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1

FASCODE for the environment (FASE)  

NASA Astrophysics Data System (ADS)

The Optical Physics Division of the Phillips Laboratory with support from the DoE Atmospheric Radiation Measurement (ARM) Program is developing a state-of-the-art line-by- line atmospheric radiative transfer model as the successor by FASCODE. The goal of this project is to create a computationally efficient model which contains the most up-to-date physics. The new model, known as FASCODE for the Environment, or `FASE', will combine the best features of FASCODE and LBLRTM, the DoE's standard radiative transfer model. FASE will also contain new features such as new cross-sections for heavy molecules, an improved solar irradiance model, and improvements to the Schumann-Runge bands and continuum. The code will be optimized for vectorized and/or parallel processing, put under configuration control for easy maintenance, and will be structured into separate modules for each function: atmospheric profiles, layer optical properties, radiative transfer, multiple- scattering, etc. This modular structure will allow for increased flexibility and easy customization of the code for specialized applications, such as a forward model for iterative inversion algorithms. Ease-of-use will be enhanced with improved input control structures and documentation to accommodate the needs of novice and advanced users. This paper addresses changes which have been made to FASCODE and LBLRTM to create FASE, and gives an overview of the modular structure and its capabilities.

Snell, Hilary E.; Moncet, Jean-Luc; Anderson, Gail P.; Chetwynd, James H.; Miller, S.; Wang, J. G.

1995-06-01

2

FASE — Future Astronomical Software Environment: How to Include Tools and Systems into the FASE Environment  

NASA Astrophysics Data System (ADS)

The new OPTICON Network 9.2 (FP7) is working on a concrete prototype of shared astronomical software environment for scalable and desktop systems (FASE). A prototype of packaging system has been defined that allows to include new tools and programs as well as major legacy systems (e.g. AIPS, CASA, IRAF/PyRAF, Starlink and ESO Common Pipeline Library) within FASE environment.

Granet, Y.; Paioro, L.; Surace, C.; Garilli, B.; Grosbøl, P.; Tody, D.; Fase Consortium

2011-07-01

3

ALTERAÇÕES DA FASE ORAL DA DEGLUTIÇÃO EM CRIANÇAS COM PARALISIA CEREBRAL Changes in the oral phase of swallowing in children with cerebral palsy  

Microsoft Academic Search

RESUMO Objetivos: Verificar as alterações na fase oral da deglutição em crianças com paralisia cerebral. Método: Foi conduzido um estudo quantitativo, observacional e transversal, desenvolvido no período de junho a agosto de 2006 no NAMI - Núcleo de Atenção Médica Integrada, em Fortaleza-CE. A amostra constituiu-se de 20 crianças na faixa etária de 1 ano e 6 meses a 8

Karise Santos Vasconcelos

2008-01-01

4

Detecção da fase impulsiva de uma explosão solar gigante até 405 GHz  

NASA Astrophysics Data System (ADS)

A explosão ocorrida no dia 25/08/2001 foi uma das mais intensas do presente ciclo solar em ondas de rádio de altas frequências. Foram medidas em ondas milimétricas e submilimétricas, aproximadamente, 105 e vários milhares de unidades de fluxo solar, respectivamente. Apresentamos um estudo deste evento em múltiplas frequências, desde microondas (1GHz), até ondas submilimétricas (405 GHz) detectadas pelo Telescópio Solar para ondas Submilimétricas (SST). Esta base de dados foi complementada utilizando-se o experimento Yohkoh, incluindo a emissão em raios-X duros e raios-g (até 100 MeV), e imagens em raios-X moles da região ativa envolvida. Enfocamos e discutimos principalmente os seguintes aspectos da fase impulsiva do evento: (i) as implicações deduzidas do espectro eletromagnético, obtido pela primeira vez até 405 GHz; (ii) a dinâmica da região ativa. Os resultados mostram que para explicar o espectro rádio observado, são necessários entre 3.5×1037 e 1.5×1039 elétrons acelerados acima de 20 keV em uma região de campo magnético entre 300 e 800 Gauss. A estimativa do fluxo de fótons que seria produzido por estes elétrons, mostra que grande parte deles não precipitou na baixa atmosfera. A evolução temporal da emissão em raios-X moles revela que a configuração magnética da região ativa foi muito dinâmica durante a fase impulsiva da explosão. Em particular, mostramos que a produção dos elétrons altamente energéticos foi iniciada junto com a aparição, na baixa coroa solar, de um novo sistema compacto de estruturas magnéticas. Este fato sugere que os locais de aceleração estão localizados na baixa atmosfera do Sol, como resultado da interação entre o novo sistema compacto e o campo magnético ambiente da região ativa.

Raulin, J.-P.; Makhmutov, V.; Kaufmann, P.; Pacini, A. A.; Luethi, T.; Hudson, H. S.; Gary, D. E.; Yoshimori, M.

2003-08-01

5

The FASES instrument development and experiment preparation for the ISS  

Microsoft Academic Search

The FASES experiments target the investigation of the stability of emulsions. The main objec-tives are the study of the surfactant adsorption at the liquid \\/ liquid interfaces, the interaction of the droplets as well as the behaviour of the liquid film between nearby drops. Particular focus is given to the dynamic droplet evolution during emulsion destabilisation. The results of the

Gerold Picker; Klaus Gollinger; Ralf Greger; Jan Dettmann; Josef Winter; Thierry Dewandre; Luigi Castiglione; Sebastien Vincent-Bonnieu; Libero Liggieri; Daniele Clausse; Mickael Antoni

2010-01-01

6

Utilidad de la vía subcutánea en la estrategia de atención al paciente con demencia en fase avanzada  

Microsoft Academic Search

In advanced dementia, the therapeutic goals should be patient comfort, adequate symptom control, and the prevention of suffering due to futile, intrusive or disproportionate procedures. To attain these goals, the subcutaneous route is a useful tool, since it allows fluid administration and the delivery of many drugs. Because it is well tolerated and easy to apply, this route can be

Rafael Hernández Palacios

2009-01-01

7

O efeito do achatamento nos pontos de equilíbrio e na dinâmica de sistemas coorbitais  

Microsoft Academic Search

Neste trabalho analisamos o efeito do achatamento do corpo principal nos pontos de equilíbrio lagrangianos e na configuração de órbitas girino-ferradura. Enfatizamos os sistemas coorbitais de satélites de Saturno, pois se encontram em relativa proximidade com o planeta, em que o efeito do achatamento se torna mais evidente. O estudo é dividido em três etapas independentes. Na primeira fase analisamos

D. C. Mourão; O. C. Winter; T. Yokoyama

2003-01-01

8

PARTICIPAÇÃO DO PAI NA GESTAÇÃO, PARTO E NASCIMENTO: UMA QUESTÃO DE CIDADANIA Regina Harumi Kitahara  

Microsoft Academic Search

RESUMO: A gestação, parto e nascimento são processos naturais que envolvem aspectos biológico, psicológicos e sociais. São fases de grandes transformações no corpo e na vida emocional da mulher, e o grau de adaptação a essas mudanças influencia no seu nível de ansiedade. Torna-se importante o acompanhamento pelos profissionais de saúde e de familiares durante estes acontecimentos tão singelos na

Simone Rossi

9

Doenças cerebrovasculares em pacientes entre 15 e 40 anos: achados neuropatológicos em 47 casos  

Microsoft Academic Search

RESUMO - As doenças cerebrovasculares em pacientes entre 15 e 40 anos são pouco estudadas na literatura latino americana, principalmente no que tange aos achados neuropatológicos. Analisamos 47 encéfalos provenientes de necrópsias completas realizadas no período de 1987 a 1997 selecionados com base na faixa etária e alteração neuropatológica básica envolvendo fenômenos vasculares. Destes 47 casos analisados, 26 eram (55,3%)

Everton M. Maggio; Mário R. Montemór-Netto; Emerson L. Gasparetto; Jorge S. Reis-Filho; Fábio A. Tironi; Luiz F. Bleggi Torres

2001-01-01

10

Demonstrating the Practical Advantages of the Scalable and Interoperable Astronomical Framework FASE: Applications to EUCLID Simulations and LUCIFER Data Reduction  

NASA Astrophysics Data System (ADS)

The European OPTICON Networks 3.6 and 9.2 in collaboration with the Virtual Observatory, during the last years have produced a detailed document, designing the requirements and the architecture of a future scalable and interoperable desktop framework for the astronomical software (FASE). A first reference implementation of the FASE framework has been developed at INAF-IASF Milano and applied to different projects we are involved in: a) the simulation software developed to study the performance of the EUCLID NISP instrument; b) the LBT LUCIFER instrument reduction pipeline used by the Italian community. An application involving graphical capabilities is also being developed exploiting FASE facilities. We show how the main architectural concepts of the FASE framework have been successfully applied to the software mentioned above, providing easy to use and install interoperable software, equipped with distributed and scalable capabilities. See also Grosbøl et al. (2012).

Paioro, L.; Garilli, B.; Franzetti, P.; Fumana, M.; Scodeggio, M.; Grosbøl, P.; Tody, D.; Surace, C.

2012-09-01

11

Evolução da morfologia de fases de blendas PA6\\/AES em extrusora de dupla rosca e moldagem por injeção  

Microsoft Academic Search

Resumo: A evolução da morfologia de fases em blendas não reativas e reativas de poliamida-6 com copolímero de acrilonitrila\\/EPDM\\/estireno (AES) em uma extrusora de rosca dupla co-rotacional foi investigada. A evolução da morfologia de fases ao longo da extrusora de rosca dupla foi monitorada através da coleta de pequenas amostras em válvulas no barril da extrusora e caracterização por microscopia

Adriane Bassani; Elias Hage Jr; Luiz A. Pessan; Ana V. Machado; José A. Covas

2005-01-01

12

Custos de alimentação para caprinos na fase de aleitamento recebendo sucedâneos com fontes de proteína láctea e de origem vegetal  

Microsoft Academic Search

5 Bolsista de Pós-doutorado da Fapemig, UFV, Viçosa - MG. Resumo: Leite em pó integral de vaca, reconstituído, e sucedâneo comercial à base de mistura de proteínas vegetais isoladas foram comparados para avaliar custo de produção no aleitamento artificial em caprinos. Os animais foram separados das mães logo após o nascimento recebendo colostro tratado nas primeiras 6 horas de vida.

Ana Gabriela Pombo; Márcia Maria Cândido da Silva

13

Seguridad del paciente en los estudios clínicos  

Cancer.gov

Información para pacientes, sus familiares y amigos, y el público en general, sobre cómo se protegen los derechos y la seguridad de las personas que participan en estudios clínicos. Conozca sobre el consentimiento formal, los consejos institucionales de revisión (IRB) y cómo se realiza la vigilancia continua de los estudios.

14

EFEITO DA CASCA DE CAFÉ (Coffea arabica, L.) NO DESEMPENHO DE NOVILHOS MESTIÇOS DE HOLANDÊS-ZEBU NA FASE DE RECRIA1  

Microsoft Academic Search

Twenty-five Holstein-zebu steers with mena weight of 250 kg, were used to evaluate rations with 0%, 10%, 20%, 30% and 40% of coffee hulls. There were no differences (P>0.05) for live weight gain, feed conversion, difference between receipt\\/cost and total dry matter and crude protein intake and neutral detergent fiber (NDF) of the roughage and total diet. NDT intake from

EDÉSIO RIBEIRO FILHO; PAULO CÉSAR DE AGUIAR PAIVA; ADAUTO FERREIRA BARCELOS; CARLOS ALBERTO; PEREIRA REZENDE; ROBERTO MACIEL CARDOSO; VERA LÚCIA BANYS

15

Gerenciamento de riscos na prática ortodôntica: como se proteger de eventuais problemas legais  

Microsoft Academic Search

Introdução: A relação profissional-paciente na área de Ortodontia e Ortopedia facial é bas- tante desgastante face à longa duração dos tratamentos e, por causa disso, muitas vezes essa relação pode se deteriorar trazendo prejuízos a ambas as partes. Objetivo: Este trabalho visa informar o leitor, em linguagem acessível, sobre os principais problemas jurídicos que podem envolver o ortodontista em sua

Ricardo Machado Cruz; Carla Pádua

2008-01-01

16

NaF Documentation  

Cancer.gov

The NaF documentation files are presented in Adobe Acrobat or Word files. PDF Generic Documentation for NaF PDF file Word Generic Documentation for NaFWord file Contact Paula M. Jacobs, Ph.D., 301-435-9181, jacobsp@mail.nih.gov, for information. Print

17

Familiares a cargo de pacientes de cáncer (PDQ®)  

Cancer.gov

Sumario informativo revisado por expertos acerca de los desafíos que enfrentan los familiares a cargo de los pacientes con cáncer. Este resumen se centra en las funciones típicas y las inquietudes de las personas a cargo del paciente y en las intervenciones útiles para esas personas.

18

Abordagem na Web para o Telemonitoramento do Eletrocardiograma de Pacientes Domésticos  

Microsoft Academic Search

This paper presents a Web based system that provides a friendly environment for heart monitoring of remote patients. The web application is able to receive the patient's electrocardiogram (ECG), storing them in a SQL database and generating events and alarms. Finally, through the web browser it is possible to access ECG records and patient's data. This work will further interact

Igor Feghali; Rodrigo V. Andreão; Marcelo V. Segatto

19

Influências nutricionais na psoríase  

Microsoft Academic Search

Resumo: A psoríase é uma doença inflamatória de pele, mediada por células T, hereditária, que sofre influência ambiental. Ingestão elevada de ômega-3, jejum, dietas hipocalóricas e vegetarianas mostram efeitos benéficos. Alguns pacientes que apresentam anticorpos antigliadina IgA\\/IgG, com sensibilidade ao glúten, melhoram após a retirada deste. O calcitriol é usado no tratamento tópico. Ingestão de álcool pode exacerbar a doença.

Maria Lúcia Diniz Araujo; Isis Suruagy; Correia Moura

2009-01-01

20

The conductivity of NaCl? NaOH and NaCl? Na 2 CO 3 crystals  

Microsoft Academic Search

Conductivity measurements were carried out on NaCl: NaOH and NaCl: Na2CO3. In both cases a decrease in conductivity with an increasing anion content and a conductivity minimum were found. In the case of NaCl: NaOH the conductivity of heavy doped crystals dropped even below the intrinsic conductivity value and conductivity hysteresis occurred.

A. Kessler; E. Mariani

1967-01-01

21

On efeito do achatamento nos pontos de equilíbrio e na dinâmica de sistemas coorbitais  

NASA Astrophysics Data System (ADS)

Neste trabalho analisamos o efeito do achatamento do corpo principal nos pontos de equilíbrio lagrangianos e na configuração de órbitas girino-ferradura. Enfatizamos os sistemas coorbitais de satélites de Saturno, pois se encontram em relativa proximidade com o planeta, em que o efeito do achatamento se torna mais evidente. O estudo é dividido em três etapas independentes. Na primeira fase analisamos as equações de movimento do problema restrito de três corpos considerando o efeito do achatamento, e através do balanceamento de forças buscamos a nova configuração dos pontos de equilíbrio lagrangianos. Concluímos, nesta etapa, que os pontos de equilíbrio estáveis apresentam um pequeno deslocamento definido pelo parâmetro de achatamento, não podendo ser mais representados por triângulos eqüiláteros. Aplicamos este resultado aos satélites coorbitais de Tetis e Dione, encontrando as posições de equilíbrio levemente deslocadas em relação ao caso sem achatamento. Na segunda fase visamos o sistema Saturno-Jano-Epimeteu, que por se tratar de um sistema de massas comparáveis, optamos por desenvolver as equações de Yoder et al (Icarus 53, pág 431-443, 1983), que permitem determinar os pontos de equilíbrio e a amplitude de oscilação angular das órbitas girino-ferradura para o problema não-restrito de três corpos, porém, no nosso estudo consideramos o efeito do achatamento do corpo principal nestas equações. Encontramos que a distância angular entre satélites, quando em posição de equilíbrio estável, diminui quanto maior for o parâmetro de achatamento do corpo principal. Além disso, a órbita de transição girino-ferradura possui largura angular menor em relação ao caso sem achatamento. Por fim, realizamos integrações numéricas para os casos reais de coorbitais de Saturno comparando com os resultados analíticos. Nestas integrações simulamos diversas órbitas girino-ferradura com diferentes parâmetros de achatamento, utilizando condições iniciais corrigidas para a presença do achatamento.

Mourão, D. C.; Winter, O. C.; Yokoyama, T.

2003-08-01

22

Na Cauda do Cometa  

Microsoft Academic Search

Quando viam um cometa, os antigos gregos imaginavam uma estrela com uma vasta cabeleira. Não à toa, a palavra deriva do termo koma, que significa cabelo. Constituídos por fragmentos de gelo e gases, os cometas possuem um núcleo sólido, que pode ter vários quilômetros de diâmetro, e uma cauda que sempre aponta na direção contrária ao Sol, devido aos ventos

M. R. Voelzke

2009-01-01

23

NA27 Trigger.  

National Technical Information Service (NTIS)

We have designed and implemented a minimum bias trigger together with a fiducial volume trigger for the experiment NA27, performed at the CERN SPS. A total of more than 3 million bubble chamber pictures have been taken with a triggered cross section small...

R. Bizzarri E. Di Capua S. Falciano M. Iori G. Marel

1985-01-01

24

S?NDROME DO X FRGIL Estudo caso-controle envolvendo pacientes prØ e pÛs-puberais com diagnÛstico confirmado por anÆlise molecular  

Microsoft Academic Search

RESUMO - A sÌndrome do X frÆgil Ø a causa mais comum de retardo mental herdado; entretanto, Ø subdiagnosticada na populaÁªo pediÆtrica. Objetivamos, neste estudo, determinar as caracterÌsticas clÌnicas prØ e pÛs-puberais mais significativas observadas entre indivÌduos que apresentam a mutaÁªo no gene FMR- 1, e que possam ser utilizadas como mØtodo de triagem dos pacientes que devem ser submetidos

Raquel Boy; Santana Correia; Juan Clinton Llerena; Maria do Carmo Machado-Ferreira

25

Electrogenic Na+ transport by Enterococcus hirae Na(+)-ATPase.  

PubMed

Energy-dependent generation of a membrane potential (delta psi) (-45 mV, interior negative) was observed in the F0F1, H(+)-ATPase-defective mutant of Enterococcus hirae. The generation of delta psi was found at high pH (but not at low pH), for which intracellular Na+ was required but not extracellular K+. The delta psi-generating activity was induced in cells cultured in media containing high concentrations of Na+, and was not observed in the Na(+)-ATPase mutants. These results suggest that E. hirae Na(+)-ATPase is responsible for the electrogenic sodium pump. PMID:7867809

Kakinuma, Y; Igarashi, K

1995-02-13

26

A study of 23Na  

Microsoft Academic Search

Levels extending up to 6.58 MeV excitation in 23Na have been studied using the 26Mg(p, alphagamma) and 23Na(alpha, alpha'gamma) reactions. The analysis of the particle-gamma angular-correlation data yielded information on the spin, branching and mixing ratio for transitions in 23Na. When combined with lifetime and direct reaction data, unique Jpi = 1\\/2- and 5\\/2- assignments were obtained for the 2.64

R. A. Lindgren; R. G. Hirko; J. G. Pronko; A. J. Howard; M. W. Sachs; D. A. Bromley

1972-01-01

27

Phase transitions in Na7-Na9 microclusters  

NASA Astrophysics Data System (ADS)

We present a wide range of properties of Na7-Na9 microclusters determined in the framework of our improved molecular-dynamics approach at fixed temperature. The Born-Oppenheimer dynamics was treated by means of an effective many-body potential, used previously for clusters, surface, and bulk properties. We have computed rotational, vibrational, and potential energies and corresponding specific heats, momenta of inertia, shapes parameters, and bond lengths of the Na microclusters over a wide range of temperatures, from 25 to 1500 K. We have determined that sodium microclusters undergo two ``phase transitions,'' one around 100 K from a crystal to a glassy or molten state, and a second one around 800 K, to a fluid state of the cluster. At low temperatures Na microclusters are essentially incompressible, but relatively easy to deform. At high temperatures Na clusters become extremely soft, and evaporation of atoms sets in.

Bulgac, Aurel; Kusnezov, Dimitri

1992-02-01

28

Quimioterapia de alta dosis prolonga en forma significativa la supervivencia en pacientes con leucemia mieloide aguda  

Cancer.gov

Los resultados preliminares de un estudio clínico grande con asignación al azar de pacientes de 16 a 60 años de edad con leucemia mieloide aguda (LMA), un cáncer de la sangre y de la médula ósea, que no había sido tratada anteriormente, muestran que los pacientes que recibieron una alta dosis de daunorrubicina, un fármaco de quimioterapia disponible comercialmente, durante la terapia inicial vivieron más que los pacientes que recibieron una dosis normal del mismo fármaco.

29

Solidification of NaCl-NaF eutectic in space  

NASA Technical Reports Server (NTRS)

Continuous and discontinuous NaF fibers, embedded in a NaCl matrix, have been produced in space and on earth, respectively. The production of continuous fibers in a eutectic mixture was attributed to the absence of convection current in the liquid during solidification in space. Image transmission and optical transmittance measurements of transverse sections of the space-grown and earth-grown ingots were made with a light microscope and a spectrometer. It was found that better optical properties were obtained from samples grown in space. This was attributed to a better alignment of NaF fibers along the ingot axis.

Yue, A. S.; Yu, J. G.

1974-01-01

30

Metodo Digital Para a Correcao Do Erro-de-Fase NA Geracao Discreta de Sinais Periodicos Em Tempo Real (Digital Method for Correction of the Phase Error in the Discrete Generation of Periodic Signals in Real Time).  

National Technical Information Service (NTIS)

The digital method presented, called the Method of the Differential Correction (MCD), permits the correction of the phase error in a periodic function to be continuously sampled. This is the case when the period of the function is not an integer multiple ...

E. W. Bergamini

1987-01-01

31

Radiotoxicidade e incorporacao de timidina-metil-tritiada em embrioes de camundongo na fase de pre-implantacao. Cultura e fertilizacao in vitro. (Radiotoxicity and incorporation of methyl-tritiated-thymidine on preimplantation mouse embryo. In vitro fertilization and culture).  

National Technical Information Service (NTIS)

In the present work different concentrations of methyl-(sup 3) H-thymidine was added to the culture medium micro drops containing the mouse zygotes at pro nuclear stage and the embryos were cultured in vitro at 37(sup 0) C in a humidified atmosphere with ...

O. K. Kikuchi H. Ohyama T. Yamada

1993-01-01

32

Optical properties of NaCl-NaF eutectics  

NASA Technical Reports Server (NTRS)

A new concept is advanced to explain the phenomenon of transmittance versus far-field infrared wavelength of the directionally solidified NaCl-NaF eutectic in terms of the two-dimensional Bragg Scattering and the polarization effect of Rayleigh scattering. This concept can be applied to other eutectic systems as long as the index of refraction of the matrix over a range of wavelength is known. Experimental data are in excellent agreement with the theoretical prediction.

Yue, A. S.; Yu, J. G.

1976-01-01

33

Condition of Si crystal formation by vaporizing Na from NaSi  

NASA Astrophysics Data System (ADS)

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.

Morito, Haruhiko; Karahashi, Taiki; Yamane, Hisanori

2012-09-01

34

Familiares a cargo de pacientes de cáncer: funciones y desafíos (PDQ®)  

Cancer.gov

Sumario informativo revisado por expertos acerca de los desafíos que enfrentan los familiares a cargo de los pacientes con cáncer. Este resumen se centra en las funciones típicas y las inquietudes de las personas a cargo del paciente y en las intervenciones útiles para esas personas.

35

Intracellular Na? and cardiac metabolism.  

PubMed

In heart failure, alterations of excitation-contraction underlie contractile dysfunction. One important defect is an elevation of the intracellular Na(+) concentration in cardiac myocytes ([Na(+)]i), which has an important impact on cytosolic and mitochondrial Ca(2+) homeostasis. While elevated [Na(+)]i is thought to compensate for decreased Ca(2+) load of the sarcoplasmic reticulum (SR), it yet negatively affects energy supply-and-demand matching and can even induce mitochondrial oxidative stress. Here, we review the mechanisms underlying these pathophysiological changes. The chain of events may constitute a vicious cycle of ion dysregulation, oxidative stress and energetic deficit, resembling characteristic cellular deficits that are considered key hallmarks of the failing heart. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes". PMID:23727097

Bay, Johannes; Kohlhaas, Michael; Maack, Christoph

2013-08-01

36

NA-NET numerical analysis net.  

National Technical Information Service (NTIS)

This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host ''na-net.orn...

J. Dongarra B. Rosener

1991-01-01

37

Bioquimioterapia ambulatoria con cisplatino, dacarbacina, interleucina-2 e interferón-alfa en pacientes con melanoma avanzado. Estudio multicéntrico en 44 pacientes  

Microsoft Academic Search

Resumen\\u000a Fundamento  Se ha descrito una importante actividad (50% de respuestas objetivas) con un pequeño número de supervivientes en los ensayos\\u000a clínicos de quimioinmunoterapia (QIT) para el melanoma diseminado. En la mayoría, la hospitalización era un requerimiento\\u000a habitual.\\u000a \\u000a \\u000a \\u000a Objetivos  Valorar la posibilidad de administración ambulatoria completa de la QIT dentro de un ensayo fase II multicéntrico con cisplatino+dacarbacina\\u000a (DTIC) en un día,

Elena Filipovich Vegas; José Ignacio Mayordomo Cámara; José Anadrés Meana García; Manuel Valladares Ayerbes; Jesús Florián Jericó; Juan José Bretón García; Remedios Blanco Guerrero; Dolores Isla Casado; Carmen Santander Lobera; Raquel Andrés Conejero; Bartolomeu Massuti Sureda; Alejandro Tres Sánchez

2003-01-01

38

22Na+ fluxes in thymic lymphocytes. I. Na+/Na+ and Na+/H+ exchange through an amiloride-insensitive pathway  

PubMed Central

The Na+ transport pathways of normal rat thymocytes were investigated. Na+ conductance was found to be lower than K+ conductance, which is consistent with reported values of membrane potential. In contrast, the isotopically measured Na+ permeability was greater than 10-fold higher than that of K+, which indicates that most of the flux is electroneutral. Cotransport with Cl- (or K+ and Cl-) and countertransport with Ca2+ were ruled out by ion substitution experiments and use of inhibitors. Countertransport for Na+ or H+ through the amiloride-sensitive antiport accounts for only 15-20% of the resting influx. In the presence of amiloride, 22Na+ uptake was increased in Na+-loaded cells, which suggests the existence of Na+/Na+ countertransport. Cytoplasmic pH determinations using fluorescent probes indicated that under certain conditions this amiloride-resistant system will also exchange Na+ for H+, as evidenced by an internal Na+- dependent acidification is proportional to internal [Na+] but inversely related to extracellular [Na+]. Moreover, 22Na+ uptake is inhibited by increasing external [H+]. The results support the existence of a substantial amiloride-insensitive, electroneutral cation exchange system capable of transporting Na+ and H+.

1984-01-01

39

The NA62 trigger system  

NASA Astrophysics Data System (ADS)

The main aim of the NA62 experiment (NA62 Technical Design Report, na62.web.cern.ch/NA62/Documents/TD_Full_doc_v1.pdf> [1]) is to study ultra-rare Kaon decays. In order to select rare events over the overwhelming background, central systems with high-performance, high bandwidth, flexibility and configurability are necessary, that minimize dead time while maximizing data collection reliability. The NA62 experiment consists of 12 sub-detector systems and several trigger and control systems, for a total channel count of less than 100,000. The GigaTracKer (GTK) has the largest number of channels (54,000), and the Liquid Krypton (LKr) calorimeter shares with it the largest raw data rate (19 GB/s).The NA62 trigger system works with 3 trigger levels. The first trigger level is based on a hardware central trigger unit, so-called L0 Trigger Processor (L0TP), and Local Trigger Units (LTU), which are all located in the experimental cavern. Other two trigger levels are based on software, and done with a computer farm located on surface. The L0TP receives information from triggering sub-detectors asynchronously via Ethernet; it processes the information, and then transmits a final trigger decision synchronously to each sub-detector through the Trigger and Timing Control (TTC) system. The interface between L0TP and the TTC system, which is used for trigger and clock distribution, is provided by the Local Trigger Unit board (LTU). The LTU can work in two modes: global and stand-alone. In the global mode, the LTU provides an interface between L0TP and TTC system. In the stand-alone mode, the LTU can fully emulate L0TP and so provides an independent way for each sub-detector for testing or calibration purposes. In addition to the emulation functionality, a further functionality is implemented that allows to synchronize the clock of the LTU with the L0TP and the TTC system. For testing and debugging purposes, a Snap Shot Memory (SSM) interface is implemented, that can work both in an input or an output mode. The trigger rates will be permanently monitored by reading counters at regular intervals.This paper describes the overall NA62 trigger system focusing on the setup for the dry and technical runs in 2012.

Krivda, M.; NA62 Collaboration

2013-08-01

40

Europlanet NA2 Science Networking  

NASA Astrophysics Data System (ADS)

Europlanet RI / NA2 Science Networking [1] focused on determining the major goals of current and future European planetary science, relating them to the Research Infrastructure that the Europlanet RI project [2] developed, and placing them in a more global context. NA2 also enhanced the ability of European planetary scientists to participate on the global scene with their own agenda-setting projects and ideas. The Networking Activity NA2 included five working groups, aimed at identifying key science issues and producing reference books on major science themes that will bridge the gap between the results of present and past missions and the scientific preparation of the future ones. Within the Europlanet RI project (2009-2012) the NA2 and NA2-WGs organized thematic workshops, an expert exchange program and training groups to improve the scientific impact of this Infrastructure. The principal tasks addressed by NA2 were: • Science activities in support to the optimal use of data from past and present space missions, involving the broad planetary science community beyond the "space club" • Science activities in support to the preparation of future planetary missions: Earth-based preparatory observations, laboratory studies, R&D on advanced instrumentation and exploration technologies for the future, theory and modeling etc. • Develop scientific activities, joint publications, dedicated meetings, tools and services, education activities, engaging the public and industries • Update science themes and addressing the two main scientific objectives • Prepare and support workshops of the International Space Science Institute (ISSI) in Bern and • Support Trans National Activities (TNAs), Joined Research Activities (JRAs) and the Integrated and Distributed Information Service (IDIS) of the Europlanet project These tasks were achieved by WG workshops organized by the NA2 working groups, by ISSI workshops and by an Expert Exchange Program. There were 17 official WG workshops and in addition there were numerous smaller NA2 WG meetings during the conferences (EPSC, EGU, etc.) and other events. The total number of NA2 meetings and workshops was 37. There were three NA2 supported ISSI workshops within the Europlanet project. The first ISSI workshop "Comparison of the plasma-spheres of Mars, Venus, and Titan" organized by K. Szego was held in December 2009. The second workshop "Quantifying the Martian Geochemical Reservoirs" by M. Toplis was held in April 2011. The third one, themed "Giant Planet Magnetodiscs and Aurorae" by N. Krupp, N. Achilleos and C. Arridge, was in November 2012. All three ISSI workshops were selected by the ISSI scientific committee to be organized within the frame of ISSI/Europlanet agreement and held in Bern. The main objective of the Expert Exchange Program was to support the activities of Europlanet RI with experts whenever needed. The programme provided funding for short visits (up to one week) of expert with the goal of improving infrastructure facilities and services offered to the scientific community by the Europlanet RI participant (contractor) laboratories or institutes. Between July 2009 and September 2012 26 applications were selected. Acknowledgement: Europlanet RI was funded by the European Commission under the 7th Framework Program, grant 228319 "Capacities Specific Programme" - Research Infrastructures Action. References: [1] http://www.europlanet-ri.eu/ [2] https://europlanet-scinet.fi/

Harri, Ari-Matti; Szego, Karoly; Genzer, Maria; Schmidt, Walter; Krupp, Norbert; Lammer, Helmut; Kallio, Esa; Haukka, Harri

2013-04-01

41

Melting of the Na layers in solid Na0.8CoO2.  

PubMed

Data of 23Na NMR spectra and relaxation measurements are interpreted as suggesting that, upon increasing temperature, the Na layers in Na0.8CoO2 adopt a 2D liquid state at T=291 K. The corresponding first order phase transition is preceded by a rapidly increasing mobility and diffusion of Na ions above 200 K. Above 291 K, the 23Na NMR response is similar to that previously observed in superionic conductors with planar Na layers. PMID:19257527

Weller, M; Sacchetti, A; Ott, H R; Mattenberger, K; Batlogg, B

2009-02-01

42

Deliquescence of NaCl-NaNO3 and KNO3-NaNO3 Salt Mixtures at 90C  

SciTech Connect

We conducted reversed deliquescence experiments in saturated NaCl-NaNO3-H2O and KNO{sub 3}-NaNO{sub 3}-H{sub 2}O systems at 90 C to determine relative humidity and solution composition. NaCl, NaNO{sub 3}, and KNO{sub 3} represent members of dust salt assemblages that are likely to deliquesce and form concentrated brines on high-level radioactive waste package surfaces in a repository environment at Yucca Mountain, NV, USA. Model predictions agree with experimental results for the NaCl-NaNO{sub 3}-H{sub 2}O system, but underestimate relative humidity by as much as 8% and solution composition by as much as 50% in the KNO{sub 3}-NaNO{sub 3}-H{sub 2}O system.

Carroll, S; Craig, L; Wolery, T

2003-12-29

43

Na3DyCl6  

PubMed Central

Single crystals of the title compound, tris­odium hexa­chloridodysprosate, Na3DyCl6, were obtained as a by-product of synthesis using dysprosium(III) chloride and sodium chloride among others. The monoclinic structure with its typical ? angle close to 90° [90.823 (4)°] is isotypic with the mineral cryolite (Na3AlF6) and the high-temperature structure of the Na3 MCl6 series, with M = Eu–Lu, Y and Sc. The isolated, almost perfect [DyCl6]3? octa­hedra are inter­connected via two crystallographically different Na+ cations: while one Na+ resides on centres of symmetry (as well as Dy3+) and also builds almost perfect, isolated [NaCl6]5? octa­hedra, the other Na+ is surrounded by seven chloride anions forming a distorted [NaCl7]6? trigonal prism with just one cap as close secondary contact.

Schurz, Christian M.; Meyer, Gerd; Schleid, Thomas

2011-01-01

44

The twins K+ and Na+ in plants.  

PubMed

In the earth's crust and in seawater, K(+) and Na(+) are by far the most available monovalent inorganic cations. Physico-chemically, K(+) and Na(+) are very similar, but K(+) is widely used by plants whereas Na(+) can easily reach toxic levels. Indeed, salinity is one of the major and growing threats to agricultural production. In this article, we outline the fundamental bases for the differences between Na(+) and K(+). We present the foundation of transporter selectivity and summarize findings on transporters of the HKT type, which are reported to transport Na(+) and/or Na(+) and K(+), and may play a central role in Na(+) utilization and detoxification in plants. Based on the structural differences in the hydration shells of K(+) and Na(+), and by comparison with sodium channels, we present an ad hoc mechanistic model that can account for ion permeation through HKTs. PMID:24810769

Benito, Begoña; Haro, Rosario; Amtmann, Anna; Cuin, Tracey Ann; Dreyer, Ingo

2014-05-15

45

The MoNA Project  

NASA Astrophysics Data System (ADS)

Many nuclear experiments involve the detection of neutrons after a reaction. This is especially true for radioactive nuclear beam experiments where the number of neutrons is often higher than in normal nuclear matter. Unlike charged particles, neutrons experience no Coulomb interaction, which makes their detection difficult. At the NSCL, this task has become even harder with the higher energies available from the coupled cyclotrons. The MoNA, or Modular Neutron Array, project is building a new neutron detector, which will achieve nearly 70% detection efficiency for neutron energies up to 250 MeV. The detector is comprised of 144 slats of scintillating plastic (200 x 10 x 10 cm) with photomultiplier tubes on each end to give position information of events. Hope College is one of nine undergraduate institutions involved in the MoNA collaboration. The construction process for Hope's sixteen neutron slats will be presented along with the results of testing showing that the slats give excellent position information. Light attenuation measurements generally exhibit the expected trends, but do not fit a standard exponential decay model precisely. A ray-tracing simulation of the slat geometry was created to investigate this behavior. Preliminary data from this program, reproducing some of the same unexpected results, will be shown.

Vanwylen, P. J.; Bychowski, J. P.; Deyoung, P. A.; Peaslee, G. F.

2002-10-01

46

The effect of Na vapor on the Na content of chondrules  

NASA Technical Reports Server (NTRS)

Chondrules contain higher concentrations of volatiles (Na) than expected for melt droplets in the solar nebula. Recent studies have proposed that chondrules may have formed under non-canonical nebular conditions such as in particle/gas-rich clumps. Such chondrule formation areas may have contained significant Na vapor. To test the hypothesis of whether a Na-rich vapor would minimize Na volatilization reaction rates in a chondrule analog and maintain the Na value of the melt, experiments were designed where a Na-rich vapor could be maintained around the sample. A starting material with a melting point lower that typical chondrules was required to keep the logistics of working with Na volatilization from NaCl within the realm of feasibility. The Knippa basalt, a MgO-rich alkali olivine basalt with a melting temperature of 1325 +/- 5 C and a Na2O content of 3.05 wt%, was used as the chondrule analog. Experiments were conducted in a 1 atm, gas-mixing furnace with the fO2 controlled by a CO/CO2 gas mixture and fixed at the I-W buffer curve. To determine the extent of Na loss from the sample, initial experiments were conducted at high temperatures (1300 C - 1350 C) for duration of up to 72 h without a Na-rich vapor present. Almost all (up to 98%) Na was volatilized in runs of 72 h. Subsequent trials were conducted at 1330 C for 16 h in the presence of a Na-rich vapor, supplied by a NaCl-filled crucible placed in the bottom of the furnace. Succeeding Knudsen cell weight-loss mass-spectrometry analysis of NaCl determined the P(sub Na) for these experimental conditions to be in the 10(exp -6) atm range. This value is considered high for nebula conditions but is still plausible for non-canonical environments. In these trials the Na2O content of the glass was maintained or in some cases increased; Na2O values ranged from 2.62% wt to 4.37% wt. The Na content of chondrules may be controlled by the Na vapor pressure in the chondrule formation region. Most heating events capable of producing chondrules are sufficient to volatile Na. Sodium volatilization reaction rates will be reduced to varying degrees from melt droplets, depending on the magnitude of the P(sub Na) generated. A combination of Na vapor during, and Na diffusion back into chondrules after, formation could maintain and/or enrich Na concentrations in chondrules.

Lewis, R. Dean; Lofgren, Gary E.; Franzen, Hugo F.; Windom, Kenneth E.

1993-01-01

47

Ion exchange equilibria between clinoptilolite and aqueous solutions of Na +\\/Cu 2+, Na +\\/Cd 2+ and Na +\\/Pb 2+  

Microsoft Academic Search

Binary ion exchange equilibrium has been studied by the batch technique using the clinoptilolite as cation exchanger. The equilibrium zeolite loading data were generated for Na+?Cu2+, Na+?Cd2+ and Na+?Pb2+ systems. Three different types of equations were used to predict experimental data: Freundlich, Langmuir and the thermodynamic equilibrium models. The last one was applied taking into account the following factors: (i)

Roman Petrus; Jolanta Warcho?

2003-01-01

48

Evaluation of Fc?RIIIB-NA1/NA2 Polymorphism in Visceral Leishmaniasis  

PubMed Central

Background: Several lines of evidence demonstrating that innate and adaptive immunity play important roles in the defense against visceral leishmaniasis (VL). A polymorphism within the Fc?RIIIB gene can lead to the expression of three variants of NA1, NA2, and the combined one (NA1/NA2) which alters affinity of IgG to its receptor. Objectives: The main aim of this study was to evaluate the Fc?RIIIB-NA1/NA2 polymorphism in the Fc?RIIIB gene of VL patients in comparison to healthy controls. Patients and Methods: In this cross-sectional study, three groups; 54 seropositive patients with clinical presentation of VL (group 1), 104 seropositive patients without clinical presentation (group 2), and 104 healthy controls (group 3) were evaluated with respect to the Fc?RIIIB-NA1/NA2 polymorphism using a PCR-SSP method. The titration of anti-leishmania antibodies was analyzed using an immunoflorescence technique. Results: Our results indicated that polymorphisms within the Fc?RIIIB gene (that lead to the expression of the NA1/NA2 isoforms) are significantly associated with VL. The results demonstrated that the genotype heterozygotic for Fc?RIIIB-NA1/NA2 expression was significantly increased in VL patients, group 1 when compared to groups 2 and 3. Conversely, there is a decrease in homozygous NA1 and NA2 genotypes in VL patients; however, the overall frequency of NA1 and NA2 alleles appear similar across the three cohorts examined. Conclusions: According to our results, it is likely that the increased frequency of the Fc?RIIIB-NA1/NA2 genotype is associated with impaired immune responses against VL and its subsequent clearance from the patient.

Abasi, Mohammad; Lotfi, Pegah; Bazmani, Ahad; Matini, Mohamad; Hajilooi, Mehrdad

2014-01-01

49

Growth of binary organic NLO crystals: m.NA-p.NA and m.NA-CNA system  

NASA Technical Reports Server (NTRS)

Experiments were carried out to grow 3.Nitroaniline (m.NA) crystals doped with 4.Nitroaniline (p.NA) and 2.chloro 4.Nitroaniline (CNA). The measured undercooling for m.NA, p.NA, and CNA were 0.21 tm K, 0.23 tm K, and 0.35 tm K respectively, where tm represents the melting temperature of the pure component. Because of the crystals' large heat of fusion and large undercooling, it was not possible to grow good quality crystals with low thermal gradients. In the conventional two-zone Bridgman furnace we had to raise the temperature of the hot zone above the decomposition temperature of CNA, p.NA, and m.NA to achieve the desired thermal gradient. To avoid decomposition, we used an unconventional Bridgman furnace. Two immiscible liquids, silicone oil and ethylene glycol, were used to build a special two-zone Bridgman furnace. A temperature gradient of 18 K/cm was achieved without exceeding the decomposition temperature of the crystal. The binary crystals, m.NA-p.NA and m.NA-CNA, were grown in centimeter size in this furnace. X-ray and optical characterization showed good optical quality.

Singh, N. B.; Henningsen, T.; Hopkins, R. H.; Mazelsky, R.

1993-01-01

50

Genetic Na + channelopathies and sinus node dysfunction  

Microsoft Academic Search

Voltage-gated Na+ channels are transmembrane proteins that produce the fast inward Na+ current responsible for the depolarization phase of the cardiac action potential. They play fundamental roles in the initiation, propagation, and maintenance of normal cardiac rhythm. Inherited mutations in SCN5A, the gene encoding the pore-forming ?-subunit of the cardiac-type Na+ channel, result in a spectrum of disease entities termed

Ming Lei; Christopher L.-H. Huang; Yanmin Zhang

2008-01-01

51

NA35 TPC track variance analysis  

SciTech Connect

We report here results of a variation analysis of NA35 TPC track data for sulfur-nucleus collisions at the CE SPS at 200 GeV/A. This analysis and comparison with simulations optimization of NA35 Data reduction methods and serves as a source information for ongoing TPC design and construction. The NA35 represent the major source of information on particle tracking limitation the high track density environment anticipated with lead and gold beam RHIC and the SPS.

Trainor, T.A.

1993-10-01

52

Maintaining the NA atmosphere of Mercury  

NASA Astrophysics Data System (ADS)

The possible sources of the Na atmosphere of Mercury are calculatively studied. The likely structure, composition, and temperature of the planet's upper crust is examined along with the probable flux of Na from depth by grain boundary diffusion and by Knudsen flow. The creation of fresh regolith is considered along with mechanisms for supplying Na from the surface to the exosphere. The implications of the calculations for the probable abundances in the regolith are discussed.

Killen, R. M.; Morgan, T. H.

1993-02-01

53

Sepsis correlated with increased erythrocyte Na+ content and Na+ - K+ pump activity.  

PubMed

The aims of the present study were twofold: (1) simultaneous determinations of Na(+) transport parameters of erythrocytes from 40 healthy donors and 28 septic patients as assessed by a score of severity of sepsis (SSS), and (2) examination of the correlation between the SSS and specific Na(+) transport abnormalities. Erythrocytes were obtained and loaded with different ionic compositions and cellular Na(+) contents before determination of the near-maximal Na(+) pump rate (Vmax), the physiological extrusion rate of Na(+) (v) and the number of ouabain-binding sites (Bmax). In erythrocytes from septic patients, the cellular Na(+) content was 28% higher (p < 0.001), with no differences in water content compared to erythrocytes from healthy donors. This elevated Na(+) content was accompanied by significantly higher values for Vmax (43%), v (24%) and Bmax (48%) of the Na(+) pump in septic erythrocytes. Moreover, significant positive correlations existed between Vmax and SSS (p = 0.028) and between cellular Na(+) content and SSS (p = 0.005). These data suggest that during sepsis, membrane alterations occur and result in an increased cellular Na(+) content. Active Na(+) transport (Vmax and v) was significantly stimulated, possibly as a consequence of a secondary response to the elevated Na(+) of cells. Both cellular Na(+) and Vmax correlated well with the severity of sepsis, suggesting that these altered transport parameters may reflect the progress of sepsis. PMID:12824698

Hsieh, Chien-Cheng; Hwang, Tsann-Long; Chen, Han-Ming; Chen, Miin-Fu; Sun, Yin-Fen; Lau, Ying-Tung

2003-01-01

54

Na+ channel expression and neuronal function in the Na+/H+ exchanger 1 null mutant mouse.  

PubMed

Mice lacking Na(+)/H(+) exchanger 1 (NHE1) suffer from recurrent seizures and die early postnatally. Although the mechanisms for seizures are not well established, our previous electrophysiological work has shown that neuronal excitability and Na(+) current density are increased in hippocampal CA1 neurons of these mutant mice. However, it is unknown whether this increased density is related to altered expression or functional regulation of Na(+) channels. In this work, we asked three questions: is the increased excitability limited to CA1 neurons, is the increased Na(+) current density related to an increased Na(+) channel expression, and, if so, which Na(+) channel subtype(s) is upregulated? Using neurophysiological, autoradiographic, and immunoblotting techniques, we showed that both CA1 and cortical neurons have an increase in membrane excitability and Na(+) current density; Na(+) channel density is selectively upregulated in the hippocampus and cortex (P < 0.05); and Na(+) channel subtype I is significantly increased in the hippocampus and Na(+) channel subtype II is increased in the cortex. Our results demonstrate that mice lacking NHE1 upregulate their Na(+) channel expression in the hippocampal and cortical regions selectively; this leads to an increase in Na(+) current density and membrane excitability. We speculate that neuronal overexcitability due to Na(+) channel upregulation in the hippocampus and cortex forms the basis of epileptic seizures in NHE1 mutant mice. PMID:12522174

Xia, Ying; Zhao, Peng; Xue, Jin; Gu, Xiang Q; Sun, Xiaolu; Yao, Hang; Haddad, Gabriel G

2003-01-01

55

Red blood cell Na+/H+ and Li+/Na+ exchange in patients with essential hypertension.  

PubMed

The increased red blood cell Li+/Na+ exchange found in a subgroup of patients with essential hypertension (EH) may reflect an increased activity of the Na+/H+ exchange. The maximal velocity of the red cells' Na+/H+ (Na+ influx promoted by an outward H+ gradient) and Li+/Na+ (Li+ efflux promoted by external Na+) exchange were therefore measured in 41 EH and in 21 normotensive controls (NT). Both transporters were significantly higher in EH than in NT (74 +/- 39 mmol/L cell x h v 43 +/- 27 for the former, P less than .03, and 0.35 +/- 0.16 v 0.26 +/- 0.10 for the latter, P less than .05). Even though more than 100 times faster, Na+/H+ exchange was weakly but significantly correlated to Li+/Na+ exchange (r = 0.29, P less than .05). Proximal tubule Na+ reabsorption (fractional renal Li+ reabsorption) was significantly greater in EH than in NT (0.78 +/- 0.07, n = 32, v 0.73 +/- 0.06, n = 10, P less than .05) but it was not correlated to either the red cells' Na+/H+ or Li+/Na+ exchanges. Therefore, hyperactivity of Na+/H+ exchange in EH may play a role in blood pressure elevation through mechanisms other than stimulation of renal Na+ reabsorption. PMID:2558690

Semplicini, A; Canessa, M; Mozzato, M G; Ceolotto, G; Marzola, M; Buzzaccarini, F; Casolino, P; Pessina, A C

1989-12-01

56

Na channel distribution in vertebrate skeletal muscle  

PubMed Central

The loose patch voltage clamp has been used to map Na current density along the length of snake and rat skeletal muscle fibers. Na currents have been recorded from (a) endplate membrane exposed by removal of the nerve terminal, (b) membrane near the endplate, (c) extrajunctional membrane far from both the endplate and the tendon, and (d) membrane near the tendon. Na current densities recorded directly on the endplate were extremely high, exceeding 400 mA/cm2 in some patches. The membrane adjacent to the endplate has a current density about fivefold lower than that of the endplate, but about fivefold higher than the membrane 100-200 micron from the endplate. Small local variations in Na current density are recorded in extrajunctional membrane. A sharp decrease in Na current density occurs over the last few hundred micrometers from the tendon. We tested the ability of tetrodotoxin to block Na current in regions close to and far from the endplate and found no evidence for toxin-resistant channels in either region. There was also no obvious difference in the kinetics of Na current in the two regions. On the basis of the Na current densities measured with the loose patch clamp, we conclude that Na channels are abundant in the endplate and near- endplate membrane and are sparse close to the tendon. The current density at the endplate is two to three orders of magnitude higher than at the tendon.

1986-01-01

57

NA-NET numerical analysis net  

SciTech Connect

This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host ``na-net.ornl.gov`` at Oak Ridge National Laboratory. Hence, members of the NA-NET do not need to remember complicated addresses or even where a member is currently located. As long as moving members change their e-mail address in the NA-NET everything works smoothly. The NA-NET system is currently located at Oak Ridge National Laboratory. It is running on the same machine that serves netlib. Netlib is a separate facility that distributes mathematical software via electronic mail. For more information on netlib consult, or send the one-line message ``send index`` to netlib{at}ornl.gov. The following report describes the current NA-NET system from both a user`s perspective and from an implementation perspective. Currently, there are over 2100 members in the NA-NET. An average of 110 mail messages pass through this facility daily.

Dongarra, J. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science]|[Oak Ridge National Lab., TN (United States); Rosener, B. [Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science

1991-12-01

58

NA-NET numerical analysis net  

SciTech Connect

This report describes a facility called NA-NET created to allow numerical analysts (na) an easy method of communicating with one another. The main advantage of the NA-NET is uniformity of addressing. All mail is addressed to the Internet host na-net.ornl.gov'' at Oak Ridge National Laboratory. Hence, members of the NA-NET do not need to remember complicated addresses or even where a member is currently located. As long as moving members change their e-mail address in the NA-NET everything works smoothly. The NA-NET system is currently located at Oak Ridge National Laboratory. It is running on the same machine that serves netlib. Netlib is a separate facility that distributes mathematical software via electronic mail. For more information on netlib consult, or send the one-line message send index'' to netlib{at}ornl.gov. The following report describes the current NA-NET system from both a user's perspective and from an implementation perspective. Currently, there are over 2100 members in the NA-NET. An average of 110 mail messages pass through this facility daily.

Dongarra, J. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science Oak Ridge National Lab., TN (United States)); Rosener, B. (Tennessee Univ., Knoxville, TN (United States). Dept. of Computer Science)

1991-12-01

59

Painful Na-channelopathies: an expanding universe.  

PubMed

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. PMID:23664154

Waxman, Stephen G

2013-07-01

60

Linfadenomegalia superficial (LAS): Correlato clínico patológico en 154 pacientes del Hospital Nacional Cayetano Heredia, Lima, Perú  

Microsoft Academic Search

Introducción: la linfadenomegalia superficial (LAS) son hallazgos clínicos frecuentes en la práctica médica que pueden ser las primeras manifestaciones de una enfermedad de trascendencia o de un síndrome clínico específico. Objetivo: realizar un correlato clínico-patológico en pacientes con LAS que acudieron por primera vez a la consulta médica sin un diagnóstico conocido. Materiales y Métodos: estudio prospectivo transversal en el

Fernando Osores Plenge; Raúl Gutiérrez Rodríguez; Oscar Guerra Amaya; Juan Cortez-Escalante; Juan C. Ferrufino Lach; Leandro Huayanay; Isaias Rodríguez; Betty Bustamante; Ciro Maguiña Vargas

2007-01-01

61

QuAlIdAde de VIdA e NÍVel de AtIVIdAde FÍSIcA de PAcIeNteS em FASe AmBulAtoRIAl dA ReABIlItAção cARdÍAcA  

Microsoft Academic Search

oRIgINAl físico (LAF): 100,0 (0,0 - 100,0); dor: 84,0 (10,0 - 100,0); estado geral de saúde: 74,5 (22,0 - 100,0); vitalidade: 80,0 (25,0 - 100,0); aspectos sociais: 87,5 (25,0 - 100,0); aspectos emocionais (AE): 100,0 (0,0 - 100,0) e saúde mental: 82,0 (40,0 - 100,0). Observou-se correlação entre tempo de RC e os domínios LAF (rs=0,46; p<0,01) e vitalidade (rs=0,35;

Educação Física

62

NaNO2-NaSO4 Combined Additive in Cold Concrete.  

National Technical Information Service (NTIS)

Experiments were conducted in which NaNO2, Na2SO4 and N(C2H4OH)3 were added to cold concrete to prevent freezing and promote strengthening. NaNO2 was added in an amount equal to 13.3% of the water content of the concrete, and Na2SO4 and N(C2H4OH)3 in amou...

1979-01-01

63

Ionization and Energy Pooling in Laser-Excited Na Vapor  

Microsoft Academic Search

We have observed ion formation (both Na+ and Na+2) and radiation from high-lying Na states when low-density vapor (~1013 cm-3) is irradiated with a cw dye laser tuned to one of the D lines. The Na+ ions probably result from photodissociation of Na+2 formed by Na(3p)-Na(3p) associative ionization, while the high-lying radiating states are formed in energy-pooling reactions.

G. H. Bearman; J. J. Leventhal

1978-01-01

64

Na+ imaging reveals little difference in action potential–evoked Na+ influx between axon and soma  

Microsoft Academic Search

In cortical pyramidal neurons, the axon initial segment (AIS) is pivotal in synaptic integration. It has been asserted that this is because there is a high density of Na+ channels in the AIS. However, we found that action potential–associated Na+ flux, as measured by high-speed fluorescence Na+ imaging, was about threefold larger in the rat AIS than in the soma.

Nechama Lasser-Ross; Michael J Gutnick; William N Ross; Ilya A Fleidervish

2010-01-01

65

Thermodynamics of ion exchange between clinoptilolite and aqueous solutions of na + \\/ k + and na + \\/ ca 2+  

Microsoft Academic Search

To provide a thermodynamic basis for understanding zeolite-water interactions in geologic systems, ion-exchange experiments were conducted at 25°C between clinoptilolite, which is the predominant zeolite mineral in altered pyroclastic and volcaniclastic rocks and aqueous mixtures of Na + \\/ K + and Na + \\/ Ca 2+ . Isotherm points were obtained by equilibrating Na-clinoptilolite, which was prepared from clinoptilolite-rich

Roberto T. Pabalan

1994-01-01

66

NaHCO3: A Source of Na Atoms for Sudden Sodium Layers.  

National Technical Information Service (NTIS)

We consider the case of sudden sodium layers which have been reported in the lower E region of the ionosphere. We suggest that dissociative electron attachment to NaHCO3, NaHCO3 + e - Na - HCO3-, can explain some of the observations, in particular at alti...

U. Von Zahn E. Murad

1990-01-01

67

Na(3)DyCl(6).  

PubMed

Single crystals of the title compound, tris-odium hexa-chloridodysprosate, Na(3)DyCl(6), were obtained as a by-product of synthesis using dysprosium(III) chloride and sodium chloride among others. The monoclinic structure with its typical ? angle close to 90° [90.823 (4)°] is isotypic with the mineral cryolite (Na(3)AlF(6)) and the high-temperature structure of the Na(3)MCl(6) series, with M = Eu-Lu, Y and Sc. The isolated, almost perfect [DyCl(6)](3-) octa-hedra are inter-connected via two crystallographically different Na(+) cations: while one Na(+) resides on centres of symmetry (as well as Dy(3+)) and also builds almost perfect, isolated [NaCl(6)](5-) octa-hedra, the other Na(+) is surrounded by seven chloride anions forming a distorted [NaCl(7)](6-) trigonal prism with just one cap as close secondary contact. PMID:21754259

Schurz, Christian M; Meyer, Gerd; Schleid, Thomas

2011-05-01

68

Negative electrodes for Na-ion batteries.  

PubMed

Research interest in Na-ion batteries has increased rapidly because of the environmental friendliness of sodium compared to lithium. Throughout this Perspective paper, we report and review recent scientific advances in the field of negative electrode materials used for Na-ion batteries. This paper sheds light on negative electrode materials for Na-ion batteries: carbonaceous materials, oxides/phosphates (as sodium insertion materials), sodium alloy/compounds and so on. These electrode materials have different reaction mechanisms for electrochemical sodiation/desodiation processes. Moreover, not only sodiation-active materials but also binders, current collectors, electrolytes and electrode/electrolyte interphase and its stabilization are essential for long cycle life Na-ion batteries. This paper also addresses the prospect of Na-ion batteries as low-cost and long-life batteries with relatively high-energy density as their potential competitive edge over the commercialized Li-ion batteries. PMID:24894102

Dahbi, Mouad; Yabuuchi, Naoaki; Kubota, Kei; Tokiwa, Kazuyasu; Komaba, Shinichi

2014-07-01

69

On the formation of transient (Na19)2 and (Na20)2 cluster dimers from molecular dynamics simulations  

Microsoft Academic Search

By using distance-dependent tight-binding molecular dynamics simulations, we discuss the possibilities to form (Na19)2 and (Na20)2 cluster dimers in sodium cluster-cluster collisions. In the case of Na19+Na19, we show that the formation of a prolate dimer-like (Na19)2 may depend on the initial relative orientations of the colliding clusters. A similar study for Na20+Na20 does not seen to show the same

F. S. Zhang; F. Spiegelmann; E. Suraud; V. Frayssé; R. Poteau; R. Glowinski; F. Chatelin

1994-01-01

70

Na-doped optical Germanium bulk crystals  

NASA Astrophysics Data System (ADS)

In an effort to develop a material for infrared (IR) optics with improved parameters, bulk crystals of optical germanium doped with Na have been first grown and studied. Single-crystalline and coarse-crystalline Ge:Na boules of different shapes and dimensions, up to 10 kg by weight, have been grown. Sodium was incorporated into the Ge crystal during the crystal growing from the melt. Despite the fact that Na contamination in the source material was not strictly controlled, the density of Na in the grown crystals determined by the neutron activation analysis as well as by the glow discharge mass spectrometry did not exceed 1015 cm-3. Just this value may be supposed to be close to the solubility limit of Na incorporated in Ge in the course of bulk crystal growth. A first demonstration of donor behavior of Na in bulk Ge crystals is made by means of a thermoelectric type of testing. An interstitial location of Na impurity has been verified by experiments on donor drift in the dc electric field. The crystals are grown with free electron density in the range from 5?1013 to 4?1014 cm-3 which is optimal for using Ge crystals as an optical material for fabricating passive elements of the IR technique. A comparison between the properties of Ge:Na crystals and Ge crystals doped with Sb, a conventional impurity in optical germanium, grown under the same technological conditions and from the same intrinsic Ge as a source material, revealed a number of advantages of Ge:Na crystals; among them, the higher transparency in the IR region, smaller radiation scattering and higher regular optical transmission, lower dislocation density, more uniform distribution of electrical and optical characteristics over the crystal volume, the identity of optical parameters in the single-crystalline, and coarse-crystalline boules. No degradation of optical elements fabricated from Ge:Na crystals was detected in the course of their commercial application, starting from 1998.

Pekar, G. S.; Singaevsky, A. F.

2012-09-01

71

Cytosolic Na+ Controls an Epithelial Na+ Channel Via the Go Guanine Nucleotide-Binding Regulatory Protein  

NASA Astrophysics Data System (ADS)

In tight Na+-absorbing epithelial cells, the rate of Na+ entry through amiloride-sensitive apical membrane Na+ channels is matched to basolateral Na+ extrusion so that cell Na+ concentration and volume remain steady. Control of this process by regulation of apical Na+ channels has been attributed to changes in cytosolic Ca2+ concentration or pH, secondary to changes in cytosolic Na+ concentration, although cytosolic Cl- seems also to be involved. Using mouse mandibular gland duct cells, we now demonstrate that increasing cytosolic Na+ concentration inhibits apical Na+ channels independent of changes in cytosolic Ca2+, pH, or Cl-, and the effect is blocked by GDP-? -S, pertussis toxin, and antibodies against the ? -subunits of guanine nucleotide-binding regulatory proteins (Go). In contrast, the inhibitory effect of cytosolic anions is blocked by antibodies to inhibitory guanine nucleotide-binding regulatory proteins (Gi1/Gi2. It thus appears that apical Na+ channels are regulated by Go and Gi proteins, the activities of which are controlled, respectively, by cytosolic Na+ and Cl-.

Komwatana, P.; Dinudom, A.; Young, J. A.; Cook, D. I.

1996-07-01

72

Na+ electrochemical gradient and Na+-Ca2+ exchange in rat proximal tubule  

SciTech Connect

The basolateral cell membrane of the rat proximal tubule contains a Na+-Ca2+ exchanger that may participate in the regulation of cytosolic calcium (Cai) and Ca2+ transport. In this work, the activity and orientation of the Na+-Ca2+ exchanger was studied in rat proximal tubules. The experiments were based on the thermodynamic notion that the exchanger is driven by the prevalence of either of two electrochemical gradients, that for Na+ (delta mu Na+) or for Ca2+ (delta mu Ca2+). Reductions in delta mu Na+, achieved by lowering extracellular Na+ (Nao) from 150 to 15 mM, increased Cai, decreased 45Ca efflux, and increased 45Ca influx. These changes occurred concurrently. When delta mu Na+ was reduced by increasing intracellular Na+ (Nai) with 10(-3) M oubain, Cai also increased. The effect of ouabain was probably dependent on Nai accumulation because the surge in Cai was prevented by exposure of the tubules to 5 mM Nao before ouabain exposure. On the other hand, when delta mu Na+ was lowered mM Nao and then by reducing Nao to 15 mM, Cai rose in two additive stages. We conclude from these data that in the rat proximal tubule the basal state of the Na+-Ca2+ exchanger is in forward mode, Nao-Cai. Moreover, the function of the Na+-Ca2+ exchanger is in accord with predictions derived from a thermodynamic analysis of its function.

Dominguez, J.H.; Rothrock, J.K.; Macias, W.L.; Price, J. (Veterans Administration Medical Center, Indianapolis, IN (USA))

1989-10-01

73

Na-site substitution effects on the thermoelectric properties of NaCo2O4  

NASA Astrophysics Data System (ADS)

The resistivity and thermopower of Na1+xCo2O4 and Na1.1-xCaxCo2O4 are measured and analyzed. In Na1+xCo2O4, whereas the resistivity increases with x, the thermopower is nearly independent of x. This suggests that the excess Na is unlikely to supply carriers, and decreases effective conduction paths in the sample. In Na1.1-xCaxCo2O4, the resistivity and the thermopower increase with x, and the Ca2+ substitution for Na+ reduces the majority carriers in NaCo2O4. This means that they are holes, which is consistent with the positive sign of the thermopower. Strong correlation in this compound is evidenced by the peculiar temperature dependence of the resistivity.

Kawata, T.; Iguchi, Y.; Itoh, T.; Takahata, K.; Terasaki, I.

1999-10-01

74

Anisotropic adsorption-induced Na + surface segregation in air-exposed Na ?-alumina  

NASA Astrophysics Data System (ADS)

X-ray photoelectron spectroscopy has been used to study the (0001) cleavage face and a perpendicular face of a Na ?-alumina single crystal exposed to ambient atmosphere. Quantitative analysis, which took into account the particular anisotropic structure of this solid and its expected effect on XPS relative line intensities, revealed Na-O rich ovelayers at the latter face. Detailed in-depth composition profiles showed that this Al-free region is several monolayers thick and that some Na-O enrichment extends deeper into the solid. The phenomena are attributed to interactions of the mobile Na + ions with H 2O molecules from the air causing Na + to segregate at this surface. The anisotropy of the effect is closely related to the two-dimensional fast ion transport in Na ?-alumina, and it has implications for the performance of Na/S electrochemical cells which use this solid as the electrolyte.

Grinbaum, Y.; Livshits, A.; Polak, M.

1986-03-01

75

Na and K Dependence of the Na/K Pump in Cystic Fibrosis Fibroblasts  

NASA Astrophysics Data System (ADS)

The Na and K dependence of the Na/K pump was measured in skin fibroblasts from patients with cystic fibrosis and age/sex-matched controls. Under basal conditions, there was no difference between control and cystic fibrosis cells in protein per cell, intracellular Na and K content, or Na/K pump activity (measured as ouabain-sensitive 86Rb uptake). There was no difference in the Na dependence of the Na/K pump between cystic fibrosis cells and control cells. In cells from patients with cystic fibrosis, the Na/K pump had a significantly lower affinity for K (Km = 1.6 mM) when compared to normals (Km = 0.9 mM). This difference was demonstrated by using two independent experimental designs.

Reznik, Vivian M.; Schneider, Jerry A.; Mendoza, Stanley A.

1981-11-01

76

NMR studies on Na+ transport in Synechococcus PCC 6311  

NASA Technical Reports Server (NTRS)

The freshwater cyanobacterium Synechococcus PCC 6311 is able to adapt to grow after sudden exposure to salt (NaCl) stress. We have investigated the mechanism of Na+ transport in these cells during adaptation to high salinity. Na+ influx under dark aerobic conditions occurred independently of delta pH or delta psi across the cytoplasmic membrane, ATPase activity, and respiratory electron transport. These findings are consistent with the existence of Na+/monovalent anion cotransport or simultaneous Na+/H+ +anion/OH- exchange. Na+ influx was dependent on Cl-, Br-, NO3-, or NO2-. No Na+ uptake occurred after addition of NaI, NaHCO3, or Na2SO4. Na+ extrusion was absolutely dependent on delta pH and on an ATPase activity and/or on respiratory electron transport. This indicates that Na+ extrusion via Na+/H+ exchange is driven by primary H+ pumps in the cytoplasmic membrane. Cells grown for 4 days in 0.5 m NaCl medium, "salt-grown cells," differ from control cells by a lower maximum velocity of Na+ influx and by lower steady-state ratios of [Na+]in/[Na+]out. These results indicate that cells grown in high-salt medium increase their capacity to extrude Na+. During salt adaptation Na+ extrusion driven by respiratory electron transport increased from about 15 to 50%.

Nitschmann, W. H.; Packer, L.

1992-01-01

77

Relationship between the Na+/H+ antiporter and Na+/substrate symport in Bacillus alcalophilus.  

PubMed Central

The Na+/H+ antiporter of the obligate alkalophile Bacillus alcalophilus facilitates growth at alkaline pH and precludes growth below pH 8.5. Thus, nonalkalophilic mutant strains do not exhibit Na+/H+ antiport activity and, interestingly, such strains concomitantly lose the ability to catalyze Na+-dependent accumulation of alpha-aminoisobutyrate [Krulwich, T. A., Mandel, D. G. Bornstein, R. F. & Guffanti, A. A. (1979) Biochem. Biophys. Res. Commun. 91, 58-62]. Several other Na+-dependent transport systems are now documented in vesicles from the wild-type strain, and it is demonstrated that these systems are defective in vesicles from the nonalkalophilic mutant KM23. Surprisingly, the defect seems to result not from the loss of Na+/H+ antiport activity per se but from a pleiotropic defect in the Na+/substrate symporters themselves. Monensin, an ionophore that catalyzes Na+/H+ exchange, does not restore respiration-driven Na+/substrate symport in KM23 vesicles. Moreover, with KM23 vesicles, efflux of alpha-aminoisobutyrate, L-malate, and L-aspartate down their respective concentration gradients is not stimulated by Na+, in contrast to the observations with wild-type vesicles. Because monensin should ameliorate a simple defect in Na+/H+ antiport activity and the antiporter should not be required for Na+/substrate symport down a concentration gradient, the results suggest that there may be a direct relationship between the antiporter and various Na+/substrate symporters. One possibility is that the systems share a Na+-translocating subunit.

Guffanti, A A; Cohn, D E; Kaback, H R; Krulwich, T A

1981-01-01

78

Catalysis of Na+ permeation in the bacterial sodium channel NaVAb  

PubMed Central

Determination of a high-resolution 3D structure of voltage-gated sodium channel NaVAb opens the way to elucidating the mechanism of ion conductance and selectivity. To examine permeation of Na+ through the selectivity filter of the channel, we performed large-scale molecular dynamics simulations of NaVAb in an explicit, hydrated lipid bilayer at 0 mV in 150 mM NaCl, for a total simulation time of 21.6 ?s. Although the cytoplasmic end of the pore is closed, reversible influx and efflux of Na+ through the selectivity filter occurred spontaneously during simulations, leading to equilibrium movement of Na+ between the extracellular medium and the central cavity of the channel. Analysis of Na+ dynamics reveals a knock-on mechanism of ion permeation characterized by alternating occupancy of the channel by 2 and 3 Na+ ions, with a computed rate of translocation of (6 ± 1) × 106 ions?s?1 that is consistent with expectations from electrophysiological studies. The binding of Na+ is intimately coupled to conformational isomerization of the four E177 side chains lining the extracellular end of the selectivity filter. The reciprocal coordination of variable numbers of Na+ ions and carboxylate groups leads to their condensation into ionic clusters of variable charge and spatial arrangement. Structural fluctuations of these ionic clusters result in a myriad of ion binding modes and foster a highly degenerate, liquid-like energy landscape propitious to Na+ diffusion. By stabilizing multiple ionic occupancy states while helping Na+ ions diffuse within the selectivity filter, the conformational flexibility of E177 side chains underpins the knock-on mechanism of Na+ permeation.

Chakrabarti, Nilmadhab; Ing, Christopher; Payandeh, Jian; Zheng, Ning; Catterall, William A.; Pomes, Regis

2013-01-01

79

El NCI inicia un estudio para evaluar la utilidad de la secuenciación genética para mejorar los resultados en los pacientes  

Cancer.gov

El Instituto Nacional del Cáncer (NCI) lanzará este mes un estudio clínico piloto denominado M-PACT con la finalidad de evaluar si el tratamiento asignado según mutaciones genéticas específicas puede brindar beneficios a pacientes con tumores sólidos metastásicos.

80

Properties of 23Na implanted targets  

NASA Astrophysics Data System (ADS)

Ten types of 23Na implanted targets have been fabricated for the purposes of investigating the effects of proton beam bombardment on the implanted sodium distribution. Targets were implanted at energies of ENa = 10-30 keV using copper, tantalum, and nickel as host materials. Thin layers (100-200 Å) of chromium and gold were also evaporated over some of the targets to provide a protective layer for the implanted sodium. The 23Na( p, ?) resonance at a lab proton energy of Ep = 309 keV was used to determine the implanted distribution. Successive resonance profile measurements are presented for each implanted target, and the concurrent loss of 23Na resulting from beam bombardment is reported. The calculated temperature rise of the targets indicates that beam heating has a negligible effect on the implanted sodium distribution, and that the principal mechanism for 23Na loss during beam bombardment is sputtering.

Brown, T. A. D.; Deryckx, K.; García, A.; Sallaska, A. L.; Snover, K. A.; Storm, D. W.; Wrede, C.

2009-10-01

81

NaY-supported molybdenum sulfide catalysts  

SciTech Connect

Molybdenum sulfide catalysts dispersed in NaY zeolites were prepared and chemically and structurally characterized. HDS activity of the sulfided catalysts was characterized. 38 refs., 5 figs., 2 tabs.

Welters, W.J.J.; Vorbeck, G.; Santen, R.A. van [Eindhoven Univ. of Technologies (Netherlands)] [and others] [Eindhoven Univ. of Technologies (Netherlands); and others

1996-07-01

82

Spontaneous proton transfer in Na zeolites  

NASA Astrophysics Data System (ADS)

First-principles room-temperature molecular dynamics (MD) simulations are conducted to investigate proton transfer (PT) in Na zeolites. The MD are performed on the unit cell containing two Al-sites, one of them saturated with H (acid site) and the second one with Na coordinated with three water molecules. The creation of the charged H 3O + cations is suppressed by the Na cation. Spontaneous barrierless PT between the O-sites in the zeolite, however, is possible. The lifetime of the hydronium cation is extremely short (?5 fs). The presence of Na + cations leads to a modified mechanism but does not suppress the proton transfer around the Al-site in zeolites.

Benco, L.; Demuth, T.; Hafner, J.; Hutschka, F.

2000-11-01

83

Hydrogen-fluorine exchange in NaBH4-NaBF4.  

PubMed

Hydrogen-fluorine exchange in the NaBH4-NaBF4 system is investigated using a range of experimental methods combined with DFT calculations and a possible mechanism for the reactions is proposed. Fluorine substitution is observed using in situ synchrotron radiation powder X-ray diffraction (SR-PXD) as a new Rock salt type compound with idealized composition NaBF2H2 in the temperature range T = 200 to 215 °C. Combined use of solid-state (19)F MAS NMR, FT-IR and DFT calculations supports the formation of a BF2H2(-) complex ion, reproducing the observation of a (19)F chemical shift at -144.2 ppm, which is different from that of NaBF4 at -159.2 ppm, along with the new absorption bands observed in the IR spectra. After further heating, the fluorine substituted compound becomes X-ray amorphous and decomposes to NaF at ~310 °C. This work shows that fluorine-substituted borohydrides tend to decompose to more stable compounds, e.g. NaF and BF3 or amorphous products such as closo-boranes, e.g. Na2B12H12. The NaBH4-NaBF4 composite decomposes at lower temperatures (300 °C) compared to NaBH4 (476 °C), as observed by thermogravimetric analysis. NaBH4-NaBF4 (1:0.5) preserves 30% of the hydrogen storage capacity after three hydrogen release and uptake cycles compared to 8% for NaBH4 as measured using Sievert's method under identical conditions, but more than 50% using prolonged hydrogen absorption time. The reversible hydrogen storage capacity tends to decrease possibly due to the formation of NaF and Na2B12H12. On the other hand, the additive sodium fluoride appears to facilitate hydrogen uptake, prevent foaming, phase segregation and loss of material from the sample container for samples of NaBH4-NaF. PMID:24071912

Rude, L H; Filsø, U; D'Anna, V; Spyratou, A; Richter, B; Hino, S; Zavorotynska, O; Baricco, M; Sørby, M H; Hauback, B C; Hagemann, H; Besenbacher, F; Skibsted, J; Jensen, T R

2013-11-01

84

Sodium sulfur technology program NaSTEC  

NASA Astrophysics Data System (ADS)

The NaSTEC program focuses on developing currently available sodium sulfur cells for use in space applications and investigating the operational parameters of the cells. The specific goals of the program are to determine the operational parameters and verify safety limits of Na/S technology battery cells; test long term zero-g operation; and create a life test database. The program approach and ground and flight test objectives are described in textual and graphic form.

Highley, Bob; Somerville, W. Andrew

85

Sodium sulfur technology program NaSTEC  

NASA Technical Reports Server (NTRS)

The NaSTEC program focuses on developing currently available sodium sulfur cells for use in space applications and investigating the operational parameters of the cells. The specific goals of the program are to determine the operational parameters and verify safety limits of Na/S technology battery cells; test long term zero-g operation; and create a life test database. The program approach and ground and flight test objectives are described in textual and graphic form.

Highley, Bob; Somerville, W. Andrew

1992-01-01

86

Sodium sulfur technology program NaSTEC  

Microsoft Academic Search

The NaSTEC program focuses on developing currently available sodium sulfur cells for use in space applications and investigating the operational parameters of the cells. The specific goals of the program are to determine the operational parameters and verify safety limits of Na\\/S technology battery cells; test long term zero-g operation; and create a life test database. The program approach and

Bob Highley; W. Andrew Somerville

1992-01-01

87

NaCd excimer emission bands  

Microsoft Academic Search

The analysis of the visible spectrum of a high pressure sodium lamp filled with sodium, cadium and xenon revealed the existence of NaCd excimer spectral features. These are four red satellite bands at 691, 697, 709 and 726.5 nm and diffuse bands peaking at 479.1 and 484.3 nm. Both spectral phenomena are related to those found earlier for the NaHg

G. Pichler; D. Veza; D. Fijan

1988-01-01

88

High-spin states in 23Na  

Microsoft Academic Search

The ¹²C(¹²C,p?)²³Na reaction has been used to study the ?-ray de-excitation of levels up to E? = 10.4 MeV in ²³Na. Branching ratios were obtained for the 5.54, 6.11, 6.24 and 6.35 MeV levels and the major modes of decay were observed for 7 levels above E? = 7 MeV. Doppler-shift attenuation measurements yielded mean lifetimes or lifetime limits for

Geoffrey George Frank; R. V. Elliott; R. H. Spear; J. A. Kuehner

1973-01-01

89

Homology of the human intestinal Na+/glucose and Escherichia coli Na+/proline cotransporters.  

PubMed Central

Cotransport proteins are responsible for the active accumulation of organic substrates in cells. Na+ gradients provide the driving force for uptake of most substrates into eukaryotes and for a few substrates in some prokaryotes. We report here the cloning and sequencing of the human intestinal Na+/glucose cotransporter (SGLT1) and compare its structure with other cloned transporters. At the DNA level and the predicted amino acid and secondary structure levels, close homology is evident between the human and rabbit intestinal Na+/glucose cotransporters, and a significant homology is found between these and the Escherichia coli Na+/proline cotransporter (putP). No homology is detectible with other known proteins. We infer from these results that the mammalian Na+/glucose and prokaryote Na+/proline cotransporters share a common ancestral gene. Images

Hediger, M A; Turk, E; Wright, E M

1989-01-01

90

Genetic Na+ channelopathies and sinus node dysfunction.  

PubMed

Voltage-gated Na+ channels are transmembrane proteins that produce the fast inward Na+ current responsible for the depolarization phase of the cardiac action potential. They play fundamental roles in the initiation, propagation, and maintenance of normal cardiac rhythm. Inherited mutations in SCN5A, the gene encoding the pore-forming alpha-subunit of the cardiac-type Na+ channel, result in a spectrum of disease entities termed Na+ channelopathies. These include multiple arrhythmic syndromes, such as the long QT syndrome type 3 (LQT3), Brugada syndrome (BrS), an inherited cardiac conduction defect (CCD), sudden infant death syndrome (SIDS) and sick sinus syndrome (SSS). To date, mutational analyses have revealed more than 200 distinct mutations in SCN5A, of which at least 20 mutations are associated with sinus node dysfunction including SSS. This review summarizes recent findings bearing upon: (i) the functional role of distinct voltage-gated Na+ currents in sino-atrial node pacemaker function; (ii) genetic Na+ channelopathy and its relationship to sinus node dysfunction. PMID:19027778

Lei, Ming; Huang, Christopher L-H; Zhang, Yanmin

2008-01-01

91

Modeling Na clusters in Ar matrices  

NASA Astrophysics Data System (ADS)

We present a microscopic model for Na clusters embedded in raregas matrices. The valence electrons of the Na cluster are described by time-dependent density-functional theory at the level of the local-density approximation (LDA). Particular attention is paid to the semi-classical picture in terms of Vlasov-LDA. The Na+ ions and Ar atoms are handled as classical particles whereby the Ar atoms carry two degrees of freedom, position and dipole polarization. The interaction between Na+ ions and electrons is mediated through local pseudo-potentials. The coupling to the Ar atoms is described by (long-range) polarization potentials and (short-range) repulsive cores. The ingredients are taken from elsewhere developed standards. A final fine-tuning is performed using the NaAr molecule as benchmark. The model is then applied to embedded systems Na8ArN. By close comparison with quantum-mechanical results, we explore the capability of the Vlasov-LDA to describe such embedded clusters. We show that one can obtain a reasonable description by appropriate adjustments in the fine-tuning phase of the model.

Fehrer, F.; Mundt, M.; Reinhard, P.-G.; Suraud, E.

2005-07-01

92

Fabrication of CIGS solar cells with a Na-doped Molayer on a Na-free substrate  

Microsoft Academic Search

The photovoltaic properties of CIGS cells on an alumina substrate were improved through the use of Na-doped Mo as the bottom layer of a Mo back contact. Na was supplied to the CIGS bulk region from an alumina\\/Na-doped Mo\\/Mo structure, similar to the Na diffusion from soda-lime glass. The diffusion of Na from the Na-doped Mo was controlled effectively compared

Jae Ho Yun; Ki Hwan Kim; Min Sik Kim; Byung Tae Ahn; Se Jin Ahn; Jeong Chul Lee; Kyung Hoon Yoon

2007-01-01

93

Determination of Na 2O from sodium aluminate NaAlO 2  

Microsoft Academic Search

The aim of the work was to find a suitable method and conditions for determining Na2O wt.% from NaAlO2. Problems were encountered while titrating NaAlO2 with hydrochloric acid. The problematic area was the pH range 4–10 where aluminum precipitates as hydroxides. The different species of the aluminate solution were determined using potentiometric and complexometric titrations. The equivalent point of the

Teemu Näykki; Anttila Raimo; Perämäki Paavo; Kurikka Antero; Nikula Päivi

2000-01-01

94

On the formation of transient (Na 19) 2 and (Na 20) 2 cluster dimers from molecular dynamics simulations  

NASA Astrophysics Data System (ADS)

By using distance-dependent tight-binding molecular dynamics simulations, we discuss the possibilities to form (Na 19) 2 and (Na 20) 2 cluster dimers in sodium cluster-cluster collisions. In the case of Na 19+Na 19, we show that the formation of a prolate dimer-like (Na 19) 2 may depend on the initial relative orientations of the colliding clusters. A similar study for Na 20+Na 20 does not seen to show the same dependence on the initial orientations in the formation of the (Na 20) 2 cluster dimer.

Zhang, F. S.; Spiegelmann, F.; Suraud, E.; Frayssé, V.; Poteau, R.; Glowinski, R.; Chatelin, F.

1994-09-01

95

Absolute quantification of Na+ bound fraction by double-quantum filtered 23Na NMR spectroscopy.  

PubMed

A method is described for the absolute quantification of double-quantum filtered spectra of spin-3/2 nuclei ((23)Na). The method was tested on a model system, a cationic exchange resin for which the number of Na(+) binding sites was quantitatively controlled. The theoretical and experimental approaches were validated on samples with different Na(+) concentrations. An excellent agreement between the results obtained by double-quantum and single-quantum acquisitions was found. This method paves the way for absolute quantification of both bound and free fractions of Na(+), which are determining factors in the characterization of salted/brined/dried food products. PMID:17897852

Mouaddab, Mohamed; Foucat, Loïc; Donnat, Jean Pierre; Renou, Jean Pierre; Bonny, Jean Marie

2007-11-01

96

Influence of sodium halides (NaF, NaCl, NaBr, NaI) on the photocatalytic performance of hydrothermally synthesized hematite photoanodes.  

PubMed

It has been suggested that a high concentration of Fe(3+) in solution, a low pH, and noncomplexing ions of high ionic strength are all essential for developing a high-quality hematite array. Our curiosity was piqued regarding the role of the electrolyte ions in the hydrothermal synthesis of hematite photoanodes. In this study, we prepared hematite photoanodes hydrothermally from precursor solutions of 0.1 M FeCl3 at pH 1.55 with a background electrolyte of 1.0 M sodium halide (NaF, NaCl, NaBr, or NaI). We compared the structures and properties of the as-obtained hematite photoanodes with those of the material prepared in 1.0 M NaNO3, the most widely adopted electrolyte in previous studies. Among our studied systems, we found that the hematite photoanode prepared in NaCl solution was the only one possessing properties similar to those of the sample obtained from the NaNO3 solution-most importantly in terms of photoelectrochemical performance (ca. 0.2 mA/cm(2) with +0.4 V vs SCE). The hematites obtained from the NaF, NaBr, and NaI solutions exhibited much lower (by approximately 2 orders of magnitude) photocurrent densities under the same conditions, possibly because of their relatively less ordered crystallinity and the absence of rodlike morphologies. Because the synthetic protocol was identical in each case, we believe that these two distinct features reflect the environments in which these hematite photoanodes were formed. Consistent with the latest studies reported in the literature of the X-ray photoelectron spectra of fast-frozen hematite colloids in aqueous solutions, it appears that the degree of surface ion loading at the electrolyte-hematite interface (Stern layer) is critical during the development of hematite photoanodes. We suspect that a lower ion surface loading benefits the hematite developing relatively higher-order and a rodlike texture, thereby improving the photoelectrochemical activity. PMID:23865744

Wang, Tsinghai; Huang, Mao-Chia; Hsieh, Yi-Kong; Chang, Wen-Sheng; Lin, Jing-Chie; Lee, Chih-Hao; Wang, Chu-Fang

2013-08-28

97

HCO3(-)-coupled Na+ influx is a major determinant of Na+ turnover and Na+/K+ pump activity in rat hepatocytes  

SciTech Connect

Recent studies in hepatocytes indicate that Na(+)-coupled HCO3- transport contributes importantly to regulation of intracellular pH and membrane HCO3- transport. However, the direction of net coupled Na+ and HCO3- movement and the effect of HCO3- on Na+ turnover and Na+/K+ pump activity are not known. In these studies, the effect of HCO3- on Na+ influx and turnover were measured in primary rat hepatocyte cultures with 22Na+, and (Na+)i was measured in single hepatocytes using the Na(+)-sensitive fluorochrome SBFI. Na+/K+ pump activity was measured in intact perfused rat liver and hepatocyte monolayers as Na(+)-dependent or ouabain-suppressible 86Rb uptake, and was measured in single hepatocytes as the effect of transient pump inhibition by removal of extracellular K+ on membrane potential difference (PD) and (Na+)i. In hepatocyte monolayers, HCO3- increased 22Na+ entry and turnover rates by 50-65%, without measurably altering 22Na+ pool size or cell volume, and HCO3- also increased Na+/K+ pump activity by 70%. In single cells, exposure to HCO3- produced an abrupt and sustained rise in (Na+)i from approximately 8 to 12 mM. Na+/K+ pump activity assessed in single cells by PD excursions during transient K+ removal increased congruent to 2.5-fold in the presence of HCO3-, and the rise in (Na+)i produced by inhibition of the Na+/K+ pump was similarly increased congruent to 2.5-fold in the presence of HCO3-. In intact perfused rat liver, HCO3- increased both Na+/K+ pump activity and O2 consumption. These findings indicate that, in hepatocytes, net coupled Na+ and HCO3- movement is inward and represents a major determinant of Na+ influx and Na+/K+ pump activity. About half of hepatic Na+/K+ pump activity appears dedicated to recycling Na+ entering in conjunction with HCO3- to maintain (Na+)i within the physiologic range.

Fitz, J.G.; Lidofsky, S.D.; Weisiger, R.A.; Xie, M.H.; Cochran, M.; Grotmol, T.; Scharschmidt, B.F. (University of California, San Francisco (USA))

1991-05-01

98

FXYD Proteins Stabilize Na,K-ATPase  

PubMed Central

FXYD proteins are a family of seven small regulatory proteins, expressed in a tissue-specific manner, that associate with Na,K-ATPase as subsidiary subunits and modulate kinetic properties. This study describes an additional property of FXYD proteins as stabilizers of Na,K-ATPase. FXYD1 (phospholemman), FXYD2 (? subunit), and FXYD4 (CHIF) have been expressed in Escherichia coli and purified. These FXYD proteins associate spontaneously in vitro with detergent-soluble purified recombinant human Na,K-ATPase (?1?1) to form ?1?1FXYD complexes. Compared with the control (?1?1), all three FXYD proteins strongly protect Na,K-ATPase activity against inactivation by heating or excess detergent (C12E8), with effectiveness FXYD1 > FXYD2 ? FXYD4. Heating also inactivates E1 ? E2 conformational changes and cation occlusion, and FXYD1 protects strongly. Incubation of ?1?1 or ?1?1FXYD complexes with guanidinium chloride (up to 6 m) causes protein unfolding, detected by changes in protein fluorescence, but FXYD proteins do not protect. Thus, general protein denaturation is not the cause of thermally mediated or detergent-mediated inactivation. By contrast, the experiments show that displacement of specifically bound phosphatidylserine is the primary cause of thermally mediated or detergent-mediated inactivation, and FXYD proteins stabilize phosphatidylserine-Na,K-ATPase interactions. Phosphatidylserine probably binds near trans-membrane segments M9 of the ? subunit and the FXYD protein, which are in proximity. FXYD1, FXYD2, and FXYD4 co-expressed in HeLa cells with rat ?1 protect strongly against thermal inactivation. Stabilization of Na,K-ATPase by three FXYD proteins in a mammalian cell membrane, as well the purified recombinant Na,K-ATPase, suggests that stabilization is a general property of FXYD proteins, consistent with a significant biological function.

Mishra, Neeraj Kumar; Peleg, Yoav; Cirri, Erica; Belogus, Talya; Lifshitz, Yael; Voelker, Dennis R.; Apell, Hans-Juergen; Garty, Haim; Karlish, Steven J. D.

2011-01-01

99

Hiperpotassemia na Vigência de Espironolactona em Pacientes com insuficiência Cardíaca descompensada Hyperkalemia During spironolactone Use in Patients with Decompensated Heart Failure  

Microsoft Academic Search

Summary Background: The incidence of hyperkalemia related to spironolactone use is low in stable heart failure; however, it has not been studied during decompensation. Objective: To evaluate the influence of spironolactone on serum potassium in decompensated heart failure (HF). Methods: In a cohort study, patients that had been hospitalized due to decompensated HF, with left ventricular ejection fraction (LVEF) <

Marcelo Villaça Lima; Marcelo Eidi Ochiai; Juliano Novaes Cardoso; Paulo César Morgado; Robinson Tadeu Munhoz; Antonio Carlos; Pereira Barretto

2008-01-01

100

Na clusters on metal supported Ar layers  

NASA Astrophysics Data System (ADS)

We investigate from a theoretical perspective structure and dynamics of Na clusters on a surface built from Ar layers grown on a metal support. The system is modeled by a hierarchical quantum-mechanical/molecular-mechanical (QM/MM) approach treating the cluster electrons with time-dependent density-functional theory, the Ar atoms classically, and the metal support as a continuous dielectric medium. Caution has been taken to describe properly the dynamical polarizability of the Ar substrate. We study the effect of the Ar substrate and particularly of the metal support on the cluster structure and dynamics. The binding of Na6 and Na8 to the Ar surface is found to by very weak and the effect of the dielectric response of the metal (DRM) turns out to be negligible. The global properties of the optical response of the Na clusters are slightly changed by the Ar substrate and the DRM while the detailed spectral fragmentation depends sensitively on any change of the environment. The deposition dynamics of small Na clusters is crucially influenced by the mechanical hardness of the metal support while the DRM makes little effect. We also study the dependence on the number of Ar layers. For the first few layers (from two to four), the deposition dynamics changes dramatically with the number of layers. The results stabilize from six layers on upwards.

Faber, B.; Dinh, P. M.; Reinhard, P. G.; Suraud, E.

2012-07-01

101

Molecular dynamics investigation of Na+ in Na2Ni2TeO6  

NASA Astrophysics Data System (ADS)

An inter-atomic potential for Na2Ni2TeO6 in the Parrinello- Rahman-Vashishta (PRV) model is parameterized empirically. The potential reproduces variety of structural and transport properties of that material in good agreement with recent experimental results. The study provides fresh insights on the migration channels and mechanism of Na+ in the system.

Sau, Kartik; Kumar, P. Padma

2014-04-01

102

Interaction of NaCl(g) and HCl(g) with condensed NA2SO4  

NASA Technical Reports Server (NTRS)

The interaction of Na2SO4(l) with NaCl(g), HCl(g) and H2O(g) was studied in atmospheric pressure flowing air and oxygen at Na2SO4(l) temperatures of 900 and 1000 C. Thermomicrogravimetric and high pressure mass spectrometric sampling techniques were used. Experimental results establish that previously reported enhanced rates of weight loss of Na2SO4(l) in the presence of NaCl(g) are due to the reaction: Na2SO4(c) + 2HCl(g) = 2NaCl(g) + SO2(g) + H2O(g) + 1/2O2(g) being driven to the right in flowing gas systems. The HCl(g) is the product of hydrolysis of NaCl caused by small but significant amounts of H2O(g) present in the system. Thermochemical calculations are used to show that even with sub-ppm levels of H2O(g) present, significant quantities of HCl(g) are produced.

Stearns, C. A.; Kohl, F. J.; Fryburg, G. C.; Miller, R. A.

1977-01-01

103

Anion-coupled Na efflux mediated by the human red blood cell Na/K pump  

SciTech Connect

The red cell Na/K pump is known to continue to extrude Na when both Na and K are removed from the external medium. Because this ouabain-sensitive flux occurs in the absence of an exchangeable cation, it is referred to as uncoupled Na efflux. This flux is also known to be inhibited by 5 mM Nao but to a lesser extent than that inhibitable by ouabain. Uncoupled Na efflux via the Na/K pump therefore can be divided into a Nao-sensitive and Nao-insensitive component. We used DIDS-treated, SO4-equilibrated human red blood cells suspended in HEPES-buffered (pHo 7.4) MgSO4 or (Tris)2SO4, in which we measured 22Na efflux, 35SO4 efflux, and changes in the membrane potential with the fluorescent dye, diS-C3 (5). A principal finding is that uncoupled Na efflux occurs electroneurally, in contrast to the pump's normal electrogenic operation when exchanging Nai for Ko. This electroneutral uncoupled efflux of Na was found to be balanced by an efflux of cellular anions. (We were unable to detect any ouabain-sensitive uptake of protons, measured in an unbuffered medium at pH 7.4 with a Radiometer pH-STAT.) The Nao-sensitive efflux of Nai was found to be 1.95 +/- 0.10 times the Nao-sensitive efflux of (SO4)i, indicating that the stoichiometry of this cotransport is two Na+ per SO4=, accounting for 60-80% of the electroneutral Na efflux. The remainder portion, that is, the ouabain-sensitive Nao-insensitive component, has been identified as PO4-coupled Na transport and is the subject of a separate paper. That uncoupled Na efflux occurs as a cotransport with anions is supported by the result, obtained with resealed ghosts, that when internal and external SO4 was substituted by the impermeant anion, tartrate i,o, the efflux of Na was inhibited 60-80%. This inhibition could be relieved by the inclusion, before DIDS treatment, of 5 mM Cli,o.

Dissing, S.; Hoffman, J.F. (Yale Univ. School of Medicine, New Haven, CT (USA))

1990-07-01

104

NaCd excimer emission bands  

NASA Astrophysics Data System (ADS)

The analysis of the visible spectrum of a high pressure sodium lamp filled with sodium, cadium and xenon revealed the existence of NaCd excimer spectral features. These are four red satellite bands at 691, 697, 709 and 726.5 nm and diffuse bands peaking at 479.1 and 484.3 nm. Both spectral phenomena are related to those found earlier for the NaHg system. An interpretation of the red satellite bands origin is given in terms of a qualitative model for the four lowest potential curves of the NaCd excimer. In this model the essential feature is the avoided crossing between B 2? 1/2 and A 2? 1/2 electronic states, which causes a complex structure of the satellite bands in the very far red wing of the sodium D lines broadened by cadmium.

Pichler, G.; Veža, D.; Fijan, D.

1988-06-01

105

Na+/K+-ATPase: Activity and inhibition  

NASA Astrophysics Data System (ADS)

The aim of the study was to give an overview of the mechanism of inhibition of Na+/K+-ATPase activity induced by some specific and non specific inhibitors. For this purpose, the effects of some ouabain like compounds (digoxin, gitoxin), noble metals complexes ([PtCl2DMSO2], [AuCl4]-, [PdCl4]2-, [PdCl(dien)]+, [PdCl(Me4dien)]+), transition metal ions (Cu2+, Zn2+, Fe2+, Co2+), and heavy metal ions (Hg2+, Pb2+, Cd2+) on the activity of Na+/K+-ATPase from rat synaptic plasma membranes (SPM), porcine cerebral cortex and human erythrocytes were discussed.

?olovi?, M.; Krsti?, D.; Krinulovi?, K.; Momi?, T.; Savi?, J.; Vuja?i?, A.; Vasi?, V.

2009-09-01

106

Classical trajectory studies of alkali atom-alkali dimer exchange reactions : Na Li2 and Li Na2  

Microsoft Academic Search

The endoergic and exoergic alkali atom-alkali dimer exchange reactions, Na+Li2-->NaLi+Li and Li+Na2-->LiNa+Na, have been studied using classical trajectory methods on LEPS surfaces exhibiting shallow potential wells at small internuclear separations. For both systems the total reaction cross section, collision lifetime, differential reaction cross section and product energy disposal were calculated for a range of initial collisional energies. Comparison with the

J. C. Whitehead

1976-01-01

107

The Na + -translocating ATPase in the plasma membrane of the marine microalga Tetraselmis viridis catalyzes Na + \\/H + exchange  

Microsoft Academic Search

Our previous investigations have established that Na + translocation across the Tetraselmis viridis plasma membrane (PM) mediated by the primary ATP-driven Na +-pump, Na +-ATPase, is accompanied by H + counter-transport [Y.V. Balnokin et al. (1999) FEBS Lett 462:402–406]. The hypothesis that the Na +-ATPase of T. viridis operates as an Na +\\/H + exchanger is tested in the present

Yurii V. Balnokin; Larissa G. Popova; Lyudmila Y. Pagis; Igor M. Andreev

2004-01-01

108

Ondas gravitatorias de transiciones de fase cosmológicas  

NASA Astrophysics Data System (ADS)

There are several projects to build Gravitational Waves (GWs) spaceborne detectors as NGO/eLISA, which could be launched before 2022. A frequency signal in the detection range (0.1 mHz - 1 Hz) would be generated in the electroweak scale. This talk focuses on GWs generation from the electroweak phase transition. FULL TEXT IN SPANISH

Leitao, L.

109

Density and Molar Volume of Melts in the Systems LiCl-NaCl, NaCl-RbCl and NaCl-CsCl.  

National Technical Information Service (NTIS)

The densities of molten NaCl-CsCl, NaCl-RbCl and LiCl-NaCl systems were measured by the hydrostatic weighing method over the entire concentration range. The molar volumes and their deviations from additivity at 800 and 850C were calculated from the experi...

M. V. Smirnov V. P. Stepanov T. Mukatov

1973-01-01

110

Extracellular allosteric Na(+) binding to the Na(+),K(+)-ATPase in cardiac myocytes.  

PubMed

Whole-cell patch-clamp measurements of the current, Ip, produced by the Na(+),K(+)-ATPase across the plasma membrane of rabbit cardiac myocytes show an increase in Ip over the extracellular Na(+) concentration range 0-50 mM. This is not predicted by the classical Albers-Post scheme of the Na(+),K(+)-ATPase mechanism, where extracellular Na(+) should act as a competitive inhibitor of extracellular K(+) binding, which is necessary for the stimulation of enzyme dephosphorylation and the pumping of K(+) ions into the cytoplasm. The increase in Ip is consistent with Na(+) binding to an extracellular allosteric site, independent of the ion transport sites, and an increase in turnover via an acceleration of the rate-determining release of K(+) to the cytoplasm, E2(K(+))2 ? E1 + 2K(+). At normal physiological concentrations of extracellular Na(+) of 140 mM, it is to be expected that binding of Na(+) to the allosteric site would be nearly saturated. Its purpose would seem to be simply to optimize the enzyme's ion pumping rate under its normal physiological conditions. Based on published crystal structures, a possible location of the allosteric site is within a cleft between the ?- and ?-subunits of the enzyme. PMID:24359741

Garcia, Alvaro; Fry, Natasha A S; Karimi, Keyvan; Liu, Chia-chi; Apell, Hans-Jürgen; Rasmussen, Helge H; Clarke, Ronald J

2013-12-17

111

Phonon Dispersion Relations in NaCl  

Microsoft Academic Search

Phonon dispersion relations in NaCl at 80°K have been determined in the crystallographic [100], [101], and [111] symmetry directions using inelastic neutron scattering. Some measurements have also been made at 300°K, and at (1.0, 0.5, 0) in reciprocal space. The results are compared with theoretical calculations: those of Karo and Hardy for their \\

G. Raunio; L. Almqvist; R. Stedman

1969-01-01

112

Mechanisms contributing to the cardiac inotropic effect of Na pump inhibition and reduction of extracellular Na  

PubMed Central

Reduction of the transsarcolemmal [Na] gradient in rabbit cardiac muscle leads to an increase in the force of contraction. This has frequently been attributed to alteration of Ca movements via the sarcolemmal Na/Ca exchange system. However, the specific mechanisms that mediate the increased force at individual contractions have not been clearly established. In the present study, the [Na] gradient was decreased by reduction of extracellular [Na] or inhibition of the Na pump by either the cardioactive steroid acetylstrophanthidin or by reduction of extracellular [K]. Contractile performance and changes in extracellular Ca (sensed by double-barreled Ca-selective microelectrodes) were studied in order to elucidate the underlying basis for the increase in force. In the presence of agents that inhibit sarcoplasmic reticulum (SR) function (10 mM caffeine, 100-500 nM ryanodine), reduction of the [Na] gradient produced increases in contractile force similar to that observed in the absence of caffeine or ryanodine. It is concluded that an intact, functioning SR is not required for the inotropic effect of [Na] gradient reduction (at least in rabbit ventricle). However, this does not exclude a possible contribution of enhanced SR Ca release in the inotropic response to [Na] gradient reduction in the absence of caffeine or ryanodine. Acetylstrophanthidin (3-5 microM) usually leads to an increase in the magnitude of extracellular Ca depletions associated with individual contractions. However, acetylstrophanthidin can also increase extracellular Ca accumulation during the contraction, especially at potentiated contractions. This extracellular Ca accumulation can be suppressed by ryanodine and it is suggested that this apparent enhancement of Ca efflux is secondary to an enhanced release of Ca from the SR. Under conditions where Ca efflux during contractions is minimized (after a rest interval in the presence of ryanodine), acetylstrophanthidin increased both the rate and the extent of extracellular Ca depletions. Thus, acetylstrophanthidin can increase both Ca influx and Ca efflux during the cardiac muscle contraction. These results can be explained by a simple model where the direction of net Ca flux via Na/Ca exchange during the action potential is determined by the changes in reversal potential of the Na/Ca exchange. Reduction of the [Na] gradient may well lead to net cellular Ca uptake (via Na/Ca exchange) and may also elevate the resting intracellular [Ca].(ABSTRACT TRUNCATED AT 400 WORDS)

1987-01-01

113

Dynamics of NaHSeO3 and NaHSeO4 single crystals by observation of 1H and 23Na spin-lattice relaxation.  

PubMed

The 1H and 23Na spin-lattice relaxation times of NaHSeO3 and NaHSeO4 single crystals grown by the slow evaporation method were measured. The phase transitions of the two crystals were studied using differential scanning calorimetry (DSC), and the environments of the 1H and 23Na nuclei in these crystals were investigated by means of 1H and 23Na NMR spectroscopy. The DSC results show that NaHSeO3 crystals do not undergo phase transitions, whereas for NaHSeO4 crystals there is a small endothermic peak at 419 K. The dimers in NaHSeO3 stabilize its structure to the extent that there are no phase transitions even in the presence of disordered hydrogen bonds. In addition, the NMR results indicate that the temperature dependencies of T1 for the 1H and 23Na nuclei in the two hydrogen-bonded crystals-the NaHSeO3 crystal with 3-coordinated SeO3 and the NaHSeO4 crystal with 4-coordinated SeO4--are significantly different. The different trends in T1 for Na in the two crystals are accompanied by different shifts of the oxygen atoms from the 3-coordinated SeO3 and the 4-coordinated SeO4 species around the Na+ ions. Thus, although the two crystals have hydrogen-bonded structures, the differences between the hydrogen bonding of the 3-coordinated SeO3 in NaHSeO3 and the hydrogen bonding of the 4-coordinated SeO4 in NaHSeO4 result in different T1 temperature dependences and different phase transitions. PMID:17481861

Lim, Ae Ran; Jang, Seo Won; Chang, Jin-Hae

2007-05-01

114

Avaliação do índice de temperatura de globo negro e umidade e desempenho de suínos nas fases de crescimento e terminação criados em sistemas em camas sobrepostas em condições de verão  

Microsoft Academic Search

RESUMO - Um estudo foi realizado com o objetivo de avaliar o sistema de criação em camas sobrepostas de maravalha e de casca de arroz, em comparação ao piso tradicional de concreto e sua influência no desempenho dos animais com base no ITGU (Índice de Temperatura de Globo negro e Umidade), no ganho de peso, no consumo de ração, na

Ilda de Fátima Ferreira Tinôco; Cecília de Fátima Souza; Paulo Armando Victoria de Oliveira; Robson Mendes de Paulo; Josiane Aparecida Campos; Cinara da Cunha Siqueira Carvalho; Marcelo Bastos Cordeiro

2007-01-01

115

o Efeito da musicoterapia na qualidade de vida e na Pressão Arterial do Paciente Hipertenso Music Therapy Effects on the Quality of Life and the Blood Pressure of Hypertensive Patients  

Microsoft Academic Search

Summary Background: Arterial Hypertension (AH) is a mass disease, with consequences for the cardiocirculatory system, since its complications raise the rates of morbidity and mortality. Controlling blood pressure (BP) reduces complications and may preserve the quality of life (QOL) of patients. Studies show positive effects of music therapy as an adjuvant in the treatment of several diseases. Objective: To evaluate

Claudia Regina de Oliveira; Paulo Zanini; César Brandão; Veiga Jardim; Claudia Maria Salgado; Mariana Cabral

2009-01-01

116

Synthesis of Na-A and/or Na-X zeolite/porous carbon composites from carbonized rice husk  

NASA Astrophysics Data System (ADS)

Na-A and/or Na-X zeolite/porous carbon composites were prepared under hydrothermal conditions by NaOH dissolution of silica first from carbonized rice husk followed by addition of NaAlO 2 and in situ crystallization of zeolites i.e., using a two-step process. When a one-step process was used, both Na-A and Na-X zeolites crystallized on the surface of carbon. Na-A or Na-X zeolite crystals were prepared on the porous carbonized rice husk at 90 °C for 2-6 h by changing the SiO 2/Al 2O 3, H 2O/Na 2O and Na 2O/SiO 2 molar ratios of precursors in the two-step process. The surface area and NH 4+-cation exchange capacity (CEC) of Na-A zeolite/porous carbon were found to be 171 m 2/g and 506 meq/100 g, respectively, while those of Na-X zeolite/porous carbon composites were 676 m 2/g and 317 meq/100 g, respectively. Na-A and Na-X zeolites are well-known microporous and hydrophilic materials while carbonized rice husk was found to be mesoporous (pores of ˜3.9 nm) and hydrophobic. These hybrid microporous-mesoporous and hydrophilic-hydrophobic composites are expected to be useful for decontamination of metal cations as well as organic contaminants simultaneously.

Katsuki, Hiroaki; Komarneni, Sridhar

2009-07-01

117

Inhibition of Na(+)-independent H+ pump by Na(+)-induced changes in cell Ca2+  

PubMed Central

Apical membrane H+ extrusion in the renal outer medullary collecting duct, inner stripe, is mediated by a Na(+)-independent H+ pump. To examine the regulation of this transporter, cell pH and cell Ca2+ were measured microfluorometrically in in vitro perfused tubules using 2',7'- bis(carboxyethyl)-5(6)-carboxyfluorescein and fura-2, respectively. Apical membrane H+ pump activity, assayed as cell pH recovery from a series of acid loads (NH3/NH+4 prepulse) in the total absence of ambient Na+, initially occurred at a slow rate (0.06 +/- 0.02 pH units/min), which was not sufficient to account for physiologic rates of H+ extrusion. Over 15-20 min after the initial acid load, the rate of Na(+)-independent cell pH recovery increased to 0.63 +/- 0.09 pH units/min, associated with a steady-state cell pH greater than the initial pre-acid load cell pH. This pattern suggested an initial suppression followed by a delayed activation of the apical membrane H+ pump. Replacement of peritubular Na+ with choline or N-methyl-D- glucosamine resulted in an initial spike increase in cell Ca2+ followed by a sustained increase in cell Ca2+. The initial rate of Na(+)- independent cell pH recovery could be increased by elimination of the Na+ removal-induced sustained cell Ca2+ elevation by: (a) performing studies in the presence of 135 mM peritubular Na+ (1 mM peritubular amiloride used to inhibit basolateral membrane Na+/H+ antiport); (b) clamping cell Ca2+ low with dimethyl-BAPTA, an intracellular Ca2+ chelating agent; or (c) removal of extracellular Ca2+. Cell acidification induced a spike increase in cell Ca2+. The late acceleration of Na(+)-independent cell pH recovery was independent of Na+ removal and of the method used to acidify the cell, but was eliminated by prevention of the cell Ca2+ spike and markedly delayed by the microfilament-disrupting agent, cytochalasin B. This study demonstrates that peritubular Na+ removal results in a sustained elevation in cell Ca2+, which inhibits the apical membrane H+ pump. In addition, rapid cell acidification associated with a spike increase in cell Ca2+ leads to a delayed activation of the H+ pump. Thus, cell Ca2+ per se, or a Ca(2+)-activated pathway, can modulate H+ pump activity.

1991-01-01

118

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

PubMed

Phospholemman (PLM) regulates cardiac Na(+)/Ca(2+) exchanger (NCX1) and Na(+)-K(+)-ATPase in cardiac myocytes. PLM, when phosphorylated at Ser(68), disinhibits Na(+)-K(+)-ATPase but inhibits NCX1. PLM regulates cardiac contractility by modulating Na(+)-K(+)-ATPase and/or NCX1. In this study, we first demonstrated that adult mouse cardiac myocytes cultured for 48 h had normal surface membrane areas, t-tubules, and NCX1 and sarco(endo)plasmic reticulum Ca(2+)-ATPase levels, and retained near normal contractility, but alpha(1)-subunit of Na(+)-K(+)-ATPase was slightly decreased. Differences in contractility between myocytes isolated from wild-type (WT) and PLM knockout (KO) hearts were preserved after 48 h of culture. Infection with adenovirus expressing green fluorescent protein (GFP) did not affect contractility at 48 h. When WT PLM was overexpressed in PLM KO myocytes, contractility and cytosolic Ca(2+) concentration ([Ca(2+)](i)) transients reverted back to those observed in cultured WT myocytes. Both Na(+)-K(+)-ATPase current (I(pump)) and Na(+)/Ca(2+) exchange current (I(NaCa)) in PLM KO myocytes rescued with WT PLM were depressed compared with PLM KO myocytes. Overexpressing the PLMS68E mutant (phosphomimetic) in PLM KO myocytes resulted in the suppression of I(NaCa) but had no effect on I(pump). Contractility, [Ca(2+)](i) transient amplitudes, and sarcoplasmic reticulum Ca(2+) contents in PLM KO myocytes overexpressing the PLMS68E mutant were depressed compared with PLM KO myocytes overexpressing GFP. Overexpressing the PLMS68A mutant (mimicking unphosphorylated PLM) in PLM KO myocytes had no effect on I(NaCa) but decreased I(pump). Contractility, [Ca(2+)](i) transient amplitudes, and sarcoplasmic reticulum Ca(2+) contents in PLM KO myocytes overexpressing the S68A mutant were similar to PLM KO myocytes overexpressing GFP. We conclude that at the single-myocyte level, PLM affects cardiac contractility and [Ca(2+)](i) homeostasis primarily by its direct inhibitory effects on Na(+)/Ca(2+) exchange. PMID:18708446

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

2008-10-01

119

Conduction of Na + and K + through the NaK Channel: Molecular and Brownian Dynamics Studies  

Microsoft Academic Search

Conduction of ions through the NaK channel, with M0 helix removed, was studied using both Brownian dynamics and molecular dynamics. Brownian dynamics simulations predict that the truncated NaK has approximately a third of the conductance of the related KcsA K+ channel, is outwardly rectifying, and has a Michaelis-Menten current-concentration relationship. Current magnitude increases when the glutamine residue located near the

Taira Vora; David Bisset; Shin-Ho Chung

2008-01-01

120

Electronic potential energy surfaces for the reaction K+NaCl=KCl+Na  

Microsoft Academic Search

The six lowest ?-bonded potential surfaces for the reaction K+NaCl=KCl+Na have been calculated on a semi-empirical model with a single valence electron in the field of the three closed shell ions. A simple method is proposed by which the energetic effects of valence-core orthogonalization, which are of crucial importance in the calculations, may be included in the potentials of the

A. C. Roach; M. S. Child

1968-01-01

121

Electronic potential energy surfaces for the reaction K+NaCl=KCl+Na  

Microsoft Academic Search

The six lowest sigma-bonded potential surfaces for the reaction K+NaCl=KCl+Na have been calculated on a semi-empirical model with a single valence electron in the field of the three closed shell ions. A simple method is proposed by which the energetic effects of valence-core orthogonalization, which are of crucial importance in the calculations, may be included in the potentials of the

A. C. Roach; M. S. Child

1968-01-01

122

Path integral study of the correlated electronic states of Na4–Na6  

Microsoft Academic Search

Feynman’s path integral formulation of quantum mechanics is used to study the correlated electronic states of Na4–Na6. Two types of simulations are performed: in the first, the nuclei are allowed to move at finite temperature in order to find the most stable geometries. In agreement with previous calculations, we find that planar structures are the most stable and that there

Randall W. Hall

1990-01-01

123

Role of Na+ conductance, Na+-H+ exchange, and Na+-K+-2Cl? symport in the regulatory volume increase of rat hepatocytes  

PubMed Central

In rat hepatocytes under hypertonic stress, the entry of Na+ (which is thereafter exchanged for K+ via Na+-K+-ATPase) plays the key role in regulatory volume increase (RVI).In the present study, the contributions of Na+ conductance, Na+-H+ exchange and Na+-K+-2Cl? symport to this process were quantified in confluent primary cultures by means of intracellular microelectrodes and cable analysis, microfluorometric determinations of cell pH and buffer capacity, and measurements of frusemide (furosemide)/bumetanide-sensitive 86Rb+ uptake, respectively. Osmolarity was increased from 300 to 400 mosmol l?1 by addition of sucrose.The experiments indicate a relative contribution of approximately 4:1:1 to hypertonicity-induced Na+ entry for the above-mentioned transporters and the overall Na+ yield equalled 51 mmol l?1 (10 min)?1.This Na+ gain is in good agreement with the stimulation of Na+ extrusion via Na+-K+-ATPase plus the actual increase in cell Na+, namely 55 mmol l?1 (10 min)?1, as was determined on the basis of ouabain-sensitive 86Rb+ uptake and by means of Na+-sensitive microelectrodes, respectively.The overall increase in Na+ and K+ activity plus the expected concomitant increase in cell Cl? equalled 68 mmol l?1, which fits well with the increase in osmotic activity expected to occur from an initial cell shrinkage to 87.5 % and a RVI to 92.6 % of control, namely 53 mosmol l?1.The prominent role of Na+ conductance in the RVI of rat hepatocytes could be confirmed on the basis of the pharmacological profile of this process, which was characterized by means of confocal laser-scanning microscopy.

Wehner, Frank; Tinel, Hanna

1998-01-01

124

In rat hepatocytes, the hypertonic activation of Na+ conductance and Na+-K+-2Cl? symport - but not Na+-H+ antiport - is mediated by protein kinase C  

PubMed Central

The initial event in the regulatory volume increase (RVI) of rat hepatocytes is an import of extracellular Na+ via Na+ conductance, Na+-K+-2Cl? symport, and Na+-H+ antiport. Here, the protein kinase inhibitors staurosporine (100 nmol l?1) and bis-indolyl-maleimide I (400 nmol l?1) were used to test for a possible contribution of protein kinase C (PKC) to the hypertonic activation of these transporters in confluent primary cultures. Stimulation of Na+ conductance was monitored: (i) by use of a differential approach based on Na+ fluxes, (ii) by means of cable analysis, and (iii) in experiments with low Na+ pulses. All three experimental protocols in concert demonstrated a block of the activation of Na+ conductance by staurosporine and bis-indolyl-maleimide I. In addition, both compounds significantly reduced the hypertonic activation of Na+-K+-2Cl? symport (quantified on the basis of furosemide-sensitive 86Rb+ uptake) to approximately 30 %. In contrast, neither staurosporine nor bis-indolyl-maleimide I had any detectable effect on the hypertonicity-induced alkalinization of cell pH via Na+-H+ antiport (determined fluorometrically). Staurosporine and bis-indolyl-maleimide I completely blocked the RVI of rat hepatocytes (quantified by means of confocal laser-scanning microscopy). The high efficiency of the block suggests an additional inhibitory effect of both compounds on the activity of Na+/K+-ATPase (determined as ouabain-sensitive 86Rb+ uptake). It is concluded that the hypertonic activation of rat hepatocyte Na+ conductance and Na+-K+-2Cl? symport - but not Na+-H+ antiport - is probably mediated by PKC.

Heinzinger, Heidrun; van den Boom, Frank; Tinel, Hanna; Wehner, Frank

2001-01-01

125

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

NASA Astrophysics Data System (ADS)

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

Cherng, Jing-Yih; Bennion, Douglas N.

1987-09-01

126

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

NASA Technical Reports Server (NTRS)

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

Cherng, Jing-Yih; Bennion, Douglas N.

1987-01-01

127

Intracellular Na+ regulation of Na+ pump sites in cultured vascular smooth muscle cells  

SciTech Connect

Enzymatically dispersed cells from canine saphenous vein and femoral artery were grown in fetal calf serum and studied at day 0 (freshly dispersed) through confluence in primary culture. Intracellular Na levels (Nai), but not intracellular K (Ki), were increased after 24 h in culture and then decreased to a steady state by 4 days. Na+ pump site number (( /sup 3/H) ouabain binding) increased through day 3 and remained elevated. Nai was still elevated at 2 days when the Na+ pump site number began to increase. Total pump turnover (maximum ouabain-inhibited /sup 86/Rb uptake) reflected the increase in Na+ pump site number. These key events precede the observed increases in both protein production and cellular proliferation. If the same cells are maintained in defined medium, without fetal calf serum, Nai, Ki, and the number of (/sup 3/H)ouabain binding sites do not change with time. These data are consistent with the suggestion that the initial mitogenic response of vascular smooth muscle cells to fetal calf serum involves an increased Na+ influx, and a Nai accumulation, caused by low Na+ pump density. The synthesis of new pump sites effects a decrease in the accumulated Nai, which may be related to cell proliferation.

Allen, J.C.; Navran, S.S.; Seidel, C.L.; Dennison, D.K.; Amann, J.M.; Jemelka, S.K.

1989-04-01

128

Inelastic and reactive collisions with polarized excited Na atoms  

SciTech Connect

Polarization effects in inelastic collisions of laser state-prepared Na(3/sup 2/P, M/sub J/) with Na/sup +/ leading to Na(3/sup 2/D) or Na(3/sup 2/S) are discussed for the energy range E/sub cm/ = 5-47.5eV. Studies with linearly polarized light can be explained with a simple ''locking'' model of the Na(P)-orbital. The investigations employing circularly polarized light are a very sensitive test of the models describing the nonadiabatic angular momentum coupling between electronic and nuclear motion. The dynamical effects of the electronic spin on the angular momentum transfer are discussed. Recent crossed-beam experiments on the Na + O/sub 2/ -> NaO = O reaction in the energy range E/sub cm/ = 0/3-0.8eV show a pronounced dependence on the electric electronic symmetry of Na. 17 refs., 11 figs.

Schmidt, H.; Hertel, I.V.; Lee, Y.T.

1985-07-01

129

Slip casting alumina with Na-CMC  

SciTech Connect

Many forming methods are in common use for engineering ceramics. Of these, slip casting is an ideal forming method because of its low cost, simplicity and flexibility, potential for uniform particle packing and suitability to the production of articles of intricate shape. Slip casting nonclay materials, such as alumina, requires the use of both a deflocculant and a binder. There are many commercially available deflocculants and binders that can be tested in alumina casting slips. However, determination of a suitable deflocculant/binder combination and quantification of the optimal additions of the deflocculant/binder pair can be time consuming. Certain deflocculants are capable of acting as binders. One such additive is sodium carboxymethylcellulose (Na-cmc), a cellulose ether. Na-cmc is a powerful binder. It is a member of the carbohydrate binder group--the binder group with the strongest binding power. It is capable of acting as a deflocculant in glazes and nonclay casting slips.

Ruys, A.J.; Sorrell, C.C. [Univ. of New South Wales, Sydney, New South Wales (Australia)

1996-11-01

130

Angiotensin II-induced hypertension increases plasma membrane Na pump activity by enhancing Na entry in rat thick ascending limbs.  

PubMed

Thick ascending limbs (TAL) reabsorb 30% of the filtered NaCl load. Na enters the cells via apical Na-K-2Cl cotransporters and Na/H exchangers and exits via basolateral Na pumps. Chronic angiotensin II (ANG II) infusion increases net TAL Na transport and Na apical entry; however, little is known about its effects on the basolateral Na pump. We hypothesized that in rat TALs Na pump activity is enhanced by ANG II-infusion, a model of ANG II-induced hypertension. Rats were infused with 200 ng·kg(-1)·min(-1) ANG II or vehicle for 7 days, and TAL suspensions were obtained. We studied plasma membrane Na pump activity by measuring changes in 1) intracellular Na (Nai) induced by ouabain; and 2) ouabain-sensitive oxygen consumption (QO2). We found that the ouabain-sensitive rise in Nai in TALs from ANG II-infused rats was 12.8 ± 0.4 arbitrary fluorescent units (AFU)·mg(-1)·min(-1) compared with only 9.9 ± 1.1 AFU·mg(-1)·min(-1) in controls (P < 0.024). Ouabain-sensitive oxygen consumption was 17 ± 5% (P < 0.043) greater in tubules from ANG II-treated than vehicle rats. ANG II infusion did not alter total Na pump expression, the number of Na pumps in the plasma membrane, or the affinity for Na. When furosemide (1.1 mg·kg(-1)·day(-1)) was coinfused with ANG II, no increase in plasma membrane Na pump activity was observed. We concluded that in ANG II-induced hypertension Na pump activity is increased in the plasma membrane of TALs and that this increase is caused by the chronically enhanced Na entry occurring in this model. PMID:23986517

Gonzalez-Vicente, Agustin; Garvin, Jeffrey L

2013-11-01

131

The two C-terminal tyrosines stabilize occluded Na/K pump conformations containing Na or K ions  

PubMed Central

Interactions of the three transported Na ions with the Na/K pump remain incompletely understood. Na/K pump crystal structures show that the extended C terminus of the Na,K–adenosine triphosphatase (ATPase) ? subunit directly contacts transmembrane helices. Deletion of the last five residues (KETYY in almost all Na/K pumps) markedly lowered the apparent affinity for Na activation of pump phosphorylation from ATP, a reflection of cytoplasmic Na affinity for forming the occluded E1P(Na3) conformation. ATPase assays further suggested that C-terminal truncations also interfere with low affinity Na interactions, which are attributable to extracellular effects. Because extracellular Na ions traverse part of the membrane’s electric field to reach their binding sites in the Na/K pump, their movements generate currents that can be monitored with high resolution. We report here electrical measurements to examine how Na/K pump interactions with extracellular Na ions are influenced by C-terminal truncations. We deleted the last two (YY) or five (KESYY) residues in Xenopus laevis ?1 Na/K pumps made ouabain resistant by either of two kinds of point mutations and measured their currents as 10-mM ouabain–sensitive currents in Xenopus oocytes after silencing endogenous Xenopus Na/K pumps with 1 µM ouabain. We found the low affinity inhibitory influence of extracellular Na on outward Na/K pump current at negative voltages to be impaired in all of the C-terminally truncated pumps. Correspondingly, voltage jump–induced transient charge movements that reflect pump interactions with extracellular Na ions were strongly shifted to more negative potentials; this signals a several-fold reduction of the apparent affinity for extracellular Na in the truncated pumps. Parallel lowering of Na affinity on both sides of the membrane argues that the C-terminal contacts provide important stabilization of the occluded E1P(Na3) conformation, regardless of the route of Na ion entry into the binding pocket. Gating measurements of palytoxin-opened Na/K pump channels additionally imply that the C-terminal contacts also help stabilize pump conformations with occluded K ions.

Vedovato, Natascia

2010-01-01

132

Coulomb excitation of radioactive 20, 21 Na  

Microsoft Academic Search

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 -ray detection, while scattered nuclei were observed by

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

2009-01-01

133

Photoelectron spectra from K and Na clusters  

NASA Astrophysics Data System (ADS)

We discuss photoelectron spectra (PES) of Na and K clusters for various charge states and various sizes. The PES were obtained in dynamical calculations with time-dependent local-density approximation (TDLDA) augmented with a self-interaction correction to arrange the correct ionization properties. Comparison with experimental data shows that TDLDA provides generally a pertinent description. A few deviations for very small systems hint at final state correlations which go beyond a mean-field description.

Pohl, A.; Reinhard, P.-G.; Suraud, E.

2003-11-01

134

23Na multiple quantum filtered NMR characterisation of Na+ binding and dynamics in animal cells: a comparative study and effect of Na+/Li + competition.  

PubMed

Double quantum and triple quantum filtered (23)Na nuclear magnetic resonance techniques were used to characterise in detail the isotropic and anisotropic binding and dynamics of intra- and extracellular Na(+) in different cellular systems, in the absence and presence of Li(+). The kinetics of Li(+) influx by different cell types was evaluated. At steady state, astrocytes accumulated more Li(+) than red blood cells (RBCs), while a higher intracellular Li(+) concentration was found in chromaffin than in SH-SY5Y cells. Anisotropic and isotropic motions were detected for extracellular Na(+) in all cellular systems studied. Isotropic intracellular Na(+) motions were observed in all types of cells, while anisotropic Na(+) motions in the intracellular compartment were only detected in RBCs. (23)Na triple quantum signal efficiency for intracellular Na(+) was SH-SY5Y > chromaffin > RBCs, while the reverse order was observed for the extracellular ions. (23)Na double quantum signal efficiency for intracellular Na(+) was non-zero only in RBCs, and for extracellular Na(+) the order RBCs > chromaffin > SH-SY5Y cells was observed. Li(+) loading generally decreased intracellular Na(+) isotropic movements in the cells, except for astrocytes incubated with a low Li(+) concentration and increased anisotropic intracellular Na(+) movements in RBCs. Li(+) effects on the extracellular signals were more complex, reflecting Li(+)/Na(+) competition for isotropic and anisotropic binding sites at the extracellular surface of cell membranes and also at the surface of the gel used for cell immobilisation. These results are relevant and contribute to the interpretation of the in vivo pharmacokinetics and sites of Li(+) action. PMID:23563802

Fonseca, Carla P; Fonseca, Luís L; Montezinho, Liliana P; Alves, Paula M; Santos, Helena; Castro, M Margarida C A; Geraldes, Carlos F G C

2013-07-01

135

NaI Detector Network at Aragats  

NASA Astrophysics Data System (ADS)

The Aragats Space Environmental Center (ASEC) [1] provides monitoring of different species of secondary cosmic rays and consists of two high altitude research stations on Mt. Aragats in Armenia. Along with solar modulation effects, ASEC detectors register several coherent enhancements associated with thunderstorm activity. The experimental techniques used allowed for the first time to simultaneously measure fluxes of the electrons, muons, gamma rays, and neutrons correlated with thunderstorm activity [2,3]. Ground-based observations by a complex of surface particle detectors, measuring in systematically and repeatable fashion, gamma quanta, electrons, muons and neutrons from atmospheric sources are necessary for proving the theory of particle acceleration and multiplication during thunderstorms. Energy spectra and correlations between fluxes of different particles, measured on Earth's surface address the important issues of research of the solar modulation effects and the atmospheric high-energy phenomena. In May 26 2011, launched 5 NaI(Tl) (thallium-doped sodium iodide) scintillation detectors and 1 plastic one in the new ASEC laboratory on Aragats to detect low energy gamma rays from the thunderclouds and short particle bursts. Including NaI(Tl) detectors in ASEC detectors system is of great importance for investigation thunderstorm phenomena because NaI(Tl) detectors have high efficiency of gamma ray detecting in comparison with plastic ones.

Avakyan, Karen; Arakelyan, Karen; Chilingarian, Ashot; Daryan, Ara; Kozliner, Lev; Mailyan, Bagrat; Hovsepyan, Gagik; Pokhsraryan, David; Sargsyan, David

2013-02-01

136

Progress of the NA62 RICH detector  

NASA Astrophysics Data System (ADS)

NA62 is the last generation Kaon experiment at CERN. Its main goal is to collect about 100 K+??+?bar nu events with 10% background. This implies to collect more than 1013 K+ decays with a backgound rejection factor better than 1012. The challenging aspect of the experiment is the suppression of Kaon decays with branching ratioes up to 10 orders of magnitude higher than the signal and similar experimental signature, such as K+??+?. To this purpose good PID (Particle IDentification) and kinematic rejection are required. Precise timing is also needed to correctly associate the ?+ with the parent K+ in an high rate environment. A RICH (Ring Imaging Cherenkov) detector is proposed as PID element, to identify ? contaminating the ? sample in the 15-35 GeV/c momentum range with inefficiency lower than 1% and to measure the arrival time with precision smaller than 100 ps. It will also be a key element for the NA62 trigger. A vacuum-proof cylindrical vessel with 4 m diameter, 17 m long, will be filled with Neon gas at atmospheric pressure. The Cherenkov light will be reflected by a mosaic of 20 hexagonal mirrors with 17 m focal length and collected by 2000 photomultipliers. The progress in the construction of the detector is described: the installation will start in January 2014, with completion foreseen in time for the first physics run of the NA62 experiment in the fall of 2014.

Lenti, Massimo

2014-01-01

137

Thermodynamics of ion exchange between clinoptilolite and aqueous solutions of na +/k + and na +/ca 2+  

NASA Astrophysics Data System (ADS)

To provide a thermodynamic basis for understanding zeolite-water interactions in geologic systems, ion-exchange experiments were conducted at 25°C between clinoptilolite, which is the predominant zeolite mineral in altered pyroclastic and volcaniclastic rocks and aqueous mixtures of Na +/K + and Na +/Ca 2+. Isotherm points were obtained by equilibrating Na-clinoptilolite, which was prepared from clinoptilolite-rich tuff from Death Valley Junction, California, USA and Na +/K + and Na +/Ca 2+ chloride solutions having different ionic concentration ratios, but constant total normalities of 0.5, 0.05, or 0.005 N. The experimental data were interpreted using a Margules thermodynamic formulation for zeolite solid solutions, coupled with the Pitzer model for aqueous activity coefficients. The isotherm data for 0.5 N Na +/K + and Na +/Ca 2+ solutions were used to derive equilibrium constants and Gibbs free energies for the ion-exchange reactions, as well as parameters for the Margules model. Using the same parameters derived from the 0.5 N data, isotherms were calculated for the 0.05 and 0.005 N solutions. The predicted values agree very well with experimental data, including other data at 0.05 N solution concentration with nitrate as the supporting anion. The results of this study indicate that a Margules solid solution model for zeolites, coupled with an activity coefficient model for aqueous solutions (e.g., Pitzer model), can successfully describe and predict binary ion-exchange equilibria between aqueous solutions and the zeolite mineral clinoptilolite over a wide range of solution composition and concentration, and may provide a foundation for quantitative understanding of ion-exchange equilibria in multicomponent geochemical systems.

Pabalan, Roberto T.

1994-11-01

138

33 CFR 147.833 - Na Kika FDS safety zone.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Na Kika FDS safety zone. 147.833 Section 147.833...ACTIVITIES SAFETY ZONES § 147.833 Na Kika FDS safety zone. (a) Description. Na Kika FDS, Mississippi Canyon 474 âAâ (MC 474...

2013-07-01

139

33 CFR 147.833 - Na Kika FDS safety zone.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Na Kika FDS safety zone. 147.833 Section 147.833...ACTIVITIES SAFETY ZONES § 147.833 Na Kika FDS safety zone. (a) Description. Na Kika FDS, Mississippi Canyon 474 âAâ (MC 474...

2010-07-01

140

33 CFR 147.833 - Na Kika FDS safety zone.  

Code of Federal Regulations, 2010 CFR

...2009-07-01 2009-07-01 false Na Kika FDS safety zone. 147.833 Section 147.833...ACTIVITIES SAFETY ZONES § 147.833 Na Kika FDS safety zone. (a) Description. Na Kika FDS, Mississippi Canyon 474 âAâ (MC 474...

2009-07-01

141

Reich e a possibilidade do bem-estar na cultura  

Microsoft Academic Search

Numa entrevista dada em 1952, Reich afirmou que o texto freudiano O mal-estar na cultura fora escrito em resposta a uma conferência que proferira na casa do Fre ud sobre o tema profilaxia das neuroses. Inspirado nesse depoimento, este trabalho procura investigar as teses reichianas que se contrapõem ao pensamento freudiano de O mal -estar na cultura. Diferenciam-se as posições

Paulo Albertini

2003-01-01

142

Genome Sequences of Cupriavidus metallidurans Strains NA1, NA4, and NE12, Isolated from Space Equipment  

PubMed Central

Cupriavidus metallidurans NA1, NA4, and NE12 were isolated from space and spacecraft-associated environments. Here, we report their draft genome sequences with the aim of gaining insight into their potential to adapt to these environments.

Monsieurs, Pieter; Mijnendonckx, Kristel; Provoost, Ann; Venkateswaran, Kasthuri; Ott, C. Mark; Leys, Natalie

2014-01-01

143

Immunohistochemical and RT-PCR detection of Na +-dependent inorganic phosphate cotransporter (NaP i-2) in rat brain  

Microsoft Academic Search

Expression of a renal Na+-dependent inorganic phosphate (Pi) cotransporter (NaPi-2) was studied in rat forebrain with reverse transcription and polymerase chain reaction (RT-PCR) and immunohistochemistry. RT-PCR analysis for total RNA from whole brain and sequencing of the PCR products showed expression of NaPi-2 mRNA in the brain. Immunohistochemical analysis revealed NaPi-2 staining in many nonpyramidal neurons of all six layers

Setsuji Hisano; Hiromi Haga; Zhunan Li; Sawako Tatsumi; Ken-Ichi Miyamoto; Eiji Takeda; Yoshihiro Fukui

1997-01-01

144

Identification of three isoforms for the Na+-dependent phosphate cotransporter (NaPi-2) in rat kidney.  

PubMed

We have isolated three unique NaPi-2-related protein cDNAs (NaPi-2alpha, NaPi-2beta, and NaPi-2gamma) from a rat kidney library. NaPi-2alpha cDNA encodes 337 amino acids which have high homology to the N-terminal half of NaPi-2 containing 3 transmembrane domains. NaPi-2beta encodes 327 amino acids which are identical to the N-terminal region of NaPi-2 containing 4 transmembrane domains, whereas the 146 amino acids in the C-terminal region are completely different. In contrast, NaPi-2gamma encodes 268 amino acids which are identical to the C-terminal half of NaPi-2. An analysis of phage and cosmid clones indicated that the three related proteins were produced by alternative splicing in the NaPi-2 gene. In a rabbit reticulocyte lysate system, NaPi-2 alpha, beta, and gamma were found to be 36, 36, and 29 kDa amino acid polypeptides, respectively. NaPi-2alpha and NaPi-2gamma were glycosylated and revealed to be 45- and 35-kDa proteins, respectively. In isolated brush-border membrane vesicles, an N-terminal antibody was reacted with 45- and 40-kDa, and a C-terminal antibody was reacted with 37-kDa protein. The sizes of these proteins corresponded to those in glycosylated forms. A functional analysis demonstrated that NaPi-2gamma and -2alpha markedly inhibited NaPi-2 activity in Xenopus oocytes. The results suggest that these short isoforms may function as a dominant negative inhibitor of the full-length transporter. PMID:9786847

Tatsumi, S; Miyamoto, K; Kouda, T; Motonaga, K; Katai, K; Ohkido, I; Morita, K; Segawa, H; Tani, Y; Yamamoto, H; Taketani, Y; Takeda, E

1998-10-30

145

Angiotensin increases Na+ entry and Na+/K+ pump activity in cultures of smooth muscle from rat aorta.  

PubMed Central

Angiotensin markedly altered the Na+ permeability of smooth muscle cells cultured from explants of rat aorta. The rate of net Na+ uptake was followed in the presence of ouabain in order to block Na+ efflux via the Na+/K+ pump. Angiotensin II (AII) or angiotensin III (AIII) increased net Na+ uptake by about 3-fold. Maximal stimulation of Na+ uptake was produced by about 10 nM AII. Bradykinin and the angiotensin antagonist [Sar1, Ileu5, Ala8]AII had no significant effect on net Na+ uptake. Angiotensin also enhanced the activity of the Na+/K+ pump, which was assayed by following the rate of ouabain-sensitive 86Rb+ uptake by the cells. AII and AIII nearly doubled ouabain-sensitive 86Rb+ uptake, but bradykinin, norepinephrine, and [Sar1, Ileu5, Ala8]AII had no effect. In the presence of ouabain, 86Rb+ uptake was not significantly affected by AII or AIII, indicating that angiotensin did not alter passive permeability to Rb+. Loading the cells with Na+, either by incubation in K+-free medium or exposure to the Na+-selective ionophore monensin, markedly increased ouabain-sensitive 86RB+ uptake. This result indicates that the activity of the Na+/K+ pump is limited by the low level of Na+ that is normally in the cells. AII had no effect on the activity of the Na+/K+ pump in Na+-loaded cells. These results suggest that AII or AIII stimulates the Na+/K+ pump in cultured aortic muscle cells by increasing its Na+ supply.

Brock, T A; Lewis, L J; Smith, J B

1982-01-01

146

DOR activation inhibits anoxic/ischemic Na+ influx through Na+ channels via PKC mechanisms in the cortex  

PubMed Central

Activation of delta-opioid receptors (DOR) is neuroprotective against hypoxic/ischemic injury in the cortex, which is at least partially related to its action against hypoxic/ischemic disruption of ionic homeostasis that triggers neuronal injury. Na+ influx through TTX-sensitive voltage-gated Na+ channels may be a main mechanism for hypoxia-induced disruption of K+ homeostasis, with DOR activation attenuating the disruption of ionic homeostasis by targeting voltage-gated Na+ channels. In the present study we examined the role of DOR in the regulation of Na+ influx in anoxia and simulated ischemia (oxygen-glucose deprivation) as well as the effect of DOR activation on the Na+ influx induced by a Na+ channel opener without anoxic/ischemic stress and explored a potential PKC mechanism underlying the DOR action. We directly measured extracellular Na+ activity in mouse cortical slices with Na+ selective electrodes and found that (1) anoxia-induced Na+ influx occurred mainly through TTX-sensitive Na+ channels; (2) DOR activation inhibited the anoxia/ischemia-induced Na+ influx; (3) veratridine, a Na+ channel opener, enhanced the anoxia-induced Na+ influx; this could be attenuated by DOR activation; (4) DOR activation did not reduce the anoxia-induced Na+ influx in the presence of chelerythrine, a broad-spectrum PKC blocker; and (5) DOR effects were blocked by PKC?II peptide inhibitor, and PKC? pseudosubstrate inhibitor, respectively. We conclude that DOR activation inhibits anoxia-induced Na+ influx through Na+ channels via PKC (especially PKC?II and PKC? isoforms) dependent mechanisms in the cortex.

Chao, Dongman; He, Xiaozhou; Yang, Yilin; Bazzy-Asaad, Alia; Lazarus, Lawrence H.; Balboni, Gianfranco; Kim, Dong H.; Xia, Ying

2012-01-01

147

Dependence of intracellular Na/sup +/ concentration on apical and basolateral membrane Na/sup +/ influx in frog skin  

SciTech Connect

An isotopic method was developed to measure the intracellular Na/sup +/ content of the transepithelial Na/sup +/ transport pool of frog skin. Isolated epithelia (no corium) were labeled with /sup 24/Na either asymmetrically, from apical (Aa) or basolateral (Ab) solutions, or symmetrically (Aab). Transport pool Na/sup +/ could be identified from the kinetics of washout of /sup 24/Na carried out in the presence of 1 mM ouabain, 100 microM amiloride, and 1 mM furosemide that served to trap cold Na/sup +/ and /sup 24/Na within the transport pool. In control epithelia, Aab averaged 64.1 neq/cm/sup 2/ (13.9 mM), and maximal inhibition of apical membrane Na/sup +/ entry with 100 microM amiloride caused Aab to decrease to 24.3 neq/cm/sup 2/ (5.3 mM). Ouabain caused Aab to increase markedly to 303 neq/cm/sup 2/ in 30 min, whereas amiloride inhibition of apical membrane Na/sup +/ entry reduced markedly the rate of increase of Aab caused by ouabain. These data, in part, confirmed the existence of an important basolateral membrane permeability to Na/sup +/ that was measured in separate studies of the bidirectional /sup 24/Na fluxes at the basolateral membranes of the cells. Both sets of data were supportive of the idea that a significant Na/sup +/ recycling exists at the basolateral membranes of the cells that contributes to the Na/sup +/ load on the pump and Na/sup +/ recycling participates in the regulation of the Na/sup +/ concentration of the Na/sup +/ transport pool of these epithelial cells.

Stoddard, J.S.; Helman, S.I.

1985-11-01

148

Zero-gravity growth of NaF-NaCl eutectics in the NASA Skylab program  

NASA Technical Reports Server (NTRS)

Continuous and discontinuous NaF fibers, embedded in a NaCl matrix, were produced in space and on earth. The production of continuous fibers in a eutectic mixture is attributed to the absence of convection current in the liquid during solidification in space. Image transmission and optical transmittance measurements of transverse sections of the space-grown and earth-grown ingots were made with a light microscope and a spectrometer. It is shown that better optical properties were obtained from samples grown in space. This was attributed to a better alignment of NaF fibers along the ingot axis. A new concept is advanced to explain the phenomenon of transmittance versus far infrared wavelength of the directionally solidified NaCl-NaF eutectic in terms of the two-dimensional Bragg Scattering and the polarization effect of Rayleigh scattering. This concept can be applied to other eutectic systems as long as the index of refraction of the matrix over a range of wavelengths is known. Experimental data are in agreement with the theoretical prediction.

Yue, A. S.; Allen, F. G.; Yu, J. G.

1976-01-01

149

Thermodynamics of the system NaF-Alf 3 . part ii: The free energies of formation of cryolite (Na 3 AlF 6 ) and chiolite (Na 5 Al 3 F 14 )  

Microsoft Academic Search

The theory of the solid-electrolyte cells\\u000a $$\\\\begin{gathered} Al\\\\left| \\\\begin{gathered} Na_3 AlF_6 \\\\hfill \\\\\\\\ NaF \\\\hfill \\\\\\\\ \\\\end{gathered} \\\\right|Na^ + \\\\left| \\\\begin{gathered} Na_3 AlF_6 \\\\hfill \\\\\\\\ Na_5 Al_3 F_{14} \\\\hfill \\\\\\\\ \\\\end{gathered} \\\\right|Al \\\\hfill \\\\\\\\ and \\\\hfill \\\\\\\\ Al\\\\left| \\\\begin{gathered} Na_3 AlF_6 \\\\hfill \\\\\\\\ Na_5 Al_3 F_{14} \\\\hfill \\\\\\\\ \\\\end{gathered} \\\\right|Na^ + \\\\left| \\\\begin{gathered} Na_5 Al_3 F_{14} \\\\hfill \\\\\\\\ AlF_3 \\\\hfill

E. W. Dewing

1970-01-01

150

Determination of Na(2)O from sodium aluminate NaAlO(2).  

PubMed

The aim of the work was to find a suitable method and conditions for determining Na(2)O wt.% from NaAlO(2). Problems were encountered while titrating NaAlO(2) with hydrochloric acid. The problematic area was the pH range 4-10 where aluminum precipitates as hydroxides. The different species of the aluminate solution were determined using potentiometric and complexometric titrations. The equivalent point of the potentiometric titration was detected using Gran's plotting method. Precipitation of aluminum hydroxides did not interfere with titrations, because in potentiometric titrations the pH value was over 10 and in complexometric titrations the pH was 4. The results were accurate and determinations were easy to carry out. Sodium was also determined by DCP-AES. PMID:18968035

Näykki, T; Raimo, A; Paavo, P; Antero, K; Päivi, N

2000-07-31

151

Novel regulation of cardiac Na pump via phospholemman.  

PubMed

As the only quantitatively significant Na efflux pathway from cardiac cells, the Na/K ATPase (Na pump) is the primary regulator of intracellular Na. The transmembrane Na gradient it establishes is essential for normal electrical excitability, numerous coupled-transport processes and, as the driving force for Na/Ca exchange, thus setting cardiac Ca load and contractility. As Na influx varies with electrical excitation, heart rate and pathology, the dynamic regulation of Na efflux is essential. It is now widely recognized that phospholemman, a 72 amino acid accessory protein which forms part of the Na pump complex, is the key nexus linking cellular signaling to pump regulation. Phospholemman is the target of a variety of post-translational modifications (including phosphorylation, palmitoylation and glutathionation) and these can dynamically alter the activity of the Na pump. This review summarizes our current understanding of the multiple regulatory mechanisms that converge on phospholemman and govern NA pump activity in the heart. The corrected Fig. 4 is reproduced below. The publisher would like to apologize for any inconvenience caused. [corrected]. PMID:23672825

Pavlovic, Davor; Fuller, William; Shattock, Michael J

2013-08-01

152

Synthesis of Na-A and/or Na-X zeolite/porous carbon composites from carbonized rice husk  

SciTech Connect

Na-A and/or Na-X zeolite/porous carbon composites were prepared under hydrothermal conditions by NaOH dissolution of silica first from carbonized rice husk followed by addition of NaAlO{sub 2} and in situ crystallization of zeolites i.e., using a two-step process. When a one-step process was used, both Na-A and Na-X zeolites crystallized on the surface of carbon. Na-A or Na-X zeolite crystals were prepared on the porous carbonized rice husk at 90 deg. C for 2-6 h by changing the SiO{sub 2}/Al{sub 2}O{sub 3}, H{sub 2}O/Na{sub 2}O and Na{sub 2}O/SiO{sub 2} molar ratios of precursors in the two-step process. The surface area and NH{sub 4}{sup +}-cation exchange capacity (CEC) of Na-A zeolite/porous carbon were found to be 171 m{sup 2}/g and 506 meq/100 g, respectively, while those of Na-X zeolite/porous carbon composites were 676 m{sup 2}/g and 317 meq/100 g, respectively. Na-A and Na-X zeolites are well-known microporous and hydrophilic materials while carbonized rice husk was found to be mesoporous (pores of {approx}3.9 nm) and hydrophobic. These hybrid microporous-mesoporous and hydrophilic-hydrophobic composites are expected to be useful for decontamination of metal cations as well as organic contaminants simultaneously. - Graphical Abstract: Novel Na-X zeolite/porous carbon composite.

Katsuki, Hiroaki [Saga Ceramics Research Laboratory, 3037-7, Arita-machi, Saga 844-0022 (Japan); Komarneni, Sridhar, E-mail: Komarneni@psu.ed [Materials Research Institute and Department of Crop and Soil Sciences, 205 Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802 (United States)

2009-07-15

153

REFLUXO GASTROESOFÁGICO NO PACIENTE ENCEFALOPATA GASTROESOPHAGEAL REFLUX IN THE NEUROLOGICALLY IMPAIRED PATIENT  

Microsoft Academic Search

O estudo da doença do refluxo gastroesofágico (DRGE) é cercado de controvérsia na criança, principal- mente devido às dificuldades para diferenciar doença e imaturidade. O refluxo de conteúdo gástrico ao esôfago em menores de quatro meses de idade é fisiológico, cau- sado por imaturidade e não por disfunção patológica do mecanismo de contenção da junção esofagogástrica (JEG)1, o que não

Lisieux Eyer de Jesus

154

Forefront of Na+/Ca2+ exchanger studies: regulation kinetics of Na+/Ca2+ exchangers.  

PubMed

Five isoforms of Na+/Ca2+ exchanger have been identified: NCX1, NCX2, NCX3, NCX-SQ1, and CALX. In all of the exchangers, the Na+/Ca2+ exchange current, which was recorded in inside-out membrane patches, was regulated by cytoplasmic Ca2+. However, the mode of regulation is different among the exchangers. NCX1, NCX2, and NCX-SQ1 are positively regulated by cytoplasmic Ca2+, but CALX is negatively regulated. NCX3 apparently has both positive and negative regulation mechanisms. In this review, I briefly summarize the Ca2+ -dependent regulation mechanisms of the exchangers. PMID:15351790

Matsuoka, Satoshi

2004-09-01

155

Structure and optic response of the Na9+ and Na55+ clusters  

NASA Astrophysics Data System (ADS)

We present the ionic geometries of Na9+ and Na55+ clusters obtained in the ``cylindrically averaged pseudopotential scheme''. Our structures are tested by calculating photoabsorption spectra and comparing them to the experimentally measured ones. We employ a local pseudopotential that has been constructed to reproduce atomic and bulk properties of sodium. Comparing the results using different pseudopotentials, we find that the position of the dipole resonance is greatly influenced by details of the pseudopotentials, showing that these must be used consistently both in the geometry optimization and the calculation of the optic response.

Kümmel, S.; Reinhard, P.-G.; Brack, M.

156

Design and implementation of the NaI(Tl)/CsI(Na) detectors output signal generator  

NASA Astrophysics Data System (ADS)

We designed and implemented a signal generator that can simulate the output of the NaI(Tl)/CsI(Na) detectors' pre-amplifier onboard the Hard X-ray Modulation Telescope (HXMT). Using the development of the FPGA (Field Programmable Gate Array) with VHDL language and adding a random constituent, we have finally produced the double exponential random pulse signal generator. The statistical distribution of the signal amplitude is programmable. The occurrence time intervals of the adjacent signals contain negative exponential distribution statistically.

Zhou, Xu; Liu, Cong-Zhan; Zhao, Jian-Ling; Zhang, Fei; Zhang, Yi-Fei; Li, Zheng-Wei; Zhang, Shuo; Li, Xu-Fang; Lu, Xue-Feng; Xu, Zhen-Ling; Lu, Fang-Jun

2014-02-01

157

Na? transport in the normal and failing heart - remember the balance.  

PubMed

In the heart, intracellular Na(+) concentration ([Na(+)]i) is a key modulator of Ca(2+) cycling, contractility and cardiac myocyte metabolism. Several Na(+) transporters are electrogenic, thus they both contribute to shaping the cardiac action potential and at the same time are affected by it. [Na(+)]i is controlled by the balance between Na(+) influx through various pathways, including the Na(+)/Ca(2+) exchanger and Na(+) channels, and Na(+) extrusion via the Na(+)/K(+)-ATPase. [Na(+)]i is elevated in HF due to a combination of increased entry through Na(+) channels and/or Na(+)/H(+) exchanger and reduced activity of the Na(+)/K(+)-ATPase. Here we review the major Na(+) transport pathways in cardiac myocytes and how they participate in regulating [Na(+)]i in normal and failing hearts. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes." PMID:23608603

Despa, Sanda; Bers, Donald M

2013-08-01

158

Vibrational satellite of Na(3d ? 3s) dipole-forbidden transition in Na/CF 4 mixture  

NASA Astrophysics Data System (ADS)

Excitation spectra of Na fluorescence in mixtures with CF 4 display a new band shifted by the energy of one-vibrational quantum of the IR active ?3-mode of CF 4 (1281 cm -1) from Na 3d states. This band is attributed to a Na(3s)⋯CF 4( ?3 = 0) ? Na(3d)⋯CF 4( ?3 = 1) transition and its intensity is explained by coupling with Na(4p)⋯CF 4( v3 = 0) resonance state which lies ˜ 180 cm -1 below in energy. An analogous satellite of the Na 6p state combined with the same vibration and lying close to the Na 7p state is reported and discussed.

Alekseev, Vadim A.; Schwentner, Nikolaus

2008-09-01

159

Minimizing Load Effects on NA4 Gear Vibration Diagnostic Parameter  

NASA Technical Reports Server (NTRS)

NA4 is a vibration diagnostic parameter, developed by researchers at NASA Glenn Research Center, for health monitoring of gears in helicopter transmissions. The NA4 reacts to the onset of gear pitting damage and continues to react to the damage as it spreads. This research also indicates NA4 reacts similarly to load variations. The sensitivity of NA4 to load changes will substantially affect its performance on a helicopter gearbox that experiences continuously changing load throughout its flight regimes. The parameter NA4 has been used to monitor gear fatigue tests at constant load. At constant load, NA4 effectively detects the onset of pitting damage and tracks damage severity. Previous research also shows that NA4 reacts to changes in load applied to the gears in the same way it reacts to the onset of pitting damage. The method used to calculate NA4 was modified to minimize these load effects. The modified NA4 parameter was applied to four sets of experimental data. Results indicate the modified NA4 is no longer sensitive to load changes, but remains sensitive to pitting damage.

Dempsey, Paula J.; Zakrajsek, James J.

2001-01-01

160

Direct interaction of Na-azide with the KATP channel  

PubMed Central

The effects of the metabolic inhibitor sodium azide were tested on excised macropatches from Xenopus oocytes expressing cloned ATP-sensitive potassium (KATP) channels of the Kir6.2/SUR1 type.In inside-out patches from oocytes expressing Kir6.2?C36 (a truncated form of Kir6.2 that expresses in the absence of SUR), intracellular Na-azide inhibited macroscopic currents with an IC50 of 11?mM. The inhibitory effect of Na-azide was mimicked by the same concentration of NaCl, but not by sucrose.Na-azide and NaCl blocked Kir6.2/SUR1 currents with IC50 of 36?mM and 19?mM, respectively. Inhibition was abolished in the absence of intracellular Mg2+. In contrast, Kir6.2?C36 currents were inhibited by Na-azide both in the presence or absence of intracellular Mg2+.Kir6.2/SUR1 currents were less sensitive to 3?mM Na-azide in the presence of MgATP. This apparent reduction in sensitivity is caused by a small activatory effect of Na-azide conferred by SUR.We conclude that, in addition to its well-established inhibitory effect on cellular metabolism, which leads to activation of KATP channels in intact cells, intracellular Na-azide has direct effects on the KATP channel. Inhibition is intrinsic to Kir6.2, is mediated by Na+, and is modulated by SUR. There is also a small, ATP-dependent, stimulatory effect of Na-azide mediated by the SUR subunit. The direct effects of 3?mM Na-azide on KATP channels are negligible in comparison to the metabolic activation produced by the same Na-azide concentration.

Trapp, Stefan; Ashcroft, Frances M

2000-01-01

161

Theoretical calculation of low-lying states of NaAr and NaXe  

NASA Technical Reports Server (NTRS)

Potential curves as well as dipole moments and linking transition moments are calculated for the ground X 2 Sigma + and low lying excited A 2 Pi, B 2 Sigma +, C 2 Sigma +, (4) 2 Sigma +, (2) 2 Pi and (1) 2 Delta states of NaAr and NaXe. Calculations are performed using a self-consistent field plus configuration-interaction procedure with the core electrons replaced by an ab initio effective core potential. The potential curves obtained are found to be considerably less repulsive than the semiempirical curves of Pascale and Vandeplanque (1974) and to agree well with existing experimental data, although the binding energies of those states having potential minima due to van der Waals interactions are underestimated. Emission bands are also calculated for the X 2 Sigma + - C 2 Sigma + excimer transitions of NaAr and NaXe using the calculated transition moments and potential curves, and shown to agree well with experiment on the short-wavelength side of the maximum.

Laskowski, B. C.; Langhoff, S. R.; Stallcop, J. R.

1981-01-01

162

The Use of VLF Phase Measurements to Associate Increased Particle Precipitation in the Region of the Brazilian Magnetic Anomaly with Magnetic Storms Aumento DA Precipitacao de Particulas NA Regiao DA Anomalia Magnetica Brasilerira, Associado a Tempestades Magneticas Atraves de Medidas de Fase Em VLF.  

National Technical Information Service (NTIS)

Phase recordings at Atibaia, Brazil, (23 deg S, 46 deg W) of 13.6 KHz VLF signal transmitted from Golfo Nuevo, Argentina (43 deg S, 65 deg W), a trajectory confined almost completely within the South Atlantic anomaly region, show significant perturbations...

M. A. Abdu I. S. Batista L. R. Piazza O. Massambani

1982-01-01

163

Interaction of NaCl/g/ and HCl/g/ with condensed Na2SO4. [in hot corrosion processes  

NASA Technical Reports Server (NTRS)

Na2SO4(l)-NaCl(g) interactions were studied at a total pressure of one atmosphere of air or oxygen for various temperatures of Na2SO4(l) and for various partial pressures of NaCl(g) and H2O(g). Mass spectrometric sampling techniques were used to identify and monitor gas phase species. Continuous recording thermomicrogravimetric measurements were conducted to determine condensed phase weight change rates. Experimental measurements were supplemented with thermodynamic calculations. Numerous experiments were performed at sample temperatures of 900 and 1000 C with 300 ppm NaCl(g). In these experiments, the reproducibility of the Na2SO4 vaporization weight loss rate and initial weight gain upon addition of NaCl(g) were found to be satisfactory. It was found that the addition of NaCl(g) to air flowing over Na2SO4(l) at 900 and 1000 C enhances the rate of weight loss of the Na2SO4(l). This enhancement increases when H2O(g) is also added to the air flow.

Stearns, C. A.; Kohl, F. J.; Fryburg, G. C.; Miller, R. A.

1977-01-01

164

The electronic structures of crystalline and aqueous solutions of NaBr and NaBrO3 using in-situ Na K and Br L edge x-ray absorption spectroscopy  

Microsoft Academic Search

The electronic structures of crystalline and aqueous solutions of NaBr and NaBrO3 were studied using in-situ Na K and Br L edge x-ray absorption spectra measured under ambient conditions. Analyses of Na K-edge x-ray absorption spectra show that NaBr and NaBrO3 strongly dissociate in aqueous solution and form Na+ hydration structures, [Na(H2O)n]+ (n = 0–6). However, the size of the

S Matsuo; P Nachimuthu; D W Lindle; R C C Perera; H Wakita

2005-01-01

165

The transported entropy of Na+ in solid state cryolite  

NASA Astrophysics Data System (ADS)

The transported entropy of Na+ in mixtures of NaF (s) and Na3AlF6 (s) is determined from thermocell experiments. The experiments were favorably described by the electric work method. The variation observed in the thermocell electromotive force (emf) with composition can be explained from the probable path of charge transfer in the electrolyte. The transported entropies are S*cry Na+ = 140 ± 7 J K-1 mol-1 for cryolite and S*NaFNa+ = 81 ± 8 J K-1 mol-1 for sodium fluoride between 380 °C and 500 °C. The value obtained for sodium in the solid cryolite makes us predict that the transported entropy for Na+ in the molten electrolyte mixture for aluminum production is substantial and that the reversible heat effects in the aluminum electrolysis cell are the same.

Sharivker, V. S.; Ratkje, S. Kjelstrup

1996-10-01

166

Electrical Resistivity of Liquid Alkali Na-based Binary Alloys  

NASA Astrophysics Data System (ADS)

The study of the electrical resistivity rL of alkali Na-based binary alloys Na1-xLix, Na1-xKx, Na1-xRbx and Na1-xCsx have been made by well-recognized model potential of Gajjar et al. The most recent exchange and correlation functions due to Farid et al (F) and Sarkar et al (S) are used for the first time in the study of electrical resistivity of liquid binary mixtures and found suitable for such study. The results, due to the inclusion of Sarkar et al's local field correction function, are found superior to those obtained due to Farid et al's local field correction function. Electrical resistivity of Na-based binary alloys compare well with the experimental data available in the literature.

Vora, Aditya M.

2007-11-01

167

Pyrophosphate-Fueled Na+ and H+ Transport in Prokaryotes  

PubMed Central

SUMMARY In its early history, life appeared to depend on pyrophosphate rather than ATP as the source of energy. Ancient membrane pyrophosphatases that couple pyrophosphate hydrolysis to active H+ transport across biological membranes (H+-pyrophosphatases) have long been known in prokaryotes, plants, and protists. Recent studies have identified two evolutionarily related and widespread prokaryotic relics that can pump Na+ (Na+-pyrophosphatase) or both Na+ and H+ (Na+,H+-pyrophosphatase). Both these transporters require Na+ for pyrophosphate hydrolysis and are further activated by K+. The determination of the three-dimensional structures of H+- and Na+-pyrophosphatases has been another recent breakthrough in the studies of these cation pumps. Structural and functional studies have highlighted the major determinants of the cation specificities of membrane pyrophosphatases and their potential use in constructing transgenic stress-resistant organisms.

Malinen, Anssi M.; Luoto, Heidi H.

2013-01-01

168

Scheelite-type NaDy(WO4)2  

PubMed Central

The title compound sodium dysprosium(III) bis­[tungs­tate(VI)], NaDy(WO4)2, has been synthesized under high temperature solution growth (HTSG) conditions in air. The compound crystallizes with the scheelite structure and is composed of isolated WO4 tetra­hedra ( symmetry) with one set of bond lengths and distorted [(Na/Dy)O8] dodeca­hedra ( symmetry; occupancy ratio Na:Dy = 1:1) with two sets of bond lengths.

Zhao, Dan; Li, Feifei; Cheng, Wendan; Zhang, Hao

2010-01-01

169

Magnesium correction to the NaKCa chemical geothermometer  

USGS Publications Warehouse

Equations and graphs have been devised to correct for the adverse effects of magnesium upon the Na-K-Ca chemical geothermometer. Either the equations or graphs can be used to determine appropriate temperature corrections for given waters with calculated NaKCa temperatures > 70??C and R 50 are probably derived from relatively cool aquifers with temperatures approximately equal to the measured spring temperature, irrespective of much higher calculated Na-K-Ca temperatures. ?? 1979.

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

1979-01-01

170

Simulation of Na D emission near Europa during eclipse  

USGS Publications Warehouse

The Cassini imaging science subsystem observed Europa in eclipse during Cassini's Jupiter flyby. The disk-resolved observations revealed a spatially nonuniform emission in the wavelength range of 200-1050 nm (clear filters). By building on observations and simulations of Europa's Na atmosphere and torus we find that electron-excited Na in Europa's tenuous atmosphere can account for the observed emission if the Na is ejected preferentially from Europa's dark terrain. Copyright 2008 by the American Geophysical Union.

Cassidy, T. A.; Johnson, R. E.; Geissler, P. E.; Leblanc, F.

2008-01-01

171

Sodium superionic conduction in Na2B12H12.  

PubMed

Impedance measurements indicate that Na2B12H12 exhibits dramatic Na(+) conductivity (on the order of 0.1 S cm(-1)) above its order-disorder phase-transition at ?529 K, rivaling that of current, solid-state, ceramic-based, Na-battery electrolytes. Superionicity may be aided by the large size, quasispherical shape, and high rotational mobility of the B12H12(2-) anions. PMID:24584582

Udovic, Terrence J; Matsuo, Motoaki; Unemoto, Atsushi; Verdal, Nina; Stavila, Vitalie; Skripov, Alexander V; Rush, John J; Takamura, Hitoshi; Orimo, Shin-ichi

2014-04-11

172

Scheelite-type NaDy(WO(4))(2).  

PubMed

The title compound sodium dysprosium(III) bis-[tungs-tate(VI)], NaDy(WO(4))(2), has been synthesized under high temperature solution growth (HTSG) conditions in air. The compound crystallizes with the scheelite structure and is composed of isolated WO(4) tetra-hedra ( symmetry) with one set of bond lengths and distorted [(Na/Dy)O(8)] dodeca-hedra ( symmetry; occupancy ratio Na:Dy = 1:1) with two sets of bond lengths. PMID:21579906

Zhao, Dan; Li, Feifei; Cheng, Wendan; Zhang, Hao

2009-01-01

173

Mutant N143P Reveals How Na+ Activates Thrombin*  

PubMed Central

The molecular mechanism of thrombin activation by Na+ remains elusive. Its kinetic formulation requires extension of the classical Botts-Morales theory for the action of a modifier on an enzyme to correctly account for the contribution of the E*, E, and E:Na+ forms. The extended scheme establishes that analysis of kcat unequivocally identifies allosteric transduction of Na+ binding into enhanced catalytic activity. The thrombin mutant N143P features no Na+-dependent enhancement of kcat yet binds Na+ with an affinity comparable to that of wild type. Crystal structures of the mutant in the presence and absence of Na+ confirm that Pro143 abrogates the important H-bond between the backbone N atom of residue 143 and the carbonyl O atom of Glu192, which in turn controls the orientation of the Glu192-Gly193 peptide bond and the correct architecture of the oxyanion hole. We conclude that Na+ activates thrombin by securing the correct orientation of the Glu192-Gly193 peptide bond, which is likely flipped in the absence of cation. Absolute conservation of the 143–192 H-bond in trypsin-like proteases and the importance of the oxyanion hole in protease function suggest that this mechanism of Na+ activation is present in all Na+-activated trypsin-like proteases.

Niu, Weiling; Chen, Zhiwei; Bush-Pelc, Leslie A.; Bah, Alaji; Gandhi, Prafull S.; Di Cera, Enrico

2009-01-01

174

Topology of the type IIa Na+/P(i) cotransporter.  

PubMed

The type IIa Na(+)/P(i) cotransporter (NaPi-IIa) plays a key role in the reabsorption of inorganic phosphate (P(i)) in the renal proximal tubule. The rat NaPi-IIa isoform is a protein of 637 residues for which different algorithms predict 8-12 transmembrane domains (TMDs). Epitope tagging experiments demonstrated that both the N and the C termini of NaPi-IIa are located intracellularly. Site-directed mutagenesis revealed two N-glycosylation sites in a large putative extracellular loop. Results from structure-function studies suggested the assembly of two similar opposed regions that possibly constitute part of the substrate translocation pathway for one phosphate ion together with three sodium ions. Apart from these topological aspects, other structural features of NaPi-IIa are not known. In this study, we have addressed the topology of NaPi-IIa using in vitro transcription/translation of HK-M0 and HK-M1 fusion vectors designed to test membrane insertion properties of cDNA sequences encoding putative NaPi-IIa TMDs. Based on the results of in vitro transcription/translation analyses, we propose a model of NaPi-IIa comprising 12 TMDs, with both N and C termini orientated intracellularly and a large hydrophilic extracellular loop between the fifth and sixth TMDs. The proposed model is in good agreement with the prediction of the NaPi-IIa structure obtained by the hidden Markov algorithm HMMTOP. PMID:17206517

Radanovic, Tamara; Gisler, Serge M; Biber, Jürg; Murer, Heini

2006-01-01

175

Angular distributions of photoelectrons from free Na clusters  

NASA Astrophysics Data System (ADS)

We explore, from a theoretical perspective, photoelectron angular distributions (PADs) of the Na clusters Na8, Na10, Na12, Na18, Na3+, Na11+, Na13+, and Na19+. The basis of the description is the time-dependent local-density approximation (TDLDA), augmented by a self-interaction correction (SIC) to describe ionization properties correctly. The scheme is solved on a numerical grid in coordinate space with absorbing bounds. We assume for each cluster system an isotropic ensemble of free clusters and develop for the case of one-photon emission analytical formulas for computing the orientation-averaged PAD on the basis of a few TDLDA-SIC calculations for properly chosen reference orientations. It turns out that all the information in the averaged PAD is contained in one anisotropy parameter. We find that this parameter varies very little with system size, but as a whole is crucially influenced by the detailed ionic structure. We also make comparisons with direct orientation averaging and consider one example reaching outside the perturbative regime.

Wopperer, P.; Faber, B.; Dinh, P. M.; Reinhard, P.-G.; Suraud, E.

2010-12-01

176

Questões mais freqüentes na área de astronomia  

NASA Astrophysics Data System (ADS)

É amplamente reconhecido que as pessoas em geral têm grande fascínio e interesse pela Astronomia. Por outro lado, o conteúdo dessa área incluído no ensino formal está longe de ser abrangente e suficiente para suprir a demanda. Esse interesse permite otimizar a divulgação e o ensino não formal de Astronomia aliando a adequação do conteúdo à expectativa das pessoas. Nesse intuito, nosso trabalho busca mapear que assuntos da Astronomia despertam mais a atenção e o interesse das pessoas e o quanto disso é estimulado pela mídia, que freqüentemente aproveita-se desse interesse de forma sensacionalista, trazendo contribuições positivas e negativas. Para esta avaliação, utilizamos as pesquisas específicas e de caracterização do público que freqüentou o MAst nos anos de 2001 a 2003, pesquisa das matérias de Astronomia veiculadas na mídia escrita da cidade do Rio de Janeiro no mesmo período, além da base de dados do programa Pergunte a um astrônomo, realizado no Observatório Nacional nos anos de 1997 a 1999. Para a análise dos dados, dividimos as perguntas em dez categorias, cada uma com suas subcategorias, tomando como referência as divisões, comissões e grupos de trabalho da IAU. Apresentamos neste trabalho os resultados dessa pesquisa, que incluem, entre outros, a predominância de questões nas categorias Observação do Céu e Sistemas Planetários enquanto nos jornais dominam as notícias de Sistemas Planetários e Espaço & Astronáutica. Outro resultado interessante indicou que as dúvidas de crianças do ensino fundamental se concentram em algumas categorias enquanto as questões de adultos são mais distribuídas por todas as categorias. Os resultados dessa pesquisa serão aplicados diretamente no aperfeiçoamento das atividades do Programa de Observação de Céu, bem como na elaboração de novos projetos e eventos realizados no MAst.

Segundo, H. A. S.; Garcia, G. C.; Caretta, C. A.; Lima, F. P.

2003-08-01

177

Mercury's Na Exosphere from MESSENGER Data  

NASA Technical Reports Server (NTRS)

MESSENGER entered orbit about Mercury on March 18, 2011. Since then, the Ultraviolet and Visible Spectrometer (UWS) channel of MESSENGER's Mercury Atmospheric and Surface Composition Spectrometer (MASCS) has been observing Mercury's exosphere nearly continuously. Daily measurements of Na brightness were fitted with non-uniform exospheric models. With Monte Carlo sampling we traced the trajectories of a representative number of test particles, generally one million per run per source process, until photoionization, escape from the gravitational well, or permanent sticking at the surface removed the atom from the simulation. Atoms were assumed to partially thermally accommodate on each encounter with the surface with accommodation coefficient 0.25. Runs for different assumed source processes are run separately, scaled and co-added. Once these model results were saved onto a 3D grid, we ran lines of sight from the MESSENGER spacecraft :0 infinity using the SPICE kernels and we computed brightness integrals. Note that only particles that contribute to the measurement can be constrained with our method. Atoms and molecules produced on the nightside must escape the shadow in order to scatter light if the excitation process is resonant-light scattering, as assumed here. The aggregate distribution of Na atoms fits a 1200 K gas, with a PSD distribution, along with a hotter component. Our models constrain the hot component, assumed to be impact vaporization, to be emitted with a 2500 K Maxwellian. Most orbits show a dawnside enhancement in the hot component broadly spread over the leading hemisphere. However, on some dates there is no dawn/dusk asymmetry. The portion of the hot/cold source appears to be highly variable.

Killen, Rosemary M.; Burger, M. H.; Cassidy, T. A.; Sarantos, M.; Vervack, R. J.; McClintock, W. El; Merkel, A. W.; Sprague, A. L.; Solomon, S. C.

2012-01-01

178

Electrode potential studies of liquid-solid equilibrium in Na{sub 3}Bi-saturated Na-Bi melts  

SciTech Connect

Liquid binary Na-Bi alloys have been studied extensively because of the interest in possible uses as electrochemically active couples in regenerative electrochemical cells, in high-energy batteries, and as potential heat-transfer media in nuclear reaction processes. Techniques used previously for thermodynamic measurements on the system have included the transpiration method, quasi-static and boiling point methods, the electromotive force (emf) method using molten salt mixtures and various solid electrolytes, and thermal analysis. Most of the thermodynamic data on Bi-Na alloys were recently assessed by Sangster and Pelton. However, no experimental thermodynamic data for liquid-solid equilibrium in liquid Na-Bi alloys saturated with solid Na{sub 3}Bi have been reported in the literature. The aim of the present work was to investigate experimentally the equilibrium between Na-Bi melts and solid Na{sub 3}Bi by the emf method in the range 638 to 973 K.

Yan, X.Y.; Langberg, D.E.; Rankin, W.J.

2000-04-01

179

Conductance and gating of epithelial Na channels from rat cortical collecting tubule. Effects of luminal Na and Li  

Microsoft Academic Search

The behavior of individual Na channels in the apical membrane of the rat cortical collecting tubule (CCT) was studied at different concentrations of the permeant ions Na and Li. Tubules were opened to expose their luminal sur- faces and bathed in K-gluconate medium to minimize tubule-to-tubule variation in cell membrane potential and intracellular Na concentration. The patch-clamp technique was used

LAWRENCE G. PALMER; GUSTAVO FRINDT

1988-01-01

180

Comparacao dos resultados obtidos com os codigos RELAP4/MOD3 e RELAP4/MOD5 na simulacao da fase de despressurizacao do acidente de perda de refrigerante primario na usina nuclear de Angra-1. (Comparison of the RELAP4/MOD3 and RELAP4/MOD5 results to the loss-of-coolant accident blowdown phase simulation on the Angra-1 nuclear power station).  

National Technical Information Service (NTIS)

It's very important to obtain information of certain thermalhydraulic parameters of the Angra 1 Nuclear Power Plant during a large LOCA in three different points: in the cold leg, in the hot leg and between the steam generator and the pump. In this way, t...

G. Sabundjian T. Neves Conti

1991-01-01

181

The substrate recognition domain in the Na +\\/dicarboxylate and Na +\\/sulfate cotransporters is located in the carboxy-terminal portion of the protein  

Microsoft Academic Search

The Na+\\/dicarboxylate cotransporter, NaDC-1, and the Na+\\/sulfate cotransporter, NaSi-1, share 43% sequence identity, but they exhibit no overlap in substrate specificity. A functional chimera, SiDC-4, was prepared from NaDC-1 and NaSi-1 by homologous recombination and expressed in Xenopus oocytes. SiDC-4 contains putative transmembrane domains 1–4 of NaSi-1 (amino acids 1–139) and putative transmembrane domains 5–11 of NaDC-1 (amino acids 141–593).

Ana M Pajor; Ning Sun; Liqun Bai; Daniel Markovich; Patricia Sule

1998-01-01

182

Estimating the hydrogen ion concentration in concentrated NaCl and Na{sub 2}SO{sub 4} electrolytes  

SciTech Connect

Combination glass electrodes were tested for determining H{sup +} concentrations in concentrated pure and mixed NaCl and Na{sub 2}SO{sub 4} solutions, as well as natural brine systems. NaCl, Na{sub 2}SO{sub 4}, and mixtures of NaCl and Na{sub 2}SO{sub 4} solutions were analyzed. Correction factors for estimating pC{sub H}{sup +} (negative logarithm of H{sup +} concentration) were determined from measured/observed pH values. Required Gran-type titrations were done with HCl and/or NaOH. The titration method is described and a step-by-step procedure provided; it has been used previously for determining pC{sub H}{sup +} values of synthetic chloride-dominated brines. Precautions are required to determine correction factors for electrolytes that react with H{sup +} or OH{sup {minus}} [sulfate brines for titration with acid; magnesium brines for titration with base because of precipitation of Mg(OH)2]. Correction factors A (pC{sub H}{sup +} = pH{sub ob} + A) from HCl titrations were similar to those from NaOH titrations where the concentration of free H{sup +} was calculated using a thermodynamic model. These values should be applicable to solns with a very large range in measured pH values (2 to 12). Because a large number of solns were titrated with HCl and the A values are similar for HCl and NaOH titrations, the A values for NaCl and Na2SO4 solns were fit as a function of molality to allow extrapolation. For NaCl solns 0 to 6.0 M, A can be obtained by multiplying the molality by 0.159. For Na2SO4 solns 0 to 2.0 M, the values of A can be obtained from (0.221 {minus} 0.549X + 0.201X{sup 2}), where X is the molality of Na{sub 2}SO{sub 4}. Orion-Ross electrode evaluations indicated that the A values did not differ significantly for different electrodes. Results suggest that the data in this report can be used to estimate A values for different NaCl and Na{sub 2}SO{sub 4} solns even for noncalibrated electrodes.

Rai, D.; Felmy, A.R.; Juracich, S.P.; Rao, F. [Pacific Northwest Lab., Richland, WA (United States)

1995-06-01

183

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

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

184

?-Opioid receptors protect from anoxic disruption of Na + homeostasis via Na + channel regulation  

Microsoft Academic Search

Hypoxic\\/ischemic disruption of ionic homeostasis is a critical trigger of neuronal injury\\/death in the brain. There is, however,\\u000a no promising strategy against such pathophysiologic change to protect the brain from hypoxic\\/ischemic injury. Here, we present\\u000a a novel finding that activation of ?-opioid receptors (DOR) reduced anoxic Na+ influx in the mouse cortex, which was completely blocked by DOR antagonism with

Xuezhi Kang; Dongman Chao; Quanbao Gu; Guanghong Ding; Yingwei Wang; Gianfranco Balboni; Lawrence H. Lazarus; Ying Xia

2009-01-01

185

A Putative Multisubunit Na+/H+ Antiporter from Staphylococcus aureus  

PubMed Central

We cloned several genes encoding an Na+/H+ antiporter of Staphylococcus aureus from chromosomal DNA by using an Escherichia coli mutant, lacking all of the major Na+/H+ antiporters, as the host. E. coli cells harboring plasmids for the cloned genes were able to grow in medium containing 0.2 M NaCl (or 10 mM LiCl). Host cells without the plasmids were unable to grow under the same conditions. Na+/H+ antiport activity was detected in membrane vesicles prepared from transformants. We determined the nucleotide sequence of the cloned 7-kbp region. We found that seven open reading frames (ORFs) were necessary for antiporter function. A promoter-like sequence was found in the upstream region from the first ORF. One inverted repeat followed by a T-cluster, which may function as a terminator, was found in the downstream region from the seventh ORF. Neither terminator-like nor promoter-like sequences were found between the ORFs. Thus, it seems that the seven ORFs comprise an operon and that the Na+/H+ antiporter consists of seven kinds of subunits, suggesting that this is a novel type of multisubunit Na+/H+ antiporter. Hydropathy analysis of the deduced amino acid sequences of the seven ORFs suggested that all of the proteins are hydrophobic. As a result of a homology search, we found that components of the respiratory chain showed sequence similarity with putative subunits of the Na+/H+ antiporter. We observed a large Na+ extrusion activity, driven by respiration in E. coli cells harboring the plasmid carrying the genes. The Na+ extrusion was sensitive to an H+ conductor, supporting the idea that the system is not a respiratory Na+ pump but an Na+/H+ antiporter. Introduction of the plasmid into E. coli mutant cells, which were unable to grow under alkaline conditions, enabled the cells to grow under such conditions.

Hiramatsu, Toshiaki; Kodama, Kazuyo; Kuroda, Teruo; Mizushima, Tohru; Tsuchiya, Tomofusa

1998-01-01

186

Electrical conductivity and dielectric properties of polypyrrole/Na+-montmorillonite (PPy/Na+-MMT) clay nanocomposites  

NASA Astrophysics Data System (ADS)

Frequency dependent ac conductivity (?ac), dielectric constant (?') and loss factor (?'') have been measured in the frequency range 100-106 Hz in polypyrrole/Na+-montmorillonite (PPy/Na+-MMT) clay nanocomposites. The nanocomposites were synthesized by in situ polymerization of pyrrole with varying amounts of Na+-MMT from 0.2 to 1.0 wt% in the presence of FeCl3 · 6H2O in an aqueous medium. All three measured quantities; ?ac, ?' and ?'' increased with the increase in MMT content in the composites at all frequencies. The frequency dependence of ?ac displayed a low frequency region of almost constant conductivity below 104 Hz, while above this frequency a rapid rise in ?ac was observed with the increase in frequency obeying a power law of frequency dependence with an exponent equal to 1. Both real and imaginary parts of the permittivity exhibited a low frequency dispersion which has been attributed to hopping of polarons and bipolarons in PPy and its composites.

Rizvi, Tasneem Zahra; Shakoor, Abdul

2009-05-01

187

H + , Na + , K + , and Amino Acid Transport in Caterpillar and Larval Mosquito Alimentary Canal  

Microsoft Academic Search

\\u000a Two principal strategies are used to energize membranes in living organisms, a Na+ strategy and a voltage strategy. In the Na+ strategy a primary Na+\\/K+ ATPase imposes both Na+ and K+ concentration gradients across cell membranes with Na+ high outside and K+ high inside the cells. The Na+ gradient, ?[Na+] is used to drive diverse secondary transporters. For example, in

William R. Harvey; Bernard A. Okech

188

Tensile Properties of NaCl-BaNr Solid Solution Single Crystals  

Microsoft Academic Search

Single crystals of NaCl-NaBr alloys to 10-mole % NaBr were tested in tension. Crystals to 1-mole % NaBr were ductile but no ductility was observed with 5- and 10-mole % NaBr crystals. Addition of 0.5-mole % NaBr appeared to cause softening, perhaps due to a scavenging effect. Microhardness showed a continuous increase with NaBr to 10 mole %, perhaps due

F. T. Wimmer; W. Kobes; M. E. Fine

1963-01-01

189

Epithelial Na+ Channel Regulation by Cytoplasmic and Extracellular Factors  

PubMed Central

Electrogenic Na+ transport across high resistance epithelial is mediated by the epithelial Na+ channel (ENaC). Our understanding of the mechanisms of ENaC regulation has continued to evolve over the two decades following the cloning of ENaC subunits. This review highlights many of the cellular and extracellular factors that regulate channel trafficking or gating.

Kashlan, Ossama B.; Kleyman, Thomas R.

2013-01-01

190

On the dynamic influence of Na+ in Mercury's magnetotail  

NASA Astrophysics Data System (ADS)

Although initially ionized at low (<10 eV) energies in Mercury's dayside magnetosphere, Na+ ions can become energized via non-adiabatic motion in the plasma sheet to energies as high as several keV. Although present in sufficient abundance to contribute to both plasma pressure and mass density, the collective influence of Na+ has not yet been confirmed. Here, observations by the Fast Imaging Plasma Spectrometer and Magnetometer on the MErcury Surface Space Environment, GEochemistry, and Ranging spacecraft demonstrate that Na+ can contribute substantially to the total pressure in Mercury's plasma sheet. We identify several examples of sustained high fluxes of Na+ particle flux that are shown to contribute to the diamagnetic depressions measured in the plasma sheet. The three-dimensional distribution functions of Na+ for these events are consistent with hot, nearly isotropic Maxwell-Boltzmann distributions. The relative pressure contribution of Na+ to the total plasma sheet content at Mercury is highly asymmetric, increasing from ~1-30% from dawn to dusk. We further identify an increase in magnetic fluctuations near the Na+ gyro-frequency at the dusk-side magnetopause when the Na+ content of the plasma sheet exceeds 1/cc. These fluctuations are non-linear and highly compressive and do not appear to be the simple left-hand-polarized ion cyclotron wave mode. Instead, these waves transition from left-hand near the magnetopause to right-hand polarization deeper inside the magnetosphere, penetrating up to high latitudes.

Gershman, Daniel J.; Raines, Jim M.; Slavin, James A.; Zurbuchen, Thomas H.; Sundberg, Torbjorn; Boardsen, Scott A.; Anderson, Brian J.; Korth, Haje; Solomon, Sean C.

2014-05-01

191

Melting of sodium clusters in electron irradiated NaCl  

Microsoft Academic Search

In this paper we present the results of the first systematic investigation of the geometrical properties of sodium nanoclusters in NaCl using the combined results of differential scanning calorimetry (DSC) and atomic force microscopy (AFM). The melting behaviour of the sodium nanoclusters which had been produced in NaCl by electron beam irradiation up to a dose of 200 MGy has

A. V. Sugonyako; D. I. Vainshtein; A. A. Turkin; H. W. den Hartog; A. A. Bukharaev

2004-01-01

192

Über die Beeinflussung der Na-Resonanzstrahlung durch Edelgase  

Microsoft Academic Search

Zusammenfassung Die Resonanzfluoreszenz von Na-Dampf in Gegenwart von Zusatzgasen wird untersucht. Es war beabsichtigt, den Beweis für die Existenz der durch Stoß erzwungenen Übergänge zu erbringen. Auf Grund der Messungen konnten aber derartige Übergänge nicht nachgewiesen werden. Als neues Resultat ergab sich, daß die Edelgase keine meßbare Auslöschung der Na-Resonanzstrahlung verursachen. Die bisher beobachtete Auslöschung ist durch die starke Linienverbreiterung

L. V. Hámos

1932-01-01

193

NaK Disposal by Spray Burning. Second Progress Report.  

National Technical Information Service (NTIS)

A total of 9.3 tons from the DFR NaK inventory of 167 tons has now been burned off using the atomized spray technique completing the disposal of the thermal syphon eutectic NaK except for approximately 1 ton which is distributed in nine non self draining ...

J. Kirk

1979-01-01

194

23Na and 27Al in ?-alumina solid electrolytes  

NASA Astrophysics Data System (ADS)

In a companion paper, we discussed second-order quadrupolar effects in solids and the theory of the NMR response of a two-dimensional (2D) fluid. This paper illustrates the theoretical treatment through a consideration of the NMR response of 23Na and 27Al in ?-alumina. It is shown that dynamical information is contained in the temperature dependence of the second-order quadrupolar shifts. The stationary and fluctuating components of the electric field gradient at the Na+ position are obtained from quadrupolar shift measurements. Utilizing these parameters in a 2D-continuum diffusion model for Na+, we are able to account for a number of experimental observations: angular, frequency, and temperature dependence of 23Na transition rates, narrowing of the 23Na satellites, and temperature dependence of the spin-lattice relaxations rates for 27Al. Reasons are given for the success of this model on the NMR time scale.

Villa, Marco; Bjorkstam, John L.

1980-12-01

195

On the scintillation response of NaI(Tl)-crystals  

SciTech Connect

Several articles have been reviewed on the scintillation response of NaI(Tl). Those publications which report results obtained with radioactive sources either dispersed throughout the NaI(Tl)-lattice or located inside the wells of NaI(Tl)-crystals match within a {+-}0.9% standard deviation of a linear scintillation response between 3 MeV and 3 keV. Several authors who placed their sources outside the crystals measured nonlinear responses of NaI(Tl) with up to {+-}7% of standard deviations between 700 and 4.5 keV. The presented analysis suggests that the observed nonlinearity is not an intrinsic effect of NaI(Tl) but could be caused, at least partly, by effects occurring at the radiation entrance surfaces of the crystals.

Leutz, H.; D`Ambrosio, C. [CERN, Geneva (Switzerland)] [CERN, Geneva (Switzerland)

1997-04-01

196

LiNa5Mo9O30  

PubMed Central

The tite compound, lithium penta­sodium nona­molybdate, LiNa5Mo9O30, was synthesized by solid-state reaction. The three-dimensional [Mo9O30]6? framework is built up from MoO6 octa­hedra and MoO5 bipyramids, linked together by edges and corners. The framework delimits two types of inter­secting tunnels running along [100] and [010] in which the Na+ and Li+ ions are located. The asymmetric unit contains one Mo, one Na and one Li site located on a twofold rotation axis. The crystal studied was a racemic twin with site a twin ratio of 0.51?(10):0.49?(10). Relationships between the structures of K2Mo3O10, K2Mo4O13, Cs2Mo7O22, Na6Mo10O33 and Na6Mo11O36 compounds are discussed.

Hamza, Hamadi; Ennajeh, Ines; Zid, Mohamed Faouzi; Driss, Ahmed

2012-01-01

197

Feasibility study for a secondary Na/S battery  

NASA Technical Reports Server (NTRS)

The feasibility of a moderate temperature Na battery was studied. This battery is to operate at a temperature in the range of 100-150 C. Two kinds of cathode were investigated: (1) a soluble S cathode consisting of a solution of Na2Sn in an organic solvent and (2) an insoluble S cathode consisting of a transition metal dichalcogenide in contact with a Na(+)ion conducting electrolyte. Four amide solvents, dimethyl acetamide, diethyl acetamide, N-methyl acetamide and acetamide, were investigated as possible solvents for the soluble S cathode. Results of stability and electrochemical studies using these solvents are presented. The dialkyl substituted amides were found to be superior. Although the alcohol 1,3-cyclohexanediol was found to be stable in the presence of Na2Sn at 130 C, its Na2Sn solutions did not appear to have suitable electrochemical properties.

Abraham, K. M.; Schiff, R.; Brummer, S. B.

1979-01-01

198

The Kinetics of Ca-Na Exchange in Excitable Tissue  

PubMed Central

A model is proposed to describe the Na-Ca exchange in excitable tissues. The present scheme requires a carrier mechanism that exchanges 3Na for 1Ca across the membrane under the electrochemical gradient of Na. The carriers, assumed to be trivalent anions, have monovalent and divalent sites; Ca and Na can compete only at the second site. The partially and fully loaded carrier-ion complexes are mobile and diffusible across the membrane. Subsequently, analytical expressions for Na and Ca unidirectional flux at steady state are derived in terms of intracellular concentration (Nai and Cai) and extracellular concentration (Nao and Cao) as well as membrane potential, EM. Published experimental flux data on cardiac muscle, squid axon, and rat synaptosomes can be satisfactorily fitted with the flux equation simply by adjusting the numerical constants.

Wong, Alan Y. K.; Bassingthwaighte, James B.

2010-01-01

199

Energetics of Sin and Si_nNa clusters  

NASA Astrophysics Data System (ADS)

Nano-sized silicon (Si_n) clusters and silicon-sodium (Si_nNa) clusters are studied using ab-initio Born-Oppemheimer molecular dynamics, focusing on their structures and energetics. Our results show that both binding and ionization energies have minima for the Si_7Na cluster, which agrees with previous experimental findings ( K. Kaya et al.), Zeitschrift fur Physik D, vol.26, 201 (1993). Our effort is to understand the origin of this phenomenon. In addition we have also investigated the charge transfer from Na to Sin in Si_nNa clusters, compared with the negatively charged Si_n^- clusters. We find, contrary to common beliefs, that the electronic structures for the Si_nNa clusters do not always resemble those of the Si_n^-. Other electronic and dynamical properties of these clusters will also be presented.

Wei, Siqing; Barnett, Robert; Landman, Uzi

1996-03-01

200

The Na-K-ATPase and Calcium-Signaling Microdomains  

NSDL National Science Digital Library

The Na-K-ATPase is an energy-transducing ion pump that converts the free energy of ATP into transmembrane ion gradients. It also serves as a functional receptor for cardiotonic steroids such as ouabain and digoxin. Binding of ouabain to the Na-K-ATPase can activate calcium signaling in a cell-specific manner. The exquisite calcium modulation via the Na-K-ATPase is achieved by the ability of the pump to integrate signals from numerous protein and non-protein molecules, including ion transporters, channels, protein kinases/phosphatases, as well as cellular Na+. This review focuses on the unique properties of the Na-K-ATPase and its role in the formation of different calcium-signaling microdomains.

Jiang Tian (University of Toledo Health Science Campus Physiology and Pharmacology); Zi-jian Xie (University of Toledo Health Science Campus)

2008-08-01

201

CP Violation results from the NA48 experiments  

NASA Astrophysics Data System (ADS)

The main goal of the NA48 experiments at the CERN SPS has been the search for direct CP violation (CPV) in neutral and charged kaon decays. In this paper selected results on CPV from the NA48 and NA48/2 experiments are presented. The direct CPV parameter Re(?'/?) has been measured by NA48 from the decay rates of neutral kaons into two pions. In the charged kaon sector, NA48/2 has measured the asymmetry Ag of the linear slope parameter g in the Dalitz plot of K± ? 3? decays. Thanks to the high statistics collected in 2003 and 2004, further CPV studies were performed in several kaon decays. Results on CPV studies in K± ? ?±?0? K± ? ?±e+e- and K± ? ?±?+?- decays will be presented, as well as in the KS ? ?+?-e+e- decay.

Anzivino, Giuseppina

2011-12-01

202

Persistent human cardiac Na+ currents in stably transfected mammalian cells  

PubMed Central

Miniature persistent late Na+ currents in cardiomyocytes have been linked to arrhythmias and sudden death. The goals of this study are to establish a stable cell line expressing robust persistent cardiac Na+ currents and to test Class 1 antiarrhythmic drugs for selective action against resting and open states. After transient transfection of an inactivation-deficient human cardiac Na+ channel clone (hNav1.5-CW with L409C/A410W double mutations), transfected mammalian HEK293 cells were treated with 1 mg/ml G-418. Individual G-418-resistant colonies were isolated using glass cylinders. One colony with high expression of persistent Na+ currents was subjected to a second colony selection. Cells from this colony remained stable in expressing robust peak Na+ currents of 996 ± 173 pA/pF at +50 mV (n = 20). Persistent late Na+ currents in these cells were clearly visible during a 4-second depolarizing pulse albeit decayed slowly. This slow decay is likely due to slow inactivation of Na+ channels and could be largely eliminated by 5 ?M batrachotoxin. Peak cardiac hNav1.5-CW Na+ currents were blocked by tetrodotoxin with an IC50 value of 2.27 ± 0.08 ?M (n = 6). At clinic relevant concentrations, Class 1 antiarrhythmics are much more selective in blocking persistent late Na+ currents than their peak counterparts, with a selectivity ratio ranging from 80.6 (flecainide) to 3 (disopyramide). We conclude that (1) Class 1 antiarrhythmics differ widely in their resting- vs. open-channel selectivity, and (2) stably transfected HEK293 cells expressing large persistent hNav1.5-CW Na+ currents are suitable for studying as well as screening potent open-channel blockers.

Wang, Ging Kuo; Russell, Gabriella; Wang, Sho-Ya

2013-01-01

203

Pseudopotential spin-density functional calculation of the ground state properties of Na2 and Na2+  

Microsoft Academic Search

The potential wnergy curves for the ground states of Na2 and Na2+ are calculated within the local spin-density approximation, using model pseudopentials to simulate core effects. Our results compare very well with the experimental data and the results of much more elaborate configuration interaction calculations. We also find that at intermediate nuclear separations, where the local density approximation breaks down,

R. Car; R. A. Meuli; J. Buttet

1980-01-01

204

The major amino acid transporter superfamily has a similar core structure as Na+-galactose and Na+-leucine transporters  

Microsoft Academic Search

The sodium solute symporters (SSS) and neurotransmitter sodium symporters (NSS) are two families of secondary transporters that are not related in amino acid sequence. Nonetheless, recent crystal structures showed that the Na+\\/galactose (SSS) and Na+\\/leucine (NSS) transporters have similar core structures. The structural relatedness highlights the need for classification methods for membrane protein structures based on other criteria than amino

Juke S. Lolkema; Dirk-Jan Slotboom

2008-01-01

205

Local structure of Ca(sub N)a pyroxenes. I. XANES study at the Na K-edge.  

National Technical Information Service (NTIS)

X-ray absorption Na K-edge spectra have been recorded on synthetic end member jadeite and on a series of natural Ca-Na pyroxenes compositionally straddling the Jd-Di. The disordered C2/c members of the series are systematically different from the ordered ...

A. Mottana T. Murata Z. Wu A. Marcelli E. Paris

1996-01-01

206

Equations of state for solid NaCl-KCl and liquid NaCl-KCl-H(sub 2)O.  

National Technical Information Service (NTIS)

The equilibrium between the solid solution of NaCl-KCl and the ternary liquid NaCl-KCl-H(sub 2)O is both scientifically interesting and geologically important. Equations of the Margules type have been derived for the two phases that accurately reproduce t...

K. S. Pitzer S. M. Sterner

1991-01-01

207

Genome Sequences of Cupriavidus metallidurans Strains NA1, NA4, and NE12, Isolated from Space Equipment.  

PubMed

Cupriavidus metallidurans NA1, NA4, and NE12 were isolated from space and spacecraft-associated environments. Here, we report their draft genome sequences with the aim of gaining insight into their potential to adapt to these environments. PMID:25059868

Monsieurs, Pieter; Mijnendonckx, Kristel; Provoost, Ann; Venkateswaran, Kasthuri; Ott, C Mark; Leys, Natalie; Van Houdt, Rob

2014-01-01

208

Structural transformation from NaHTi 3O 7 nanotube to Na 2Ti 6O 13 nanorod  

NASA Astrophysics Data System (ADS)

NaHTi 3O 7 nanotubes were synthesized by the hydrothermal method. Temperature effects of the nanotubes are examined by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), thermal gravity analysis (TGA), and Raman spectroscopy. With increasing the annealing temperature NaHTi 3O 7 nanotubes undergo a slight degradation and more degradation of the tubular shape, respectively at 300 and 500 ?C, and finally become complete Na 2Ti 6O 13 nanorods after annealing at 700 ?C for 1 hour. The structure characters and lattice dynamics of both nanotubes and nanorods were investigated. The transformation mechanism between NaHTi 3O 7 nanotubes and Na 2Ti 6O 13 nanorods is discussed to be attributed to release of the structural water in the interlayer space during self-oriented attachments, and to take more stable configuration with low energy.

Zhu, K. R.; Yuan, Y.; Zhang, M. S.; Hong, J. M.; Deng, Y.; Yin, Z.

2007-12-01

209

Identification and functional analysis of three isoforms for the Na+-dependent phosphate co-transporter (NaPi-2) in rat kidney.  

PubMed

We have isolated three unique NaPi-2-related protein cDNAs (NaPi-2alpha, NaPi-2beta and NaPi-2gamma) from a rat kidney library. NaPi-2alpha cDNA encodes 337 amino acids which have high homology to the N-terminal half of NaPi-2 containing three transmembrane domains. NaPi-2beta encodes 327 amino acids which are identical to the N-terminal region of NaPi-2 containing four transmembrane domains, whereas the 146 amino acids in the C-terminal region are completely different. In contrast, NaPi-2gamma encodes 268 amino acids which are identical to the C-terminal half of NaPi-2. An analysis of phage and cosmid clones indicated that the three related proteins were produced by alternative splicing in the NaPi-2 gene. In a rabbit reticulocyte lysate system, NaPi-2alpha, beta and gamma were found to be 36, 36 and 29 kDa polypeptides, respectively. NaPi-2alpha and NaPi-2gamma were glycosylated and revealed to be 45 and 35 kDa proteins, respectively. A functional analysis demonstrated that NaPi-2gamma and alpha markedly inhibited NaPi-2 activity in Xenopus oocytes. The results suggest that these short isoforms may function as a dominant-negative inhibitor of the full-length transporter. PMID:11143982

Miyamoto, K; Tatsumi, S; Segawa, H; Ohkido, I; Takeda, E

2000-01-01

210

Na+-sulfate cotransporter SLC13A1.  

PubMed

Sulfate is essential for normal physiology. The kidney plays a major role in sulfate homeostasis. Sulfate is freely filtered and strongly reabsorbed in the proximal tubule. The apical membrane Na(+)-sulfate cotransporter NaS1 (SLC13A1) mediates sulfate (re)absorption across renal proximal tubule and small intestinal epithelia. NaS1 encodes a 595-amino acid (? 66 kDa) protein with 13 putative transmembrane domains. Its substrate preferences are sodium and sulfate, thiosulfate, and selenate, and its activity is inhibited by molybdate, selenate, tungstate, thiosulfate, succinate, and citrate. NaS1 is primarily expressed in the kidney (proximal tubule) and intestine (duodenum to colon). NaS1 expression is down-regulated in the renal cortex by high sulfate diet, hypothyroidism, vitamin D depletion, glucocorticoids, hypokalemia, metabolic acidosis, and NSAIDs and up-regulated by low sulfate diet, thyroid hormone, vitamin D supplementation, growth hormone, chronic renal failure, and during post-natal growth. Disruption of murine NaS1 gene leads to hyposulfatemia and hypersulfaturia, as well as changes in metabolism, growth, fecundity, behavior, gut physiology, and liver detoxification. This suggests that NaS1 is an important sulfate transporter and its disruption leads to perturbed sulfate homeostasis, which contributes to numerous pathophysiological conditions. PMID:24193406

Markovich, Daniel

2014-01-01

211

Activation of the Na+, K(+)-ATPase in Narcine brasiliensis.  

PubMed Central

The in vivo activation and turnover rates of the sodium pump (Na+, K(+)-ATPase) were investigated in the electrocytes of the electric organ of the elasmobranch Narcine brasiliensis. The Narcine electric organ appears to be an excellent model for the study of sodium pump activation in an excitable tissue. The sodium transmembrane gradient and high-energy phosphagens were concurrently measured by 23Na and 31P NMR spectroscopy. The resting electric organ, which depends primarily on anaerobic metabolism, displays a high concentration of phosphocreatine (PCr). It has an intracellular sodium concentration ([Na+]i) of 20 +/- 10 milliequivalents/liter as estimated by NMR. Electrical stimulation of the nerves innervating the electric organ results in an increase in [Na+]i in the electrolyte and rapid depletion of PCr. Ouabain causes an 85% decrease in utilization of high-energy phosphagens, indicating that rapid PCr turnover in this tissue is mainly due to Na+, K(+)-ATPase activity. From these data we can determine that the rate of sodium pump turnover increases by greater than 3 orders of magnitude within several hundred milliseconds. In excised unstimulated electric organ slices, changes in [Na+]i equivalent to those occurring with stimulation, but induced by hyperosmolar conditions, do not result in increased PCr hydrolysis. We conclude that cholinergic stimulation of the electric organ causes a rapid and extremely large increase in sodium pump turnover, which is regulated predominantly by factors other than [Na+]i. Images

Blum, H; Nioka, S; Johnson, R G

1990-01-01

212

The Na, K-ATPase in the failing human heart.  

PubMed

The Na, K-ATPase consists of alpha- and beta-subunits and actively transports Na out and K into the myocyte. It is the receptor for cardiac glycosides exerting its positive inotropic effect by inhibiting enzyme activity, decreasing the driving force for the Na/Ca-exchange and increasing cellular content and release of Ca during depolarization. The specific binding capacity for cardiac glycosides is utilized as a tool for Na, K-ATPase quantification with high accuracy and precision. In treatment of patients with heart failure cardiac glycosides improve symptoms and reduce the need for hospitalization without affecting mortality. In endomyocardial biopsies from patients with compromised cardiac function total Na, K-ATPase concentration is decreased by approximately 40% and a correlation between decrease in heart function and decrease in Na, K-ATPase concentration exists. At the subunit level, the alpha1-, alpha3- and beta1-proteins are reduced in human heart failure. During digitalization approximately 30% of remaining Na, K-pumps are occupied by digoxin. Thus, a total of not less than half the Na, K-pumps may be out of function in the myocardium of digitalised heart failure patients. It is still a matter of debate whether a digitalis-like factor exists. There is a pressing need for the identification of its precise chemical structure, properties and quantitative relation to the Na, K-ATPase. It is recommended that cardiac glycosides are prescribed to heart failure patients who are still having heart failure symptoms after institution of mortality reducing therapy. Cardiac glycoside treatment is still the only safe inotropic drug for oral use that improves hemodynamics in patients with compromised cardiac function. PMID:12650869

Schwinger, Robert H G; Bundgaard, Henning; Müller-Ehmsen, Jochen; Kjeldsen, Keld

2003-03-15

213

Absorption spectra of Na atoms in dense He  

NASA Astrophysics Data System (ADS)

We present an analysis of Na-He collisional profiles at high density and very low temperature in a unified line shape semi-classical theory which contains the impact as well the quasistatic limits. Clearly understanding the variation of shape of the two fine-structure components of the 3 s-3 p line with increasing helium density allows us to understand experimental spectra of a Na atom attached to He nanodroplets. We compare our collisional approach to path integral Monte Carlo calculations using the same ab initio Na-He molecular potentials.

Allard, Nicole F.; Nakayama, Akira; Spiegelman, Fernand; Kielkopf, John F.; Stienkemeier, Frank

2013-03-01

214

[Energetic applications: Na+/K+-ATPase and neuromuscular transmission].  

PubMed

Na/K-ATPase electrogenic activity and its indispensable role in maintaining gradients suggest that the modifications in isoform distribution and the functioning of the sodium pump have a major influence on both the neuronal functions, including excitability, and motor efficiency. This article proposes to clarify the involvement of Na/K-ATPase in the transmission of nerve influx within the peripheral nerve and then in the genesis, the maintenance, and the physiology of muscle contraction by comparing the data found in the literature with our work on neuron and muscle characterization of Na/K-ATPase activity and isoforms. PMID:19230940

Rigoard, P; Chaillou, M; Fares, M; Sottejeau, Y; Giot, J-P; Honfo-Ga, C; Rohan, J; Lapierre, F; Maixent, J-M

2009-03-01

215

Two-frequency lidar technique for mesospheric Na temperature measurements  

NASA Technical Reports Server (NTRS)

This paper describes a new two-frequency lidar for measuring Na temperature profiles. The laser oscillator is tuned to the two operating frequencies by observing the Doppler-free structure of the Na D2 fluorescence spectrum in a vapor cell. The lidar technique and initial observations of the temperature profile between 82 and 102 km are described. Absolute temperature accuracies at the Na layer peak of better than + or - 3 K with a vertical resolution of 1 km and an integration period of approximately 5 min were achieved.

She, C. Y.; Latifi, H.; Yu, J. R.; Alvarez, R. J., II; Bills, R. E.

1990-01-01

216

Angular distribution of electrons emitted from Na clusters  

NASA Astrophysics Data System (ADS)

The angular distribution of photoelectron emission is explored from a theoretical perspective using time-dependent density-functional theory as a tool. We discuss the principal features of one- and two-photon processes for Na3+ with a simple jellium background. As more realistic test cases, we consider Na9+ and Na41+ with detailed ionic structure and compare the results with a jellium description. We find that high-frequency photons are required to resolve ionic details. Moreover, it is desirable to have simultaneously energy-resolved angular distributions to disentangle the details of the electronic structure.

Pohl, A.; Reinhard, P.-G.; Suraud, E.

2004-08-01

217

The kinetics of contact noise in NaBeta alumina  

NASA Astrophysics Data System (ADS)

The kinetics of interfacial chemical reaction noise at sodium amalgam and NaI propylene carbonate contacts to NaBeta Alumina are examined by determining the time and temperature dependence of the noise. The rate constant for the reaction noise is larger for amalgam contacts and increases with sodium concentration in both cases. The noise is thermally activated with an activation energy of 0.5eV, which is similar to that of bulk diffusion noise in NaBeta Alumina.

Kuo, Chu K.; Brophy, James J.

1988-01-01

218

NaFe(TeO3)2  

PubMed Central

The hydro­thermally prepared title compound, sodium iron(III) bis­[trioxotellurate(IV)], is isotypic with its GaIII analogue and consists of corrugated layers with an overall composition of [FeTe2O6]? together with Na+ cations. The layers extend parallel to (001) and are made up of [Fe2O10] edge-shared octa­hedral dimers and TeO3 trigonal pyramids sharing vertices. The Na+ cations are located in the cavities of this arrangement and link adjacent [FeTe2O6]? layers via distorted [NaO8] polyhedra.

Weil, Matthias; Stoger, Berthold

2008-01-01

219

Angular distribution of electrons emitted from Na clusters  

SciTech Connect

The angular distribution of photoelectron emission is explored from a theoretical perspective using time-dependent density-functional theory as a tool. We discuss the principal features of one- and two-photon processes for Na{sub 3}{sup +} with a simple jellium background. As more realistic test cases, we consider Na{sub 9}{sup +} and Na{sub 41}{sup +} with detailed ionic structure and compare the results with a jellium description. We find that high-frequency photons are required to resolve ionic details. Moreover, it is desirable to have simultaneously energy-resolved angular distributions to disentangle the details of the electronic structure.

Pohl, A.; Reinhard, P.-G.; Suraud, E. [Institut fuer Theoretische Physik, Universitaet Erlangen, Staudtstrasse 7, D-91058 Erlangen (Germany); Laboratoire Physique Theorique, Universite P. Sabatier, 118 Route de Narbonne, F-31062 Toulouse cedex, France and Institut fuer Theoretische Physik, Universitaet Erlangen, Staudtstrasse 7, D-91058 Erlangen (Germany)

2004-08-01

220

Phyla- and Subtype-Selectivity of CgNa, a Na+ Channel Toxin from the Venom of the Giant Caribbean Sea Anemone Condylactis Gigantea  

PubMed Central

Because of their prominent role in electro-excitability, voltage-gated sodium (NaV) channels have become the foremost important target of animal toxins. These toxins have developed the ability to discriminate between closely related NaV subtypes, making them powerful tools to study NaV channel function and structure. CgNa is a 47-amino acid residue type I toxin isolated from the venom of the Giant Caribbean Sea Anemone Condylactis gigantea. Previous studies showed that this toxin slows the fast inactivation of tetrodotoxin-sensitive NaV currents in rat dorsal root ganglion neurons. To illuminate the underlying NaV subtype-selectivity pattern, we have assayed the effects of CgNa on a broad range of mammalian isoforms (NaV1.2–NaV1.8) expressed in Xenopus oocytes. This study demonstrates that CgNa selectively slows the fast inactivation of rNaV1.3/?1, mNaV1.6/?1 and, to a lesser extent, hNaV1.5/?1, while the other mammalian isoforms remain unaffected. Importantly, CgNa was also examined on the insect sodium channel DmNaV1/tipE, revealing a clear phyla-selectivity in the efficacious actions of the toxin. CgNa strongly inhibits the inactivation of the insect NaV channel, resulting in a dramatic increase in peak current amplitude and complete removal of fast and steady-state inactivation. Together with the previously determined solution structure, the subtype-selective effects revealed in this study make of CgNa an interesting pharmacological probe to investigate the functional role of specific NaV channel subtypes. Moreover, further structural studies could provide important information on the molecular mechanism of NaV channel inactivation.

Billen, Bert; Debaveye, Sarah; Beress, Laszlo; Tytgat, Jan

2010-01-01

221

Phyla- and Subtype-Selectivity of CgNa, a Na Channel Toxin from the Venom of the Giant Caribbean Sea Anemone Condylactis Gigantea.  

PubMed

Because of their prominent role in electro-excitability, voltage-gated sodium (Na(V)) channels have become the foremost important target of animal toxins. These toxins have developed the ability to discriminate between closely related Na(V) subtypes, making them powerful tools to study Na(V) channel function and structure. CgNa is a 47-amino acid residue type I toxin isolated from the venom of the Giant Caribbean Sea Anemone Condylactis gigantea. Previous studies showed that this toxin slows the fast inactivation of tetrodotoxin-sensitive Na(V) currents in rat dorsal root ganglion neurons. To illuminate the underlying Na(V) subtype-selectivity pattern, we have assayed the effects of CgNa on a broad range of mammalian isoforms (Na(V)1.2-Na(V)1.8) expressed in Xenopus oocytes. This study demonstrates that CgNa selectively slows the fast inactivation of rNa(V)1.3/?(1), mNa(V)1.6/?(1) and, to a lesser extent, hNa(V)1.5/?(1), while the other mammalian isoforms remain unaffected. Importantly, CgNa was also examined on the insect sodium channel DmNa(V)1/tipE, revealing a clear phyla-selectivity in the efficacious actions of the toxin. CgNa strongly inhibits the inactivation of the insect Na(V) channel, resulting in a dramatic increase in peak current amplitude and complete removal of fast and steady-state inactivation. Together with the previously determined solution structure, the subtype-selective effects revealed in this study make of CgNa an interesting pharmacological probe to investigate the functional role of specific Na(V) channel subtypes. Moreover, further structural studies could provide important information on the molecular mechanism of Na(V) channel inactivation. PMID:21833172

Billen, Bert; Debaveye, Sarah; Béress, Lászlo; Garateix, Anoland; Tytgat, Jan

2010-01-01

222

Characterization of Na-X, NaA, and coal fly ash zeolites and their amorphous precursors by IR, MAS NMR and XPS  

Microsoft Academic Search

By fusion with sodium hydroxide followed by a hydrothermal reaction, fly ash and Alenriched fly ash were converted into Na-X and Na-A zeolites, respectively. The authentic Na-X, Na-A and fly ash zeolites as well as their amorphous precursors have been characterized by IR, 29Si and 27Al MAS NMR, XPS\\/AES, TG, and comparative ion-exchange studies of Cs and K with Na

N. Shigemoto; S. Sugiyama; H. Hayashi; K. Miyaura

1995-01-01

223

(23)Na multiple-quantum MAS NMR of the perovskites NaNbO(3) and NaTaO(3).  

PubMed

The distorted perovskites NaTaO(3) and NaNbO(3) have been studied using (23)Na multiple-quantum (MQ) MAS NMR. NaTaO(3) was prepared by high temperature solid state synthesis and the NMR spectra are consistent with the expected room temperature structure of the material (space group Pbnm), with a single crystallographic sodium site. Two samples of NaNbO(3) were studied. The first, a commercially available sample which was annealed at 900 degrees C, showed two crystallographic sodium sites, as expected for the room temperature structure of the material (space group Pbcm). The second sample, prepared by a low temperature hydrothermal method, showed the presence of four sodium sites, two of which match the expected room temperature structure and the second pair, another polymorph of the material (space group P21ma). This is consistent with powder X-ray diffraction data which showed weak extra peaks which can be accounted for by the presence of this second polymorph. Density functional theory (DFT) calculations support our conclusions, and aid assignment of the NMR spectra. Finally, we discuss the measured NMR parameters in relation to other studies of sodium in high coordination sites in the solid state. PMID:16855721

Ashbrook, Sharon E; Le Pollès, Laurent; Gautier, Régis; Pickard, Chris J; Walton, Richard I

2006-08-01

224

Structure determination in 55-atom Li-Na and Na-K nanoalloys  

NASA Astrophysics Data System (ADS)

The structure of 55-atom Li-Na and Na-K nanoalloys is determined through combined empirical potential (EP) and density functional theory (DFT) calculations. The potential energy surface generated by the EP model is extensively sampled by using the basin hopping technique, and a wide diversity of structural motifs is reoptimized at the DFT level. A composition comparison technique is applied at the DFT level in order to make a final refinement of the global minimum structures. For dilute concentrations of one of the alkali atoms, the structure of the pure metal cluster, namely, a perfect Mackay icosahedron, remains stable, with the minority component atoms entering the host cluster as substitutional impurities. At intermediate concentrations, the nanoalloys adopt instead a core-shell polyicosahedral (p-Ih) packing, where the element with smaller atomic size and larger cohesive energy segregates to the cluster core. The p-Ih structures show a marked prolate deformation, in agreement with the predictions of jelliumlike models. The electronic preference for a prolate cluster shape, which is frustrated in the 55-atom pure clusters due to the icosahedral geometrical shell closing, is therefore realized only in the 55-atom nanoalloys. An analysis of the electronic densities of states suggests that photoelectron spectroscopy would be a sufficiently sensitive technique to assess the structures of nanoalloys with fixed size and varying compositions.

Aguado, Andrés; López, José M.

2010-09-01

225

Dianion formation from anion-alkali metal charge exchange reactions: TCNQ^- + Na -> TCNQ^-- + Na^+  

NASA Astrophysics Data System (ADS)

The interaction of an electron with an anion is characterized by a long-range coulomb repulsion and a short range polarizability attraction giving rise to a coulomb barrier. The permanent addition of an extra electron to a negatively charged anion requires tunneling through the barrier or attachment of the electron over the top of this coulomb barrier followed by disposal of the excess energy. Charge-exchange collisions of an anion with an alkali atom utilize the latter channel to produce permanent dianions with cross sections of ˜1 å^2. We have previously examined the reaction TCNQ-F4^- + Xe -> TCNQ-F4^-- + Xe^+ and reported a delayed threshold and quantum phase interference effects in the charge exchange cross section.ootnotetextS. Yu. Ovchinnikov, et al. Phys. Rev. A, 73, 64704(2006) Employing sodium as the collision partner, the cross section is seen to increase with decreasing energy with a threshold below 180 eV (com). A new apparatus has been constructed to allow measurements down to energies below the expected threshold (˜41 eV, laboratory energy based upon a 1 eV second electron affinity). This method has been used to study the reaction TCNQ^- + NA -> TCNQ^-- + Na^+ and will provide one of the first measurements of second electron affinities for molecular anions.

Smith, Byron; Compton, Robert; Ovchinnikov, Serge; Holm, Anne; Nielsen, Steen

2011-10-01

226

Transmembrane helices 3 and 4 are involved in substrate recognition by the Na+/dicarboxylate cotransporter, NaDC1.  

PubMed

The Na(+)/dicarboxylate cotransporters (NaDC1) from mouse (m) and rabbit (rb) differ in their ability to handle glutarate. Substrate-dependent inward currents, measured using two-electrode voltage clamp, were similar for glutarate and succinate in Xenopus oocytes expressing mNaDC1. In contrast, currents evoked by glutarate in rbNaDC1 were only about 5% of the succinate-dependent currents. To identify domains involved in glutarate transport, we constructed a series of chimeric transporters between mouse and rabbit NaDC1. Although residues found in multiple transmembrane helices (TM) participate in glutarate transport, the most important contribution is made by TM 3 and 4 and the associated loops. The R(M3-4) chimera, consisting of rbNaDC1 with substitution of TM 3-4 from mNaDC1, had a decreased K(0.5)(glutarate) of 4 mM compared with 15 mM in wild-type rbNaDC1 without any effect on K(0.5)(succinate). The chimeras were also characterized using dual-label competitive uptakes with (14)C-glutarate and (3)H-succinate to calculate the transport specificity ratio (TSR), a measure of relative catalytic efficiency with the two substrates. The TSR analysis provides evidence for functional coupling in the transition state between TM 3 and 4. We conclude that TM 3 and 4 contain amino acid residues that are important determinants of substrate specificity and catalytic efficiency in NaDC1. PMID:16475819

Oshiro, Naomi; King, Steven C; Pajor, Ana M

2006-02-21

227

High-NA HPCS optical fibers for medical diagnosis and treatment  

Microsoft Academic Search

Hard Plastic Clad Silica (HPCS) optical fibers with pure silica cores have been developed which are robust and have NA(Numerical Aperture)>0.50. Improved clad only HPCS fibers have been produced for both new 'standard' and 'high' NA versions. Based on new cladding formulations, the 'standard' NA fiber has an NA of 0.41, while the new ultrahigh NA fiber has an NA

Bolesh J. Skutnik

2010-01-01

228

Na double-edge magneto-optic filter for Na lidar profiling of wind and temperature in the lower atmosphere.  

PubMed

A Na double-edge magneto-optic filter is proposed for incorporation into the receiver of a three-frequency Na Doppler lidar to extend its wind and temperature measurements into the lower atmosphere. Two prototypes based on cold- and hot-cell designs were constructed and tested with laser scanning and quantum mechanics modeling. The hot-cell filter exhibits superior performances over the cold-cell filter containing buffer gas. Lidar simulations, metrics, and error analyses show that simultaneous wind and temperature measurements are feasible in the altitude range of 20-50 km using the hot-cell filter and reasonable Na lidar parameters. PMID:19148254

Huang, Wentao; Chu, Xinzhao; Williams, B P; Harrell, S D; Wiig, Johannes; She, C-Y

2009-01-15

229

Tb/Na tobermorite: Thermal behaviour and high temperature products  

SciTech Connect

By heating a sample of Tb/Na tobermorite we obtained a phase which was identified through its X-ray diffraction (XRD) pattern, as terbium silicate apatite. Subsequently this compound has been directly prepared by solid state reaction and we carried out a structural refinement from XRD data in space group P6{sub 3}/m obtaining cell parameters a=9.39199(4) A and c=6.84041(5) A. Terbium silicate apatite heated in melted NaF led to Tb{sub 4}O{sub 7} crystals. - Graphical Abstract: By heating over 900 deg. C Tb/Na tobermorite a terbium silicate apatite was obtained. The same product has been independently prepared and structurally characterized from powder diffraction data. Attempts of crystallizing terbium silicate apatite from melted NaF led to Tb{sub 4}O{sub 7} crystals.

Garra, Walter [Dipartimento di Chimica e Chimica Industriale, Universita di Pisa, via Risorgimento, 35, 56126 Pisa (Italy); Marchetti, Fabio, E-mail: fama@dcci.unipi.i [Dipartimento di Chimica e Chimica Industriale, Universita di Pisa, via Risorgimento, 35, 56126 Pisa (Italy); Merlino, Stefano [Dipartimento di Scienze della Terra, Universita di Pisa, via S. Maria, 53, 56126 Pisa (Italy)

2009-06-15

230

Interpretation of Na-K-Mg relations in geothermal waters  

USGS Publications Warehouse

When using a Na-K-???Mg triangular diagram as an aid in the interpretation of a geothermal water, the estimated temperature of last water-rock equilibration may change by as much as 50??C, depending on which of the many Na/K geothermometers one assumes is correct. A particular geothermometer may work well in one place and not in another because of differences in the mineralogy of the phases that are in contact with the reservoir fluid. The position of the full equilibrium line that is used for geothermometry and for assessing degrees of departure from equilibrium also changes as the assumed K/???Mg geothermometer equation changes. The degree of ambiguity can be evaluated by utilizing the results of all the recently published Na/K geothermometers on a single Na-K-???Mg triangular plot.

Fournier, R. O.

1990-01-01

231

Project ELaNa and NASA's CubeSat Initiative.  

National Technical Information Service (NTIS)

This slide presentation reviews the NASA program to use expendable lift vehicles (ELVs) to launch nanosatellites for the purpose of enhancing educational research. The Education Launch of Nanosatellite (ELaNa) project, run out of the Launch Services Progr...

G. L. Skrobot

2010-01-01

232

Reactions of NaCl with Gaseous SO3, SO2, and O2  

NASA Technical Reports Server (NTRS)

Hot corrosion of gas turbine engine components involves deposits of Na2SO4 which are produced by reactions between NaCl and oxides of sulfur. For the present investigation, NaCl single crystals were exposed at 100 to 850 C to gaseous mixtures of SO3, SO2, and O2. The products formed during this exposure depend, primarily, on the temperatures. The four product films were: NaCl-SO3; Na2S2O7; Na2SO4; and NaCl-Na2SO4. The kinetics of the reactions were measured.

Fielder, W. L.; Stearns, C. A.; Kohl, F. J.

1983-01-01

233

Reactions of NaCl with gaseous SO3, SO2, and O2  

NASA Technical Reports Server (NTRS)

Hot corrosion of gas turbine engine components involves deposits of Na2SO4 which are produced by reactions between NaCl and oxides of sulfur. For the present investigation, NaCl single crystals were exposed at 100 to 850 C to gaseous mixtures of SO3, SO2, and O2. The products formed during this exposure depend, primarily, on the temperatures. The four product films were: NaCl-SO3; Na2S2O7; Na2SO4; and NaCl-Na2SO4. The kinetics of the reactions were measured.

Fielder, W. L.; Stearns, C. A.; Kohl, F. J.

1984-01-01

234

Hydrolysis of NaBH4 Using Electroless Ni Catalyst  

Microsoft Academic Search

The development of new storage materials will facilitate the use of hydrogen as a major energy vector in the near future. Chemical hydrides like NaBH4 have been tested as a possible precursor material for supplying hydrogen. In this study, catalytic hydrolysis of alkaline NaBH4 solution is studied using a Ni-based catalyst. The Ni catalysts were synthesized by Pd catalyzation and

Leelarani Katam

2007-01-01

235

The molecular environment of intracellular sodium: 23Na NMR relaxation.  

PubMed

The comprehensive approach described in the accompanying paper is illustrated here with the 23Na signal of a concentrated solution of bovine serum albumin (BSA) in saline and the intracellular (Nai) 23Na resonance of a dense suspension of Na(+)-loaded yeast cells. We use frequency shift reagents to discriminate the latter from the extracellular resonance. We find that the Nai signal corresponds to that of an effective single population of Na+ ions exhibiting a single type c spectrum. This is true despite the fact that the yeast protoplasm is too large and too compartmentalized for a given Na+ ion to sample its entirety on the relevant NMR timescale. Our results show clearly that, in addition to the decay of transverse magnetization, the recovery of longitudinal magnetization is biexponential. This is required for a type c spectrum but has not often been detected. The temperature dependence of the relaxation rate constants of the Nai resonance is not consistent with either a simple Debye process or a discrete exchange mechanism connecting two sites in the fast limit. We have fitted the data using an asymmetric continuous distribution of correlation times for the fluctuations of electric field gradients sensed by the Nai nuclei. The analogous distribution function for the Na+ in a 44% (w/w) BSA solution is quite similar to that of the Nai at the same temperature. This suggests that while the macromolecular environment of the Nai ions is quite congested, it is also isotropic on quite a small spatial scale. Also, one can use the correlation time distribution function, obtained from fitting the relaxation data, to calculate a relaxometry curve. This is useful because experimental 23Na relaxometry is difficult. The calculated curve may be a reasonable model for the mostly extracellular 23Na resonance encountered in vivo. PMID:1751346

Rooney, W D; Springer, C S

1991-10-01

236

Neutral Phospholipids Stimulate Na,K-ATPase Activity  

PubMed Central

Membrane proteins interact with phospholipids either via an annular layer surrounding the transmembrane segments or by specific lipid-protein interactions. Although specifically bound phospholipids are observed in many crystal structures of membrane proteins, their roles are not well understood. Na,K-ATPase is highly dependent on acid phospholipids, especially phosphatidylserine, and previous work on purified detergent-soluble recombinant Na,K-ATPase showed that phosphatidylserine stabilizes and specifically interacts with the protein. Most recently the phosphatidylserine binding site has been located between transmembrane segments of ?TM8–10 and the FXYD protein. This paper describes stimulation of Na,K-ATPase activity of the purified human ?1?1 or ?1?1FXYD1 complexes by neutral phospholipids, phosphatidylcholine, or phosphatidylethanolamine. In the presence of phosphatidylserine, soy phosphatidylcholine increases the Na,K-ATPase turnover rate from 5483 ± 144 to 7552 ± 105 (p < 0.0001). Analysis of ?1?1FXYD1 complexes prepared with native or synthetic phospholipids shows that the stimulatory effect is structurally selective for neutral phospholipids with polyunsaturated fatty acyl chains, especially dilinoleoyl phosphatidylcholine or phosphatidylethanolamine. By contrast to phosphatidylserine, phosphatidylcholine or phosphatidylethanolamine destabilizes the Na,K-ATPase. Structural selectivity for stimulation of Na,K-ATPase activity and destabilization by neutral phospholipids distinguish these effects from the stabilizing effects of phosphatidylserine and imply that the phospholipids bind at distinct sites. A re-examination of electron densities of shark Na,K-ATPase is consistent with two bound phospholipids located between transmembrane segments ?TM8–10 and TMFXYD (site A) and between TM2, -4, -6, -and 9 (site B). Comparison of the phospholipid binding pockets in E2 and E1 conformations suggests a possible mechanism of stimulation of Na,K-ATPase activity by the neutral phospholipid.

Haviv, Haim; Habeck, Michael; Kanai, Ryuta; Toyoshima, Chikashi; Karlish, Steven J. D.

2013-01-01

237

Reductive amination of carbohydrates using NaBH(OAc) 3  

Microsoft Academic Search

An improved protocol for reductive amination of carbohydrates is developed. This derivatization facilitates the detection of oligosaccharides in HPLC-UV and mass spectrometric applications by enhancing the signal of the carbohydrates. In this study, reductive amination was achieved using NaBH(OAc)3.This reducing agent is an attractive alternative to the toxic, but extensively used reducing agent, NaBH3CN. Several types of carbohydrates were successfully

Dilusha S. Dalpathado; Hui Jiang; Marcus A. Kater; Heather Desaire

2005-01-01

238

NaCa exchange current in mammalian heart cells  

Microsoft Academic Search

Electrogenic Na-Ca exchange has been known to act in the cardiac sarcolemma as a major mechanism for extruding Ca ions1-3. Ionic flux measurements in cardiac vesicles have recently suggested that the exchange ratio is probably 3 Na:l Ca (refs 4, 5), although a membrane current generated by such a process has not been isolated. Using the intracellular perfusion technique6,7 combined

Junko Kimura; Akinori Noma; Hiroshi Irisawa

1986-01-01

239

NaCoDAE: Navy Conversational Decision Aids Environment  

Microsoft Academic Search

This report documents NaCoDAE, the Navy Conversational Decision Aids Environmentbeing developed at the Navy Center for Applied Research in ArtificialIntelligence (NCARAI), which is a branch of the Naval Research Laboratory. NaCoDAE is a software prototype that is being developed under the Practical Advancesin Case-Based Reasoning project, which is funded by the Office for Naval Research,for the purpose of assisting Navy

Leonard A. Breslow; David W. Aha

1998-01-01

240

Na + Xe collisions in the presence of two nonresonant lasers  

NASA Technical Reports Server (NTRS)

Na+Xe collisions in the presence of two distinct laser fields (rhodamine 110 and Nd:glass) are investigated with reference to the response to nonresonant radiation of alkali metals collisionally perturbed by a buffer gas. It is found that the excited Na-asterisk (4s)+Xe state is produced with a measurable cross section due to two-photon absorption with field intensities as low as 10 MW/sq cm.

De Vries, P. L.; Chang, C. H.; George, T. F.; Laskowski, B.; Stallcop, J. R.

1980-01-01

241

Surface-polishing process for NaI crystals  

SciTech Connect

Darkening of large arrays of NaI used in high energy physics experiments at SLAC has prompted an investigation of methods for annealing radiation damage. As part of this research, it has been necessary to repolish the flat faces of the NaI crystals. The final polishing parameters are given in this document as well as an indication of some techniques which did not work.

Francis, J.

1982-09-01

242

High-spin states in ²³Na  

Microsoft Academic Search

The ¹²C(¹²C,p g)²³Na reaction was used to study the ; gamma -ra y deexcitation of levels up to E\\/sub x\\/ = 10.4 MeV in ²³Na. ; Doppler-shift attenuation measurements yielded mean lifetimes or life time limits ; for 22 levels. Branching ratios were obtained for the 5.54, were observed for 7 ; levels above E\\/sub x\\/ = 7 MeV. Angular

G. G. Frank; R. V. Elliott; R. H. Spear; J. A. Kuehner

1973-01-01

243

Non-Resonant Ionization and Fragmentation Pathways in Na2  

Microsoft Academic Search

With the help of molecular beam, time-of-flight (TOF) mass spectrometer, and Nd:YAG laser we have investigated multi-photon ionization and dissociation patterns of Na2 molecules. One prominent feature of TOF spectra obtained with 532nm photons can be assigned to 3-photon ionization followed by 1-photon dissociation. This channel yields Na^+ fragments with kinetic energy of about 0.67eV, the highest kinetic energy release

Lutz Hüwel; Mao Sheng Liu; Roy Anunciado

2008-01-01

244

CsI(Na) Scintillation Plate with High Spatial Resolution  

Microsoft Academic Search

A two dimensional CsI(Na) scintillation plate with high spatial resolution has been developed by growing CsI(Na) crystal on a special fiber plate with fiber size of 20 ¿m. The number of photons at the output were 34 photons for 55Fe and 260 photons for 129I respectively. The spatial resolution measured by electron beam excitation showed approximately 30 ¿m of FWHM.

Michihiro Ito; Masahiro Yamaguchi; Koichiro Oba

1987-01-01

245

Chemicobiological effects of herbicide MCPA-Na on plasma proteins.  

PubMed

Under physiological conditions, the potential hematological toxicity of herbicide 2-methyl-4-chlorophenoxyacetic acid sodium (MCPA-Na) was discussed by fluorescence probe technology and spectroscopy methods including three-dimensional (3D) fluorescence, UV absorption and circular dichroism (CD) spectra. In vitro, MCPA-Na bound with bovine serum albumin (BSA) and formed new complex at ground state by electrostatic force and hydrogen bond. During the process, non-radiation energy transfer from BSA to MCPA-Na occurred and the distance r between donor and acceptor was obtained based on Förster theory. The binding site was investigated by fluorescence probe method and the results implied MCPA-Na was absorbed on domain II of BSA molecule. The enthalpy change (?H(?)), Gibbs free energy change (?G(?)) and entropy change (?S(?)) were calculated at four different temperatures according to Van't Hoff isobar equation and Gibbs-Helmholtz equation. Negative value of ?G(?) indicated the process of binding was a spontaneous and irreversible process, which gave a broad hint that MCPA-Na was likely to be poisonous. CD spectra exhibited significant changes of secondary structures in BSA molecule and three-dimensional fluorescence spectra indicated the tryptophan residue in BSA was placed in a less hydrophobic environment, which presented additional evidence to caution the danger of MCPA-Na residue in food. Meanwhile, the mechanism and geometry of the binding was analyzed at molecular level. PMID:21670962

Zhang, Hua-xin; Liu, Lin

2012-03-01

246

Hyper NA polarized imaging of 45nm DRAM  

NASA Astrophysics Data System (ADS)

In this paper, we will present experimental results on 45nm node patterning of DRAM and some technical issues for polarized illumination in hyper NA imaging. First, practical k1 limit of 1.2NA ArF immersion system is investigated through experiment. Process window and mask error enhancement factors are measured with respect to various design rules, i.e., different k1 levels at fixed NA. Reasonable process window and MEEF value of around 3 are achieved in DRAM gate and isolation layers at around 0.28 k1 regime. It is obvious that feasibility of this lowered k1 was realized by the help of polarized illumination when we compared the results with that of 60nm patterning at 0.93NA tool - corresponding k1 is 0.29 - without polarized illumination. Then consideration about degree of polarization state must come next to the benefit of polarized illumination. Input polarization state is changed by birefringence of lens or mask materials but it is very difficult to correlate the birefringence level and critical dimension of patterns experimentally. Double exposing method was contrived to measure the effect of degree of polarization on DICD. And we also measure the polarization dependent transmittance of light on mask by using 1.2NA immersion scanner. As a result, birefringence and mask feature interaction with light seems not to be a serious issue for 45nm hyper NA polarized imaging.

Lim, Chang-Moon; Park, Sarohan; Hyun, Yoon-Suk; Kim, Jin-Soo; Eom, Tae-Seung; Park, Jun-Taek; Moon, Seung-Chan; Kim, Jin-Woong

2007-03-01

247

Bacterial Na+-translocating ferredoxin:NAD+ oxidoreductase.  

PubMed

The anaerobic acetogenic bacterium Acetobacterium woodii carries out a unique type of Na(+)-motive, anaerobic respiration with caffeate as electron acceptor, termed "caffeate respiration." Central, and so far the only identified membrane-bound reaction in this respiration pathway, is a ferredoxin:NAD(+) oxidoreductase (Fno) activity. Here we show that inverted membrane vesicles of A. woodii couple electron transfer from reduced ferredoxin to NAD(+) with the transport of Na(+) from the outside into the lumen of the vesicles. Na(+) transport was electrogenic, and accumulation was inhibited by sodium ionophores but not protonophores, demonstrating a direct coupling of Fno activity to Na(+) transport. Results from inhibitor studies are consistent with the hypothesis that Fno activity coupled to Na(+) translocation is catalyzed by the Rnf complex, a membrane-bound, iron-sulfur and flavin-containing electron transport complex encoded by many bacterial and some archaeal genomes. Fno is a unique type of primary Na(+) pump and represents an early evolutionary mechanism of energy conservation that expands the redox range known to support life. In addition, it explains the lifestyle of many anaerobic bacteria and gives a mechanistic explanation for the enigma of the energetic driving force for the endergonic reduction of ferredoxin with NADH plus H(+) as reductant in a number of aerobic bacteria. PMID:20921383

Biegel, Eva; Müller, Volker

2010-10-19

248

Effects of Ca(2+) channel blockers on amiloride-sensitive Na(+) permeable channels and Na(+) transport in fetal rat alveolar type II epithelium.  

PubMed

A beta-adrenergic agonist (beta-agonist), terbutaline, stimulated amiloride-sensitive Na(+) absorption in fetal rat alveolar type II epithelium, contributing to the clearance of lung fluid. Cytosolic Ca(2+) plays an important role in terbutaline-stimulated Na(+) absorption, since Ca(2+)-activated, amiloride-sensitive Na(+)-permeable channels are involved in transcellular Na(+) absorption and terbutaline stably elevates the cytosolic Ca(2+) concentration by stimulating Ca(2+) influx. Therefore, we studied whether Ca(2+) channel blockers (Ni(2+), verapamil, and nifedipine) affect terbutaline-stimulated transcellular Na(+) absorption. Ni(2+) partially blocked the channel responsible for the terbutaline-stimulated Na(+) absorption at the Na(+) entry pathway across the apical membrane of the epithelium, but did not diminish the terbutaline-stimulated transcellular Na(+) absorption. By measuring the capacity of the Na(+),K(+)-pump activity, we determined that the rate-limiting step of the terbutaline-stimulated transcellular Na(+) absorption was the extrusion step across the basolateral membrane by the Na(+),K(+)-pump. The other Ca(2+) channel blockers, verapamil and nifedipine, had effects identical to those of Ni(2+). Based upon these observations, we conclude that, in the beta-agonist-stimulated fetal rat alveolar type II epithelium, Ca(2+) channel blockers diminish amiloride-sensitive channels, but do not affect transcellular Na(+) absorption, since under the beta-agonist-stimulated condition the Na(+),K(+)-pump is the rate-limiting step in Na(+) transport. PMID:11996897

Marunaka, Yoshinori; Niisato, Naomi

2002-04-15

249

The K\\/Na and Ca\\/Na ratios and rapeseed yield, under soil salinity or sodicity  

Microsoft Academic Search

Rapeseed (Brassica napus) is a crop relatively tolerant to salt and sodium. Our objective was to study the interactions between Na, K and Ca and their relationship with its yield under the isolated effects of soil salinity or sodicity.

Claudia A. Porcelli; Flavio H. Gutierrez Boem; Ratil S. Lavado

1995-01-01

250

Na(+)-translocating cytochrome bo terminal oxidase from Vitreoscilla: some parameters of its Na+ pumping and orientation in synthetic vesicles.  

PubMed

Vitreoscilla cytochrome bo ubiquinol oxidase is similar in some properties to the Escherichia coli enzyme, but unlike the latter, the Vitreoscilla oxidase functions as a primary Na+ pump. When purified Vitreoscilla cytochrome bo is incorporated into liposomes made from Vitreoscilla phospholipids and energized with a quinol substrate, it translocates Na+, not H+, across the vesicle membrane. Since protonophores CCCP (carbonyl cyanide m-chlorophenylhydrazone) and DTHB (3,5-di-tert-butyl-4-hydroxybenzaldehyde) stimulated the Na+ pumping, it is unlikely that it is a secondary effect due to the presence of Na+/H+ antiporter activity in the preparations. The efficiency of the Na+ pumping was 3.93 Na+ pumped per O2 consumed when ascorbate/TMPD was used as the substrate. The cytochrome has a K(m) and Kcat for Na+ of 2.9 mM and 277 s-1, respectively. When ferricytochrome c was entrapped within liposomes prepared from Vitreoscilla phospholipids, it was reduced by Q1H2 (ubiquinol-1) but not by ascorbate/TMPD (N,N,N',N'-tetramethyl-1,4-phenylenediamine). Although Q1H2 was oxidized by cytochrome bo in solution at a rate approximately 14 times that of the latter substrate, the rate of accumulation of Na+ within cytochrome bo vesicles driven by the membrane impermeable ascorbate/TMPD was 1.23 times that of the membrane permeable ubiquinol. These data allowed a calculation that in these synthetic proteoliposomes the cytochrome bo molecules are only 51% directed inward; a value of 61% inward-directed was estimated by measuring the ascorbate/TMPD oxidase activity of the proteoliposomes before and after disrupting them with Triton X-100. A random orientation of the E. coli cytochrome bo oxidase in proteoliposomes has also been reported. PMID:8794772

Park, C; Moon, J Y; Cokic, P; Webster, D A

1996-09-10

251

NMR investigation on the occurrence of Na species in porous carbons prepared by NaOH activation  

Microsoft Academic Search

A detailed investigation was conducted about the process of alkali activation of charred rice hulls using NaOH. A carbon-rich precursor was initially prepared from the pyrolysis of rice hulls under N2 atmosphere, part of it being leached with HF to remove silica. The precursor was then mixed with NaOH, heat-treated at activation temperatures from 600 to 800°C, and part of

Jair C. C. Freitas; Miguel A. Schettino; Alfredo G. Cunha; Francisco G. Emmerich; Antonio C. Bloise; Eduardo R. de Azevedo; Tito J. Bonagamba

2007-01-01

252

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

PubMed Central

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.

Babes, A; Fendler, K

2000-01-01

253

Inwardly permeating Na ions generate the voltage-dependence of resurgent Na current in cerebellar Purkinje neurons  

PubMed Central

Voltage-gated Na channels of cerebellar Purkinje neurons express an endogenous open-channel blocking protein. This blocker binds channels at positive potentials and unbinds at negative potentials, generating a resurgent Na current and permitting rapid firing. The macroscopic voltage-dependence of resurgent current raises the question of whether the blocker directly senses membrane potential or whether voltage-dependence is conferred indirectly. Because we previously found that inwardly permeating Na ions facilitate dissociation of the blocker, we measured voltage-clamped currents in different Na gradients to test the role of permeating ions in generating the voltage-dependence of unblock. In reverse gradients, outward resurgent currents were tiny or absent, suggesting that unblock normally requires “knockoff” by Na. Inward resurgent currents at strongly negative potentials, however, were larger in reverse than in control gradients. Moreover, occupancy of the blocked state was prolonged both in reverse gradients and in control gradients with reduced Na concentrations, indicating that block is more stable when inward currents are small. Accordingly, reverse gradients shifted the voltage-dependence of block, such that resurgent currents were evoked even after conditioning at negative potentials. Additionally, in control gradients, peak resurgent currents decreased linearly with driving force during the conditioning step, suggesting that the stability of block varies directly with inward Na current amplitude. Thus, the voltage-dependence of blocker unbinding results almost entirely from repulsion by Na ions occupying the external pore. The lack of voltage sensitivity of the blocking protein suggests that the blocker’s binding site lies outside the membrane field, in the permeation pathway.

Aman, Teresa K.; Raman, Indira M.

2010-01-01

254

Assessing use-dependent inhibition of the cardiac Na ± current (I Na) in the PatchXpress automated patch clamp  

Microsoft Academic Search

IntroductionThe cardiac Na+ current (INa) underlies the rapid depolarization of the cardiac myocyte, and block of the current slows cardiac conduction and increases the risk of ventricular arrhythmia. A feature of Na+ channel block termed use-dependence is important to the assessment of blocking potency. We developed a robust automated patch clamp assay to rapidly and routinely assess the use-dependent block

Jacob R. Penniman; David C. Kim; Joseph J. Salata; John P. Imredy

2010-01-01

255

NaCl Taste Thresholds in 13 Inbred Mouse Strains  

PubMed Central

Molecular mechanisms of salty taste in mammals are not completely understood. We use genetic approaches to study these mechanisms. Previously, we developed a high-throughput procedure to measure NaCl taste thresholds, which involves conditioning mice to avoid LiCl and then examining avoidance of NaCl solutions presented in 48-h 2-bottle preference tests. Using this procedure, we measured NaCl taste thresholds of mice from 13 genealogically divergent inbred stains: 129P3/J, A/J, BALB/cByJ, C3H/HeJ, C57BL/6ByJ, C57BL/6J, CBA/J, CE/J, DBA/2J, FVB/NJ, NZB/BlNJ, PWK/PhJ, and SJL/J. We found substantial strain variation in NaCl taste thresholds: mice from the A/J and 129P3/J strains had high thresholds (were less sensitive), whereas mice from the BALB/cByJ, C57BL/6J, C57BL/6ByJ, CE/J, DBA/2J, NZB/BINJ, and SJL/J had low thresholds (were more sensitive). NaCl taste thresholds measured in this study did not significantly correlate with NaCl preferences or amiloride sensitivity of chorda tympani nerve responses to NaCl determined in the same strains in other studies. To examine whether strain differences in NaCl taste thresholds could have been affected by variation in learning ability or sensitivity to toxic effects of LiCl, we used the same method to measure citric acid taste thresholds in 4 inbred strains with large differences in NaCl taste thresholds but similar acid sensitivity in preference tests (129P3/J, A/J, C57BL/6J, and DBA/2J). Citric acid taste thresholds were similar in these 4 strains. This suggests that our technique measures taste quality–specific thresholds that are likely to represent differences in peripheral taste responsiveness. The strain differences in NaCl taste sensitivity found in this study provide a basis for genetic analysis of this phenotype.

Ishiwatari, Yutaka

2012-01-01

256

NaCl taste thresholds in 13 inbred mouse strains.  

PubMed

Molecular mechanisms of salty taste in mammals are not completely understood. We use genetic approaches to study these mechanisms. Previously, we developed a high-throughput procedure to measure NaCl taste thresholds, which involves conditioning mice to avoid LiCl and then examining avoidance of NaCl solutions presented in 48-h 2-bottle preference tests. Using this procedure, we measured NaCl taste thresholds of mice from 13 genealogically divergent inbred stains: 129P3/J, A/J, BALB/cByJ, C3H/HeJ, C57BL/6ByJ, C57BL/6J, CBA/J, CE/J, DBA/2J, FVB/NJ, NZB/BlNJ, PWK/PhJ, and SJL/J. We found substantial strain variation in NaCl taste thresholds: mice from the A/J and 129P3/J strains had high thresholds (were less sensitive), whereas mice from the BALB/cByJ, C57BL/6J, C57BL/6ByJ, CE/J, DBA/2J, NZB/BINJ, and SJL/J had low thresholds (were more sensitive). NaCl taste thresholds measured in this study did not significantly correlate with NaCl preferences or amiloride sensitivity of chorda tympani nerve responses to NaCl determined in the same strains in other studies. To examine whether strain differences in NaCl taste thresholds could have been affected by variation in learning ability or sensitivity to toxic effects of LiCl, we used the same method to measure citric acid taste thresholds in 4 inbred strains with large differences in NaCl taste thresholds but similar acid sensitivity in preference tests (129P3/J, A/J, C57BL/6J, and DBA/2J). Citric acid taste thresholds were similar in these 4 strains. This suggests that our technique measures taste quality-specific thresholds that are likely to represent differences in peripheral taste responsiveness. The strain differences in NaCl taste sensitivity found in this study provide a basis for genetic analysis of this phenotype. PMID:22293936

Ishiwatari, Yutaka; Bachmanov, Alexander A

2012-07-01

257

Interaction of NaCl with solid water  

NASA Astrophysics Data System (ADS)

The interaction of NaCl with solid water, deposited on tungsten at 80 K, was investigated with metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS) (He I). We have studied the ionization of Cl(3p) and the 1b1, 3a1, and 1b2 bands of molecular water. The results are supplemented by first-principles density functional theory (DFT) calculations of the electronic structure of solvated Cl- ions. We have prepared NaCl/water interfaces at 80 K, NaCl layers on thin films of solid water, and H2O ad-layers on thin NaCl films; they were annealed between 80 and 300 K. At 80 K, closed layers of NaCl on H2O, and vice versa, are obtained; no interpenetration of the two components H2O and NaCl was observed. However, ionic dissociation of NaCl takes place when H2O and NaCl are in direct contact. Above 115 K solvation of the ionic species Cl- becomes significant. Our results are compatible with a transition of Cl- species from an interface site (Cl in direct contact with the NaCl lattice) to an energetically favored configuration, where Cl species are solvated. The DFT calculations show that Cl- species, surrounded by their solvation shell, are nevertheless by some extent accessed by MIES because the Cl(3p)-charge cloud extends through the solvation shell. Water desorption is noticeable around 145 K, but is not complete before 170 K, about 15 K higher than for pure solid water. Above 150 K the NaCl-induced modification of the water network gives rise to gas phase like structures in the water spectra. In particular, the 3a1 emission turns into a well-defined peak. This suggests that under these conditions water molecules interact mainly with Cl- rather than among themselves. Above 170 K only Cl is detected on the surface and desorbs around 450 K.

Borodin, A.; Höfft, O.; Kahnert, U.; Kempter, V.; Poddey, A.; Blöchl, P. E.

2004-11-01

258

Hydration valve controlled non-selective conduction of Na(+) and K(+) in the NaK channel.  

PubMed

The Na(+) and K(+) channels are essential to neural signaling, but our current knowledge at the atomic level is mainly limited to the conducting mechanism of K(+). Unlike a K(+) channel having four equivalent K(+)-binding sites in its selectivity filter, a NaK channel has a vestibule in the middle part of its selectivity filter, and can conduct both Na(+) and K(+) ions. However, the underlying mechanism for non-selective ion conduction in NaK remains elusive. Here we find four small grottos connecting with the vestibule of the NaK selectivity filter, which form a vestibule-grotto complex perpendicular to the filter pore with a few water molecules within it. It is shown that two or more of the water molecules coming to the vestibule to coordinate the cation are necessary for conducting both Na(+) and K(+) ions, while only one water molecule in the vestibule will obstruct ion permeation. Thus, the complex with the aid of interior water movement forms a dynamic hydration valve which is flexible in conveying different cations through the vestibule. Similar exquisite hydration valve mechanisms are expected to be utilized by other non-selective cation channels, and the results should shed new light on the importance of water in neural signaling. PMID:20388493

Shen, Rong; Guo, Wanlin; Zhong, Wenyu

2010-08-01

259

A sodium calcium arsenate, NaCa(AsO(4)).  

PubMed

The title compound, NaCa(AsO(4)), was synthesized using a hydro-thermal method at 633-643?K. It has a dense structure composed of alternating layers of distorted [CaO(6)] octa-hedra and layers of [AsO(4)] tetra-hedra and distorted [NaO(6)] octa-hedra, stacked along the a axis. The As, Ca and two O atoms lie on the mirror plane at y = 1/4 (i.e. 4c), while the Na atom lies on an inversion centre (1/2, 1/2, 0) (i.e. 4b). Each distorted [CaO(6)] octa-hedron shares four equatorial common O vertices with four neighboring octa-hedra, forming a layer parallel to (100), whereas each distorted [NaO(6)] octa-hedron shares two opposite edges with two neighboring ones, forming a chain running along [010]. Each isolated [AsO(4)] tetra-hedron shares two edges with two different [NaO(6)] octa-hedra in one [NaO(6)] chain and a vertex with another chain. Simultaneously the above [AsO(4)] tetra-hedron located in a four-membered [CaO(6)] ring shares one edge of its base facet with one [CaO(6)] octa-hedron and three corners with three other [CaO(6)] octa-hedra of one [CaO(6)] layer, and the remaining apex is shared with another [CaO(6)] layer. [NaO(6)] octa-hedra and [CaO(6)] octa-hedra are linked to each other by sharing edges and vertices. PMID:22199467

Lin, Jinru; Sun, Wei; Mi, Jin-Xiao; Pan, Yuanming

2011-12-01

260

A sodium calcium arsenate, NaCa(AsO4)  

PubMed Central

The title compound, NaCa(AsO4), was synthesized using a hydro­thermal method at 633–643?K. It has a dense structure composed of alternating layers of distorted [CaO6] octa­hedra and layers of [AsO4] tetra­hedra and distorted [NaO6] octa­hedra, stacked along the a axis. The As, Ca and two O atoms lie on the mirror plane at y = 1/4 (i.e. 4c), while the Na atom lies on an inversion centre (1/2, 1/2, 0) (i.e. 4b). Each distorted [CaO6] octa­hedron shares four equatorial common O vertices with four neighboring octa­hedra, forming a layer parallel to (100), whereas each distorted [NaO6] octa­hedron shares two opposite edges with two neighboring ones, forming a chain running along [010]. Each isolated [AsO4] tetra­hedron shares two edges with two different [NaO6] octa­hedra in one [NaO6] chain and a vertex with another chain. Simultaneously the above [AsO4] tetra­hedron located in a four-membered [CaO6] ring shares one edge of its base facet with one [CaO6] octa­hedron and three corners with three other [CaO6] octa­hedra of one [CaO6] layer, and the remaining apex is shared with another [CaO6] layer. [NaO6] octa­hedra and [CaO6] octa­hedra are linked to each other by sharing edges and vertices.

Lin, Jinru; Sun, Wei; Mi, Jin-Xiao; Pan, Yuanming

2011-01-01

261

Na sup + uptake into colonic enterocyte membrane vesicles  

SciTech Connect

Na{sup +} uptake was studied in colonic enterocyte membrane vesicles prepared from normal and dexamethasone-treated rats. Vesicles from rats treated with dexamethasone demonstrated a fivefold greater {sup 22}Na{sup +} uptake compared with vesicles from normal rats. Most of the tracer uptake in membranes derived from treated rats occurred through a conductive, amiloride-blockable pathway located in vesicles with low native K{sup +} permeability and high Cl{sup {minus}} permeability. Kinetic analysis of the amiloride inhibition curve revealed the presence of two amiloride-blockable pathways, one with a high affinity accounting for 85% of the uptake, and one with a low affinity accounting for only 12% of the uptake. Only the low-affinity pathway was detected with vesicles from normal rats. The high sensitivity to amiloride, the dependence on dexamethasone pretreatment, and the relative permeabilities to K{sup +} and Cl{sup {minus}} indicate that most of the {sup 22}Na{sup +} uptake in membranes derived from treated rats is through a Na{sup +}-specific channel located in apical membrane vesicles. Preincubation of the isolated cells from dexamethasone-treated rats at 37{degree}C in Ca{sup 2+}-free solutions before homogenization and membrane vesicle purification caused a 5- to 10-fold increase in amiloride-blockable {sup 22}Na{sup +} uptake compared with vesicles derived from cells maintained at 0{degree}C. The addition of Ca{sup 2+}, but not of Mg{sup 2+}, to the incubation solution markedly reduced this temperature-dependent enhancement in {sup 22}Na{sup +} uptake. These results suggest that Na{sup +} transport in colonic enterocytes from dexamethasone-treated rats is regulated by a Ca{sup 2+}-dependent, temperature-sensitive process which causes a sustained change in the apical membrane.

Bridges, R.J.; Garty, H.; Benos, D.J.; Rummel, W. (Univ. of Saarland, Hamburg (West Germany) Weizmann Institute of Science, Rehovot (Israel) Univ. of Alabama, Birmingham (USA))

1988-04-01

262

New CsI:Na-selenium x-ray detector  

NASA Astrophysics Data System (ADS)

Digital x-ray imager known to flat-panel detector has been studied for the application of a various medical modalities. Currently, two types of detection methods have been realized in digital radiography. One is an indirect conversion method and the other is a direct conversion method. we have been developing a new x-ray detector that combines a columnar CsI:Na scintillation layer with a photosensitive a-Se with dielectric thin film. In this structure, an x-ray is converted to visible light in a CsI:Na scintillation layer and visible light is then converted to electric charges in a-Se layer. The electron-hole pairs can be also generated from x-ray interaction in the a-Se photoconductor, which can improve the detection efficiency of electric charge. We designed the thickness of CsI:Na scintillator by using computer simulation. MCNP is a general-purpose, continuous-energy, generalized-geometry, time-dependent, coupled neutron / photon / electron Monte Carlo transport code. The spectra of x-ray absorption was simulated by using MCNP 4C code. The morphology of the vacuum deposited CsI:Na scintillator and the parylene film were analyzed. Photoluminescence characterization of CsI:Na showed a light emission peak centered at 420nm as expected, which matched the absorption spectrum of amorphous selenium(a-Se). For an electric field of 10V/?m, the dark currents of our detector were below 370 pA/cm2 and the SNR of CsI:Na coupled a-Se detector with a dielectric layer was 1.8 times greater than that without CsI:Na layer.

Seok, Dae Woo; Choi, Jang Yong; Kang, Sang Sik; Jang, Gi Won; Mun, Chi Woong; Nam, Sang Hee

2004-05-01

263

The Na+/H+ exchanger present in trout erythrocyte membranes is not responsible for the amiloride-insensitive Na+/Li+ exchange activity.  

PubMed

The protein responsible for the Na+/Li+ exchange activity across the erythrocyte membrane has not been cloned or isolated. It has been suggested that a Na+/H+ exchanger could be responsible for the Na+/Li+ exchange activity across the erythrocyte membrane. Previously, we reported that in the trout erythrocyte, the Li+/H+ exchange activity (mediated by the Na+/H+ exchanger beta NHE) and the Na+/Li+ exchange activity respond differently to cAMP, DMA (dimethyl-amiloride) and O2. We concluded that the DMA insensitive Na+/Li+ exchange activity originates from a different protein. To further examine these findings, we measured Li+ efflux in fibroblasts expressing the beta NHE as the only Na+/H+ exchanger. Moreover, the internal pH of these cells was monitored with a fluorescent probe. Our findings indicate that acidification of fibroblasts expressing the Na+/H+ exchanger beta NHE, induces a Na+ stimulated Li+ efflux activity in trout erythrocytes. This exchange activity, however, is DMA sensitive and therefore differs from the DMA insensitive Na+/Li+ exchange activity. In these fibroblasts no significant DMA insensitive Na+/Li+ exchange activity was found. These results support the hypothesis that the trout erythrocyte Na+/Li+ exchange activity is not mediated by the Na+/H+ exchanger (beta NHE) present in these membranes. PMID:9425603

van Norren, K; Gorissen, R; Borgese, F; Borggreven, J M; De Pont, J J

1997-12-01

264

High Pressure Study of K-Na Hollandite Solid Solution  

NASA Astrophysics Data System (ADS)

(Na, K)AlSi3O8 aluminosilicates hollandite-type materials with their dense structure, in which all Si and Al are in six-fold coordination, are considered as a possible repository of potassium and sodium in the Earth's lower mantle. Phase relations in the system KAlSi3O8 - NaAlSi3O8 have been examined by other workers at pressures of 5 - 23 GPa and temperatures of 700 - 1200°C, indicating that the maximum solubility of NaAlSi3O8 component into KAlSi3O8 hollandite-type structure at 1000°C is about 40 mol%. At higher Na content the high pressure phase appears to be that of the calcium-ferrite type structure. However, in the last few years there have been a number of reports of natural occurrences of NaAlSi3O8 hollandite in shock-induced melt veins of chondrite. Aim of our research is, therefore, to extent the study of the phase relation of the K-Na system at higher temperature and to determine the physical-chemical properties and high-pressure behaviour of silicate hollandite-type structures containing K and Na in different concentrations. A series of synthesis experiments has been done with the multi-anvil presses at the Bayerisches Geoinstitut in the pressure range 13-25 GPa and 1700°C, using KxNa1-xAlSi3O8 (x = 1, 0.7, 0.5, 0.4) glasses as the starting materials. X-ray powder diffraction analysis and electron microprobe measurements of the run products show that at 20GPa, pure K0.7Na0.3AlSi3O8 hollandite has been synthesized, with the lattice parameters of a = 9.3133 (5) Å, c = 2.7226 (2) Å, V = 236.15 (2) Å3. At 22 GPa, pure K0.5Na0.5AlSi3O8 hollandite has been synthesized, with the lattice parameters of a = 9.2984 (4) Å, c = 2.71920 (17) Å, V = 235.103 (15) Å3. The pressure stability field of KxNa1-xAlSi3O8 hollandite appears therefore larger than in the study of privious work. High-pressure X-ray powder and single-crystal diffraction and Raman spectroscopy experiments for this composition are in progress. Preliminary experiments using a NaAlSi3O8 end-member glass yield no hollandite-type structure at 22.5GPa and 1700°C. Further synthesis experiments are planned to determine the experimental P-T stability field of NaAlSi3O8 hollandite.

Liu, J.; Boffa-Ballaran, T.; Dubrovinsky, L.; Frost, D.

2005-12-01

265

Direct 23Na NMR observation of mixed cations residing inside a G-quadruplex channel.  

PubMed

We report direct (23)Na NMR observation for the presence of mixed cations (Na(+)/K(+), Na(+)/Rb(+), Na(+)/Sr(2+)) inside the G-quadruplex channel formed by the self-association of guanosine 5'-monophosphate at pH 8. PMID:17308634

Ida, Ramsey; Kwan, Irene C M; Wu, Gang

2007-02-28

266

Na(+)-Ca2+ exchanger: physiology and pharmacology.  

PubMed

The Na(+)-Ca2+ exchanger in the plasma membrane is a bidirectional electrogenic ion transporter that couples the translocation of Na+ in one direction with that of Ca2+ in the opposite direction. This system is involved in regulation of intracellular Ca2+ concentration via the forward mode (Ca2+ extrusion) or the reverse mode (Ca2+ influx). There are two types of the plasma membrane Na(+)-Ca2+ exchanger in an animal, and they are called the cardiac type and rod outer segment type. In addition, there is an electroneutral Na(+)-Ca2+ exchanger present in mitochondria. Recent studies by the molecular biology technique show that there are at least 8 isoforms of the cardiac type (NCX1), and there are two other exchangers in the brain (NCX2 and NCX3). Due to new techniques of molecular biology and electrophysiology, much evidence is accumulating with respect to the structure, mechanism, regulation, and physiological and pathological roles of the Na(+)-Ca2+ exchanger. This review summarizes recent progress in this research field that is of pharmacological interest. PMID:9195292

Matsuda, T; Takuma, K; Baba, A

1997-05-01

267

Explosive decomposition of heavily irradiated NaCl  

NASA Astrophysics Data System (ADS)

In heavily irradiated NaCl explosions can be initiated during irradiation or later, after the irradiation, when the samples are heated to temperatures in the range 100-250°. As a result of the irradiation Na and Cl2 precipitates, dislocations and voids are produced, along with stored energy (the maximum value observed until now ˜ 76kJ/mol, which is about 18.5% of the enthalpy of formation of NaCl, 411.2kJ/mol). This implies that heavily irradiated NaCl is a highly energetic material. We have observed that the samples, which revealed large radiation-induced voids, explode rather easily. In these samples the instability connected with large voids (hot spots) probably initiates the explosive release of stored energy, which is in many cases accompanied by characteristic (explosive) sounds. In this paper we will discuss the nature of the explosions and show that a basically stable insulating compound, such as NaCl, may become unstable after heavy irradiation.

Vainshtein, D. I.; Hartog, H. W. Den

268

The Na?/L-proline transporter PutP.  

PubMed

The Na?/L-proline transporter PutP is a member of the Na?/solute symporter family (TC 2A.21, SLC5), which contains several hundred proteins of pro- and eukaryotic origin. Within the family, the capability of L-proline uptake is restricted to proteins of prokaryotes. PutP contributes to the use of L-proline as a nutrient. In addition, the transporter may supply cells with compatible solute during adaptation to osmotic stress. Based on these and other functions, PutP is of significance for various bacteria-host interactions including the virulence of human pathogens. A homology model of Escherichia coli PutP was generated based on the crystal structure of the Vibrio parahaemolyticus Na+/galactose symporter. According to the model, PutP has a core structure of five plus five transmembrane domains forming an inverted repeat similar as originally revealed by the crystal structure of the Na+/leucine transporter LeuT. The homology model is experimentally verified by Cys cross-linking and site-directed spin labeling in combination with electron paramagnetic resonance spectroscopy. The putative sites of Na? and L-proline binding are described, and a putative transport mechanism is discussed. PMID:22201772

Jung, Heinrich; Hilger, Daniel; Raba, Michael

2012-01-01

269

Preparation and characterization of NaCS-CMC/PDMDAAC capsules.  

PubMed

A novel capsule system composed of sodium cellulose sulfate (NaCS), carboxymethyl cellulose (CMC) and poly[dimethyl(diallyl)ammonium chloride] (PDMDAAC) was prepared for improving the properties of NaCS/PDMDAAC capsules. The process parameters, such as CMC concentration (0, 2, 4, 6 and 8 g/L), NaCS concentration (20, 25, 30, 35 and 40 g/L), PDMDAAC concentration (20, 30, 40, 50, 60, 70 and 80 g/L), reaction time and temperature were investigated to understand their effects on the diameter, membrane thickness and mechanical strength of capsules. The optimum operation conditions for preparing NaCS-CMC/PDMDAAC capsules were determined as 6-8 g/L CMC, 35-40 g/L NaCS, 60 g/L PDMDAAC and polymerization for 30-40 min. Diffusion of substances with low molecular weight into capsules was investigated, and diffusion coefficients were calculated according to the developed model. The yeast of Candida krusei was chosen as representative cell to evaluate the effects of different cell loading on capsule mechanical strength. Meanwhile the encapsulated osmophilic C. krusei cells were cultured in 250 mL shaking flasks for 72 h to determine the cell leaking properties in short and long term. PMID:16199144

Chen, Guo; Yao, Shan-jing; Guan, Yi-xin; Lin, Dong-qiang

2005-11-10

270

Effects of Osmoprotectants upon NaCl Stress in Rice.  

PubMed Central

Plants accumulate a number of osmoprotective substances in response to NaCl stress, one of them being proline (Pro). While characterizing some of the changes in solute accumulation in NaCl-stressed rice (Oryza sativa L.), we identified several other potential osmoprotectants. One such substance, trehalose, begins to accumulate in small amounts in roots after 3 d. We performed a series of experiments to compare the effects of Pro and trehalose on ion accumulation to determine whether the two chemicals protect the same physiological processes. We found that Pro either has no effect or, in some cases, exasperates the effect of NaCl on growth inhibition, chlorophyll loss, and induction of a highly sensitive marker for plant stress, the osmotically regulated salT gene. By contrast, low to moderate concentrations of trehalose reduce Na+ accumulation, salT expression, and growth inhibition. Somewhat higher concentrations (10 mM) prevent NaCl-induced loss of chlorophyll in blades, preserve root integrity, and enhance growth. The results of this study indicate that during osmotic stress trehalose or carbohydrates might be more important for rice than Pro.

Garcia, A. B.; Engler, JdA.; Iyer, S.; Gerats, T.; Van Montagu, M.; Caplan, A. B.

1997-01-01

271

Ouabain Binding Site in a Functioning Na+/K+ ATPase*  

PubMed Central

The Na+/K+ ATPase is an almost ubiquitous integral membrane protein within the animal kingdom. It is also the selective target for cardiotonic derivatives, widely prescribed inhibitors for patients with heart failure. Functional studies revealed that ouabain-sensitive residues distributed widely throughout the primary sequence of the protein. Recently, structural work has brought some consensus to the functional observations. Here, we use a spectroscopic approach to estimate distances between a fluorescent ouabain and a lanthanide binding tag (LBT), which was introduced at five different positions in the Na+/K+ ATPase sequence. These five normally functional LBT-Na+/K+ ATPase constructs were expressed in the cell membrane of Xenopus laevis oocytes, operating under physiological internal and external ion conditions. The spectroscopic data suggest two mutually exclusive distances between the LBT and the fluorescent ouabain. From the estimated distances and using homology models of the LBT-Na+/K+ ATPase constructs, approximate ouabain positions could be determined. Our results suggest that ouabain binds at two sites along the ion permeation pathway of the Na+/K+ ATPase. The external site (low apparent affinity) occupies the same region as previous structural findings. The high apparent affinity site is, however, slightly deeper toward the intracellular end of the protein. Interestingly, in both cases the lactone ring faces outward. We propose a sequential ouabain binding mechanism that is consistent with all functional and structural studies.

Sandtner, Walter; Egwolf, Bernhard; Khalili-Araghi, Fatemeh; Sanchez-Rodriguez, Jorge E.; Roux, Benoit; Bezanilla, Francisco; Holmgren, Miguel

2011-01-01

272

Links between hydrothermal environments, pyrophosphate, na(+), and early evolution.  

PubMed

The discovery that photosynthetic bacterial membrane-bound inorganic pyrophosphatase (PPase) catalyzed light-induced phosphorylation of orthophosphate (Pi) to pyrophosphate (PPi) and the capability of PPi to drive energy requiring dark reactions supported PPi as a possible early alternative to ATP. Like the proton-pumping ATPase, the corresponding membrane-bound PPase also is a H(+)-pump, and like the Na(+)-pumping ATPase, it can be a Na(+)-pump, both in archaeal and bacterial membranes. We suggest that PPi and Na(+) transport preceded ATP and H(+) transport in association with geochemistry of the Earth at the time of the origin and early evolution of life. Life may have started in connection with early plate tectonic processes coupled to alkaline hydrothermal activity. A hydrothermal environment in which Na(+) is abundant exists in sediment-starved subduction zones, like the Mariana forearc in the W Pacific Ocean. It is considered to mimic the Archean Earth. The forearc pore fluids have a pH up to 12.6, a Na(+)-concentration of 0.7 mol/kg seawater. PPi could have been formed during early subduction of oceanic lithosphere by dehydration of protonated orthophosphates. A key to PPi formation in these geological environments is a low local activity of water. PMID:21461648

Holm, Nils G; Baltscheffsky, Herrick

2011-10-01

273

PTCDA on Cu(111) partially covered with NaCl  

NASA Astrophysics Data System (ADS)

The organic molecule 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) was studied by means of scanning tunneling microscopy (STM) on thin insulating NaCl films grown on a Cu(111) single crystal. The deposition of approximately two monolayers (ML) of sodium chloride onto a Cu(111) substrate at a sample temperature of about 350 K causes a rather rough growth of (100)-oriented NaCl islands up to a local height of 4 ML. For submonolayer coverages (0.1 and 0.4 ML) of PTCDA on a Cu(111) surface partly covered with NaCl, two different rod structures of PTCDA were found on the copper surface, which are in contrast to previously published data for PTCDA on Cu(111) showing a herringbone-like arrangement. These findings can be explained by the formation of a Nax-PTCDA complex. On NaCl covered areas, single PTCDA molecules adsorb at vacancies of [010] and [001] oriented steps of the NaCl(100) islands. In this case, the electrostatic forces between the polar step edges and the PTCDA molecules are dominant. The terraces of the alkali halide surface are free of PTCDA molecules.

Karacuban, H.; Koch, S.; Fendrich, M.; Wagner, Th; Möller, R.

2011-07-01

274

Estragole blocks neuronal excitability by direct inhibition of Na+ channels  

PubMed Central

Estragole is a volatile terpenoid, which occurs naturally as a constituent of the essential oils of many plants. It has several pharmacological and biological activities. The objective of the present study was to investigate the mechanism of action of estragole on neuronal excitability. Intact and dissociated dorsal root ganglion neurons of rats were used to record action potential and Na+ currents with intracellular and patch-clamp techniques, respectively. Estragole blocked the generation of action potentials in cells with or without inflexions on their descendant (repolarization) phase (Ninf and N0 neurons, respectively) in a concentration-dependent manner. The resting potentials and input resistances of Ninf and N0 cells were not altered by estragole (2, 4, and 6 mM). Estragole also inhibited total Na+ current and tetrodotoxin-resistant Na+ current in a concentration-dependent manner (IC50 of 3.2 and 3.6 mM, respectively). Kinetic analysis of Na+ current in the presence of 4 mM estragole showed a statistically significant reduction of fast and slow inactivation time constants, indicating an acceleration of the inactivation process. These data demonstrate that estragole blocks neuronal excitability by direct inhibition of Na+ channel conductance activation. This action of estragole is likely to be relevant to the understanding of the mechanisms of several pharmacological effects of this substance.

Silva-Alves, K.S.; Ferreira-da-Silva, F.W.; Peixoto-Neves, D.; Viana-Cardoso, K.V.; Moreira-Junior, L.; Oquendo, M.B.; Oliveira-Abreu, K.; Albuquerque, A.A.C.; Coelho-de-Souza, A.N.; Leal-Cardoso, J.H.

2013-01-01

275

High-NA HPCS optical fibers for medical diagnosis and treatment  

NASA Astrophysics Data System (ADS)

Hard Plastic Clad Silica (HPCS) optical fibers with pure silica cores have been developed which are robust and have NA(Numerical Aperture)>0.50. Improved clad only HPCS fibers have been produced for both new 'standard' and 'high' NA versions. Based on new cladding formulations, the 'standard' NA fiber has an NA of 0.41, while the new ultrahigh NA fiber has an NA of 0.54. Mechanical strength and preliminary fatigue data are presented along with spectral characterization data. For the first time significant results were obtained for clad only high NA fibers, The fibers are useful for diagnostic and surgical applications. Short to medium length time to failure results, indicate that the static fatigue parameters of the new high numerical aperture (NA) optical fibers are at least as good as those for former standard NA (0.37) HPCS fibers, which is an advance from previous results on the older formulation high NA fibers.

Skutnik, Bolesh J.

2010-02-01

276

Effects of K+-deficient diets with and without NaCl supplementation on Na+, K+, and H2O transporters' abundance along the nephron.  

PubMed

Dietary potassium (K(+)) restriction and hypokalemia have been reported to change the abundance of most renal Na(+) and K(+) transporters and aquaporin-2 isoform, but results have not been consistent. The aim of this study was to reexamine Na(+), K(+) and H(2)O transporters' pool size regulation in response to removing K(+) from a diet containing 0.74% NaCl, as well as from a diet containing 2% NaCl (as found in American diets) to blunt reducing total diet electrolytes. Sprague-Dawley rats (n = 5-6) were fed for 6 days with one of these diets: 2% KCl, 0.74% NaCl (2K1Na, control chow) compared with 0.03% KCl, 0.74% NaCl (0K1Na); or 2% KCl, 2%NaCl (2K2Na) compared with 0.03% KCl, 2% NaCl (0K2Na, Na(+) replete). In both 0K1Na and 0K2Na there were significant decreases in: 1) plasma [K(+)] (<2.5 mM); 2) urinary K(+) excretion (<5% of control); 3) urine osmolality and plasma [aldosterone], as well as 4) an increase in urine volume and medullary hypertrophy. The 0K2Na group had the lowest [aldosterone] (172.0 ± 17.4 pg/ml) and lower blood pressure (93.2 ± 4.9 vs. 112.0 ± 3.1 mmHg in 2K2Na). Transporter pool size regulation was determined by quantitative immunoblotting of renal cortex and medulla homogenates. The only differences measured in both 0K1Na and 0K2Na groups were a 20-30% decrease in cortical ?-ENaC, 30-40% increases in kidney-specific Ste20/SPS1-related proline/alanine-rich kinase, and a 40% increase in medullary sodium pump abundance. The following proteins were not significantly changed in both the 0 K groups: Na(+)/H(+) exchanger isoform 3; Na(+)-K(+)-Cl(-) cotransporter; Na(+)-Cl(-) cotransporter, oxidative stress response kinase-1; renal outer medullary K(+) channel; autosomal recessive hypercholesterolemia; c-Src, aquaporin 2 isoform; or renin. Thus, despite profound hypokalemia and renal K(+) conservation, we did not confirm many of the changes that were previously reported. We predict that changes in transporter distribution and activity are likely more important for conserving K(+) than changes in total abundance. PMID:22496411

Nguyen, Mien T X; Yang, Li E; Fletcher, Nicholas K; Lee, Donna H; Kocinsky, Hetal; Bachmann, Sebastian; Delpire, Eric; McDonough, Alicia A

2012-07-01

277

Effects of K+-deficient diets with and without NaCl supplementation on Na+, K+, and H2O transporters' abundance along the nephron  

PubMed Central

Dietary potassium (K+) restriction and hypokalemia have been reported to change the abundance of most renal Na+ and K+ transporters and aquaporin-2 isoform, but results have not been consistent. The aim of this study was to reexamine Na+, K+ and H2O transporters' pool size regulation in response to removing K+ from a diet containing 0.74% NaCl, as well as from a diet containing 2% NaCl (as found in American diets) to blunt reducing total diet electrolytes. Sprague-Dawley rats (n = 5–6) were fed for 6 days with one of these diets: 2% KCl, 0.74% NaCl (2K1Na, control chow) compared with 0.03% KCl, 0.74% NaCl (0K1Na); or 2% KCl, 2%NaCl (2K2Na) compared with 0.03% KCl, 2% NaCl (0K2Na, Na+ replete). In both 0K1Na and 0K2Na there were significant decreases in: 1) plasma [K+] (<2.5 mM); 2) urinary K+ excretion (<5% of control); 3) urine osmolality and plasma [aldosterone], as well as 4) an increase in urine volume and medullary hypertrophy. The 0K2Na group had the lowest [aldosterone] (172.0 ± 17.4 pg/ml) and lower blood pressure (93.2 ± 4.9 vs. 112.0 ± 3.1 mmHg in 2K2Na). Transporter pool size regulation was determined by quantitative immunoblotting of renal cortex and medulla homogenates. The only differences measured in both 0K1Na and 0K2Na groups were a 20–30% decrease in cortical ?-ENaC, 30–40% increases in kidney-specific Ste20/SPS1-related proline/alanine-rich kinase, and a 40% increase in medullary sodium pump abundance. The following proteins were not significantly changed in both the 0 K groups: Na+/H+ exchanger isoform 3; Na+-K+-Cl? cotransporter; Na+-Cl? cotransporter, oxidative stress response kinase-1; renal outer medullary K+ channel; autosomal recessive hypercholesterolemia; c-Src, aquaporin 2 isoform; or renin. Thus, despite profound hypokalemia and renal K+ conservation, we did not confirm many of the changes that were previously reported. We predict that changes in transporter distribution and activity are likely more important for conserving K+ than changes in total abundance.

Nguyen, Mien T. X.; Yang, Li E.; Fletcher, Nicholas K.; Lee, Donna H.; Kocinsky, Hetal; Bachmann, Sebastian; Delpire, Eric

2012-01-01

278

Differential sensitivity of stomatal and non-stomatal components to NaCl or Na2SO4 salinity in horsegram, Macrotyloma uniflorum (Lam.)  

Microsoft Academic Search

14CO2 assimilation rate (P), leaf diffusive conductance (gs), photosynthetic electron flow, and activities of enzymes of Calvin cycle were studied in a horsegram [Macrotyloma uniflorum (Lam.)] in response to salinity induced by NaCl or Na2SO4. A significant reduction in P and gs by both salt treatments was registered. Na2SO4 caused a greater reduction in gs than the NaCl salinity. Studies

P. Sreenivasulu Reddy; S. Ramanjulu; C. Sudhakar; K. Veeranjaneyulu

1998-01-01

279

Correlation between Intracellular Activities of Ca2+ and Na+ in Rat Cortical Collecting Duct – A Possible Coupling Mechanism between Na+-K+ATPase and Basolateral K+ Conductance  

Microsoft Academic Search

In principal cells of rat cortical collecting ducts (CCD) the K+ conductance of the basolateral membrane is functionally coupled to the Na+-K+-ATPase. Inhibition of the Na+-K+-ATPase by ouabain resulted in a decrease of this conductance. This inhibition was absent in the presence of amiloride. In the present study we attempted to measure the activities of intracellular Na+ ([Na+]i) and intracellular

Eberhard Schlatter; Sabine Haxelmans; Ieva Ankorina

1996-01-01

280

Contractile abnormalities of mouse muscles expressing hyperkalemic periodic paralysis mutant NaV1.4 channels do not correlate with Na+ influx or channel content.  

PubMed

Hyperkalemic periodic paralysis (HyperKPP) is characterized by myotonic discharges that occur between episodic attacks of paralysis. Individuals with HyperKPP rarely suffer respiratory distress even though diaphragm muscle expresses the same defective Na(+) channel isoform (NaV1.4) that causes symptoms in limb muscles. We tested the hypothesis that the extent of the HyperKPP phenotype (low force generation and shift toward oxidative type I and IIA fibers) in muscle is a function of 1) the NaV1.4 channel content and 2) the Na(+) influx through the defective channels [i.e., the tetrodotoxin (TTX)-sensitive Na(+) influx]. We measured NaV1.4 channel protein content, TTX-sensitive Na(+) influx, force generation, and myosin isoform expression in four muscles from knock-in mice expressing a NaV1.4 isoform corresponding to the human M1592V mutant. The HyperKPP flexor digitorum brevis muscle showed no contractile abnormalities, which correlated well with its low NaV1.4 protein content and by far the lowest TTX-sensitive Na(+) influx. In contrast, diaphragm muscle expressing the HyperKPP mutant contained high levels of NaV1.4 protein and exhibited a TTX-sensitive Na(+) influx that was 22% higher compared with affected extensor digitorum longus (EDL) and soleus muscles. Surprisingly, despite this high burden of Na(+) influx, the contractility phenotype was very mild in mutant diaphragm compared with the robust abnormalities observed in EDL and soleus. This study provides evidence that HyperKPP phenotype does not depend solely on the NaV1.4 content or Na(+) influx and that the diaphragm does not depend solely on Na(+)-K(+) pumps to ameliorate the phenotype. PMID:24714718

Lucas, Brooke; Ammar, Tarek; Khogali, Shiemaa; DeJong, Danica; Barbalinardo, Michael; Nishi, Cameron; Hayward, Lawrence J; Renaud, Jean-Marc

2014-06-01

281

Local structure analysis of NaNbO3  

NASA Astrophysics Data System (ADS)

NaNbO3 has an antiferroelectric structure at room temperature and finds important technological applications. It exhibits an unusual complex sequence of temperature-and pressure-driven structural phase transitions. NaNbO3 shows unambiguous evidence for the presence of the ferroelectric R3c phase coexisting with an antiferroelectric phase (Pbcm) over a wide range of temperatures. We have carried out atomic pair-distribution function (PDF) analysis on NaNbO3 to understand the phase transitions. High-energy X-ray PDF using powder samples were carried out at the SPring-8, which is provided to become rhombohedral structure if A-site atoms did order and to become orthorhombic structure if A-site atoms did disorder.

Yoneda, Y.; Fu, D.; Kohara, S.

2014-04-01

282

The NA62 Liquid Krypton calorimeter readout module  

NASA Astrophysics Data System (ADS)

The NA62 experiment [1] at CERN SPS (Super Proton Synchrotron) accelerator will be focused on precision tests of the Standard Model via studies of ultra-rare decays of charged kaons. The high resolution Liquid Krypton (LKr) calorimeter of the former NA48 experiment [2], together with other detectors, will provide a photon-veto with hermetic coverage from zero out to large angles from the decay region. The old backend electronics [3] does not satisfy the NA62 specifications and the study of a new readout system began in 2008. This paper presents the Calorimeter REAdout Module (CREAM), an upgrade project for the backend part of the LKr data acquisition chain [3]. The CREAMs will provide 40 MHz sampling of 13248 calorimeter channels, data buffering during the SPS spill, zero suppression, and programmable trigger sums for the experiment trigger processor.

Ceccucci, A.; Fantechi, R.; Farthouat, P.; Lamanna, G.; Ryjov, V.

2011-12-01

283

Na3Al(AsO4)2  

PubMed Central

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

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

2013-01-01

284

Raman spectrum of Na 2SO 4 (phase V)  

NASA Astrophysics Data System (ADS)

The Raman spectrum of Na 2SO 4 in its stable low-temperature phase (space group D 242h) has been measured at temperatures of 10 and 295 K. Spectral features have been observed that were not reported in the earlier study of Montero. All of the 21 Raman-active vibrational modes have been identified and assigned to symmetry species. The division into lattice and sulfate internal modes is well obeyed in Na 2SO 4. Other weaker features are assigned variously to isotope modes and Fermi resonance modes, and the coupling between two internal modes is analyzed. The Raman spectrum indicates that there is no phase change in Na 2SO 4 (V) between 10 and 295 K.

Choi, Byoung-Koo; Lockwood, D. J.

1989-10-01

285

NaCl as a retrospective and accident dosemeter.  

PubMed

NaCl is a cheap and widely available material. This study investigated the potential of NaCl in the form of a household salt as a retrospective and accident dosemeter using optically stimulated luminescence (OSL). Samples of the investigated household salt were stimulated using blue light of linearly modulated power. Attention was concentrated on sensitivity, dose dependence of the OSL signal, fading, optimisation of the read-out procedure and application of analytical protocols that do not require a specific calibration. A potential of NaCl as a complementary dosemeter within emergency preparedness was considered. The behaviour of the OSL signal observed was found to be favourable for dosimetry. PMID:21068016

Ekendahl, Daniela; Judas, Libor

2011-04-01

286

Superconducting properties and electronic structure of NaBi  

NASA Astrophysics Data System (ADS)

Resistivity, dc magnetization, and heat capacity measurements are reported for superconducting NaBi. Tc, the electronic contribution to the specific heat ?, the ?Cp/?Tc ratio, and the Debye temperature are found to be 2.15?K, 3.4?mJ?mol?1?K?2, 0.78, and 140?K respectively. The calculated electron–phonon coupling constant (?ep = 0.62) implies that NaBi is a moderately coupled superconductor. The upper critical field and coherence length are found to be 250?Oe and 115?nm, respectively. Electronic structure calculations show NaBi to be a good metal, in agreement with the experiments; the px and py orbitals of Bi dominate the electronic states at the Fermi Energy.

Kushwaha, S. K.; Krizan, J. W.; Xiong, J.; Klimczuk, T.; Gibson, Q. D.; Liang, T.; Ong, N. P.; Cava, R. J.

2014-05-01

287

Superconducting properties and electronic structure of NaBi.  

PubMed

Resistivity, dc magnetization, and heat capacity measurements are reported for superconducting NaBi. T(c), the electronic contribution to the specific heat ?, the ?C(p)/?T(c) ratio, and the Debye temperature are found to be 2.15?K, 3.4?mJ?mol(-1)?K(-2), 0.78, and 140?K respectively. The calculated electron-phonon coupling constant (?(ep) = 0.62) implies that NaBi is a moderately coupled superconductor. The upper critical field and coherence length are found to be 250?Oe and 115?nm, respectively. Electronic structure calculations show NaBi to be a good metal, in agreement with the experiments; the p(x) and p(y) orbitals of Bi dominate the electronic states at the Fermi Energy. PMID:24804822

Kushwaha, S K; Krizan, J W; Xiong, J; Klimczuk, T; Gibson, Q D; Liang, T; Ong, N P; Cava, R J

2014-05-28

288

Multibubble sonoluminescence pulses from Na atoms in viscous liquid.  

PubMed

Multibubble sonoluminescence pulses of Na and continuum emissions were measured from NaCl-ethylene glycol solution saturated with Xe at 28 kHz. The Na emission consisted of multiple-peak pulses and single pulses. The intrinsic pulse width estimated from single pulses was 0.37 ns, which differs from 10-165 ns obtained by previous work. High-speed shadowgraphs of bubble dynamics and high-speed movies (32000 fps) of sonoluminescence were observed. The observations suggest that the multiple-peak pulse is due to the superposition of single peaks resulting from bubbles fragmented from a characteristic bubble which repeats the fragmentation and coalescence. This phenomenon may be specific to viscous liquids. PMID:22559461

Choi, Pak-Kon; Sawada, Yosuke; Takeuchi, Yuuta

2012-05-01

289

GaN single crystal growth using high-purity Na as a flux  

Microsoft Academic Search

GaN single crystals were synthesized at 750–775°C and 5MPa of N2 for 200–300h using Na–Ga melts with the mole fractions of Na\\/(Ga+Na) of 0.60–0.67 in the starting melt. When 99% pure Na was used, almost all the melt surface was covered with a GaN polycrystalline layer which prevented the single crystal growth. By using 99.95% Na, no polycrystalline layer formed

Masato Aoki; Hisanori Yamane; Masahiko Shimada; Seiji Sarayama; Francis J DiSalvo

2002-01-01

290

Is potassium co-transported by the cardiac NaCa exchange?  

Microsoft Academic Search

It has been suggested that the stoichiometry of the electrogenic Na-Ca exchange is 3Na:1Ca. Recently, however, it was reported in rod outer segments that the stoichiometry of Na-Ca exchange is not 3Na:1Ca but 4Na:1Ca+1K. In cardiac cells, the reversal potential has always been measured in the absence of K or at a very low K concentration. We have, therefore, re-examined

K. Yasui; J. Kimura

1990-01-01

291

Na 2 SO 4 -induced accelerated oxidation (hot corrosion) of nickel  

Microsoft Academic Search

The Na2SO4-induced accelerated oxidation of nickel has been studied at 1000C. It has been found that low oxygen activities in the Na2SO4, which are produced by the formation of NiO, cause the sulfur activity of the Na2SO4 to be increased. Nickel and sulfur from the Na2SO4 combine to form nickel sulfide and the oxide ion activity of the Na2SO4 is

J. A. Goebel; F. S. Pettit

1970-01-01

292

Excitatory Sympathetic Reflex in NaCl-Sensitive Spontaneously Hypertensive Rats  

Microsoft Academic Search

We have previously demonstrated blunted reflex responses of lumbar sympathetic nerve activity during volume expansion in NaCl-sensitive spontaneously hypertensive rats maintained on basal (1% NaCl) diets compared with NaCl-resistant spontaneously hypertensive rats, Wistar-Kyoto rats, and Sprague-Dawley rats. The current study tested the hypothesis that chronic ingestion of a high (8%) NaCl diet further blunts cardiopulmonary reflex function in the NaCl-sensitive

Yoshinari Nakamura; David A. Calhoun; Yiu-Fai Chen; J. Michael Wyss; Suzanne Oparil

2009-01-01

293

Salicylic acid alleviates NaCl-induced changes in the metabolism of Matricaria chamomilla plants  

Microsoft Academic Search

Influence of 100 mM NaCl and 50 ?M salicylic acid (SA) and their combination on the metabolism of chamomile (Matricaria chamomilla) during 7 days was studied. NaCl reduced growth and selected physiological parameters and SA in combined treatment (NaCl + SA)\\u000a reversed majority of these symptoms. Application of SA reduced NaCl-induced increase of Na+ in the rosettes, but not in the roots. Accumulation of total

Jozef Ková?ik; Bo?ivoj Klejdus; Josef Hedbavny; Martin Ba?kor

2009-01-01

294

Inherited defect in a Na+, K+ -co-transport system in erythrocytes from essential hypertensive patients  

Microsoft Academic Search

The Na+ and K+ electrochemical gradients across cell membranes are believed to be maintained by the action of a Na+, K+-pump1-3. In human erythrocytes this pump exchanges internal Na+ for external K+ in approximately a 1.5 ratio4,5. Thus, when Na+-loaded\\/K+-depleted erythrocytes are incubated in physiological conditions they tend to recover their original low Na+\\/high K+ content. Surprisingly, in erythrocytes from

Ricardo P. Garay; Georges Dagher; Marie-Gabrielle Pernollet; Marie-Aude Devynck; Philippe Meyer

1980-01-01

295

Na sup + -Ca sup 2+ exchange in human neutrophils  

SciTech Connect

The pathway for inward Ca{sup 2+} movements in isolated human neutrophils was investigated. One-way {sup 45}Ca{sup 2+} influx into resting, steady-state cells amounted to {approximately}6 {mu}mol{center dot}1 cell water{sup {minus}1}{center dot}min{sup {minus}1}. This uptake can be entirely accounted for on the basis of a carrier-mediated exchange of external Ca{sup 2+} for internal Na{sup +}. The counter transport exhibited trans stimulation of {sup 45}Ca{sup 2+} influx by internal Na{sup +} with a Hill coefficient of {approx equal}2.6. There was substrate saturation by external Ca{sup 2+} and by external Na{sup +}; the two ions competed for the same binding sites. The exchange was noncompetitively inhibited by benzamil and by some other amiloride analogues bearing a substituent on the terminal nitrogen atom of the guanidino group. Membrane depolarization enhanced the rate of {sup 45}Ca{sup 2+} entry, suggesting an electrogenic process; this voltage dependence was consistent with a coupling ratio of {approximately}3 Na{sup +}:1 Ca{sup 2+}. Hence, the Na{sup +}-Ca{sup 2+} exchange mechanism of neutrophils displays many features in common with those of other cell types. Studies in cells exposed to the tripeptide N-formyl-methionyl-leucyl-phenylalanine (FMLP) indicate activation of the counter-transport system by the chemotatic factor. Thus, Na{sup +}-Ca{sup 2+} exchange may be at least partly responsible for the increase in {sup 45}Ca{sup 2+} influx and transient rise in intracellular free Ca{sup 2+} that are seen following stimulation.

Simchowitz, L.; Cragoe, E.J. Jr. (Washington Univ. School of Medicine, St. Louis, MO (USA) Merck Sharp Dohme Research Laboratories, West Point, PA (USA))

1988-01-01

296

The effect of antidiuretic hormone on Na movement across frog skin  

PubMed Central

1. The effect of antidiuretic hormone (ADH) on the movement and distribution of Na was studied. This was done using three different approaches: (a) the measurement of Na and 22Na in slices of epithelium of skins which were exposed to Ringer of varied composition containing 22Na, (b) the measurement of the influx of Na from the outer to the inner bathing solution with 22Na added to the outside, and (c) the use of a recently introduced technique which permits the direct evaluation of the flux from the outer solution ? epithelium, (JOT), i.e. the flux across the barrier which is generally regarded as the site of ADH activity. 2. ADH increased the influx from the outer to the inner bathing solution of Na (50%) not only when the concentration of Na on the outside was 115 mM (i.e. higher than in the epithelium) but even when the concentration was 1 mM (67%). 3. When the skin was bathed with 1mM-Na Ringer on the outside, ADH increased the unidirectional Na flux JOT by 56% (Rana pipiens) and 71% (Leptodactylus ocellatus). When the concentration was 115 mM a small increase (17%) was observed in paired skins of R. pipiens. Under this condition no change was observed in L. ocellatus. 4. The amount of epithelial sodium which is labelled by 22Na added to the outside was taken to reflect the amount of Na involved in Na transport across the epithelium. Depending on whether the concentration of Na on the outside was high (115 mM) or low (1 mM), ADH produced an increase, or a decrease, of both the total Na content and the amount of 22Na exchanged. 5. When the concentration of Na on the outside was low, ADH increased the total influx and JOT in spite of the fact that it lowers the total Na content and does not affect the exchangeable pool of Na. This observation is inconsistent with the view that the effect of ADH is due to the fact that the increased permeability of the outer barrier allows more Na into the cell, and that the resulting increase of Na concentration in the cytoplasm accelerates the Na pumps at the inner side of the cells. 6. It is concluded that ADH speeds up Na movements at the outward facing barrier, and that this exchange which facilitates the penetration of Na into a transporting compartment produces also a gain or a loss of Na in compartments not directly involved in Na transport across the epithelium. One compartment which is not involved in Na transport might be the cytoplasm of the epithelial cells.

Cereijido, M.; Rotunno, Catalina A.

1971-01-01

297

Synthesis, photophysical properties, and photocatalytic applications of Bi doped NaTaO3 and Bi doped Na2Ta2O6 nanoparticles  

NASA Astrophysics Data System (ADS)

Phase formation and photophysical properties of bismuth doped sodium tantalum oxide (perovskite, defect pyrochlore) nanoparticles prepared by a hydrothermal method were studied in detail. It was revealed that the synthesis conditions like NaOH concentration and bismuth precursor (NaBiO3·2H2O) markedly affect the crystal structure of sodium tantalum oxide. At low NaOH concentration and high bismuth precursor (NaBiO3·2H2O) content, Bi doped Na2Ta2O6 (defect pyrochlore) phase was predominantly formed, while at higher NaOH concentration, Bi doped NaTaO3 (perovskite) phase was formed. It was observed that the defect pyrochlore (Bi doped Na2Ta2O6) phase was formed and stabilized by the presence of dopant precursor (NaBiO3·2H2O). The chemical analysis of the samples confirmed the doping of Bi3+ cations in both phases. Doping of bismuth enabled visible light absorption up to 500 nm in perovskite and defect pyrochlore type sodium tantalum oxide. Bi doped NaTaO3 samples showed better performance for the photocatalytic degradation of rhodamine B than that of Bi doped Na2Ta2O6, under visible light irritation (?>420 nm). The present results shed light on phase formation of sodium tantalate and these results are useful in understanding properties of NaTaO3 based compounds, synthesized by the hydrothermal method.

Kanhere, Pushkar; Tang, Yuxin; Zheng, Jianwei; Chen, Zhong

2013-12-01

298

Gas exchange and growth responses of ectomycorrhizal Picea mariana, Picea glauca, and Pinus banksiana seedlings to NaCl and Na2SO4.  

PubMed

Black spruce (PICEA MARIANA), white spruce (PICEA GLAUCA), and jack pine (PINUS BANKSIANA) seedlings were inoculated with HEBELOMA CRUSTULINIFORME or LACCARIA BICOLOR and subjected to NaCl and Na (2)SO (4) treatments. The effects of ectomycorrhizas on salt uptake, growth, gas exchange, and needle necrosis varied depending on the tree and fungal species. In jack pine seedlings, ectomycorrhizal (ECM) fungi reduced shoot and root dry weights and in the ECM white spruce, there was a small increase in dry weights. Sodium chloride treatment reduced net photosynthesis and transpiration rates in the three studied tree species. However, NaCl-treated black spruce and jack pine colonized by H. CRUSTULINIFORME maintained relatively high photosynthetic and transpiration rates and needle necrosis of NaCl-treated black spruce seedlings was reduced by the ECM fungi. Higher concentrations of Na (+) were found in shoots compared with roots of the three examined conifer species. ECM fungi reduced the concentrations of Na (+) mainly in the shoots and this reduction was greater in plants treated with NaCl compared with Na (2)SO (4). Shoots contained generally higher concentrations of Cl (-) compared with roots. In the NaCl-treated black spruce and white spruce, both ECM species significantly reduced Cl (-) concentrations. Our results point to overall greater phytotoxicity of NaCl compared with Na (2)SO (4) and support our earlier findings which demonstrated beneficial effects of ECM fungi for woody plants exposed to NaCl stress. PMID:16755463

Nguyen, H; Calvo Polanco, M; Zwiazek, J J

2006-09-01

299

Kinetic study of the reactions Na + O sub 2 + N sub 2 and Na + N sub 2 O over an extended temperature range  

Microsoft Academic Search

An investigation is presented of the recombination reaction Na + Oâ + Nâ by the technique of pulsed photolysis of a Na atom precursor followed by time-resolved laser induced fluorescence spectroscopy of Na atoms at λ = 589 nm. Termolecular behavior was demonstrated, and absolute third-order rate constants were obtained over the temperature range 233-1118 K. A fit of this

J. M. C. Plane; B. Rajasekhar

1989-01-01

300

Pancreatic ?-cell Na+ channels control global Ca2+ signaling and oxidative metabolism by inducing Na+ and Ca2+ responses that are propagated into mitochondria.  

PubMed

Communication between the plasma membrane and mitochondria is essential for initiating the Ca(2+) and metabolic signals required for secretion in ? cells. Although voltage-dependent Na(+) channels are abundantly expressed in ? cells and activated by glucose, their role in communicating with mitochondria is unresolved. Here, we combined fluorescent Na(+), Ca(2+), and ATP imaging, electrophysiological analysis with tetrodotoxin (TTX)-dependent block of the Na(+) channel, and molecular manipulation of mitochondrial Ca(2+) transporters to study the communication between Na(+) channels and mitochondria. We show that TTX inhibits glucose-dependent depolarization and blocks cytosolic Na(+) and Ca(2+) responses and their propagation into mitochondria. TTX-sensitive mitochondrial Ca(2+) influx was largely blocked by knockdown of the mitochondrial Ca(2+) uniporter (MCU) expression. Knockdown of the mitochondrial Na(+)/Ca(2+) exchanger (NCLX) and Na(+) dose response analysis demonstrated that NCLX mediates the mitochondrial Na(+) influx and is tuned to sense the TTX-sensitive cytosolic Na(+) responses. Finally, TTX blocked glucose-dependent mitochondrial Ca(2+) rise, mitochondrial metabolic activity, and ATP production. Our results show that communication of the Na(+) channels with mitochondria shape both global Ca(2+) and metabolism signals linked to insulin secretion in ? cells.- Nita, I. I., Hershfinkel, M., Kantor, C., Rutter, G. A., Lewis, E. C., Sekler, I. Pancreatic ?-cell Na(+) channels control global Ca(2+) signaling and oxidative metabolism by inducing Na(+) and Ca(2+) responses that are propagated into mitochondria. PMID:24719357

Nita, Iulia I; Hershfinkel, Michal; Kantor, Chase; Rutter, Guy A; Lewis, Eli C; Sekler, Israel

2014-08-01

301

Shoot Na+ Exclusion and Increased Salinity Tolerance Engineered by Cell Type-Specific Alteration of Na+ Transport in Arabidopsis[W][OA  

PubMed Central

Soil salinity affects large areas of cultivated land, causing significant reductions in crop yield globally. The Na+ toxicity of many crop plants is correlated with overaccumulation of Na+ in the shoot. We have previously suggested that the engineering of Na+ exclusion from the shoot could be achieved through an alteration of plasma membrane Na+ transport processes in the root, if these alterations were cell type specific. Here, it is shown that expression of the Na+ transporter HKT1;1 in the mature root stele of Arabidopsis thaliana decreases Na+ accumulation in the shoot by 37 to 64%. The expression of HKT1;1 specifically in the mature root stele is achieved using an enhancer trap expression system for specific and strong overexpression. The effect in the shoot is caused by the increased influx, mediated by HKT1;1, of Na+ into stelar root cells, which is demonstrated in planta and leads to a reduction of root-to-shoot transfer of Na+. Plants with reduced shoot Na+ also have increased salinity tolerance. By contrast, plants constitutively expressing HKT1;1 driven by the cauliflower mosaic virus 35S promoter accumulated high shoot Na+ and grew poorly. Our results demonstrate that the modification of a specific Na+ transport process in specific cell types can reduce shoot Na+ accumulation, an important component of salinity tolerance of many higher plants.

M?ller, Inge S.; Gilliham, Matthew; Jha, Deepa; Mayo, Gwenda M.; Roy, Stuart J.; Coates, Juliet C.; Haseloff, Jim; Tester, Mark

2009-01-01

302

The voltage-gated Na+ channel NaVBP has a role in motility, chemotaxis, and pH homeostasis of an alkaliphilic Bacillus  

PubMed Central

The prokaryotic voltage-gated Na+ channel, NaChBac, is one of a growing channel superfamily of unknown function. Here we show that NaVBP, the NaChBac homologue encoded by ncbA in alkaliphilic Bacillus pseudofirmus OF4, is a voltage-gated Na+ channel potentiated by alkaline pH. NaVBP has roles in motility, chemotaxis, and pH homeostasis at high pH. Reduced motility of bacteria lacking functional NaVBP was reversed by restoration of the native channel but not by a mutant NaVBP engineered to be Ca2+-selective. Motile ncbA mutant cells and wild-type cells treated with a channel inhibitor exhibited behavior opposite to the wild type in response to chemoeffectors. Mutants lacking functional NaVBP were also defective in pH homeostasis in response to a sudden alkaline shift in external pH under conditions in which cytoplasmic [Na+] is limiting for this crucial process. The defect was exacerbated by mutation of motPS, the motility channel genes. We hypothesize that activation of NaVBP at high pH supports diverse physiological processes by a combination of direct and indirect effects on the Na+ cycle and the chemotaxis system.

Ito, Masahiro; Xu, Haoxing; Guffanti, Arthur A.; Wei, Yi; Zvi, Lior; Clapham, David E.; Krulwich, Terry A.

2004-01-01

303

The voltage-gated Na+ channel NaVBP has a role in motility, chemotaxis, and pH homeostasis of an alkaliphilic Bacillus.  

PubMed

The prokaryotic voltage-gated Na(+) channel, NaChBac, is one of a growing channel superfamily of unknown function. Here we show that Na(V)BP, the NaChBac homologue encoded by ncbA in alkaliphilic Bacillus pseudofirmus OF4, is a voltage-gated Na(+) channel potentiated by alkaline pH. Na(V)BP has roles in motility, chemotaxis, and pH homeostasis at high pH. Reduced motility of bacteria lacking functional Na(V)BP was reversed by restoration of the native channel but not by a mutant Na(V)BP engineered to be Ca(2+)-selective. Motile ncbA mutant cells and wild-type cells treated with a channel inhibitor exhibited behavior opposite to the wild type in response to chemoeffectors. Mutants lacking functional Na(V)BP were also defective in pH homeostasis in response to a sudden alkaline shift in external pH under conditions in which cytoplasmic [Na(+)] is limiting for this crucial process. The defect was exacerbated by mutation of motPS, the motility channel genes. We hypothesize that activation of Na(V)BP at high pH supports diverse physiological processes by a combination of direct and indirect effects on the Na(+) cycle and the chemotaxis system. PMID:15243157

Ito, Masahiro; Xu, Haoxing; Guffanti, Arthur A; Wei, Yi; Zvi, Lior; Clapham, David E; Krulwich, Terry A

2004-07-20

304

Performance of lime-BHA solidified plating sludge in the presence of Na2SiO3 and Na2CO3.  

PubMed

This research investigated the performance of lime-BHA (black rice husk ash) solidified plating sludge with 2 wt% NaO from Na(2)SiO(3) and Na(2)CO(3) at the level of 0, 30 and 50 wt%. The sludge was evaluated for strength development, leachability, solution chemistry and microstructure. The lime-BHA solidified plating sludge with Na(2)SiO(3) and Na(2)CO(3) had higher early strength when compared to the control. The addition of Na(2)SiO(3) and Na(2)CO(3) increased the OH(-) concentration and decreased the Ca(2+) and heavy metal ions in solution after the first minute. The XRD patterns showed that the addition of Na(2)SiO(3) resulted in the formation of calcium silicate hydrates, while the addition of Na(2)CO(3) resulted in CaCO(3). The heavy metals from the plating sludge, especially Zn, were immobilized in calcium zincate and calcium zinc silicate forms for the lime-BHA with and without Na(2)SiO(3) solidified wastes, while samples with Na(2)CO(3) contained Zn that was fixed in the form of CaZnCO(3). The cumulative leaching of Fe, Cr and Zn from the lime-BHA solidified plating sludge decreased significantly when activators were added, especially Na(2)CO(3). PMID:21549500

Piyapanuwat, Rungroj; Asavapisit, Suwimol

2011-09-01

305

Intercalated polyaniline\\/Na-montmorillonite nanocomposites via oxidative polymerization  

Microsoft Academic Search

This work focuses on the preparation, characterization and electrical conductive properties of intercalated polyaniline\\/Na-montmorillonite\\u000a nanocomposites. These materials consisting of polyaniline and Na-montmorillonite were prepared by oxidative polymerization\\u000a with benzoyl peroxide as oxidizing agent. The synthesized nanocomposites were investigated by a series of characterization\\u000a techniques; including Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermal\\u000a analysis. X-ray diffraction and

Meltem Çelik; Mü?erref Önal

2007-01-01

306

Brain Na+, K+-ATPase Activity In Aging and Disease  

PubMed Central

Na+/K+ pump or sodium- and potassium-activated adenosine 5’-triphosphatase (Na+, K+-ATPase), its enzymatic version, is a crucial protein responsible for the electrochemical gradient across the cell membranes. It is an ion transporter, which in addition to exchange cations, is the ligand for cardenolides. This enzyme regulates the entry of K+ with the exit of Na+ from cells, being the responsible for Na+/K+ equilibrium maintenance through neuronal membranes. This transport system couples the hydrolysis of one molecule of ATP to exchange three sodium ions for two potassium ions, thus maintaining the normal gradient of these cations in animal cells. Oxidative metabolism is very active in brain, where large amounts of chemical energy as ATP molecules are consumed, mostly required for the maintenance of the ionic gradients that underlie resting and action potentials which are involved in nerve impulse propagation, neurotransmitter release and cation homeostasis. Protein phosphorylation is a key process in biological regulation. At nervous system level, protein phosphorylation is the major molecular mechanism through which the function of neural proteins is modulted in response to extracellular signals, including the response to neurotransmitter stimuli. It is the major mechanism of neural plasticity, including memory processing. The phosphorylation of Na+, K+-ATPase catalytic subunit inhibits enzyme activity whereas the inhibition of protein kinase C restores the enzyme activity. The dephosphorylation of neuronal Na+, K+-ATPase is mediated by calcineurin, a serine / threonine phosphatase. The latter enzyme is involved in a wide range of cellular responses to Ca2+ mobilizing signals, in the regulation of neuronal excitability by controlling the activity of ion channels, in the release of neurotransmitters and hormones, as well as in synaptic plasticity and gene transcription. In the present article evidence showing Na+, K+-ATPase involvement in signaling pathways, enzyme changes in diverse neurological diseases as well as during aging, have been summarized. Issues refer mainly to Na+, K+-ATPase studies in ischemia, brain injury, depression and mood disorders, mania, stress, Alzheimer´s disease, learning and memory, and neuronal hyperexcitability and epilepsy.

de Lores Arnaiz, Georgina Rodriguez; Ordieres, Maria Graciela Lopez

2014-01-01

307

Na+ and Li+ NASICON Superionic Conductors Thick Films  

Microsoft Academic Search

For microionic applications, superionic conductors have been elaborated in the form of thick films, using silk-screen printable powders. Na3Zr2Si2PO12, Na3.1Zr1.55Si2.3P0.7O11 and Li0.8Zr1.8Ta0.2(PO4)3 compositions are synthesized by a sol-gel process involving hydrolysis-polycondensation reactions of metal-organic alcoholic solutions. A thermal treatment (600°C-800°C) allows to obtain very fine particles (<1 mum) with the pure NASICON phase. Inks are prepared with these powders, an

H. Perthuis; G. Velasco; Ph. Colomban

1984-01-01

308

Preparation and characterisation of mesoporous photoactive Na-titanate microspheres  

Microsoft Academic Search

Mesoporous Na-titanate microspheres were fabricated by a simple low temperature hydrothermal synthesis. Microspheres were obtained after treating TiO2 (Degussa P-25) with a mixture of sodium hydroxide (NaOH) and hydrogen peroxide (H2O2) at 25°C and 80°C. The as-prepared powders were characterised by X-ray diffraction, N2 adsorption–desorption measurements and scanning electron microscope\\/energy dispersive X-ray spectroscopy. The as-prepared microspheres were calcined at 550°C

Ibrahim El Saliby; Laszlo Erdei; Ho Kyong Shon; Jong Beom Kim; Jong-Ho Kim

2011-01-01

309

Tb/Na tobermorite: Thermal behaviour and high temperature products  

NASA Astrophysics Data System (ADS)

By heating a sample of Tb/Na tobermorite we obtained a phase which was identified through its X-ray diffraction (XRD) pattern, as terbium silicate apatite. Subsequently this compound has been directly prepared by solid state reaction and we carried out a structural refinement from XRD data in space group P6 3/ m obtaining cell parameters a=9.39199(4) Å and c=6.84041(5) Å. Terbium silicate apatite heated in melted NaF led to Tb 4O 7 crystals.

Garra, Walter; Marchetti, Fabio; Merlino, Stefano

2009-06-01

310

Clean demarcation of cartilage tissue 23Na by inversion recovery.  

PubMed

Monitoring the sodium concentration in vivo using 23Na MRI can be an important tool for assessing the onset of tissue disorders. Practical clinical 23Na MRI methods furthermore often do not allow one to use sufficiently small voxel sizes such that only the tissue of interest is seen, but a large signal contamination can arise from sodium in synovial fluid. Here we demonstrate that applying an inversion recovery (IR) technique allows one to distinctly select either the cartilage-bound or the free sodium for visualization in an image. The results are validated both ex vivo and in vivo. PMID:18502158

Rong, Peng; Regatte, Ravinder R; Jerschow, Alexej

2008-08-01

311

Coulomb excitation of the proton-dripline nucleus Na20  

Microsoft Academic Search

The low-energy structure of the proton dripline nucleus Na20 has been studied using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. A 1.7-MeV\\/nucleon Na20 beam of ~5×106 ions\\/s was Coulomb excited by a 0.5-mg\\/cm2natTi target. Scattered beam and target particles were detected by the BAMBINO segmented Si detector while gamma rays were detected by two TIGRESS HPGe clover detectors

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

2009-01-01

312

Frequency dependence of photoelectron angular distributions in small Na clusters  

NASA Astrophysics Data System (ADS)

We investigate from a theoretical perspective photoelectron angular distributions (PADs) in small Na clusters in relation to recently available experimental results. We consider various (increasingly refined) levels of theory in order to better understand relevant physical trends. It is found that PADs are extremely sensitive to all details of the modeling such that a detailed description of the final state and the ionic background is necessary. Finally, we compare the theoretical description with recent experimental data on the cluster anion Na7- and find a satisfying agreement for full time-dependent local-density approximation (TDLDA) with ionic background.

Wopperer, P.; Dinh, P. M.; Suraud, E.; Reinhard, P.-G.

2012-01-01

313

Interstellar Na I and Ca II absorption in intercloud regions  

NASA Technical Reports Server (NTRS)

The weak interstellar absorption lines of Na I, Ca II, and H I formed in the intercloud medium toward eight nearly unreddened stars are analyzed. Compared with the corresponding column densities within a standard cloud, the Na I/H column-density ratio is smaller by a factor probably in excess of 17, while the Ca II/H column-density ratio is about normal. These results imply that the local intercloud medium extensively contains low-density H I regions in which the temperature is at least about 2500 K and the depletion of calcium is less severe than in the clouds, by a factor of 20.

Hobbs, L. M.

1975-01-01

314

Russian Scientific-Educational Project: Kazan-GeoNa-2017  

NASA Astrophysics Data System (ADS)

For the further successful development of educational and scientific - educational activity of the Russian Federation, the Republic Tatarstan, Kazan is offered the national project - the International Center of the Science and the Internet of Technologies. "GeoNa" (Geometry of Nature - "GeoNa" is developed - wisdom, enthusiasm, pride, grandeur), which includes a modern complex of conference halls (up to 4 thousand places), the Center the Internet of Technologies, 3D Planetarium - development of the Moon, PhysicsLand, an active museum of natural sciences, an oceanarium, training a complex «Spheres of Knowledge», botanical and landscape oases.

Gusev, A.; Alibekova, N.

2012-09-01

315

Factors associated with determination of root ²²Na (+) influx in the salt accumulation halophyte Suaeda maritima.  

PubMed

Salinity is an increasing problem for agricultural production worldwide. The result of low-affinity Na(+) uptake is toxic to the cytoplasm of most crop plants. Nevertheless, the pathways for this low-affinity Na(+) uptake are still uncertain. In this work we used ²²Na(+) isotope tracing technology to investigate factors associated with determination of root ²²Na(+) influx in the salt accumulation halophyte Suaeda maritima. We found that a 2 min of exposure to the ²²Na(+) labeled uptake solution was optimal for determining ²²Na(+) influx into excised roots of S. maritima and that 7 min of blotting is suitable in ²²Na(+) influx experiments. ²²Na(+) influx did not increase linearly with the increasing external Na(+) concentration, in the range tested, of 2 to 300 mM NaCl. But root ²²Na(+) influx and root Na(+) concentration were well correlated. ²²Na(+) influx into excised roots of S. maritima was not, however, well correlated with the plant size. All the above results indicated further that this ²²Na(+) isotope influx procedure is a good method for quantify Na(+) uptake rate by the roots of the salt accumulation halophyte. PMID:20217274

Zhang, Jin-Lin; Wetson, Anne M; Wang, Suo-Min; Gurmani, Ali R; Bao, Ai-Ke; Wang, Chun-Mei

2011-01-01

316

Na + \\/K + pump and endothelial cell survival: [Na + ] i \\/[K + ] i -independent necrosis triggered by ouabain, and protection against apoptosis mediated by elevation of [Na + ] i  

Microsoft Academic Search

Recent studies have demonstrated the tissue-specific effect of Na +\\/K + pump inhibition by ouabain and other cardiac glycosides on cell viability. The vascular endothelium is an initial target of cardiac glycosides employed for the management of congestive heart failure as well as circulating endogenous ouabain-like substances (EOLS), the production of which is augmented in volume-expanded hypertension. This study examined

Sergei N. Orlov; Nathalie Thorin-Trescases; Dimitri Pchejetski; Sebastien Taurin; Nada Farhat; Johanne Tremblay; Eric Thorin; Pavel Hamet

2004-01-01

317

Investigation of the thermonuclear 18Ne(?,p)21Na reaction rate via resonant elastic scattering of 21Na + p  

NASA Astrophysics Data System (ADS)

The 18Ne(?,p)21Na reaction is thought to be one of the key breakout reactions from the hot CNO cycles to the rp process in type I x-ray bursts. In this work, the resonant properties of the compound nucleus 22Mg have been investigated by measuring the resonant elastic scattering of 21Na + p. An 89-MeV 21Na radioactive beam delivered from the CNS Radioactive Ion Beam Separator bombarded an 8.8 mg/cm2 thick polyethylene (CH2)n target. The 21Na beam intensity was about 2×105 pps, with a purity of about 70% on target. The recoiled protons were measured at the center-of-mass scattering angles of ?c.m.?175.2?, 152.2?, and 150.5? by three sets of ?E-E telescopes, respectively. The excitation function was obtained with the thick-target method over energies Ex(22Mg)=5.5-9.2 MeV. In total, 23 states above the proton-threshold in 22Mg were observed, and their resonant parameters were determined via an R-matrix analysis of the excitation functions. We have made several new J? assignments and confirmed some tentative assignments made in previous work. The thermonuclear 18Ne(?,p)21Na rate has been recalculated based on our recommended spin-parity assignments. The astrophysical impact of our new rate has been investigated through one-zone postprocessing x-ray burst calculations. We find that the 18Ne(?,p)21Na rate significantly affects the peak nuclear energy generation rate, reaction fluxes, and onset temperature of this breakout reaction in these astrophysical phenomena.

Zhang, L. Y.; He, J. J.; Parikh, A.; Xu, S. W.; Yamaguchi, H.; Kahl, D.; Kubono, S.; Mohr, P.; Hu, J.; Ma, P.; Chen, S. Z.; Wakabayashi, Y.; Wang, H. W.; Tian, W. D.; Chen, R. F.; Guo, B.; Hashimoto, T.; Togano, Y.; Hayakawa, S.; Teranishi, T.; Iwasa, N.; Yamada, T.; Komatsubara, T.; Zhang, Y. H.; Zhou, X. H.

2014-01-01

318

In Situ SAXS/WAXS of Zeolite Microwave Synthesis: NaY, NaA, and Beta Zeolites  

SciTech Connect

A custom waveguide apparatus is constructed to study the microwave synthesis of zeolites by in situ small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). The WR-284 waveguide is used to heat precursor solutions using microwaves at a frequency of 2.45 GHz. The reaction vessels are designed to include sections of thin-walled glass, which permit X-rays to pass through the precursor solutions with minimal attenuation. Slots were machined into the waveguide to provide windows for X-ray energy to enter and scatter from solutions during microwave heating. The synthesis of zeolites with conventional heating is also studied using X-ray scattering in the same reactor. SAXS studies show that the crystallization of beta zeolite and NaY zeolite is preceded by a reorganization of nanosized particles in their precursor solutions or gels. The evolution of these particles during the nucleation and crystallization stages of zeolite formation depends on the properties of the precursor solution. The synthesis of NaA and NaX zeolites and sodalite from a single zeolite precursor is studied by microwave and conventional heating. Microwave heating shifts the selectivity of this synthesis in favor of NaA and NaX over sodalite; conventional heating leads to the formation of sodalite for synthesis from the same precursor. The use of microwave heating also led to a more rapid onset of NaA zeolite product crystallization compared to conventional heating. Pulsed and continuous microwave heating are compared for zeolite synthesis. The resulting rates of formation of the zeolite products, and the relative amounts of the products determined from the WAXS spectra, are similar when either pulsed or continuous microwave heating is applied in the reactor while maintaining the same synthesis temperature. The consequences of these results in terms of zeolite synthesis are discussed.

Panzarella,B.; Tompsett, G.; Conner, W.; Jones, K.

2007-01-01

319

Surface carboxylation of porous regenerated cellulose beads by 4-acetamide-TEMPO\\/NaClO\\/NaClO 2 system  

Microsoft Academic Search

A commercial regenerated bead cellulose was suspended in water at pH 4.8, and oxidized with NaClO2 used as a primary oxidant and catalytic amounts of NaClO and 4-acetamide-2,2,6,6-tetramethylpiperidinyl-1-oxyl radical. Carboxylate\\u000a groups were formed up to 1.87 mmol\\/g in the beads by the oxidation of C6 primary hydroxyls to carboxylates without significant\\u000a weight losses or morphological changes. The spherical shapes, highly porous

Masayuki Hirota; Naoyuki Tamura; Tsuguyuki Saito; Akira Isogai

2009-01-01

320

The Na+-responsive ntp operon is indispensable for homeostatis of K+ and Na+ in Enterococcus hirae at limited proton potential.  

PubMed

Enterococcus hirae ATCC 9790 grew well in Na+-deficient, low-K+ medium, but growth was inhibited by carbonylcyanide m-chlorophenylhydrazone (CCCP). Growth inhibition and decrease of cellular K+ levels in the presence of CCCP were relieved by the addition of Na+ and a high concentration of K+. In contrast, in the mutant defective in Na+-ATPase or the NtpJ component of the KtrII K+ uptake system, CCCP-induced growth inhibition was rescued by a high concentration of K+ but not of Na+. These transporters are thus indispensable for homeostatis of K+ and Na+ at low proton potential. PMID:9733699

Kawano, M; Igarashi, K; Kakinuma, Y

1998-09-01

321

Sodium ion mobility in Na(x)CoO2 (0.6 < x < 0.75) cobaltites studied by 23Na MAS NMR.  

PubMed

Various P2 and P'3-Na(x)CoO(2) phases, with x ranging approximately from 0.6 to 0.75, have been studied by variable-temperature (23)Na magic angle spinning (MAS) NMR. Signal modification versus temperature plots clearly show that Na(+) ions are not totally mobile at room temperature on the NMR time scale. As the temperature increases, the line shape change of the (23)Na MAS NMR signal differs for the P2 and P'3 stackings and is interpreted by the differences of Na(+) ion sites and of sodium diffusion pathways in the two structures. PMID:19419150

Carlier, Dany; Blangero, Maxime; Ménétrier, Michel; Pollet, Michaël; Doumerc, Jean-Pierre; Delmas, Claude

2009-08-01

322

XeNA: an access negotiation framework using XACML  

Microsoft Academic Search

XeNA is a new model for the negotiation of access within an extended eXtensible Access Control Markup Language (XACML) architecture. We bring together trust management through a negotiation pro- cess and access control management within the same architecture. The negotiation process based on re- source classification methodology occurs before the ac- cess control management. A negotiation module at the core

Diala Abi Haidar; Nora Cuppens-boulahia; Frédéric Cuppens; Hervé Debar

2009-01-01

323

Global structure of small Na clusters in different approaches  

Microsoft Academic Search

We compare the shapes of small Na clusters as they result from the jellium model, the cylindrically averaged pseudopotential scheme, and the distance-dependent tight-binding approach. Although these are three distinctively different approaches, we find a good agreement amongst the results, showing that all three models, taken in their appropriate domain of descriptive power, give an equally reliable picture of metal

F. Spiegelmann; R. Poteau; B. Montag; P.-G. Reinhard

1998-01-01

324

Cesium selectivity of (Al+Na)-substituted tobermorite  

Microsoft Academic Search

Several synthetic tobermorites with different levels of [Al+Na] substitution were prepared from two different types of starting materials and their cation exchange and cesium selective properties were investigated. The substituted tobermorites were found to have high cation exchange capacities and very high selectivities for Cs[sup +] ion. Cesium selectivity of the substituted tobermorites was demonstrated in the presence of divalent

O. P. Shrivastava; S. Komarneni

1994-01-01

325

Altered erythrocyte Na-K pump in anorectic patients  

SciTech Connect

The status of the erythrocyte sodium pump was evaluated in a group of patients suffering from anorexia nervosa and a group of healthy female control subjects. Anorectic patients showed significantly higher mean values of digoxin-binding sites/cell (ie, the number of Na-K-ATPase units) with respect to control subjects while no differences were found in the specific /sup 86/Rb uptake (which reflects the Na-K-ATPase activity) between the two groups. A significant correlation was found between relative weight and the number of Na-K-ATPase pump units (r = -0.66; P less than 0.0001). Anorectic patients showed lower serum T3 concentrations (71.3 +/- 53 ng/dL) with respect to control subjects (100.8 +/- 4.7 ng/dL; P less than 0.0005) and a significant negative correlation between T3 levels and the number of pump units (r = -0.52; P less than 0.003) was found. This study therefore shows that the erythrocyte Na-K pump may be altered in several anorectic patients. The authors suggest that this feature could be interrelated with the degree of underweight and/or malnutrition.

Pasquali, R.; Strocchi, E.; Malini, P.; Casimirri, F.; Ambrosioni, E.; Melchionda, N.; Labo, G.

1985-07-01

326

Transcriptional Regulation of the Intestinal Luminal Na+ and Cl? Transporters  

PubMed Central

The epithelial apical membrane Na+/H+ exchangers (NHE2, NHE3) and Cl?/HCO3? exchangers (DRA and PAT-1) are key luminal membrane transporters involved in electroneutral NaCl absorption in the mammalian intestine. During the past decade, there has been a surge of studies focusing on short-term regulation of these electrolyte transporters particularly for NHE3 regulation. However, the long-term regulation of the electrolyte transporters involving transcriptional mechanisms and transcription factors that govern their basal regulation or dysregulation in diseased states has only now started to unfold with the cloning and characterization of their gene promoters. This review updates the readers with a detailed analysis of the core promoters of NHE2, NHE3, DRA and PAT-1 and outlines the transcription factors involved in their basal regulation as well as in response to both physiological (butyrate, protein kinases, probiotics) and pathophysioloical (cytokines and high levels of serotonin) stimuli. The available information on the transcriptional regulation of the recently identified NHE8 isoform is also highlighted. This review, therefore, bridges a gap in our knowledge of the transcriptional mechanisms underlying the alterations in the gene expression of intestinal epithelial luminal membrane Na+ and Cl? transporters involved in electroneutral NaCl absorption. An understanding of the mechanisms of modulation of gene expression of these transporters is important for a better assessment of the pathophysiology of diarrhea associated with inflammatory and infectious diseases and may aid in designing better management protocols.

Malakooti, Jaleh; Saksena, Seema; Gill, Ravinder K; Dudeja, Pradeep K.

2012-01-01

327

Precise Atomic and Nuclear Physics Experiments with Trapped ^21Na  

NASA Astrophysics Data System (ADS)

We have recently observed 40,000 trapped ^21Na atoms in our experiment at the LBNL 88'' Cyclotron. Our bigger improved traps are due to redesign of our production target and oven assembly, yielding brighter atomic beams from our Zeeman-slowing apparatus. We are currently refining our technique to measure the 1.9 GHz ground state hyperfine splitting of ^21Na. Using a pulsed trap-pump-probe scheme, we anticipate a precision better than 100 Hz with our current trap sizes and based on studies using stable ^23Na. We have observed the ? ^+ from our trapped atoms using an in-vacuum plastic scintillator, and also the ? and ? backgrounds present in our trapping chamber. These measurements will guide several planned improvements to our apparatus to achieve larger traps and cleaner ? signals. We estimate that 100,000 trapped ^21Na atoms will be necessary for a precise 1% measurement of the parity violating beta decay asymmetry parameter, which would probe for possible right-handed charged electroweak currents. Current status and data will be presented. Be there or be square. our experiment

Vetter, P. A.; Freedman, S. J.; Fujikawa, B. K.; Gwinner, G.; Rowe, M. A.; Shang, S. Q.; Wasserman, E. G.

1997-04-01

328

Synthesis of Na-zeolites from fly ash  

Microsoft Academic Search

The present study focuses on the synthesis of zeolites after fly ash activation, the major objectives being: (a) to study the activation processes; (b) to elucidate the activation conditions for maximum synthesis efficiency; (c) to optimize the conditions for the monomineral synthesis; and (d) to test synthesis efficiencies for different fly ash types. Fly ash was activated by NaOH and

Xavier Querol; Felicià Plana; Andrés Alastuey; Angel López-Soler

1997-01-01

329

Stainless Steel NaK Circuit Integration and Fill Submission  

NASA Technical Reports Server (NTRS)

The Early Flight Fission Test Facilities (EFF-TF) team has been tasked by the Marshall Space Flight Center Nuclear Systems Office to design, fabricate, and test an actively pumped alkali metal flow circuit. The system, which was originally designed to hold a eutectic mixture of sodium potassium (NaK), was redesigned to hold lithium; but due to a shift in focus, it is once again being prepared for use with NaK. Changes made to the actively pumped, high temperature loop include the replacement of the expansion reservoir, addition of remotely operated valves, and modification of the support table. Basic circuit components include: reactor segment, NaK to gas heat exchanger, electromagnetic (EM) liquid metal pump, load/drain reservoir, expansion reservoir, instrumentation, and a spill reservoir. A 37-pin partial-array core (pin and flow path dimensions are the same as those in a full design) was selected for fabrication and test. This document summarizes the integration and fill of the pumped liquid metal NaK flow circuit.

Garber, Anne E.

2006-01-01

330

AgI-NaI Aerosols as Ice Nuclei  

Microsoft Academic Search

The ice-nucleating properties of cloud-seeding aerosols produced by burning a solution af AgI and NaI in acetone have been studied in a laboratory cloud chamber. The ice-forming ability of these mixed aerosols is not influenced as markedly by the supersaturation in the test cloud as is the case with \\

S. C. Mossop; K. O. L. F. Jayaweera

1969-01-01

331

Project ELaNa and NASA's CubeSat Initiative  

NASA Technical Reports Server (NTRS)

This slide presentation reviews the NASA program to use expendable lift vehicles (ELVs) to launch nanosatellites for the purpose of enhancing educational research. The Education Launch of Nanosatellite (ELaNa) project, run out of the Launch Services Program is requesting proposals for CubeSat type payload to provide information that will aid or verify NASA Projects designs while providing higher educational research

Skrobot, Garrett Lee

2010-01-01

332

Catadioptric projection lens for 1.3 NA scanner  

NASA Astrophysics Data System (ADS)

In the history of DUV (Deep Ultra Violet) microlithographic lens design, three kinds of leaps have occurred to maintain the progress of technology in the semiconductor industry. The first step is the application of aspherical elements. This allowed us to increase NA up to around 0.9. The second innovation is water immersion. Thanks to the 1.44 refractive index of water, and because the numerical aperture (NA) is defined as the product of the sine of the maximum ray angle on the image plane and the refractive index in the image space, even with a lower maximum ray angle on the imaging plane than dry with a lens, we can achieve NA of 1.07. The latest technological jump is the development of catadioptric lens systems, which are roughly defined as the combined usage of refractive element(s) and reflective element(s). The catadioptric system allows us to achieve a full field 1.3NA projection lens that is used in our scanner NSR-S610C. In this paper we discuss optical design concepts and some challenges for catadioptric lenses. In addition, current lens performance including wavefront, lens flare, and image vibration are shown.

Matsuyama, Tomoyuki; Ohmura, Yasuhiro; Fujishima, Yohei; Koyama, Takashi

2007-03-01

333

NaCl plus chitosan as a dietary salt to prevent the development of hypertension in spontaneously hypertensive rats  

Microsoft Academic Search

The effect of NaCl plus 3% chitosan on the systolic blood pressure of spontaneously hypertensive rats (SHR) were evaluated and compared with NaCl plus KCl (NaCl, 49.36% + KCl 49.36%) and chitosan or NaCl treatment alone. In SHR, administration of NaCl plus chitosan (44 mM Na\\/day) for two months significantly decreased the systolic blood pressure greater than of NaCl plus

Sung-Hoon Park; Noton Kumar Dutta; Min-Won Baek; Dong-Jae Kim; Yi-Rang Na; Seung-Hyeok Seok; Byoung-Hee Lee; Ji-Eun Cho; Geon-Sik Cho; Jae-Hak Park

2009-01-01

334

Intracellular and extracellular concentrations of Na+ modulate Mg2+ transport in rat ventricular myocytes.  

PubMed

Apparent free cytoplasmic concentrations of Mg2+ ([Mg2+]i) and Na+ ([Na+]i) were estimated in rat ventricular myocytes using fluorescent indicators, furaptra (mag-fura-2) for Mg2+ and sodium-binding benzofuran isophthalate for Na+, at 25 degrees C in Ca2+-free conditions. Analysis included corrections for the influence of Na+ on furaptra fluorescence found in vitro and in vivo. The myocytes were loaded with Mg2+ in a solution containing 24 mM Mg2+ either in the presence of 106 mM Na+ plus 1 mM ouabain (Na+ loading) or in the presence of only 1.6 mM Na+ to deplete the cells of Na+ (Na+ depletion). The initial rate of decrease in [Mg2+]i from the Mg2+-loaded cells was estimated in the presence of 140 mM Na+ and 1 mM Mg2+ as an index of the rate of extracellular Na+-dependent Mg2+ efflux. Average [Na+]i, when estimated from sodium-binding benzofuran isophthalate fluorescence in separate experiments, increased from 12 to 31 mM and 47 mM after Na+ loading for 1 and 3 h, respectively, and decreased to approximately 0 mM after 3 h of Na+ depletion. The intracellular Na+ loading significantly reduced the initial rate of decrease in [Mg2+]i, on average, by 40% at 1 h and by 64% at 3 h, suggesting that the Mg2+ efflux was inhibited by intracellular Na+ with 50% inhibition at approximately 40 mM. A reduction of the rate of Mg2+ efflux was also observed when Na+ was introduced into the cells through the amphotericin B-perforated cell membrane (perforated patch-clamp technique) via a patch pipette that contained 130 mM Na+. When the cells were heavily loaded with Na+ with ouabain in combination with intracellular perfusion from the patch pipette containing 130 mM Na+, removal of extracellular Na+ caused an increase in [Mg2+]i, albeit at a very limited rate, which could be interpreted as reversal of the Mg2+ transport, i.e., Mg2+ influx driven by reversed Na+ gradient. Extracellular Na+ dependence of the rate of Mg2+ efflux revealed that the Mg2+ efflux was activated by extracellular Na+ with half-maximal activation at 55 mM. These results contribute to a quantitative characterization of the Na+-Mg2+ exchange in cardiac myocytes. PMID:16085772

Tashiro, Michiko; Tursun, Pulat; Konishi, Masato

2005-11-01

335

Localization of Na(+)/K(+)-ATPase in silkworm brain: a possible mechanism for protection of Na(+)/K(+)-ATPase from Ca(2+).  

PubMed

In mammalian blood, the Na(+) concentration is higher than the K(+) concentration, whereas in hemolymph of lepidopterous insects, the K(+) concentration is higher than the Na(+) concentration. Na(+)/K(+)-ATPase regulates Na(+) and K(+) concentrations in mammalian blood. Therefore, the absence of Na(+)/K(+)-ATPase in lepidopterous insects might be expected. However, we have observed that Na(+)/K(+)-ATPase is abundant in nerve tissues of larvae of silkworm, a lepidopterous insect. Furthermore, we found that silkworm Na(+)/K(+)-ATPase was completely inhibited by 3 mM Ca(2+)in vitro (Homareda, 2010), although the Ca(2+) concentration is very high (30-50 mM) in the hemolymph of silkworm larvae. To investigate the reason why silkworm Na(+)/K(+)-ATPase is not inhibited by Ca(2+)in vivo, we observed the localization of Na(+)/K(+)-ATPase in nerve tissues using immunohistochemical techniques. Na(+)/K(+)-ATPase was distributed in the cortex and neuropile but not in the perineurium of the silkworm brain, while plasma membrane Ca(2+)-ATPase appeared to distribute in the perineurium as well as in the cortex and neuropile. These results support a possibility that neuronal Na(+)/K(+)-ATPase is protected from a high Ca(2+) concentration by the blood-brain barrier consisting of perineurial glial cells with plasma membrane Ca(2+)-ATPase. PMID:23274012

Homareda, Haruo; Otsu, Masahiro

2013-03-01

336

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

PubMed Central

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

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

2009-01-01

337

Dietary Na(+)-restriction prevents development of functional Na+ channels in taste cell apical membranes: proof by in vivo membrane voltage perturbation.  

PubMed

1. Chorda tympani (CT) neural responses to NaCl were recorded while the potential across the apical membrane of taste cells was perturbed by voltage clamp in rats fed a Na(+)-restricted diet pre- and postnatally (Na(+)-restricted rats) and in controls. 2. Control rats gave CT responses that were enhanced at negative voltage clamp and suppressed at positive voltage clamp. In contrast, CT responses from Na(+)-restricted rats were virtually voltage insensitive. 3. Analysis of the voltage-sensitivity of the CT response shows that Na(+)-restricted rats have < 10% of the density of functional apical Na+ channels normally present in control rats demonstrating that early dietary Na(+)-restriction prevents the functional expression of these key elements in salt taste transduction. Furthermore, the data demonstrate the value of this technique in assessing involvement of distinct cellular domains in taste transduction. PMID:8283226

Ye, Q; Stewart, R E; Heck, G L; Hill, D L; DeSimone, J A

1993-10-01

338

Effects of Na2MoO4 and Na2WO4 on molybdenum and tungsten electrodes for the alkali metal thermoelectric converter (AMTEC)  

NASA Technical Reports Server (NTRS)

The effects of adding Na2MoO4 and Na2WO4 to porous Mo and W electrodes, respectively, on the performance and impedance characteristics of the electrodes in an alkali metal thermoelectric converter (AMTEC) were investigated. It was found that corrosion of the porous electrode by Na2MoO4 or Na2WO4 to form Na2MO3O6 and WO2, respectively, and recrystallization of the Mo or W as the salt evaporates, result in major morphological changes including a loss of columnar structure and a significant increase in porosity. This effect is more pronounced in Na2MoO4/Mo electrodes, due to the lower stability of Na2MoO4.

Williams, R. M.; Wheeler, B. L.; Jeffries-Nakamura, B.; Loveland, M. E.; Bankston, C. P.

1988-01-01

339

Stoichiometric relationship between Na(+) ions transported and glucose consumed in human erythrocytes: Bayesian analysis of (23)Na and (13)C NMR time course data.  

PubMed

We examined the response of Na(+),K(+)-ATPase (NKA) to monensin, a Na(+) ionophore, with and without ouabain, an NKA inhibitor, in suspensions of human erythrocytes (red blood cells). A combination of (13)C and (23)Na NMR methods allowed the recording of intra- and extracellular Na(+), and (13)C-labeled glucose time courses. The net influx of Na(+) and the consumption of glucose were measured with and without NKA inhibited by ouabain. A Bayesian analysis was used to determine probability distributions of the parameter values of a minimalist mathematical model of the kinetics involved, and then used to infer the rates of Na(+) transported and glucose consumed. It was estimated that the numerical relationship between the number of Na(+) ions transported by NKA per molecule of glucose consumed by a red blood cell was close to the ratio 6.0:1.0, agreeing with theoretical prediction. PMID:23601315

Puckeridge, Max; Chapman, Bogdan E; Conigrave, Arthur D; Grieve, Stuart M; Figtree, Gemma A; Kuchel, Philip W

2013-04-16

340

Functional identification and characterization of sodium binding sites in Na symporters.  

PubMed

Sodium cotransporters from several different gene families belong to the leucine transporter (LeuT) structural family. Although the identification of Na(+) in binding sites is beyond the resolution of the structures, two Na(+) binding sites (Na1 and Na2) have been proposed in LeuT. Na2 is conserved in the LeuT family but Na1 is not. A biophysical method has been used to measure sodium dissociation constants (Kd) of wild-type and mutant human sodium glucose cotransport (hSGLT1) proteins to identify the Na(+) binding sites in hSGLT1. The Na1 site is formed by residues in the sugar binding pocket, and their mutation influences sodium binding to Na1 but not to Na2. For the canonical Na2 site formed by two -OH side chains, S392 and S393, and three backbone carbonyls, mutation of S392 to cysteine increased the sodium Kd by sixfold. This was accompanied by a dramatic reduction in the apparent sugar and phlorizin affinities. We suggest that mutation of S392 in the Na2 site produces a structural rearrangement of the sugar binding pocket to disrupt both the binding of the second Na(+) and the binding of sugar. In contrast, the S393 mutations produce no significant changes in sodium, sugar, and phlorizin affinities. We conclude that the Na2 site is conserved in hSGLT1, the side chain of S392 and the backbone carbonyl of S393 are important in the first Na(+) binding, and that Na(+) binding to Na2 promotes binding to Na1 and also sugar binding. PMID:24191006

Loo, Donald D F; Jiang, Xuan; Gorraitz, Edurne; Hirayama, Bruce A; Wright, Ernest M

2013-11-19

341

Functional identification and characterization of sodium binding sites in Na symporters  

PubMed Central

Sodium cotransporters from several different gene families belong to the leucine transporter (LeuT) structural family. Although the identification of Na+ in binding sites is beyond the resolution of the structures, two Na+ binding sites (Na1 and Na2) have been proposed in LeuT. Na2 is conserved in the LeuT family but Na1 is not. A biophysical method has been used to measure sodium dissociation constants (Kd) of wild-type and mutant human sodium glucose cotransport (hSGLT1) proteins to identify the Na+ binding sites in hSGLT1. The Na1 site is formed by residues in the sugar binding pocket, and their mutation influences sodium binding to Na1 but not to Na2. For the canonical Na2 site formed by two –OH side chains, S392 and S393, and three backbone carbonyls, mutation of S392 to cysteine increased the sodium Kd by sixfold. This was accompanied by a dramatic reduction in the apparent sugar and phlorizin affinities. We suggest that mutation of S392 in the Na2 site produces a structural rearrangement of the sugar binding pocket to disrupt both the binding of the second Na+ and the binding of sugar. In contrast, the S393 mutations produce no significant changes in sodium, sugar, and phlorizin affinities. We conclude that the Na2 site is conserved in hSGLT1, the side chain of S392 and the backbone carbonyl of S393 are important in the first Na+ binding, and that Na+ binding to Na2 promotes binding to Na1 and also sugar binding.

Loo, Donald D. F.; Jiang, Xuan; Gorraitz, Edurne; Hirayama, Bruce A.; Wright, Ernest M.

2013-01-01

342

Semi-volatiles at Mercury: Sodium (Na) and potassium (K)  

NASA Technical Reports Server (NTRS)

Several lines of evidence now suggest that Mercury is a planet rich in moderately-volatile elements such as Na and K. Recent mid-infrared spectral observations of Mercury's equatorial and mid-latitude region near 120 degrees mercurian longitude indicate the presence of plagioclase feldspar. Spectra of Mercury's surface exhibit spectral activity similar to labradorite (plagioclase feldspar with NaAlSi3O8: 30-50 percent) and bytownite (NaAlSi3O8: 10-30 percent). These surface studies were stimulated by the relatively large abundance of Na and K observed in Mercury's atmosphere. An enhanced column of K is observed at the longitudes of Caloris Basin and of the antipodal terrain. Extreme heating at these 'hot' longitudes and severe fracturing suffered from the large impact event could lead to enhanced outgassing from surface or subsurface materials. Alternatively, sputtering from a surface enriched in K could be the source of the observed enhancement. Recent microwave measurements of Mercury also give indirect evidence of a mercurian regolith less FeO-rich than the Moon. An anomalously high index of refraction derived from the whole-disk integrated phase curve of Danjon may also be indicative of surface sulfides contributing to a regolith that is moderately volatile-rich. The recent exciting observations of radar-bright spots at high latitudes also indicate that a substance of high volume scattering, like ice, is present in shadowed regions. Other radar-bright spots have been seen at locations of Na enhancements on the atmosphere. All combined, these pieces of evidence point to a planet that is not severely depleted in volatiles or semi-volatiles.

Sprague, A.

1994-01-01

343

Quantum mechanical calculation of 23 Na NMR shieldings in silicates and aluminosilicates  

Microsoft Academic Search

To assist in the assignment and interpretation of 23Na NMR spectra in silicate and aluminosilicate minerals and glasses we have calculated the 23Na NMR shieldings and the electric field gradients (EFG) at the Na for a number of Na-containing species. Included are Na(OH2)\\u000a n\\u000a \\u000a +, n?=?1, 2, 4, 5, 6 and 8, and Na+ complexes with SiH3OH, SiH3ONa and O(SiH3)2.

J. A. Tossell

1999-01-01

344

Na sup + pump in renal tubular cells is regulated by endogenous Na sup + -K sup + -ATPase inhibitor from hypothalamus  

SciTech Connect

Bovine hypothalamus contains a high affinity, specific, reversible inhibitor of mammalian Na{sup +}-K{sup +}-ATPase. Kinetic analysis using isolated membrane fractions showed binding and dissociation rates of the hypothalamic factor (HF) to be (like ouabain) relatively long (off rate = 60 min). To determine whether the kinetics of inhibition in intact cells might be more consistent with regulation of physiological processes in vivo, binding and dissociation reactions of HF in intact renal epithelial cells (LLC-PK{sup 1}) were studied using {sup 86}Rb{sup +} uptake and ({sup 3}H)ouabain binding. As with membranes, a 60-min incubation with HF inhibited Na{sup +}-K{sup +}-ATPase in LLC-PK{sub 1} cells. In contrast to membrane studies, no prolonged incubation with LLC-PK{sub 1} was needed to observe inhibition of Na{sup +}-K{sup +}-ATPase. HF caused a 33% inhibition of ouabain-sensitive {sup 86}Rb{sup +} influx within 10 min. Incubation of cells with HF followed by washout showed rapid reversal of pump inhibition and a doubling of pump activity. The dose-response curve for HF inhibition of LLC-PK{sub 1} {sup 86}Rb{sup +} uptake showed a sigmoidal shape consistent with an allosteric binding reaction. Thus HF is a potent regulator of Na{sup +}-K{sup +}-ATPase activity in intact renal cells, with binding and dissociation reactions consistent with relevant physiological processes.

Cantiello, H.F.; Chen, E.; Ray, S.; Haupert, G.T. Jr. (Harvard medical School, Boston, MA (USA))

1988-10-01

345

Perfil do nível de atividade física na vida diária de pacientes portadores de DPOC no Brasil* Profile of the level of physical activity in the daily lives of patients with COPD in Brazil  

Microsoft Academic Search

Objective: To evaluate characteristics of physical activities in daily life in COPD patients in Brazil, correlating those characteristics with physiological variables. Methods: Physical activities in daily life were evaluated in 40 COPD patients (18 males; 66 ± 8 years of age; FEV 1 = 46 ± 16 % of predicted; body mass index = 27 ± 6 kg\\/m 2 )

Nidia Aparecida Hernandes; Denilson de Castro Teixeira; Vanessa Suziane Probst; Antonio Fernando Brunetto; Ercy Mara; Cipulo Ramos; Fábio Pitta

2009-01-01

346

Energetics of phosphate frameworks containing zinc and cobalt: NaZnPO 4, NaH(ZnPO 4) 2, NaZnPO 4·H 2O, NaZnPO 4· {4}/{3}H 2O, and NaCo xZn 1-xPO 4· {4}/{3}H 2O  

NASA Astrophysics Data System (ADS)

Differential scanning calorimetry and high temperature oxide melt solution calorimetry were used to study the enthalpy of the ?- ? phase transformation of NaZnPO 4 and enthalpies of formation of ?-NaZnPO 4, NaH(ZnPO 4) 2, NaZnPO 4·H 2O, and NaCo xZn 1-xPO 4· {4}/{3}H 2O ( x=0, 0.1, 0.2, 0.3). The enthalpies of formation from the oxides of cobalt substituted in NaZnPO 4· {4}/{3}H 2O do not depend on cobalt content, confirming similar acid-base interactions for Zn-PO 4 and Co-PO 4. While water molecules stabilize zinc phosphate frameworks through solvating a cation or forming extra hydrogen bonds, the partial substitution of water for sodium oxide to form NaH(ZnPO 4) 2 represents the formation of an acidic compound with weaker acid-base interactions and less exothermic enthalpy of formation from oxides than Na 2(ZnPO 4) 2.

Le, So-Nhu; Navrotsky, Alexandra

2007-09-01

347

Structure of NaI ion pairs in water clusters  

NASA Astrophysics Data System (ADS)

The structural properties of the thermodynamically stable NaI salt ion pairs in water clusters have been investigated by means of Monte Carlo simulations with model potentials. Attention was also paid to the structure of single ion-water Na +(H 2O) n and I -(H 2O) n clusters, which are found to be non-spherically symmetric at room temperature. In agreement with earlier studies, I -(H 2O) n clusters exhibit surface structures, with the "hydrophobic" iodide ion sitting at the surface of a water network, while room-temperature Na +(H 2O) n clusters exhibit a solvation shell structure, where solvent molecules beyond the first solvation shell tend to accumulate on one side of the cluster instead of forming a spherical droplet. Both "contact" ion pairs (CIP) and solvent-separated ion pairs (SSIP) are found to have surface structures for the smaller clusters while both interior and surface structures may exist at room temperature for cluster size of 32. A remarkable feature of the ion pair cluster structural properties is that they are very much akin to those for individual ion-water clusters, especially for SSIPs, and some insight into the ion pair cluster structures can thus be gained from single ion-water cluster structures. We propose that the (small) extent of solvent-solvent hydrogen bonding and the magnitude of the (large) solvent dipole moments in the clusters can be used to illustrate the extent of the perturbation introduced by the ions or the ion pairs in the solvent environments. In contrast to the ion pair free energetics investigated in previous work, ion-water and salt-water cluster structural properties are rather insensitive to the choice of model potentials, whether one employs non-polarizable optimized potentials for liquid simulations (OPLS) such as TIP4P/OPLS or polarizable optimized potentials for cluster simulations. The structure of NaI(H 2O) n CIP and SSIP clusters have implications for the NaI(H 2O) n cluster photodissociation dynamics. The large solvent dipole moments obtained for NaI(H 2O) n clusters are indicative of increasingly larger local solvent dipoles in the clusters, which may then grow large enough to dipole-bind an electron upon cluster photoexcitation. Photoexcitation of the larger clusters might then proceed via a different route than it does for the small clusters and isolated NaI possibly involving a charge-transfer-to-solvent excited state akin to that of I -(H 2O) n clusters. For the NaI photodissociation pathway, the surface structure of the small NaI(H 2O) n clusters may imply a slow change in the reaction dynamics with cluster size.

Peslherbe, Gilles H.; Ladanyi, Branka M.; Hynes, James T.

2000-08-01

348

INTEX-NA: Intercontinental Chemical Transport Experiment - North America  

NASA Technical Reports Server (NTRS)

INTEX-NA is an integrated atmospheric chemistry field experiment to be performed over North America using the NASA DC-8 and P-3B aircraft as its primary platforms. It seeks to understand the exchange of chemicals and aerosols between continents and the global troposphere. The constituents of interest are ozone and its precursors (hydrocarbons, NOX and HOX), aerosols, and the major greenhouse gases (CO2, CH4, N2O). INTEX-NA will provide the observational database needed to quantify inflow, outflow, and transformations of chemicals over North America. INTEX-NA is to be performed in two phases. Phase A will take place during the period of May-August 2004 and Phase B during March-June 2006. Phase A is in summer when photochemistry is most intense and climatic issues involving aerosols and carbon cycle are most pressing, and Phase B is in spring when Asian transport to North America is at its peak. INTEX-NA will coordinate its activities with concurrent measurement programs including satellites (e. g. Terra, Aura, Envisat), field activities undertaken by the North American Carbon Program (NACP), and other U.S. and international partners. However, it is being designed as a 'stand alone' mission such that its successful execution is not contingent on other programs. Synthesis of the ensemble of observation from surface, airborne, and space platforms, with the help of global/regional models is an important It is anticipated that approximately 175 flight hours for each of the aircraft (DC-8 and P-3B) will be required for each Phase. Principal operational sites are tentatively selected to be Bangor, ME; Wallops Island, VA; Seattle, WA; Rhinelander, WI; Lancaster, CA; and New Orleans, LA. These coastal and continental sites can support large missions and are suitable for INTEX-NA objectives. The experiment will be supported by forecasts from meteorological and chemical models, satellite observations, surface networks, and enhanced O3,-sonde releases. In addition to characterizing Atlantic-outflow and Pacific-inflow, INTEX-NA will characterize air masses transported between the U.S., Canada, and Mexico. INTEX-NA will be the first continental scale inflow, outflow, and transformation experiment to be performed over North America. It will provide the most comprehensive observational data set to date to understand the O3/NOX/HOX/aerosol photochemical system and the carbon cycle. One of the critical needs of the carbon cycle research is to obtain large-scale vertical and horizontal concentration gradients of CO2, throughout the troposphere over continental source/sink regions. INTEX-NA is ideally suited to perform this role. Coastal and continental operational sites will allow us to develop a curtain profile of greenhouse gases (e. g. CO2,) and other key pollutants across North America. Such information is central to our quantitative understanding of chemical budgets on the continental scale. We expect to provide a number of satellite under-flights over land and water to test and validate observations from the appropriate satellite platform (e. g. Aura). We plan to develop strong collaborations with other national and international observational programs. Results from INTEX-NA should directly benefit the development of environmental policy for air quality and climate change.

Singh, Hanwant B.; Jacob, D.; Pfister, L.; Hipskind, R. Stephen (Technical Monitor)

2002-01-01

349

Acidic residues involved in cation and substrate interactions in the Na+/dicarboxylate cotransporter, NaDC-1.  

PubMed

The role of acidic amino acid residues in cation recognition and selectivity by the Na+/dicarboxylate cotransporter, NaDC-1, was investigated by site-directed mutagenesis and expression in Xenopus oocytes. Four of the residues tested, Asp-52, Glu-74, Glu-101, and Glu-332, were found to be unimportant for transport activity. However, substitutions of Asp-373 and Glu-475, conserved residues found in transmembrane domains M8 and M9, respectively, altered transport kinetics. Replacements of Asp-373 with Ala, Glu, Asn, and Gln resulted in changes in sodium affinity and cation selectivity in NaDC-1, indicating that the carbonyl oxygen at this position may play a role in the topological organization of the cation-binding site. In contrast, substitutions of Glu-475 led to dramatic reductions in transport activity and changes in transport kinetics. Substitution with Gln led to a transporter with increased substrate and sodium affinity, while the E475D mutant was inactive. The E475A mutant appeared to have poor sodium binding. Substrate-induced currents in the E475A mutant exhibited a strong voltage dependence, and a reversal of the current was seen at -30 mV. The results suggest that Glu-475 may play a role in cation binding and possibly also in mediating anion channel activity. Remarkably, mutations of both Asp-373 and Glu-475 affected the Km for succinate in NaDC-1, suggesting dual roles for these residues in determining the affinity for substrate and cations. We propose that at least one of the cation-binding sites and the substrate-binding site are close together in the carboxy-terminal portion of NaDC-1, and thus transmembrane domains M8 and M9 are candidate structures for the formation of the translocation pathway. PMID:10360950

Griffith, D A; Pajor, A M

1999-06-01

350

Structure Modification on Quaternary Rare Earth Thiophosphates: NaYbP 2S 6, NaSmP 2S 6, and KSmP 2S 7  

NASA Astrophysics Data System (ADS)

Three rare earth quaternary compounds, NaYbP 2S 6, NaSmP 2S 6, and KSmP 2S 7, are synthesized using alkali metal halide or polychalcogenides flux. NaYbP 2S 6 was prepared from the stoichiometric reaction of Yb/S/P/NaCl flux at 700°C, and NaSmP 2S 6 and KSmP 2S 7 were prepared from Sm/S/P/Na 2S (K 2S x) flux at 750°C. The structures were determined by the single-crystal X-ray diffraction technique. The air-sensitive dark-red crystals of NaYbP 2S 6 crystallize in the triclinic space group P-1 with a=6.8241(10) Å, b=7.0371(10) Å, c=9.107(2) Å, ?=87.17(2)°, ?=87.62(2)°, ?=88.30(2)°, and Z=2. The yellow plate crystals of NaSmP 2S 6 crystallize in the monoclinic space group P2 1/ a with a=11.0717(10) Å, b=7.2999(1) Å, c=11.579(3) Å, ?=111.30(2)°, and Z=4. The pale yellow plate crystals of KSmP 2S 7 crystallize in the monoclinic space group P2 1/ a with a=8.981(2) Å, b=12.254(2) Å, c=9.609(1) Å, ?=90.27(2)°, and Z=4. NaYbP 2S 6 and NaSmP 2S 6 are derivatives of the MIMIIIP 2S 6 family. NaYbP 2S 6 has a flat monolayered structure, and there are weak interactions between neighboring layers. In NaSmP 2S 6, two MPS 3-type layers are condensed together. The ordering features of sodium and rare earth metal cations in two-dimensional layers are different: Na and Yb atoms are arranged in pairing fashion in NaYbP 2S 6, while Na and Sm atoms are arranged in a triangular pattern in NaSmP 2S 6. The structure of KSmP 2S 7 is similar to that of ABiP 2S 7 ( A=K, Rb), where corrugated layers are formed from Sm 3+ and [P 2S 7] 4- units. The optically measured band gaps of NaYbP 2S 6 and NaSmP 2S 6 are 1.85 eV and 2.54 eV, respectively.

Goh, Eun-Young; Kim, Eun-Jeong; Kim, Sung-Jin

2001-08-01

351

Adsorption, surface restructuring and alloy formation in the {Na}/{Au(111) } system  

NASA Astrophysics Data System (ADS)

The adsorption of Na on the reconstructed Au(111) surface has been studied by scanning tunneling microscopy, low-energy electron diffraction (LEED), thermal desorption spectroscopy and Auger electron spectroscopy. Upon deposition at 85 K, adsorbed Na atoms order spontaneously at coverages between 0.2 and 0.6 monolayers (ML) on the reconstructed substrate. A sequence of hexagonal overlayer structures is observed by LEED. Annealing the Na-covered sample to 300 K results in irreversible changes of the surface structures: Intermixed Na?Au surface layers are formed for ?Na > 0.25 ML. A well-ordered c(4 × 2) substitutional structure develops at ?Na ? 0.50 ML, where every fourth Au surface atom is replaced a Na atom. The structures formed at 300 K are metastable, and upon annealing to 600 K the equilibrium surface configurations evolve: For small Na coverages the periodicity of the Au(111) Chevron phase is reduced. At ?Na ? 0.23 ML the Na atoms induce a surface phase transformation of the Au(111) Chevron phase into a poorly ordered domain structure with an isotropically contracted surface layer and hexagonal symmetry. At even higher coverages a mixed NaAu 2 structure is formed in the topmost layer which covers the entire surface at ?Na ? 0.50 ML. The NaAu 2 structure is arranged in a hexagonal lattice with a (1.08?3 × 1.08?3)R30° geometry where the Au atoms form a honeycomb structure whose central sites are occupied by Na atoms. The lattice misfit between the surface and the second layer leads to a regular hexagonal Moiré pattern of ? 38 Å periodicity and ? 0.5 Å corrugation. This phase is regarded as a two-dimensional alloy. With adsorbed Na multilayers, Na atoms penetrate into deeper substrate layers and a thin NaAu 2 alloy film is formed.

Barth, J. V.; Behm, R. J.; Ertl, G.

1995-11-01

352

Increased Na-K transport in glomerular mesangial cell membrane from spontaneously hypertensive rats.  

PubMed

To investigate the differences in the Na-K transport of the mesangial cell (MC) membrane in hypertension versus normotension, the activity of the Na-K pump and the passive cation permeability were measured in serially passaged cultured MC obtained from both spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. When Na-K pump was active, Na-K pump activity, described as ouabain-sensitive 86Rb uptake, was significantly greater in the cultured MC from SHR than WKY rats. The outward Na-K cotransport, described as the washout rate constant of bumetanide-sensitive 86Rb washout, was also greater in SHR MC than in WKY rat MC. When Na-K pump was inhibited by 1 mM ouabain, overall intracellular Na uptake was significantly greater in SHR MC. A greater 5-(N,N-hexamethylene)amiloride-sensitive Na uptake in SHR MC accounted for this difference. There was no difference in the intracellular concentration of Na and K in the cultured MC from the 2 strains when Na-K pump was active. It is concluded that there is an increased activity of Na-K pump in the cultured MC from SHR, and that this abnormality may be innate to SHR cells. It is also suggested that an increase in Na-K cotransport and Na-H antiport may explain this difference, and that these abnormalities observed in the SHR kidney may be involved in the pathogenesis of hypertension in this model. PMID:1316559

Kuriyama, S; Nakamura, K; Kaguchi, Y; Tomonari, H; Tokutome, G; Hashimoto, T; Sakai, O

1992-01-01

353

Investigation of Sodium Distribution in Phosphate Glasses Using Spin-Echo {sup 23}Na NMR  

SciTech Connect

The spatial arrangement of sodium cations for a series of sodium phosphate glasses, xNa{sub 2}O(100-x)P{sub 2}O{sub 5} (x<55), were investigated using {sup 23}Na spin-echo NMR spectroscopy. The spin-echo decay rate is a function of the Na-Na homonuclear dipolar coupling and is related to the spatial proximity of neighboring Na nuclei. The spin-echo decay rate in these sodium phosphate glasses increases non-linearly with higher sodium number density, and thus provides a measure of the Na-Na extended range order. The results of these {sup 23}Na NMR experiments are discussed within the context of several structural models, including a decimated crystal lattice model, cubic dilation lattice model, a hard sphere (HS) random distribution model and a pair-wise cluster hard sphere model. While the experimental {sup 23}Na spin-echo M{sub 2} are described adequately by both the decimated lattice and the random HS model, it is demonstrated that the slight non-linear behavior of M{sub 2} as a function of sodium number density is more correctly described by the random distribution in the HS model. At low sodium number densities the experimental M{sub 2} is inconsistent with models incorporating Na-Na clustering. The ability to distinguish between Na-Na clusters and non-clustered distributions becomes more difficult at higher sodium concentrations.

ALAM, TODD M.; BOYLE, TIMOTHY J.; BROW, RICHARD K.; CLICK, CAROL C.; CONZONE, SAM; McLAUGHLIN, JAY; ZWANZIGER, JOE

1999-09-16

354

Heterogeneous reactions of HNO3(g) + NaCl(s) yields HCl(g) + NaNO3(s) and N2O5(g) + NaCl(s) yields ClNO2(g) + NaNO3(s)  

NASA Technical Reports Server (NTRS)

The heterogeneous reactions of HNO3(g) + NaCl(s) yields HCl(g) + NaNO3(s) (eq 1) and N2O5(g) + NaCl(s) yields ClNO2(g) + NaNO3(S) (eq 2) were investigated over the temperature range 223-296 K in a flow-tube reactor coupled to a quadrupole mass spectrometer. Either a chemical ionization mass spectrometer (CIMS) or an electron-impact ionization mass spectrometer (EIMS) was used to provide suitable detection sensitivity and selectivity. In order to mimic atmospheric conditions, partial pressures of HNO3 and N2O5 in the range 6 x 10(exp -8) - 2 x 10(exp -6) Torr were used. Granule sizes and surface roughness of the solid NaCl substrates were determined by using a scanning electron microscope. For dry NaCl substrates, decay rates of HNO3 were used to obtain gamma(1) = 0.013 +/- 0.004 (1sigma) at 296 K and > 0.008 at 223 K, respectively. The error quoted is the statistical error. After all corrections were made, the overall error, including systematic error, was estimated to be about a factor of 2. HCl was found to be the sole gas-phase product of reaction 1. The mechanism changed from heterogeneous reaction to predominantly physical adsorption when the reactor was cooled from 296 to 223 K. For reaction 2 using dry salts, gamma(2) was found to be less than 1.0 x 10(exp -4) at both 223 and 296 K. The gas-phase reaction product was identified as ClNO2 in previous studies using an infrared spectrometer. An enhancement in reaction probability was observed if water was not completely removed from salt surfaces, probably due to the reaction of N2O5(g) + H2O(s) yields 2HNO3(g). Our results are compared with previous literature values obtained using different experimental techniques and conditions. The implications of the present results for the enhancement of the hydrogen chloride column density in the lower stratosphere after the El Chichon volcanic eruption and for the chemistry of HCl and HNO3 in the marine troposphere are discussed.

Leu, Ming-Taun; Timonen, Raimo S.; Keyser, Leon F.; Yung, Yuk L.

1995-01-01

355

Phospholemman Overexpression Inhibits Na+-K+-ATPase in Adult Rat Cardiac Myocytes: Relevance to Decreased Na+ pump Activity in Post-Infarction Myocytes  

PubMed Central

Messenger RNA levels of phospholemman (PLM), a member of the FXYD family of small single-span membrane proteins with putative ion-transport regulatory properties, were increased in postinfarction (MI) rat myocytes. We tested the hypothesis that the previously observed reduction in Na+-K+-ATPase activity in MI rat myocytes was due to PLM overexpression. In rat hearts harvested 3 and 7 days post-MI, PLM protein expression was increased by 2- and 4-fold, respectively. To simulate increased PLM expression post-MI, PLM was overexpressed in normal adult rat myocytes by adenovirus-mediated gene transfer. PLM overexpression did not affect the relative level of phosphorylation on serine68 of PLM. Na+-K+-ATPase activity was measured as ouabain-sensitive Na+-K+ pump current (Ip). Compared to control myocytes overexpressing green fluorescent protein alone, Ip measured in myocytes overexpressing PLM was significantly (P<0.0001) lower at similar membrane voltages, pipette Na+ ([Na+]pip) and extracellular K+ concentrations ([K+]o). From ?70 to +60 mV, neither [Na+]pip nor [K+]o required to attain half-maximal Ip was significantly different between control and PLM myocytes. This phenotype of decreased Vmax without appreciable changes in Km for Na+ and K+ in PLM overexpressed myocytes was similar to that observed in MI rat myocytes. Inhibition of Ip by PLM overexpression was not due to decreased Na+-K+-ATPase expression since there were no changes in either protein or messenger RNA levels of either ?1 or ?2 isoforms of Na+-K+-ATPase. In native rat cardiac myocytes, PLM co-immunoprecipitated with ?-subunits of Na+-K+-ATPase. Inhibition of Na+-K+-ATPase by PLM overexpression, in addition to previously reported decrease in Na+-K+-ATPase expression, may explain altered Vmax but not Km of Na+-K+-ATPase in postinfarction rat myocytes.

Zhang, Xue-Qian; Moorman, J. Randall; Ahlers, Belinda A.; Carl, Lois L.; Lake, Douglas E.; Song, Jianliang; Mounsey, J. Paul; Tucker, Amy L.; Chan, Yiu-mo; Rothblum, Lawrence I.; Stahl, Richard C.; Carey, David J.; Cheung, Joseph Y.

2005-01-01

356

Crystal structure of new synthetic Ca,Na carbonate-borate Ca2Na(Na x Ca0.5 - x )[B{3/ t }B{2/?}O8(OH)(O1 - x OH x )](CO3)  

NASA Astrophysics Data System (ADS)

New Ca,Na carbonate-borate Ca2Na(Na x Ca0.5 - x ) [B{3/ t }B{2/?}O8(OH)(O1 - x OH x )](CO3) crystals ( x ˜ 0.4) have been synthesized by the hydrothermal method in the Ca(OH)2-H3BO3-Na2CO3-NaCl-system at t = 250°C and P = 70-80 atm; the structure parameters are found to be a = 11.1848(3) Å, b = 6.4727(2) Å, c = 25.8181(7) Å, ? = 96.364(3)°, V = 1857.60(9) Å3, sp. gr. C2/ c, Z = 8, and ?calcd = 2.801 g/cm3 (Xcalibur S autodiffractometer (CCD), 2663 reflections with I > 2? ( I), direct solution, refinement by the least-squares method in the anisotropic approximation of thermal atomic vibrations, hydrogen localization, R 1 = 0.0387). The structure is based on boron-oxygen layers of pentaborate radicals 5(2? + 3T). Ca and Na polyhedra and CO3 triangles are located between the layers. A crystallochemical analysis of the new Ca,Na carbonate-borate has established its similarity to natural Na,Ca pentaborates (heidornite and tuzlaite) and synthetic Na,Ba-decaborate.

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

2012-05-01

357

Preferential Interaction of Na+ over K+ to Carboxylate-functionalized Silver Nanoparticles  

EPA Science Inventory

Elucidating mechanistic interactions between specific ions (Na+/ K+) and nanoparticle surfaces to alter particle stability in polar media has received little attention. We investigated relative preferential binding of Na+ and K+ to carboxylate-functionalized silver nanoparticles ...

358

Mass spectrometric and theoretical study of the mixed complex NaCeCl 4(g)  

NASA Astrophysics Data System (ADS)

The vaporization of the NaCl-CeCl 3 system was investigated at 919-1046 K by means of Knudsen effusion mass spectrometry. The vapor species NaCl, Na 2Cl 2, CeCl 3, and NaCeCl 4 were found in the equilibrium vapor and their partial pressures were evaluated. Theoretical calculations of the NaCeCl 4(g) structure were performed and the thermodynamic functions of this molecule were evaluated. The enthalpy change of the dissociation reaction NaCeCl 4(g)=NaCl(g)+CeCl 3(g) was determined by the third-law method as 238.0±6.5 kJ mol -1. The volatility enhancement of CeCl 3 by the formation of the vapor complex NaCeCl 4 was estimated from obtained thermodynamic data of gaseous and condensed phases.

Kapala, J.; Roszak, S.; Lisek, I.; Miller, M.

1998-11-01

359

Translocation mechanism of NaCa exchange in single cardiac cells of guinea pig  

Microsoft Academic Search

We have studied in single cardiac ventricular cells of guinea pig the ionic translocation mechanism of the electrogenic Na-Ca exchange, i.e., whether Na and Ca ions countercross the membrane simultaneously or consecutively with \\

JINMING Li

1990-01-01

360

An Improved Automated Determination of Na(+)-K(+)-Activated Adenosine Triphosphatase.  

National Technical Information Service (NTIS)

To increase the capacity of measuring Na(+)-K(+)-activated adenosine triphosphatase (Na-KATPase) activity in large numbers of samples, an automated ATPase assay was developed. Technicon AA II technology and AAI components were used to measure inorganic ph...

D. P. Collin J. I. Davis A. N. Charney

1976-01-01

361

Homeostatic function of astrocytes: Ca2+ and Na+ signalling  

PubMed Central

The name astroglia unifies many non-excitable neural cells that act as primary homeostatic cells in the nervous system. Neuronal activity triggers multiple homeostatic responses of astroglia that include increase in metabolic activity and synthesis of neuronal preferred energy substrate lactate, clearance of neurotransmitters and buffering of extracellular K+ ions to name but a few. Many (if not all) of astroglial homeostatic responses are controlled by dynamic changes in the cytoplasmic concentration of two cations, Ca2+ and Na+. Intracellular concentration of these ions is tightly controlled by several transporters and can be rapidly affected by the activation of respective fluxes through ionic channels or ion exchangers. Here, we provide a comprehensive review of astroglial Ca2+ and Na+ signalling.

Parpura, Vladimir; Verkhratsky, Alexei

2012-01-01

362

The NA62 liquid Krypton calorimeter's new readout system  

NASA Astrophysics Data System (ADS)

The NA62 experiment [1] at CERN SPS (Super Proton Synchrotron) accelerator aims at studying Kaon decays with high precision. The high resolution Liquid Krypton (LKr) calorimeter, built for the NA48 [2] experiment, is a crucial part of the experiment photon-veto system; to cope with the new requirements, the back-end electronics of the LKr had to be completely renewed. Due to the huge number of the calorimeter readout channels ( ~ 14 K) and the maintenance requirement over 10 years of the experiment lifetime, the decision to sub-contract the development and production to industry was taken in 2011. This paper presents the primary test results of the Calorimeter REAdout Module (CREAM) [3] prototype delivered by the manufacturer in March 2013. All essential features, analog performance, data processing and readout, are covered.

Ceccucci, A.; Fantechi, R.; Farthouat, P.; Lamanna, G.; Rouet, J.; Ryjov, V.; Venditti, S.

2014-01-01

363

Cesium selectivity of (Al+Na)-substituted tobermorite  

SciTech Connect

Several synthetic tobermorites with different levels of [Al+Na] substitution were prepared from two different types of starting materials and their cation exchange and cesium selective properties were investigated. The substituted tobermorites were found to have high cation exchange capacities and very high selectivities for Cs[sup +] ion. Cesium selectivity of the substituted tobermorites was demonstrated in the presence of divalent cations such as Ca[sup 2+], Mg[sup 2+], Ba[sup 2+] and univalent cations such as Na[sup +], K[sup +] and Li[sup +] which are one hundred times more concentrated than the cesium ion. The uptake of Cs is maximum in the presence of highly hydrated Mg[sup 2+] and Li[sup +] ions whereas it is minimum in the presence of less hydrated K[sup +] and Ba[sup 2+] ions due to steric limitations of the tobermorite structure.

Shrivastava, O.P.; Komarneni, S. (Pennsylvania State Univ., University Park, PA (United States). Materials Research Lab.)

1994-01-01

364

Temperaturleitfähigkeit von Na 3UO 4 bis 600°C  

NASA Astrophysics Data System (ADS)

The thermal diffusivity of Na 3UO 4 with densities between 80 and 96% T.D. was measured with a laser-flash diffusivity apparatus. The samples were analysed metallographically and showed second phases with volume concentrations between 5 and 10%. The data of thermal diffusivity were corrected to zero porosity. Using literature data for the specific heat and density, the thermal conductivity of Na 3UO 4 was calculated. It follows the relationship: ? = {1}/{(74.6 + 0.052T)}; [ T] = ° C; [ ?]= W/ cmK; 20° C ? T? 600° C. The standard deviation is ( ??/ ?) 100 = ±6%. The coefficient of correlation for 1/ ? = f( T) was determined to be r = 0.97. The difference in the porosity correction of the thermal conductivity and thermal diffusivity is discussed. Relationships for both properties are recommended.

Schulz, B.

1983-02-01

365

First principles molecular dynamics of molten NaCl  

NASA Astrophysics Data System (ADS)

First principles Hellmann-Feynman molecular dynamics (HFMD) results for molten NaCl at a single state point are reported. The effect of induction forces on the structure and dynamics of the system is studied by comparison of the partial radial distribution functions and the velocity and force autocorrelation functions with those calculated from classical MD based on rigid-ion and shell-model potentials. The first principles results reproduce the main structural features of the molten salt observed experimentally, whereas they are incorrectly described by both rigid-ion and shell-model potentials. Moreover, HFMD Green-Kubo self-diffusion coefficients are in closer agreement with experimental data than those predicted by classical MD. A comprehensive discussion of MD results for molten NaCl based on different ab initio parametrized polarizable interionic potentials is also given.

Galamba, N.; Costa Cabral, B. J.

2007-03-01

366

1 nA beam position monitoring system  

SciTech Connect

A system has been developed at Jefferson Lab for measuring transverse position of very low current beams delivered to the Experimental Hall B of the Continuous Electron Beam Accelerator Facility (CEBAF). At the heart of the system is a position sensitive cavity operating at 1497 MHz. The cavity utilizes a unique design which achieves a high sensitivity to beam position at a relatively low cavity Q. The cavity output RF signal is processed using a down-converter and a commercial lock-in amplifier operating at 100 kHz. The system interfaces with a VME based EPICS control system using the IEEE, 488 bus. The main features of the system are simple and robust design, and wide dynamic range capable of handling beam currents from 1 nA to 1000 nA with an expected resolution better than 100 {mu}m. This paper outlines the design of the system.

Ursic, R.; Flood, R.; Piller, C. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)] [and others

1997-06-01

367

Ultra-violet excited laser emission in Na2  

NASA Astrophysics Data System (ADS)

Laser emission at different wavelengths in the range of 903 914 nm and around 2.5 ?m has been observed upon excitation of Na2 by uv radiation from an excimer laser at 351 nm and an excimer pumped dye laser in this wavelength range. The emission is attributed to a cascade emissionC^1 Pi _u to 2^1 sum _g^ + followed by2^1 sum _g^ + to A^1 sum _u^ + . In addition, coupled with the laser emission around 910 nm, broad-band fluorescence peaking around 855.5 nm is observed which, eventually, may be the first observation of theb^3 sum _g^ + to x^3 sum _u^ + bound-free transition in Na2.

Shahdin, S.; Wellegehausen, B.; Ma, Z. G.

1982-11-01

368

Coupled plasmon and phonon dynamics in embedded Na clusters  

NASA Astrophysics Data System (ADS)

We investigate, from a theoretical perspective, the coupled electronic and ionic/atomic dynamics of Na clusters embedded in Ar matrices. The system is described by time-dependent density-functional theory for cluster electrons and classical motion for Na+ ions as well as for Ar atoms. The interaction with the surrounding Ar atoms is modelled by polarization potentials plus core repulsion. We use this model to study coupled electronic and ionic/atomic motion in embedded clusters following a very short laser pulse. For excitations in the non-linear regime, we find clear signs for the coherent coupling of the Mie plasmon resonance with ionic vibrations (phonons). In addition, an incoherent line stretching is observed which can be traced back to the turning point of ionic vibrations. The coupling to the atomic motion of the surroundings leads to a slow and far reaching rearrangement of the matrix.

Fehrer, F.; Reinhard, P. G.; Suraud, E.

2006-01-01

369

Study of the K±??±?? decay by the NA62 experiment  

NASA Astrophysics Data System (ADS)

A study of the dynamics of the rare decay K±??±?? has been performed on a sample of 232 decay candidates, with an estimated background of 17.4±1.1 events, collected by the NA62 experiment at CERN in 2007. The results are combined with those from a measurement conducted by the NA48/2 Collaboration at CERN. The combined model-independent branching ratio in the kinematic range z=(>0.2 is BMI(z>0.2)=(0.965±0.063)×10?6, and the combined branching ratio in the full kinematic range assuming a Chiral Perturbation Theory description is B(K)=(1.003±0.056)×10?6. A detailed comparison of the results with the previous measurements is performed.

Lazzeroni, C.; Romano, A.; Ceccucci, A.; Danielsson, H.; Falaleev, V.; Gatignon, L.; Goy Lopez, S.; Hallgren, B.; Maier, A.; Peters, A.; Piccini, M.; Riedler, P.; Frabetti, P. L.; Gersabeck, E.; Kekelidze, V.; Madigozhin, D.; Misheva, M.; Molokanova, N.; Movchan, S.; Potrebenikov, Yu.; Shkarovskiy, S.; Zinchenko, A.; Rubin, P.; Baldini, W.; Cotta Ramusino, A.; Dalpiaz, P.; Fiorini, M.; Gianoli, A.; Norton, A.; Petrucci, F.; Savrié, M.; Wahl, H.; Bizzeti, A.; Bucci, F.; Iacopini, E.; Lenti, M.; Veltri, M.; Antonelli, A.; Moulson, M.; Raggi, M.; Spadaro, T.; Eppard, K.; Hita-Hochgesand, M.; Kleinknecht, K.; Renk, B.; Wanke, R.; Winhart, A.; Winston, R.; Bolotov, V.; Duk, V.; Gushchin, E.; Ambrosino, F.; Di Filippo, D.; Massarotti, P.; Napolitano, M.; Palladino, V.; Saracino, G.; Anzivino, G.; Imbergamo, E.; Piandani, R.; Sergi, A.; Cenci, P.; Pepe, M.; Costantini, F.; Doble, N.; Giudici, S.; Pierazzini, G.; Sozzi, M.; Venditti, S.; Balev, S.; Collazuol, G.; DiLella, L.; Gallorini, S.; Goudzovski, E.; Lamanna, G.; Mannelli, I.; Ruggiero, G.; Cerri, C.; Fantechi, R.; Kholodenko, S.; Kurshetsov, V.; Obraztsov, V.; Semenov, V.; Yushchenko, O.; D'Agostini, G.; Leonardi, E.; Serra, M.; Valente, P.; Fucci, A.; Salamon, A.; Bloch-Devaux, B.; Peyaud, B.; Engelfried, J.; Coward, D.; Kozhuharov, V.; Litov, L.; Arcidiacono, R.; Bifani, S.; Biino, C.; Dellacasa, G.; Marchetto, F.; Numao, T.; Retière, F.

2014-05-01

370

Concentrations of Na+ and Cl- in transplacental ultrafiltrate in sheep.  

PubMed Central

1. Maternal blood was made transiently hypertonic by rapid I.V. infusion of a concentrated mannitol solution into pregnant ewes bearing lambs with an indwelling flow sensor and vascular catheters. 2. The transplacental flows of water and of Na+ and Cl- were calculated from the umbilical arteriovenous differences in the concentrations of 125I-labelled albumin and electrolytes, and the fetal placental blood flow. 3. The reflection coefficients of Na+ and Cl- were calculated by means of the Patlak equation and found to be 0.85 +/- 0.04 and 0.68 +/- 0.04 (means +/- S.E.M.). The filtration coefficient was 1.02 x 10(-7) +/- 0.12 x 10(-7) cm5 dyne-1 s-1. 4. The results fitted best to an equivalent pore radius in the placental barrier smaller than the currently accepted 0.44 nm but not less than 0.35 nm.

Faber, J J; Anderson, D F

1995-01-01

371

Competition between Na + and Li + for Unsealed and Cytoskeleton-Depleted Human Red Blood Cell Membrane: A 23Na Multiple Quantum Filtered and 7Li NMR Relaxation Study  

NASA Astrophysics Data System (ADS)

Evidence for competition between Li + and Na + for binding sites of human unsealed and cytoskeleton-depleted human red blood cell (csdRBC) membranes was obtained from the effect of added Li + upon the 23Na double quantum filtered (DQF) and triple quantum filtered (TQF) NMR signals of Na +-containing red blood cell (RBC) membrane suspensions. We found that, at low ionic strength, the observed quenching effect of Li + on the 23Na TQF and DQF signal intensity probed Li +/Na + competition for isotropic binding sites only. Membrane cytoskeleton depletion significantly decreased the isotropic signal intensity, strongly affecting the binding of Na + to isotropic membrane sites, but had no effect on Li +/Na + competition for those sites. Through the observed 23Na DQF NMR spectra, which allow probing of both isotropic and anisotropic Na + motion, we found anisotropic membrane binding sites for Na + when the total ionic strength was higher than 40 mM. This is a consequence of ionic strength effects on the conformation of the cytoskeleton, in particular on the dimer-tetramer equilibrium of spectrin. The determinant involvement of the cytoskeleton in the anisotropy of Na + motion at the membrane surface was demonstrated by the isotropy of the DQF spectra of csdRBC membranes even at high ionic strength. Li + addition initially quenched the isotropic signal the most, indicating preferential Li +/Na + competition for the isotropic membrane sites. High ionic strength also increased the intensity of the anisotropic signal, due to its effect on the restructuring of the membrane cytoskeleton. Further Li + addition competed with Na + for those sites, quenching the anisotropic signal. 7Li T1 relaxation data for Li +-containing suspensions of unsealed and csdRBC membranes, in the absence and presence of Na + at low ionic strength, showed that cytoskeleton depletion does not affect the affinity of Na + for the RBC membrane, but increases the affinity of Li + by 50%. This clearly indicates that cytoskeleton depletion favors Li + relative to Na + binding, and thus Li +/Na + competition for its isotropic sites. Thus, this relaxation technique proves to be very sensitive to alkali metal binding to the membrane, detecting a more pronounced steric hindrance effect of the cytoskeleton network to binding of the larger hydrated Li + ion to the membrane phosphate groups.

Srinivasan, Chandra; Minadeo, Nicole; Toon, Jason; Graham, Daniel; Mota de Freitas, Duarte; Geraldes, Carlos F. G. C.

1999-09-01

372

A Versatile Low Temperature Synthetic Route to Zintl Phase Precursors: Na4Si4, Na4Ge4 and K4Ge4 as Examples  

PubMed Central

Na4Si4 and Na4Ge4 are ideal chemical precursors for inorganic clathrate structures, clusters, and nanocrystals. The monoclinic Zintl phases, Na4Si4 and Na4Ge4, contain isolated homo-tetrahedranide [Si4]4? and [Ge4]4? clusters surrounded by alkali metal cations. In this study, a simple scalable route has been applied to prepare Zintl phases of composition Na4Si4 and Na4Ge4 using the reaction between NaH and Si or Ge at low temperature (420 °C for Na4Si4 and 270 °C for Na4Ge4). The method was also applied to K4Ge4, using KH and Ge as raw materials, to show the versatility of this approach. The influence of specific reaction conditions on the purity of these Zintl phases has been studied by controlling five factors: the method of reagent mixing (manual or ball milled), the stoichiometry between raw materials, the reaction temperature, the heating time and the gas flow rate. Moderate ball-milling and excess NaH or KH facilitate the formation of pure Na4Si4, Na4Ge4 or K4Ge4 at 420 °C (Na4Si4) or 270 °C (both M4Ge4 compounds, M = Na, K). TG/DSC analysis of the reaction of NaH and Ge indicates that ball milling reduces the temperature for reaction and confirms the formation temperature. This method provides large quantities of high quality Na4Si4 and Na4Ge4 without the need for specialized laboratory equipment, such as Schlenk lines, niobium/tantalum containers, or an arc welder, thereby expanding the accessibility and chemical utility of these phases by making them more convenient to prepare. This new synthetic method may also be extended to lithium-containing Zintl phases (LiH is commercially available) as well as to alkali metal-tetrel Zintl compounds of other compositions, e.g. K4Ge9.

Ma, Xuchu; Xu, Fen; Atkins, Tonya; Goforth, Andrea M.; Neiner, Doinita; Navrotsky, Alexandra; Kauzlarich, Susan M.

2010-01-01

373

Neutron diffraction study of NaNO 2 ferroelectric nanowires  

Microsoft Academic Search

For the first time the temperature evolution of the structure of ferroelectric nanowires of NaNO2 was studied by neutron diffraction from room temperature up to melting, i.e. in ferro- and paraelectric phases. Samples were produced in natural chrysotile asbestos with average channel diameter 6±1.5nm. It is demonstrated that in the ferroelectric phase the structure is consistent with the bulk but

S. Borisov; T. Hansen; Yu. Kumzerov; A. Naberezhnov; V. Simkin; O. Smirnov; A. Sotnikov; M. Tovar; S. Vakhrushev

2004-01-01

374

Mode coupling in low NA plastic optical fibers  

NASA Astrophysics Data System (ADS)

Using the power flow equation and experimental measurements, investigated in this article is the state of mode coupling in low NA (0.3) step-index plastic optical fibers for laser beam launch. Results show the coupling length Lc at which the equilibrium mode distribution is achieved and the length zs of the fiber required for achieving the steady-state mode distribution. Numerical results obtained using the power flow equation agree well with experimental measurements.

Savovi?, Svetislav; Kova?evi?, Milan S.; Djordjevich, Alexandar; Baji?, Jovan S.; Stupar, Dragan Z.; Stepniak, Grzegorz

2014-08-01

375

Pressure-dependent Knight shift in Na and Cs metal  

Microsoft Academic Search

We present an experimental and theoretical study of the pressure dependence of the Knight shift of 23Na and 133Cs in sodium and cesium metal, respectively. The sodium shift has been measured, employing the diamond-anvil cell technique, up to about 8 GPa, and our previous discovery of a shift minimum around 1.5 GPa has been confirmed. The temperature dependence of the

St. Kluthe; R. Markendorf; M. Mali; J. Roos; D. Brinkmann

1996-01-01

376

Electrogenic NaCa exchange in retinal rod outer segment  

Microsoft Academic Search

Previous work has suggested that a Na-Ca exchanger may have a key role in visual transduction in retinal rods1-10. This exchanger is thought to maintain a low internal free Ca2+ concentration in darkness4-10 and to contribute to the rod's recovery after light by removing any internally released Ca2+ (refs 1, 2, 6-8). Little else is known about this transport mechanism

King-Wai Yau; Kei Nakatani

1984-01-01

377

Ferroelectric phase transitions in NaCa-halide perovskites  

Microsoft Academic Search

We have used lattice statics and dynamics, as well as molecular dynamics to investigate the possibility of structural phase transitions in NaCaX3 compounds in which X is one of the halides; F, Cl, Br, I. These simulations were done using 320-ion clusters and ab initio potentials with no adjustable parameters. Our computations lead to the prediction that these compounds all

J. W. Flocken; W. N. Mei; R. A. Guenther; J. R. Hardy; P. J. Edwardson; L. L. Boyer

1990-01-01

378

Global structure of small Na clusters in different approaches  

NASA Astrophysics Data System (ADS)

We compare the shapes of small Na clusters as they result from the jellium model, the cylindrically averaged pseudopotential scheme, and the distance-dependent tight-binding approach. Although these are three distinctively different approaches, we find a good agreement amongst the results, showing that all three models, taken in their appropriate domain of descriptive power, give an equally reliable picture of metal clusters.

Spiegelmann, F.; Poteau, R.; Montag, B.; Reinhard, P.-G.

1998-05-01

379

Substrate–Na + complex formation: Coupling mechanism for ?-aminobutyrate symporters  

Microsoft Academic Search

Crystal structures of transmembrane transport proteins belonging to the important families of neurotransmitter-sodium symporters reveal how they transport neurotransmitters across membranes. Substrate-induced structural conformations of gated neurotransmitter-sodium symporters have been in the focus of research, however, a key question concerning the mechanism of Na+ ion coupling remained unanswered. Homology models of human glial transporter subtypes of the major inhibitory neurotransmitter

Anna Palló; Ágnes Simon; Ákos Bencsura; László Héja; Julianna Kardos

2009-01-01

380

Fragmentation in collisions of Na9+ clusters with Cs atoms  

NASA Astrophysics Data System (ADS)

We have evaluated charge transfer, excitation and fragmentation cross sections in Na9+ + Cs collisions using a molecular close-coupling formalism and a postcollisional rate-equation model. The calculated charge transfer cross sections are in good agreement with recent experimental measurements below v = 0.04 au. We show that the relative abundance of the different fragments depend critically on the cluster temperature and the spectrometer time-of-flight window.

Hervieux, P. A.; Zarour, B.; Hanssen, J.; Politis, M. F.; Martín, F.

2001-08-01

381

Readout Electronics of the NA62 Gigatracker System  

Microsoft Academic Search

A crucial detector of the NA62 experiment is the beam spectrometer named Gigatracker. It consists of three stations of hybrid silicon pixels sensors with 150 ps (rms) of time resolution and 100 mum (rms) of space resolution. In addition the system operates under a high radiation environment and a high density of particles (up to 1.5 MHz\\/mm2 in the centre

G. Dellacasa; S. Garbolino; F. Marchetto; S. Martoiu; G. Mazza; A. Rivetti; R. Wheadon; A. Ceccucci; M. Fiorini; P. Jarron; J. Kaplon; A. Kluge; M. Noy; P. Riedler; S. Tiuraniemi; V. Carassiti; A. Cotta Ramusino; S. Chiozzi; F. Petrucci; E. Cortina; E. Martin

2010-01-01

382

Coulomb excitation of radioactive ²¹Na and its stable mirror ²¹Ne  

Microsoft Academic Search

The low-energy structures of the mirror nuclei ²¹Ne and radioactive ²¹Na have been examined by using Coulomb excitation at the TRIUMF-ISAC radioactive ion beam facility. Beams of 5x10 ions\\/s were accelerated to 1.7 MeV\\/A and Coulomb excited in a 0.5 mg\\/cm² {sup nat}Ti target. Scattered beam and target particles were detected by the segmented Si detector BAMBINO, while rays were

M. A. Schumaker; C. E. Svensson; G. A. Demand; P. Finlay; P. E. Garrett; K. L. Green; G. F. Grinyer; K. G. Leach; A. A. Phillips; J. Wong; D. Cline; A. B. Hayes; A. Whitbeck; G. Hackman; A. C. Morton; C. J. Pearson; A. Andreyev; G. C. Ball; L. Buchmann; R. Churchman

2008-01-01

383

The 1999 Quadrantids and the lunar Na atmosphere  

NASA Astrophysics Data System (ADS)

Enhancements of the Na emission and temperature from the lunar atmosphere were reported during the Leonid meteor showers of 1995, 1997 and 1998. Here we report a search for similar enhancement during the 1999 Quadrantids, which have the highest mass flux of any of the major streams. No enhancements were detected. We suggest that different chemical-physical properties of the Leonid and Quadrantid streams may be responsible for the difference.

Verani, S.; Barbieri, C.; Benn, C. R.; Cremonese, G.; Mendillo, M.

2001-10-01

384

Results on correlations and fluctuations from NA49  

Microsoft Academic Search

The large acceptance and high momentum resolution as well as the significant\\u000aparticle identification capabilities of the NA49 experiment at the CERN SPS\\u000aallow for a broad study of fluctuations and correlations in hadronic\\u000ainteractions. In the first part recent results on event-by-event charge and p_t\\u000afluctuations are presented. Charge fluctuations in central Pb+Pb reactions are\\u000ainvestigated at three different

S. V. Afanasiev; T. Anticic; B. Baatar; D. Barna; J. Bartke; R. A. Barton; M. Behler; L. Betev; H. Bia?kowska; A. Billmeier; C. Blume; C. O. Blyth; B. Boimska; M. Botje; J. Bracinik; R. Bramm; R. Brun; V. Cerny; O. Chvala; J. G. Cramer; P. Csató; P. Dinkelaker; V. Eckardt; P. Filip; H. G. Fischer; Z. Fodor; P. Foka; P. Freund; V. Friese; J. Gál; M. Ga?dzicki; G. Georgopoulos; E. G?adysz; S. Hegyi; C. Höhne; G. Igo; P. G. Jones; K. Kadija; V. I. Kolesnikov; T. Kollegger; M. Kowalski; I. Kraus; M. Kreps; M. van Leeuwen; R. Lednický; P. Lévai; A. I. Malakhov; S. Margetis; C. Markert; B. W. Mayes; G. L. Melkumov; C. Meurer; A. Mischke; M. Mitrovski; J. Molnár; J. M. Nelson; G. Pálla; A. D. Panagiotou; K. Perl; A. Petridis; M. Pikna; L. Pinsky; F. Pühlhofer; J. G. Reid; R. Renfordt; W. Retyk; C. Roland; G. Roland; A. Rybicki; T. Sammer; A. Sandoval; H. Sann; N. Schmitz; P. Seyboth; F. Siklér; B. Sitar; E. Skrzypczak; J. Smolik; G. T. A. Squier; R. Stock; H. Ströbele; T. Susa; I. Szentpétery; J. Sziklai; T. A. Trainor; D. Varga; M. Vassiliou; G. I. Veres; G. Vesztergombi; D. Vrani?; S. Wenig; A. Wetzler; C. Whitten; I. K. Yoo; J. Zaranek; J. Zimányi

2003-01-01

385

Spatiotemporal chaos from a continuous Na/sub 2/ laser  

SciTech Connect

We report on the observation of spatiotemporal chaos in a multimode continuous Na/sub 2/ ring laser optically pumped by a single-mode Ar/sup +/ laser. Measurements of the intensity of the emitted beam at two different points of the beam cross section reveal different temporal behavior of those two signals. Power spectra, fractal dimensions, and correlations indicate that both signals are chaotic and are generated by a common attractor.

Klische, W.; Weiss, C.O.; Wellegehausen, B.

1989-01-15

386

CONCENTRAÇÃO NA AGROINDÚSTRIA CANAVIEIRA MINEIRA PÓS-DESREGULAMENTAÇÃO SETORIAL  

Microsoft Academic Search

O objetivo deste trabalho foi verificar a concentração na agroindústria canavieira do Estado de Minas Gerais pós-desregulamentação setorial. Os resultados (obtidos via CR4 e CR8, índices de Hirschmann-Herfindahl, de Rosenbluth e entropia) apontaram para um aumento da concentração da produção de cana. Este aumento da concentração, dado principalmente mediante crescimento das empresas de grande porte, justifica-se pela reestruturação do setor

Amarildo Hersen; Pery Francisco Assis Shikida; Vanessa de Souza Dahmer; Marcia Janaina Snoz

2008-01-01

387

The Offline Software Framework of the NA61/SHINE Experiment  

NASA Astrophysics Data System (ADS)

NA61/SHINE (SHINE = SPS Heavy Ion and Neutrino Experiment) is an experiment at the CERN SPS using the upgraded NA49 hadron spectrometer. Among its physics goals are precise hadron production measurements for improving calculations of the neutrino beam flux in the T2K neutrino oscillation experiment as well as for more reliable simulations of cosmic-ray air showers. Moreover, p+p, p+Pb and nucleus+nucleus collisions will be studied extensively to allow for a study of properties of the onset of deconfinement and search for the critical point of strongly interacting matter. Currently NA61/SHINE uses the old NA49 software framework for reconstruction, simulation and data analysis. The core of this legacy framework was developed in the early 1990s. It is written in different programming and scripting languages (C, pgi-Fortran, shell) and provides several concurrent data formats for the event data model, which includes also obsolete parts. In this contribution we will introduce the new software framework, called Shine, that is written in C++ and designed to comprise three principal parts: a collection of processing modules which can be assembled and sequenced by the user via XML files, an event data model which contains all simulation and reconstruction information based on STL and ROOT streaming, and a detector description which provides data on the configuration and state of the experiment. To assure a quick migration to the Shine framework, wrappers were introduced that allow to run legacy code parts as modules in the new framework and we will present first results on the cross validation of the two frameworks.

Sipos, Roland; Laszlo, Andras; Marcinek, Antoni; Paul, Tom; Szuba, Marek; Unger, Michael; Veberic, Darko; Wyszynski, Oskar

2012-12-01

388

I Ca(TTX) Channels Are Distinct from Those Generating the Classical Cardiac Na + Current  

Microsoft Academic Search

The Na+ current component ICa(TTX) is functionally distinct from the main body of Na+ current, INa. It was proposed that ICa(TTX) channels are INa channels that were altered by bathing media containing Ca2+, but no, or very little, Na+. It is known that Na+-free conditions are not required to demonstrate ICa(TTX). We show here that Ca2+ is also not required.

Ye Chen-Izu; Qun Sha; Stephen R. Shorofsky; Shawn W. Robinson; W. Gil Wier; L. Goldman; C. William Balke

2001-01-01

389

Caustic Recycle from Hanford Tank Waste Using Large Area NaSICON Structures (LANS)  

SciTech Connect

This report presents the results of a 5-day test of an electrochemical bench-scale apparatus using a proprietary (NAS-GY) material formulation of a (Na) Super Ion Conductor (NaSICON) membrane in a Large Area NaSICON Structures (LANS) configuration. The primary objectives of this work were to assess system performance, membrane seal integrity, and material degradation while removing Na from Group 5 and 6 tank waste from the Hanford Site.

Fountain, Matthew S.; Sevigny, Gary J.; Balagopal, S.; Bhavaraju, S.

2009-03-31

390

Hofmeister effects of anions on the kinetics of partial reactions of the Na+,K+-ATPase.  

PubMed Central

The effects of lyotropic anions, particularly perchlorate, on the kinetics of partial reactions of the Na+,K+-ATPase from pig kidney were investigated by two different kinetic techniques: stopped flow in combination with the fluorescent label RH421 and a stationary electrical relaxation technique. It was found that 130 mM NaClO4 caused an increase in the Kd values of both the high- and low-affinity ATP-binding sites, from values of 7.0 (+/- 0.6) microM and 143 (+/- 17) microM in 130 mM NaCl solution to values of 42 (+/- 3) microM and 660 (+/- 100) microM in 130 mM NaClO4 (pH 7.4, 24 degrees C). The half-saturating concentration of the Na+-binding sites on the E1 conformation was found to decrease from 8-10 mM in NaCl to 2.5-3.5 mM in NaClO4 solution. The rate of equilibration of the reaction, E1P(Na+)3 left arrow over right arrow E2P + 3Na+, decreased from 393 (+/- 51) s-1 in NaCl solution to 114 (+/- 15) s-1 in NaClO4. This decrease is attributed predominantly to an inhibition of the E1P(Na+)3 --> E2P(Na+)3 transition. The effects can be explained in terms of electrostatic interactions due to perchlorate binding within the membrane and/or protein matrix of the Na+,K+-ATPase membrane fragments and alteration of the local electric field strength experienced by the protein. The kinetic results obtained support the conclusion that the conformational transition E1P(Na+)3 --> E2P(Na+)3 is a major charge translocating step of the pump cycle.

Ganea, C; Babes, A; Lupfert, C; Grell, E; Fendler, K; Clarke, R J

1999-01-01

391

Its Dependence on ExtraceUular and Intracellular pH and on External Na + Concentration  

Microsoft Academic Search

Intracellular microelectrode techniques and extracellular pH mea- surements were used to study the dependence of apical Na+\\/H § exchange on mucosal and intracellular pH and on mucosal solution Na § concentration ((Na+)o). When mucosal solution pH (pHo) was decreased in gallbladders bathed in Na § containing solutions, aNai fell. The effect of pHo is consistent with titration of a single

GUILLERMO A. ALTENBERG

392

Excitatory sympathetic reflex in NaCl-sensitive spontaneously hypertensive rats.  

PubMed

We have previously demonstrated blunted reflex responses of lumbar sympathetic nerve activity during volume expansion in NaCl-sensitive spontaneously hypertensive rats maintained on basal (1% NaCl) diets compared with NaCl-resistant spontaneously hypertensive rats, Wistar-Kyoto rats, and Sprague-Dawley rats. The current study tested the hypothesis that chronic ingestion of a high (8%) NaCl diet further blunts cardiopulmonary reflex function in the NaCl-sensitive spontaneously hypertensive rat. After 3 weeks of a 1% or 8% NaCl diet, male rats of all four strains were instrumented with femoral arterial and venous cannulas and lumbar nerve recording electrodes at 10 weeks of age. Two days later, conscious rats were infused with whole blood to expand blood volume. NaCl-sensitive spontaneously hypertensive rats maintained on a 1% NaCl diet had blunted responses of nerve activity to acute volume expansion compared with control strains. NaCl-sensitive spontaneously hypertensive rats maintained on an 8% NaCl diet had increases in nerve activity responses to volume expansion. In a second experiment, the volume expansion protocol was repeated in anesthetized NaCl-sensitive spontaneously hypertensive rats that had been subjected to sinoaortic denervation after 3 weeks of a 1% or 8% NaCl diet. After sinoaortic denervation, an increase in nerve activity was again observed during volume expansion in animals fed the 8% NaCl diet. In animals fed the 1% NaCl diet, changes in nerve activity were variable. The excitatory response was significantly reduced after bilateral vagotomy. These studies suggest that blood pressure regulation in NaCl-sensitive spontaneously hypertensive rats is a complex interaction of excitatory and inhibitory sympathetic reflex systems that is altered by high dietary NaCl exposure. PMID:8349320

Nakamura, Y; Calhoun, D A; Chen, Y F; Wyss, J M; Oparil, S

1993-09-01

393

Kinetic properties of Na + \\/H + exchange in cultured bovine pigmented ciliary epithelial cells  

Microsoft Academic Search

Uptake studies with22Na were performed in cultured bovine pigmented ciliary epithelial cells, in order to characterize mechanisms of Na+ transport. A large part of Na+ uptake was sensitive to amiloride, quinidine and harmaline. Na+ uptake was stimulated by intracellular acidification (using the NH4+ prepulse technique), and was inhibited with increasing extracellular proton concentration. Decreasing extracellular pH from 7.5 to 7.0

Horst Helbig; Christoph Korbmacher; Susanne Berweck; Dagmar Kiihner; Michael Wiederholt

1988-01-01

394

Membrane Na+-pyrophosphatases can transport protons at low sodium concentrations.  

PubMed

Membrane-bound Na(+)-pyrophosphatase (Na(+)-PPase), working in parallel with the corresponding ATP-energized pumps, catalyzes active Na(+) transport in bacteria and archaea. Each ~75-kDa subunit of homodimeric Na(+)-PPase forms an unusual funnel-like structure with a catalytic site in the cytoplasmic part and a hydrophilic gated channel in the membrane. Here, we show that at subphysiological Na(+) concentrations (<5 mM), the Na(+)-PPases of Chlorobium limicola, four other bacteria, and one archaeon additionally exhibit an H(+)-pumping activity in inverted membrane vesicles prepared from recombinant Escherichia coli strains. H(+) accumulation in vesicles was measured with fluorescent pH indicators. At pH 6.2-8.2, H(+) transport activity was high at 0.1 mM Na(+) but decreased progressively with increasing Na(+) concentrations until virtually disappearing at 5 mM Na(+). In contrast, (22)Na(+) transport activity changed little over a Na(+) concentration range of 0.05-10 mM. Conservative substitutions of gate Glu(242) and nearby Ser(243) and Asn(677) residues reduced the catalytic and transport functions of the enzyme but did not affect the Na(+) dependence of H(+) transport, whereas a Lys(681) substitution abolished H(+) (but not Na(+)) transport. All four substitutions markedly decreased PPase affinity for the activating Na(+) ion. These results are interpreted in terms of a model that assumes the presence of two Na(+)-binding sites in the channel: one associated with the gate and controlling all enzyme activities and the other located at a distance and controlling only H(+) transport activity. The inherent H(+) transport activity of Na(+)-PPase provides a rationale for its easy evolution toward specific H(+) transport. PMID:24158447

Luoto, Heidi H; Nordbo, Erika; Baykov, Alexander A; Lahti, Reijo; Malinen, Anssi M

2013-12-01

395

Mass spectrometric determination of partial pressures of ions in the saturated vapor over the NaF-Na3AlF6 system  

NASA Astrophysics Data System (ADS)

Mass spectrometric determination of absolute partial pressures of basic charged species Na2F+ and AlF4- in the saturated vapor over the NaF-Na3AlF6 system (1:1 molar ratio) was carried out in the 974-1090 K temperature range. The ion pressures were 5-8 orders of magnitude lower than the pressures of basic molecular components NaAlF4 and NaF. Particular attention was given to the equality of device sensitivity constants for positive and negative ions. Absolute device calibration was carried out using the measured ion currents Na2F+ and AlF4- and the equilibrium constant of heterolytic dissociation available in the literature.

Abramov, S. V.; Chilingarov, N. S.; Borshchevsky, A. Ya; Sidorov, L. N.

2004-01-01

396

Recent Work with Laser Trapped Radioactive ^21Na Atoms  

NASA Astrophysics Data System (ADS)

^21Na(t_1/2=22 seconds) is produced on-line at the 88" Cyclotron at LBNL and is transferred to a magneto-optical trap where it is stored. Recent improvements to our apparatus, mainly in our oven and target, have resulted in 40,000 trapped ^21Na atoms. This number of atoms provides enough activity for ?-decay studies, our goal being precision measurements of fundamental weak interaction parameters (for example from the electron-neutrino correlations and the parity violating ?-asymmetry of spin-polarized nuclei). We have detected ?'s from our trapped sample and are currently investigating transferring our atoms to a second laser trap to provide a cleaner environment for ?-decay studies. We have also made a precise measurement of the atomic ground state hyperfine splitting of ^21Na using our trapped atoms. We induce transitions between the 3S_1/2(F=1) and the 3S_1/2(F=2) states with microwaves and probe the atoms with a laser pulse. The atomic fluorescence measures how many atoms make the transition as a function of microwave frequency. Our resolution improves the precision on the ground state hyperfine splitting by a factor of 100. This work is supported by DOE contract DE-AC03-76SF00098.

Rowe, Mary; Freedman, Stuart; Fujikawa, Brian; Gwinner, Gerald; Shang, Song-Quan; Vetter, Paul

1997-10-01

397

Bioactive tantalum metal prepared by NaOH treatment.  

PubMed

Untreated tantalum metal formed an apatite on its surface in simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma. However, it took an induction period as long as 4 weeks for apatite formation. The tantalum metal formed the apatite within 1 week when it was previously soaked in a 0.2 or 0.5M NaOH aqueous solution at 60 degrees C for 24 h to form a sodium tantalate hydrogel layer on its surface. The decrease in the induction period of apatite formation was attributed to the catalytic effect of the Ta-OH groups on the surface of the tantalum metal for apatite nucleation and acceleration of the apatite nucleation by an increased ionic activity product of the apatite in the fluid due to the release of Na(+) ions. The NaOH-treated tantalum metal can form apatite in a short period even in the living body and bond to the bone through this apatite layer. This indicates that a highly bioactive tantalum metal can be obtained by a simple chemical treatment. PMID:10644961

Miyazaki, T; Kim, H M; Miyaji, F; Kokubo, T; Kato, H; Nakamura, T

2000-04-01

398

Fases de la luna (Alternate title: Lunar phases)  

NSDL National Science Digital Library

What causes the phases of the moon? This informational piece, part of an interactive laboratory series for grades 8-12, introduces students to three interactive lab activities about moon phases. In the first activity, students virtually view the moon from a fixed location in space to determine which half of the moon is lighted by the sun as it moves through its phases. In the second activity, students choose the shading of the moon as it would appear from the Earth. Nine questions with printable results are provided. The third activity simulates the moon revolving around the Earth. As the moon revolves, a window shows the view of the moon from Earth. Students control the speed of the simulation and can jump to any phase of the moon. Copyright 2005 Eisenhower National Clearinghouse

University of Utah. Astrophysics Science Project Integrating Research and Education (ASPIRE)

2003-01-01

399

ROS-mediated vascular homeostatic control of root-to-shoot soil Na delivery in Arabidopsis.  

PubMed

Sodium (Na) is ubiquitous in soils, and is transported to plant shoots via transpiration through xylem elements in the vascular tissue. However, excess Na is damaging. Accordingly, control of xylem-sap Na concentration is important for maintenance of shoot Na homeostasis, especially under Na stress conditions. Here we report that shoot Na homeostasis of Arabidopsis thaliana plants grown in saline soils is conferred by reactive oxygen species (ROS) regulation of xylem-sap Na concentrations. We show that lack of A. thaliana respiratory burst oxidase protein F (AtrbohF; an NADPH oxidase catalysing ROS production) causes hypersensitivity of shoots to soil salinity. Lack of AtrbohF-dependent salinity-induced vascular ROS accumulation leads to increased Na concentrations in root vasculature cells and in xylem sap, thus causing delivery of damaging amounts of Na to the shoot. We also show that the excess shoot Na delivery caused by lack of AtrbohF is dependent upon transpiration. We conclude that AtrbohF increases ROS levels in wild-type root vasculature in response to raised soil salinity, thereby limiting Na concentrations in xylem sap, and in turn protecting shoot cells from transpiration-dependent delivery of excess Na. PMID:23064146

Jiang, Caifu; Belfield, Eric J; Mithani, Aziz; Visscher, Anne; Ragoussis, Jiannis; Mott, Richard; Smith, J Andrew C; Harberd, Nicholas P

2012-11-14

400

Single Ion Occupancy and Steady-state Gating of Na Channels in Squid Giant Axon  

Microsoft Academic Search

The properties of the small fraction of tetrodotoxin (TTX)-sensitive Na channels that remain open in the steady state were studied in internally dialyzed voltage clamped squid giant axons. The observed Ussing flux ratio exponent ( n ? ) of 0.97 ? 0.03 (calculated from simultaneous measurements of TTX-sensitive current and 22 Na ef- flux) and nonindependent behavior of Na current

Robert F. Rakowski; David C. Gadsby; Paul De Weer

2002-01-01

401

ROS-mediated vascular homeostatic control of root-to-shoot soil Na delivery in Arabidopsis  

PubMed Central

Sodium (Na) is ubiquitous in soils, and is transported to plant shoots via transpiration through xylem elements in the vascular tissue. However, excess Na is damaging. Accordingly, control of xylem-sap Na concentration is important for maintenance of shoot Na homeostasis, especially under Na stress conditions. Here we report that shoot Na homeostasis of Arabidopsis thaliana plants grown in saline soils is conferred by reactive oxygen species (ROS) regulation of xylem-sap Na concentrations. We show that lack of A. thaliana respiratory burst oxidase protein F (AtrbohF; an NADPH oxidase catalysing ROS production) causes hypersensitivity of shoots to soil salinity. Lack of AtrbohF-dependent salinity-induced vascular ROS accumulation leads to increased Na concentrations in root vasculature cells and in xylem sap, thus causing delivery of damaging amounts of Na to the shoot. We also show that the excess shoot Na delivery caused by lack of AtrbohF is dependent upon transpiration. We conclude that AtrbohF increases ROS levels in wild-type root vasculature in response to raised soil salinity, thereby limiting Na concentrations in xylem sap, and in turn protecting shoot cells from transpiration-dependent delivery of excess Na.

Jiang, Caifu; Belfield, Eric J; Mithani, Aziz; Visscher, Anne; Ragoussis, Jiannis; Mott, Richard; Smith, J Andrew C; Harberd, Nicholas P

2012-01-01

402

Electrogenicity of the Na +ATPase from the marine microalga Tetraselmis (Platymonas) viridis and associated H + countertransport  

Microsoft Academic Search

Sodium accumulation by the Na+-ATPase in the plasma membrane (PM) vesicles isolated from the marine alga Tetraselmis (Platymonas) viridis was shown to be accompanied by ?? generation across the vesicle membrane (positive inside) and H+ efflux from the vesicle lumen. Na+ accumulation was assayed with 22Na+; ?? generation was detected by recording absorption changes of oxonol VI; H+ efflux was

Yurii V. Balnokin; Larissa G. Popova; Igor M. Andreev

1999-01-01

403

Na(+)-functionalized carbon quantum dots: a new draw solute in forward osmosis for seawater desalination.  

PubMed

A new type of biocompatible draw solute, Na(+)-functionalized carbon quantum dots (Na_CQDs) with ultra-small size and rich ionic species, in forward osmosis (FO) is developed for seawater desalination. The aqueous dispersion of Na_CQDs demonstrates a high osmotic pressure, which allows high FO water flux and negligible reverse solute permeation. PMID:24870226

Guo, Chun Xian; Zhao, Dieling; Zhao, Qipeng; Wang, Peng; Lu, Xianmao

2014-06-12

404

Extracellular Na+ and initiation of DNA synthesis: role of intracellular pH and K+  

PubMed Central

Initiation of DNA synthesis in confluent quiescent 3T3 cell cultures stimulated by epidermal growth factor (EGF), vasopressin, and insulin was abolished by removing extracellular Na+. The inhibition was reversible, time- and Na+-concentration-dependent, and not due to an effect on binding or internalization of 125I-EGF. Stimulation by combinations of other growth factors with different mechanisms of action was also affected by decreasing extracellular Na+, but with different half-maximal Na+ concentrations. When choline was used as an osmotic substitute for Na+, the decrease in DNA synthesis was correlated with the decrease in intracellular K+. In contrast, when sucrose was used there was stimulation of the Na+-K+ pump and maintenance of intracellular K+ that resulted in a somewhat higher rate of DNA synthesis at lowered extracellular Na+ compared to choline. Mitogenesis induced by epidermal growth factor, vasopressin, and insulin led to cytoplasmic alkalinization as determined by an increase in uptake of the weak acid 5,5-dimethyloxazolidine-2,4-dione. Experimental decrease in extracellular Na+ blocked this cellular alkalinization. Therefore, under some conditions the supply of extracellular Na+ may limit cellular proliferation because of a reduction in the provision of Na+ to the Na+/H+ antiport and resultant failure of alkalinization. We conclude that Na+ flux and its effect on intracellular K and pH has a major role in the complex system that regulates proliferation.

1984-01-01

405

Plasma membrane electron transport coupled to Na(+) extrusion in the halotolerant alga Dunaliella.  

PubMed

The halotolerant alga Dunaliella adapts to exceptionally high salinity and maintains low [Na(+)](in) at hypersaline solutions, suggesting that it possesses efficient mechanisms for regulating intracellular Na(+). In this work we examined the possibility that Na(+) export in Dunaliella is linked to a plasma membrane electron transport (redox) system. Na(+) extrusion was induced in Dunaliella cells by elevation of intracellular Na(+) with Na(+)-specific ionophores. Elevation of intracellular Na(+) was found to enhance the reduction of an extracellular electron acceptor ferricyanide (FeCN). The quinone analogs NQNO and dicumarol inhibited FeCN reduction and led to accumulation of Na(+) by inhibition of Na(+) extrusion. These inhibitors also diminished the plasma membrane potential in Dunaliella. Anaerobic conditions elevated, whereas FeCN partially decreased intracellular Na(+) content. Cellular NAD(P)H level decreased upon enhancement of plasma membrane electron transport. These results are consistent with the operation of an electrogenic NAD(P)H-driven redox system coupled to Na(+) extrusion in Dunaliella plasma membrane. We propose that redox-driven Na(+) extrusion and recycling in Dunaliella evolved as means of adaptation to hypersaline environments. PMID:11245805

Katz, A; Pick, U

2001-04-01

406

Relationship between PPAR? activation and NO on proximal tubular Na+ transport in the rat  

Microsoft Academic Search

BACKGROUND: Nitric oxide (NO) regulates renal proximal tubular (PT) Na+ handling through modulation of Na+-K+ ATPase. Peroxisome Proliferator Activated Receptor? (PPAR?), a nuclear transcription factor, is expressed in PTs and has been reported to influence NO generation\\/activity in renal tissues. This study tested the hypothesis that PPAR? interacts with NO and thereby affects renal tubular Na+ transport. Urinary excretion of

Mohammad A Newaz; Kasturi Ranganna; Adebayo O Oyekan

2004-01-01

407

Abertura Financeira e Vulnerabilidade Externa na América Latina: os impactos sobre Brasil, México e Argentina  

Microsoft Academic Search

Resumo: Este trabalho, na primeira seção, define o que costuma ser entendido como um processo de abertura financeira, identifica os níveis que compõem este processo, e lista as principais justificativas teóricas costumeiramente apresentadas para a implementação deste tipo de política. Na segunda seção, discute-se teoricamente o impacto dos processos de liberalização financeira na autonomia de política econômica e no grau

Juan Pablo Painceira; Marcelo Dias Carcanholo

408

Determination of the driving force of the Na + pump in toad bladder by means of vasopressin  

Microsoft Academic Search

Summary Vasopressin stimulates Na+ transport across toad bladder largely or entirely by decreasing the resistance to Na+ entry into the transporting epithelial cells. Therefore, the hormone should induce proportional changes in short circuit current (IS) and tissue conductance; the ratio of these changes should equal the driving force (ENa) of the Na+ pump.

Jacob Yonath; Mortimer M. Civan

1971-01-01

409

On the concentration dependence of the nature of polyelectrolyte solutions as detected by 23Na relaxation  

NASA Astrophysics Data System (ADS)

Dependence of 23Na nuclear magnetic relaxation on concentration and degree of polymerization is reported for solutions of Na polystyrenesulfonate. In the concentration range 10 -1 ? c 10 -1 eq/e, 23Na relaxation is far outside the extreme-narrowing limit and relaxation rates depend on the degree of polymerization. These phenomena seem to disappear outside this range.

Levij, M.; De Bleijser, J.; Leyte, J. C.

1982-03-01

410

Regulation by endothelin-1 of Na +Ca 2+ exchange current (I NaCa) from guinea-pig isolated ventricular myocytes  

Microsoft Academic Search

Summary The cardiac Na+-Ca2+ exchanger participates in Ca homeostasis, and Na+-Ca2+ exchanger-mediated ionic current (INaCa) also contributes to the regulation of cardiac action potential duration. Moreover, INaCa can contribute to arrhythmogenesis under conditions of cellular Ca overload. Although it has been shown that the peptide hormone endothelin-1 (ET-1) can phosphorylate the cardiac Na+-Ca2+ exchanger via protein kinase C (PKC), little

Y. H. Zhang; A. F. James; J. C. Hancox

2001-01-01

411

Interaction of the antiepileptic drug lamotrigine with recombinant rat brain type IIA Na + channels and with native Na + channels in rat hippocampal neurones  

Microsoft Academic Search

Actions of the new antiepileptic drug lamotrigine (LTG, Lamictal) were characterised using recombinant rat brain type IIA Na+ channels expressed in Chinese hamster ovary (CHO) cells and native Na+ channels in rat hippocampal pyramidal neurones, using whole-cell recording and intracellular recording techniques. In CHO cells, LTG caused a tonic inhibition of Na+ currents in a concentration-dependent and voltage-dependent manner. The

Xinmin Xie; Barrie Lancaster; Tim Peakman; John Garthwaite

1995-01-01

412

The ?1 Na + ?K + pump of the Dahl salt-sensitive rat exhibits altered Na + modulation of K + transport in red blood cells  

Microsoft Academic Search

The properties of the 1 Na+-K+ pump were compared in Dahl salt-sensitive (DS) and salt-resistant (DR) strains by measuring ouabain-sensitive luxes (mmol\\/liter cell x hr = FU, Mean ± se) in red blood cells (RBCs) and varying internal (\\u000ai\\u000a) and external (\\u000ao\\u000a) Na+ and K+ concentrations. Kinetic parameters of several modes of operation, i.e., Na+\\/ K+,

Mitzy Canessa; José R. Romero; Nelson Ruiz-Opazo; Victoria L. M. Herrera

1993-01-01

413

Occlusion of /sup 22/Na+ and /sup 86/Rb+ in membrane-bound and soluble protomeric alpha beta-units of Na,K-ATPase  

SciTech Connect

In this work, we examined occlusion of /sup 22/Na+ and /sup 86/Rb+ in membranous and detergent-solubilized Na,K-ATPase from outer renal medulla. Optimum conditions for occlusion of /sup 22/Na+ were provided by formation of the phosphorylated complex from the beta,gamma-bidentate complex of chromium (III) with ATP (CrATP). Release of occluded cations occurred at equally slow rates in soluble and membrane-bound Na,K-ATPase. Values of /sup 22/Na+ occlusion as high as 11 nmol/mg of protein were measured, corresponding to 1.8-2.7 mol of Na+/mol of phosphorylated Na,K-ATPase as determined by /sup 32/P incorporation from (gamma-/sup 32/P)CrATP. Maximum capacity for phosphorylation from (gamma-/sup 32/P)CrATP was 6 nmol/mg of protein and equal to capacities for binding of (48V)vanadate and (/sup 3/H)ouabain. The stoichiometry for occlusion of Rb+ was close to 2 Rb+ ions/phosphorylation site. In an analytical ultracentrifuge, the soluble Na+- or Rb+-occluded complexes showed sedimentation velocities (S20,w = 6.8-7.4) consistent with monomeric alpha beta-units. The data show that soluble monomeric alpha beta-units of Na,K-ATPase can occlude Rb+ or Na+ with the same stoichiometry as the membrane-bound enzyme. The structural basis for occlusion of cations in Na,K-ATPase is suggested to be the formation of a cavity inside a monomeric alpha beta-unit constituting the minimum protein unit required for active Na,K-transport.

Vilsen, B.; Andersen, J.P.; Petersen, J.; Jorgensen, P.L.

1987-08-05

414

Un nouveau tetraedre azote NaN 4: Preparation et structure de NaGe 2N 3  

NASA Astrophysics Data System (ADS)

The NaGe 2N 3 nitride is prepared from the NaGeON oxynitride. It presents a normal tetrahedral structure related to the wurtzite type. The unit cell is orthorhombic with a = 9.8662(15), b = 5.7830(9), and c = 5.1221(5) Å, space group Cmc2 1 (No. 36). The structure refinement has been made using multicomponent profile analysis of time-of-flight neutron diffraction data. The germanium and sodium atoms are ordered among one-half of the tetrahedral sites built up by the slightly distorted hexagonal close-packing of the nitrogen atoms. It is the first example of a stable entirely nitrided environment for the sodium atom.

Guyader, J.; L'Haridon, P.; Laurent, Y.; Jacquet, R.; Roult, G.

1984-09-01

415

Investigation of influence of NaOH and NaCl activating solutions on bentonite stabilization in suspension fertilizers  

NASA Astrophysics Data System (ADS)

1. INTRODUCTION Regular plants growth and their metabolic activity are determined by the macro- (C, H, O, N, P, S, K, Ca, Mg) and micronutrients (Fe, Mn, Zn, Cu, B, Mo, Cl, Ni). The role of these elements is very important, the excess as well as the deficiency have the negative influence on their development [1]. In order to increase yields and quality of crops a mineral, organic and mineral-organic fertilizers are applied. In the last years suspension fertilizers have been of great significance, taking the agricultural benefits into consideration. Suspension fertilizers are products of a new generation on account of higher nutrients concentrations than in the majority of other fertilizers, what makes them more efficient. Suspension fertilizers differ from solid fertilizers in more regular distribution on field. Nutrients are more concentrated what is economically relevant on account of the facilitated transportation. Examinations indicated, that nutrients from suspension fertilizers are more available than from solid fertilizers. The high concentration of nutrients in fertilizer is obtained by introducing a substance which holds them regularly in the suspension. Bentonites are the substances used for stabilization of suspension fertilizers most often [2,3]. Bentonites belong to ore of clay minerals, primarily made from minerals of smectite group, montmorillonite especially [4]. Bentonite loams were formulated as a result of Aluminium Silicate-bearing Rocks weathering and subsequent sedimentation in the aqueous environment. Characteristic features of rocks of the smectite group are their ability to absorb water (swelling), to form thixotrophic suspensions which aren't undergoing sedimentation process for a long time; as well as susceptibility to absorb cations and organic substances [4,5]. Therefore investigations have been carried out in order to evaluate the possibility of application of diverse loamy raw materials as suspension stabilizers for fertilizer purposes. In this paper research aimed at activating Jaroszów bentonite were presented. 2. MATERIALS AND METHODS The studies on activating clay minerals were carried out using the exchange of Ca2+, K+, Mg2+ ions to Na+ ions. For activation process the NaOH and NaCl solutions of concentrations 0,1M and 2,0M respectively were applied. For the purposes mentioned above 5g of weighed portion of mineral were introduced into four 250 ml conical flasks, two of them were filled with 100 ml of 0,1M and 2.0 M NaOH solution. Two remaining flasks were filled with 100 ml of 0,1M and 2.0 M NaCl solution. The samples preparred acoording to this instructions were shaken for 1 and 8 hours, and subsequently subjected to a vacuum filtration in order to separete solid fraction from filtrate. Mineral which remaied on the filter was dried in temperature of 110oC for 2 hours. 1g of dried mineral was collected for further examinations, mixed with 100 ml of distilled water and poured into the 25 ml measuring cylinder. Then every day for 14 days a change of the volume of deposit, suspension and pure solution above the suspension have been measured. 3. RESULTS DISCUSSION "Jaroszów" bentonite, activated with Na+ ions using 0,1M NaOH solution constitutes the most beneficial agent stabilizing the solid phase in the aqueous environment. The time factor didn't have considerable influence on bentonite activation. Results were similar for 1h as well as 8h. The addition of NaOH sustained suspension on respectively high level, about 80% vol., after 14 measurement days.

Hoffmann, Krystyna; Hoffmann, Józef; Mik?a, Daniel; Huculak-Mä Czka, Marta; Skut, Jakub

2010-05-01

416

In vitro characterization of naturally occurring influenza H3NA- viruses lacking the NA gene segment: toward a new mechanism of viral resistance?  

PubMed

Among a panel of 788 clinical influenza H3N2 isolates, two isolates were characterized by an oseltamivir-resistant phenotype linked to the absence of any detectable NA activity. Here, we established that the two H3NA- isolates lack any detectable full-length NA segment, and one of these could be rescued by reverse genetics in the absence of any NA segment sequence. We found that the absence of NA segment induced a moderate growth defect of the H3NA- viruses as on cultured cells. The glycoproteins density at the surface of H3NA- virions was unchanged as compared to H3N2 virions. The HA protein as well as residues 188 and 617 of the PB1 protein were shown to be strong determinants of the ability of H3NA- viruses to grow in the absence of the NA segment. The significance of these findings about naturally occurring seven-segment influenza A viruses is discussed. PMID:20627352

Moules, V; Ferraris, O; Terrier, O; Giudice, E; Yver, M; Rolland, J P; Bouscambert-Duchamp, M; Bergeron, C; Ottmann, M; Fournier, E; Traversier, A; Boule, C; Rivoire, A; Lin, Y; Hay, A; Valette, M; Marquet, R; Rosa-Calatrava, M; Naffakh, N; Schoehn, G; Thomas, D; Lina, B

2010-09-01

417

Alkali-metal adsorption on dissimilar alkali-metal monolayers preadsorbed on Cu(001): Li on Na and Na on Li  

NASA Astrophysics Data System (ADS)

An adsorption system of metal-on-metal growth is presented. The adsorption of alkali-metal atoms on monolayers of dissimilar alkali metals preadsorbed on the Cu(001) surface has been studied by Auger-electron spectroscopy, work-function change, and low-energy electron-diffraction intensity analysis. We have examined the following three adsorption systems on Cu(001) at 180 K; Na on a full monolayer of Li, Li on a full monolayer of Na, and Na on a submonolayer of Li, namely, the c(2×2) structure of Li adatoms. It is found that a simple overlayer formation of Na takes place on the full Li monolayer, while Li atoms substitute Na adatoms for Li adsorption on the full Na monolayer. For adsorption of Na on the Li-c(2×2) structure whose coverage is 5/8 of the full Li monolayer, it is found that Na atoms compress the Li adlayer to become denser monolayers. The Na atoms do not intermix with Li adatoms, but they form islands of the c(2×2) structure on Cu(001).

Mizuno, Seigi; Tochihara, Hiroshi; Kawamura, Takaaki

1994-12-01

418

Diffusion and the dynamics of displacive phase transitions in cryolite (Na 3 AlF 6 ) and chiolite (Na 5 Al 3 F 14 ): Multinuclear NMR studies  

Microsoft Academic Search

Cryolite is a mixed-cation perovskite (Na2(NaAl)F6) which undergoes a monoclinic to orthorhombic displacive phase transition at ~550° C. Chiolite (Na5Al3F14) is associated with cryolite in natural deposits, and consists of sheets of corner sharing [AlF6] octahedra interlayered with edge-sharing [NaF6] octahedra. Multi-nuclear NMR line shape and relaxation time (T1) studies were performed on cryolite and chiolite in order to gain

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

1994-01-01

419

Functional and structural characterization of the zebrafish Na+-sulfate cotransporter 1 (NaS1) cDNA and gene (slc13a1).  

PubMed

Sulfate plays an essential role during growth, development and cellular metabolism. In this study, we characterized the function and structure of the zebrafish (Danio rerio) Na+-sulfate cotransporter 1 (NaS1) cDNA and gene (slc13a1). Zebrafish NaS1 encodes a protein of 583 amino acids with 13 putative transmembrane domains. Expression of zebrafish NaS1 protein in Xenopus oocytes led to Na+-sulfate cotransport, which was significantly inhibited by thiosulfate, selenate, molybdate, and tungstate. Zebrafish NaS1 transport kinetics were: V(max) = 1,731.670 +/- 92.853 pmol sulfate/oocyte.hour and K(m) = 1.414 +/- 0.275 mM for sulfate and V(max) = 307.016 +/- 32.992 pmol sulfate/oocyte x hour, K(m) = 24.582 +/- 4.547 mM and n (Hill coefficient) = 1.624 +/- 0.354 for sodium. Zebrafish NaS1 mRNA is developmentally expressed in embryos from day 1 postfertilization and in the intestine, kidney, brain, and eye of adult zebrafish. The zebrafish NaS1 gene slc13a1 contains 15 exons spanning 8,716 bp. Characterization of the zebrafish NaS1 contributes to a greater understanding of sulfate transporters in a well-defined genetic model and will allow the elucidation of evolutionary and functional relationships among vertebrate sulfate transporters. PMID:18544660

Markovich, Daniel; Romano, Alessandro; Storelli, Carlo; Verri, Tiziano

2008-08-15

420

Seasonal variations of midlatitude mesospheric Na layer and their tidal period perturbations based on full diurnal cycle Na lidar observations of 2002-2008  

NASA Astrophysics Data System (ADS)

The Na lidar facility at Colorado State University (41°N, 105°W) started the full diurnal cycle observations of mesopause region temperature and zonal and meridional winds as well as mesospheric Na density in May 2002. In this paper, monthly means and seasonal variations of the density of mesospheric Na based on lidar observations from May 2002 to December 2008 are reported along with the amplitude and phase of tidal period perturbations. The revealed seasonal behaviors of mesospheric Na layer are generally consistent with published nocturnal climatology, with thick layers and high abundance in winter but thin layers and low abundance near summer. Tidal amplitudes of Na density are large in February-April and August-November with a dominant peak between 85 and 90 km; they are weak in summer months (May-July). The Na density tidal phase profiles, while showing downward progression, show a significant and abrupt phase shift (ideally 180 degrees). The center altitude of this phase shifting (termed switching altitude) is found to coincide with the fractional tidal amplitude (tidal amplitude over diurnal mean) minimum about 2-4 km above the centroid altitude of the associated Na layer. Taking advantage of the established temperature tidal climatology deduced from the same data set, the tidal phase behaviors between temperature and Na density and associated fractional Na density tidal amplitudes are discussed in terms of the theoretical prediction by Gardner and Shelton (1985).

Yuan, Tao; She, C.-Y.; Kawahara, Takuya D.; Krueger, D. A.

2012-06-01

421

Effects of Na 2WO 4 and Na 2SiO 3 additives in electrolytes on microstructure and properties of PEO coatings on Q235 carbon steel  

Microsoft Academic Search

Ceramic coatings were achieved on Q235 carbon steel by plasma electrolytic oxidation in aluminate system with and without Na2WO4 and Na2SiO3 additives in electrolyte. Influence of Na2WO4 and Na2SiO3 on surface morphology, phase and elemental composition of PEO coatings were examined by means of scanning electron microscope (SEM), thin-film X-ray diffraction (TF-XRD) and energy dispersive X-ray spectroscopy (EDS). Effects of

Yunlong Wang; Zhaohua Jiang; Zhongping Yao

2009-01-01

422

Nonuniformity of NaOH concentration and effective bubble diameter in CO 2 injection into aqueous NaOH solution  

Microsoft Academic Search

Mixed CO2-N2 gas was blown into an aqueous NaOH solution through a submerged nozzle of 3 mm ID, and the net absorption rate of CO2 from the gas bubbles during their ascent was determined. The size distribution and the rising velocity of bubbles were also\\u000a measured. The enhancement factor was estimated from the reported reaction rate constant as 1.16 to

Y. Fukunaka; M. F. Jiang; T. Yamamoto; Z. Asaki; Y. Kondo

1989-01-01

423

Investigation of the Structure and Summary Crystallization of Graham Glass with the Help of Infrared Spectroscopy (Izsledvane Strukturata I Protsesa NA Sumarna Kristalizatsiya NA Gremovo Stklo S Pomoshchta NA Infrachervena Spektroskopiya).  

National Technical Information Service (NTIS)

The ir spectra are shown of a large no. of samples of Graham glass, partially crystd. I, cryst. Na3P3O9, and mech. mixts. of I and cryst. Na3P3O9. The intensity of the absorption band at 475/cm. decreased and that at 514/cm. increased with increasing degr...

I. V. Gutsov M. Arnaudov B. Yordanov

1967-01-01

424

Spectrophotometric Investigation of U(VI) Chloride Complexation in the NaCl/NaClO{sub 4} System  

SciTech Connect

Post closure radioactive release scenarios from geologic salt formation, such as the WIPP (Waste Isolation Pilot Plant)(USA) include hydrologic transport of radionuclides through a chloride saturated aquifer. Consequently, the understanding of actinide solution chemistry in brines is essential for modeling requiring accurate knowledge of the interaction between AnO{sub 2}{sup 2+} and chloride ions. Complexation constants of two U(VI) chloride species, UO{sub 2}Cl{sup +} and UO{sub 2}Cl{sub 2}{sup 0}, have been intensively studied for about 40 years using different methods. However, large uncertainties reflect the general difficulty in determining accurate stability constants of weak complexes. In order to model the behavior of U(VI) in brines, we studied the formation of its chloride complexes by UV-Vis spectroscopy as a function of the NaCl concentration at 25 C. The experiments were performed at constant ionic strength by varying the concentration ratio of NaCl and NaClO{sub 4}. Deconvolution resulted in single component absorption spectra for UO{sub 2}Cl{sup +} and UO{sub 2}Cl{sub 2}{sup 0}. The apparent stability constants of UO{sub 2}Cl{sup +} and UO{sub 2}Cl{sub 2}{sup 0} are at different ionic strengths and the experimental data are used to parameterize using the SIT approach.

Paviet-Hartmann, P.; Lin, M.R.; Runde, W.H.

1998-11-30

425

23Na magnetic resonance imaging-determined tissue sodium in healthy subjects and hypertensive patients.  

PubMed

High dietary salt intake is associated with hypertension; the prevalence of salt-sensitive hypertension increases with age. We hypothesized that tissue Na(+) might accumulate in hypertensive patients and that aging might be accompanied by Na(+) deposition in tissue. We implemented (23)Na magnetic resonance imaging to measure Na(+) content of soft tissues in vivo earlier, but had not studied essential hypertension. We report on a cohort of 56 healthy control men and women, and 57 men and women with essential hypertension. The ages ranged from 22 to 90 years. (23)Na magnetic resonance imaging measurements were made at the level of the calf. We observed age-dependent increases in Na(+) content in muscle in men, whereas muscle Na(+) content did not change with age in women. We estimated water content with conventional MRI and found no age-related increases in muscle water in men, despite remarkable Na(+) accumulation, indicating water-free Na(+) storage in muscle. With increasing age, there was Na(+) deposition in the skin in both women and men; however, skin Na(+) content remained lower in women. Similarly, this sex difference was found in skin water content, which was lower in women than in men. In contrast to muscle, increasing Na(+) content was paralleled with increasing skin water content. When controlled for age, we found that patients with refractory hypertension had increased tissue Na(+) content, compared with normotensive controls. These observations suggest that (23)Na magnetic resonance imaging could have utility in assessing the role of tissue Na(+) storage for cardiovascular morbidity and mortality in longitudinal studies. PMID:23339169

Kopp, Christoph; Linz, Peter; Dahlmann, Anke; Hammon, Matthias; Jantsch, Jonathan; Müller, Dominik N; Schmieder, Roland E; Cavallaro, Alexander; Eckardt, Kai-Uwe; Uder, Michael; Luft, Friedrich C; Titze, Jens

2013-03-01

426

Excitatory amino acid-stimulated uptake of /sup 22/Na+ in primary astrocyte cultures  

SciTech Connect

In this study we have found that L-glutamic acid, as well as being taken up by a Na+-dependent mechanism, will stimulate the uptake of 22Na+ by primary astrocyte cultures from rat brain in the presence of ouabain. By simultaneously measuring the uptake of 22Na+ and L-3H-glutamate a stoichiometry of 2-3 Na+ per glutamate was measured, implying electrogenic uptake. Increasing the medium K+ concentration to depolarize the cells inhibited L-3H-glutamate uptake, while calculations of the energetics of the observed L-3H-glutamate accumulation also supported an electrogenic mechanism of at least 2 Na+:1 glutamate. In contrast, kinetic analysis of the Na+ dependence of L-3H-glutamate uptake indicated a stoichiometry of Na+ to glutamate of 1:1, but further analysis showed that the stoichiometry cannot be resolved by purely kinetic studies. Studies with glutamate analogs, however, showed that kainic acid was a very effective stimulant of 22Na+ uptake, but 3H-kainic acid showed no Na+ -dependent uptake. Furthermore, while L-3H-glutamate uptake was very sensitive to lowered temperatures, glutamate-stimulated 22Na+ uptake was relatively insensitive. These results indicate that glutamate-stimulated uptake of 22Na+ in primary astrocytes cultures cannot be explained solely by cotransport of Na+ with glutamate, and they suggest that direct kainic acid-type receptor induced stimulation of Na+ uptake also occurs. Since both receptor and uptake effects involve transport of Na+, accurate measurements of the Na+ :glutamate stoichiometry for uptake can only be done using completely specific inhibitors of these 2 systems.

Kimelberg, H.K.; Pang, S.; Treble, D.H.

1989-04-01

427

Na sup + and H sup + transport in human jejunal brush-border membrane vesicles  

SciTech Connect

The authors have examined pH gradient-driven Na{sup +} uptake and Na{sup +}-driven H{sup +} transport in brush-border membrane vesicles prepared from jejunal tissue obtained from organ donors by measuring the influx of {sup 22}Na and the fluorescence quenching of acridine orange (AO). Vesicle preparation by either Ca{sup 2+} or Mg{sup 2+} precipitation showed no difference in {sup 22}Na uptake or AO fluorescence quenching and dissipatio