Conductivity Of Na Research Articles

Two-pore channels regulate endomembrane tension to enable remodeling and resolution of phagolysosomes

Phagocytes promptly resolve ingested targets to replenish lysosomes and maintain their responsiveness. The resolution process requires that degradative hydrolases, solute transporters, and proteins involved in lipid traffic are delivered and made active in phagolysosomes. It also involves extensive membrane remodeling. We report that cation channels that localize to phagolysosomes were essential for resolution. Specifically, the conductance of Na+ by two-pore channels (TPCs) and the presence of a Na+ gradient between the phagolysosome lumen and the cytosol were critical for the controlled release of membrane tension that permits deformation of the limiting phagolysosome membrane. In turn, membrane deformation was a necessary step to efficiently transport the cholesterol extracted from cellular targets, permeabilizing them to hydrolases. These results place TPCs as regulators of endomembrane remodeling events that precede target degradation in cases when the target is bound by a cholesterol-containing membrane. The findings may help to explain lipid metabolism dysfunction and autophagic flux impairment reported in TPC KO mice and establish stepwise regulation to the resolution process that begins with lysis of the target.

Halogen Doping Mechanism and Interface Strengthening in the Na3SbS4 Electrolyte via Solid-State Synthesis.

Good-performing sodium solid electrolytes (SSEs) are essential for constructing all-solid-state sodium-ion batteries operating at ambient temperature. Sulfide solid electrolyte, Na3SbS4 (NBS), an excellent SSE with good chemical stability in humid air, can be synthesized with low-cost processing. However, Na3SbS4-based electrolytes with liquid-phase synthesis exhibit conductivities below milli-Siemens per centimeter. Thus, a series of halogen-doped samples formulated as Na3-xSbS4-xMx (0 ≤ x ≤ 0.3, M = Cl, Br, and I) were experimentally prepared in this study using the solid-state method to improve the battery performance. X-ray diffraction with refinement analysis and Raman spectroscopy were employed to understand deeply the connection between the crystal structure and conductivity of Na+ ions. In addition, symmetric sodium batteries with Na2.85SbS3.85Br0.15 were tested at room temperature, and pristine Na3SbS4 was used as the control group. The result showed that the symmetric sodium battery assembled with the Na2.85SbS3.85Br0.15 electrolyte can stably cycle for longer than 100 h at a current density of 0.1 mA/cm2. This research provides a method to manufacture novel SSEs by elaborating the effect of halogen doping in NBS.

Ion conduction in Na＋ containing ionogels based on the UiO-66 metal organic framework

▪ conducting materials are critical to the development of solid-state sodium batteries which may enable the use of sodium metal anodes. Ionogels are hybrid liquid–solid electrolytes that are made by embedding an ionic liquid into a suitable solid framework. In this study, ionogels based on the UiO-66 type metal organic framework (MOF) porous structure were prepared. Three isostructural MOFs were synthesized and used: (i) the UiO-66 material, (ii) an amine functionalized MOF (UiO-66- ▪ ) and iii) a hydroxyl functionalized MOF (UiO-66- ▪ ). A mixture of sodium bis(fluorosulfonyl)imide (NaFSI) and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI) was embedded in the pores of the MOFs. FTIR and conductivity spectroscopy were used to asses the interaction of the mobile species with the MOF structure as well as ion transport and electric relaxation properties of the materials. We found that the conductivity of the ionogels is strongly influenced by the functionalized linker used. The UiO-66- ▪ -based ionogels present an encouraging conductivity increase trend when sodium ions are present, whereas the UiO-66- ▪ -based ionogels present the highest conductivity in the order of 0.3 mScm−1 at 293 K, albeit this is very likely due to highly mobile protons. While further studies are needed to understand which species are dominating the ion conduction, this investigation offers an insight into the behavior of MOF-based ionogels and may guide further work in the field.

In Situ TEM Study of Structural Changes in Na-β″-Alumina Using Electron Beam Irradiation.

Real-time structural changes in Na-β″-alumina were observed in situ using transmission electron microscopy (TEM) with electron beam irradiation. Na-β″-alumina has been widely investigated as a solid electrolyte material for sodium–sulfur secondary batteries owing to its high ionic conductivity. This high conductivity is known to be due to the Na+ ions on the loosely packed conduction planes of Na-β″-alumina. In the present study, we acquired real-time videos of the generation of spinel blocks caused by the conduction of Na+ ions. In addition, by observing Na extraction during electron beam irradiation, we experimentally confirmed that spinel block generation originates from the Na+ ion conduction, which has been a subject of recent debate.

Tetrahedral Alignment and Covalent Bonding Enable Fast Sodium Conduction in Na3XS4 (X = P, V)

Tetrahedral Alignment and Covalent Bonding Enable Fast Sodium Conduction in Na₃XS₄ (X = P, V)

Determining the origin of poor electronic conductivity and ultrafast ionic conductivity in Na3V2(PO4)2FO2 based on first principles and ab initio molecular dynamics methods.

Sodium ion technology is increasingly investigated as a low-cost solution for grid storage applications. Among the reported cathode materials for sodium-ion batteries, Na3V2(PO4)2FO2 is considered as one of the most promising materials due to its high operation voltage and good cyclability. Here, the de-sodiumization process of Na3V2(PO4)2FO2 has been systematically examined using first-principles calculations to uncover the fundamental questions at the atomic level. Four stable intermediate products during the de-sodiumization process are firstly determined based on the convex hull, and three voltage platforms are then predicted. Except for two voltage platforms (3.37 V and 3.75 V) close to the experimental values, the platform up to 5.28 V exceeds the stability window (4.8 V) of a typical electrolyte, which was not observed experimentally. Excitingly, the change of volume is only 2% during the sodiumization process, which should be the reason for the good cycling stability of this material. Electronic structure analysis also reveals that the valence states of V ions will be changed from V5+ to V4+ during the sodiumization process, resulting in a weak Jahn-Teller distortion in VO5F octahedra, and then making the lattice-constants asymmetrically change. More seriously, combined with a bandgap of 2.0 eV, the conduction band minimum mainly composed of V-t2g non-bonding orbitals has strong localized characteristics, which should be the intrinsic origin of poor electron transport properties for NaxV2(PO4)2FO2. Nonetheless, benefiting from the layer-like structure features with F-segmentation, this material has an ultrafast sodium ionic conductivity comparable to that of NASICON, with an activation energy of only 82 meV. Therefore, our results indicate that maintaining layer-like features and regulating V atoms will be important directions to improve the performance of NaxV2(PO4)2FO2.

Phase Formation and Ionic Conductivity of Na1 + 2xZnxZr2 – x(PO4)3 Phosphates

Phase Formation and Ionic Conductivity of Na1 + 2xZnxZr2 – x(PO4)3 Phosphates

On the Crystal Structure and Conductivity of Na3P

As a potential material for Na‐ion battery systems and on the basis of a structural discussion of compounds formerly believed to crystallize in the so‐called Na3As type the structure of Na3P has been reinvestigated. Na3P is found to crystallize in the Cu3P type, analogous to Na3As and is described by a three times larger unit cell [P63cm, a = 8.61224(10) Å and c = 8.81949(10) Å] compared to the former model [P63/mmc, a = 4.9512(5) Å and c = 8.7874(13) Å]. As a structural manifestation of this symmetry reduction corrugated layers of Na and P atoms are observed which had formerly to be described as planar. The high purity of the material further enables the determination of its properties, showing mainly semiconducting behavior with a conductivity of 12 S·cm–1 at room temperature.

Дипольное упорядочение и ионная проводимость в NASICON-подобных структурах типа Na-=SUB=-3-=/SUB=-Fe-=SUB=-2-=/SUB=-(PO-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=-

Abstract The problems of the structural features, the dielectric and conducting properties of Na_3Fe_2(PO_4)_3 polycrystals prepared by hot pressing have been studied. The Na_3Fe_2(PO_4)_3 polycrystals in the α and β phases are shown to have higher conducting properties than the α and β phases of the single crystals grown by the solution–melt method. The regularities of the appearance of the dipole ordering, the ionic and superionic conductivities related to phase transitions and structural changes in the {[Fe_2(PO_4)_3]^3–}_3∞ rhombohedral crystalline frame during polymorphic transformations are refined. The problems of the relaxation polarization in the α and β phases of Na_3Fe_2(PO_4)_3 are discussed. A model for explaining the dipole ordering and the ionic conductivity in Na_3Fe_2(PO_4)_3 is proposed.

Effects of sintering atmosphere (N2 and O2) on dielectric properties and electrical conductivity of Na(Nb1−xTax)O3 ceramics

Na(Nb1−xTax)O3 (NNT, x = 0, 0.05, and 0.10) ceramics were prepared by conventional solid-state reaction method in the oxygen (O2) and nitrogen (N2) sintering atmospheres, respectively. The phase structure, surface microstructure, dielectric constant (ε), dielectric loss (tan δ), and frequency dispersion of AC conductivity (σac) of the NNT ceramics have been investigated. The results show that the NNT ceramics are of antiferroelectric orthorhombic phase. The values of ε of the NNT ceramics sintered in N2 are larger than those sintered in O2 at all temperatures, and the Curie temperature (TC) of the NNT ceramics sintered in N2 or O2 decreases from about 370 °C to 330 °C as x increases from 0 to 0.10. The electrical conductivity analysis shows that the quasi-static activation energies (Ea) at 1 Hz of the samples sintered in O2 are larger than in N2, especially for x = 0. These results are expected to promote the research and applications of the NNT-based systems.

First principle investigation of hydrogen behavior in M doped Cu2O (M = Na, Li and Ti)

We study the hydrogen effect on the electronic, magnetic and optical properties of Cu$_2$O in presence of different dopants (Na, Li and Ti). The electronic properties calculations show that hydrogen changes the conductivity of Cu$_2$O from p to n-type. The results show that interstitial hydrogen atom prefers to locate in the tetrahedral site in Cu$_2$O system and it decreases the band gap value of the later. The Na or Li doping Cu$_2$O preserves the p-type conductivity of Cu$_2$O, while hydrogen is the source of n-type conductivity in Na or Li doped Cu$_2$O systems. Ti doping increases the band gap value of Cu$_2$O and makes it an n-type semiconductor. Hydrogen increases the optical transmittance of M doped Cu$_2$O.

Temperature dependence of dielectric properties of sodium potassium niobate ceramics for different values of x (Na1−xKxNbO3)

ABSTRACTDielectric constant, loss tangent and electrical conductivity of Na1−xKxNbO3 (X = 0.08 and 0.17)(SPN) ceramic pellets have been measured at 10, 100 and 1000 kHz frequencies and at temperature varying from room temperature to 425°C. The dielectric constant increases with increase of temperature up to 400°C at all the three frequencies, and thereafter, it decreases with further increase of temperature, i.e., it shows a structural transition at about 400°C. The loss tangent also shows similar behaviour as dielectric constant shows. Some variations may be due to relaxation effects and impurities etc. around the sensitive transition region, which are seem to play prominent role in this soft mode region. Electrical conductivity increases with increase in temperature at all the three frequencies.

SY 03-3 OVERVIEW OF SOMATIC MUTATIONS AND EPIGENETIC REGULATION OF ALDOSTERONE PRODUCING ADENOMA (APA)

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Evolvement of microstructure and lattice thermal conductivity in Na doped PbTe–PbS pseudo−binary system

PbTe–PbS pseudo−binary is a renowned thermoelectric system largely due to its phase separation driven low thermal conductivity. To understand the thermal conductivity evolvement as well as its correlation with microstructural features (especially the nano-scale precipitates), systematic transmission electron microscope studies were performed in this work on a series of PbTe–PbS samples with gradually varying PbS or Na content. We confirmed the co-existence of two groups of precipitates in these samples, i.e. INPs (incipient nano-precipitates) ∼5 nm and PbS-rich ones ranging from 10 to a few hundreds of nano-meters. We also studied their individual size and concentration evolvement with varying PbS and Na. The effect of evolving microstructures on phonon transport was discussed and understood in a modified Callaway model, which conclusively led to the conclusion that significant impedance on heat conduction could only be realized in the case of nano-precipitates with a proper size and number density distribution.

Structural origin of the superionic Na conduction in Na2B10H10closo-borates and enhanced conductivity by Na deficiency for high performance solid electrolytes

Na superionic conduction in Na2B10H10closo-borate originates from the Oh-connected diffusion network, which is highly correlated with the anion disorder.

Phase Relationship and Ionic Conductivity in Na–SrSiO3 Ionic Conductor

The Na–SrSiO3 as a potential high‐conductivity ionic conductor for intermediate temperature solid oxide electrochemical cells (SOECs) has drawn much attention recently. Some of these studies questioned the feasibility of Na doping and therefore the creation of oxygen vacancies, while others suggested an alternative phase responsible for the ionic conduction. In this study, a systematic investigation was carried out to understand the ionic conduction in Na–SrSiO3. Through in situ high‐temperature X‐ray diffraction, thermal analysis, microstructural characterization, and electrical conductivity measurement, Na–SrSiO3 was shown as a two‐phase material, one being slightly Na‐doped SrSiO3 and another being amorphous Na2Si2O5. The former was an electrical insulator whereas the latter was a good ionic conductor. It was also found that the amorphous Na2Si2O5 phase was unstable at the temperature ≥500°C, crystallizing into the insulating polycrystalline Na2Si2O5 which causes conductivity to “bend‐over” at higher temperatures. A preliminary Ab Initio Molecular Dynamics (AIMD) simulation suggested that the amorphous Na2Si2O5 be predominantly a Na+ conductor.

Synthesis of a Bimetallic Dodecaborate LiNaB12H12 with Outstanding Superionic Conductivity

Metal dodecaborates M_2/_nB_(12)H_(12) (n denotes the valence of the metal M), containing icosahedral polyatomic anion [B_(12)H_(12)]^(2−), have been attracting increasing interest as potential energy materials, especially in the context of hydrogen storage and superionic conductivity. M_2/_nB_(12)H_(12) are commonly formed as dehydrogenation intermediates from metal borohydrides M(BH_4)_n, like LiBH_4 and Mg(BH_4)_2, which are well-known as potential high-density hydrogen storage materials. The strong B−B bond in the icosahedral [B_(12)H_(12)]^(2−), however, is regarded to be the key factor that prevents the rehydrogenation of dodecaborates. In order to elucidate the mechanism as well as to provide effective solutions to this problem, a novel solvent-free synthesis route of anhydrous M_2/nB_(12)H_(12) (here M means Li, Na, and K) has been developed. Thermal stability and transformations of the anhydrous single phase Li_2B_(12)H_(12) suggested the formation of the high temperature polymorph of Li_2B_(12)H_(12) during the dehydrogenation of LiBH_4, while concurrently emphasized the importance of further investigation on the decomposition mechanism of metal borohydrides and metal dodecaborates. The high stability of icosahedral [B_(12)H_(12)]^(2−), on the other hand, favors its potential application as solid electrolyte. Recently, Na^+ conductivity of Na_2B_(12)H_(12) was reported to be 0.1 S/cm above its order−disorder phase transition at ∼529 K, which is comparable to that of a polycrystalline β”-Al_2O_3 (0.24 S/cm at 573 K) solid state Na-electrolyte. Mechanistic understanding on the diffusion behavior of cation and further improvement of ionic conductivity at a lower temperature, however, are important in order to facilitate the practical application of metal dodecaborates as superionic conductors.

The Molecular Mechanism of Cardiac Sodium Channel Current Reduction with Metabolic Stress

Background Human cardiomyopathy is associated with decreased cardiac Na + channel current (I Na ), and Na + channel changes have been implicated in the increased risk of sudden death in heart failure. We have reported that in cardiomyopathy, elevated intracellular NADH downregulates I Na acutely to a magnitude seen in Brugada syndrome through protein kinase C (PKC) activation without changing the channel membrane expression. The decrease in I Na can be ameliorated by NAD + and protein kinase A (PKA) activators. Here, we investigate the molecular mechanism by which I Na is changed during metabolic stress. Methods HEK293 cells stably expressing human cardiac channel (Na v 1.5) were used to measure single channel currents at –40, –60, and –80 mV using the cell-attached voltage-clamp configuration. Results The single channel currents and conductance of Na v 1.5 were significantly decreased by NADH (100 µM) and phorbol 12-myristate 13-acetate (PMA, 30 nM) ( P + (500 µM) or forskolin (1 µM) restored the single channel currents and conductance to the untreated level ( P >.05 vs untreated group, P Conclusions Because we have already shown no reduction in cell surface channel number with metabolic stress, the decrease of macroscopic current of cardiac Na v 1.5 induced by NADH and PKC results from a decrease of single channel conductance, whereas NAD + and PKA elevate the single channel conductance. These results are consistent with the time course of the current changes seen with NADH/NAD + .

Mixing of hydrothermal water and groundwater near hot springs, Yellowstone National Park (USA): hydrology and geochemistry

Studies of hot springs have focused mainly on the properties of fluids and solids. Fewer studies focus on the relationship between the hot springs and groundwater/surface-water environments. The differences in temperature and dissolved solids between hot-spring water and typical surface water and groundwater allow interactions to be traced. Electromagnetic terrain (EMT) conductivity is a nonintrusive technique capable of mapping mixing zones between distinct subsurface waters. These interactions include zones of groundwater/surface-water exchange and groundwater mixing. Herein, hydrogeological techniques are compared with EMT conductivity to trace hot-spring discharge interactions with shallow groundwater and surface water. Potentiometric-surface and water-quality data determined the hydrogeochemistry of two thermally influenced areas in Yellowstone National Park, Wyoming (USA). Data from the sites revealed EMT conductivity contrasts that reflected the infiltration of conductive hot-spring discharge to local groundwater systems. The anomalies reflect higher temperatures and conductivity for Na+–Cl−-rich hydrothermal fluids compared to the receiving groundwater. EMT conductivity results suggested hot springs are fed by conduits largely isolated from shallow groundwater; mixing of waters occurs after hot-spring discharge infiltrates groundwater from the surface and, generally, not by leakage in the subsurface. A model was proposed to explain the growth of sinter mounds.

Sensitivity analysis to explain the excitability in a pyramidal neuron with application to Alzheimer’s disease

Intrinsic excitability is one of the pillars of neuronal behaviour . Combined experimental and modelling studies of neuronal excitability often provide an important insight into the brain functions. In this work we analyse a unified model that we derived for CA1/3 pyramidal neurons in Hodgkin-Huxley formalism [1]. We explore the variations of the model behaviour through parameter sensitivity analysis. Model validation against the experimental current clamp data shows that our model reproduces the behaviour of pyramidal cells very well. A characteristic feature of CA1/3 pyramidal cell response is a higher frequency of the first spike pairs. We define an excitability measure that quantifies parameter sensitivity in our model and takes into account this unique feature of the response. The analysis shows that the outward currents have a considerable influence on both excitability and the number of action potentials. An increase of high-voltage activated inward currents often decreases excitability, whereas an increase of low-voltage activated inward currents results in a large increase of it. Moreover, the outward currents in our model have a profound impact on the number of action potentials. Counter-intuitively, we find that either a decrease or increase of total Na+ current can result in an increase of excitability, as shown in Fig. ​Fig.11 Figure 1 Sensitivity analysis of the maximal conductance of the combined Na+-currents; panel (a) shows the excitability measure ranging over the given percentages of the maximal conductance of Na+-currents; the original value of the maximal conductance is marked ...