segmentation strategies. The accumulation of Na+ inhibited Ca2+ absorption in leaves of L. barbarum, while in the A. nummularia and A. canescens, Ca2+ influx induced [Ca2+]cyt which preserved a less-depolarized PM and then inhibited K efflux. The maintaining of cellular K+/Na+ homeostasis in A. nummularia and A. canescens might be achieved by the induction of [Ca2+]cyt under the NaHCO3 treatment.

Electrical Conductivity of Cancrinite-Type Na8 - 2 x Ca x [Al6Si6O24][CO3] · 2H2O ( x ≤ 0.03) Crystals

NASA Astrophysics Data System (ADS)

Sorokin, N. I.

2018-05-01

The electrical conductivity of crystals of artificial cancrinite Na8 - 2 x Ca x [Al6Si6O24][CO3] · 2H2O ( x ≤ 0.03) has been studied in the temperature range of 498-604 K. These crystals were grown by hydrothermal synthesis on a seed in the Na2O-Al2O3-SiO2-H2O system ( t = 380-420°C, P = 3 × 107-9 × 107 Pa). The ionic conductivity of a single-crystal sample (sp. gr. P63), measured along the crystallographic axis c, is low: σ = 8 × 10-7 S/cm at 300°C. The electric transport activation energy is E a = 0.81 ± 0.05 eV. The relationship between the ionic conductivity and specific features of the atomic structure of cancrinites is discussed.

Na+,K+-ATPase functionally interacts with the plasma membrane Na+,Ca2+ exchanger to prevent Ca2+ overload and neuronal apoptosis in excitotoxic stress.

PubMed

Sibarov, Dmitry A; Bolshakov, Artemiy E; Abushik, Polina A; Krivoi, Igor I; Antonov, Sergei M

2012-12-01

Using a fluorescent viability assay, immunocytochemistry, patch-clamp recordings, and Ca(2+) imaging analysis, we report that ouabain, a specific ligand of the Na(+),K(+)-ATPase cardiac glycoside binding site, can prevent glutamate receptor agonist-induced apoptosis in cultured rat cortical neurons. In our model of excitotoxicity, a 240-min exposure to 30 μM N-methyl-d-aspartate (NMDA) or kainate caused apoptosis in ∼50% of neurons. These effects were accompanied by a significant decrease in the number of neurons that were immunopositive for the antiapoptotic peptide Bcl-2. Apoptotic injury was completely prevented when the agonists were applied together with 0.1 or 1 nM ouabain, resulting in a greater survival of neurons, and the percentage of neurons expressing Bcl-2 remained similar to those obtained without agonist treatments. In addition, subnanomolar concentrations of ouabain prevented the increase of spontaneous excitatory postsynaptic current's frequency and the intracellular Ca(2+) overload induced by excitotoxic insults. Loading neurons with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid or inhibition of the plasma membrane Na(+),Ca(2+)-exchanger by 2-(2-(4-(4-nitrobenzyloxy)phenyl)ethyl)isothiourea methanesulfonate (KB-R7943) eliminated ouabain's effects on NMDA- or kainite-evoked enhancement of spontaneous synaptic activity. Our data suggest that during excitotoxic insults ouabain accelerates Ca(2+) extrusion from neurons via the Na(+),Ca(2+) exchanger. Because intracellular Ca(2+) accumulation caused by the activation of glutamate receptors and boosted synaptic activity represents a key factor in triggering neuronal apoptosis, up-regulation of Ca(2+) extrusion abolishes its development. These antiapoptotic effects are independent of Na(+),K(+)-ATPase ion transport function and are initiated by concentrations of ouabain that are within the range of an endogenous analog, suggesting a novel functional role for Na(+),K(+)-ATPase in

Na/Ca Ratio in Large Benthic Foraminifera as a Novel Proxy for Past Ocean Calcium

NASA Astrophysics Data System (ADS)

Rosenthal, Y.; Hauzer, H.; Evans, D.; Erez, J.

2017-12-01

Culture experiments with Operculina ammonoides (a large symbiont bearing benthic foraminifer and an extant relative of the Eocene Nummulites) were carried out varying seawater [Ca], temperature and salinity. The main results of these experiments are: 1. Na/Ca in these foraminifera shells varies with the Na/Ca ratio in the seawater 2. Na/Ca shows small, non-systematic variations with temperature (22-28 ºC) that are within our analytical precision. 3. Na/Ca in the shells show very low changes, increasing linearly with salinity. The sensitivity to salinity is very low compared to that caused by changes of Na/Ca in seawater. Over the seawater experimental range of Na/Ca (10-18 mM), a change of 5 ppt salinity induced a slight Na/Ca increase comparable to the analytical error for Na, or that caused by temperature. Initial reconstructions of seawater [Ca], based on these calibrations, generally agree well with previous models and reconstructions confirming that seawater [Ca] concentrations were substantially higher during the early-mid Cenozoic than today.

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.

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

Osmolality- and Na+ -dependent effects of hyperosmotic NaCl solution on contractile activity and Ca2+ cycling in rat ventricular myocytes.

PubMed

Ricardo, Rafael A; Bassani, Rosana A; Bassani, José W M

2008-01-01

Hypertonic NaCl solutions have been used for small-volume resuscitation from hypovolemic shock. We sought to identify osmolality- and Na(+)-dependent components of the effects of the hyperosmotic NaCl solution (85 mOsm/kg increment) on contraction and cytosolic Ca(2+) concentration ([Ca(2+)](i)) in isolated rat ventricular myocytes. The biphasic change in contraction and Ca(2+) transient amplitude (decrease followed by recovery) was accompanied by qualitatively similar changes in sarcoplasmic reticulum (SR) Ca(2+) content and fractional release and was mimicked by isosmotic, equimolar increase in extracellular [Na(+)] ([Na(+)](o)). Raising osmolality with sucrose, however, augmented systolic [Ca(2+)](i) monotonically without change in SR parameters and markedly decreased contraction amplitude and diastolic cell length. Functional SR inhibition with thapsigargin abolished hyperosmolality effects on [Ca(2+)](i). After 15-min perfusion, both hyperosmotic solutions slowed mechanical relaxation during twitches and [Ca(2+)](i) decline during caffeine-evoked transients, raised diastolic and systolic [Ca(2+)](i), and depressed systolic contractile activity. These effects were greater with sucrose solution, and were not observed after isosmotic [Na(+)](o) increase. We conclude that under the present experimental conditions, transmembrane Na(+) redistribution apparently plays an important role in determining changes in SR Ca(2+) mobilization, which markedly affect contractile response to hyperosmotic NaCl solutions and attenuate the osmotically induced depression of contractile activity.

ROS-activated Ca/calmodulin kinase IIδ is required for late INa augmentation leading to cellular Na and Ca overload

PubMed Central

Wagner, Stefan; Ruff, Hanna M.; Weber, Sarah L.; Bellmann, Sarah; Sowa, Thomas; Schulte, Timo; Grandi, Eleonora; Bers, Donald M.; Backs, Johannes; Belardinelli, Luiz; Maier, Lars S.

2011-01-01

Rationale In heart failure (HF), CaMKII expression and reactive oxygen species (ROS) are increased. Both ROS and CaMKII can increase late INa leading to intracellular Na accumulation and arrhythmias. It has been shown that ROS can activate CaMKII via oxidation. Objective We tested whether CaMKIIδ is required for ROS-dependent late INa regulation and if ROS-induced Ca released from the sarcoplasmic reticulum (SR) is involved. Methods and Results 40 µmol/L H2O2 significantly increased CaMKII oxidation and autophosphorylation in permeabilized rabbit cardiomyocytes. Without free [Ca]i (5 mmol/L BAPTA/1 mmol/L Br2-BAPTA) or after SR depletion (caffeine 10 mmol/L, thapsigargin 5 µmol/L) the H2O2-dependent CaMKII oxidation and autophosphorylation was abolished. H2O2 significantly increased SR Ca spark frequency (confocal microscopy) but reduced SR Ca load. In wildtype (WT) mouse myocytes, H2O2 increased late INa (whole cell patch-clamp). This increase was abolished in CaMKIIδ−/− myocytes. H2O2-induced [Na]i and [Ca]i accumulation (SBFI and Indo-1 epifluorescence) was significantly slowed in CaMKIIδ−/− myocytes (vs. WT). CaMKIIδ−/− myocytes developed significantly less H2O2-induced arrhythmias, and were more resistant to hypercontracture. Opposite results (increased late INa, [Na]i and [Ca]i accumulation) were obtained by overexpression of CaMKIIδ in rabbit myocytes (adenoviral gene transfer) reversible with CaMKII inhibition (10 µmol/L KN93 or 0.1 µmol/L AIP). Conclusion Free [Ca]i and a functional SR are required for ROS activation of CaMKII. ROS-activated CaMKIIδ enhances late INa, which may lead to cellular Na and Ca overload. This may be of relevance in HF, where enhanced ROS production meets increased CaMKII expression. PMID:21252154

Optical measurements of Na-Ca-K exchange currents in intact outer segments isolated from bovine retinal rods

PubMed Central

1991-01-01

The properties of Na-Ca-K exchange current through the plasma membrane of intact rod outer segments (ROS) isolated from bovine retinas were studied with the optical probe neutral red. Small cellular organelles such as bovine ROS do not offer an adequate collecting area to measure Na-Ca-K exchange currents with electrophysiological techniques. This study demonstrates that Na-Ca-K exchange current in bovine ROS can be measured with the dye neutral red and dual-wavelength spectrophotometry. The binding of neutral red is sensitive to transport of cations across the plasma membrane of ROS by the effect of the translocated cations on the surface potential of the intracellular disk membranes (1985. J. Membr. Biol. 88: 249-262). Electrogenic Na+ fluxes through the ROS plasma membrane were measured with a resolution of 10(5) Na+ ions/ROS per s, equivalent to a current of approximately 0.01 pA; maximal electrogenic Na-Ca-K exchange flux in bovine ROS was equivalent to a maximal exchange current of 1-2 pA. Electrogenic Na+ fluxes were identified as Na-Ca-K exchange current based on a comparison between electrogenic Na+ flux and Na(+)-stimulated Ca2+ release with respect to flux rate, Na+ dependence, and ion selectivity. Neutral red monitored the net entry of a single positive charge carried by Na+ for each Ca2+ ion released (i.e., monitored the Na-Ca-K exchange current). Na-Ca-K exchange in the plasma membrane of bovine ROS had the following properties: (a) Inward Na-Ca-K exchange current required internal Ca2+ (half-maximal stimulation at a free Ca2+ concentration of 0.9 microM), whereas outward Na-Ca-K exchange current required both external Ca2+ (half-maximal stimulation at a free Ca2+ concentration of 1.1 microM) and external K+. (b) Inward Na-Ca-K exchange current depended in a sigmoidal manner on the external Na+ concentration, identical to Na(+)-stimulated Ca2+ release measured with Ca(2+)- indicating dyes. (c) The neutral red method was modified to measure Ca(2

Nanoscale modulations in (KLa)(CaW)O{sub 6} and (NaLa)(CaW)O{sub 6}

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

Licurse, Mark W., E-mail: mlicurse@seas.upenn.edu; Borisevich, Albina Y., E-mail: albinab@ornl.gov; Davies, Peter K., E-mail: davies@seas.upenn.edu

2012-07-15

Complex nanoscale modulations are identified in two new A-site ordered perovskites, (KLa)(CaW)O{sub 6} and (NaLa)(CaW)O{sub 6}. In (KLa)(CaW)O{sub 6}, selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM) show an incommensurate nanocheckerboard modulation with {approx}9.4 Multiplication-Sign 9.4a{sub p} periodicity (a{sub p} Almost-Equal-To 4 A for the cubic perovskite aristotype). For (NaLa)(CaW)O{sub 6} a one-dimensional modulation is observed with a {approx}16(1 1 0)a{sub p} repeat; the Left-Pointing-Angle-Bracket 1 1 0 Right-Pointing-Angle-Bracket orientation of the nanostripes is different from the Left-Pointing-Angle-Bracket 1 0 0 Right-Pointing-Angle-Bracket stripes observed in other mixed A-site systems. Studies using high temperature x-ray diffraction suggest the formationmore » of the complex modulations is associated with small deviations from the ideal 1:1:1:1 stoichiometry of the (A{sup +}La{sup 3+})(CaW)O{sub 6} phases. Z-contrast images acquired on an aberration-corrected microscope provide evidence for deviations from stoichiometry with a {approx}1:15 periodic arrangement of La{sub 4/3}(CaW)O{sub 6}:(NaLa)(CaW)O{sub 6} nano-phases. - Graphical abstract: Complex nanoscale modulations are identified in two new A-site ordered perovskites, (KLa)(CaW)O{sub 6} and (NaLa)(CaW)O{sub 6}. In (KLa)(CaW)O{sub 6}, selected-area electron diffraction and high-resolution transmission electron microscopy show a two-dimensional, nanocheckerboard modulation. For (NaLa)(CaW)O{sub 6} a one-dimensional modulation is observed; the Left-Pointing-Angle-Bracket 1 1 0 Right-Pointing-Angle-Bracket orientation of the nanostripes is different from the Left-Pointing-Angle-Bracket 1 0 0 Right-Pointing-Angle-Bracket stripes observed in other mixed A-site systems. Highlights: Black-Right-Pointing-Pointer Two new A-site ordered perovskites were synthesized, (KLa)(CaW)O{sub 6} and (NaLa)(CaW)O{sub 6}. Black

Superhalogen properties of hetero-binuclear anions MM‧F4- and MM″F5- (M = Li, Na, M‧ = Be, Mg, Ca; M″ = B, Al, Ga)

NASA Astrophysics Data System (ADS)

Yang, Hui; Li, Ying; He, Hui-Min; Tong, Jing; Wu, Di; Li, Zhi-Ru

2017-09-01

Hetero-binuclear superhalogen anions, namely MM‧F4- and MM″F5- (M = Li, Na; M‧ = Be, Mg, Ca; M″ = B, Al, Ga), have been theoretically characterized at the MP2(FULL)/6-311+G(3df) level. It is found that two central atoms can be linked by at most three fluorine ligands. The large vertical electron detachment energies (VDEs, 7.449-8.978 eV) verify the superhalogen identity of these anions. The VDEs of both MM‧F4- and MM″F5- decrease when the atomic size of M increases whereas increase with the size of M‧ and M″. Besides, the extra electron distribution also has effect on the VDEs of such superhalogen anions.

Structure and superconductivity in the ternary silicide CaAlSi

NASA Astrophysics Data System (ADS)

Ma, Rong; Huang, Gui-Qin; Liu, Mei

2007-06-01

Using the linear response-linearized Muffin-tin orbital (LR-LMTO) method, we study the electronic band structure, phonon spectra, electron-phonon coupling and superconductivity for c-axis ferromagnetic-like (F-like) and antiferromagnetic-like (AF-like) structures in ternary silicide CaAlSi. The following conclusions are drawn from our calculations. If Al and Si atoms are assumed to arrange along the c axis in an F-like long-range ordering (-Al-Al-Al-and-Si-Si-Si-), one could obtain the ultrasoft B1g phonon mode and thus very strong electron-phonon coupling in CaAlSi. However, the appearance of imaginary frequency phonon modes indicates the instability of such a structure. For Al and Si atoms arranging along the c axis in an AF-like long-range ordering (-Al-Si-Al-), the calculated electron-phonon coupling constant is equal to 0.8 and the logarithmically averaged frequency is 146.8 K. This calculated result can correctly yield the superconducting transition temperature of CaAlSi by the standard BCS theory in the moderate electron-phonon coupling strength. We propose that an AF-like superlattice model for Al (or Si) atoms along the c direction may mediate the inconsistency estimated from theory and experiment, and explain the anomalous superconductivity in CaAlSi.

Adrenergic-agonist-induced Ca2+ fluxes in rat parotid cells are not Na+-dependent.

PubMed Central

Helman, J; Roth, G S; Baum, B J

1985-01-01

We investigated the hypothesis that extracellular Na+ is required for the rapid mobilization of Ca2+ by rat parotid cells after adrenergic stimulation. When Na+ salts in the media were osmotically replaced with either choline chloride (+atropine) or sucrose, efflux of 45Ca2+ from preloaded cells, caused by 10 microM-(-)-adrenaline, was unchanged. Similarly adrenaline stimulated 45Ca2+ uptake into cells under nonsteady-state conditions in the presence or absence of Na+. Monensin, a Na+ ionophore, was able to elicit a modest increase in 45Ca2+ efflux, compared with controls. Studies of net 45Ca2+ flux, performed under near-steady-state conditions, showed that adrenaline caused net 45Ca2+ accumulation, whereas monensin caused net 45Ca2+ release. The effect of monensin required the presence of Na+ in the incubation medium. Both 1 mM-LaCl3 and 0.1 mM-D-600 prevented adrenaline-stimulated 45Ca2+ uptake into cells, but had no effect on monensin-induced changes. We conclude that (1) the rapid mobilization of Ca2+ by adrenergic agonists seen in rat parotid cells does not require a Na+out greater than Na+in gradient and (2) the nature of the monensin effect is quite different from the adrenergic-agonist-induced response. PMID:2413840

Sodium recognition by the Na+/Ca2+ exchanger in the outward-facing conformation.

PubMed

Marinelli, Fabrizio; Almagor, Lior; Hiller, Reuben; Giladi, Moshe; Khananshvili, Daniel; Faraldo-Gómez, José D

2014-12-16

Na(+)/Ca(2+) exchangers (NCXs) are ubiquitous membrane transporters with a key role in Ca(2+) homeostasis and signaling. NCXs mediate the bidirectional translocation of either Na(+) or Ca(2+), and thus can catalyze uphill Ca(2+) transport driven by a Na(+) gradient, or vice versa. In a major breakthrough, a prokaryotic NCX homolog (NCX_Mj) was recently isolated and its crystal structure determined at atomic resolution. The structure revealed an intriguing architecture consisting of two inverted-topology repeats, each comprising five transmembrane helices. These repeats adopt asymmetric conformations, yielding an outward-facing occluded state. The crystal structure also revealed four putative ion-binding sites, but the occupancy and specificity thereof could not be conclusively established. Here, we use molecular-dynamics simulations and free-energy calculations to identify the ion configuration that best corresponds to the crystallographic data and that is also thermodynamically optimal. In this most probable configuration, three Na(+) ions occupy the so-called Sext, SCa, and Sint sites, whereas the Smid site is occupied by one water molecule and one H(+), which protonates an adjacent aspartate side chain (D240). Experimental measurements of Na(+)/Ca(2+) and Ca(2+)/Ca(2+) exchange by wild-type and mutagenized NCX_Mj confirm that transport of both Na(+) and Ca(2+) requires protonation of D240, and that this side chain does not coordinate either ion at Smid. These results imply that the ion exchange stoichiometry of NCX_Mj is 3:1 and that translocation of Na(+) across the membrane is electrogenic, whereas transport of Ca(2+) is not. Altogether, these findings provide the basis for further experimental and computational studies of the conformational mechanism of this exchanger.

Sodium recognition by the Na+/Ca2+ exchanger in the outward-facing conformation

PubMed Central

Marinelli, Fabrizio; Almagor, Lior; Hiller, Reuben; Giladi, Moshe; Khananshvili, Daniel; Faraldo-Gómez, José D.

2014-01-01

Na+/Ca2+ exchangers (NCXs) are ubiquitous membrane transporters with a key role in Ca2+ homeostasis and signaling. NCXs mediate the bidirectional translocation of either Na+ or Ca2+, and thus can catalyze uphill Ca2+ transport driven by a Na+ gradient, or vice versa. In a major breakthrough, a prokaryotic NCX homolog (NCX_Mj) was recently isolated and its crystal structure determined at atomic resolution. The structure revealed an intriguing architecture consisting of two inverted-topology repeats, each comprising five transmembrane helices. These repeats adopt asymmetric conformations, yielding an outward-facing occluded state. The crystal structure also revealed four putative ion-binding sites, but the occupancy and specificity thereof could not be conclusively established. Here, we use molecular-dynamics simulations and free-energy calculations to identify the ion configuration that best corresponds to the crystallographic data and that is also thermodynamically optimal. In this most probable configuration, three Na+ ions occupy the so-called Sext, SCa, and Sint sites, whereas the Smid site is occupied by one water molecule and one H+, which protonates an adjacent aspartate side chain (D240). Experimental measurements of Na+/Ca2+ and Ca2+/Ca2+ exchange by wild-type and mutagenized NCX_Mj confirm that transport of both Na+ and Ca2+ requires protonation of D240, and that this side chain does not coordinate either ion at Smid. These results imply that the ion exchange stoichiometry of NCX_Mj is 3:1 and that translocation of Na+ across the membrane is electrogenic, whereas transport of Ca2+ is not. Altogether, these findings provide the basis for further experimental and computational studies of the conformational mechanism of this exchanger. PMID:25468964

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.

Expression of cardiac sarcolemmal Na sup + -Ca sup 2+ exchange activity in Xenopus laevis oocytes

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

Longoni, S.; Coady, M.J.; Ikeda, T.

1988-12-01

Injection of Xenopus laevis oocytes with rabbit heart poly(A){sup +}RNA results in expression of Na{sup +} inside (Na{sub i}{sup +})-dependent Ca{sup 2+} uptake activity. The activity was measured by first loading the oocytes with Na{sup +} using nystatin and then incubating the oocytes in K{sup +} or Na{sup +} medium containing {sup 45}Ca. The expressed Na{sup +} gradient-dependent Ca{sup 2+} uptake was five to eight times that observed with water-injected oocytes or with poly(A){sup +}RNA-injected oocytes for which the Na{sup +} load step had been omitted. Induced activity was related to the amount of RNA injected and was insensitive tomore » nifedipine. Fractionation of the poly(A){sup +}RNA on a sucrose gradient determined that the active message had a size range between 3 and 8 kb. The properties of the Na{sup +} gradient-dependent Ca{sup 2+} uptake indicated that Na{sup +}-Ca{sup 2+} exchange activity had been expressed in X. laevis oocytes. The result may be useful for cloning and identifying the molecular component responsible for Na{sup +}-Ca{sup 2+} exchange.« less

Na and Ca components of action potentials in amphioxus muscle cells

PubMed Central

Hagiwara, S.; Kidokoro, Y.

1971-01-01

1. The ionic mechanism of the action potential produced in lamella-like muscle cells of amphioxus, Branchiostoma californiense, was investigated with intracellular recording and polarization techniques. 2. The resting potential and action potential overshoot in normal saline are -53±5 mV (S.D.) and +29±10 mV (S.D.) respectively. 3. The action potential is eliminated by tetrodotoxin (3 μM) and by replacing NaCl in the saline with Tris-chloride but maintained by replacing Na with Li. 4. After elimination of the normal action potential by tetrodotoxin or replacing Na with Tris, the addition of procaine (7·3 mM) to the external saline makes the membrane capable of producing a regenerative potential change. 5. The peak potential of the regenerative response depends on external Ca concentration in a manner predicted by the Nernst equation with Ca concentrations close to normal. 6. The Ca dependent response is reversibly suppressed by Co or La ions. 7. Similar regenerative responses are obtained when Ca is substituted with Sr or Ba. 8. It is concluded that two independent mechanisms of ionic permeability increase occur in the membrane of amphioxus muscle cell, one to Na and the other to Ca. PMID:5158595

Phase Compositions of Self Reinforcement Al2O3/CaAl12O19 Composite using X-ray Diffraction Data and Rietveld Technique

NASA Astrophysics Data System (ADS)

Asmi, D.; Low, I. M.; O'Connor, B.

2008-03-01

The analysis of x-ray diffraction (XRD) patterns by the Rietveld technique was tested to the quantitatively phase compositions of self reinforcement Al2O3/CaAl12O19 composite. Room-temperature XRD patterns revealed that α-Al2O3 was the only phase presence in the CA0 sample, whereas the α-Al2O3 and CaAl12O19 phases were found for CA5, CA15, CA30, and CA50 samples. The peak intensity of CA6 in the self reinforcement Al2O3/CaAl12O19 composites increased in proportion with increase in CaAl12O19 content in contrast to α-Al2O3. The diffraction patterns for CA100 sample shows minor traces of α-Al2O3 even in relatively low peak intensity. It is suggesting that the in-situ reaction sintering of raw materials were not react completely to form 100 wt% CaAl12O19 at temperature 1650 °C. Quantitative phase compositions of self reinforcement Al2O3/CaAl12O19 composites by Rietveld analysis with XRD data has been well demonstrated. The results showed that the GOF values are relatively low and the fluctuation in the difference plots shows a reasonable fit between the observed and the calculated plot.

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. %.

Na/Ca exchange in the basolateral membrane of the A6 cell monolayer: role in Cai homeostasis.

PubMed

Brochiero, E; Raschi, C; Ehrenfeld, J

1995-05-01

The presence of a Na/Ca exchanger in A6 cells was investigated by measuring intracellular calcium (Cai) fluctuations and the 45Ca fluxes through the basolateral membranes (blm) of the cell monolayer. Removal of Na+ from the medium produced a transient increase in Cai followed by a regulatory phase returning Cai to control levels in 3-4 min, this phase being greatly accelerated (< 60 s) by NaCl addition (apparent Km of approximately 5 mM Na+). The Cai increase was only found with the Na(+)-free medium on the basolateral side of the cell monolayer. A twofold increase in the 45Ca influx was observed under these conditions. In Ca(2+)- depleted cells, the initial Cai increase after Ca2+ addition to the medium was greater when the putative Na/Ca exchanger was not functioning (i.e. in a Na(+)-free medium). 45Ca effluxes through the blm of the monolayer were greatly and transiently increased by a Na(+)-free medium on the serosal side and blocked by orthovanadate (1 mM). The Cai increased induced by a hypo-osmotic shock was greater in cells bathed in a Na(+)-medium, conditions expected to block the activity of the Na/Ca exchanger. These findings support the hypothesis that a Na/Ca exchanger is present on the blm of A6 cells and affirm its role in Cai homeostasis in steady-state conditions and following osmotic shock. In addition, a Ca2+ pump also located on the blm and Ca2+ stores sensitive to inositol 1,4,5-trisphosphate were found to be implicated in Cai homeostasis.

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

NASA Technical Reports Server (NTRS)

Cherng, Jing-Yih; Bennion, Douglas N.

1987-01-01

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.

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.

Pressure induced coordination change of Al in silicate melts from Al K edge XANES of high pressure NaAlSi2O6-NaAlSi3O8 glasses

NASA Astrophysics Data System (ADS)

Li, Dien; Secco, R. A.; Bancroft, G. M.; Fleet, M. E.

Aluminum K-edge XANES spectra of high pressure and high temperature (4.4 GPa and 1575°C) glasses along the NaAlSi2O6 (Jd)-NaAlSi3O8 (Ab) join are reported using synchrotron radiation, and shown to provide direct experimental evidence for the pressure-induced coordination change of Al. Five- and six-fold coordinated Al (5Al and 6Al), characterized by Al K-edge positions at 1567.8 and 1568.7 eV, respectively, first appear in glass of composition Jd60Ab40 and increase in proportion progressively with increasing Jd content. The end-member jadeite glass contains about 6% of each of 5Al and 6Al. The present direct measurements confirm literature suggestions for the important role of Al in controlling viscosity and diffusion in mantle melts.

Characterization of ZnAl cast alloys with Na addition

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

Gancarz, Tomasz, E-mail: t.gancarz@imim.pl; Cempura, Grzegorz; Skuza, Wojciech

2016-01-15

This study was aimed at evaluating the microstructural change and thermal, electrical and mechanical properties with the addition of Na to eutectic ZnAl alloys. Solders based on eutectic ZnAl containing 0.2 to 3.0 (wt.%) of Na were developed for high temperature solder. Differential scanning calorimetry (DSC) measurements were performed to determine the melting temperatures of the alloys. Thermal linear expansion and electrical resistivity measurements were performed over − 50 °C to 300 °C and 30 °C to 300 °C temperature ranges, respectively. The microstructure of the specimens was analyzed using scanning (SEM) and transmission electron microscopy (TEM) techniques. Chemical microanalysismore » was performed by energy-dispersive X-ray spectroscopy (EDS) on SEM and TEM. The precipitates of NaZn{sub 13} were confirmed by X-ray diffraction (XRD) measurements and selected area electron diffraction (SAED) techniques. The addition of Na to eutectic ZnAl alloy increased the electrical resistivity and reduced the coefficient of thermal expansion; however, the melting point did not change. The mechanical properties, strain and microhardness increased with Na content in alloys. - Highlights: • High temperature soldering materials of ZnAl with Na were designed and characterized. • Precipitates of NaZn{sub 13}were observed and confirmed using TEM and XRD. • Addition of Na to eutectic ZnAl cussed increased mechanical properties. • NaZn{sub 13} caused increased electrical resistivity and microhardness, and reduced the CTE.« less

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.

Paraquat adsorption on NaX and Al-MCM-41.

PubMed

Rongchapo, Wina; Deekamwong, Krittanun; Loiha, Sirinuch; Prayoonpokarach, Sanchai; Wittayakun, Jatuporn

2015-01-01

The aim of this work is to determine paraquat adsorption capacity of zeolite NaX and Al-MCM-41. All adsorbents were synthesized by hydrothermal method using rice husk silica. For Al-MCM-41, aluminum (Al) was added to the synthesis gel of MCM-41 with Al content of 10, 15, 20 and 25 wt%. The faujasite framework type of NaX and mesoporous characteristic of Al-MCM-41 were confirmed by X-ray diffraction. Surface area of all adsorbents determined by N2 adsorption-desorption analysis was higher than 650 m2/g. Al content and geometry were determined by X-ray fluorescence and 27Al nuclear magnetic resonance, respectively. Morphology of Al-MCM-41 were studied by transmission electron microscopy; macropores and defects were observed. The paraquat adsorption experiments were conducted using a concentration range of 80-720 mg/L for NaX and 80-560 mg/L for Al-MCM-41. The paraquat adsorption isotherms from all adsorbents fit well with the Langmuir model. The adsorption capacity of NaX was 120 mg/g-adsorbent. Regarding Al-MCM-41, the 10% Al-MCM-41 exhibited the lowest capacity of 52 mg/g-adsorbent while the other samples had adsorption capacity of 66 mg/g-adsorbent.

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}

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

Mijares, Alfredo; Altamirano, Francisco; Kolster, Juan

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{supmore » 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

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

Spectroscopic and structural investigation for the ground and excited states of CaNa+ molecular ion

NASA Astrophysics Data System (ADS)

Jellali, Soulef; Habli, Héla; Mejrissi, Leila; Hamdi, Rafika; Oujia, Brahim; Xavier Gadéa, Florent

2018-04-01

In the current theoretical study, we investigated several electronic states correlated with the {Ca+Na+} and {Ca++Na} asymptotic limits of different symmetries (Σ+, Π, Δ). Our calculations were based on ab intio method using semi-empirical pseudo-potential theory of both cores Na+ and Ca2+ and Full Configuration Interaction (FCI). Hence, we computed the adiabatic potential energy curves (PECs) and vibrational levels of the ground state along with several higher states of (CaNa)+ molecular ion. From these curves, we extracted all related spectroscopic parameters (De, D0, Te, Re, Be, ωe and ωeχe). Dipolar properties of (CaNa)+ such as Permanent and Transition Dipole Moments (PDM, TDM) were determined and analyzed. Numerous Avoided Crossings (ACs) were detected in PECs and their reflections were clearly observed in PDM and TDM functions. The strong interactions could lead to significant charge or excitation transfer for atom-ion collisions in the diverse charge or excited states.

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.

Phase Composition and Hardening of Castable Al - Ca - Ni - Sc Alloys Containing 0.3% Sc

NASA Astrophysics Data System (ADS)

Belov, N. A.; Naumova, E. A.; Bazlova, T. A.; Doroshenko, V. V.

2017-05-01

The phase composition of aluminum alloys of the Al - Ca - Ni - Sc system containing 0.3 wt.% Sc is studied. It is shown that the aluminum solid solution may be in equilibrium not only with binary phases (Al4Ca, Al3Sc and Al3Ni) but also with a ternary Al9NiCa compound. The temperature of attainment of maximum hardening due to precipitation of nanoparticles of phase Al3Sc is determined for all the alloys studied. Principal possibility of creation of castable alloys based on an (Al) + Al4Ca + Al9NiCa eutectic, the hardening heat treatment of which does not require quenching, is substantiated.

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

Effects of hydrogen fugacity and confining pressure on the interdiffusion rate of NaSi-CaAl in plagioclase

NASA Astrophysics Data System (ADS)

Yund, Richard A.; Snow, Eleanour

1989-08-01

Average? values for NaSi-CaAl interdiffusion in the compositional interval from An0 to An26 have been determined at 1000°C by the method of lamellar homogenization. At 1500 MPa confining pressure (P), ? increases 1 order of magnitude (5.0×10-21 to 4.0×10-20 m2/s) for 4 orders of magnitude increase in hydrogen fugacity (0.029, Mn3O4-Mn2O3 buffer, to 197 MPa, FeO-Fe3O4 buffer). At constant hydrogen fugacity (fH2), ? increases rapidly at low pressure and becomes nearly independent of P above 1000 MPa. (For fH2 = 0.1 MPa, ? = 2.8 × 10-22 m2/s at P = 0.1 MPa, 5.0 × 10-21 at P = 500, 1.3×10-20 at P = 1000, and 1.4×10-20 at P = 1500). The dependence of ? on increasing pressure, when a hydrogen-related species is present, is believed to be due to an increase in the concentration of the structural defect associated with increase in the hydrogen impurity. In most crustal igneous rocks, which are internally buffered near quartz-fayalite-magnetite, the dependence of ? on fH2 is relatively minor compared to the effect of confining pressure.

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.

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

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).

Diffusion and the dynamics of displacive phase transitions in cryolite (Na3AlF6) and chiolite (Na5Al3F14): Multi-nuclear NMR studies

NASA Astrophysics Data System (ADS)

Spearing, Dane R.; Stebbins, Jonathan F.; Farnan, Ian

1994-10-01

Cryolite is a mixed-cation perovskite (Na2(NaAl)F6) which undergoes a monoclinic to orthorhombic displacive phase transition at ˜550° C. Chiolite (Na5Al3F14) is associated with cryolite in natural deposits, and consists of sheets of corner sharing [AlF6] octahedra interlayered with edge-sharing [NaF6] octahedra. Multi-nuclear NMR line shape and relaxation time (T1) studies were performed on cryolite and chiolite in order to gain a better understanding of the atomic motions associated with the phase transition in cryolite, and Na diffusion in cryolite and chiolite. 27Al, 23Na, and 19F static NMR spectra and T1's in cryolite suggest that oscillatory motions of the [AlF6] octahedra among four micro-twin and anti-phase domains in α-cryolite begin at least 150° C below the transition temperature and persist above it. Variable temperature 23Na MAS NMR further indicates diffusional exchange at a rate of at least 13 kHz between the Na sites by the time the transition temperature is reached. 27Al and 23Na T1's show the same behavior with increasing temperature, indicating the same relaxation mechanisms are responsible for both. The first order nature of the cryolite transition is apparent as a jump in the 23Na and 27Al T1's. Above the transition temperature, the T1's decrease slightly indicating that the motions responsible for the drop in T1, are still present above the transition, further supporting the dynamic nature of the high temperature phase of cryolite. Chiolite 23Na static spectra decrease in linewidth with increasing temperature, indicating increased Na diffusion, which is interpreted as occurring within the [NaF6] sheets in the chiolite structure, but not between the two different Na sites. 27Al and 23Na T1's show similar behavior as in cryolite, but there is no discontinuity due to a phase transition. 19F T1's are constant from room temperature to 150° C indicating no oscillatory motion of the [AlF6] octahedra in chiolite.

Thermodynamic Model of the Na-Al-Si-O-F Melts

NASA Astrophysics Data System (ADS)

Dolejs, D.; Baker, D. R.

2004-05-01

Fluorine is a common volatile element in magmatic-hydrothermal systems, but its solution mechanisms in highly polymerized silicate melts are poorly known. We have developed a thermodynamic model for fluorosilicate liquids which links experimentally determined phase equilibria and spectroscopic information on melt structure. The model is applicable to crystallization of fluoride minerals or fluoride-silicate immiscibility in natural felsic melts. Configurational properties of the liquid are defined by mixing of alkali fluoride, polyhedral aluminofluoride and silicofluoride species and non-bridging terminations of the silicate network. Abundances of individual structural species are described by a homogeneous equilibrium, representing melt depolymerization: F- (free) + O0 (bridging) = F0 (terminal) + O- (non-bridging), which is a replacement of one oxygen bridge, Si-O-Si, by two terminations, Si-F | Na-O-Si. In cryolite-bearing systems, the self-dissociation of octahedral aluminofluoride complexes: Na3[AlF6] = Na[AlF4] + 2 NaF, and the short-range order between (O,F)-corners and (Si,NaAl)-centers of tetrahedra: Si-O-Si + 2 [NaAl]-F = [NaAl]-O-[NaAl] + 2 Si-F, represent two additional interaction mechanisms. Portrayal of these equilibria in ternary Thompson reaction space allows to decrease the number of interaction mechanisms by linearly combining melt depolymerization with tetrahedral short-range order. In this formulation, the interaction parameters are incorporated directly in configurational properties, thus the complete melt speciation can be calculated, and the activities of any macroscopic species are readily derived. The model has been applied to subsystems of the Na2O-NaAlO2-SiO2-F2O-1 compositional space. Activity-composition relationships in the villiaumite-sodium silicate binaries require clustering of silicate tetrahedra in fluoride solvent. Phase-equilibria in cryolite-nepheline and cryolite-albite systems illustrate an overall increase of Na3AlF6 self

Oxidation of Ca-α-SiAlON Powders Prepared by Combustion Synthesis

PubMed Central

Li, Jinfu; Li, Zhongmin; Wang, Enhui; Wang, Zhanjun; Yin, Xiaowei; Zhang, Zuotai

2015-01-01

The oxidation of Ca-α-SiAlON synthesized by the combustion synthesis (CS) method with different additives was investigated in air atmosphere using thermogravimetric (TG) analysis in a temperature range from 1453 K to 1653 K. The experimental results indicated that oxidation was controlled by mixed chemical and diffusion steps. The oxidation products by XRD analysis were composed of SiO2 and CaAl2Si2O8 at low oxidation temperature, whereas the SiO2-Al2O3-CaO ternary glassy phase was formed at elevated temperature. The deviation of oxidation resistance from each sample may be due to the morphological difference brought about by different additive additions. This study reveals the effects of additives on the oxidation resistance of synthesized Ca-α-SiAlON powders. PMID:28793657

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.

Kinetics Study on the Effect of NaCl on the CaSO4 Dissolution Behavior

NASA Astrophysics Data System (ADS)

Song, Jingyao; Shi, Peiyang; Wang, Yeguang; Jiang, Maofa

2018-01-01

The study of the dissolution kinetics of CaSO4 is essential for the control of the dissolution and recrystallization behavior of CaSO4. In this work, the kinetic behavior of CaSO4 dissolved in NaCl solution was investigated by means of conductivity meter. The results show that with the increase of concentration of NaCl, the temperature rise and the time prolonged, the dissolution rate of dihydrate CaSO4 gradually increases, and the dissolved apparent activation energy is gradually decreased. When the NaCl concentration is 1.8%, the dissolution kinetic equation is 1-(1-α) 1/3=5.46*10-4exp (-9147/RT) t; When the NaCl concentration is 3.0%, the dissolution kinetic equation is 1-(1-α) 1/3=2.81×10-4 exp (-6753/RT)t; When the NaCl concentration is 3.6%, the dissolution kinetic equation is 1-(1-α) 1/3=3.07×l0-4exp(-6103/RT)t.

Deformation processed Al/Ca nano-filamentary composite conductors for HVDC applications

NASA Astrophysics Data System (ADS)

Czahor, C. F.; Anderson, I. E.; Riedemann, T. M.; Russell, A. M.

2017-07-01

Efficient long-distance power transmission is necessary as the world continues to implement renewable energy sources, often sited in remote areas. Light, strong, high-conductivity materials are desirable for this application to reduce both construction and operational costs. In this study an Al/Ca (11.5% vol.) composite with nano-filamentary reinforcement was produced by powder metallurgy then extruded, swaged, and wire drawn to a maximum true strain of 12.7. The tensile strength increased exponentially as the filament size was reduced to the sub-micron level. In an effort to improve the conductor’s ability to operate at elevated temperatures, the deformation-processed wires were heat-treated at 260°C to transform the Ca-reinforcing filaments to Al2Ca. Such a transformation raised the tensile strength by as much as 28%, and caused little change in ductility, while the electrical conductivity was reduced by only 1% to 3%. Al/Al2Ca composites are compared to existing conductor materials to show how implementation could affect installation and performance.

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

Tissintite, (Ca, Na,$${\\square}$$)AlSi 2O 6, 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, (Ca 0.45Na 0.31more » $${\\square}$$ 0.24)(Al 0.97Fe 0.03Mg 0.01)(Si 1.80Al 0.20)O 6, 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) Å 3, 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 Å 3, 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

Tissintite, (Ca, Na,$${\\square}$$)AlSi 2O 6, a highly-defective, shock-induced, high-pressure clinopyroxene in the Tissint martian meteorite

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

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

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, (Ca 0.45Na 0.31more » $${\\square}$$ 0.24)(Al 0.97Fe 0.03Mg 0.01)(Si 1.80Al 0.20)O 6, 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) Å 3, 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 Å 3, 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

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).

Ca2+ permeability and Na+ conductance in cellular toxicity caused by hyperactive DEG/ENaC channels.

PubMed

Matthewman, Cristina; Miller-Fleming, Tyne W; Miller, David M; Bianchi, Laura

2016-12-01

Hyperactivated DEG/ENaC channels cause neuronal death mediated by intracellular Ca 2+ overload. Mammalian ASIC1a channels and MEC-4(d) neurotoxic channels in Caenorhabditis elegans both conduct Na + and Ca 2+ , raising the possibility that direct Ca 2+ influx through these channels contributes to intracellular Ca 2+ overload. However, we showed that the homologous C. elegans DEG/ENaC channel UNC-8(d) is not Ca 2+ permeable, yet it is neurotoxic, suggesting that Na + influx is sufficient to induce cell death. Interestingly, UNC-8(d) shows small currents due to extracellular Ca 2+ block in the Xenopus oocyte expression system. Thus, MEC-4(d) and UNC-8(d) differ both in current amplitude and Ca 2+ permeability. Given that these two channels show a striking difference in toxicity, we wondered how Na + conductance vs. Ca 2+ permeability contributes to cell death. To address this question, we built an UNC-8/MEC-4 chimeric channel that retains the calcium permeability of MEC-4 and characterized its properties in Xenopus oocytes. Our data support the hypothesis that for Ca 2+ -permeable DEG/ENaC channels, both Ca 2+ permeability and Na + conductance contribute to toxicity. However, for Ca 2+ -impermeable DEG/ENaCs (e.g., UNC-8), our evidence shows that constitutive Na + conductance is sufficient to induce toxicity, and that this effect is enhanced as current amplitude increases. Our work further refines the contribution of different channel properties to cellular toxicity induced by hyperactive DEG/ENaC channels. Copyright © 2016 the American Physiological Society.

Ca2+ permeability and Na+ conductance in cellular toxicity caused by hyperactive DEG/ENaC channels

PubMed Central

Matthewman, Cristina; Miller-Fleming, Tyne W.; Miller, David M.

2016-01-01

Hyperactivated DEG/ENaC channels cause neuronal death mediated by intracellular Ca2+ overload. Mammalian ASIC1a channels and MEC-4(d) neurotoxic channels in Caenorhabditis elegans both conduct Na+ and Ca2+, raising the possibility that direct Ca2+ influx through these channels contributes to intracellular Ca2+ overload. However, we showed that the homologous C. elegans DEG/ENaC channel UNC-8(d) is not Ca2+ permeable, yet it is neurotoxic, suggesting that Na+ influx is sufficient to induce cell death. Interestingly, UNC-8(d) shows small currents due to extracellular Ca2+ block in the Xenopus oocyte expression system. Thus, MEC-4(d) and UNC-8(d) differ both in current amplitude and Ca2+ permeability. Given that these two channels show a striking difference in toxicity, we wondered how Na+ conductance vs. Ca2+ permeability contributes to cell death. To address this question, we built an UNC-8/MEC-4 chimeric channel that retains the calcium permeability of MEC-4 and characterized its properties in Xenopus oocytes. Our data support the hypothesis that for Ca2+-permeable DEG/ENaC channels, both Ca2+ permeability and Na+ conductance contribute to toxicity. However, for Ca2+-impermeable DEG/ENaCs (e.g., UNC-8), our evidence shows that constitutive Na+ conductance is sufficient to induce toxicity, and that this effect is enhanced as current amplitude increases. Our work further refines the contribution of different channel properties to cellular toxicity induced by hyperactive DEG/ENaC channels. PMID:27760755

Modulation of the reaction cycle of the Na+:Ca2+, K+ exchanger.

PubMed

Vedovato, Natascia; Rispoli, Giorgio

2007-09-01

Ca(2+) concentration in retinal photoreceptor rod outer segment (OS) strongly affects the generator potential kinetics and the receptor light adaptation. The response to intense light stimuli delivered in the dark produce potential changes exceeding 40 mV: since the Ca(2+) extrusion in the OS is entirely controlled by the Na(+):Ca(2+), K(+) exchanger, it is important to assess how the exchanger ion transport rate is affected by the voltage and, in general, by intracellular factors. It is indeed known that the cardiac Na(+):Ca(2+) exchanger is regulated by Mg-ATP via a still unknown metabolic pathway. In the present work, the Na(+):Ca(2+), K(+) exchanger regulation was investigated in isolated OS, recorded in whole-cell configuration, using ionic conditions that activated maximally the exchanger in both forward and reverse mode. In all species examined (amphibia: Rana esculenta and Ambystoma mexicanum; reptilia: Gecko gecko), the forward (reverse) exchange current increased about linearly for negative (positive) voltages and exhibited outward (inward) rectification for positive (negative) voltages. Since hyperpolarisation increases Ca(2+) extrusion rate, the recovery of the dark level of Ca(2+) (and, in turn, of the generator potential) after intense light stimuli results accelerated. Mg-ATP increased the size of forward and reverse exchange current by a factor of approximately 2.3 and approximately 2.6, respectively, without modifying their voltage dependence. This indicates that Mg-ATP regulates the number of active exchanger sites and/or the exchanger turnover number, although via an unknown mechanism.

Reduction of CaO and MgO Slag Components by Al in Liquid Fe

NASA Astrophysics Data System (ADS)

Mu, Haoyuan; Zhang, Tongsheng; Fruehan, Richard J.; Webler, Bryan A.

2018-05-01

This study documents laboratory-scale observations of reactions between Fe-Al alloys (0.1 to 2 wt pct Al) with slags and refractories. Al in steels is known to reduce oxide components in slag and refractory. With continued development of Al-containing Advanced High-Strength Steel (AHSS) grade, the effects of higher Al must be examined because reduction of components such as CaO and MgO could lead to uncontrolled modification of non-metallic inclusions. This may lead to castability or in-service performance problems. In this work, Fe-Al alloys and CaO-MgO-Al2O3 slags were melted in an MgO crucible and samples were taken at various times up to 60 minutes. Inclusions from these samples were characterized using an automated scanning electron microscope equipped with energy dispersive x-ray analysis (SEM/EDS). Initially Al2O3 inclusions were modified to MgAl2O4, then MgO, then MgO + CaO-Al2O3-MgO liquid inclusions. Modification of the inclusions was faster at higher Al levels. Very little Ca modification was observed except at 2 wt pct Al level. The thermodynamic feasibility of inclusion modification and some of the mass transfer considerations that may have led to the differences in the Mg and Ca modification behavior were discussed.

Identification of residues that control Li+ versus Na+ dependent Ca2+ exchange at the transport site of the mitochondrial NCLX.

PubMed

Roy, Soumitra; Dey, Kuntal; Hershfinkel, Michal; Ohana, Ehud; Sekler, Israel

2017-06-01

The Na + /Ca 2+ /Li + exchanger (NCLX) is a member of the Na + /Ca 2+ exchanger family. NCLX is unique in its capacity to transport both Na + and Li + , unlike other members, which are Na + selective. The major aim of this study was twofold, i.e., to identify NCLX residues that confer Li + or Na + selective Ca 2+ transport and map their putative location on NCLX cation transport site. We combined molecular modeling to map transport site of NCLX with euryarchaeal H + /Ca 2+ exchanger, CAX_Af, and fluorescence analysis to monitor Li + versus Na + dependent mitochondrial Ca 2+ efflux of transport site mutants of NCLX in permeabilized cells. Mutation of Asn149, Pro152, Asp153, Gly176, Asn467, Ser468, Gly494 and Asn498 partially or strongly abolished mitochondrial Ca 2+ exchange activity in intact cells. In permeabilized cells, N149A, P152A, D153A, N467Q, S468T and G494S demonstrated normal Li + /Ca 2+ exchange activity but a reduced Na + /Ca 2+ exchange activity. On the other hand, D471A showed dramatically reduced Li + /Ca 2+ exchange, but Na + /Ca 2+ exchange activity was unaffected. Finally, simultaneous mutation of four putative Ca 2+ binding residues was required to completely abolish both Na + /Ca 2+ and Li + /Ca 2+ exchange activities. We identified distinct Na + and Li + selective residues in the NCLX transport site. We propose that functional segregation in Li + and Na + sites reflects the functional properties of NCLX required for Ca 2+ exchange under the unique membrane potential and ion gradient across the inner mitochondrial membrane. The results of this study provide functional insights into the unique Li + and Na + selectivity of the mitochondrial exchanger. This article is part of a Special Issue entitled: ECS Meeting edited by Claus Heizmann, Joachim Krebs and Jacques Haiech. Copyright © 2017 Elsevier B.V. All rights reserved.

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. Copyright © 2012 S. Karger AG, Basel.

Synthesis and structural characterization of the hexagonal anti-perovskite Na{sub 2}CaVO{sub 4}F

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

Green, Robert L., E-mail: rgreen@flpoly.org; Avdeev, Maxim; School of Chemistry, The University of Sydney, Sydney, NSW 2006

The structural details of the ordered hexagonal oxyfluoride Na{sub 2}CaVO{sub 4}F prepared by solid-state synthesis using stoichiometric amounts of V{sub 2}O{sub 5}, CaCO{sub 3}, Na{sub 2}CO{sub 3} and NaF were characterized using high-resolution neutron powder diffraction. The structural changes between 25 °C and 750 °C revealed that the two structural subunits in this material behave different when heated: there is an expansion of the face-shared FNa{sub 4}Ca{sub 2} octahedra while the VO{sub 4} tetrahedra due to increased thermal disorder reveal marginal bond contractions. Bond valences and the global instability index point to significant structural disorder at 750 °C. - Graphicalmore » abstract: The structure of the novel oxyfluoride Na{sub 2}CaVO{sub 4}F is studied at room temperature and high-temperatures. The structure can be viewed as layers of compression and elongation of polyhedral subunits, which change as a function of temperature. - Highlights: • The novel oxyfluoride, Na{sub 2}CaVO{sub 4}F, is synthesized via solid-state method. • High-resolution neutron diffraction data is used to analyze the structure of Na{sub 2}CaVO{sub 4}F. • Structural subunits exhibit expansion and contraction with increasing temperature. • Higher temperatures increase instability within the structure of Na{sub 2}CaVO{sub 4}F.« less

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

NASA Astrophysics Data System (ADS)

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

2016-08-01

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

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

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

Martens, E., E-mail: evelien.martens@csiro.a; Jacques, D.; Van Gerven, T.

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 leachingmore » 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.« less

Phase Transformation and Creep of Mg-Al-Ca Based Die-Cast Alloys

NASA Astrophysics Data System (ADS)

Suzuki, Akane; Saddock, Nicholas D.; Jones, J. Wayne; Pollock, Tresa M.

The microstructure and microstructural stability of die-cast AC53 (Mg-5Al-3Ca) and AXJ530 (Mg-5Al-3Ca-0.15Sr) have been investigated in detail by transmission electron microscopy (TEM). Both alloys have an as-cast microstructure of α-Mg with (Mg, Al)2Ca (dihexagonal C36) eutectic at grain boundaries. During aging at 573 K, the C36 phase transforms to Al2Ca (cubic Cl5) phase. These two phases have a crystallographic orientation relationship of (0001)C36//{111}C15 and [2110]C36//[011]C15, and the transformation from C36 to C15 occurs by a shear-assisted process. Despite this change in the phase constitution, the network structure of the intermetallic compound(s) surrounding α-Mg grains is fairly stable, morphologically, even after prolonged exposure at elevated temperature. In the α-Mg matrix phase, precipitation of Al2Ca was observed after aging for 360 ks at 573 K. The precipitates are disc-shaped with a habit plane of {111}C15//(0001)α. AXJ530 shows higher creep resistance than AC53. The dislocation substructure that evolved during creep deformation was investigated in both alloys, and the basal and non-basal slip of a-dislocation and other slip modes of a+c- dislocations were observed. The relationship between creep properties and microstructure is discussed.

"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…

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.

L-type Ca(2+) currents overlapping threshold Na(+) currents: could they be responsible for the "slip-mode" phenomenon in cardiac myocytes?

PubMed

Piacentino, Valentino; Gaughan, John P; Houser, Steven R

2002-03-08

Phosphorylation of Na channels has been suggested to increase their Ca permeability. Termed "slip-mode conductance" (SMC), this hypothesis predicts that Ca influx via protein kinase A (PKA)-modified Na channels can induce sarcoplasmic reticulum (SR) Ca release. We tested this hypothesis by determining if SR Ca release is graded with I(Na) in the presence of activated PKA (with Isoproterenol, ISO). V(m), I(m), and [Ca](i) were measured in feline (n=26) and failing human (n=19) ventricular myocytes. Voltage steps from -70 through -40 mV were used to grade I(Na). Na channel antagonists (tetrodotoxin), L-type Ca channel (I(Ca,L)) antagonists (nifedipine, cadmium, verapamil), and agonists (Bay K 8644, FPL 64176) were used to separate SMC from I(Ca,L). In the absence of ISO, I(Na) was associated with SR Ca release in human but not feline myocytes. After ISO, graded I(Na) was associated with small amounts of SR Ca release in feline myocytes and the magnitude of release increased in human myocytes. I(Na)-related SR Ca release was insensitive to tetrodotoxin (n=10) but was blocked by nifedipine (n=10) and cadmium (n=3). SR Ca release was induced over the same voltage range in the absence of ISO with Bay K 8644 and FPL 64176 (n=9). Positive voltage steps (to 0 mV) to fully activate Na channels (SMC) in the presence of ISO and Verapamil only caused SR Ca release when block of I(Ca,L) was incomplete. We conclude that PKA-mediated increases in I(Ca,L) and SR Ca loading can reproduce many of the experimental features of SMC.

Tetragonal Almandine, (Fe,Mg,Ca,Na)3(Al,Si,Mg)2Si3O12, a New High-Pressure Mineral from the Shergotty Impact on Mars: an Integrated FESEM-EPMA-Synchrotron Diffraction Investigation

NASA Astrophysics Data System (ADS)

Ma, C.; Tschauner, O. D.

2016-12-01

The combination of FESEM-EDS-EBSD, EPMA, and synchrotron microdiffraction is developing into a powerful tool for identification of micron-scale minerals in rocks such as high-pressure phases in shocked meteorites. During a nanomineralogy investigation of the Shergotty meteorite using this approach, we have identified a new shock-induced high-pressure silicate, majoritic almandine with a tetragonal I41/a structure, in an impact melt pocket. The Shergotty meteorite, which fell in the Gaya district, Bihar, India in 1865, is a Martian basaltic shergottite with shock features. Tetragonal almandine in Shergotty occurs as aggregates of subhedral crystals, 0.8 - 2.5 µm in diameter, along with stishovite in the central region of a shock melt pocket, showing an empirical formula of (Fe1.16Ca0.75Mg0.61Na0.42Mn0.03K0.01)(Al1.16Si0.63Mg0.19Ti0.02)Si3O12. Its general formula is (Fe,Mg,Ca,Na)3(Al,Si,Mg)2Si3O12. EBSD indicated this phase has a garnet-related structure. Synchrotron X-ray diffraction revealed that this garnet has actually a tetragonal structure (I41/a) with unit cell dimensions: a = 11.585(9) Å, c = 11.63(4) Å, V = 1561(7) Å3, and Z = 8. Tetragonal almandine is the polymorph of cubic almandine, a new high-pressure garnet mineral, formed by shock metamorphism via the Shergotty impact event on Mars. It apparently crystallized from Fe-rich shock-induced melt under high-pressure and high-temperature conditions.

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.

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

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

Jeon, Dongho; Jun, Yubin; Jeong, Yeonung

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) porositymore » 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}.« less

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.

Study on the Anti-Poison Performance of Al-Y-P Master Alloy for Impurity Ca in Aluminum Alloys.

PubMed

Zuo, Min; Dong, Yu; Zhao, Degang; Wang, Yan; Teng, Xinying

2017-11-26

In this article, the anti-poison performance of novel Al-6Y-2P master alloy for impurity Ca in hypereutectic Al-Si alloys was investigated in detail. According to the microstructural analysis, it can be found that the primary Si and eutectic Si particles could be relatively modified and refined. In order to investigate the influence mechanism of Ca on the limited refinement performance of Al-6Y-2P master alloy, types of Al-xSi-2Ca-3Y-1P (x = 0, 6, 12, 18, and 30) alloys were prepared. It is observed that Ca takes the form of more stable Ca3P2 compounds by reacting with YP, and the surface of Ca3P2 particles are unsmooth, and even some have wrinkles in Al Al-2Ca-3Y-1P alloy. With the increase of Si content in Al-xSi-2Ca-3Y-1P (x = 6, 12, 18 and 30) systems, the multi-encapsulation structures, i.e., the phosphide (AlP and YP), hexagonal Al2Si2Ca, the Al3Si2Y2 or primary Si from inside to outside in order were examined.The excapsulation of YP and AlP caused by Al2Si2Ca might be the reason for the limited refinement effect of Al-6Y-2P master alloy for hypereutectic Al-18Si alloys.

Solvent Free Transesterification of Glycerol Into Glycerol Carbonate Over Nanostructured CaAl Hydrotalcite Catalyst.

PubMed

Devarajan, Arulselvan; Thiripuranthagan, Sivakumar; Radhakrishnan, Ramakrishnan; Kumaravel, Sakthivel

2018-07-01

Drastic increase in green house gases due to fossil fuels usage urges the mankind to look for alternative fuel resources. Biodiesel is one of the alternative fuels which attracted the attention of many researchers. In recent years, bio-diesel drags much attention as an alternative clean fuel. Glycerol is an unavoidable byproduct in the transesterification process of vegetable oils into bio diesel and therefore market is flooded with glycerol. So it is high time to find ways of utilizing the abundant glycerol into value added products. Herein we report the catalytic transesterification of glycerol using dimethyl carbonate over MgAl-hydrotalcite (MgAl-HT), CaAl-hydrotalcite (CaAl-HT) and nano structured CaAl-HT catalysts. All the catalysts were characterized by XRD, FT-IR, TPD-CO2, BET, SEM and HR-TEM techniques. Among them Ca4Al-HT was found to be best in terms of conversion of glycerol (82.4%) and selectivity (95.9%) towards glycerol carbonate. The effect of CTAB template concentration in the nano synthesis of Ca4Al-HT on conversion and selectivity was studied and Ca4Al-HT synthesized with 0.4 moles of CTAB showed the best conversion of glycerol (98.7%) and the highest selectivity towards glycerol carbonate (97.9%). The recyclability test performed with the best catalyst showed that the catalyst was recyclable even after 5 cycles. Valorization of glycerol yields glycerol carbonate (GC) which is a very good polar solvent with high boiling point, building block in several organic syntheses and used in the production of surfactants, poly urethanes etc.

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

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.%.

Thermodynamic properties of Na2O-SiO2-CaO melts at 1000 to 1100 °C

NASA Astrophysics Data System (ADS)

Neudorf, D. A.; Elliott, J. F.

1980-12-01

The thermodynamic properties of Na2O-SiO2 and Na2O-SiO2-CaO melts have been measured using the galvanic cellbegin{array}{*{20}c} {O_2 (g), (Na_2 O), Pt} \\ {Na_2 O - WO_3 liq} \\ left| begin{gathered} Na^ + \\ β - alumina \\ right| begin{array}{*{20}c} {Pt,(Na_2 O), O_2 (g)} \\ {Na_2 O - SiO_2 - CaO liq} \\ Activities of Na2O were calculated from the reversible emf of the cell. This is possible because the activity of Na2O in the Na2O-WO3 liquid is known from previous work. Data for the binary Na2O-SiO2 system were obtained between 1000 and 1100 °C and for compositions ranging from 25 wt pct to 40 wt pct Na2O. At 1050 °C, Loga_{Na_2 O} varied from approximately 10.2 at 25 wt pct Na2O to approximately -8.3 at 40 wt pct Na2O, the dependence with respect to composition being nearly linear. The Gibbs-Duhem equation was used to calculate the activities of SiO2(s), and the integral mixing properties, G M, HM, and S M, were derived. At the di-silicate composition, G M = -83 kJ/mol, H M = -41 kJ mol and S M = 33 J/mol K at 1000 °C. (Standard states are pure, liquid Na2O and pure, solid tridymite.) The activity data are interpreted in terms of the polymeric nature of silicate melts. Activities of Na2O in the Na2O-CaO-SiO2 system were measured for the 25, 30 and 35 wt pct Na2O binary compositions with up to 10 wt pct CaO added. The addition of CaO caused an increase in the activity of Na2O at constantN_{Na_2 O} /N_{SiO_2 } . The experimental data agree well with the behavior predicted by Richardson’s ternary mixing model.

Effects of Ca/Sr ratio control on optical and scintillation properties of Eu-doped Li(Ca,Sr)AlF6 single crystals

NASA Astrophysics Data System (ADS)

Yokota, Yuui; Tanaka, Chieko; Kurosawa, Shunsuke; Yamaji, Akihiro; Ohashi, Yuji; Kamada, Kei; Nikl, Martin; Yoshikawa, Akira

2018-05-01

Eu-doped Li(Ca,Sr)AlF6 [Eu:LiCSAF] single crystals with various Ca/Sr ratios were grown by the micro-pulling-down method, and their optical and scintillation properties were investigated to reveal the effects of Ca/Sr ratio on optical and scintillation properties of the Eu:LiCSAF single crystals. The Li(Ca1-x-ySrxEuy)AlF6 single crystals could be grown in 0 ≤ x ≤ 0.1, 0.5 ≤ x ≤ 1.0 and y = 0.02 while the Eu:LiCSAF crystals with x = 0.2, 0.25 and 0.4 included two colquiriite-type phases with different lattice parameters. The Li(Ca1-x-ySrxEuy)AlF6 single crystal with x = 0.25 and y = 0.02 showed the highest light yield under neutron irradiation.

Phase Diagram of the Al-Ca-Fe-Si System and Its Application for the Design of Aluminum Matrix Composites

NASA Astrophysics Data System (ADS)

Belov, Nikolay A.; Naumova, Evgeniya A.; Akopyan, Torgom K.; Doroshenko, Vitaliy V.

2018-05-01

The phase composition of aluminum alloys in the Al-Ca-Fe-Si system, including the distribution of phases in the solid state and solidification reactions, has been studied. It is shown that the addition of iron and silicon to Al-Ca alloys leads to the formation of ternary Al2CaSi2 and Al10CaFe2 compounds. The equilibrium between these compounds implies the occurrence of the quaternary L → Al + Al4Ca + Al2CaSi2 + Al10CaFe2 eutectic reaction. The alloys near this eutectic have the best structure, which is typical of aluminum matrix composites. It is shown that Al-Ca alloys can have high manufacturability during both shape casting and rolling. This is due to the combination of a narrow temperature range of solidification and a favorable morphology for the eutectic, which has a fine structure. The combination of the mechanical and physical properties of the Al-Ca eutectic-based alloys significantly exceed those of branded alloys based on aluminum-silicon eutectics.

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

Effect of Substituted Ca on the Thermoelectric and Optoelectronic Properties of NaRh2O4 Under Pressure

NASA Astrophysics Data System (ADS)

Rahnamaye Aliabad, H. A.; Hosseini, N.

2018-03-01

In this paper, we have used the first principle calculations for investigation of the structural, optoelectronic and thermoelectric properties of NaRh2O4 compound and substituted with Ca onto the Na sites under pressure. The results show that there are two direct band gaps for the NaRh2O4 compound and three indirect band gaps for the CaRh2O4 compound at the top of the Fermi level. The size of the band gaps increases almost linearly with the increase of the pressure up to 37 GPa. The calculated density of states for the CaRh2O4 compound show that the Ca-3 p state plays a key role for enhancement of the thermoelectric figure of merit ( ZT). We found that the static dielectric function value decreases along the x, y and z directions for the CaRh2O4 compound with the increase of the pressure while it is constant along the x and y directions for the NaRh2O4 compound. The birefringence properties with metallic nature are achieved from the optical spectra. The thermoelectric results show that the maximum peak of the ZT shifts towards the higher value of temperature for the NaRh2O4 compound. The Ca substitution onto the Na sites in the NaRh2O4 compound enhances the ZT value of 0.79 at 250 K.

Na(+)/Ca(2+) exchange regulates Ca(2+)-dependent duodenal mucosal ion transport and HCO(3)(-) secretion in mice.

PubMed

Dong, Hui; Sellers, Zachary M; Smith, Anders; Chow, Jimmy Y C; Barrett, Kim E

2005-03-01

Stimulation of muscarinic receptors in duodenal mucosa raises intracellular Ca(2+), which regulates ion transport, including HCO(3)(-) secretion. However, the underlying Ca(2+) handling mechanisms are poorly understood. The aim of the present study was to determine whether Na(+)/Ca(2+) exchanger (NCX) plays a role in the regulation of duodenal mucosal ion transport and HCO(3)(-) secretion by controlling Ca(2+) homeostasis. Mouse duodenal mucosa was mounted in Ussing chambers. Net ion transport was assessed as short-circuit current (I(sc)), and HCO(3)(-) secretion was determined by pH-stat. Expression of NCX in duodenal mucosae was analyzed by Western blot, and cytosolic Ca(2+) in duodenocytes was measured by fura 2. Carbachol (100 muM) increased I(sc) in a biphasic manner: an initial transient peak within 2 min and a later sustained plateau starting at 10 min. Carbachol-induced HCO(3)(-) secretion peaked at 10 min. 2-Aminoethoxydiphenylborate (2-APB, 100 muM) or LiCl (30 mM) significantly reduced the initial peak in I(sc) by 51 or 47%, respectively, and abolished the plateau phase of I(sc) without affecting HCO(3)(-) secretion induced by carbachol. Ryanodine (100 muM), caffeine (10 mM), and nifedipine (10 muM) had no effect on either response to carbachol. In contrast, nickel (5 mM) and KB-R7943 (10-30 muM) significantly inhibited carbachol-induced increases in duodenal mucosal I(sc) and HCO(3)(-) secretion. Western blot analysis showed expression of NCX1 proteins in duodenal mucosae, and functional NCX in duodenocytes was demonstrated in Ca(2+) imaging experiments where Na(+) depletion elicited Ca(2+) entry via the reversed mode of NCX. These results indicate that NCX contributes to the regulation of Ca(2+)-dependent duodenal mucosal ion transport and HCO(3)(-) secretion that results from stimulation of muscarinic receptors.

A novel red phosphor Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} for near UV white light-emitting diodes

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

Yang, Zhigang; Zhao, Zhengyan; Shi, Yurong

2013-10-15

Graphical abstract: - Highlights: • Novel red phosphor Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} was prepared by solid-state reaction. • Excitation spectra suggested an obvious absorption in near-ultraviolet region. • Under 392 nm excitation, the phosphors exhibited a red emission at 614 nm. • Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} could be potentially applied in near UV white LEDs. - Abstract: A novel red phosphor Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} was synthesized using a solid-state reaction method, and its luminescence characteristics and charge compensators effect (Li{sup +}, Na{sup +}, K{sup +}) were investigated. The excitation spectra showed a obviousmore » absorption in near-ultraviolet region. Under 392 nm excitation, the phosphors exhibited an intense red emission at 614 nm. The Commission Internationale de l’Eclairage (CIE) chromaticity coordinates and quantum efficiency (QE) were (0.65, 0.35) and 62.3%, respectively. The good color saturation, high quantum efficiency and small thermal-quenching properties indicate that Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 3+} could be potentially applied in near UV white light-emitting diodes.« less

KH+Ti co-doped NaAlH4 for high-capacity hydrogen storage

NASA Astrophysics Data System (ADS)

Wang, Ping; Kang, Xiang-Dong; Cheng, Hui-Ming

2005-10-01

A method for preparation of Ti-doped NaAlH4 with high hydrogen capacity was developed, in which the NaH/Al mixture was mechanically milled with a catalytic amount of KH together with metallic Ti. The addition of KH was found to result in a pronounced improvement in the dehydriding performance of the Na3AlH6/NaH+Al step. As a result, the practical cycling hydrogen capacity has been markedly enhanced from 3.3 wt % for the Ti-doped hydride to 4.7 wt % for KH+Ti co-doped material. Moreover, the pronounced enhancement on hydrogen capacity arising upon adding KH was observed to persist in the following dehydrogenation/hydrogenation cycles. Structural investigation shows that the addition of KH has led to a lattice expansion. Moreover, it was found that the enthalpy change of the Na3AlH6/NaH+Al decomposition step underwent a considerable decrease upon adding KH. Therefore, the observed property improvement may be ascribed to a favorable thermodynamic adjustment arising upon the addition of KH.

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

(Sr{sub 1-x}Na{sub x})(Cd{sub 1-x}Mn{sub x}){sub 2}As{sub 2}: A new charge and spin doping decoupled diluted magnetic semiconductors with CaAl{sub 2}Si{sub 2}-type structure

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

Chen, Bijuan; Deng, Zheng; Li, Wenmin

2016-08-28

We report the synthesis and characterization of a new bulk diluted ferromagnetic semiconductor via Na and Mn co-doping in SrCd{sub 2}As{sub 2} with a hexagonal CaAl{sub 2}Si{sub 2}-type structure. Together with carrier doping via (Sr,Na) substitution, spin doping via (Cd,Mn) substitution results in ferromagnetic order with Curie temperature of T{sub C} up to 13 K. Negative magnetoresistance is assigned to weak localization at low temperatures, where the magnetization of samples becomes saturated. The hexagonal structure of (Sr{sub 1−x}Na{sub x})(Cd{sub 1−x}Mn{sub x}){sub 2}As{sub 2} can be acted as a promising candidate for spin manipulations owing to its relatively small coercive field ofmore » less than 24 Oe.« less

Precursor preparation for Ca-Al layered double hydroxide to remove hexavalent chromium coexisting with calcium and magnesium chlorides

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

Zhong, Lihua; He, Xiaoman; Qu, Jun

Al(OH){sub 3} and Ca(OH){sub 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 kineticsmore » 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. - Graphical abstract: Activated Ca-Al hydroxides (C{sub 3}A) transformed into Ca-Al-OH compound when agitated in water. Ca-Al precursor (C{sub 3}A) was agitated in a hexavalent chromium (Cr(VI)) solution to form Al-Ca-CrO{sub 4} LDH product. Ca-Al-CrO{sub 4} LDH phase occurred preferentially to Ca-Al-MCl{sub 2} LDH phases in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist. - Highlights: • Activated Ca-Al hydroxides transformed into LDH when agitated in water with some inorganic substances. • Hexavalent Cr was incorporated in the LDH structure at high adsorption capacity. • Ca-Al-Cr LDH phase occurred preferentially to Ca-Al-MCl{sub 2} LDH phases with coexistence. • The prepared Ca-Al hydroxides had high performance as adsorbent even with high salinity of the solution.« less

Directionally solidified Eu doped CaF2/Li3AlF6 eutectic scintillator for neutron detection

NASA Astrophysics Data System (ADS)

Kamada, Kei; Hishinuma, Kousuke; Kurosawa, Shunsuke; Shoji, Yasuhiro; Pejchal, Jan; Ohashi, Yuji; Yokota, Yuui; Yoshikawa, Akira

2015-12-01

Eu doped CaF2/Li3AlF6 eutectics were grown by μ-PD method. The directionally solidified eutectic with well-aligned 600 nm diameter Eu:CaF2 scintillator fibers surrounded with Li3AlF6 was prepared. The grown eutectics showed an emission peak at 422 nm ascribed to Eu2+ 4f-5d transition from Eu:CaF2 scintillation fiber. Li concentration in the Eu:CaF2-Li3AlF6 eutectic is around 0.038 mol/cm3,which is two times higher than that of LiCaAlF6 single crystal (0.016 mol/cm3). The light yield of Eu:CaF2-Li3AlF6 eutectic was around 7000 ph/neutron. The decay time was about 550 ns (89%) and 1450 ns (11%).

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

PubMed

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

2007-08-30

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

The therapeutic potential of Na+ and Ca2+ channel blockers in pain management.

PubMed

Sabido-David, Cibele; Faravelli, Laura; Salvati, Patricia

2004-10-01

Chronic pain affects a large percentage of the population, representing a socio-economic burden. Current treatments are characterised by suboptimal efficacy and/or side effects that limit their use. Among several approaches to treating chronic pain, voltage-sensitive Ca(2+) and Na(+) channels are promising targets. This review evaluates the preclinical evidence that supports the involvement of these targets, with specific attention to those subtypes that appear more strictly correlated with pain generation and sustainment, as well as those compounds that modulate the activity of Ca(2+) and/or Na(+) channels that are currently in clinical development for chronic pain conditions.

Na/Ca Intermixing around Silicate and Phosphate Groups in Bioactive Phosphosilicate Glasses Revealed by Heteronuclear Solid-State NMR and Molecular Dynamics Simulations.

PubMed

Mathew, Renny; Stevensson, Baltzar; Edén, Mattias

2015-04-30

We characterize the intermixing of network-modifying Na(+)/Ca(2+) ions around the silicate (QSi(n)) and phosphate (QP(n)) tetrahedra in a series of 16 Na2O–CaO–SiO2–P2O5 glasses, whose P content and silicate network connectivity were varied independently. The set includes both bioactive and bioinactive compositions and also encompasses two soda-lime-silicate members devoid of P, as well as two CaO–SiO2 glasses and one Na2O–SiO2–P2O5 glass. The various Si/P↔Na/Ca contacts were probed by molecular dynamics (MD) simulations together with heteronuclear magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) experimentation utilizing (23)Na{(31)P} and (23)Na{(29)Si} REDOR, as well as (31)P{ (23)Na} and (29)Si{(23)Na} REAPDOR. We introduce an approach for quantifying the extent of Na(+)/Ca(2+) ordering around a given QP(n) or QSi(n) group, encoded by the preference factor 0⩽ PM ⩽ 1 conveying the relative weights of a random cation intermixing (PM = 0) and complete preference/ordering (PM = 1) for one of the species M, which represents either Na(+) or Ca(2+). The MD-derived preference factors reveal phosphate and silicate species surrounded by Na(+)/Ca(2+) ions intermixed nearly randomly (PM ≲ 0.15), except for the QSi(4) and QSi(1) groups, which manifest more significant cation ordering with preference for Na+ and Ca2+, respectively. The overall weak preferences are essentially independent of the Si and P contents of the glass, whereas PM primarily correlates with the total amount of network modifiers: as the latter is increased, the Na/Ca distribution around the {QP(0), QSi(1), QSi(2)} groups with preference for Ca2(+ )tend to randomize (i.e., PCa decreases), while the PNa-values grow slightly for the {QP(1), QSi(3), QSi(4)} species already preferring coordination of Na. The set of experimental preference factors {PCa} for the orthophosphate (QP(0)) groups extracted from (31)P{(23)Na} REAPDOR NMR-derived M2(P–Na) dipolar second moments agrees

Critical contribution of Na+-Ca2+ exchanger to the Ca2+-mediated vasodilation activated in endothelial cells of resistance arteries.

PubMed

Lillo, Mauricio A; Gaete, Pablo S; Puebla, Mariela; Ardiles, Nicolás M; Poblete, Inés; Becerra, Alvaro; Simon, Felipe; Figueroa, Xavier F

2018-04-01

Na + -Ca 2+ exchanger (NCX) contributes to control the intracellular free Ca 2+ concentration ([Ca 2+ ] i ), but the functional activation of NCX reverse mode (NCXrm) in endothelial cells is controversial. We evaluated the participation of NCXrm-mediated Ca 2+ uptake in the endothelium-dependent vasodilation of rat isolated mesenteric arterial beds. In phenylephrine-contracted mesenteries, the acetylcholine (ACh)-induced vasodilation was abolished by treatment with the NCXrm blockers SEA0400, KB-R7943, or SN-6. Consistent with that, the ACh-induced hyperpolarization observed in primary cultures of mesenteric endothelial cells and in smooth muscle of isolated mesenteric resistance arteries was attenuated by KB-R7943 and SEA0400, respectively. In addition, both blockers abolished the NO production activated by ACh in intact mesenteric arteries. In contrast, the inhibition of NCXrm did not affect the vasodilator responses induced by the Ca 2+ ionophore, ionomycin, and the NO donor, S-nitroso- N-acetylpenicillamine. Furthermore, SEA0400, KB-R7943, and a small interference RNA directed against NCX1 blunted the increase in [Ca 2+ ] i induced by ACh or ATP in cultured endothelial cells. The analysis by proximity ligation assay showed that the NO-synthesizing enzyme, eNOS, and NCX1 were associated in endothelial cell caveolae of intact mesenteric resistance arteries. These results indicate that the activation of NCXrm has a central role in Ca 2+ -mediated vasodilation initiated by ACh in endothelial cells of resistance arteries.-Lillo, M. A., Gaete, P. S., Puebla, M., Ardiles, N. M., Poblete, I., Becerra, A., Simon, F., Figueroa, X. F. Critical contribution of Na + -Ca 2+ exchanger to the Ca 2+ -mediated vasodilation activated in endothelial cells of resistance arteries.

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

PubMed Central

Haase, Andreas; Hartung, Klaus

2009-01-01

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

The effect of NaCl/g/ on the Na2SO4-induced hot corrosion of NiAl

NASA Technical Reports Server (NTRS)

Smeggil, J. G.; Bornstein, N. S.; Decrescente, M. A.

1977-01-01

Studies have been performed to examine the effect of NaCl vapor on the Na2SO4-induced hot corrosion of the alumina former NiAl. In the incubation period associated with such hot corrosion, NaCl(g) has been shown to be effective in removing aluminum from below the protective alumina scale and redepositing it as Al2O3 whiskers on the surface of the Na2SO4-coated sample. Similar effects seen in simple oxidation are associated with isothermal rupturing of the protective alumina scale.

Na+/Ca2+ exchange and regulation of cytoplasmic concentration of calcium in rat cerebellar neurons treated with glutamate.

PubMed

Storozhevykh, T P; Sorokina, E G; Vabnitz, A V; Senilova, Ya E; Tukhbatova, G R; Pinelis, V G

2007-07-01

In the present work, the forward and/or reversed Na+/Ca2+ exchange in cerebellar granular cells was suppressed by substitution of Na+o by Li+ before, during, and after exposure to glutamate for varied time and also using the inhibitor KB-R7943 of the reversed exchange. After glutamate challenge for 1 min, Na+o/Li+ substitution did not influence the recovery of low [Ca2+]i in a calcium-free medium. A 1-h incubation with 100 microM glutamate induced in the neurons a biphasic and irreversible [Ca2+]i rise (delayed calcium deregulation (DCD)), enhancement of [Na+]i, and decrease in the mitochondrial potential. If Na+o had been substituted by Li+ before the application of glutamate, i.e. the exchange reversal was suppressed during the exposure to glutamate, the number of cells with DCD was nearly fourfold lowered. However, addition of the Na+/K+-ATPase inhibitor ouabain (0.5 mM) not preventing the exchange reversal also decreased DCD in the presence of glutamate. Both exposures decreased the glutamate-caused loss of intracellular ATP. Glucose deprivation partially abolished protective effects of the Na+o/Li+ substitution and ouabain. KB-R7943 (10 microM) increased 7.4-fold the number of cells with the [Ca2+]i decreased to the basal level after the exposure to glutamate. Thus, reversal of the Na+/Ca2+ exchange reinforced the glutamate-caused perturbations of calcium homeostasis in the neurons and slowed the recovery of the decreased [Ca2+]i in the post-glutamate period. However, for development of DCD, in addition to the exchange reversal, other factors are required, in particular a decrease in the intracellular concentration of ATP.

Mg-Al-Ca In-Situ Composites with a Refined Eutectic Structure and Their Compressive Properties

NASA Astrophysics Data System (ADS)

Shi, Ling-Ling; Xu, Jian; Ma, Evan

2008-05-01

In a series of Mg x (Al2Ca)100- x (76 ≤ x ≤ 87) ternary alloys near the Mg-(Mg,Al)2Ca pseudo-binary eutectic point, different phases and morphologies based on ultrafine eutectic microstructure have been obtained by controlling the composition and changing the cooling rate via either induction melting or copper mold casting. For 81 ≤ x ≤ 87, the chill-cast alloys with ductile Mg dendrites embedded in an ultrafine [Mg + (Mg,Al)2Ca] eutectic matrix exhibit gradually increased fracture strength from 415 to 491 MPa with the decrease of Mg content. At x = 79, the Mg79Al14Ca7 alloy contains hard (Mg,Al)2Ca precipitates coexisting with ductile Mg dendrite, dispersed in the strong eutectic matrix. This alloy exhibits the highest compressive fracture strength (600 MPa), and the specific strength reaches 3.4 × 105 N·m·kg-1. The alloys all exhibit substantial plastic strain (5 to 6 pct). The attainment of such a combination of strength and plasticity is an interesting and useful step in improving the mechanical properties of lightweight Mg alloys.

Microstructure, Tensile Properties, and Corrosion Behavior of Die-Cast Mg-7Al-1Ca- xSn Alloys

NASA Astrophysics Data System (ADS)

Wang, Feng; Dong, Haikuo; Sun, Shijie; Wang, Zhi; Mao, Pingli; Liu, Zheng

2018-02-01

The microstructure, tensile properties, and corrosion behavior of die-cast Mg-7Al-1Ca- xSn ( x = 0, 0.5, 1.0, and 2.0 wt.%) alloys were studied using OM, SEM/EDS, tensile test, weight loss test, and electrochemical test. The experimental results showed that Sn addition effectively refined grains and intermetallic phases and increased the amount of intermetallic phases. Meanwhile, Sn addition to the alloys suppressed the formation of the (Mg,Al)2Ca phase and resulted in the formation of the ternary CaMgSn phase and the binary Mg2Sn phase. The Mg-7Al-1Ca-0.5Sn alloy exhibited best tensile properties at room temperature, while Mg-7Al-1Ca-1.0Sn alloy exhibited best tensile properties at elevated temperature. The corrosion resistance of studied alloys was improved by the Sn addition, and the Mg-7Al-1Ca-0.5Sn alloy presented the best corrosion resistance.

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.

Crystal structure of Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2} and luminescence properties of Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 2+}

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

Iwata, Tomoyuki; Haniuda, Masahide; Fukuda, Koichiro

2008-01-15

The crystal structure of Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2} was determined from laboratory X-ray powder diffraction data (CuK{alpha}{sub 1}) using the Rietveld method, with the anisotropic displacement parameters being assigned for all atoms. The crystal structure is cubic (space group I4-bar 3d, Z=2) with lattice dimensions a=1.200950(5) nm and V=1.73211(1) nm{sup 3}. The reliability indices calculated from the Rietveld method were R{sub wp}=8.48% (S=1.21), R{sub p}=6.05%, R{sub B}=1.27% and R{sub F}=1.01%. The validity of the structural model was verified by the three-dimensional electron density distribution, the structural bias of which was reduced as much as possible using the maximum-entropy methods-basedmore » pattern fitting (MPF). The reliability indices calculated from the MPF were R{sub B}=0.75% and R{sub F}=0.56%. In the structural model there are one Ca site, two Al sites, two O sites and one Cl site. This compound is isomorphous with Ca{sub 12}Al{sub 10.6}Si{sub 3.4}O{sub 32}Cl{sub 5.4}. Europium-doped sample Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2}:Eu{sup 2+} was prepared and the photoluminescence properties were presented. The excitation spectrum consisted of two wide bands, which were located at about 268 and 324 nm. The emission spectrum, when excited at 324 nm, resulted in indigo light with a peak at about 442 nm. - Graphical abstract: A portion of the crystal structure of Ca{sub 12}Al{sub 14}O{sub 32}Cl{sub 2} showing eight-membered AlO{sub 4} rings and Ca-Cl-Ca unit.« less

Sensitivity of Rabbit Ventricular Action Potential and Ca2+ Dynamics to Small Variations in Membrane Currents and Ion Diffusion Coefficients

PubMed Central

Lo, Yuan Hung; Peachey, Tom; Abramson, David; McCulloch, Andrew

2013-01-01

Little is known about how small variations in ionic currents and Ca2+ and Na+ diffusion coefficients impact action potential and Ca2+ dynamics in rabbit ventricular myocytes. We applied sensitivity analysis to quantify the sensitivity of Shannon et al. model (Biophys. J., 2004) to 5%–10% changes in currents conductance, channels distribution, and ion diffusion in rabbit ventricular cells. We found that action potential duration and Ca2+ peaks are highly sensitive to 10% increase in L-type Ca2+ current; moderately influenced by 10% increase in Na+-Ca2+ exchanger, Na+-K+ pump, rapid delayed and slow transient outward K+ currents, and Cl− background current; insensitive to 10% increases in all other ionic currents and sarcoplasmic reticulum Ca2+ fluxes. Cell electrical activity is strongly affected by 5% shift of L-type Ca2+ channels and Na+-Ca2+ exchanger in between junctional and submembrane spaces while Ca2+-activated Cl−-channel redistribution has the modest effect. Small changes in submembrane and cytosolic diffusion coefficients for Ca2+, but not in Na+ transfer, may alter notably myocyte contraction. Our studies highlight the need for more precise measurements and further extending and testing of the Shannon et al. model. Our results demonstrate usefulness of sensitivity analysis to identify specific knowledge gaps and controversies related to ventricular cell electrophysiology and Ca2+ signaling. PMID:24222910

Effects of NaBF4 + NaF on the Tensile and Impact Properties of Al-Si-Mg-Fe Alloys

NASA Astrophysics Data System (ADS)

Chen, Zongning; Wang, Tongmin; Zhao, Yufei; Zheng, Yuanping; Kang, Huijun

2015-05-01

NaBF4 + NaF were found to play three roles, i.e., Fe-eliminator, grain refiner, and eutectic modifier, in treating A356 alloy with a high Fe content. The joint effects led to significant improvement in both tensile and impact properties of thus treated alloy. The multiple reactions between the NaBF4 + NaF and Al-Si-Mg-Fe system are suggested to form Fe2B, AlB2, and Na in the melt, as per thermodynamic analysis. The three are responsible for Fe removal, grain refinement, and eutectic modification, respectively. When NaBF4 and NaF are mixed in weight ratio of 1:1, an optimum addition rate is in the range between 1.0 and 2.0 wt pct for treating AlSi7Mg0.3Fe0.65 alloy, based on the results of tensile and impact tests. Excessive addition of the salt may deteriorate the mechanical properties of the alloy, basically owing to overmodification of Si and contamination of salt inclusions.

Mass determination near N = 20 for Al and Na isotopes

DOE PAGES

Gallant, A. T.; Alanssari, M.; Bale, J. C.; ...

2017-08-31

We report on the mass measurements of 31;32Na and 29;34;35Al, performed with the TITAN Penning trap mass spectrometer at TRIUMF. The mass excesses were found to be 12246(14) keV and 18638(37) keV for 31;32Na and -18207:77(37) keV, -3000:5(29) keV, and -223:7(73) keV for 29;34;35Al, respectively. Our measurements con rm the observation of a crossover in the two-neutron separation energies of 33Mg and 34Al. We did not observe the recently reported, long-lived, isomeric state of 34Al, but, based on the previously measured half-lives, the mass value of the ground state was determined.

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

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

Avila, M. L.; Rehm, K. E.; Almaraz-Calderon, S.

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 agreementmore » with previous experiments and with statistical-model calculations. As a result, 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.« less

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

DOE PAGES

Avila, M. L.; Rehm, K. E.; Almaraz-Calderon, S.; ...

2016-12-19

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 agreementmore » with previous experiments and with statistical-model calculations. As a result, 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.« less

The crystal structure of synthetic simmonsite, Na 2LiAlF 6

NASA Astrophysics Data System (ADS)

Ross, Kirk C.; Mitchell, Roger H.; Chakhmouradian, Anton R.

2003-04-01

The structure of the synthetic fluoroperovskite, Na 2LiAlF 6 (simmonsite), has been determined by powder X-ray diffraction using the Rietveld method of structure refinement. The compound adopts space group P2 1/ n [#14; a=5.2842(1); b=5.3698(1); c=7.5063(2) Å; β=89.98(1)°; Z=4), and is a member of the cryolite (Na 2NaAlF 6) structural group characterized by ordering of the B-site cations (Li, Al) and tilting of the BF 6 octahedra according to the tilt scheme a-b-c+. Rotations of the B-site polyhedra are less ( ΦLi=14.9°; ΦAl=17.0°) than those found in cryolite ( ΦNa=18.6; ΦAl=23.5°) because of the larger difference in the ionic radii of the B-site cations in cryolite as compared to those in simmonsite. Na at the A-site is displaced from the special position resulting in 10- and 8-fold coordination in simmonsite and cryolite, respectively. By analogy with the synthetic compound, naturally occurring simmonsite is considered to adopt space group P2 1/ n (#14) and not the P2 1(#4) or P2 1/ m(#11) space groups.

Adjustment of the ratio of Ca/P in the ceramic coating on Mg alloy by plasma electrolytic oxidation

NASA Astrophysics Data System (ADS)

Yao, Zhongping; Li, Liangliang; Jiang, Zhaohua

2009-04-01

The ceramic coatings containing Ca and P were prepared on AZ91D Mg alloy by plasma electrolytic oxidation technique in NaOH system and Na 2SiO 3 system, respectively. The phase composition, morphology and the element distribution of the coatings was studied by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The corrosion resistance of the coatings was examined by polarizing curve methods in a 0.9% NaCl solution. In NaOH system, there were a large number of micro-holes distributing evenly on the surface of the coating, and the coating was mainly composed of Mg, Al, P and Ca. In Na 2SiO 3 system, the micro-holes in the coatings were reduced greatly in number and the distribution of the micro-holes was uneven, and the coating was mainly composed of Mg, Al, Si, P and Ca. The ratio of Ca/P in the coating can be controlled by the adjustment of the technique parameters to a certain extent. The adjustment of the concentration of Ca 2+ in the electrolyte was an effective method to change the ratio of Ca/P in the coating in both systems; the reaction time and the working voltage for the adjustment of the ratio of Ca/P in the coating was more suitable for the NaSi 2O 3 system than the NaOH system. The polarizing curve tests showed the coatings improved the corrosion resistance of the AZ91D Mg alloy in 0.9% NaCl solution by nearly two orders of magnitude.

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.

Effects of Al2O3 and CaO/SiO2 Ratio on Phase Equilbria in the ZnO-"FeO"-Al2O3-CaO-SiO2 System in Equilibrium with Metallic Iron

NASA Astrophysics Data System (ADS)

Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

2011-02-01

The phase equilibria and liquidus temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2 system in equilibrium with metallic iron have been determined experimentally in the temperature range 1383 K to 1573 K (1150 °C to 1300 °C). The experimental conditions were selected to characterize lead blast furnace and imperial smelting furnace slags. The results are presented in a form of pseudoternary sections ZnO-"FeO"-(Al2O3 + CaO + SiO2) with fixed CaO/SiO2 and (CaO + SiO2)/Al2O3 ratios. It was found that wustite and spinel are the major primary phases in the composition range investigated. Effects of Al2O3 concentration as well as the CaO/SiO2 ratio on the primary phase field, the liquidus temperature, and the partitioning of ZnO between liquid and solid phases have been discussed for zinc-containing slags.

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

NASA Astrophysics Data System (ADS)

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

2013-02-01

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

Determination of fracture toughness of calcium phosphate coatings deposited onto Ti6Al4V substrate by using indentation technique

NASA Astrophysics Data System (ADS)

Aydin, Ibrahim; Cetinel, Hakan; Pasinli, Ahmet

2012-09-01

In this study, fracture toughness values of calcium phosphate (CaP) coatings deposited onto Ti6Al4V substrate were determined by using Vickers indentation method. In this new patent holding method, the activation processes were performed with NaOH and NaOH+H2O2 on the Ti6Al4V material surface. Thicknesses of CaP coatings were measured from cross-sections of the samples by using optical microscopy. Vickers indentation tests were performed by using microhardness tester. Young's modulus values of the coatings were determined by using ultra microhardness tester. As a result, fracture toughness (K1C) values of the CaP coatings produced by using two different activation processes, were calculated by using experimental study results. These were found to be 0.43 MPa m1/2 and 0.39 MPa m1/2, respectively. It was determined that the CaP coating on Ti6Al4V activated by NaOH+H2O2 had higher fracture toughness than the CaP coating on Ti6Al4V activated by NaOH.

Forsterite-Anorthite-CaTschermak-Enstatite (FACE): A geobarometer for plagioclase-bearing peridotites

NASA Astrophysics Data System (ADS)

Fumagalli, P.; Borghini, G.; Rampone, E.; Poli, S.

2017-12-01

Plagioclase peridotites can be the result of either metamorphic recrystallization, or diffuse melt-rock interactions. Although they represent an important geodynamic marker of shallow mantle exhumation, the accurate estimation of their barometric evolution is poorly constrained. Systematic correlations between pressure and composition of coexisting minerals within the plagioclase stability field have been reported in previous experimental studies. In this experimental study we present new constraints on the stability of plagioclase as a function of different Na2O/CaO bulk ratios, and we present a new geobarometer for mantle rocks. Experiments have been performed in a single-stage piston cylinder at 5-10 kbar, 1050-1150 °C at nominally anhydrous conditions using seeded gels of peridotite compositions (Na2O/CaO = 0.08-0.13; XCr = Cr/(Cr + Al) = 0.07-0.10). As expected, the increase of the bulk Na2O/CaO extends the plagioclase stability to higher pressure; in the Na2O enriched fertile lherzolite the plagioclase-spinel transition occurs between 9 and 10 kbar, 1100 °C; in the fertile lherzolite with Na2O/CaO = 0.08, it occurs between 8 and 9 kbar, 1100 °C. The present data together with previous experimental results provide a consistent database, covering a wide range of P-T conditions (3-9 kbar, 1000-1150 °C) and variable bulk compositions to be used to define and calibrate a geobarometer for plagioclase-bearing mantle rocks. We have empirically calibrated by least squares regression analysis of experimental data combined with MonteCarlo simulation the following pressure sensitive equilibrium: Mg2SiO4 Ol + CaAl2Si2O8 Pl = CaAl2SiO6 Cpx + Mg2Si2O6 OpxForsterite Anorthite Ca-Tschermak Enstatite We derive the following equation: P = 7.2 (±2.9) + 0.0078 (±0.0021) T + 0.0022 (±0.0001) T lnK R2= 0.93 where P is expressed in kbar and T in kelvin. K is the equilibrium constant K = aCa-Ts*aen / aan *afo, where aCaTs, aen, aan and afo are the activities of Ca-Tschermak in

Synthesis and hydration behavior of calcium zirconium aluminate (Ca{sub 7}ZrAl{sub 6}O{sub 18}) cement

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

Kang, Eun-Hee; Yoo, Jun-Sang; Kim, Bo-Hye

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.more » 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.« less

Enhanced adsorption of U(VI) and 241Am(III) from wastewater using Ca/Al layered double hydroxide@carbon nanotube composites.

PubMed

Chen, Haijun; Chen, Zhe; Zhao, Guixia; Zhang, Zhibin; Xu, Chao; Liu, Yunhai; Chen, Jing; Zhuang, Li; Haya, Tasawar; Wang, Xiangke

2018-04-05

Ca/Al layered double hydroxide decorated carbon nanotube (Ca/Al-LDH@CNTs) composites were fabricated by co-precipitation method and hydrothermal aged treatment. The prepared Ca/Al-LDH@CNTs was characterized by SEM, TEM, EDS, XRD, FT-IR, UV-vis and XPS techniques, and applied to remove U(VI) from aqueous solutions under various environmental conditions (i.e., pH, ionic strength, temperature and contact time). The results indicated that the adsorption of U(VI) on Ca/Al-LDH@CNTs was four times higher than that of U(VI) on bare CNTs. The kinetic investigations reflected the chemisorption of U(VI) on Ca/Al-LDH@CNTs through oxygen-containing functional groups. The adsorption isotherms demonstrated that the adsorption of U(VI) was well fitted by Langmuir model and the maximum adsorption capacity of U(VI) on Ca/Al-LDH@CNTs was calculated to be 382.9 mg g -1 at 289.15 K. The thermodynamic parameters calculated from temperature-dependent isotherms suggested that U(VI) adsorption on Ca/Al-LDH@CNTs were endothermic and spontaneous process. Furthermore, Ca/Al-LDH@CNTs could remove ∼91% of 241 Am(III) at pH = 8.0, which confirmed Ca/Al-LDH@CNTs as a promising material for multiply low level radionuclides' pollution remediation. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Confined NaAlH4 nanoparticles inside CeO2 hollow nanotubes towards enhanced hydrogen storage.

PubMed

Gao, Qili; Xia, Guanglin; Yu, Xuebin

2017-10-05

NaAlH 4 has been widely regarded as a potential hydrogen storage material due to its favorable thermodynamics and high energy density. The high activation energy barrier and high dehydrogenation temperature, however, significantly hinder its practical application. In this paper, CeO 2 hollow nanotubes (HNTs) prepared by a simple electrospinning technique are adopted as functional scaffolds to support NaAlH 4 nanoparticles (NPs) towards advanced hydrogen storage performance. The nanoconfined NaAlH 4 inside CeO 2 HNTs, synthesized via the infiltration of molten NaAlH 4 into the CeO 2 HNTs under high hydrogen pressure, exhibited significantly improved dehydrogenation properties compared with both bulk and ball-milled CeO 2 HNTs-catalyzed NaAlH 4 . The onset dehydrogenation temperature of the NaAlH 4 @CeO 2 composite was reduced to below 100 °C, with only one main dehydrogenation peak appearing at 130 °C, which is 120 °C and 50 °C lower than for its bulk counterpart and for the ball-milled CeO 2 HNTs-catalyzed NaAlH 4 , respectively. Moreover, ∼5.09 wt% hydrogen could be released within 30 min at 180 °C, while only 1.6 wt% hydrogen was desorbed from the ball-milled NaAlH 4 under the same conditions. This significant improvement is mainly attributed to the synergistic effects contributed by the CeO 2 HNTs, which could act as not only a structural scaffold to fabricate and confine the NaAlH 4 NPs, but also as an effective catalyst to enhance the hydrogen storage performance of NaAlH 4 .

Improvement of Corrosion Resistance of Binary Mg-Ca Alloys Using Duplex Aluminum-Chromium Coatings

NASA Astrophysics Data System (ADS)

Daroonparvar, Mohammadreza; Yajid, Muhamad Azizi Mat; Yusof, Noordin Mohd; Bakhsheshi-Rad, Hamid Reza; Adabi, Mohsen; Hamzah, Esah; Kamali, Hussein Ali

2015-07-01

Al-AlCr was coated on Mg-Ca and Mg-Zn-Ce-La alloys using physical vapor deposition method. The surface morphology of the specimens was characterized by x-ray diffraction, scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy, and atomic force microscopy (AFM). The AFM results indicated that the average surface roughness of Al-AlCr coating on the Mg-Ca alloy is much lower than that of Al-AlCr coating on the Mg-Zn-Ce-La alloy. However, Al-AlCr coating on the Mg-Ca alloy presented a more compact structure with fewer pores, pinholes, and cracks than Al-AlCr coating on the Mg-Zn-Ce-La alloy. Electrochemical studies revealed that the novel coating (Al-AlCr) can remarkably reduce the corrosion rate of the Mg-Ca alloy in 3.5 wt.% NaCl solution. It was seen that the anodic current density of the Al-AlCr-coated Mg-Ca alloy was very small when compared to the Al-AlCr-coated Mg-Zn-Ce-La and uncoated alloys. Impedance modulus ( Z) of the Al-AlCr-coated samples was higher than that of the bare Mg alloys. Z of Al-AlCr-coated Mg-Ca alloy was higher than that of the Al-AlCr-coated Mg-Zn-Ce-La alloy at low frequency.

Self-Propagating Combustion Synthesis, Luminescent Properties and Photocatalytic Activities of Pure Ca12Al14O33: Tb3+(Sm3+)

NASA Astrophysics Data System (ADS)

Liu, Rong; Yan, Yongsheng; Ma, Changchang

2018-03-01

The dual-functional Ca12Al14O33: Tb3+ and Ca12Al14O33: Sm3+ materials were prepared by the Self-Propagating Combustion Synthesis (SPCS) technology. The structure, morphology and light absorption property were investigated by XRD、FT-IR、UV-Vis DRS and SEM etc.. The doping of Tb3+ and Sm3+ ions had not changed cubic structure of Ca12Al14O33 but leaded to the slight lattice dilatation and the red-shifts of absorption peaks/edges. The excitation and emission spectra indicated that Ca12Al14O33: Tb3+ and Ca12Al14O33: Sm3+ are superior green and red luminescent materials, respectively, and displayed the distinctly refined structure characteristics which had importantly reference value for the energy level investigation of Tb3+ and Sm3+ ions. Meanwhile, Ca12Al14O33: Tb3+ and Ca12Al14O33: Sm3+ also exhibited the improved photocatalytic degradation for removing dye MB compared with bare Ca12Al14O33.

Ciguatoxin extracted from poisonous moray eels Gymnothorax javanicus triggers acetylcholine release from Torpedo cholinergic synaptosomes via reversed Na(+)-Ca2+ exchange.

PubMed

Molgó, J; Gaudry-Talarmain, Y M; Legrand, A M; Moulian, N

1993-09-17

Ciguatoxin (CTX) (0.1 pM to 10 nM) added to a suspension of Torpedo synaptosomes incubated in Ca(2+)-free medium caused no detectable acetylcholine (ACh) release. However, subsequent addition of Ca2+ caused a large ACh release that depended on time of exposure, dose of CTX and on [Ca2+]. Tetrodotoxin completely prevented CTX-induced Ca(2+)-dependent ACh release. Simultaneous blockade of Ca2+ channel subtypes by FTX, a toxin extracted from the venom of the spider Agelenopsis aperta, omega-conotoxin and Gd3+ did not prevent ACh release caused by CTX, upon addition of Ca2+. These results suggest that CTX activates the reversed operation of the Na+/Ca2+ exchange system allowing the entry of Ca2+ in exchange for Na+. It is concluded that Torpedo synaptosomes are endowed with Na+ channels sensitive to pico- to nanomolar concentrations of CTX.

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

Involvement of mitochondrial Na+–Ca2+ exchange in intestinal pacemaking activity

PubMed Central

Kim, Byung Joo; Jun, Jae Yeoul; So, Insuk; Kim, Ki Whan

2006-01-01

AIM: Interstitial cells of Cajal (ICCs) are the pacemaker cells that generate slow waves in the gastrointestinal (GI) tract. We have aimed to investigate the involvement of mitochondrial Na+-Ca2+ exchange in intestinal pacemaking activity in cultured interstitial cells of Cajal. METHODS: Enzymatic digestions were used to dissociate ICCs from the small intestine of a mouse. The whole-cell patch-clamp configuration was used to record membrane currents (voltage clamp) and potentials (current clamp) from cultured ICCs. RESULTS: Clonazepam and CGP37157 inhibited the pacemaking activity of ICCs in a dose-dependent manner. Clonazepam from 20 to 60 µmol/L and CGP37157 from 10 to 30 µmol/L effectively inhibited Ca2+ efflux from mitochondria in pacemaking activity of ICCs. The IC50s of clonazepam and CGP37157 were 37.1 and 18.2 µmol/L, respectively. The addition of 20 µmol/L NiCl2 to the internal solution caused a “wax and wane” phenomenon of pacemaking activity of ICCs. CONCLUSION: These results suggest that mitochondrial Na+-Ca2+ exchange has an important role in intestinal pacemaking activity. PMID:16521198

First investigations on the quaternary system Na2O-K2O-CaO-SiO2: synthesis and crystal structure of the mixed alkali calcium silicate K1.08Na0.92Ca6Si4O15

NASA Astrophysics Data System (ADS)

Kahlenberg, Volker; Mayerl, Michael Jean-Philippe; Schmidmair, Daniela; Krüger, Hannes; Tribus, Martina

2018-04-01

In the course of an exploratory study on the quaternary system Na2O-K2O-CaO-SiO2 single crystals of the first anhydrous sodium potassium calcium silicate have been obtained from slow cooling of a melt in the range between 1250 and 1050 °C. Electron probe micro analysis suggested the following idealized molar ratios of the oxides for the novel compound: K2O:Na2O:CaO:SiO2 = 1:1:12:8 (or KNaCa6Si4O15). Single-crystal diffraction measurements on a crystal with chemical composition K1.08Na0.92Ca6Si4O15 resulted in the following basic crystallographic data: monoclinic symmetry, space group P 21/ c, a = 8.9618(9) Å, b = 7.3594(6) Å, c = 11.2453(11) Å, β= 107.54(1)°, V = 707.2(1) Å3, Z = 2. Structure solution was performed using direct methods. The final least-squares refinement converged at a residual of R(|F|) = 0.0346 for 1288 independent reflections and 125 parameters. From a structural point of view, K1.08Na0.92Ca6Si4O15 belongs to the group of mixed-anion silicates containing [Si2O7]- and [SiO4]-units in the ratio 1:2. The mono- and divalent cations occupy a total of four crystallographically independent positions located in voids between the tetrahedra. Three of these sites are exclusively occupied by calcium. The fourth site is occupied by 54(1)% K and 46%(1) Na, respectively. Alternatively, the structure can be described as a heteropolyhedral framework based on corner-sharing silicate tetrahedra and [CaO6]-octahedra. The network can build up from kröhnkite-like [Ca(SiO4)2O2]-chains running along [001]. A detailed comparison with other A2B6Si4O15-compounds including topological and group-theoretical aspects is presented.

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.

Departure gate of acidic Ca2+ confirmed

PubMed Central

Jentsch, Thomas J; Hoegg-Beiler, Maja B; Vogt, Janis

2015-01-01

More potent, but less known than IP3 that liberates Ca2+ from the ER, NAADP releases Ca2+ from acidic stores. The notion that TPC channels mediate this Ca2+ release was questioned recently by studies suggesting that TPCs are rather PI(3,5)P2-activated Na+ channels. Ruas et al (2015) now partially reconcile these views by showing that TPCs significantly conduct both cations and confirm their activation by both NAADP and PI(3,5)P2. They attribute the failure of others to observe TPC-dependent NAADP-induced Ca2+ release in vivo to inadequate mouse models that retain partial TPC function. PMID:26022292

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

NASA Astrophysics Data System (ADS)

Dolejš, David; Baker, Don R.

2005-12-01

Fluorine is a common volatile element in magmatic-hydrothermal systems, but its solution mechanisms and thermodynamic description in highly polymerized silicate melts are poorly known. We have developed a thermodynamic model for fluorosilicate liquids that links experimentally determined phase equilibria and spectroscopic information on melt structure. The model is applicable to crystallization of fluoride minerals, fluoride-silicate immiscibility in natural felsic melts, and metallurgical processes. Configurational properties of fluorosilicate melts are described by mixing on three site levels (sublattices): (1) alkali fluoride, polyhedral aluminofluoride and silicofluoride species and nonbridging terminations of the aluminosilicate network, (2) alkali-aluminate and silicate tetrahedra within the network and (3) bridging oxygen, nonbridging oxygen and terminal fluorine atoms on tetrahedral apices of the network. Abundances of individual chemical species are described by a homogeneous equilibrium representing melt depolymerization: F - (free) + O 0 (bridging) = F 0 (terminal) + O - (nonbridging) which corresponds to a replacement of an oxygen bridging two tetrahedra by a pair of terminations, one with F and the other with an O and a charge-balancing Na. In cryolite-bearing systems two additional interaction mechanisms occur: (1) the self-dissociation of octahedral aluminofluoride complexes: [AlF 6] = [AlF 4] + 2 [F], and (2) the short-range order between (O,F)-corners and (Si,NaAl)-centers of tetrahedra: Si-O-Si + 2 [NaAl]-F = [NaAl]-O-[NaAl] + 2 Si-F. Portrayal of these equilibria in ternary Thompson reaction space allows for the decrease in the number of interaction mechanisms by linearly combining melt depolymerization with tetrahedral short-range order. In this formulation, the nonideal thermodynamic properties are represented by reaction energies of homogeneous equilibria, thus defining directly individual chemical species concentrations and configurational

Vasoconstriction triggered by hydrogen sulfide: Evidence for Na+,K+,2Cl-cotransport and L-type Ca2+ channel-mediated pathway.

PubMed

Orlov, Sergei N; Gusakova, Svetlana V; Smaglii, Liudmila V; Koltsova, Svetlana V; Sidorenko, Svetalana V

2017-12-01

This study examined the dose-dependent actions of hydrogen sulfide donor sodium hydrosulphide (NaHS) on isometric contractions and ion transport in rat aorta smooth muscle cells (SMC). Isometric contraction was measured in ring aortas segments from male Wistar rats. Activity of Na + /K + -pump and Na + ,K + ,2Cl - cotransport was measured in cultured endothelial and smooth muscle cells from the rat aorta as ouabain-sensitive and ouabain-resistant, bumetanide-sensitive components of the 86 Rb influx, respectively. NaHS exhibited the bimodal action on contractions triggered by modest depolarization ([K + ] o =30 mM). At 10 -4 M, NaHS augmented contractions of intact and endothelium-denuded strips by ~ 15% and 25%, respectively, whereas at concentration of 10 -3  M it decreased contractile responses by more than two-fold. Contractions evoked by 10 -4  M NaHS were completely abolished by bumetanide, a potent inhibitor of Na + ,K + ,2Cl - cotransport, whereas the inhibition seen at 10 -3  M NaHS was suppressed in the presence of K + channel blocker TEA. In cultured SMC, 5×10 -5  M NaHS increased Na + ,K + ,2Cl - - cotransport without any effect on the activity of this carrier in endothelial cells. In depolarized SMC, 45 Ca influx was enhanced in the presence of 10 -4  M NaHS and suppressed under elevation of [NaHS] up to 10 -3  M. 45 Ca influx triggered by 10 -4  M NaHS was abolished by bumetanide and L-type Ca 2+ channel blocker nicardipine. Our results strongly suggest that contractions of rat aortic rings triggered by low doses of NaHS are mediated by activation of Na + ,K + ,2Cl - cotransport and Ca 2+ influx via L-type channels.

A thermodynamic model for the prediction of phase equilibria and speciation in the H 2O-CO 2-NaCl-CaCO 3-CaSO 4 system from 0 to 250 °C, 1 to 1000 bar with NaCl concentrations up to halite saturation

NASA Astrophysics Data System (ADS)

Li, Jun; Duan, Zhenhao

2011-08-01

A thermodynamic model is developed for the calculation of both phase and speciation equilibrium in the H 2O-CO 2-NaCl-CaCO 3-CaSO 4 system from 0 to 250 °C, and from 1 to 1000 bar with NaCl concentrations up to the saturation of halite. The vapor-liquid-solid (calcite, gypsum, anhydrite and halite) equilibrium together with the chemical equilibrium of H+,Na+,Ca, CaHCO3+,Ca(OH)+,OH-,Cl-, HCO3-,HSO4-,SO42-, CO32-,CO,CaCO and CaSO 4(aq) in the aqueous liquid phase as a function of temperature, pressure and salt concentrations can be calculated with accuracy close to the experimental results. Based on this model validated from experimental data, it can be seen that temperature, pressure and salinity all have significant effects on pH, alkalinity and speciations of aqueous solutions and on the solubility of calcite, halite, anhydrite and gypsum. The solubility of anhydrite and gypsum will decrease as temperature increases (e.g. the solubility will decrease by 90% from 360 K to 460 K). The increase of pressure may increase the solubility of sulphate minerals (e.g. gypsum solubility increases by about 20-40% from vapor pressure to 600 bar). Addition of NaCl to the solution may increase mineral solubility up to about 3 molality of NaCl, adding more NaCl beyond that may slightly decrease its solubility. Dissolved CO 2 in solution may decrease the solubility of minerals. The influence of dissolved calcite on the solubility of gypsum and anhydrite can be ignored, but dissolved gypsum or anhydrite has a big influence on the calcite solubility. Online calculation is made available on www.geochem-model.org/model.

Corrosion resistance and in-vitro bioactivity of BaO containing Na2O-CaO-P2O5 phosphate glass-ceramic coating prepared on 316 L, duplex stainless steel 2205 and Ti6Al4V

NASA Astrophysics Data System (ADS)

Edathazhe, Akhila B.; Shashikala, H. D.

2018-03-01

The phosphate glass with composition 11Na2O-15BaO-29CaO-45P2O5 was coated on biomedical implant materials such as stainless steel 316 L, duplex stainless steel (DSS) 2205 and Ti6Al4V alloy by thermal enamelling method. The structural properties and composition of glass coated substrates were studied by x-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive x-ray spectroscopy (EDS) analysis. The coatings were partially crystalline in nature with porous structure and pore size varied from micro to nanometer range. The polarization curve was obtained for uncoated and coated substrates from electrochemical corrosion test which was conducted at 37 °C in Hank’s balanced salt solution (HBSS). The corrosion resistance of 316 L substrate increased after coating, whereas it decreased in case of DSS 2205 and Ti6Al4V. The XRD and SEM/EDS studies indicated the bioactive hydroxyapatite (HAp) layer formation on all the coated surfaces after electrochemical corrosion test, which improved the corrosion resistance. The observed electrochemical corrosion behavior can be explained based on protective HAp layer formation, composition and diffusion of ions on glass coated surfaces. The in-vitro bioactivity test was carried out at 37 °C in HBS solution for 14 days under static conditions for uncoated and coated substrates. pH and ion release rate measurements from the coated samples were conducted to substantiate the electrochemical corrosion test. The lower ion release rates of Na+ and Ca2+ from coated 316 L supported its higher electrochemical corrosion resistance among coated samples. Among the uncoated substrates, DSS showed higher electrochemical corrosion resistance. Amorphous calcium-phosphate (ACP) layer formation on all the coated substrates after in-vitro bioactivity test was confirmed by XRD, SEM/EDS and ion release measurements. The present work is a comparative study of corrosion resistance and bioactivity of glass coated and uncoated

Inhibiting Na+/K+ ATPase can impair mitochondrial energetics and induce abnormal Ca2+ cycling and automaticity in guinea pig cardiomyocytes.

PubMed

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.

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.

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

2017-05-01

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.

Acid mist and soil Ca and Al alter the mineral nutrition and physiology of red spruce

Treesearch

P.G. Schaberg; D.H. DeHayes; G.J. Hawley; G.R. Strimbeck; J.R. Cumming; P.F. Murakami; C.H. Borer

2000-01-01

We examined the effects and potential interactions of acid mist and soil solution Ca and Al treatments on foliar cation concentrations, membrane-associated Ca (mCa), ion leaching, growth, carbon exchange, and cold tolerance of red spruce (Picea rubens Sarg.) saplings. Soil solution Ca additions increased foliar Ca and Zn concentrations, and increased...

Raman spectroscopic study of synthesized Na-bearing majoritic garnets

NASA Astrophysics Data System (ADS)

Okamoto, K.

2003-12-01

Majoritic garnets in diamond have been considered as the sample from mantle transition zone (e.g. Moore and Gurney, 1985). For non-destructive, in-situ Raman analysis, Gillet et al. (2002) systematically checked chemistry and Raman peak of various majoritic garnets in diamond. They treated majoritic component as number of excess-silica than 3.0 per formula unit. However, in the basaltic system, majorite garnets also have significant amounts of Na. Na substitution is coupled with Si and Ti as follows; Na +Ti = Ca +Al (Ringwood and Lovering, 1970), Na +Si = Ca + Al (Sobolev and Labrentav, 1971; Ringwood and Major, 1971) or Na + Si = Mg + Al (Gasparik, 1989). Each component in garnet is defined as follows; Mj (majorite) component = ((Si-3)-Na)/2), NaSi (Na2MSi5O12 where M= Ca, Mg, Fe2+) component = (Na-T)/2, and NaTi component = Ti/2. Okamoto and Maruyama (2003) conducted UHP experiments in the MORB + H2O system (KNCFMATSH) at 10-19 GPa. They show that 1) Mj and NaTi component are constant and lower than 0.1 at T = 900 \\deg C, and 2) NaSi component increases drastically above 15 GPa although it is neglibly small at P<15 GPa. Raman spectra was newly analyzed using Okamoto and Maruyama (2003)'s run charges. Above 15 GPa, there is a characteristic sharp peak at 910 cm-1 and broad shoulder between 800 and 900 cm-1 as well as broad band near 960 cm-1. Gillet et at (2002) concluded that the former peak at 910cm-1 is the only reliable signature for the majoritic garnet (Si>3). They also implied that the latter two broad peaks are diagnostic feature for Ti rich garnet (> 1wt% of TiO2) as well as peak at 1030 cm-1. However, in all P range (10-19 GPa) of the present study, TiO2 is higher than 1wt%, and there is a peak at 1030 cm-1. Additional Ti-free experiment at 16 GPa, 1200 \\deg C clearly revealed that Na-bearing majoritic garnet has a significant shoulder at 800-900 cm-1. Ref; Gasparik (1989) CMP, 102,389, Gillet et al. (2002) Am.Min., 87, 312, Moore and Gurney (1985

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.

Phase Diagram of Quaternary System NaBr-KBr-CaBr2-H2O at 323 K

NASA Astrophysics Data System (ADS)

Cui, Rui-Zhi; Wang, Wei; Yang, Lei; Sang, Shi-Hua

2018-03-01

The phase equilibria in the system NaBr-KBr-CaBr2-H2O at 323 K were studied using the isothermal dissolution equilibrium method. Using the experimental solubilities of salts data, phase diagram was constructed. The phase diagram have two invariant points, five univariant curves, and four crystallization fields. The equilibrium solid phases in the system are NaBr, NaBr · 2H2O, KBr, and CaBr2 · 4H2O. The solubilities of salts in the system at 323 K were calculated by Pitzer's equation. There is shown that the calculated solubilities agree well with experimental data.

Triphenyltin impairs a protein kinase A (PKA)-dependent increase of cytosolic Na{sup +} and Ca{sup 2+} and PKA-independent increase of cytosolic Ca{sup 2+} associated with insulin secretion in hamster pancreatic {beta}-cells

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

Miura, Yoshikazu; Matsui, Hisao

2006-11-01

Oral administration of triphenyltin chloride (TPT) (60 mg/kg body weight) inhibits the insulin secretion by decreasing the cytoplasmic Ca{sup 2+} concentration ([Ca{sup 2+}] {sub i}) induced by glucose-dependent insulinotropic polypeptide (GIP) in pancreatic {beta}-cells of the hamster. To test the possibility that the abnormal level of [Ca{sup 2+}] {sub i} induced by TPT administration could be due to a defect in the cAMP-dependent cytoplasmic Na{sup +} concentration ([Na{sup +}] {sub i}) in the {beta}-cells, we investigated the effects of TPT administration on the changes of [Na{sup +}] {sub i} induced by GIP, glucagon-like peptide-1 (GLP-1), or forskolin, an activator ofmore » adenylyl cyclase, and on the changes of [Na{sup +}] {sub i} or [Ca{sup 2+}] {sub i} induced by 6-Bnz-cAMP, an activator of protein kinase A (PKA), and 8-pCPT-2'-O-Me-cAMP, an activator of Epac. The [Na{sup +}] {sub i} and [Ca{sup 2+}] {sub i} were measured in islet cells loaded with sodium-binding benzofuran isophthalate (SBFI) and fura-2, respectively. In the presence of 135 mM Na{sup +}, TPT administration significantly reduced the rise in [Na{sup +}] {sub i} by 10 nM GLP-1, 10 {mu}M forskolin, and 50 {mu}M 6-Bnz-cAMP, but had not effect in a Na{sup +}-free medium. In the presence of 135 mM Na{sup +}, TPT administration also reduced the rise in [Ca{sup 2+}] {sub i} by 8-pCPT-2'-O-Me-cAMP plus10 {mu}M H-89, a inhibitor of PKA, and 6-Bnz-cAMP. Moreover, TPT administration significantly reduced the insulin secretion by 2 mM db-cAMP, GLP-1, GIP, and 8-pCPT-2'-O-Me-cAMP with and without H-89, and that by 6-Bnz-cAMP and forskolin. Our study suggested that TPT has inhibitory effects on the cellular Ca{sup 2+} response due to a reduced Na{sup +} permeability through PKA-dependent mechanisms in hamster islet cells. Also TPT has the reduction of [Ca{sup 2+}] {sub i} related to Na{sup +}-dependent insulin secretion after an activation of Epac.« less

Effects of Levetiracetam, Carbamazepine, Phenytoin, Valproate, Lamotrigine, Oxcarbazepine, Topiramate, Vinpocetine and Sertraline on Presynaptic Hippocampal Na(+) and Ca(2+) Channels Permeability.

PubMed

Sitges, María; Chiu, Luz María; Reed, Ronald C

2016-04-01

Ion channels are targets of various antiepileptic drugs. In cerebral presynaptic nerve endings Na(+) and Ca(2+) channels are particularly abundant, as they control neurotransmitter release, including the release of glutamate (Glu), the most concentrated excitatory amino acid neurotransmitter in the brain. Several pre-synaptic channels are implicated in the mechanism of action of the pro-convulsive agent, 4-aminopyridine (4-AP). In the present study the effects of levetiracetam and other established and newer (vinpocetine) anti-epileptic drugs, as well as of the anti-depressant, sertraline on the increase in Ca(2+) induced by 4-AP in hippocampal isolated nerve endings were investigated. Also the effects of some of the anti-seizure drugs on the selective increase in Ca(2+) induced by high K(+), or on the selective increase in Na(+) induced by veratridine were tested. Sertraline and vinpocetine effectively inhibited the rise in Ca(2+) induced by 4-AP, which was dependent on the out-in Na(+) gradient and tetrodotoxin sensitive. Carbamazepine, phenytoin, lamotrigine and oxcarbazepine inhibited the rise in Ca(2+) induced by 4-AP too, but at higher concentrations than sertraline and vinpocetine, whereas levetiracetam, valproic acid and topiramate did not. The three latter antiepileptic drugs also failed in modifying other responses mediated by the activation of brain presynaptic Na(+) or Ca(2+) channels, including Glu release. This indicates that levetiracetam, valproic acid and topiramate mechanisms of action are unrelated with a decrease in presynaptic Na(+) or Ca(2+) channels permeability. It is concluded that depolarized cerebral isolated nerve endings represent a useful tool to unmask potential antiepileptic drugs targeting presynaptic Na(+) and/or Ca(2+) channels in the brain; such as vinpocetine or the anti-depressant sertraline, which high effectiveness to control seizures in the animal in vivo has been demonstrated.

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. Ca-Al precursor (C3A) was agitated in a hexavalent chromium (Cr(VI)) solution to form Al-Ca-CrO4 LDH product. Ca-Al-CrO4 LDH phase occurred preferentially to Ca-Al-MCl2 LDH phases in the solutions of calcium and magnesium chlorides, it incorporates Cr(VI) preferentially to the chloride salts when they coexist.

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

PubMed

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

2016-07-05

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

Kinetics of dissolution of sapphire in melts in the CaO-Al2O3-SiO2 system

NASA Astrophysics Data System (ADS)

Shaw, Cliff S. J.; Klausen, Kim B.; Mao, Huahai

2018-05-01

The dissolution rate of sapphire in melts in the CAS system of varying silica activity, viscosity and degree of alumina saturation has been determined at 1600 °C and 1.5 GPa. After an initiation period of up to 1800 s, dissolution is controlled by diffusion of cations through the boundary layer adjacent to the dissolving sapphire. The dissolution rate decreases with increasing silica activity, viscosity and molar Al2O3/CaO. The calculated diffusion matrix for each solvent melt shows that CAS 1 and 9 which have molar Al2O3/CaO of 0.33 and 0.6 and dissolution rate constants of 0.65 × 10-6 and 0.59 × 10-6 m/s0.5 have similar directions and magnitudes of diffusive coupling: DCaO-Al2O3 and DAl2O3-CaO are both negative are approximately equal. The solvent with the fastest dissolution rate: CAS 4, which has a rate constant of 1.5 × 10-6 m/s0.5 and Al2O3/CaO of 0.31 has positive DCaO-Al2O3 and negative DAl2O3-CaO and the absolute values vary by a factor of 4. Although many studies show that aluminium is added to the melts via the reaction: Si4+ =Al3+ + 0.5Ca2+ the compositional profiles show that this reaction is not the only one involved in accommodating the aluminium added during sapphire dissolution. Rather, aluminium is incorporated as both tetrahedrally coordinated Al charge balanced by Ca and as aluminium not charge balanced by Ca (termed Alxs). This reaction: AlIV -Ca =Alxs +CaNBO where CaNBO is a non-bridging oxygen associated with calcium, may involve the formation of aluminium triclusters. The shape of the compositional profiles and oxide-oxide composition paths is controlled by the aluminium addition reaction. When Alxs exceeds 2%, CaO diffusion becomes increasingly anomalous and since the bond strength of Alxs correlates with CaO/CaO + Al2O3, the presence of more than 2% Alxs leads to significantly slower dissolution than when Alxs is absent or at low concentration. Thus, dissolution is controlled by diffusion of cations through the boundary layer, but this

Structural mechanism of the formation of mineral Na-tveitite-a new type of phase with a fluorite-derivative structure-in the NaF-CaF{sub 2}-(Y,Ln)F{sub 3} natural system

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

Golubev, A. M., E-mail: fluorides@ns.crys.ras.ru; Otroshchenko, L. P.; Sobolev, B. P.

2012-03-15

Relationships between the chemical compositions and structures of the mineral tveitite from the southern Norway pegmatites (with the idealized formula Ca{sub 14}Y{sub 5}F{sub 43}) and Na-tveitite from the Rov mountain (Keivy, Kola Peninsula) Na{sub 2.5}Ca{sub 10}Ln{sub 1.5}Y{sub 5}F{sub 42} are considered. According to the structural mechanism of its formation, Na-tveitite is a nanocomposite crystal based on the crystalline matrix Ca{sub 14}Y{sub 5}F{sub 43} with the ordered arrangement of {l_brace}Ca{sub 8}[CaY{sub 5}]F{sub 69}{r_brace} clusters which contain anionic {l_brace}F{sub 13}{r_brace} cuboctahedra with F{sup 1-} at the center. When Na-tveitite is formed, 29% of these clusters are statistically replaced by Na-'Y' clusters {l_brace}[Na{submore » 0.5}(Y,Ln){sub 0.5}]{sub 14}F{sub 64}{r_brace} with {l_brace}F{sub 8}{r_brace} cubes at the center (analogs of matrix fluorite groups {l_brace}Ca{sub 14}F{sub 64}{r_brace}). This replacement gives rise to composition-imperfect (Na, Ca, 'Y') cationic positions and occupancy-deficient F positions, which correspond to {l_brace}F{sub 13}{r_brace} cuboctahedra and the {l_brace}F{sub 8}{r_brace} cubes that replace them. The difference between Na-tveitite and fluorite phases M{sub 1-x}R{sub x}F{sub 2+x} is as follows: its matrix is the structure of the ordered phase (tveitite) into which Na-containing rare earth fragments of fluorite-type structure are incorporated instead of ordered-phase structural blocks (clusters).« less

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.

Signaling mechanisms that link salt retention to hypertension: endogenous ouabain, the Na(+) pump, the Na(+)/Ca(2+) exchanger and TRPC proteins.

PubMed

Blaustein, Mordecai P; Hamlyn, John M

2010-12-01

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, salt retention may be the result of minor renal injury or small genetic variation in renal salt transport mechanisms. How salt retention actually leads to the increase in peripheral vascular resistance (the hallmark of hypertension) and the elevation of blood pressure remains 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 Ca(2+) 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 Ca(2+) 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. Copyright © 2010 Elsevier B.V. All rights reserved.

Luminescent properties of Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} and its potential application in white light emitting diodes

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

Wang, Zhijun, E-mail: wangzhijunmail@yahoo.com.cn; Li, Panlai; Li, Ting

2013-06-01

Graphical abstract: Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} phosphor can be effectively excited by an ultraviolet and near-ultraviolet light, and produce a bright blue emission centered at 436 nm. The CIE chromaticity coordinations (x, y) of Na{sub 2}CaSiO{sub 4}:Eu{sup 2+}(NSCE)/Li{sub 2}SrSiO{sub 4}:Eu{sup 2+}(LSSE) vary with the molar ratio of the two constituents. When NSCE/LSSE is 1:3, the CIE chromaticity coordination is (0.332, 0.346), which is close to that of the natural sunlight (0.33, 0.33). The results indicate that Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} may be a promising blue phosphor for UV chip-based multi-phosphor converted white light emitting diodes. Highlights: ► Na{sub 2}CaSiO{sub 4}:Eu{supmore » 2+} shows the blue emission with a peak at 436 nm and broad excitation band in the UV/n-UV range. ► White light with CIE coordinates (0.332, 0.346) is generated by mixing the blue phosphor with the Li{sub 2}SrSiO{sub 4}:Eu{sup 2+} yellow phosphor. ► Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} would be a promising blue phosphor candidate for UV chip-based multi-phosphor converted white LEDs. - Abstract: A novel blue phosphor Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} is synthesized by a high temperature solid-state reaction, and its luminescent properties are systematically studied. Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} can be effectively excited by the 354 nm radiation, and create blue emission (436 nm). The emission intensity of Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} is influenced by the Eu{sup 2+} doping content, and the optimal doping content is 1.5%, and the concentration quenching mechanism of Eu{sup 2+} in Na{sub 2}CaSiO{sub 4} can be attributed to the multipolar interaction. The white light with CIE coordinates (0.332, 0.346) is generated by mixing the blue phosphor Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} with the yellow phosphor Li{sub 2}SrSiO{sub 4}:Eu{sup 2+}. The results indicate that Na{sub 2}CaSiO{sub 4}:Eu{sup 2+} may be a potential blue emitting phosphor for UV chip-based multi

Ionic mechanisms of transient inward current in the absence of Na(+)-Ca2+ exchange in rabbit cardiac Purkinje fibres.

PubMed Central

Han, X; Ferrier, G R

1992-01-01

1. Membrane currents were measured with a two-microelectrode technique in voltage clamped rabbit cardiac Purkinje fibres under conditions known to cause intracellular calcium overload and to eliminate or minimize Na(+)-Ca2+ exchange. 2. Increasing [Ca2+]o from 2.5 to 5 mM or above and substituting external sodium with either sucrose, choline or Li+ induced an oscillatory transient inward current (TI) which peaked 200-300 ms after repolarization from a previous depolarizing pulse. The TI quickly disappeared upon return to normal Tyrode solution. Both the rate and configuration of action potentials of Purkinje fibres also returned to control upon return to Tyrode solution after 30 min of high Ca2+ exposure, if the Ca2+ concentration was 30 mM or less. 3. The TI in Na(+)-free solution was Ca2+ dependent. Either zero or low (2.5 mM) [Ca2+]o, or replacement of [Ca2+]o by BaCl prevented induction of the TI current upon repolarization from a previous depolarizing pulse. 4. In the presence of 30 mM-CaCl2 and with choline chloride as the substitute for NaCl, TI had a distinct reversal potential (Erev) of -25 mV. The time-to-peak TI, either inward or outward, did not shift significantly with change in voltage. Both inward and outward TI were simultaneously abolished by exposure to 1 microM-ryanodine, suggesting they were both activated by transient release of Ca2+ from the sarcoplasmic reticulum. The occurrence of TI in the absence of [Na+]o is not compatible with an electrogenic Na(+)-Ca2+ exchange mechanism. The existence of a clear-cut reversal potential suggests that an ionic channel may be responsible for the TI under these conditions. 5. Both the magnitude of peak TI and the Erev were affected by changes of CaCl2 concentration. (i) Under steady-state conditions, peak inward TI was significantly increased when the [Ca2+]o was elevated from 5 to 15 mM. The peak TI in the outward direction was significantly increased when [Ca2+]o was elevated from 15 to 30 mM; however

The kinetic enhancement of hydrogen cycling in NaAlH(4) by melt infusion into nanoporous carbon aerogel.

PubMed

Stephens, Robert D; Gross, Adam F; Van Atta, Sky L; Vajo, John J; Pinkerton, Frederick E

2009-05-20

Enhanced kinetic performance and reversibility have been achieved with uncatalyzed NaAlH4 by incorporation into nanoporous carbon aerogel. Aerogel with a pore size distribution peaked at 13 nm and a pore volume of 0.8 cm(3) g(-1) was filled with NaAlH4 to 94% capacity by melt infusion at 189 degrees C under 183 bar H(2) gas overpressure. Dehydrogenation to NaH + Al with reasonable kinetics was accomplished at 150 degrees C, well below the NaAlH4 melting temperature (183 degrees C), compared to hydrogen release above 230 degrees C for bulk uncatalyzed NaAlH4. Uncatalyzed bulk samples did not rehydrogenate under laboratory conditions, whereas NaAlH4 in a carbon aerogel host was readily rehydrogenated at approximately 160 degrees C and 100 bar H(2) to approximately 85% of its initial capacity. Ball-milled NaAlH4 catalyzed with 4 mol% TiCl3 showed somewhat better kinetics compared to the infused aerogel; nevertheless, the large kinetic enhancement obtained by incorporation into carbon aerogel, even in the absence of a catalyst, demonstrates the substantial benefit of confining the NaAlH4 to nanoscale dimensions.

Biochemical responses of the mycorrhizae in Pinus massoniana to combined effects of Al, Ca and low pH.

PubMed

Kong, F X; Liu, Y; Hu, W; Shen, P P; Zhou, C L; Wang, L S

2000-02-01

Biochemical responses of Pinus massoniana, with and without the inoculation mycorrhizal fungus Pisolithus tinctorius at the root, to artificial acid rain (pH 2.0) and various Ca/Al ratios were investigated. Some enzymes associated with the nutritive metabolism, such as acid phosphatase, alkaline phosphatase, nitrate reductase, mannitol dehydrogenase and trehalase, in the roots, stems and leaves of plant were obviously inhibited by the artificial acid rain and Al. After treatment with pH 2.0 + Ca/Al (0/1 or 1/10) artificial acid rain, the protein content in the organs was decreased. However, the activities of superoxide dismutase (SOD) and peroxidase (POD) and glutathione (GSH) concentrations were induced. It demonstrated that acid rain and Al could induce oxygen radicals in plant. Compared with the treatments with lower pH or Al, respectively, the combination of lower pH and Al concentration was more toxic to P. massoniana. Al toxicity could be ameliorated by the addition of Ca and the amelioration was the most when the ratio was 1/1 among the various Ca/Al ratio. Infection with mycorrhizal fungus P. tinctorius at the root of P. massoniana increased the ability of the plant to resist the toxicity of artificial acid rain and Al stress.

Insight into Ca-Substitution Effects on O3-Type NaNi1/3 Fe1/3 Mn1/3 O2 Cathode Materials for Sodium-Ion Batteries Application.

PubMed

Sun, Liqi; Xie, Yingying; Liao, Xiao-Zhen; Wang, Hong; Tan, Guoqiang; Chen, Zonghai; Ren, Yang; Gim, Jihyeon; Tang, Wan; He, Yu-Shi; Amine, Khalil; Ma, Zi-Feng

2018-04-18

O3-type NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NaNFM) is well investigated as a promising cathode material for sodium-ion batteries (SIBs), but the cycling stability of NaNFM still needs to be improved by using novel electrolytes or optimizing their structure with the substitution of different elements sites. To enlarge the alkali-layer distance inside the layer structure of NaNFM may benefit Na + diffusion. Herein, the effect of Ca-substitution is reported in Na sites on the structural and electrochemical properties of Na 1- x Ca x /2 NFM (x = 0, 0.05, 0.1). X-ray diffraction (XRD) patterns of the prepared Na 1- x Ca x /2 NFM samples show single α-NaFeO 2 type phase with slightly increased alkali-layer distance as Ca content increases. The cycling stabilities of Ca-substituted samples are remarkably improved. The Na 0.9 Ca 0.05 Ni 1/3 Fe 1/3 Mn 1/3 O 2 (Na 0.9 Ca 0.05 NFM) cathode delivers a capacity of 116.3 mAh g -1 with capacity retention of 92% after 200 cycles at 1C rate. In operando XRD indicates a reversible structural evolution through an O3-P3-P3-O3 sequence of Na 0.9 Ca 0.05 NFM cathode during cycling. Compared to NaNMF, the Na 0.9 Ca 0.05 NFM cathode shows a wider voltage range in pure P3 phase state during the charge/discharge process and exhibits better structure recoverability after cycling. The superior cycling stability of Na 0.9 Ca 0.05 NFM makes it a promising material for practical applications in sodium-ion batteries. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Density Measurements of Low Silica CaO-SiO2-Al2O3 Slags

NASA Astrophysics Data System (ADS)

Muhmood, Luckman; Seetharaman, Seshadri

2010-08-01

Density measurements of a low-silica CaO-SiO2-Al2O3 system were carried out using the Archimedes principle. A Pt 30 pct Rh bob and wire arrangement was used for this purpose. The results obtained were in good agreement with those obtained from the model developed in the current group as well as with other results reported earlier. The density for the CaO-SiO2 and the CaO-Al2O3 binary slag systems also was estimated from the ternary values. The extrapolation of density values for high-silica systems also showed good agreement with previous works. An estimation for the density value of CaO was made from the current experimental data. The density decrease at high temperatures was interpreted based on the silicate structure. As the mole percent of SiO2 was below the 33 pct required for the orthosilicate composition, discrete {text{SiO}}4^{4 - } tetrahedral units in the silicate melt would exist along with O2- ions. The change in melt expansivity may be attributed to the ionic expansions in the order of {text{Al}}^{ 3+ } - {text{O}}^{ 2- } < {text{Ca}}^{ 2+ } - {text{O}}^{ 2- } < {text{Ca}}^{ 2+ } - {text{O}}^{ - } Structural changes in the ternary slag also could be correlated to a drastic change in the value of enthalpy of mixing.

Hydrogen Generation from Al-NiCl2/NaBH4 Mixture Affected by Lanthanum Metal

PubMed Central

Qiang Sun, Wen; Fan, Mei-Qiang; Fei, Yong; Pan, Hua; Wang, Liang Liang; Yao, Jun

2012-01-01

The effect of La on Al/NaBH4 hydrolysis was elaborated in the present paper. Hydrogen generation amount increases but hydrogen generation rate decreases with La content increasing. There is an optimized composition that Al-15 wt% La-5 wt% NiCl2/NaBH4 mixture (Al-15 wt% La-5 wt% NiCl2/NaBH4 weight ratio, 1 : 3) has 126 mL g−1 min−1 maximum hydrogen generation rate and 1764 mL g−1 hydrogen generation amount within 60 min. The efficiency is 88%. Combined with NiCl2, La has great effect on NaBH4 hydrolysis but has little effect on Al hydrolysis. Increasing La content is helpful to decrease the particle size of Al-La-NiCl2 in the milling process, which induces that the hydrolysis byproduct Ni2B is highly distributed into Al(OH)3 and the catalytic reactivity of Ni2B/Al(OH)3 is increased therefore. But hydrolysis byproduct La(OH)3 deposits on Al surface and leads to some side effect. The Al-La-NiCl2/NaBH4 mixture has good stability in low temperature and its hydrolytic performance can be improved with increasing global temperature. Therefore, the mixture has good safety and can be applied as on board hydrogen generation material. PMID:22619596

Hydrogen generation from Al-NiCl2/NaBH4 mixture affected by lanthanum metal.

PubMed

Sun, Wen Qiang; Fan, Mei-Qiang; Fei, Yong; Pan, Hua; Wang, Liang Liang; Yao, Jun

2012-01-01

The effect of La on Al/NaBH(4) hydrolysis was elaborated in the present paper. Hydrogen generation amount increases but hydrogen generation rate decreases with La content increasing. There is an optimized composition that Al-15 wt% La-5 wt% NiCl(2)/NaBH(4) mixture (Al-15 wt% La-5 wt% NiCl(2)/NaBH(4) weight ratio, 1 : 3) has 126 mL g(-1 )min(-1) maximum hydrogen generation rate and 1764 mL g(-1) hydrogen generation amount within 60 min. The efficiency is 88%. Combined with NiCl(2), La has great effect on NaBH(4) hydrolysis but has little effect on Al hydrolysis. Increasing La content is helpful to decrease the particle size of Al-La-NiCl(2) in the milling process, which induces that the hydrolysis byproduct Ni(2)B is highly distributed into Al(OH)(3) and the catalytic reactivity of Ni(2)B/Al(OH)(3) is increased therefore. But hydrolysis byproduct La(OH)(3) deposits on Al surface and leads to some side effect. The Al-La-NiCl(2)/NaBH(4) mixture has good stability in low temperature and its hydrolytic performance can be improved with increasing global temperature. Therefore, the mixture has good safety and can be applied as on board hydrogen generation material.

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

Experimental calibration of Forsterite-Anorthite-Ca-Tschermak-Enstatite (FACE) geobarometer for mantle peridotites

NASA Astrophysics Data System (ADS)

Fumagalli, P.; Borghini, G.; Rampone, E.; Poli, S.

2017-06-01

The crystallization of plagioclase-bearing assemblages in mantle rocks is witness of mantle exhumation at shallow depth. Previous experimental works on peridotites have found systematic compositional variations in coexisting minerals at decreasing pressure within the plagioclase stability field. In this experimental study we present new constraints on the stability of plagioclase as a function of different Na2O/CaO bulk ratios, and we present a new geobarometer for mantle rocks. Experiments have been performed in a single-stage piston cylinder at 5-10 kbar, 1050-1150 °C at nominally anhydrous conditions using seeded gels of peridotite compositions (Na2O/CaO = 0.08-0.13; X Cr = Cr/(Cr + Al) = 0.07-0.10) as starting materials. As expected, the increase of the bulk Na2O/CaO ratio extends the plagioclase stability to higher pressure; in the studied high-Na fertile lherzolite (HNa-FLZ), the plagioclase-spinel transition occurs at 1100 °C between 9 and 10 kbar; in a fertile lherzolite (FLZ) with Na2O/CaO = 0.08, it occurs between 8 and 9 kbar at 1100 °C. This study provides, together with previous experimental results, a consistent database, covering a wide range of P- T conditions (3-9 kbar, 1000-1150 °C) and variable bulk compositions to be used to define and calibrate a geobarometer for plagioclase-bearing mantle rocks. The pressure sensitive equilibrium: Mg_{2}SiO_{4}^Ol\\limits_{Forsterite} + CaAl_{2}Si_{2}O_{8}^{Pl\\limits_{Anorthite} = CaAl_{2}SiO_{6}^{Cpx}\\limits_{Ca-Tschermak} + Mg_{2}Si_{2}O_{6}^{Opx}\\limits_{Enstatite}, has been empirically calibrated by least squares regression analysis of experimental data combined with Monte Carlo simulation. The result of the fit gives the following equation: P=7.2( ± 2.9)+0.0078( ± 0.0021)T{{ }}+0.0022( ± 0.0001)T ln K, {R^2}=0.93, where P is expressed in kbar and T in kelvin. K is the equilibrium constant K = a CaTs × a en/ a an × a fo, where a CaTs, a en, a an and a fo are the activities of Ca-Tschermak in

Czochralski growth of 2 in. Ca3Ta(Ga,Al)3Si2O14 single crystals for piezoelectric applications

NASA Astrophysics Data System (ADS)

Yoshikawa, Akira; Shoji, Yasuhiro; Ohashi, Yuji; Yokota, Yuui; Chani, Valery I.; Kitahara, Masanori; Kudo, Tetsuo; Kamada, Kei; Kurosawa, Shunsuke; Medvedev, Andrey; Kochurikhin, Vladimir

2016-10-01

Growth of 2-in. diameter Al-substituted Ca3TaGa3Si2O14 crystals by Czochralski method is reported. The crystals were grown from the melt of Ca3TaGa1.5Al1.5Si2O14 composition and had langasite structure. No inclusions of secondary phases were detected in these crystals. The Ca3Ta(Ga,Al)3Si2O14 mixed crystals produced using non-substituted Ca3TaGa3Si2O14 seeds were defective. They had cracks and/or poly-crystalline structure. However, those grown on the seed of approximately Ca3TaGa1.5Al1.5Si2O14 composition were defect-free. Phase diagram of the Ca3TaGa3Si2O14-Ca3TaAl3Si2O14 pseudo-binary system and segregation phenomenon are discussed in some details. Homogeneity of the crystals was evaluated by measuring 2D-mapping of leaky surface acoustic wave (LSAW) velocities for Y-cut Ca3TaGa1.5Al1.5Si2O14 substrate. Although some inhomogeneities were observed due to slight variations in chemical composition, the crystal had acceptable homogeneity for applications in acoustic wave devices exhibiting the LSAW velocity variation within ±0.048%.

Impedance and dielectric relaxation spectroscopy studies on the calcium modified Na0.5Bi0.44Ca0.06TiO2.97 ceramics

NASA Astrophysics Data System (ADS)

Wang, W. G.; Li, X. Y.

2017-12-01

Na0.5Bi0.44Ca0.06TiO2.97 ceramics were synthetized by conventional solid-state reaction. XRD measurement analysis shows that the Na0.5Bi0.44Ca0.06TiO2.97 sample is the single perovskite structures. The oxide ion conductivity of the Na0.5Bi0.44Ca0.06TiO2.97 sample was investigated by AC impedance spectroscopy measurement. The bulk conductivity of Na0.5Bi0.44Ca0.06TiO2.97 sample can arrive at 2.22×10-4 S/cm at 573 K in air atmosphere. By changing measuring temperature of dielectric frequency spectroscopy measurement, the activation energy E and pre-exponential factor τ0 are E= 0.81 eV, τ0=1.5×10-13 s for Na0.5Bi0.44Ca0.06TiO2.97 sample, respectively. Judging from the relaxation parameters, the dielectric loss peaks correspond to oxide ion via vacancies diffusion in Na0.5Bi0.44Ca0.06TiO2.97 sample. Compared with the same dopant amount Na0.5Bi0.5Ti0.94Mg0.06O2.94 compound, the better oxygen vacancy mobility and larger specific free volume Vsf might be responsible for the favourable oxide ion conductivity in the Na0.5Bi0.44Ca0.06TiO2.97 sample, indicating that calcium modified Na0.5Bi0.5TiO3 materials are promising for intermediate-temperature solid electrochemical devices.

Discharge properties of Mg-Al-Mn-Ca and Mg-Al-Mn alloys as anode materials for primary magnesium-air batteries

NASA Astrophysics Data System (ADS)

Yuasa, Motohiro; Huang, Xinsheng; Suzuki, Kazutaka; Mabuchi, Mamoru; Chino, Yasumasa

2015-11-01

The discharge behaviors of rolled Mg-6 mass%Al-0.3 mass%Mn-2 mass%Ca (AMX602) and Mg-6 mass%Al-0.3 mass%Mn (AM60) alloys used as anodes for Magnesium-air batteries were investigated. The AMX602 alloy exhibited superior discharge properties compared to the AM60 alloy, especially at low current density. The discharge products of the AMX602 alloy were dense and thin, and many cracks were observed at all current densities. In addition, the discharge products were detached at some sites. These sites often corresponded to the positions of Al2Ca particles. The comparison of the discharge and corrosion tests indicated that the dense and thin discharge products of AMX602 were easily cracked by dissolution of the Mg matrix around Al2Ca particles, and the cracks promoted the penetration of the electrolyte into the discharge products, retaining the discharge activity. In contrast, concerning the AM60 alloy, thick discharge products were formed on the surface during discharge, and cracking of the discharge products hardly occurred, degrading the discharge properties. Localized and deeply corroded pits that could result from the detachment of metal pieces from the anode during discharge were partly observed in the AM60 alloy. It is suggested that these detached metal pieces are another reason for the low discharge properties of the AM60 alloy.

A Reaction Between High Mn-High Al Steel and CaO-SiO2-Type Molten Mold Flux: Part I. Composition Evolution in Molten Mold Flux

NASA Astrophysics Data System (ADS)

Kim, Min-Su; Lee, Su-Wan; Cho, Jung-Wook; Park, Min-Seok; Lee, Hae-Geon; Kang, Youn-Bae

2013-04-01

In order to elucidate the reaction mechanism between high Mn-high Al steel such as twin-induced plasticity steel and molten mold flux composed mainly of CaO-SiO2 during continuous casting process, a series of laboratory-scale experiments were carried out in the present study. Molten steel and molten flux were brought to react in a refractory crucible in a temperature range between 1713 K to 1823 K (1440 °C to 1550 °C) and composition evolution in the steel and the flux was analyzed using inductively coupled plasma atomic emission spectroscopy, X-ray fluorescence, and electron probe microanalysis. The amount of SiO2 in the flux was significantly reduced by Al in the steel; thus, Al2O3 was accumulated in the flux as a result of a chemical reaction, 4[Al] + 3(SiO2) = 3[Si] + 2(Al2O3). In order to find a major factor which governs the reaction, a number of factors ((pct CaO/pct SiO2), (pct Al2O3), [pct Al], [pct Si], and temperature) were varied in the experiments. It was found that the above chemical reaction was mostly governed by [pct Al] in the molten steel. Temperature had a mild effect on the reaction. On the other hand, (pct CaO/pct SiO2), (pct Al2O3), and [pct Si] did not show any noticeable effect on the reaction. Apart from the above reaction, the following reactions are also thought to happen simultaneously: 2[Mn] + (SiO2) = [Si] + 2(MnO) and 2[Fe] + (SiO2) = [Si] + 2(FeO). These oxide components were subsequently reduced by Al in the molten steel. Na2O in the molten flux was gradually decreased and the decrease was accelerated by increasing [pct Al] and temperature. Possible reactions affecting the Al2O3 accumulation are summarized.

Experimental Determination of the Effect of the Ratio of B/Al on Glass Dissolution along the Nepheline (NaAlSiO 4) – Malinkoite (NaBSiO 4) Join

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

Pierce, Eric M; Reed, Lunde R; Shaw, Wendy J

2010-03-27

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 to 25 mol%) and B 2O 3 (20 to 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).more » Analysis 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 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. But despite the changes in the B/Al ratio and B coordination, the 29Si spectra maintain a chemical shift between -88 to -84 ppm for each glass. Unlike the 29Si spectra, the 27Al resonances shift to more positive 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). Raman spectroscopy was use to augment the results collected from MAS-NMR and demonstrated that NeB4 (glass sample with the highest B content) was glass-glass phase separated (e.g., heterogeneous glass). 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 for all homogeneous glasses. The temperature dependence shows an order of magnitude increase in the dissolution rate with a 67°C increase in temperature and

Preparation and characterization of polyaniline-containing Na-AlMCM-41 as composite material with semiconductor behavior.

PubMed

Anunziata, Oscar A; Gómez Costa, Marcos B; Sánchez, Rodolfo D

2005-12-15

Composite material formed from a mesoporous aluminosilicate, Na-AlMCM-41, with conducting polyaniline (PANI) has been synthesized by an in situ polymerization technique. Studies of aniline adsorption over mesoporous Na-AlMCM-41 synthesized in our laboratory allowed us to find the modes in which aniline interacts with the active sites of Na-AlMCM-41. In order to obtain the best reaction conditions to polymerize aniline onto Na-AlMCM-41, aniline was first polymerized to produce pure PANI. Hence, the oxidative in situ polymerization was carried out by two procedures, differing in the polymerization time and in static or stirring conditions. Studies of infrared spectroscopy and UV-vis spectroscopy indicated that higher polymerization time and static conditions allowed us to obtain mainly polyaniline in emeraldine form on the host. The N(2) isotherm of the polyaniline/Na-AlMCM-41 composite (PANI/MCM) indicated that the shape was similar to that of MCM, but the shift to saturation transition to lower partial pressure shows that the channels are occupied by PANI and they are now narrowed. The thermal properties of PANI, Na-AlMCM-41, and composite were investigated by TGA analyses and we found that the polymer shows higher thermal stability when it is forming the composite. Scanning electron microscopy indicated that PANI is not on the outer surface of the host. Conductivity studies show that PANI/Na-AlMCM-41 exhibits semiconductor behavior at room temperature and its conductivity was 7.0 x 10(-5) S/cm, smaller than that of pure polyaniline. PANI/Na-AlMCM-41 conductivity shows an increase as temperature increases. Magnetic measurements at room temperature confirmed that the composite has paramagnetic behavior; at lower temperatures the composite became diamagnetic.

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.

Ca2 Al2 SiO7 :Ce3+ phosphors for mechanoluminescence dosimetry.

PubMed

Tiwari, Geetanjali; Brahme, Nameeta; Sharma, Ravi; Bisen, D P; Sao, Sanjay Kumar; Sahu, Ishwar Prasad

2016-12-01

A series of Ce 3+ ion single-doped Ca 2 Al 2 SiO 7 phosphors was synthesized by a combustion-assisted method at an initiating temperature of 600 °C. The samples were annealed at 1100 °C for 3 h and their X-ray diffraction patterns confirmed a tetragonal structure. The phase structure, particle size, surface morphology and elemental analysis were analyzed using X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy techniques. Thermoluminescence (TL) intensity increased with increase in ultraviolet (UV) light exposure time up to 15 min. With further increase in the UV irradiation time the TL intensity decreases. The increase in TL intensity indicates that trap concentration increased with UV exposure time. A broad peak at 121 °C suggested the existence of a trapping level. The peak of mechanoluminescence (ML) intensity versus time curve increased linearly with increasing impact velocity of the moving piston. Mechanoluminescence intensity increased with increase in UV irradiation time up to 15 min. Under UV-irradiation excitation, the TL and ML emission spectra of Ca 2 Al 2 SiO 7 :Ce 3+ phosphor showed the characteristic emission of Ce 3+ peaking at 400 nm (UV-violet) and originating from the Ce 3+ transitions of 5d-4f ( 2 F 5/2 and 2 F 7/2 ). The photoluminescence (PL) emission spectra for Ca 2 Al 2 SiO 7 :Ce 3+ were similar to the ML/TL emission spectra. The mechanism of ML excitation and the suitability of the Ca 2 Al 2 SiO 7 :Ce 3+ phosphor for radiation dosimetry are discussed. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of K+ and Na+ on calcium-dependent electron-dense particles in the monoaminergic synaptic vesicles of rat pineal nerves fixed in Ca2+-containing solutions.

PubMed

Pellegrino de Iraldi, A; Corazza, J P

1983-01-01

The effect of K+ and Na+ on the Ca2+ binding site in the dense core of monoaminergic vesicles of pineal nerves was investigated in the rat. Rat pineal glands, bisected immediately after decapitation, were incubated at room temperature in solutions containing high K+ or high Na+ in the presence or absence of Ca2+. Fixation was performed in glutaraldehyde-osmium tetroxide in collidine buffer, with and without CaCl2. It was confirmed that, after fixation in Ca2+-containing solutions, an electron-dense particle, located in the vesicle core, which can be considered a calcium deposit, appears within the synaptic vesicles. It was observed that this Ca2+ deposit may be modified by incubation in a high K+ or high Na+ milieu before fixation in Ca2+ containing solutions. When the incubation was carried out with high K+ and high Ca2+ simultaneously, Ca2+ deposits were considerably increased. With K+ alone, no Ca2+ deposits were apparent, as when electrical stimulation is applied before fixation. This effect was not observed when the incubation was done in high Na+. Consecutive incubations in high K+ and high Na+, respectively, restored the capability of the vesicle cores to bind Ca2+. Prolonged incubation in high Na+ before fixation increased Ca2+ deposits within the vesicles. These findings are in line with data on the effect of these ions upon the storage and release of biogenic amines and suggest that these ions modify the capability of synaptic vesicles to bind Ca2+.

Chronic lithium treatment up-regulates cell surface Na(V)1.7 sodium channels via inhibition of glycogen synthase kinase-3 in adrenal chromaffin cells: enhancement of Na(+) influx, Ca(2+) influx and catecholamine secretion after lithium withdrawal.

PubMed

Yanagita, Toshihiko; Maruta, Toyoaki; Nemoto, Takayuki; Uezono, Yasuhito; Matsuo, Kiyotaka; Satoh, Shinya; Yoshikawa, Norie; Kanai, Tasuku; Kobayashi, Hideyuki; Wada, Akihiko

2009-09-01

In cultured bovine adrenal chromaffin cells expressing Na(V)1.7 isoform of voltage-dependent Na(+) channels, we have previously reported that lithium chloride (LiCl) inhibits function of Na(+) channels independent of glycogen synthase kinase-3 (GSK-3) (Yanagita et al., 2007). Here, we further examined the effects of chronic lithium treatment on Na(+) channels. LiCl treatment (1-30 mM, > or = 12 h) increased cell surface [(3)H]saxitoxin ([(3)H]STX) binding by approximately 32% without altering the affinity of [(3)H]STX binding. This increase was prevented by cycloheximide and actinomycin D. SB216763 and SB415286 (GSK-3 inhibitors) also increased cell surface [(3)H]STX binding by approximately 31%. Simultaneous treatment with LiCl and SB216763 or SB415286 did not produce an increased effect on [(3)H]STX binding compared with either treatment alone. LiCl increased Na(+) channel alpha-subunit mRNA level by 32% at 24 h. LiCl accelerated alpha-subunit gene transcription by 35% without altering alpha-subunit mRNA stability. In LiCl-treated cells, LiCl inhibited veratridine-induced (22)Na(+) influx as in untreated cells. However, washout of LiCl after chronic treatment enhanced veratridine-induced (22)Na(+) influx, (45)Ca(2+) influx and catecholamine secretion by approximately 30%. Washout of LiCl after 24 h treatment shifted concentration-response curve of veratridine upon (22)Na(+) influx upward, without altering its EC(50) value. Ptychodiscus brevis toxin-3 allosterically enhanced veratridine-induced (22)Na(+) influx by two-fold in untreated and LiCl-treated cells. Whole-cell patch-clamp analysis indicated that I-V curve and steady-state inactivation/activation curves were comparable between untreated and LiCl-treated cells. Thus, GSK-3 inhibition by LiCl up-regulated cell surface Na(V)1.7 via acceleration of alpha-subunit gene transcription, enhancing veratridine-induced Na(+) influx, Ca(2+) influx and catecholamine secretion.

Novel technique for preparing Ca- and P-containing ceramic coating on Ti-6Al-4V by micro-arc oxidation.

PubMed

Yu, Sirong; Yang, Xizhen; Yang, Long; Liu, Yaohui; Yu, Yingjie

2007-11-01

A novel technique for preparing the Ca- and P-containing ceramic coating on Ti-6Al-4V alloy by micro-arc oxidation (MAO) was developed successfully in this paper. In the new technique, Ti alloy first was micro-arc oxidated in P-containing electrolyte, and then it was micro-arc oxidated in Ca-containing electrolyte. This technique can avoid the undesired chemical reaction between Ca-containing salt and P-containing salt in electrolyte. The surface morphologies, composition, and phases of MAO coatings were studied by means of SEM, EDS, and XRD. The results show that the P- and Ca-containing coating on Ti-6Al-4V alloy contains Ti, TiO(2) (rutile), alpha-Ca(PO(3))(2), CaTiO(3), and AlTi(3). There are many small and uniform pores in the coating. Most of these pores are coterminous. The microhardness of the coating is 720 HV and higher than that of Ti-6Al-4V alloy (220 HV). The coating is more wear-resistant than Ti-6Al-4V alloy under the lubricant of the artificial saliva and not easy to desquamate from the substrate of Ti-6Al-4V alloy.

Dual-wavelength Nd:CaLnAlO4 lasers at 1.365 and 1.390 μm

NASA Astrophysics Data System (ADS)

Loiko, Pavel; Maria Serres, Josep; Mateos, Xavier; Xu, Xiaodong; Xu, Jun; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc; Major, Arkady

2018-02-01

Tetragonal calcium rare-earth aluminates, CaLnAlO4, are attractive laser host crystals. The emission of Nd3+ ions at 1.3- 1.4 μm due to the 4F3/2 -> 4I13/2 transition is of interest for medicine, fiber optics, and light conversion. We report on compact Nd:CaLnAlO4 lasers using a plane-plane cavity. With an a-cut 0.8 at.% Nd:CaYAlO4 crystal diode-pumped at 802 nm, a maximum continuous-wave output power of 365 mW was achieved at 1.365 & 1.390 μm corresponding to the σ-polarization. The 4F3/2 -> 4I13/2 laser performance of the Nd:CaLnAlO4 crystals was compared to that from a monoclinic Nd:KGd(WO4)2. At the 4F3/2-> 4I11/2 transition (1.08 μm), a Nd:CaYAlO4 micro-laser generated multi-watt output (>4 W) with a slope efficiency of 39%.

Iron isotope effect in the iron arsenide superconductor (Ca0.4Na0.6)Fe2As2

NASA Astrophysics Data System (ADS)

Tsuge, Y.; Nishio, T.; Iyo, A.; Tanaka, Y.; Eisaki, H.

2014-05-01

We report a new sample synthesis technique for polycrystalline (Ca1-xNax)Fe2As2 (0Ca0.4Na0.6)Fe2As2 with three types of iron isotopes (54Fe, natural Fe, and 57Fe). We synthesized isotope samples carefully not to give rise to a difference in the Na content x between different isotope samples, which becomes potentially a factor for an extrinsic difference in the superconducting transition temperature Tc between those samples. No significant difference in lattice parameters between those samples is shown by measurements of powder x-ray diffraction (XRD), implying that the Na content in samples is well-controlled. Our estimate of the iron isotope coefficient αFe defined by -d InTc/d lnMFe, where MFe is the iron isotope mass, is -0.19. These indicate that in (Ca0.4Na0.6)Fe2As2, the iron isotope coefficient becomes definitely negative. We discuss the implications of this fact, considering previous measurements of an iron isotope effect in different iron-based superconductors.

Synthesis of ternary Si clathrates in the A-Al-Si (A = Na and K) system

NASA Astrophysics Data System (ADS)

Imai, Motoharu; Singh, Shiva Kumar; Nishio, Mitsuaki; Yamada, Takahiro; Yamane, Hisanori

2015-07-01

With the aim of producing functional materials based on earth-abundant elements, we examined the synthesis of the ternary type-I clathrates A8AlxSi46-x (A = Na and K). The type-I Si clathrate K7.9(1)Al7.1(1)Si38.9(4), having a lattice parameter of 10.434(1) Å, was successfully synthesized via the direct reaction of K, Al, and Si by optimization of both the synthesis temperature and the molar ratios among the raw ingredients. K8Al7Si39 exhibited metallic conduction: its electrical resistivity increased with increasing temperature. The high pressure synthesis of Na8AlxSi46-x was also examined, using a belt-type apparatus and employing a mixture of NaSi, Al, and Si as the reagents. In this manner, the type-I Si clathrate Na8.7(9)Al0.5(1)Si45(2), having a lattice parameter of 10.211(1) Å, was synthesized at 5.5 GPa and 1570 K.

Structural implications of weak Ca2+ block in Drosophila cyclic nucleotide-gated channels.

PubMed

Lam, Yee Ling; Zeng, Weizhong; Derebe, Mehabaw Getahun; Jiang, Youxing

2015-09-01

Calcium permeability and the concomitant calcium block of monovalent ion current ("Ca(2+) block") are properties of cyclic nucleotide-gated (CNG) channel fundamental to visual and olfactory signal transduction. Although most CNG channels bear a conserved glutamate residue crucial for Ca(2+) block, the degree of block displayed by different CNG channels varies greatly. For instance, the Drosophila melanogaster CNG channel shows only weak Ca(2+) block despite the presence of this glutamate. We previously constructed a series of chimeric channels in which we replaced the selectivity filter of the bacterial nonselective cation channel NaK with a set of CNG channel filter sequences and determined that the resulting NaK2CNG chimeras displayed the ion selectivity and Ca(2+) block properties of the parent CNG channels. Here, we used the same strategy to determine the structural basis of the weak Ca(2+) block observed in the Drosophila CNG channel. The selectivity filter of the Drosophila CNG channel is similar to that of most other CNG channels except that it has a threonine at residue 318 instead of a proline. We constructed a NaK chimera, which we called NaK2CNG-Dm, which contained the Drosophila selectivity filter sequence. The high resolution structure of NaK2CNG-Dm revealed a filter structure different from those of NaK and all other previously investigated NaK2CNG chimeric channels. Consistent with this structural difference, functional studies of the NaK2CNG-Dm chimeric channel demonstrated a loss of Ca(2+) block compared with other NaK2CNG chimeras. Moreover, mutating the corresponding threonine (T318) to proline in Drosophila CNG channels increased Ca(2+) block by 16 times. These results imply that a simple replacement of a threonine for a proline in Drosophila CNG channels has likely given rise to a distinct selectivity filter conformation that results in weak Ca(2+) block. © 2015 Lam et al.

Transitions in Al Coordination during Gibbsite Crystallization Using High-Field 27 Al and 23 Na MAS NMR Spectroscopy

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

Hu, Jian Zhi; Zhang, Xin; Jaegers, Nicholas R.

Mechanisms of nucleation and growth of Al hydroxides such as gibbsite from aqueous solution, particularly in highly alkaline conditions, remain poorly understood. In this work, quantitative 27Al and 22Na MAS NMR experiments were conducted on solid samples extracted from the crystallization of gibbsite from an amorphous aluminum hydroxide gel precursor. The use of high magnetic field and fast sample spinning allowed transitional tetrahedral (AlT) and pentahedral (AlP) aluminum species to be observed along with the octahedral aluminum (AlO) that dominates the gibbsite product. Low-coordinated Al species could be detected at concentrations as low as 0.1% of the total Al sites.more » It is established that (a) AlT and AlP coexist on the surface of growing gibbsites even with a combined percentage over the total Al sites of less than 1%; (b) Different synthesis methods generate gibbsite with varying amounts of low-coordinated Al; (c) the amorphous gel precursor contains a significant amount of low-coordinated Al sites with AO: AlP: AlT ratios of approximately 4:2:1; (d) upon hydration, the external, low-coordinated Al sites become six-fold coordinated by interacting with the oxygen in H2O and the 27Al MAS NMR peak position shifts to that for the AlO sites; (e) gibbsite with increased long range order is synthesized over longer times by gradually incorporating residual AlP and AlT sites into octahedrally-coordinated AlO sites; (f) trace Na is predominantly a surface species on gibbsite particles. These findings provide a basis for understanding the gibbsite crystallization mechanism, along with a general means of characterizing gibbsite surface properties that are of equal importance for understanding related processes such as dissolution behavior.« less

Secondary electron emission and glow discharge properties of 12CaO·7Al2O3 electride for fluorescent lamp applications.

PubMed

Watanabe, Satoru; Watanabe, Toshinari; Ito, Kazuhiro; Miyakawa, Naomichi; Ito, Setsuro; Hosono, Hideo; Mikoshiba, Shigeo

2011-06-01

12CaO·7Al 2 O 3 electride, a sub-nanoporous compound having a work function of 2.4 eV, was examined as a candidate cathode material in fluorescent lamps. The electron emission yield was higher and the discharge voltage was lower for 12CaO·7Al 2 O 3 than for existing cathode materials such as Ni, Mo or W; therefore, the energy consumption of the fluorescent lamps can be improved using 12CaO·7Al 2 O 3 cathodes. Prototype glow-discharge lamps using 12CaO·7Al 2 O 3 were constructed and exhibited reasonable durability.

Secondary electron emission and glow discharge properties of 12CaO·7Al2O3 electride for fluorescent lamp applications

PubMed Central

Watanabe, Satoru; Watanabe, Toshinari; Ito, Kazuhiro; Miyakawa, Naomichi; Ito, Setsuro; Hosono, Hideo; Mikoshiba, Shigeo

2011-01-01

12CaO·7Al2O3 electride, a sub-nanoporous compound having a work function of 2.4 eV, was examined as a candidate cathode material in fluorescent lamps. The electron emission yield was higher and the discharge voltage was lower for 12CaO·7Al2O3 than for existing cathode materials such as Ni, Mo or W; therefore, the energy consumption of the fluorescent lamps can be improved using 12CaO·7Al2O3 cathodes. Prototype glow-discharge lamps using 12CaO·7Al2O3 were constructed and exhibited reasonable durability. PMID:27877401

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. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Effects of Ca, Cu, Al and La on pectin gel strength: implications for plant cell walls.

PubMed

McKenna, Brigid A; Nicholson, Timothy M; Wehr, J Bernhard; Menzies, Neal W

2010-06-16

Rheology of Ca-pectate gels is widely studied, but the behaviour of pectate gels formed by Cu, Al and La is largely unknown. It is well known that gel strength increases with increasing Ca concentration, and it is hypothesised that this would also be the case for other cations. Pectins are a critical component of plant cell walls, imparting various physicochemical properties. Furthermore, the mechanism of metal toxicity in plants is hypothesised to be, in the short term, related to metal interactions with cell wall pectin. This study investigated the influence of Ca, Cu, Al and La ion concentrations at pH 4 on the storage modulus as a function of frequency for metal-pectin gels prepared from pectin (1%) with a degree of esterification of 30%. Gels were formed in situ over 6d in metal chloride solution adjusted daily to pH 4. Cation concentration was varied to develop a relationship between gel strength and cation concentration. At similar levels of cation saturation, gel strength increased in the order of La<Ca < or =AlCa gels being the most swollen. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Understanding the Relationship Between Structure and Thermophysical Properties of CaO-SiO2-MgO-Al2O3 Molten Slags

NASA Astrophysics Data System (ADS)

Sun, Yongqi; Wang, Hao; Zhang, Zuotai

2018-04-01

In the present work, the relationship between the microscopic structure and macroscopic thermophysical properties in a basic CaO-SiO2-MgO-Al2O3 quaternary system was identified using Fourier transformation infrared, Raman and 27Al magic angular spinning nuclear magnetic resonance (MAS-NMR) techniques. The Raman spectra quantitatively proved that with increasing Al2O3 content, the concentrations of the symmetric units of Q 0(Si) and Q 2(Si) decreased, while those of the asymmetric units of Q 1(Si) and Q 3(Si) increased; consequently, the degree of polymerization of the networks increased, which resulted in an increase in slag viscosity. The 27Al MAS-NMR spectra demonstrated that three structural units of Al atoms, namely, AlO4, AlO5, and AlO6, mainly existed in the networks. With increasing Al2O3 content, the concentration of AlO4 slightly decreased, while those of AlO5 and AlO6 increased; overall, Al2O3 acted as a network former in the present system. The increasing Al2O3 content led to additional AlO6 and Si-NBO-Ca-NBO-Al frameworks, which replaced Si-NBO-Ca-NBO-Si in the networks (NBO: non-bridging oxygen) and induced a change in the primarily precipitated crystalline phase from Ca2MgSi2O7 and Ca2Al2SiO7 to MgAlO4.

Formation of Intermetallic Phases in Al-Sc Alloys Prepared by Molten Salt Electrolysis at Elevated Temperatures

NASA Astrophysics Data System (ADS)

Wang, Zengjie; Guan, Chunyang; Liu, Qiaochu; Xue, Jilai

Molten salts electrolysis method to prepare Al-RE alloys has attracted increasing attention recently. CaCl2 and Na3AlF6 were the most often used melts for this purpose. In this work, Al-Sc alloys prepared by electrolytic deposition process in both CaCl2 and Na3AlF6 melts were investigated, respectively. It was found that Sc distributes almost uniformly and Sc contents increase with increasing current intensity in both melts. Current efficiency was measured for comparison among various current densities applied. The alloy products were analyzed using XRD and SEM, where the formation behaviors of Al-Sc intermetallics were investigated in details. The experimental and theoretical results demonstrate that Al3Sc and Al0.968Sc0.032 are the major precipitates in the Al-Sc alloys prepared by molten electrolysis. The results are useful for selection and optimization of the molten salts compositions and the parameters of electrolysis operation.

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.

Optical properties of white organic light-emitting devices fabricated utilizing a mixed CaAl12O19:Mn4+ and Y3Al5O12:Ce3+ color conversion layer.

PubMed

Jeong, H S; Kim, S H; Lee, K S; Jeong, J M; Yoo, T W; Kwon, M S; Yoo, K H; Kim, T W

2013-06-01

White organic light-emitting devices (OLEDs) were fabricated by combining a blue OLED with a color conversion layer made of mixed Y3Al5O12:Ce3+ green and Ca2AlO19:Mn4+ red phosphors. The X-ray diffraction patterns showed that Ce3+ ions in the Y3Al5O12:Ce3+ phosphors completely substituted for the Y3+ ions and the Mn4+ ions in the CaAl12O19:Mn4+ phosphors completely substituted for the Ca2+ ions. Electroluminescence spectra at 11 V for the OLEDs fabricated utilizing a color conversion layer showed that the Commission Internationale de l'Eclairage coordinates for the Y3Al5O12:Ce3+ and CaAl12O19:Mn4+ phosphors mixed at the ratio of 1:5 and 1:10 were (0.31, 0.34) and (0.32, 0.37), respectively, indicative of a good white color.

Massive Ca-induced Membrane Fusion and Phospholipid Changes Triggered by Reverse Na/Ca Exchange in BHK Fibroblasts

PubMed Central

Yaradanakul, Alp; Wang, Tzu-Ming; Lariccia, Vincenzo; Lin, Mei-Jung; Shen, Chengcheng; Liu, Xinran; Hilgemann, Donald W.

2008-01-01

Baby hamster kidney (BHK) fibroblasts increase their cell capacitance by 25–100% within 5 s upon activating maximal Ca influx via constitutively expressed cardiac Na/Ca exchangers (NCX1). Free Ca, measured with fluo-5N, transiently exceeds 0.2 mM with total Ca influx amounting to ∼5 mmol/liter cell volume. Capacitance responses are half-maximal when NCX1 promotes a free cytoplasmic Ca of 0.12 mM (Hill coefficient ≈ 2). Capacitance can return to baseline in 1–3 min, and responses can be repeated several times. The membrane tracer, FM 4-64, is taken up during recovery and can be released at a subsequent Ca influx episode. Given recent interest in signaling lipids in membrane fusion, we used green fluorescent protein (GFP) fusions with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) and diacylglycerol (DAG) binding domains to analyze phospholipid changes in relation to these responses. PI(4,5)P2 is rapidly cleaved upon activating Ca influx and recovers within 2 min. However, PI(4,5)P2 depletion by activation of overexpressed hM1 muscarinic receptors causes only little membrane fusion, and subsequent fusion in response to Ca influx remains massive. Two results suggest that DAG may be generated from sources other than PI(4,5)P in these protocols. First, acylglycerols are generated in response to elevated Ca, even when PI(4,5)P2 is metabolically depleted. Second, DAG-binding C1A-GFP domains, which are brought to the cell surface by exogenous ligands, translocate rapidly back to the cytoplasm in response to Ca influx. Nevertheless, inhibitors of PLCs and cPLA2, PI(4,5)P2-binding peptides, and PLD modification by butanol do not block membrane fusion. The cationic agents, FM 4-64 and heptalysine, bind profusely to the extracellular cell surface during membrane fusion. While this binding might reflect phosphatidylserine (PS) “scrambling” between monolayers, it is unaffected by a PS-binding protein, lactadherin, and by polylysine from the cytoplasmic side

Microwave dielectric properties of CaCu3Ti4O12-Al2O3 composite

NASA Astrophysics Data System (ADS)

Rahman, Mohd Fariz Ab; Abu, Mohamad Johari; Karim, Saniah Ab; Zaman, Rosyaini Afindi; Ain, Mohd Fadzil; Ahmad, Zainal Arifin; Mohamed, Julie Juliewatty

2016-07-01

(1-x)CaCu3Ti4O12 + (x)Al2O3 composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO3, CuO and TiO2 powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al2O3 were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sintered samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl2O4 and Corundum (Al2O3) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al2O3 (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al2O3 (x = 0.01) was remarkably reduced the dielectric loss while slightly increased the dielectric permittivity. However, further addition of Al2O3 was reduced both dielectric loss and permittivity at least for an order of magnitude.

Synthesis and effect of Ce and Mn co-doping on photoluminescence characteristics of Ca6AlP5O20:Eu novel phosphors.

PubMed

Shinde, K N; Dhoble, S J

2013-01-01

A series of Ca6AlP5O20 doped with rare earths (Eu and Ce) and co-doped (Eu, Ce and Eu,Mn) were prepared by combustion synthesis. Under Hg-free excitation, Ca6AlP5O20:Eu exhibited Eu(2+) (486 nm) emission in the blue region of the spectrum and under near Hg excitation (245 nm), Ca6AlP5O20:Ce phosphor exhibited Ce(3+) emission (357 nm) in the UV range. Photoluminescence (PL) peak intensity increased in Ca6AlP5O20:Eu,Ce and Ca6AlP5O20:Eu, Mn phosphors due to co-activators of Ce(3+) and Mn(2+) ions. As a result, these ions played an important role in PL emission in the present matrix. Ca6AlP5O20:Eu, Ce and Ca6AlP5O20:Eu, Mn phosphors provided energy transfer mechanisms via Ce(3+) → Eu(2+) and Eu(2+) → Mn(2+), respectively. Eu ions acted as activators and Ce ions acted as sensitizers. Ce emission energy was well matched with Eu excitation energy in the case of Ca6AlP5O20:Eu, Ce and Eu ions acted as activators and Mn ions acted as sensitizers in Ca6AlP5O20:Eu, Mn. This study included synthesis of new and efficient phosphate phosphors. The impact of doping and co-doping on photoluminescence properties and energy transfer mechanisms were investigated and we propose a feasible interpretation. Copyright © 2012 John Wiley & Sons, Ltd.

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.

CGP37157, an inhibitor of the mitochondrial Na+/Ca2+ exchanger, protects neurons from excitotoxicity by blocking voltage-gated Ca2+ channels.

PubMed

Ruiz, A; Alberdi, E; Matute, C

2014-04-10

Inhibition of the mitochondrial Na(+)/Ca(2+) exchanger (NCLX) by CGP37157 is protective in models of neuronal injury that involve disruption of intracellular Ca(2+) homeostasis. However, the Ca(2+) signaling pathways and stores underlying neuroprotection by that inhibitor are not well defined. In the present study, we analyzed how intracellular Ca(2+) levels are modulated by CGP37157 (10 μM) during NMDA insults in primary cultures of rat cortical neurons. We initially assessed the presence of NCLX in mitochondria of cultured neurons by immunolabeling, and subsequently, we analyzed the effects of CGP37157 on neuronal Ca(2+) homeostasis using cameleon-based mitochondrial Ca(2+) and cytosolic Ca(2+) ([Ca(2+)]i) live imaging. We observed that NCLX-driven mitochondrial Ca(2+) exchange occurs in cortical neurons under basal conditions as CGP37157 induced a decrease in [Ca(2)]i concomitant with a Ca(2+) accumulation inside the mitochondria. In turn, CGP37157 also inhibited mitochondrial Ca(2+) efflux after the stimulation of acetylcholine receptors. In contrast, CGP37157 strongly prevented depolarization-induced [Ca(2+)]i increase by blocking voltage-gated Ca(2+) channels (VGCCs), whereas it did not induce depletion of ER Ca(2+) stores. Moreover, mitochondrial Ca(2+) overload was reduced as a consequence of diminished Ca(2+) entry through VGCCs. The decrease in cytosolic and mitochondrial Ca(2+) overload by CGP37157 resulted in a reduction of excitotoxic mitochondrial damage, characterized here by a reduction in mitochondrial membrane depolarization, oxidative stress and calpain activation. In summary, our results provide evidence that during excitotoxicity CGP37157 modulates cytosolic and mitochondrial Ca(2+) dynamics that leads to attenuation of NMDA-induced mitochondrial dysfunction and neuronal cell death by blocking VGCCs.

CGP37157, an inhibitor of the mitochondrial Na+/Ca2+ exchanger, protects neurons from excitotoxicity by blocking voltage-gated Ca2+ channels

PubMed Central

Ruiz, A; Alberdi, E; Matute, C

2014-01-01

Inhibition of the mitochondrial Na+/Ca2+ exchanger (NCLX) by CGP37157 is protective in models of neuronal injury that involve disruption of intracellular Ca2+ homeostasis. However, the Ca2+ signaling pathways and stores underlying neuroprotection by that inhibitor are not well defined. In the present study, we analyzed how intracellular Ca2+ levels are modulated by CGP37157 (10 μM) during NMDA insults in primary cultures of rat cortical neurons. We initially assessed the presence of NCLX in mitochondria of cultured neurons by immunolabeling, and subsequently, we analyzed the effects of CGP37157 on neuronal Ca2+ homeostasis using cameleon-based mitochondrial Ca2+ and cytosolic Ca2+ ([Ca2+]i) live imaging. We observed that NCLX-driven mitochondrial Ca2+ exchange occurs in cortical neurons under basal conditions as CGP37157 induced a decrease in [Ca2]i concomitant with a Ca2+ accumulation inside the mitochondria. In turn, CGP37157 also inhibited mitochondrial Ca2+ efflux after the stimulation of acetylcholine receptors. In contrast, CGP37157 strongly prevented depolarization-induced [Ca2+]i increase by blocking voltage-gated Ca2+ channels (VGCCs), whereas it did not induce depletion of ER Ca2+ stores. Moreover, mitochondrial Ca2+ overload was reduced as a consequence of diminished Ca2+ entry through VGCCs. The decrease in cytosolic and mitochondrial Ca2+ overload by CGP37157 resulted in a reduction of excitotoxic mitochondrial damage, characterized here by a reduction in mitochondrial membrane depolarization, oxidative stress and calpain activation. In summary, our results provide evidence that during excitotoxicity CGP37157 modulates cytosolic and mitochondrial Ca2+ dynamics that leads to attenuation of NMDA-induced mitochondrial dysfunction and neuronal cell death by blocking VGCCs. PMID:24722281

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

PubMed Central

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

2017-01-01

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

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

Dechlorination of Hexachlorobenzene in Contaminated Soils Using a Nanometallic Al/CaO Dispersion Mixture: Optimization through Response Surface Methodology

PubMed Central

Jiang, Yuhui; Shang, Yixuan; Yu, Shuyao; Liu, Jianguo

2018-01-01

Hexachlorobenzene (HCB) contamination of soils remains a significant environmental challenge all over the world. Reductive stabilization is a developing technology that can decompose the HCB with a dechlorination process. A nanometallic Al/CaO (n-Al/CaO) dispersion mixture was developed utilizing ball-milling technology in this study. The dechlorination efficiency of HCB in contaminated soils by the n-Al/CaO grinding treatment was evaluated. Response surface methodology (RSM) was employed to investigate the effects of three variables (soil moisture content, n-Al/CaO dosage and grinding time) and the interactions between these variables under the Box-Behnken Design (BBD). A high regression coefficient value (R2 = 0.9807) and low p value (<0.0001) of the quadratic model indicated that the model was accurate in predicting the experimental results. The optimal soil moisture content, n-Al/CaO dosage, and grinding time were found to be 7% (m/m), 17.7% (m/m), and 24 h, respectively, in the experimental ranges and levels. Under optimal conditions, the dechlorination efficiency was 80%. The intermediate product analysis indicated that dechlorination was the process by stepwise loss of chloride atoms. The main pathway observed within 24 h was HCB → pentachlorobenzene (PeCB) → 1,2,3,4-tetrachlorobenzene (TeCB) and 1,2,4,5-TeCB. The results indicated that the moderate soil moisture content was crucial for the hydrodechlorination of HCB. A probable mechanism was proposed wherein water acted like a hydrogen donor and promoted the hydrodechlorination process. The potential application of n-Al/CaO is an environmentally-friendly and cost-effective option for decontamination of HCB-contaminated soils. PMID:29702570

Dechlorination of Hexachlorobenzene in Contaminated Soils Using a Nanometallic Al/CaO Dispersion Mixture: Optimization through Response Surface Methodology.

PubMed

Jiang, Yuhui; Shang, Yixuan; Yu, Shuyao; Liu, Jianguo

2018-04-27

Hexachlorobenzene (HCB) contamination of soils remains a significant environmental challenge all over the world. Reductive stabilization is a developing technology that can decompose the HCB with a dechlorination process. A nanometallic Al/CaO (n-Al/CaO) dispersion mixture was developed utilizing ball-milling technology in this study. The dechlorination efficiency of HCB in contaminated soils by the n-Al/CaO grinding treatment was evaluated. Response surface methodology (RSM) was employed to investigate the effects of three variables (soil moisture content, n-Al/CaO dosage and grinding time) and the interactions between these variables under the Box-Behnken Design (BBD). A high regression coefficient value ( R ² = 0.9807) and low p value (<0.0001) of the quadratic model indicated that the model was accurate in predicting the experimental results. The optimal soil moisture content, n-Al/CaO dosage, and grinding time were found to be 7% (m/m), 17.7% (m/m), and 24 h, respectively, in the experimental ranges and levels. Under optimal conditions, the dechlorination efficiency was 80%. The intermediate product analysis indicated that dechlorination was the process by stepwise loss of chloride atoms. The main pathway observed within 24 h was HCB → pentachlorobenzene (PeCB) → 1,2,3,4-tetrachlorobenzene (TeCB) and 1,2,4,5-TeCB. The results indicated that the moderate soil moisture content was crucial for the hydrodechlorination of HCB. A probable mechanism was proposed wherein water acted like a hydrogen donor and promoted the hydrodechlorination process. The potential application of n-Al/CaO is an environmentally-friendly and cost-effective option for decontamination of HCB-contaminated soils.

Constraining the astrophysical 23Mg(p, γ)24Al reaction rate using the 23Na(d,p)24Na reaction

NASA Astrophysics Data System (ADS)

Bennett, E. A.; Catford, W. N.; Christian, G.; Dede, S.; Hallam, S.; Lotay, G.; Ota, S.; Saastamoinen, A.; Wilkinson, R.

2017-09-01

The 23Mg(p, γ)24Al reaction provides an escape from the Ne-Na cycle in classical novae and is therefore important in understanding nova nucleosynthesis in the A > 20 mass range. Although several resonances may contribute to the overall rate at novae temperatures, the resonance at 475 keV is thought to be dominant. The strength of this resonance has been directly measured using a radioactive 23Mg beam impinging on a windowless H2 gas target; however, recent high-precision 24Al mass measurements have called this result into question. Here we make an indirect measurement using the 23Na(d,p)24Na reaction in inverse kinematics to study the mirror state of the 475 keV resonance in 24Na. The experiment, performed at the Texas A&M Cyclotron Institute, utilized the TIARA silicon array, four HPGe detectors, and the MDM spectrometer to measure the excited states of the 24Na nucleus. Preliminary results from the experiment will be presented along with progress from the ongoing analysis.

Interaction of Corundum, Wollastonite and Quartz With H2O-NaCl Solutions at 800 C and 10 Kbar

NASA Astrophysics Data System (ADS)

Newton, R. C.; Manning, C. E.

2005-12-01

Aqueous fluids are potentially important transport agents in subduction zones and other high-P metamorphic environments. Recent studies indicate that at high P and T, the solubilities of major rock-forming elements are strongly enhanced by the formation of metal-chloride complexes, metal-hydroxide complexes and polynuclear metal-hydroxide clusters. However, the relative abundances of these species and the energetics of their interactions in high-pressure environments remains largely unknown. We measured the solubilities of corundum (Al2O3) and wollastonite (CaSiO3) at 800 °C and 10 kbar in H2O-NaCl solutions to halite saturation (XNaCl = 0.6) . Both minerals show marked enhancement of solubility with increasing salinity. Al2O3 mol fraction rises rapidly to XNaCl = 0.1, and then declines slowly towards halite saturation. Quenched experimental fluids have neutral pH. Modeling based on ideal solution of ions and molecules leads to a simple dissolution reaction and corresponding molality (m=mol/kg H2O) expression: Al2O3(cor) + Na+ + 3H2O = NaAl(OH)4 + Al(OH)2+ and mAl2O3 = [0.0232(aNaCl)1/4(aH2O)3/2+0.00123][1+2XNaCl/(1-XNaCl)] where H2O and NaCl activities are given by aH2O = (2-XNaCl)/(2+XNaCl) and aNaCl = 4(XNaCl)2/(1 + XNaCl)2. Wollastonite solubility in NaCl solutions is accurately described by: mCaSiO3 = 0.6734XNaCl + 0.1183(XNaCl)1/2 + 0.0204. There is a roughly 50-fold enhancement of dissolved wollastonite at halite saturation. Quenched experimental fluids are strongly basic (pH=11). A consistent dissolution reaction must therefore be similar to: CaSiO3(wo) + Na+ + Cl- = CaCl+ + OH- + HNaSiO3 Quartz solubility declines monotonically from mSiO2 = 1.248 in pure H2O to 0.20 at halite saturation. Quenched fluids are neutral, indicating that quartz does not react with solvent NaCl. The only salinity control on solubility is decrease of H2O activity. The simple dissolution behaviors to be deduced from measurements on these minerals suggest that fluid

12CaO-7Al2O3 Electride Hollow Cathode

NASA Technical Reports Server (NTRS)

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

Crystal growth, polarized spectra, and laser performance of Yb:CaGdAlO4 crystal

NASA Astrophysics Data System (ADS)

Di, J. Q.; Xu, X. D.; Xia, C. T.; Zheng, L. H.; Aka, G.; Yu, H. H.; Sai, Q. L.; Guo, X. Y.; Zhu, L.

2016-04-01

In this paper, the crystal growth, polarized spectra, and laser performance of Yb:CaGdAlO4 crystal were reported. The segregation coefficient of Yb3+ ions was calculated to be 0.47. The cell parameters were determined to be a  =  b  =  0.3658 nm, c  =  1.1985 nm. The peak absorption cross-section was calculated to be 2.65  ×  10-20 cm2 at 979 nm and the peak stimulated emission cross-section was 2.23  ×  10-20 cm2 at 980 nm for the π polarization. The continuous-wave (CW) laser operations of uncoated Yb:CaGdAlO4 crystals with 5  ×  5  ×  3 mm3 in size were demonstrated. A maximum output power of 1.6 W at 1048 nm was obtained with a slope efficiency of 28%. The results show that Yb:CaGdAlO4 crystal is a promising laser medium.

Dendritic Na+ spikes enable cortical input to drive action potential output from hippocampal CA2 pyramidal neurons

PubMed Central

Sun, Qian; Srinivas, Kalyan V; Sotayo, Alaba; Siegelbaum, Steven A

2014-01-01

Synaptic inputs from different brain areas are often targeted to distinct regions of neuronal dendritic arbors. Inputs to proximal dendrites usually produce large somatic EPSPs that efficiently trigger action potential (AP) output, whereas inputs to distal dendrites are greatly attenuated and may largely modulate AP output. In contrast to most other cortical and hippocampal neurons, hippocampal CA2 pyramidal neurons show unusually strong excitation by their distal dendritic inputs from entorhinal cortex (EC). In this study, we demonstrate that the ability of these EC inputs to drive CA2 AP output requires the firing of local dendritic Na+ spikes. Furthermore, we find that CA2 dendritic geometry contributes to the efficient coupling of dendritic Na+ spikes to AP output. These results provide a striking example of how dendritic spikes enable direct cortical inputs to overcome unfavorable distal synaptic locale to trigger axonal AP output and thereby enable efficient cortico-hippocampal information flow. DOI: http://dx.doi.org/10.7554/eLife.04551.001 PMID:25390033

Functional coupling between the Na+/Ca2+ exchanger and nonselective cation channels during histamine stimulation in guinea pig tracheal smooth muscle.

PubMed

Algara-Suárez, Paola; Romero-Méndez, Catalina; Chrones, Tom; Sánchez-Armass, Sergio; Meza, Ulises; Sims, Stephen M; Espinosa-Tanguma, Ricardo

2007-07-01

Airway smooth muscle (ASM) contracts partly due to an increase in cytosolic Ca(2+). In this work, we found that the contraction caused by histamine depends on external Na(+), possibly involving nonselective cationic channels (NSCC) and the Na(+)/Ca(2+) exchanger (NCX). We performed various protocols using isometric force measurement of guinea pig tracheal rings stimulated by histamine. We observed that force reached 53 +/- 1% of control during external Na(+) substitution by N-methyl-D-glucamine(+), whereas substitution by Li(+) led to no significant change (91 +/- 1%). Preincubation with KB-R7943 decreased the maximal force developed (52.3 +/- 5.6%), whereas preincubation with nifedipine did not (89.7 +/- 1.8%). Also, application of the nonspecific NCX blocker KB-R7943 and nifedipine on histamine-precontracted tracheal rings reduced force to 1 +/- 3%, significantly different from nifedipine alone (49 +/- 6%). Moreover, nonspecific NSCC inhibitors SKF-96365 and 2-aminoethyldiphenyl borate reduced force to 1 +/- 1% and 19 +/- 7%, respectively. Intracellular Ca(2+) measurements in isolated ASM cells showed that KB-R7943 and SKF-96365 reduced the peak and sustained response to histamine (0.20 +/- 0.1 and 0.19 +/- 0.09 for KB-R, 0.43 +/- 0.16 and 0.47 +/- 0.18 for SKF, expressed as mean of differences). Moreover, Na(+)-free solution only inhibited the sustained response (0.54 +/- 0.25). These data support an important role for NSCC and NCX during histamine stimulation. We speculate that histamine induces Na(+) influx through NSCC that promotes the Ca(2+) entry mode of NCX and Ca(V)1.2 channel activation, thereby causing contraction.

A deformation-processed Al-matrix/Ca-nanofilamentary composite with low density, high strength, and high conductivity

DOE PAGES

Tian, Liang

2017-03-06

Light, strong materials with high conductivity are desired for many applications such as power transmission conductors, fly-by-wire systems, and downhole power feeds. However, it is difficult to obtain both high strength and high conductivity simultaneously in a material. In this study, an Al/Ca (20 vol%) nanofilamentary metal-metal composite was produced by powder metallurgy and severe plastic deformation. Fine Ca metal powders (~200 µm) were produced by centrifugal atomization, mixed with pure Al powder, and deformed by warm extrusion, swaging, and wire drawing to a true strain of 12.9. The Ca powder particles became fine Ca nanofilaments that reinforce the compositemore » substantially by interface strengthening. The conductivity of the composite is slightly lower than the rule-of-mixtures prediction due to minor quantities of impurity inclusions. As a result, the elevated temperature performance of this composite was also evaluated by differential scanning calorimetry and resistivity measurements.« less

A deformation-processed Al-matrix/Ca-nanofilamentary composite with low density, high strength, and high conductivity

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

Tian, Liang

Light, strong materials with high conductivity are desired for many applications such as power transmission conductors, fly-by-wire systems, and downhole power feeds. However, it is difficult to obtain both high strength and high conductivity simultaneously in a material. In this study, an Al/Ca (20 vol%) nanofilamentary metal-metal composite was produced by powder metallurgy and severe plastic deformation. Fine Ca metal powders (~200 µm) were produced by centrifugal atomization, mixed with pure Al powder, and deformed by warm extrusion, swaging, and wire drawing to a true strain of 12.9. The Ca powder particles became fine Ca nanofilaments that reinforce the compositemore » substantially by interface strengthening. The conductivity of the composite is slightly lower than the rule-of-mixtures prediction due to minor quantities of impurity inclusions. As a result, the elevated temperature performance of this composite was also evaluated by differential scanning calorimetry and resistivity measurements.« less

The measurement of sulfate mineral solubilities in the Na-K-Ca-Cl-SO 4-H 2O system at temperatures of 100, 150 and 200°C

NASA Astrophysics Data System (ADS)

Freyer, Daniela; Voigt, Wolfgang

2004-01-01

At T > 100°C development of thermodynamic models suffers from missing experimental data, particularly for solubilities of sulfate minerals in mixed solutions. Solubilities in Na +-K +-Ca 2+-Cl --SO 42-/H 2O subsystems were investigated at 150, 200°C and at selected compositions at 100°C. The apparatus used to examine solid-liquid phase equilibria under hydrothermal conditions has been described. In the system NaCl-CaSO 4-H 2O the missing anhydrite (CaSO 4) solubilities at high NaCl concentrations up to halite saturation have been determined. In the system Na 2SO 4-CaSO 4-H 2O the observed glauberite (Na 2SO 4 · CaSO 4) solubility is higher than that predicted by the high temperature model of Greenberg and Møller (1989), especially at 200°C. At high salt concentrations, solubilities of both anhydrite and glauberite increase with increasing temperature. Stability fields of the minerals syngenite (K 2SO 4 · CaSO 4 · H 2O) and goergeyite (K 2SO 4 · 5 CaSO 4 · H 2O) were determined, and a new phase was found at 200°C in the K 2SO 4-CaSO 4-H 2O system. Chemical and single crystal structure analysis give the formula K 2SO 4 · CaSO 4. The structure is isostructural with palmierite (K 2SO 4 · PbSO 4). The glaserite ("3 K 2SO 4 · Na 2SO 4") appears as solid solution in the system Na 2SO 4-K 2SO 4-H 2O. Its solubility and stoichiometry was determined as a function of solution composition.

The influence of Na+ and Ca2+ 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 R d 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 R d 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 R d 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. Copyright © 2016 Elsevier B.V. All rights reserved.

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

NASA Technical Reports Server (NTRS)

Kimura, Makoto; El-Goresy, Ahmed; Palme, Herbert; Zinner, Ernst

1993-01-01

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.

Recent Progress in Graphite Intercalation Compounds for Rechargeable Metal (Li, Na, K, Al)-Ion Batteries.

PubMed

Xu, Jiantie; Dou, Yuhai; Wei, Zengxi; Ma, Jianmin; Deng, Yonghong; Li, Yutao; Liu, Huakun; Dou, Shixue

2017-10-01

Lithium-ion batteries (LIBs) with higher energy density are very necessary to meet the increasing demand for devices with better performance. With the commercial success of lithiated graphite, other graphite intercalation compounds (GICs) have also been intensively reported, not only for LIBs, but also for other metal (Na, K, Al) ion batteries. In this Progress Report, we briefly review the application of GICs as anodes and cathodes in metal (Li, Na, K, Al) ion batteries. After a brief introduction on the development history of GICs, the electrochemistry of cationic GICs and anionic GICs is summarized. We further briefly summarize the use of cationic GICs and anionic GICs in alkali ion batteries and the use of anionic GICs in aluminium-ion batteries. Finally, we reach some conclusions on the drawbacks, major progress, emerging challenges, and some perspectives on the development of GICs for metal (Li, Na, K, Al) ion batteries. Further development of GICs for metal (Li, Na, K, Al) ion batteries is not only a strong supplement to the commercialized success of lithiated-graphite for LIBs, but also an effective strategy to develop diverse high-energy batteries for stationary energy storage in the future.

Nanostructure and surface activation of mayenite (12CaO·7Al2O3) ceramics via femtosecond laser irradiation in solvents

NASA Astrophysics Data System (ADS)

Visbal, Heidy; Hirano, Minami; Omura, Takuya; Shimizu, Masahiro; Takaishi, Taigo; Hirao, Kazuyuki

2017-07-01

Mayenite (12CaO·7Al2O3) is a highly interesting functional material due to the wide variety of its possible future applications. In this study, we used femtosecond laser irradiation in several solvents with varying polarities to increase the specific surface area of 12CaO·7Al2O3 ceramics and reduce their particle size without any structural degradation or loss of crystallinity. We observed that when femtosecond laser irradiation was applied to solvents bearing hydroxyl groups, a smaller particle size was obtained with the particle size decreasing as the polarity of the solvent increased. Using infrared spectroscopy, we confirmed the presence of hydroxyl and carbonyl surface functional groups at the surface of 12CaO·7Al2O3 ceramics after femtosecond laser irradiation. This is attributed to the direct chemical bonds breaking of the solvent via multiphoton ionization and/or tunneling ionization, followed by the Coulomb explosion and the subsequent production of ions that are adsorbed on the surfaces of 12CaO·7Al2O3 ceramics. Femtosecond laser irradiation in polar solvents with hydroxyl groups can reduce the particle size and increase the specific surface area without degradation or loss of crystallinity of 12CaO·7Al2O3 ceramics. Additionally, this method can be used for the surface modification and introduction of functional groups on the 12CaO·7Al2O3 ceramics surface.

Ultrafine Nanocrystalline CeO2@C-Containing NaAlH4 with Fast Kinetics and Good Reversibility for Hydrogen Storage.

PubMed

Zhang, Xin; Liu, Yongfeng; Wang, Ke; Li, You; Gao, Mingxia; Pan, Hongge

2015-12-21

A nanocrystalline CeO2@C-containing NaAlH4 composite is successfully synthesized in situ by hydrogenating a NaH-Al mixture doped with CeO2@C. Compared with NaAlH4 , the as-prepared CeO2@C-containing NaAlH4 composite, with a minor amount of excess Al, exhibits significantly improved hydrogen storage properties. The dehydrogenation onset temperature of the hydrogenated [NaH-Al-7 wt % CeO2@C]-0.04Al sample is 77 °C lower than that of the pristine sample because of a reduced kinetic barrier. More importantly, the dehydrogenated sample absorbs ∼4.7 wt % hydrogen within 35 min at 100°C and 10 MPa of hydrogen. Compositional and structural analyses reveal that CeO2 is converted to CeH2 during ball milling and that the newly formed CeH2 works with the excess of Al to synergistically improve the hydrogen storage properties of NaAlH4. Our findings will aid in the rational design of novel catalyst-doped complex hydride systems with low operating temperatures, fast kinetics, and long-term cyclability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Na+/Ca2+, K+ exchanger NCKX4 is required for efficient cone-mediated vision.

PubMed

Vinberg, Frans; Wang, Tian; De Maria, Alicia; Zhao, Haiqing; Bassnett, Steven; Chen, Jeannie; Kefalov, Vladimir J

2017-06-26

Calcium (Ca 2+ ) plays an important role in the function and health of neurons. In vertebrate cone photoreceptors, Ca 2+ controls photoresponse sensitivity, kinetics, and light adaptation. Despite the critical role of Ca 2+ in supporting the function and survival of cones, the mechanism for its extrusion from cone outer segments is not well understood. Here, we show that the Na + /Ca 2+ , K + exchanger NCKX4 is expressed in zebrafish, mouse, and primate cones. Functional analysis of NCKX4-deficient mouse cones revealed that this exchanger is essential for the wide operating range and high temporal resolution of cone-mediated vision. We show that NCKX4 shapes the cone photoresponse together with the cone-specific NCKX2: NCKX4 acts early to limit response amplitude, while NCKX2 acts late to further accelerate response recovery. The regulation of Ca 2+ by NCKX4 in cones is a novel mechanism that supports their ability to function as daytime photoreceptors and promotes their survival.

The Electrochemical Co-reduction of Mg-Al-Y Alloys in the LiCl-NaCl-MgCl2-AlF3-YCl3 Melts

NASA Astrophysics Data System (ADS)

Li, Mei; Liu, Yaochen; Han, Wei; Wang, Shanshan; Zhang, Milin; Yan, Yongde; Shi, Weiqun

2015-04-01

The electrochemical formation of Mg-Al-Y alloys was studied in the LiCl-NaCl-MgCl2 melts by the addition of AlF3 and YCl3 on a molybdenum electrode at 973 K (700 °C). In order to reduce the volatilization of salt solvent in the electrolysis process, the volatile loss of LiCl-NaCl-MgCl2 and LiCl-KCl-MgCl2 melts was first measured in the temperature range from 873 K to 1023 K (600 °C to 750 °C). Then, the electrochemical behaviors of Mg(II), Al(III), Y(III) ions and alloy formation processes were investigated by cyclic voltammetry, chronopotentiometry, and open circuit chronopotentiometry. The cyclic voltammograms indicate that the under-potential deposition of magnesium and yttrium on pre-deposited Al leads to formation of Mg-Al and Al-Y intermetallic compounds. The Mg-Al-Y alloys were prepared by galvanostatic electrolysis in the LiCl-NaCl-MgCl2-AlF3-YCl3 melts and characterized by X-ray diffraction and scanning electron microscopy with energy dispersive spectrometry. Composition of the alloys was analyzed by inductively coupled plasma-atomic emission spectrometer, and current efficiency was also determined by the alloy composition.

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.

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.

Interaction of overlayers of Al and Rb with single-crystalline surfaces of Bi2Sr2CaCu2O8

NASA Astrophysics Data System (ADS)

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

1990-03-01

Photoemission results from Al and Rb interfaces with single crystals of Bi2Sr2CaCu2O8 high-temperature superconductors are reported. The Al and Rb adsorbates are found to react quite differently with the Bi2Sr2CaCu2O8 substrate. While adatoms of Rb significantly affect only the Bi and O atoms in the top atomic layer, the Al adsorbate profoundly disrupts the bonding character of the whole Bi2Sr2CaCu2O8 material. For Al, the Bi and Cu states are strongly reduced, and the Sr and O states show evidence of oxidized components. In addition, Al causes a strong out-diffusion of oxygen from the bulk. The differences in the reactivity of Al and Rb are discussed in terms of the different mobility of the two atoms.

Microchip Yb:CaLnAlO4 lasers with up to 91% slope efficiency.

PubMed

Loiko, Pavel; Serres, Josep Maria; Mateos, Xavier; Xu, Xiaodong; Xu, Jun; Jambunathan, Venkatesan; Navratil, Petr; Lucianetti, Antonio; Mocek, Tomas; Zhang, Xuzhao; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc; Major, Arkady

2017-07-01

Multi-watt continuous-wave (CW) operation of tetragonal rare-earth calcium aluminate Yb:CaLnAlO 4 (Ln=Gd,Y)) crystals in plano-plano microchip lasers was demonstrated with an almost quantum-defect-limited slope efficiency. Pumped at 978 nm by an InGaAs laser diode, a 3.4 mm long 8 at. % Yb:CaGdAlO 4 laser generated 7.79 W at 1057-1065 nm with a slope efficiency of η=84% (with respect to the absorbed pump power). An even higher η=91% was achieved with a 2.5 mm long 3 at. % Yb:CaYAlO 4 laser, from which 5.06 W were extracted at 1048-1056 nm. Both lasers produced linearly polarized output (σ-polarization) with an almost circular diffraction-limited beam (Mx,y2<1.1). The output performance of the developed lasers was modeled, yielding an internal loss coefficient as low as 0.004-0.007  cm -1 . In addition, their spectroscopic properties were revisited.

Electrochemical reduction behavior of simplified simulants of vitrified radioactive waste in molten CaCl2

NASA Astrophysics Data System (ADS)

Katasho, Yumi; Yasuda, Kouji; Nohira, Toshiyuki

2018-05-01

The electrochemical reduction of two types of simplified simulants of vitrified radioactive waste, simulant 1 (glass component only: SiO2, B2O3, Na2O, Al2O3, CaO, Li2O, and ZnO) and simulant 2 (also containing long-lived fission product oxides, ZrO2, Cs2O, PdO, and SeO2), was investigated in molten CaCl2 at 1103 K. The behavior of each element was predicted from the potential-pO2- diagram constructed from thermodynamic data. After the immersion of simulant 1 into molten CaCl2 without electrolysis, the dissolution of Na, Li, and Cs was confirmed by inductively coupled plasma atomic emission spectrometry and mass spectrometry analysis of the samples. The scanning electron microscopy/energy dispersive X-ray and X-ray diffraction analyses of simulants 1 and 2 electrolyzed at 0.9 V vs. Ca2+/Ca confirmed that most of SiO2 had been reduced to Si. After the electrolysis of simulants 1 and 2, Al, Zr, and Pd remained in the solid phase. In addition, SeO2 was found to remain partially in the solid phase and partially evaporate, although a small quantity dissolved into the molten salt.

Understanding the Reaction Chemistry of 2,2':5',2''-Terthiophene Films with Vapor-Deposited Ag, Al, and Ca

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

Sang, Lingzi; Matz, Dallas L.; Pemberton, Jeanne E.

The reaction chemistry of vapor-deposited 2,2':5',2''-terthiophene (α-3T) solid-state thin films with postdeposited Ag, Al, and Ca is investigated in ultrahigh vacuum using Raman spectroscopy. Vapor-deposited Ag forms nanoparticles on these films and induces considerable surface enhanced Raman scattering (SERS) along with a change in molecular symmetry of adjacent α-3T and formation of Ag–S bonds; no other reaction chemistry is observed. Vapor-deposited Al and Ca undergo chemical reaction with α-3T initiated by metal-to-α-3T electron transfer. For Al, the resulting product is predominantly amorphous carbon through initial radical formation and subsequent decomposition reactions. For Ca, the spectral evidence suggests two pathways: onemore » leading to α-3T polymerization and the other resulting in thiophene ring opening, both initiated by radical formation through Ca-to-α-3T electron transfer. These interfacial reactions reflect the complex chemistry that can occur between low work function metals and thiophene-based oligomers. This reactivity is strongly correlated with metal work function.« less

Understanding the Reaction Chemistry of 2,2':5',2"-Terthiophene Films with Vapor-Deposited Ag, Al, and Ca

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

Sang, Lingzi; Matz, Dallas L.; Pemberton, Jeanne E.

The reaction chemistry of vapor-deposited 2,2':5',2''-terthiophene (α-3T) solid-state thin films with postdeposited Ag, Al, and Ca is investigated in ultrahigh vacuum using Raman spectroscopy. Vapor-deposited Ag forms nanoparticles on these films and induces considerable surface enhanced Raman scattering (SERS) along with a change in molecular symmetry of adjacent α-3T and formation of Ag–S bonds; no other reaction chemistry is observed. Vapor-deposited Al and Ca undergo chemical reaction with α-3T initiated by metal-to-α-3T electron transfer. For Al, the resulting product is predominantly amorphous carbon through initial radical formation and subsequent decomposition reactions. For Ca, the spectral evidence suggests two pathways: onemore » leading to α-3T polymerization and the other resulting in thiophene ring opening, both initiated by radical formation through Ca-to-α-3T electron transfer. These interfacial reactions reflect the complex chemistry that can occur between low work function metals and thiophene-based oligomers. This reactivity is strongly correlated with metal work function.« less

Solubility of Anhydrite (CaSO4) in NaCl-H2O Fluids at High T and P

NASA Astrophysics Data System (ADS)

Newton, R. C.; Manning, C. E.

2003-12-01

Weight losses of single crystals of a very pure natural anhydrite exposed to NaCl solutions of 0-0.3 mol fraction were measured at 600-800 \\deg C and 6-14 kbar. Experimental charges were contained in welded Pt capsules in 1.91 cm-diameter piston-cylinder apparatus with NaCl pressure medium for 5-72 hr. Measurements in initially pure H2O were made with HM, NNO, and MnO2 buffers, as well as without buffering. At 800 \\deg C and 10 kbar, CaSO4 molalities are: MnO2, 0.014 mol/kg H2O; HM, 0.017; NNO, 0.148; and unbuffered, 0.026. Variation in oxygen fugacity thus has a large effect on CaSO4 solubility, increasing with H2S/SO2 in the fluid. Unbuffered (self-buffered) charges gave solubilities much closer to HM than NNO. Melting occurred in the NNO experiment at this P and T. NaCl increases CaSO4 solubility enormously, with m(CaSO4) reaching 5.4, or 23.5 wt. %, at 800 \\deg C, 10 kbar and X(NaCl)=0.3. There is also a very large increase with temperature. Regression of all the data give: log(m-mo) = -1.533 + 0.00291T + (1.441 + 0.00016T)logX(NaCl) + 0.0413(P-10) where mo is molality in pure H2O, P is in kbar, and T is in Kelvins. The very large carrying capacity for sulfate in even mildly saline fluids at high P and T, together with the high oxygen potential generated when these solutions react with FeO in rocks to yield pyrrhotite, indicates that such fluids should be considered as principal agents in S-rich, highly oxidizing processes such as Pinatubo-type volcanic eruptions, certain deep-crustal granulite facies metamorphism, as in Bamble, Norway and Shevaroy Hills, S. India, and the anhydrite-related, oxidized Au ore deposits like Abitibi, Ontario, and Kalgoorlie, Australia.

[Characterization and optimization of the NaOH-EDTA extracts for solution 31P-NMR analysis of organic phosphorus in river sediments].

PubMed

Zhang, Wen-Qiang; Shan, Bao-Qing; Zhang, Hong; Tang, Wen-Zhong

2014-01-01

Optimization and mechanism of NaOH-EDTA extraction solutions were studied in phosphorus (P) pollution river sediments, which were Fe, Al-rich sediment, by solution 31P nuclear magnetic resonance spectroscopy (31P-NMR). Different proportions of NaOH and EDTA showed different extraction efficiency on total P (TP) and organic P (Po) in the sediment. The concentration of Po in NaOH + EDTA extract was higher than that in NaOH extract. The mechanism was that the TP and Po were released under the conditions of EDTA chelating with Fe and Al. The concentration of TP and Po were the highest in 1.00 mol x L(-1) NaOH +75 mmol x L(-1) EDTA extract and 0.25 mol x L(-1) NaOH + 50 mmol x L(-1) EDTA extract, which were 3.88 mg x g(-1) and 0.24 mg x g(-1), respectively. The extractions of Fe, Mn, Ca, Mg, Al were increasing as the EDTA increased under the same NaOH concentration. Extraction efficiency of Fe, Mn, Ca showed negative correlation with the pH of the extracting solution (P < 0.01). Exponential relationship was found between the extraction of Al and the pH of the extraction solution (P < 0.01) because of the AlO2- and EDTA-Al complex. The quality of spectra of NaOH-EDTA extract was better than that of NaOH extract. Six P species were detected in different extractions, including phosphonates, orthophosphate, pyrophosphate, orthophosphate monoesters, phospholipids and deoxyribonucleic acids. Therefore, 0. 25 mol x L(-1) NaOH + 50 mmol x L(-1) EDTA was the optimization extraction solution for Po analysis in Fe and Al-rich river sediment by 31P-NMR.

Preparation of Ferrotitanium Alloys by Electrolysis-Assisted Calciothermic Reduction of Ilmenite in Equimolar CaCl2-NaCl Electrolyte: Effect of Calcium Oxide

NASA Astrophysics Data System (ADS)

Zhou, Zhongren; Zhang, Yingjie; Hua, Yixin; Xu, Cunying; Dong, Peng; Zhang, Qibo; Wang, Ding

2018-04-01

The effect of CaO content on the preparation of ferrotitanium alloys from ilmenite with the method of the electrolysis-assisted calciothermic reduction has been investigated by use of ilmenite powders as raw materials that positions them next to the cathodic molybdenum plate, equimolar CaCl2-NaCl molten salt with 2-7 mol.% CaO as electrolyte and graphite as anode at 700°C with cell voltage of 2.8 V under argon atmosphere. It is demonstrated that increasing the reactant CaO content is beneficial to the calciothermic reduction of ilmenite and the intermediate CaTiO3. Experimental results also show that after 14 h of calciothermic reduction process, the products are ferrotitanium alloys and the specific energy consumption is only about 10.21 kWh kg-1 when adding 5 mol.% CaO into equimolar CaCl2-NaCl molten salt and approximately 14.40 kWh kg-1 when CaO content is increased to 7 mol.%.

Al-Mg isotopic evidence for episodic alteration of Ca-Al-rich inclusions from Allende

NASA Astrophysics Data System (ADS)

Fagan, T. J.; Guan, Y.; MacPherson, G. J.

2007-08-01

Textures, mineral assemblages, and Al-Mg isotope systematics indicate a protracted, episodic secondary mineralization history for Allende Ca-Al-rich inclusions (CAIs). Detailed observations from one type B1 CAI, one B2, one compact type A (CTA), and one fluffy type A (FTA) indicate that these diverse types of CAIs are characterized by two distinct textural and mineralogic types of secondary mineralization: (1) grossular-rich domains, concentrated along melilite grain boundaries in CAI interiors, and (2) feldspathoid-bearing domains, confined mostly to CAI margins just interior to the Wark-Lovering rim sequence. The Al-Mg isotopic compositions of most secondary minerals in the type B1 CAI, and some secondary minerals in the other CAIs, show no resolvable excesses of 26Mg, whereas the primary CAI phases mostly yield correlated excesses of 26Mg with increasing Al/Mg corresponding to "canonical" initial 26Al/27Al ˜ 4.5-5 × 10-5. These secondary minerals formed at least 3 Ma after the primary CAI minerals. All but two analyses of secondary minerals from the fluffy type-A CAI define a correlated increase in 26Mg/24Mg with increasing Al/Mg, yielding (26Al/27Al)0 = (4.9 ± 2.8) × 10-6. The secondary minerals in this CAI formed 1.8-3.2 Ma after the primary CAI minerals. In both cases, the timing of secondary alteration is consistent with, but does not necessarily require, alteration in an asteroidal setting. One grossular from the type B2 CAI, and several grossular and secondary feldspar analyses from the compact type A CAI, have excesses of 26Mg consistent with initial 26Al/27Al ˜ 4.5 × 10-5. Especially in the compact type A CAI, where 26Mg/24Mg in grossular correlates with increasing Al/Mg, these 26Mg excesses are almost certainly due to in situ decay of 26Al. They indicate a nebular setting for formation of the grossular. The preservation of these diverse isotopic patterns indicates that heating on the Allende parent body was not pervasive enough to reset isotopic

Optically stimulated luminescence in doped NaCl

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

Gaikwad, S. U., E-mail: gaikwadsonali09@yahoo.com; Patil, R. R.; Kulkarni, M. S.

NaCl:Ca,Cu,P NaCl:Mg,Cu,P OSL phosphors are synthesized. Intense OSL is observed in these samples which is 14 times more than Al{sub 2}O{sub 3}:C. Same samples coated with PVA (poly vinyl actetae) polymer also show similar OSL properties and these coated samples are found to be less susceptible to the moisture due to protected layer of hydrophobic polymer. These coated samples may be useful as OSL dosimetersdue to high sensitivity and less or no susceptibility to moisture.

Investigations on FCAM-III (Ca2.38Mg2.09Fe3+10.61Fe2+1.59Al9.33O36): A new homologue of the aenigmatite structure-type in the system CaO-MgO-Fe2O3-Al2O3

NASA Astrophysics Data System (ADS)

Zöll, Klaus; Kahlenberg, Volker; Krüger, Hannes; Tropper, Peter

2018-02-01

In the course of a systematic study of a part of the quaternary system Fe2O3-CaO-Al2O3-MgO (FCAM) the previously unknown compound Ca2.38Mg2.09Fe3+10.61Fe2+1.59Al9.33O36 (FCAM-III) has been synthesized. By analogy with the so-called SFCA series [1-5], our investigation in the system of FCAM shows the existence of a stoichiometric homologous series M14+6nO20+8n, where M = Fe, Ca, Al, Mg and n = 1 or 2. In air, we can prove the formation of coexisting FCAM-III and FCAM-I solid solutions at 1400 °C. By increasing the temperature up to 1425 °C FCAM-I disappears completely and FCAM-III co-exists with magnesiumferrite and a variety of calcium iron oxides. At 1450 °C FCAM-III breaks down to a mixture of FCAM-I again as well as magnesioferrite and melt. Small single-crystals of FCAM-III up to 35 μm in size could be retrieved from the 1425 °C experiment and were subsequently characterized using electron microprobe analysis and synchroton X-ray single-crystal diffraction. Finally the Fe2+/Fetot ratio was calculated from the total iron content based on the crystal-chemical formula obtained from EMPA measurements and charge balance considerations. FCAM-III or Ca2.38Mg2.09Fe3+10.61Fe2+1.59Al9.33O36 has a triclinic crystal structure (space group P 1 ̅). The basic crystallographic data are: a = 10.223(22) Å, b = 10.316(21) Å, c = 14.203(15) Å, α = 93.473(50)°, β = 107.418(67)°, γ = 109.646(60)°, V = 1323.85(2) ų, Z = 1. Using Schreinemaker's technique to analyze the phase relations in the system Fe2O3-CaO-Al2O3-MgO it was possible to obtain the semi-quantitative stability relations between the participating phases and construct a topologically correct phase sequence as a function of T and fO2. The analysis shows that Ca2Al0.5Fe1.5O5 (C2A0.25F0.75) and CaAl1.5Fe2.5O7 (CA0.75F1.25) with higher calculated Fe2+ contents are preferably formed at lower oxygen fugacity and react to CaAl0.5Fe1.5O4 (CA0.25F0.75) by increasing fO2. Spinel-type magnesium

Metastable Phase Relations in the System Ca(sub O)-Al2(sub O)3-MgO-TiO(sub 2): Applications to Ca- And Al-Rich Inclusions

NASA Technical Reports Server (NTRS)

Keller, L. P.; Han, J.

2017-01-01

Introduction: High temperature phases such as corundum, hibonite, grossite, and perovskite are among the earliest phases that condensed in the early solar nebula. Recent work has shown that defect-structured phases occur in some ultrarefractory inclusions as metastable, possibly more kinetically-favored alternatives to the thermodynamically predicted stable phase assemblages [1-4]. For example, Han et al. have shown that non-stoichiometry in hibonite is accommodated by extra "spinel" blocks in the structure instead of the equilibrium assemblages hibonite+corundum or hibonite+spinel. To explore these relations, we have conducted a series of experiments in the system CaO-Al2O3- MgO-TiO2. Here we discuss the compositions and mineralogy of the experimental samples and how they relate to phases in refractory inclusions with a focus on perovskite and spinel. Methods: For the series of annealing studies, a CaO-Al2O3 eutectic melt is allowed to react with a pure alumina crucible at 1,530degC for either 4 hours or 5 days, followed by quenching in air. Later experiments were similar except that additions of 5 wt% MgO, and CaTiO(sub 3) were used to explore the effect of minor elements on the phase assemblages. The experimental conditions resulted in reaction zones approximately 100-300 ?m wide consisting of a hibonite layer immediately adjacent to the corundum, followed by a grossite layer, and finally krotite with residual quenched melt. For the experiments with Mg, spinel is distributed in all layers but is mainly concentrated in the krotite layer. In the Ti-bearing experiments, perovskite precipitated in association with the krotite and residual melt. In addition to the experiments, we also analyzed perovskite grains in the FUN inclusion SHAL [5] and a large compact type A CAI from Allende. The experiments and refractory inclusions were analyzed using a JEOL 7600F SEM and quantitative analyses were obtained using the JEOL 8530F field-emission electron microprobe.

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.

The Effects of Dy Addition on Microstructure and Mechanical Properties of the As-Cast Mg-5Al-3Ca-2Nd Alloys.

PubMed

Son, Hyeon-Taek; Kim, Yong-Ho; Yoo, Hyo-Sang

2018-03-01

The microstructure of the as-cast Mg-5Al-3Ca-2Nd-xDy alloys consists of α-Mg matrix, (Mg, Al)2Ca eutectic phase, Al-Nd and Al-Dy intermetallic compounds. α-Mg matrix morphology was changed from dendritic to equiaxed with the increase Dy addition. And grain size was remarkably refined. As Dy content was increased, yield strength was improved due to the refined grains and the homogeneous distribution of Al-Dy phase.

Long-Term Changes in Calcium (Ca) Sources in Base-Poor Forest Ecosystem: Insight from Stable Ca-Isotopes in Tree Rings

NASA Astrophysics Data System (ADS)

Farkas, J.; Dejeant, A.; Orwig, D.; Jacobsen, S. B.

2009-12-01

of radiogenic 87Sr/86Sr, as the latter is not discriminated by vital effects. Assuming that the long-term δ44/40Ca and Ca/Sr trends in tree-rings indeed reflect the evolving composition of soil Ca reservoir, the data could be explained by one of the following mechanisms: (i) via selective weathering of apatite (Ca-phosphate) by roots in association with fungus that could provide the source of isotopically light Ca with low Na/Ca ratios (cf. Blum et al. 2002, Nature, 417, 729-731). Alternatively, (ii) the Ca reserves stored in organic matter in the upper soil horizons, as a fairly insoluble Ca-oxalate, were mobilized during times of enhanced acidification (low soil-pH), thus providing the flux of isotopically light Ca to the lower soil nutrient pool. The plausibility of the above scenarios will be tested against new Ca isotope data measured in igneous apatites as well as biological Ca-oxalates.

CaMn 2Al 10: 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 CaMn 2Al 10, 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 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]more » ≈ 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 T C ~ 0. Our experiments indicate that CaMn 2Al 10 is a rare example of a system where the weak and itinerant Mn-based magnetism is poised on the verge of order.« less

Effects of aqueous extract of Hibiscus sabdariffa on renal Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities in Wistar rats.

PubMed

Olatunji, Lawrence A; Usman, Taofeek O; Adebayo, Joseph O; Olatunji, Victoria A

2012-09-01

To investigate the effects of oral administration of aqueous extract of Hibiscus sabdariffa on renal Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities in rats. The 25 and 50 mg/(kg·d) of aqueous extracts of H. sabdariffa were respectively given to rats in the experimental groups for 28 d, and rats in the control group received an appropriate volume of distilled water as vehicle. Na(+)-K(+)-ATPase and Ca(2+)-Mg(2+)-ATPase activities in the kidney were assayed by spectrophotometric method. Administrations of 25 and 50 mg/(kg·d) of aqueous extract of H. sabdariffa significantly decreased the Ca(2+)-Mg(2+)-ATPase activity in the kidney of rats (P<0.05). However, the renal Na(+)-K(+)-ATPase activity of the experimental rats was not affected by either dose of the extract. And the plasma Na(+), K(+) and Ca(2+) levels of the experimental rats had no significant changes. Administration of either dose of the extract did not result in any significant changes in body and kidney weights, the concentrations of plasma albumin and total protein, and alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase activities. However, concentrations of creatinine and urea were significantly reduced by 50 mg/kg of the extract (P<0.05). The present study indicates that oral administration of aqueous extract of H. sabdariffa may preserve the renal function despite a decreased renal Ca(2+)-Mg(2+)-ATPase activity.

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.

Electrophysiological properties of myocytes isolated from the mouse atrioventricular node: L-type ICa, IKr, If, and Na-Ca exchange.

PubMed

Choisy, Stéphanie C; Cheng, Hongwei; Orchard, Clive H; James, Andrew F; Hancox, Jules C

2015-11-01

The atrioventricular node (AVN) is a key component of the cardiac pacemaker-conduction system. This study investigated the electrophysiology of cells isolated from the AVN region of adult mouse hearts, and compared murine ionic current magnitude with that of cells from the more extensively studied rabbit AVN. Whole-cell patch-clamp recordings of ionic currents, and perforated-patch recordings of action potentials (APs), were made at 35-37°C. Hyperpolarizing voltage commands from -40 mV elicited a Ba(2+)-sensitive inward rectifier current that was small at diastolic potentials. Some cells (Type 1; 33.4 ± 2.2 pF; n = 19) lacked the pacemaker current, If, whilst others (Type 2; 34.2 ± 1.5 pF; n = 21) exhibited a clear If, which was larger than in rabbit AVN cells. On depolarization from -40 mV L-type Ca(2+) current, IC a,L, was elicited with a half maximal activation voltage (V0.5) of -7.6 ± 1.2 mV (n = 24). IC a,L density was smaller than in rabbit AVN cells. Rapid delayed rectifier (IK r) tail currents sensitive to E-4031 (5 μmol/L) were observed on repolarization to -40 mV, with an activation V0.5 of -10.7 ± 4.7 mV (n = 8). The IK r magnitude was similar in mouse and rabbit AVN. Under Na-Ca exchange selective conditions, mouse AVN cells exhibited 5 mmol/L Ni-sensitive exchange current that was inwardly directed negative to the holding potential (-40 mV). Spontaneous APs (5.2 ± 0.5 sec(-1); n = 6) exhibited an upstroke velocity of 37.7 ± 16.2 V/s and ceased following inhibition of sarcoplasmic reticulum Ca(2+) release by 1 μmol/L ryanodine, implicating intracellular Ca(2+) cycling in murine AVN cell electrogenesis. © 2015 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

Synthesis and luminescence properties of blue-emitting phosphor Ca12 Al14 O32 F2 :Eu2+ for white light-emitting diode.

PubMed

Chen, Wanping; Zhang, Xinzhu; Wang, Liping

2017-09-01

A blue-emitting phosphor Ca 12 Al 14 O 32 F 2 :Eu 2+ was synthesized using a high-temperature solid-state reaction under a reductive atmosphere. The X-ray diffraction measurements indicate that a pure phase Ca 12 Al 14 O 32 F 2 :Eu 2+ can be obtained for low doping concentration of Eu 2+ . The phosphor has a strong absorption in the range 270-420 nm with a maximum at ~340 nm and blue emission in the range 400-500 nm with chromatic coordination of (0.152, 0.045). The optimal doping concentration is ~0.24. In addition, the luminescence properties of the as-synthesized phosphor were evaluated by comparison with those of Ca 12 Al 14 O 32 Cl 2 :Eu 2+ and the commercially available phosphor BaMgAl 10 O 17 :Eu 2+ . The emission intensity of Ca 12 Al 14 O 32 F 2 :Eu 2+ was ~72% that of BaMgAl 10 O 17 :Eu 2+ under excitation at λ = 375 nm. The results indicate that Ca 12 Al 14 O 32 F 2 :Eu 2+ has potential application as a near-UV-convertible blue phosphor for white light-emitting diodes. Copyright © 2017 John Wiley & Sons, Ltd.

Unveiling Vela: time variability of interstellar lines in the direction of the Vela supernova remnant - II. Na D and Ca II

NASA Astrophysics Data System (ADS)

Kameswara Rao, N.; Lambert, David L.; Reddy, Arumalla B. S.; Gupta, Ranjan; Muneer, S.; Singh, Harinder P.

2017-05-01

In a survey conducted between 2011 and 2012 of interstellar Na I D line profiles in the direction of the Vela supernova remnant (SNR), a few lines of sight showed dramatic changes in low-velocity absorption components with respect to profiles from 1993 to 1994 reported by Cha & Sembach. Three stars - HD 63578, HD 68217 and HD 76161 - showed large decrease in strength over the 1993-2012 interval. HD 68217 and HD 76161 are associated with the Vela SNR whereas HD 63578 is associated with γ2 Velorum wind bubble. Here, we present high spectral resolution observations of Ca II K lines obtained with the Southern African Large Telescope towards these three stars along with simultaneous observations of Na I D lines. These new spectra confirm that the Na D interstellar absorption weakened drastically between 1993-1994 and 2011-2012 but show for the first time that the Ca II K line is unchanged between 1993-1994 and 2015. This remarkable contrast between the behaviour of Na D and Ca II K absorption lines is a puzzle concerning gas presumably affected by the outflow from the SNR and the wind from γ2 Velorum.

The Na+/Ca2+, K+ exchanger NCKX4 is required for efficient cone-mediated vision

PubMed Central

Vinberg, Frans; Wang, Tian; De Maria, Alicia; Zhao, Haiqing; Bassnett, Steven; Chen, Jeannie; Kefalov, Vladimir J

2017-01-01

Calcium (Ca2+) plays an important role in the function and health of neurons. In vertebrate cone photoreceptors, Ca2+ controls photoresponse sensitivity, kinetics, and light adaptation. Despite the critical role of Ca2+ in supporting the function and survival of cones, the mechanism for its extrusion from cone outer segments is not well understood. Here, we show that the Na+/Ca2+, K+ exchanger NCKX4 is expressed in zebrafish, mouse, and primate cones. Functional analysis of NCKX4-deficient mouse cones revealed that this exchanger is essential for the wide operating range and high temporal resolution of cone-mediated vision. We show that NCKX4 shapes the cone photoresponse together with the cone-specific NCKX2: NCKX4 acts early to limit response amplitude, while NCKX2 acts late to further accelerate response recovery. The regulation of Ca2+ by NCKX4 in cones is a novel mechanism that supports their ability to function as daytime photoreceptors and promotes their survival. DOI: http://dx.doi.org/10.7554/eLife.24550.001 PMID:28650316

Loparite, a rare-earth ore (Ce, Na, Sr, Ca)(Ti, Nb, Ta, Fe+3)O3

USGS Publications Warehouse

Hedrick, James B.; Sinha, Shyama P.; Kosynkin, Valery 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.

Recent Progress in Graphite Intercalation Compounds for Rechargeable Metal (Li, Na, K, Al)‐Ion Batteries

PubMed Central

Xu, Jiantie; Dou, Yuhai; Wei, Zengxi; Li, Yutao; Liu, Huakun; Dou, Shixue

2017-01-01

Abstract Lithium‐ion batteries (LIBs) with higher energy density are very necessary to meet the increasing demand for devices with better performance. With the commercial success of lithiated graphite, other graphite intercalation compounds (GICs) have also been intensively reported, not only for LIBs, but also for other metal (Na, K, Al) ion batteries. In this Progress Report, we briefly review the application of GICs as anodes and cathodes in metal (Li, Na, K, Al) ion batteries. After a brief introduction on the development history of GICs, the electrochemistry of cationic GICs and anionic GICs is summarized. We further briefly summarize the use of cationic GICs and anionic GICs in alkali ion batteries and the use of anionic GICs in aluminium‐ion batteries. Finally, we reach some conclusions on the drawbacks, major progress, emerging challenges, and some perspectives on the development of GICs for metal (Li, Na, K, Al) ion batteries. Further development of GICs for metal (Li, Na, K, Al) ion batteries is not only a strong supplement to the commercialized success of lithiated‐graphite for LIBs, but also an effective strategy to develop diverse high‐energy batteries for stationary energy storage in the future. PMID:29051856

Effects of Combining Na and Sr additions on Eutectic Modification in Al-Si alloy

NASA Astrophysics Data System (ADS)

Zhu, G. L.; Gu, N. J.; Zhou, B. J.

2017-09-01

Experiments were designed to investigate the effects of strontium and sodium modified on the eutectic silicon for Al-Si alloy. It was found that combining addition of Na and Sr did not appear to cause deleterious interactions of modification, at at the same time, Sr-Na was fairly constant with holding time and without obvious modification fading. Addition of Na-Sr modifier could take effect quickly and decrease incubation period.

Enhancement of Mechanical Properties of Extruded Mg-9Al-1Zn-1MM-0.7CaO-0.3Mn Alloy Through Pre-aging Treatment

NASA Astrophysics Data System (ADS)

Jeong, Seok Hoan; Kim, Yong Joo; Kong, Kyung Ho; Cho, Tae Hee; Kim, Young Kyun; Lim, Hyun Kyu; Kim, Won Tae; Kim, Do Hyang

2018-03-01

The effect of pre-aging treatment before extrusion has been investigated in Mg-9.0Al-1.0Zn-1MM-0.7CaO-0.3Mn alloy. The as-cast microstructure consists of α-Mg dendrite with secondary solidification phase particles, (Mg, Al)2Ca, β-Mg17Al12 and Al11RE3 at the inter-dendritic region. After extrusion, β-Mg17Al12 precipitates are present, but higher density and more homogeneous distribution in pre-aged alloy. In addition, μm-scale banded bulk β-Mg17Al12 particles are generated during extrusion. Al11RE3 particles are broken into small particles, and are aligned along the extrusion direction. (Mg, Al)2Ca particles are only slightly elongated along the extrusion direction, providing stronger particle stimulated nucleation (PSN) effect by severe deformation during extrusion. The mechanical properties can be significantly enhanced by introducing pre-aging treatment, i.e. β-Mg17Al12 precipitates provide grain refining and strengthening effects and (Mg, Al)2Ca particles provide PSN effect.

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.

Na+/Ca2+ exchange in cardiac myocytes. Effect of ouabain on voltage dependence.

PubMed

Lee, H C; Clusin, W T

1987-02-01

Sarcolemmal sodium/calcium exchange activity was examined in individual chick embryonic myocardial cell aggregates that were loaded with quin 2. The baseline [Ca2+]i was 68 +/- 4 nM (n = 29). Abrupt superfusion with sodium-free lithium solution produced a fourfold increase in steady-state [Ca2+]i to 290 +/- 19 nM, which was reversible upon sodium restitution. Other methods of increasing [Ca2+]i such as KCl-depolarization or caffeine produced a dose-dependent increase in quin 2 fluorescence, accompanied by sustained contracture. The [Ca2+]i increase in zero sodium was linear, and its half-time (t1/2) of 15.1 +/- 0.1 s was similar to that of the sodium-free contracture (t1/2 = 14.4 +/- 0.5 s) under the same conditions. The sodium-dependent [Ca2+]i increase was not significantly greater when potassium served as the sodium substitute instead of lithium. This suggests that sodium/calcium exchange has little voltage dependence in this situation. However, in aggregates pretreated with ouabain (2.5 microM), the [Ca2+]i increase was almost threefold greater with potassium than with lithium (P less than 0.007). Ouabain therefore potentiated the effect of membrane potential on calcium influx. We propose that elevation of [Na2+]i is a prerequisite for voltage dependence of the sodium/calcium exchange under the conditions studied. Sodium loading will then drastically increase calcium influx during the action potential while inducing an outward membrane current that could accelerate repolarization.

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

Melting and subsolidus reactions in the system K2O-CaO-Al2O3-SiO2-H2O

NASA Astrophysics Data System (ADS)

Johannes, Wilhelm

1980-09-01

Beginning of melting and subsolidus relationships in the system K2O-CaO-Al2O3-SiO2-H2O have been experimentally investigated at pressures up to 20 kbars. The equilibria discussed involve the phases anorthite, sanidine, zoisite, muscovite, quartz, kyanite, gas, and melt and two invariant points: Point [Ky] with the phases An, Or, Zo, Ms, Qz, Vapor, and Melt; point [Or] with An, Zo, Ms, Ky, Qz, Vapor, and Melt. The invariant point [Ky] at 675° C and 8.7 kbars marks the lowest solidus temperature of the system investigated. At pressures above this point the hydrated phases zoisite and muscovite are liquidus phases and the solidus temperatures increase with increasing pressure. At 20 kbars beginning of melting occurs at 740 °C. The solidus temperatures of the quinary system K2O-CaO-Al2O3-SiO2-H2O are almost 60° C (at 20 kbars) and 170° C (at 2kbars) below those of the limiting quaternary system CaO-Al2O3-SiO2-H2O. The maximum water pressure at which anorthite is stable is lowered from 14 to 8.7 kbars in the presence of sanidine. The stability limits of anorthite+ vapor and anorthite+sanidine+vapor at temperatures below 700° C are almost parallel and do not intersect. In the wide temperature — pressure range at pressures above the reaction An+Or+Vapor = Zo+Ms+Qz and temperatures below the melting curve of Zo+Ms+Ky+Qz+Vapor, the feldspar assemblage anorthite+sanidine is replaced by the hydrated phases zoisite and muscovite plus quartz. CaO-Al2O3-SiO2-H2O. Knowledge of the melting relationships involving the minerals zoisite and muscovite contributes to our understanding of the melting processes occuring in the deeper parts of the crust. Beginning of melting in granites and granodiorites depends on the composition of plagioclase. The solidus temperatures of all granites and granodiorites containing plagioclases of intermediate composition are higher than those of the Ca-free alkali feldspar granite system and below those of the Na-free system discussed in this

Ca2+ toxicity due to reverse Na+/Ca2+ exchange contributes to degeneration of neurites of DRG neurons induced by a neuropathy-associated Nav1.7 mutation

PubMed Central

Estacion, M.; Vohra, B. P. S; Liu, S.; Hoeijmakers, J.; Faber, C. G.; Merkies, I. S. J.; Lauria, G.; Black, J. A.

2015-01-01

Gain-of-function missense mutations in voltage-gated sodium channel Nav1.7 have been linked to small-fiber neuropathy, which is characterized by burning pain, dysautonomia and a loss of intraepidermal nerve fibers. However, the mechanistic cascades linking Nav1.7 mutations to axonal degeneration are incompletely understood. The G856D mutation in Nav1.7 produces robust changes in channel biophysical properties, including hyperpolarized activation, depolarized inactivation, and enhanced ramp and persistent currents, which contribute to the hyperexcitability exhibited by neurons containing Nav1.8. We report here that cell bodies and neurites of dorsal root ganglion (DRG) neurons transfected with G856D display increased levels of intracellular Na+ concentration ([Na+]) and intracellular [Ca2+] following stimulation with high [K+] compared with wild-type (WT) Nav1.7-expressing neurons. Blockade of reverse mode of the sodium/calcium exchanger (NCX) or of sodium channels attenuates [Ca2+] transients evoked by high [K+] in G856D-expressing DRG cell bodies and neurites. We also show that treatment of WT or G856D-expressing neurites with high [K+] or 2-deoxyglucose (2-DG) does not elicit degeneration of these neurites, but that high [K+] and 2-DG in combination evokes degeneration of G856D neurites but not WT neurites. Our results also demonstrate that 0 Ca2+ or blockade of reverse mode of NCX protects G856D-expressing neurites from degeneration when exposed to high [K+] and 2-DG. These results point to [Na+] overload in DRG neurons expressing mutant G856D Nav1.7, which triggers reverse mode of NCX and contributes to Ca2+ toxicity, and suggest subtype-specific blockade of Nav1.7 or inhibition of reverse NCX as strategies that might slow or prevent axon degeneration in small-fiber neuropathy. PMID:26156380

Microstructure, mechanical properties and stretch formability of Mg-3Al-0.5Ca-0.2Gd alloy processed at various finish rolling temperatures

NASA Astrophysics Data System (ADS)

Kang, Qiang; Jiang, Haitao; Zhang, Yun

2018-04-01

Effects of various finish rolling temperatures on the microstructure, texture, mechanical properties and stretch formability of rolled and annealed Mg-3Al-0.5Ca-0.2Gd (wt%) alloy were investigated in this paper, and it was found that compared with grain size and second phase particles, the basal textures, tensile properties and stretch formability Mg-3Al-0.5Ca-0.2Gd alloy are more sensitive to the increasing finishing rolling temperature. For the rolled and annealed Mg-3Al-0.5Ca-0.2Gd alloy, their grains barely grow up and second phase particles are slightly coarsened, while their basal poles are obviously weakened and tilted with increasing finish rolling temperature. Consequently, the weakened and RD-tilted basal textures are beneficial to the gradually improved elongation and stretch formability of Mg-3Al-0.5Ca-0.2Gd alloy. It is investigated that the gradually activated non-basal slips, e. g. 〈c 〉, 〈c + a〉 dislocations due to the increasing finish rolling temperature could contribute to the weakened RD-tilted textures in rolled and annealed Mg-3Al-0.5Ca-0.2Gd alloy.

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.

The bovine TRPV3 as a pathway for the uptake of Na+, Ca2+, and NH4+

PubMed Central

Liebe, Franziska; Liebe, Hendrik

2018-01-01

Absorption of ammonia from the gastrointestinal tract results in problems that range from hepatic encephalopathy in humans to poor nitrogen efficiency of cattle with consequences for the global climate. Previous studies on epithelia and cells from the native ruminal epithelium suggest functional involvement of the bovine homologue of TRPV3 (bTRPV3) in ruminal NH4+ transport. Since the conductance of TRP channels to NH4+ has never been studied, bTRPV3 was overexpressed in HEK-293 cells and investigated using the patch-clamp technique and intracellular calcium imaging. Control cells contained the empty construct. Divalent cations blocked the conductance for monovalent cations in both cell types, with effects higher in cells expressing bTRPV3. In bTRPV3 cells, but not in controls, menthol, thymol, carvacrol, or 2-APB stimulated whole cell currents mediated by Na+, Cs+, NH4+, and K+, with a rise in intracellular Ca2+ observed in response to menthol. While only 25% of control patches showed single-channel events (with a conductance of 40.8 ± 11.9 pS for NH4+ and 25.0 ± 5.8 pS for Na+), 90% of bTRPV3 patches showed much larger conductances of 127.8 ± 4.2 pS for Na+, 240.1 ± 3.6 pS for NH4+, 34.0 ± 1.7 pS for Ca2+, and ~ 36 pS for NMDG+. Open probability, but not conductance, rose with time after patch excision. In conjunction with previous research, we suggest that bTRPV3 channels may play a role in the transport of Na+, K+, Ca2+ and NH4+ across the rumen with possible repercussions for understanding the function of TRPV3 in other epithelia. PMID:29494673

The bovine TRPV3 as a pathway for the uptake of Na+, Ca2+, and NH4.

PubMed

Schrapers, Katharina T; Sponder, Gerhard; Liebe, Franziska; Liebe, Hendrik; Stumpff, Friederike

2018-01-01

Absorption of ammonia from the gastrointestinal tract results in problems that range from hepatic encephalopathy in humans to poor nitrogen efficiency of cattle with consequences for the global climate. Previous studies on epithelia and cells from the native ruminal epithelium suggest functional involvement of the bovine homologue of TRPV3 (bTRPV3) in ruminal NH4+ transport. Since the conductance of TRP channels to NH4+ has never been studied, bTRPV3 was overexpressed in HEK-293 cells and investigated using the patch-clamp technique and intracellular calcium imaging. Control cells contained the empty construct. Divalent cations blocked the conductance for monovalent cations in both cell types, with effects higher in cells expressing bTRPV3. In bTRPV3 cells, but not in controls, menthol, thymol, carvacrol, or 2-APB stimulated whole cell currents mediated by Na+, Cs+, NH4+, and K+, with a rise in intracellular Ca2+ observed in response to menthol. While only 25% of control patches showed single-channel events (with a conductance of 40.8 ± 11.9 pS for NH4+ and 25.0 ± 5.8 pS for Na+), 90% of bTRPV3 patches showed much larger conductances of 127.8 ± 4.2 pS for Na+, 240.1 ± 3.6 pS for NH4+, 34.0 ± 1.7 pS for Ca2+, and ~ 36 pS for NMDG+. Open probability, but not conductance, rose with time after patch excision. In conjunction with previous research, we suggest that bTRPV3 channels may play a role in the transport of Na+, K+, Ca2+ and NH4+ across the rumen with possible repercussions for understanding the function of TRPV3 in other epithelia.

The Temperature and Structure Dependence of Surface Tension of CaO-SiO2-Na2O-CaF2 Mold Fluxes

NASA Astrophysics Data System (ADS)

Gao, Qiang; Min, Yi; Jiang, Maofa

2018-06-01

The surface tension of mold flux is one of the most important properties and varies with the temperature from the top to the bottom of the mold, which influences the adhesion and lubrication between the liquid mold flux and the solidified shell, further influencing the quality of the continuous billet. In the present paper, the effect of temperature on the surface tension of CaO-SiO2-Na2O-CaF2 mold-flux melts with different CaO/SiO2 mass ratios was investigated using the maximum-pull method. Furthermore, the microstructure of mold fluxes was analyzed using FT-IR and Raman spectra to discuss the change mechanism of surface tension. The results indicated that the temperature dependence of surface tension was different with different CaO/SiO2 mass ratios, and agreed with the modification of melt structure. When the CaO/SiO2 mass ratio was 0.67 and 0.85, the change of surface tension with temperature was relatively stable, and the influence of temperature on the structure was small. When the CaO/SiO2 mass ratio was 1.03 and 1.16, with an increase of temperature, the surface tension decreased linearly and the changing amplitude was large; the degree of polymerization of melts and average radii of silicon-oxygen anions also decreased, which intensified the molecular thermal motion and weakened the intermolecular interaction, resulting in a decrease of surface tension of melts.

The Temperature and Structure Dependence of Surface Tension of CaO-SiO2-Na2O-CaF2 Mold Fluxes

NASA Astrophysics Data System (ADS)

Gao, Qiang; Min, Yi; Jiang, Maofa

2018-02-01

The surface tension of mold flux is one of the most important properties and varies with the temperature from the top to the bottom of the mold, which influences the adhesion and lubrication between the liquid mold flux and the solidified shell, further influencing the quality of the continuous billet. In the present paper, the effect of temperature on the surface tension of CaO-SiO2-Na2O-CaF2 mold-flux melts with different CaO/SiO2 mass ratios was investigated using the maximum-pull method. Furthermore, the microstructure of mold fluxes was analyzed using FT-IR and Raman spectra to discuss the change mechanism of surface tension. The results indicated that the temperature dependence of surface tension was different with different CaO/SiO2 mass ratios, and agreed with the modification of melt structure. When the CaO/SiO2 mass ratio was 0.67 and 0.85, the change of surface tension with temperature was relatively stable, and the influence of temperature on the structure was small. When the CaO/SiO2 mass ratio was 1.03 and 1.16, with an increase of temperature, the surface tension decreased linearly and the changing amplitude was large; the degree of polymerization of melts and average radii of silicon-oxygen anions also decreased, which intensified the molecular thermal motion and weakened the intermolecular interaction, resulting in a decrease of surface tension of melts.

Measurement and Modeling of Setschenow Constants for Selected Hydrophilic Compounds in NaCl and CaCl2 Simulated Carbon Storage Brines.

PubMed

Burant, Aniela; Lowry, Gregory V; Karamalidis, Athanasios K

2017-06-20

Carbon capture, utilization, and storage (CCUS), a climate change mitigation strategy, along with unconventional oil and gas extraction, generates enormous volumes of produced water containing high salt concentrations and a litany of organic compounds. Understanding the aqueous solubility of organic compounds related to these operations is important for water treatment and reuse alternatives, as well as risk assessment purposes. The well-established Setschenow equation can be used to determine the effect of salts on aqueous solubility. However, there is a lack of reported Setschenow constants, especially for polar organic compounds. In this study, the Setschenow constants for selected hydrophilic organic compounds were experimentally determined, and linear free energy models for predicting the Setschenow constant of organic chemicals in concentrated brines were developed. Solid phase microextraction was employed to measure the salting-out behavior of six selected hydrophilic compounds up to 5 M NaCl and 2 M CaCl 2 and in Na-Ca-Cl brines. All compounds, which include phenol, p-cresol, hydroquinone, pyrrole, hexanoic acid, and 9-hydroxyfluorene, exhibited log-linear behavior up to these concentrations, meaning Setschenow constants previously measured at low salt concentrations can be extrapolated up to high salt concentrations for hydrophilic compounds. Setschenow constants measured in NaCl and CaCl 2 brines are additive for the compounds measured here; meaning Setschenow constants measured in single salt solutions can be used in multiple salt solutions. The hydrophilic compounds in this study were selected to elucidate differences in salting-out behavior based on their chemical structure. Using data from this study, as well as literature data, linear free energy relationships (LFERs) for prediction of NaCl, CaCl 2 , LiCl, and NaBr Setschenow constants were developed and validated. Two LFERs were improved. One LFER uses the Abraham solvation parameters, which include

Electrochemical Behavior of Al-B4C Metal Matrix Composites in NaCl Solution

PubMed Central

Han, Yu-Mei; Chen, X.-Grant

2015-01-01

Aluminum based metal matrix composites (MMCs) have received considerable attention in the automotive, aerospace and nuclear industries. One of the main challenges using Al-based MMCs is the influence of the reinforcement particles on the corrosion resistance. In the present study, the corrosion behavior of Al-B4C MMCs in a 3.5 wt.% NaCl solution were investigated using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. Results indicated that the corrosion resistance of the composites decreased when increasing the B4C volume fraction. Al-B4C composite was susceptible to pitting corrosion and two types of pits were observed on the composite surface. The corrosion mechanism of the composite in the NaCl solution was primarily controlled by oxygen diffusion in the solution. In addition, the galvanic couples that formed between Al matrix and B4C particles could also be responsible for the lower corrosion resistance of the composites. PMID:28793574

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.

Suppressive Effect of Carvedilol on Na+/Ca2+ Exchange Current in Isolated Guinea-Pig Cardiac Ventricular Myocytes.

PubMed

Tashiro, Miyuki; Watanabe, Yasuhide; Yamakawa, Tomomi; Yamashita, Kanna; Kita, Satomi; Iwamoto, Takahiro; Kimura, Junko

2017-01-01

Carvedilol ((+/-)-1-(carbazol-4-yloxy)-3-[[2-(o-methoxyphenoxy)ethyl]amino]-2-propanol), a β-adrenoceptor-blocker, has multi-channel blocking and vasodilator properties. This agent dose-dependently improves left ventricular function and reduces mortality in patients with arrhythmia and chronic heart failure. However, the effect of carvedilol on the cardiac Na+/Ca2+ exchanger (NCX1) has not been investigated. We examined the effects of carvedilol and metoprolol, 2 β-blockers, on Na+/Ca2+ exchange current (INCX) in guinea-pig cardiac ventricular cells and fibroblasts expressing dog cardiac NCX1. Carvedilol suppressed INCX in a concentration-dependent manner but metoprolol did not. IC50 values for the Ca2+ influx (outward) and efflux (inward) components of INCX were 69.7 and 61.5 µmol/l, respectively. Carvedilol at 100 μmol/l inhibited INCX in CCL39 cells expressing wild type NCX1 similar to mutant NCX1 without the intracellular regulatory loop. Carvedilol at 30 µmol/l abolished ouabain-induced delayed afterdepolarizations. Carvedilol inhibited cardiac NCX in a concentration-dependent manner in isolated cardiac ventricles, but metoprolol did not. We conclude that carvedilol inhibits NCX1 at supratherapeutic concentrations. © 2016 S. Karger AG, Basel.

Growth of GaN single crystals by a Ca- and Ba-added Na flux method

NASA Astrophysics Data System (ADS)

Ukegawa, H.; Konishi, Y.; Fujimori, T.; Miyoshi, N.; Imade, M.; Yoshimura, M.; Kitaoka, Y.; Sasaki, T.; Mori, Y.

2011-02-01

GaN substrates are desirable for fabricating ultra-violet LEDs and LDs, and high-power and high-frequency transistors. High-quality GaN single crystals can be obtained by using Na flux method, but the growth habit of bulk crystals must be controlled. In this study, we investigated the effects of additives (Ca, Ba) on the growth habit and impurity concentration in the crystals. The aspect ratio (c/a) of the crystals was increased by increasing the amount of additives, showing that the growth habit could be changed from the pyramidal shape to the prism shape. Ba concentration was below the detection limit (1x1015 atoms/cm3).

A Study of Electrochemical Machining of Ti-6Al-4V in NaNO3 solution

NASA Astrophysics Data System (ADS)

Li, Hansong; Gao, Chuanping; Wang, Guoqian; Qu, Ningsong; Zhu, Di

2016-10-01

The titanium alloy Ti-6Al-4V is used in many industries including aviation, automobile manufacturing, and medical equipment, because of its low density, extraordinary corrosion resistance and high specific strength. Electrochemical machining (ECM) is a non-traditional machining method that allows applications to all kinds of metallic materials in regardless of their mechanical properties. It is widely applied to the machining of Ti-6Al-4V components, which usually takes place in a multicomponent electrolyte solution. In this study, a 10% NaNO3 solution was used to make multiple holes in Ti-6Al-4V sheets by through-mask electrochemical machining (TMECM). The polarization curve and current efficiency curve of this alloy were measured to understand the electrical properties of Ti-6Al-4V in a 10% NaNO3 solution. The measurements show that in a 10% NaNO3 solution, when the current density was above 6.56 A·cm-2, the current efficiency exceeded 100%. According to polarization curve and current efficiency curve, an orthogonal TMECM experiment was conducted on Ti-6Al-4V. The experimental results suggest that with appropriate process parameters, high-quality holes can be obtained in a 10% NaNO3 solution. Using the optimized process parameters, an array of micro-holes with an aperture of 2.52 mm to 2.57 mm and maximum roundness of 9 μm were produced using TMECM.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

Sound velocities of Na0.4Mg0.6Al1.6Si0.4O4 NAL and CF phases to 73 GPa determined by Brillouin scattering method

NASA Astrophysics Data System (ADS)

Dai, Lidong; Kudo, Yuki; Hirose, Kei; Murakami, Motohiko; Asahara, Yuki; Ozawa, Haruka; Ohishi, Yasuo; Hirao, Naohisa

2013-03-01

The sound velocities of two aluminum-rich phases in the lower mantle, hexagonal new Al-rich phase (NAL) and its corresponding high-pressure polymorph orthorhombic Ca-ferrite-type phase (CF), were determined with the Brillouin scattering method in a pressure range from 9 to 73 GPa at room temperature. Both NAL and CF samples have identical chemical composition of Na0.4Mg0.6Al1.6Si0.4O4 (40 % NaAlSiO4-60 % MgAl2O4). Infrared laser annealing in the diamond anvil cell was performed to minimize the stress state of the sample and obtain the high-quality Brillouin spectra. The results show shear modulus at zero pressure G 0 = 121.960 ± 0.087 GPa and its pressure derivative G' = 1.961 ± 0.009 for the NAL phase, and G 0 = 129.653 ± 0.059 GPa and G' = 2.340 ± 0.004 for the CF phase. The zero-pressure shear velocities of the NAL and CF phases are obtained to be 5.601 ± 0.005 km/sec and 5.741 ± 0.001 km/sec, respectively. We also found that shear velocity increases by 2.5 % upon phase transition from NAL to CF at around 40 GPa.

Structure and dielectric properties of Na0.5Bi0.5TiO3-CaTiO3 solid solutions

NASA Astrophysics Data System (ADS)

Birks, E.; Dunce, M.; Ignatans, R.; Kuzmin, A.; Plaude, A.; Antonova, M.; Kundzins, K.; Sternberg, A.

2016-02-01

Despite wide studies of Na0.5Bi0.5TiO3, structure of this material and its connection with the observed physical properties still raise numerous questions due to mutually contradicting results obtained. Here, structure and dielectric properties of poled and unpoled Na0.5Bi0.5TiO3-CaTiO3 solid solutions are studied, projecting the obtained concentration dependence of structure and dielectric properties on pure Na0.5Bi0.5TiO3 as the end member of this material group. X-ray diffraction patterns for Na0.5Bi0.5TiO3-CaTiO3 solid solutions reveal dominating of an orthorhombic Pnma phase, even for the compositions approaching the end composition (Na0.5Bi0.5TiO3), whereas structure of pure Na0.5Bi0.5TiO3 can be considered, assuming coexistence of rhombohedral and orthorhombic phases. This allows one to avoid appearance of a large difference of rhombohedral distortions between the unpoled and poled Na0.5Bi0.5TiO3, if the rhombohedral distortion is calculated as for single R3c phase. Features of dielectric permittivity, corresponding to the observed structural phase transition, are identified. It is discussed that the rhombohedral R3c phase is responsible for appearance of the frequency-dependent shoulder of dielectric permittivity temperature dependence, characteristic for unpoled Na0.5Bi0.5TiO3.

Dielectric properties and nonlinear I-V electrical behavior of (Li1+, Al3+) co-doped CaCu3Ti4O12 ceramics

NASA Astrophysics Data System (ADS)

Sun, Li; Ni, Qing; Guo, Jianqin; Cao, Ensi; Hao, Wentao; Zhang, Yongjia; Ju, Lin

2018-06-01

(Li1+, Al3+) co-doped CaCu3Ti4O12 ceramics (CaCu3-2 x Li x Al x Ti4O12, x = 0.05, 0.1, 0.15) were prepared by a sol-gel method and were sintered at 1020-1080 °C for 8 h to improve the geometric microstructure, dielectric and nonlinear I-V electrical properties. Notably, very high dielectric constant of 1 × 105 with good dielectric-frequency as well as dielectric-temperature stability can be achieved in CaCu2.8Li0.1Al0.1Ti4O12 ceramic sintered at 1060 °C. The average grain sizes, resistivity and the non-Ohmic properties are also improved compared to pure CaCu3Ti4O12. These results indicate that (Li1+, Al3+) co-doping at the Cu2+ site can improve the dielectric properties of CaCu3Ti4O12, supporting the internal barrier layer capacitance effect of Schottky barriers at grain boundaries.

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

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.

Intracellular Ca2+ regulation by the leech giant glial cell.

PubMed

Nett, W; Deitmer, J W

1998-02-15

1. We have measured the intracellular Ca2+ concentration, [Ca2+]i, and the intracellular Na+ concentration, [Na+]i, with the fluorescent dyes fura-2 (for Ca2+) and SBFI (for Na+) in situ in giant glial cells of the central nervous system of the leech Hirudo medicinalis. 2. The basal [Ca2+]i was 79 +/- 35 nM (n = 27) in cells voltage clamped at -70 to -80 mV, and 75 +/- 29 nM (mean +/- S.D., n = 82) in unclamped cells at a mean membrane potential of -67 +/- 6 mV. 3. Removal of external Na+ evoked a small reversible [Ca2+]i increase of 29 +/- 21 nM (n = 27) in cells voltage clamped at -70 to -80 mV, and of 35 +/- 18 nM (n = 37) in unclamped cells. This [Ca2+]i increase, and the time constant of the subsequent [Ca2+]i recovery after Na+ re-addition, did not change significantly with the holding potential between -110 and -60 mV. 4. The basal [Na+]i was 5.6 +/- 1.3 mM (n = 18). Increasing [Na+]i by inhibiting the Na+-K+ pump with 100 microM ouabain had no effect on the [Ca2+]i rise upon removal of external Na+. 5. The time course of recovery from a [Ca2+]i load mediated by voltage-dependent Ca2+ influx during depolarization in high K+ was unaffected by the removal of external Na+. 6. Cyclopiazonic acid (10 muM), an inhibitor of the endoplasmic reticulum Ca2+-ATPase, caused a transient increase in [Ca2+]i of 28 +/- 11 nM (n = 5), and significantly slowed the recovery from imposed [Ca2+]i loads. 7. Iontophoretic injection of orthovanadate, an inhibitor of P-type ATPases including the plasma membrane Ca2+-ATPase, caused a persistent increase in the basal [Ca2+]i of 163 +/- 101 nM (n = 5) in standard saline, and of 427 +/- 338 nM in Na+-free saline (n = 5). Vanadate injection significantly slowed the recovery from [Ca2+]i loads. Removal of external Na+ during vanadate injection induced an additional, reversible [Ca2+]i increase of 254 +/- 64 nM (n = 3). 8. The results suggest that the low basal [Ca2+]i in these glial cells is predominantly maintained by a Ca2+-ATPase in

Phase Equilibria in the System "FeO"-CaO-SiO2-Al2O3-MgO at Different CaO/SiO2 Ratios

NASA Astrophysics Data System (ADS)

Jang, Kyoung-oh; Ma, Xiaodong; Zhu, Jinming; Xu, Haifa; Wang, Geoff; Zhao, Baojun

2017-06-01

The "FeO"-containing slags play an important role in the operation of an ironmaking blast furnace (BF), in particular the primary slags such as the system "FeO"-CaO-SiO2-Al2O3-2 mass pct MgO with CaO/SiO2 weight ratios of 1.3, 1.5, and 1.8 saturated with metallic iron. To investigate the characteristics of such a slag system and its behavior in BF, the phase equilibria and liquidus temperatures in the slag system have been experimentally determined using the high-temperature equilibration and quenching technique followed by an electron probe X-ray microanalysis (EPMA). Isotherms between 1553 K and 1603 K (1280 °C and 1330 °C) were determined in the primary phase fields of dicalcium silicate, melilite, spinel, and monoxide [(Mg,Fe2+)O]. Pseudo-ternary phase diagrams of (CaO + SiO2)-Al2O3-"FeO" with a fixed MgO concentration at 2 mass pct and at CaO/SiO2 ratios of 1.3, 1.5, and 1.8 have been discussed, respectively, simplifying the complexity of the slag system for easy understanding and applying in BF operation. It was found that the liquidus temperatures increase in melilite and spinel primary phase fields, but decrease in dicalcium silicate and monoxide primary phase fields with increasing Al2O3/(CaO + SiO2) ratio. In addition, the liquidus temperatures decrease with increasing "FeO" concentration in dicalcium silicate and melilite primary phase fields, while showing an increasing trend in the spinel and monoxide primary phase fields. The data resulted from this study can be used to improve and optimize currently available database of thermodynamic models used in FactSage.

AmeriFlux CA-Na1 New Brunswick - 1967 Balsam Fir - Nashwaak Lake Site 01 (Mature balsam fir forest)

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

Bourque, Charles P.-A.

This is the AmeriFlux version of the carbon flux data for the site CA-Na1 New Brunswick - 1967 Balsam Fir - Nashwaak Lake Site 01 (Mature balsam fir forest). Site Description - immature balsam fir forest

Electrical conductivity optimization of the Na3AlF6-Al2O3-Sm2O3 molten salts system for Al-Sm intermediate binary alloy production

NASA Astrophysics Data System (ADS)

Liao, Chun-fa; Jiao, Yun-fen; Wang, Xu; Cai, Bo-qing; Sun, Qiang-chao; Tang, Hao

2017-09-01

Metal Sm has been widely used in making Al-Sm magnet alloy materials. Conventional distillation technology to produce Sm has the disadvantages of low productivity, high costs, and pollution generation. The objective of this study was to develop a molten salt electrolyte system to produce Al-Sm alloy directly, with focus on the electrical conductivity and optimal operating conditions to minimize the energy consumption. The continuously varying cell constant (CVCC) technique was used to measure the conductivity for the Na3AlF6-AlF3-LiF-MgF2-Al2O3-Sm2O3 electrolysis medium in the temperature range from 905 to 1055°C. The temperature ( t) and the addition of Al2O3 ( W(Al2O3)), Sm2O3 ( W(Sm2O3)), and a combination of Al2O3 and Sm2O3 into the basic fluoride system were examined with respect to their effects on the conductivity ( κ) and activation energy. The experimental results showed that the molten electrolyte conductivity increases with increasing temperature ( t) and decreases with the addition of Al2O3 or Sm2O3 or both. We concluded that the optimal operation conditions for Al-Sm intermediate alloy production in the Na3AlF6-AlF3-LiF-MgF2-Al2O3-Sm2O3 system are W(Al2O3) + W(Sm2O3) = 3wt%, W(Al2O3): W(Sm2O3) = 7:3, and a temperature of 965 to 995°C, which results in satisfactory conductivity, low fluoride evaporation losses, and low energy consumption.

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.

Thermally and optically stimulated radiative processes in Eu and Y co-doped LiCaAlF6 crystal

NASA Astrophysics Data System (ADS)

Fukuda, Kentaro; Yanagida, Takayuki; Fujimoto, Yutaka

2015-06-01

Yttrium co-doping was attempted to enhance dosimeter performance of Eu doped LiCaAlF6 crystal. Eu doped and Eu, Y co-doped LiCaAlF6 were prepared by the micro-pulling-down technique, and their dosimeter characteristics such as optically stimulated luminescence (OSL) and thermally stimulated luminescence (TSL) were investigated. By yttrium co-doping, emission intensities of OSL and TSL were enhanced by some orders of magnitude. In contrast, scintillation characteristics of yttrium co-doped crystal such as intensity of prompt luminescence induced by X-ray and light yield under neutron irradiation were degraded.

Inhibiting Mitochondrial Na+/Ca2+ Exchange Prevents Sudden Death in a Guinea Pig Model of Heart Failure

PubMed Central

Liu, Ting; Takimoto, Eiki; Dimaano, Veronica L.; DeMazumder, Deeptankar; Kettlewell, Sarah; Smith, Godfrey; Sidor, Agnieszka; Abraham, Theodore P.; O’Rourke, Brian

2014-01-01

Rationale In cardiomyocytes from failing hearts, insufficient mitochondrial Ca2+ ([Ca2+]m) accumulation secondary to cytoplasmic Na+ overload decreases NAD(P)H/NAD(P)+ redox potential and increases oxidative stress when workload increases. These effects are abolished by enhancing [Ca2+]m with acute treatment with CGP-37157 (CGP), an inhibitor of the mitochondrial Na+/Ca2+ exchanger. Objective To determine if chronic CGP treatment mitigates contractile dysfunction and arrhythmias in an animal model of heart failure (HF) and sudden cardiac death (SCD). Methods and Results Here, we describe a novel guinea-pig HF/SCD model employing aortic constriction combined with daily β-adrenergic receptor stimulation (ACi) and show that chronic CGP treatment (ACi+CGP) attenuates cardiac hypertrophic remodeling, pulmonary edema, and interstitial fibrosis and prevents cardiac dysfunction and SCD. In the ACi group 4 weeks after pressure-overload, fractional shortening and the rate of left ventricular pressure development decreased by 36% and 32%, respectively, compared to sham-operated controls; in contrast, cardiac function was completely preserved in the ACi+CGP group. CGP treatment also significantly reduced the incidence of premature ventricular beats and prevented fatal episodes of ventricular fibrillation, but did not prevent QT prolongation. Without CGP treatment, mortality was 61% in the ACi group within 4 weeks of aortic constriction, while the death rate in the ACi+CGP group was not different from sham-operated animals. Conclusions The findings demonstrate the critical role played by altered mitochondrial Ca2+ dynamics in the development of HF and HF-associated SCD; moreover, they reveal a novel strategy for treating SCD and cardiac decompensation in HF. PMID:24780171

Sperm Na+, K+-ATPase and Ca2+-ATPase activity: A preliminary study of comparison of swim up and density gradient centrifugation methods for sperm preparation

NASA Astrophysics Data System (ADS)

Lestari, Silvia W.; Larasati, Manggiasih D.; Asmarinah, Mansur, Indra G.

2018-02-01

As one of the treatment for infertility, the success rate of Intrauterine Insemination (IUI) is still relatively low. Several sperm preparation methods, swim-up (SU) and the density-gradient centrifugation (DGC) are frequently used to select for better sperm quality which also contribute to IUI failure. Sperm selection methods mainly separate the motile from the immotile sperm, eliminating the seminal plasma. The sperm motility involves the structure and function of sperm membrane in maintaining the balance of ion transport system which is regulated by the Na+, K+-ATPase, and Ca2+-ATPase enzymes. This study aims to re-evaluate the efficiency of these methods in selecting for sperm before being used for IUI and based the evaluation on sperm Na+,K+-ATPase and Ca2+-ATPase activities. Fourteen infertile men from couples who underwent IUI were involved in this study. The SU and DGC methods were used for the sperm preparation. Semen analysis was performed based on the reference value of World Health Organization (WHO) 2010. After isolating the membrane fraction of sperms, the Na+, K+-ATPase activity was defined as the difference in the released inorganic phosphate (Pi) with and without the existence of 10 mM ouabain in the reaction, while the Ca2+-ATPase was determined as the difference in Pi contents with and without the existence of 55 µm CaCl2. The prepared sperm demonstrated a higher percentage of motile sperm compared to sperm from the whole semen. Additionally, the percentage of motile sperm of post-DGC showed higher result than the sperm from post-SU. The velocity of sperm showed similar pattern with the percentage of motile sperm, in which the velocity of prepared sperm was higher than the sperm from whole semen. Furthermore, the sperm velocity of post-DGC was higher compared to the sperm from post-SU. The Na+, K+-ATPase activity of prepared sperm was higher compared to whole semen, whereas Na+, K+-ATPase activity in the post DGC was higher than post SU. The Ca2

Low-Temperature Sintering of AlN Ceramics by Sm2O3-Y2O3-CaO Sintering Additives Formed via Decomposition of Nitrate Solutions

NASA Astrophysics Data System (ADS)

Zhan, Jun; Cao, Ye; Zhang, Hao; Guo, Jun; Zhang, Jianhua; Geng, Chunlei; Shi, Changdong; Cui, Song; Tang, Wenming

2017-01-01

The Sm, Y and Ca anhydrous nitrates were mixed with the AlN powder in ethanol and then decomposed into the Sm2O3-Y2O3-CaO sintering additives via calcining. Low-temperature sintering of the AlN ceramics was carried out at temperature range from 1675 to 1750 °C. Effects of the composition and adding amount of the sintering additives on the phases, microstructures and properties of the AlN ceramics were investigated. During sintering the AlN ceramics, main secondary phases of CaYAl3O7 and CaSmAl3O7 form. The relative density, bending strength and thermal conductivity of the AlN ceramics increase with the increase in the rare-earth oxides in them. The thermal conductivity of the sintered AlN ceramics is also greatly affected by the distribution of the secondary phases. As sintered at 1750 °C, the AlN ceramics by adding the sintering additives of 2 wt.% Sm2O3, 2 wt.% Y2O3 and 1 wt.% CaO formed via decomposition of their nitrates is fully dense and have the optimal bending strength and thermal conductivity of 402.1 MPa and 153.7 W/(m K), respectively.

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.

Recombination luminescence of CaSO4:Tb3+ and CaSO4:Gd3+phosphors

NASA Astrophysics Data System (ADS)

Kudryavtseva, Irina; Lushchik, Aleksandr; Maaroos, Aarne; Azmaganbetova, Zhannur; Nurakhmetov, Turlybek; Salikhoja, Zhussupbek

2012-08-01

A comparative study of the excitation of luminescence by VUV radiation as well as of thermally and photostimulated luminescence has been carried out for CaSO4:Tb3+ and CaSO4:Gd3+ phosphors, where Na+ or F- ions are used for charge compensation. The distinction in hole processes for the phosphors with Na+ or F- compensators is determined by the differing thermal stability of the holes localized at/near Tb3+Na+ and Gd3+Na+ (up to 100-160 K) or at/near Tb3+F- V Ca and Gd3+F- V Ca centers involving also a cation vacancy (up to 400-550 K). Tunnel luminescence in the pairs of localized electrons and holes nearby Tb3+ or Gd3+ has been detected. The mechanisms of electron-hole, hole-electron and tunnel recombination luminescence as well as a subsequent released energy transfer to RE3+ ions are considered.

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.

Voltage-dependent Ca2+ release from the SR of feline ventricular myocytes is explained by Ca2+-induced Ca2+ release.

PubMed

Piacentino, V; Dipla, K; Gaughan, J P; Houser, S R

2000-03-15

1. Direct voltage-gated (voltage-dependent Ca2+ release, VDCR) and Ca2+ influx-gated (Ca2+-induced Ca2+ release, CICR) sarcoplasmic reticulum (SR) Ca2+ release were studied in feline ventricular myocytes. The voltage-contraction relationship predicted by the VDCR hypothesis is sigmoidal with large contractions at potentials near the Ca2+ equilibrium potential (ECa). The relationship predicted by the CICR hypothesis is bell-shaped with no contraction at ECa. 2. The voltage dependence of contraction was measured in ventricular myocytes at physiological temperature (37 C), resting membrane potential and physiological [K+]. Experiments were performed with cyclic adenosine 3',5'-monophosphate (cAMP) in the pipette or in the presence of the beta-adrenergic agonist isoproterenol (isoprenaline; ISO). 3. The voltage-contraction relationship was bell-shaped in Na+-free solutions (to eliminate the Na+ current and Na+-Ca2+ exchange, NCX) but the relationship was broader than the L-type Ca2+ current (ICa,L)-voltage relationship. 4. Contractions induced with voltage steps from normal resting potentials to -40 mV are thought to represent VDCR rather than CICR. We found that cAMP and ISO shifted the voltage dependence of ICa,L activation to more negative potentials so that ICa,L was always present with steps to -40 mV. ICa,L at -40 mV inactivated when the holding potential was decreased (VŁ = -57.8 +/- 0.49 mV). 5. ISO increased inward current, SR Ca2+ load and contraction in physiological [Na+] and a broad bell-shaped voltage-contraction relationship was observed. Inhibition of reverse-mode NCX, decreasing ICa,L and decreasing SR Ca2+ loading all decreased contractions at strongly positive potentials near ECa. 6. The voltage-contraction relationship in 200 microM cadmium (Cd2+) was bell-shaped, supporting a role of ICa,L rather than VDCR. 7. All results could be accounted for by the CICR hypothesis, and many results exclude the VDCR hypothesis.

Voltage-dependent Ca2+ release from the SR of feline ventricular myocytes is explained by Ca2+-induced Ca2+ release

PubMed Central

Piacentino, Valentino; Dipla, Konstantina; Gaughan, John P; Houser, Steven R

2000-01-01

Direct voltage-gated (voltage-dependent Ca2+ release, VDCR) and Ca2+ influx-gated (Ca2+-induced Ca2+ release, CICR) sarcoplasmic reticulum (SR) Ca2+ release were studied in feline ventricular myocytes. The voltage-contraction relationship predicted by the VDCR hypothesis is sigmoidal with large contractions at potentials near the Ca2+ equilibrium potential (ECa). The relationship predicted by the CICR hypothesis is bell-shaped with no contraction at ECa. The voltage dependence of contraction was measured in ventricular myocytes at physiological temperature (37 °C), resting membrane potential and physiological [K+]. Experiments were performed with cyclic adenosine 3′,5′-monophosphate (cAMP) in the pipette or in the presence of the β-adrenergic agonist isoproterenol (isoprenaline; ISO). The voltage-contraction relationship was bell-shaped in Na+-free solutions (to eliminate the Na+ current and Na+-Ca2+ exchange, NCX) but the relationship was broader than the L-type Ca2+ current (ICa,L)-voltage relationship. Contractions induced with voltage steps from normal resting potentials to -40 mV are thought to represent VDCR rather than CICR. We found that cAMP and ISO shifted the voltage dependence of ICa,L activation to more negative potentials so that ICa,L was always present with steps to -40 mV. ICa,L at -40 mV inactivated when the holding potential was decreased (V½ =−57·8 ± 0·49 mV). ISO increased inward current, SR Ca2+ load and contraction in physiological [Na+] and a broad bell-shaped voltage-contraction relationship was observed. Inhibition of reverse-mode NCX, decreasing ICa,L and decreasing SR Ca2+ loading all decreased contractions at strongly positive potentials near ECa. The voltage-contraction relationship in 200 μM cadmium (Cd2+) was bell-shaped, supporting a role of ICa,L rather than VDCR. All results could be accounted for by the CICR hypothesis, and many results exclude the VDCR hypothesis. PMID:10718736

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.

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

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

Daniel A. Mosher; Xia Tang; Ronald J. Brown

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 exchangermore » optimization, reaction kinetics modeling, thermochemical finite element analysis, powder densification development and material neutralization were elements included in the effort.« less

Inhibition of the reverse mode of the Na+/Ca2+ exchange by KB-R7943 augments arrhythmogenicity in the canine heart during rapid heart rates.

PubMed

Shinada, Takuro; Hirayama, Yoshiyuki; Maruyama, Mitsunori; Ohara, Toshihiko; Yashima, Masaaki; Kobayashi, Yoshinori; Atarashi, Hirotsugu; Takano, Teruo

2005-07-01

To test the hypothesis that the reverse mode of the Na+/Ca2+ exchange augmented by a rapid heart rate has an antiarrhythmic effect by shortening the action potential duration, we examined the effects of KB-R7943 (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl] isothiourea methanesulfonate), a selective inhibitor of the reverse mode of the Na+/Ca2+ exchange, to attenuate this effect. We recorded the electrocardiogram, monophasic action potential (MAP), and left ventricular pressure in canine beating hearts. In comparison to the control, KB-R7943 significantly increased the QTc value and MAP duration. MAP alternans and left ventricular pressure alternans were observed after changing the cycle length to 300 milliseconds in the control studies. KB-R7943 magnified both types of alternans and produced spatially discordant alternans between right and left ventricles. Early after-depolarizations and nonsustained ventricular tachycardia occurred in the presence of KB-R7943. Our data suggest that the reverse mode of the Na+/Ca2+ exchange may contribute to suppression of arrhythmias by abbreviating action potential duration under pathophysiological conditions. This conclusion is based on further confirmation by future studies of the specificity of KB-R7943 for block of the reverse mode of the Na+/Ca2+ exchange.

Synthesis of Multicolor Core/Shell NaLuF4:Yb3+/Ln3+@CaF2 Upconversion Nanocrystals

PubMed Central

Li, Hui; Hao, Shuwei; Yang, Chunhui; Chen, Guanying

2017-01-01

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:Yb3+/Ln3+@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. PMID:28336867

High-pressure phase relations and thermodynamic properties of CaAl 4Si 2O 11 CAS phase

NASA Astrophysics Data System (ADS)

Akaogi, M.; Haraguchi, M.; Yaguchi, M.; Kojitani, H.

2009-03-01

Phase relations in CaAl4Si2O11 were examined at 12-23 GPa and 1000-1800 °C by multianvil experiments. A three-phase mixture of grossular, kyanite and corundum is stable below about 13 GPa at 1000-1800 °C. At higher pressure and at temperature below about 1200 °C, a mixture of grossular, stishovite and corundum is stable, indicating the decomposition of kyanite. Above about 1200 °C, CaAl4Si2O11 CAS phase is stable at pressure higher than about 13 GPa. The triple point is placed at 14.7 GPa and 1280 °C. The equilibrium boundary of formation of CAS phase from the mixture of grossular, kyanite and corundum has a small negative slope, and that from the mixture of grossular, stishovite and corundum has a strongly negative slope, while the decomposition boundary of kyanite has a small positive slope. Enthalpies of the transitions were measured by high-temperature drop-solution calorimetry. The enthalpy of formation of CaAl4Si2O11 CAS phase from the mixture of grossular, kyanite and corundum was 139.5 ± 15.6 kJ/mol, and that from the mixture of grossular, stishovite and corundum was 94.2 ± 15.4 kJ/mol. The transition boundaries calculated using the measured enthalpy data were consistent with those determined by the high-pressure experiments. The boundaries in this study are placed about 3 GPa higher in pressure and about 200 °C lower in temperature than those by Zhai and Ito [Zhai, S., Ito, E., 2008. Phase relations of CaAl4Si2O11 at high-pressure and high-temperature with implications for subducted continental crust into the deep mantle. Phys. Earth Planet. Inter. 167, 161-167]. Combining the thermodynamic data measured in this study with those in the literature, dissociation boundary of CAS phase into a mixture of Ca-perovskite, corundum and stishovite and that of grossular into Ca-perovskite plus corundum were calculated to further constrain the stability field of CAS phase. The result suggests that the stability of CAS phase would be limited at the bottom of

Crystallization Behavior of the CaO-Al2O3-MgO System Studied with a Confocal Laser Scanning Microscope

NASA Astrophysics Data System (ADS)

Jung, Sung Suk; Sohn, Il

2012-12-01

The crystallization behavior of a calcium-aluminate system with various MgO content from 2.5 to 7.5 wt pct and CaO/Al2O3 ratios between 0.8 and 1.2 has been examined using a confocal laser scanning microscope (CLSM). CCT (continuous cooling transformation) and time temperature transformation (TTT) diagrams were constructed to identify the primary crystal phase of slag at different compositions and at cooling rates between 25 and 800 K/minutes. In the slag at a CaO/Al2O3 ratio of 1.0, crystallization temperature increased during isothermal and continuous cooling with higher MgO content, and the shortest incubation time was observed at 5 wt pct MgO. When MgO content was fixed to be 5 wt pct, crystallization temperature increased with lower CaO/Al2O3 ratio. According to the slag composition, cooling rates and temperature, the primary phase could be CA, or C5A3, or C3A, or C3MA2, or MgO, and the crystal morphology changes from dendrites to faceted crystals to columnar crystals in this composition range.

Pressure-induced shift of T c and structural transition in “122” type pnictide superconductor Ca 0.34Na 0.66Fe 2As 2

DOE PAGES

Zhang, Sijia; Zhao, Kan; Yu, Xiaohui; ...

2016-07-11

Here, the effect of pressure on superconductivity of “122” type Ca 1-xNa xFe 2As 2 (x=0.66 single crystal is investigated through the temperature dependence of resistanc measurement. Optimal Na doped (Ca 0.34Na 0.66)Fe 2As 2 shows a superconductin transition with T c ~ 33 K at ambient pressure. With application of pressure, T decreases nearly linearly with d Tc/d P ~ -1.7K/GPa at pressures lower than 2 GPa and disappears gradually at higher pressure. The disappearance of superconductivit is also companied with the recovery of standard Fermi liquid behaviors of th normal-state transport properties. Moreover, (Ca 0.34Na 0.66)Fe 2As 2more » exhibits a tetragona (T) to collapsed-tetragonal (c T) transition at about 3 GPa. The evolution o non-Fermi liquid behaviors and superconductivity under pressure are both relate to the interband fluctuations.« less

Structure-property relationships in an Al matrix Ca nanofilamentary composite conductor with potential application in high-voltage power transmission

NASA Astrophysics Data System (ADS)

Tian, Liang

This study investigated the processing-structure-properties relationships in an Al/Ca composites using both experiments and modeling/simulation. A particular focus of the project was understanding how the strength and electrical conductivity of the composite are related to its microstructure in the hope that a conducting material with light weight, high strength, and high electrical conductivity can be developed to produce overhead high-voltage power transmission cables. The current power transmission cables (e.g., Aluminum Conductor Steel Reinforced (ACSR)) have acceptable performance for high-voltage AC transmission, but are less well suited for high-voltage DC transmission due to the poorly conducting core materials that support the cable weight. This Al/Ca composite was produced by powder metallurgy and severe plastic deformation by extrusion and swaging. The fine Ca metal powders have been produced by centrifugal atomization with rotating liquid oil quench bath, and a detailed study about the atomization process and powder characteristics has been conducted. The microstructure of Al/Ca composite was characterized by electron microscopy. Microstructure changes at elevated temperature were characterized by thermal analysis and indirect resistivity tests. The strength and electrical conductivity were measured by tensile tests and four-point probe resistivity tests. Predicting the strength and electrical conductivity of the composite was done by micro-mechanics-based analytical modeling. Microstructure evolution was studied by mesoscale-thermodynamics-based phase field modeling and a preliminary atomistic molecular dynamics simulation. The application prospects of this composite was studied by an economic analysis. This study suggests that the Al/Ca (20 vol. %) composite shows promise for use as overhead power transmission cables. Further studies are needed to measure the corrosion resistance, fatigue properties and energized field performance of this composite.

Trace element and petrologic clues to the formation of forsterite-bearing Ca-Al-rich inclusions in the Allende meteorite

NASA Astrophysics Data System (ADS)

Wark, D. A.; Boynton, W. V.; Keays, R. R.; Palme, H.

1987-03-01

This work presents new trace element and petrographic data for three forsterite-bearing, Ca-Al-rich inclusions from the Allende meteorite: TE, 818a, and 110-A. Such inclusions form a continuum with Type B1 and B2 Ca-Al-rich inclusions (CAIs), and the authors refer to them as "Type B3" CAIs. Textures, mineral chemistries, crystal-chemically fractionated REE patterns, and other properties suggest that Type B3 crystallized from partly molten evaporative residues. They also present evidence that 818a was strongly re-heated and modified in the nebula after its initial crystallization: it consists of a core of coarse-grained Ti-Al-pyroxene (Tpx), forsterite, spinel and metal grains and a thick, surrounding mantle of melilite.

A molecular dynamics study of the atomic structure of (CaO)x(Al2O3)1-x glass with x = 0.625 close to the eutectic

NASA Astrophysics Data System (ADS)

Thomas, B. W. M.; Mead, R. N.; Mountjoy, G.

2006-05-01

Aluminate glasses are difficult to prepare as they do not contain traditional network formers, but they are promising materials for optical applications. The atomic structure of calcium aluminate glasses has been studied using several experimental techniques. The current study uses molecular dynamics to obtain a model of a (CaO)0.625(Al2O3)0.375 glass close to the eutectic. The glass consists of a tetrahedral alumina network with average network polymerization \\langle Q^{n}\\rangle of n = 3.3. Ca acts as a network modifier with average coordination of 6.2. Ca is typically coordinated to three bridging oxygens (Ob) and three non-bridging oxygens (Onb), with Ca-Onb bonds noticeably shorter than the Ca-Ob bonds. A new method of analysing modifier cation coordination is presented, which specifically shows the distribution of Ca coordination NCaO in terms of combinations of NCaOb and NCaOnb. Ob is most often coordinated to two Al plus two Ca, and Onb is most often coordinated to one Al plus three Ca. The typical coordinations of Ca, Ob, and Onb all have a noticeable similarity to those for the 5CaO·3Al2O3 crystal. The Ca-Ca distribution shows a clear similarity to that for (CaO)0.5(SiO2)0.5 glass, and this is attributed to the equal atomic number densities of Ca in these glasses.

Coupled phase and aqueous species equilibrium of the H 2O-CO 2-NaCl-CaCO 3 system from 0 to 250 °C, 1 to 1000 bar with NaCl concentrations up to saturation of halite

NASA Astrophysics Data System (ADS)

Duan, Zhenhao; Li, Dedong

2008-10-01

A model is developed for the calculation of coupled phase and aqueous species equilibrium in the H 2O-CO 2-NaCl-CaCO 3 system from 0 to 250 °C, 1 to 1000 bar with NaCl concentrations up to saturation of halite. The vapor-liquid-solid (calcite, halite) equilibrium together with the chemical equilibrium of H +, Na +, Ca 2+, CaHCO3+, Ca(OH) +, OH -, Cl -, HCO3-, CO32-, CO 2(aq) and CaCO 3(aq) in the aqueous liquid phase as a function of temperature, pressure, NaCl concentrations, CO 2(aq) concentrations can be calculated, with accuracy close to those of experiments in the stated T- P- m range, hence calcite solubility, CO 2 gas solubility, alkalinity and pH values can be accurately calculated. The merit and advantage of this model is its predictability, the model was generally not constructed by fitting experimental data. One of the focuses of this study is to predict calcite solubility, with accuracy consistent with the works in previous experimental studies. The resulted model reproduces the following: (1) as temperature increases, the calcite solubility decreases. For example, when temperature increases from 273 to 373 K, calcite solubility decreases by about 50%; (2) with the increase of pressure, calcite solubility increases. For example, at 373 K changing pressure from 10 to 500 bar may increase calcite solubility by as much as 30%; (3) dissolved CO 2 can increase calcite solubility substantially; (4) increasing concentration of NaCl up to 2 m will increase calcite solubility, but further increasing NaCl solubility beyond 2 m will decrease its solubility. The functionality of pH value, alkalinity, CO 2 gas solubility, and the concentrations of many aqueous species with temperature, pressure and NaCl (aq) concentrations can be found from the application of this model. Online calculation is made available on www.geochem-model.org/models/h2o_co2_nacl_caco3/calc.php.

Rapamycin (sirolimus) protects against hypoxic damage in primary heart cultures via Na+/Ca2+ exchanger activation.

PubMed

El-Ani, Dalia; Stav, Hagit; Guetta, Victor; Arad, Michael; Shainberg, Asher

2011-07-04

Rapamycin (sirolimus) is an antibiotic that inhibits protein synthesis through mammalian targeting of rapamycin (mTOR) signaling, and is used as an immunosuppressant in the treatment of organ rejection in transplant recipients. Rapamycin confers preconditioning-like protection against ischemic-reperfusion injury in isolated mouse heart cultures. Our aim was to further define the role of rapamycin in intracellular Ca(2+) homeostasis and to investigate the mechanism by which rapamycin protects cardiomyocytes from hypoxic damage. We demonstrate here that rapamycin protects rat heart cultures from hypoxic-reoxygenation (H/R) damage, as revealed by assays of lactate dehydrogenase (LDH) and creatine kinase (CK) leakage to the medium, by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) measurements, and desmin immunostaining. As a result of hypoxia, intracellular calcium levels ([Ca(2+)](i)) were elevated. However, treatment of heart cultures with rapamycin during hypoxia attenuated the increase of [Ca(2+)](i). Rapamycin also attenuated (45)Ca(2+) uptake into the sarcoplasmic reticulum (SR) of skinned heart cultures in a dose- and time-dependent manner. KB-R7943, which inhibits the "reverse" mode of Na(+)/Ca(2+) exchanger (NCX), protected heart cultures from H/R damage with or without the addition of rapamycin. Rapamycin decreased [Ca(2+)](i) following its elevation by extracellular Ca(2+) ([Ca(2+)](o)) influx, thapsigargin treatment, or depolarization with KCl. We suggest that rapamycin induces cardioprotection against hypoxic/reoxygenation damage in primary heart cultures by stimulating NCX to extrude Ca(2+) outside the cardiomyocytes. According to our findings, rapamycin preserves Ca(2+) homeostasis and prevents Ca(2+) overload via extrusion of Ca(2+) surplus outside the sarcolemma, thereby protecting the cells from hypoxic stress. Copyright © 2011 Elsevier Inc. All rights reserved.

Effects of X-ray irradiation on the Eu3+ → Eu2+ conversion in CaAl2O4 phosphors

NASA Astrophysics Data System (ADS)

Gomes, Manassés A.; Carvalho, Jéssica C.; Andrade, Adriano B.; Rezende, Marcos V.; Macedo, Zélia S.; Valerio, Mário E. G.

2018-01-01

This paper reports structural and luminescence properties of Eu-doped CaAl2O4 produced by an alternative sol-gel method using coconut water. Results of differential thermal analysis (DTA), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) allowed us to identify the best synthesis conditions for sample preparation. Simultaneous measurements of X-ray absorption spectroscopy (XAS) and X-ray excited optical luminescence (XEOL) were also performed in the X-ray energy range of the Eu LIII edge. Results from photoluminescence (PL) showed only the characteristic Eu3+ emission. However, radioluminescence emission spectra from Eu-doped CaAl2O4 shows a process of conversion of Eu3+ to Eu2+, which is induced by X-ray irradiation and is dependent on the radiation dose energy. X-ray absorption near edge structure (XANES) measurements corroborate Eu reduction due to irradiation, showing that only the Eu3+ ion is present in stable form in the CaAl2O4.

Effects of Partial Substitutions of NaCl with KCl, CaSO4 and MgSO4 on the Quality and Sensorial Properties of Pork Patties.

PubMed

Davaatseren, Munkhtugs; Chun, Ji-Yeon; Cho, Hyung-Yong; Min, Sang-Gi; Choi, Mi-Jung

2014-01-01

This study investigated the effects of NaCl replacers (KCl, CaSO4, and MgSO4) on the quality and sensorial properties of pork patty. In the characteristics of spray-dried salt particles, KCl showed the largest particle size with low viscosity in solution. Meanwhile CaSO4 treatment resulted in the smallest particle size and the highest viscosity (p<0.05). In comparison of the qualities of pork patties manufactured by varying level of Na replacers, MgSO4 treatment exhibited low cooking loss comparing to control (p<0.05). Textural properties of KCl and MgSO4 treatments showed similar pattern, i.e., low level of the replacers caused harder and less adhesive texture than those of control (p<0.05), whereas the hardness of these products was not different with control when the replacers were added more than 1.0%. The addition of CaSO4 also manifested harder and less adhesive than control (p<0.05), but the textural properties of CaSO4 treatment was not affected by level of Ca-salt. Eventually, sensorial properties indicated that KCl and CaSO4 influenced negative effects on pork patties. In contrast, MgSO4 showed better sensorial properties in juiciness intensity, tenderness intensity as well as overall acceptability than control, reflecting that MgSO4 was an effective Na-replacer in meat product formulation.

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.

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

... SECURITIES AND EXCHANGE COMMISSION [Release No. IC-29881; 812-13987] Wells Fargo Bank, N.A., et al... entered against Wells Fargo Bank, N.A. (``Wells Fargo Bank'') on December 9, 2011 by the United States.... Applicants: Wells Fargo Bank, First International Advisors, LLC (``First International''), Metropolitan West...

Characterization of Bacillus subtilis YfkE (ChaA): a calcium-specific Ca2+/H+ antiporter of the CaCA family.

PubMed

Fujisawa, Makoto; Wada, Yuko; Tsuchiya, Takahiro; Ito, Masahiro

2009-08-01

YfkE, a protein from Bacillus subtilis, exhibits homology to the Ca(2+):Cation Antiporter (CaCA) Family. In a fluorescence-based assay of everted membrane vesicles prepared from Na(+)(Ca(2+))/H(+) antiporter-defective mutant Escherichia coli KNabc, YfkE exhibited robust Ca(2+)/H(+) antiport activity, with a K (m) for Ca(2+) estimated at 12.5 muM at pH 8.5 and 113 muM at pH 7.5. Neither Na(+) nor K(+) served as a substrate. Mg(2+) also did not serve as a substrate, but inhibited the Ca(2+)/H(+) antiporter activity. The Ca(2+) transport capability of YfkE was also observed directly by transport assays in everted membrane vesicles using radiolabeled (45)Ca(2+). Transcriptional analysis from the putative yfkED operon using beta-garactosidase activity as a reporter revealed that both of the yfkE and yfkD genes are regulated by forespore-specific sigma factor, SigG, and the general stress response regulator, SigB. These results suggest that YfkE may be needed for Ca(2+) signaling in the sporulation or germination process in B. subtilis. ChaA is proposed as the designation for YfkE of B. subtilis.

Micelle-Assisted Synthesis of Al2O3 ·CaO Nanocatalyst: Optical Properties and Their Applications in Photodegradation of 2,4,6-Trinitrophenol

PubMed Central

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

2013-01-01

Calcium oxide (CaO) nanoparticles are known to exhibit unique property due to their high adsorption capacity and good catalytic activity. In this work the CaO nanocatalysts were prepared by hydrothermal method using anionic surfactant, sodium dodecyl sulphate (SDS), as a templating agent. The as-synthesized nanocatalysts were further used as substrate for the synthesis of alumina doped calcium oxide (Al2O3 ·CaO) nanocatalysts via deposition-precipitation method at the isoelectric point of CaO. The Al2O3 ·CaO nanocatalysts were characterized by FTIR, XRD, TGA, TEM, and FESEM techniques. The catalytic efficiencies of these nanocatalysts were studied for the photodegradation of 2,4,6-trinitrophenol (2,4,6-TNP), which is an industrial pollutant, spectrophotometrically. The effect of surfactant and temperature on size of nanocatalysts was also studied. The smallest particle size and highest percentage of degradation were observed at critical micelle concentration of the surfactant. The direct optical band gap of the Al2O3 ·CaO nanocatalyst was found as 3.3 eV. PMID:24311980

Effects of NaCl and CaCl2 on Water Transport across Root Cells of Maize (Zea mays L.) Seedlings 1

PubMed Central

Azaizeh, Hassan; Gunse, Benito; Steudle, Ernst

1992-01-01

The effect of salinity and calcium levels on water flows and on hydraulic parameters of individual cortical cells of excised roots of young maize (Zea mays L. cv Halamish) plants have been measured using the cell pressure probe. Maize seedlings were grown in one-third strength Hoagland solution modified by additions of NaCl and/or extra calcium so that the seedlings received one of four treatments: control; +100 millimolar NaCl; +10 millimolar CaCl2; +100 millimolar NaCl + 10 millimolar CaCl2. From the hydrostatic and osmotic relaxations of turgor, the hydraulic conductivity (Lp) and the reflection coefficient (σs) of cortical cells of different root layers were determined. Mean Lp values in the different layers (first to third, fourth to sixth, seventh to ninth) of the four different treatments ranged from 11.8 to 14.5 (Control), 2.5 to 3.8 (+NaCl), 6.9 to 8.7 (+CaCl2), and 6.6 to 7.2 · 10−7 meter per second per megapascal (+NaCl + CaCl2). These results indicate that salinization of the growth media at regular calcium levels (0.5 millimolar) decreased Lp significantly (three to six times). The addition of extra calcium (10 millimolar) to the salinized media produced compensating effects. Mean cell σs values of NaCl ranged from 1.08 to 1.16, 1.15 to 1.22, 0.94 to 1.00, and 1.32 to 1.46 in different root cell layers of the four different treatments, respectively. Some of these σs values were probably overestimated due to an underestimation of the elastic modulus of cells, σs values of close to unity were in line with the fact that root cell membranes were practically not permeable to NaCl. However, the root cylinder exhibited some permeability to NaCl as was demonstrated by the root pressure probe measurements that resulted in σsr of less than unity. Compared with the controls, salinity and calcium increased the root cell diameter. Salinized seedlings grown at regular calcium levels resulted in shorter cell length compared with control (by a factor of 2

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.

Ca II and Na I absorption in the QSO S4 0248 + 430 due to an intervening galaxy

NASA Technical Reports Server (NTRS)

Womble, Donna S.; Junkkarinen, Vesa T.; Cohen, Ross D.; Burbidge, E. Margaret

1990-01-01

Observations of the QSO S4 0248 + 430 and a nearby anonymous galaxy are presented. Two absorption components are found in both Ca II H and K and Na I D1 and D2 at z(a) = 0.0515, 0.0523. Column densities of log N(Ca II) = 13.29, 13.50, and log N(Na I) = 13.79, 14.18 are found for z(a) = 0.0515, 0.0523 absorption systems, respectively. The column density ratios imply considerable calcium depletion and disk-type absorbing gas. At least one and possibly both absorption components are produced by high-velocity gas. A broadband image of the field shows an asymmetrical armlike feature or possible tidal tail covering and extending past the position of the QSO. The presence of this extended feature and the apparent difference between the absorption velocities and galaxy rotation velocity suggest that the absorbing gas is not ordinary disk gas, but rather is a result of tidal disruption.

Optical properties of BaO added bioactive Na2O-CaO-P2O5 glasses

NASA Astrophysics Data System (ADS)

Edathazhe, Akhila B.; Shashikala, H. D.

2018-04-01

This paper deals with the effect of BaO addition on the optical properties of bioactive Na2O-CaO-P2O5 glasses for biomedical optics applications. The phosphate glasses with composition (26-x)Na2O-xBaO-29CaO-45P2O5 (x = 0, 5, 10, 15 mol%) have been prepared by melt-quenching technique at 1100°C. The refractive index of glasses increased with BaO content. The optical band gap and Urbach energy of synthesized glasses were derived from the optical absorption spectra by using UV-Visible spectrometer. The addition of 5 mol% of BaO increased the band gap energy of glasses due to the formation of ionic cross-links in the glass structure. The defect and interstitial bonds formation in theglasses decreased with BaO additions as indicated by reductions in the Urbach energy values. No such variations in the band gap and Urbach energy values of glasses were observed with BaO content from 5 to 15 mol%. The molar and oxide ion polarizability values were calculated from the band gap and molar volume of glasses. The increase in the calculated optical basicity and metallization criteria of glasses supported the rise in band gap energy values with BaO additions. As the melting temperature of glasses decreased from 1200 to 1100°C, the refractive index increased as supported by the measured density values. The band gap energy is not changed with melting temperature. The Urbach energy decreased with decrease in melting temperature in case of BaO-free Na2O-CaO-P2O5 glasses, whereas it increased in case of BaO added glasses due to the role of BaO as modifying oxide.

Experimental study on the relationship between the mineral production capability and the physiochemical properties in the coproduction of Q phase-3CaO·3Al2O3·CaSO4 cement clinker.

PubMed

He, Chao; Tian, Chaochao; Li, Gang; Mei, Yahe; Zhang, Quanguo; Jiao, Youzhou

2018-01-01

A coproduction tests of quaternary (Q) phase(6CaO·4Al2O3·MgO·SiO2) -3CaO·3Al2O3·CaSO4 cement clinker and an experimental study on the relationship between the mineral production capability and the physiochemical properties are conducted in a two-stage multiphase reaction test bed with Changguang coal. X-ray diffractometer (XRD) analyses are performed on the coproduction clinker samples. The results demonstrate that, with the reduction in particle sizes of the coal powder and the additives and expanded screening level differences between them, both the proportion of Q phase and the mass of 3CaO·3Al2O3·CaSO4 in the clinker increase accordingly. When mixed coal powder particles are prepared through reducing particle sizes and expanding screening level differences between coal powder and additives, the additives CaO and MgO are more likely to be enclosed by coal powder to form globular polymerized particles. In addition, this preparation aids in polymerization and promotes even distribution of CaO, MgO and coal minerals, thus facilitating clinker mineral formation reactions of inorganic substances in the mixed coal powder. Target minerals, such as 2CaO·SiO2 and Q phase, are found in both industrial high-calcium limestone and low-calcium limestone coproduction clinker samples. A diffraction peak of free CaO is also evident in both samples. Compared with a coproduction clinker sample of high-calcium limestone, that of low-calcium limestone exhibits higher diffraction peaks for 2CaO·SiO2 and Q phase. With the current state of the art, it is not yet the optimum choice to substitute CaCO3 for CaO in Q-phase cement clinker coproduction. Before the technology matures and gains practical application, further study on the form and the mixing process of calcium-based additives for cement clinker coproduction will be required.

Experimental study on the relationship between the mineral production capability and the physiochemical properties in the coproduction of Q phase-3CaO·3Al2O3·CaSO4 cement clinker

PubMed Central

Tian, Chaochao; Li, Gang; Mei, Yahe; Zhang, Quanguo; Jiao, Youzhou

2018-01-01

A coproduction tests of quaternary (Q) phase(6CaO·4Al2O3·MgO·SiO2) -3CaO·3Al2O3·CaSO4 cement clinker and an experimental study on the relationship between the mineral production capability and the physiochemical properties are conducted in a two-stage multiphase reaction test bed with Changguang coal. X-ray diffractometer (XRD) analyses are performed on the coproduction clinker samples. The results demonstrate that, with the reduction in particle sizes of the coal powder and the additives and expanded screening level differences between them, both the proportion of Q phase and the mass of 3CaO·3Al2O3·CaSO4 in the clinker increase accordingly. When mixed coal powder particles are prepared through reducing particle sizes and expanding screening level differences between coal powder and additives, the additives CaO and MgO are more likely to be enclosed by coal powder to form globular polymerized particles. In addition, this preparation aids in polymerization and promotes even distribution of CaO, MgO and coal minerals, thus facilitating clinker mineral formation reactions of inorganic substances in the mixed coal powder. Target minerals, such as 2CaO·SiO2 and Q phase, are found in both industrial high-calcium limestone and low-calcium limestone coproduction clinker samples. A diffraction peak of free CaO is also evident in both samples. Compared with a coproduction clinker sample of high-calcium limestone, that of low-calcium limestone exhibits higher diffraction peaks for 2CaO·SiO2 and Q phase. With the current state of the art, it is not yet the optimum choice to substitute CaCO3 for CaO in Q-phase cement clinker coproduction. Before the technology matures and gains practical application, further study on the form and the mixing process of calcium-based additives for cement clinker coproduction will be required. PMID:29634732

NaAlTi 3O 8, A Novel Anode Material for Sodium Ion Battery

DOE PAGES

Ma, Xuetian; An, Ke; Bai, Jianmin; ...

2017-03-13

Sodium ion batteries are being considered as an alternative to lithium ion batteries in large-scale energy storage applications owing to the low cost. In this paper, a novel titanate compound, NaAlTi 3O 8, 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 andmore » extraction. The influence of synthesis conditions on electrochemical performances was investigated and discussed. Finally, NaAlTi 3O 8 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.« less

Serum concentration of Na, K, Ca, Mg, P, Zn and Cu in patients with essential arterial hypertension.

PubMed

Uza, G; Pavel, O; Kovacs, A; Uza, D; Vlaicu, R

1984-01-01

Serum concentration of Na, K, Ca, Mg and inorganic phosphate as well as serum levels of Zn and Cu were determined in control subjects and in patients with essential arterial hypertension (EAH) divided according to the stage of the disease. No significant differences were found between the serum mean levels of Na, K, Ca, Mg, Zn and Cu in controls and in patients with EAH. A significant decrease of the serum Zn was noted in the third stage of EAH. A number of cases with hypomagnesemia and/or hypopotassemia probably caused by a long term uncontrolled therapy was also detected. The concentration of inorganic phosphate was significantly lower in patients with EAH associated with overweight than in hypertensive patients with normal body weight and in controls. It is considered that a sustained study of the complex interrelationship between electrolyte interaction and the functional aspects of the arterial wall could still contribute to a better understanding of pathogenic aspects of EAH and of its complications including those subsequent to modern diuretic therapy.

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

PubMed

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

2015-02-01

This study aims to investigate the solubility of a series of titanium (TiO2 )-containing bioactive glasses and their subsequent effect on cell viability. Five glasses were synthesized in the composition range SiO2 -Na2 O-CaO with 5 mol % of increments TiO2 substituted for SiO2 . Glass solubility was investigated with respect to (1) exposed surface area, (2) particle size, (3) incubation time, and (4) compositional effects. Ion release profiles showed that sodium (Na(+) ) presented high release rates after 1 day and were unchanged between 7 and 14 days. Calcium (Ca(2+) ) release presented a significant change at each time period and was also composition dependent, where a reduction in Ca(2+) release is observed with an increase in TiO2 concentration. Silica (Si(4+) ) release did not present any clear trends while no titanium (Ti(4+) ) was released. Cell numbers were found to increase up to 44%, compared to the growing control population, with a reduction in particle size and with the inclusion of TiO2 in the glass composition. © 2014 Wiley Periodicals, Inc.

Precursor routes to quaternary intermetallics: Synthesis, crystal structure, and physical properties of clathrate-II Cs8Na16Al24Si112

NASA Astrophysics Data System (ADS)

Wei, Kaya; Dong, Yongkwan; Nolas, George S.

2016-05-01

A new quaternary clathrate-II composition, Cs8Na16Al24Si112, was synthesized by kinetically controlled thermal decomposition (KCTD) employing both NaSi and NaAlSi as the precursors and CsCl as a reactive flux. The crystal structure and composition of Cs8Na16Al24Si112 were investigated using both Rietveld refinement and elemental analysis, and the temperature dependent transport properties were investigated. Our results indicate that KCTD with multiple precursors is an effective method for the synthesis of multinary inorganic phases that are not easily accessible by traditional solid-state synthesis or crystal growth techniques.

Investigation the influences of B2O3 and R2O on the structure and crystallization behaviors of CaO-Al2O3 based F-free mold flux

NASA Astrophysics Data System (ADS)

Li, Jiangling; Kong, Bowen; Gao, Xiangyu; Liu, Qingcai; Shu, Qifeng; Chou, Kuochih

2018-04-01

The influences of B2O3 and R2O on the structure and crystallization of CaO-Al2O3 based F-free mold flux were investigated by Raman Spectroscopy and Differential Scanning Calorimetry Technique, respectively, for developing a new type of F-free mold flux. The results of structural investigations showed that B3+ is mainly in the form of [BO3]. And [BO3] appears to form BIII-O-Al linkage which will produce a positive effect on forming [AlO4] network. The number of bridging oxygen and the degree of polymerization of [AlO4] network structure for CaO-Al2O3 system were also increased with the increasing of B2O3. On the contrary, with the addition of R2O into CaO-Al2O3-B2O3 system, the number of bridging oxygen and the degree of polymerization of [AlO4] network were decreased. DSC results showed that the crystallization process became more sluggish with the increase of B2O3, which indicated that the crystallization ability was weakened. While the quenched mold fluxes crystallized more rapidly when introducing R2O. In other word, the crystallization rates of CaO-Al2O3 based slags were accelerated by the introduction of R2O. The liquidus temperature and crystallization temperature were decreased with the increasing amount of B2O3 or by addition of R2O into CaO-Al2O3 system. Only one kind of crystal was precipitated in 8% B2O3 and %R2O-containing samples, which was CaAl2O4 identified by SEM-EDS. When the content of B2O3 increased from 8% to 16%, Ca3B2O6 is clearly observed, demonstrating that the crystallization ability of Ca3B2O6 is enhanced by the increasing concentration of B2O3 in mold flux. The Ca/Al ratio of the generated calcium aluminate has been altered from 1:2 to 1:4 with the increasing of B2O3. The size of CaAl2O4 crystal is gradually increased with the addition of R2O. The crystallization ability of CaAl2O4 is promoted by R2O.

AAuAl (A = Ca, Sc, and Ti): Peierls Distortion, Atomic Coloring, and Structural Competition

DOE PAGES

Pham, Joyce; Miller, Gordon J.

2018-04-02

Using density functional theory, the crystal structure variation of AAuAl (A = Ca, Sc, and Ti) from orthorhombic Co 2Si-type to distorted hexagonal Fe 2P-type and then Ni 2In-type structures is shown to correlate with their electronic structures and valence electron counts, sizes of the active metals A, and site preferences for Au and Al atoms, which are arranged to maximize Au–Al nearest neighbor contacts. An evaluation of chemical pressure imposed by the varying A metals using total energy vs volume calculations indicates that larger unit cell volumes favor the orthorhombic structure, whereas smaller volumes favor the hexagonal structures. Themore » electronic origin of the Mg 2Ga-type crystal structure of ScAuAl, refined as a distorted Fe 2P-type supercell doubled along the c-axis, indicates a Peierls-type distortion mechanism of the Au chains along the c-axis.« less

AAuAl (A = Ca, Sc, and Ti): Peierls Distortion, Atomic Coloring, and Structural Competition

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

Pham, Joyce; Miller, Gordon J.

Using density functional theory, the crystal structure variation of AAuAl (A = Ca, Sc, and Ti) from orthorhombic Co 2Si-type to distorted hexagonal Fe 2P-type and then Ni 2In-type structures is shown to correlate with their electronic structures and valence electron counts, sizes of the active metals A, and site preferences for Au and Al atoms, which are arranged to maximize Au–Al nearest neighbor contacts. An evaluation of chemical pressure imposed by the varying A metals using total energy vs volume calculations indicates that larger unit cell volumes favor the orthorhombic structure, whereas smaller volumes favor the hexagonal structures. Themore » electronic origin of the Mg 2Ga-type crystal structure of ScAuAl, refined as a distorted Fe 2P-type supercell doubled along the c-axis, indicates a Peierls-type distortion mechanism of the Au chains along the c-axis.« less

Inhibiting mitochondrial Na+/Ca2+ exchange prevents sudden death in a Guinea pig model of heart failure.

PubMed

Liu, Ting; Takimoto, Eiki; Dimaano, Veronica L; DeMazumder, Deeptankar; Kettlewell, Sarah; Smith, Godfrey; Sidor, Agnieszka; Abraham, Theodore P; O'Rourke, Brian

2014-06-20

In cardiomyocytes from failing hearts, insufficient mitochondrial Ca(2+) accumulation secondary to cytoplasmic Na(+) overload decreases NAD(P)H/NAD(P)(+) redox potential and increases oxidative stress when workload increases. These effects are abolished by enhancing mitochondrial Ca(2+) with acute treatment with CGP-37157 (CGP), an inhibitor of the mitochondrial Na(+)/Ca(2+) exchanger. Our aim was to determine whether chronic CGP treatment mitigates contractile dysfunction and arrhythmias in an animal model of heart failure (HF) and sudden cardiac death (SCD). Here, we describe a novel guinea pig HF/SCD model using aortic constriction combined with daily β-adrenergic receptor stimulation (ACi) and show that chronic CGP treatment (ACi plus CGP) attenuates cardiac hypertrophic remodeling, pulmonary edema, and interstitial fibrosis and prevents cardiac dysfunction and SCD. In the ACi group 4 weeks after pressure overload, fractional shortening and the rate of left ventricular pressure development decreased by 36% and 32%, respectively, compared with sham-operated controls; in contrast, cardiac function was completely preserved in the ACi plus CGP group. CGP treatment also significantly reduced the incidence of premature ventricular beats and prevented fatal episodes of ventricular fibrillation, but did not prevent QT prolongation. Without CGP treatment, mortality was 61% in the ACi group <4 weeks of aortic constriction, whereas the death rate in the ACi plus CGP group was not different from sham-operated animals. The findings demonstrate the critical role played by altered mitochondrial Ca(2+) dynamics in the development of HF and HF-associated SCD; moreover, they reveal a novel strategy for treating SCD and cardiac decompensation in HF. © 2014 American Heart Association, Inc.

Combined modification by LiAl11O17 and NaAl11O17 to enhance the electrochemical performance of Li4Ti5O12

NASA Astrophysics Data System (ADS)

Zhang, Bo; Han, Jian-Ping; Wang, Li-Ying; Lun, Ning; Zhu, Hui-Ling; Yin, Long-Wei; Li, Hui; Qi, Yong-Xin; Bai, Yu-Jun

2018-07-01

The intrinsically moderate Li-ion diffusion coefficient and poor electronic conductivity of Li4Ti5O12 (LTO) restricts the practical application in Li-ion batteries. In view of the rapid two-dimensional diffusion channels in ionic conductor of LiNaAl22O34 for Li-ions, the LTO modified by combining equivalent molar ratio of LiAl11O17 with NaAl11O17 (LNAO) was fabricated by a simple reaction between LiNO3, Na2CO3, Al(NO3)3ṡ9H2O and LTO at various sintering temperatures. The product with a LNAO/LTO mass ratio of 0.0106 and calcined at 600 °C achieved reversible capacities of 163.8, 160.6, 156.5, 150.9, 132.9 and 163.4 mAh g-1 at the current rates of 100, 200, 400, 800, 1600 and 100 mA g-1, respectively. Even cycled 800 times at 500 mA g-1, a capacity of 147.9 mAh g-1 was retained. The outstanding cycling and rate performance is attributable to the simultaneously formed LNAO coating on the LTO particles and superficial Al3+ doping in the LTO, achieving combined improvement in the ionic and electronic conductivities of LTO and thus boosting the comprehensive electrochemical performance of LTO.

Na(+)/Ca(2+) exchanger inhibition exerts a positive inotropic effect in the rat heart, but fails to influence the contractility of the rabbit heart.

PubMed

Farkas, A S; Acsai, K; Nagy, N; Tóth, A; Fülöp, F; Seprényi, G; Birinyi, P; Nánási, P P; Forster, T; Csanády, M; Papp, J G; Varró, A; Farkas, A

2008-05-01

The Na(+)/Ca(2+) exchanger (NCX) may play a key role in myocardial contractility. The operation of the NCX is affected by the action potential (AP) configuration and the intracellular Na(+) concentration. This study examined the effect of selective NCX inhibition by 0.1, 0.3 and 1.0 microM SEA0400 on the myocardial contractility in the setting of different AP configurations and different intracellular Na(+) concentrations in rabbit and rat hearts. The concentration-dependent effects of SEA0400 on I(Na/Ca) were studied in rat and rabbit ventricular cardiomyocytes using a patch clamp technique. Starling curves were constructed for isolated, Langendorff-perfused rat and rabbit hearts. The cardiac sarcolemmal NCX protein densities of both species were compared by immunohistochemistry. SEA0400 inhibited I(Na/Ca) with similar efficacy in the two species; there was no difference between the inhibitions of the forward or reverse mode of the NCX in either species. SEA0400 increased the systolic and the developed pressure in the rat heart in a concentration-dependent manner, for example, 1.0 microM SEA0400 increased the maximum systolic pressures by 12% relative to the control, whereas it failed to alter the contractility in the rabbit heart. No interspecies difference was found in the cardiac sarcolemmal NCX protein densities. NCX inhibition exerted a positive inotropic effect in the rat heart, but it did not influence the contractility of the rabbit heart. This implies that the AP configuration and the intracellular Na(+) concentration may play an important role in the contractility response to NCX inhibition.

GPR55 agonist lysophosphatidylinositol and lysophosphatidylcholine inhibit endothelial cell hyperpolarization via GPR-independent suppression of Na+-Ca2+ exchanger and endoplasmic reticulum Ca2+ refilling.

PubMed

Bondarenko, Alexander I; Montecucco, Fabrizio; Panasiuk, Olga; Sagach, Vadim; Sidoryak, Nataliya; Brandt, Karim J; Mach, François

2017-02-01

Lysophosphatidylinositol (LPI) and lysophosphatidylcholine (LPC) are lipid signaling molecules that induce endothelium-dependent vasodilation. In addition, LPC suppresses acetylcholine (Ach)-induced responses. We aimed to determine the influence of LPC and LPI on hyperpolarizing responses in vitro and in situ endothelial cells (EC) and identify the underlying mechanisms. Using patch-clamp method, we show that LPI and LPC inhibit EC hyperpolarization to histamine and suppress Na + /Ca 2+ exchanged (NCX) currents in a concentration-dependent manner. The inhibition is non-mode-specific and unaffected by intracellular GDPβS infusion and tempol, a superoxide dismutase mimetic. In excised mouse aorta, LPI strongly inhibits the sustained and the peak endothelial hyperpolarization induced by Ach, but not by SKA-31, an opener of Ca 2+ -dependent K + channels of intermediate and small conductance. The hyperpolarizing responses to consecutive histamine applications are strongly reduced by NCX inhibition. In a Ca 2+ -re-addition protocol, bepridil, a NCX inhibitor, and KB-R7943, a blocker of reversed NCX, inhibit the hyperpolarizing responses to Ca 2+ -re-addition following Ca 2+ stores depletion. These finding indicate that LPC and LPI inhibit endothelial hyperpolarization to Ach and histamine independently of G-protein coupled receptors and superoxide anions. Reversed NCX is critical for ER Ca 2+ refilling in EC. The inhibition of NCX by LPI and LPC underlies diminished endothelium-dependent responses and endothelial dysfunction accompanied by increased levels of these lipids in the blood. Copyright © 2017 Elsevier Inc. All rights reserved.

Multishelled CaO Microspheres Stabilized by Atomic Layer Deposition of Al2 O3 for Enhanced CO2 Capture Performance.

PubMed

Armutlulu, Andac; Naeem, Muhammad Awais; Liu, Hsueh-Ju; Kim, Sung Min; Kierzkowska, Agnieszka; Fedorov, Alexey; Müller, Christoph R

2017-11-01

CO 2 capture and storage is a promising concept to reduce anthropogenic CO 2 emissions. The most established technology for capturing CO 2 relies on amine scrubbing that is, however, associated with high costs. Technoeconomic studies show that using CaO as a high-temperature CO 2 sorbent can significantly reduce the costs of CO 2 capture. A serious disadvantage of CaO derived from earth-abundant precursors, e.g., limestone, is the rapid, sintering-induced decay of its cyclic CO 2 uptake. Here, a template-assisted hydrothermal approach to develop CaO-based sorbents exhibiting a very high and cyclically stable CO 2 uptake is exploited. The morphological characteristics of these sorbents, i.e., a porous shell comprised of CaO nanoparticles coated by a thin layer of Al 2 O 3 (<3 nm) containing a central void, ensure (i) minimal diffusion limitations, (ii) space to accompany the substantial volumetric changes during CO 2 capture and release, and (iii) a minimal quantity of Al 2 O 3 for structural stabilization, thus maximizing the fraction of CO 2 -capture-active CaO. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Investigation of properties of the Ca2+ influx and of the Ca2+-activated K+ efflux (Gárdos effect) in vanadate-treated and ATP-depleted human red blood cells.

PubMed

Kaiserová, K; Lakatos, B; Peterajová, E; Orlický, J; Varecka, L'

2002-12-01

In this study the properties of the 45Ca2+ influx in human red blood cells (RBC) induced by NaVO3 or ATP-depletion were compared. Both NaVO3-induced and ATP-depletion-induced 45Ca2+ influxes were in the range 10(-6)-10(-5) mol Ca2+ x l(-1)cells x h(-1). The saturatability of ATP-depletion-induced 45Ca2+ influx with Ca2+ was much less pronounced than that of NaVO3-induced 45Ca2+ influx. The NaVO3-induced Ca2+ influx was sensitive to nifedipine (IC50 = 50 micromol/l) and Cu2+ (IC50 = 9 micromol/l) but these inhibitors had only a marginal effect when ATP-depletion was used as the Ca2+ influx inducer. On the other hand, polymyxin B (PXB) (1-5 mg/ml) strongly stimulated the ATP-depletion-induced 45Ca2+ influx whereas its effect on the NaVO3-induced Ca2+ influx was biphasic, with about 10% stimulation at lower PXB concentrations and an inhibition of 40% at higher concentrations. SDS-PAGE revealed that both NaVO3 and PXB induced changes in the protein phosphorylation pattern in the presence of Ca2+. NaVO3 stimulated the phosphorylation of several proteins and this effect was counteracted by PXB. The comparison of the kinetics and temperature dependencies of the Gárdos effect induced by NaVO3 and the ATP-depletion showed marked differences. The ability of NaVO3 to induce the Gárdos effect dramatically increased in ATP-depleted cells. These findings indicate that the 45Ca2+ influxes preceding the activation of the Ca2+-activated K+ efflux (Gárdos effect) stimulated by NaVO3 and by ATP-depletion, are mediated by different transport pathways. In addition, obtained results demonstrate that ATP-depletion and NaVO3-treatment exert additive action in triggering the Gárdos effect.

Wetting of Sn-Zn-Ga and Sn-Zn-Na Alloys on Al and Ni Substrate

NASA Astrophysics Data System (ADS)

Gancarz, Tomasz; Bobrowski, Piotr; Pawlak, Sylwia; Schell, Norbert; Chulist, Robert; Janik, Katarzyna

2018-01-01

Wetting of Al and Ni substrate by Sn-Zn eutectic-based alloys with 0.5 (wt.%) of Ga and 0.2 (wt.%) of Na was studied using the sessile drop method in the presence of ALU33® flux. Spreading tests were performed for 60 s, 180 s, and 480 s of contact, at temperatures of 503 K, 523 K and 553 K (230°C, 250°C, and 280°C). After cleaning the flux residue from solidified samples, the spreading areas of Sn-Zn0.5Ga and Sn-Zn0.2Na on Al and Ni substrate were determined. Selected, solidified solder-pad couples were cross-sectioned and subjected to scanning electron microscopy with energy dispersive spectroscopy, x-ray diffraction study and synchrotron measurements of the interfacial microstructure and identification of the phases. The growth of the intermetallic Ni5Zn21 phase layer was studied at the solder/Ni substrate interface, and the kinetics of the formation and growth of the intermetallic layer were determined. The formation of interlayers was not observed on the Al pads. On the contrary, dissolution of the Al substrate and migration of Al-rich particles into the bulk of the solder were observed.

The Partial Molar Volume and Compressibility of the FeO Component in Model Basalts (Mixed CaAl2Si2O8-CaMgSi2O6-CaFeSi2O6 Liquids) at 0 GPa: evidence of Fe2+ in 6-fold coordination

NASA Astrophysics Data System (ADS)

Guo, X.; Lange, R. A.; Ai, Y.

2010-12-01

FeO is an important component in magmatic liquids and yet its partial molar volume at one bar is not as well known as that for Fe2O3 because of the difficulty of performing double-bob density measurements under reducing conditions. Moreover, there is growing evidence from spectroscopic studies that Fe2+ occurs in 4, 5, and 6-fold coordination in silicate melts, and it is expected that the partial molar volume and compressibility of the FeO component will vary accordingly. We have conducted both density and relaxed sound speed measurements on four liquids in the An-Di-Hd (CaAl2Si2O8-CaMgSi2O6-CaFeSi2O6) system: (1) Di-Hd (50:50), (2) An-Hd (50:50), (3) An-Di-Hd (33:33:33) and (4) Hd (100). Densities were measured between 1573 and 1838 K at one bar with the double-bob Archimedean method using molybdenum bobs and crucibles in a reducing gas (1%CO-99%Ar) environment. The sound speeds were measured under similar conditions with a frequency-sweep acoustic interferometer, and used to calculate isothermal compressibility. All the density data for the three multi-component (model basalt) liquids were combined with density data on SiO2-Al2O3-CaO-MgO-K2O-Na2O liquids (Lange, 1997) in a fit to a linear volume equation; the results lead to a partial molar volume (±1σ) for FeO =11.7 ± 0.3(±1σ) cm3/mol at 1723 K. This value is similar to that for crystalline FeO at 298 K (halite structure; 12.06 cm3/mol), which suggests an average Fe2+ coordination of ~6 in these model basalt compositions. In contrast, the fitted partial molar volume of FeO in pure hedenbergite liquid is 14.6 ± 0.3 at 1723 K, which is consistent with an average Fe2+ coordination of 4.3 derived from EXAFS spectroscopy (Rossano, 2000). Similarly, all the compressibility data for the three multi-component liquids were combined with compressibility data on SiO2-Al2O3-CaO-MgO liquids (Ai and Lange, 2008) in a fit to an ideal mixing model for melt compressibility; the results lead to a partial molar

Microwave dielectric properties of CaCu{sub 3}Ti{sub 4}O{sub 12}-Al{sub 2}O{sub 3} composite

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

Rahman, Mohd Fariz Ab; Abu, Mohamad Johari; Zaman, Rosyaini Afindi

2016-07-19

(1-x)CaCu{sub 3}Ti{sub 4}O{sub 12} + (x)Al{sub 2}O{sub 3} composite (0 ≤ x ≤0.25) was prepared via conventional solid-state reaction method. The fabrication of sample was started with synthesizing stoichiometric CCTO from CaCO{sub 3}, CuO and TiO{sub 2} powders, then wet-mixed in deionized water for 24 h. The process was continued with calcined CCTO powder at 900 °C for 12 h before sintered at 1040 °C for 10 h. Next, the calcined CCTO powder with different amount of Al{sub 2}O{sub 3} were mixed for 24 h, then palletized and sintered at 1040 °C for 10. X-ray diffraction analysis on the sinteredmore » samples showed that CCTO powder was in a single phase, meanwhile the trace of secondary peaks which belong to CaAl{sub 2}O{sub 4} and Corundum (Al{sub 2}O{sub 3}) could be observed in the other samples Scanning electron microscopy analysis showed that the grain size of the sample is firstly increased with addition of Al{sub 2}O{sub 3} (x = 0.01), then become smaller with the x > 0.01. Microwave dielectric properties showed that the addition of Al{sub 2}O{sub 3} (x = 0.01) was remarkably reduced the dielectric loss while slightly increased the dielectric permittivity. However, further addition of Al{sub 2}O{sub 3} was reduced both dielectric loss and permittivity at least for an order of magnitude.« less

Photoelectron velocity-map imaging and theoretical studies of heteronuclear metal carbonyls MNi(CO){sub 3}{sup −} (M = Mg, Ca, Al)

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

Xie, Hua, E-mail: ljiang@dicp.ac.cn, E-mail: xiehua@dicp.ac.cn, E-mail: zctang@dicp.ac.cn; Zou, Jinghan; Yuan, Qinqin

2016-03-28

The heteronuclear metal carbonyl anions MNi(CO){sub 3}{sup −} (M = Mg, Ca, Al) have been investigated using photoelectron velocity-map imaging spectroscopy. Electron affinities of neutral MNi(CO){sub 3} (M = Mg, Ca, Al) are measured from the photoelectron spectra to be 1.064 ± 0.063, 1.050 ± 0.064, and 1.541 ± 0.040 eV, respectively. The C–O stretching mode in these three clusters is observed and the vibrational frequency is determined to be 2049, 2000, and 2041 cm{sup −1} for MgNi(CO){sub 3}, CaNi(CO){sub 3}, and AlNi(CO){sub 3}, respectively. Density functional theory calculations are carried out to elucidate the geometric and electronic structures and to aid the experimental assignments. Itmore » has been found that three terminal carbonyls are preferentially bonded to the nickel atom in these heterobinuclear nickel carbonyls MNi(CO){sub 3}{sup −1/0}, resulting in the formation of the Ni(CO){sub 3} motif. Ni remains the 18-electron configuration for MgNi(CO){sub 3} and CaNi(CO){sub 3} neutrals, but not for AlNi(CO){sub 3}. This is different from the homobinuclear nickel carbonyl Ni–Ni(CO){sub 3} with the involvement of three bridging ligands. Present findings would be helpful for understanding CO adsorption on alloy surfaces.« less

Model study of ATP and ADP buffering, transport of Ca(2+) and Mg(2+), and regulation of ion pumps in ventricular myocyte

NASA Technical Reports Server (NTRS)

Michailova, A.; McCulloch, A.

2001-01-01

We extended the model of the ventricular myocyte by Winslow et al. (Circ. Res 1999, 84:571-586) by incorporating equations for Ca(2+) and Mg(2+) buffering and transport by ATP and ADP and equations for MgATP regulation of ion transporters (Na(+)-K(+) pump, sarcolemmal and sarcoplasmic Ca(2+) pumps). The results indicate that, under normal conditions, Ca(2+) binding by low-affinity ATP and diffusion of CaATP may affect the amplitude and time course of intracellular Ca(2+) signals. The model also suggests that a fall in ATP/ADP ratio significantly reduces sarcoplasmic Ca(2+) content, increases diastolic Ca(2+), lowers systolic Ca(2+), increases Ca(2+) influx through L-type channels, and decreases the efficiency of the Na(+)/Ca(2+) exchanger in extruding Ca(2+) during periodic voltage-clamp stimulation. The analysis suggests that the most important reason for these changes during metabolic inhibition is the down-regulation of the sarcoplasmic Ca(2+)-ATPase pump by reduced diastolic MgATP levels. High Ca(2+) concentrations developed near the membrane might have a greater influence on Mg(2+), ATP, and ADP concentrations than that of the lower Ca(2+) concentrations in the bulk myoplasm. The model predictions are in general agreement with experimental observations measured under normal and pathological conditions.