Properties Of Na Research Articles

Photoluminescent Properties of Na<sup>+</sup>, Bi<sup>3+</sup> Co-Doped CaWO<sub>4</sub>: Eu<sup>3+</sup> Phosphor for PDPs

The photoluminescent properties of Na, Bi co-doped CaWO4:Eu3+ phosphor under vacuum ultraviolet (VUV) region excited was investigated. A red emission of CaWO4:Eu3+ can be observed under 147 nm excitation. It was also found that the photoluminescence intensity of Na doped CaWO4:Eu3+ would be enhanced than the un-doped phosphors due to Na+ ions would act as a charge compensator and it can restrict the generation of defects in CaWO4:Eu3+. Additionally, the photoluminescence enhancement of Na+, Bi3+ co-doped CaWO4:Eu3+ should due to the energy transfer between WO42-, Bi3+ and Eu3+, and Bi3+ ions would act as a medium for the energy transfer, via WO42-Bi3+Eu3+. These are expected to be applying in plasma display panels.

Magnetic Structure and Properties of the Na2CoP2O7 Pyrophosphate Cathode for Sodium-Ion Batteries: A Supersuperexchange-Driven Non-Collinear Antiferromagnet

The crystal and magnetic structure and properties of the Na(2)CoP(2)O(7) Na(+)-ion battery cathode material have been characterized by magnetic susceptibility, specific heat, and variable-temperature neutron powder diffraction measurements. Na(2)CoP(2)O(7) crystallizes in the orthorhombic space group Pna2(1) with a = 15.4061(3) Å, b = 10.28854(9) Å, and c = 7.70316(15) Å, having a layered structure with slabs of [CoP(2)O(7)](∞) separated by Na cations. The magnetic property measurements and neutron diffraction data analysis reveal that the material undergoes long-range ordering to a noncollinear antiferromagnetic G-type structure below T(N) ≈ 6.5 K. The magnetic structure is rationalized as a result of supersuperexchange between Co(2+) atoms linked by phosphate groups.

Phase separation in Na–K liquid alloy

The quasi-chemical expression for weakly interacting binary alloy has been applied to obtain energy parameters and their temperature derivatives for Na–K liquid alloy at 384 K. These energy parameters have then been used to calculate thermodynamic functions, such as free energy of mixing, heat of mixing, entropy of mixing and microscopic functions, such as concentration fluctuation in long wavelength limit, Warren–Cowley short-range order parameter, ratio of mutual and self-diffusion coefficients. The analysis reveals that the energy parameters are temperature dependent and the Na–K liquid alloy at 384 K is a weakly interacting homocoordination system. The observed thermodynamic properties of Na–K alloy in molten state have successfully been explained by assuming Na2K complex on the basis of the quasi-chemical formalism for a weakly interacting system.

Properties of Na+ currents conducted by a skeletal muscle L-type Ca2+ channel pore mutant (SkEIIIK)

Four glutamate residues residing at corresponding positions within the four conserved membrane-spanning repeats of L-type Ca2+ channels are important structural determinants for the passage of Ca2+ across the selectivity filter. Mutation of the critical glutamate in Repeat III in the a1S subunit of the skeletal L-type channel (Cav1.1) to lysine virtually eliminates passage of Ca2+ during step depolarizations. In this study, we examined the ability of this mutant Cav1.1 channel (SkEIIIK) to conduct inward Na+ current. When 150 mM Na+ was present as the sole monovalent cation in the bath solution, dysgenic (Cav1.1 null) myotubes expressing SkEIIIK displayed slowly-activating, non-inactivating, nifedipine-sensitive inward currents with a reversal potential (45.6 ± 2.5 mV) near that expected for Na+. Ca2+ block of SkEIIIK-mediated Na+ current was revealed by the substantial enhancement of Na+ current amplitude after reduction of Ca2+ in the external recording solution from 10 mM to near physiological 1 mM. Inward SkEIIIK-mediated currents were potentiated by either ±Bay K 8644 (10 mM) or 200-ms depolarizing prepulses to +90 mV. In contrast, outward monovalent currents were reduced by ±Bay K 8644 and were unaffected by strong depolarization, indicating a preferential potentiation of inward Na+ currents through the mutant Cav1.1 channel. Taken together, our results show that SkEIIIK functions as a non-inactivating, junctionally-targeted Na+ channel when Na+ is the sole monvalent cation present and urge caution when interpreting the impact of mutations designed to ablate Ca2+ permeability mediated by CaV channels on physiological processes that extend beyond channel gating and permeability.

Influence of BaTiO3 Content on the Structure and Properties of Na0.5Bi0.5TiO3 Crystals

Lead‐free Na0.5Bi0.5TiO3–x%BaTiO3 single crystals of different compositions (x=0, 2, 4, 4.5 and 5.5) were grown using a top‐seeded solution growth method. Temperature‐dependent X‐ray diffraction revealed the presence of a high‐temperature tetragonal phase that existed over a narrow composition range of 0<x<2, at temperatures far in excess of the ferroelectric Curie temperature Tc. Polarized light microscopy images confirmed the presence of tetragonal domains in NBT that persisted until Tc+250°C; whereas for x>4, rhombohedral domains were found that persisted on heating to only about Tc‐150°C. Investigations of the properties revealed a dramatic increase in the dielectric constant (upto 500%), a decrease in the coercive field (300%), and an increase in the longitudinal piezoelectric constant (1000%) with modest increases in x, as the high‐temperature tetragonal ferroelastic phase was suppressed and as the morphotropic‐phase boundary approached.

ゾル-ゲル法により合成したNa2xMg1-xTi4 (PO4) 6の焼結と性質

ゾル-ゲル法により合成したNa2xMg1-xTi4 (PO4) 6の焼結と性質

The Na+ pump and intracellular signaling mechanisms

The main properties of Na+ /K(+)-ATPase as a natural receptor for cardiotonic steroids have been discusses. Primary attention is focused on structural and functional differences between the alpha-subunit isoforms of Na+/K(+)-ATPase in different tissues. General information on the role of the Na pump in signaling cascades in kidney epithelial cells, cardiomyocytes and neurons is presented. The data obtained indicate that, in neurons, several alpha-isoforms of Na+/K(+)-ATPase possessing different sensitivity to ouabain may have different signaling functions.

Thermodynamic and kinetic properties of Na+-motive NADH: Quinone oxidoreductase

Thermodynamic and kinetic properties of Na+-motive NADH: Quinone oxidoreductase

PROCESSING AND PROPERTIES OF Na0.5Bi0.5TiO3 PIEZOELECTRIC CERAMICS MODIFIED WITH La, Mn AND Fe

Although a great deal of work has been done to understand defect chemistry in "soft" and "hard" PZT-based materials, there is little understanding of how defect chemistry influences the properties of lead-free piezoelectric materials. This paper reports a systematic investigation of doping on the ferroelectric and piezoelectric properties in Na 0.5 Bi 0.5 TiO 3 (NBT)-based ceramics. NBT-based ceramics have been synthesized by traditional solid state routes using several different dopants including lanthanum, manganese, and iron in 1 mol%. The addition of iron and manganese lead to an increase in the coercive field (E c ), a decrease in the piezoelectric coefficient (d33), and an increase in the thermal depoling temperature (T depole ), similar to the behavior of "hard" PZT. Lanthanum, on the other hand, leads to a decrease in the E c , an increase in d33, and a decrease in T depole similar to that seen in "soft" PZT.

Energy-efficient action potentials in hippocampal mossy fibers

Action potentials in nonmyelinated axons are considered to contribute substantially to activity-dependent brain metabolism. Here we show that fast Na + current decay and delayed K + current onset during action potentials in nonmyelinated mossy fibers of the rat hippocampus minimize the overlap of their respective ion fluxes. This results in total Na + influx and associated energy demand per action potential of only 1.3 times the theoretical minimum, in contrast to the factor of 4 used in previous energy budget calculations for neural activity. Analysis of ionic conductance parameters revealed that the properties of Na + and K + channels are matched to make axonal action potentials energy-efficient, minimizing their contribution to activity-dependent metabolism.

Features of structure and properties of Na n C60 (n = 2, 3) fullerides synthesized in toluene

The structure and electron properties of NanC60 (n = 2, 3) sodium fullerides synthesized from simple compounds in toluene were studied. It was shown that Na2C60 fulleride forms a face-centered cubic lattice at temperatures above 300 K. As the temperature is lowered, the phase transition to a structure with a simple cubic lattice takes place. The temperature dependences of the properties of Na3C60 with a more complex structure exhibit features that are presumably due to sodium atom redistribution in the Na3C60 fulleride lattice and the formation of sodium ion clusters.

Synthesis, Crystal Structure and Properties of Na2MnO2

AbstractNa2MnO2 was prepared via the azide/nitrate route. Stoichiometric mixtures of the precursors (Mn2O3, NaN3 and NaNO3) were heated in an appropriate regime up to 390 °C and annealed at this temperature for 20 h, in specially designed silver containers. As the most prominent feature, the crystal structure of Na2MnO2 (C2/c, Z = 12, a = 12.5026(9), b = 12.1006(9), c = 6.0939(4) Å, β = 117.94(0)°, 1556 independent reflections, R1 = 3.83 % (all data)) forms a three dimensional framework polyanion of corner sharing MnO4‐tetrahedra. The connectivity pattern of the tetrahedral building units corresponds to the moganite structure, a rare SiO2 modification. According to measurements of the magnetic susceptibility in the temperature range from 2 to 750 K, Na2MnO2 shows antiferromagnetic ordering below 250 K. Evaluation of the high temperature data employing the Curie‐Weiss law revealed a magnetic moment of μeff = 5.93 μB, confirming the presence of divalent manganese.

Metal–insulator transition in

Abstract Powder Na 0.75 Co 1 - x Ru x O 2 ( 0 ⩽ x ⩽ 0.5 ) samples were synthesized and characterized by X-ray diffraction analysis. The measurements of their resistivity and susceptibility were carried out. A metal–insulator transition was found with increasing Ru content in Na 0.75 Co 1 - x Ru x O 2 samples. It is suggested that the partial substitution of Ru for Co ions results in the Anderson localization of electrons in CoO 2 layers. Unlike Na 0.75 CoO 2 sample, in Na 0.75 Co 1 - x Ru x O 2 ( x = 0.02 ) sample, the disappearance of a magnetic transition near T c = 22 K , which is caused by spin density wave formation, also indicates that a small amount Ru substitution may result in the disorder in CoO 2 layers. The substitution effect of Ru on transport and magnetic properties in Na 0.75 Co 1 - x Ru x O 2 system is discussed.

Dynamic properties of confined hydration layers

Prompted by the recent discovery that water and aqueous monovalent Na+ solutions remain fluid-like when confined to films of a few molecular layers between mica surfaces,[Raviv et al., Nature, 2001, 413, 51-54; and Raviv and Klein, Science, 2002, 297, 1540-1543] we now extend the previous study by comparing the shear- and normal-force properties of 0.1 M Na+, Cs+ and Ni2+ salt solutions which demonstrate a diverse range of behaviours under confinement. In the case of hydrated Na+ we extend the previous study to higher pressures, up to approximately 10 atmospheres, and record similar fluidity of the hydration layers at these elevated pressures. Aqueous Cs+ films under confinement between mica sheets have been found to be unable to support an applied load--that is to say they do not demonstrate any hydration repulsion regime--as a result of their lower hydration energy [see Goldberg et al., Phys. Chem. Chem. Phys., 2008, 10, 4939-4945] which contrasts with the properties of Na+. We show that 0.1 M Ni2+ solution remains close to its bulk viscosity down to nanometre thin films, but does not demonstrate a hydration repulsion. By comparing the properties of this range of cations, with differing valency and hydration, we aim to examine the conditions under which ions serve as effective lubricants and what we call the 'hydration lubrication' mechanism.

Microwave dielectric properties of NaxNd(2-x)/3TiO3 solid solutions

Na(x)Nd((2-x)/3)TiO(3) solid solutions possess tetragonal or orthorhombic perovskite structure, where the A-sites are characterized by 2 kinds of cations (Na(+), Nd(3+)) and vacancies. We have measured microwave dielectric properties of Na(x)Nd((2-x)/3)TiO(3) solid solutions (x = 0.05 to 0.5) to investigate an effect of the compositional ordering in the A-sites of the perovskite structure. According to powder x-ray diffraction, the A-site is disordered in the composition range of x = 0.29 to 0.5. A compositional ordering (Na(+), vacancy / Nd(3+)) in A-sites appeared when x = 0.05 to 0.2. The quality factor (Q x f), where Q is the inverse of dielectric loss and f is frequency, was found to be slightly improved with decreasing Na content in the range of x = 0.05 to 0.2, suggesting that the Q x f of the Na(x)Nd((2-x)/3)TiO(3) solid solutions depends on the compositional ordering in A-sites.

Thyroid Hormone-Induced Alterations in Membrane Structure-Function Relationships: Studies on Kinetic Properties of Rat Kidney Microsomal Na+,K+-ATPase and Lipid/Phospholipid Profiles

The effects of thyroidectomy (Tx) and subsequent treatment with 3,5,3'-triiodothyronine (T(3)) or combined replacement therapy (T(R)) with T(3 )and thyroxine (T(4)) on the substrate and temperature kinetics properties of Na+,K+-ATPase and lipid/phospholipid makeup of rat kidney microsomes were examined. Enzyme activity was somewhat high in the hypothyroid (Tx) animals and increased significantly following T(3) treatment, while T(R) treatment caused a decrease. In the Tx and T(3) groups enzyme activity resolved in two kinetic components, while in the T(R) group the enzyme showed allosteric behavior up to 0.5 mM: ATP concentration. The K(m) and V(max) values of both the components decreased in Tx animals without affecting the catalytic efficiency. T(3) treatment caused a significant increase in the V(max) of both the components, with a significant increase in the catalytic efficiency, while the K(m) values were not upregulated. The T(R) regimen lowered the K(m) and V(max) of component II but improved the catalytic efficiency. Thyroid status-dependent changes were also noted in the temperature kinetics of the enzyme. Regression analysis revealed that changes in the substrate and temperature kinetics parameters correlated with specific phospholipid components.

Plasma‐Assisted Synthesis and Properties of Na3N.

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Plasma-Assisted Synthesis and Properties of Na3N

Dark-blue sodium nitride, Na(3)N, was prepared by the reaction of metallic sodium or liquid Na-K alloy with plasma-activated nitrogen at low pressure. The compound crystallizes in the cubic anti-ReO(3)-type structure (space group Pm3m with a = 4.73301(6) Angstrom and Z = 1) according to powder and single-crystal X-ray diffraction data. Na(3)N decomposes above 104 degrees C into the elements, with DeltaH(f) estimated at +64(2) kJ/mol.

Studies of surface properties of Na- and La-montmorillonites

This paper presents possible applications of thermal analysis, sorptometry and porosimetry to study physico-chemical properties of Na- and La-montmorillonite samples, especially for determination of total surface heterogeneity. The quasi-isothermal thermogravimetric (Q-TG) mass loss and its first derivative (Q-DTG) curves with respect to temperature and time obtained during programmed liquid thermodesorption under quasi-isothermal conditions have been used to study adsorbed layers and heterogeneous properties of the Na- and La-montmorillonites. Calculations of the desorption energy distribution functions by analytical procedure using mass loss Q-TG and differential mass loss Q-DTG curves of thermodesorption under quasi-isothermal conditions of polar and non-polar liquid vapours preadsorbed on a material surface are presented. Parameters relating to porosity of samples were determined by sorptometry, mercury porosimetry and atomic force microscopy (AFM). From nitrogen sorption isotherms from sorptometry and porosimetry methods, the fractal dimensions of montmorillonites have been calculated. Moreover, a new approach is proposed to calculate fractal dimensions of materials obtained from Q-TG curve; this is compared with values obtained by the above methods. The total heterogeneous properties (energy distribution function and pore-size distribution functions) of samples studied were estimated. The radius and pore volume of the tested samples calculated on the basis of thermogravimetry, sorptometry and porosimetry techniques were compared and good correlations obtained.

Electronic structure and thermoelectric properties of Na and Ni-doped Ca3Co2O6

The electronic structures of Ca3Co2O6, Na and Ni doped models were studied by the quantum chemical software of Cambride Serial Total Energy Package (CASTEP) that is based on density function theory (DFT) and pseudo-potential. The electronic conductivity, seebeck coefficient, thermal conductivity and figure of merit (Z) were computed. The energy band structure reveals the form of the impurity levels due to the substitutional impurity in semiconductors. Na-doped model shows the character of p-type semiconductor, but Ni-doped model is n-type semiconductor. The calculation results show that the electric conductivity of the doped model is higher than that of the non-doped model, while the Seebeck coefficient and thermal conductivity of the doped model are lower than those of the non-doped one. Because of the great increase of the electric conductivity, Z of Na-doped model is enhanced and thermoelectric properties are improved. On the other hand, as the large decline of Seebeck coefficient, Z of Ni-doped model is less than that of the non-doped model.