Human Na(v)1.8: enhanced persistent and ramp currents contribute to distinct firing properties of human DRG neurons.

PubMed

Han, Chongyang; Estacion, Mark; Huang, Jianying; Vasylyev, Dymtro; Zhao, Peng; Dib-Hajj, Sulayman D; Waxman, Stephen G

2015-05-01

Although species-specific differences in ion channel properties are well-documented, little has been known about the properties of the human Nav1.8 channel, an important contributor to pain signaling. Here we show, using techniques that include voltage clamp, current clamp, and dynamic clamp in dorsal root ganglion (DRG) neurons, that human Na(v)1.8 channels display slower inactivation kinetics and produce larger persistent current and ramp current than previously reported in other species. DRG neurons expressing human Na(v)1.8 channels unexpectedly produce significantly longer-lasting action potentials, including action potentials with half-widths in some cells >10 ms, and increased firing frequency compared with the narrower and usually single action potentials generated by DRG neurons expressing rat Na(v)1.8 channels. We also show that native human DRG neurons recapitulate these properties of Na(v)1.8 current and the long-lasting action potentials. Together, our results demonstrate strikingly distinct properties of human Na(v)1.8, which contribute to the firing properties of human DRG neurons.

Reactive species modify NaV1.8 channels and affect action potentials in murine dorsal root ganglia neurons

PubMed Central

Schink, Martin; Leipolcf, Enrico; Schirmeyer, Jana; Schönherr, Roland; Hoshi, Toshinori; Heinemann, Stefan H.

2016-01-01

Dorsal root ganglia (DRG) neurons are important relay stations between the periphery and the central nervous system and are essential for somatosensory signaling. Reactive species are produced in a variety of physiological and pathophysiological conditions and are known to alter electric signaling. Here we studied the influence of reactive species on the electrical properties of DRG neurons from mice with the whole-cell patch-clamp method. Even mild stress induced by either low concentrations of chloramine-T (10 µM) or low-intensity blue-light irradiation profoundly diminished action potential frequency but prolonged single action potentials in wild-type neurons. The impact on evoked action potentials was much smaller in neurons deficient of the tetrodotoxin (TTX)-resistant voltage-gated sodium channel NaV1.8 (NaV1.8−/−), the channel most important for the action potential upstroke in DRG neurons. Low concentrations of chloramine-T caused a significant reduction of NaV1.8 peak current and at higher concentrations progressively slowed down inactivation. Blue light had a smaller effect on amplitude but slowed down NaV1.8 channel inactivation. The observed effects were less apparent for TTX-sensitive NaV channels. NaV1.8 is an important reactive-species-sensitive component in the electrical signaling of DRG neurons, potentially giving rise to loss-of-function and gain-of-function phenomena depending on the type of reactive species and their effective concentration and time of exposure. PMID:26383867

Reactive species modify NaV1.8 channels and affect action potentials in murine dorsal root ganglion neurons.

PubMed

Schink, Martin; Leipold, Enrico; Schirmeyer, Jana; Schönherr, Roland; Hoshi, Toshinori; Heinemann, Stefan H

2016-01-01

Dorsal root ganglion (DRG) neurons are important relay stations between the periphery and the central nervous system and are essential for somatosensory signaling. Reactive species are produced in a variety of physiological and pathophysiological conditions and are known to alter electric signaling. Here we studied the influence of reactive species on the electrical properties of DRG neurons from mice with the whole-cell patch-clamp method. Even mild stress induced by either low concentrations of chloramine-T (10 μM) or low-intensity blue light irradiation profoundly diminished action potential frequency but prolonged single action potentials in wild-type neurons. The impact on evoked action potentials was much smaller in neurons deficient of the tetrodotoxin (TTX)-resistant voltage-gated sodium channel NaV1.8 (NaV1.8(-/-)), the channel most important for the action potential upstroke in DRG neurons. Low concentrations of chloramine-T caused a significant reduction of NaV1.8 peak current and, at higher concentrations, progressively slowed down inactivation. Blue light had a smaller effect on amplitude but slowed down NaV1.8 channel inactivation. The observed effects were less apparent for TTX-sensitive NaV channels. NaV1.8 is an important reactive-species-sensitive component in the electrical signaling of DRG neurons, potentially giving rise to loss-of-function and gain-of-function phenomena depending on the type of reactive species and their effective concentration and time of exposure.

A sodium channel knockin mutant (NaV1.4-R669H) mouse model of hypokalemic periodic paralysis

PubMed Central

Wu, Fenfen; Mi, Wentao; Burns, Dennis K.; Fu, Yu; Gray, Hillery F.; Struyk, Arie F.; Cannon, Stephen C.

2011-01-01

Hypokalemic periodic paralysis (HypoPP) is an ion channelopathy of skeletal muscle characterized by attacks of muscle weakness associated with low serum K+. HypoPP results from a transient failure of muscle fiber excitability. Mutations in the genes encoding a calcium channel (CaV1.1) and a sodium channel (NaV1.4) have been identified in HypoPP families. Mutations of NaV1.4 give rise to a heterogeneous group of muscle disorders, with gain-of-function defects causing myotonia or hyperkalemic periodic paralysis. To address the question of specificity for the allele encoding the NaV1.4-R669H variant as a cause of HypoPP and to produce a model system in which to characterize functional defects of the mutant channel and susceptibility to paralysis, we generated knockin mice carrying the ortholog of the gene encoding the NaV1.4-R669H variant (referred to herein as R669H mice). Homozygous R669H mice had a robust HypoPP phenotype, with transient loss of muscle excitability and weakness in low-K+ challenge, insensitivity to high-K+ challenge, dominant inheritance, and absence of myotonia. Recovery was sensitive to the Na+/K+-ATPase pump inhibitor ouabain. Affected fibers had an anomalous inward current at hyperpolarized potentials, consistent with the proposal that a leaky gating pore in R669H channels triggers attacks, whereas a reduction in the amplitude of action potentials implies additional loss-of-function changes for the mutant NaV1.4 channels. PMID:21881211

SCN5A (NaV1.5) Variant Functional Perturbation and Clinical Presentation: Variants of a Certain Significance.

PubMed

Kroncke, Brett M; Glazer, Andrew M; Smith, Derek K; Blume, Jeffrey D; Roden, Dan M

2018-05-01

Accurately predicting the impact of rare nonsynonymous variants on disease risk is an important goal in precision medicine. Variants in the cardiac sodium channel SCN5A (protein Na V 1.5; voltage-dependent cardiac Na+ channel) are associated with multiple arrhythmia disorders, including Brugada syndrome and long QT syndrome. Rare SCN5A variants also occur in ≈1% of unaffected individuals. We hypothesized that in vitro electrophysiological functional parameters explain a statistically significant portion of the variability in disease penetrance. From a comprehensive literature review, we quantified the number of carriers presenting with and without disease for 1712 reported SCN5A variants. For 356 variants, data were also available for 5 Na V 1.5 electrophysiological parameters: peak current, late/persistent current, steady-state V1/2 of activation and inactivation, and recovery from inactivation. We found that peak and late current significantly associate with Brugada syndrome ( P <0.001; ρ=-0.44; Spearman rank test) and long QT syndrome disease penetrance ( P <0.001; ρ=0.37). Steady-state V1/2 activation and recovery from inactivation associate significantly with Brugada syndrome and long QT syndrome penetrance, respectively. Continuous estimates of disease penetrance align with the current American College of Medical Genetics classification paradigm. Na V 1.5 in vitro electrophysiological parameters are correlated with Brugada syndrome and long QT syndrome disease risk. Our data emphasize the value of in vitro electrophysiological characterization and incorporating counts of affected and unaffected carriers to aid variant classification. This quantitative analysis of the electrophysiological literature should aid the interpretation of Na V 1.5 variant electrophysiological abnormalities and help improve Na V 1.5 variant classification. © 2018 American Heart Association, Inc.

Structure and function of splice variants of the cardiac voltage-gated sodium channel Na(v)1.5.

PubMed

Schroeter, Annett; Walzik, Stefan; Blechschmidt, Steve; Haufe, Volker; Benndorf, Klaus; Zimmer, Thomas

2010-07-01

Voltage-gated sodium channels mediate the rapid upstroke of the action potential in excitable tissues. The tetrodotoxin (TTX) resistant isoform Na(v)1.5, encoded by the SCN5A gene, is the predominant isoform in the heart. This channel plays a key role for excitability of atrial and ventricular cardiomyocytes and for rapid impulse propagation through the specific conduction system. During recent years, strong evidence has been accumulated in support of the expression of several Na(v)1.5 splice variants in the heart, and in various other tissues and cell lines including brain, dorsal root ganglia, breast cancer cells and neuronal stem cell lines. This review summarizes our knowledge on the structure and putative function of nine Na(v)1.5 splice variants detected so far. Attention will be paid to the distinct biophysical properties of the four functional splice variants, to the pronounced tissue- and species-specific expression, and to the developmental regulation of Na(v)1.5 splicing. The implications of alternative splicing for SCN5A channelopathies, and for a better understanding of genotype-phenotype correlations, are discussed. Copyright 2010 Elsevier Ltd. All rights reserved.

Different role of TTX-sensitive voltage-gated sodium channel (NaV 1) subtypes in action potential initiation and conduction in vagal airway nociceptors.

PubMed

Kollarik, M; Sun, H; Herbstsomer, R A; Ru, F; Kocmalova, M; Meeker, S N; Undem, B J

2018-04-15

The action potential initiation in the nerve terminals and its subsequent conduction along the axons of afferent nerves are not necessarily dependent on the same voltage-gated sodium channel (Na V 1) subunits. The action potential initiation in jugular C-fibres within airway tissues is not blocked by TTX; nonetheless, conduction of action potentials along the vagal axons of these nerves is often dependent on TTX-sensitive channels. This is not the case for nodose airway Aδ-fibres and C-fibres, where both action potential initiation and conduction is abolished by TTX or selective Na V 1.7 blockers. The difference between the initiation of action potentials within the airways vs. conduction along the axons should be considered when developing Na V 1 blocking drugs for topical application to the respiratory tract. The action potential (AP) initiation in the nerve terminals and its subsequent AP conduction along the axons do not necessarily depend on the same subtypes of voltage-gated sodium channels (Na V 1s). We evaluated the role of TTX-sensitive and TTX-resistant Na V 1s in vagal afferent nociceptor nerves derived from jugular and nodose ganglia innervating the respiratory system. Single cell RT-PCR was performed on vagal afferent neurons retrogradely labelled from the guinea pig trachea. Almost all of the jugular neurons expressed the TTX-sensitive channel Na V 1.7 along with TTX-resistant Na V 1.8 and Na V 1.9. Tracheal nodose neurons also expressed Na V 1.7 but, less frequently, Na V 1.8 and Na V 1.9. Na V 1.6 were expressed in ∼40% of the jugular and 25% of nodose tracheal neurons. Other Na V 1 α subunits were only rarely expressed. Single fibre recordings were made from the vagal nodose and jugular nerve fibres innervating the trachea or lung in the isolated perfused vagally-innervated preparations that allowed for selective drug delivery to the nerve terminal compartment (AP initiation) or to the desheathed vagus nerve (AP conduction). AP initiation in

Mice with an NaV1.4 sodium channel null allele have latent myasthenia, without susceptibility to periodic paralysis

PubMed Central

Wu, Fenfen; Mi, Wentao; Fu, Yu; Struyk, Arie

2016-01-01

Over 60 mutations of SCN4A encoding the NaV1.4 sodium channel of skeletal muscle have been identified in patients with myotonia, periodic paralysis, myasthenia, or congenital myopathy. Most mutations are missense with gain-of-function defects that cause susceptibility to myotonia or periodic paralysis. Loss-of-function from enhanced inactivation or null alleles is rare and has been associated with myasthenia and congenital myopathy, while a mix of loss and gain of function changes has an uncertain relation to hypokalaemic periodic paralysis. To better define the functional consequences for a loss-of-function, we generated NaV1.4 null mice by deletion of exon 12. Heterozygous null mice have latent myasthenia and a right shift of the force-stimulus relation, without evidence of periodic paralysis. Sodium current density was half that of wild-type muscle and no compensation by retained expression of the foetal NaV1.5 isoform was detected. Mice null for NaV1.4 did not survive beyond the second postnatal day. This mouse model shows remarkable preservation of muscle function and viability for haploinsufficiency of NaV1.4, as has been reported in humans, with a propensity for pseudo-myasthenia caused by a marginal Na+ current density to support sustained high-frequency action potentials in muscle. PMID:27048647

3.0 V High Energy Density Symmetric Sodium-Ion Battery: Na4V2(PO4)3∥Na3V2(PO4)3.

PubMed

Yao, Xuhui; Zhu, Zixuan; Li, Qi; Wang, Xuanpeng; Xu, Xiaoming; Meng, Jiashen; Ren, Wenhao; Zhang, Xinhe; Huang, Yunhui; Mai, Liqiang

2018-03-28

Symmetric sodium-ion batteries (SIBs) are considered as promising candidates for large-scale energy storage owing to the simplified manufacture and wide abundance of sodium resources. However, most symmetric SIBs suffer from suppressed energy density. Here, a superior congeneric Na 4 V 2 (PO 4 ) 3 anode is synthesized via electrochemical preintercalation, and a high energy density symmetric SIB (Na 3 V 2 (PO 4 ) 3 as a cathode and Na 4 V 2 (PO 4 ) 3 as an anode) based on the deepened redox couple of V 4+ /V 2+ is built for the first time. When measured in half cell, both electrodes show stabilized electrochemical performance (over 3000 cycles). The symmetric SIBs exhibit an output voltage of 3.0 V and a cell-level energy density of 138 W h kg -1 . Furthermore, the sodium storage mechanism under the expanded measurement range of 0.01-3.9 V is disclosed through an in situ X-ray diffraction technique.

High-Throughput Screening of Na(V)1.7 Modulators Using a Giga-Seal Automated Patch Clamp Instrument.

PubMed

Chambers, Chris; Witton, Ian; Adams, Cathryn; Marrington, Luke; Kammonen, Juha

2016-03-01

Voltage-gated sodium (Na(V)) channels have an essential role in the initiation and propagation of action potentials in excitable cells, such as neurons. Of these channels, Na(V)1.7 has been indicated as a key channel for pain sensation. While extensive efforts have gone into discovering novel Na(V)1.7 modulating compounds for the treatment of pain, none has reached the market yet. In the last two years, new compound screening technologies have been introduced, which may speed up the discovery of such compounds. The Sophion Qube(®) is a next-generation 384-well giga-seal automated patch clamp (APC) screening instrument, capable of testing thousands of compounds per day. By combining high-throughput screening and follow-up compound testing on the same APC platform, it should be possible to accelerate the hit-to-lead stage of ion channel drug discovery and help identify the most interesting compounds faster. Following a period of instrument beta-testing, a Na(V)1.7 high-throughput screen was run with two Pfizer plate-based compound subsets. In total, data were generated for 158,000 compounds at a median success rate of 83%, which can be considered high in APC screening. In parallel, IC50 assay validation and protocol optimization was completed with a set of reference compounds to understand how the IC50 potencies generated on the Qube correlate with data generated on the more established Sophion QPatch(®) APC platform. In summary, the results presented here demonstrate that the Qube provides a comparable but much faster approach to study Na(V)1.7 in a robust and reliable APC assay for compound screening.

Pure Single-Crystalline Na1.1V3O7.9 Nanobelts as Superior Cathode Materials for Rechargeable Sodium-Ion Batteries.

PubMed

Yuan, Shuang; Liu, Yong-Bing; Xu, Dan; Ma, De-Long; Wang, Sai; Yang, Xiao-Hong; Cao, Zhan-Yi; Zhang, Xin-Bo

2015-03-01

Pure single-crystalline Na 1.1 V 3 O 7.9 nanobelts are successfully synthesized for the first time via a facile yet effective strategy. When used as cathode materials for Na-ion batteries, the novel nanobelts exhibit excellent electrochemical performance. Given the ease and effectiveness of the synthesis route as well as the very promising electrochemical performance, the results obtained may be extended to other next-generation cathode materials for Na-ion batteries.

Knockdown of sodium channel NaV1.6 blocks mechanical pain and abnormal bursting activity of afferent neurons in inflamed sensory ganglia

PubMed Central

Xie, Wenrui; Strong, Judith A.; Ye, Ling; Mao, Ju-Xian; Zhang, Jun-Ming

2013-01-01

Inflammatory processes in the sensory ganglia contribute to many forms of chronic pain. We previously showed that local inflammation of the lumbar sensory ganglia rapidly leads to prolonged mechanical pain behaviors and high levels of spontaneous bursting activity in myelinated cells. Abnormal spontaneous activity of sensory neurons occurs early in many preclinical pain models, and initiates many other pathological changes, but its molecular basis is not well understood. The sodium channel isoform NaV1.6 can underlie repetitive firing and excitatory persistent and resurgent currents. We used in vivo knockdown of this channel via local injection of siRNA to examine its role in chronic pain following local inflammation of the rat lumbar sensory ganglia. In normal DRG, quantitative PCR showed that cells capable of firing repetitively had significantly higher relative expression of NaV1.6. In inflamed DRG, spontaneously active bursting cells expressed high levels of NaV1.6′ immunoreactivity. In vivo knockdown of NaV1.6 locally in the lumbar DRG at the time of DRG inflammation completely blocked development of pain behaviors and abnormal spontaneous activity, while having only minor effects on unmyelinated C-cells. Current research on isoform-specific sodium channel blockers for chronic pain is largely focused on NaV1.8, because it is present primarily in unmyelinated C fiber nociceptors, or on NaV1.7, because lack of this channel causes congenital indifference to pain. However, the results suggest that NaV1.6 may be a useful therapeutic target for chronic pain, and that some pain conditions may be primarily mediated by myelinated A-fiber sensory neurons. PMID:23622763

Boron Substituted Na 3 V 2 (P 1 -x B x O 4 ) 3 Cathode Materials with Enhanced Performance for Sodium-Ion Batteries

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

Hu, Pu; Wang, Xiaofang; Wang, Tianshi

The development of excellent performance of Na-ion batteries remains great challenge owing to the poor stability and sluggish kinetics of cathode materials. Herein, B substituted Na 3V 2P 3–xB xO 12 (0 ≤ x ≤ 1) as stable cathode materials for Na-ion battery is presented. A combined experimental and theoretical investigations on Na 3V 2P 3–xB xO 12 (0 ≤ x ≤ 1) are undertaken to reveal the evolution of crystal and electronic structures and Na storage properties associated with various concentration of B. X-ray diffraction results indicate that the crystal structure of Na 3V 2P 3–xB xO 12 (0more » ≤ x ≤ 1/3) consisted of rhombohedral Na 3V 2(PO 4) 3 with tiny shrinkage of crystal lattice. X-ray absorption spectra and the calculated crystal structures all suggest that the detailed local structural distortion of substituted materials originates from the slight reduction of V–O distances. Na 3V 2P 3-1/6B 1/6O 12 significantly enhances the structural stability and electrochemical performance, giving remarkable enhanced capacity of 100 and 70 mAh g -1 when the C-rate increases to 5 C and 10 C. Spin-polarized density functional theory (DFT) calculation reveals that, as compared with the pristine Na 3V 2(PO 4) 3, the superior electrochemical performance of the substituted materials can be attributed to the emergence of new boundary states near the band gap, lower Na + diffusion energy barriers, and higher structure stability.« less

Direct evidence for high affinity blockade of NaV1.6 channel subtype by huwentoxin-IV spider peptide, using multiscale functional approaches.

PubMed

Gonçalves, Tânia C; Boukaiba, Rachid; Molgó, Jordi; Amar, Muriel; Partiseti, Michel; Servent, Denis; Benoit, Evelyne

2018-05-01

The Chinese bird spider huwentoxin-IV (HwTx-IV) is well-known to be a highly potent blocker of Na V 1.7 subtype of voltage-gated sodium (Na V ) channels, a genetically validated analgesic target, and thus promising as a potential lead molecule for the development of novel pain therapeutics. In the present study, the interaction between HwTx-IV and Na V 1.6 channel subtype was investigated using multiscale (from in vivo to individual cell) functional approaches. HwTx-IV was approximatively 2 times more efficient than tetrodotoxin (TTX) to inhibit the compound muscle action potential recorded from the mouse skeletal neuromuscular system in vivo, and 30 times more effective to inhibit nerve-evoked than directly-elicited muscle contractile force of isolated mouse hemidiaphragms. These results strongly suggest that the inhibition of nerve-evoked skeletal muscle functioning, produced by HwTx-IV, resulted from a toxin-induced preferential blockade of Na V 1.6, compared to Na V 1.4, channel subtype. This was confirmed by whole-cell automated patch-clamp experiments performed on human embryonic kidney (HEK)-293 cells overexpressing hNa V 1.1-1.8 channel subtypes. HwTx-IV was also approximatively 850 times more efficient to inhibit TTX-sensitive than TTX-resistant sodium currents recorded from mouse dorsal root ganglia neurons. Finally, based on our data, we predict that blockade of the Na V 1.6 channel subtype was involved in the in vivo toxicity of HwTx-IV, although this toxicity was more than 2 times lower than that of TTX. In conclusion, our results provide detailed information regarding the effects of HwTx-IV and allow a better understanding of the side-effect mechanisms involved in vivo and of channel subtype interactions resulting from the toxin activity. Copyright © 2018 Elsevier Ltd. All rights reserved.

Divergent actions of the pyrethroid insecticides S-bioallethrin, tefluthrin, and deltamethrin on rat Na{sub v}1.6 sodium channels

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

Tan Jianguo; Soderlund, David M., E-mail: dms6@cornell.ed

2010-09-15

We expressed rat Na{sub v}1.6 sodium channels in combination with the rat {beta}{sub 1} and {beta}{sub 2} auxiliary subunits in Xenopus laevis oocytes and evaluated the effects of the pyrethroid insecticides S-bioallethrin, deltamethrin, and tefluthrin on expressed sodium currents using the two-electrode voltage clamp technique. S-Bioallethrin, a type I structure, produced transient modification evident in the induction of rapidly decaying sodium tail currents, weak resting modification (5.7% modification at 100 {mu}M), and no further enhancement of modification upon repetitive activation by high-frequency trains of depolarizing pulses. By contrast deltamethrin, a type II structure, produced sodium tail currents that were {approx}more » 9-fold more persistent than those caused by S-bioallethrin, barely detectable resting modification (2.5% modification at 100 {mu}M), and 3.7-fold enhancement of modification upon repetitive activation. Tefluthrin, a type I structure with high mammalian toxicity, exhibited properties intermediate between S-bioallethrin and deltamethrin: intermediate tail current decay kinetics, much greater resting modification (14.1% at 100 {mu}M), and 2.8-fold enhancement of resting modification upon repetitive activation. Comparison of concentration-effect data showed that repetitive depolarization increased the potency of tefluthrin {approx} 15-fold and that tefluthrin was {approx} 10-fold more potent than deltamethrin as a use-dependent modifier of Na{sub v}1.6 sodium channels. Concentration-effect data from parallel experiments with the rat Na{sub v}1.2 sodium channel coexpressed with the rat {beta}{sub 1} and {beta}{sub 2} subunits in oocytes showed that the Na{sub v}1.6 isoform was at least 15-fold more sensitive to tefluthrin and deltamethrin than the Na{sub v}1.2 isoform. These results implicate sodium channels containing the Na{sub v}1.6 isoform as potential targets for the central neurotoxic effects of pyrethroids.« less

Calcium triggers reversal of calmodulin on nested anti-parallel sites in the IQ motif of the neuronal voltage-dependent sodium channel NaV1.2.

PubMed

Hovey, Liam; Fowler, C Andrew; Mahling, Ryan; Lin, Zesen; Miller, Mark Stephen; Marx, Dagan C; Yoder, Jesse B; Kim, Elaine H; Tefft, Kristin M; Waite, Brett C; Feldkamp, Michael D; Yu, Liping; Shea, Madeline A

2017-05-01

Several members of the voltage-gated sodium channel family are regulated by calmodulin (CaM) and ionic calcium. The neuronal voltage-gated sodium channel Na V 1.2 contains binding sites for both apo (calcium-depleted) and calcium-saturated CaM. We have determined equilibrium dissociation constants for rat Na V 1.2 IQ motif [IQRAYRRYLLK] binding to apo CaM (~3nM) and (Ca 2+ ) 4 -CaM (~85nM), showing that apo CaM binding is favored by 30-fold. For both apo and (Ca 2+ ) 4 -CaM, NMR demonstrated that Na V 1.2 IQ motif peptide (Na V 1.2 IQp ) exclusively made contacts with C-domain residues of CaM (CaM C ). To understand how calcium triggers conformational change at the CaM-IQ interface, we determined a solution structure (2M5E.pdb) of (Ca 2+ ) 2 -CaM C bound to Na V 1.2 IQp . The polarity of (Ca 2+ ) 2 -CaM C relative to the IQ motif was opposite to that seen in apo CaM C -Na v 1.2 IQp (2KXW), revealing that CaM C recognizes nested, anti-parallel sites in Na v 1.2 IQp . Reversal of CaM may require transient release from the IQ motif during calcium binding, and facilitate a re-orientation of CaM N allowing interactions with non-IQ Na V 1.2 residues or auxiliary regulatory proteins interacting in the vicinity of the IQ motif. Copyright © 2017 Elsevier B.V. All rights reserved.

Scorpion β-toxin interference with NaV channel voltage sensor gives rise to excitatory and depressant modes

PubMed Central

Leipold, Enrico; Borges, Adolfo

2012-01-01

Scorpion β toxins, peptides of ∼70 residues, specifically target voltage-gated sodium (NaV) channels to cause use-dependent subthreshold channel openings via a voltage–sensor trapping mechanism. This excitatory action is often overlaid by a not yet understood depressant mode in which NaV channel activity is inhibited. Here, we analyzed these two modes of gating modification by β-toxin Tz1 from Tityus zulianus on heterologously expressed NaV1.4 and NaV1.5 channels using the whole cell patch-clamp method. Tz1 facilitated the opening of NaV1.4 in a use-dependent manner and inhibited channel opening with a reversed use dependence. In contrast, the opening of NaV1.5 was exclusively inhibited without noticeable use dependence. Using chimeras of NaV1.4 and NaV1.5 channels, we demonstrated that gating modification by Tz1 depends on the specific structure of the voltage sensor in domain 2. Although residue G658 in NaV1.4 promotes the use-dependent transitions between Tz1 modification phenotypes, the equivalent residue in NaV1.5, N803, abolishes them. Gating charge neutralizations in the NaV1.4 domain 2 voltage sensor identified arginine residues at positions 663 and 669 as crucial for the outward and inward movement of this sensor, respectively. Our data support a model in which Tz1 can stabilize two conformations of the domain 2 voltage sensor: a preactivated outward position leading to NaV channels that open at subthreshold potentials, and a deactivated inward position preventing channels from opening. The results are best explained by a two-state voltage–sensor trapping model in that bound scorpion β toxin slows the activation as well as the deactivation kinetics of the voltage sensor in domain 2. PMID:22450487

Highly Durable Na2V6O16·1.63H2O Nanowire Cathode for Aqueous Zinc-Ion Battery.

PubMed

Hu, Ping; Zhu, Ting; Wang, Xuanpeng; Wei, Xiujuan; Yan, Mengyu; Li, Jiantao; Luo, Wen; Yang, Wei; Zhang, Wencui; Zhou, Liang; Zhou, Zhiqiang; Mai, Liqiang

2018-03-14

Rechargeable aqueous zinc-ion batteries are highly desirable for grid-scale applications due to their low cost and high safety; however, the poor cycling stability hinders their widespread application. Herein, a highly durable zinc-ion battery system with a Na 2 V 6 O 16 ·1.63H 2 O nanowire cathode and an aqueous Zn(CF 3 SO 3 ) 2 electrolyte has been developed. The Na 2 V 6 O 16 ·1.63H 2 O nanowires deliver a high specific capacity of 352 mAh g -1 at 50 mA g -1 and exhibit a capacity retention of 90% over 6000 cycles at 5000 mA g -1 , which represents the best cycling performance compared with all previous reports. In contrast, the NaV 3 O 8 nanowires maintain only 17% of the initial capacity after 4000 cycles at 5000 mA g -1 . A single-nanowire-based zinc-ion battery is assembled, which reveals the intrinsic Zn 2+ storage mechanism at nanoscale. The remarkable electrochemical performance especially the long-term cycling stability makes Na 2 V 6 O 16 ·1.63H 2 O a promising cathode for a low-cost and safe aqueous zinc-ion battery.

Repeated functional convergent effects of NaV1.7 on acid insensitivity in hibernating mammals

PubMed Central

Liu, Zhen; Wang, Wei; Zhang, Tong-Zuo; Li, Gong-Hua; He, Kai; Huang, Jing-Fei; Jiang, Xue-Long; Murphy, Robert W.; Shi, Peng

2014-01-01

Hibernating mammals need to be insensitive to acid in order to cope with conditions of high CO2; however, the molecular basis of acid tolerance remains largely unknown. The African naked mole-rat (Heterocephalus glaber) and hibernating mammals share similar environments and physiological features. In the naked mole-rat, acid insensitivity has been shown to be conferred by the functional motif of the sodium ion channel NaV1.7. There is now an opportunity to evaluate acid insensitivity in other taxa. In this study, we tested for functional convergence of NaV1.7 in 71 species of mammals, including 22 species that hibernate. Our analyses revealed a functional convergence of amino acid sequences, which occurred at least six times independently in mammals that hibernate. Evolutionary analyses determined that the convergence results from both parallel and divergent evolution of residues in the functional motif. Our findings not only identify the functional molecules responsible for acid insensitivity in hibernating mammals, but also open new avenues to elucidate the molecular underpinnings of acid insensitivity in mammals. PMID:24352952

Repeated functional convergent effects of NaV1.7 on acid insensitivity in hibernating mammals.

PubMed

Liu, Zhen; Wang, Wei; Zhang, Tong-Zuo; Li, Gong-Hua; He, Kai; Huang, Jing-Fei; Jiang, Xue-Long; Murphy, Robert W; Shi, Peng

2014-02-07

Hibernating mammals need to be insensitive to acid in order to cope with conditions of high CO2; however, the molecular basis of acid tolerance remains largely unknown. The African naked mole-rat (Heterocephalus glaber) and hibernating mammals share similar environments and physiological features. In the naked mole-rat, acid insensitivity has been shown to be conferred by the functional motif of the sodium ion channel NaV1.7. There is now an opportunity to evaluate acid insensitivity in other taxa. In this study, we tested for functional convergence of NaV1.7 in 71 species of mammals, including 22 species that hibernate. Our analyses revealed a functional convergence of amino acid sequences, which occurred at least six times independently in mammals that hibernate. Evolutionary analyses determined that the convergence results from both parallel and divergent evolution of residues in the functional motif. Our findings not only identify the functional molecules responsible for acid insensitivity in hibernating mammals, but also open new avenues to elucidate the molecular underpinnings of acid insensitivity in mammals.

New Defective Brannerite-Type Vanadates. I. Synthesis and Study of Mn 1- x- yφ xNa yV 2-2 x-yMo 2 x+yO 6 Solid Solutions

NASA Astrophysics Data System (ADS)

Masłowska, Bogna; Ziółkowski, Jacek

1994-05-01

MnV 2O 6 of the brannerite-type structure (below 540°C) doped with MoO 3 and Na 2O forms isomorphous solid solutions MnNaφ = Mn 1- x-yφ xNa yV 2-2 x-yMo 2 x+ yO 6 (φ cation vacancy in the original Mn position), belonging to the pseudoternary MnV 2O 6-NaVMoO 6-MoO 3 system. Particular cases are MnNa = Mn 1- yNa y V 2- yMo yO 6 ( x = 0), Mnφ = Mn 1- xφ xV 2-2 xMo 2 xO 6 ( y = 0), and Naφ = Na 1- xφ xV 1- xMo 1+ xO 6 ( x + y = 1). MnV 2O 6 and NaVMoO 6 show miscibility in the entire composition range (MnNa). The opposite boundary of MnNaφ passes through the (100 x, 100 y) points (45, 0), (33, 30), and (30, 70). The phase diagram of the pseudobinary MnV 2O 6-NaVMoO 6 system (determined with DTA) shows (i) a narrow double-lens-type solidus-liquidus gap at high values of y , (ii) two peritectic meltings at lower y (yielding the high temperature β-MnNa and Mn 2V 2O 7), and (iii) little area of β-MnNa. Lattice parameters of MnNa (determined with X-ray diffraction) reveal small deviations from Vegard's law. As the ionic radii of both dopants (Na + and Mo 6+) are, respectively, larger than those of mother ions (Mn 2+ and V 5+), the unit cell increases in all directions with rising y along the MnNa series of solid solutions. However, due to the anisotropy of the structure, parameter c is strongly sensitive to Na/Mn substitution, b is ruled by Mo/V, and a is weakly influenced by Mo/V. Close analogy to the behavior of the previously studied MnV 2O 6-LiVMoO 6-MoO 6 system is discussed.

1D nanostructured Na7V4(P2O7)4(PO4) as high-potential and superior-performance cathode material for sodium-ion batteries.

PubMed

Deng, Chao; Zhang, Sen

2014-06-25

Tailoring materials into nanostructure offers unprecedented opportunities in the utilization of their functional properties. High-purity Na7V4(P2O7)4(PO4) with 1D nanostructure is prepared as a cathode material for rechargeable Na-ion batteries. An efficient synthetic approach is developed by carefully controlling the crystal growth in the molten sodium phosphate. Based on the XRD, XPS, TG, and morphological characterization, a molten-salt assisted mechanism for nanoarchitecture formation is revealed. The prepared Na7V4(P2O7)4(PO4) nanorod has rectangle sides and preferential [001] growth orientation. GITT evaluation indicates that the sodium de/intercalation of Na7V4(P2O7)4(PO4) nanorod involves V(3+)/V(4+) redox reaction and Na5V(3.5+)4(P2O7)4(PO4) as intermediate phase, which results in two pairs of potential plateaus at the equilibrium potentials of 3.8713 V (V(3+)/V(3.5+)) and 3.8879 V (V(3.5+)/V(4+)), respectively. The unique nanoarchitecture of the phase-pure Na7V4(P2O7)4(PO4) facilitates its reversible sodium de/intercalation, which is beneficial to the high-rate capability and the cycling stability. The Na7V4(P2O7)4(PO4) cathode delivers 80% of the capacity (obtained at C/20) at the 10 C rate and 95% of the initial capacity after 200 cycles. Therefore, it is feasible to design and fabricate an advanced rechargeable sodium-ion battery by employment of 1D nanostructured Na7V4(P2O7)4(PO4) as the cathode material.

Scalable and template-free synthesis of nanostructured Na{sub 1.08}V{sub 6}O{sub 15} as high-performance cathode material for lithium-ion batteries

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

Zheng, Shili, E-mail: slzheng@ipe.ac.cn; Wang, Xinran; Yan, Hong

2016-09-15

Highlights: • Nanostructured Na{sub 1.08}V{sub 6}O{sub 15} was synthesized through additive-free sol-gel process. • Prepared Na{sub 1.08}V{sub 6}O{sub 15} demonstrated high capacity and sufficient cycling stability. • The reaction temperature was optimized to allow scalable Na{sub 1.08}V{sub 6}O{sub 15} fabrication. - Abstract: Developing high-capacity cathode material with feasibility and scalability is still challenging for lithium-ion batteries (LIBs). In this study, a high-capacity ternary sodium vanadate compound, nanostructured NaV{sub 6}O{sub 15}, was template-free synthesized through sol-gel process with high producing efficiency. The as-prepared sample was systematically post-treated at different temperature and the post-annealing temperature was found to determine the cycling stabilitymore » and capacity of NaV{sub 6}O{sub 15}. The well-crystallized one exhibited good electrochemical performance with a high specific capacity of 302 mAh g{sup −1} when cycled at current density of 0.03 mA g{sup −1}. Its relatively long-term cycling stability was characterized by the cell performance under the current density of 1 A g{sup −1}, delivering a reversible capacity of 118 mAh g{sup −1} after 300 cycles with 79% capacity retention and nearly 100% coulombic efficiency: all demonstrating its significant promise of proposed strategy for large-scale synthesis of NaV{sub 6}O{sub 15} as cathode with high-capacity and high energy density for LIBs.« less

Development of a μO-Conotoxin Analogue with Improved Lipid Membrane Interactions and Potency for the Analgesic Sodium Channel NaV1.8*

PubMed Central

Deuis, Jennifer R.; Dekan, Zoltan; Inserra, Marco C.; Lee, Tzong-Hsien; Aguilar, Marie-Isabel; Craik, David J.; Lewis, Richard J.; Alewood, Paul F.; Mobli, Mehdi; Schroeder, Christina I.; Henriques, Sónia Troeira; Vetter, Irina

2016-01-01

The μO-conotoxins MrVIA, MrVIB, and MfVIA inhibit the voltage-gated sodium channel NaV1.8, a well described target for the treatment of pain; however, little is known about the residues or structural elements that define this activity. In this study, we determined the three-dimensional structure of MfVIA, examined its membrane binding properties, performed alanine-scanning mutagenesis, and identified residues important for its activity at human NaV1.8. A second round of mutations resulted in (E5K,E8K)MfVIA, a double mutant with greater positive surface charge and greater affinity for lipid membranes compared with MfVIA. This analogue had increased potency at NaV1.8 and was analgesic in the mouse formalin assay. PMID:27026701

A novel µ-conopeptide, CnIIIC, exerts potent and preferential inhibition of NaV1.2/1.4 channels and blocks neuronal nicotinic acetylcholine receptors

PubMed Central

Favreau, Philippe; Benoit, Evelyne; Hocking, Henry G; Carlier, Ludovic; D' hoedt, Dieter; Leipold, Enrico; Markgraf, René; Schlumberger, Sébastien; Córdova, Marco A; Gaertner, Hubert; Paolini-Bertrand, Marianne; Hartley, Oliver; Tytgat, Jan; Heinemann, Stefan H; Bertrand, Daniel; Boelens, Rolf; Stöcklin, Reto; Molgó, Jordi

2012-01-01

BACKGROUND AND PURPOSE The µ-conopeptide family is defined by its ability to block voltage-gated sodium channels (VGSCs), a property that can be used for the development of myorelaxants and analgesics. We characterized the pharmacology of a new µ-conopeptide (µ-CnIIIC) on a range of preparations and molecular targets to assess its potential as a myorelaxant. EXPERIMENTAL APPROACH µ-CnIIIC was sequenced, synthesized and characterized by its direct block of elicited twitch tension in mouse skeletal muscle and action potentials in mouse sciatic and pike olfactory nerves. µ-CnIIIC was also studied on HEK-293 cells expressing various rodent VGSCs and also on voltage-gated potassium channels and nicotinic acetylcholine receptors (nAChRs) to assess cross-interactions. Nuclear magnetic resonance (NMR) experiments were carried out for structural data. KEY RESULTS Synthetic µ-CnIIIC decreased twitch tension in mouse hemidiaphragms (IC50= 150 nM), and displayed a higher blocking effect in mouse extensor digitorum longus muscles (IC = 46 nM), compared with µ-SIIIA, µ-SmIIIA and µ-PIIIA. µ-CnIIIC blocked NaV1.4 (IC50= 1.3 nM) and NaV1.2 channels in a long-lasting manner. Cardiac NaV1.5 and DRG-specific NaV1.8 channels were not blocked at 1 µM. µ-CnIIIC also blocked the α3β2 nAChR subtype (IC50= 450 nM) and, to a lesser extent, on the α7 and α4β2 subtypes. Structure determination of µ-CnIIIC revealed some similarities to α-conotoxins acting on nAChRs. CONCLUSION AND IMPLICATIONS µ-CnIIIC potently blocked VGSCs in skeletal muscle and nerve, and hence is applicable to myorelaxation. Its atypical pharmacological profile suggests some common structural features between VGSCs and nAChR channels. PMID:22229737

Pain thresholds, supra-threshold pain and lidocaine sensitivity in patients with erythromelalgia, including the I848Tmutation in NaV 1.7.

PubMed

Helås, T; Sagafos, D; Kleggetveit, I P; Quiding, H; Jönsson, B; Segerdahl, M; Zhang, Z; Salter, H; Schmelz, M; Jørum, E

2017-09-01

Nociceptive thresholds and supra-threshold pain ratings as well as their reduction upon local injection with lidocaine were compared between healthy subjects and patients with erythromelalgia (EM). Lidocaine (0.25, 0.50, 1.0 or 10 mg/mL) or placebo (saline) was injected intradermally in non-painful areas of the lower arm, in a randomized, double-blind manner, to test the effect on dynamic and static mechanical sensitivity, mechanical pain sensitivity, thermal thresholds and supra-threshold heat pain sensitivity. Heat pain thresholds and pain ratings to supra-threshold heat stimulation did not differ between EM-patients (n = 27) and controls (n = 25), neither did the dose-response curves for lidocaine. Only the subgroup of EM-patients with mutations in sodium channel subunits Na V 1.7, 1.8 or 1.9 (n = 8) had increased lidocaine sensitivity for supra-threshold heat stimuli, contrasting lower sensitivity to strong mechanical stimuli. This pattern was particularly clear in the two patients carrying the Na V 1.7 I848T mutations in whom lidocaine's hyperalgesic effect on mechanical pain sensitivity contrasted more effective heat analgesia. Heat pain thresholds are not sensitized in EM patients, even in those with gain-of-function mutations in Na V 1.7. Differential lidocaine sensitivity was overt only for noxious stimuli in the supra-threshold range suggesting that sensitized supra-threshold encoding is important for the clinical pain phenotype in EM in addition to lower activation threshold. Intracutaneous lidocaine dose-dependently blocked nociceptive sensations, but we did not identify EM patients with particular high lidocaine sensitivity that could have provided valuable therapeutic guidance. Acute pain thresholds and supra-threshold heat pain in controls and patients with erythromelalgia do not differ and have the same lidocaine sensitivity. Acute heat pain thresholds even in EM patients with the Na V 1.7 I848T mutation are normal and only nociceptor

Electrochemical behavior of LiV3O8 positive electrode in hybrid Li,Na-ion batteries

NASA Astrophysics Data System (ADS)

Maletti, S.; Sarapulova, A.; Tsirlin, A. A.; Oswald, S.; Fauth, F.; Giebeler, L.; Bramnik, N. N.; Ehrenberg, H.; Mikhailova, D.

2018-01-01

Vanadium(V)-containing oxides show superior intercalation properties for alkaline ions, although the performance of the material strongly depends on its surface morphology. In this work, intercalation activity of LiV3O8, prepared by a conventional solid state synthesis, is demonstrated for the first time in non-aqueous Li,Na-ion hybrid batteries with Na as negative electrode, and different Na/Li ratios in the electrolyte. In the pure Na-ion cell, one Na per formula unit of LiV3O8 can be reversibly inserted at room temperature via a two-step process, while further intercalation leads to gradual amorphisation of the material, with a specific capacity of 190 mAhg-1 after 10 cycles in the potential window of 0.8-3.4 V. Hybrid Li,Na-ion batteries feature simultaneous intercalation of Li+ and Na+ cations into LiV3O8, resulting in the formation of a second phase. Depending on the electrolyte composition, this second phase bears structural similarities either to Li0.7Na0.7V3O8 in Na-rich electrolytes, or to Li4V3O8 in Li-rich electrolytes. The chemical diffusion coefficients of Na+ and Li+ in crystalline LiV3O8 are very close, hence explaining the co-intercalation of these cations. As DFT calculations show, once formed, the Li0.7Na0.7V3O8-type structure favors intercalation of Na+, whereas the LiV3O8-type prefers to accommodate Li+ cations.

Characterization of the honeybee AmNaV1 channel and tools to assess the toxicity of insecticides.

PubMed

Gosselin-Badaroudine, Pascal; Moreau, Adrien; Delemotte, Lucie; Cens, Thierry; Collet, Claude; Rousset, Matthieu; Charnet, Pierre; Klein, Michael L; Chahine, Mohamed

2015-07-23

Pollination is important for both agriculture and biodiversity. For a significant number of plants, this process is highly, and sometimes exclusively, dependent on the pollination activity of honeybees. The large numbers of honeybee colony losses reported in recent years have been attributed to colony collapse disorder. Various hypotheses, including pesticide overuse, have been suggested to explain the disorder. Using the Xenopus oocytes expression system and two microelectrode voltage-clamp, we report the functional expression and the molecular, biophysical, and pharmacological characterization of the western honeybee's sodium channel (Apis Mellifera NaV1). The NaV1 channel is the primary target for pyrethroid insecticides in insect pests. We further report that the honeybee's channel is also sensitive to permethrin and fenvalerate, respectively type I and type II pyrethroid insecticides. Molecular docking of these insecticides revealed a binding site that is similar to sites previously identified in other insects. We describe in vitro and in silico tools that can be used to test chemical compounds. Our findings could be used to assess the risks that current and next generation pesticides pose to honeybee populations.

Differential state-dependent modification of rat Na{sub v}1.6 sodium channels expressed in human embryonic kidney (HEK293) cells by the pyrethroid insecticides tefluthrin and deltamethrin

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

He, Bingjun; Soderlund, David M., E-mail: dms6@cornell.edu

2011-12-15

We expressed rat Na{sub v}1.6 sodium channels in combination with the rat {beta}1 and {beta}2 auxiliary subunits in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on expressed sodium currents using the whole-cell patch clamp technique. Both pyrethroids produced concentration-dependent, resting modification of Na{sub v}1.6 channels, prolonging the kinetics of channel inactivation and deactivation to produce persistent 'late' currents during depolarization and tail currents following repolarization. Both pyrethroids also produced concentration dependent hyperpolarizing shifts in the voltage dependence of channel activation and steady-state inactivation. Maximal shifts in activation, determined from the voltagemore » dependence of the pyrethroid-induced late and tail currents, were {approx} 25 mV for tefluthrin and {approx} 20 mV for deltamethrin. The highest attainable concentrations of these compounds also caused shifts of {approx} 5-10 mV in the voltage dependence of steady-state inactivation. In addition to their effects on the voltage dependence of inactivation, both compounds caused concentration-dependent increases in the fraction of sodium current that was resistant to inactivation following strong depolarizing prepulses. We assessed the use-dependent effects of tefluthrin and deltamethrin on Na{sub v}1.6 channels by determining the effect of trains of 1 to 100 5-ms depolarizing prepulses at frequencies of 20 or 66.7 Hz on the extent of channel modification. Repetitive depolarization at either frequency increased modification by deltamethrin by {approx} 2.3-fold but had no effect on modification by tefluthrin. Tefluthrin and deltamethrin were equally potent as modifiers of Na{sub v}1.6 channels in HEK293 cells using the conditions producing maximal modification as the basis for comparison. These findings show that the actions of tefluthrin and deltamethrin of Na{sub v}1.6 channels in

Backbone resonance assignments of complexes of human voltage-dependent sodium channel NaV1.2 IQ motif peptide bound to apo calmodulin and to the C-domain fragment of apo calmodulin.

PubMed

Mahling, Ryan; Kilpatrick, Adina M; Shea, Madeline A

2017-10-01

Human voltage-gated sodium channel Na V 1.2 has a single pore-forming α-subunit and two transmembrane β-subunits. Expressed primarily in the brain, Na V 1.2 is critical for initiation and propagation of action potentials. Milliseconds after the pore opens, sodium influx is terminated by inactivation processes mediated by regulatory proteins including calmodulin (CaM). Both calcium-free (apo) CaM and calcium-saturated CaM bind tightly to an IQ motif in the C-terminal tail of the α-subunit. Our thermodynamic studies and solution structure (2KXW) of a C-domain fragment of apo 13 C, 15 N- CaM (CaM C ) bound to an unlabeled peptide with the sequence of rat Na V 1.2 IQ motif showed that apo CaM C (a) was necessary and sufficient for binding, and (b) bound more favorably than calcium-saturated CaM C . However, we could not monitor the Na V 1.2 residues directly, and no structure of full-length CaM (including the N-domain of CaM (CaM N )) was determined. To distinguish contributions of CaM N and CaM C , we used solution NMR spectroscopy to assign the backbone resonances of a complex containing a 13 C, 15 N-labeled peptide with the sequence of human Na V 1.2 IQ motif (Na V 1.2 IQp ) bound to apo 13 C, 15 N-CaM or apo 13 C, 15 N-CaM C . Comparing the assignments of apo CaM in complex with Na V 1.2 IQp to those of free apo CaM showed that residues within CaM C were significantly perturbed, while residues within CaM N were essentially unchanged. The chemical shifts of residues in Na V 1.2 IQp and in the C-domain of CaM were nearly identical regardless of whether CaM N was covalently linked to CaM C . This suggests that CaM N does not influence apo CaM binding to Na V 1.2 IQp .

Gain-of-function mutation of a voltage-gated sodium channel NaV1.7 associated with peripheral pain and impaired limb development.

PubMed

Tanaka, Brian S; Nguyen, Phuong T; Zhou, Eray Yihui; Yang, Yong; Yarov-Yarovoy, Vladimir; Dib-Hajj, Sulayman D; Waxman, Stephen G

2017-06-02

Dominant mutations in voltage-gated sodium channel Na V 1.7 cause inherited erythromelalgia, a debilitating pain disorder characterized by severe burning pain and redness of the distal extremities. Na V 1.7 is preferentially expressed within peripheral sensory and sympathetic neurons. Here, we describe a novel Na V 1.7 mutation in an 11-year-old male with underdevelopment of the limbs, recurrent attacks of burning pain with erythema, and swelling in his feet and hands. Frequency and duration of the episodes gradually increased with age, and relief by cooling became less effective. The patient's sister had short stature and reported similar complaints of erythema and burning pain, but with less intensity. Genetic analysis revealed a novel missense mutation in Na V 1.7 (2567G>C; p.Gly856Arg) in both siblings. The G856R mutation, located within the DII/S4-S5 linker of the channel, substitutes a highly conserved non-polar glycine by a positively charged arginine. Voltage-clamp analysis of G856R currents revealed that the mutation hyperpolarized (-11.2 mV) voltage dependence of activation and slowed deactivation but did not affect fast inactivation, compared with wild-type channels. A mutation of Gly-856 to aspartic acid was previously found in a family with limb pain and limb underdevelopment, and its functional assessment showed hyperpolarized activation, depolarized fast inactivation, and increased ramp current. Structural modeling using the Rosetta computational modeling suite provided structural clues to the divergent effects of the substitution of Gly-856 by arginine and aspartic acid. Although the proexcitatory changes in gating properties of G856R contribute to the pathophysiology of inherited erythromelalgia, the link to limb underdevelopment is not well understood. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

NaV channel variants in patients with painful and nonpainful peripheral neuropathy

PubMed Central

Wadhawan, Samir; Pant, Saumya; Golhar, Ryan; Kirov, Stefan; Thompson, John; Jacobsen, Leslie; Qureshi, Irfan; Ajroud-Driss, Senda; Freeman, Roy; Simpson, David M.; Smith, A. Gordon; Hoke, Ahmet

2017-01-01

Objective: To examine the incidence of nonsynonymous missense variants in SCN9A (NaV1.7), SCN10A (NaV1.8), and SCN11A (NaV1.9) in patients with painful and nonpainful peripheral neuropathy. Methods: Next-generation sequencing was performed on 457 patient DNA samples provided by the Peripheral Neuropathy Research Registry (PNRR). The patient diagnosis was as follows: 278 idiopathic peripheral neuropathy (67% painful and 33% nonpainful) and 179 diabetic distal polyneuropathy (77% painful and 23% nonpainful). Results: We identified 36 (SCN9A), 31 (SCN10A), and 15 (SCN11A) nonsynonymous missense variants, with 47.7% of patients carrying a low-frequency (minor allele frequency <5%) missense variant in at least 1 gene. The incidence of previously reported gain-of-function missense variants was low (≤3%), and these were detected in patients with and without pain. There were no significant differences in missense variant allele frequencies of any gene, or SCN9A haplotype frequencies, between PNRR patients with painful or nonpainful peripheral neuropathy. PNRR patient SCN9A and SCN11A missense variant allele frequencies were not significantly different from the Exome Variant Server, European American (EVS-EA) reference population. For SCN10A, there was a significant increase in the alternate allele frequency of the common variant p.V1073A and low-frequency variant pS509P in PNRR patients compared with EVS-EA and the 1000 Genomes European reference populations. Conclusions: These results suggest that identification of a genetically defined subpopulation for testing of NaV1.7 inhibitors in patients with peripheral neuropathy is unlikely and that additional factors, beyond expression of previously reported disease “mutations,” are more important for the development of painful neuropathy than previously discussed. PMID:29264398

Effects of the β1 auxiliary subunit on modification of Rat Na{sub v}1.6 sodium channels expressed in HEK293 cells by the pyrethroid insecticides tefluthrin and deltamethrin

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

He, Bingjun; Soderlund, David M., E-mail: dms6@cornell.edu

We expressed rat Na{sub v}1.6 sodium channels with or without the rat β1 subunit in human embryonic kidney (HEK293) cells and evaluated the effects of the pyrethroid insecticides tefluthrin and deltamethrin on whole-cell sodium currents. In assays with the Na{sub v}1.6 α subunit alone, both pyrethroids prolonged channel inactivation and deactivation and shifted the voltage dependence of channel activation and steady-state inactivation toward hyperpolarization. Maximal shifts in activation were ~ 18 mV for tefluthrin and ~ 24 mV for deltamethrin. These compounds also caused hyperpolarizing shifts of ~ 10–14 mV in the voltage dependence of steady-state inactivation and increased inmore » the fraction of sodium current that was resistant to inactivation. The effects of pyrethroids on the voltage-dependent gating greatly increased the size of sodium window currents compared to unmodified channels; modified channels exhibited increased probability of spontaneous opening at membrane potentials more negative than the normal threshold for channel activation and incomplete channel inactivation. Coexpression of Na{sub v}1.6 with the β1 subunit had no effect on the kinetic behavior of pyrethroid-modified channels but had divergent effects on the voltage-dependent gating of tefluthrin- or deltamethrin-modified channels, increasing the size of tefluthrin-induced window currents but decreasing the size of corresponding deltamethrin-induced currents. Unexpectedly, the β1 subunit did not confer sensitivity to use-dependent channel modification by either tefluthrin or deltamethrin. We conclude from these results that functional reconstitution of channels in vitro requires careful attention to the subunit composition of channel complexes to ensure that channels in vitro are faithful functional and pharmacological models of channels in neurons. - Highlights: • We expressed Na{sub v}1.6 sodium channels with or without β1 subunits in HEK293 cells. • Tefluthrin and

Glucose-assisted synthesis of Na3V2(PO4)3/C composite as an electrode material for high-performance sodium-ion batteries

NASA Astrophysics Data System (ADS)

Li, Guangqiang; Jiang, Danlu; Wang, Hui; Lan, Xinzheng; Zhong, Honghai; Jiang, Yang

2014-11-01

A novel electrode material for sodium-ion batteries (NIBs), Na3V2(PO4)3 with a rhombohedral, Na+ superionic conductor (NASICON)-type structure, was synthesised via a solid-state carbon-thermal reduction reaction assisted by mechanochemical activation. Electron microscopy analysis showed that the synthesised Na3V2(PO4)3 particles had an average size of 300 nm, being coated with a uniform layer of carbon 3 nm in thickness. As a cathode material, Na3V2(PO4)3/C exhibited an initial specific discharge capacity of 98.17 mAh g-1 at 0.1C for potentials ranging from 2.5 to 3.8 V. This was owing to the V3+/V4+ redox couple, which corresponded to the two-phase transition between Na3V2(PO4)3 and NaV2(PO4)3. The cathode lost 4.92% of its discharge specific capacity after 50 cycles. As an anode material, Na3V2(PO4)3/C exhibited an initial specific discharge capacity of 63.2 mAh g-1 at 0.1C for potentials ranging from 1.0 to 2.5 V. This was owing to the V2+/V3+ redox couple, which corresponded to the two-phase transition between Na3V2(PO4)3 and Na4V2(PO4)3. The anode lost approximately 5.41% of its discharge specific capacity after 50 cycles. The three-dimensional channel structure of NaV2(PO4)3 and the changes induced in its lattice parameters during the charge/discharge processes were simulated on the basis of density functional theory.

Preventing structural degradation from Na3V2(PO4)3 to V2(PO4)3: F-doped Na3V2(PO4)3/C cathode composite with stable lifetime for sodium ion batteries

NASA Astrophysics Data System (ADS)

Chen, Yanjun; Xu, Youlong; Sun, Xiaofei; Zhang, Baofeng; He, Shengnan; Li, Long; Wang, Chao

2018-02-01

A prospective NASICON-type F-doped Na3V2(PO4)2.93F0.07/C (F-0.07-NVP/C) composite is synthesized by a solid-state reaction method. F-doping can restrain the structural degradation from Na3V2(PO4)3 to V2(PO4)3 and enhance the structural stability. Meanwhile, it can decrease the particle size to diminish the pathway of Na+ diffusion, which can increase ionic conductivity efficiently. The kinetic behavior is significantly improved and it is beneficial to reinforcing the electrochemical performance of F-doping composites. Compared with Undoped-NVP/C sample, F-0.07-NVP/C composite delivers a 113 mAh g-1 discharge capacity at 10 mA g-1, which is very close to the theoretical capacity (117 mAh g-1). As for cycle performance, a reversible capacity of 97.8 mAh g-1 can be obtained and it retains 86% capacity after 1000 cycles at 200 mA g-1. F-0.07-NVP/C composite presents the highest DNa+ (2.62 × 10-15 cm2s-1), two orders of magnitude higher than the undoped sample (4.8 × 10-17 cm2s-1). This outstanding electrochemical performance is ascribed to the synergetic effect from improved kinetic behavior and enhanced structural stability due to F-doping. Hence, the F-doped composite would be a promising cathode material in SIB for energy storage and conversion.

Mo-doped Na3V2(PO4)3@C composites for high stable sodium ion battery cathode

NASA Astrophysics Data System (ADS)

Wang, Xiaoxiao; Wang, Wanwan; Zhu, Baichuan; Qian, Fangfang; Fang, Zhen

2018-03-01

NASICON-type Na3V2(PO4)3 (NVP) with superior electrochemical performance has attracted enormous attention with the development of sodium ion batteries. The structural aggregation as well as poor conductivity of NVP hinder its application in high rate perforamance cathode with long stablity. In this paper, Na3V2- x Mo x (PO4)3@C was successfully prepared through two steps method, including sol-gel and solid state thermal reduction. The optimal doping amount of Mo was defined by experiment. When x was 0.15, the Na3V1.85Mo0.15(PO4)3@C sample has the best cycle performance and rate performance. The discharge capacity of Na3V1.85Mo0.15(PO4)3@C could reach 117.26 mA·h·g-1 at 0.1 C. The discharge capacity retention was found to be 94.5% after 600 cycles at 5 C.

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.

Multi-heteroatom doped carbon coated Na3V2(PO4)3 derived from ionic liquids.

PubMed

Zhang, Lu-Lu; Zhou, Ying-Xian; Li, Tao; Ma, Di; Yang, Xue-Lin

2018-03-28

Multi-heteroatom (N, S and F) doped carbon coated Na 3 V 2 (PO 4 ) 3 (labeled as NVP/C-ILs) derived from an ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM]TF2N) has been successfully fabricated. The as-prepared Na 3 V 2 (PO 4 ) 3 particles are well dispersed and closely coated with a multi-heteroatom (N, S and F) doped carbon layer. As a cathode for sodium-ion batteries, the NVP/C-ILs electrode exhibits high reversible specific capacity (117.5 mA h g -1 at 1C), superior rate performance (93.4 mA h g -1 at 10C) and excellent cycling stability (∼95% capacity retention ratio at 10C over 1000 cycles). The impressive electrochemical performance of NVP/C-ILs can be attributed to effectively conductive networks for electrons and Na + ions induced by a joint effect of N, S and F doping on carbon. The use of multi-heteroatom doped carbon coated Na 3 V 2 (PO 4 ) 3 provides a facile and effective strategy for the fabrication of high performance electrode materials with low intrinsic electrical conductivity.

Structure-activity relationships for the action of 11 pyrethroid insecticides on rat Na{sub v}1.8 sodium channels expressed in Xenopus oocytes

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

Choi, J.-S.; Soderlund, David M.

2006-03-15

Pyrethroid insecticides bind to voltage-sensitive sodium channels and modify their gating kinetics, thereby disrupting nerve function. This paper describes the action of 11 structurally diverse commercial pyrethroid insecticides on the rat Na{sub v}1.8 sodium channel isoform, the principal carrier of the tetrodotoxin-resistant, pyrethroid-sensitive sodium current of sensory neurons, expressed in Xenopus laevis oocytes. All 11 compounds produced characteristic sodium tail currents following a depolarizing pulse that ranged from rapidly-decaying monoexponential currents (allethrin, cismethrin and permethrin) to persistent biexponential currents (cyfluthrin, cyhalothrin, cypermethrin and deltamethrin). Tail currents for the remaining compounds (bifenthrin, fenpropathrin, fenvalerate and tefluthrin) were monoexponential and decayed withmore » kinetics intermediate between these extremes. Reconstruction of currents carried solely by the pyrethroid-modified subpopulation of channels revealed two types of pyrethroid-modified currents. The first type, found with cismethrin, allethrin, permethrin and tefluthrin, activated relatively rapidly and inactivated partially during a 40-ms depolarization. The second type, found with cypermethrin, cyfluthrin, cyhalothrin, deltamethrin, fenpropathrin and fenvalerate, activated more slowly and did not detectably inactivate during a 40-ms depolarization. Only bifenthrin did not produce modified currents that fit clearly into either of these categories. In all cases, the rate of activation of modified channels was strongly correlated with the rate of tail current decay following repolarization. Modification of Na{sub v}1.8 sodium channels by cyfluthrin, cyhalothrin, cypermethrin and deltamethrin was enhanced 2.3- to 3.4-fold by repetitive stimulation; this effect appeared to result from the accumulation of persistently open channels rather than preferential binding to open channel states. Fenpropathrin was the most effective compound

The V-ATPase subunit A is essential for salt tolerance through participating in vacuolar Na+ compartmentalization in Salicornia europaea.

PubMed

Lv, Sulian; Jiang, Ping; Tai, Fang; Wang, Duoliya; Feng, Juanjuan; Fan, Pengxiang; Bao, Hexigeduleng; Li, Yinxin

2017-12-01

The V-ATPase subunit A participates in vacuolar Na + compartmentalization in Salicornia europaea regulating V-ATPase and V-PPase activities. Na + sequestration into the vacuole is an efficient strategy in response to salinity in many halophytes. However, it is not yet fully understood how this process is achieved. Particularly, the role of vacuolar H + -ATPase (V-ATPase) in this process is controversial. Our previous proteomic investigation in the euhalophyte Salicornia europaea L. found a significant increase of the abundance of V-ATPase subunit A under salinity. Here, the gene encoding this subunit named SeVHA-A was characterized, and its role in salt tolerance was demonstrated by RNAi directed downregulation in suspension-cultured cells of S. europaea. The transcripts of genes encoding vacuolar H + -PPase (V-PPase) and vacuolar Na + /H + antiporter (SeNHX1) also decreased significantly in the RNAi cells. Knockdown of SeVHA-A resulted in a reduction in both V-ATPase and vacuolar H + -PPase (V-PPase) activities. Accordingly, the SeVHA-A-RNAi cells showed increased vacuolar pH and decreased cell viability under different NaCl concentrations. Further Na + staining showed the reduced vacuolar Na + sequestration in RNAi cells. Taken together, our results evidenced that SeVHA-A participates in vacuolar Na + sequestration regulating V-ATPase and V-PPase activities and thereby vacuolar pH in S. europaea. The possible mechanisms underlying the reduction of vacuolar V-PPase activity in SeVHA-A-RNAi cells were also discussed.

Intracellular pH regulation in unstimulated Calliphora salivary glands is Na+ dependent and requires V-ATPase activity.

PubMed

Schewe, Bettina; Blenau, Wolfgang; Walz, Bernd

2012-04-15

Salivary gland cells of the blowfly Calliphora vicina have a vacuolar-type H(+)-ATPase (V-ATPase) that lies in their apical membrane and energizes the secretion of a KCl-rich primary saliva upon stimulation with serotonin (5-hydroxytryptamine). Whether and to what extent V-ATPase contributes to intracellular pH (pH(i)) regulation in unstimulated gland cells is unknown. We used the fluorescent dye BCECF to study intracellular pH(i) regulation microfluorometrically and show that: (1) under resting conditions, the application of Na(+)-free physiological saline induces an intracellular alkalinization attributable to the inhibition of the activity of a Na(+)-dependent glutamate transporter; (2) the maintenance of resting pH(i) is Na(+), Cl(-), concanamycin A and DIDS sensitive; (3) recovery from an intracellular acid load is Na(+) sensitive and requires V-ATPase activity; (4) the Na(+)/H(+) antiporter is not involved in pH(i) recovery after a NH(4)Cl prepulse; and (5) at least one Na(+)-dependent transporter and the V-ATPase maintain recovery from an intracellular acid load. Thus, under resting conditions, the V-ATPase and at least one Na(+)-dependent transporter maintain normal pH(i) values of pH 7.5. We have also detected the presence of a Na(+)-dependent glutamate transporter, which seems to act as an acid loader. Despite this not being a common pH(i)-regulating transporter, its activity affects steady-state pH(i) in C. vicina salivary gland cells.

Controlled phase stability of highly Na-active triclinic structure in nanoscale high-voltage Na2-2xCo1+xP2O7 cathode for Na-ion batteries

NASA Astrophysics Data System (ADS)

Song, Hee Jo; Kim, Jae-Chan; Dar, Mushtaq Ahmad; Kim, Dong-Wan

2018-02-01

With the increasing demand for high energy density in energy-storage systems, a high-voltage cathode is essential in rechargeable Li-ion and Na-ion batteries. The operating voltage of a triclinic-polymorph Na2CoP2O7, also known as the rose form, is above 4.0 V (vs. Na/Na+), which is relatively high compared to that of other cathode materials. Thus, it can be employed as a potential high-voltage cathode material in Na-ion batteries. However, it is difficult to synthesize a pure rose phase because of its low phase stability, thus limiting its use in high-voltage applications. Herein, compositional-engineered, rose-phase Na2-2xCo1+xP2O7/C (x = 0, 0.1 and 0.2) nanopowder are prepared using a wet-chemical method. The Na2-2xCo1+xP2O7/C cathode shows high electrochemical reactivity with Na ions at 4.0 V, delivering high capacity and high energy density.

A novel frequency analysis method for assessing K(ir)2.1 and Na (v)1.5 currents.

PubMed

Rigby, J R; Poelzing, S

2012-04-01

Voltage clamping is an important tool for measuring individual currents from an electrically active cell. However, it is difficult to isolate individual currents without pharmacological or voltage inhibition. Herein, we present a technique that involves inserting a noise function into a standard voltage step protocol, which allows one to characterize the unique frequency response of an ion channel at different step potentials. Specifically, we compute the fast Fourier transform for a family of current traces at different step potentials for the inward rectifying potassium channel, K(ir)2.1, and the channel encoding the cardiac fast sodium current, Na(v)1.5. Each individual frequency magnitude, as a function of voltage step, is correlated to the peak current produced by each channel. The correlation coefficient vs. frequency relationship reveals that these two channels are associated with some unique frequencies with high absolute correlation. The individual IV relationship can then be recreated using only the unique frequencies with magnitudes of high absolute correlation. Thus, this study demonstrates that ion channels may exhibit unique frequency responses.

Differential effects of five 'classical' scorpion {beta}-toxins on rNa{sub v}1.2a and DmNav1 provide clues on species-selectivity

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

Bosmans, Frank; Martin-Eauclaire, Marie-France; Tytgat, Jan

2007-01-01

In general, scorpion {beta}-toxins have been well examined. However, few in-depth studies have been devoted to species selectivity and affinity comparisons on the different voltage-activated Na{sup +} channels since they have become available as cloned channels that can be studied in heterologous expression systems. As a result, their classification is largely historical and dates from early in vivo experiments on mice and cockroach and fly larvae. In this study, we aimed to provide an updated overview of selectivity and affinity of scorpion {beta}-toxins towards voltage-activated Na{sup +} channels of vertebrates or invertebrates. As pharmacological tools, we used the classic {beta}-toxinsmore » AaHIT, Css II, Css IV, Css VI and Ts VII and tested them on the neuronal vertebrate voltage-activated Na{sup +} channel, rNa{sub v}1.2a. For comparison, its invertebrate counterpart, DmNav1, was also tested. Both these channels were expressed in Xenopus laevis oocytes and the currents measured with the two-electrode voltage-clamp technique. We supplemented this data with several binding displacement studies on rat brain synaptosomes. The results lead us to propose a general classification and a novel nomenclature of scorpion {beta}-toxins based on pharmacological activity.« less

Experimental studies of the NaK 1 3Δ state

NASA Astrophysics Data System (ADS)

Huennekens, J.; Prodan, I.; Marks, A.; Sibbach, L.; Galle, E.; Morgus, T.; Li, Li

2000-11-01

The NaK 1 3Δ state has been studied by the perturbation-facilitated optical-optical double resonance technique. Mixed singlet-triplet levels, A(2)1Σ+(vA,J)˜b(1)3Π(vb,J), were pumped from thermally populated rovibrational levels of the ground state, X(1)1Σ+(vX,J±1), using a single-mode cw dye laser. A single-mode cw Ti:Sapphire laser was then used to further excite the NaK molecules to various 1 3Δ(vΔ,NΔ,JΔ) rovibrational levels which were detected by observing collision-induced 3Λ→a(1)3Σ+ fluorescence in the green part of the spectrum. The measured energies of the 1 3Δ(vΔ,NΔ) levels were fit to a Dunham expansion, and the Dunham coefficients were used to construct the RKR potential curve. Absolute numbering of the 1 3Δ state vibrational levels was established by a comparison of experimental and calculated 1 3Δ(vΔ,NΔ,JΔ)←b(1)3Π(vb,Jb) absorption line strengths. A deperturbation program was used to determine the vibration-dependent 1 3Δ state spin-orbit interaction parameter. Hyperfine structure of the 1 3Δ state was studied, and the Fermi-contact interaction term for this state was determined to be ˜0.0111 cm-1.

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

Polar materials with isolated V 4+ S = 1/2 Triangles: NaSr 2V 3O 3(Ge 4O 13)Cl and KSr 2V 3O 3(Ge 4O 13)Cl

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

Sanjeewa, Liurukara D.; McGuire, Michael A.; McMillen, Colin D.

Here, crystals of ASr 2V 3O 3(Ge 4O 13)Cl, A = Na, K, were synthesized from high-temperature hydrothermal brines, and their structure and magnetic properties were investigated. These materials present a unique combination of a salt inclusion lattice, a polar crystal structure, and isolated V 4+ ( S = 1/2) trimer magnetic clusters. The structures consist of a trimeric V 3O 13 unit based on V 4+ ( S = 1/2), having rigorous 3-fold symmetry with a short V–V separation of 3.325(3) Å. The trinuclear V 4+ units are formed by three edge shared VO 6 octahedra sharing a centralmore » μ3-oxygen atom, which also imparts a polar sense on the structure. The V 3O 13 units are isolated from one another by tetranuclear Ge 4O 13 units, which are similarly arranged in a polar fashion, providing a unique opportunity to study the magnetic behavior of this triangular d 1 system as a discrete unit. Magnetization measurements indicate spin-1/2 per V atom at high temperature, and spin-1/2 per V 3 trimer at low temperature, where two V moments in each triangle are antiferromagnetically aligned and the third remains paramagnetic. The crossover between these two behaviors occurs between 20 and 100 K and is well-described by a model incorporating strong antiferromagnetic intra-trimer interactions and weak but nonzero inter-trimer interactions. More broadly, the study highlights the ability to obtain new materials with interesting structure–property relationships via chemistry involving unconventional solvents and reaction conditions.« less

Polar materials with isolated V 4+ S = 1/2 Triangles: NaSr 2V 3O 3(Ge 4O 13)Cl and KSr 2V 3O 3(Ge 4O 13)Cl

DOE PAGES

Sanjeewa, Liurukara D.; McGuire, Michael A.; McMillen, Colin D.; ...

2017-01-03

Here, crystals of ASr 2V 3O 3(Ge 4O 13)Cl, A = Na, K, were synthesized from high-temperature hydrothermal brines, and their structure and magnetic properties were investigated. These materials present a unique combination of a salt inclusion lattice, a polar crystal structure, and isolated V 4+ ( S = 1/2) trimer magnetic clusters. The structures consist of a trimeric V 3O 13 unit based on V 4+ ( S = 1/2), having rigorous 3-fold symmetry with a short V–V separation of 3.325(3) Å. The trinuclear V 4+ units are formed by three edge shared VO 6 octahedra sharing a centralmore » μ3-oxygen atom, which also imparts a polar sense on the structure. The V 3O 13 units are isolated from one another by tetranuclear Ge 4O 13 units, which are similarly arranged in a polar fashion, providing a unique opportunity to study the magnetic behavior of this triangular d 1 system as a discrete unit. Magnetization measurements indicate spin-1/2 per V atom at high temperature, and spin-1/2 per V 3 trimer at low temperature, where two V moments in each triangle are antiferromagnetically aligned and the third remains paramagnetic. The crossover between these two behaviors occurs between 20 and 100 K and is well-described by a model incorporating strong antiferromagnetic intra-trimer interactions and weak but nonzero inter-trimer interactions. More broadly, the study highlights the ability to obtain new materials with interesting structure–property relationships via chemistry involving unconventional solvents and reaction conditions.« less

K + block is the mechanism of functional asymmetry in bacterial Na v channels

DOE PAGES

Ngo, Van; Wang, Yibo; Haas, Stephan; ...

2016-01-04

Crystal structures of several bacterial Na v channels have been recently published and molecular dynamics simulations of ion permeation through these channels are consistent with many electrophysiological properties of eukaryotic channels. Bacterial Na v channels have been characterized as functionally asymmetric, and the mechanism of this asymmetry has not been clearly understood. To address this question, we combined non-equilibrium simulation data with two-dimensional equilibrium unperturbed landscapes generated by umbrella sampling and Weighted Histogram Analysis Methods for multiple ions traversing the selectivity filter of bacterial Na vAb channel. This approach provided new insight into the mechanism of selective ion permeation inmore » bacterial Nav channels. The non-equilibrium simulations indicate that two or three extracellular K + ions can block the entrance to the selectivity filter of Na vAb in the presence of applied forces in the inward direction, but not in the outward direction. The block state occurs in an unstable local minimum of the equilibrium unperturbed free-energy landscape of two K+ ions that can be ‘locked’ in place bymodest applied forces. In contrast to K +, three Na + ions move favorably through the selectivity filter together as a unit in a loose “knock-on” mechanism of permeation in both inward and outward directions, and there is no similar local minimum in the two-dimensional free-energy landscape of two Na + ions for a block state. The useful work predicted by the non-equilibrium simulations that is required to break the K + block is equivalent to large applied potentials experimentally measured for two bacterial Na v channels to induce inward currents of K + ions. Here, these results illustrate how inclusion of non-equilibrium factors in the simulations can provide detailed information about mechanisms of ion selectivity that is missing from mechanisms derived from either crystal structures or equilibrium unperturbed

Experimental Study of the NaK 3(1)Pi State.

PubMed

Laub; Mazsa; Webb; La Civita J; Prodan; Jabbour; Namiotka; Huennekens

1999-02-01

We report the results of an optical-optical double resonance experiment to determine the NaK 3(1)Pi state potential energy curve. In the first step, a narrow band cw dye laser (PUMP) is tuned to line center of a particular 2(A)1Sigma+(v', J') <-- 1(X)1Sigma+(v", J") transition, and its frequency is then fixed. A second narrowband tunable cw Ti:Sapphirelaser (PROBE) is then scanned, while 3(1)Pi --> 1(X)1Sigma+ violet fluorescence is monitored. The Doppler-free signals accurately map the 3(1)Pi(v, J) ro-vibrational energy levels. These energy levels are then fit to a Dunham expansion to provide a set of molecular constants. The Dunham constants, in turn, are used to construct an RKR potential curve. Resolved 3(1)Pi(v, J) --> 1(X)1Sigma+(v", J") fluorescence scans are also recorded with both PUMP and PROBE laser frequencies fixed. Comparison between observed and calculated Franck-Condon factors is used to determine the absolute vibrational numbering of the 3(1)Pi state levels and to determine the variation of the 3(1)Pi --> 1(X)1Sigma+ transitiondipole moment with internuclear separation. The recent theoretical calculation of the NaK 3(1)Pi state potential reported by Magnier and Millié (1996, Phys. Rev. A 54, 204) is in excellent agreement with the present experimental RKR curve. Copyright 1999 Academic Press.

Impaired action potential initiation in GABAergic interneurons causes hyperexcitable networks in an epileptic mouse model carrying a human Na(V)1.1 mutation.

PubMed

Hedrich, Ulrike B S; Liautard, Camille; Kirschenbaum, Daniel; Pofahl, Martin; Lavigne, Jennifer; Liu, Yuanyuan; Theiss, Stephan; Slotta, Johannes; Escayg, Andrew; Dihné, Marcel; Beck, Heinz; Mantegazza, Massimo; Lerche, Holger

2014-11-05

Mutations in SCN1A and other ion channel genes can cause different epileptic phenotypes, but the precise mechanisms underlying the development of hyperexcitable networks are largely unknown. Here, we present a multisystem analysis of an SCN1A mouse model carrying the NaV1.1-R1648H mutation, which causes febrile seizures and epilepsy in humans. We found a ubiquitous hypoexcitability of interneurons in thalamus, cortex, and hippocampus, without detectable changes in excitatory neurons. Interestingly, somatic Na(+) channels in interneurons and persistent Na(+) currents were not significantly changed. Instead, the key mechanism of interneuron dysfunction was a deficit of action potential initiation at the axon initial segment that was identified by analyzing action potential firing. This deficit increased with the duration of firing periods, suggesting that increased slow inactivation, as recorded for recombinant mutated channels, could play an important role. The deficit in interneuron firing caused reduced action potential-driven inhibition of excitatory neurons as revealed by less frequent spontaneous but not miniature IPSCs. Multiple approaches indicated increased spontaneous thalamocortical and hippocampal network activity in mutant mice, as follows: (1) more synchronous and higher-frequency firing was recorded in primary neuronal cultures plated on multielectrode arrays; (2) thalamocortical slices examined by field potential recordings revealed spontaneous activities and pathological high-frequency oscillations; and (3) multineuron Ca(2+) imaging in hippocampal slices showed increased spontaneous neuronal activity. Thus, an interneuron-specific generalized defect in action potential initiation causes multisystem disinhibition and network hyperexcitability, which can well explain the occurrence of seizures in the studied mouse model and in patients carrying this mutation. Copyright © 2014 the authors 0270-6474/14/3414874-16$15.00/0.

Combined sodium ion sensitivity in agonist binding and internalization of vasopressin V1b receptors.

PubMed

Koshimizu, Taka-Aki; Kashiwazaki, Aki; Taniguchi, Junichi

2016-05-03

Reducing Na(+) in the extracellular environment may lead to two beneficial effects for increasing agonist binding to cell surface G-protein coupled receptors (GPCRs): reduction of Na(+)-mediated binding block and reduce of receptor internalization. However, such combined effects have not been explored. We used Chinese Hamster Ovary cells expressing vasopressin V1b receptors as a model to explore Na(+) sensitivity in agonist binding and receptor internalization. Under basal conditions, a large fraction of V1b receptors is located intracellularly, and a small fraction is in the plasma membrane. Decreases in external Na(+) increased cell surface [(3)H]AVP binding and decreased receptor internalization. Substitution of Na(+) by Cs(+) or NH4(+) inhibited agonist binding. To suppress receptor internalization, the concentration of NaCl, but not of CsCl, had to be less than 50 mM, due to the high sensitivity of the internalization machinery to Na(+) over Cs(+). Iso-osmotic supplementation of glucose or NH4Cl maintained internalization of the V1b receptor, even in a low-NaCl environment. Moreover, iodide ions, which acted as a counter anion, inhibited V1b agonist binding. In summary, we found external ionic conditions that could increase the presence of high-affinity state receptors at the cell surface with minimum internalization during agonist stimulations.

Combined sodium ion sensitivity in agonist binding and internalization of vasopressin V1b receptors

PubMed Central

Koshimizu, Taka-aki; Kashiwazaki, Aki; Taniguchi, Junichi

2016-01-01

Reducing Na+ in the extracellular environment may lead to two beneficial effects for increasing agonist binding to cell surface G-protein coupled receptors (GPCRs): reduction of Na+-mediated binding block and reduce of receptor internalization. However, such combined effects have not been explored. We used Chinese Hamster Ovary cells expressing vasopressin V1b receptors as a model to explore Na+ sensitivity in agonist binding and receptor internalization. Under basal conditions, a large fraction of V1b receptors is located intracellularly, and a small fraction is in the plasma membrane. Decreases in external Na+ increased cell surface [3H]AVP binding and decreased receptor internalization. Substitution of Na+ by Cs+ or NH4+ inhibited agonist binding. To suppress receptor internalization, the concentration of NaCl, but not of CsCl, had to be less than 50 mM, due to the high sensitivity of the internalization machinery to Na+ over Cs+. Iso-osmotic supplementation of glucose or NH4Cl maintained internalization of the V1b receptor, even in a low-NaCl environment. Moreover, iodide ions, which acted as a counter anion, inhibited V1b agonist binding. In summary, we found external ionic conditions that could increase the presence of high-affinity state receptors at the cell surface with minimum internalization during agonist stimulations. PMID:27138239

Ordered and disordered polymorphs of Na(Ni 2/3Sb 1/3)O₂: Honeycomb-ordered cathodes for Na-ion batteries

DOE PAGES

Ma, Jeffrey; Wu, Lijun; Bo, Shou -Hang; ...

2015-04-14

Na-ion batteries are appealing alternatives to Li-ion battery systems for large-scale energy storage applications in which elemental cost and abundance are important. Although it is difficult to find Na-ion batteries which achieve substantial specific capacities at voltages above 3 V (vs Na⁺/Na), the honeycomb-layered compound Na(Ni 2/3Sb 1/3)O₂ can deliver up to 130 mAh/g of capacity at voltages above 3 V with this capacity concentrated in plateaus at 3.27 and 3.64 V. Comprehensive crystallographic studies have been carried out in order to understand the role of disorder in this system which can be prepared in both “disordered” and “ordered” forms,more » depending on the synthesis conditions. The average structure of Na(Ni 2/3Sb 1/3)O₂ is always found to adopt an O3-type stacking sequence, though different structures for the disordered (R3¯ m, #166, a = b = 3.06253(3) Å and c = 16.05192(7) Å) and ordered variants ( C2/m, #12, a = 5.30458(1) Å, b = 9.18432(1) Å, c = 5.62742(1) Å and β = 108.2797(2)°) are demonstrated through the combined Rietveld refinement of synchrotron X-ray and time-of-flight neutron powder diffraction data. However, pair distribution function studies find that the local structure of disordered Na(Ni 2/3Sb 1/3)O₂ is more correctly described using the honeycomb-ordered structural model, and solid state NMR studies confirm that the well-developed honeycomb ordering of Ni and Sb cations within the transition metal layers is indistinguishable from that of the ordered phase. The disorder is instead found to mainly occur perpendicular to the honeycomb layers with an observed coherence length of not much more than 1 nm seen in electron diffraction studies. When the Na environment is probed through ²³Na solid state NMR, no evidence is found for prismatic Na environments, and a bulk diffraction analysis finds no evidence of conventional stacking faults. The lack of long range coherence is instead attributed to disorder among

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

High-Resolution Structure and Mechanism of an F/V-Hybrid Rotor Ring in a Na+-coupled ATP Synthase

PubMed Central

Matthies, Doreen; Zhou, Wenchang; Klyszejko, Adriana L.; Anselmi, Claudio; Yildiz, Özkan; Brandt, Karsten; Müller, Volker; Faraldo-Gómez, José D.; Meier, Thomas

2014-01-01

All rotary ATPases catalyze the interconversion of ATP and ADP-Pi through a mechanism that is coupled to the transmembrane flow of H+ or Na+. Physiologically, however, F/A-type enzymes specialize in ATP synthesis driven by downhill ion diffusion, while eukaryotic V-type ATPases function as ion pumps. To begin to rationalize the molecular basis for this functional differentiation, we solved the crystal structure of the Na+-driven membrane rotor of the Acetobacterium woodii ATP synthase, at 2.1 Å resolution. Unlike known structures, this rotor ring is a 9:1 heteromer of F- and V-type c-subunits, and therefore features a hybrid configuration of ion-binding sites along its circumference. Molecular and kinetic simulations are used to dissect the mechanisms of Na+ recognition and rotation of this c-ring, and to explain the functional implications of the V-type c-subunit. These structural and mechanistic insights indicate an evolutionary path between synthases and pumps involving adaptations in the rotor ring. PMID:25381992

Experimental Study of the NaK 3 1Π State

NASA Astrophysics Data System (ADS)

Laub, E.; Mazsa, I.; Webb, S. C.; La Civita, J.; Prodan, I.; Jabbour, Z. J.; Namiotka, R. K.; Huennekens, J.

1999-02-01

We report the results of an optical-optical double resonance experiment to determine the NaK 31Π state potential energy curve. In the first step, a narrow band cw dye laser (PUMP) is tuned to line center of a particular 2(A)1Σ+(v‧,J‧) ← 1(X)1Σ+(v",J") transition, and its frequency is then fixed. A second narrowband tunable cw Ti:Sapphirelaser (PROBE) is then scanned, while 31Π → 1(X)1Σ+violet fluorescence is monitored. The Doppler-free signals accurately map the 31Π(v,J) ro-vibrational energy levels. These energy levels are then fit to a Dunham expansion to provide a set of molecular constants. The Dunham constants, in turn, are used to construct an RKR potential curve. Resolved 31Π(v,J) → 1(X)1Σ+(v",J") fluorescence scans are also recorded with both PUMP and PROBE laser frequencies fixed. Comparison between observed and calculated Franck-Condon factors is used to determine the absolute vibrational numbering of the 31Π state levels and to determine the variation of the 31Π → 1(X)1Σ+transitiondipole moment with internuclear separation. The recent theoretical calculation of the NaK 31Π state potential reported by Magnier and Millié (1996,Phys. Rev. A54, 204) is in excellent agreement with the present experimental RKR curve.

FTIR spectra of the solid solutions (Na0.88K0.12)VO3, (Na0.5K0.5)VO3, and Na(V0.66P0.34)O3

NASA Astrophysics Data System (ADS)

de Waal, D.; Heyns, A. M.

1992-03-01

It is known that three different solid solutions, (Na0.88K0.12)VO3, (Na0.5K0.5)VO3 and Na(V0.66P0.34)O3, form in the (Na,K)(V,P)O3 system. These compounds all have monoclinic crystal structures similar to the pure alkali metal metavanadates containing small cations, e.g. Li+ and Na+ (Space group C2/c). Metavanadates with large cations like K+, Rb+, C+s and NH+4 form orthorhombic crystals, space group Pbcm. All those are structurally related to the silicate pyroxenes. Na(V0.66P0.34)O3 and (Na0.88K0.12)VO3 have the same modified diopside structure as (alpha) - NaVO3 while (Na0.5K0.5)VO3 adopts the true diopside structure. The infrared spectra of the three solid solutions are reported here in comparison with those of (alpha) -NaVO3 and KVO3. The results are also correlated with those obtained in two independent high pressure Raman studies of NH4VO3 and RbVO3 as the introduction of a larger cation like K+ should increase the pressure in the structure.

High-Performance 2.6 V Aqueous Asymmetric Supercapacitors based on In Situ Formed Na0.5 MnO2 Nanosheet Assembled Nanowall Arrays.

PubMed

Jabeen, Nawishta; Hussain, Ahmad; Xia, Qiuying; Sun, Shuo; Zhu, Junwu; Xia, Hui

2017-08-01

The voltage limit for aqueous asymmetric supercapacitors is usually 2 V, which impedes further improvement in energy density. Here, high Na content Birnessite Na 0.5 MnO 2 nanosheet assembled nanowall arrays are in situ formed on carbon cloth via electrochemical oxidation. It is interesting to find that the electrode potential window for Na 0.5 MnO 2 nanowall arrays can be extended to 0-1.3 V (vs Ag/AgCl) with significantly increased specific capacitance up to 366 F g -1 . The extended potential window for the Na 0.5 MnO 2 electrode provides the opportunity to further increase the cell voltage of aqueous asymmetric supercapacitors beyond 2 V. To construct the asymmetric supercapacitor, carbon-coated Fe 3 O 4 nanorod arrays are synthesized as the anode and can stably work in a negative potential window of -1.3 to 0 V (vs Ag/AgCl). For the first time, a 2.6 V aqueous asymmetric supercapacitor is demonstrated by using Na 0.5 MnO 2 nanowall arrays as the cathode and carbon-coated Fe 3 O 4 nanorod arrays as the anode. In particular, the 2.6 V Na 0.5 MnO 2 //Fe 3 O 4 @C asymmetric supercapacitor exhibits a large energy density of up to 81 Wh kg -1 as well as excellent rate capability and cycle performance, outperforming previously reported MnO 2 -based supercapacitors. This work provides new opportunities for developing high-voltage aqueous asymmetric supercapacitors with further increased energy density. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dysfunction of NaV1.4, a skeletal muscle voltage-gated sodium channel, in sudden infant death syndrome: a case-control study.

PubMed

Männikkö, Roope; Wong, Leonie; Tester, David J; Thor, Michael G; Sud, Richa; Kullmann, Dimitri M; Sweeney, Mary G; Leu, Costin; Sisodiya, Sanjay M; FitzPatrick, David R; Evans, Margaret J; Jeffrey, Iona J M; Tfelt-Hansen, Jacob; Cohen, Marta C; Fleming, Peter J; Jaye, Amie; Simpson, Michael A; Ackerman, Michael J; Hanna, Michael G; Behr, Elijah R; Matthews, Emma

2018-04-14

Sudden infant death syndrome (SIDS) is the leading cause of post-neonatal infant death in high-income countries. Central respiratory system dysfunction seems to contribute to these deaths. Excitation that drives contraction of skeletal respiratory muscles is controlled by the sodium channel NaV1.4, which is encoded by the gene SCN4A. Variants in NaV1.4 that directly alter skeletal muscle excitability can cause myotonia, periodic paralysis, congenital myopathy, and myasthenic syndrome. SCN4A variants have also been found in infants with life-threatening apnoea and laryngospasm. We therefore hypothesised that rare, functionally disruptive SCN4A variants might be over-represented in infants who died from SIDS. We did a case-control study, including two consecutive cohorts that included 278 SIDS cases of European ancestry and 729 ethnically matched controls without a history of cardiovascular, respiratory, or neurological disease. We compared the frequency of rare variants in SCN4A between groups (minor allele frequency <0·00005 in the Exome Aggregation Consortium). We assessed biophysical characterisation of the variant channels using a heterologous expression system. Four (1·4%) of the 278 infants in the SIDS cohort had a rare functionally disruptive SCN4A variant compared with none (0%) of 729 ethnically matched controls (p=0·0057). Rare SCN4A variants that directly alter NaV1.4 function occur in infants who had died from SIDS. These variants are predicted to significantly alter muscle membrane excitability and compromise respiratory and laryngeal function. These findings indicate that dysfunction of muscle sodium channels is a potentially modifiable risk factor in a subset of infant sudden deaths. UK Medical Research Council, the Wellcome Trust, National Institute for Health Research, the British Heart Foundation, Biotronik, Cardiac Risk in the Young, Higher Education Funding Council for England, Dravet Syndrome UK, the Epilepsy Society, the Eunice Kennedy

Novel Rechargeable M3V2(PO4)3//Zinc (M = Li, Na) Hybrid Aqueous Batteries with Excellent Cycling Performance

PubMed Central

Zhao, H. B.; Hu, C. J.; Cheng, H. W.; Fang, J. H.; Xie, Y. P.; Fang, W. Y.; Doan, T. N. L.; Hoang, T. K. A.; Xu, J. Q.; Chen, P.

2016-01-01

A rechargeable hybrid aqueous battery (ReHAB) containing NASICON-type M3V2(PO4)3 (M = Li, Na) as the cathodes and Zinc metal as the anode, working in Li2SO4-ZnSO4 aqueous electrolyte, has been studied. Both of Li3V2(PO4)3 and Na3V2(PO4)3 cathodes can be reversibly charge/discharge with the initial discharge capacity of 128 mAh g−1 and 96 mAh g−1 at 0.2C, respectively, with high up to 84% of capacity retention ratio after 200 cycles. The electrochemical assisted ex-XRD confirm that Li3V2(PO4)3 and Na3V2(PO4)3 are relative stable in aqueous electrolyte, and Na3V2(PO4)3 showed more complicated electrochemical mechanism due to the co-insertion of Li+ and Na+. The effect of pH of aqueous electrolyte and the dendrite of Zn on the cycling performance of as designed MVP/Zn ReHABs were investigated, and weak acidic aqueous electrolyte with pH around 4.0–4.5 was optimized. The float current test confirmed that the designed batteries are stable in aqueous electrolytes. The MVP//Zn ReHABs could be a potential candidate for future rechargeable aqueous battery due to their high safety, fast dynamic speed and adaptable electrochemical window. Moreover, this hybrid battery broadens the scope of battery material research from single-ion-involving to double-ions -involving rechargeable batteries. PMID:27174224

Novel Rechargeable M3V2(PO4)3//Zinc (M = Li, Na) Hybrid Aqueous Batteries with Excellent Cycling Performance

NASA Astrophysics Data System (ADS)

Zhao, H. B.; Hu, C. J.; Cheng, H. W.; Fang, J. H.; Xie, Y. P.; Fang, W. Y.; Doan, T. N. L.; Hoang, T. K. A.; Xu, J. Q.; Chen, P.

2016-05-01

A rechargeable hybrid aqueous battery (ReHAB) containing NASICON-type M3V2(PO4)3 (M = Li, Na) as the cathodes and Zinc metal as the anode, working in Li2SO4-ZnSO4 aqueous electrolyte, has been studied. Both of Li3V2(PO4)3 and Na3V2(PO4)3 cathodes can be reversibly charge/discharge with the initial discharge capacity of 128 mAh g-1 and 96 mAh g-1 at 0.2C, respectively, with high up to 84% of capacity retention ratio after 200 cycles. The electrochemical assisted ex-XRD confirm that Li3V2(PO4)3 and Na3V2(PO4)3 are relative stable in aqueous electrolyte, and Na3V2(PO4)3 showed more complicated electrochemical mechanism due to the co-insertion of Li+ and Na+. The effect of pH of aqueous electrolyte and the dendrite of Zn on the cycling performance of as designed MVP/Zn ReHABs were investigated, and weak acidic aqueous electrolyte with pH around 4.0-4.5 was optimized. The float current test confirmed that the designed batteries are stable in aqueous electrolytes. The MVP//Zn ReHABs could be a potential candidate for future rechargeable aqueous battery due to their high safety, fast dynamic speed and adaptable electrochemical window. Moreover, this hybrid battery broadens the scope of battery material research from single-ion-involving to double-ions -involving rechargeable batteries.

Ultrasonic-assisted solution combustion synthesis of porous Na3V2(PO4)3/C: formation mechanism and sodium storage performance

NASA Astrophysics Data System (ADS)

Chen, Qiuyun; Liu, Qing; Chu, Xiangcheng; Zhang, Yiling; Yan, Youwei; Xue, Lihong; Zhang, Wuxing

2017-04-01

Solution combustion synthesis (SCS) is an effective and rapid method for synthesizing nanocrystalline materials. However, the control over size, morphology, and microstructure are rather limited in SCS. Here, we develop a novel ultrasonic-assisted solution combustion route to synthesize the porous and nano-sized Na3V2(PO4)3/C composites, and reveal the effects of ultrasound on the structural evolution of NVP/C. Due to the cavitation effects generated from ultrasonic irradiation, the ultrasonic-assisted SCS can produce honeycomb precursor, which can be further transformed into porous Na3V2(PO4)3/C with reticular and hollow structures after thermal treatment. When used as cathode material for Na-ion batteries, the porous Na3V2(PO4)3/C delivers an initial discharge capacity of 118 mAh g-1 at 0.1 C and an initial coulombic efficiency of 85%. It can retain 93.8% of the initial capacity after 120 cycles at 0.2 C. The results demonstrate that ultrasonic-assisted SCS can be a new strategy to design crystalline nanomaterials with tunable microstructures.

A neural network potential energy surface for the NaH2 system and dynamics studies on the H(2S) + NaH(X1Σ+) → Na(2S) + H2(X1Σg+) reaction.

PubMed

Wang, Shufen; Yuan, Jiuchuang; Li, Huixing; Chen, Maodu

2017-08-02

In order to study the dynamics of the reaction H( 2 S) + NaH(X 1 Σ + ) → Na( 2 S) + H 2 (X 1 Σ g + ), a new potential energy surface (PES) for the ground state of the NaH 2 system is constructed based on 35 730 ab initio energy points. Using basis sets of quadruple zeta quality, multireference configuration interaction calculations with Davidson correction were carried out to obtain the ab initio energy points. The neural network method is used to fit the PES, and the root mean square error is very small (0.00639 eV). The bond lengths, dissociation energies, zero-point energies and spectroscopic constants of H 2 (X 1 Σ g + ) and NaH(X 1 Σ + ) obtained on the new NaH 2 PES are in good agreement with the experiment data. On the new PES, the reactant coordinate-based time-dependent wave packet method is applied to study the reaction dynamics of H( 2 S) + NaH(X 1 Σ + ) → Na( 2 S) + H 2 (X 1 Σ g + ), and the reaction probabilities, integral cross-sections (ICSs) and differential cross-sections (DCSs) are obtained. There is no threshold in the reaction due to the absence of an energy barrier on the minimum energy path. When the collision energy increases, the ICSs decrease from a high value at low collision energy. The DCS results show that the angular distribution of the product molecules tends to the forward direction. Compared with the LiH 2 system, the NaH 2 system has a larger mass and the PES has a larger well at the H-NaH configuration, which leads to a higher ICS value in the H( 2 S) + NaH(X 1 Σ + ) → Na( 2 S) + H 2 (X 1 Σ g + ) reaction. Because the H( 2 S) + NaH(X 1 Σ + ) → Na( 2 S) + H 2 (X 1 Σ g + ) reaction releases more energy, the product molecules can be excited to a higher vibrational state.

Regulation of branchial V-H(+)-ATPase, Na(+)/K(+)-ATPase and NHE2 in response to acid and base infusions in the Pacific spiny dogfish (Squalus acanthias).

PubMed

Tresguerres, Martin; Katoh, Fumi; Fenton, Heather; Jasinska, Edyta; Goss, Greg G

2005-01-01

To study the mechanisms of branchial acid-base regulation, Pacific spiny dogfish were infused intravenously for 24 h with either HCl (495+/- 79 micromol kg(-1) h(-1)) or NaHCO(3) (981+/-235 micromol kg(-1) h(-1)). Infusion of HCl produced a transient reduction in blood pH. Despite continued infusion of acid, pH returned to normal by 12 h. Infusion of NaHCO(3) resulted in a new steady-state acid-base status at approximately 0.3 pH units higher than the controls. Immunostained serial sections of gill revealed the presence of separate vacuolar proton ATPase (V-H(+)-ATPase)-rich or sodium-potassium ATPase (Na(+)/K(+)-ATPase)-rich cells in all fish examined. A minority of the cells also labeled positive for both transporters. Gill cell membranes prepared from NaHCO(3)-infused fish showed significant increases in both V-H(+)-ATPase abundance (300+/-81%) and activity. In addition, we found that V-H(+)-ATPase subcellular localization was mainly cytoplasmic in control and HCl-infused fish, while NaHCO(3)-infused fish demonstrated a distinctly basolateral staining pattern. Western analysis in gill membranes from HCl-infused fish also revealed increased abundance of Na(+)/H(+) exchanger 2 (213+/-5%) and Na(+)/K(+)-ATPase (315+/-88%) compared to the control.

Layered P2-Na 2/3 Co 1/2 Ti 1/2 O 2 as a high-performance cathode material for sodium-ion batteries

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

Sabi, Noha; Doubaji, Siham; Hashimoto, Kazuki

Layered oxides are regarded as promising cathode materials for sodium-ion batteries. We present Na2/3Co1/2Ti1/2O2 as a potential new cathode material for sodium-ion batteries. The crystal features and morphology of the pristine powder were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The cathode material is evaluated in galvanostatic charge-discharge and galvanostatic intermittent titration tests, as well as ex-situ X-ray diffraction analysis. Synthesized by a high-temperature solid state reaction, Na2/3Co1/2Ti1/2O2 crystallizes in P2-type structure with P6(3)/mmc space group. The material presents reversible electrochemical behavior and delivers a specific discharge capacity of 100 mAh g(-1) when tested in Na halfmore » cells between 2.0 and 4.2 V (vs. Na+/Na), with capacity retention of 98% after 50 cycles. Furthermore, the electrochemical cycling of this titanium-containing material evidenced a reduction of the potential jumps recorded in the NaxCoO2 parent phase, revealing a positive impact of Ti substitution for Co. The ex-situ XRD measurements confirmed the reversibility and stability of the material. No structural changes were observed in the XRD patterns, and the P2-type structure was stable during the charge/discharge process between 2.0 and 4.2 V vs. Na+/Na. These outcomes will contribute to the progress of developing low cost electrode materials for sodium-ion batteries. (C) 2017 Elsevier B.V. All rights reserved.« less

Determination of 20Ne(p ,γ )21Na cross sections from Ep=500 -2000 keV

NASA Astrophysics Data System (ADS)

Lyons, S.; Görres, J.; deBoer, R. J.; Stech, E.; Chen, Y.; Gilardy, G.; Liu, Q.; Long, A. M.; Moran, M.; Robertson, D.; Seymour, C.; Vande Kolk, B.; Wiescher, M.; Best, A.

2018-06-01

Background: The reaction 20Ne(p ,γ )21Na influences the nucleosynthesis of Ne, Na, and Mg isotopes while contributing to hydrogen burning in several stellar sites, such as red giants, asymptotic giant branch (AGB) stars, massive stars, and oxygen-neon (ONe) novae. In the relevant temperature range for these environments (T = 0.05-0.5 GK), the main contributions to this reaction rate are from the direct capture process as well as the high-energy tail of a subthreshold resonance in the ground-state transition at Ex = 2425 keV in the 21Na compound nucleus. Purpose: The previous measurement of this reaction reports cross sections with large uncertainties for the ground-state transition. At higher energies, where the subthreshold resonance makes a smaller contribution to the total cross section, only upper limits are provided. This work aims to reduce the uncertainty in the cross section where direct capture dominates, as well as provide cross-section data in previously unmeasured regions. Method: The 20Ne(p ,γ )21Na reaction was measured over a wide proton energy range (Ep = 0.5-2.0 MeV) at θlab = 90∘. Transitions to the ground state and to the 332 and 2425 keV excited states were observed. The primary transitions to these three bound states were utilized in an R -matrix analysis to determine the contributions of the direct capture and the subthreshold resonance to the total cross section. Results: The cross sections of the present measurements have been found to be in good agreement with the previous data at low energy. Significantly improved cross-section measurements have been obtained over the Ep = 1300-1900 keV region. The narrow resonance at Ec.m. = 1113 keV (Ex = 3544.3 keV) has also been remeasured and its strength has been found to be in good agreement with previous measurements. Conclusions: An extrapolation of the S factor of 20Ne(p ,γ )21Na has been made to low energies using the R -matrix fit. The reaction rate from the subthreshold resonance was

A computational study of Na behavior on graphene

NASA Astrophysics Data System (ADS)

Malyi, Oleksandr I.; Sopiha, Kostiantyn; Kulish, Vadym V.; Tan, Teck L.; Manzhos, Sergei; Persson, Clas

2015-04-01

We present the first ab initio and molecular dynamics study of Na adsorption and diffusion on ideal graphene that considers Na-Na interaction and dispersion forces. From density functional theory (DFT) calculations using the generalized gradient approximation (GGA), the binding energy (vs. the vacuum reference state) of -0.75 eV is higher than the cohesive energy of Na metal (E1.07 eV). The binding energy approaches the Na metal cohesive energy (EcohDFT - D = - 1.21 eV) when dispersion correction is included (DFT-D), with Eb = -1.14 eV. Both DFT and DFT-D predict that the increase of Na concentration on graphene results in formation of Na complexes. This is evidenced by smaller Bader charge on Na atoms of Na dimer, 0.55e (0.48e for DFT) compared to 0.86e (for both DFT and DFT-D) for the single atom adsorption as well as by the formation of a Nasbnd Na bond identified by analysis of the electron density. These results suggest that ideal graphene is not a promising anode material for Na-ion batteries. Analysis of diffusion pathways for a Na dimer shows that the dimer remains stable during the diffusion, and computed migration barriers are significantly lower for the dimer than that for the single atom diffusion. This indicates that Na-Na interaction should be taken into account during the analysis of Na transport on graphene. Finally, we show that the typical defects (vacancy and divacancy) induce significant strengthening of the Nasbnd C interaction. In particular, the largest change to the interaction is computed for vacancy-defected graphene, where the found lowest binding energy (vs. the metal reference state) is about 1.15 eV (1.21 eV for DFT) lower than that for ideal graphene.

Na1.25Ni1.25Fe1.75(PO4)3 nanoparticles as a janus electrode material for Li-ion batteries

NASA Astrophysics Data System (ADS)

Karegeya, Claude; Mahmoud, Abdelfattah; Hatert, Frédéric; Vertruyen, Bénédicte; Cloots, Rudi; Lippens, Pierre-Emmanuel; Boschini, Frédéric

2018-06-01

A solvothermal method was used to prepare Na1.25Ni1.25Fe1.75(PO4)3 nanoparticles, a new promising electrode material for lithium-ion batteries. The composition and the crystal structure were determined by 57Fe Mössbauer spectroscopy and powder X-ray diffraction Rietveld refinements and confirmed by magnetic measurements. The structural formula □0.75Na1.25Ni1.25Fe1.75(PO4)3 was obtained showing a significant amount of Na vacancies, which enhances Li diffusion. Na1.25Ni1.25Fe1.75(PO4)3 was used as negative and positive electrode material and shows excellent electrochemical performances. As negative electrode in the voltage range 0.03-3.5 V vs. Li+/Li, the first discharge at current density of 40 mA g-1 delivers a specific capacity of 1186 mAh g-1, which is almost three times its theoretical capacity (428 mAh g-1). Then, reversible capacity of 550 mAh g-1 was obtained at 50 mA g-1 with high rate capability (150 mAh g-1 at 500 mA g-1) and capacity retention of 350 cycles. As positive electrode material, specific capacities of about 145 and 99 mAh g-1 were delivered at current densities of 5 and 50 mA g-1, respectively, in the voltage range of 1.5-4.5 V vs. Li+/Li. In addition, we show that the use of solvothermal synthesis contributes to the synthesis of small sized particles leading to good electrochemical performances.

Observation of double-well potential of NaH C 1Σ+ state: Deriving the dissociation energy of its ground state

NASA Astrophysics Data System (ADS)

Chu, Chia-Ching; Huang, Hsien-Yu; Whang, Thou-Jen; Tsai, Chin-Chun

2018-03-01

Vibrational levels (v = 6-42) of the NaH C 1Σ+ state including the inner and outer wells and the near-dissociation region were observed by pulsed optical-optical double resonance fluorescence depletion spectroscopy. The absolute vibrational quantum number is identified by comparing the vibrational energy difference of this experiment with the ab initio calculations. The outer well with v up to 34 is analyzed using the Dunham expansion and a Rydberg-Klein-Rees (RKR) potential energy curve is constructed. A hybrid double-well potential combined with the RKR potential, the ab initio calculation, and a long-range potential is able to describe the whole NaH C 1Σ+ state including the higher vibrational levels (v = 35-42). The dissociation energy of the NaH C 1Σ+ state is determined to be De(C) = 6595.10 ± 5 cm-1 and then the dissociation energy of the NaH ground state De(X) = 15 807.87 ± 5 cm-1 can be derived.

Peierls instability as the insulating origin of the Na/Si(111)-(3 × 1) surface with a Na coverage of 2/3 monolayers

NASA Astrophysics Data System (ADS)

Kang, Myung Ho; Kwon, Se Gab; Jung, Sung Chul

2018-03-01

Density functional theory (DFT) calculations are used to investigate the insulating origin of the Na/Si(111)-(3 × 1) surface with a Na coverage of 2/3 monolayers. In the coverage definition, one monolayer refers to one Na atom per surface Si atom, so this surface contains an odd number of electrons (i.e., three Si dangling-bond electrons plus two Na electrons) per 3 × 1 unit cell. Interestingly, this odd-electron surface has been ascribed to a Mott-Hubbard insulator to account for the measured insulating band structure with a gap of about 0.8 eV. Here, we instead propose a Peierls instability as the origin of the experimental band gap. The concept of Peierls instability is fundamental in one-dimensional metal systems but has not been taken into account in previous studies of this surface. Our DFT calculations demonstrate that the linear chain structure of Si dangling bonds in this surface is energetically unstable with respect to a × 2 buckling modulation, and the buckling-induced band gap of 0.79 eV explains well the measured insulating nature.

Crystal Structure of the Ternary Complex of a NaV C-Terminal Domain, a Fibroblast Growth Factor Homologous Factor, and Calmodulin

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

Wang, Chaojian; Chung, Ben C.; Yan, Haidun

2012-11-13

Voltage-gated Na{sup +} (Na{sub V}) channels initiate neuronal action potentials. Na{sub V} channels are composed of a transmembrane domain responsible for voltage-dependent Na{sup +} conduction and a cytosolic C-terminal domain (CTD) that regulates channel function through interactions with many auxiliary proteins, including fibroblast growth factor homologous factors (FHFs) and calmodulin (CaM). Most ion channel structural studies have focused on mechanisms of permeation and voltage-dependent gating but less is known about how intracellular domains modulate channel function. Here we report the crystal structure of the ternary complex of a human NaV CTD, an FHF, and Ca{sup 2+}-free CaM at 2.2 {angstrom}.more » Combined with functional experiments based on structural insights, we present a platform for understanding the roles of these auxiliary proteins in NaV channel regulation and the molecular basis of mutations that lead to neuronal and cardiac diseases. Furthermore, we identify a critical interaction that contributes to the specificity of individual NaV CTD isoforms for distinctive FHFs.« less

Half-metallicity in new Heusler alloys NaTO2 (T=Sc, Ti, V, Cr, and Mn): A first-principles study

NASA Astrophysics Data System (ADS)

Rajabi, Kh; Ahmadian, F.

2018-03-01

On the basis of the full-potential linearized augmented plane wave (FPLAPW) method within density functional theory (DFT), electronic structure and magnetic properties of Heusler alloys NaTO2 (T = Sc, Ti, V, Cr, and Mn) were investigated. The negative values of formation energy showed that these compounds can be experimentally synthesized. Results showed that in all compounds, AlCu2Mn-type structure was the most favorable one. The NaTO2 (T = Sc, Ti, V, Cr, and Mn) alloys were HM ferromagnets except NaScO2 (in both structures which were nonmagnetic semiconductors) and NaVO2 (in AlCu2Mn-type structure which was a magnetic semiconductor). The origin of half-metallicity was also verified in HM alloys. NaCrO2 and NaVO2 alloys had higher half-metallic band gaps in comparison with Heusler alloys including and excluding transition metals. The total magnetic moments of HM NaTO2 (T = Ti, V, Cr, and Mn) alloys obeyed Slater-Pauling rule (Mtot = Ztot-12). Among NaTO2 (T = Sc, Ti, V, Cr, and Mn) alloys, NaCrO2 had the highest robustness of half-metallicity with variation of lattice constant in both structures.

Ranolazine inhibits shear sensitivity of endogenous Na+ current and spontaneous action potentials in HL-1 cells

PubMed Central

Strege, Peter; Beyder, Arthur; Bernard, Cheryl; Crespo-Diaz, Ruben; Behfar, Atta; Terzic, Andre; Ackerman, Michael; Farrugia, Gianrico

2012-01-01

NaV1.5 is a mechanosensitive voltage-gated Na+ channel encoded by the gene SCN5A, expressed in cardiac myocytes and required for phase 0 of the cardiac action potential (AP). In the cardiomyocyte, ranolazine inhibits depolarizing Na+ current and delayed rectifier (IKr) currents. Recently, ranolazine was also shown to be an inhibitor of NaV1.5 mechanosensitivity. Stretch also accelerates the firing frequency of the SA node, and fluid shear stress increases the beating rate of cultured cardiomyocytes in vitro. However, no cultured cell platform exists currently for examination of spontaneous electrical activity in response to mechanical stimulation. In the present study, flow of solution over atrial myocyte-derived HL-1 cultured cells was used to study shear stress mechanosensitivity of Na+ current and spontaneous, endogenous rhythmic action potentials. In voltage-clamped HL-1 cells, bath flow increased peak Na+ current by 14 ± 5%. In current-clamped cells, bath flow increased the frequency and decay rate of AP by 27 ± 12% and 18 ± 4%, respectively. Ranolazine blocked both responses to shear stress. This study suggests that cultured HL-1 cells are a viable in vitro model for detailed study of the effects of mechanical stimulation on spontaneous cardiac action potentials. Inhibition of the frequency and decay rate of action potentials in HL-1 cells are potential mechanisms behind the antiarrhythmic effect of ranolazine. PMID:23018927

Solution phase synthesis of Na{sub 0.28}V{sub 2}O{sub 5} nanobelts into nanorings and the electrochemical performance in Li battery

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

Nagaraju, Ganganagappa, E-mail: nagarajugn@rediffmail.com; Department of Chemistry, Central College Campus, Bangalore University, Bangalore; Chandrappa, Gujjarahalli Thimmanna

2012-11-15

Graphical abstract: Hydrothermal method has been adopted first time to prepare Na{sub 0.28}V{sub 2}O{sub 5} nanorings/nanobelts without using any organic surfactant/solvents at 130–160 °C for 1–2 days. TEM analyses reveal that the products consist of nanorings of width about 500 nm and thickness of about 100 nm with inner diameter of 5–7 m. Nanobelts of width 70–100 nm and several tens of micrometers in length are observed. The electrochemical results show that Na{sub 0.28}V{sub 2}O{sub 5} exhibits an initial discharge capacity of 320 mAh g{sup −1} and its capacity still retained 175 mAh g{sup −1} even after 69 cycles. Highlights:more » ► We are the first to report Na{sub 0.28}V{sub 2}O{sub 5} nanorings/nanobelts by solution method. ► Synthesis via hydrothermal method at 130–160 °C/1–2d in acidic medium. ► We have carried out without using any surfactant/templates/organic solvents. ► Shows discharge capacity of 320 mAh g{sup −1} and reach 175 mAh g{sup −1} after 69 cycles. ► A probable reaction mechanism for Na{sub 0.28}V{sub 2}O{sub 5} nanorings formation is also proposed. -- Abstract: In this paper, we are the first to report a simple one step hydrothermal method to synthesize Na{sub 0.28}V{sub 2}O{sub 5} nanorings/nanobelts without using any organic surfactant/solvents at 130–160 °C for 1–2 days. The obtained products have been characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, morphology by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and electrochemical discharge–charge test for lithium battery. XRD pattern exhibit a monoclinic Na{sub 0.28}V{sub 2}O{sub 5} structure. FTIR spectrum shows band at 958 cm{sup −1} is assigned to V=O stretching vibration, which is sensitive to intercalation and suggests that Na{sup +} ions are inserted between the vanadium oxide layers. TEM analyses reveal

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.

The electrochemical exploration of double carbon-wrapped Na3V2(PO4)3: Towards long-time cycling and superior rate sodium-ion battery cathode

NASA Astrophysics Data System (ADS)

Li, Sijie; Ge, Peng; Zhang, Chenyang; Sun, Wei; Hou, Hongshuai; Ji, Xiaobo

2017-10-01

Na3V2(PO4)3 (NVP) is a very promising cathode material in sodium ion battery for rapidly emerging large-scale energy storage with its classical 3D NASCION structure. However, the cycling life and rate performances are restricted its low electronic conductivity. To overcome these, the double carbon-wrapped Na3V2(PO4)3 composite is firstly designed through rheological phase approach, delivering enhanced electrochemical properties. The unique double carbon layers are composed of uniform amorphous carbons as protecting framework for stabilizing the structure, as well as the graphitized carbon sheets playing the role of conductive network for better electronic conductivity. This double carbon-wrapped Na3V2(PO4)3 composite exhibits a high reversible capacity of 99.8 mAh g-1 over 500 cycles at 1 C (110 mA g-1), yielding the coulombic efficiency of ∼99.8%. Meanwhile, it displays an initial capacity of 73 mAh g-1 at 100 C and remains 55 mAh g-1 at an ultra-rate of 200 C. Even after cycling at 200 C over 12 000 cycles, the Na+-storage capacity of 40 mAh g-1 with a retention of 72.7% is still obtained, highlighting its excellent long cycling life and remarkable rate performances.

Experimental Studies of the NaK 3^1Π and 1^3Δ States

NASA Astrophysics Data System (ADS)

Prodan, I. D.; Marks, A.; Sibbach, L.; Laub, E.; Mazsa, I.; Webb, S.; La Civita, J.; Galle, E.; Jabbour, Z. J.; Namiotka, R. K.; Morgus, T.; Huennekens, J.; Li, Li

2000-06-01

We report the results of optical-optical double resonance experiments designed to study the 3^1Π and 1^3Δ states of NaK. In the first step, a narrow band cw dye laser (PUMP) was tuned to excite a particular 2(A)^1Σ^+(v_A, J') level [or 2(A)^1Σ^+(v_A, J') ~ 1(b)^3Π(v_b, J') mixed level], and its frequency was then fixed. A second narrow band tunable cw Ti:Sapphire laser (PROBE) was then scanned over transitions to various 3^1Π(v_Π, J) [or 1^3Δ(v_Δ, J)] levels while 3^1Π arrow 1(X)^1Σ^+ violet fluorescence [or collision-induced ^3Λ arrow 1(a)^3Σ^+ green fluorescence] was monitored. The Doppler-free signals accurately map the 3^1Π and 1^3Δ state ro-vibrational energy levels. These energy levels were then fit to Dunham expansions to provide experimental molecular constants, allowing the construction of RKR potential curves that have been compared to recent theoretical calculations. Comparison between observed and calculated Franck-Condon factors was used to determine variation of the 3^1Πarrow1(X)^1Σ^+ transition dipole moment with internuclear separation. A deperturbation analysis of the 1^3Δ state was performed to determine the spin-orbit constant for that state. The 1^3Δ state hyperfine structure, due to the Fermi contact interaction between the electron spin and the sodium atom nuclear spin, was also studied.

Effect of stabilization annealing on SCC susceptibility of β-annealed Ti-6Al-4V alloy in 0.6 M NaCl solution

NASA Astrophysics Data System (ADS)

Jeong, Daeho; Park, Jiho; Ahn, Soojin; Sung, Hyokyung; Kwon, Yongnam; Kim, Sangshik

2018-01-01

The effect of stabilization annealing on the stress corrosion cracking (SCC) susceptibility of β-annealed Ti-6Al-4V (Ti64) alloy was examined in an aqueous 0.6 M NaCl solution under various applied potentials of +0.1, -0.05 and -0.1 V vs Ecorr, respectively, at a strain rate of 10 -6 s -1. The stabilization annealing substantially improved the resistance to SCC of β-annealed Ti64 alloy in 0.6 M NaCl solution under cathodic applied potentials, while the effect was marginal under an anodic applied potential. It was also noted that the areal fraction between ductile and brittle fracture of β-annealed Ti64 specimens, which were slow strain rate tested in 0.6 M NaCl solution, varied with stabilization annealing and applied potentials. The effect of stabilization annealing on the SCC behavior of β-annealed Ti64 alloy in SCC-causing environment was discussed based on the micrographic and fractographic observation.

The 21 Na (p,γ) 22 Mg reaction from Ec.m. =200 to 1103 keV in novae and x-ray bursts

NASA Astrophysics Data System (ADS)

D'Auria, J. M.; Azuma, R. E.; Bishop, S.; Buchmann, L.; Chatterjee, M. L.; Chen, A. A.; Engel, S.; Gigliotti, D.; Greife, U.; Hunter, D.; Hussein, A.; Hutcheon, D.; Jewett, C. C.; José, J.; King, J. D.; Laird, A. M.; Lamey, M.; Lewis, R.; Liu, W.; Olin, A.; Ottewell, D.; Parker, P.; Rogers, J.; Ruiz, C.; Trinczek, M.; Wrede, C.

2004-06-01

The long-lived radioactive nuclide 22 Na ( t1/2 =2.6 yr) is an astronomical observable for understanding the physical processes of oxygen-neon novae. Yields of 22Na in these events are sensitive to the unknown total rate of the 21 Na (p,γ) 22 Mg reaction. Using a high intensity 21 Na beam at the TRIUMF-ISAC facility, the strengths of seven resonances in 22 Mg , of potential astrophysical importance, have been directly measured at center of mass energies from Ec.m. =200 to 1103 keV . We report the results obtained for these resonances and their respective contributions to the 21 Na (p,γ) 22 Mg rate in novae and x-ray bursts, and their impact on 22 Na production in novae.

Superconductivity could occur Na-supersaturated NaCl

NASA Astrophysics Data System (ADS)

Hanaki, Koji

1997-04-01

A flow-into electron and a flow-out hole mean flow-into of two unit electric c harges. Even if an exciton consisting of an electron and a hole is a neutral q uasi-particle, overlapping of excitons, namely, the bose condensation changes into a superconductor where half the electric current is due to holes moving t oward the reverse direction. The Meisner effect of the bose condensation comes from the precession of the each exciton under the magnetic field^1. Moreo ver, the present mechanism is supported with that superconducting material alw ays has two kinds of carriers. The superconductivity of NaCl comes from the ab ove-mentioned theory. Free stable holes at first and then electrons are produc ed in NaCl when considerable number of Cl^- lattice vacancies are brought in NaCl mainly because some electrons in the Cl-3p filled band fall into the v acancies. The coexistence of two kinds of stable carriers does not always mean the presence of excitons like VO with electrons not paired and localized in e ach V atom though. While, the absorption spectrum of the NaCl has already conf irmed the presence of excitons; the strength of the spectrum seems to indicate the formation of the bose condensation. Thus we could expect a new supercondu ctor. 1) Hanaki B.Am.P.Soc.,40-1(1995)568

Painful Na-channelopathies: an expanding universe.

PubMed

Waxman, Stephen G

2013-07-01

The universe of painful Na-channelopathies--human disorders caused by mutations in voltage-gated sodium channels--has recently expanded in three dimensions. We now know that mutations of sodium channels cause not only rare genetic 'model disorders' such as inherited erythromelalgia and channelopathy-associated insensitivity to pain but also common painful neuropathies. We have learned that mutations of NaV1.8, as well as mutations of NaV1.7, can cause painful Na-channelopathies. Moreover, recent studies combining atomic level structural models and pharmacogenomics suggest that the goal of genomically guided pain therapy may not be unrealistic. Copyright © 2013 Elsevier Ltd. All rights reserved.

[Excitation and relaxation of metastable state NaK(1 3Pi) at high vibrational levels].

PubMed

Luan, Nan-Nan; Cai, Qin; Zhang, Li-Ping; Dai, Kang; Shen, Yi-Fan

2011-11-01

The authors have investigated collision vibrational energy transfer rate constants in NaK[1 3Pi(v)] and He system. Pump laser excitation of the spin-forbidden band was used to produce very highly vibrationally excited metastable state NaK[1 3Pi (v = 22, 21, 20)]. The probe laser was used to excite the 1 3Pi (v = 22, 21, 20) to 5 3Pi(v'). Laser induced fluorescence (LIF) from 5 3Pi --> 1 3Sigma+ transition was used to follow the collision dynamics. The semilog plots of time-resolved LIF was obtained. The slopes yielded the effective lifetimes. From such data several Stern-Volmer plots could be constructed and the relaxation rate constants could be extracted for the sum of all processes that give rise to the decay of the prepared vibrational state. The rate constants (in units of 10(-11) cm3 x s(-1)) for v being 22, 21 and 20 are 1.4 +/- 0.1, 1.2 +/- 0.1 and 1.0 +/- 0.1, respectively. The vibrational relaxation rate is increasing with vibrational quantum number. In order to determine the importance of multiquantum relaxation, it is necessary to measure the relative population of both the prepared state and collisionally populated states. By the kinetic equations governing up to Delta(v) = 2 transitions, the time dependence of populations of the vibrational states were obtained. With the help of the integrating the population equations over all time, the importance of the two-quantum relaxation could be studied experimentally. By varying the delay between the pump and the probe laser, the He pressure dependent vibrational state specific decay could be measured. The time evolutions and relative intensities of the three states v = 22, 21 and 20 by preparing v = 22 were obtained. Using experimental data the rate constants (in units of 10(-11) cm3 x s(-1)) for v = 22 --> 21 and v = 22 --> 20 are 0.67 +/- 0.15 and 0.49 +/- 0.12, respectively. The single quantum relaxation accounts for only about 48% of the total relaxation out of v = 22. Multi-quantum relaxation (Delta(v

High-resolution infrared studies of the v 10, v 11, v 14, and v 18 levels of [1.1.1]propellane

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

Kirkpatrick, Robynne W.; Masiello, Tony; Martin, Matthew A.

2012-11-15

This paper is a continuation of earlier work for which the high resolution infrared spectrum of [1.1.1]propellane was measured and its k and l structure resolved for the first time. Here we present results from an analysis of more than 16,000 transitions involving three fundamental bands v 10 (E'-A1'), v 11 (E'-A1'), v 14 (A2''-A1') and two difference bands (v 10- v 18) (E'-E'') and (v 11-v 18) (E'-E"). Additional information about v18 was also obtained from the difference band (v 15+v 18)-v 18 (E'-E") and the binary combination band (v 15+v 18) (E'-A1'). Through the use of the groundmore » state constants reported in an earlier paper [1], rovibrational constants have been determined for all the vibrational states involved in these bands. The rovibrational parameters for the v 18(E'') state were obtained from combination-differences and showed no need to include interactions with other states. The v 10(E') state analysis was also straight-forward, with only a weak Coriolis interaction with the levels of the v 14(A2'') state. The latter levels are much more affected by a strong Coriolis interaction with the levels of the nearby v 11(E') state and also by a small but significant interaction with another state, presumably the v16(E'') state, that is not directly observed. Gaussian calculations (B3LYP/cc-pVTZ) computed at the anharmonic level aided the analyses by providing initial values for many of the parameters. These theoretical results generally compare favorably with the final parameter values deduced from the spectral analyses. Finally, evidence was obtained for several level crossings between the rotational levels of the v 11 and v 14 states and, using a weak coupling term corresponding to a Δk = ±5, Δl = ∓1 matrix element, it was possible to find transitions from the ground state that, combined with transitions to the same upper state, give a value of C 0 = 0.1936519(4) cm -1. This result, combined with the value of B 0 = 0.28755833(14) cm-1 reported

Effect of Al substitution on the enhanced electrochemical performance and strong structure stability of Na3V2(PO4)3/C composite cathode for sodium-ion batteries

NASA Astrophysics Data System (ADS)

Chen, Yanjun; Xu, Youlong; Sun, Xiaofei; Wang, Chao

2018-01-01

In this study, a promising cathode material in Na-ion batteries, Al-doped NASICON-type Na3V2-xAlx(PO4)3/C (0 ≤ × ≤0.03) samples are synthesized and characterized. The doping effects on the crystal structure are investigated by XRD and XPS, indicating that low dose of Al3+ doping generates no damage on the structure of the material, and aluminum is substituted for the vanadium site successfully. Electron microscopy and Raman data show that amorphous carbon coated on the matrix can enhance the electron conductivity. The electrochemical kinetic response of Al3+ doping are tested based on "slow-charge and rapid-discharge" electrochemical mode, results from before and after the cycles show that the doping samples have strong structure stability and excellent electrochemical performance because of low internal resistances and high ion conductivity. Thus, Na3V1.98Al0.02(PO4)3/C exhibits an initial reversible capacity of 102.7 mAh g-1 at 10 mA g-1 in the potential range between 2.3 and 3.8 V and delivers a discharge value of 95 mAh g-1vs. 59.9 mAh g-1 of NVP/C at current density of 70 mA g-1 discharge after 50 cycles. The ionic conductivity of Na3V1.98Al0.02(PO4)3/C sample at 3.4 V after 50 cycles at 10 mA g-1 charge 200 mA g-1 discharge is 1.31 × 10-12 cm2s-1, four orders of magnitude higher than the undoped one(7.79 × 10-17 cm2s-1).

Concentration dependence of Li+/Na+ diffusion in manganese hexacyanoferrates

NASA Astrophysics Data System (ADS)

Takachi, Masamitsu; Fukuzumi, Yuya; Moritomo, Yutaka

2016-06-01

Manganese hexacyanoferrates (Mn-HCFs) with a jungle-gym-type structure are promising cathode materials for Li+/Na+ secondary batteries (LIBs/SIBs). Here, we investigated the diffusion constants D Li/D Na of Li+/Na+ against the Li+/Na+ concentration x Na/x Li and temperature (T) of A 1.32Mn[Fe(CN)6]0.833.6H2O (A = Li and Na). We evaluated the activation energy E\\text{a}\\text{Li}/E\\text{a}\\text{Na} of D Li/D Na against x Na/x Li. We found that E\\text{a}\\text{Na} steeply increases with x Na from 0.41 eV at x Na = 0.69 to 0.7 eV at 1.1. The increase in E\\text{a}\\text{Na} is ascribed to the occupancy effect of the Na+ site. The increase in E\\text{a}\\text{Li} is suppressed, probably because the number of Li+ sites is three times that of Na+ sites.

Electron doping evolution of the magnetic excitations in NaFe 1-xCo xAs

DOE PAGES

Carr, Scott V.; Zhang, Chenglin; Song, Yu; ...

2016-06-13

We use time-of-flight (TOF) inelastic neutron scattering (INS) spectroscopy to investigate the doping dependence of magnetic excitations across the phase diagram of NaFe 1-xCo xAs with x = 0, 0.0175, 0.0215, 0.05, and 0.11. The effect of electron-doping by partially substituting Fe by Co is to form resonances that couple with superconductivity, broaden and suppress low energy (E 80 meV) spin excitations compared with spin waves in undoped NaFeAs. However, high energy (E > 80 meV) spin excitations are weakly Co-doping dependent. Integration of the local spin dynamic susceptibility "(!) of NaFe 1-xCo xAs reveals a total fluctuating moment ofmore » 3.6 μ2 B/Fe and a small but systematic reduction with electron doping. The presence of a large spin gap in the Cooverdoped nonsuperconducting NaFe0.89Co0.11As suggests that Fermi surface nesting is responsible for low-energy spin excitations. These results parallel Ni-doping evolution of spin excitations in BaFe 2-xNi xAs 2, confirming the notion that low-energy spin excitations coupling with itinerant electrons are important for superconductivity, while weakly doping dependent high-energy spin excitations result from localized moments.« less

3D Interconnected Carbon Fiber Network-Enabled Ultralong Life Na3 V2 (PO4 )3 @Carbon Paper Cathode for Sodium-Ion Batteries.

PubMed

Kretschmer, Katja; Sun, Bing; Zhang, Jinqiang; Xie, Xiuqiang; Liu, Hao; Wang, Guoxiu

2017-03-01

Sodium-ion batteries (NIBs) are an emerging technology, which can meet increasing demands for large-scale energy storage. One of the most promising cathode material candidates for sodium-ion batteries is Na 3 V 2 (PO 4 ) 3 due to its high capacity, thermal stability, and sodium (Na) Superionic Conductor 3D (NASICON)-type framework. In this work, the authors have significantly improved electrochemical performance and cycling stability of Na 3 V 2 (PO 4 ) 3 by introducing a 3D interconnected conductive network in the form of carbon fiber derived from ordinary paper towel. The free-standing Na 3 V 2 (PO 4 ) 3 -carbon paper (Na 3 V 2 (PO 4 ) 3 @CP) hybrid electrodes do not require a metallic current collector, polymeric binder, or conducting additives to function as a cathode material in an NIB system. The Na 3 V 2 (PO 4 ) 3 @CP cathode demonstrates extraordinary long term cycling stability for 30 000 deep charge-discharge cycles at a current density of 2.5 mA cm -2 . Such outstanding cycling stability can meet the stringent requirements for renewable energy storage. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Slowly inactivating component of Na+ current in peri-somatic region of hippocampal CA1 pyramidal neurons

PubMed Central

Park, Yul Young; Johnston, Daniel

2013-01-01

The properties of voltage-gated ion channels on the neuronal membrane shape electrical activity such as generation and backpropagation of action potentials, initiation of dendritic spikes, and integration of synaptic inputs. Subthreshold currents mediated by sodium channels are of interest because of their activation near rest, slow inactivation kinetics, and consequent effects on excitability. Modulation of these currents can also perturb physiological responses of a neuron that might underlie pathological states such as epilepsy. Using nucleated patches from the peri-somatic region of hippocampal CA1 neurons, we recorded a slowly inactivating component of the macroscopic Na+ current (which we have called INaS) that shared many biophysical properties with the persistent Na+ current, INaP, but showed distinctively faster inactivating kinetics. Ramp voltage commands with a velocity of 400 mV/s were found to elicit this component of Na+ current reliably. INaS also showed a more hyperpolarized I-V relationship and slower inactivation than those of the fast transient Na+ current (INaT) recorded in the same patches. The peak amplitude of INaS was proportional to the peak amplitude of INaT but was much smaller in amplitude. Hexanol, riluzole, and ranolazine, known Na+ channel blockers, were tested to compare their effects on both INaS and INaT. The peak conductance of INaS was preferentially blocked by hexanol and riluzole, but the shift of half-inactivation voltage (V1/2) was only observed in the presence of riluzole. Current-clamp measurements with hexanol suggested that INaS was involved in generation of an action potential and in upregulation of neuronal excitability. PMID:23236005

Effects of Mg doping on the remarkably enhanced electrochemical performance of Na 3V 2(PO 4) 3 cathode materials for sodium ion batteries

DOE PAGES

Li, Hui; Yu, Xiqian; Bai, Ying; ...

2015-01-01

Na 3V 2-xMg x(PO 4) 3/C composites with different Mg 2+ doping contents (x=0, 0.01, 0.03, 0.05, 0.07 and 0.1) were prepared by a facile sol-gel method. The doping effects on the crystal structure were investigated by XRD, XPS and EXAFS. The results show that low dose doping Mg 2+ does not alter the structure of the material, and magnesium is successfully substituted for vanadium site. The Mg doped Na 3V 2-xMg x(PO 4) 3/C composites exhibit significant improvements on the electrochemistry performances in terms of the rate capability and cycle performance, especially for the Na 3V 1.95Mg 0.05(PO 4)more » 3/C. For example, when the current density increased from 1 C to 30 C, the specific capacity only decreased from 112.5 mAh g-1 to 94.2 mAh g -1 showing very good rate capability. Moreover, even cycling at a high rate of 20 C, an excellent capacity retention of 81% is maintained from the initial value of 106.4 mAh g-1 to 86.2 mAh g-1 at the 50th cycle. Enhanced rate capability and cycle performance can be attributed to the optimized particle size, structural stability and enhanced ionic and electronic conductivity induced by Mg doping.« less

The NaK 1 1,3delta states: theoretical and experimental studies of fine and hyperfine structure of rovibrational levels near the dissociation limit.

PubMed

Wilkins, A D; Morgus, L; Hernandez-Guzman, J; Huennekens, J; Hickman, A P

2005-09-22

Earlier high-resolution spectroscopic studies of the fine and hyperfine structure of rovibrational levels of the 1 3delta state of NaK have been extended to include high lying rovibrational levels with v < or = 59, of which the highest levels lie within approximately 4 cm(-1) of the dissociation limit. A potential curve is determined using the inverted perturbation approximation method that reproduces these levels to an accuracy of approximately 0.026 cm(-1). For the largest values of v, the outer turning points occur near R approximately 12.7 angstroms, which is sufficiently large to permit the estimation of the C6 coefficient for this state. The fine and hyperfine structure of the 1 3delta rovibrational levels has been fit using the matrix diagonalization method that has been applied to other states of NaK, leading to values of the spin-orbit coupling constant A(v) and the Fermi contact constant b(F). New values determined for v < or = 33 are consistent with values determined by a simpler method and reported earlier. The measured fine and hyperfine structure for v in the range 44 < or = v < or = 49 exhibits anomalous behavior whose origin is believed to be the mixing between the 1 3delta and 1 1delta states. The matrix diagonalization method has been extended to treat this interaction, and the results provide an accurate representation of the complicated patterns that arise. The analysis leads to accurate values for A(v) and b(F) for all values of v < or = 49. For higher v (50 < or = v < or = 59), several rovibrational levels have been assigned, but the pattern of fine and hyperfine structure is difficult to interpret. Some of the observed features may arise from effects not included in the current model.

Ranolazine vs phenytoin: greater effect of ranolazine on the transient Na(+) current than on the persistent Na(+) current in central neurons.

PubMed

Terragni, Benedetta; Scalmani, Paolo; Colombo, Elisa; Franceschetti, Silvana; Mantegazza, Massimo

2016-11-01

Voltage-gated Na(+) channels (NaV) are involved in pathologies and are important targets of drugs (NaV-blockers), e.g. some anti-epileptic drugs (AEDs). Besides the fast inactivating transient Na(+) current (INaT), they generate a slowly inactivating "persistent" current (INaP). Ranolazine, a NaV-blocker approved for treatment of angina pectoris, is considered a preferential inhibitor of INaP and has been proposed as a novel AED. Although it is thought that classic NaV-blockers used as AEDs target mainly INaT, they can also reduce INaP. It is important to disclose specific features of novel NaV-blockers, which could be necessary for their effect as AEDs in drug resistant patients. We have compared the action of ranolazine and of the classic AED phenytoin in transfected cells expressing the neuronal NaV1.1 Na(+) channel and in neurons of neocortical slices. Our results show that the relative block of INaT versus INaP of ranolazine and phenytoin is variable and depends on Na(+) current activation conditions. Strikingly, ranolazine blocks with less efficacy INaP and more efficacy INaT than phenytoin in conditions mimicking pathological states (i.e. high frequency firing and long lasting depolarizations). The effects are consistent with binding of ranolazine to both open/pre-open and inactivated states; larger INaT block at high stimulation frequencies is caused by the induction of a slow inactivated state. Thus, contrary than expected, ranolazine is not a better INaP blocker than phenytoin in central neurons, and phenytoin is not a better INaT blocker than ranolazine. Nevertheless, they show a complementary action and could differentially target specific pathological dysfunctions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Scalable synthesis of Na3V2(PO4)(3)/C porous hollow spheres as a cathode for Na-ion batteries

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

Mao, JF; Luo, C; Gao, T

2015-01-01

Na3V2(PO4)(3) (NVP) has been considered as a very promising cathode material for sodium-ion batteries (SIBs) due to its typical NASICON structure, which provides an open and three dimensional (3D) framework for Na+ migration. However, the low electronic conductivity of NVP limits its rate capability and cycling ability. In this study, carbon coated hollow structured NVP/C composites are synthesized via a template-free and scalable ultrasonic spray pyrolysis process, where the carbon coated NVP particles are uniformly decorated on the inner and outer surfaces of the porous hollow carbon spheres. When evaluated as a cathode material for SIBs, the unique NVP/C porousmore » hollow sphere cathode delivers an initial discharge capacity of 99.2 mA h g(-1) and retains 89.3 mA h g(-1) after 300 charge/discharge cycles with a very low degradation rate of 0.035% per cycle. For comparison, the NVP/C composite, prepared by the traditional sol-gel method, delivers a lower initial discharge capacity of 97.4 mA h g(-1) and decreases significantly to 71.5 mA h g(-1) after 300 cycles. The superior electrochemical performance of NVP/C porous hollow spheres is attributed to their unique porous, hollow and spherical structures, as well as the carbon-coating layer, which provides a high contact area between electrode/electrolyte, high electronic conductivity, and high mechanical strength.« less

Magnetization and Hall effect under high pressure in NaV 6O 11

NASA Astrophysics Data System (ADS)

Naka, T.; Matsumoto, T.; Kanke, Y.; Murata, K.

1995-02-01

We have investigated the pressure dependences of magnetization and the Hall coefficient in the ferromagnetic vanadium oxide NaV 6O 11 up to 1.2 GPa. Structural transitions (hexagonal-hexagonal-orthorhombic) occur at TH = 245 K and TL = 35 K at ambient pressure. Meanwhile, the susceptibility obeys the Curie-Weiss law X = C/( T - θ) with antiferromagnetic correlation of θ < 0 at T > TH, with ferromagnetic correlation of θ < 0 at T < TH. The spontaneous magnetization appears below Tc = 64.2 K. With increasing pressure, Tc and magnetization M( T < Tc) decrease, while TH increases. The sign of the Hall coefficient changes continuously (negative-positive-negative) at around T ≈ 170 K and 75 K.

Voltage-dependent neuromodulation of Na+ channels by D1-like dopamine receptors in rat hippocampal neurons.

PubMed

Cantrell, A R; Scheuer, T; Catterall, W A

1999-07-01

Activation of D1-like dopamine (DA) receptors reduces peak Na+ current in acutely isolated hippocampal neurons through phosphorylation of the alpha subunit of the Na+ channel by cAMP-dependent protein kinase (PKA). Here we report that neuromodulation of Na+ currents by DA receptors via PKA is voltage-dependent in the range of -110 to -70 mV and is also sensitive to concurrent activation of protein kinase C (PKC). Depolarization enhanced the ability of D1-like DA receptors to reduce peak Na+ currents via the PKA pathway. Similar voltage-dependent modulation was observed when PKA was activated directly with the membrane-permeant PKA activator DCl-cBIMPS (cBIMPS; 20 microM), indicating that the membrane potential dependence occurs downstream of PKA. PKA activation caused only a small (-2.9 mV) shift in the voltage dependence of steady-state inactivation and had no effect on slow inactivation or on the rates of entry into the fast or slow inactivated states, suggesting that another mechanism is responsible for coupling of membrane potential changes to PKA modulation. Activation of PKC with a low concentration of the membrane-permeant diacylglycerol analog oleylacetyl glycerol also potentiated modulation by SKF 81297 or cBIMPS, and these effects were most striking at hyperpolarized membrane potentials where PKA modulation was not stimulated by membrane depolarization. Thus, activation of D1-like DA receptors causes a strong reduction in Na+ current via the PKA pathway, but it is effective primarily when it is combined with depolarization or activation of PKC. The convergence of these three distinct signaling modalities on the Na+ channel provides an intriguing mechanism for integration of information from multiple signaling pathways in the hippocampus and CNS.

Shape-Control of a 0D/1D NaFe0.9Mn0.1PO4 Nano-Complex by Electrospinning

NASA Astrophysics Data System (ADS)

Shin, Mi-Ra; Son, Jong-Tae

2018-03-01

NaFePO4 with a maricite structure was one of the most promising candidates for sodium ion batteries (SIBs) due to its advantages of environmental friendly and having low cost. However, it has low electrochemical conductivity and energy density, which impose limitations on its application as commercial cathode materials. In this study, other transition-metal ions such as Mn2+ were substituted into the iron (Fe2+) site in NaFePO4 to increase the surface area and the number of nanofibers in the prepared one-dimensional (1D) nano-sized material with 0D/1D dimensions to enhance the energy density. Also, the 0D/1D NaFe0.9Mn0.1PO4 cathode material has increased electrochemical conductivity because the fiber size was reduced to the nano-scale level by using the electrospinning method in order to decrease the diffusion path of Na-ions. The morphology of the 0D/1D nanofiber was evaluated by Field-emission scanning electron microscope and atomic force microscope analyses. The NaFe0.9Mn0.1PO4 nanofibers had a diameter of approximately 180 nm, while the spherical particle had a diameter 1 μm. The 0D/1D nano-sized cathode material show a discharge capacity of 27 mAhg -1 at a 0.05 C rate within the 2.0 4.5 V voltage range and a low R ct of 110 Ω.

Expression of Na+-glucose cotransporter (SGLT1) in visceral and parietal mesothelium of rabbit pleura.

PubMed

Sironi, Chiara; Bodega, Francesca; Porta, Cristina; Zocchi, Luciano; Agostoni, Emilio

2007-10-15

Indirect evidence for a solute-coupled liquid absorption from rabbit pleural space indicated that it should be caused by a Na(+)/H(+)-Cl(-)/HCO(3)(-) double exchanger and a Na(+)-glucose cotransporter [Agostoni, E., Zocchi, L., 1998. Mechanical coupling and liquid exchanges in the pleural space. In: Antony, V.B. (Ed.), Clinics in Chest Medicine: Diseases of the Pleura, vol. 19. Saunders, Philadelphia, pp. 241-260]. In this research we tried to obtain molecular evidence for Na(+)-glucose cotransporter (SGLT1) in visceral and parietal mesothelium of rabbit pleura. To this end we performed immunoblot assays on total protein extracts of scraped visceral or parietal mesothelium of rabbits. These showed two bands: one at 72kDa (m.w. of SGLT1), and one at 55kDa (which should also provide Na(+)-glucose cotransport). Both bands disappeared in assays in which SGLT1 antibody was preadsorbed with specific antigen. Molecular evidence for Na(+)/K(+) ATPase (alpha1 subunit) was also provided. Immunoblot assays for SGLT1 on cultured mesothelial cells of rabbit pleura showed a band at 72kDa, and in some cases also at 55kDa, irrespectively of treatment with a differentiating agent. Solute-coupled liquid absorption hinders liquid filtration through parietal mesothelium caused by Starling forces, and favours liquid absorption through visceral mesothelium caused by these forces.

Studies of Inelastic Collisions of NaK and NaCs Molecules with Atomic Perturbers

NASA Astrophysics Data System (ADS)

Jones, Joshua A.

We have investigated collisions of NaK molecules in the first excited state [2(A)1Sigma+], with Ar and He collision partners using laser-induced fluorescence spectroscopy (LIF) and polarization-labeling (PL) spectroscopy in a two-step excitation scheme. Additionally, we have investigated collisions of NaCs molecules in the first excited state [2(A)1Sigma +] with Ar and He perturbers using the LIF technique. We use a pump-probe, two-step excitation process. The pump laser prepares the molecule in a particular ro-vibrational (v, J) level in the A state. The probe laser frequency is scanned over transitions to the 31Π in NaK or to the 53Π in NaCs. In addition to observing strong direct lines, we also see weak collisional satellite lines that arise from collisions in the intermediate state that take the molecule from the prepared level (v, J) to level (v, J + Delta J). The ratio of the intensity of the collisional line to the intensity of the direct line in LIF and PL yield information about population and orientation transfer. Our results show a propensity for DeltaJ=even collisions of NaK with Ar and an even stronger propensity for collisions with He. Collisions of NaCs with Ar do not show any such J=even propensity. Preliminary investigations of collisions of NaCs with He seem to indicate a slight J=even propensity. In addition, we observe that rotationally inelastic collisions of excited NaK molecules with potassium atoms destroy almost all of the orientation, while collisions with argon destroy about one third to two thirds and collisions with helium destroy only about zero to one third of the initial orientation.

Role of alkali carbonate and salt in topochemical synthesis of K1/2Na1/2NbO3 and NaNbO3 templates

NASA Astrophysics Data System (ADS)

Lee, Jae-Seok; Jeon, Jae-Ho; Choi, Si-Young

2013-11-01

Since the properties of lead-free piezoelectric materials have thus far failed to meet those of lead-based materials, either chemical doping or morphological texturing should be employed to improve the piezoelectric properties of lead-free piezoelectric ceramics. The goal of this study was to synthesize plate-like K1/2Na1/2NbO3 and NaNbO3 particles, which are the most favorable templates for morphological texturing of K1/2Na1/2NbO3 ceramics. To achieve this goal, Bi2.5Na3.5Nb5O18 precursors in a plate-like shape were first synthesized and subsequently converted into K1/2Na1/2NbO3 or NaNbO3 particles that retain the morphology of Bi2.5Na3.5Nb5O18. In this study, we found that sodium or potassium carbonate does not play a major role in converting the Bi2.5Na3.5Nb5O18 precursor to K1/2Na1/2NbO3 or NaNbO3, on the contrary to previous reports; however, the salt contributes to the conversion reaction. All synthesis processes have been performed via a molten salt method, and scanning electron microscopy, scanning probe microscopy, and inductively coupled plasma mass spectroscopy were used to characterize the synthesized K1/2Na1/2NbO3 or NaNbO3 templates.

Studies of rotationally inelastic collisions of NaK and NaCs with Ar and He perturbers

NASA Astrophysics Data System (ADS)

Jones, J.; Faust, C.; Richter, K.; Wolfe, C. M.; Ashman, S.; Malenda, R. F.; Weiser, P.; Carlus, S.; Fragale, A.; Hickman, A. P.; Huennekens, J.

2013-05-01

We report studies of rotationally inelastic collisions of Ar and He atoms with the molecules NaK and NaCs prepared in various ro-vibrational levels of the A1Σ+ electronic state. We use laser induced fluorescence (LIF) and polarization labeling (PL) spectroscopy in a pump-probe, two step excitation process. The pump excites the molecule to a ro-vibrational level (v , J) in the A state. The probe laser is scanned over transitions to the 31 Π state in NaK or the 53 Π state in NaCs. In addition to strong direct lines, we observe weak satellite lines that arise from collision-induced transitions of the A state level (v , J) to (v , J + ΔJ) . The ratio of intensities of the satellite line to the direct line in LIF and PL yields information about population and orientation transfer. Preliminary results show a strong propensity for collisions with ΔJ =even for NaK; the propensity is larger for He than for Ar. Collisions of NaCs with He show a similar propensity, but collisions of NaCs with Ar do not. Theoretical calculations are also underway. For He-NaK, we have completed potential surface calculations using GAMESS and coupled channel scattering calculations of rotational energy transfer and transfer of orientation. Work supported by NSF and XSEDE.

ECO2N V. 2.0: A New TOUGH2 Fluid Property Module for Mixtures of Water, NaCl, and CO 2

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

Pan, L.; Spycher, N.; Doughty, C.

2014-12-01

ECO2N V2.0 is a fluid property module for the TOUGH2 simulator (Version 2.1) that was designed for applications to geologic sequestration of CO 2 in saline aquifers and enhanced geothermal reservoirs. ECO2N V2.0 is an enhanced version of the previous ECO2N V1.0 module (Pruess, 2005). It expands the temperature range up to about 300°C whereas V1.0 can only be used for temperatures below about 110°C. V2.0 includes a comprehensive description of the thermodynamics and thermophysical properties of H 2O - NaCl -CO 2 mixtures, that reproduces fluid properties largely within experimental error for the temperature, pressure and salinity conditions ofmore » interest (10 °C < T < 300 °C; P < 600 bar; salinity up to halite saturation). This includes density, viscosity, and specific enthalpy of fluid phases as functions of temperature, pressure, and composition, as well as partitioning of mass components H 2O, NaCl and CO 2 among the different phases. In particular, V2.0 accounts for the effects of water on the thermophysical properties of the CO 2-rich phase, which was ignored in V1.0, using a model consistent with the solubility models developed by Spycher and Pruess (2005, 2010). In terms of solubility models, V2.0 uses the same model for partitioning of mass components among the different phases (Spycher and Pruess, 2005) as V1.0 for the low temperature range (<99°C) but uses a new model (Spycher and Pruess, 2010) for the high temperature range (>109°C). In the transition range (99-109°C), a smooth interpolation is applied to estimate the partitioning as a function of the temperature. Flow processes can be modeled isothermally or non-isothermally, and phase conditions represented may include a single (aqueous or CO 2-rich) phase, as well as two-phase mixtures. Fluid phases may appear or disappear in the course of a simulation, and solid salt may precipitate or dissolve. This report gives technical specifications of ECO2N V2.0 and includes instructions for

The Na(+) transporter, TaHKT1;5-D, limits shoot Na(+) accumulation in bread wheat.

PubMed

Byrt, Caitlin Siobhan; Xu, Bo; Krishnan, Mahima; Lightfoot, Damien James; Athman, Asmini; Jacobs, Andrew Keith; Watson-Haigh, Nathan S; Plett, Darren; Munns, Rana; Tester, Mark; Gilliham, Matthew

2014-11-01

Bread wheat (Triticum aestivum L.) has a major salt tolerance locus, Kna1, responsible for the maintenance of a high cytosolic K(+) /Na(+) ratio in the leaves of salt stressed plants. The Kna1 locus encompasses a large DNA fragment, the distal 14% of chromosome 4DL. Limited recombination has been observed at this locus making it difficult to map genetically and identify the causal gene. Here, we decipher the function of TaHKT1;5-D, a candidate gene underlying the Kna1 locus. Transport studies using the heterologous expression systems Saccharomyces cerevisiae and Xenopus laevis oocytes indicated that TaHKT1;5-D is a Na(+) -selective transporter. Transient expression in Arabidopsis thaliana mesophyll protoplasts and in situ polymerase chain reaction indicated that TaHKT1;5-D is localised on the plasma membrane in the wheat root stele. RNA interference-induced silencing decreased the expression of TaHKT1;5-D in transgenic bread wheat lines which led to an increase in the Na(+) concentration in the leaves. This indicates that TaHKT1;5-D retrieves Na(+) from the xylem vessels in the root and has an important role in restricting the transport of Na(+) from the root to the leaves in bread wheat. Thus, TaHKT1;5-D confers the essential salinity tolerance mechanism in bread wheat associated with the Kna1 locus via shoot Na(+) exclusion and is critical in maintaining a high K(+) /Na(+) ratio in the leaves. These findings show there is potential to increase the salinity tolerance of bread wheat by manipulation of HKT1;5 genes. © 2014 The Authors The Plant Journal © 2014 John Wiley & Sons Ltd.

Polarization Spectroscopy and Collisions in NaK

NASA Astrophysics Data System (ADS)

Wolfe, C. M.; Ashman, S.; Huennekens, J.; Beser, B.; Bai, J.; Lyyra, A. M.

2009-05-01

We report current work to study transfer of population and orientation in collisions of NaK molecules with argon and potassium atoms using polarization labeling (PL) and laser-induced fluorescence (LIF) spectroscopy. In the PL experiment, a circularly polarized pump laser excites a specific NaK A^1&+circ;(v=16, J) <- X^1&+circ;(v=0, J±1) transition, creating an orientation (non-uniform MJ level distribution) in both levels. The linear polarized probe laser is scanned over various 3^1π(v=8, J' ±1) <- A^1&+circ;(v=16, J') transitions. The probe laser passes through a crossed linear polarizer before detection, and signal is recorded if the probe laser polarization has been modified by the vapor (which occurs when it comes into resonance with an oriented level). In addition to strong direct transitions (J' = J), we also observe weak collisional satellite lines (J' = J±n with n = 1, 2, 3, ...) indicating that orientation is transferred to adjacent rotational levels during a collision. An LIF experiment (with linear polarized pump and probe beams) gives information on the collisional transfer of population. From these data, cross sections for both processes can be determined. We experimentally distinguish collisions of NaK with argon atoms from collisions with alkali atoms.

The influence of excess K2O on the electrical properties of (K,Na)1/2Bi1/2TiO3 ceramics

NASA Astrophysics Data System (ADS)

Li, Linhao; Li, Ming; Sinclair, Derek C.

2018-04-01

The solid solution (KxNa0.50-x)Bi0.50TiO3 (KNBT) between Na1/2Bi1/2TiO3 and K1/2Bi1/2TiO3 (KBT) has been extensively researched as a candidate lead-free piezoelectric material because of its relatively high Curie temperature and good piezoelectric properties, especially near the morphotropic phase boundary (MPB) at x ˜ 0.10 (20 mol. % KBT). Here, we show that low levels of excess K2O in the starting compositions, i.e., (Ky+0.03Na0.50-y)Bi0.50TiO3.015 (y-series), can significantly change the conduction mechanism and electrical properties compared to a nominally stoichiometric KNBT series (KxNa0.50-x)Bi0.50TiO3 (x-series). Impedance spectroscopy measurements reveal significantly higher bulk conductivity (σb) values for y ≥ 0.10 samples [activation energy (Ea) ≤ 0.95 eV] compared to the corresponding x-series samples which possess bandgap type electronic conduction (Ea ˜ 1.26-1.85 eV). The largest difference in electrical properties occurs close to the MPB composition (20 mol. % KBT) where y = 0.10 ceramics possess σb (at 300 °C) that is 4 orders of magnitude higher than that of x = 0.10 and the oxide-ion transport number in the former is ˜0.70-0.75 compared to <0.05 in the latter (between 600 and 800 °C). The effect of excess K2O can be rationalised on the basis of the (K + Na):Bi ratio in the starting composition prior to ceramic processing. This demonstrates the electrical properties of KNBT to be sensitive to low levels of A-site nonstoichiometry and indicates that excess K2O in KNBT starting compositions to compensate for volatilisation can lead to undesirable high dielectric loss and leakage currents at elevated temperatures.

Critical increase in Na-doping facilitates acceptor band movements that yields ~180 meV shallow hole conduction in ZnO bulk crystals

PubMed Central

Parmar, Narendra S.; Yim, Haena; Choi, Ji-Won

2017-01-01

Stable p-type conduction in ZnO has been a long time obstacle in utilizing its full potential such as in opto-electronic devices. We designed a unique experimental set-up in the laboratory for high Na-doping by thermal diffusion in the bulk ZnO single crystals. SIMS measurement shows that Na concentration increases by 3 orders of magnitude, to ~3 × 1020 cm−3 as doping temperature increases to 1200 °C. Electronic infrared absorption was measured for Na-acceptors. Absorption bands were observed near (0.20–0.24) eV. Absorption bands blue shifted by 0.04 eV when doped at 1200 °C giving rise to shallow acceptor level. NaZn band movements as a function of doping temperature are also seen in Photoluminescence emission (PL), Photoluminescence excitation (PLE) and UV-Vis transmission measurements. Variable temperature Hall measurements show stable p-type conduction with hole binding energy ~0.18 eV in ZnO samples that were Na-doped at 1200 °C. PMID:28272444

β-NaVOPO 4 obtained by a low-temperature synthesis process: A new 3.3 V cathode for sodium-ion batteries

DOE PAGES

He, Guang; Huq, Ashfia; Manthiram, Arumugam; ...

2016-02-02

Vanadyl phosphates (VOPO 4) represent a class of attractive cathodes in lithium-ion batteries. However, the exploration of this type of materials in sodium-ion batteries is rare. Here, we report for the first time the synthesis of orthorhombic β-NaVOPO 4 by first chemically extracting lithium from beta-LiVOPO 4 and then inserting sodium into the obtained β-VOPO 4 by a microwave-assisted solvothermal process with NaI, which serves both as a reducing agent and sodium source. Intermediate Na xVOPO 4 compositions with x = 0.3, 0.5, and 0.8 have also been obtained by controlling the amount of NaI in the reaction mixture. Jointmore » Rietveld refinement of synchrotron X-ray diffraction (XRD) and neutron diffraction confirms that the fully sodiated β-NaVOPO 4 is isostructural with the lithium counterpart β-LiVOPO 4. Bond valence sum maps suggest that sodium ions possibly diffuse along the [010] direction in the lattice, similar to the ionic conduction pathway in β-LiVOPO 4. Although the initial discharge capacity is low due to the protons in the structure, it steadily increases with cycling with a long plateau at 3.3 V. As a result, ex situ XRD data of cycled β-VOPO 4 and β-NaVOPO 4 electrodes confirm the reversible reaction in sodium cells involving the V 4+/V 5+ redox couple.« less

Na[superscript +] binding to meizothrombin desF1

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

Papaconstantinou, M.E.; Gandhi, P.S.; Chen, Z.

2009-06-10

Meizothrombin is the physiologically active intermediate generated by a single cleavage of prothrombin at R320 to separate the A and B chains. Recent evidence has suggested that meizothrombin, like thrombin, is a Na{sup +}-activated enzyme. In this study we present the first X-ray crystal structure of human meizothrombin desF1 solved in the presence of the active site inhibitor PPACK at 2.1 {angstrom} resolution. The structure reveals a Na{sup +} binding site whose architecture is practically identical to that of human thrombin. Stopped-flow measurements of Na{sup +} binding to meizothrombin desF1 document a slow phase of fluorescence change with a kmore » obs decreasing hyperbolically with increasing [Na{sup +}], consistent with the existence of three conformations in equilibrium, E*, E and E:Na{sup +}, as for human thrombin. Evidence that meizothrombin exists in multiple conformations provides valuable new information for studies of the mechanism of prothrombin activation.« less

Giant strain with low cycling degradation in Ta-doped [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}]TiO{sub 3} lead-free ceramics

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

Liu, Xiaoming; Tan, Xiaoli, E-mail: xtan@iastate.edu

2016-07-21

Non-textured polycrystalline [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}](Ti{sub 1−x}Ta{sub x})O{sub 3} ceramics are fabricated and their microstructures and electrical properties are characterized. Transmission electron microscopy reveals the coexistence of the rhombohedral R3c and tetragonal P4bm phases in the form of nanometer-sized domains in [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}]TiO{sub 3} with low Ta concentration. When the composition is x = 0.015, the electrostrain is found to be highly asymmetric under bipolar fields of ±50 kV/cm. A very large value of 0.62% is observed in this ceramic, corresponding to a large-signal piezoelectric coefficient d{sub 33}* of 1240 pm/V (1120 pm/V under unipolar loading). These values are greater thanmore » most previously reported lead-free polycrystalline ceramics and can even be compared with some lead-free piezoelectric single crystals. Additionally, this ceramic displays low cycling degradation; its electrostrain remains above 0.55% even after undergoing 10 000 cycles of ±50 kV/cm bipolar fields at 2 Hz. Therefore, Ta-doped [Bi{sub 1/2}(Na{sub 0.8}K{sub 0.2}){sub 1/2}]TiO{sub 3} ceramics show great potential for large displacement devices.« less

Quinone Reduction by the Na+-Translocating NADH Dehydrogenase Promotes Extracellular Superoxide Production in Vibrio cholerae▿ †

PubMed Central

Lin, Po-Chi; Türk, Karin; Häse, Claudia C.; Fritz, Günter; Steuber, Julia

2007-01-01

The pathogenicity of Vibrio cholerae is influenced by sodium ions which are actively extruded from the cell by the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR). To study the function of the Na+-NQR in the respiratory chain of V. cholerae, we examined the formation of organic radicals and superoxide in a wild-type strain and a mutant strain lacking the Na+-NQR. Upon reduction with NADH, an organic radical was detected in native membranes by electron paramagnetic resonance spectroscopy which was assigned to ubisemiquinones generated by the Na+-NQR. The radical concentration increased from 0.2 mM at 0.08 mM Na+ to 0.4 mM at 14.7 mM Na+, indicating that the concentration of the coupling cation influences the redox state of the quinone pool in V. cholerae membranes. During respiration, V. cholerae cells produced extracellular superoxide with a specific activity of 10.2 nmol min−1 mg−1 in the wild type compared to 3.1 nmol min−1 mg−1 in the NQR deletion strain. Raising the Na+ concentration from 0.1 to 5 mM increased the rate of superoxide formation in the wild-type V. cholerae strain by at least 70%. Rates of respiratory H2O2 formation by wild-type V. cholerae cells (30.9 nmol min−1 mg−1) were threefold higher than rates observed with the mutant strain lacking the Na+-NQR (9.7 nmol min−1 mg−1). Our study shows that environmental Na+ could stimulate ubisemiquinone formation by the Na+-NQR and hereby enhance the production of reactive oxygen species formed during the autoxidation of reduced quinones. PMID:17322313

The Na+-Translocating NADH:Quinone Oxidoreductase Enhances Oxidative Stress in the Cytoplasm of Vibrio cholerae

PubMed Central

Muras, Valentin; Dogaru-Kinn, Paul; Minato, Yusuke; Häse, Claudia C.

2016-01-01

ABSTRACT We searched for a source of reactive oxygen species (ROS) in the cytoplasm of the human pathogen Vibrio cholerae and addressed the mechanism of ROS formation using the dye 2′,7′-dichlorofluorescein diacetate (DCFH-DA) in respiring cells. By comparing V. cholerae strains with or without active Na+-translocating NADH:quinone oxidoreductase (Na+-NQR), this respiratory sodium ion redox pump was identified as a producer of ROS in vivo. The amount of cytoplasmic ROS detected in V. cholerae cells producing variants of Na+-NQR correlated well with rates of superoxide formation by the corresponding membrane fractions. Membranes from wild-type V. cholerae showed increased superoxide production activity (9.8 ± 0.6 μmol superoxide min−1 mg−1 membrane protein) compared to membranes from the mutant lacking Na+-NQR (0.18 ± 0.01 μmol min−1 mg−1). Overexpression of plasmid-encoded Na+-NQR in the nqr deletion strain resulted in a drastic increase in the formation of superoxide (42.6 ± 2.8 μmol min−1 mg−1). By analyzing a variant of Na+-NQR devoid of quinone reduction activity, we identified the reduced flavin adenine dinucleotide (FAD) cofactor of cytoplasmic NqrF subunit as the site for intracellular superoxide formation in V. cholerae. The impact of superoxide formation by the Na+-NQR on the virulence of V. cholerae is discussed. IMPORTANCE In several studies, it was demonstrated that the Na+-NQR in V. cholerae affects virulence in a yet unknown manner. We identified the reduced FAD cofactor in the NADH-oxidizing NqrF subunit of the Na+-NQR as the site of superoxide formation in the cytoplasm of V. cholerae. Our study provides the framework to understand how reactive oxygen species formed during respiration could participate in the regulated expression of virulence factors during the transition from aerobic to microaerophilic (intestinal) habitats. This hypothesis may turn out to be right for many other pathogens which, like V. cholerae, depend on

Magnesium/Lithium-Ion Hybrid Battery with High Reversibility by Employing NaV3O8·1.69H2O Nanobelts as a Positive Electrode.

PubMed

Rashad, Muhammad; Li, Xianfeng; Zhang, Huamin

2018-06-27

Recently, magnesium-ion batteries (MIBs) have been under remarkable research focus owing to their appealingly high energy density and natural abundance of magnesium. Nevertheless, MIBs exhibit a very limited performance because of sluggish solid-state Mg 2+ ion diffusion and high polarizability, which hinder their progress toward commercialization. Herein, we report a Mg 2+ /Li + hybrid-ion battery (MLIB) with NaV 3 O 8 ·1.69H 2 O (NVO) nanobelts synthesized at room temperature working as the positive electrode. In the hybrid-ion system, Li + intercalates/deintercalates along with a small amount of Mg 2+ adsorption at the NVO cathode, whereas the anode side of the cell is dominated by Mg 2+ deposition/dissolution. As a result, the MLIB exhibits a much higher rate capability (i.e., 446 mA h g -1 at 20 mA g -1 ) than the previously reported MLIBs. MLIB maintains a high specific capacity of 200 mA h g -1 at 80 mA g -1 for 150 cycles, showing excellent stability. Moreover, the effect of different Li-ion concentrations (i.e., 0.5-2.0 M) in the electrolyte and cutoff voltage (ranging from 2 to 2.6 V) on the specific capacities are investigated. The current study highlights a strategy to exploit the Mg 2+ /Li + hybrid electrolyte system with various electrode materials for high-performance MIBs.

Molecular evolution of respiratory syncytial virus subgroup A genotype NA1 and ON1 attachment glycoprotein (G) gene in central Vietnam.

PubMed

Yoshihara, Keisuke; Le, Minh Nhat; Nagasawa, Koo; Tsukagoshi, Hiroyuki; Nguyen, Hien Anh; Toizumi, Michiko; Moriuchi, Hiroyuki; Hashizume, Masahiro; Ariyoshi, Koya; Dang, Duc Anh; Kimura, Hirokazu; Yoshida, Lay-Myint

2016-11-01

We performed molecular evolutionary analyses of the G gene C-terminal 3rd hypervariable region of RSV-A genotypes NA1 and ON1 strains from the paediatric acute respiratory infection patients in central Vietnam during the 2010-2012 study period. Time-scaled phylogenetic analyses were performed using Bayesian Markov Chain Monte Carlo (MCMC) method, and pairwise distances (p-distances) were calculated. Bayesian Skyline Plot (BSP) was constructed to analyze the time-trend relative genetic diversity of central Vietnam RSV-A strains. We also estimated the N-glycosylation sites within G gene hypervariable region. Amino acid substitutions under positive and negative selection pressure were examined using Conservative Single Likelihood Ancestor Counting (SLAC), Fixed Effects Likelihood (FEL), Internal Fixed Effects Likelihood (IFEL) and Mixed Effects Model for Episodic Diversifying Selection (MEME) models. The majority of central Vietnam ON1 strains detected in 2012 were classified into lineage 1 with few positively selected substitutions. As for the Vietnamese NA1 strains, four lineages were circulating during the study period with a few positive selection sites. Shifting patterns of the predominantly circulating NA1 lineage were observed in each year during the investigation period. Median p-distance of central Vietnam NA1 strains was wider (p-distance=0.028) than that of ON1 (p-distance=0.012). The molecular evolutionary rate of central Vietnam ON1 strains was estimated to be 2.55×10 -2 (substitutions/site/year) and was faster than NA1 (7.12×10 -3 (substitutions/site/year)). Interestingly, the evolutionary rates of both genotypes ON1 and NA1 strains from central Vietnam were faster than the global strains respectively. Furthermore, the shifts of N-glycosylation pattern within the G gene 3rd hypervariable region of Vietnamese NA1 strains were observed in each year. BSP analysis indicated the rapid growth of RSV-A effective population size in early 2012. These results

Na+ Interactions with the Neutral Amino Acid Transporter ASCT1*

PubMed Central

Scopelliti, Amanda J.; Heinzelmann, Germano; Kuyucak, Serdar; Ryan, Renae M.; Vandenberg, Robert J.

2014-01-01

The alanine, serine, cysteine transporters (ASCTs) belong to the solute carrier family 1A (SLC1A), which also includes the excitatory amino acid transporters (EAATs) and the prokaryotic aspartate transporter GltPh. Acidic amino acid transport by the EAATs is coupled to the co-transport of three Na+ ions and one proton, and the counter-transport of one K+ ion. In contrast, neutral amino acid exchange by the ASCTs does not require protons or the counter-transport of K+ ions and the number of Na+ ions required is not well established. One property common to SLC1A family members is a substrate-activated anion conductance. We have investigated the number and location of Na+ ions required by ASCT1 by mutating residues in ASCT1 that correspond to residues in the EAATs and GltPh that are involved in Na+ binding. Mutations to all three proposed Na+ sites influence the binding of substrate and/or Na+, or the rate of substrate exchange. A G422S mutation near the Na2 site reduced Na+ affinity, without affecting the rate of exchange. D467T and D467A mutations in the Na1 site reduce Na+ and substrate affinity and also the rate of substrate exchange. T124A and D380A mutations in the Na3 site selectively reduce the affinity for Na+ and the rate of substrate exchange without affecting substrate affinity. In many of the mutants that reduce the rate of substrate transport the amplitudes of the substrate-activated anion conductances are not substantially affected indicating altered ion dependence for channel activation compared with substrate exchange. PMID:24808181

Low-temperature glasslike properties in (NaCl)1-x(NaCN)x

NASA Astrophysics Data System (ADS)

Watson, Susan K.; Pohl, R. O.

1995-04-01

Thermal conductivity, internal friction, transverse sound velocity (60 mK to 300 K), and specific-heat data (100 mK to 40 K) for (NaCl)1-x(NaCN)x (x=0, 0.025, 0.05, 0.1, 0.76, 1) show a progression from crystalline to glasslike behavior as the CN- concentration is increased from 0 to 76 %. The evolution of glasslike properties is compared to that in other crystals in which glasslike properties evolve with increasing disorder, e.g., (KBr)1-x(KCN)x and Ba1-xLaxF2-x. For (KBr)1-x(KCN)x, Sethna and Chow have shown that as the concentration of the almost freely rotating CN- ions is increased the average potential barrier for CN- reorientation also increases through elastic quadrupolar interactions. For x~0.5, only a small density of low-energy states is left, which equals that observed in structural glasses. In Ba1-xLaxF2-x, on the other hand, the crystal field for small doping x is so large that no atomic motion occurs at low temperatures. (NaCl)1-x(NaCN)x is shown to represent an intermediate case, in that the crystal field is non-negligible at small x, yet glasslike low-energy excitations indicative of very small potential barrier heights evolve with increasing x. It is argued that random internal strains cause a decrease of the barrier heights in these crystals, which lead to the low-energy excitations. It is proposed that random strains have a similar effect in other disordered crystals as in Ba1-xLaxF2-x, which for small x show no low-energy mobile states, yet which for large x become glasslike.

Na Diffusion in Quasi One-Dimensional Ion Conductor NaMn2O4 Observed by μ+SR

NASA Astrophysics Data System (ADS)

Umegaki, Izumi; Nozaki, Hiroshi; Harada, Masashi; Månsson, Martin; Sakurai, Hiroya; Kawasaki, Ikuto; Watanabe, Isao; Sugiyama, Jun

A quasi one-dimensional (1D) compound, NaMn2O4, in which Mn2O4 zigzag chains form a 1D channel along the b-axis and Na ions locate at the center of the channel, is thought to be a good Na ionic conductor. In order to study Na-ion diffusion, we have measured μ+SR spectra using a powder sample in the temperature range between 100 and 500 K. A diffusive behavior was clearly observed above 325 K. Assuming a thermal activate process for jump diffusion of Na-ion between two nearest neighboring sites, a self diffusion coefficient of Na ion (DNa) and its activation energy (Ea) were estimated as DNa = (3.1 ± 0.2) × 10 - 11 cm2/s at 350 K and Ea = 180(9) meV.

Pharmacology of the Nav1.1 domain IV voltage sensor reveals coupling between inactivation gating processes.

PubMed

Osteen, Jeremiah D; Sampson, Kevin; Iyer, Vivek; Julius, David; Bosmans, Frank

2017-06-27

The Na v 1.1 voltage-gated sodium channel is a critical contributor to excitability in the brain, where pathological loss of function leads to such disorders as epilepsy, Alzheimer's disease, and autism. This voltage-gated sodium (Na v ) channel subtype also plays an important role in mechanical pain signaling by primary afferent somatosensory neurons. Therefore, pharmacologic modulation of Na v 1.1 represents a potential strategy for treating excitability disorders of the brain and periphery. Inactivation is a complex aspect of Na v channel gating and consists of fast and slow components, each of which may involve a contribution from one or more voltage-sensing domains. Here, we exploit the Hm1a spider toxin, a Na v 1.1-selective modulator, to better understand the relationship between these temporally distinct modes of inactivation and ask whether they can be distinguished pharmacologically. We show that Hm1a inhibits the gating movement of the domain IV voltage sensor (VSDIV), hindering both fast and slow inactivation and leading to an increase in Na v 1.1 availability during high-frequency stimulation. In contrast, ICA-121431, a small-molecule Na v 1.1 inhibitor, accelerates a subsequent VSDIV gating transition to accelerate entry into the slow inactivated state, resulting in use-dependent block. Further evidence for functional coupling between fast and slow inactivation is provided by a Na v 1.1 mutant in which fast inactivation removal has complex effects on slow inactivation. Taken together, our data substantiate the key role of VSDIV in Na v channel fast and slow inactivation and demonstrate that these gating processes are sequential and coupled through VSDIV. These findings provide insight into a pharmacophore on VSDIV through which modulation of inactivation gating can inhibit or facilitate Na v 1.1 function.

Advancement of technology towards developing Na-ion batteries

NASA Astrophysics Data System (ADS)

Jamesh, Mohammed Ibrahim; Prakash, A. S.

2018-02-01

The Na-ion-batteries are considered much attention for the next-generation power-sources due to the high abundance of Na resources that lower the cost and become the alternative for the state of the art Li-ion batteries in future. In this review, the recently reported potential cathode and anode candidates for Na-ion-batteries are identified in-light-of-their high-performance for the development of Na-ion-full-cells. Further, the recent-progress on the Na-ion full-cells including the strategies used to improve the high cycling-performance (stable even up-to 50000 cycles), operating voltage (even ≥ 3.7 V), capacity (>350 mAhg-1 even at 1000 mAg-1 (based-on-mass-of-the-anode)), and energy density (even up-to 400 Whkg-1) are reviewed. In addition, Na-ion-batteries with the electrodes containing reduced graphene oxide, and the recent developments on symmetric Na-ion-batteries are discussed. Further, this paper identifies the promising Na-ion-batteries including the strategies used to assemble full-cell using hard-carbon-anodes, Na3V2(PO4)3 cathodes, and other-electrode-materials. Then, comparison between aqueous and non-aqueous Na-ion-batteries in terms of voltage and energy density has been given. Later, various types of electrolytes used for Na-ion-batteries including aqueous, non-aqueous, ionic-liquids and solid-state electrolytes are discussed. Finally, commercial and technological-developments on Na-ion-batteries are provided. The scientific and engineering knowledge gained on Na-ion-batteries afford conceivable development for practical application in near future.

Effect of Na poisoning catalyst (V2O5-WO3/TiO2) on denitration process and SO3 formation

NASA Astrophysics Data System (ADS)

Xiao, Haiping; Chen, Yu; Qi, Cong; Ru, Yu

2018-03-01

This paper aims to study the effect of alkali metal sodium (Na) poisoning on the performance of the Selective Catalytic Reduction (SCR) catalyst. The result showed that Na2SO4 poisoning leads to a reduced denitration rate of the SCR catalyst and an increase in the SO3 generation rate. Na2O poisoning leads to a significant reduction in the denitration rate of the SCR catalyst and marginally improves the formation of SO3. The maximum of the SO3 generation rate for a Na2SO4-poisoned catalyst reached 1.35%, whereas it was only 0.85% for the SCR catalyst. When the SO2 was contained in flue gas, the denitration rate for the Na2O-poisoned catalyst clearly increased by more than 28%. However, the effect of SO2 on the Na2SO4-poisoned catalyst was very slight. The denitration rate of the SCR catalyst decreased with an increase in the Na content. The BET and XRD results showed that Na poisoning of the catalyst decreased the number of acid sites, the reducibility of the catalyst, the surface area, and pore volume. The H2-TPR and NH3-TPD results show that Na decreases the number of acid sites and the reducibility of the catalyst. The FT-IR and XPS results showed that Na2O poisoning led to the decrease of V5+dbnd O bonds and the consumptions of oxygen atoms. Na2SO4 poisoning can improve surface adsorbed oxygen, which was beneficial for the SO2-SO3 conversion reaction.

Solvothermal synthesis and structural characterization of a three-dimensional metal organic polymer [NaZn(1,2,4-BTC)] (1,2,4-BTC=1,2,4-benzenetricarboxylate)

NASA Astrophysics Data System (ADS)

Wang, Lei; Shi, Zhan; Li, Guanghua; Fan, Yong; Fu, Wensheng; Feng, Shouhua

2004-01-01

A new three-dimensional metal-organic polymer, [NaZn(1,2,4-BTC)] (where 1,2,4-BTC=1,2,4-benzenetricarboxylate), has been prepared under solvothermal conditions and characterized by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2 1/ c, with cell parameters: a=9.7706(4) Å, b=12.3549(5) Å, c=6.8897(3) Å, β=91.640(2)°, V=831.35(6) Å 3 and Z=4. In the three-dimensional structure of the compound, each Zn atom is five-coordinated in distorted trigonal bipyramidal geometry, while the sixfold coordination of Na corresponds to a slightly distorted triangular prism. The organic ligand, 1,2,4-BTC, shows a novel and unprecedented coordination mode: 11 bonds to 10 metals with each carboxylate function exhibiting different linkages. It remains stable when desolvated and when heated up to 410 °C.

SABRE: A New NaI(T1) Dark Matter Direct Detection Experiment

NASA Astrophysics Data System (ADS)

Shields, Emily; Xu, Jingke; Calaprice, Frank

SABRE (Sodium-iodide with Active Background REjection) is a new NaI(Tl) experiment designed to test the DAMA/LIBRA claim for a positive WIMP-dark matter annual modulation signal. SABRE will consist of highly pure NaI(Tl) crystals in an active liquid scintillator veto that will be placed deep underground. The scintillator vessel will provide a veto against external backgrounds and those arising from detector components, especially the 3 keV signature from the decay of 40K in the crystal. Through the use of crystal purification techniques and the veto, we aim for a 40K background significantly lower than that of the DAMA/LIBRA experiment. We present our work developing low-background NaI(Tl) crystals using a highly pure NaI powder and the development of the veto.

NA62 and NA48/2 results on search for Heavy Neutral Leptons

NASA Astrophysics Data System (ADS)

Lamanna, Gianluca; Aliberti, R.; Ambrosino, F.; Ammendola, R.; Angelucci, B.; Antonelli, A.; Anzivino, G.; Arcidiacono, R.; Barbanera, M.; Biagioni, A.; Bician, L.; Biino, C.; Bizzeti, A.; Blazek, T.; Bloch-Devaux, B.; Bonaiuto, V.; Boretto, M.; Bragadireanu, M.; Britton, D.; Brizioli, F.; Brunetti, M. B.; Bryman, D.; Bucci, F.; Capussela, T.; Ceccucci, A.; Cenci, P.; Cerny, V.; Cerri, C.; Checcucci, B.; Conovaloff, A.; Cooper, P.; Cortina Gil, E.; Corvino, M.; Costantini, F.; Cotta Ramusino, A.; Coward, D.; D'Agostini, G.; Dainton, J.; Dalpiaz, P.; Danielsson, H.; De Simone, N.; Di Filippo, D.; Di Lella, L.; Doble, N.; Dobrich, B.; Duval, F.; Duk, V.; Engelfried, J.; Enik, T.; Estrada-Tristan, N.; Falaleev, V.; Fantechi, R.; Fascianelli, V.; Federici, L.; Fedotov, S.; Filippi, A.; Fiorini, M.; Fry, J.; Fu, J.; Fucci, A.; Fulton, L.; Gamberini, E.; Gatignon, L.; Georgiev, G.; Ghinescu, S.; Gianoli, A.; Giorgi, M.; Giudici, S.; Gonnella, F.; Goudzovski, E.; Graham, C.; Guida, R.; Gushchin, E.; Hahn, F.; Heath, H.; Husek, T.; Hutanu, O.; Hutchcroft, D.; Iacobuzio, L.; Iacopini, E.; Imbergamo, E.; Jenninger, B.; Kampf, K.; Kekelidze, V.; Kholodenko, S.; Khoriauli, G.; Khotyantsev, A.; Kleimenova, A.; Korotkova, A.; Koval, M.; Kozhuharov, V.; Kucerova, Z.; Kudenko, Y.; Kunze, J.; Kurochka, V.; Kurshetsov, V.; Lanfranchi, G.; Lamanna, G.; Latino, G.; Laycock, P.; Lazzeroni, C.; Lenti, M.; Lehmann Miotto, G.; Leonardi, E.; Lichard, P.; Litov, L.; Lollini, R.; Lomidze, D.; Lonardo, A.; Lubrano, P.; Lupi, M.; Lurkin, N.; Madigozhin, D.; Mannelli, I.; Mannocchi, G.; Mapelli, A.; Marchetto, F.; Marchevski, R.; Martellotti, S.; Massarotti, P.; Massri, K.; Maurice, E.; Medvedeva, M.; Mefodev, A.; Menichetti, E.; Migliore, E.; Minucci, E.; Mirra, M.; Misheva, M.; Molokanova, N.; Moulson, M.; Movchan, S.; Napolitano, M.; Neri, I.; Newson, F.; Norton, A.; Noy, M.; Numao, T.; Obraztsov, V.; Ostankov, A.; Padolski, S.; Page, R.; Palladino, V.; Parkinson, C.; Pedreschi, E.; Pepe, M.; Perrin-Terrin, M.; Peruzzo, L.; Petrov, P.; Petrucci, F.; Piandani, R.; Piccini, M.; Pinzino, J.; Polenkevich, I.; Pontisso, L.; Potrebenikov, Yu.; Protopopescu, D.; Raggi, M.; Romano, A.; Rubin, P.; Ruggiero, G.; Ryjov, V.; Salamon, A.; Santoni, C.; Saracino, G.; Sargeni, F.; Semenov, V.; Sergi, A.; Shaikhiev, A.; Shkarovskiy, S.; Soldi, D.; Sougonyaev, V.; Sozzi, M.; Spadaro, T.; Spinella, F.; Sturgess, A.; Swallow, J.; Trilov, S.; Valente, P.; Velghe, B.; Venditti, S.; Vicini, P.; Volpe, R.; Vormstein, M.; Wahl, H.; Wanke, R.; Wrona, B.; Yushchenko, O.; Zamkovsky, M.; Zinchenko, A.

2018-05-01

In this paper we present new results on upper limits for the search of Heavy Neutral Leptons (HNL) with data collected by NA48/2 (2003-2004), NA62-RK (2007) and NA62 (2015) CERN experiments. The data collected with different trigger configuration allow to search for both long and short living heavy neutrinos in the mass range below the kaon mass. In addition the status of the search for K+ → π+vv with the NA62 detector will be briefly presented.

Crebanine inhibits voltage-dependent Na+ current in guinea-pig ventricular myocytes.

PubMed

Xiao-Shan, He; Qing, Lin; Yun-Shu, Ma; Ze-Pu, Yu

2014-01-01

To study the effects of crebanine on voltage-gated Na(+) channels in cardiac tissues. Single ventricular myocytes were enzymatically dissociated from adult guinea-pig heart. Voltage-dependent Na(+) current was recorded using the whole cell voltage-clamp technique. Crebanine reversibly inhibited Na(+) current with an IC50 value of 0.283 mmol·L(-1) (95% confidence range: 0.248-0.318 mmol·L(-1)). Crebanine at 0.262 mmol·L(-1) caused a negative shift (about 12 mV) in the voltage-dependence of steady-state inactivation of Na(+) current, and retarded its recovery from inactivation, but did not affect its activation curve. In addition to blocking other voltage-gated ion channels, crebanine blocked Na(+) channels in guinea-pig ventricular myocytes. Crebanine acted as an inactivation stabilizer of Na(+) channels in cardiac tissues. Copyright © 2014 China Pharmaceutical University. Published by Elsevier B.V. All rights reserved.

Application of 23Na MRI to Monitor Chemotherapeutic Response in RIF-1 Tumors1

PubMed Central

Babsky, Andriy M; Hekmatyar, Shahryar K; Zhang, Hong; Solomon, James L; Bansal, Navin

2005-01-01

Abstract Effects of an alkylating anticancer drug, cyclophosphamide (Cp), on 23Na signal intensity (23Na SI) and water apparent diffusion coefficient (ADC) were examined in subcutaneously-implanted radiation-induced fibrosarcoma (RIF-1) tumors by in vivo 23Na and 1H magnetic resonance imaging (MRI). MRI experiments were performed on untreated control (n = 5) and Cp-treated (n = 6) C3H mice, once before Cp injection (300 mg/kg) then daily for 3 days after treatment. Tumor volumes were significantly lower in treated animals 2 and 3 days posttreatment. At the same time points, MRI experiments showed an increase in both 23Na SI and water ADC in treated tumors, whereas control tumors did not show any significant changes. The correlation between 23Na SI and water ADC changes was dramatically increased in the Cp-treated group, suggesting that the observed increases in 23Na SI and water ADC were caused by the same mechanism. Histologic sections showed decreased cell density in the regions of increased 23Na and water ADC SI. Destructive chemical analysis showed that Cp treatment increased the relative extracellular space and tumor [Na+]. We conclude that the changes in water ADC and 23Na SI were largely due to an increase in extracellular space. 23Na MRI and 1H water ADC measurements may provide valuable noninvasive techniques for monitoring chemotherapeutic responses. PMID:16026645

Na(+) transport, and the E(1)P-E(2)P conformational transition of the Na(+)/K(+)-ATPase.

PubMed Central

Babes, A; Fendler, K

2000-01-01

We have used admittance analysis together with the black lipid membrane technique to analyze electrogenic reactions within the Na(+) branch of the reaction cycle of the Na(+)/K(+)-ATPase. ATP release by flash photolysis of caged ATP induced changes in the admittance of the compound membrane system that are associated with partial reactions of the Na(+)/K(+)-ATPase. Frequency spectra and the Na(+) dependence of the capacitive signal are consistent with an electrogenic or electroneutral E(1)P <--> E(2)P conformational transition which is rate limiting for a faster electrogenic Na(+) dissociation reaction. We determine the relaxation rate of the rate-limiting reaction and the equilibrium constants for both reactions at pH 6.2-8.5. The relaxation rate has a maximum value at pH 7.4 (approximately 320 s(-1)), which drops to acidic (approximately 190 s(-1)) and basic (approximately 110 s(-1)) pH. The E(1)P <--> E(2)P equilibrium is approximately at a midpoint position at pH 6.2 (equilibrium constant approximately 0.8) but moves more to the E(1)P side at basic pH 8.5 (equilibrium constant approximately 0.4). The Na(+) affinity at the extracellular binding site decreases from approximately 900 mM at pH 6.2 to approximately 200 mM at pH 8.5. The results suggest that during Na(+) transport the free energy supplied by the hydrolysis of ATP is mainly used for the generation of a low-affinity extracellular Na(+) discharge site. Ionic strength and lyotropic anions both decrease the relaxation rate. However, while ionic strength does not change the position of the conformational equilibrium E(1)P <--> E(2)P, lyotropic anions shift it to E(1)P. PMID:11053130

Structural and spectroscopic studies of a rare non-oxido V(v) complex crystallized from aqueous solution† †Electronic supplementary information (ESI) available: Tables containing crystallographic data and structure refinements for Na[V(L)2]·2H2O(cr) (CCDC 1413557) (Table S1) and Na[VO2(HL)](cr) (CCDC 1418830) (Table S2), concentrations of the solution samples for NMR (Table S3), 13C NMR spectra of V(v)/glutaroimide-dioxime complexes in H2 17O (Fig. S1), ESI-MS spectra of V(v)/glutaroimide-dioxime complexes in 17O-enriched H2O diluted and sprayed in methanol (Fig. S2), and EPR spectra of Na[V(L)2]·2H2O(s) at 4 K and 300 K (Fig. S3). CCDC 1413557–1418830. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc03958d Click here for additional data file. Click here for additional data file.

PubMed Central

Leggett, C. J.; Parker, B. F.; Zhang, Z.; Dau, P. D.; Lukens, W. W.; Peterson, S. M.; Cardenas, A. J. P.; Warner, M. G.; Gibson, J. K.; Arnold, J.

2016-01-01

A non-oxido V(v) complex with glutaroimide-dioxime (H3L), a ligand for recovering uranium from seawater, was synthesized from aqueous solution as Na[V(L)2]·2H2O, and the structure determined by X-ray diffraction. It is the first non-oxido V(v) complex that has been directly synthesized in and crystallized from aqueous solution. The distorted octahedral structure contains two fully deprotonated ligands (L3–) coordinating to V5+, each in a tridentate mode via the imide N (R V–N = 1.96 Å) and oxime O atoms (R V–O = 1.87–1.90 Å). Using 17O-labelled vanadate as the starting material, concurrent 17O/51V/1H/13C NMR, in conjunction with ESI-MS, unprecedentedly demonstrated the stepwise displacement of the oxido V 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 O bonds by glutaroimide-dioxime and verified the existence of the “bare” V5

A new global analytical potential energy surface of NaH2+ system and dynamical calculation for H(2S) + NaH+(X2Σ+) → Na+(1S) + H2(X1Σg+) reaction

NASA Astrophysics Data System (ADS)

Yuan, Meiling; Li, Wentao; Yuan, Jiuchuang

2018-05-01

A new global potential energy surface (PES) of the NaH2+ system is constructed by fitting 27,621 ab initio energy points with the neural network method. The root mean square error of the new PES is only 4.1609 × 10-4 eV. Based on the new PES, dynamical calculations have been performed using the time-dependent quantum wave packet method. These results are then compared with the H(2S) + LiH+(X2Σ+) → Li+(1S) + H2(X1Σg+) reaction. The direct abstract mechanism is found to play an important role in the reaction because only forward scattering signals on the differential cross section results for all calculated collision energies.

Rational Design of Na(Li1/3 Mn2/3 )O2 Operated by Anionic Redox Reactions for Advanced Sodium-Ion Batteries.

PubMed

Kim, Duho; Cho, Maenghyo; Cho, Kyeongjae

2017-09-01

In an effort to develop high-energy-density cathodes for sodium-ion batteries (SIBs), low-cost, high capacity Na(Li 1/3 Mn 2/3 )O 2 is discovered, which utilizes the labile O 2p-electron for charge compensation during the intercalation process, inspired by Li 2 MnO 3 redox reactions. Na(Li 1/3 Mn 2/3 )O 2 is systematically designed by first-principles calculations considering the Li/Na mixing enthalpy based on the site preference of Na in the Li sites of Li 2 MnO 3 . Using the anionic redox reaction (O 2- /O - ), this Mn-oxide is predicted to show high redox potentials (≈4.2 V vs Na/Na + ) with high charge capacity (190 mAh g -1 ). Predicted cathode performance is validated by experimental synthesis, characterization, and cyclic performance studies. Through a fundamental understanding of the redox reaction mechanism in Li 2 MnO 3 , Na(Li 1/3 Mn 2/3 )O 2 is designed as an example of a new class of promising cathode materials, Na(Li 1/3 M 2/3 )O 2 (M: transition metals featuring stabilized M 4+ ), for further advances in SIBs. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A new high-energy cathode for a Na-ion battery with ultrahigh stability.

PubMed

Park, Young-Uk; Seo, Dong-Hwa; Kwon, Hyung-Soon; Kim, Byoungkook; Kim, Jongsoon; Kim, Haegyeom; Kim, Inkyung; Yoo, Han-Ill; Kang, Kisuk

2013-09-18

Large-scale electric energy storage is a key enabler for the use of renewable energy. Recently, the room-temperature Na-ion battery has been rehighlighted as an alternative low-cost technology for this application. However, significant challenges such as energy density and long-term stability must be addressed. Herein, we introduce a novel cathode material, Na1.5VPO4.8F0.7, for Na-ion batteries. This new material provides an energy density of ~600 Wh kg(-1), the highest value among cathodes, originating from both the multielectron redox reaction (1.2 e(-) per formula unit) and the high potential (~3.8 V vs Na(+)/Na) of the tailored vanadium redox couple (V(3.8+)/V(5+)). Furthermore, an outstanding cycle life (~95% capacity retention for 100 cycles and ~84% for extended 500 cycles) could be achieved, which we attribute to the small volume change (2.9%) upon cycling, the smallest volume change among known Na intercalation cathodes. The open crystal framework with two-dimensional Na diffusional pathways leads to low activation barriers for Na diffusion, enabling excellent rate capability. We believe that this new material can bring the low-cost room-temperature Na-ion battery a step closer to a sustainable large-scale energy storage system.

AqSo_NaCl: Computer program to calculate p-T-V-x properties in the H2O-NaCl fluid system applied to fluid inclusion research and pore fluid calculation

NASA Astrophysics Data System (ADS)

Bakker, Ronald J.

2018-06-01

The program AqSo_NaCl has been developed to calculate pressure - molar volume - temperature - composition (p-V-T-x) properties, enthalpy, and heat capacity of the binary H2O-NaCl system. The algorithms are designed in BASIC within the Xojo programming environment, and can be operated as stand-alone project with Macintosh-, Windows-, and Unix-based operating systems. A series of ten self-instructive interfaces (modules) are developed to calculate fluid inclusion properties and pore fluid properties. The modules may be used to calculate properties of pure NaCl, the halite-liquidus, the halite-vapourus, dew-point and bubble-point curves (liquid-vapour), critical point, and SLV solid-liquid-vapour curves at temperatures above 0.1 °C (with halite) and below 0.1 °C (with ice or hydrohalite). Isochores of homogeneous fluids and unmixed fluids in a closed system can be calculated and exported to a.txt file. Isochores calculated for fluid inclusions can be corrected according to the volumetric properties of quartz. Microthermometric data, i.e. dissolution temperatures and homogenization temperatures, can be used to calculated bulk fluid properties of fluid inclusions. Alternatively, in the absence of total homogenization temperature the volume fraction of the liquid phase in fluid inclusions can be used to obtain bulk properties.

Role of intermediate phase for stable cycling of Na7V4(P2O7)4PO4 in sodium ion battery

PubMed Central

Lim, Soo Yeon; Kim, Heejin; Chung, Jaehoon; Lee, Ji Hoon; Kim, Byung Gon; Choi, Jeon-Jin; Chung, Kyung Yoon; Cho, Woosuk; Kim, Seung-Joo; Goddard, William A.; Jung, Yousung; Choi, Jang Wook

2014-01-01

Sodium ion batteries offer promising opportunities in emerging utility grid applications because of the low cost of raw materials, yet low energy density and limited cycle life remain critical drawbacks in their electrochemical operations. Herein, we report a vanadium-based ortho-diphosphate, Na7V4(P2O7)4PO4, or VODP, that significantly reduces all these drawbacks. Indeed, VODP exhibits single-valued voltage plateaus at 3.88 V vs. Na/Na+ while retaining substantial capacity (>78%) over 1,000 cycles. Electronic structure calculations reveal that the remarkable single plateau and cycle life originate from an intermediate phase (a very shallow voltage step) that is similar both in the energy level and lattice parameters to those of fully intercalated and deintercalated states. We propose a theoretical scheme in which the reaction barrier that arises from lattice mismatches can be evaluated by using a simple energetic consideration, suggesting that the presence of intermediate phases is beneficial for cell kinetics by buffering the differences in lattice parameters between initial and final phases. We expect these insights into the role of intermediate phases found for VODP hold in general and thus provide a helpful guideline in the further understanding and design of battery materials. PMID:24379365

Role of intermediate phase for stable cycling of Na7V4(P2O7)4PO4 in sodium ion battery.

PubMed

Lim, Soo Yeon; Kim, Heejin; Chung, Jaehoon; Lee, Ji Hoon; Kim, Byung Gon; Choi, Jeon-Jin; Chung, Kyung Yoon; Cho, Woosuk; Kim, Seung-Joo; Goddard, William A; Jung, Yousung; Choi, Jang Wook

2014-01-14

Sodium ion batteries offer promising opportunities in emerging utility grid applications because of the low cost of raw materials, yet low energy density and limited cycle life remain critical drawbacks in their electrochemical operations. Herein, we report a vanadium-based ortho-diphosphate, Na7V4(P2O7)4PO4, or VODP, that significantly reduces all these drawbacks. Indeed, VODP exhibits single-valued voltage plateaus at 3.88 V vs. Na/Na(+) while retaining substantial capacity (>78%) over 1,000 cycles. Electronic structure calculations reveal that the remarkable single plateau and cycle life originate from an intermediate phase (a very shallow voltage step) that is similar both in the energy level and lattice parameters to those of fully intercalated and deintercalated states. We propose a theoretical scheme in which the reaction barrier that arises from lattice mismatches can be evaluated by using a simple energetic consideration, suggesting that the presence of intermediate phases is beneficial for cell kinetics by buffering the differences in lattice parameters between initial and final phases. We expect these insights into the role of intermediate phases found for VODP hold in general and thus provide a helpful guideline in the further understanding and design of battery materials.

HYDRATE v1.5 OPTION OF TOUGH+ v1.5

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

Moridis, George

HYDRATE v1.5 is a numerical code that for the simulation of the behavior of hydrate-bearing geologic systems, and represents the third update of the code since its first release [Moridis et al., 2008]. It is an option of TOUGH+ v1.5 [Moridis and Pruess, 2014], a successor to the TOUGH2 [Pruess et al., 1999, 2012] family of codes for multi-component, multiphase fluid and heat flow developed at the Lawrence Berkeley National Laboratory. HYDRATE v1.5 needs the TOUGH+ v1.5 core code in order to compile and execute. It is written in standard FORTRAN 95/2003, and can be run on any computational platformmore » (workstation, PC, Macintosh) for which such compilers are available. By solving the coupled equations of mass and heat balance, the fully operational TOUGH+HYDRATE code can model the non-isothermal gas release, phase behavior and flow of fluids and heat under conditions typical of common natural CH 4-hydrate deposits (i.e., in the permafrost and in deep ocean sediments) in complex geological media at any scale (from laboratory to reservoir) at which Darcy's law is valid. TOUGH+HYDRATE v1.5 includes both an equilibrium and a kinetic model of hydrate formation and dissociation. The model accounts for heat and up to four mass components, i.e., water, CH 4, hydrate, and water-soluble inhibitors such as salts or alcohols. These are partitioned among four possible phases (gas phase, liquid phase, ice phase and hydrate phase). Hydrate dissociation or formation, phase changes and the corresponding thermal effects are fully described, as are the effects of inhibitors. The model can describe all possible hydrate dissociation mechanisms, i.e., depressurization, thermal stimulation, salting-out effects and inhibitor-induced effects.« less

Effect of ENaC Modulators on Rat Neural Responses to NaCl

PubMed Central

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

2014-01-01

The effects of small molecule ENaC activators N,N,N-trimethyl-2-((4-methyl-2-((4-methyl-1H-indol-3-yl)thio)pentanoyl)oxy)ethanaminium iodide (Compound 1) and N-(2-hydroxyethyl)-4-methyl-2-((4-methyl-1H-indol-3-yl)thio)pentanamide (Compound 2), were tested on the benzamil (Bz)-sensitive NaCl chorda tympani (CT) taste nerve response under open-circuit conditions and under ±60 mV applied lingual voltage-clamp, and compared with the effects of known physiological activators (8-CPT-cAMP, BAPTA-AM, and alkaline pH), and an inhibitor (ionomycin+Ca2+) of ENaC. The NaCl CT response was enhanced at −60 mV and suppressed at +60 mV. In every case the CT response (r) versus voltage (V) curve was linear. All ENaC activators increased the open-circuit response (ro) and the voltage sensitivity (κ, negative of the slope of the r versus V curve) and ionomycin+Ca2+ decreased ro and κ to zero. Compound 1 and Compound 2 expressed a sigmoidal-saturating function of concentration (0.25–1 mM) with a half-maximal response concentration (k) of 0.49 and 1.05 mM, respectively. Following treatment with 1 mM Compound 1, 8-CPT-cAMP, BAPTA-AM and pH 10.3, the Bz-sensitive NaCl CT response to 100 mM NaCl was enhanced and was equivalent to the Bz-sensitive CT response to 300 mM NaCl. Plots of κ versus ro in the absence and presence of the activators or the inhibitor were linear, suggesting that changes in the affinity of Na+ for ENaC under different conditions are fully compensated by changes in the apical membrane potential difference, and that the observed changes in the Bz-sensitive NaCl CT response arise exclusively from changes in the maximum CT response (rm). The results further suggest that the agonists enhance and ionomycin+Ca2+ decreases ENaC function by increasing or decreasing the rate of release of Na+ from its ENaC binding site to the receptor cell cytosol, respectively. Irrespective of agonist type, the Bz-sensitive NaCl CT response demonstrated a maximum response enhancement

NaV1.4 mutations cause hypokalaemic periodic paralysis by disrupting IIIS4 movement during recovery

PubMed Central

Lehmann-Horn, Frank; Fan, Chunxiang; Wolf, Markus; Winston, Vern; Merlini, Luciano

2014-01-01

Hypokalaemic periodic paralysis is typically associated with mutations of voltage sensor residues in calcium or sodium channels of skeletal muscle. To date, causative sodium channel mutations have been studied only for the two outermost arginine residues in S4 voltage sensor segments of domains I to III. These mutations produce depolarization of skeletal muscle fibres in response to reduced extracellular potassium, owing to an inward cation-selective gating pore current activated by hyperpolarization. Here, we describe mutations of the third arginine, R3, in the domain III voltage sensor i.e. an R1135H mutation which was found in two patients in separate families and a novel R1135C mutation identified in a third patient in another family. Muscle fibres from a patient harbouring the R1135H mutation showed increased depolarization tendency at normal and reduced extracellular potassium compatible with the diagnosis. Additionally, amplitude and rise time of action potentials were reduced compared with controls, even for holding potentials at which all NaV1.4 are fully recovered from inactivation. These findings may be because of an outward omega current activated at positive potentials. Expression of R1135H/C in mammalian cells indicates further gating defects that include significantly enhanced entry into inactivation and prolonged recovery that may additionally contribute to action potential inhibition at the physiological resting potential. After S4 immobilization in the outward position, mutant channels produce an inward omega current that most likely depolarizes the resting potential and produces the hypokalaemia-induced weakness. Gating current recordings reveal that mutations at R3 inhibit S4 deactivation before recovery, and molecular dynamics simulations suggest that this defect is caused by disrupted interactions of domain III S2 countercharges with S4 arginines R2 to R4 during repolarization of the membrane. This work reveals a novel mechanism of disrupted S

76 FR 20835 - Amendment of VOR Federal Airways V-1, V-7, V-11 and V-20; Kona, HI

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-14

...; Airspace Docket No. 10-AWP-20] Amendment of VOR Federal Airways V-1, V-7, V-11 and V-20; Kona, HI AGENCY..., HI; V-1, V-7, V-11 and V-20. The FAA is taking this action due to procedural changes requiring..., (76 FR 13082), amends VOR Federal Airways V-1, V-7 V-11 and V-20; Kona, HI. These VHF Omnidirectional...

Mechanism of Na accumulation at extended defects in Si from first-principles

NASA Astrophysics Data System (ADS)

Park, Ji-Sang; Chan, Maria K. Y.

2018-04-01

Sodium (Na) impurities in silicon solar cells are considered to play an important role in potential-induced degradation (PID), a significant cause of solar cell degradation and failure. Shorting due to Na accumulation at extended defects has been suggested as a culprit for PID. However, it is not clear how the extended defects are decorated by Na impurities. Using first-principles density functional theory calculations, we find that Na impurities segregate from the bulk into extended defects such as intrinsic stacking faults and Σ3 (111) grain boundaries. The energy barrier required for Na to escape from the extended defects is substantial and similar to the sum of the barrier energy in bulk Si (1.1-1.2 eV) and the segregation energy to the stacking fault (˜0.7 eV). Surprisingly, the migration barrier for Na diffusion within the extended defects is even higher than the energy barrier for escaping. The results suggest that the extended defects likely accumulate Na as the impurities segregate to the defects from the bulk, rather than because of migration through the extended defects.

The V1V2 EOS for Detonation Products

NASA Astrophysics Data System (ADS)

Partom, Yehuda

2010-10-01

Many equations of state (EOS) for detonation products have been proposed and used. Some of them are in analytical form and some in tabular form. The most popular is the Jones-Wilkins-Lee (JWL) EOS. One of the main parameters of a product's EOS is the so-called adiabatic gamma along its main isentrope (γs). For JWL EOSs γs(V) varies in a nonmonotonic way. Going down from the CJ point along the main isentrope, it first increases to create a hump, and then, as V goes to infinity, gamma decreases to perfect gas-like behavior with gamma around 1.3. But according to Davis [1], γs(V) should decrease monotonically with V. Accordingly, in this article we investigate the following: (1) Is the hump in γs(V) necessary? and (2) Is it possible to construct a product's EOS with a monotonic γs(V) that is consistent with experimental data? We find that (1) it is possible to construct a product's EOS without a hump in γs(V); and (2) without a hump in γs(V) there are not enough degrees of freedom to reproduce cylinder test data.

Salt and cadmium stress tolerance caused by overexpression of the Glycine Max Na+/H+ Antiporter (GmNHX1) gene in duckweed (Lemna turionifera 5511).

PubMed

Yang, Lin; Han, Yujie; Wu, Di; Yong, Wang; Liu, Miaomiao; Wang, Sutong; Liu, Wenxin; Lu, Meiyi; Wei, Ying; Sun, Jinsheng

2017-11-01

Cadmium (Cd) pollution has aroused increasing attention due to its toxicity. It has been proved that Na + /H + Antiporter (NHX1) encodes a well-documented protein in Na + /H + trafficking, which leads to salt tolerance. This study showed that Glycine max Na + /H + Antiporter (GmNHX1) improved short-term cadmium and salt resistance in Lemna turionifera 5511. Expression of GmNHX1 prevented root from abscission and cell membrane damage, which also can enhance antioxidant system, inhibited of reactive oxygen species (ROS) accumulation and cause a less absorption of Cd under cadmium and salt stress. The cadmium tolerance suggested that NHX1 was involved under the cadmium stress. Copyright © 2017. Published by Elsevier B.V.

The enhancement of neutral metal Na layer above thunderstorms

NASA Astrophysics Data System (ADS)

Yu, Bingkun; Xue, Xianghui; Lu, Gaopeng; Kuo, Chengling; Dou, Xiankang; Gao, Qi; Qie, Xiushu; Wu, Jianfei; Tang, Yihuan

2017-04-01

Na (sodium) exists as layers of atoms in the mesosphere/lower thermosphere (MLT) at altitudes between 80 and 105 km. It has lower ionization potential of 5.139 eV than atmospheric species, such as O2 (12.06 eV). Tropospheric thunderstorms affect the lower ionosphere and the ionospheric sporadic E (Es) at 100 km can also be influenced by lightning. The mechanism is expected to be associated with transient luminous events (TLE) as red sprites and gigantic jets at upper atmosphere. However, measurements of ionospheric electric fields of 20mV·m-1 above thunderstorms are less than estimated value (>48 0mV·m-1) to excite ionization in the lower ionosphere. We found an enhancement of Na layer above thunderstorms. The increase of Na density in the statistical result can be as much as 500 cm-3 and it will have an impact on ionospheric chemistry and modify the conductivity properties of the MLT region. The ionospheric observations made with two digisondes near the Na lidar, the thunderstorm model, ionosphere model, and Na chemistry model are all used to discuss the possible mechanisms responsible for the enhancement of Na layer after thunderstorms.

Rabies Virus Infection in Eptesicus fuscus Bats Born in Captivity (Naïve Bats)

PubMed Central

Davis, April D.; Jarvis, Jodie A.; Pouliott, Craig; Rudd, Robert J.

2013-01-01

The study of rabies virus infection in bats can be challenging due to quarantine requirements, husbandry concerns, genetic differences among animals, and lack of medical history. To date, all rabies virus (RABV) studies in bats have been performed in wild caught animals. Determining the RABV exposure history of a wild caught bat based on the presence or absence of viral neutralizing antibodies (VNA) may be misleading. Previous studies have demonstrated that the presence of VNA following natural or experimental inoculation is often ephemeral. With this knowledge, it is difficult to determine if a seronegative, wild caught bat has been previously exposed to RABV. The influence of prior rabies exposure in healthy, wild caught bats is unknown. To investigate the pathogenesis of RABV infection in bats born in captivity (naïve bats), naïve bats were inoculated intramuscularly with one of two Eptesicus fuscus rabies virus variants, EfV1 or EfV2. To determine the host response to a heterologous RABV, a separate group of naïve bats were inoculated with a Lasionycteris noctivagans RABV (LnV1). Six months following the first inoculation, all bats were challenged with EfV2. Our results indicate that naïve bats may have some level of innate resistance to intramuscular RABV inoculation. Additionally, naïve bats inoculated with the LnV demonstrated the lowest clinical infection rate of all groups. However, primary inoculation with EfV1 or LnV did not appear to be protective against a challenge with the more pathogenic EfV2. PMID:23741396

Rabies virus infection in Eptesicus fuscus bats born in captivity (naïve bats).

PubMed

Davis, April D; Jarvis, Jodie A; Pouliott, Craig; Rudd, Robert J

2013-01-01

The study of rabies virus infection in bats can be challenging due to quarantine requirements, husbandry concerns, genetic differences among animals, and lack of medical history. To date, all rabies virus (RABV) studies in bats have been performed in wild caught animals. Determining the RABV exposure history of a wild caught bat based on the presence or absence of viral neutralizing antibodies (VNA) may be misleading. Previous studies have demonstrated that the presence of VNA following natural or experimental inoculation is often ephemeral. With this knowledge, it is difficult to determine if a seronegative, wild caught bat has been previously exposed to RABV. The influence of prior rabies exposure in healthy, wild caught bats is unknown. To investigate the pathogenesis of RABV infection in bats born in captivity (naïve bats), naïve bats were inoculated intramuscularly with one of two Eptesicus fuscus rabies virus variants, EfV1 or EfV2. To determine the host response to a heterologous RABV, a separate group of naïve bats were inoculated with a Lasionycteris noctivagans RABV (LnV1). Six months following the first inoculation, all bats were challenged with EfV2. Our results indicate that naïve bats may have some level of innate resistance to intramuscular RABV inoculation. Additionally, naïve bats inoculated with the LnV demonstrated the lowest clinical infection rate of all groups. However, primary inoculation with EfV1 or LnV did not appear to be protective against a challenge with the more pathogenic EfV2.

In Operando XRD and TXM Study on the Metastable Structure Change of NaNi 1/3Fe 1/3Mn 1/3O 2 under Electrochemical Sodium-Ion Intercalation

DOE PAGES

Xie, Yingying; Wang, Hong; Xu, Guiliang; ...

2016-09-02

In operando XRD and TXM-XANES approaches demonstrate that structure evolution in NaNi 1/3Fe 1/3Mn 1/3O 2 during cycling follows a continuous change, and the formation of a nonequilibrium solid solution phase in the existence of two phases. Here, an O3' and P3' monoclinic phase occur, and redox couples of Ni 3+/Ni 4+ and Fe 3+/Fe 4+ are mainly responsible in the charge voltage range from 4.0 to 4.3 V.

Structural transformation during Li/Na insertion and theoretical cyclic voltammetry of the δ-NH4V4O10 electrode: a first-principles study.

PubMed

Sarkar, Tanmay; Kumar, Parveen; Bharadwaj, Mridula Dixit; Waghmare, Umesh

2016-04-14

A double layer δ-NH4V4O10, due to its high energy storage capacity and excellent rate capability, is a very promising cathode material for Li-ion and Na-ion batteries for large-scale renewable energy storage in transportation and smart grids. While it possesses better stability, and higher ionic and electronic conductivity than the most widely explored V2O5, the mechanisms of its cyclability are yet to be understood. Here, we present a theoretical cyclic voltammetry as a tool based on first-principles calculations, and uncover structural transformations that occur during Li(+)/Na(+) insertion (x) into (Lix/Nax)NH4V4O10. Structural distortions associated with single-phase and multi-phase structural changes during the insertion of Li(+)/Na(+), identified through the analysis of voltage profile and theoretical cyclic voltammetry are in agreement with the reported experimental electrochemical measurements on δ-NH4V4O10. We obtain an insight into its electronic structure with a lower band gap that is responsible for the high rate capability of (Lix/Nax) δ-NH4V4O10. The scheme of theoretical cyclic voltammetry presented here will be useful for addressing issues of cyclability and energy rate in other electrode materials.

Quantitative (23) Na MRI of human knee cartilage using dual-tuned (1) H/(23) Na transceiver array radiofrequency coil at 7 tesla.

PubMed

Moon, Chan Hong; Kim, Jung-Hwan; Zhao, Tiejun; Bae, Kyongtae Ty

2013-11-01

To develop quantitative dual-tuned (DT) (1) H/(23) Na MRI of human knee cartilage in vivo at 7 Tesla (T). A sensitive (23) Na transceiver array RF coil was developed at 7T. B1 fields generated by the transceiver array coil were characterized and corrected in the (23) Na images. Point spread function (PSF) of the (23) Na images was measured, and the signal decrease due to partial-volume-effect was compensated in [(23) Na] quantification of knee cartilage. SNR and [(23) Na] in anterior femoral cartilage were measured from seven healthy subjects. SNR of (23) Na image with the transceiver array coil was higher than that of birdcage coil. SNR in the cartilage at 2-mm isotropic resolution was 26.80 ± 3.69 (n = 7). B1 transmission and reception fields produced by the DT coil at 7T were similar to each other. Effective full-width-half-maximum of (23) Na image was ∼5 mm at 2-mm resolution. Mean [(23) Na] was 288.13 ± 29.50 mM (n = 7) in the anterior femoral cartilage of normal subjects. We developed a new high-sensitivity (23) Na RF coil for knee MRI at 7T. Our (1) H/(23) Na MRI allowed quantitative measurement of [(23) Na] in knee cartilage by measuring PSF and cartilage thickness from (23) Na and (1) H image, respectively. Copyright © 2013 Wiley Periodicals, Inc.

Applications of “Tender” Energy (1-5 keV) X-ray Absorption Spectroscopy in Life Sciences

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

Northrup, Paul; Leri, Alessandra; Tappero, Ryan

The “tender” energy range of 1 to 5 keV, between the energy ranges of most “hard” (>5 keV) and “soft” (<1 keV) synchrotron X-ray facilities, offers some unique opportunities for synchrotron-based X-ray absorption fine structure spectroscopy in life sciences. In particular the K absorption edges of Na through Ca offer opportunities to study local structure, speciation, and chemistry of many important biological compounds, structures and processes. This is an area of largely untapped science, in part due to a scarcity of optimized facilities. Such measurements also entail unique experimental challenges. Lastly, this brief review describes the technique, its experimental challenges,more » recent progress in development of microbeam measurement capabilities, and several highlights illustrating applications in life sciences.« less

Applications of “Tender” Energy (1-5 keV) X-ray Absorption Spectroscopy in Life Sciences

DOE PAGES

Northrup, Paul; Leri, Alessandra; Tappero, Ryan

2016-02-15

The “tender” energy range of 1 to 5 keV, between the energy ranges of most “hard” (>5 keV) and “soft” (<1 keV) synchrotron X-ray facilities, offers some unique opportunities for synchrotron-based X-ray absorption fine structure spectroscopy in life sciences. In particular the K absorption edges of Na through Ca offer opportunities to study local structure, speciation, and chemistry of many important biological compounds, structures and processes. This is an area of largely untapped science, in part due to a scarcity of optimized facilities. Such measurements also entail unique experimental challenges. Lastly, this brief review describes the technique, its experimental challenges,more » recent progress in development of microbeam measurement capabilities, and several highlights illustrating applications in life sciences.« less

Epigenetic silencing of Na,K-ATPase β1 subunit gene ATP1B1 by methylation in clear cell renal cell carcinoma

PubMed Central

Selvakumar, Ponniah; Owens, Tori A; David, Justin M; Petrelli, Nicholas J; Christensen, Brock C; Lakshmikuttyamma, Ashakumary; Rajasekaran, Ayyappan K

2014-01-01

The Na,K-ATPase or sodium pump carries out the coupled extrusion of Na+ and uptake of K+ across the plasma membranes of cells of most higher eukaryotes. We have shown earlier that Na,K-ATPase-β1 (NaK-β) protein levels are highly reduced in poorly differentiated kidney carcinoma cells in culture and in patients' tumor samples. The mechanism(s) regulating the expression of NaK-β in tumor tissues has yet to be explored. We hypothesized that DNA methylation plays a role in silencing the NaK-β gene (ATP1B1) expression in kidney cancers. In this study, to the best of our knowledge we provide the first evidence that ATP1B1 is epigenetically silenced by promoter methylation in both renal cell carcinoma (RCC) patients’ tissues and cell lines. We also show that knockdown of the von Hippel-Lindau (VHL) tumor suppressor gene in RCC cell lines results in enhanced ATP1B1 promoter AT hypermethylation, which is accompanied by reduced expression of NaK-β. Furthermore, treatment with 5-Aza-2′-deoxycytidine rescued the expression of ATP1B1 mRNA as well as NaK-β protein in these cells. These data demonstrate that promoter hypermethylation is associated with reduced NaK-β expression, which might contribute to RCC initiation and/or disease progression. PMID:24452105

Epigenetic silencing of Na,K-ATPase β 1 subunit gene ATP1B1 by methylation in clear cell renal cell carcinoma.

PubMed

Selvakumar, Ponniah; Owens, Tori A; David, Justin M; Petrelli, Nicholas J; Christensen, Brock C; Lakshmikuttyamma, Ashakumary; Rajasekaran, Ayyappan K

2014-04-01

The Na,K-ATPase or sodium pump carries out the coupled extrusion of Na(+) and uptake of K(+) across the plasma membranes of cells of most higher eukaryotes. We have shown earlier that Na,K-ATPase-β 1 (NaK-β) protein levels are highly reduced in poorly differentiated kidney carcinoma cells in culture and in patients' tumor samples. The mechanism(s) regulating the expression of NaK-β in tumor tissues has yet to be explored. We hypothesized that DNA methylation plays a role in silencing the NaK-β gene (ATP1B1) expression in kidney cancers. In this study, to the best of our knowledge we provide the first evidence that ATP1B1 is epigenetically silenced by promoter methylation in both renal cell carcinoma (RCC) patients' tissues and cell lines. We also show that knockdown of the von Hippel-Lindau (VHL) tumor suppressor gene in RCC cell lines results in enhanced ATP1B1 promoter AT hypermethylation, which is accompanied by reduced expression of NaK-β. Furthermore, treatment with 5-Aza-2'-deoxycytidine rescued the expression of ATP1B1 mRNA as well as NaK-β protein in these cells. These data demonstrate that promoter hypermethylation is associated with reduced NaK-β expression, which might contribute to RCC initiation and/or disease progression.

Optical and Magnetic Resonance Studies of Na-Diffused ZnO Bulk Single Crystals

NASA Astrophysics Data System (ADS)

Glaser, E. R.; Garces, N. Y.; Parmar, N. S.; Lynn, K. G.

2013-03-01

Photoluminescence (PL) and optically-detected magnetic resonance (ODMR) at 24 GHz were performed on bulk ZnO crystals after diffusion of Na impurities that were explored as an alternate doping source for p-type conductivity. PL at 2K revealed strong bandedge excitonic recombination at 3.361 eV and a broad ``orange'' PL band at 2.17 eV with FWHM of ~0.5 eV. This ``orange'' emission is very similar to that reported previously[1] from thermoluminescence measurements of intentionally Na-doped bulk ZnO and, thus, strongly suggests the incorporation and activation of the Na-diffused impurities. ODMR performed on this ``orange'' PL revealed two signals. The first was a sharp feature with g-value of ~1.96 and is a well-known ``fingerprint'' of shallow donors in ZnO. The second signal consisted of a pair of lines with an intensity ratio of ~3:1 and with g-tensors (g∥,g⊥ ~2.008-2.029) very similar to ESR signals attributed previously[2] to holes bound to Na impurities located at the axial and non-axial Zn host lattice sites in Na-doped ZnO. Thus, the ``orange'' PL can be tentatively assigned to radiative recombination between residual shallow donors and deep Na-related hole traps.

Na+/H+ Exchange Activity in the Plasma Membrane of Arabidopsis1

PubMed Central

Qiu, Quan-Sheng; Barkla, Bronwyn J.; Vera-Estrella, Rosario; Zhu, Jian-Kang; Schumaker, Karen S.

2003-01-01

In plants, Na+/H+ exchangers in the plasma membrane are critical for growth in high levels of salt, removing toxic Na+ from the cytoplasm by transport out of the cell. The molecular identity of a plasma membrane Na+/H+ exchanger in Arabidopsis (SOS1) has recently been determined. In this study, immunological analysis provided evidence that SOS1 localizes to the plasma membrane of leaves and roots. To characterize the transport activity of this protein, purified plasma membrane vesicles were isolated from leaves of Arabidopsis. Na+/H+ exchange activity, monitored as the ability of Na to dissipate an established pH gradient, was absent in plants grown without salt. However, exchange activity was induced when plants were grown in 250 mm NaCl and increased with prolonged salt exposure up to 8 d. H+-coupled exchange was specific for Na, because chloride salts of other monovalent cations did not dissipate the pH gradient. Na+/H+ exchange activity was dependent on Na (substrate) concentration, and kinetic analysis indicated that the affinity (apparent Km) of the transporter for Na+ is 22.8 mm. Data from two experimental approaches supports electroneutral exchange (one Na+ exchanged for one proton): (a) no change in membrane potential was measured during the exchange reaction, and (b) Na+/H+ exchange was unaffected by the presence or absence of a membrane potential. Results from this research provide a framework for future studies into the regulation of the plant plasma membrane Na+/H+ exchanger and its relative contribution to the maintenance of cellular Na+ homeostasis during plant growth in salt. PMID:12805632

Determination of neutron capture cross sections of 232Th at 14.1 MeV and 14.8 MeV using the neutron activation method

NASA Astrophysics Data System (ADS)

Lan, Chang-Lin; Zhang, Yi; Lv, Tao; Xie, Bao-Lin; Peng, Meng; Yao, Ze-En; Chen, Jin-Gen; Kong, Xiang-Zhong

2017-04-01

The 232Th(n, γ)233Th neutron capture reaction cross sections were measured at average neutron energies of 14.1 MeV and 14.8 MeV using the activation method. The neutron flux was determined using the monitor reaction 27Al(n,α)24Na. The induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector. The experimentally determined cross sections were compared with the data in the literature, and the evaluated data of ENDF/B-VII.1, JENDL-4.0u+, and CENDL-3.1. The excitation functions of the 232Th(n,γ)233Th reaction were also calculated theoretically using the TALYS1.6 computer code. Supported by Chinese TMSR Strategic Pioneer Science and Technology Project-The Th-U Fuel Physics Term (XDA02010100) and National Natural Science Foundation of China (11205076, 21327801)

Dependence of Na+ pump current on external monovalent cations and membrane potential in rabbit cardiac Purkinje cells.

PubMed Central

Bielen, F V; Glitsch, H G; Verdonck, F

1991-01-01

1. The effect of membrane potential and various extracellular monovalent cations on the Na+ pump current (Ip) was studied on isolated, single Purkinje cells of the rabbit heart by means of whole-cell recording. 2. Ip was identified as current activated by external K+ or its congeners NH4+ and Tl+. The current was blocked by dihydroouabain (1-5 x 10(-4) M) over the whole range of membrane potentials tested. 3. In Na(+)-containing solution half-maximum Ip activation (K0.5) occurred at 0.4 mM-Tl+, 1.9 mM-K+ and 5.7 mM-NH4+ (holding potential, -20 mV). 4. The pump current (Ip)-voltage (V) relationship of the cells in Na(+)-containing media with K+ or its congeners at the tested concentrations greater than K0.5 displayed a steep positive slope at negative membrane potentials between -120 and -20 mV. Little voltage dependence of Ip was observed at more positive potentials up to +40 mV. At even more positive potentials Ip measured at 2 and 5.4 mM-K+ decreased. 5. Lowering the concentration of K+ or its congeners below the K0.5 value in Na(+)-containing solution induced a region of negative slope of the Ip-V curve at membrane potentials positive to -20 mV. 6. The shape of the Ip-V relationship remained unchanged when the K+ concentration (5.4 mM) of the Na(+)-containing medium was replaced by NH4+ or Tl+ concentrations of similar potency to activate Ip (20 mM-NH4+ or 2 mM-Tl+). 7. In Na(+)-free, choline-containing solution half-maximum Ip activation occurred at 0.13 mM-K+ (holding potential, -20 mV). 8. At negative membrane potentials the positive slope of the Ip-V curve was flatter in Na(+)-free than in Na(+)-containing media. A reduced voltage dependence of Ip persisted, regardless of whether choline ions or Li+ were used as a Na+ substitute. 9. Lowering the K+ concentration of the Na(+)-free, choline-containing solution to 0.05 mM evoked an extended region of negative slope in the Ip-V relationship at membrane potentials between -40 and +60 mV. 10. It is concluded that

pH-Specific structural speciation of the ternary V(V)-peroxido-betaine system: a chemical reactivity-structure correlation.

PubMed

Gabriel, C; Kioseoglou, E; Venetis, J; Psycharis, V; Raptopoulou, C P; Terzis, A; Voyiatzis, G; Bertmer, M; Mateescu, C; Salifoglou, A

2012-06-04

Vanadium involvement in cellular processes requires deep understanding of the nature and properties of its soluble and bioavailable forms arising in aqueous speciations of binary and ternary systems. In an effort to understand the ternary vanadium-H(2)O(2)-ligand interactions relevant to that metal ion's biological role, synthetic efforts were launched involving the physiological ligands betaine (Me(3)N(+)CH(2)CO(2)(-)) and H(2)O(2). In a pH-specific fashion, V(2)O(5), betaine, and H(2)O(2) reacted and afforded three new, unusual, and unique compounds, consistent with the molecular formulation K(2)[V(2)O(2)(O(2))(4){(CH(3))(3)NCH(2)CO(2))}]·H(2)O (1), (NH(4))(2)[V(2)O(2)(O(2))(4){(CH(3))(3)NCH(2)CO(2))}]·0.75H(2)O (2), and {Na(2)[V(2)O(2)(O(2))(4){(CH(3))(3)NCH(2)CO(2))}(2)]}(n)·4nH(2)O (3). All complexes 1-3 were characterized by elemental analysis; UV/visible, FT-IR, Raman, and NMR spectroscopy in solution and the solid state; cyclic voltammetry; TGA-DTG; and X-ray crystallography. The structures of 1 and 2 reveal the presence of unusual ternary dinuclear vanadium-tetraperoxido-betaine complexes containing [(V(V)═O)(O(2))(2)] units interacting through long V-O bonds. The two V(V) ions are bridged through the oxygen terminal of one of the peroxide groups bound to the vanadium centers. The betaine ligand binds only one of the two V(V) ions. In the case of the third complex 3, the two vanadium centers are not immediate neighbors, with Na(+) ions (a) acting as efficient oxygen anchors and through Na-O bonds holding the two vanadium ions in place and (b) providing for oxygen-containing ligand binding leading to a polymeric lattice. In 1 and 3, interesting 2D (honeycomb) and 1D (zigzag chains) topologies of potassium nine-coordinate polyhedra (1) and sodium octahedra (3), respectively, form. The collective physicochemical properties of the three ternary species 1-3 project the chemical role of the low molecular mass biosubstrate betaine in binding V(V

Binding of benzocaine in batrachotoxin-modified Na+ channels. State- dependent interactions

PubMed Central

1994-01-01

Hille (1977. Journal of General Physiology. 69:497-515) first proposed a modulated receptor hypothesis (MRH) to explain the action of benzocaine in voltage-gated Na+ channels. Using the MRH as a framework, we examined benzocaine binding in batrachotoxin (BTX)-modified Na+ channels under voltage-clamp conditions using either step or ramp command signals. We found that benzocaine binding is strongly voltage dependent. At -70 mV, the concentration of benzocaine that inhibits 50% of BTX-modified Na+ currents in GH3 cells (IC50) is 0.2 mM, whereas at +50 mV, the IC50 is 1.3 mM. Dose-response curves indicate that only one molecule of benzocaine is required to bind with one BTX-modified Na+ channel at -70 mV, whereas approximately two molecules are needed at +50 mV. Upon treatment with the inactivation modifier chloramine-T, the binding affinity of benzocaine is reduced significantly at -70 mV, probably as a result of the removal of the inactivated state of BTX- modified Na+ channels. The same treatment, however, enhances the binding affinity of cocaine near this voltage. External Na+ ions appear to have little effect on benzocaine binding, although they do affect cocaine binding. We conclude that two mechanisms underlie the action of local anesthetics in BTX-modified Na+ channels. Unlike open-channel blockers such as cocaine and bupivacaine, neutral benzocaine binds preferentially with BTX-modified Na+ channels in a closed state. Furthermore, benzocaine can be modified chemically so that it behaves like an open-channel blocker. This compound also elicits a use- dependent block in unmodified Na+ channels after repetitive depolarizations, whereas benzocaine does not. The implications of these findings for the MRH theory will be discussed. PMID:8195785

Structure of the Nav1.4-β1 Complex from Electric Eel.

PubMed

Yan, Zhen; Zhou, Qiang; Wang, Lin; Wu, Jianping; Zhao, Yanyu; Huang, Gaoxingyu; Peng, Wei; Shen, Huaizong; Lei, Jianlin; Yan, Nieng

2017-07-27

Voltage-gated sodium (Na v ) channels initiate and propagate action potentials. Here, we present the cryo-EM structure of EeNa v 1.4, the Na v channel from electric eel, in complex with the β1 subunit at 4.0 Å resolution. The immunoglobulin domain of β1 docks onto the extracellular L5 I and L6 IV loops of EeNa v 1.4 via extensive polar interactions, and the single transmembrane helix interacts with the third voltage-sensing domain (VSD III ). The VSDs exhibit "up" conformations, while the intracellular gate of the pore domain is kept open by a digitonin-like molecule. Structural comparison with closed Na v PaS shows that the outward transfer of gating charges is coupled to the iris-like pore domain dilation through intricate force transmissions involving multiple channel segments. The IFM fast inactivation motif on the III-IV linker is plugged into the corner enclosed by the outer S4-S5 and inner S6 segments in repeats III and IV, suggesting a potential allosteric blocking mechanism for fast inactivation. Copyright © 2017 Elsevier Inc. All rights reserved.

Multiple roles for the Na,K-ATPase subunits, Atp1a1 and Fxyd1, during brain ventricle development

PubMed Central

Chang, Jessica T.; Lowery, Laura Anne; Sive, Hazel

2012-01-01

Formation of the vertebrate brain ventricles requires both production of cerebrospinal fluid (CSF), and its retention in the ventricles. The Na,K-ATPase is required for brain ventricle development, and we show here that this protein complex impacts three associated processes. The first requires both the alpha subunit (Atp1a1) and the regulatory subunit, Fxyd1, and leads to formation of a cohesive neuroepithelium, with continuous apical junctions. The second process leads to modulation of neuroepithelial permeability, and requires Atp1a1, which increases permeability with partial loss of function and decreases it with overexpression. In contrast, fxyd1 overexpression does not alter neuroepithelial permeability, suggesting that its activity is limited to neuroepithelium formation. RhoA regulates both neuroepithelium formation and permeability, downstream of the Na,K-ATPase. A third process, likely to be CSF production, is RhoA-independent, requiring Atp1a1, but not Fxyd1. Consistent with a role for Na,K-ATPase pump function, the inhibitor ouabain prevents neuroepithelium formation, while intracellular Na+ increases after Atp1a1 and Fxyd1 loss of function. These data include the first reported role for Fxyd1 in the developing brain, and indicate that the Na,K-ATPase regulates three aspects of brain ventricle development essential for normal function - formation of a cohesive neuroepithelium, restriction of neuroepithelial permeability, and production of CSF. PMID:22683378

Measurement of the strengths of the resonances at 417, 458, 611, 632 and 1222 keV in the 22Ne(p, γ)23Na reaction

NASA Astrophysics Data System (ADS)

Ferraro, Federico

2018-01-01

The 22Ne(p, γ)23Na reaction is part of the NeNa cycle of hydrogen burning. This cycle plays a key role in the nucleosynthesis of the elements between 20Ne and 27Al in red giant stars, asymptotic giant stars and classical nova explosions. The strengths of the resonances at proton energies above 400 keV are still affected by high uncertainty. In order to reduce this uncertainty, a precision study of some of the most intense resonances between 400 keV and 1250 keV has been performed at the HZDR 3 MV Tandetron. The target, made of 22Ne implanted in a 0.22 mm thick Ta backing, has been characterized using the 1222 keV and 458 keV resonances, well known in literature. Subsequently, the strengths of the resonances at 417, 458, 611, 632 and 1222 keV were determined. Two HPGe detectors equipped with active anti-Compton shielding have been used.

New hydrogen titanium phosphate sulfate electrodes for Li-ion and Na-ion batteries

NASA Astrophysics Data System (ADS)

Zhao, Ran; Mieritz, Daniel; Seo, Dong-Kyun; Chan, Candace K.

2017-03-01

NASICON-type materials with general formula AxM2(PO4)3 (A = Li or Na, M = Ti, V, and Fe) are promising candidates for Li- and Na-ion batteries due to their open three-dimensional framework structure. Here we report the electrochemical properties of hydrogen titanium phosphate sulfate, H0.4Ti2(PO4)2.4(SO4)0.6 (HTPS), a new mixed polyanion material with NASICON structure. Micron-sized HTPS aggregates with crystallite grain size of ca. 23 nm are synthesized using a sol-gel synthesis in an acidic medium. The properties of the as-synthesized HTPS, ball-milled HTPS, and samples prepared as carbon composites using an in-situ glucose decomposition reaction are investigated. A capacity of 148 mAh g-1 corresponding to insertion of 2 Li+ per formula unit is observed in the ball-milled HTPS over the potential window of 1.5-3.4 V vs. Li/Li+. Lithiation at ca. 2.8 and 2.5 V is determined to occur through filling of the M1 and M2 sites, respectively. Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) are used characterize the HTPS before and after cycling. Evaluation of the HTPS in a Na-ion cell is also performed. A discharge capacity of 93 mAh g-1 with sodiation at ca. 2.9 and 2.2 V vs. Na/Na+ is observed.

26 CFR 1.414(v)-1 - Catch-up contributions.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 26 Internal Revenue 5 2014-04-01 2014-04-01 false Catch-up contributions. 1.414(v)-1 Section 1.414(v)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Pension, Profit-Sharing, Stock Bonus Plans, Etc. § 1.414(v)-1 Catch-up...

26 CFR 1.414(v)-1 - Catch-up contributions.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 26 Internal Revenue 5 2013-04-01 2013-04-01 false Catch-up contributions. 1.414(v)-1 Section 1.414(v)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Pension, Profit-Sharing, Stock Bonus Plans, Etc. § 1.414(v)-1 Catch-up...

26 CFR 1.414(v)-1 - Catch-up contributions.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 26 Internal Revenue 5 2012-04-01 2011-04-01 true Catch-up contributions. 1.414(v)-1 Section 1.414(v)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Pension, Profit-Sharing, Stock Bonus Plans, Etc. § 1.414(v)-1 Catch-up...

26 CFR 1.414(v)-1 - Catch-up contributions.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 26 Internal Revenue 5 2011-04-01 2011-04-01 false Catch-up contributions. 1.414(v)-1 Section 1.414(v)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Pension, Profit-Sharing, Stock Bonus Plans, Etc. § 1.414(v)-1 Catch-up...

26 CFR 1.414(v)-1 - Catch-up contributions.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 26 Internal Revenue 5 2010-04-01 2010-04-01 false Catch-up contributions. 1.414(v)-1 Section 1.414(v)-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES Pension, Profit-Sharing, Stock Bonus Plans, Etc. § 1.414(v)-1 Catch-up contributions...

V&V of MCNP 6.1.1 Beta Against Intermediate and High-Energy Experimental Data

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

Mashnik, Stepan G

This report presents a set of validation and verification (V&V) MCNP 6.1.1 beta results calculated in parallel, with MPI, obtained using its event generators at intermediate and high-energies compared against various experimental data. It also contains several examples of results using the models at energies below 150 MeV, down to 10 MeV, where data libraries are normally used. This report can be considered as the forth part of a set of MCNP6 Testing Primers, after its first, LA-UR-11-05129, and second, LA-UR-11-05627, and third, LA-UR-26944, publications, but is devoted to V&V with the latest, 1.1 beta version of MCNP6. The MCNP6more » test-problems discussed here are presented in the /VALIDATION_CEM/and/VALIDATION_LAQGSM/subdirectories in the MCNP6/Testing/directory. README files that contain short descriptions of every input file, the experiment, the quantity of interest that the experiment measures and its description in the MCNP6 output files, and the publication reference of that experiment are presented for every test problem. Templates for plotting the corresponding results with xmgrace as well as pdf files with figures representing the final results of our V&V efforts are presented. Several technical “bugs” in MCNP 6.1.1 beta were discovered during our current V&V of MCNP6 while running it in parallel with MPI using its event generators. These “bugs” are to be fixed in the following version of MCNP6. Our results show that MCNP 6.1.1 beta using its CEM03.03, LAQGSM03.03, Bertini, and INCL+ABLA, event generators describes, as a rule, reasonably well different intermediate- and high-energy measured data. This primer isn’t meant to be read from cover to cover. Readers may skip some sections and go directly to any test problem in which they are interested.« less

Na-Zn liquid metal battery

NASA Astrophysics Data System (ADS)

Xu, Junli; Kjos, Ole Sigmund; Osen, Karen Sende; Martinez, Ana Maria; Kongstein, Ole Edvard; Haarberg, Geir Martin

2016-11-01

A new kind of membrane free liquid metal battery was developed. The battery employs liquid sodium and zinc as electrodes both in liquid state, and NaCl-CaCl2 molten salts as electrolyte. The discharge flat voltage is in the range of about 1.4 V-1.8 V, and the cycle efficiency achieved is about 90% at low discharge current densities (below 40 mA cm-2). Moreover, this battery can also be charged and discharged at high current density with good performance. The discharge flat voltage is above 1.1 V when it is discharged at 100 mA cm-2, while it is about 0.8 V with 100% cycle efficiency when it is discharged at 200 mA cm-2. Compared to other reported liquid metal battery, this battery has lower cost, which suggests broad application prospect in energy storage systems for power grid.

USEEIO v1.1-Matrices

EPA Science Inventory

This dataset provides the basic building blocks for the USEEIO v1.1 model and life cycle results per $1 (2013 USD) demand for all goods and services in the model in the producer's price (see BEA 2015). The methodology underlying USEEIO is described in Yang, Ingwersen et al., 2017...

Serological Profile of Torque Teno Sus Virus Species 1 (TTSuV1) in Pigs and Antigenic Relationships between Two TTSuV1 Genotypes (1a and 1b), between Two Species (TTSuV1 and -2), and between Porcine and Human Anelloviruses

PubMed Central

Huang, Yao-Wei; Harrall, Kylie K.; Dryman, Barbara A.; Opriessnig, Tanja; Vaughn, Eric M.; Roof, Michael B.

2012-01-01

The family Anelloviridae includes human and animal torque teno viruses (TTVs) with extensive genetic diversity. The antigenic diversity among anelloviruses has never been assessed. Using torque teno sus virus (TTSuV) as a model, we describe here the first investigation of the antigenic relationships among different anelloviruses. Using a TTSuV genotype 1a (TTSuV1a) or TTSuV1b enzyme-linked immunosorbent assay (ELISA) based on the respective putative ORF1 capsid antigen and TTSuV1-specific real-time PCR, the combined serological and virological profile of TTSuV1 infection in pigs was determined and compared with that of TTSuV2. TTSuV1 is likely not associated with porcine circovirus-associated disease (PCVAD), because both the viral loads and antibody levels were not different between affected and unaffected pigs and because there was no synergistic effect of concurrent PCV2/TTSuV1 infections. We did observe a higher correlation of IgG antibody levels between anti-TTSuV1a and -TTSuV1b than between anti-TTSuV1a or -1b and anti-TTSuV2 antibodies in these sera, implying potential antigenic cross-reactivity. To confirm this, rabbit antisera against the putative capsid proteins of TTSuV1a, TTSuV1b, or TTSuV2 were generated, and the antigenic relationships among these TTSuVs were analyzed by an ELISA and by an immunofluorescence assay (IFA) using PK-15 cells transfected with one of the three TTSuV ORF1 constructs. The results demonstrate antigenic cross-reactivity between the two genotypes TTSuV1a and TTSuV1b but not between the two species TTSuV1a or -1b and TTSuV2. Furthermore, an anti-genogroup 1 human TTV antiserum did not react with any of the three TTSuV antigens. These results have important implications for an understanding of the diversity of anelloviruses as well as for the classification and vaccine development of TTSuVs. PMID:22811540

Investigation of sodium insertion–extraction in olivine Na x FePO 4 (0 ≤ x ≤ 1) using first-principles calculations

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

Saracibar, A.; Carrasco, J.; Saurel, D.

Olivine NaFePO4 has recently attracted the attention of the scientific community as a promising cathode material for Na-ion batteries. In this work we combine density functional theory (DFT) calculations and high resolution synchrotron X-ray diffraction (HRXRD) experiments to study the phase stability of NaxFePO4 along the whole range of sodium compositions (0 ≤ x ≤ 1). DFT calculations reveal the existence of two intermediate structures governing the phase stability at x = 2/3 and x = 5/6. This is in contrast to isostructural LiFePO4, which is a broadly used cathode in Li-ion batteries. Na2/3FePO4 and Na5/6FePO4 ground states both alignmore » vacancies diagonally within the ab plane, coupled to a Fe2+/Fe3+ alignment. HRXRD data for NaxFePO4 (2/3 < x < 1) materials show common superstructure reflections up to x = 5/6 within the studied compositions. The computed intercalation voltage profile shows a voltage difference of 0.16 V between NaFePO4 and Na2/3FePO4 in agreement with the voltage discontinuity observed experimentally during electrochemical insertion.« less

Evaluation to the effect of B2O3-La2O3-SrO-Na2O-Al2O3 bonding agent on Ti6Al4V-porcelain bonding.

PubMed

Zhao, C Q; Wu, S Q; Lu, Y J; Gan, Y L; Guo, S; Lin, J J; Huang, T T; Lin, J X

2016-10-01

Low-fusing bonding agents have been widely applied in Ti-ceramics restorations. As an important category, borate bonding agents have great potentials in increasing Ti-porcelain bonding. The purpose of this study is to evaluate the effect of borate bonding agent with addition of Na2O and Al2O3 on Ti6Al4V-porcelain bonding. The thermal properties of borate bonding agent, such as glass transition temperature (Tg) and crystallization peak temperature (Tp), were investigated to establish the sintering process. And the coefficient of thermal expansion (CTE) was to evaluate the matching effect of porcelain to Ti6Al4V. The bond strength was analyzed by the three point bending test. The microscopic morphology of the borate bonding agent surface after sintering, the interface of Ti-borate bonding agent-porcelain, and the fracture mode after porcelains fracture, were studied to assess the influence of borate bonding agent on Ti6Al4V-ceramics. With the addition of Na2O and Al2O3, the porcelain residues were observed increased indication on the Ti6Al4V surface after porcelain fracture and the bond strength was acquired the maximum (49.45MPa) in the bonding agent composition of 75.70B2O3-5.92La2O3-11.84SrO-4.67Na2O-1.87Al2O3. Those results suggest that borate bonding agent is an effective way to improve the Ti6Al4V-ceramics bond strength. And the addition of Na2O and Al2O3 strengthen this effect. Copyright © 2016 Elsevier Ltd. All rights reserved.

Global distribution of NA1 genotype of respiratory syncytial virus and its evolutionary dynamics assessed from the past 11 years.

PubMed

Haider, Md Shakir Hussain; Deeba, Farah; Khan, Wajihul Hasan; Naqvi, Irshad H; Ali, Sher; Ahmed, Anwar; Broor, Shobha; Alsenaidy, Hytham A; Alsenaidy, Abdulrahman M; Dohare, Ravins; Parveen, Shama

2018-06-01

Respiratory syncytial virus (RSV) is a potent pathogen having global distribution. The main purpose of this study was to gain an insight into distribution pattern of the NA1 genotype of group A RSV across the globe together with its evolutionary dynamics. We focused on the second hypervariable region of the G protein gene and used the same for Phylogenetic, Bayesian and Network analyses. Eighteen percent of the samples collected from 500 symptomatic pediatric patients with acute respiratory tract infection (ARI) were found to be positive for RSV during 2011-15 from New Delhi, India. Of these, group B RSV was predominant and clustered into two different genotypes (BA and SAB4). Similarly, group A viruses clustered into two genotypes (NA1 and ON1). The data set from the group A viruses included 543 sequences from 23 different countries including 67 strains from India. The local evolutionary dynamics suggested consistent virus population of NA1 genotype in India during 2009 to 2014. The molecular clock analysis suggested that most recent common ancestor of group A and NA1 genotype have emerged in during the years 1953 and 2000, respectively. The global evolutionary rates of group A viruses and NA1 genotype were estimated to be 3.49 × 10 -3 (95% HPD, 2.90-4.17 × 10 -3 ) and 3.56 × 10 -3 (95% HPD, 2.91 × 10 -3 -4.18 × 10 -3 ) substitution/site/year, respectively. Analysis of the NA1 genotype of group A RSV reported during 11 years i.e. from 2004 to 2014 showed its dominance in 21 different countries across the globe reflecting its evolutionary dynamics. The Network analysis showed highly intricate but an inconsistent pattern of haplotypes of NA1 genotype circulating in the world. Present study seems to be first comprehensive attempt on global distribution and evolution of NA1 genotype augmenting the optimism towards the vaccine development. Copyright © 2018 Elsevier B.V. All rights reserved.

Search for a Hypothetical 16.7 MeV Gauge Boson and Dark Photons in the NA64 Experiment at CERN

NASA Astrophysics Data System (ADS)

Banerjee, D.; Burtsev, V. E.; Chumakov, A. G.; Cooke, D.; Crivelli, P.; Depero, E.; Dermenev, A. V.; Donskov, S. V.; Dusaev, R. R.; Enik, T.; Charitonidis, N.; Feshchenko, A.; Frolov, V. N.; Gardikiotis, A.; Gerassimov, S. G.; Gninenko, S. N.; Hösgen, M.; Jeckel, M.; Karneyeu, A. E.; Kekelidze, G.; Ketzer, B.; Kirpichnikov, D. V.; Kirsanov, M. M.; Konorov, I. V.; Kovalenko, S. G.; Kramarenko, V. A.; Kravchuk, L. V.; Krasnikov, N. V.; Kuleshov, S. V.; Lyubovitskij, V. E.; Lysan, V.; Matveev, V. A.; Mikhailov, Yu. V.; Peshekhonov, D. V.; Polyakov, V. A.; Radics, B.; Rojas, R.; Rubbia, A.; Samoylenko, V. D.; Tikhomirov, V. O.; Tlisov, D. A.; Toropin, A. N.; Trifonov, A. Yu.; Vasilishin, B. I.; Vasquez Arenas, G.; Volkov, P. V.; Volkov, V.; Ulloa, P.; NA64 Collaboration

2018-06-01

We report the first results on a direct search for a new 16.7 MeV boson (X ) which could explain the anomalous excess of e+e- pairs observed in the excited Be* 8 nucleus decays. Because of its coupling to electrons, the X could be produced in the bremsstrahlung reaction e-Z →e-Z X by a 100 GeV e- beam incident on an active target in the NA64 experiment at the CERN Super Proton Synchrotron and observed through the subsequent decay into a e+e- pair. With 5.4 ×1010 electrons on target, no evidence for such decays was found, allowing us to set first limits on the X -e- coupling in the range 1.3 ×10-4≲ɛe≲4.2 ×10-4 excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A') from nonobservation of the decay A'→e+e- of the bremsstrahlung A' with a mass ≲23 MeV .

Luminorefrigeration: vibrational cooling of NaCs.

PubMed

Wakim, A; Zabawa, P; Haruza, M; Bigelow, N P

2012-07-02

We demonstrate the use of optical pumping of kinetically ultracold NaCs to cool an initial vibrational distribution of electronic ground state molecules X(1)Σ(+)(v ≥ 4) into the vibrational ground state X(1)Σ(+)(v=0). Our approach is based on the use of simple, commercially available multimode diode lasers selected to optically pump population into X(1)Σ(+)(v=0). We investigate the impact of the cooling process on the rotational state distribution of the vibrational ground state, and observe that an initial distribution, J(initial)=0-2 is only moderately affected resulting in J(final)=0-4. This method provides an inexpensive approach to creation of vibrational ground state ultracold polar molecules.

Ultrahigh Storage and Fast Diffusion of Na and K in Blue Phosphorene Anodes.

PubMed

Mukherjee, Sankha; Kavalsky, Lance; Singh, Chandra Veer

2018-03-14

In the wake of blue phosphorene's (BP) computational discovery and experimental realization, it has emerged as a versatile material with interesting optical, electrical, and mechanical properties. In this study, using first principles density functional theory calculations, we have investigated the adsorption and diffusion of Na and K over monolayer BP to assess its suitability as Na-ion and K-ion battery anodes. The optimized adsorption energies were found to be -0.96 eV for Na and -1.54 eV for K, which are sufficiently large to ensure stability and safety during operation. In addition, BP could adsorb Na and K atoms up to a stoichiometric ratio of 1:1 which yields a high storage capacity of 865 mA h/g for both adatom species. Through examination of the electronic structure and projected density of states of BP as a function of Na/K concentration, we predict that the band gap of the system increasingly shrinks, and in the case of maximum K adsorption, the band gap diminishes completely. Additionally, the diffusion of Na and K over BP is observed to be ultrafast, especially for K, and anisotropic with modest energy barriers of 0.11 and 0.093 eV for Na and K, respectively. Building upon these findings, we employed vibrational analysis techniques with transition state theory to incorporate kinetic effects and predicted a diffusivity of 7.2 × 10 -5 cm 2 /s for Na and 8.58 × 10 -5 cm 2 /s for K on BP. Given these advantages, that is, ultrahigh capacity, electrical conductivity, and high Na/K diffusivity, we conclude that BP can be considered as an excellent candidate for anodes in Na- and K-ion batteries.

Functional characterization of Na(+)/H(+) exchangers in primary cultures of prairie dog gallbladder.

PubMed

Narins, S C; Park, E H; Ramakrishnan, R; Garcia, F U; Diven, J N; Balin, B J; Hammond, C J; Sodam, B R; Smith, P R; Abedin, M Z

2004-01-15

Gallbladder Na(+) absorption is linked to gallstone formation in prairie dogs. We previously reported Na(+)/H(+) exchanger (NHE1-3) expression in native gallbladder tissues. Here we report the functional characterization of NHE1, NHE2 and NHE3 in primary cultures of prairie dog gallbladder epithelial cells (GBECs). Immunohistochemical studies showed that GBECs grown to confluency are homogeneous epithelial cells of gastrointestinal origin. Electron microscopic analysis of GBECs demonstrated that the cells form polarized monolayers characterized by tight junctions and apical microvilli. GBECs grown on Snapwells exhibited polarity and developed transepithelial short-circuit current, I(sc), (11.6 +/- 0.5 microA. cm(-2)), potential differences, V(t) (2.1 +/- 0.2 mV), and resistance, R(t) (169 +/- 12 omega. cm(2)). NHE activity in GBECs assessed by measuring dimethylamiloride-inhibitable (22)Na(+) uptake under a H(+) gradient was the same whether grown on permeable Snapwells or plastic wells. The basal rate of (22)Na(+) uptake was 21.4 +/- 1.3 nmol x mg prot(-1) x min(-1), of which 9.5 +/- 0.7 (approximately 45%) was mediated through apically-restricted NHE. Selective inhibition with HOE-694 revealed that NHE1, NHE2 and NHE3 accounted for approximately 6%, approximately 66% and approximately 28% of GBECs' total NHE activity, respectively. GBECs exhibited saturable NHE kinetics ( V(max) 9.2 +/- 0.3 nmol x mg prot(-1) x min(-1); K(m) 11.4 +/- 1.4 m M Na(+)). Expression of NHE1, NHE2 and NHE3 mRNAs was confirmed by RT-PCR analysis. These results demonstrate that the primary cultures of GBECs exhibit Na(+) transport characteristics similar to native gallbladder tissues, suggesting that these cells can be used as a tool for studying the mechanisms of gallbladder ion transport both under physiologic conditions and during gallstone formation.

Periaqueductal gray knockdown of V2, not V1a and V1b receptor influences nociception in the rat. yj6676@yahoo.com.

PubMed

Yang, Jun; Yang, Yu; Chen, Jian-Min; Wang, Gen; Xu, Hong-Tao; Liu, Wen-Yan; Lin, Bao-Cheng

2007-01-01

Our pervious study has proved that arginine vasopressin (AVP) in periaqueductal gray (PAG) plays a role in antinociception. After establishing a model of local special gene knockdown, the nociceptive effect of vasopressin receptor subunit in PAG was investigated in the rat. Microinjection of short-interfering RNA (siRNA) into PAG, which targeted vasopressin receptor subtypes (V(1a), V(1b) and V(2)), locally weakened the associated mRNA expression and depressed the related receptor synthesis in a dose-dependent manner, in which the significant inhibitive effect occurred on from 7th day to 14th day following 1microg or 2microg siRNA administration. PAG knockdown of V(2) receptor gene markedly decreased pain threshold in from 6th day to 13th day after siRNA administration, whereas local knockdown of either V(1a) or V(1b) receptor gene could not influence pain threshold. The data suggest that V(2) rather than V(1a) and V(1b) receptor in PAG involves in nociception.

Na+-dependent and Na+-independent betaine transport across the apical membrane of rat renal epithelium.

PubMed

Cano, Mercedes; Calonge, María L; Ilundáin, Anunciación A

2015-10-01

The low renal excretion of betaine indicates that the kidney efficiently reabsorbs the betaine filtered by the glomeruli but the mechanisms involved in such a process have been scarcely investigated. We have detected concentrative and non-concentrative betaine transport activity in brush-border membrane vesicles (BBMV) from rat renal cortex and medulla. The concentrative system is the Sodium/Imino-acid Transporter 1 (SIT1) because it is Na+- and Cl--dependent, electrogenic and is inhibited by an anti-SIT1 antibody. Its apparent affinity constant for betaine, Kt, is 1.1±0.5 mM and its maximal transport velocity, Vmax, 0.5±0.1 nmol betaine/mg protein/s. Inhibitors of the Na+/Cl-/betaine uptake are L-proline (75%) and cold betaine, L-carnitine and choline (40-60%). Neither creatine, TEA, taurine, β-alanine, GABA nor glycine significantly inhibited Na+/Cl-/betaine uptake. The non-concentrative betaine transport system is Na+- and H+-independent, electroneutral, with a Kt for betaine of 47±7 μM and a Vmax of 7.8±1 pmol betaine/mg protein/s. Its transport activity is nearly abolished by betaine, followed by L-carnitine (70-80%) and proline (40-50%), but a difference from the Na+/Cl-/betaine transport is that it is inhibited by TEA (approx. 50%) and unaffected by choline. The underlying carrier functions as an antiporter linking betaine entry into the BBMV with the efflux of either L-carnitine or betaine, an exchange unaffected by the anti-SIT1 antibody. As far as we know this is the first work reporting that betaine crosses the apical membrane of rat renal epithelium by SIT1 and by a Na+- and H+-independent transport system. Copyright © 2015 Elsevier B.V. All rights reserved.

Mutation of the Na+/K+-ATPase Atp1a1a.1 causes QT interval prolongation and bradycardia in zebrafish.

PubMed

Pott, Alexander; Bock, Sarah; Berger, Ina M; Frese, Karen; Dahme, Tillman; Keßler, Mirjam; Rinné, Susanne; Decher, Niels; Just, Steffen; Rottbauer, Wolfgang

2018-05-08

The genetic underpinnings that orchestrate the vertebrate heart rate are not fully understood yet, but of high clinical importance, since diseases of cardiac impulse formation and propagation are common and severe human arrhythmias. To identify novel regulators of the vertebrate heart rate, we deciphered the pathogenesis of the bradycardia in the homozygous zebrafish mutant hiphop (hip) and identified a missense-mutation (N851K) in Na + /K + -ATPase α1-subunit (atp1a1a.1). N851K affects zebrafish Na + /K + -ATPase ion transport capacity, as revealed by in vitro pump current measurements. Inhibition of the Na + /K + -ATPase in vivo indicates that hip rather acts as a hypomorph than being a null allele. Consequently, reduced Na + /K + -ATPase function leads to prolonged QT interval and refractoriness in the hip mutant heart, as shown by electrocardiogram and in vivo electrical stimulation experiments. We here demonstrate for the first time that Na + /K + -ATPase plays an essential role in heart rate regulation by prolonging myocardial repolarization. Copyright © 2018. Published by Elsevier Ltd.

Measurements of $$\\pi ^\\pm $$ π ± , K $$^\\pm $$ ± , p and $${\\bar{\\text {p}}}$$ p ¯ spectra in proton-proton interactions at 20, 31, 40, 80 and 158  $$\\text{ GeV }/c$$ GeV / c with the NA61/SHINE spectrometer at the CERN SPS: The NA61/SHINE Collaboration

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

Aduszkiewicz, A.; Ali, Y.; Andronov, E.

Measurements of inclusive spectra and mean multiplicities ofmore » $$\\pi^\\pm$$, K$$^\\pm$$, p and $$\\bar{\\textrm{p}}$$ produced in inelastic p+p interactions at incident projectile momenta of 20, 31, 40, 80 and 158 GeV/c ($$\\sqrt{s} = $$ 6.3, 7.7, 8.8, 12.3 and 17.3 GeV, respectively) were performed at the CERN Super Proton Synchrotron using the large acceptance NA61/SHINE hadron spectrometer. Spectra are presented as function of rapidity and transverse momentum and are compared to predictions of current models. The measurements serve as the baseline in the NA61/SHINE study of the properties of the onset of deconfinement and search for the critical point of strongly interacting matter.« less

The enhancement of neutral metal Na layer above thunderstorms

NASA Astrophysics Data System (ADS)

Yu, B.; Xue, X.; Lu, G.; Dou, X.; Gao, Q.; Qie, X.; Wu, J.; Tang, Y.; Holzworth, R.

2016-12-01

Na (sodium) exists as layers of atoms in the mesosphere/lower thermosphere (MLT) at altitudes between 80 and 105 km. It has lower ionization potential of 5.139 eV than atmospheric species, such as O2 (12.06 eV). Tropospheric thunderstorms affect the lower ionosphere and the ionospheric sporadic E (Es) at 100 km can also be influenced by lightning. The mechanism is expected to be associated with transient luminous events (TLE) as red sprites and gigantic jets at upper atmosphere. However, measurements of ionospheric electric fields of 20mV·m-1 above thunderstorms are less than estimated value (>48 0mV·m-1) to excite ionization in the lower ionosphere. We found an enhancement of Na layer above thunderstorms. The increase of Na density in the statistical result can be as much as 500 cm-3 and it will have an impact on ionospheric chemistry and modify the conductivity properties of the MLT region.

Specificity of V1-V2 Orientation Networks in the Primate Visual Cortex

PubMed Central

Roe, Anna W.; Ts'o, Daniel Y.

2015-01-01

The computation of texture and shape involves integration of features of various orientations. Orientation networks within V1 tend to involve cells which share similar orientation selectivity. However, emergent properties in V2 require the integration of multiple orientations. We now show that, unlike interactions within V1, V1-V2 orientation interactions are much less synchronized and are not necessarily orientation dependent. We find V1-V2 orientation networks are of two types: a more tightly synchronized, orientation-preserving network and a less synchronized orientation-diverse network. We suggest that such diversity of V1-V2 interactions underlies the spatial and functional integration required for computation of higher order contour and shape in V2. PMID:26314798

Depolarization of the conductance-voltage relationship in the NaV1.5 mutant, E1784K, is due to altered fast inactivation.

PubMed

Peters, Colin H; Yu, Alec; Zhu, Wandi; Silva, Jonathan R; Ruben, Peter C

2017-01-01

E1784K is the most common mixed long QT syndrome/Brugada syndrome mutant in the cardiac voltage-gated sodium channel NaV1.5. E1784K shifts the midpoint of the channel conductance-voltage relationship to more depolarized membrane potentials and accelerates the rate of channel fast inactivation. The depolarizing shift in the midpoint of the conductance curve in E1784K is exacerbated by low extracellular pH. We tested whether the E1784K mutant shifts the channel conductance curve to more depolarized membrane potentials by affecting the channel voltage-sensors. We measured ionic currents and gating currents at pH 7.4 and pH 6.0 in Xenopus laevis oocytes. Contrary to our expectation, the movement of gating charges is shifted to more hyperpolarized membrane potentials by E1784K. Voltage-clamp fluorimetry experiments show that this gating charge shift is due to the movement of the DIVS4 voltage-sensor being shifted to more hyperpolarized membrane potentials. Using a model and experiments on fast inactivation-deficient channels, we show that changes to the rate and voltage-dependence of fast inactivation are sufficient to shift the conductance curve in E1784K. Our results localize the effects of E1784K to DIVS4, and provide novel insight into the role of the DIV-VSD in regulating the voltage-dependencies of activation and fast inactivation.

Exclusion of Na+ via Sodium ATPase (PpENA1) Ensures Normal Growth of Physcomitrella patens under Moderate Salt Stress1

PubMed Central

Lunde, Christina; Drew, Damian P.; Jacobs, Andrew K.; Tester, Mark

2007-01-01

The bryophyte Physcomitrella patens is unlike any other plant identified to date in that it possesses a gene that encodes an ENA-type Na+-ATPase. To complement previous work in yeast (Saccharomyces cerevisiae), we determined the importance of having a Na+-ATPase in planta by conducting physiological analyses of PpENA1 in Physcomitrella. Expression studies showed that PpENA1 is up-regulated by NaCl and, to a lesser degree, by osmotic stress. Maximal induction is obtained after 8 h at 60 mm NaCl or above. No other abiotic stress tested led to significant increases in PpENA1 expression. In the gametophyte, strong expression was confined to the rhizoids, stem, and the basal part of the leaf. In the protonemata, expression was ubiquitous with a few filaments showing stronger expression. At 100 mm NaCl, wild-type plants were able to maintain a higher K+-to-Na+ ratio than the PpENA1 (ena1) knockout gene, but at higher NaCl concentrations no difference was observed. Although no difference in chlorophyll content was observed between ena1 and wild type at 100 mm NaCl, the impaired Na+ exclusion in ena1 plants led to an approximately 40% decrease in growth. PMID:17556514

High performance sodium-ion hybrid capacitor based on Na2Ti2O4(OH)2 nanostructures

NASA Astrophysics Data System (ADS)

Babu, Binson; Shaijumon, M. M.

2017-06-01

Hybrid Na-ion capacitors bridge the performance gap between Na-ion batteries and supercapacitors and offer excellent energy and power characteristics. However, designing efficient anode and cathode materials with improved kinetics and long cycle life is essential for practical implementation of this technology. Herein, layered sodium titanium oxide hydroxide, Na2Ti2O4(OH)2, synthesized through hydrothermal technique, is studied as efficient anode material for hybrid Na-ion capacitor. Half-cell electrochemical studies vs. Na/Na+ showed excellent performance for Na2Ti2O4(OH)2 electrode, with ∼57.2% of the total capacity (323.3 C g-1 at 1.0 mV s-1) dominated by capacitive behavior and the remaining due to Na-intercalation. The obtained values are in good agreement with Trasatti plots indicating the potential of this material as efficient anode for hybrid Na-ion capacitor. Further, a full cell Na-ion capacitor is fabricated with Na2Ti2O4(OH)2 as anode and chemically activated Rice Husk Derived Porous Carbon (RHDPC-KOH) as cathode by using organic electrolyte. The hybrid device, operated at a maximum cell voltage of 4 V, exhibits stable electrochemical performance with a maximum energy density of ∼65 Wh kg-1 (at 500 W kg-1, 0.20 A g-1) and with more than ∼ 93% capacitive retention after 3000 cycles.

Collisional Transfer of Population and Orientation in NaK

NASA Astrophysics Data System (ADS)

Wolfe, C. M.; Ashman, S.; Huennekens, J.; Beser, B.; Bai, J.; Lyyra, A. M.

2010-03-01

We report current work to study transfer of population and orientation in collisions of NaK molecules with argon and potassium atoms using polarization labeling (PL) and laser- induced fluorescence (LIF) spectroscopy. In the PL experiment, a circularly polarized pump laser excites a specific NaK A^1&+circ;(v'=16, J') <- X^1&+circ;(v''=0, J'±1) transition, creating an orientation (non-uniform MJ' level distribution) in both levels. The linearly polarized probe laser is scanned over various 3^1π(v, J'±1) <- A^1&+circ;(v'=16, J') transitions. The probe laser passes through a crossed linear polarizer before detection, and signal is recorded if the probe laser polarization has been modified by the vapor (which occurs when it comes into resonance with an oriented level). Using both spectroscopic methods, analysis of weak collisional satellite lines adjacent to these directly populated lines, as a function of argon buffer gas pressure and cell temperature, allows us to discern separately the effects collisions with argon atoms and potassium atoms have on the population and orientation of the molecule. In addition, code has been written which provides a theoretical analysis of the process, through a solution of the density matrix equations of motion for the system.

K+ and NH4(+) modulate gill (Na+, K+)-ATPase activity in the blue crab, Callinectes ornatus: fine tuning of ammonia excretion.

PubMed

Garçon, D P; Masui, D C; Mantelatto, F L M; McNamara, J C; Furriel, R P M; Leone, F A

2007-05-01

To better comprehend the mechanisms of ionic regulation, we investigate the modulation by Na+, K+, NH4(+) and ATP of the (Na+, K+)-ATPase in a microsomal fraction from Callinectes ornatus gills. ATP hydrolysis obeyed Michaelis-Menten kinetics with KM=0.61+/-0.03 mmol L(-1) and maximal rate of V=116.3+/-5.4 U mg(-1). Stimulation by Na+ (V=110.6+/-6.1 U mg(-1); K0.5=6.3+/-0.2 mmol L(-1)), Mg2+ (V=111.0+/-4.7 U mg(-1); K0.5=0.53+/-0.03 mmol L(-1)), NH4(+) (V=173.3+/-6.9 U mg(-1); K0.5=5.4+/-0.2 mmol L(-1)) and K+ (V=116.0+/-4.9 U mg(-1); K0.5=1.5+/-0.1 mmol L(-1)) followed a single saturation curve, although revealing site-site interactions. In the absence of NH4(+), ouabain (K(I)=74.5+/-1.2 micromol L(-1)) and orthovanadate inhibited ATPase activity by up to 87%; the inhibition patterns suggest the presence of F0F1 and K+-ATPases but not Na+-, V- or Ca2+-ATPase as contaminants. (Na+, K+)-ATPase activity was synergistically modulated by K+ and NH4(+). At 10 mmol L(-1) K+, increasing NH4(+) concentrations stimulated maximum activity to V=185.9+/-7.4 U mg(-1). However, at saturating NH4(+) (50 mmol L(-1)), increasing K+ concentrations did not stimulate activity further. Our findings provide evidence that the C. ornatus gill (Na+, K+)-ATPase may be particularly well suited for extremely efficient active NH4(+) excretion. At elevated NH4(+) concentrations, the enzyme is fully active, regardless of hemolymph K+ concentration, and K+ cannot displace NH4(+) from its exclusive binding sites. Further, the binding of NH4(+) to its specific sites induces an increase in enzyme apparent affinity for K+, which may contribute to maintaining K+ transport, assuring that exposure to elevated ammonia concentrations does not lead to a decrease in intracellular potassium levels. This is the first report of modulation by ammonium ions of C. ornatus gill (Na+, K+)-ATPase, and should further our understanding of NH4(+) excretion in benthic crabs.

β decay of Na32

NASA Astrophysics Data System (ADS)

Mattoon, C. M.; Sarazin, F.; Hackman, G.; Cunningham, E. S.; Austin, R. A. E.; Ball, G. C.; Chakrawarthy, R. S.; Finlay, P.; Garrett, P. E.; Grinyer, G. F.; Hyland, B.; Koopmans, K. A.; Leslie, J. R.; Phillips, A. A.; Schumaker, M. A.; Scraggs, H. C.; Schwarzenberg, J.; Smith, M. B.; Svensson, C. E.; Waddington, J. C.; Walker, P. M.; Washbrook, B.; Zganjar, E.

2007-01-01

The β-decay of Na32 has been studied using β-γ coincidences. New transitions and levels are tentatively placed in the level scheme of Mg32 from an analysis of γ-γ and β-γ-γ coincidences. The observation of the indirect feeding of the 2321 keV state in Mg32 removes some restrictions previously placed on the spin assignment for this state. No evidence of a state at 2117 keV in Mg32 is found. Previously unobserved weak transitions up to 5.4 MeV were recorded but could not be placed in the decay scheme of Na32.

Desorption induced by electronic transitions of Na from SiO2: relevance to tenuous planetary atmospheres.

NASA Astrophysics Data System (ADS)

Yakshinskiy, B. V.; Madey, T. E.

2000-04-01

The authors have studied the desorption induced by electronic transitions (DIET) of Na adsorbed on model mineral surfaces, i.e. amorphous, stoichiometric SiO2 films. They find that electron stimulated desorption (ESD) of atomic Na occurs for electron energy thresholds as low as ≡4 eV, that desorption cross-sections are high (≡1×10-19cm2 at 11 eV), and that desorbing atoms are 'hot', with suprathermal velocities. The estimated Na desorption rate from the lunar surface via ESD by solar wind electrons is a small fraction of the rate needed to sustain the Na atmosphere. However, the solar photon flux at energies ≥5 eV exceeds the solar wind electron flux by orders of magnitude; there are sufficient ultraviolet photons incident on the lunar surface to contribute substantially to the lunar Na atmosphere via PSD of Na from the surface.

Effects of S(+)-efonidipine on the rabbit sinus node action potential and calcium channel subunits Ca(V)1.2, Ca(V)1.3 and Ca(V)3.1.

PubMed

Tanaka, Hikaru; Namekata, Iyuki; Ogawa, Toru; Tsuneoka, Yayoi; Komikado, Chisa; Takahara, Akira; Iida-Tanaka, Naoko; Izumi-Nakaseko, Hiroko; Tsuru, Hiromichi; Adachi-Akahane, Satomi

2010-12-15

The effect of S(+)-efonidipine on sinus node action potential and calcium channel α-subunits was examined. The slope of the phase 4 depolarization of isolated rabbit sinus node tissue was significantly reduced by S(+)-efonidipine (1 μM), slightly reduced by nifedipine (1 μM), but was not affected by R(-)-efonidipine. S(+)-efonidipine (1 μM), inhibited the expressed Ca(V)1.2, Ca(V)1.3 and Ca(V)3.1 channel currents by 75.7%, 75.3% and 94.0%, nifedipine 84.0%, 43.2% and 14.9%, and R(-)-efonidipine 30.0%, 19.6% and 92.8%, respectively. Thus, the prolongation of the phase 4 depolarization of the rabbit sinus node by S(+)-efonidipine may be explained by blockade of the Ca(V)1.3 channel current. Copyright © 2010 Elsevier B.V. All rights reserved.

Search for a Hypothetical 16.7 MeV Gauge Boson and Dark Photons in the NA64 Experiment at CERN.

PubMed

Banerjee, D; Burtsev, V E; Chumakov, A G; Cooke, D; Crivelli, P; Depero, E; Dermenev, A V; Donskov, S V; Dusaev, R R; Enik, T; Charitonidis, N; Feshchenko, A; Frolov, V N; Gardikiotis, A; Gerassimov, S G; Gninenko, S N; Hösgen, M; Jeckel, M; Karneyeu, A E; Kekelidze, G; Ketzer, B; Kirpichnikov, D V; Kirsanov, M M; Konorov, I V; Kovalenko, S G; Kramarenko, V A; Kravchuk, L V; Krasnikov, N V; Kuleshov, S V; Lyubovitskij, V E; Lysan, V; Matveev, V A; Mikhailov, Yu V; Peshekhonov, D V; Polyakov, V A; Radics, B; Rojas, R; Rubbia, A; Samoylenko, V D; Tikhomirov, V O; Tlisov, D A; Toropin, A N; Trifonov, A Yu; Vasilishin, B I; Vasquez Arenas, G; Volkov, P V; Volkov, V; Ulloa, P

2018-06-08

We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e^{+}e^{-} pairs observed in the excited ^{8}Be^{*} nucleus decays. Because of its coupling to electrons, the X could be produced in the bremsstrahlung reaction e^{-}Z→e^{-}ZX by a 100 GeV e^{-} beam incident on an active target in the NA64 experiment at the CERN Super Proton Synchrotron and observed through the subsequent decay into a e^{+}e^{-} pair. With 5.4×10^{10} electrons on target, no evidence for such decays was found, allowing us to set first limits on the X-e^{-} coupling in the range 1.3×10^{-4}≲ε_{e}≲4.2×10^{-4} excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A^{'}) from nonobservation of the decay A^{'}→e^{+}e^{-} of the bremsstrahlung A^{'} with a mass ≲23  MeV.

Phase transition studies of Na3Bi system under uniaxial strain

NASA Astrophysics Data System (ADS)

Nie, Tiaoping; Meng, Lijun; Li, Yanru; Luan, Yanhua; Yu, Jun

2018-03-01

We investigated the electronic properties and phase transitions of Na3Bi in four structural phases (space groups P63/mmc, P \\overline{3} c1, Fm \\overline{3} m and Cmcm) under constant-volume uniaxial strain using the first-principles method. For P63/mmc and P \\overline{3} c1-Na3Bi, an important phase transition from a topological Dirac semimetal (TDS) to a topological insulator appears under compression strain around 4.5%. The insulating gap increases with the increasing compressive strain and up to around 0.1 eV at a strain of 10%. However, both P63/mmc and P \\overline{3} c1-Na3Bi still keep the properties of a TDS within a tensile strain of 0-10%, although the Dirac points move away from the Γ point along Γ-A in reciprocal space as the tensile strain increases. The Na3Bi with space group Fm \\overline{3} m is identified as a topological semimetal with the inverted bands between Na-3s and Bi-6p and a parabolic dispersion in the vicinity of Γ point. Interestingly, for Fm \\overline{3} m-Na3Bi, both compression and tensile strain lead to a TDS which is identified by calculating surface Fermi arcs and topological invariants at time-reversal planes (k z   =  0 and k z   =  π/c) in reciprocal space. Additionally, we confirmed the high pressure phase Cmcm-Na3Bi is an ordinary insulator with a gap of about 0.62 eV. It is noteworthy that its gap almost keeps constant around 0.60 eV within a compression strain of 0-10%. In contrast, a remarkable phase transition from an insulator to a metal phase appears under tensile strain. Moreover, this phase transition is highly sensitive to tensile strain and takes place only at a strain 1.0%. These strain-induced electronic structures and phase transitions of the Na3Bi system in various phases are important due to their possible applications under high pressure in future electronic devices.

A Quaternary Sodium Superionic Conductor - Na 10.8Sn 1.9PS 11.8

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

Yu, Zhaoxin; Shang, Shun -Li; Gao, Yue

Sulfide-based Na-ion conductors are promising candidates as solid-state electrolytes (SSEs) for fabrication of solid-state Na-ion batteries (NIBs) because of their high ionic conductivities and low grain boundary resistance. Currently, most of the sulfide-based Na-ion conductors with high conductivities are focused on Na 3PS 4 phases and its derivatives. It is desirable to develop Na-ion conductors with new composition and crystal structure to achieve superior ionic conductivities. Here we report a new quaternary Na-ion conductor, Na 10.8Sn 1.9PS 11.8, exhibiting a high ionic conductivity of 0.67 mS cm –1 at 25 °C. This high ionic conductivity originates from the presence ofmore » a large number of intrinsic Na-vacancies and three-dimensional Na-ion conduction pathways, which has been confirmed by single-crystal X-ray diffraction and first-principles calculations. In conclusion, the Na 10.8Sn 1.9PS 11.8 phase is further evaluated as an electrolyte in a Na-Sn alloy/TiS 2 battery, demonstrating its potential application in all-solid-state NIBs.« less

A Quaternary Sodium Superionic Conductor - Na 10.8Sn 1.9PS 11.8

DOE PAGES

Yu, Zhaoxin; Shang, Shun -Li; Gao, Yue; ...

2018-01-31

Sulfide-based Na-ion conductors are promising candidates as solid-state electrolytes (SSEs) for fabrication of solid-state Na-ion batteries (NIBs) because of their high ionic conductivities and low grain boundary resistance. Currently, most of the sulfide-based Na-ion conductors with high conductivities are focused on Na 3PS 4 phases and its derivatives. It is desirable to develop Na-ion conductors with new composition and crystal structure to achieve superior ionic conductivities. Here we report a new quaternary Na-ion conductor, Na 10.8Sn 1.9PS 11.8, exhibiting a high ionic conductivity of 0.67 mS cm –1 at 25 °C. This high ionic conductivity originates from the presence ofmore » a large number of intrinsic Na-vacancies and three-dimensional Na-ion conduction pathways, which has been confirmed by single-crystal X-ray diffraction and first-principles calculations. In conclusion, the Na 10.8Sn 1.9PS 11.8 phase is further evaluated as an electrolyte in a Na-Sn alloy/TiS 2 battery, demonstrating its potential application in all-solid-state NIBs.« less

Structure, microstructure and infrared studies of Ba{sub 0.06}(Na{sub 1/2}Bi{sub 1/2}){sub 0.94}TiO{sub 3}-NaNbO{sub 3} ceramics

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

Roy, Sumit K., E-mail: sumit.sxc13@gmail.com; Singh, S. N., E-mail: snsphyru@gmail.com; Prasad, K., E-mail: k.prasad65@gmail.com

2016-05-06

Lead-free solid solutions (1-x)Ba{sub 0.06}(Na{sub 1/2}Bi{sub 1/2}){sub 0.94}TiO{sub 3}-xNaNbO{sub 3} (0 ≤ x ≤ 1.0) were prepared by conventional ceramic fabrication technique. X-ray diffraction and Rietveld refinement analyses of these ceramics were carried out using X’Pert HighScore Plus software to determine the crystal symmetry, space group and unit cell dimensions. Rietveld refinement revealed that NaNbO{sub 3} with orthorhombic structure was completely diffused into Ba{sub 0.06}(Na{sub 1/2}Bi{sub 1/2}){sub 0.94}TiO{sub 3} lattice having the rhombohedral-tetragonal symmetry. EDS and SEM studies were carried out in order to evaluate the quality and purity of the compounds. SEM images showed a change in grain shapemore » with the increase of NaNbO{sub 3} content. FTIR spectra confirmed the formation of solid solution.« less

One- and two-electron reduced 1,2-diketone ligands in [CrIII(L*)3] (S = 0) and Na2(Et2O)2[VIV(LRed)3] (S = 1/2).

PubMed

Spikes, Geoffrey H; Sproules, Stephen; Bill, Eckhard; Weyhermüller, Thomas; Wieghardt, Karl

2008-12-01

The electronic structures of chromium and vanadium centers coordinated by three reduced 1,2-diketones have been elucidated by using density functional theory (DFT) calculations and a host of physical methods: X-ray crystallography; cyclic voltammetry; ultraviolet-visible (UV-vis), nuclear magnetic resonance (NMR), and electron paramagnetic resonance (EPR) spectroscopy; and magnetic susceptibility measurements. The metal center in octahedral [CrIII(L*)3]0 (1), a CrIII (d3) ion is coupled antiferromagnetically to three monoanionic ligand pi-radicals affording an S ) 0 ground state. In contrast, Na2(Et2O)2[VIV(LRed)3] (2) (S ) 1/2), possesses a central VIV (d1) ion O,OE-coordinated to three closed-shell, doubly reduced ligands which in turn are coordinated by two Na cations enforcing a trigonal prismatic geometry at the vanadium center. 2 can be oxidized electrochemically by one and two electrons generating a monoanion, [V(L)3]1-, and a neutral species, [V(L)3]0, respectively. DFT calculations atthe B3LYP level show that the one-electron oxidized product contains an octahedral VIV ion coupled antiferromagnetically to one monoanionic ligand pi-radical [VIV(L*)(LRed)2]1- (S ) 0). In contrast, the two-electron oxidized product contains a VIII ion coupled antiferromagnetically to three ligand pi-radicals in an octahedral field[VIII(L*)3]0 (S ) 1/2).

Most effective way to improve the hydrogen storage abilities of Na-decorated BN sheets: applying external biaxial strain and an electric field.

PubMed

Tang, Chunmei; Zhang, Xue; Zhou, Xiaofeng

2017-02-15

Density functional calculations were used to investigate the hydrogen storage abilities of Na-atoms-decorated BN sheets under both external biaxial strain and a vertical electric field. The Na atom generally has the weakest binding strength to a given substrate compared with the other elements in the periodic table [PANS, 2016, 113, 3735]. Consequently, it is understudied in comparison to other elements and there are few reports about the hydrogen storage abilities of Na-decorated nanomaterials. We calculated that the average binding energy (E b ) of Na atoms to the pure BN sheet is 1.08 eV, which is smaller than the cohesive energy of bulk Na (1.11 eV). However, the E b can be increased to 1.15 eV under 15% biaxial strain, and further up to 1.53 eV with the control of both 15% biaxial strain and a 5.14 V nm -1 electric field (E-field). Therefore, the application of biaxial strain and an external upward E-field can prevent clustering of the Na atoms on the surface of a BN sheet, which is crucial for the hydrogen storage. Each Na atom on the surface of a BN sheet can adsorb only one H 2 molecule when no strain or E-field is applied; however, the absorption increases to five H 2 molecules under 15% biaxial strain and six H 2 molecules under both 15% biaxial strain combined with a 5.14 V nm -1 E-field. The average adsorption energies for H 2 of BN-(Na-mH 2 ) (m = 1-6) are within the range of practical applications (0.2-0.6 eV). The hydrogen gravimetric density of the periodic BN-(Na-6H 2 ) 4 structure is 9 wt%, which exceeds the 5.5 wt% value that should be met by 2017 as specified by the US Department of Energy. On the other side, removal of the biaxial strain and E-field can help to desorb the H 2 molecule. These findings suggest a new route to design hydrogen storage materials under near-ambient conditions.

Modulation of voltage-gated Na+ and K+ channels by pumiliotoxin 251D: a "joint venture" alkaloid from arthropods and amphibians.

PubMed

Vandendriessche, Thomas; Abdel-Mottaleb, Yousra; Maertens, Chantal; Cuypers, Eva; Sudau, Alexander; Nubbemeyer, Udo; Mebs, Dietrich; Tytgat, Jan

2008-03-01

Certain amphibians provide themselves with a chemical defense by accumulating lipophilic alkaloids into skin glands from dietary arthropods. Examples of such alkaloids are pumiliotoxins (PTXs). In general, PTXs are known as positive modulators of voltage-gated sodium channels (VGSCs). Unlike other PTXs, PTX 251D does not share this characteristic. However, mice and insect studies showed that PTX 251D is highly toxic and to date the basis of its toxicity remains unknown. In this work, we searched for the possible target of PTX 251D. The toxin was therefore made synthetically and tested on four VGSCs (mammalian rNa(v)1.2/beta(1), rNa(v)1.4/beta(1), hNa(v)1.5/beta(1) and insect Para/tipE) and five voltage-gated potassium channels (VGPCs) (mammalian rK(v)1.1-1.2, hK(v)1.3, hK(v)11.1 (hERG) and insect Shaker IR) expressed heterologously in Xenopus laevis oocytes, using the two-electrode voltage clamp technique. PTX 251D not only inhibited the Na(+) influx through the mammalian VGSCs but also affected the steady-state activation and inactivation. Interestingly, in the insect ortholog, the inactivation process was dramatically affected. Additionally, PTX 251D inhibited the K(+) efflux through all five tested VGPCs and slowed down the deactivation kinetics of the mammalian VGPCs. hK(v)1.3 was the most sensitive channel, with an IC(50) value 10.8+/-0.5 microM. To the best of our knowledge this is the first report of a PTX affecting VGPCs.

Projectile n distributions following charge transfer of Ar+ and Na+ in a Na Rydberg target

NASA Astrophysics Data System (ADS)

MacAdam, K. B.; Gray, L. G.; Rolfes, R. G.

1990-11-01

The n distributions produced by charge transfer of Ar+ and Na+ ions in a target of Na(nl) Rydberg atoms were extensively measured at intermediate velocities. The 60-2100-eV ions bombarded a laser-excited atomic-beam target. The projectiles were neutralized by capture into Rydberg states of Ar and Na and were analyzed by field ionization in an inhomogeneous-field detector whose response over states and energies was carefully mapped. The choice of initially prepared Na states, 24d, 25s, 28d, 29s, 33d, and 34s, allowed a comparison of l=0 and >=2 targets at nearly equal binding energies over a range of reduced velocity v~=0.187 to 1.95. Capture populates m sublevels broadly, not merely m~=0. Overlapping contributions from adiabatic and diabatic modes of field ionization were accommodated in the analysis, which used a maximum-entropy-principle parametric form to fit the observed final-state distributions. The peak of the distributions, nmax, shifts upward from a value less than the initial state ni to a value one to three units higher than ni at v~ between 0.7 and 0.9 and ultimately shifts downward below ni as v~ is further increased. The distributions become significantly sharper where the maximum upward shift occurs. Two ratios were defined to express the widths of final-state distributions in relative terms, one measuring the spread of orbital kinetic energy and the other the spread of Bohr-orbit velocity. By these ratios a universal behavior over energies, states, and projectile species is observed, and small differences between l=0 and >=2 targets may be seen. A theoretical understanding of the present results, which span velocities where both molecular and perturbative theories are normally used, will require a quantal formulation that models the free-ranging response that is a hallmark of the high-quantum-number limit.

24Na at Ex=4.7 -5.9 MeV from 22Ne(3He,p )

NASA Astrophysics Data System (ADS)

Fortune, H. T.

2018-04-01

Abstract. Analysis of data from the 22Ne(3He,p ) 24Na reaction has been extended to include 18 angular distributions for states between 4.7 and 5.9 MeV. A distorted-wave Born-approximation analysis allows the determination of ℓ value(s) for most of them. Results for Jπ are compared with previous information. In general, agreement is good. Some apparent disagreements between current and past results are indicative of population of a different state in this reaction than the nearby one listed in the compilation.

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

Low temperature synthesis and characterization of Na–M–(O)–F phases with M=Ti, V

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

Nava-Avendaño, Jessica; Ayllón, José A.; Frontera, Carlos

2015-03-15

Na{sub 5}Ti{sub 3}O{sub 3}F{sub 11} was prepared by the microwave assisted method, and presents a chiolite related structure with cell parameters a=10.5016(5), b=10.4025(5), and c=10.2911(5) Å and Cmca (no. 64) space group. From solvothermal synthesis at 100 °C the cryolite Na{sub 3−δ}VO{sub 1−δ}F{sub 5+δ} was prepared, which crystallizes in the monoclinic system with a=5.5403(2), b=5.6804(2), c=7.9523(2) Å, β=90.032(7)° cell parameters and P2{sub 1}/n (no. 14) space group. Under similar synthesis conditions but with higher HF concentration the chiolite-type phase Na{sub 5−δ}V{sub 3}F{sub 14} was achieved, which exhibits a=10.5482(2), b=10.4887(1) and c=10.3243(1) Å cell parameters and Cmc2{sub 1} (no. 36) spacemore » group. A single crystal also having the chiolite structure was synthesized at 200 °C which exhibits tetragonal symmetry (a=7.380(3) and c=10.381(11) Å and space group P4{sub 2}2{sub 1}2 (no. 94)). Bond valence sum indicates that it contains V{sup 4+} and therefore can be formulated as Na{sub 5}V{sub 3}O{sub 3}F{sub 11}. - Graphical abstract: Na{sub 5}M{sub 3}(O,F){sub 14} with M=Ti and V having chiolite structure and Na{sub 3−δ}VO{sub 1−δ}F{sub 5+δ} cryolite were prepared by means of microwave-assisted and solvothermal synthesis. - Highlights: • Na{sub 5}Ti{sub 3}O{sub 3}F{sub 11} chiolite was prepared by a microwave assisted method and characterized. • Na{sub 3−δ}VO{sub 1−δ}F{sub 5+δ} and Na{sub 5−δ}V{sub 3}F{sub 14} were prepared by solvothermal synthesis. • The compounds were structurally characterized by diffraction techniques. • O/F distribution was estimated by applying Pauling’s second rule.« less

Functionalized Fullerene Targeting Human Voltage-Gated Sodium Channel, hNav1.7.

PubMed

Hilder, Tamsyn A; Robinson, Anna; Chung, Shin-Ho

2017-08-16

Mutations of hNa v 1.7 that cause its activities to be enhanced contribute to severe neuropathic pain. Only a small number of hNa v 1.7 specific inhibitors have been identified, most of which interact with the voltage-sensing domain of the voltage-activated sodium ion channel. In our previous computational study, we demonstrated that a [Lys 6 ]-C 84 fullerene binds tightly (affinity of 46 nM) to Na v Ab, the voltage-gated sodium channel from the bacterium Arcobacter butzleri. Here, we extend this work and, using molecular dynamics simulations, demonstrate that the same [Lys 6 ]-C 84 fullerene binds strongly (2.7 nM) to the pore of a modeled human sodium ion channel hNa v 1.7. In contrast, the fullerene binds only weakly to a mutated model of hNa v 1.7 (I1399D) (14.5 mM) and a model of the skeletal muscle hNa v 1.4 (3.7 mM). Comparison of one representative sequence from each of the nine human sodium channel isoforms shows that only hNa v 1.7 possesses residues that are critical for binding the fullerene derivative and blocking the channel pore.

E&V Guidebook, Version 1.1

DTIC Science & Technology

1989-08-15

checklist 14.1] Chapter 3, Language-related issues, extracts from the Ada language reference manua! [,_D 1982] those features exp!icitly a!owcd to vay...welcome. Please send comments electronically (preferred) to szymansk~aja;po.sei.cmu.edu, or by regular mail to Mr. Raymond Szymanski , AFWAL/AAAF, Wright...of Tool Features for the Ada Programming Support Environment (APSE) 4-3 4.3 E&V Report: DoD APSE Analysis 4-4 4.4 Classification Schema/E&V Taxonomy

Depolarization of the conductance-voltage relationship in the NaV1.5 mutant, E1784K, is due to altered fast inactivation

PubMed Central

Yu, Alec; Zhu, Wandi; Silva, Jonathan R.; Ruben, Peter C.

2017-01-01

E1784K is the most common mixed long QT syndrome/Brugada syndrome mutant in the cardiac voltage-gated sodium channel NaV1.5. E1784K shifts the midpoint of the channel conductance-voltage relationship to more depolarized membrane potentials and accelerates the rate of channel fast inactivation. The depolarizing shift in the midpoint of the conductance curve in E1784K is exacerbated by low extracellular pH. We tested whether the E1784K mutant shifts the channel conductance curve to more depolarized membrane potentials by affecting the channel voltage-sensors. We measured ionic currents and gating currents at pH 7.4 and pH 6.0 in Xenopus laevis oocytes. Contrary to our expectation, the movement of gating charges is shifted to more hyperpolarized membrane potentials by E1784K. Voltage-clamp fluorimetry experiments show that this gating charge shift is due to the movement of the DIVS4 voltage-sensor being shifted to more hyperpolarized membrane potentials. Using a model and experiments on fast inactivation-deficient channels, we show that changes to the rate and voltage-dependence of fast inactivation are sufficient to shift the conductance curve in E1784K. Our results localize the effects of E1784K to DIVS4, and provide novel insight into the role of the DIV-VSD in regulating the voltage-dependencies of activation and fast inactivation. PMID:28898267

Suppression of NaNO3 crystal nucleation by glycerol: micro-Raman observation on the efflorescence process of mixed glycerol/NaNO3/water droplets.

PubMed

Yu, Jun-Ying; Zhang, Yun; Zeng, Guang; Zheng, Chuan-Ming; Liu, Yong; Zhang, Yun-Hong

2012-02-09

Although the hygroscopicity of a NaNO(3)/water microdroplet and a polyalcohol/water microdroplet, two of the most important aerosols in atmosphere, has been widely studied, little is known about the relationship between the hygroscopic behavior of mixed NaNO(3)/polyalcohol/water droplets and their structures on the molecular level. In this study, the hygroscopicity of mixed glycerol/NaNO(3)/water droplets deposited on a hydrophobic substrate was studied by micro-Raman spectroscopy with organic-to-inorganic molar ratios (OIRs) of 0.5, 1, and 2. In the mixed glycerol/NaNO(3)/water droplets, glycerol molecules tended to combine with Na(+) and NO(3)(-) ions by electrostatic interaction and hydrogen bonding, respectively. On the basis of the analyses of the changes of symmetric stretching (v(s)-CH(2)), asymmetric stretching (v(a)-CH(2)), their area ratio (Av(a)-CH(2)/Av(s)-CH(2)) of glycerol, and symmetric stretching band of NO(3)(-) (ν(1)-NO(3)(-)) with relative humidity (RH), it was found that the conformation of glycerol was transformed from αα mainly to γγ and partly to αγ with a decreasing RH in the mixed droplets, contrary to the case in the glycerol/water droplet. In addition, the glycerol with γγ and αγ conformation had strong interaction with Na(+) and NO(3)(-) respectively, which suppressed the formation of contact of ions and delayed the efflorescence relative humidity (ERH) for the mixed droplets compared to the NaNO(3)/water droplet. © 2012 American Chemical Society

Identification, synthesis and evaluation of SARS-CoV and MERS-CoV 3C-like protease inhibitors.

PubMed

Kumar, Vathan; Tan, Kian-Pin; Wang, Ying-Ming; Lin, Sheng-Wei; Liang, Po-Huang

2016-07-01

Severe acute respiratory syndrome (SARS) led to a life-threatening form of atypical pneumonia in late 2002. Following that, Middle East Respiratory Syndrome (MERS-CoV) has recently emerged, killing about 36% of patients infected globally, mainly in Saudi Arabia and South Korea. Based on a scaffold we reported for inhibiting neuraminidase (NA), we synthesized the analogues and identified compounds with low micromolar inhibitory activity against 3CL(pro) of SARS-CoV and MERS-CoV. Docking studies show that a carboxylate present at either R(1) or R(4) destabilizes the oxyanion hole in the 3CL(pro). Interestingly, 3f, 3g and 3m could inhibit both NA and 3CL(pro) and serve as a starting point to develop broad-spectrum antiviral agents. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structural variability in neptunium(V) oxalate compounds: synthesis and structural characterization of Na2NpO2(C2O4)OH.H2O.

PubMed

Bean, Amanda C; Garcia, Eduardo; Scott, Brian L; Runde, Wolfgang

2004-10-04

Reaction of a (237)Np(V) stock solution in the presence of oxalic acid, calcium chloride, and sodium hydroxide under hydrothermal conditions produces single crystals of a neptunium(V) oxalate, Na(2)NpO(2)(C(2)O(4))OH.H(2)O. The structure consists of one-dimensional chains running down the a axis and is the first example of a neptunium(V) oxalate compound containing hydroxide anions.

High-Performance Na-O2 Batteries Enabled by Oriented NaO2 Nanowires as Discharge Products.

PubMed

Khajehbashi, S Mohammad B; Xu, Lin; Zhang, Guobin; Tan, Shuangshuang; Zhao, Yan; Wang, Lai-Sen; Li, Jiantao; Luo, Wen; Peng, Dong-Liang; Mai, Liqiang

2018-06-13

Na-O 2 batteries are emerging rechargeable batteries due to their high theoretical energy density and abundant resources, but they suffer from sluggish kinetics due to the formation of large-size discharge products with cubic or irregular particle shapes. Here, we report the unique growth of discharge products of NaO 2 nanowires inside Na-O 2 batteries that significantly boosts the performance of Na-O 2 batteries. For this purpose, a high-spin Co 3 O 4 electrocatalyst was synthesized via the high-temperature oxidation of pure cobalt nanoparticles in an external magnetic field. The discharge products of NaO 2 nanowires are 10-20 nm in diameter and ∼10 μm in length, characteristics that provide facile pathways for electron and ion transfer. With these nanowires, Na-O 2 batteries have surpassed 400 cycles with a fixed capacity of 1000 mA h g -1 , an ultra-low over-potential of ∼60 mV during charging, and near-zero over-potential during discharging. This strategy not only provides a unique way to control the morphology of discharge products to achieve high-performance Na-O 2 batteries but also opens up the opportunity to explore growing nanowires in novel conditions.

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.

L-changing depopulation of Na s and p Rydberg states by ion impact

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

Rolfes, R.G.; Smith, D.B.; MacAdam, K.B.

1988-04-01

Ar/sup +/ and Na/sup +/ ion beams bombarding Na ns and np Rydberg-state targets at impact velocities near the Bohr-orbital velocity of the target atoms (i.e., v-italic-tildeapprox. =1) induce transitions to (n-1)l states (lgreater than or equal to2) with larger-than-geometric cross sections. Depopulation of ns states proceeds directly into the full n-1, lgreater than or equal to2 manifold rather than populating the np or (n-1)p states as the first of a sequence of dipole-allowed steps. Depopulation of np states leads to a distribution of final states that is dominated by the nearer or high-l part of the n-1 manifold. nmore » dependences of the cross section for ns depopulation are given at several energies for n = 32--41 and at a single energy for np, n = 26--32. The absolute cross section for Na(36s) depopulation falls gradually but steadily for reduced velocities v-italic-tilde increasing from 0.3 to 1.35. Bombardment of Na 39s and 39p states in applied fields 0--18.5 V/cm reveals that the final-state distributions become narrower as manifold states are Stark shifted close to the initial states. No theoretical results are available for direct comparison with these experiments, but the method of coupled channels seems to be the most suitable candidate.« less

OsHKT1;4-mediated Na(+) transport in stems contributes to Na(+) exclusion from leaf blades of rice at the reproductive growth stage upon salt stress.

PubMed

Suzuki, Kei; Yamaji, Naoki; Costa, Alex; Okuma, Eiji; Kobayashi, Natsuko I; Kashiwagi, Tatsuhiko; Katsuhara, Maki; Wang, Cun; Tanoi, Keitaro; Murata, Yoshiyuki; Schroeder, Julian I; Ma, Jian Feng; Horie, Tomoaki

2016-01-19

Na(+) exclusion from leaf blades is one of the key mechanisms for glycophytes to cope with salinity stress. Certain class I transporters of the high-affinity K(+) transporter (HKT) family have been demonstrated to mediate leaf blade-Na(+) exclusion upon salinity stress via Na(+)-selective transport. Multiple HKT1 transporters are known to function in rice (Oryza sativa). However, the ion transport function of OsHKT1;4 and its contribution to the Na(+) exclusion mechanism in rice remain to be elucidated. Here, we report results of the functional characterization of the OsHKT1;4 transporter in rice. OsHKT1;4 mediated robust Na(+) transport in Saccharomyces cerevisiae and Xenopus laevis oocytes. Electrophysiological experiments demonstrated that OsHKT1;4 shows strong Na(+) selectivity among cations tested, including Li(+), Na(+), K(+), Rb(+), Cs(+), and NH4 (+), in oocytes. A chimeric protein, EGFP-OsHKT1;4, was found to be functional in oocytes and targeted to the plasma membrane of rice protoplasts. The level of OsHKT1;4 transcripts was prominent in leaf sheaths throughout the growth stages. Unexpectedly however, we demonstrate here accumulation of OsHKT1;4 transcripts in the stem including internode II and peduncle in the reproductive growth stage. Moreover, phenotypic analysis of OsHKT1;4 RNAi plants in the vegetative growth stage revealed no profound influence on the growth and ion accumulation in comparison with WT plants upon salinity stress. However, imposition of salinity stress on the RNAi plants in the reproductive growth stage caused significant Na(+) overaccumulation in aerial organs, in particular, leaf blades and sheaths. In addition, (22)Na(+) tracer experiments using peduncles of RNAi and WT plants suggested xylem Na(+) unloading by OsHKT1;4. Taken together, our results indicate a newly recognized function of OsHKT1;4 in Na(+) exclusion in stems together with leaf sheaths, thus excluding Na(+) from leaf blades of a japonica rice cultivar in the

Contributions of the Na+/K+-ATPase, NKCC1, and Kir4.1 to hippocampal K+ clearance and volume responses

PubMed Central

Larsen, Brian Roland; Assentoft, Mette; Cotrina, Maria L.; Hua, Susan Z.; Nedergaard, Maiken; Kaila, Kai; Voipio, Juha; MacAulay, Nanna

2015-01-01

Bursts of network activity in the brain are associated with a transient increase in extracellular K+ concentration. The excess K+ is removed from the extracellular space by mechanisms proposed to involve Kir4.1-mediated spatial buffering, the Na+/K+/2Cl− cotransporter (NKCC1), and/or Na+/K+-ATPase activity. Their individual contribution to [K+]o management has been of extended controversy. The present study aimed, by several complementary approaches, to delineate the transport characteristics of Kir4.1, NKCC1, and Na+/K+-ATPase and to resolve their involvement in clearance of extracellular K+ transients. Primary cultures of rat astrocytes displayed robust NKCC1 activity with [K+]o increases above basal levels. Increased [K+]o produced NKCC1-mediated swelling of cultured astrocytes and NKCC1 could thereby potentially act as a mechanism of K+ clearance while concomitantly mediate the associated shrinkage of the extracellular space. In rat hippocampal slices, inhibition of NKCC1 failed to affect the rate of K+ removal from the extracellular space while Kir4.1 enacted its spatial buffering only during a local [K+]o increase. In contrast, inhibition of the different isoforms of Na+/K+-ATPase reduced post-stimulusclearance of K+ transients. The glia-specific α2/β2 subunit composition of Na+/K+-ATPase, when expressed in Xenopus oocytes, displayed a K+ affinity and voltage-sensitivity that would render this astrocyte-specific subunit composition specifically geared for controlling [K+]o during neuronal activity. In rat hippocampal slices, simultaneous measurements of the extracellular space volume revealed that neither Kir4.1, NKCC1, nor Na+/K+-ATPase accounted for the stimulus-induced shrinkage of the extracellular space. Thus, NKCC1 plays no role in activity-induced extracellular K+ recovery in native hippocampal tissue while Kir4.1 and Na+/K+-ATPase serve temporally distinct roles. PMID:24482245

Na(+)-dependent transport of taurine is found only on the abluminal membrane of the blood-brain barrier.

PubMed

Rasgado-Flores, Hector; Mokashi, Ashwini; Hawkins, Richard A

2012-01-01

Luminal and abluminal plasma membranes were isolated from bovine brain microvessels and used to identify and characterize Na(+)-dependent and facilitative taurine transport. The calculated transmembrane potential was -59 mV at time 0; external Na(+) (or choline under putative zero-trans conditions) was 126 mM (T=25 °C). The apparent affinity constants of the taurine transporters were determined over a range of taurine concentrations from 0.24 μM to 11.4 μM. Abluminal membranes had both Na(+)-dependent taurine transport as well as facilitative transport while luminal membranes only had facilitative transport. The apparent K(m) for facilitative and Na(+)-dependent taurine transport were 0.06±0.02 μM and 0.7±0.1 μM, respectively. The Na(+)-dependent transport of taurine was voltage dependent over the range of voltages studied (-25 to -101 mV). The transport was over 5 times greater at -101 mV compared to when V(m) was -25 mV. The sensitivity to external osmolality of Na(+)-dependent transport was studied over a range of osmolalities (229 to 398 mOsm/kg H(2)O) using mannitol as the osmotic agent to adjust the osmolality. For these experiments the concentration of Na(+) was maintained constant at 50mM, and the calculated transmembrane potential was -59 mV. The Na(+)-dependent transport system was sensitive to osmolality with the greatest rate observed at 229 mOsm/kg H(2)O. Copyright © 2011 Elsevier Inc. All rights reserved.

Structure and temperature-dependent phase transitions of lead-free Bi 1/2Na 1/2TiO 3-Bi 1/2K 1/2TiO 3-K 0.5Na 0.5NbO 3 piezoceramics

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

Anton, Eva-Maria; Schmitt, Ljubomira Ana; Hinterstein, Manuel

2014-05-28

Structure and phase transitions of (1-y)((1-x)Bi 1/2Na 1/2TiO 3-xBi 1/2K 1/2TiO 3)-yK 0.5Na 0.5NbO 3 (x; y) piezoceramics (0.1 ≤ x ≤ 0.4; 0 ≤ y ≤ 0.05) were investigated by transmission electron microscopy, neutron diffraction, temperature-dependent x-ray diffraction, and Raman spectroscopy. The local crystallographic structure at room temperature (RT) does not change by adding K 0.5Na 0.5NbO 3 to Bi 1/2Na 1/2TiO 3-xBi 1/2K 1/2TiO 3 for x = 0.2 and 0.4. The average crystal structure and microstructure on the other hand develop from mainly long-range polar order with ferroelectric domains to short-range order with polar nanoregions displaying amore » more pronounced relaxor character. The (0.1; 0) and (0.1; 0.02) compositions exhibit monoclinic Cc space group symmetry, which transform into Cc + P4bm at 185 and 130 °C, respectively. This high temperature phase is stable at RT for the morphotropic phase boundary compositions of (0.1; 0.05) and all compositions with x = 0.2. For the compositions of (0.1; 0) and (0.1; 0.02), local structural changes on heating are evidenced by Raman; for all other compositions, changes in the long-range average crystal structure were observed.« less

The NAv1.7 blocker protoxin II reduces burn injury-induced spinal nociceptive processing.

PubMed

Torres-Pérez, Jose Vicente; Adamek, Pavel; Palecek, Jiri; Vizcaychipi, Marcela; Nagy, Istvan; Varga, Angelika

2018-01-01

Controlling pain in burn-injured patients poses a major clinical challenge. Recent findings suggest that reducing the activity of the voltage-gated sodium channel Na v 1.7 in primary sensory neurons could provide improved pain control in burn-injured patients. Here, we report that partial thickness scalding-type burn injury on the rat paw upregulates Na v 1.7 expression in primary sensory neurons 3 h following injury. The injury also induces upregulation in phosphorylated cyclic adenosine monophosphate response element-binding protein (p-CREB), a marker for nociceptive activation in primary sensory neurons. The upregulation in p-CREB occurs mainly in Na v 1.7-immunopositive neurons and exhibits a peak at 5 min and, following a decline at 30 min, a gradual increase from 1 h post-injury. The Na v 1.7 blocker protoxin II (ProTxII) or morphine injected intraperitoneally 15 min before or after the injury significantly reduces burn injury-induced spinal upregulation in phosphorylated serine 10 in histone H3 and phosphorylated extracellular signal-regulated kinase 1/2, which are both markers for spinal nociceptive processing. Further, ProTxII significantly reduces the frequency of spontaneous excitatory post-synaptic currents in spinal dorsal horn neurons following burn injury. Together, these findings indicate that using Na v 1.7 blockers should be considered to control pain in burn injury. • Burn injury upregulates Na v 1.7 expression in primary sensory neurons. • Burn injury results in increased activity of Na v 1.7-expressing primary sensory neurons. • Inhibiting Na v 1.7 by protoxin II reduces spinal nociceptive processing. • Na v 1.7 represents a potential target to reduce pain in burn injury.

Cortical and subcortical connections of V1 and V2 in early postnatal macaque monkeys.

PubMed

Baldwin, Mary K L; Kaskan, Peter M; Zhang, Bin; Chino, Yuzo M; Kaas, Jon H

2012-02-15

Connections of primary (V1) and secondary (V2) visual areas were revealed in macaque monkeys ranging in age from 2 to 16 weeks by injecting small amounts of cholera toxin subunit B (CTB). Cortex was flattened and cut parallel to the surface to reveal injection sites, patterns of labeled cells, and patterns of cytochrome oxidase (CO) staining. Projections from the lateral geniculate nucleus and pulvinar to V1 were present at 4 weeks of age, as were pulvinar projections to thin and thick CO stripes in V2. Injections into V1 in 4- and 8-week-old monkeys labeled neurons in V2, V3, middle temporal area (MT), and dorsolateral area (DL)/V4. Within V1 and V2, labeled neurons were densely distributed around the injection sites, but formed patches at distances away from injection sites. Injections into V2 labeled neurons in V1, V3, DL/V4, and MT of monkeys 2-, 4-, and 8-weeks of age. Injections in thin stripes of V2 preferentially labeled neurons in other V2 thin stripes and neurons in the CO blob regions of V1. A likely thick stripe injection in V2 at 4 weeks of age labeled neurons around blobs. Most labeled neurons in V1 were in superficial cortical layers after V2 injections, and in deep layers of other areas. Although these features of adult V1 and V2 connectivity were in place as early as 2 postnatal weeks, labeled cells in V1 and V2 became more restricted to preferred CO compartments after 2 weeks of age. Copyright © 2011 Wiley-Liss, Inc.

Selection of drug-resistant HIV-1 during the early phase of viral decay is uncommon in treatment-naïve patients initiated on a three- or four-drug antiretroviral regimen including lamivudine.

PubMed

Bergroth, Tobias; Ekici, Halime; Gisslén, Magnus; Loes, Sabine Kinloch-de; Goh, Li-Ean; Freedman, Andrew; Lampe, Fiona; Johnson, Margaret A; Sönnerborg, Anders

2009-01-01

Therapy failure due to drug resistance development is a common phenomenon in HIV-infected patients. However, when the drug pressure leads to the earliest selection of drug-resistant HIV-1 populations is still unclear. In this study, the extent to which selection of the HIV-1 reverse transcriptase M184I/V mutations occur during the initial phase of viral decay in treatment-naïve HIV-1 infected patients receiving antiretroviral therapy (ART) was examined. Plasma virus from three cohorts of treatment-naïve patients initiating quadruple (n = 43), triple (n = 14) or dual (n = 15) lamivudine-containing ART were analyzed for M184I/V during the first 6 months of therapy using direct sequencing and a sensitive selective real-time PCR method. Among quadruple ART patients, who all were treated at primary HIV-1 infection, only one patient developed M184V after 6 weeks of therapy, having had wild-type virus at baseline. No mutations were found in chronically infected patients on triple ART. In patients on dual therapy, M184I/V mutants were found frequently. Selection of M184I/V mutants was found to be rare during the initial phase of viral decay after initiation of ART in adherent patients given a three or four-drug combination, in contrast to those receiving a less potent regimen. The results suggest that triple and quadruple lamivudine + PI or PI/r containing ART given to treatment-naïve adherent patients is potent enough to prevent development of resistance during the first months of therapy.

Studies of Rotationally and Vibrationally Inelastic Collisions of NaK with Atomic Perturbers

NASA Astrophysics Data System (ADS)

Richter, Kara M.

This dissertation discusses investigations of vibrationally and rotationally inelastic collisions of NaK with argon, helium and potassium as collision partners. We have investigated collisions of NaK molecules in the 2(A) 1Sigma+, state with argon and helium collision partners in a laser-induced fluorescence (LIF) experiment. The pump laser prepares the molecules in particular ro-vibrational (v, J) levels in the 2(A) 1Sigma+, state. These excited molecules then emit fluorescence as they make transitions back to the ground [2(X)1Sigma +] state, and this fluorescence is collected by a Bomem Fourier-transform spectrometer. Weak collisional satellite lines appear flanking strong, direct lines in the recorded spectra. These satellite lines are due to collisions of the NaK molecule in the 2(A)1Sigma+, state with noble gas and alkali atom perturbers, which carry population to nearby rotational levels [(v, J) →(v, J + DeltaJ)] or to various rotational levels of nearby vibrational levels, [(v, J)→ (v + Deltav, J + DeltaJ)]. Ratios of the intensity of each collisional line to the intensity of the direct line then yields information pertaining to the transfer of population in the collision. Our results show a propensity for DeltaJ = even collisions of NaK with noble gas atoms, which is slightly more pronounced for collisions with helium than with argon. Such a DeltaJ = even propensity was not observed in the vibrationally inelastic collisions. Although it would be desirable to operate in the single collision regime, practical considerations make that difficult to achieve. Therefore, we have developed a method to estimate the effects of multiple collisions on our measured rate coefficients and have obtained approximate corrected values.

Rotationally inelastic collisions of He and Ar with NaK: Theory and Experiment

NASA Astrophysics Data System (ADS)

Price, T. J.; Towne, A. C.; Richter, K.; Jones, J.; Hickman, A. P.; Huennekens, J.; Faust, C.; Malenda, R. F.; Ross, A. J.; Crozet, P.; Talbi, D.; Forrey, R. C.

2016-05-01

Rotationally inelastic thermal collisions of NaK A1Σ+ molecules with He and Ar have been studied at Lehigh and Lyon. In both laboratories, a pump laser excites a particular ro-vibrational level A1Σ+ (v , J). Strong transitions from the pumped (v , J) level and weaker transitions from collisionally-populated levels (v ,J' = J + ΔJ) occur. Ratios of line intensities yield information about population and orientation transfer. At Lyon, we also identify v changing collisions. A strong propensity for ΔJ = even transitions is observed for He and Ar. Theoretical calculations are underway; we've calculated He-NaK and Ar-NaK potential surfaces using GAMESS and performed coupled channel scattering calculations for JM -->J'M' transitions. Semiclassical formulas for the cross sections have been obtained and agree well with our quantum mechanical calculations. Using the vector model, where J precesses with polar angle θ about the z-axis, we derived the distribution of final polar angles θ' and final M' states. We identify a special case where the θ' distribution is a Lorentzian centered at θ. Work supported by NSF, XSEDE and CNRS (PICS).

Condition of Si crystal formation by vaporizing Na from NaSi

NASA Astrophysics Data System (ADS)

Morito, Haruhiko; Karahashi, Taiki; Yamane, Hisanori

2012-09-01

NaSi was heated at various Na vapor pressures (pNa 0.1-1.2 atm) and temperatures (973-1173 K) to investigate the condition of Si crystal formation from NaSi by Na evaporation. Silicon single crystals 1-3 mm in diameter were grown by evaporation of Na from Na-Si melt at 1173 K and pNa=0.74 atm.

Sodium Channel Nav1.8 Underlies TTX-Resistant Axonal Action Potential Conduction in Somatosensory C-Fibers of Distal Cutaneous Nerves.

PubMed

Klein, Amanda H; Vyshnevska, Alina; Hartke, Timothy V; De Col, Roberto; Mankowski, Joseph L; Turnquist, Brian; Bosmans, Frank; Reeh, Peter W; Schmelz, Martin; Carr, Richard W; Ringkamp, Matthias

2017-05-17

Voltage-gated sodium (Na V ) channels are responsible for the initiation and conduction of action potentials within primary afferents. The nine Na V channel isoforms recognized in mammals are often functionally divided into tetrodotoxin (TTX)-sensitive (TTX-s) channels (Na V 1.1-Na V 1.4, Na V 1.6-Na V 1.7) that are blocked by nanomolar concentrations and TTX-resistant (TTX-r) channels (Na V 1.8 and Na V 1.9) inhibited by millimolar concentrations, with Na V 1.5 having an intermediate toxin sensitivity. For small-diameter primary afferent neurons, it is unclear to what extent different Na V channel isoforms are distributed along the peripheral and central branches of their bifurcated axons. To determine the relative contribution of TTX-s and TTX-r channels to action potential conduction in different axonal compartments, we investigated the effects of TTX on C-fiber-mediated compound action potentials (C-CAPs) of proximal and distal peripheral nerve segments and dorsal roots from mice and pigtail monkeys ( Macaca nemestrina ). In the dorsal roots and proximal peripheral nerves of mice and nonhuman primates, TTX reduced the C-CAP amplitude to 16% of the baseline. In contrast, >30% of the C-CAP was resistant to TTX in distal peripheral branches of monkeys and WT and Na V 1.9 -/- mice. In nerves from Na V 1.8 -/- mice, TTX-r C-CAPs could not be detected. These data indicate that Na V 1.8 is the primary isoform underlying TTX-r conduction in distal axons of somatosensory C-fibers. Furthermore, there is a differential spatial distribution of Na V 1.8 within C-fiber axons, being functionally more prominent in the most distal axons and terminal regions. The enrichment of Na V 1.8 in distal axons may provide a useful target in the treatment of pain of peripheral origin. SIGNIFICANCE STATEMENT It is unclear whether individual sodium channel isoforms exert differential roles in action potential conduction along the axonal membrane of nociceptive, unmyelinated peripheral nerve

V-1 regulates capping protein activity in vivo.

PubMed

Jung, Goeh; Alexander, Christopher J; Wu, Xufeng S; Piszczek, Grzegorz; Chen, Bi-Chang; Betzig, Eric; Hammer, John A

2016-10-25

Capping Protein (CP) plays a central role in the creation of the Arp2/3-generated branched actin networks comprising lamellipodia and pseudopodia by virtue of its ability to cap the actin filament barbed end, which promotes Arp2/3-dependent filament nucleation and optimal branching. The highly conserved protein V-1/Myotrophin binds CP tightly in vitro to render it incapable of binding the barbed end. Here we addressed the physiological significance of this CP antagonist in Dictyostelium, which expresses a V-1 homolog that we show is very similar biochemically to mouse V-1. Consistent with previous studies of CP knockdown, overexpression of V-1 in Dictyostelium reduced the size of pseudopodia and the cortical content of Arp2/3 and induced the formation of filopodia. Importantly, these effects scaled positively with the degree of V-1 overexpression and were not seen with a V-1 mutant that cannot bind CP. V-1 is present in molar excess over CP, suggesting that it suppresses CP activity in the cytoplasm at steady state. Consistently, cells devoid of V-1, like cells overexpressing CP described previously, exhibited a significant decrease in cellular F-actin content. Moreover, V-1-null cells exhibited pronounced defects in macropinocytosis and chemotactic aggregation that were rescued by V-1, but not by the V-1 mutant. Together, these observations demonstrate that V-1 exerts significant influence in vivo on major actin-based processes via its ability to sequester CP. Finally, we present evidence that V-1's ability to sequester CP is regulated by phosphorylation, suggesting that cells may manipulate the level of active CP to tune their "actin phenotype."

Approaching Piezoelectric Response of Pb-Piezoelectrics in Hydrothermally Synthesized Bi0.5(Na1- xK x)0.5TiO3 Nanotubes.

PubMed

Ghasemian, Mohammad Bagher; Rawal, Aditya; Liu, Yun; Wang, Danyang

2018-06-20

A large piezoelectric coefficient of 76 pm/V along the diameter direction, approaching that of lead-based piezoelectrics, is observed in hydrothermally synthesized Pb-free Bi 0.5 (Na 0.8 K 0.2 ) 0.5 TiO 3 nanotubes. The 30-50 nm diameter nanotubes are formed through a scrolling and wrapping mechanism without the need of a surfactant or template. A molar ratio of KOH/NaOH = 0.5 for the mineralizers yields the Na/K ratio of ∼0.8:0.2, corresponding to an orthorhombic-tetragonal (O-T) phase boundary composition. X-ray diffraction patterns along with transmission electron microscopy analysis ascertain the coexistence of orthorhombic and tetragonal phases with (110) and (001) orientations along the nanotube length direction, respectively. 23 Na NMR spectroscopy confirms the higher degree of disorder in Bi 0.5 (Na 1- x K x ) 0.5 TiO 3 nanotubes with O-T phase coexistence. These findings present a significant advance toward the application of Pb-free piezoelectric materials.

75 FR 6860 - Airworthiness Directives; International Aero Engines AG (IAE) V2500-A1, V2522-A5, V2524-A5, V2525...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-12

... Airworthiness Directives; International Aero Engines AG (IAE) V2500-A1, V2522-A5, V2524-A5, V2525-D5, V2527-A5, V2527E-A5, V2527M-A5, V2528-D5, V2530-A5, and V2533-A5 Turbofan Engines AGENCY: Federal Aviation... airworthiness directive (AD) for all International Aero Engines AG (IAE) V2500-A1, V2525-D5 and V2528-D5...

Metadynamics Simulations Reveal a Na+ Independent Exiting Path of Galactose for the Inward-Facing Conformation of vSGLT

PubMed Central

Bisha, Ina; Rodriguez, Alex; Laio, Alessandro; Magistrato, Alessandra

2014-01-01

Sodium-Galactose Transporter (SGLT) is a secondary active symporter which accumulates sugars into cells by using the electrochemical gradient of Na+ across the membrane. Previous computational studies provided insights into the release process of the two ligands (galactose and sodium ion) into the cytoplasm from the inward-facing conformation of Vibrio parahaemolyticus sodium/galactose transporter (vSGLT). Several aspects of the transport mechanism of this symporter remain to be clarified: (i) a detailed kinetic and thermodynamic characterization of the exit path of the two ligands is still lacking; (ii) contradictory conclusions have been drawn concerning the gating role of Y263; (iii) the role of Na+ in modulating the release path of galactose is not clear. In this work, we use bias-exchange metadynamics simulations to characterize the free energy profile of the galactose and Na+ release processes toward the intracellular side. Surprisingly, we find that the exit of Na+ and galactose is non-concerted as the cooperativity between the two ligands is associated to a transition that is not rate limiting. The dissociation barriers are of the order of 11–12 kcal/mol for both the ion and the substrate, in line with kinetic information concerning this type of transporters. On the basis of these results we propose a branched six-state alternating access mechanism, which may be shared also by other members of the LeuT-fold transporters. PMID:25522004

Evidence for rotation of V1-ATPase

PubMed Central

Imamura, Hiromi; Nakano, Masahiro; Noji, Hiroyuki; Muneyuki, Eiro; Ohkuma, Shoji; Yoshida, Masasuke; Yokoyama, Ken

2003-01-01

VoV1-ATPase is responsible for acidification of eukaryotic intracellular compartments and ATP synthesis of Archaea and some eubacteria. From the similarity to FoF1-ATP synthase, VoV1-ATPase has been assumed to be a rotary motor, but to date there are no experimental data to support this. Here we visualized the rotation of single molecules of V1-ATPase, a catalytic subcomplex of VoV1-ATPase. V1-ATPase from Thermus thermophilus was immobilized onto a glass surface, and a bead was attached to the D or F subunit through the biotin-streptavidin linkage. In both cases we observed ATP-dependent rotations of beads, the direction of which was always counterclockwise viewed from the membrane side. Given that three ATP molecules are hydrolyzed per one revolution, rates of rotation agree consistently with rates of ATP hydrolysis at saturating ATP concentrations. This study provides experimental evidence that VoV1-ATPase is a rotary motor and that both D and F subunits constitute a rotor shaft. PMID:12598655

Physical Parameters of Erupting Luminous Blue Variables: NGC 2363-V1 Caught in the Act

NASA Astrophysics Data System (ADS)

Drissen, Laurent; Crowther, Paul A.; Smith, Linda J.; Robert, Carmelle; Roy, Jean-René; Hillier, D. John

2001-01-01

A quantitative study of the luminous blue variable NGC 2363-V1 in the Magellanic galaxy NGC 2366 (D=3.44 Mpc) is presented, based on ultraviolet and optical Hubble Space Telescope STIS spectroscopy. Contemporary WFPC2 and William Herschel Telescope imaging reveals a modest V-band brightness increase of ~0.2 mag per year between 1996 January-1997 November, reaching V=17.4 mag, corresponding to MV=-10.4 mag. Subsequently, V1 underwent a similar decrease in V-band brightness, together with a UV brightening of 0.35 mag from 1997 November to 1999 November. The optical spectrum of V1 is dominated by H emission lines, with Fe II, He I and Na I also detected. In the ultraviolet, a forest of Fe absorption features and numerous absorption lines typical of mid-B supergiants (such as Si II, Si III, Si IV, C III, C IV) are observed. From a spectral analysis with the non-LTE, line-blanketed code of Hillier & Miller, we derive stellar parameters of T*=11 kK, R*=420 Rsolar, log (L/Lsolar)=6.35 during 1997 November, and T*=13 kK, R*=315 Rsolar, log (L/Lsolar)=6.4 for 1999 July. The wind properties of V1 are also exceptional, with M~=4.4×10-4Msolar yr-1 and v∞~=300 km s-1, allowing for a clumped wind (filling factor=0.3) and assuming H/He~4 by number. The presence of Fe lines in the UV and optical spectrum of V1 permits an estimate of the heavy elemental abundance of NGC 2363 from our spectral synthesis. Although some deficiencies remain, allowance for charge exchange reactions in our calculations supports a SMC-like metallicity, that has previously been determined for NGC 2363 from nebular oxygen diagnostics. Considering a variety of possible progenitor stars, V1 has definitely undergone a giant eruption, with a substantial increase in stellar luminosity, radius, and almost certainly mass-loss rate, such that its stellar radius increased at an average rate of ~4 km s-1 during 1992 October-1995 February. The stellar properties of V1 are compared to other LBVs, including η Car

P-type single-crystalline ZnO films obtained by (Na,N) dual implantation through dynamic annealing process

NASA Astrophysics Data System (ADS)

Zhang, Zhiyuan; Huang, Jingyun; Chen, Shanshan; Pan, Xinhua; Chen, Lingxiang; Ye, Zhizhen

2018-02-01

Single-crystalline ZnO films were grown by plasma-assisted molecular beam epitaxy technique on c-plane sapphire substrates. The films have been implanted with fixed fluence of 130 keV Na and 90 keV N ions at 460 °C. It is observed that dually-implanted single crystalline ZnO films exhibit p-type characteristics with hole concentration in the range of 1.24 × 1016-1.34 × 1017 cm-3, hole mobilities between 0.65 and 8.37 cm2 V-1 s-1, and resistivities in the range of 53.3-80.7 Ω cm by Hall-effect measurements. There are no other secondary phase appearing, with (0 0 2) (c-plane) orientation after ion implantation as identified by the X-ray diffraction pattern. It is obtained that Na and N ions were successfully implanted and activated as acceptors measured by XPS and SIMS results. Also compared to other similar studies, lower amount of Na and N ions make p-type characteristics excellent as others deposited by traditional techniques. It is concluded that Na and N ion implantation and dynamic annealing are essential in forming p-type single-crystalline ZnO films.

V-1 regulates capping protein activity in vivo

PubMed Central

Jung, Goeh; Wu, Xufeng S.; Piszczek, Grzegorz; Chen, Bi-Chang; Betzig, Eric; Hammer, John A.

2016-01-01

Capping Protein (CP) plays a central role in the creation of the Arp2/3-generated branched actin networks comprising lamellipodia and pseudopodia by virtue of its ability to cap the actin filament barbed end, which promotes Arp2/3-dependent filament nucleation and optimal branching. The highly conserved protein V-1/Myotrophin binds CP tightly in vitro to render it incapable of binding the barbed end. Here we addressed the physiological significance of this CP antagonist in Dictyostelium, which expresses a V-1 homolog that we show is very similar biochemically to mouse V-1. Consistent with previous studies of CP knockdown, overexpression of V-1 in Dictyostelium reduced the size of pseudopodia and the cortical content of Arp2/3 and induced the formation of filopodia. Importantly, these effects scaled positively with the degree of V-1 overexpression and were not seen with a V-1 mutant that cannot bind CP. V-1 is present in molar excess over CP, suggesting that it suppresses CP activity in the cytoplasm at steady state. Consistently, cells devoid of V-1, like cells overexpressing CP described previously, exhibited a significant decrease in cellular F-actin content. Moreover, V-1–null cells exhibited pronounced defects in macropinocytosis and chemotactic aggregation that were rescued by V-1, but not by the V-1 mutant. Together, these observations demonstrate that V-1 exerts significant influence in vivo on major actin-based processes via its ability to sequester CP. Finally, we present evidence that V-1’s ability to sequester CP is regulated by phosphorylation, suggesting that cells may manipulate the level of active CP to tune their “actin phenotype.” PMID:27791032

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.

Glucocorticoids Suppress Renal Cell Carcinoma Progression by Enhancing Na,K-ATPase Beta-1 Subunit Expression

PubMed Central

Huynh, Thu P.; Barwe, Sonali P.; Lee, Seung J.; McSpadden, Ryan; Franco, Omar E.; Hayward, Simon W.; Damoiseaux, Robert; Grubbs, Stephen S.; Petrelli, Nicholas J.; Rajasekaran, Ayyappan K.

2015-01-01

Glucocorticoids are commonly used as palliative or chemotherapeutic clinical agents for treatment of a variety of cancers. Although steroid treatment is beneficial, the mechanisms by which steroids improve outcome in cancer patients are not well understood. Na,K-ATPase beta-subunit isoform 1 (NaK-β1) is a cell-cell adhesion molecule, and its expression is down-regulated in cancer cells undergoing epithelial-to mesenchymal-transition (EMT), a key event associated with cancer progression to metastatic disease. In this study, we performed high-throughput screening to identify small molecules that could up-regulate NaK-β1 expression in cancer cells. Compounds related to the glucocorticoids were identified as drug candidates enhancing NaK-β1 expression. Of these compounds, triamcinolone, dexamethasone, and fluorometholone were validated to increase NaK-β1 expression at the cell surface, enhance cell-cell adhesion, attenuate motility and invasiveness and induce mesenchymal to epithelial like transition of renal cell carcinoma (RCC) cells in vitro. Treatment of NaK-β1 knockdown cells with these drug candidates confirmed that these compounds mediate their effects through up-regulating NaK-β1. Furthermore, we demonstrated that these compounds attenuate tumor growth in subcutaneous RCC xenografts and reduce local invasiveness in orthotopically-implanted tumors. Our results strongly indicate that the addition of glucocorticoids in the treatment of RCC may improve outcome for RCC patients by augmenting NaK-β1 cell-cell adhesion function. PMID:25836370

The first Fe-based Na+-ion cathode with two distinct types of polyanions: Fe 3P 5SiO 19

DOE PAGES

Kan, W. H.; Huq, A.; Manthiram, A.

2015-05-15

We report the synthesis, structure, and electrochemistry of the first Na +-ion cathode with two distinct types of polyanions: Fe 3P 5SiO 19. The Fe-based cathode has a reversible capacity of ca. 70 mAh g -1; ca. 1.7 Na + ions per formula can be inserted/extracted at an average voltage of 2.5 V versus Na +/Na.

Densities of L-Glutamic Acid HCl Drug in Aqueous NaCl and KCl Solutions at Different Temperatures

NASA Astrophysics Data System (ADS)

Ryshetti, Suresh; Raghuram, Noothi; Rani, Emmadi Jayanthi; Tangeda, Savitha Jyostna

2016-04-01

Densities (ρ ) of (0.01 to 0.07) {mol}{\\cdot } {kg}^{-1} L-Glutamic acid HCl (L-HCl) drug in water, and in aqueous NaCl and KCl (0.5 and 1.0) {mol}{\\cdot } {kg}^{-1} solutions have been reported as a function of temperature at T = (298.15, 303.15, 308.15, and 313.15) K and atmospheric pressure. The accurate density (ρ ) values are used to estimate the various parameters such as the apparent molar volume (V_{2,{\\upphi }}), the partial molar volume (V2^{∞}), the isobaric thermal expansion coefficient (α 2), the partial molar expansion (E2^{∞}), and Hepler's constant (partial 2V2^{∞}/partial T2)P. The Cosphere overlap model is used to understand the solute-solvent interactions in a ternary mixture (L-HCl drug + NaCl or KCl + water). Hepler's constant (partial 2V2^{∞}/partial T2)_P is utilized to interpret the structure-making or -breaking ability of L-HCl drug in aqueous NaCl and KCl solutions, and the results are inferred that L-HCl drug acts as a structure maker, i.e., kosmotrope in aqueous NaCl solutions and performs as a structure breaker, i.e., chaotrope in aqueous KCl solutions.

Protection of pigs against pandemic swine origin H1N1 influenza A virus infection by hemagglutinin- or neuraminidase-expressing attenuated pseudorabies virus recombinants.

PubMed

Klingbeil, Katharina; Lange, Elke; Blohm, Ulrike; Teifke, Jens P; Mettenleiter, Thomas C; Fuchs, Walter

2015-03-02

Influenza is an important respiratory disease of pigs, and may lead to novel human pathogens like the 2009 pandemic H1N1 swine-origin influenza virus (SoIV). Therefore, improved influenza vaccines for pigs are required. Recently, we demonstrated that single intranasal immunization with a hemagglutinin (HA)-expressing pseudorabies virus recombinant of vaccine strain Bartha (PrV-Ba) protected pigs from H1N1 SoIV challenge (Klingbeil et al., 2014). Now we investigated enhancement of efficacy by prime-boost vaccination and/or intramuscular administration. Furthermore, a novel PrV-Ba recombinant expressing codon-optimized N1 neuraminidase (NA) was included. In vitro replication of this virus was only slightly affected compared to parental virus. Unlike HA, the abundantly expressed NA was efficiently incorporated into PrV particles. Immunization of pigs with the two PrV recombinants, either singly or in combination, induced B cell proliferation and the expected SoIV-specific antibodies, whose titers increased substantially after boost vaccination. After immunization of animals with either PrV recombinant H1N1 SoIV challenge virus replication was significantly reduced compared to PrV-Ba vaccinated or naïve controls. Protective efficacy of HA-expressing PrV was higher than of NA-expressing PrV, and not significantly enhanced by combination. Despite higher serum antibody titers obtained after intramuscular immunization, transmission of challenge virus to naïve contact animals was only prevented after intranasal prime-boost vaccination with HA-expressing PrV-Ba. Copyright © 2015 Elsevier B.V. All rights reserved.

Network interactions: non-geniculate input to V1.

PubMed

Muckli, Lars; Petro, Lucy S

2013-04-01

The strongest connections to V1 are fed back from neighbouring area V2 and from a network of higher cortical areas (e.g. V3, V5, LOC, IPS and A1), transmitting the results of cognitive operations such as prediction, attention and imagination. V1 is therefore at the receiving end of a complex cortical processing cascade and not only at the entrance stage of cortical processing of retinal input. One elegant strategy to investigate this information-rich feedback to V1 is to eliminate feedforward input, that is, exploit V1's retinotopic organisation to isolate subregions receiving no direct bottom-up stimulation. We highlight the diverse mechanisms of cortical feedback, ranging from gain control to predictive coding, and conclude that V1 is involved in rich internal communication processes. Copyright © 2013 Elsevier Ltd. All rights reserved.

Regulation of Na+ channel inactivation by the DIII and DIV voltage-sensing domains.

PubMed

Hsu, Eric J; Zhu, Wandi; Schubert, Angela R; Voelker, Taylor; Varga, Zoltan; Silva, Jonathan R

2017-03-06

Functional eukaryotic voltage-gated Na + (Na V ) channels comprise four domains (DI-DIV), each containing six membrane-spanning segments (S1-S6). Voltage sensing is accomplished by the first four membrane-spanning segments (S1-S4), which together form a voltage-sensing domain (VSD). A critical Na V channel gating process, inactivation, has previously been linked to activation of the VSDs in DIII and DIV. Here, we probe this interaction by using voltage-clamp fluorometry to observe VSD kinetics in the presence of mutations at locations that have been shown to impair Na V channel inactivation. These locations include the DIII-DIV linker, the DIII S4-S5 linker, and the DIV S4-S5 linker. Our results show that, within the 10-ms timeframe of fast inactivation, the DIV-VSD is the primary regulator of inactivation. However, after longer 100-ms pulses, the DIII-DIV linker slows DIII-VSD deactivation, and the rate of DIII deactivation correlates strongly with the rate of recovery from inactivation. Our results imply that, over the course of an action potential, DIV-VSDs regulate the onset of fast inactivation while DIII-VSDs determine its recovery. © 2017 Hsu et al.

Nonpeptide vasopressin receptor antagonists: development of selective and orally active V1a, V2 and V1b receptor ligands.

PubMed

Serradeil-Le Gal, C; Wagnon, J; Valette, G; Garcia, G; Pascal, M; Maffrand, J P; Le Fur, G

2002-01-01

The involvement of vasopressin (AVP) in several pathological states has been reported recently and the selective blockade of the different AVP receptors could offer new clinical perspectives. During the past few years, various selective, orally active AVP V1a (OPC-21268, SR49059 (Relcovaptan)), V2 (OPC-31260, OPC-41061 (Tolvaptan), VPA-985 (Lixivaptan), SR121463, VP-343, FR-161282) and mixed V1a/V2 (YM-087 (Conivaptan), JTV-605, CL-385004) receptor antagonists have been intensively studied in various animal models and have reached, Phase IIb clinical trials for some of them. For many years now, our laboratory has focused on the identification of nonpeptide vasopressin antagonists with suitable oral bioavailability. Using random screening on small molecule libraries, followed by rational SAR and modelization, we identified a chemical series of 1-phenylsulfonylindolines which first yielded SR49059, a V1a receptor antagonist prototype. This compound displayed high affinity for animal and human V1a receptors and antagonized various V1a AVP-induced effects in vitro and in vivo (intracellular [Ca2+] increase, platelet aggregation, vascular smooth muscle cell proliferation, hypertension and coronary vasospasm). We and others have used this compound to study the role of AVP in various animal models. Recent findings from clinical trials show a potential interest for SR49059 in the treatment of dysmenorrhea and in Raynaud's disease. Structural modifications and simplifications performed in the SR49059 chemical series yielded highly specific V2 receptor antagonists (N-arylsulfonyl-oxindoles), amongst them SR121463 which possesses powerful oral aquaretic properties in various animal species and in man. SR121463 is well-tolerated and dose-dependently increases urine output and decreases urine osmolality. It induces free water-excretion without affecting electrolyte balance in contrast to classical diuretics (e.g. furosemide and hydrochlorothiazide). Notably, in cirrhotic rats

2D Electrides as Promising Anode Materials for Na-Ion Batteries from First-Principles Study.

PubMed

Hu, Junping; Xu, Bo; Yang, Shengyuan A; Guan, Shan; Ouyang, Chuying; Yao, Yugui

2015-11-04

Searching for suitable anodes with good performance is a key challenge for rechargeable Na-ion batteries (NIBs). Using the first-principles method, we predict that 2D nitrogen electride materials can be served as anode materials for NIBs. Particularly, we show that Ca2N meets almost all the requirements of a good NIB anode. Each formula unit of a monolayer Ca2N sheet can absorb up to four Na atoms, corresponding to a theoretical specific capacity of 1138 mAh·g(-1). The metallic character for both pristine Ca2N and its Na intercalated state NaxCa2N ensures good electronic conduction. Na diffusion along the 2D monolayer plane can be very fast even at room temperature, with a Na migration energy barrier as small as 0.084 eV. These properties are key to the excellent rate performance of an anode material. The average open-circuit voltage is calculated to be 0.18 V vs Na/Na(+) for the chemical stoichiometry of Na2Ca2N and 0.09 V for Na4Ca2N. The relatively low average open-circuit voltage is beneficial to the overall voltage of the cell. In addition, the 2D monolayers have very small lattice change upon Na intercalation, which ensures a good cycling stability. All these results demonstrate that the Ca2N monolayer could be an excellent anode material for NIBs.

Thermal decomposition of sodium amide, NaNH2, and sodium amide hydroxide composites, NaNH2-NaOH.

PubMed

Jepsen, Lars H; Wang, Peikun; Wu, Guotao; Xiong, Zhitao; Besenbacher, Flemming; Chen, Ping; Jensen, Torben R

2016-09-14

Sodium amide, NaNH 2 , has recently been shown to be a useful catalyst to decompose NH 3 into H 2 and N 2 , however, sodium hydroxide is omnipresent and commercially available NaNH 2 usually contains impurities of NaOH (<2%). The thermal decomposition of NaNH 2 and NaNH 2 -NaOH composites is systematically investigated and discussed. NaNH 2 is partially dissolved in NaOH at T > 100 °C, forming a non-stoichiometric solid solution of Na(OH) 1-x (NH 2 ) x (0 < x < ∼0.30), which crystallizes in an orthorhombic unit cell with the space group P2 1 2 1 2 1 determined by synchrotron powder X-ray diffraction. The composite xNaNH 2 -(1 - x)NaOH (∼0.70 < x < 0.72) shows a lowered melting point, ∼160 °C, compared to 200 and 318 °C for neat NaNH 2 and NaOH, respectively. We report that 0.36 mol of NH 3 per mol of NaNH 2 is released below 400 °C during heating in an argon atmosphere, initiated at its melting point, T = 200 °C, possibly due to the formation of the mixed sodium amide imide solid solution. Furthermore, NaOH reacts with NaNH 2 at elevated temperatures and provides the release of additional NH 3 .

Electronic structure and molecular dynamics of Na2Li

NASA Astrophysics Data System (ADS)

Malcolm, Nathaniel O. J.; McDouall, Joseph J. W.

Following the first report (Mile, B., Sillman, P. D., Yacob, A. R. and Howard, J. A., 1996, J. chem. Soc. Dalton Trans , 653) of the EPR spectrum of the mixed alkali-metal trimer Na2Li a detailed study has been made of the electronic structure and structural dynamics of this species. Two isomeric forms have been found: one of the type, Na-Li-Na, of C , symmetry and another, Li-Na-Na, of C symmetry. Also, there are two linear saddle points which correspond to 'inversion' transition structures, and a saddle point of C symmetry which connects the two minima. A molecular dynamics investigation of these species shows that, at the temperature of the reported experiments (170 K), the C minimum is not 'static', but undergoes quite rapid inversion. At higher temperatures the C minimum converts to the C form, but by a mechanism very different from that suggested by minimum energy path considerations. 2 2v s s 2v 2v s

Rotationally inelastic collisions of He and Ar with NaK: Theory and Experiment

NASA Astrophysics Data System (ADS)

Richter, K.; Price, T. J.; Jones, J.; Faust, C.; Hickman, A. P.; Huennekens, J.; Malenda, R. F.; Ross, A. J.; Harker, H.; Crozet, P.; Forrey, R. C.

2015-05-01

Rotationally inelastic collisions of NaK A1Σ+ molecules with He and Ar are studied. At Lehigh, we use pump-probe polarization labeling (PL) and laser-induced fluorescence (LIF) spectroscopy. At Lyon, Fourier transform (FT)-resolved LIF spectra are recorded. In both cases, the pump laser excites a particular ro-vibrational level A1Σ+ (v , J). We observe strong direct lines corresponding to transitions from the (v , J) level pumped, and weak satellite lines corresponding to transitions from collisionally-populated levels (v ,J' = J + ΔJ). The ratios of satellite to direct line intensities in LIF and PL yield population and orientation transfer information. A strong propensity for ΔJ = even transitions is observed for both He and Ar perturbers. In the FT fluorescence experiment we also observe v-changing collisions. Ab initio potential surface and scattering calculations are underway for collisions in the A1Σ+ and X1Σ+ states. For He-NaK we have calculated potential surfaces using GAMESS and carried out coupled channel scattering calculations of transfer of population, orientation, and alignment. Calculations of v-changing collision cross sections are also in progress. Work supported by NSF, XSEDE and CNRS (PICS).

Evidence for a potential tumor suppressor role for the Na,K-ATPase ß1-subunit

PubMed Central

Inge, Landon J.; Rajasekaran, Sigrid A.; Yoshimoto, Koji; Mischel, Paul S.; McBride, William; Landaw, Elliot; Rajasekaran, Ayyappan K.

2009-01-01

Summary The Na,K-ATPase, consisting of two essential subunits (α, ß), plays a critical role in the regulation of ion homeostasis in mammalian cells. Recent studies indicate that reduced expression of the ß1 isoform (NaK-ß1) is commonly observed in carcinoma and is associated with events involved in cancer progression. In this study, we present evidence that repletion of NaK-ß1 in Moloney sarcoma virus-transformed Madin-Darby canine kidney cells (MSV-MDCK), a highly tumorigenic cell line, inhibits anchorage independent growth and suppresses tumor formation in immunocompromised mice. Additionally, using an in vitro cell-cell aggregation assay, we showed that cell aggregates of NaK-ß1 subunit expressing MSV-MDCK cells have reduced extracellular regulated kinase (ERK) 1/2 activity compared with parental MSV-MDCK cells. Finally, using immunohistochemistry and fully quantitative image analysis approaches, we showed that the levels of phosphorylated ERK 1/2 are inversely correlated to the NaK-ß1 levels in the tumors. These findings reveal for the first time that NaK-ß1 has a potential tumor-suppressor function in epithelial cells. PMID:18228203

Integrated synthesis of zeolites 4A and Na-P1 using coal fly ash for application in the formulation of detergents and swine wastewater treatment.

PubMed

Cardoso, Ariela M; Horn, Martha B; Ferret, Lizete S; Azevedo, Carla M N; Pires, Marçal

2015-04-28

Several researchers have reported zeolite synthesis using coal ash for a wide range of applications. However, little attention has been given to green processes, including moderate synthesis conditions, using waste as raw material and effluent reuse or reduction. In this study, Brazilian coal fly ashes were used for integrated synthesis of zeolites 4A and Na-P1 by two different routes and under moderate operating conditions (temperature and pressure). Both procedures produced zeolites with similar conversions (zeolite 4A at 82% purity and zeolite Na-P1 at 57-61%) and high CEC values (zeolites 4A: 4.5meqCa(2+)g(-1) and zeolites Na-P1: 2.6-2.8meqNH4(+)g(-1)). However, process 1 generated less effluent for the zeolite mass produced (7mLg(-1)), with low residual Si and Al levels and 74% of the Si available in the coal fly ash incorporated into the zeolite, while only 55% is used in process 2. For use as a builder in detergents, synthetic zeolite 4A exhibited conformity parameters equal to or greater than those of the commercial zeolite adopted as reference. Treatment of swine wastewater with zeolite Na-P1 resulted in a high removal capacity for total ammoniacal nitrogen (31mgg(-1)). Copyright © 2015 Elsevier B.V. All rights reserved.

A Voltage Dependent Non-Inactivating Na+ Channel Activated during Apoptosis in Xenopus Oocytes

PubMed Central

Englund, Ulrika H.; Gertow, Jens; Kågedal, Katarina; Elinder, Fredrik

2014-01-01

Ion channels in the plasma membrane are important for the apoptotic process. Different types of voltage-gated ion channels are up-regulated early in the apoptotic process and block of these channels prevents or delays apoptosis. In the present investigation we examined whether ion channels are up-regulated in oocytes from the frog Xenopus laevis during apoptosis. The two-electrode voltage-clamp technique was used to record endogenous ion currents in the oocytes. During staurosporine-induced apoptosis a voltage-dependent Na+ current increased three-fold. This current was activated at voltages more positive than 0 mV (midpoint of the open-probability curve was +55 mV) and showed almost no sign of inactivation during a 1-s pulse. The current was resistant to the Na+-channel blockers tetrodotoxin (1 µM) and amiloride (10 µM), while the Ca2+-channel blocker verapamil (50 µM) in the bath solution completely blocked the current. The intracellular Na+ concentration increased in staurosporine-treated oocytes, but could be prevented by replacing extracellular Na+ whith either K+ or Choline+. Prevention of this influx of Na+ also prevented the STS-induced up-regulation of the caspase-3 activity, suggesting that the intracellular Na+ increase is required to induce apoptosis. Taken together, we have found that a voltage dependent Na+ channel is up-regulated during apoptosis and that influx of Na+ is a crucial step in the apoptotic process in Xenopus oocytes. PMID:24586320

Integrated responses of Na+/HCO3- cotransporters and V-type H+-ATPases in the fish gill and kidney during respiratory acidosis.

PubMed

Perry, S F; Furimsky, M; Bayaa, M; Georgalis, T; Shahsavarani, A; Nickerson, J G; Moon, T W

2003-12-30

Using degenerate primers, followed by 3' and 5' RACE and "long" PCR, a continuous 4050-bp cDNA was obtained and sequenced from rainbow trout (Oncorhynchus mykiss) gill. The cDNA included an open reading frame encoding a deduced protein of 1088 amino acids. A BLAST search of the GenBank protein database demonstrated that the trout gene shared high sequence similarity with several vertebrate Na(+)/HCO(3)(-) cotransporters (NBCs) and in particular, NBC1. Protein alignment revealed that the trout NBC is >80% identical to vertebrate NBC1s and phylogenetic analysis provided additional evidence that the trout NBC is indeed a homolog of NBC1. Using the same degenerate primers, a partial cDNA (404 bp) for NBC was obtained from eel (Anguilla rostrata) kidney. Analysis of the tissue distribution of trout NBC, as determined by Northern blot analysis and real-time PCR, indicated high transcript levels in several absorptive/secretory epithelia including gill, kidney and intestine and significant levels in liver. NBC mRNA was undetectable in eel gill by real-time PCR. In trout, the levels of gill NBC1 mRNA were increased markedly during respiratory acidosis induced by exposure to hypercarbia; this response was accompanied by a transient increase in branchial V-type H(+)-ATPase mRNA levels. Assuming that the branchial NBC1 is localised to basolateral membranes of gill cells and operates in the influx mode (HCO(3)(-) and Na(+) entry into the cell), it would appear that in trout, the expression of branchial NBC1 is transcriptionally regulated to match the requirements of gill pHi regulation rather than to match trans-epithelial HCO(3)(-) efflux requirements for systemic acid-base balance. By analogy with mammalian systems, NBC1 in the kidney probably plays a role in the tubular reabsorption of both Na(+) and HCO(3)(-). During periods of respiratory acidosis, levels of renal NBC1 mRNA increased (after a transient reduction) in both trout and eel, presumably to increase HCO(3

Coulomb excitation of radioactive 20, 21Na

NASA Astrophysics Data System (ADS)

Schumaker, M. A.; Cline, D.; Hackman, G.; Pearson, C.; Svensson, C. E.; Wu, C. Y.; Andreyev, A.; Austin, R. A. E.; Ball, G. C.; Bandyopadhyay, D.; Becker, J. A.; Boston, A. J.; Boston, H. C.; Buchmann, L.; Churchman, R.; Cifarelli, F.; Cooper, R. J.; Cross, D. S.; Dashdorj, D.; Demand, G. A.; Dimmock, M. R.; Drake, T. E.; Finlay, P.; Gallant, A. T.; Garrett, P. E.; Green, K. L.; Grint, A. N.; Grinyer, G. F.; Harkness, L. J.; Hayes, A. B.; Kanungo, R.; Lisetskiy, A. F.; Leach, K. G.; Lee, G.; Maharaj, R.; Martin, J.-P.; Moisan, F.; Morton, A. C.; Mythili, S.; Nelson, L.; Newman, O.; Nolan, P. J.; Orce, J. N.; Padilla-Rodal, E.; Phillips, A. A.; Porter-Peden, M.; Ressler, J. J.; Roy, R.; Ruiz, C.; Sarazin, F.; Scraggs, D. P.; Waddington, J. C.; Wan, J. M.; Whitbeck, A.; Williams, S. J.; Wong, J.

2009-12-01

The low-energy structures of the radioactive nuclei 20, 21Na have been examined using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of ˜ 5×106 ions/s were accelerated to 1.7MeV/A and Coulomb excited in a 0.5mg/cm^2 natTi target. Two TIGRESS HPGe clover detectors perpendicular to the beam axis were used for γ -ray detection, while scattered nuclei were observed by the Si detector BAMBINO. For 21Na , Coulomb excitation from the 3/2+ ground state to the first excited 5/2+ state was observed, while for 20Na , Coulomb excitation was observed from the 2+ ground state to the first excited 3+ and 4+ states. For both beams, B ( λ L) values were determined using the 2+ rightarrow 0+ de-excitation in 48Ti as a reference. The resulting B( E2) ↓ value for 21Na is 137±9 e^2fm^4, while the resulting B( λ L) ↓ values for 20Na are 55±6 e^2fm^4 for the 3+ rightarrow 2+ , 35.7±5.7 e^2 fm^4 for the 4+ rightarrow 2+ , and 0.154±0.030 μ_ N^2 for the 4+ rightarrow 3+ transitions. This analysis significantly improves the measurement of the 21Na B( E2) value, and provides the first experimental determination of B( λ L) values for the proton dripline nucleus 20Na .-1

Direct detection of sub-GeV dark matter with scintillating targets

DOE PAGES

Derenzo, Stephen; Essig, Rouven; Massari, Andrea; ...

2017-07-28

We suggest a novel experimental concept for detecting MeV-to-GeV-mass dark matter, in which the dark matter scatters off electrons in a scintillating target and produces a signal of one or a few photons. New large-area photodetectors are needed to measure the photon signal with negligible dark counts, which could be constructed from transition edge sensor (TES) or microwave kinetic inductance detector (MKID) technology. Alternatively, detecting two photons in coincidence may allow the use of conventional photodetectors like photomultiplier tubes. Here we describe why scintillators may have distinct advantages over other experiments searching for a low ionization signal from sub-GeV darkmore » matter, as there are fewer potential sources of spurious backgrounds. We discuss various target choices, but focus on calculating the expected dark matter-electron scattering rates in three scintillating crystals: sodium iodide (NaI), cesium iodide (CsI), and gallium arsenide (GaAs). Among these, GaAs has the lowest band gap (1.52 eV) compared to NaI (5.9 eV) or CsI (6.4 eV), which in principle allows it to probe dark matter masses as low as ~0.5 MeV, compared to ~1.5 MeV with NaI or CsI. We compare these scattering rates with those expected in silicon (Si) and germanium (Ge). The proposed experimental concept presents an important complementary path to existing efforts, and its potential advantages may make it the most sensitive direct-detection probe of dark matter down to MeV masses.« less

Direct detection of sub-GeV dark matter with scintillating targets

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

Derenzo, Stephen; Essig, Rouven; Massari, Andrea

We suggest a novel experimental concept for detecting MeV-to-GeV-mass dark matter, in which the dark matter scatters off electrons in a scintillating target and produces a signal of one or a few photons. New large-area photodetectors are needed to measure the photon signal with negligible dark counts, which could be constructed from transition edge sensor (TES) or microwave kinetic inductance detector (MKID) technology. Alternatively, detecting two photons in coincidence may allow the use of conventional photodetectors like photomultiplier tubes. Here we describe why scintillators may have distinct advantages over other experiments searching for a low ionization signal from sub-GeV darkmore » matter, as there are fewer potential sources of spurious backgrounds. We discuss various target choices, but focus on calculating the expected dark matter-electron scattering rates in three scintillating crystals: sodium iodide (NaI), cesium iodide (CsI), and gallium arsenide (GaAs). Among these, GaAs has the lowest band gap (1.52 eV) compared to NaI (5.9 eV) or CsI (6.4 eV), which in principle allows it to probe dark matter masses as low as ~0.5 MeV, compared to ~1.5 MeV with NaI or CsI. We compare these scattering rates with those expected in silicon (Si) and germanium (Ge). The proposed experimental concept presents an important complementary path to existing efforts, and its potential advantages may make it the most sensitive direct-detection probe of dark matter down to MeV masses.« less

Electrophysiological evidence for Na+-coupled bicarbonate transport in cultured rat hepatocytes.

PubMed

Fitz, J G; Persico, M; Scharschmidt, B F

1989-03-01

Recent observations suggest that hepatocytes exhibit basolateral electrogenic Na+-coupled HCO3- transport. In these studies, we have further investigated this transport mechanism in primary culture of rat hepatocytes using intracellular microelectrodes to measure membrane potential difference (PD) and the pH-sensitive fluorochrome 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein to measure intracellular pH (pHi). In balanced media containing 25 mM HCO3-, PD averaged -32.1 +/- 0.6 (SE) mV and pHi averaged 7.22 +/- 0.03. PD became more negative (hyperpolarized) when extracellular [HCO3-] was increased and less negative (depolarized) when extracellular HCO3- was decreased. Acute replacement of extracellular Na+ by choline also resulted in membrane depolarization of 18.0 +/- 1.6 mV, suggesting net transfer of negative charge. This decrease in PD upon Na+ removal was HCO3- -dependent, amiloride insensitive, and inhibited by the disulfonic stilbene 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS). PD also decreased upon acute exposure to SITS. The degree of depolarization seen with removal of Na+ or HCO3- correlated directly with resting PD (r = 0.81 and 0.95, respectively), suggesting a voltage-dependent mechanism. Removal of extracellular Na+ also decreased pHi to 7.06 +/- 0.02, and this acidification was decreased in the absence of HCO3- or in the presence of SITS or amiloride. These studies provide direct evidence for electrogenic Na+-coupled HCO3- transport in rat hepatocytes. Further, they suggest that it represents a major pathway for conductive movement of Na+ across the membrane and that it contributes, along with Na+-H+ exchange, to the intracellular acidification observed upon removal of extracellular Na+.(ABSTRACT TRUNCATED AT 250 WORDS)

Common mechanisms of inhibition for the Na+/glucose (hSGLT1) and Na+/Cl−/GABA (hGAT1) cotransporters

PubMed Central

Hirayama, Bruce A; Díez-Sampedro, Ana; Wright, Ernest M

2001-01-01

Electrophysiological methods were used to investigate the interaction of inhibitors with the human Na+/glucose (hSGLT1) and Na+/Cl−/GABA (hGAT1) cotransporters. Inhibitor constants were estimated from both inhibition of substrate-dependent current and inhibitor-induced changes in cotransporter conformation. The competitive, non-transported inhibitors are substrate derivatives with inhibition constants from 200 nM (phlorizin) to 17 mM (esculin) for hSGLT1, and 300 nM (SKF89976A) to 10 mM (baclofen) for hGAT1. At least for hSGLT1, values determined using either method were proportional over 5-orders of magnitude. Correlation of inhibition to structure of the inhibitors resulted in a pharmacophore for glycoside binding to hSGLT1: the aglycone is coplanar with the pyranose ring, and binds to a hydrophobic/aromatic surface of at least 7×12Å. Important hydrogen bond interactions occur at five positions bordering this surface. In both hSGLT1 and hGAT1 the data suggests that there is a large, hydrophobic inhibitor binding site ∼8Å from the substrate binding site. This suggests an architectural similarity between hSGLT1 and hGAT1. There is also structural similarity between non-competitive and competitive inhibitors, e.g., phloretin is the aglycone of phlorizin (hSGLT1) and nortriptyline resembles SKF89976A without nipecotic acid (hGAT1). Our studies establish that measurement of the effect of inhibitors on presteady state currents is a valid non-radioactive method for the determination of inhibitor binding constants. Furthermore, analysis of the presteady state currents provide novel insights into partial reactions of the transport cycle and mode of action of the inhibitors. PMID:11588102

76 FR 13082 - Amendment of VOR Federal Airways V-1, V-7, V-11 and V-20; Kona, HI

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-10

... V-20; Kona, HI AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule. SUMMARY: This action amends four VHF Omnidirectional Range (VOR) Federal airways in the vicinity of Kona, HI; V- 1, V-7... Keahole Airport property Kailua-Kona, HI. This will enhance the management of aircraft operations over...

Synthesis and characterization of sodium vanadium oxide gels: the effects of water (n) and sodium (x) content on the electrochemistry of Na(x)V2O5·nH2O.

PubMed

Lee, Chia-Ying; Marschilok, Amy C; Subramanian, Aditya; Takeuchi, Kenneth J; Takeuchi, Esther S

2011-10-28

Sodium vanadium oxide gels, Na(x)V(2)O(5)·nH(2)O, of varying sodium content (0.12 < x < 0.32) were prepared by careful control of an ion exchange process. The water content (0.23 > n > 0.01) and interlayer spacing were found to be inversely proportional to the sodium level (x), thus control of sodium (x) content provided a direct, chimie douce approach for control of hydration level (n) and interlayer spacing, without the need for high temperature treatment to affect dehydration. Notably, the use of high temperatures to modify hydration levels can result in crystallization and collapse of the interlayer structure, highlighting the distinct advantage of our novel chimie douce synthesis strategy. Subsequent to synthesis and characterization, results from an electrochemical study of a series of Na(x)V(2)O(5)·nH(2)O samples highlight the significant impact of interlayer water on delivered capacity of the layered materials. Specifically, the sodium vanadium oxide gels with higher sodium content and lower water content provided higher capacities in lithium based cells, where capacity delivered to 2.0 V under C/20 discharge ranged from 170 mAh/g for Na(0.12)V(2)O(5)·0.23H(2)O to 300 mAh/g for Na(0.32)V(2)O(5)·0.01H(2)O. The capacity differences were maintained as the cells were cycled. This journal is © the Owner Societies 2011

Nano-glass ceramic cathodes for Li+/Na+ mixed-ion batteries

NASA Astrophysics Data System (ADS)

He, Wen; Zhang, Xudong; Jin, Chao; Wang, Yaoyao; Mossin, Susanne; Yue, Yuanzheng

2017-02-01

Electrode materials can display superior electrochemical performances and behavior via the nanoscale design. Here, the low-temperature synthesis of nano-glass ceramics (NGCs) is based on inheriting the network structure of yeast polyphosphate metabolism. The NGCs-3 sample synthesized with a molar ratio of Fe/V = 7:6 is composed of nano-domains of semiconducting oxide glass (Li2O-Na2O-Fe2O3-V2O5-P2O5, LNFVP), nanocrystalline particles (Li9Fe3P8O29, Li0.6V1.67O3.67 and VOPO4), and nanopores connected by interfaces. We have clarified the mixing ion transport mechanism and the electrochemical reactions, and the influences of molar ratio of Fe/V on the structure and electrochemical properties of NGCs. This nanoscale design offers a new possibility improved the electrochemical performances of Li+/Na+ mixed-ion batteries (LNMIBs). The NGCs-3 electrode exhibits a higher discharge capacity (145 mAh g-1) and energy storage density (525 Whkg-1) at 5C, and the capacity retention reaches 70% after 1000 cycles. More importantly, we have established a direct relationship between the electrochemical kinetics and nanostructure of NGC electrode materials.

Extracellular acidosis and very low [Na+ ] inhibit NBCn1- and NHE1-mediated net acid extrusion from mouse vascular smooth muscle cells.

PubMed

Bonde, L; Boedtkjer, E

2017-10-01

The electroneutral Na + , HCO3- cotransporter NBCn1 and Na + /H + exchanger NHE1 regulate acid-base balance in vascular smooth muscle cells (VSMCs) and modify artery function and structure. Pathological conditions - notably ischaemia - can dramatically perturb intracellular (i) and extracellular (o) pH and [Na + ]. We examined effects of low [Na + ] o and pH o on NBCn1 and NHE1 activity in VSMCs of small arteries. We measured pH i by 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein-based fluorescence microscopy of mouse mesenteric arteries and induced intracellular acidification by NH4+ prepulse technique. NBCn1 activity - defined as Na + -dependent, amiloride-insensitive net base uptake with CO 2 /HCO3- present - was inhibited equally when pH o decreased from 7.4 (22 mm HCO3-/5% CO 2 ) by metabolic (pH o 7.1/11 mm HCO3-: 22 ± 8%; pH o 6.8/5.5 mm HCO3-: 61 ± 7%) or respiratory (pH o 7.1/10% CO 2 : 35 ± 11%; pH o 6.8/20% CO 2 : 56 ± 7%) acidosis. Extracellular acidosis more prominently inhibited NHE1 activity - defined as Na + -dependent net acid extrusion without CO 2 /HCO3- present - at both pH o 7.1 (45 ± 9%) and 6.8 (85 ± 5%). Independently of pH o , lowering [Na + ] o from 140 to 70 mm reduced NBCn1 and NHE1 activity <20% whereas transport activities declined markedly (25-50%) when [Na + ] o was reduced to 35 mm. Steady-state pH i decreased more during respiratory (ΔpH i /ΔpH o  = 71 ± 4%) than metabolic (ΔpH i /ΔpH o  = 30 ± 7%) acidosis. Extracellular acidification inhibits NBCn1 and NHE1 activity in VSMCs. NBCn1 is equivalently inhibited when pCO 2 is raised or [HCO3-] o decreased. Lowering [Na + ] o inhibits NBCn1 and NHE1 markedly only below the typical physiological and pathophysiological range. We propose that inhibition of Na + -dependent net acid extrusion at low pH o protects against cellular Na + overload at the cost of intracellular acidification. © 2017 Scandinavian Physiological Society. Published by

Na+/H+ and Na+/NH4+ exchange activities of zebrafish NHE3b expressed in Xenopus oocytes

PubMed Central

Ito, Yusuke; Kato, Akira; Hirata, Taku; Hirose, Shigehisa

2014-01-01

Zebrafish Na+/H+ exchanger 3b (zNHE3b) is highly expressed in the apical membrane of ionocytes where Na+ is absorbed from ion-poor fresh water against a concentration gradient. Much in vivo data indicated that zNHE3b is involved in Na+ absorption but not leakage. However, zNHE3b-mediated Na+ absorption has not been thermodynamically explained, and zNHE3b activity has not been measured. To address this issue, we overexpressed zNHE3b in Xenopus oocytes and characterized its activity by electrophysiology. Exposure of zNHE3b oocytes to Na+-free media resulted in significant decrease in intracellular pH (pHi) and intracellular Na+ activity (aNai). aNai increased significantly when the cytoplasm was acidified by media containing CO2-HCO3− or butyrate. Activity of zNHE3b was inhibited by amiloride or 5-ethylisopropyl amiloride (EIPA). Although the activity was accompanied by a large hyperpolarization of ∼50 mV, voltage-clamp experiments showed that Na+/H+ exchange activity of zNHE3b is electroneutral. Exposure of zNHE3b oocytes to medium containing NH3/NH4+ resulted in significant decreases in pHi and aNai and significant increase in intracellular NH4+ activity, indicating that zNHE3b mediates the Na+/NH4+ exchange. In low-Na+ (0.5 mM) media, zNHE3b oocytes maintained aNai of 1.3 mM, and Na+-influx was observed when pHi was decreased by media containing CO2-HCO3− or butyrate. These results provide thermodynamic evidence that zNHE3b mediates Na+ absorption from ion-poor fresh water by its Na+/H+ and Na+/NH4+ exchange activities. PMID:24401990

Antigenicity of the 2015-2016 seasonal H1N1 human influenza virus HA and NA proteins.

PubMed

Clark, Amelia M; DeDiego, Marta L; Anderson, Christopher S; Wang, Jiong; Yang, Hongmei; Nogales, Aitor; Martinez-Sobrido, Luis; Zand, Martin S; Sangster, Mark Y; Topham, David J

2017-01-01

Antigenic drift of the hemagglutinin (HA) and neuraminidase (NA) influenza virus proteins contributes to reduced vaccine efficacy. To analyze antigenic drift in human seasonal H1N1 viruses derived from the 2009 pandemic H1N1 virus (pH1N1-like viruses) accounts for the limited effectiveness (around 40%) of vaccination against pH1N1-like viruses during the 2015-2016 season, nasal washes/swabs collected from adult subjects in the Rochester, NY area, were used to sequence and isolate the circulating viruses. The HA and NA proteins from viruses circulating during the 2015-2016 season encoded eighteen and fourteen amino acid differences, respectively, when compared to A/California/04/2009, a strain circulating at the origin of the 2009 pandemic. The circulating strains belonged to subclade 6B.1, defined by HA amino acid substitutions S101N, S179N, and I233T. Hemagglutination-inhibiting (HAI) and HA-specific neutralizing serum antibody (Ab) titers from around 50% of pH1N1-like virus-infected subjects and immune ferrets were 2-4 fold lower for the 2015-2016 circulating strains compared to the vaccine strain. In addition, using a luminex-based mPlex HA assay, the binding of human sera from subjects infected with pH1N1-like viruses to the HA proteins from circulating and vaccine strains was not identical, strongly suggesting antigenic differences in the HA protein. Additionally, NA inhibition (NAI) Ab titers in human sera from pH1N1-like virus-infected subjects increased after the infection and there were measurable antigenic differences between the NA protein of circulating strains and the vaccine strain using both ferret and human antisera. Despite having been vaccinated, infected subjects exhibited low HAI Ab titers against the vaccine and circulating strains. This suggests that poor responses to the H1N1 component of the vaccine as well as antigenic differences in the HA and NA proteins of currently circulating pH1N1-like viruses could be contributing to risk of

Na-Ion Intercalation and Charge Storage Mechanism in 2D Vanadium Carbide

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

Bak, Seong-Min; Qiao, Ruimin; Yang, Wanli

Two-dimensional vanadium carbide MXene containing surface functional groups (denoted as V2CTx, where Tx are surface functional groups) was synthesized and studied as anode material for Na-ion batteries. V2CTx anode exhibits reversible charge storage with good cycling stability and high rate capability through electrochemical test. The charge storage mechanism of V2CTx material during Na+ intercalation/deintercalation and the redox reaction of vanadium were studied using a combination of synchrotron based X-ray diffraction (XRD), hard X-ray absorption near edge spectroscopy (XANES) and soft X-ray absorption spectroscopy (sXAS). Experimental evidence of a major contribution of redox reaction of vanadium to the charge storage andmore » the reversible capacity of V2CTx during sodiation/desodiation process have been provided through V K-edge XANES and V L2,3-edge sXAS results. A correlation between the CO32- content and Na+ intercalation/deintercalation states in the V2CTx electrode observed from C and O K-edge in sXAS results imply that some additional charge storage reactions may take place between the Na+-intercalated V2CTx and the carbonate based non-aqueous electrolyte. The results of this study will provide valuable information for the further studies on V2CTx as anode material for Na-ion batteries and capacitors.« less

High pressure experimental studies on Na3Fe(PO4)(CO3) and Na3Mn(PO4)(CO3): Extensive pressure behaviors of carbonophosphates family

NASA Astrophysics Data System (ADS)

Gao, Jing; Huang, Weifeng; Wu, Xiang; Qin, Shan

2018-04-01

Carbon-bearing phases in the Earth's interior have profound implications for the long-term Earth carbon cycle. Here we investigate high-pressure behaviors of carbonophosphates bonshtedtite Na3Fe(PO4)(CO3) and sidorenkite Na3Mn(PO4)(CO3) in diamond anvil cells up to ∼12 GPa at room temperature. Modifications in in situ synchrotron X-ray diffraction patterns and Raman spectra confirm the structural stability of carbonophosphates within the pressure region. Fitting the third-order Birch-Murnaghan equation of state to the volume compression curve, the isothermal bulk modulus parameters are obtained to be K0 = 56(1) GPa, K0' = 3.3(1), V0 = 303.3(3) Å3 for Na3Fe(PO4)(CO3) and K0 = 54(1) GPa, K0' = 3.4(1), V0 = 313.4(2) Å3 for Na3Mn(PO4)(CO3). Crystallographic axes exhibit an elastic anisotropy with a more compressible c-axis relative to the ab-plane. An inverse linear correlation between the K0 value and the ionic radius of M2+ (M = Mg, Fe, Mn) is well determined for carbonophosphates. The pressure-dependence responsiveness of [PO4] and [CO3] in carbonophosphates show a negative relationship to the M2+ radius. We also discussed the effect of [PO4] group on the structural variations and high-pressure behaviors of carbonates. Furthermore, the geochemical properties of carbonophosphates hold implications to diamond genesis.

Salt Stress in Thellungiella halophila Activates Na+ Transport Mechanisms Required for Salinity Tolerance1

PubMed Central

Vera-Estrella, Rosario; Barkla, Bronwyn J.; García-Ramírez, Liliana; Pantoja, Omar

2005-01-01

Salinity is considered one of the major limiting factors for plant growth and agricultural productivity. We are using salt cress (Thellungiella halophila) to identify biochemical mechanisms that enable plants to grow in saline conditions. Under salt stress, the major site of Na+ accumulation occurred in old leaves, followed by young leaves and taproots, with the least accumulation occurring in lateral roots. Salt treatment increased both the H+ transport and hydrolytic activity of salt cress tonoplast (TP) and plasma membrane (PM) H+-ATPases from leaves and roots. TP Na+/H+ exchange was greatly stimulated by growth of the plants in NaCl, both in leaves and roots. Expression of the PM H+-ATPase isoform AHA3, the Na+ transporter HKT1, and the Na+/H+ exchanger SOS1 were examined in PMs isolated from control and salt-treated salt cress roots and leaves. An increased expression of SOS1, but no changes in levels of AHA3 and HKT1, was observed. NHX1 was only detected in PM fractions of roots, and a salt-induced increase in protein expression was observed. Analysis of the levels of expression of vacuolar H+-translocating ATPase subunits showed no major changes in protein expression of subunits VHA-A or VHA-B with salt treatment; however, VHA-E showed an increased expression in leaf tissue, but not in roots, when the plants were treated with NaCl. Salt cress plants were able to distribute and store Na+ by a very strict control of ion movement across both the TP and PM. PMID:16244148

Developmental pathway for potent V1V2-directed HIV-neutralizing antibodies

PubMed Central

Doria-Rose, Nicole A.; Schramm, Chaim A.; Gorman, Jason; Moore, Penny L.; Bhiman, Jinal N.; DeKosky, Brandon J.; Ernandes, Michael J.; Georgiev, Ivelin S.; Kim, Helen J.; Pancera, Marie; Staupe, Ryan P.; Altae-Tran, Han R.; Bailer, Robert T.; Crooks, Ema T.; Cupo, Albert; Druz, Aliaksandr; Garrett, Nigel J.; Hoi, Kam H.; Kong, Rui; Louder, Mark K.; Longo, Nancy S.; McKee, Krisha; Nonyane, Molati; O’Dell, Sijy; Roark, Ryan S.; Rudicell, Rebecca S.; Schmidt, Stephen D.; Sheward, Daniel J.; Soto, Cinque; Wibmer, Constantinos Kurt; Yang, Yongping; Zhang, Zhenhai; Mullikin, James C.; Binley, James M.; Sanders, Rogier W.; Wilson, Ian A.; Moore, John P.; Ward, Andrew B.; Georgiou, George; Williamson, Carolyn; Abdool Karim, Salim S.; Morris, Lynn; Kwong, Peter D.; Shapiro, Lawrence; Mascola, John R.

2015-01-01

Summary Antibodies capable of neutralizing HIV-1 often target variable regions 1 and 2 (V1V2) of the HIV-1 envelope, but the mechanism of their elicitation has been unclear. Here we define the developmental pathway by which such antibodies are generated and acquire the requisite molecular characteristics for neutralization. Twelve somatically related neutralizing antibodies (CAP256-VRC26.01-12) were isolated from CAPRISA-donor CAP256; each antibody contained the protruding tyrosine-sulfated, anionic antigen-binding loop (CDR H3) characteristic of this category of antibodies. Their unmutated ancestor emerged between weeks 30–38 post-infection with a 35-residue CDR H3, and neutralized the virus that superinfected this individual 15 weeks after initial infection. Improved neutralization breadth occurred by week 59 with modest affinity maturation, and was preceded by extensive diversification of the virus population. HIV-1 V1V2-directed neutralizing antibodies can thus develop relatively rapidly through initial selection of B cells with a long CDR H3, and limited subsequent somatic hypermutation, an important vaccine insight. PMID:24590074

Rare emergence of drug resistance in HIV-1 treatment-naïve patients receiving elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide for 144 weeks.

PubMed

Margot, Nicolas; Cox, Stephanie; Das, Moupali; McCallister, Scott; Miller, Michael D; Callebaut, Christian

2018-06-01

The single tablet regimen (STR) composed of elvitegravir (E), cobicistat (C), emtricitabine (F), and tenofovir alafenamide (TAF) (E/C/F/TAF) was compared to the STR composed of E, C, F, and tenofovir disoproxil fumarate (TDF) (E/C/F/TDF) in 2 phase 3 studies in 1733 HIV-1 infected treatment-naïve adults. Superior efficacy of E/C/F/TAF compared to E/C/F/TDF was demonstrated at Week 144 with 84% treatment success compared to 80%, respectively, along with significantly better outcomes of bone and renal safety. Analyze the emergence of HIV-1 resistance in treatment-naïve adults receiving E/C/F/TAF for 144 weeks. We conducted an integrated resistance analysis of the 2 Phase 3 studies, comprising pretreatment HIV-1 sequencing for all participants (N = 1733) and post-baseline HIV-1 resistance analysis for participants with virologic failure (HIV-1 RNA ≥400 copies/mL). Primary resistance-associated mutations (RAMs) were observed pre-treatment in 7.4% (NRTI-RAMs), 18.1% (NNRTI-RAMs), and 3.3% (PI-RAMs) of enrolled subjects. Baseline HIV-1 subtype or pre-existing RAMs did not affect E/C/F/TAF treatment response at week 144. Virologic failure resistance analyses were conducted for 28/866 (3.2%) and 30/867 (3.5%) patients in the E/C/F/TAF and E/C/F/TDF arms, respectively. Over the 3-year study, the rate of resistance emergence remained low at 1.4% in each group (12/866 in E/C/F/TAF; 12/867 in E/C/F/TDF). Resistant virus emerged in 24 patients who developed resistance to antiretrovirals in the regimens (E/C/F/TAF: M184V/I [1.3%], INSTI-RAMs [0.9%], K65R/N [0.2%]; E/C/F/TDF: M184V/I [1.0%], INSTI-RAMs [0.9%], K65R/N [0.5%]). Resistance emergence was rare (1.4%) with similar patterns of emergent mutations in both groups. M184V/I was the most prevalent RAM (1.2% overall). Copyright © 2018 Elsevier B.V. All rights reserved.

Spastin-Interacting Protein NA14/SSNA1 Functions in Cytokinesis and Axon Development

PubMed Central

Chang, Jaerak; Blackstone, Craig

2014-01-01

Hereditary spastic paraplegias (HSPs) are a genetically diverse group of inherited neurological disorders (SPG1-72) with the cardinal feature of prominent lower-extremity spasticity due to a length-dependent axonopathy of corticospinal motor neurons. The most frequent form of autosomal dominant HSP results from mutations of the SPG4 gene product spastin. This is an ATPase associated with diverse cellular activities (AAA) protein that binds to and severs microtubules. While spastin participates in crucial cellular processes such as cytokinesis, endosomal tubulation, and axon development, its role in HSP pathogenesis remains unclear. Spastin interacts in cells with the NA14 protein, a major target for auto-antibodies in Sjögren's syndrome (nuclear autoantigen 1; SSNA1). Our analysis of endogenous spastin and NA14 proteins in HeLa cells and rat cortical neurons in primary culture revealed a clear distribution of both proteins to centrosomes, with NA14 localizing specifically to centrioles. Stable NA14 knockdown in cell lines dramatically affected cell division, in particular cytokinesis. Furthermore, overexpression of NA14 in neurons significantly increased axon outgrowth and branching, while also enhancing neuronal differentiation. We postulate that NA14 may act as an adaptor protein regulating spastin localization to centrosomes, temporally and spatially regulating the microtubule-severing activity of spastin that is particularly critical during the cell cycle and neuronal development. PMID:25390646

Effect of Cooling Rate on SCC Susceptibility of β-Processed Ti-6Al-4V Alloy in 0.6M NaCl Solution

NASA Astrophysics Data System (ADS)

Ahn, Soojin; Park, Jiho; Jeong, Daeho; Sung, Hyokyung; Kwon, Yongnam; Kim, Sangshik

2018-03-01

The effects of cooling rate on the stress corrosion cracking (SCC) susceptibility of β-processed Ti-6Al-4V (Ti64) alloy, including BA/S specimen with furnace cooling and BQ/S specimen with water quenching, were investigated in 0.6M NaCl solution under various applied potentials using a slow strain rate test technique. It was found that the SCC susceptibility of β-processed Ti64 alloy in aqueous NaCl solution decreased with fast cooling rate, which was particularly substantial under an anodic applied potential. The micrographic and fractographic analyses suggested that the enhancement with fast cooling rate was related to the random orientation of acicular α platelets in BQ/S specimen. Based on the experimental results, the effect of cooling rate on the SCC behavior of β-processed Ti64 alloy in aqueous NaCl solution was discussed.

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

Phase diagram and neutron spin resonance of superconducting NaFe 1 - x Cu x As

DOE PAGES

Tan, Guotai; Song, Yu; Zhang, Rui; ...

2017-02-03

In this paper, we use transport and neutron scattering to study the electronic phase diagram and spin excitations of NaFe 1-xCu xAs single crystals. Similar to Co- and Ni-doped NaFeAs, a bulk superconducting phase appears near x≈2% with the suppression of stripe-type magnetic order in NaFeAs. Upon further increasing Cu concentration the system becomes insulating, culminating in an antiferromagnetically ordered insulating phase near x≈50%. Using transport measurements, we demonstrate that the resistivity in NaFe 1-xCu xAs exhibits non-Fermi-liquid behavior near x≈1.8%. Our inelastic neutron scattering experiments reveal a single neutron spin resonance mode exhibiting weak dispersion along c axis inmore » NaFe 0.98Cu 0.02As. The resonance is high in energy relative to the superconducting transition temperature T c but weak in intensity, likely resulting from impurity effects. These results are similar to other iron pnictides superconductors despite that the superconducting phase in NaFe 1-xCu xAs is continuously connected to an antiferromagnetically ordered insulating phase near x≈50% with significant electronic correlations. Finally, therefore, electron correlations is an important ingredient of superconductivity in NaFe 1-xCu xAs and other iron pnictides.« less

Rotationally inelastic collisions of He and Ar with NaK: Experiment and theory

NASA Astrophysics Data System (ADS)

Malenda, R. F.; Jones, J.; Faust, C.; Richter, K.; Wolfe, C. M.; Hickman, A. P.; Huennekens, J.; Talbi, D.; Gatti, F.

2012-06-01

We are investigating collisions of the ground (X^1&+circ;) and first excited (A^1&+circ;) electronic states of NaK using both experimental and theoretical methods. Potential surfaces for HeNaK (fixed NaK bond length) are used for coupled channel calculations of cross sections for rotational energy transfer and also for collisional transfer of orientation and alignment. Additional calculations use the MCTDH wavepacket method. The measurements of the A state collisions involve a pump--probe excitation scheme using polarization labeling and laser-induced fluorescence spectroscopy. The pump excites a particular ro-vibrational level (v,J) of the A state from the X state, and the probe laser is scanned over various transitions to the 3^1π state. In addition to strong direct transitions, weak satellite lines are observed that arise from collisionally-induced transitions from the (v,J) level to (v,J'=J+δJ). This method provides information about the cross sections for transfer of population and orientation for A state levels, and it can be adapted to transitions starting in the X state. For the A state we observe a strong δJ=even propensity for both He and Ar perturbers. Preliminary results for the X state do not show this propensity.

X-ray diffraction and infrared spectroscopy studies of Ba(Fe1/2Nb1/2)O3-(Na1/2Bi1/2)TiO3 ceramics

NASA Astrophysics Data System (ADS)

Chandra, K. P.; Yadav, Anjana; Prasad, K.

2018-05-01

Ceramics (1-x)Ba(Fe1/2Nb1/2)O3-x(Na1/2Bi1/2)TiO3; 0≤x≤1.0 were prepared by conventional ceramic synthesis technique. Rietveld refinements of X-ray diffraction data of these ceramics were carried out using FullProf software and determined their crystal symmetry, space group and unit cell dimensions. Rietveld refinement revealed that Ba(Fe1/2Nb1/2)O3 has cubic structure with space group Pm 3 ¯ m and Na1/2Bi1/2)TiO3 has rhombohedral structure with space group R3c. Addition of (Na1/2Bi1/2)TiO3 to Ba(Fe1/2Nb1/2)O3 resulted in the change of unit cell structure from cubic to tetragonal (P4/mmm) for x = 0.75 and the X-Ray diffraction peaks slightly shift towards higher Bragg's angle, suggesting slight decrease in unit cell volume. SEM studies were carried out in order to access the quality of the prepared ceramics which showed a change in grain shapes with the increase of (Na1/2Bi1/2)TiO3 content. FTIR spectra confirmed the formation of perovskite type solid solutions.

A fluorescent combinatorial logic gate with Na+, H+-enabled OR and H+-driven low-medium-high ternary logic functions.

PubMed

Spiteri, Jasmine M A; Mallia, Carl J; Scerri, Glenn J; Magri, David C

2017-12-06

A novel fluorescent molecular logic gate with a 'fluorophore-spacer 1 -receptor 1 -spacer 2 -receptor 2 ' format is demonstrated in 1 : 1 (v/v) methanol/water. The molecule consists of an anthracene fluorophore, and tertiary alkyl amine and N-(2-methoxyphenyl)aza-15-crown-5 ether receptors. In the presence of threshold concentrations of H + and Na + , the molecule switches 'on' as an AND logic gate with a fluorescence quantum yield of 0.21 with proton and sodium binding constants of log β H+ = 9.0 and log β Na+ = 3.2, respectively. At higher proton levels, protonation also occurs at the anilinic nitrogen atom ether with a log β H+ = 4.2, which allows for Na + , H + -enabled OR (OR + AND circuit) and H + -driven ternary logic functions. The reported molecule is compared and contrasted to classic anthracene-based Na + and H + logic gates. We propose that such logic-based molecules could be useful tools for probing the vicinity of Na + , H + antiporters in biological systems.

Removal of As(V) and Sb(V) in aqueous solution by Mg/Al-layered double hydroxide-incorporated polyethersulfone polymer beads (PES-LDH).

PubMed

Lee, Sang-Ho; Choi, Heechul; Kim, Kyoung-Woong

2018-03-13

To develop a novel granular adsorbent to remove arsenic and antimony from water, calcined Mg/Al-layered double-hydroxide (CLDH)-incorporated polyethersulfone (PES) granular adsorbents (PES-LDH) were prepared using a core-shell method having 25% PES in an N,N-dimethylformamide solution. The PES-LDH displayed a spherical hollow shape having a rough surface and the average particle size of 1-2 mm. On the PES-LDH surface, nanosized CLDH (100-150 nm) was successfully immobilized by consolidation between PES and CLDH. The adsorption of Sb(V) by PES-LDH was found to be more favorable than for As(V), with the maximum adsorption capacity of As(V) and Sb(V) being 7.44 and 22.8 mg/g, respectively. The regeneration results indicated that a 0.5 M NaOH and 5 M NaCl mixed solution achieved an 80% regeneration efficiency in As(V) adsorption and desorption. However, the regeneration efficiency of Sb(V) gradually decreased due to its strong binding affinity, even though the PES-LDH showed much higher Sb(V) adsorption efficiency than As(V). This study suggested that PES-LDH could be a promising granular adsorbent for the remediation of As(V) and Sb(V) contained in wastewater.

Structural and optical properties of Tb and Na-Tb co-doped Ca3V2O8 phosphors prepared by sol-gel process

NASA Astrophysics Data System (ADS)

Parab, Shambhu S.; Salker, A. V.

2018-01-01

A malic acid assisted sol-gel route was successfully employed to prepare two distinct series of green emitting Ca3V2O8 phosphors. In the first series, Tb was solely doped whereas in the second series Na and Tb were doped simultaneously in the Ca3V2O8 crystal lattice. X-ray diffraction studies proved the utility of adopted preparative method by confirming the monophasic formation of all compounds from both the series. Spectral analysis like Raman spectroscopy, UV-DRS were undertaken to analyse the local structure, crystallinity and absorptive characteristics. XPS validated the presence of desired oxidation states of all the elements present. Finally, photoluminescence studies were done to elucidate the scope of prepared compounds as green emitting phosphors and also to understand the effect of both doping schemes on the luminescence. Intense green emission was observed in both the cases. Tb concentration of 0.08 was found to be optimum in case of Tb singly doped compounds whereas Tb = 0.12 showed highest intensity among the Na-Tb co-doped samples. Moreover, a red shift in the excitation wavelength was observed after Na doping signifying a change in the local electronic environment which in turn has affected the luminescence pattern. Local crystallinity and vacancy concentrations were found to have a major say on the emission intensities.

The Na+/K+-ATPase and the amyloid-beta peptide aβ1-40 control the cellular distribution, abundance and activity of TRPC6 channels.

PubMed

Chauvet, Sylvain; Boonen, Marielle; Chevallet, Mireille; Jarvis, Louis; Abebe, Addis; Benharouga, Mohamed; Faller, Peter; Jadot, Michel; Bouron, Alexandre

2015-11-01

The Na(+)/K(+)-ATPase interacts with the non-selective cation channels TRPC6 but the functional consequences of this association are unknown. Experiments performed with HEK cells over-expressing TRPC6 channels showed that inhibiting the activity of the Na(+)/K(+)-ATPase with ouabain reduced the amount of TRPC6 proteins and depressed Ca(2+) entry through TRPC6. This effect, not mimicked by membrane depolarization with KCl, was abolished by sucrose and bafilomycin-A, and was partially sensitive to the intracellular Ca(2+) chelator BAPTA/AM. Biotinylation and subcellular fractionation experiments showed that ouabain caused a multifaceted redistribution of TRPC6 to the plasma membrane and to an endo/lysosomal compartment where they were degraded. The amyloid beta peptide Aβ(1-40), another inhibitor of the Na(+)/K(+)-ATPase, but not the shorter peptide Aβ1-16, reduced TRPC6 protein levels and depressed TRPC6-mediated responses. In cortical neurons from embryonic mice, ouabain, veratridine (an opener of voltage-gated Na(+) channel), and Aβ(1-40) reduced TRPC6-mediated Ca(2+) responses whereas Aβ(1-16) was ineffective. Furthermore, when Aβ(1-40) was co-added together with zinc acetate it could no longer control TRPC6 activity. Altogether, this work shows the existence of a functional coupling between the Na(+)/K(+)-ATPase and TRPC6. It also suggests that the abundance, distribution and activity of TRPC6 can be regulated by cardiotonic steroids like ouabain and the naturally occurring peptide Aβ(1-40) which underlines the pathophysiological significance of these processes. Copyright © 2015 Elsevier B.V. All rights reserved.

The effect of NaOH concentration on the steam-hydrothermally treated bioactive microarc oxidation coatings containing Ca, P, Si and Na on pure Ti surface.

PubMed

Zhou, Rui; Wei, Daqing; Cao, Jianyun; Feng, Wei; Cheng, Su; Du, Qing; Li, Baoqiang; Wang, Yaming; Jia, Dechang; Zhou, Yu

2015-04-01

The microarc oxidation (MAO) coating covered pure Ti plates are steam-hydrothermally treated in autoclaves containing NaOH solutions with different concentrations of 0, 0.001, 0.01, 0.1 and 1mol·L(-1). Due to the composition of Ti, O, Ca, P, Si and Na elements in the MAO coating, anatase and hydroxyapatite (HA) crystals are generated from the previously amorphous MAO coating after the steam-hydrothermal treatment. Meanwhile, it is noticed that the amount of HA crystals increases but showing a decline trend in aspect ratio in morphologies with the increasing of NaOH concentration. Interestingly, the steam-hydrothermally treated MAO coatings exhibit better bonding strength with Ti substrate (up to 43.8±1.1MPa) than that of the untreated one (20.1±3.1MPa). In addition, benefiting from the corrosive attack of the dissolved NaOH in water vapor on the MAO coating, Ti-OH is also formed on the steam-hydrothermally treated MAO coating surface, which can trigger apatite nucleation. Thus, the steam-hydrothermally treated MAO coatings exhibit good apatite-inducing ability. Copyright © 2015 Elsevier B.V. All rights reserved.

Rotationally inelastic collisions of excited NaK and NaCs molecules with noble gas and alkali atom perturbers.

PubMed

Jones, J; Richter, K; Price, T J; Ross, A J; Crozet, P; Faust, C; Malenda, R F; Carlus, S; Hickman, A P; Huennekens, J

2017-10-14

We report measurements of rate coefficients at T ≈ 600 K for rotationally inelastic collisions of NaK molecules in the 2(A) 1 Σ + electronic state with helium, argon, and potassium atom perturbers. Several initial rotational levels J between 14 and 44 were investigated. Collisions involving molecules in low-lying vibrational levels (v = 0, 1, and 2) of the 2(A) 1 Σ + state were studied using Fourier-transform spectroscopy. Collisions involving molecules in a higher vibrational level, v = 16, were studied using pump/probe, optical-optical double resonance spectroscopy. In addition, polarization spectroscopy measurements were carried out to study the transfer of orientation in these collisions. Many, but not all, of the measurements were carried out in the "single-collision regime" where more than one collision is unlikely to occur within the lifetime of the excited molecule. The analysis of the experimental data, which is described in detail, includes an estimate of effects of multiple collisions on the reported rate coefficients. The most significant result of these experiments is the observation of a strong propensity for ΔJ = even transitions in collisions involving either helium or argon atoms; the propensity is much stronger for helium than for argon. For the initial rotational levels studied experimentally, almost all initial orientation is preserved in collisions of NaK 2(A) 1 Σ + molecules with helium. Roughly between 1/3 and 2/3 of the orientation is preserved in collisions with argon, and almost all orientation is destroyed in collisions with potassium atoms. Complementary measurements on rotationally inelastic collisions of NaCs 2(A) 1 Σ + with argon do not show a ΔJ = even propensity. The experimental results are compared with new theoretical calculations of collisions of NaK 2(A) 1 Σ + with helium and argon. The calculations are in good agreement with the absolute magnitudes of the experimentally determined rate coefficients and accurately