Discussions about the Nature of Science in a Course on the History of Astronomy. (Spanish Title: Discusiones sobre la Naturaleza de la Ciencia en un Curso sobre Historia de la Astronomía.) Discussões sobre a Natureza da Ciência em um Curso sobre a História da Astronomia

NASA Astrophysics Data System (ADS)

Pires de Andrade, Victória Flório; L'Astorina, Bruno

2010-07-01

There are an increasing number of researches in science education that affirm the importance of discussions on the "nature of science" in basic education level as well as in teacher training. The history of science applied to education is a way to contextualize epistemological discussions, allowing both the understanding of scientific content and learning about science concepts. We present some reasonably consensual definitions on the nature of science that have been widely discussed by the academic community. We show also some episodes in the history of astronomy which can lead to discussions involving some aspects of the nature of science, and how they can do it. Hay un número creciente de investigaciones en la enseñanza de las ciencias que afirman la importancia de debates sobre la "naturaleza de la ciencia" en la educación básica y formación del profesorado. La historia de la ciencia aplicada a la educación es una manera de contextualizar los debates de la epistemología, lo que permite tanto la comprensión de los contenidos científicos como el aprendizaje de conceptos científicos. En esto trabajo, presentamos algunas definiciones bastante consensuales sobre la naturaleza de la ciencia que han sido ampliamente discutidas por la comunidad académica y mostramos cómo algunos episodios en la historia de la astronomía pueden llevar a discusiones sobre algunos aspectos de la naturaleza de la ciencia. Há um número crescente de pesquisas na área de ensino de ciências que afirmam a importância de discussões sobre a "natureza da ciência" na educação básica e na formação de professores. A história da ciência aplicada ao ensino é uma maneira de contextualizar discussões epistemológicas, permitindo tanto a compreensão de conteúdos científicos quanto o aprendizado de noções sobre as ciências. Neste trabalho apresentamos algumas definições razoavelmente consensuais sobre a natureza da ciência que foram amplamente discutidas pela

Determinacion de periodos fundamentales del suelo mediante vibraciones ambientales en el municipio de Humacao, Puerto Rico

NASA Astrophysics Data System (ADS)

Cintron Aponte, Rommel

La tecnica de Nakamura ha sido utilizada a nivel mundial para determinar periodos fundamentales del suelo. La tecnica consiste en calcular y graficar cocientes espectrales H/V de vibraciones ambientales registradas sobre el suelo. Mediciones de vibraciones ambientales fueron tomadas en 151 lugares dentro del municipio de Humacao, localizado al este de Puerto Rico. Los datos se procesaron utilizando espectros de Fourier y espectros de potencia. La tecnica fue validada al compararla con los resultados de cocientes espectrales H/V de registros de sismos debiles y tambien con una modelacion numerica realizada con datos de un ensayo "downhole". Las graficas de los cocientes espectrales H/V fueron divididas en casos y grupos, los cuales dependen de la facilidad para identificar el periodo fundamental pico y amplitudes en frecuencias menores de 1 Hz, respectivamente. Los resultados obtenidos con ambos espectros fueron comparados y se concluye que los mismos se complementan para proveer resultados mas confiables. Se crearon mapas de periodos fundamentales, factores de amplitud, isoperiodos y clasificacion sismica de sitio. Los mapas de isoperiodos fueron realizados en las zonas mas pobladas sobre depositos de suelo. El mapa de periodos fundamentales del suelo mostro buena correlacion con la geologia local. El mapa de clasificacion sismica derivado de periodos de sitio fue comparado con el mapa de clasificacion sismica derivado de barrenos geotecnicos. El mapa de clasificacion obtenido de periodos puede sobreestimar un poco algunas clasificaciones del suelo. Sin embargo, este mapa puede proveer un estimado aproximado de la velocidad de onda de corte promedio del suelo hasta una profundidad de 100 pies (30 metros).

Digitalización de diapositivas del Sol en H α

NASA Astrophysics Data System (ADS)

Missio, H.; Montenegro, C.; Montenegro, R.

El objetivo de este trabajo ha sido el de obtener imágenes digitalizadas de las diapositivas tomadas del Sol en luz de hidrógeno de la línea correspondiente a Hα, y de esta manera llegar a convertir las mismas a un archivo digital para poder ser tratadas luego por computadora y poder contabilizar con exactitud, mediante un programa adecuado para tal fin, las zonas activas del Sol en la imagen digitalizada. En principio, para llegar a esto se pensó en la utilización de medios accesibles, y como detector se utilizó un fototransistor ubicado dentro de un soporte rectangular sobre dos ejes de desplazamiento X e Y. Se han obtenido con este procedimiento imágenes de buena calidad, construídas a partir de tres datos digitalizados en cada barrido que aportan la posición X e Y y la intensidad del pixel en ese punto indicada en 255 tonos de grises.

Estudio del comportamiento tribologico y de las interacciones de superficie de nuevos nanofluidos ionicos

NASA Astrophysics Data System (ADS)

Espinosa Rodriguez, Tulia

tribocorrosion processes. The formation of a coating layer on magnesium alloys from phosphonate imidazolium ionic liquids by immersion and by chronoamperometry has been described. The new coatings reduce the abrasive wear in the magnesium-aluminium alloy but they are not effective in the magnesium-zinc alloy, which prevent the formation of continuous coatings. Los liquidos ionicos son sales liquidas a temperatura ambiente o bajas temperaturas que presentan excelentes propiedades fisico-quimicas. En el presente trabajo se estudian como lubricantes en problemas tribologicos complejos como la lubricacion de metales contra si mismos, el desarrollo de lubricantes base agua y de nuevas superficies autolubricadas. Cuando no es posible reducir la friccion y desgaste mediante lubricacion, como en las aleaciones de magnesio, los liquidos ionicos se han estudiado como precursores de recubrimientos protectores. Se han determinado las interacciones superficiales y los procesos de corrosion sobre cobre y sobre acero con diferentes liquidos ionicos proticos y aproticos para desarrollar nuevos lubricantes y aditivos. En el contacto cobre/cobre, excepto el liquido ionico protico derivado del oleato, todos los liquidos ionicos estudiados presentan mejor comportamiento tribologico que el lubricante comercial Polialfaolefina 6. En el contacto acero/zafiro, los nuevos liquidos ionicos proticos son buenos lubricantes cuando se utilizan en estado puro, y, como aditivos en agua, generan peliculas adsorbidas sobre la superficie del metal reduciendo la friccion y el desgaste tras la evaporacion del agua. Para evitar el periodo de alta friccion inicial en presencia de agua, se han generado peliculas superficiales de liquido ionico sobre el acero en condiciones estaticas. El mejor comportamiento lubricante tanto en el contacto cobre/cobre como en el contacto acero/zafiro se obtiene para el liquido ionico protico derivado del anion adipato, con dos grupos carboxilicos. Las interacciones de los grupos

La estructura dinámica del cinturón de Kuiper interior y la formación de Urano y Neptuno

NASA Astrophysics Data System (ADS)

Melita, M. D.; Brunini, A.

De acuerdo a los más recientes estudios sobre la formación de Urano y Neptuno, éstos podrían haber sufrido una importante migración radial hacia el exterior, debido al intercambio de momento angular con los planetesimales presentes en esa región durante las últimas etapas de la formación del Sistema Solar. Esta migración radial habría tenido importantes consecuencias sobre la presente estructura dinámica del cinturón cometario de Kuiper. Tal como lo reflejan las observaciones, la mayoría de los cuerpos observados en el cinturón de Kuiper se encuentran en resonancia de movimientos medios exteriores con Neptuno, hecho que también se refleja en la presente órbita de Plutón. En el presente trabajo se estudia tanto numérica como analíticamente la influencia de la variación de las masas de Urano y Neptuno durante el proceso de migración sobre las probabilidades de captura en algunas de las resonancias exteriores de Neptuno. Se estudia también la influencia de encuentros gravitacionales mutuos sobre la estabilidad de las órbitas resonantes. Este estudio ofrece argumentos de plausibilidad para explicar por qué ninguno de los objetos descubiertos en el cinturón de Kuiper se encontraría en la resonancia 2:1.

Modelo analítico del efecto de PRS sobre satélites GPS

NASA Astrophysics Data System (ADS)

Meza, A.; Brunini, C.; Usandivaras, J. C.

El sistema GPS (Global Position System) es, hoy en día, la herramienta de navegación y posicionamiento más potente y lo será sin duda en la próxima década. Gran parte de su valiosa utilidad se debe a la alta precisión que permite lograr y ésta, a su vez, depende, entre otras causas, de la precisión con que se conocen las órbitas de los satélites. La presión de radiación solar (PRS) fija el límite de la precisión con que pueden calcularse en la actualidad las efemérides satelitarias. El objetivo de este trabajo es proponer una mejor resolución de este fenómeno. El modelo analítico aquí presentado, se basa en el análisis del comportamiento de los residuos de un ajuste por mínimos cuadrados en el que se utiliza el modelo de PRS propuesto por Beutler. El mismo consiste en un modelo determinista del fenómeno con dos parámetros libres. Los resultados obtenidos ponen de manifiesto que, aún después de aplicar dichos parámetros, prevalecen en los residuos efectos semidiurnos en las componentes radial,tangencial y normal. Estos resultados obtenidos se comparan con los de un trabajo desarrollado por el Instituto de Berne (Beutler et al., 1994), en el que se utilizaron como pseudo-observaciones las órbitas precisas del IGS (CODE). El intervalo de integración escogido por este centro fueron las semanas 680 y 681. En resumen se tienen arcos de 14 días para todos los satélites, donde las efemérides precisas de los mismos para los 14 días fueron utilizados como pseudo-observaciones. El modelo de fuerza que empleó dicho centro fue básicamente el tradicional en lo que respecta al modelo de las fuerzas gravitacionales, y para la PRS utilizo el modelo standard de Beutler. Los parámetros de este modelo junto con las 6 condiciones iniciales (posición y velocidad) fueron ajustados por el método general de mínimos cuadrados. Los residuos en la componente radial, tangencial y normal, para los satélites con un buen comportamiento, presentan una

DISYUNTIVAS EN LAS CONCEPCIONES SOBRE AUTONOMÍA Y BENEFICENCIA QUE AFECTAN LA TERAPÉUTICA DEL INTENTO SUICIDA.

PubMed

Mondragón, Liliana; Monroy, Zuraya; Ito, Ma Emily; Medina-Mora, Dra Ma Elena

2010-06-01

El objetivo del trabajo es conocer las disyuntivas entre los principios de beneficencia y autonomía, que se presentan en la relación médico-paciente, durante la terapéutica del intento de suicidio.La investigación se realizó en dos hospitales psiquiátricos de la Ciudad de México. La muestra incluyó a tres sujetos con intento de suicidio, mayores de 18 años, que eran atendidos en consulta externa a causa de una lesión autoinfligida en el último año, y a tres psiquiatras que trataban a estos pacientes. La información se obtuvo previo consentimiento informado en entrevistas individuales. Se llevó a cabo un análisis de discurso argumentado para encontrar los significados que los participantes otorgaron a los principios bioéticos y las posibles disyuntivas entre éstos.Las discordancias entre la beneficencia y la autonomía estuvieron relacionadas con el beneficio del tratamiento, el respeto por los valores y las creencias de los pacientes, entre otros. Este trabajo presenta consideraciones éticas relevantes en el escenario clínico, al ofrecer al psiquiatra un análisis bioético que le permita actuar de acuerdo con la beneficencia y respetando la autonomía del paciente frente a casos de intento de suicidio y, de esta forma procurar una mejor atención para ellos.

Investigaccion-accion en la sala de clases sobre las creencias de la cultura de la ciencia de un grupo de estudiantes universitarios y su relacion reciproca con el aprendizaje de las ciencias biologicas

NASA Astrophysics Data System (ADS)

Cordova-Santiago, Lizzette Astrid

La investigacion---accion que se llevo a cabo en la sala de clases tenia como punto de partida las creencias de la cultura de la ciencia de un grupo de estudiantes universitarios para luego examinar sus implicaciones en el proceso de aprendizaje de las Ciencias Biologicas. ¿Que se supone que hagan las creencias en relacion con el aprendizaje? ¿En que consiste incorporar este aspecto a la practica educativa universitaria? Utilizando el modelo de Kemmis y McTaggart (1987) la investigacion-accion se planteo como un proceso dinamico en cuatro momentos en espiral constituidos por la planificacion, la accion, la observacion y la reflexion. Cada una de las fases tuvo una intencion retrospectiva y prospectiva formando una espiral de autorreflexion del conocimiento y la accion. Se llevaron a cabo audio grabaciones en clases y analisis de documentos. Ademas, la profesora-investigadora hizo un portafolio para reflexionar sobre las creencias de la cultura de la ciencia que tienen los estudiantes y las creencias del aprendizaje que tiene la profesora y sobre como la comprension de estos elementos ayudo a mejorar su practica educativa a traves del tiempo. Los resultados obtenidos apuntan a que las creencias de la cultura de la ciencia que tiene el grupo de estudiantes son diversas. Ellos si creen que la ciencia tiene una cultura la cual describieron como: complicada y desconocida que evoluciona constantemente, que es un conjunto de metodos, que es altamente tecnologica, que resuelve problemas de salud, ayuda a interpretar la realidad del mundo que los rodea y su origen y que existen unas intersecciones entre la ciencia y el poder. Sobre las creencias del proceso de aprendizaje de la profesora-investigadora, estas senalan que el modelaje de actores, la vision de la academia que tiene ella asi como la participacion y negociacion entre todos los involucrados en el proceso educativo, son factores que inciden en el proceso de aprendizaje.

Sobre el estado evolutivo de β Pictoris

NASA Astrophysics Data System (ADS)

Brunini, A.; Benvenuto, O. G.

Desde el descubrimiento de fuertes excesos infrarrojos en β Pictoris, esta estrella ha sido muy estudiada y es considerada candidata a poseer un sistema planetario propio. β Pic está rodeada de un disco asimétrico de polvo que se observa de canto y que esta vacío a distancias <= 40 AU. Esto se considera una fuerte evidencia en favor de la presencia de (al menos) un planeta gigante. Recientemente se han observado líneas de material circunestelar que se han interpretado como consecuencia de la caída de objetos cometarios sobre esta estrella. Recientemente se ha utilizado la existencia del disco de polvo para atribuir una edad corta (pre - secuencia principal) a βPic. Sin embargo, la evaporación de estos cometas provee suficiente polvo como para explicar la presencia del disco observado sin necesidad de edades cortas. En este trabajo mostramos que la comparación entre la tasa de impactos cometarios estimada en el Sistema Solar para diferentes etapas de su evolución y los datos observados en β Pic indica edades avanzadas para β Pic. Esta estimación debe tomarse con cautela ya que depende de la estructura de los sistemas planetarios. Además mostramos que, desde el punto de vista de la evolución estelar y con las incertezas presentes en la luminosidad y la temperatura efectiva, existe un continuo de edades posible para β Pic. Sin embargo, empleando los datos provenientes de los flujos cometarios encontramos que una edad prolongada es consistente con ambos tratamientos.

El diseño final del espectrógrafo de banco (EBASIM) para CASLEO

NASA Astrophysics Data System (ADS)

Simmons, J.; Levato, H.

Utilizando el código de óptica ACCOS V se ha finalizado el diseño del espectrógrafo de banco para CASLEO. En una comunicación anterior habíamos indicado que utilizaríamos un colimador de 150 mm de diámetro con un radio de curvatura de 1540 mm. Para el espejo cámara, que tiene un diámetro de 200 mm, el radio de curvatura es de 1200 mm, ambos radios con una tolerancia no mayor a los 3 mm. En la presente, se informa sobre los detalles finales del cálculo del espectrógrafo que incluye el cómputo para 5 longitudes de onda diferentes y alrededor de 100 rayos. En todos los casos el 75 % de energía está dentro de un diámetro de 13 micrones. El diseño ha sido probado entre 3500 Å hasta 9000 Å con resultados satisfactorios.

Once daily maraviroc 300 mg or 150 mg in combination with ritonavir-boosted darunavir 800/100 mg.

PubMed

Okoli, Chinyere; Siccardi, Marco; Thomas-William, Sathish; Dufty, Ngozi; Khonyongwa, Kirstin; Ainsworth, Jonathan; Watson, John; Cook, Roseanne; Gandhi, Kate; Hickinbottom, Geraldine; Owen, Andrew; Taylor, Stephen

2012-03-01

To describe the pharmacokinetics of maraviroc when dosed at 150 or 300 mg once daily with 800/100 mg of darunavir/ritonavir. A retrospective case-note review of HIV-infected adults taking maraviroc was conducted. Patients on a maraviroc-based regimen for a minimum of 5 weeks were grouped as receiving: (i) 300 mg of maraviroc twice daily with 245 mg of tenofovir/200 mg of emtricitabine; (ii) 300 mg of maraviroc once daily with 800/100 mg of darunavir/ritonavir once daily; and (iii) 150 mg of maraviroc once daily with 800/100 mg of darunavir/ritonavir once daily. C(trough) and C(peak) data were collected at 2, 12 or 24 h post-dose. Sixty-six patients were included, providing 115 samples. The median (IQR) C(peak) was 378 (350-640) ng/mL for 300 mg of maraviroc twice daily with 245 mg of tenofovir/200 mg of emtricitabine (n=9), 728 (378-935) ng/mL for 300 mg of maraviroc once daily with darunavir/ritonavir (n=29) and 364 (104-624) ng/mL for 150 mg of maraviroc once daily with darunavir/ritonavir (n=2; P=0.24). The median (IQR) C(trough) was 46 (33-61) ng/mL for 300 mg of maraviroc twice daily with 245 mg of tenofovir/200 mg of emtricitabine (n=12), 70 (49-97) ng/mL for 300 mg of maraviroc once daily with darunavir/ritonavir (n=34) and 43 (35-55) ng/mL for 150 mg of maraviroc once daily with darunavir/ritonavir (n=17; P=0.001). The maraviroc C(trough) in black patients (n=34) was 61 (45-110) ng/mL and in white patients (n=29) it was 49 (42-70) ng/mL (P=0.04). The C(peak) in black patients (n=20) was 800 (397-1060) ng/mL versus 387 (336-723) ng/mL in white patients (n=20; P=0.02). Once daily coadministration of 300 mg of maraviroc with 800/100 mg of darunavir/ritonavir was well tolerated and had favourable pharmacokinetics when compared with 300 mg of maraviroc twice daily with 245 mg of tenofovir/200 mg of emtricitabine. A 24% higher C(trough) and 107% higher C(peak) was seen in black patients compared with white patients.

Esomeprazole 40 mg provides more effective intragastric acid control than lansoprazole 30 mg, omeprazole 20 mg, pantoprazole 40 mg and rabeprazole 20 mg in patients with gastro-oesophageal reflux symptoms.

PubMed

Röhss, Kerstin; Lind, Tore; Wilder-Smith, Clive

2004-10-01

To compare the effect of esomeprazole 40 mg with lansoprazole 30 mg, omeprazole 20 mg, pantoprazole 40 mg and rabeprazole 20 mg on intragastric pH during single and repeated dosing in four separate studies in patients with symptoms of gastro-oesophageal reflux disorder (GERD). In four randomised crossover studies, patients with symptoms of GERD received once-daily treatment with esomeprazole 40 mg or lansoprazole 30 mg (study A), omeprazole 20 mg (study B), pantoprazole 40 mg (study C) and rabeprazole 20 mg (study D) for 5 days. Continuous 24-h intragastric pH recording was performed on days 1 (except study B) and 5. Percentage of time over 24 h with intragastric pH greater than 4, 24-h median pH and the proportion of patients with pH greater than 4 for greater than or equal to 12 h and 16 h during the 24-h recording periods were investigated. In all four studies, esomeprazole 40 mg OD maintained intragastric pH greater than 4 for a significantly higher mean percentage of the 24-h period compared with all other proton pump inhibitors (PPIs) on days 1 (esomeprazole 40.6% versus lansoprazole 33.4%, P=0.0182; esomeprazole 50.3% versus pantoprazole 29.1%, P<0.001; esomeprazole 41.0% versus rabeprazole 29.4%, P=0.002) and 5 (esomeprazole 57.7% versus lansoprazole 44.5%, P<0.0001; esomeprazole 69.8% versus omeprazole 43.7%, P<0.0001; esomeprazole 67.0% versus pantoprazole 44.8%, P<0.001; esomeprazole 59.4% versus rabeprazole 44.5%, P<0.0001). Higher 24-h median pH and a higher proportion of patients with intragastric pH greater than 4 for greater than or equal to 12 h and 16 h were reported with esomeprazole 40 mg OD than with all the other PPIs in each study. Esomeprazole 40 mg provides greater acid control in more patients and maintains intragastric pH greater than 4 for a longer period than lansoprazole 30 mg, omeprazole 20 mg, pantoprazole 40 mg and rabeprazole 20 mg in patients with symptoms of GERD.

DISYUNTIVAS EN LAS CONCEPCIONES SOBRE AUTONOMÍA Y BENEFICENCIA QUE AFECTAN LA TERAPÉUTICA DEL INTENTO SUICIDA1

PubMed Central

Mondragón, Liliana; Monroy, Zuraya; Ito, Ma. Emily; Medina-Mora, Dra. Ma. Elena

2010-01-01

El objetivo del trabajo es conocer las disyuntivas entre los principios de beneficencia y autonomía, que se presentan en la relación médico-paciente, durante la terapéutica del intento de suicidio. La investigación se realizó en dos hospitales psiquiátricos de la Ciudad de México. La muestra incluyó a tres sujetos con intento de suicidio, mayores de 18 años, que eran atendidos en consulta externa a causa de una lesión autoinfligida en el último año, y a tres psiquiatras que trataban a estos pacientes. La información se obtuvo previo consentimiento informado en entrevistas individuales. Se llevó a cabo un análisis de discurso argumentado para encontrar los significados que los participantes otorgaron a los principios bioéticos y las posibles disyuntivas entre éstos. Las discordancias entre la beneficencia y la autonomía estuvieron relacionadas con el beneficio del tratamiento, el respeto por los valores y las creencias de los pacientes, entre otros. Este trabajo presenta consideraciones éticas relevantes en el escenario clínico, al ofrecer al psiquiatra un análisis bioético que le permita actuar de acuerdo con la beneficencia y respetando la autonomía del paciente frente a casos de intento de suicidio y, de esta forma procurar una mejor atención para ellos. PMID:20830214

Desgarros del epitelio pigmentario de la retina: factores de riesgo, mecanismo y control terapéutico.

PubMed

Clemens, Christoph R; Eter, Nicole

2017-07-11

Los desgarros del epitelio pigmentario de la retina (EPR) se asocian en la mayoría de los casos con los desprendimientos vascularizados del EPR debido a una degeneración macular asociada a la edad (DMAE), y normalmente implican una pérdida adversa de la agudeza visual. Estudios recientes indican que ha habido un aumento en la incidencia de desgarros del EPR desde la introducción de fármacos anti-factor de crecimiento del endotelio vascular (anti-VEGF) así como una asociación temporal entre el desgarro y la inyección intravítrea. Dado que el número de pacientes con DMAE y el número de inyecciones anti-VEGF va en aumento, tanto la dificultad de prevenir desgarros del EPR como el tratamiento tras la formación de los desgarros han adquirido una mayor relevancia. De forma paralela, la evolución de la imagenología de la retina ha contribuido de manera significativa a comprender mejor el desarrollo de los desgarros del EPR en los últimos años. Esta revisión resume los conocimientos que se poseen actualmente sobre el desarrollo, los factores pronósticos y las estrategias terapéuticas de los desgarros del EPR antes y después de que estos se formen. © 2017 S. Karger AG, Basel.

Cathodic Deposition of Mg(OH)2 Coatings on Pure mg in Three mg Salts Aqueous Solutions

NASA Astrophysics Data System (ADS)

Yongjun, Zhang; Xiaomeng, Pei; Shugong, Jia

Film-forming effects of cathodic deposition on pure Mg substrate at constant DC in aqueous solutions of magnesium nitrate (Mg(NO3)2ṡ6H2O), magnesium chloride (MgCl2ṡ6H2O) and magnesium sulfate (MgSO4ṡ7H2O) respectively were investigated systematically. Typical processes were studied by potentiodynamic cathodic polarization and galvanostatic polarization and typical samples were analyzed by SEM and XRD. The results indicate that the depositing efficiency is not only the highest but stablest, and deposited coatings show the best uniformity with Mg(NO3)2ṡ6H2O solution employed as depositing medium and applied current density ≥1.0mA cm-2. Cathodic deposition leads to regular mass loss of Mg substrate. The cathodic polarization curve of pure Mg in magnesium nitrate solution shows more obvious pseudo-passivation, several Tafel regions with different slopes appearing before diffusion-limited current density region, and oxygen consumption is the major cathodic reduction reaction under specified current density. However, hydrogen evolution reaction is dominant in both Mg chloride and Mg sulfate solutions. The deposition coatings are all composed of continuous and uniform mesh-like “basic layer” adjacent to substrate and discrete distributed snowball-like particles on the microscopic scale. The phase compositions are all crystal Mg(OH)2, and the coatings deposited in Mg chloride solution have (011) preferred orientation.

Efficacy and Safety of Doxepin 1 mg, 3 mg, and 6 mg in Adults with Primary Insomnia

PubMed Central

Roth, Thomas; Rogowski, Roberta; Hull, Steven; Schwartz, Howard; Koshorek, Gail; Corser, Bruce; Seiden, David; Lankford, Alan

2007-01-01

Study Objectives: To evaluate the efficacy and safety of doxepin 1, 3, and 6 mg in insomnia patients. Design: Adults (18-64 y) with chronic primary insomnia (DSM-IV) were randomly assigned to one of four sequences of 1 mg, 3 mg, and 6 mg of doxepin, and placebo in a crossover study. Treatment periods consisted of 2 polysomnographic assessment nights with a 5-day or 12-day drug-free interval between periods. Efficacy was assessed using polysomnography (PSG) and patient-reported measures. Safety analyses included measures of residual sedation and adverse events. Measurements and Results: Sixty-seven patients were randomized. Wake time during sleep, the a priori defined primary endpoint, was statistically significantly improved at the doxepin 3 mg and 6 mg doses versus placebo. All three doses had statistically significant improvements versus placebo for PSG-defined wake after sleep onset, total sleep time, and overall sleep efficiency (SE). SE in the final third-of-the-night also demonstrated statistically significant improvement at all doses. The doxepin 6 mg dose significantly reduced subjective latency to sleep onset. All three doxepin doses had a safety profile comparable to placebo. There were no statistically significant differences in next-day residual sedation, and sleep architecture was generally clinically preserved. Conclusions: In adults with primary insomnia, doxepin 1 mg, 3 mg, and 6 mg was well-tolerated and produced improvement in objective and subjective sleep maintenance and duration endpoints that persisted into the final hour of the night. The side-effect profile was comparable to placebo, with no reported anticholinergic effects, no memory impairment, and no significant hangover/next-day residual effects. These data demonstrate that doxepin 1 mg, 3 mg, and 6 mg is efficacious in improving the sleep of patients with chronic primary insomnia. Citation: Roth T; Rogowski R; Hull S; Schwartz H; Koshorek G; Corser B; Seiden D. Efficacy and safety of

The effect of the MgO buffer layer thickness on magnetic anisotropy in MgO/Fe/Cr/MgO buffer/MgO(001)

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

Kozioł-Rachwał, Anna, E-mail: a.koziolrachwal@aist.go.jp; AGH University of Science and Technology, Faculty of Physics and Applied Computer Science, al. Mickiewicza 30, 30-059 Kraków; Nozaki, Takayuki

2016-08-28

The relationship between the magnetic properties and MgO buffer layer thickness d was studied in epitaxial MgO/Fe(t)/Cr/MgO(d) layers grown on MgO(001) substrate in which the Fe thickness t ranged from 0.4 nm to 1.1 nm. For 0.4 nm ≤ t ≤ 0.7 nm, a non-monotonic coercivity dependence on the MgO buffer thickness was shown by perpendicular magneto-optic Kerr effect magnetometry. For thicker Fe films, an increase in the buffer layer thickness resulted in a spin reorientation transition from perpendicular to the in-plane magnetization direction. Possible origins of these unusual behaviors were discussed in terms of the suppression of carbon contamination at the Fe surface and changes inmore » the magnetoelastic anisotropy in the system. These results illustrate a method to control magnetic anisotropy in MgO/Fe/Cr/MgO(d) via an appropriate choice of MgO buffer layer thickness d.« less

AB Initio Characterization of MgCCH, MgCCH(+), and MgC2, and Pathways to their Formation in the Interstellar Medium

NASA Technical Reports Server (NTRS)

Woon, David E.

1996-01-01

A study of Mg-bearing compounds has been performed in order to determine molecular properties which are critical for planning new astronomical searches and laboratory studies. The primary focus of the work is on MgCCH, MgCCH(+), and the isomers of MgC2. Only MgCCH has been identified in laboratory studies. Additional calculations have been carried out on MgH, MgNC, MgCN, and their cations in an effort to evaluate pathways to the formation of MgCCH and MgCCH(+) in the InterStellar Medium (ISM) or in circumstellar envelopes. Correlated ab initio methods and correlation-consistent basis sets have been employed. Properties including structures, rotational constants, dipole moments, and harmonic frequencies are reported. A transition state between linear MgCC and cyclic MgC2 has been characterized and was found to yield a minimal barrier (approx. 0.5 kcal/mole), indicating easy interconversion to the cyclic form. Direct reactions in the ISM between Mg or Mg(+) and HCCH are precluded by energetic considerations, but a number of ion- molecule or neutral-neutral exchange reactions between CCH and various Mg-containing species offer plausible pathways to MgCCH or MgCCH(+). Weakly bound MgH may react with CCH to form MgCCH, but MgH has not been detected. Both MgNC and MgCN have been observed, but reactions with CCH are slightly endothermic by 1-3 kcal/mole. Although MgH(+), MgNC(+), and MgCN(+) have not been detected, their reactions with CCH to form MgCCH(+) are all exothermic. With only a small barrier separating linear MgCC and cyclic MgC2, the dissociative recombination of MgCCH(+) with an electron is expected to yield cyclic MgC2, and regenerate Mg and CCH. New astronomical searches for MgCCH, MgCCH(+), cyclic MgC2, MgNC(+), and MgCN(+) will provide further insight into organo-magnesium astrochemistry.

Observations of local interstellar Mg I and Mg II

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

Bruhweiler, F.C.; Oegerle, W.; Weiler, E.

1984-11-01

Copernicus and IUE observations of 5 stars within 50 pc of the Sun were combined to study the ionization of magnesium in the Local Interstellar Medium (LISM). The high resolution Copernicus spectrometer was used to detect interstellar MG I 2852 in the spectra of alpha Gru, alpha Eri, and alpha Lyr, while placing upper limits on Mg I in the spectra of alpha CMa and alpha PsA. Observations of Mg II 2795, 2802 for these stars were also obtained with IUE and Copernicus. The column densities of Mg I and Mg II are used to place constraints on the temperaturemore » of the LISM.« less

Observations of Local Interstellar Mg I and Mg II

NASA Technical Reports Server (NTRS)

Bruhweiler, F. C.; Oegerle, W.; Weiler, E.; Stencel, R. E.; Kondo, Y.

1984-01-01

Copernicus and IUE observations of 5 stars within 50 pc of the Sun were combined to study the ionization of magnesium in the local interstellar medium (LISM). The high resolution Copernicus spectrometer was used to detect interstellar MG I 2852 in the spectra of alpha Gru, alpha Eri, and alpha Lyr, while placing upper limits on Mg I in the spectra of alpha CMa and alpha PsA. Observations of Mg II 2795, 2802 for these stars were also obtained with IUE and Copernicus. The column densities of Mg I and Mg II are used to place constraints on the temperature of the LISM.

Main reinforcement effects of precipitation phase Mg2Cu3Si, Mg2Si and MgCu2 on Mg-Cu-Si alloys by ab initio investigation

NASA Astrophysics Data System (ADS)

Shi, Xue-Feng; Wang, Hai-Chen; Tang, Ping-Ying; Tang, Bi-Yu

2017-09-01

To predict and compare the main reinforcement effects of the key precipitation phases Mg2Cu3Si, Mg2Si and MgCu2 in Mg-Cu-Si alloy, the structural, mechanical and electronic properties of these phases have been studied by ab initio calculations. The lowest formation enthalpy and cohesive energy indicate that Mg2Cu3Si has the strongest alloying ability and structural stability. The mechanical modulus indicates that Mg2Cu3Si has the strongest resistance to reversible shear/volume distortion and has maximum hardness. The characterization of brittle (ductile) behavior manifests that MgCu2 has favorable ductility. Meanwhile the evaluation of elastic anisotropy indicates that Mg2Si possesses elastic isotropy. Debye temperature prediction shows that Mg2Si and Mg2Cu3Si have better thermal stability. To achieve an unbiased interpretation on the phase stability and mechanical behavior of these precipitation phases, the density of states and differential charge densities are also analyzed. The current study deepens the comprehensive understanding of main reinforcement effects of these precipitation phases on Mg-Cu-Si alloys, and also benefits to optimize the overall performances of Mg-Cu-Si alloy from the hardness, ductility and thermal stability by controlling these second precipitation phases during the heat treatment process.

Re-examining the 26Mg(α ,α')26Mg reaction: Probing astrophysically important states in 26Mg

NASA Astrophysics Data System (ADS)

Adsley, P.; Brümmer, J. W.; Li, K. C. W.; Marín-Lámbarri, D. J.; Kheswa, N. Y.; Donaldson, L. M.; Neveling, R.; Papka, P.; Pellegri, L.; Pesudo, V.; Pool, L. C.; Smit, F. D.; van Zyl, J. J.

2017-11-01

Background: The 22Ne(α ,n )25Mg reaction is one of the neutron sources for the s process in massive stars. The properties of levels in 26Mg above the α -particle threshold control the strengths of the 22Ne(α ,n )25Mg and 22Ne(α ,γ )26Mg reactions. The strengths of these reactions as functions of temperature are one of the major uncertainties in the s process. Purpose: Information on the existence, spin, and parity of levels in 26Mg can assist in constraining the strengths of the 22Ne(α ,γ )26Mg and 22Ne(α ,n )25Mg reactions, and therefore in constraining s -process abundances. Methods: Inelastically scattered α particles from a 26Mg target were momentum-analyzed in the K600 magnetic spectrometer at iThemba LABS, South Africa. The differential cross sections of states were deduced from the focal-plane trajectory of the scattered α particles. Based on the differential cross sections, spin and parity assignments to states are made. Results: A newly assigned 0+ state was observed in addition to a number of other states, some of which can be associated with states observed in other experiments. Some of the deduced Jπ values of the states observed in the present study show discrepancies with those assigned in a similar experiment performed at RCNP Osaka. The reassignments and additions of the various states can strongly affect the reaction rate at low temperatures. Conclusion: The number, location, and assignment of levels in 26Mg that may contribute to the 22Ne+α reactions are not clear. Future experimental investigations of 26Mg must have an extremely good energy resolution to separate the contributions from different levels. Coincidence experiments of 26Mg provide a possible route for future investigations.

Sc(2)MgGa(2) and Y(2)MgGa(2).

PubMed

Sahlberg, Martin; Andersson, Yvonne

2009-03-01

Scandium magnesium gallide, Sc(2)MgGa(2), and yttrium magnesium gallide, Y(2)MgGa(2), were synthesized from the corresponding elements by heating under an argon atmosphere in an induction furnace. These intermetallic compounds crystallize in the tetragonal Mo(2)FeB(2)-type structure. All three crystallographically unique atoms occupy special positions and the site symmetries of (Sc/Y, Ga) and Mg are m2m and 4/m, respectively. The coordinations around Sc/Y, Mg and Ga are pentagonal (Sc/Y), tetragonal (Mg) and triangular (Ga) prisms, with four (Mg) or three (Ga) additional capping atoms leading to the coordination numbers [10], [8+4] and [6+3], respectively. The crystal structure of Sc(2)MgGa(2 )was determined from single-crystal diffraction intensities and the isostructural Y(2)MgGa(2) was identified from powder diffraction data.

Improving the characteristics of foundry alloys AlSiCuMg during manufacturing

NASA Astrophysics Data System (ADS)

Fragoso, Bruno Filipe Marques

As piroxenas sao um vasto grupo de silicatos minerais encontrados em muitas rochas igneas e metamorficas. Na sua forma mais simples, estes silicatos sao constituidas por cadeias de SiO3 ligando grupos tetrahedricos de SiO4. A formula quimica geral das piroxenas e M2M1T2O6, onde M2 se refere a catioes geralmente em uma coordenacao octaedrica distorcida (Mg2+, Fe2+, Mn2+, Li+, Ca2+, Na+), M1 refere-se a catioes numa coordenacao octaedrica regular (Al3+, Fe3+, Ti4+, Cr3+, V3+, Ti3+, Zr4+, Sc3+, Zn2+, Mg2+, Fe2+, Mn2+), e T a catioes em coordenacao tetrahedrica (Si4+, Al3+, Fe3+). As piroxenas com estrutura monoclinica sao designadas de clinopiroxenes. A estabilidade das clinopyroxenes num espectro de composicoes quimicas amplo, em conjugacao com a possibilidade de ajustar as suas propriedades fisicas e quimicas e a durabilidade quimica, tem gerado um interesse mundial devido a suas aplicacoes em ciencia e tecnologia de materiais. Este trabalho trata do desenvolvimento de vidros e de vitro-cerâmicos baseadas de clinopiroxenas para aplicacoes funcionais. O estudo teve objectivos cientificos e tecnologicos; nomeadamente, adquirir conhecimentos fundamentais sobre a formacao de fases cristalinas e solucoes solidas em determinados sistemas vitro-cerâmicos, e avaliar a viabilidade de aplicacao dos novos materiais em diferentes areas tecnologicas, com especial enfase sobre a selagem em celulas de combustivel de oxido solido (SOFC). Com este intuito, prepararam-se varios vidros e materiais vitro-cerâmicos ao longo das juntas Enstatite (MgSiO3) - diopsidio (CaMgSi2O6) e diopsidio (CaMgSi2O6) - Ca - Tschermak (CaAlSi2O6), os quais foram caracterizados atraves de um vasto leque de tecnicas. Todos os vidros foram preparados por fusao-arrefecimento enquanto os vitro-cerâmicos foram obtidos quer por sinterizacao e cristalizacao de fritas, quer por nucleacao e cristalizacao de vidros monoliticos. Estudaram-se ainda os efeitos de varias substituicoes ionicas em composicoes de

Percepcion de los profesores universitarios acerca del concepto cultura cientifica y de sus implicaciones en el nuevo bachillerato del Recinto de Rio Piedras de la Universidad de Puerto Rico

NASA Astrophysics Data System (ADS)

Ramos Pastrana, Nilsa

El Senado Academico del Recinto de Rio Piedras de la Universidad de Puerto Rico aprobo en el ano academico 2005-2006 la Certificacion 46, que contiene los lineamientos de un nuevo bachillerato. Este nuevo bachillerato introdujo cambios significativos en el curriculo tradicional. Entre ellos se encuentra la reduccion del componente de educacion general y el de Ciencias Biologicas en particular. La reduccion de creditos en el componente de Ciencias Biologicas ha obligado a reevaluar el concepto de cultura cientifica que desarrollan esos cursos. El proposito del estudio consistio en auscultar las percepciones de los profesores de las Facultades de Administracion de Empresas, Humanidades, Ciencias Sociales, Ciencias Naturales, Educacion y Estudios Generales del Recinto de Rio Piedras de la Universidad de Puerto Rico en torno al concepto de cultura cientifica, los contenidos disciplinares del curso de Ciencias Biologicas y la reduccion de creditos en el nuevo bachillerato. Las preguntas que guiaron la investigacion fueron: ¿cuales son las percepciones que tienen los profesores de las Facultades de Administracion de Empresas, Ciencias Sociales, Estudios Generales, Ciencias Naturales, Humanidades y Educacion, en torno al concepto de cultura cientifica y los contenidos disciplinares del curso de Ciencias Biologicas? ¿cuales son las percepciones que tienen los profesores de Ciencias Biologicas en torno al concepto cultura cientifica y los contenidos disciplinares del curso de Ciencias Biologicas? ¿existen diferencias significativas por facultad, genero, experiencia, rango y nombramiento en las percepciones que tienen los profesores del Recinto de Rio Piedras de la Universidad de Puerto Rico sobre los elementos que caracterizan la cultura cientifica y los contenidos biologicos que deben tener los egresados del Recinto? ¿que implicaciones curriculares tienen estos testimonios en el desarrollo del concepto de cultura cientifica en el nuevo bachillerato? Para realizar la

Desarrollo de un instrumento para medir percepciones sobre el contexto de construccion del conocimiento cientifico de estudiantes universitarios de nuevo ingreso

NASA Astrophysics Data System (ADS)

Garcia-Ramirez, Jaime Antonio

En esta investigacion, se desarrollo un instrumento que permite medir percepciones relacionadas al contexto de constriccion del conocimiento cientifico. Se examinaron instrumentos existentes y se encontro que el VOSTS (Views on science, technology, and society), instrumento desarrollado empiricamente en Canada por Aikenhead, Ryan y Fleming, podia traducirse y validarse en el contexto cultural puertorriqueno. El instrumento es extenso, consta de 113 reactivos, cada uno con una premisa basica relacionada a la tematica ciencia, tecnologia y sociedad y un numero de alternativas relacionadas a la premisa que oscila entre siete y trece. Se delimito su utilizacion a los quince reactivos identificados por los autores como relacionados a la construccion social del conocimiento cientifico. Metodologicamente, se procedio a utilizar el modelo de adaptacion intercultural, que permite que el instrumento desarrollado satisfaga las dimensiones de equivalencia semantica, de contenido, tecnica, de criterio y conceptual, atemperado asi al instrumento original. Se cumplio con este proposito mediante la traduccion de la version original en ingles al espanol y viceversa. Se utilizaron comites para examinar la traduccion y la retro-traduccion del instrumento. Se realizo una prueba piloto con estudiantes universitarios de nuevo ingreso, utilizando el instrumento traducido para asegurar su intelegibilidad. La confiabilidad del instrumento se determino mediante la intervencion de un panel de expertos quienes clasificaron las distintas posiciones dentro de cada reactivo en: realista, con merito e ingenua; se transformaron estas opciones en valores numericos lo que permitio establecer una escala Likert para cada una. Se suministro el instrumento a una muestra de estudiantes universitarios de nuevo ingreso con caracteristicas similares a las de la poblacion puertorriquena en cuanto a ejecucion en las pruebas de aptitud verbal y matematica del College Board. Los resultados de sus contestaciones

Mechanical Properties of Mg2Si/Mg Composites via Powder Metallurgy Process

NASA Astrophysics Data System (ADS)

Muramatsu, Hiroshi; Kondoh, Katsuyoshi; Yuasa, Eiji; Aizawa, Tatsuhiko

The mechanical properties of the Mg2Si/Mg composites solid-state synthesized from the mixed Mg-Si powders have been investigated. The macro-hardness (HRE) and the tensile strength of the composites increase with increasing the Si content and decreasing the Si size. The particle size of the synthesized Mg2Si depends on the initial Si size; the mechanical properties of the Mg2Si/Mg composite are remarkably improved by using fine Si particles or by decreasing the grain size of Mg matrix grains when the powder mixture was prepared via bulk mechanical alloying process.

Mg Incorporation Efficiency in Pulsed MOCVD of N-Polar GaN:Mg

NASA Astrophysics Data System (ADS)

Marini, Jonathan; Mahaboob, Isra; Hogan, Kasey; Novak, Steve; Bell, L. D.; Shahedipour-Sandvik, F.

2017-10-01

We report on the effect of growth polarity and pulsed or δ -doped growth mode on impurity incorporation in metalorganic chemical vapor deposition-grown GaN. In Ga-polar orientation, up to 12× enhancement in Mg concentration for given Mg flow rate is observed, resulting in enhanced p-type conductivity for these samples. In contrast, this enhancement effect is greatly diminished for N-polar samples, falling off with increasing Mg flow and showing maximum enhancement of 2.7× at 30 nmol/min Mg flow. At higher Mg flow rates, Mg incorporation at normal levels did not correspond to p-type conductivity, which may be due to Mg incorporation at nonacceptor sites. Concentrations of C, O, and Si were also investigated, revealing dependence on Mg flow in N-polar pulsed samples. Carbon incorporation was found to decrease with increasing Mg flow, and oxygen incorporation was found to remain high across varied Mg flow. These effects combine to result in N-polar samples that are not p-type when using the pulsed growth mode.

Desarrollo de fotonovelas para concienciar sobre trastornos de la conducta alimentaria en latinos en los Estados Unidos

PubMed Central

Reyes-Rodríguez, Mae Lynn; García, Marissa; Silva, Yormeri; Sala, Margarita; Quaranta, Michela; Bulik, Cynthia M.

2016-01-01

Resumen El objetivo de este estudio fue desarrollar fotonovelas, un tipo de novela gráfica popular en la población latina, para crear conciencia y educar sobre los trastornos de la conducta alimentaria (TCA). Cuatro caricaturas ilustradas y guiones adaptados para adultos y adolescentes de ambos sexos fueron presentados en discusiones focales y en una entrevista de profundidad. Diecisiete latinos adultos (14 mujeres; 3 hombres) y 10 adolescentes (9 féminas; 1 varón) participaron en el estudio. Los participantes encontraron las fotonovelas interesantes y que captaban más la atención que los folletos tradicionales. El uso del espanglish y la clarificación de las diferencias entre los TCA fueron sugeridos por las adolescentes femeninas. Los adultos varones sugirieron cambiar el título, que se enfocara en las consecuencias en la salud de los TCA para que llame la atención en los hombres a leer la historia. Basado en la aceptación encontrada en este estudio, la fotonovela pudiera ser una avenida prometedora para crear conciencia y educar a la comunidad latina sobre los TCA en los Estados Unidos. PMID:27313838

Interstellar fossil Mg-26 and its possible relationship to excess meteoritic Mg-26

NASA Technical Reports Server (NTRS)

Clayton, Donald D.

1986-01-01

A plausible scenario is advanced for explainig a linear correlation found in some solar system solids between their Mg-26/Mg-24 isotopic ratios and their Al/Mg elemental abundance ratios. This scenario involves three stages: (1) the mechanical aggregation of an average ensemble of Al-bearing dust particles that is postulated to be modestly enriched in the Al/Mg abundance ratio because the aggregated particles themselves are; (2) the extraction, perhaps but not necessarily by hot distillation, of almost all Mg, leaving an aggregate with a large Al/Mg ratio and a large Mg-26 excess; and (3) the uptake of normal ambient Mg by the resulting hot Al-rich solid as it cools in Mg-rich vapor. A linear correlation in solids between their Mg-26/Mg-24 isotopic ratio and their aluminum enrichment may be a fossil correlation inherited from interstellar dust.

Mg Content Dependence of EML-PVD Zn-Mg Coating Adhesion on Steel Strip

NASA Astrophysics Data System (ADS)

Jung, Woo Sung; Lee, Chang Wook; Kim, Tae Yeob; De Cooman, Bruno C.

2016-09-01

The effect of coating thickness and Mg concentration on the adhesion strength of electromagnetic levitation physical vapor deposited Zn-Mg alloy coatings on steel strip was investigated. The phase fraction of Zn, Mg2Zn11, and MgZn2 was determined for a coating Mg concentration in the 0 to 15 wt pct range. Coatings with a Mg content less than 5 pct consisted of an Zn and Mg2Zn11 phase mixture. The coatings showed good adhesion strength and ductile fracture behavior. Coatings with a higher Mg concentration, which consisted of a Mg2Zn11 and MgZn2 phase mixture, had a poor adhesion strength and a brittle fracture behavior. The adhesion strength of PVD Zn-Mg alloy coatings was found to be related to the pure Zn phase fraction. The effect of coating thickness on adhesion strength was found to be negligible. The microstructure of the interface between steel and Zn-Mg alloy coatings was investigated in detail by electron microscopy, electron diffraction, and atom probe tomography.

MgCu metallic glass

NASA Astrophysics Data System (ADS)

Durandurdu, Murat

2018-03-01

We generate an amorphous MgCu model using the rapid solidification of the melt through a first-principles molecular dynamics approach within a generalised gradient approximation and reveal, for the first time, its structural features and mechanical properties in details. The liquid and glassy MgCu are found to acquire slightly distinct local structures. Yet in both forms of MgCu, most Cu atoms have a tendency to form the ideal and defective icosahedrons while Mg atoms are arranged in complex configurations. The mean coordination number of Cu and Mg at 300 K is 11.31 and 13.73, respectively. The short-range order of MgCu glass is projected to be different than the known crystalline MgCu and Mg2Cu phases. The mechanical properties of MgCu glass and the CsCl-type MgCu crystal are computed and compared. On the basis of the enthalpy analyses, a possible pressure-induced crystallisation of the MgCu glass into a CsCl-type structure is proposed to occur at around 11 GPa.

Effect of Mg interlayer on perpendicular magnetic anisotropy of CoFeB films in MgO/Mg/CoFeB/Ta structure

NASA Astrophysics Data System (ADS)

Ma, Q. L.; Iihama, S.; Kubota, T.; Zhang, X. M.; Mizukami, S.; Ando, Y.; Miyazaki, T.

2012-09-01

The effects of Mg metallic interlayer on the magnetic properties of thin CoFeB films in MgO/Mg (tMg)/CoFeB (1.2 nm)/Ta structures were studied in this letter. Our experimental result shows that the CoFeB film exhibits perpendicular magnetic anisotropy (PMA) when the CoFeB and MgO layers are separated by a metallic Mg layer with a maximum thickness of 0.8 nm. The origin of PMA was discussed by considering the preferential transmission of the Δ1 symmetry preserved by the Mg interlayer in crystallized MgO/Mg/CoFeB/Ta. In addition, the thin Mg interlayer also contributes to enhancing the thermal stability and reducing the effective damping constant and coercivity of the CoFeB film.

Quasicrystal-reinforced Mg alloys.

PubMed

Kyun Kim, Young; Tae Kim, Won; Hyang Kim, Do

2014-04-01

The formation of the icosahedral phase (I-phase) as a secondary solidification phase in Mg-Zn-Y and Mg-Zn-Al base systems provides useful advantages in designing high performance wrought magnesium alloys. The strengthening in two-phase composites (I-phase + α -Mg) can be explained by dispersion hardening due to the presence of I-phase particles and by the strong bonding property at the I-phase/matrix interface. The presence of an additional secondary solidification phase can further enhance formability and mechanical properties. In Mg-Zn-Y alloys, the co-presence of I and Ca 2 Mg 6 Zn 3 phases by addition of Ca can significantly enhance formability, while in Mg-Zn-Al alloys, the co-presence of the I-phase and Mg 2 Sn phase leads to the enhancement of mechanical properties. Dynamic and static recrystallization are significantly accelerated by addition of Ca in Mg-Zn-Y alloy, resulting in much smaller grain size and more random texture. The high strength of Mg-Zn-Al-Sn alloys is attributed to the presence of finely distributed Mg 2 Sn and I-phase particles embedded in the α -Mg matrix.

Hydriding and dehydriding rates of Mg, Mg-10TaF5, and Mg-10NbF5 prepared via reactive mechanical grinding

NASA Astrophysics Data System (ADS)

Song, Myoung Youp; Kwak, Young Jun; Lee, Seong Ho; Park, Hye Ryoung

2015-01-01

In this work, TaF5 and NbF5 were chosen as additives to enhance the hydriding and dehydriding rates of Mg. Mg, Mg-10TaF5, and Mg-10NbF5 samples were prepared by reactive mechanical grinding. The hydriding and dehydriding properties of the samples were then examined. Mg-10TaF5 had the largest amount of hydrogen absorbed for 30 min and the highest initial dehydriding rate after incubation period, followed in order by Mg-10NbF5, and Mg. At 593 K under 12 bar H2 at the first cycle, Mg-10TaF5 absorbed 3.63 wt% H for 5 min and 4.53 wt% H for 30 min. At 593 K under 1.0 bar H2 at the first cycle, Mg-10TaF5 desorbed 0 wt% H for 2.5 min, 0.59 wt% H for 5 min, 3.42 wt% H for 30 min, and 4.24 wt% H for 60 min. The reactive mechanical grinding of Mg with TaF5 or NbF5 is believed to have facilitated the nucleation and to have decreased the diffusion distances of hydrogen atoms. These two effects are believed to have increased the hydriding and dehydriding rates of Mg. The MgF2 and Ta2H formed in Mg-10TaF5, and the MgF2, NbH2, and NbF3 formed in Mg-10NbF5 are considered to have enhanced both of these effects.

Variation in mangrove forest structure and sediment characteristics in Bocas del Toro, Panama

USGS Publications Warehouse

Lovelock, C.E.; Feller, Ilka C.; McKee, K.L.; Thompson, R.

2005-01-01

Mangrove forest structure and sediment characteristics were examined in the extensive mangroves of Bocas del Toro, Republic of Panama. Forest structure was characterized to determine if spatial vegetation patterns were repeated over the Bocas del Toro landscape. Using a series of permanent plots and transects we found that the forests of Bocas del Toro were dominated by Rhizophora mangle with very few individuals of Avicennia germinans and Laguncularia racemosa. Despite this low species diversity, there was large variation in forest structure and in edaphic conditions (salinity, concentration of available phosphorus, Eh and sulphide concentration). Aboveground biomass varied 20-fold, from 6.8 Mg ha-1 in dwarf forests to 194.3 Mg ha-1 in the forests fringing the land. But variation in forest structure was predictable across the intertidal zone. There was a strong tree height gradient from seaward fringe (mean tree height 3.9 m), decreasing in stature in the interior dwarf forests (mean tree height 0.7 m), and increasing in stature in forests adjacent to the terrestrial forest (mean tree height 4.1 m). The predictable variation in forest structure emerges due to the complex interactions among edaphic and plant factors. Identifying predictable patterns in forest structure will aid in scaling up the ecosystem services provided by mangrove forests in coastal landscapes. Copyright 2005 College of Arts and Sciences.

The Influence of MgH2 on the Assessment of Electrochemical Data to Predict the Degradation Rate of Mg and Mg Alloys

PubMed Central

Mueller, Wolf-Dieter; Hornberger, Helga

2014-01-01

Mg and Mg alloys are becoming more and more of interest for several applications. In the case of biomaterial applications, a special interest exists due to the fact that a predictable degradation should be given. Various investigations were made to characterize and predict the corrosion behavior in vitro and in vivo. Mostly, the simple oxidation of Mg to Mg2+ ions connected with adequate hydrogen development is assumed, and the negative difference effect (NDE) is attributed to various mechanisms and electrochemical results. The aim of this paper is to compare the different views on the corrosion pathway of Mg or Mg alloys and to present a neglected pathway based on thermodynamic data as a guideline for possible reactions combined with experimental observations of a delay of visible hydrogen evolution during cyclic voltammetry. Various reaction pathways are considered and discussed to explain these results, like the stability of the Mg+ intermediate state, the stability of MgH2 and the role of hydrogen overpotential. Finally, the impact of MgH2 formation is shown as an appropriate base for the prediction of the degradation behavior and calculation of the corrosion rate of Mg and Mg alloys. PMID:24972140

Gabapentina a dosis de 300 vs. 450 mg como premedicación anestésica para hipertensión reactiva, ansiedad y analgesia.

PubMed

Rascón-Martínez, Dulce María; Guzmán-Sánchez, Joaquín Antonio; Corral-Urdapilleta, Nora Paulina; Arguelles-Uribe, Gema Damaris; Velázquez-Loeza, Jazmín; Soto-Palma, Gustavo; Carrillo-Torres, Orlando

Observar el comportamiento de la gabapentina para aminorar la hipertensión reactiva secundaria a ansiedad y dolor en pacientes sometidos a cirugía oftálmica, así como el consumo de opiáceos entre los grupos. Ensayo clínico controlado aleatorizado y doble ciego que analizó a 125 pacientes divididos en tres grupos: grupo A, gabapentina 300 mg; grupo B, gabapentina 450 mg; grupo C, amaranto en grageas como control 2 horas antes del procedimiento quirúrgico. Se utilizó la prueba de ji al cuadrado para variables sociodemográficas y ANOVA de un factor para variables numéricas continuas. Se consideró como significativo un valor de p < 0.05 para un estudio de dos colas con un poder beta del 80%. La ansiedad y la analgesia transoperatoria y posoperatoria tuvieron diferencias significativas entre los grupos. Se encontró menor consumo de opiáceos en los grupos que usaron gabapentina. La gabapentina por vía oral, 300 o 450 mg, 2 horas antes de la cirugía, reduce el dolor, la ansiedad y el consumo de opiáceos durante el posoperatorio en pacientes sometidos a cirugía oftalmológica. Copyright: © 2018 SecretarÍa de Salud

Spontaneously intermixed Al-Mg barriers enable corrosion-resistant Mg/SiC multilayer coatings

DOE PAGES

Soufli, Regina; Fernandez-Perea, Monica; Baker, Sherry L.; ...

2012-07-24

Magnesium/silicon carbide (Mg/SiC) has the potential to be the best-performing reflective multilayercoating in the 25–80 nm wavelength region but suffers from Mg-related corrosion, an insidious problem which completely degrades reflectance. We have elucidated the origins and mechanisms of corrosion propagation within Mg/SiC multilayers. Based on our findings, we have demonstrated an efficient and simple-to-implement corrosion barrier for Mg/SiC multilayers. In conclusion, the barrier consists of nanometer-scale Mg and Al layers that intermix spontaneously to form a partially amorphous Al-Mg layer and is shown to prevent atmospheric corrosion while maintaining the unique combination of favorable Mg/SiC reflective properties.

Mechanical Properties of Mg-Gd and Mg-Y Solid Solutions

NASA Astrophysics Data System (ADS)

Kula, Anna; Jia, Xiaohui; Mishra, Raj K.; Niewczas, Marek

2016-12-01

The mechanical properties of Mg-Gd and Mg-Y solid solutions have been studied under uniaxial tension and compression between 4 K and 298 K (-269 °C and 25 °C). The results reveal that Mg-Gd alloys exhibit higher strength and ductility under tension and compression attributed to the more effective solid solution strengthening and grain-boundary strengthening effects. Profuse twinning has been observed under compression, resulting in a material texture with strong dominance of basal component parallel to compression axis. Under tension, twining is less active and the texture evolution is controlled mostly by slip. The alloys exhibit pronounced yield stress asymmetry and significantly different work-hardening behavior under tension and compression. Increasing of Gd and/or Y concentration leads to the reduction of the tension-compression asymmetry due to the weakening of the recrystallization texture and more balanced twinning and slip activity during plastic deformation. The results suggest that under compression of Mg-Y alloys slip is more active than twinning in comparison to Mg-Gd alloys.

Control Al/Mg intermetallic compound formation during ultrasonic-assisted soldering Mg to Al.

PubMed

Xu, Zhiwu; Li, Zhengwei; Li, Jiaqi; Ma, Zhipeng; Yan, Jiuchun

2018-09-01

To prevent the formation of Al/Mg intermetallic compounds (IMCs) of Al 3 Mg 2 and Al 12 Mg 17 , dissimilar Al/Mg were ultrasonic-assisted soldered using Sn-based filler metals. A new IMC of Mg 2 Sn formed in the soldered joints during this process and it was prone to crack at large thickness. The thickness of Mg 2 Sn was reduced to 22 μm at 285 °C when using Sn-3Cu as the filler metal. Cracks were still observed inside the blocky Mg 2 Sn. The thickness of Mg 2 Sn was significantly reduced when using Sn-9Zn as the filler metal. A 17 μm Mg 2 Sn layer without crack was obtained at a temperature of 200 °C, ultrasonic power of Mode I, and ultrasonic time of 2 s. The shear strengths of the joints using Sn-9Zn was much higher than those using Sn-3Cu because of the thinner Mg 2 Sn layer in the former joints. Sn whiskers were prevented by using Sn-9Zn. A cavitation model during ultrasonic assisted soldering was proposed. Copyright © 2018 Elsevier B.V. All rights reserved.

The millimeter-wave spectrum of the MgH and MgD radicals

NASA Technical Reports Server (NTRS)

Ziurys, L. M.; Barclay, W. L., Jr.; Anderson, M. A.

1993-01-01

The pure rotational spectrum of MgH radical (X 2 Sigma (+)) in its ground state v = 0 and v = 1 vibrational modes has been observed in the laboratory using millimeter/submillimeter direct absorption spectroscopy. The rotational spectra of two isotopically substituted species, MgD and (Mg-26)H, have been detected as well. All six hyperfine components of the N = 0 -1 transition of MgH in its v = 0 and v = 1 states have been directly measured to an accuracy of +/-50 kHz, and the five components have been observed for (Mg-26)H. The N = 0 +/-1 and N = 1 -2 transitions of MgD have also been detected. Rotational, fine structure, and hyperfine constants were determined for all species from a nonlinear least-squared fit to the data using a 2 Sigma Hamiltonian.

DEL phenotype.

PubMed

Kwon, Dong H; Sandler, S G; Flegel, Willy A

2017-09-01

DEL red blood cells (RBCs) type as D- by routine serologic methods and are transfused routinely, without being identified as expressing a very weak D antigen, to D- recipients. DEL RBCs are detected only by adsorption and elution of anti-D or by molecular methods. Most DEL phenotypes have been reported in population studies conducted in East Asia, although DEL phenotypes have been detected also among Caucasian individuals. Approximately 98 percent of DEL phenotypes in East Asians are associated with the RHD*DEL1 or RHD*01EL.01 allele. The prevalence of DEL phenotypes has been reported among D- Han Chinese (30%), Japanese (28%), and Korean (17%) populations. The prevalence of DEL phenotypes is significantly lower among D- Caucasian populations (0.1%). Among the 3-5 percent of African individuals who are D-, there are no reports of the DEL phenotype. Case reports from East Asia indicate that transfusion of DEL RBCs to D- recipients has been associated with D alloimmunization. East Asian immigrants constitute 2.1 percent of the 318.9 million persons residing in the United States, and an estimated 2.8 percent are blood donors. Using these statistics, we estimate that 68-683 units of DEL RBCs from donors of East Asian ancestry are transfused as D- annually in the United States. Given the reports from East Asia of D alloimmunization attributed to transfusion of DEL RBCs, one would expect an occasional report of D alloimmunization in the United States following transfusion of DEL RBCs to a D- recipient. If such cases do occur, the most likely reason that they are not detected is the absence of active post-transfusion monitoring for formation of anti-D.

Estudio de la estructura logica utilizada en la ensenanza y el aprendizaje de los conceptos sobre el comportamiento de gases en el curso introductorio de quimica a nivel universitario

NASA Astrophysics Data System (ADS)

Costa Diaz, Agnes

El estudio que se presenta es de caracter cualitativo, un estudio multicasos donde se estudia la estructura logica utilizada por cuatro (4) profesores universitarios que ensenan el curso introductorio de quimica, en la planificacion, presentacion y evaluacion del tema sobre el comportamiento de los gases. Se utilizaron varias fuentes de informacion como: cuestionarios de profesores y estudiantes, entrevistas, grabaciones videomagnetofonicas, materiales didacticos y una prueba conceptual, entre otros. La informacion recopilada fue analizada de acuerdo al orden logico del contenido presentado, el estilo de ensenanza del profesor, las tecnicas y estrategias utilizadas para el desarrollo de destrezas de pensamiento, el ambiente fisico en el salon de clase y los instrumentos de evaluacion y avaluo. El estudio demuestra que lo que los profesores piensan y planifican para hacer sus presentaciones no necesariamente es lo que ocurre en el salon de clases. El desarrollo de destrezas de pensamiento, que constituye una prioridad de los profesores, no se elaboran efectivamente. El uso de las estrategias de resolucion de problemas numericos predomino. La participacion del estudiante en el salon de clases fue limitada y no se logro demostrar el desarrollo de las destrezas de pensamiento deseadas. Aunque los profesores tienen su propio estilo de ensenanza, el orden logico del contenido presentado en clase fue el mismo o siguio muy de cerca el orden establecido por el libro de texto. Los profesores utilizaron preferentemente la tiza y la pizarra para sus presentaciones y la dinamica en el salon de clases fue esencialmente tradicional. Los profesores hicieron su presentacion y los estudiantes copiaron pasivamente la informacion. Las evaluaciones de los estudiantes fueron esencialmente, pruebas escritas de seleccion multiple de acuerdo con el estilo en que se les enseno. El avaluo fue casi inexistente. La prueba conceptual administrada revela un aprendizaje pobre en los conceptos mas

The Interplay of Al and Mg Speciation in Advanced Mg Battery Electrolyte Solutions

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

See, Kimberly A.; Chapman, Karena W.; Zhu, Lingyang

2016-01-13

Mg batteries are an attractive alternative to Li-based energy storage due to the possibility of higher volumetric capacities with the added advantage of using sustainable materials. A promising emerging electrolyte for Mg batteries is the magnesium aluminum chloride complex (MACC) which shows high Mg electrodeposition and stripping efficiencies and relatively high anodic stabilities. As prepared, MACC is inactive with respect to Mg deposition; however, efficient Mg electrodeposition can be achieved following an electrolytic conditioning process. Through the use of Raman spectroscopy, surface enhanced Raman spectroscopy, 27Al and 35Cl nuclear magnetic resonance spectroscopy, and pair distribution function analysis, we explore themore » active vs inactive complexes in the MACC electrolyte and demonstrate the codependence of Al and Mg speciation. These techniques report on significant changes occurring in the bulk speciation of the conditioned electrolyte relative to the as-prepared solution. Analysis shows that the active Mg complex in conditioned MACC is very likely the [Mg2(μ–Cl)3·6THF]+ complex that is observed in the solid state structure. Additionally, conditioning creates free Cl– in the electrolyte solution, and we suggest the free Cl– adsorbs at the electrode surface to enhance Mg electrodeposition.« less

Relativistic quasiparticle band structures of Mg2Si, Mg2Ge, and Mg2Sn: Consistent parameterization and prediction of Seebeck coefficients

NASA Astrophysics Data System (ADS)

Shi, Guangsha; Kioupakis, Emmanouil

2018-02-01

We apply density functional and many-body perturbation theory calculations to consistently determine and parameterize the relativistic quasiparticle band structures of Mg2Si, Mg2Ge, and Mg2Sn, and predict the Seebeck coefficient as a function of doping and temperature. The quasiparticle band gaps, including spin-orbit coupling effects, are determined to be 0.728 eV, 0.555 eV, and 0.142 eV for Mg2Si, Mg2Ge, and Mg2Sn, respectively. The inclusion of the semicore electrons of Mg, Ge, and Sn in the valence is found to be important for the accurate determination of the band gaps of Mg2Ge and Mg2Sn. We also developed a Luttinger-Kohn Hamiltonian and determined a set of band parameters to model the near-edge relativistic quasiparticle band structure consistently for all three compounds that can be applied for thermoelectric device simulations. Our calculated values for the Seebeck coefficient of all three compounds are in good agreement with the available experimental data for a broad range of temperatures and carrier concentrations. Our results indicate that quasiparticle corrections are necessary for the accurate determination of Seebeck coefficients at high temperatures at which bipolar transport becomes important.

Laser cooling of MgCl and MgBr in theoretical approach

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

Wan, Mingjie; Shao, Juxiang; Huang, Duohui

Ab initio calculations for three low-lying electronic states (X{sup 2}Σ{sup +}, A{sup 2}Π, and 2{sup 2}Π) of MgCl and MgBr molecules, including spin-orbit coupling, are performed using multi-reference configuration interaction plus Davidson correction method. The calculations involve all-electronic basis sets and Douglas–Kroll scalar relativistic correction. Spectroscopic parameters well agree with available theoretical and experimental data. Highly diagonally distributed Franck-Condon factors f{sub 00} for A{sup 2}Π{sub 3/2,1/2} (υ′ = 0) → X{sup 2}Σ{sup +}{sub 1/2} (υ″ = 0) are determined for both MgCl and MgBr molecules. Suitable radiative lifetimes τ of A{sup 2}Π{sub 3/2,1/2} (υ′ = 0) states for rapid lasermore » cooling are also obtained. The proposed laser drives A{sup 2}Π{sub 3/2} (υ′ = 0) → X{sup 2}Σ{sup +}{sub 1/2} (υ″ = 0) transition by using three wavelengths (main pump laser λ{sub 00}; two repumping lasers λ{sub 10} and λ{sub 21}). These results indicate the probability of laser cooling MgCl and MgBr molecules.« less

Efectos combinados de la ampliación de la atención primaria de salud y de las transferencias condicionadas de dinero en efectivo sobre la mortalidad infantil en Brasil, 1998–2010*

PubMed Central

Guanais, Frederico C.

2015-01-01

Objetivos. Examiné los efectos combinados del acceso a la atención primaria mediante el Programa de Salud Familiar (PSF) y las transferencias condicionadas de dinero en efectivo del Programa Bolsa Familia (PBF) sobre la mortalidad infantil posneonatal (MIPN) en Brasil. Métodos. Empleé un análisis ecológico longitudinal usando datos en panel de 4 583 municipios brasileños de 1998 al 2010, con 54 253 observaciones en total. Estimé modelos de regresión de efectos fijos por mínimos cuadrados ordinarios, con la tasa de MIPN como la variable dependiente y el PSF, el PBF y sus interacciones como las principales variables independientes de interés. Resultados. La asociación de una mayor cobertura del PSF con una menor tasa de MIPN se volvió más fuerte conforme aumentaba la cobertura del PBF. En los promedios de todas las demás variables, cuando la cobertura de PBF era 25%, la MIPN predicha fue 5,24 (intervalo de confianza [IC] de 95% = 4,95, 5,53) para una cobertura del PSF de 0%, y de 3,54 (IC de 95% = 2,77, 4,31) para una cobertura del PSF de 100%. Cuando la cobertura del PBF era de 60%, la MIPN predicha fue 4,65 (IC de 95% = 4,36, 4,94) para una cobertura del PSF de 0%, y de 1,38 (IC de 95% = 0,88, 1,89) para una cobertura del PSF de 100%. Conclusiones. El efecto del PSF depende de la ampliación del PBF. Para las poblaciones empobrecidas y subatendidas, la combinación de intervenciones tanto del lado de la oferta como del lado de la demanda podría ser necesaria para mejorar los resultados en salud.

Estudio ab initio del mecanismo de la reacción HSO + O3

NASA Astrophysics Data System (ADS)

Nebot Gil, I.

La reacción entre el radical HSO y el ozono ha sido ampliamente estudiada desde el punto de vista experimental debido a la importancia que tiene el radical HSO en la oxidación de los compuestos de azufre reductores y a que puede contribuir a la producción de H2SO4 [1-4]. Se realizaron diversos estudios teóricos sobre la cinética de la reacción entre el radical HSO y el ozono. La reacción del HSO con el ozono presenta tres canales diferentes : HSO + O3 &rightarrow &HSO2 + O2 &rightarrow &HS + 2 O2 &rightarrow &SO + OH + O2 La controversia existente entre los grupos experimentales sobre cuál de las tres vías es la predominante, se ha resuelto mediante un estudio teórico de todas ellas utilizando métodos ab initio. La estructura de todos los reactivos, productos, intermedios y estados de transición ha sido optimizada a nivel ab initio utilizando los métodos UMP2 /6-31G** y QCISD/6-31G**.

Hydrogen sorption in Pd-decorated Mg-MgO core-shell nanoparticles

NASA Astrophysics Data System (ADS)

Callini, E.; Pasquini, L.; Piscopiello, E.; Montone, A.; Antisari, M. Vittori; Bonetti, E.

2009-06-01

Mg nanoparticles with metal-oxide core-shell morphology were synthesized by inert-gas condensation and decorated by in situ Pd deposition. Transmission electron microscopy and x-ray diffraction underline the formation of a noncontinuous layer with Pd clusters on top of the MgO shell. Even in the presence of a thick MgO interlayer, a modest (2 at. %) Pd decoration deeply enhances the hydrogen sorption properties: previously inert nanoparticles exhibit metal-hydride transformation with fast kinetics and gravimetric capacity above 5 wt %.

National Drug IQ Challenge

MedlinePlus

... del coeficiente intelectual (CI) sobre las drogas y el alcohol 2016 National Drug IQ Challenge 2016 Reto ... del coeficiente intelectual (CI) sobre las drogas y el alcohol 2015 National Drug IQ Challenge 2015 Reto ...

Chondrogenic differentiation of ATDC5-cells under the influence of Mg and Mg alloy degradation.

PubMed

Martinez Sanchez, Adela H; Feyerabend, Frank; Laipple, Daniel; Willumeit-Römer, Regine; Weinberg, Annelie; Luthringer, Bérengère J C

2017-03-01

Biodegradable magnesium (Mg)-based materials are a potential alternative to permanent implants for application in children. Nevertheless effects of those materials on growth plate cartilage and chondrogenesis have not been previously evaluated. In vitro differentiation of ATDC5 cells was evaluated under the influence of pure Mg (PMg), Mg with 10wt% of gadolinium (Mg-10Gd) and Mg with 2wt% of silver (Mg-2Ag) degradation products (extracts) and direct cell culture on the materials. Gene expression showed an inhibitory effect on ATDC5 mineralization with the three extracts and a chondrogenic potential of Mg-10Gd. Cells cultured in Mg-10Gd and Mg-2Ag extracts showed the same proliferation and morphology than cells cultured in growth conditions. Mg-10Gd induced an increase in production of ECM and a bigger cell size, similar to the effects found with differentiation conditions. An increased metabolic activity was observed in cells cultured under the influence of Mg-10Gd extracts, indicated by an acidic pH during most of the culture period. After 7days of culture on the materials, ATDC5 growth, distribution and ECM synthesis were higher on Mg-10Gd samples, followed by Mg-2Ag and PMg, which was influenced by the homogeneity and composition of the degradation layer. This study confirmed the tolerance of ATDC5 cells to Mg-based materials and a chondrogenic effect of Mg-10Gd. Further studies in vitro and in vivo are necessary to evaluate cell reactions to those materials, as well as the effects on bone growth and the biocompatibility of the alloying system in the body. Copyright © 2016 Elsevier B.V. All rights reserved.

Modulation of Mg2+ influx and cytoplasmic free Mg2+ concentration in rat ventricular myocytes.

PubMed

Tashiro, Michiko; Inoue, Hana; Konishi, Masato

2018-06-16

To examine whether TRPM7, a member of the melastatin family of transient receptor potential channels, is a physiological pathway for Mg 2+ entry in mammalian cells, we studied the effect of TRPM7 regulators on cytoplasmic free Mg 2+ concentration ([Mg 2+ ] i ) of rat ventricular myocytes. Acutely isolated single cells were AM-loaded with the fluorescent indicator furaptra, and [Mg 2+ ] i was estimated at 25 °C. After [Mg 2+ ] i was lowered by soaking the cells with a high-K + and Mg 2+ -Ca 2+ -free solution, [Mg 2+ ] i was recovered by extracellular perfusion of Ca 2+ -free Tyrode's solution that contained 1 mM Mg 2+ . The initial rate of increase in [Mg 2+ ] i was analyzed as the Mg 2+ influx rate. The Mg 2+ influx rate was increased by the TRPM7 activator, naltriben (2-50 μM), in a concentration-dependent manner with a half maximal effective concentration (EC 50 ) of 24 μM. This EC 50 value is similar to that reported for the activation of recombinant TRPM7 overexpressed in HEK293 cells. Naltriben (50 μM) caused little change in basal [Mg 2+ ] i (~ 0.9 mM) in Ca 2+ -free Tyrode's solution, but significantly raised [Mg 2+ ] i to 1.31 ± 0.03 mM in 94 min after the removal of extracellular Na + . Re-introduction of extracellular Na + lowered [Mg 2+ ] i back to the basal level even in the presence of naltriben. Application of 10 μM NS8593, an inhibitor of TRPM7, significantly lowered [Mg 2+ ] i to 0.72 ± 0.03 mM in 50-60 min independent of extracellular Na + . The results suggest that Mg 2+ entry through TRPM7 significantly contributes to physiological Mg 2+ homeostasis in mammalian heart cells.

Hydrodechlorination of Tetrachloromethane over Palladium Catalysts Supported on Mixed MgF₂-MgO Carriers.

PubMed

Bonarowska, Magdalena; Wojciechowska, Maria; Zieliński, Maciej; Kiderys, Angelika; Zieliński, Michał; Winiarek, Piotr; Karpiński, Zbigniew

2016-11-25

Pd/MgO, Pd/MgF₂ and Pd/MgO-MgF₂ catalysts were investigated in the reaction of CCl₄ hydrodechlorination. All the catalysts deactivated in time on stream, but the degree of deactivation varied from catalyst to catalyst. The MgF₂-supported palladium with relatively large metal particles appeared the best catalyst, characterized by good activity and selectivity to C₂-C₅ hydrocarbons. Investigation of post-reaction catalyst samples allowed to find several details associated with the working state of hydrodechlorination catalysts. The role of support acidity was quite complex. On the one hand, a definite, although not very high Lewis acidity of MgF₂ is beneficial for shaping high activity of palladium catalysts. The MgO-MgF₂ support characterized by stronger Lewis acidity than MgF₂ contributes to very good catalytic activity for a relatively long reaction period (~5 h) but subsequent neutralization of stronger acid centers (by coking) eliminates them from the catalyst. On the other hand, the role of acidity evolution, which takes place when basic supports (like MgO) are chlorided during HdCl reactions, is difficult to assess because different events associated with distribution of chlorided support species, leading to partial or even full blocking of the surface of palladium, which plays the role of active component in HdCl reactions.

Ultrafast Synthesis and Related Phase Evolution of Mg2Si and Mg2Sn Compounds

NASA Astrophysics Data System (ADS)

Zhang, Qiang; Lu, Qiangbing; Yan, Yonggao; Su, Xianli; Tang, Xinfeng

2017-05-01

Both Mg2Si and Mg2Sn compounds were synthesized by an ultra-fast self-propagating high-temperature synthesis (SHS) method. The data regarding SHS were obtained via theoretical calculation combined with experiments, showing that the adiabatic temperature T ad and ignition temperature T ig of Mg2Si are a little higher than those of Mg2Sn. The mechanism of phase evolution and the concomitant microstructure evolution during the synthesis process of Mg2Si and Mg2Sn compounds were investigated by adopting SHS technique coupled with a sudden quenching treatment. Differential scanning calorimetry (DSC), field emission scanning electron microscopy (FESEM), and x-ray powder diffraction (XRD) results indicate that Mg2Si compound can be directly synthesized through the reaction of Mg and Si elements at around 850 K. Correspondingly, the formation of Mg2Sn needs to undergo melting of Sn and the subsequent feeble reaction between Mg and Sn elements before the large scale transformation at 730 K. As the groundwork, this research embodies great significance for future study on the ultrafast SHS process of the ternary Mg2Si1- x Sn x solid solutions.

Preliminary study of the characteristics of a high Mg containing Al-Mg-Si alloy

NASA Astrophysics Data System (ADS)

Yan, F.; McKay, B. J.; Fan, Z.; Chen, M. F.

2012-01-01

An Al-20Mg-4Si high Mg containing alloy has been produced and its characteristics investigated. The as-cast alloy revealed primary Mg2Si particles evenly distributed throughout an α-Al matrix with a β-Al3Mg2 fully divorced eutectic phase observed in interdendritic regions. The Mg2Si particles displayed octahedral, truncated octahedral, and hopper morphologies. Additions of Sb, Ti and Zr had a refining influence reducing the size of the Mg2Si from 52 ± 4 μm to 25 ± 0.1 μm, 35 ± 1 μm and 34 ± 1 μm respectively. HPDC tensile test samples could be produced with a 0.6 wt.% Mn addition which prevented die soldering. Solution heating for 1 hr was found to dissolve the majority of the Al3Mg2 eutectic phase with no evidence of any effect on the primary Mg2Si. Preliminary results indicate that the heat treatment has a beneficial effect on the elongation and the UTS.

Trastornos mentales y consumo de drogas en la población víctima del conflicto armado en tres ciudades de Colombia.

PubMed

Castaño, Guillermo; Sierra, Gloria; Sánchez, Daniela; Torres, Yolanda; Salas, Carolina; Buitrago, Carolina

2018-05-01

Introducción. La violencia en sus diferentes modalidades incrementa el riesgo de trastornos mentales y de consumo de drogas.Objetivos. Estimar la prevalencia de los trastornos mentales, del uso y abuso de drogas, así como los factores asociados en víctimas de desplazamiento forzado en tres ciudades colombianas.Materiales y métodos. Se hizo un estudio de prevalencia en una muestra de 1.026 personas entre los 13 y los 65 años de edad, a quienes se entrevistó utilizando el instrumento Composite International Diagnostic Interview y el Alcohol Use Disorders Identification Test de la Organización Mundial de la Salud, así como un cuestionario sobre el consumo de drogas modificado a partir de la encuesta del Sistema Interamericano de Datos Uniformes sobre Drogas de la Comisión Interamericana para el Control del Abuso de Drogas de la Organización de Estados Americanos, y otro sobre aspectos relacionados con el desplazamiento forzado. El análisis se hizo mediante el programa estadístico SPSS™, versión 21.Resultados. La prevalencia de vida de los trastornos mentales fue la siguiente: fobia específica, 17,7 %; depresión mayor, 16,4 %; estrés postraumático, 9,9 %; trastorno oposicionista desafiante, 8,9 %; ansiedad por separación, 7,2 %; trastornos de conducta, 5,8 %, y déficit de atención, 5,6 %. La prevalencia de vida del consumo de alcohol fue de 68,7 %; de tabaco, 31,3 %, de marihuana, 11,2 %, de cocaína, 3,5 %, de basuco, 2,0 %, de inhalables, 2,3 %, y de medicamentos ansiolíticos sin receta, 2,5 %, en tanto que 0,7 % de los entrevistados se había inyectado drogas. El presentar cualquiera de los trastornos mentales se asoció con el sexo femenino (odds ratio, OR=1,61; IC95% 1,21-2,14), así como el haber sido sometido a más de un desplazamiento forzado (OR=1,47; IC95 1,05-2,05). El consumo de cualquiera de las drogas se asoció con ser hombre (OR=5,38; IC95% 2,35-12,34).Conclusiones. La alta prevalencia de trastornos mentales y de consumo de

Formation and Corrosion Resistance of Mg-Al Hydrotalcite Film on Mg-Gd-Zn Alloy

NASA Astrophysics Data System (ADS)

Ba, Z. X.; Dong, Q. S.; Kong, S. X.; Zhang, X. B.; Xue, Y. J.; Chen, Y. J.

2017-06-01

An environment-friendly technique for depositing a Mg-Al hydrotalcite (HT) (Mg6Al2(OH)16-CO3ṡ4H2O) conversion film was developed to protect the Mg-Gd-Zn alloy from corrosion. The morphology and chemical compositions of the film were analyzed by scanning electronic microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Raman spectroscopy (RS), respectively. The electrochemical test and hydrogen evolution test were employed to evaluate the biocorrosion behavior of Mg-Gd-Zn alloy coated with the Mg-Al HT film in the simulated body fluid (SBF). It was found that the formation of Mg-Al HT film was a transition from amorphous precursor to a crystalline HT structure. The HT film can effectively improve the corrosion resistance of magnesium alloy. It indicates that the process provides a promising approach to modify Mg-Gd-Zn alloy.

The combination of amlodipine/valsartan 5/160 mg produces less peripheral oedema than amlodipine 10 mg in hypertensive patients not adequately controlled with amlodipine 5 mg

PubMed Central

Schrader, J; Salvetti, A; Calvo, C; Akpinar, E; Keeling, L; Weisskopf, M; Brunel, P

2009-01-01

Aims: To demonstrate the benefit of the combination amlodipine/valsartan 5/160 mg over amlodipine 10 mg, in producing a lower incidence of peripheral oedema for a comparable mean sitting systolic blood pressure (MSSBP) reduction. Methods: After a 4-week amlodipine 5 mg run-in phase, inadequately controlled hypertension patients (aged ≥ 55 years, MSSBP ≥ 130 and ≤ 160 mmHg) were randomised to receive amlodipine/valsartan 5/160 mg or amlodipine 10 mg for 8 weeks, followed by amlodipine/valsartan 5/160 mg for 4 weeks for all patients. Primary variables were MSSBP change from baseline to week 8 and incidence of peripheral oedema reported as an AE. Resolution of peripheral oedema was assessed 4 weeks after switching patients from amlodipine 10 mg to amlodipine/ valsartan 5/160 mg. Results: At week 8, MSSBP showed greater reduction with amlodipine/valsartan 5/160 mg than amlodipine 10 mg (least square mean: −8.01 vs.−5.95 mmHg, p<0.001 for non-inferiority and p=0.002 for superiority). Systolic control, overall BP control and systolic response rate at week 8 were significantly higher with combination than amlodipine 10 mg (34 vs. 26%; 57 vs. 50%; 36.57 vs. 27.77%, respectively). Incidence of peripheral oedema was significantly lower with the combination than amlodipine 10 mg (6.6 vs. 31.1%, p<0.001). Peripheral oedema resolved in 56% patients who switched from amlodipine 10 mg to the combination, without the loss of effect on BP reduction. Conclusion: In non-responders to amlodipine 5 mg, treatment with amlodipine/valsartan 5/160 mg induced significantly less peripheral oedema than amlodipine 10 mg for similar BP reduction. Peripheral oedema resolved in > 50% patients switching from amlodipine 10 mg to the combination. PMID:19196360

Ultra-high Strength Nanostructured Mg

DTIC Science & Technology

2014-03-31

27709-2211 Nanostructured Mg and Mg alloys, Mg metallic glass, Cryomilling, Powder consolidation, Spark plasma sintering , Deformation mechanisms REPORT...mechanically milled powder and high pressure on spark plasma sintering of Mg-Cu-Gd metallic glasses; (9) microstructure and mechanical behavior of Mg-10Li-3Al...pressure on spark plasma sintering of Mg– Cu–Gd metallic glasses, Acta Materialia , (07 2013): 4414. doi: Baolong Zheng, Ying Li, Weizong Xu

Melting relations in the MgO-MgSiO3 system up to 70 GPa

NASA Astrophysics Data System (ADS)

Ohnishi, Satoka; Kuwayama, Yasuhiro; Inoue, Toru

2017-06-01

Melting experiments in a binary system MgO-MgSiO3 were performed up to 70 GPa using a CO2 laser heated diamond anvil cell. The quenched samples were polished and analyzed by a dualbeam focused ion beam (FIB) and a field emission scanning electron microscope (FE-SEM), respectively. The liquidus phase and the eutectic composition were determined on the basis of textual and chemical analyses of sample cross sections. Our experimental results show that the eutectic composition is the Si/Mg molar ratio of 0.76 at 35 GPa and it decreases with increasing pressure. Above 45 GPa, it becomes relatively constant at about 0.64-0.65 Si/Mg molar ratio. Using our experimental data collected at a wide pressure range up to 70 GPa together with previous experimental data, we have constructed a thermodynamic model of the eutectic composition of the MgO-MgSiO3 system. The eutectic composition extrapolated to the pressure and temperature conditions at the base of the mantle is about 0.64 Si/Mg molar ratio. The modeled eutectic composition is quite consistent with a previous prediction from ab initio calculations (de Koker et al. in Earth Planet Sci Lett 361:58-63, 2013), suggesting that the simple assumption of a non-ideal regular solution model can well describe the melting relation of the MgO-MgSiO3 system at high pressure. Our results show that the liquidus phase changes from MgO-periclase to MgSiO3-bridgmanite at 35 GPa for the simplified pyrolite composition ( 0.7 Si/Mg molar ratio), while MgSiO3-bridgmanite is the liquidus phase at the entire lower mantle conditions for the chondritic composition ( 0.84 Si/Mg molar ratio).

Enhancing phosphate adsorption by Mg/Al layered double hydroxide functionalized biochar with different Mg/Al ratios.

PubMed

Li, Ronghua; Wang, Jim J; Zhou, Baoyue; Awasthi, Mukesh Kumar; Ali, Amjad; Zhang, Zengqiang; Gaston, Lewis A; Lahori, Altaf Hussain; Mahar, Amanullah

2016-07-15

Mg/Al ratio plays a significant role for anion adsorption by Mg/Al-layered double hydroxides (Mg/Al-LDHs) modified biochar. In this study, Mg/Al-LDHs biochar with different Mg/Al ratios (2, 3, 4) were prepared by co-precipitation for phosphate removal from aqueous solution. Factors on phosphate adsorption including Mg/Al ratio, pH, and the presence of other inorganic anions were investigated through batch experiments. Increasing Mg/Al ratio in the Mg/Al-LDHs biochar composites generally enhanced phosphate adsorption with Langmuir adsorption maximum calculated at 81.83mg phosphorous (P) per gram of 4:1Mg/Al-LDHs biochar at pH3.0. The adsorption process was best described by the pseudo-second-order kinetic model. Solution pH had greater effects on the phosphate adsorption by Mg/Al LDHs biochar composites with lower Mg/Al ratios. The presence of other inorganic anions decreased the phosphate adsorption efficiency in the order of F(-) > SO4(2-) > NO2(-) >Cl(-). Phosphate adsorption mechanism involves ion exchange, electrostatic attraction and surface inner-sphere complex formation. Overall, Mg/Al-LDHs biochar composites offer a potential alternative of carbon-based adsorbent for phosphate removal from aqueous solution. Copyright © 2016 Elsevier B.V. All rights reserved.

Magnesium and cadmium containing Heusler phases REPd2Mg, REPd2Cd, REAg2Mg, REAu2Mg and REAu2Cd

NASA Astrophysics Data System (ADS)

Johnscher, Michael; Stein, Sebastian; Niehaus, Oliver; Benndorf, Christopher; Heletta, Lukas; Kersting, Marcel; Höting, Christoph; Eckert, Hellmut; Pöttgen, Rainer

2016-02-01

Twenty-eight new Heusler phases REPd2Mg, REPd2Cd, REAg2Mg, REAu2Mg and REAu2Cd with different rare earth elements were synthesized from the elements in sealed niobium ampoules in a water-cooled sample chamber of an induction furnace. The samples were characterized by powder X-ray diffraction. The cell volumes show the expected lanthanide contraction. The structures of YPd2Cd, GdPd2Cd, GdAu2Cd, Y1.12Ag2Mg0.88 and GdAg2Mg were refined based on single crystal diffractometer data. The magnetic properties were determined for fifteen phase pure samples. LuAu2Mg is a weak Pauli paramagnet with a susceptibility of 1.0(2) × 10-5 emu mol-1 at room temperature. The remaining samples show stable trivalent rare earth ions and most of them order magnetically at low temperatures. The ferromagnet GdAg2Mg shows the highest ordering temperature of TC = 98.3 K. 113Cd and 89Y MAS NMR spectra of YAu2Cd and YPd2Cd confirm the presence of unique crystallographic sites. The resonances are characterized by large Knight shifts, whose magnitude can be correlated with electronegativity trends.

The [Y/Mg] clock works for evolved solar metallicity stars

NASA Astrophysics Data System (ADS)

Slumstrup, D.; Grundahl, F.; Brogaard, K.; Thygesen, A. O.; Nissen, P. E.; Jessen-Hansen, J.; Van Eylen, V.; Pedersen, M. G.

2017-08-01

Aims: Previously [Y/Mg] has been proven to be an age indicator for solar twins. Here, we investigate if this relation also holds for helium-core-burning stars of solar metallicity. Methods: High resolution and high signal-to-noise ratio (S/N) spectroscopic data of stars in the helium-core-burning phase have been obtained with the FIES spectrograph on the NOT 2.56 m telescope and the HIRES spectrograph on the Keck I 10 m telescope. They have been analyzed to determine the chemical abundances of four open clusters with close to solar metallicity; NGC 6811, NGC 6819, M 67 and NGC 188. The abundances are derived from equivalent widths of spectral lines using ATLAS9 model atmospheres with parameters determined from the excitation and ionization balance of Fe lines. Results from asteroseismology and binary studies were used as priors on the atmospheric parameters, where especially the log g is determined to much higher precision than what is possible with spectroscopy. Results: It is confirmed that the four open clusters are close to solar metallicity and they follow the [Y/Mg] vs. age trend previously found for solar twins. Conclusions: The [Y/Mg] vs. age clock also works for giant stars in the helium-core burning phase, which vastly increases the possibilities to estimate the age of stars not only in the solar neighborhood, but in large parts of the Galaxy, due to the brighter nature of evolved stars compared to dwarfs. Based on spectroscopic observations made with two telescopes: the Nordic Optical Telescope operated by NOTSA at the Observatorio del Roque de los Muchachos (La Palma, Spain) of the Instituto de Astrofísica de Canarias and the Keck I Telescope at the W.M. Keck Observatory (Mauna Kea, Hawaii, USA) operated by the California Institute of Technology, the University of California and the National Aeronautics and Space Administration.

[Sinusal penetration of amoxicillin-clavulanic acid. Formulation 1 g./125 mg., twice daily versus formulation 500 mg./125 mg., three times daily].

PubMed

Jehl, F; Klossek, J M; Peynegre, R; Serrano, E; Castillo, L; Bobin, S; Desprez, D; Renault, C; Neel, V; Rouffiac, E; Borie, C

2002-10-19

In order to meet the evolution of pneumococcus resistance to beta-lactam antibiotics, a new formulation of amoxicillin (AMX) and clavulanic acid (CA), with twice as much AMX (1 g/125 mg vs. 500 mg/125 mg) was developed for the treatment of acute pneumonia in patients at risk. This formulation can also be used in the treatment of acute maxillary sinusitis using a 1 g/125 mg regimen twice-daily. Compare the sinusal penetration of AMX and CA (1 g/125 mg twice-daily vs. 500 mg/125 mg three times a day) when administered at both regimens to demonstrate equivalent pharmacokinetic and pharmacodynamic behaviour of the former when compared to the latter. Concentrations of AMX and CA were measured in the anterior ethmoid, maxillary, posterior ethmoid sinus and in the middle nasa concha in 62 patients undergoing surgery for nasosinusal polyps. Patients randomised in two groups corresponding to 2 oral regimens, received either 1 g/125 mg twice a day or 500 mg/125 mg three times a day for 4 days. The last dose in both groups was administered 1 h 30, 3, 5 or 8 hrs prior to surgery. Serum samples were taken simultaneously to tissue samples. AMX and CA were measured by high performance liquid chromatography. Exogenous and above all endogenous blood contamination were taken into account with the hematocrit as well as blood and tissue haemoglobin concentrations. Comparisons of tissue concentrations were made for each sampling time, according to values obtained for a specific tissue with both doses on one hand, and on the other to values obtained with a specific dose in different tissues. The calculated pharmacodynamic parameters, which are considered to be predictive for bacteriological and clinical efficacy, result directly from tissue concentrations of AMX. tissue inhibitory quotients (IQtissue = Tissue concentration/MIC). time above MICs for serum and tissue concentrations (T > MIC). As regards AMX, whatever the dose, at 1 h 30 and at 3 hrs, tissue concentrations did not differ

Mg-Ca Alloys Produced by Reduction of CaO: Understanding of ECO-Mg Alloy Production

NASA Astrophysics Data System (ADS)

Jung, In-Ho; Lee, Jin Kyu; Kim, Shae K.

2017-04-01

There have been long debates about the environment conscious (ECO) Mg technology which utilizes CaO to produce Ca-containing Mg alloys. Two key process technologies of the ECO-Mg process are the chemical reduction of CaO by liquid Mg and the maintenance of melt cleanliness during the alloying of Ca. Thermodynamic calculations using FactSage software were performed to explain these two key issues. In addition, an experimental study was performed to compare the melt cleanliness of the Ca-containing Mg alloys produced by the conventional route with metallic Ca and the ECO-Mg route with CaO.

Synthesis of Mg(OH) 2, MgO, and Mg nanoparticles using laser ablation of magnesium in water and solvents

NASA Astrophysics Data System (ADS)

Phuoc, Tran X.; Howard, Bret. H.; Martello, Donald V.; Soong, Yee; Chyu, Minking K.

2008-11-01

Laser ablation of magnesium in deionized water (DW), solutions of DW and sodium dodecyl sulfate (SDS) with different concentrations, acetone and 2-propanol has been conducted. The results showed that ablation in acetone and 2-propanol yielded MgO and Mg nanocrystallites as isolated particles and agglomerated chains probably intermixed with organic residues resulting from the alteration/decomposition of the solvents under the high-energy conditions. Brucite-like Mg(OH) 2 particles were mainly produced by laser ablation of Mg in either DW or DW-SDS solutions. Ablation in DW yielded particles of fiber-like shapes having a diameter of about 5-10 nm and length as long as 150 nm. Materials produced in DW-SDS solutions were composed of various size and shape particles. Some had rough surfaces with irregular shapes. Small particles were about 20-30 nm and larger particles were about 120 nm. Particles with rod-like, triangular, and plate-like shapes were also observed.

The MG Composite

PubMed Central

Burns, Ted M.; Conaway, Mark; Sanders, Donald B.

2010-01-01

Objective: To study the concurrent and construct validity and test-retest reliability in the practice setting of an outcome measure for myasthenia gravis (MG). Methods: Eleven centers participated in the validation study of the Myasthenia Gravis Composite (MGC) scale. Patients with MG were evaluated at 2 consecutive visits. Concurrent and construct validities of the MGC were assessed by evaluating MGC scores in the context of other MG-specific outcome measures. We used numerous potential indicators of clinical improvement to assess the sensitivity and specificity of the MGC for detecting clinical improvement. Test-retest reliability was performed on patients at the University of Virginia. Results: A total of 175 patients with MG were enrolled at 11 sites from July 1, 2008, to January 31, 2009. A total of 151 patients were seen in follow-up. Total MGC scores showed excellent concurrent validity with other MG-specific scales. Analyses of sensitivities and specificities of the MGC revealed that a 3-point improvement in total MGC score was optimal for signifying clinical improvement. A 3-point improvement in the MGC also appears to represent a meaningful improvement to most patients, as indicated by improved 15-item myasthenia gravis quality of life scale (MG-QOL15) scores. The psychometric properties were no better for an individualized subscore made up of the 2 functional domains that the patient identified as most important to treat. The test-retest reliability coefficient of the MGC was 98%, with a lower 95% confidence interval of 97%, indicating excellent test-retest reliability. Conclusions: The Myasthenia Gravis Composite is a reliable and valid instrument for measuring clinical status of patients with myasthenia gravis in the practice setting and in clinical trials. PMID:20439845

Diffusion coefficients of Mg isotopes in MgSiO3 and Mg2SiO4 melts calculated by first-principles molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Liu, Xiaohui; Qi, Yuhan; Zheng, Daye; Zhou, Chen; He, Lixin; Huang, Fang

2018-02-01

The mass dependence of diffusion coefficient (D) can be described in the form of Di/Dj = (mj/mi)β, where m denotes masses of isotope i and j, and β is an empirical parameter as used to quantify the diffusive transport of isotopes. Recent advances in computation techniques allow theoretically calculation of β values. Here, we apply first-principles Born-Oppenheimer molecular dynamics (MD) and pseudo-isotope method (taking mj/mi = 1/24, 6/24, 48/24, 120/24) to estimate β for MgSiO3 and Mg2SiO4 melts. Our calculation shows that β values for Mg calculated with 24Mg and different pseudo Mg isotopes are identical, indicating the reliability of the pseudo-isotope method. For MgSiO3 melt, β is 0.272 ± 0.005 at 4000 K and 0 GPa, higher than the value calculated using classical MD simulations (0.135). For Mg2SiO4 melt, β is 0.184 ± 0.006 at 2300 K, 0.245 ± 0.007 at 3000 K, and 0.257 ± 0.012 at 4000 K. Notably, β values of MgSiO3 and Mg2SiO4 melts are significantly higher than the value in basalt-rhyolite melts determined by chemical diffusion experiments (0.05). Our results suggest that β values are not sensitive to the temperature if it is well above the liquidus, but can be significantly smaller when the temperature is close to the liquidus. The small difference of β between silicate liquids with simple compositions of MgSiO3 and Mg2SiO4 suggests that the β value may depend on the chemical composition of the melts. This study shows that first-principles MD provide a promising tool to estimate β of silicate melts.

CONTAMINACIÓN AMBIENTAL, VARIABILIDAD CLIMÁTICA Y CAMBIO CLIMÁTICO: UNA REVISIÓN DEL IMPACTO EN LA SALUD DE LA POBLACIÓN PERUANA

PubMed Central

Gonzales, Gustavo F.; Zevallos, Alisson; Gonzales-Castañeda, Cynthia; Nuñez, Denisse; Gastañaga, Carmen; Cabezas, César; Naeher, Luke; Levy, Karen; Steenland, Kyle

2015-01-01

RESUMEN El presente artículo es una revisión sobre la contaminación del agua, el aire y el efecto del cambio climático en la salud de la población peruana. Uno de los principales contaminantes del aire es el material particulado menor de 2,5 μ (PM 2,5), en la ciudad de Lima, anualmente 2300 muertes prematuras son atribuibles a este contaminante. Otro problema es la contaminación del aire domiciliario por el uso de cocinas con combustible de biomasa, donde la exposición excesiva a PM 2,5 dentro de las casas es responsable de aproximadamente 3000 muertes prematuras anuales entre adultos, con otro número desconocido de muertes entre niños debido a infecciones respiratorias. La contaminación del agua tiene como principales causas los desagües vertidos directamente a los ríos, minerales (arsénico) de varias fuentes, y fallas de las plantas de tratamiento. En el Perú, el cambio climático puede impactar en la frecuencia y severidad del fenómeno de El Niño oscilación del sur (ENSO) que se ha asociado con un incremento en los casos de enfermedades como cólera, malaria y dengue. El cambio climático incrementa la temperatura y puede extender las áreas afectadas por enfermedades transmitidas por vectores, además de tener efecto en la disponibilidad del agua y en la contaminación del aire. En conclusión, el Perú, pasa por una transición de factores de riesgo ambientales, donde coexisten riesgos tradicionales y modernos, y persisten los problemas infecciosos y crónicos, algunos de los cuales se asocian con problemas de contaminación de agua y de aire. PMID:25418656

Constraints on the ^22Ne(α,n)^25Mg reaction rate from ^natMg+n Total and ^25Mg(n,γ ) Cross Sections

NASA Astrophysics Data System (ADS)

Koehler, Paul

2002-10-01

The ^22Ne(α,n)^25Mg reaction is the neutron source during the s process in massive and intermediate mass stars as well as a secondary neutron source during the s process in low mass stars. Therefore, an accurate determination of this rate is important for a better understanding of the origin of nuclides heavier than iron as well as for improving s-process models. Also, because the s process produces seed nuclides for a later p process in massive stars, an accurate value for this rate is important for a better understanding of the p process. Because the lowest observed resonance in direct ^22Ne(α,n)^25Mg measurements is considerably above the most important energy range for s-process temperatures, the uncertainty in this rate is dominated by the poorly known properties of states in ^26Mg between this resonance and threshold. Neutron measurements can observe these states with much better sensitivity and determine their parameters much more accurately than direct ^22Ne(α,n)^25Mg measurements. I have analyzed previously reported Mg+n total and ^25Mg(n,γ ) cross sections to obtain a much improved set of resonance parameters for states in ^26Mg in this region, and an improved estimate of the uncertainty in the ^22Ne(α,n)^25Mg reaction rate. This work was supported by the U.S. DOE under contract No. DE-AC05-00OR22725 with UT-Battell, LLC.

Measuring one nucleon transfer reaction 24Mg( p, d)23Mg for astrophysical reaction rates

NASA Astrophysics Data System (ADS)

Lee, E. J.; Chae, K. Y.

2017-12-01

The level structure of a radionuclide 23Mg has been studied by using the 24Mg( p, d)23Mg one nucleon transfer reaction measurement for the astrophysical 19Ne(α, γ)23Mg reaction rate. A 41 MeV proton beam was produced and accelerated at the 25 MV tandem accelerator of the Holifield Radioactive Ion Beam Facility of the Oak Ridge National Laboratory in the United States. The beam particles impinged on an isotopically-enriched 24Mg solid target. Angular distributions of recoiling deuterons were extracted by using a large area silicon strip detector array. By comparing the experimentally-obtained angular distributions with zero range distorted wave Born approximation calculations, spins and parities of three energy levels of 23Mg could be constrained for the first time, which is very important information needed to understand the 19Ne(α, γ)23Mg reaction rate.

The Recrystallization Behavior of Unalloyed Mg and a Mg-Al Alloy

NASA Astrophysics Data System (ADS)

Murphy, Aeriel D.; Allison, John E.

2018-02-01

The static recrystallization behavior of pure Mg and Mg-4Al was characterized over a range of annealing temperatures. The electron backscatter diffraction grain orientation spread technique was used to quantify the level of recrystallization at various annealing times. Recrystallization kinetics were characterized using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) relationship and it was found that two sequential annealing stages exist. Stage 1 involves heterogeneous nucleation of recrystallization in regions with a high stored energy, including twins and grain boundaries, and can be represented by an Avrami exponent of n 1 ranging from 0.35 to 0.6. During Stage 2, recrystallization occurred predominately in the interior of deformed grains with incomplete recrystallization generally observed even at annealing times in excess of two weeks. The second recrystallization stage exhibited a much lower Avrami exponent, n 2, ranging from 0.02 to 0.2. Increasing the starting grain size in the pure Mg condition led to a significant delay in recrystallization. The addition of Al had a minimal effect on the recrystallization kinetics of Mg.

Esomeprazole 40 mg provides improved intragastric acid control as compared with lansoprazole 30 mg and rabeprazole 20 mg in healthy volunteers.

PubMed

Wilder-Smith, Clive H; Röhss, Kerstin; Nilsson-Pieschl, Catharina; Junghard, Ola; Nyman, Lars

2003-01-01

To compare the effects of standard-dose esomeprazole with those of standard doses of lansoprazole and rabeprazole on intragastric pH during repeated daily oral dosing in healthy volunteers. In two standardized, randomized crossover studies, Helicobacter pylori negative healthy volunteers (study A: 19 males, 5 females; study B: 13 males, 10 females) received esomeprazole 40 mg and either lansoprazole 30 mg (study A) or rabeprazole 20 mg (study B) orally once daily in the morning for 5 days. Continuous 24-hour intragastric pH recording was performed on day 5. The intragastric pH was maintained >4 for 65% (95% CI 59.5-71.3) of the 24-hour period with esomeprazole and for 53% of the time (95% CI 47.0-58.9) with lansoprazole in study A (p < 0.001). In study B, the proportion of time with pH >4 was 61% (95% CI 53.6-68.3) with esomeprazole versus 45% (95% CI 37.7-52.5) with rabeprazole (p = 0.005). The 24-hour median pH and the proportion of volunteers with intragastric pH >4 for > or =12 h and > or =16 h were significantly higher with esomeprazole than with either lansoprazole or rabeprazole. Esomeprazole 40 mg provides significantly more effective and more sustained gastric acid control than lansoprazole 30 mg or rabeprazole 20 mg in healthy volunteers. Copyright 2003 S. Karger AG, Basel

Three diverse target preparations: 14C (12 mg/cm 2), 71Ga 24Mg (12 mg/cm 271Ga, 3 mg/cm 224Mg), and 66,67Zn (1.8-14.9 mg/cm 2)

NASA Astrophysics Data System (ADS)

Lozowski, W. R.

1989-10-01

A natural-carbon analog of fluffy, intractable 14C powder was produced. With it, a method was developed to produce a pressed disk of 14C of 12.7-mg/cm 2 thickness and 1.27-cm diameter, bound with 2.1 wt.% of adhesive. Aluminized Mylar cover foils and a fritted-disc filter were used to contain the target for ( overlinep, p') experiments. Reduction of 71Ga 2O 3 to the metal was accomplished with an efficiency of 94.3% in a small electroplating cell. Magnesium was chosen as the companion element because 50 at.% could be tolerated in the (p, n) experiment, and GaMg has a melting point of 646 K. A 1.27-cm diameter target, supported at the edge by a Mg foil, was produced in several simple steps. Directly rollable 66,67Zn foils were obtained from an electroplating cell with a Pt screen anode and a highly polished tungsten-carbide cathode. Plating times of 3 h provided metal-recovery efficiencies ranging from 94.2 to 96.5%. The as-deposited foils had many holes but were hole-free and shiny after reduction of 25% by pack rolling.

Magnesium isotope fractionation between brucite [Mg(OH)2] and Mg aqueous species: Implications for silicate weathering and biogeochemical processes

NASA Astrophysics Data System (ADS)

Li, Weiqiang; Beard, Brian L.; Li, Chengxiang; Johnson, Clark M.

2014-05-01

Brucite, with its octahedral structure, has a lattice configuration that is similar to the Mg-bearing octahedral layers in phyllosilicates. Understanding stable Mg isotope fractionation between brucite and aqueous solution therefore bears on interpretation of Mg isotope data in natural weathering systems. In this study, we experimentally determined Mg isotope fractionation between brucite and two Mg aqueous species, the free Mg aquo ion ([Mg(OH2)6]2+) and EDTA-bonded Mg (Mg-EDTA2-). Results from recrystallization and brucite synthesis experiments suggest mild preferential partitioning of light Mg isotopes into brucite compared to Mg aquo ions at low temperatures, where measured ΔMgbrucite-Mg26 fractionation increased from ca. -0.3‰ at 7 °C, to ca. -0.2‰ at 22 °C, to ca. 0‰ at 40 °C. MgO hydrolysis experiments in EDTA-bearing solutions suggest that the ΔMgbrucite-Mg-EDTA26 fractionation is ⩾+2.0‰ at 22 °C, indicating that light Mg isotopes strongly partition into Mg-EDTA complex relative to brucite, as well as relative to Mg aquo ions. Magnesium atoms in brucite, Mg aquo ions, and Mg-EDTA complexes are all octahedrally coordinated, and the measured Mg isotope fractionations correlate with average bond lengths for Mg. Aqueous Mg ions have the shortest bond length among the three phases, and enrich heavy Mg isotopes relative to brucite and Mg-EDTA. In contrast, Mg-EDTA has the longest average bond length for Mg, and enriches light Mg isotopes relative to Mg aquo ions and brucite; the relatively long Mg-EDTA bond suggests that organically bound Mg may commonly have low 26Mg/24Mg ratios, which may explain proposed "vital" effects for stable Mg isotopes. Such relations between bond length and Mg isotope fractionation could be extended to other phyllosilicates such as serpentine- and clay-group minerals where Mg is also octahedrally coordinated.

Atomic simulations of deformation mechanisms of crystalline Mg/amorphous Mg-Al nanocomposites

NASA Astrophysics Data System (ADS)

Song, H. Y.; Li, Y. L.

2015-09-01

The effects of amorphous boundary (AB) spacing on the deformation behavior of crystalline/amorphous (C/A) Mg/Mgsbnd Al nanocomposites under tensile load are investigated using molecular dynamics method. The results show that the plasticity of nano-polycrystal Mg can be enhanced with the introduction of C/A interfaces. For samples 5.2 nm in AB spacing and larger, the superior tensile ductility and nearly perfect plastic flow behavior occur during plastic deformation. The studies indicate that the cooperative interactions between crystalline and amorphous are the main reason for excellent ductility enhancements in C/A Mg/Mgsbnd Al nanocomposites.

Ca-Mg Carbonate Cements in Ophiolite-Hosted Creek Waters of the Del Puerto Ophiolite, CA, and their Potential Significance as a Planetary Biosignature

NASA Astrophysics Data System (ADS)

Blank, J. G.

2015-12-01

Serpentinization, the reaction at moderate pressure and temperature of water with olivine and pyroxene that are common in basalts and ultramafic rocks, results in the formation of alkaline fluids and the precipitation of a variety of secondary minerals. Terrestrial localities where active serpentinization is occurring are ideal Mars analogs for examining the characteristics of an environment that possesses two of the key features that we assume necessary to host life: water and an internally generated energy source. This study focuses on a related but different feature present where active serpentinization is occurring - namely, carbonate cements forming under plain air in the vicinity of Adobe Springs, CA. This site is located in the Del Puerto ophiolite about 150 km ESE of San Francisco, in the Coast Range of California. Two alkaline spring water compositions have been described at the site, a Ca-OH water (which is not currently being emitted by the active springs), and a Mg-CO3 water. Abundant dolomitic and calcitic carbonate cements are found in the creek drainages near the springs, associated with a diverse microbial community. We conducted a systematic study of the carbonate cements using SEM, EMP, XRD, TEM, and SIMS, focusing on sub-mm variations in texture, mineral chemistry and stable isotope (COH) composition. We compared our measurements with thermodynamic modeling results constrained by chemical analysis of water chemistry from the site and known partition coefficients and stable isotope fractionation factors. The wide range of carbonate compositions and textures observed at the Adobe Springs site suggests that more than one process is involved in their precipitation, including the possibility of microbially mediated dolomite mineralization. These carbonate cements could be a mineralogic biomarker of serpentinization and microbiological processes on Mars and other rocky planets and, therefore, prime targets for future astrobiological investigations.

La implantacion del enfoque constructivista en el aula de ciencia: Estudio de caso multiple

NASA Astrophysics Data System (ADS)

Arroyo Betancourt, Luz I.

participantes basado en lo que estas manifestaron en su practica didactica. Dos maestras coinciden en una vision constructivista social de la construccion del conocimiento, del aprendizaje y de los metodos didacticos. La otra manifesto una vision constructivista piagetiana en el aprendizaje, los metodos didacticos y en la construccion del conocimiento. Se espera que este trabajo, ademas de promover los estudios de caso sobre el enfoque constructivista de ensenanza en el contexto puertorriqueno, sirva para que los maestros, que estan transformando su enfoque educativo de uno tradicional a uno constructivista, tengan una vision mas clara de la implantacion de este enfoque. Se espera ademas que sirva para que el Departamento de Educacion y sus programas de adiestramiento y readiestramiento en servicio, asi como las universidades y sus programas de preparacion de maestros, tomen en cuenta los resultados y recomendaciones de este estudio al revisar sus programas.

Mg concentration profile and its control in the low temperature grown Mg-doped GaN epilayer

NASA Astrophysics Data System (ADS)

Liu, S. T.; Yang, J.; Zhao, D. G.; Jiang, D. S.; Liang, F.; Chen, P.; Zhu, J. J.; Liu, Z. S.; Liu, W.; Xing, Y.; Zhang, L. Q.; Wang, W. J.; Li, M.; Zhang, Y. T.; Du, G. T.

2018-01-01

In this work, the Cp2Mg flux and growth pressure influence to Mg doping concentration and depth profiles is studied. From the SIMS measurement we found that a transition layer exists at the bottom region of the layer in which the Mg doping concentration changes gradually. The thickness of transition layer decreases with the increases of Mg doping concentration. Through analysis, we found that this is caused by Ga memory effect which the Ga atoms stay residual in MOCVD system will react with Mg source, leading a transition layer formation and improve the growth rate. And the Ga memory effect can be well suppressed by increasing Mg doping concentration and growth pressure and thus get a steep Mg doping at the bottom region of p type layer.

Celulas solares e sensores de filme fino de silicio depositados sobre substratos flexiveis =

NASA Astrophysics Data System (ADS)

Pinto, Emilio Sergio Marins Vieira

Celulas solares flexiveis de filmes finos de silicio sao geralmente fabricadas a baixa temperatura sobre substratos de plastico ou a mais elevadas temperaturas sobre folhas de aco. Esta tese reporta o estudo da deposicao de filmes finos sobre diferentes substratos de plastico, transparentes e coloridos, para celulas solares do tipo sobrestrato e substrato, respectivamente. Como objetivo co-lateral, os filmes dopados depositados sobre plastico foram usados como sensores de deformacao, utilizando as suas propriedades piezo-resistivas. Elevadas taxas de deposicao dos filmes de silicio depositados sobre plastico foram obtidas a baixa temperatura do substrato (150ºC) por rf-PECVD. A influencia de diferentes parametros de deposicao sobre as propriedades e taxa de deposicao dos filmes resultantes foram estudados e correlacionados. Celulas solares de filmes finos de silicio amorfo e microcristalino foram desenvolvidas a baixas temperaturas sobre plasticos. Eficiencias de 5 - 6.5% foram alcancadas para as celulas amorfas e 7.5% para as celulas microcristalinas. Efeitos de aprisionamento da luz foram estudados atraves da texturizacao por ablacao laser de substratos de plastico e corrosao umida de TCO sobre plastico. Filmes finos de silicio microcristalino, depositados por HW-CVD, com fator piezoresistivo de -32.2, foram usados para fabricar sensores de deformacao em uma membrana plastica muito fina (15 μm). Estruturas de teste em textil e a miniaturizacao dos sensores piezoresistivos depositados sobre substratos flexiveis de poliimida foram abordados.

Quasicrystal-reinforced Mg alloys

PubMed Central

Kyun Kim, Young; Tae Kim, Won; Hyang Kim, Do

2014-01-01

The formation of the icosahedral phase (I-phase) as a secondary solidification phase in Mg–Zn–Y and Mg–Zn–Al base systems provides useful advantages in designing high performance wrought magnesium alloys. The strengthening in two-phase composites (I-phase + α-Mg) can be explained by dispersion hardening due to the presence of I-phase particles and by the strong bonding property at the I-phase/matrix interface. The presence of an additional secondary solidification phase can further enhance formability and mechanical properties. In Mg–Zn–Y alloys, the co-presence of I and Ca2Mg6Zn3 phases by addition of Ca can significantly enhance formability, while in Mg–Zn–Al alloys, the co-presence of the I-phase and Mg2Sn phase leads to the enhancement of mechanical properties. Dynamic and static recrystallization are significantly accelerated by addition of Ca in Mg–Zn–Y alloy, resulting in much smaller grain size and more random texture. The high strength of Mg–Zn–Al–Sn alloys is attributed to the presence of finely distributed Mg2Sn and I-phase particles embedded in the α-Mg matrix. PMID:27877660

A fundamental study on the [(μ-Cl) 3 Mg 2 (THF) 6 ] + dimer electrolytes for rechargeable Mg batteries

DOE PAGES

Liu, Tianbiao; Cox, Jonathan T.; Hu, Dehong; ...

2015-01-05

We present a fundamental study on [(μ-Cl) 3 Mg 2 (THF) 6 ] + dimer electrolytes using various physical methods including Subambient Pressure Ionization with Nanoelectrospray Mass spectrometry (SPIN-MS), Raman spectroscopy, 25Mg{ 1H} NMR, 27Al{ 1H} NMR and electrochemical analysis. For the first time, long time sought THF solvated [MgCl] + species was experimentally characterized by SPIN mass spectrometry in the solution of the Mgdimer containing electrolyte, confirming the mono-Cl- abstraction reaction between MgCl 2 and an Al Lewis acid. Solvated MgCl 2 in the electrolyte was confirmed by Raman spectroscopy. The experimental results establish the previously proposed dimerization equilibriummore » of solvated [MgCl] + and MgCl2 with [(μ-Cl) 3Mg 2(THF)6] +. 25Mg{ 1H} NMR, 27Al{ 1H} NMR and electrochemical analysis on chloration reaction of [(μ-Cl) 3Mg 2(THF) 6]AlPh 3Cl with external Cl- led to further insights on the coordination chemistry of the dimer electrolyte. Finally, a comprehensive mechanism is proposed for the reversible electrochemical Mg deposition and stripping and Mg 2+ and Cl- ion transports of the Mg dimer electrolytes in rechargeable Mg batteries.« less

Growth dynamics controllable deposition of homoepitaxial MgO films on the IBAD-MgO substrates

NASA Astrophysics Data System (ADS)

Wang, Wei; Liu, Lin-Fei; Yao, Yan-Jie; Lu, Sai-Dan; Wu, Xiang; Zheng, Tong; Liu, Shun-Fan; Li, Yi-Jie

2018-03-01

Homoepitaxial MgO (Homo-MgO) films, deposited by RF magnetic sputtering method in various experimental conditions, were systematically studied using growth dynamics in older to fully understand their growth mechanism. The results showed that high quality Homo-MgO films could be obtained at high oxygen partial pressure and the thickness of Homo-MgO films were seriously affected by the ratio of O2/Ar. Moreover, an interesting phenomenon we addressed was the growth mode changed with varying the sputtering power, leading to different surface morphology. Most importantly, apart from Homo-MgO films, our theory can also be appropriate for other oxide films grown by RF magnetic sputtering technology.

Lumacaftor-Ivacaftor in Patients with Cystic Fibrosis Homozygous for Phe508del CFTR.

PubMed

Wainwright, Claire E; Elborn, J Stuart; Ramsey, Bonnie W; Marigowda, Gautham; Huang, Xiaohong; Cipolli, Marco; Colombo, Carla; Davies, Jane C; De Boeck, Kris; Flume, Patrick A; Konstan, Michael W; McColley, Susanna A; McCoy, Karen; McKone, Edward F; Munck, Anne; Ratjen, Felix; Rowe, Steven M; Waltz, David; Boyle, Michael P

2015-07-16

Cystic fibrosis is a life-limiting disease that is caused by defective or deficient cystic fibrosis transmembrane conductance regulator (CFTR) protein activity. Phe508del is the most common CFTR mutation. We conducted two phase 3, randomized, double-blind, placebo-controlled studies that were designed to assess the effects of lumacaftor (VX-809), a CFTR corrector, in combination with ivacaftor (VX-770), a CFTR potentiator, in patients 12 years of age or older who had cystic fibrosis and were homozygous for the Phe508del CFTR mutation. In both studies, patients were randomly assigned to receive either lumacaftor (600 mg once daily or 400 mg every 12 hours) in combination with ivacaftor (250 mg every 12 hours) or matched placebo for 24 weeks. The primary end point was the absolute change from baseline in the percentage of predicted forced expiratory volume in 1 second (FEV1) at week 24. A total of 1108 patients underwent randomization and received study drug. The mean baseline FEV1 was 61% of the predicted value. In both studies, there were significant improvements in the primary end point in both lumacaftor-ivacaftor dose groups; the difference between active treatment and placebo with respect to the mean absolute improvement in the percentage of predicted FEV1 ranged from 2.6 to 4.0 percentage points (P<0.001), which corresponded to a mean relative treatment difference of 4.3 to 6.7% (P<0.001). Pooled analyses showed that the rate of pulmonary exacerbations was 30 to 39% lower in the lumacaftor-ivacaftor groups than in the placebo group; the rate of events leading to hospitalization or the use of intravenous antibiotics was lower in the lumacaftor-ivacaftor groups as well. The incidence of adverse events was generally similar in the lumacaftor-ivacaftor and placebo groups. The rate of discontinuation due to an adverse event was 4.2% among patients who received lumacaftor-ivacaftor versus 1.6% among those who received placebo. These data show that lumacaftor in

Effect of MgO spacer and annealing on interface and magnetic properties of ion beam sputtered NiFe/Mg/MgO/CoFe layer structures

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

Bhusan Singh, Braj; Chaudhary, Sujeet

2012-09-15

The effect of variation in the thickness of ion assisted ion beam sputtered MgO spacer layer deposited at oxygen ion assisted energy of 50 eV on the extent of magnetic coupling of NiFe and CoFe layers in Si/NiFe(10 nm)/Mg(1 nm)/MgO(2,4,6 nm)/CoFe(10 nm) sandwich structure is investigated. At MgO spacer layer thickness of 4 nm, the separate reversal of magnetizations of the two ferromagnetic layers is observed in the hystresis loop recorded along easy direction. This results in a 3.5 Oe wide plateau like region during magnetization reversal, which became 4.5 Oe at 6 nm thin MgO. At 2 nm thinmore » MgO, the absence of plateau during magnetization reversal region revealed ferromagnetic coupling between the two ferromagnetic layers, which is understood to arise due to the growth of very thin and low density (1.22 gm/cc) MgO spacer layer, indicating the presence of pinholes as revealed by x-ray reflectometry. After vaccum annealing (200 Degree-Sign C/1 h), the plateau region for 4 and 6 nm thin MgO case decreased to 1.5 Oe and 2.0 Oe, respectively, due to enhanced interface roughness/mixing. In addition, an enhancement of the in-plane magnetic anisotropy is also observed.« less

Many Mg-Mg bonds form the core of the Mg16Cp*8Br4K cluster anion: the key to a reassessment of the Grignard reagent (GR) formation process?

PubMed

Kruczyński, T; Henke, F; Neumaier, M; Bowen, K H; Schnöckel, H

2016-02-01

It caused a sensation eight years ago, when the first room temperature stable molecular compound with a Mg-Mg bond (LMgMgL, L = chelating ligand) containing magnesium in the oxidation state +1 was prepared. Here, we report the preparation of a [Mg 16 Cp*8Br 4 K] - cluster anion (Cp* = pentamethylcyclopentadiene) with 27 Mg-Mg bonds. It has been obtained through the reaction of KCp* with a metastable solution of MgBr in toluene. A highly-resolved Fourier transform mass spectrum (FT-MS) of this cluster anion, brought into vacuum by electrospraying its solution in THF, provides the title cluster's stoichiometry. This Mg 16 cluster together with experiments on the metastable solution of MgBr show that: during the formation process of GRs (Grignard reagents) which are involved in most of sophisticated syntheses of organic products, not the highly reactive MgBr radical as often presumed, but instead the metalloid Mg 16 Cp*8Br 4 cluster anion and its related cousins that are the operative intermediates along the pathway from Mg metal to GRs ( e.g. Cp*MgBr).

High-pressure Phase Relation In The MgAl2O4-Mg2SiO4 System

NASA Astrophysics Data System (ADS)

Kojitani, H.; Hisatomi, R.; Akaogi, M.

2005-12-01

High-pressure and high-temperature experiments indicate that high-pressure phases of oceanic basalts contain Al-rich phases. MgAl2O4 with calcium ferrite-type crystal structure is considered as a main component of such the Al-rich phases. Since the calcium ferrite-type MgAl2O4 can be synthesized at only the maximum pressure of a Kawai-type high-pressure apparatus with tungsten carbide (WC) anvils, the amount of a synthesized sample is very limited. Therefore, the crystal structure of the calcium ferrite-type MgAl2O4 has been hardly known in detail due to these difficulties in sample synthesis. In our high-pressure experiments in the MgO-Al2O3-SiO2 system, it was shown that Mg2SiO4 component could be dissolved in the MgAl2O4 calcium ferrite. In this study, we tried to synthesize a single phase MgAl2O4 calcium ferrite sample and to make the Rietveld refinement of the XRD pattern of the sample. The high-pressure phase relations in the MgAl2O4-Mg2SiO4 system were studied to know the stability field of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions. Lattice parameters-composition relation of the MgAl2O4-Mg2SiO4 calcium ferrite solid solutions was also determined. High-pressure and high-temperature experiments were performed by using a Kawai-type high-pressure apparatus at Gakushuin University. WC anvils with truncated edge length of 1.5 mm were used. Heating was made by a Re heater. Temperature was measured by a Pt/Pt-13%Rh thermocouple. Starting materials for the phase relation experiments were the mixture of MgO, Al2O3 and SiO2 with bulk compositions of MgAl2O4:Mg2SiO4 = 90:10, 78:22, 70:30 and 50:50. The starting materials were held at 21-27 GPa and 1600 °C for 3 hours and then were recovered by the quenching method. The MgAl2O4 calcium ferrite sample for the Rietveld analysis was prepared by heating MgAl2O4 spinel at 27 GPa and about 2200 °C for one hour. Powder X-ray diffraction (XRD) profiles of obtained samples were measured by using a X-ray diffractometer

A systematic study of 25Mg NMR in paramagnetic transition metal oxides: applications to Mg-ion battery materials.

PubMed

Lee, Jeongjae; Seymour, Ieuan D; Pell, Andrew J; Dutton, Siân E; Grey, Clare P

2016-12-21

Rechargeable battery systems based on Mg-ion chemistries are generating significant interest as potential alternatives to Li-ion batteries. Despite the wealth of local structural information that could potentially be gained from Nuclear Magnetic Resonance (NMR) experiments of Mg-ion battery materials, systematic 25 Mg solid-state NMR studies have been scarce due to the low natural abundance, low gyromagnetic ratio, and significant quadrupole moment of 25 Mg (I = 5/2). This work reports a combined experimental 25 Mg NMR and first principles density functional theory (DFT) study of paramagnetic Mg transition metal oxide systems Mg 6 MnO 8 and MgCr 2 O 4 that serve as model systems for Mg-ion battery cathode materials. Magnetic parameters, hyperfine shifts and quadrupolar parameters were calculated ab initio using hybrid DFT and compared to the experimental values obtained from NMR and magnetic measurements. We show that the rotor assisted population transfer (RAPT) pulse sequence can be used to enhance the signal-to-noise ratio in paramagnetic 25 Mg spectra without distortions in the spinning sideband manifold. In addition, the value of the predicted quadrupolar coupling constant of Mg 6 MnO 8 was confirmed using the RAPT pulse sequence. We further apply the same methodology to study the NMR spectra of spinel compounds MgV 2 O 4 and MgMn 2 O 4 , candidate cathode materials for Mg-ion batteries.

Mg-MOF-74/MgF₂ Composite Coating for Improving the Properties of Magnesium Alloy Implants: Hydrophilicity and Corrosion Resistance.

PubMed

Liu, Wei; Yan, Zhijie; Ma, Xiaolu; Geng, Tie; Wu, Haihong; Li, Zhongyue

2018-03-07

Surface modification on Mg alloys is highly promising for their application in the field of bone repair. In this study, a new metal-organic framework/MgF₂ (Mg-MOF-74/MgF₂) composite coating was prepared on the surface of AZ31B Mg alloy via pre-treatment of hydrofluoric acid and in situ hydrothermal synthesis methods. The surface topography of the composite coating is compact and homogeneous, and Mg-MOF-74 has good crystallinity. The corrosion resistance of this composite coating was investigated through Tafel polarization test and immersion test in simulated body fluid at 37 °C. It was found that Mg-MOF-74/MgF₂ composite coating significantly slowed down the corrosion rate of Mg alloy. Additionally, Mg-MOF-74/MgF₂ composite coating expresses super-hydrophilicity with the water contact angle of nearly 0°. In conclusion, on the basis of MgF₂ anticorrosive coating, the introduction of Mg-MOF-74 further improves the biological property of Mg alloys. At last, we propose that the hydrophilicity of the composite coating is mainly owing to the large number of hydroxyl groups, the high specific surface area of Mg-MOF-74, and the rough coating produced by Mg-MOF-74 particles. Hence, Mg-MOF-74 has a great advantage in enhancing the hydrophilicity of Mg alloy surface.

Toward understanding the roaming mechanism in H + MgH → Mg + HH reaction

DOE PAGES

Mauguiere, Frederic A. L.; Collins, Peter; Stamatiadis, Stamatis; ...

2016-02-26

The roaming mechanism in the reaction H + MgH →Mg + HH is investigated by classical and quantum dynamics employing an accurate ab initio threedimensional ground electronic state potential energy surface. The reaction dynamics are explored by running trajectories initialized on a four-dimensional dividing surface anchored on three-dimensional normally hyperbolic invariant manifold associated with a family of unstable orbiting periodic orbits in the entrance channel of the reaction (H + MgH). By locating periodic orbits localized in the HMgH well or involving H orbiting around the MgH diatom, and following their continuation with the total energy, regions in phase spacemore » where reactive or nonreactive trajectories may be trapped are found. In this way roaming reaction pathways are deduced in phase space. Patterns similar to periodic orbits projected into configuration space are found for the quantum bound and resonance eigenstates. Roaming is attributed to the capture of the trajectories in the neighborhood of certain periodic orbits. As a result, the complex forming trajectories in the HMgH well can either return to the radical channel or “roam” to the MgHH minimum from where the molecule may react.« less

Refinements in an Mg/MgH2/H2O-Based Hydrogen Generator

NASA Technical Reports Server (NTRS)

Kindler, Andrew; Huang, Yuhong

2010-01-01

Some refinements have been conceived for a proposed apparatus that would generate hydrogen (for use in a fuel cell) by means of chemical reactions among magnesium, magnesium hydride, and steam. The refinements lie in tailoring spatial and temporal distributions of steam and liquid water so as to obtain greater overall energy-storage or energy-generation efficiency than would otherwise be possible. A description of the prior art is prerequisite to a meaningful description of the present refinements. The hydrogen-generating apparatus in question is one of two versions of what was called the "advanced hydrogen generator" in "Fuel-Cell Power Systems Incorporating Mg-Based H2 Generators" (NPO-43554), NASA Tech Briefs, Vol. 33, No. 1 (January 2009), page 52. To recapitulate: The apparatus would include a reactor vessel that would be initially charged with magnesium hydride. The apparatus would exploit two reactions: The endothermic decomposition reaction MgH2-->Mg + H2, which occurs at a temperature greater than or equal to 300 C, and The exothermic oxidation reaction MgH2 + H2O MgO + 2H2, which occurs at a temperature greater than or equal to 330 C.

Uncovering the Local Magnesium Environment in the Metal–Organic Framework Mg 2 (dobpdc) Using 25 Mg NMR Spectroscopy

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

Xu, Jun; Blaakmeer, E. S. Merijn; Lipton, Andrew S.

The incorporation of N,N'-dimethylethylenediamine into an expanded MOF-74 framework has yielded a material (mmen-Mg2(dobpdc)) exhibiting “step-shaped” CO2 adsorption isotherms. The coordination of mmen at the Mg open metal center is essential for the unique cooperative adsorption mechanism elucidated for this material. Despite its importance for carbon capture, there is as yet no experimental structure determination available for the underlying metal– organic framework Mg2(dobpdc). Our 25Mg solid-state NMR data unravel the local Mg environments in several Mg2(dobpdc) samples, unambiguously confirming the formation of fivecoordinate Mg centers in the activated material and six-coordinate Mg centers in the solvent- or diamine-loaded samples, suchmore » as mmen-Mg2(dobpdc). A fraction of the Mg centers are locally disordered due to the framework deformation accompanied by the guest distributions and dynamics.« less

Acerca del moho

EPA Pesticide Factsheets

El moho forma parte del medio ambiente natural. Afuera del hogar, el moho juega un papel en la naturaleza al desintegrar materias organicas tales como las hojas que se han caido o los arboles muertos. El moho puede crecer adentro del hogar cuando las espor

Zolpidem 10 mg given at daytime is not antagonized by 300 mg caffeine in man.

PubMed

Mattila, M J; Nurminen, M L; Vainio, P; Vanakoski, J

1998-07-01

Caffeine counteracts various effects of traditional benzodiazepines (BZDs). As zolpidem, a short-acting hypnotic, is an atypical GABAA-BZD agonist, we investigated when caffeine would counteract the effects of zolpidem as well. In daytime study I, zolpidem 10 mg (capsule) and caffeine 150 or 300 mg (in decaffeinated coffee) were given, alone and in combinations, to parallel groups (n = 15-17) of healthy students in double-blind and placebo-controlled manner. Objective and subjective tests were done before and 45 min and 90 min after intake. Ranked delta values (changes from baseline) were analysed by one-way contrast ANOVA and Scheffe's tests. In daytime study II, four healthy subjects took zolpidem 10 mg alone, and together with blinded caffeine 250 mg or (at -45 min) erythromycin 750 mg. Objective and subjective effects were measured and plasma zolpidem concentrations assayed at baseline and 45 min and 90 min after zolpidem intake. In study I, practice effects after placebo (ad + 30%) were seen for letter cancellation and digit symbol substitution but not for flicker fusion tests. Zolpidem alone significantly impaired (P < 0.05 vs delta placebo) letter cancellation and digit symbol substitution at 45 min and 90 min, lowered the flicker fusion threshold at 45 min, and caused subjective drowsiness, mental slowness, clumsiness and feeling of poor performance. Caffeine alone showed a non-significant trend to improve objective performance. The combined effects of zolpidem and either dose of caffeine matched those measured after zolpidem alone. Zolpidem + caffeine 300 mg was not stronger than zolpidem + caffeine 150 mg in impairing immediate memory and causing subjective sedation. In study II, zolpidem caused objective and subjective sedation; neither caffeine nor erythromycin modulated the effects of zolpidem or plasma zolpidem concentrations. The sedative effects of 10 mg of zolpidem are not antagonized by 150-300 mg of caffeine in pharmacodynamic or pharmacokinetic

Produccion Gaseosa del Cometa Halley: Erupciones Y Fotodisociacion del Radical OH

NASA Astrophysics Data System (ADS)

Silva, A. M.; Mirabel, I. F.

1990-11-01

RESUMEN:En este trabajo informamos la detecci6n de 20 erupciones en la li'nea de =18cm (1667MHz) del radical OH en el Cometa Halley.Las observaciones incluyen todos los monitoreos existentes y se extienden desde 120 dias antes del perihelio hasta 90 dias despues.Se detectan bruscos crecimientos en el flujo medido,hasta un factor 1O,seguidos por decaimientos lentos asociados con la fotodisociaci6n del OH. Se obtuvieron valores para el tiempo de vida fotoquimico del OH y del H2O basandose en el modelo desarrollado previamente por Silva(1988). Esos tiempos de vida estan de acuerdo con predicciones teoricas y con las observaciones en el Ultravioleta, y los resultados, los que son fuertemente dependientes de la velocidad heliocentrica del Coineta (variando hasta un factor 6), han sido calculados para varios rangos de velocidad entre +28 y -28 km/seg. Key wo'L :

Mechanism of magnetoresistance ratio enhancement in MgO/NiFe/MgO heterostructure by rapid thermal annealing

NASA Astrophysics Data System (ADS)

Zhao, Chong-Jun; Liu, Yang; Zhang, Jing-Yan; Sun, Li; Ding, Lei; Zhang, Peng; Wang, Bao-Yi; Cao, Xing-Zhong; Yu, Guang-Hua

2012-08-01

To reveal thermal effects on the film quality/microstructure evolution and the resulted magnetoresistance (MR) ratio in MgO/NiFe/MgO heterostructures, positron annihilation spectroscopy studies have been performed. It is found that the ionic interstitials in the MgO layers recombine with the nearby vacancies at lower annealing temperatures (200-300 °C) and lead to a slow increase in sample MR. Meanwhile, vacancy defects agglomeration/removal and ordering acceleration in MgO will occur at higher annealing temperatures (450-550 °C) and the improved MgO and MgO/NiFe interfaces microstructure are responsible for the observed significant MR enhancement.

Efficacy and tolerability of the single-pill combination of aliskiren 300 mg/amlodipine 10 mg in hypertensive patients not controlled by olmesartan 40 mg/amlodipine 10 mg.

PubMed

Axthelm, Christoph; Sieder, Christian; Meister, Franziska; Kaiser, Edelgard

2012-01-01

We aimed to investigate whether the single pill combination (SPC) of aliskiren 300 mg and amlodipine 10 mg (ALIS 300/AMLO 10) improves blood pressure (BP) reduction in hypertensive patients not adequately controlled by the SPC olmesartan 40 mg and amlodipine 10 mg (OLM 40/AMLO 10). Open-label, non-randomized single-arm study. Patients with stage 2 hypertension were titrated to the SPC OLM 40/AMLO 10 (4-week Phase 1). If hypertension was not controlled they were switched to the SPC ALIS 300/AMLO 10 (4-week Phase 2). In the optional 4-week study extension hydrochlorothiazide (HCT) 12.5 mg was added. EudraCT 2009-016693-33. In the 342 patients treated, OLM 40/AMLO 10 reduced systolic BP (SBP)/diastolic BP (DBP) by 24.5/14.5 mmHg by end of Phase 1. Those 187 patients with uncontrolled hypertension at the end of Phase 1 switched to ALIS 300/AMLO 10 experienced a further SBP reduction of 5.1 mmHg (95% confidence interval [CI] 3.7 to 6.5, p < 0.0001) and a DBP reduction of 4.8 mmHg (95% CI 3.8 to 5.8; p < 0.0001) in Phase 2. DBP or SBP responder rates were achieved by 51.3% or 44.4%, respectively, SBP and DBP normalization by 36.4%. In 65 patients whose BP was not controlled in Phase 2, SPC ALIS 300/AMLO 10/HCT 12.5 mg decreased SBP/DBP by further 8.1/6.7 mmHg (p < 0.0001 each). No deaths or serious adverse events were noted. Significant adverse events leading to study discontinuation were reported in 2.6% (Phase 1), 2.7% (Phase 2), and 0% (extension). Limitations included the open-label, single-arm non-randomized design, and the relatively short duration. In this switch study reflecting clinical practice, patients with moderate hypertension not controlled by the SPC OLM 40/AMLO 10 achieved a clinically and statistically significant reduction of blood pressure from the SPC ALIS 300/AMLO 10 and the optional addition of HCT. All drug combinations were well tolerated.

Alterations of Mg2+ After Hemorrhagic Shock.

PubMed

Lee, Mun-Young; Yang, Dong Kwon; Kim, Shang-Jin

2017-11-01

Hemorrhagic shock is generally characterized by hemodynamic instability with cellular hypoxia and diminishing cellular function, resulting from an imbalance between systemic oxygen delivery and consumption and redistribution of fluid and electrolytes. Magnesium (Mg) is the fourth most abundant cation overall and second most abundant intracellular cation in the body and an essential cofactor for the energy production and cellular metabolism. Data for blood total Mg (tMg; free-ionized, protein-bound, and anion-bound forms) and free Mg 2+ levels after a traumatic injury are inconsistent and only limited information is available on hemorrhagic effects on free Mg 2+ as the physiologically active form. The aim of this study was to determine changes in blood Mg 2+ and tMg after hemorrhage in rats identifying mechanism and origin of the changes in blood Mg 2+ . Hemorrhagic shock produced significant increases in blood Mg 2+ , plasma tMg, Na + , K + , Cl - , anion gap, partial pressures of oxygen, glucose, and blood urea nitrogen but significant decreases in RBC tMg, blood Ca 2+ , HCO 3 - , pH, partial pressures of carbon dioxide, hematocrit, hemoglobin, total cholesterol, and plasma/RBC ATP. During hemorrhagic shock, K + , anion gap, and BUN showed significant positive correlations with changes in blood Mg 2+ level, while Ca 2+ , pH, and T-CHO correlated to Mg 2+ in a negative manner. In conclusion, hemorrhagic shock induced an increase in both blood-free Mg 2+ and tMg, resulted from Mg 2+ efflux from metabolic damaged cell with acidosis and ATP depletion.

Meningiomas del foramen magno: Reporte de 12 casos y revisión de la literatura

PubMed Central

Campero, Álvaro; Ajler, Pablo; Roman, Guillermo; Rivadeneira, Conrado

2017-01-01

Resumen Objetivo: El propósito del presente trabajo es presentar los resultados de 12 pacientes con diagnóstico de meningiomas del foramen magno (MFM), de localización anterior o lateral, operados con técnicas microquirúrgicas. Método: Desde Junio de 2005 a Diciembre de 2016, 12 pacientes con diagnóstico de MFM fueron intervenidos quirúrgicamente. Se evaluó: edad, sexo, localización de la lesión (anterior o lateral), sintomatología, tipo de abordaje utilizado y resultados postoperatorios. Resultados: De los pacientes intervenidos, 8 fueron mujeres y 4 varones. La edad promedio fue de 47 años. La localización fue anterior en 8 casos y lateral en 4 casos. La sintomatología más frecuente fue dolor occipito-cervical (8 casos), seguido de tetraparesia (3 casos). En los pacientes con MFM de localización anterior se realizó un abordaje extremo-lateral transcondilar (ELTC), mientras que en los tumores laterales el abordaje fue extremo-lateral retrocondilar (ELRC). En 10 casos la resección fue completa. En dos pacientes fue necesario dejar una pequeña lámina de meningioma sobre la arteria vertebral y a nivel del foramen yugular. Como complicaciones postoperatorias, 3 pacientes presentaron una paresia del XII nervio craneano y 2 pacientes paresia del XI nervio craneano; además, 1 paciente presentó una fístula de LCR. Conclusión: La cirugía de los MFM de localización anterior y lateral puede ser realizada de forma segura y efectiva. Es necesario: a) buen conocimiento anatómico de la región; b) disecar los músculos de la nuca en 2 planos, exponiendo el triángulo suboccipital y la arteria vertebral (AV); 3) realizar un abordaje ELRC en los tumores laterales, y ELTC en los tumores anteriores; y 4) buena técnica microquirúrgica. PMID:29142778

High-Capacity Mg-Organic Batteries Based on Nanostructured Rhodizonate Salts Activated by Mg-Li Dual-Salt Electrolyte.

PubMed

Tian, Jing; Cao, Dunping; Zhou, Xuejun; Hu, Jiulin; Huang, Minsong; Li, Chilin

2018-04-24

A magnesium battery is a promising candidate for large-scale transportation and stationary energy storage due to the security, low cost, abundance, and high volumetric energy density of a Mg anode. But there are still some obstacles retarding the wide application of Mg batteries, including poor kinetics of Mg-ion transport in lattices and low theoretical capacity in inorganic frameworks. A Mg-Li dual-salt electrolyte enables kinetic activation by dominant intercalation of Li-ions instead of Mg-ions in cathode lattices without the compromise of a stable Mg anode process. Here we propose a Mg-organic battery based on a renewable rhodizonate salt ( e. g., Na 2 C 6 O 6 ) activated by a Mg-Li dual-salt electrolyte. The nanostructured organic system can achieve a high reversible capacity of 350-400 mAh/g due to the existence of high-density carbonyl groups (C═O) as redox sites. Nanocrystalline Na 2 C 6 O 6 wired by reduced graphene oxide enables a high-rate performance of 200 and 175 mAh/g at 2.5 (5 C) and 5 A/g (10 C), respectively, which also benefits from a high intrinsic diffusion coefficient (10 -12 -10 -11 cm 2 /s) and pesudocapacitance contribution (>60%) of Na 2 C 6 O 6 for Li-Mg co-intercalation. The suppressed exfoliation of C 6 O 6 layers by a firmer non-Li pinning via Na-O-C or Mg-O-C and a dendrite-resistive Mg anode lead to a long-term cycling for at least 600 cycles. Such an extraordinary capacity/rate performance endows the Mg-Na 2 C 6 O 6 system with high energy and power densities up to 525 Wh/kg and 4490 W/kg (based on active cathode material), respectively, exceeding the level of high-voltage insertion cathodes with typical inorganic structures.

Kinetic analysis of MgB2 layer formation in advanced internal magnesium infiltration (AIMI) processed MgB2 wires

PubMed Central

Li, G. Z.; Sumption, M. D.; Collings, E. W.

2015-01-01

Significantly enhanced critical current density (Jc) for MgB2 superconducting wires can be obtained following the advanced internal Mg infiltration (AIMI) route. But unless suitable precautions are taken, the AIMI-processed MgB2 wires will exhibit incomplete MgB2 layer formation, i.e. reduced superconductor core size and hence suppressed current-carrying capability. Microstructural characterization of AIMI MgB2 wires before and after the heat treatment reveals that the reaction mechanism changes from a “Mg infiltration-reaction” at the beginning of the heat treatment to a “Mg diffusion-reaction” once a dense MgB2 layer is formed. A drastic drop in the Mg transport rate from infiltration to diffusion causes the termination of the MgB2 core growth. To quantify this process, a two-stage kinetic model is built to describe the MgB2 layer formation and growth. The derived kinetic model and the associated experimental observations indicate that fully reacted AIMI-processed MgB2 wires can be achieved following the optimization of B particle size, B powder packing density, MgB2 reaction activation energy and its response to the additions of dopants. PMID:26973431

Porous Ceramic Composite ZrO2(MgO)-MgO for Osteoimplantology

NASA Astrophysics Data System (ADS)

Buyakov, A. S.; Kulkov, S. N.

2017-02-01

Pore and crystalline structure, biocompatibility of ceramic composite ZrO2(MgO)-MgO were studied. The main mechanical characteristics were determined and it has been shown that compression strength directly depends on microstresses obtained from X-ray data. In-vitro studies of mesenchymal stromal stem cells (MMSC), cultivated on material surface are shown that cell proliferation and differentiation of MMSC goes throw osteogenic type.

Investigación del USGS sobre el ecosistema de arrecifes de coral en el Atlántico

USGS Publications Warehouse

Kuffner, Ilsa B.; Yates, Kimberly K.; Zawada, David G.; Richey, Julie N.; Kellogg, Christina A.; Toth, Lauren T.; Torres-Garcia, Legna M.

2015-10-23

Los arrecifes de coral son estructuras sólidas, biomineralizadas que protegen comunidades costeras actuando como barreras protectoras de peligros tales como los huracanes y los tsunamis. Estos proveen arena a las playas a través de procesos naturales de erosión, fomentan la industria del turismo, las actividades recreacionales y proveen hábitats pesqueros esenciales. La conti-nua degradación mundial de ecosistemas de arrecifes de coral está bien documentada. Existe la necesidad de enfoque y organización de la ciencia para entender los procesos complejos físicos y biológicos e interacciones que están afectando el estado de los arrecifes coralinos y su capacidad para responder a un entorno cambiante.

Bioequivalence of a single 400-mg dose of imatinib 100-mg oral tablets and a 400-mg tablet in healthy adult Korean volunteers.

PubMed

Lee, Hae Won; Seong, Sook Jin; Park, Sung Min; Lee, Joomi; Gwon, Mi-Ri; Kim, Hyun-Ju; Lim, Sung Mook; Lim, Mi-Sun; Kim, Woomi; Yang, Dong Heon; Yoon, Young-Ran

2015-06-01

Imatinib mesylate (IM) is a selective tyrosine kinase inhibitor for the treatment of chronic myeloid leukemia and gastrointestinal stromal tumors. A new once-daily 400-mg film-coated tablet of imatinib has been developed by a pharmaceutical company in Korea. The present study was designed to assess and compare the PK parameters, bioavailability, and bioequivalence of the new imatinib 400-mg formulation (test) versus the conventional 100-mg formulation (reference) administered as a single 400-mg dose in healthy adult male volunteers. This randomized, open-label, single-dose, two-way crossover study was conducted in healthy Korean male volunteers. Eligible subjects were randomly assigned in a 1 : 1 ratio to receive 400 mg of the test (one 400-mg tablet) or reference (four 100-mg tablets) formulation, followed by a 2-week washout period and administration of the alternate formulation. Serial blood samples were collected at 0 (predose), 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 10, 12, 24, 48, and 72 hours after administration. Plasma imatinib concentrations were determined using liquid chromatography coupled with tandem mass spectrometry. The formulations were to be considered bioequivalent if the 90% confidence intervals (CIs) of the adjusted geometric mean ratios for Cmax, AUC(0-t), and AUC(0-∞)ž were within the predetermined range of 0.80 - 1.25. In total, 35 subjects completed the study. No serious adverse event was reported during the study. The 90% CIs of the adjusted geometric mean ratios of the test formulation to the reference formulation for C(max), AUC(0-t) and AUC(0-∞)ž of imatinib were all within the bioequivalence criteria range of 0.8 - 1.25. The test formulation of imatinib met the Korean regulatory requirements for bioequivalence. Both imatinib formulations were well-tolerated in all subjects.

Mg-MOF-74/MgF2 Composite Coating for Improving the Properties of Magnesium Alloy Implants: Hydrophilicity and Corrosion Resistance

PubMed Central

Liu, Wei; Yan, Zhijie; Ma, Xiaolu; Geng, Tie; Wu, Haihong

2018-01-01

Surface modification on Mg alloys is highly promising for their application in the field of bone repair. In this study, a new metal–organic framework/MgF2 (Mg-MOF-74/MgF2) composite coating was prepared on the surface of AZ31B Mg alloy via pre-treatment of hydrofluoric acid and in situ hydrothermal synthesis methods. The surface topography of the composite coating is compact and homogeneous, and Mg-MOF-74 has good crystallinity. The corrosion resistance of this composite coating was investigated through Tafel polarization test and immersion test in simulated body fluid at 37 °C. It was found that Mg-MOF-74/MgF2 composite coating significantly slowed down the corrosion rate of Mg alloy. Additionally, Mg-MOF-74/MgF2 composite coating expresses super-hydrophilicity with the water contact angle of nearly 0°. In conclusion, on the basis of MgF2 anticorrosive coating, the introduction of Mg-MOF-74 further improves the biological property of Mg alloys. At last, we propose that the hydrophilicity of the composite coating is mainly owing to the large number of hydroxyl groups, the high specific surface area of Mg-MOF-74, and the rough coating produced by Mg-MOF-74 particles. Hence, Mg-MOF-74 has a great advantage in enhancing the hydrophilicity of Mg alloy surface. PMID:29518933

Adsorption of arginine, glycine and aspartic acid on Mg and Mg-based alloy surfaces: A first-principles study

NASA Astrophysics Data System (ADS)

Fang, Zhe; Wang, Jianfeng; Yang, Xiaofan; Sun, Qiang; Jia, Yu; Liu, Hairong; Xi, Tingfei; Guan, Shaokang

2017-07-01

Studying the adsorption behaviors of biomolecules on the surface of Mg and Mg-based alloy has a fundamental and important role for related applications in biotechnology. In the present work, we systematically investigate and compare the adsorption properties of three typical amino acids, i.e., Arg (arginine), Gly (glycine) and Asp (aspartic acid), which form RGD tripeptide, on the Mg (0 0 0 1) surface with various doping (Zn, Y, and Nd), and aim to realize proper binding between biomolecules and Mg and Mg-based biomedical materials. Our results show that flat adsorption configurations of the functional groups binding to the surfaces are favored in energy for all the three selected amino acids. In specific, for the amino acids adsorped on clean Mg (0 0 0 1) surface, the adsorption energy (Eads) of Arg is found to be -1.67 eV for the most stable configuration, with amino and guanidyl groups binding with the surface. However, Gly (Asp) is found to binding with the surface through amino and carboxyl groups, with a -1.16 eV (-1.15 eV) binding energy. On the 2% Zn doped Mg (0 0 0 1) alloy surface (Mg-Zn (2%)), the Eads are significantly increased to be -1.91 eV, -1.32 eV and -1.35 eV for Arg, Gly and Asp, respectively. While the Mg-Y (1%) and Mg-Nd (1%) slightly weaken the adsorption of three amino acids. Moreover, we have performed detail discussions of the binding properties between amino acids and surfaces by projected density of states (PDOS) combined with charge transfer analyses. Our studies provide a comprehensive understanding on the interactions between amino acids and Mg and Mg-based alloy surfaces, with respect to facilitate the applications of Mg and Mg-based biomedical alloys in biosensing, drug delivery, biomolecule coating and other fields in biotechnology.

Critical current densities of powder-in-tube MgB2 tapes fabricated with nanometer-size Mg powder

NASA Astrophysics Data System (ADS)

Yamada, H.; Hirakawa, M.; Kumakura, H.; Matsumoto, A.; Kitaguchi, H.

2004-03-01

We fabricated powder-in-tube MgB2/Fe tapes using a powder mixture of nanometer-size Mg and commercial amorphous B and investigated the transport properties. High-purity nanometer-size Mg powder was fabricated by applying the thermal plasma method. 5-10 mol % SiC powder doping was tried to enhance the Jc properties. We found that the use of nanometer-size Mg powder was effective to increase the Jc values. The transport Jc values of the nondoped and 10 mol % SiC-doped tapes prepared with nanometer-size Mg powder reached 90 and 250 A/mm2 at 4.2 K and 10 T, respectively. These values were about five times higher than those of the tapes prepared with commercial Mg powder.

Apollo 15 Mg- and Fe-norites - A redefinition of the Mg-suite differentiation trend

NASA Technical Reports Server (NTRS)

Lindstrom, M. M.; Marvin, U. B.; Mittlefehldt, D. W.

1989-01-01

The Apollo 15 highland rocks from the Apennine Front include clasts of mafic plutonic rocks from deep in the lunar crust that were brought to the surface by the Imbrium and Serenitatis impacts. The Apollo 15 norites exhibit wide variations in mineral and bulk compositions and include Fe-norites that plot between the three major pristine rock fields on a diagram of Mg' in mafic minerals vs An in paglioclase. Based on assemblages and compositions of minerals, and on ratios of elemental abundances, it is concluded that these Apollo 15 Fe-norites are differentiated members of the Mg-norite suite. The Apollo 15 and 17 norites and troctolites form a closely related suite of rocks, whose variations in mineral compositions represent the main differentiation trend of the Mg-suite. This trend in mineral compositions has a steeper slope than the previous Mg-suite field. The parent magmas for these Mg-suite rocks formed by partial melting deep in the lunar mantle. Differentiation by fractional crystallization may also have included assimilation of crustal components as the magmas rose from the mantle and crystallized plutons in the lower crust.

Enhanced voltage-controlled magnetic anisotropy in magnetic tunnel junctions with an MgO/PZT/MgO tunnel barrier

NASA Astrophysics Data System (ADS)

Chien, Diana; Li, Xiang; Wong, Kin; Zurbuchen, Mark A.; Robbennolt, Shauna; Yu, Guoqiang; Tolbert, Sarah; Kioussis, Nicholas; Khalili Amiri, Pedram; Wang, Kang L.; Chang, Jane P.

2016-03-01

Compared with current-controlled magnetization switching in a perpendicular magnetic tunnel junction (MTJ), electric field- or voltage-induced magnetization switching reduces the writing energy of the memory cell, which also results in increased memory density. In this work, an ultra-thin PZT film with high dielectric constant was integrated into the tunneling oxide layer to enhance the voltage-controlled magnetic anisotropy (VCMA) effect. The growth of MTJ stacks with an MgO/PZT/MgO tunnel barrier was performed using a combination of sputtering and atomic layer deposition techniques. The fabricated MTJs with the MgO/PZT/MgO barrier demonstrate a VCMA coefficient, which is ˜40% higher (19.8 ± 1.3 fJ/V m) than the control sample MTJs with an MgO barrier (14.3 ± 2.7 fJ/V m). The MTJs with the MgO/PZT/MgO barrier also possess a sizeable tunneling magnetoresistance (TMR) of more than 50% at room temperature, comparable to the control MTJs with an MgO barrier. The TMR and enhanced VCMA effect demonstrated simultaneously in this work make the MgO/PZT/MgO barrier-based MTJs potential candidates for future voltage-controlled, ultralow-power, and high-density magnetic random access memory devices.

[Utility of treatment with atorvastatin 40 mg plus ezetimibe 10 mg versus atorvastatin 80 mg in reducing the levels of LDL cholesterol in patients with ischaemic stroke or transient ischaemic attack].

PubMed

Palacio, Enrique; Viadero-Cervera, Raquel; Revilla, Marián; Larrosa-Campo, Davinia; Acha-Salazar, Olga; Novo-Robledo, Francisco; Oterino, Agustín

2016-03-01

After an ischaemic stroke, to reduce LDL cholesterol (LDLc) levels decreases the risk of recurrence. The risk of recurrence is lower with more intense reductions in LDLc levels. To evaluate the efficacy and security of atorvastatin 40 mg plus ezetimibe 10 mg after ischaemic stroke or transient ischaemic attack (TIA). We retrospectively evaluated stroke or TIA patients admitted to our hospital who received atorvastatin 40 mg plus ezetimibe 10 mg (n = 34) or atorvastatin 80 mg (n = 52) at discharge. We analyzed changes in lipid parameters and established as a primary outcome LDLc <= 70 mg/dL and/or reduction in LDLc >= 50%. Furthermore, safety parameters were assessed. Predictors associated with primary outcome achievement were treatment with atorvastatin 40 mg plus ezetimibe 10 mg (odds ratio: 11.94; 95% CI: 2.82-50.64; p = 0.001) and male (odds ratio: 4.76; 95% CI: 1.35-16.67; p = 0.02). Treatment with atorvastatin 40 mg plus ezetimibe 10 mg achieved significantly greater reductions in LDLc (p < 0.001), total cholesterol (p < 0.001) and non-HDLc (p < 0.001). Both treatments were safe and well tolerated, with a low number of secondary effects. Compared with atorvastatin 80 mg, atorvastatin 40 mg plus ezetimibe 10 mg increases the likelihood of achieving LDLc goals after ischaemic stroke or transient ischaemic attack. Both treatments were safe and well tolerated.

Formation of Al3Ti/Mg composite by powder metallurgy of Mg-Al-Ti system.

PubMed

Yang, Zi R; Qi Wang, Shu; Cui, Xiang H; Zhao, Yu T; Gao, Ming J; Wei, Min X

2008-07-01

An in situ titanium trialuminide (Al 3 Ti)-particle-reinforced magnesium matrix composite has been successfully fabricated by the powder metallurgy of a Mg-Al-Ti system. The reaction processes and formation mechanism for synthesizing the composite were studied by differential scanning calorimetry (DSC), x-ray diffractometry (XRD), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Al 3 Ti particles are found to be synthesized in situ in the Mg alloy matrix. During the reaction sintering of the Mg-Al-Ti system, Al 3 Ti particles are formed through the reaction of liquid Al with as-dissolved Ti around the Ti particles. The formed intermetallic particles accumulate at the original sites of the Ti particles. As sintering time increases, the accumulated intermetallic particles disperse and reach a relatively homogeneous distribution in the matrix. It is found that the reaction process of the Mg-Al-Ti system is almost the same as that of the Al-Ti system. Mg also acts as a catalytic agent and a diluent in the reactions and shifts the reactions of Al and Ti to lower temperatures. An additional amount of Al is required for eliminating residual Ti and solid-solution strengthening of the Mg matrix.

Estudio numerico y experimental del proceso de soldeo MIG sobre la aleacion 6063--T5 utilizando el metodo de Taguchi

NASA Astrophysics Data System (ADS)

Meseguer Valdenebro, Jose Luis

improvement on mechanical properties in aluminum metal joint. Los procesos de soldadura por arco electrico representan unas de las tecnicas mas utilizadas en los procesos de fabricacion de componentes mecanicos en la industria moderna. Los procesos de soldeo por arco se han adaptado a las necesidades actuales, haciendose un modo de fabricacion flexible y versatil. Los resultados obtenidos numericamente en el proceso de soldadura son validados experimentalmente. Los principales metodos numericos mas empleados en la actualidad son tres, metodo por diferencias finitas, metodos por elementos finitos y metodo por volumenes finitos. El metodo numerico mas empleado para el modelado de uniones soldadas, es el metodo por elementos finitos, debido a que presenta una buena adaptacion a las condiciones geometricas y de contorno ademas de que existe una diversidad de programas comerciales que utilizan el metodo por elementos finitos como base de calculo. Este trabajo de investigacion presenta un estudio experimental de una union soldada mediante el proceso MIG de la aleacion de aluminio 6063-T5. El metodo numerico se valida experimentalmente aplicando el metodo de los elementos finitos con el programa de calculo ANSYS. Los resultados experimentales obtenidos son: las curvas de enfriamiento, el tiempo critico de enfriamiento t4/3, geometria del cordon, microdurezas obtenidas en la union soldada, zona afectada termicamente y metal base, dilucion del proceso, areas criticas intersecadas entre las curvas de enfriamiento y la curva TTP. Los resultados numericos son: las curvas del ciclo termico, que representan tanto el calentamiento hasta alcanzar la temperatura maxima y un posterior enfriamiento. Se calculan el tiempo critico de enfriamiento t4/3, el rendimiento termico y se representa la geometria del cordon obtenida experimentalmente. La zona afectada termicamente se obtiene diferenciando las zonas que se encuentran a diferentes temperaturas, las areas criticas intersecadas entre las

Descripción del coronógrafo a ser instalado en Argentina (MICA)

NASA Astrophysics Data System (ADS)

Stenborg, G.; Francile, C.; Schwenn, R.; Epple, A.; Rovira, M.

El ``Coronógrafo de espejo para Argentina'' es un telescopio solar terrestre a ser colocado en el Observatorio Astronómico Félix Aguilar (El Leoncito), antes de finalizar 1996, como parte de un programa de ciencia bilateral entre Alemania y Argentina. Eclipses fotográficos de alta resolución han revelado que la corona solar es altamente estructurada y variable. De hecho, está contínuamente deformada y moldeada por los movimientos convectivos de los extremos de los arcos magnéticos en la fotosfera, estando, en muchas oportunidades, afectada por explosivas liberaciones de energía. MICA, en conjunción con otros telescopios solares espaciales y terrestres, tratará de contribuir al entendimiento de cuestiones fundamentales de la física solar. Entre ellas: cómo la corona está siendo calentada, dónde y cómo el viento solar es acelerado, qué causa los transitorios coronales, etc. Para ello investigará la distribución de los parámetros del plasma y su evolución con el tiempo, la estructura espacial de la corona en fina y gran escala, procesos que ocurren en los transitorios coronales y factores que los disparan, etc. Para responder a estas cuestiones MICA observará la atmósfera solar por sobre el limbo entre 1.1 y 2 radios solares aproximadamente, usando un nuevo tipo de sistema coronográfico que permite suprimir el brillo del disco solar suficientemente bien, tomando las imágenes con una cámara CCD de 1024x1024 pixels, codificada en 12 bits, pudiendo el mismo ser operado en forma remota. En la presente exposición describiremos las características del instrumento, cómo será controlado y qué esperamos observar basados en las imágenes obtenidas por los telescopios de similares características LASCO C1 a bordo del SOHO y PICO (ubicado en el Observatorio de Pic du Midi, Francia).

Effect of Mg on the Microstructure and Corrosion Resistance of the Continuously Hot-Dip Galvanizing Zn-Mg Coating

PubMed Central

Dong, Anping; Li, Baoping; Lu, Yanling; Zhu, Guoliang; Xing, Hui; Shu, Da; Sun, Baode; Wang, Jun

2017-01-01

The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner was calculated. The results indicates that the phase composition of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner is the same as Zn-Mg binary phase diagram, suggesting Al in the Zn-Mg (ZM) coatings mainly concentrates on the interfacial layer between the coating and steel substrate. The microstructure of continuously hot-dip galvanizing ZM coatings with 0.20 wt % Al containing 1.0–3.0 wt % Mg was investigated using tunneling electron microscopy (TEM). The morphology of Zn in the coating changes from bulk to strip and finally to mesh-like, and the MgZn2 changes from rod-like to mesh-like with the Mg content increasing. Al in the ZM coatings mainly segregates at the Fe2Al5 inhibition layer and the Mg added to the Zn bath makes this inhibition layer thinner and uneven. Compared to GI coating, the time of the first red rust appears increases by more than two-fold and expansion rate of red rust reduces by more than four-fold in terms of salt spray experiment. The ZM coating containing 2.0 wt % Mg has the best corrosion resistance. The enhanced corrosion resistance of ZM coatings mainly depends on different corrosion products. PMID:28829393

Effect of Mg on the Microstructure and Corrosion Resistance of the Continuously Hot-Dip Galvanizing Zn-Mg Coating.

PubMed

Dong, Anping; Li, Baoping; Lu, Yanling; Zhu, Guoliang; Xing, Hui; Shu, Da; Sun, Baode; Wang, Jun

2017-08-22

The microstructure of continuously hot-dip galvanizing Zn-Mg coating was investigated in order to obtain the mechanism of the effects of Mg on the corrosion resistance. In this paper, the vertical section of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner was calculated. The results indicates that the phase composition of the Zn-0.20 wt % Al-Mg ternary phase diagram near the Al-low corner is the same as Zn-Mg binary phase diagram, suggesting Al in the Zn-Mg (ZM) coatings mainly concentrates on the interfacial layer between the coating and steel substrate. The microstructure of continuously hot-dip galvanizing ZM coatings with 0.20 wt % Al containing 1.0-3.0 wt % Mg was investigated using tunneling electron microscopy (TEM). The morphology of Zn in the coating changes from bulk to strip and finally to mesh-like, and the MgZn₂ changes from rod-like to mesh-like with the Mg content increasing. Al in the ZM coatings mainly segregates at the Fe₂Al₅ inhibition layer and the Mg added to the Zn bath makes this inhibition layer thinner and uneven. Compared to GI coating, the time of the first red rust appears increases by more than two-fold and expansion rate of red rust reduces by more than four-fold in terms of salt spray experiment. The ZM coating containing 2.0 wt % Mg has the best corrosion resistance. The enhanced corrosion resistance of ZM coatings mainly depends on different corrosion products.

Spin injection into silicon in three-terminal vertical and four-terminal lateral devices with Fe/Mg/MgO/Si tunnel junctions having an ultrathin Mg insertion layer

NASA Astrophysics Data System (ADS)

Sato, Shoichi; Nakane, Ryosho; Hada, Takato; Tanaka, Masaaki

2017-12-01

We demonstrate that the spin injection/extraction efficiency is enhanced by an ultrathin Mg insertion layer (⩽2 nm) in Fe /Mg /MgO /n+-Si tunnel junctions. In diode-type vertical three-terminal devices fabricated on a Si substrate, we observe the narrower three-terminal Hanle (N-3TH) signals indicating true spin injection into Si and estimate the spin polarization in Si to be 16% when the thickness of the Mg insertion layer is 1 nm, whereas no N-3TH signal is observed without the Mg insertion. This means that the spin injection/extraction efficiency is enhanced by suppressing the formation of a magnetically dead layer at the Fe/MgO interface. We also observe clear spin transport signals, such as nonlocal Hanle signals and spin-valve signals, in a lateral four-terminal device with the same Fe /Mg /MgO /n+-Si tunnel junctions fabricated on a Si-on-insulator substrate. It is found that both the intensity and linewidth of the spin signals are affected by the geometrical effects (device geometry and size). We have derived analytical functions taking into account the device structures, including channel thickness and electrode size, and estimated important parameters: spin lifetime and spin polarization. Our analytical functions explain the experimental results very well. Our study shows the importance of suppressing a magnetically dead layer and provides a unified understanding of spin injection/detection signals in different device geometries.

[Y/Mg] stellar dating calibration

NASA Astrophysics Data System (ADS)

Titarenko, A.; Recio-Blanco, A.; de Laverny, P.; Hayden, M.; Guiglion, G.; Worley, C.

2018-04-01

Gaia DR1 has opened a new era of stellar age dating, that is crucial for many astrophysical objectives. In addition, the Gaia based isochrone fitting ages can be compared to other chemical clocks like the [Y/Mg] one (Nissen et al. 2015). In our work we have used ESO archived data of the AMBRE project (de Laverny et al. 2013) for UVES spectra, in order to evaluate the age [Y/Mg] abundance correlation for turn off stars. 310 turn off stars of the UVES-archive (setups 564 and 580) are included in the TGAS database. Isochrone fitting ages were derived. We have applied the GAUGUIN procedure for those stars to derive the Mg and the Y abundances. As the result we present the [Y/Mg] vs stellar age dependence for ~40 TO-stars.

Fiber Laser Welding-Brazing Characteristics of Dissimilar Metals AZ31B Mg Alloys to Copper with Mg-Based Filler

NASA Astrophysics Data System (ADS)

Zhao, Xiaoye; Tan, Caiwang; Meng, Shenghao; Chen, Bo; Song, Xiaoguo; Li, Liqun; Feng, Jicai

2018-03-01

Fiber laser welding-brazing of 1-mm-thick AZ31B Mg alloys to 1.5-mm-thick copper (T2) with Mg-based filler was performed in a lap configuration. The weld appearance, interfacial microstructure and mechanical properties were investigated with different heat inputs. The results indicated that processing windows for optimizing appropriate welding parameters were relatively narrow in this case. Visually acceptable joints with certain strength were achieved at appropriate welding parameters. The maximum tensile-shear fracture load of laser-welded-brazed Mg/Cu joint could reach 1730 N at the laser power of 1200 W, representing 64.1% joint efficiency relative to AZ31Mg base metal. The eutectic structure (α-Mg + Mg2Cu) and Mg-Cu intermetallic compound was observed at the Mg/Cu interface, and Mg-Al-Cu ternary intermetallic compound were identified between intermetallics and eutectic structure at high heat input. All the joints fractured at the Mg-Cu interface. However, the fracture mode was found to differ. For laser power of 1200 W, the surface was characterized by tearing edge, while that with poor joint strength was almost dominated by smooth surface or flat tear pattern.

Información general sobre los mosquitos

EPA Pesticide Factsheets

Una consecuencia más importante de algunas picaduras de mosquitos es la trasmisión de ciertas enfermedades graves como el paludismo, la fiebre del dengue y varias formas de encefalitis, que incluyen el virus del Nilo occidental.

Incentivos para atraer y retener personal de salud de zonas rurales del Perú: un estudio cualitativo

PubMed Central

Huicho, Luis; Canseco, Francisco Díez; Lema, Claudia; Miranda, J. Jaime; Lescano, Andrés G.

2014-01-01

El objetivo fue identificar incentivos de atracción y retención en zonas rurales y distantes de Ayacucho, Perú. Fueron realizadas entrevistas en profundidad con 80 médicos, enfermeras, obstetras y técnicos (20 por grupo) de las zonas más pobres y con 11 funcionarios. No existen políticas sistemáticas de atracción y retención de personal de salud en Ayacucho. Los principales incentivos, en orden de importancia, fueron mejoras salariales, oportunidades de formación y capacitación, estabilidad laboral y nombramiento, mejoras en infraestructura y equipos, e incremento del personal. Se mencionaron también mejoras en la vivienda y alimentación, mayor cercanía con la familia y reconocimiento por el sistema de salud. Existen coincidencias y singularidades entre los distintos grupos sobre los incentivos clave para estimular el trabajo rural, que deben considerarse al diseñar políticas públicas. Las iniciativas del Estado deben comprender procesos rigurosos de monitoreo y evaluación, para asegurar que las mismas tengan el impacto deseado. PMID:22488318

Mg isotope fractionation during microbe-mineral interactions

NASA Astrophysics Data System (ADS)

Kim, Insu; Ryu, Jong-sik; Lee, Kwang-sik; Lee, Dongho

2014-05-01

Magnesium is involved in various biogeochemical processes important to the global climate change over geological time-scale. Mg isotopes allow us to directly trace the Mg cycle in the Earth's surface but the factors controlling Mg isotopic compositions have not fully understood yet. Here, we conducted a batch experiment using two bacterial species (Shewanella putrefaciens and Burkholderia fungorum) and three major Mg-bearing minerals (biotite, dolomite and hornblende). All elemental concentrations increased by 336 h and then reached to steady-state values, of which Mg concentrations varied depending on minerals and bacterial species. This result indicates that the mineral dissolution is affect by the presence of microbes, which either provide organic acids or attach onto mineral surface. The Mg isotopic compositions of initial minerals biotite, dolomite and hornblende are -0.35o of biotite, -0.99o of dolomite, and -0.24o of hornblende, in δ26Mg. Similarly, δ26Mg values increased by 336 h and reached to steady-state values, which also varied with minerals and microbes. During dissolution of three minerals, the light isotope of Mg is preferentially incorporated into the dissolved phases and then the dissolved δ26Mg values become consistent with those of minerals with the time.

K{sub 2}Mg{sub 5-x}Sn{sub 3} and K{sub 3}Mg{sub 18}Tt{sub 11} (Tt=Sn, pb) with two types of Mg-Sn/Pb frameworks

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

Lei, Xiao-Wu, E-mail: xwlei10@163.co

2011-04-15

K{sub 2}Mg{sub 5-x}Sn{sub 3} (x=0.28) and K{sub 3}Mg{sub 18}Tt{sub 11} (Tt=Sn, Pb) have been synthesized by reacting the mixture of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction studies. K{sub 2}Mg{sub 5-x}Sn{sub 3} (x=0.28) is isostructural with Ni{sub 7-x}SbQ{sub 2} (Q=Se, Te) series and features 2D corrugated [Mg{sub 5-x}Sn{sub 3}] layers that are separated by K{sup +} cations. The structure of K{sub 3}Mg{sub 18}Tt{sub 11} (Tt=Sn, Pb) is closely related to the Ho{sub 2}Rh{sub 12}As{sub 7} structural type and features 3D [Mg{sub 18}Tt{sub 11}] framework composed of 1D [Mg{sub 18}Tt{sub 11}] columns that aremore » interconnected via Mg-Tt bonds, forming 1D hexagonal tunnels occupied by the K+ cations. Electronic structure calculations indicate that Mg atoms can function as either electron donor or as a participator in the network along with Tt atoms. Magnetic property measurements and band structure calculations indicate that these compounds are metallic. -- Graphical abstract: Two new K-Mg-Tt phases, K{sub 2}Mg{sub 5-x}Sn{sub 3} (x=0.28) and K{sub 3}Mg{sub 18}Tt{sub 11} (Tt=Sn, Pb), have been synthesized and structurally characterized. K{sub 2}Mg{sub 5-x}Sn{sub 3} is isostructural with Ni{sub 7-x}SbQ{sub 2} (Q=Se, Te) and features a 2D corrugated [Mg{sub 5}Sn{sub 3}] layer that is separated by K{sup +} cations, and K{sub 3}Mg{sub 18}Tt{sub 11} (Tt=Sn, Pb) is closely related to the Ho{sub 2}Rh{sub 12}As{sub 7} structure type and features a 3D [Mg{sub 18}Tt{sub 11}] network with 1D hexagonal tunnels along the c-axis occupied by K{sup +} cations. Display Omitted Research highlights: Two new polar intermetallics, K{sub 2}Mg{sub 5-x}Sn{sub 3} (x=0.28) and K{sub 3}Mg{sub 18}Tt{sub 11} (Tt=Sn, Pb). Electronic structure calculations were performed by both TB-LMTO and EHTB methods. Mg atom can function as either electron donor or participator in the network.« less

Structure and lattice dynamics of the wide band gap semiconductors MgSiN2 and MgGeN2

NASA Astrophysics Data System (ADS)

Râsander, M.; Quirk, J. B.; Wang, T.; Mathew, S.; Davies, R.; Palgrave, R. G.; Moram, M. A.

2017-08-01

We have determined the structural and lattice dynamical properties of the orthorhombic, wide band gap semiconductors MgSiN2 and MgGeN2 using density functional theory. In addition, we present the structural properties and Raman spectra of MgSiN2 powder. The structural properties and lattice dynamics of the orthorhombic systems are compared to those of wurtzite AlN. We find clear differences in the lattice dynamics between MgSiN2, MgGeN2 and AlN, for example, we find that the highest phonon frequency in MgSiN2 is about 100 cm-1 higher than the highest frequency in AlN, and that MgGeN2 is much softer. We also provide the Born effective charge tensors and dielectric tensors of MgSiN2, MgGeN2 and AlN. Phonon related thermodynamic properties, such as the heat capacity and the entropy, have also been evaluated and are found to be in very good agreement with available experimental results.

A randomized controlled clinical trial of levofloxacin 750 mg versus 500 mg intravenous infusion in the treatment of community-acquired pneumonia.

PubMed

Zhao, Xu; Wu, Ju-Fang; Xiu, Qing-Yu; Wang, Chen; Zhang, De-Ping; Huang, Jian-An; Xie, Can-Mao; Sun, Sheng-Hua; Lv, Xiao-Ju; Si, Bin; Xiao, Zu-Ke; Zhang, Ying-Yuan

2014-10-01

The objective of this study was to compare the efficacy and safety of levofloxacin 750 mg for 5 days versus 500 mg for 7-14 days intravenous (IV) in the treatment of community-acquired pneumonia (CAP). This clinical trial was the first of its kind conducted in Chinese people and also in Asian population. A total of 241 were enrolled and randomized to 750 mg group (n = 121) or 500 mg (n = 120) group from 10 study centers. The median treatment duration was 5.0 days in 750 mg and 9.0 days in 500 mg group. The median total dose was 3750 mg in 750 mg and 4500 mg in 500 mg group. The bacterial eradication rate was 100% in both groups. The overall efficacy rate in 750 mg group was 86.2% (94/109), and 84.7% (94/111), in 500 mg group of full analysis set visit 4, 95% confidence interval of 1.6% (-7.8-10.9%); the statistical results showed that 750 mg group was non-inferior to 500 mg group. The most common clinical adverse drug reactions were injection site adverse reactions in both 750 mg group and 500 mg group; the other common adverse drug reactions were insomnia, nausea, skin rash, etc. The most common drug-related laboratory abnormalities were neutrophil percentage decreased, decreased white blood cell count, alanine aminotransferase, and aspartate aminotransferase elevation in both 750 mg group and 500 mg group. Most of adverse drug reactions were mild in severity and well-tolerated. In summary, the regimen of levofloxacin 750 mg IV for 5 days was at least as effective and well tolerated as 500 mg IV for 7-14 days for the treatment of CAP. Copyright © 2014. Published by Elsevier Inc.

Defect-Tolerant Diffusion Channels for Mg 2+ Ions in Ribbon-Type Borates: Structural Insights into Potential Battery Cathodes MgVBO 4 and Mg x Fe 2–xB 2O 5

DOE PAGES

Bo, Shou-Hang; Grey, Clare P.; Khalifah, Peter G.

2015-06-10

The reversible room temperature intercalation of Mg 2+ ions is difficult to achieve, but may offer substantial advantages in the design of next-generation batteries if this electrochemical process can be successfully realized. Two types of quadruple ribbon-type transition metal borates (Mg xFe 2-xB 2O 5 and MgVBO 4) with high theoretical capacities (186 mAh/g and 360 mAh/g) have been synthesized and structurally characterized through the combined Rietveld refinement of synchrotron and time-of-flight neutron diffraction data. Neither MgVBO 4 nor Mg xFe 2-xB 2O 5 can be chemically oxidized at room temperature, though Mg can be dynamically removed from themore » latter phase at elevated temperatures (approximately 200 - 500 °C). Findings show that Mg diffusion in the Mg xFe 2-xB 2O 5 structure is more facile for the inner two octahedral sites than for the two outer octahedral sites in the ribbons, a result supported by both the refined site occupancies after Mg removal and by bond valence sum difference map calculations of diffusion paths in the pristine material. Mg diffusion in this pyroborate Mg xFe 2-xB 2O 5 framework is also found to be tolerant to the presence of Mg/Fe disorder since Mg ions can diffuse through interstitial channels which bypass Fe-containing sites.« less

A Transient Rise in Free Mg2+ Ions Released from ATP-Mg Hydrolysis Contributes to Mitotic Chromosome Condensation.

PubMed

Maeshima, Kazuhiro; Matsuda, Tomoki; Shindo, Yutaka; Imamura, Hiromi; Tamura, Sachiko; Imai, Ryosuke; Kawakami, Syoji; Nagashima, Ryosuke; Soga, Tomoyoshi; Noji, Hiroyuki; Oka, Kotaro; Nagai, Takeharu

2018-02-05

For cell division, negatively charged chromatin, in which nucleosome fibers (10 nm fibers) are irregularly folded [1-5], must be condensed into chromosomes and segregated. While condensin and other proteins are critical for organizing chromatin into the appropriate chromosome shape [6-17], free divalent cations such as Mg 2+ and Ca 2+ , which condense chromatin or chromosomes in vitro [18-28], have long been considered important, especially for local condensation, because the nucleosome fiber has a net negative charge and is by itself stretched like "beads on a string" by electrostatic repulsion. For further folding, other positively charged factors are required to decrease the charge and repulsion [29]. However, technical limitations to measure intracellular free divalent cations, but not total cations [30], especially Mg 2+ , have prevented us from elucidating their function. Here, we developed a Förster resonance energy transfer (FRET)-based Mg 2+ indicator that monitors free Mg 2+ dynamics throughout the cell cycle. By combining this indicator with Ca 2+ [31] and adenosine triphosphate (ATP) [32] indicators, we demonstrate that the levels of free Mg 2+ , but not Ca 2+ , increase during mitosis. The Mg 2+ increase is coupled with a decrease in ATP, which is normally bound to Mg 2+ in the cell [33]. ATP inhibited Mg 2+ -dependent chromatin condensation in vitro. Chelating Mg 2+ induced mitotic cell arrest and chromosome decondensation, while ATP reduction had the opposite effect. Our results suggest that ATP-bound Mg 2+ is released by ATP hydrolysis and contributes to mitotic chromosome condensation with increased rigidity, suggesting a novel regulatory mechanism for higher-order chromatin organization by the intracellular Mg 2+ -ATP balance. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Desarrollo de la Escala sobre el Estigma Relacionado con el VIH/SIDA para Profesionales de la Salud mediante el uso de métodos mixtos123

PubMed Central

Varas-Díaz, Nelson; Neilands, Torsten B.; Guilamo-Ramos, Vincent; Cintrón Bou, Francheska N.

2009-01-01

El estigma relacionado con el VIH/SIDA continúa siendo un obstáculo para la prevención primaria y secundaria del VIH. Las consecuencias para las personas que viven con la enfermedad han sido muy documentadas y continúan siendo una gran preocupación para las personas que proveen servicios de salud y para aquellas que investigan el tema. Estas consecuencias son preocupantes cuando el estigma emana de profesionales de la salud porque se puede limitar el acceso a los servicios. Uno de los principales obstáculos para la investigación del estigma relacionado con el VIH en Puerto Rico es la falta de instrumentos cuantitativos para evaluar las manifestaciones del estigma entre profesionales de la salud. El objetivo principal de este estudio fue desarrollar y probar las propiedades psicométricas de una escala sobre el estigma relacionado con el VIH/SIDA culturalmente apropiada para personas que proveen servicios de salud puertorriqueñas y desarrollar una versión corta de la escala que pudiera usarse en escenarios clínicos con tiempo limitado. El instrumento desarrollado estuvo basado en evidencia cualitativa recopilada entre profesionales y estudiantes de profesiones de la salud puertorriqueños/as (n=80) y administrado a una muestra de 421 profesionales de la salud en adiestramiento. La escala contenía 12 dimensiones del estigma relacionado con el VIH/SIDA. El análisis cuantitativo corroboró 11 de ellas, teniendo como resultado un instrumento con validez y confiabilidad satisfactoria. Estas dimensiones, a su vez, fueron subcomponentes de un factor de estigma general superior. PMID:20333258

Comparative study on the structure and electrochemical hydriding properties of MgTi, Mg 0.5Ni 0.5Ti and MgTi 0.5Ni 0.5 alloys prepared by high energy ball milling

NASA Astrophysics Data System (ADS)

Rousselot, Steeve; Guay, Daniel; Roué, Lionel

MgTi, Mg 0.5Ni 0.5Ti and MgTi 0.5Ni 0.5 alloys doped with 10 wt.% Pd were prepared by high energy ball milling and evaluated as hydrogen storage electrodes for Ni-MH batteries. X-ray diffraction analyses indicated that the Mg 0.5Ni 0.5Ti and MgTi 0.5Ni 0.5 alloys could be monophased or composed of a nanoscale mixture of MgTi + NiTi and MgTi + MgNi phases, respectively. Their hydrogen storage characteristics were investigated electrochemically in KOH electrolyte. No activation step was observed during the cycling of the Mg-Ti-Ni electrodes in contrast to that observed with the MgTi electrode. The highest hydrogen discharge capacity was obtained with the MgTi 0.5Ni 0.5 electrode (536 mAh g -1) compared to 401 and 475 mAh g -1 for the Mg 0.5Ni 0.5Ti and MgTi electrodes, respectively. The ternary Mg-Ti-Ni alloys showed a better cycle life with an average capacity decay rate per cycle lower than 1.5% compared to ∼7% for the binary MgTi electrode. The Mg-Ni-Ti electrodes also displayed a much higher discharge rate capability than the binary MgTi electrode, especially with the Mg 0.5Ni 0.5Ti electrode. The origin of this was established on the basis of the anodic polarization curves, where a substantial decrease of the concentration overpotential (reflecting a higher hydrogen diffusivity) was observed for the Mg 0.5Ni 0.5Ti electrode.

Density functional theory (DFT) study on the hydrolysis behavior of degradable Mg/Mg alloys for biomedical applications

NASA Astrophysics Data System (ADS)

Nezafati, Marjan

Magnesium-based (Mg and/or Mg alloys) materials possess many advantageous physicochemical/biological characteristics such as good biocompatibility and similarity of the mechanical properties to the human bone tissue, which renders this material a promising candidate for the biomedical and implant applications. One of the most attractive features of Mg-based materials is the degradability in the physiological environment. With the burst of research on the biodegradable materials for the healthcare device applications, Mg and its alloys attracted a strong attention in the bioengineering field in recent years. However, the major limitation of applying Mg-based materials to biomedical applications is the fast degradation/corrosion rate with regards to the healing process time-span. In the present thesis, an atomistic model employing the density-functional theory (DFT) has been developed to study the hydrolysis process by understanding the influences of commonly used alloying elements (zinc (Zn), calcium (Ca), aluminum (Al), and yttrium (Y)) and the crystallographic orientation of the dissolution surfaces (basal (0001), prism (1010), and pyramidal (1011) planes) on the corrosion behavior. These parameters are known to strongly impact the initial hydrolysis phenomena of Mg-based materials. To develop the atomistic computational model, we have implemented the Dmol3 software package in conjunction with PBE (Perdew, Burke and Ernzerhof) correlation energy functional in the GGA (generalized gradient approximation) scheme. Throughout the thesis, we performed three sets of calculations, i) surface energy, ii) dissolution potential, and iii) water adsorption computations, to examine the hydrolysis mechanism and the subsequent corrosion/degradation of Mg/Mg alloys. The total energy changes of various Mg-based systems in different conditions for these surface energies, dissolution behavior, and tendency of the system for adsorbing the water molecule were quantified. The results

Effect of organic ligands on Mg partitioning and Mg isotope fractionation during low-temperature precipitation of calcite

NASA Astrophysics Data System (ADS)

Mavromatis, Vasileios; Immenhauser, Adrian; Buhl, Dieter; Purgstaller, Bettina; Baldermann, Andre; Dietzel, Martin

2016-04-01

Calcite growth experiments have been performed at 25 oC and 1 bar pCO2 in the presence of aqueous Mg and six organic ligands in the concentration range from 10-5 to 10-3 M. These experiments were performed in order to quantify the effect of distinct organic ligands on the Mg partitioning and Mg stable isotope fractionation during its incorporation in calcite at similar growth rates normalized to total surface area. The organic ligands used in this study comprise of (i) acetate acid, (ii) citrate, (iii) glutamate, (iv) salicylate, (v) glycine and (vi) ethylenediaminetetraacetic acid (EDTA), containing carboxyl- and amino-groups. These fuctional groups are required for bacterial activity and growth as well as related to biotic and abiotic mineralization processes occurring in sedimentary and earliest diagenetic aquatic environments (e.g. soil, cave, lacustrine, marine). The results obtained in this study indicate that the presence of organic ligands promotes an increase in the partition coefficient of Mg in calcite (DMg = (Mg/Ca)calcite (Mg/Ca)fluid). This behaviour can be explained by the temporal formation of aqueous Mg-ligand complexes that are subsequently adsorbed on the calcite surfaces and thereby reducing the active growth sites of calcite. The increase of DMg values as a function of the supersaturation degree of calcite in the fluid phase can be described by the linear equation LogDMg =0.3694 (±0.0329)×SIcalcite - 1.9066 (±0.0147); R2=0.92 In contrast, the presence of organic ligands, with exception of citrate, does not significantly affect the Mg isotope fractionation factor between calcite and reactive fluid (Δ26Mgcalcite-fluid = -2.5 ±0.1). Citrate likely exhibits larger fractionation between the Mg-ligand complexes and free aqueous Mg2+, compared to the other organic ligands studied in this work, as evidenced by the smaller Δ26Mgcalcite-fluid values. These results indicate that in Earth's surface calcite precipitating environments that are

Effect of Cold Rolling on Age Hardening in Excess Mg-Type Al-Mg-Si Alloys Including Some Minor Elements

NASA Astrophysics Data System (ADS)

Ogawa, Yurie; Matsuda, Kenji; Kawabata, Tokimasa; Uetani, Yasuhiro; Ikeno, Susumu

It has been known that transition metals improve the mechanical property of Al-Mg-Si alloy. The thermo-mechanical treatment is also effective to improve the strength of Al-Mg-Si alloy. In this work, the aging behavior of deformed excess Mg-type Al-Mg-Si alloy including Ag,Cu,Pt was investigated by hardness test and TEM observation. The value of the maximum hardness increased and the aging time to the maximum hardness became shorter by increasing the amount of the deformation. The age-hardening ability (ΔHV) was decreased with increasing amount of the deformation. The effect of additional element on AHV was also similar to the result of the deformation described above. Comparing the value of the maximum hardness for the alloys aged at 423-523 K, the ex. Mg-Cu alloy was the highest, the ex. Mg-Ag alloy was middle, and the ex. Mg and ex. Mg-Pt alloys were the lowest because of total amounts of added elements.

A fundamental study on the [(μ-Cl)3Mg2(THF)6]+ dimer electrolytes for rechargeable Mg batteries†

PubMed Central

Cox, Jonathan T.; Hu, Dehong; Deng, Xuchu; Hu, Jianzhi; Hu, Mary Y.; Xiao, Jie; Shao, Yuyan; Tang, Keqi; Liu, Jun

2016-01-01

The long sought solvated [MgCl]+ species in the Mg-dimer electrolytes was characterized by soft mass spectrometry. The presented study provides an insightful understanding on the electrolyte chemistry of rechargeable Mg batteries. PMID:25562393

Biocompatibility Assessment of Novel Bioresorbable Alloys Mg-Zn-Se and Mg-Zn-Cu for Endovascular Applications: In- Vitro Studies.

PubMed

Persaud-Sharma, Dharam; Budiansky, Noah; McGoron, Anthony J

2013-01-01

Previous studies have shown that using biodegradable magnesium alloys such as Mg-Zn and Mg-Zn-Al possess the appropriate mechanical properties and biocompatibility to serve in a multitude of biological applications ranging from endovascular to orthopedic and fixation devices. The objective of this study was to evaluate the biocompatibility of novel as-cast magnesium alloys Mg-1Zn-1Cu wt.% and Mg-1Zn-1Se wt.% as potential implantable biomedical materials, and compare their biologically effective properties to a binary Mg-Zn alloy. The cytotoxicity of these experimental alloys was evaluated using a tetrazolium based- MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and a lactate dehydrogenase membrane integrity assay (LDH). The MTS assay was performed on extract solutions obtained from a 30-day period of alloy immersion and agitation in simulated body fluid to evaluate the major degradation products eluted from the alloy materials. Human foreskin fibroblast cell growth on the experimental magnesium alloys was evaluated for a 72 hour period, and cell death was quantified by measuring lactate dehydrogenase concentrations. Both Mg-Zn-Se and Mg-Zn-Cu alloys exhibit low cytotoxicity levels which are suitable for biomaterial applications. The Mg-Zn-Cu alloy was found to completely degrade within 72 hours, resulting in lower human foreskin fibroblast cell viability. The Mg-Zn-Se alloy was shown to be less cytotoxic than both the Mg-Zn-Cu and Mg-Zn alloys.

Biocompatibility Assessment of Novel Bioresorbable Alloys Mg-Zn-Se and Mg-Zn-Cu for Endovascular Applications: In- Vitro Studies

PubMed Central

Budiansky, Noah; McGoron, Anthony J.

2013-01-01

Previous studies have shown that using biodegradable magnesium alloys such as Mg-Zn and Mg-Zn-Al possess the appropriate mechanical properties and biocompatibility to serve in a multitude of biological applications ranging from endovascular to orthopedic and fixation devices. The objective of this study was to evaluate the biocompatibility of novel as-cast magnesium alloys Mg-1Zn-1Cu wt.% and Mg-1Zn-1Se wt.% as potential implantable biomedical materials, and compare their biologically effective properties to a binary Mg-Zn alloy. The cytotoxicity of these experimental alloys was evaluated using a tetrazolium based- MTS (3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and a lactate dehydrogenase membrane integrity assay (LDH). The MTS assay was performed on extract solutions obtained from a 30-day period of alloy immersion and agitation in simulated body fluid to evaluate the major degradation products eluted from the alloy materials. Human foreskin fibroblast cell growth on the experimental magnesium alloys was evaluated for a 72 hour period, and cell death was quantified by measuring lactate dehydrogenase concentrations. Both Mg-Zn-Se and Mg-Zn-Cu alloys exhibit low cytotoxicity levels which are suitable for biomaterial applications. The Mg-Zn-Cu alloy was found to completely degrade within 72 hours, resulting in lower human foreskin fibroblast cell viability. The Mg-Zn-Se alloy was shown to be less cytotoxic than both the Mg-Zn-Cu and Mg-Zn alloys. PMID:24058329

Effect of Mg content on the thermal stability and mechanical behaviour of PLLA/Mg composites processed by hot extrusion.

PubMed

Cifuentes, S C; Lieblich, M; López, F A; Benavente, R; González-Carrasco, J L

2017-03-01

In the field of bioabsorbable composites for biomedical applications, extrusion has been employed as a method to prepare homogeneous blends of polymeric matrices with bioactive ceramic fillers. In this work, the suitability of processing poly-l-lactic acid/Magnesium (PLLA/Mg) composites by hot extrusion has been assessed by a systematic characterization of PLLA/Mg composites containing different amounts of Mg particles up to 7wt%. The results show that extrusion causes a reduction of almost 20% in the viscosity average molecular weight of PLLA, which further decreases with increasing Mg content. Extrusion gave always rise to a homogeneous distribution of Mg particles within the PLLA matrix. This composite processing was not compromised by the degradation of the polymeric matrix because the processing temperature was always below the onset degradation temperature. In the processing conditions employed in the present work, degradation of the composite slightly increases as more Mg is added up to 5wt%, but is very high at 7wt%. This was also evident from the mechanical behaviour, so that Mg particles improved the stiffness and compression strength of neat PLLA until 5wt% of Mg content, which dropped drastically when the material had 7wt% of Mg. The filler strengthening factor decreases with the increment in Mg content. In order to obtain an optimised contribution of Mg particles, a balance between thermal degradation and mechanical resistance of PLLA must be achieved. Copyright © 2016 Elsevier B.V. All rights reserved.

Aceptabilidad del diagnóstico rápido casero para HIV entre hombres gay y otros hombres que tienen sexo con hombres (G&HSH) de la Ciudad de Buenos Aires

PubMed Central

Balán, Iván C.; Carballo-Diéguez, Alex; Marone, Rubén O.; Pando, María A.; Barreda, Victoria; Ávila, María M.

2011-01-01

Resumen El uso del diagnóstico rápido para HIV en Argentina, así como otros países de Latinoamérica, ha sido limitado hasta el momento. Este trabajo reporta los resultados provenientes de un estudio cualitativo realizado entre hombres gays y otros hombres que tienen sexo con hombres (G&HSH) de la Ciudad de Buenos Aires, Argentina. El objetivo principal del mismo fue conocer las ventajas y desventajas que los hombres G&HSH perciben en relación al diagnóstico rápido casero para HIV. Se realizaron ocho grupos focales con 73 participantes en los cuales se discutió acerca de las ventajas y desventajas del uso de los diagnósticos rápidos. Las respuestas fueron codificadas utilizando un programa para análisis de datos cualitativos (NVivo) y analizadas temáticamente. Los participantes describieron numerosas ventajas sobre el uso del diagnóstico rápido casero, aunque algunos reportaron importantes preocupaciones dentro de las cuales se destaca la posibilidad de impulsos suicidas si alguien recibe un resultado positivo estando solo. En términos generales se observó una gran aceptabilidad para el uso del diagnóstico rápido si el mismo es realizado por personal de salud en lugares acondicionados para este fin. PMID:25284951

Aceptabilidad del diagnóstico rápido casero para HIV entre hombres gay y otros hombres que tienen sexo con hombres (G&HSH) de la Ciudad de Buenos Aires.

PubMed

Balán, Iván C; Carballo-Diéguez, Alex; Marone, Rubén O; Pando, María A; Barreda, Victoria; Avila, María M

2011-03-01

El uso del diagnóstico rápido para HIV en Argentina, así como otros países de Latinoamérica, ha sido limitado hasta el momento. Este trabajo reporta los resultados provenientes de un estudio cualitativo realizado entre hombres gays y otros hombres que tienen sexo con hombres (G&HSH) de la Ciudad de Buenos Aires, Argentina. El objetivo principal del mismo fue conocer las ventajas y desventajas que los hombres G&HSH perciben en relación al diagnóstico rápido casero para HIV. Se realizaron ocho grupos focales con 73 participantes en los cuales se discutió acerca de las ventajas y desventajas del uso de los diagnósticos rápidos. Las respuestas fueron codificadas utilizando un programa para análisis de datos cualitativos (NVivo) y analizadas temáticamente. Los participantes describieron numerosas ventajas sobre el uso del diagnóstico rápido casero, aunque algunos reportaron importantes preocupaciones dentro de las cuales se destaca la posibilidad de impulsos suicidas si alguien recibe un resultado positivo estando solo. En términos generales se observó una gran aceptabilidad para el uso del diagnóstico rápido si el mismo es realizado por personal de salud en lugares acondicionados para este fin.

PubMed

López Gómez, Juan José; Pérez Castrillón, José Luis; Romero Bobillo, Enrique; De Luis Román, Daniel A

2016-11-29

La obesidad interfiere con el metabolismo óseo a través de factores mecánicos, hormonales e inflamatorios. El principal tratamiento de dicha enfermedad es la dieta, modificación de la cantidad y tipo de alimento. Este tratamiento nutricional tiene una influencia sobre el metabolismo óseo en dos sentidos: modifica el efecto del sobrepeso y la obesidad sobre el hueso e interviene directamente en el turnoveróseo a través de las características de los nutrientes utilizados. Esta revisión analiza la evidencia del efecto sobre el hueso del descenso de peso y del patrón dietético utilizado. Por otra parte, se valorarán las modificaciones que se pueden realizar en la dieta indicada en un paciente obeso para prevenir la pérdida ósea, a corto y largo plazo, y disminuir el riesgo de fractura.

Atomic simulation of mechanical behavior of Mg in a super-lattice of nanocrystalline Mg and amorphous Mg-Al alloy

NASA Astrophysics Data System (ADS)

Song, H. Y.; An, M. R.; Li, Y. L.; Deng, Q.

2014-12-01

The mechanical properties of a super-lattice architecture composed of nanocrystalline Mg and Mg-Al amorphous alloy are investigated using molecular dynamics simulation. The results indicate that deformation mechanism of nanocrystalline Mg is obviously affected by the amorphous boundary spacing and temperature. The strength of the material increases with the decrease of amorphous boundary spacing, presenting a Hall-Petch effect at both 10 K and 300 K. A stress platform and following stiffness softening, as well as a linear strengthening in the plastic stage, are observed when the amorphous boundary spacing below 8.792 nm at 10 K. The implying reason may be that the amorphous boundary acts as the dislocations emission and absorption source. However, the second stress peak is not observed for the models at 300 K. Instead, the flow stress in plastic stage is a nearly constant value. The simulation demonstrates the emergence of the new grain, accompanied by the deformation twins and stacking faults associated with the plastic behaviors at 300 K. The general conclusions derived from this work may provide a guideline for the design of high-performance hexagonal close-packed metals.

Effectiveness of barnidipine 10 or 20 mg plus losartan 50-mg combination versus losartan 100-mg monotherapy in patients with essential hypertension not controlled by losartan 50-mg monotherapy: A 12-week, multicenter, randomized, open-label, parallel-group study.

PubMed

Parati, Gianfranco; Giglio, Alessia; Lonati, Laura; Destro, Maurizio; Ricci, Alessandra Rossi; Cagnoni, Francesca; Pini, Claudio; Venco, Achille; Maresca, Andrea Maria; Monza, Michela; Grandi, Anna Maria; Omboni, Stefano

2010-07-01

Increasing the dose or adding a second antihypertensive agent are 2 possible therapeutic choices when blood pressure (BP) is poorly controlled with monotherapy. This study investigated the effectiveness and tolerability of barnidipine 10 or 20 mg added to losartan 50 mg versus losartan 100 mg alone in patients with mild to moderate essential hypertension whose BP was uncontrolled by losartan 50-mg monotherapy. This was a 12-week, multicenter, randomized, open-label, parallel-group study. Eligible patients (aged 30-74 years) had uncontrolled hypertension, defined as office sitting diastolic BP (DBP) > or =90 mm Hg and/or systolic BP (SBP) > or =140 mm Hg, and mean daytime DBP > or =85 mm Hg and/or SBP > or =135 mm Hg. All were being treated with losartan 50 mg at enrollment. After a 1-week run-in period while taking losartan 50 mg, patients were randomly assigned to 6 weeks of treatment with open-label barnidipine 10 mg plus losartan 50 mg or losartan 100-mg monotherapy. At the end of this period, patients with uncontrolled BP had barnidipine doubled to 20 mg and continued for an additional 6 weeks, whereas patients not achieving control on treatment with losartan 100 mg were discontinued. Office BP was measured at each visit, whereas 24-hour ambulatory BP monitoring (ABPM) was performed at randomization and at the final visit (ie, after 12 weeks of treatment, or at 6 weeks for patients not controlled on losartan 100 mg). The intent-to-treat population included all randomized patients who received at least one dose of study treatment and had valid ABPM recordings at baseline and the final visit. The primary end point was the change in daytime DBP between baseline and 12 weeks of treatment, compared between the combination treatment and monotherapy. Adverse events (AEs) were evaluated during each study visit. A total of 93 patients were enrolled (age range, 30-75 years; 60% [56/93] men). After the 1-week run-in period, 68 patients were randomly assigned to 6 weeks of

Incidence of deep vein thrombosis is increased with 30 mg twice daily dosing of enoxaparin compared with 40 mg daily.

PubMed

Riha, Gordon M; Van, Philbert Y; Differding, Jerome A; Schreiber, Martin A

2012-05-01

The purpose of this study was to analyze whether 2 standard dosing regimens of enoxaparin (30 mg twice daily vs 40 mg once daily) would result in different deep vein thrombosis (DVT) rates and anti-factor Xa activity (anti-Xa) in surgical patients. Patients who required enoxaparin for prophylaxis were followed prospectively. Demographics were recorded. Patients underwent standardized duplex screening. Peak anti-Xa levels were drawn on 4 consecutive days. Sixty-three patients were followed up (28 patients on 30 mg twice daily, 35 patients on 40 mg once daily). There was no significant difference in demographics between groups. Twenty-five percent of patients on 30 mg twice daily developed a DVT, whereas 2.9% of patients on 40 mg once daily developed a DVT. Patients on 30 mg twice daily had significantly lower anti-Xa levels. The incidence of DVT is increased in surgical patients who receive 30 mg twice daily dosing of enoxaparin compared with 40 mg daily. Dosing of 40 mg once daily results in significantly higher peak anti-Xa levels compared with 30 mg twice daily. Copyright © 2012 Elsevier Inc. All rights reserved.

Preparation and Bond Properties of Thermal Barrier Coatings on Mg Alloy with Sprayed Al or Diffused Mg-Al Intermetallic Interlayer

NASA Astrophysics Data System (ADS)

Fan, Xizhi; Wang, Ying; Zou, Binglin; Gu, Lijian; Huang, Wenzhi; Cao, Xueqiang

2014-02-01

Sprayed Al or diffused Mg-Al layer was designed as interlayer between the thermal barrier coatings (TBCs) and Mg alloy substrate. The effects of the interlayer on the bond properties of the coats were investigated. Al layers were prepared by arc spraying and atmospheric plasma spraying (APS), respectively. Mg-Al diffused layer was obtained after the heat treatment of the sprayed sample (Mg alloy with APS Al coat) at 400 °C. The results show that sprayed Al interlayer does not improve the bond stability of TBCs. The failure of the TBCs on Mg alloy with Al interlayer occurs mainly due to the low strength of Al layer. Mg-Al diffused layer improves corrosion resistance of substrate and the bond interface. The TBCs on Mg alloy with Mg-Al diffused interlayer shows better bond stability than the sample of which the TBCs is directly sprayed on Mg alloy substrate by APS.

Chlorophyll-a Photosynthesis and Mg Isotope Fractionation

NASA Astrophysics Data System (ADS)

Black, J.; Yin, Q.; Casey, B. H.

2006-12-01

Mg is the metal center of all the chlorophyll pigments and therefore at the center of the process of photosynthesis. Chlorophyll (Chl) is often used as a biomarker of photosynthesis and is an enormous contributor to the global carbon cycle. Biosynthetic processes fractionate isotopes of light elements and this led us to examine the isotopic composition of Mg in Chl, as another potential biomarker. Here we detail the Mg isotopic composition of Chl-a, extracted from cultures of Synechococcus elongatus, and the culture medium (Black et al., 2006). After Chl extraction, the Mg was liberated from Chl and purified on cation-exchange columns, with a final yield of 100 ± 5%. ^{26}Mg/^{24}Mg and ^{25}Mg/^{24}Mg, were measured relative to Cambridge 1 and DSM3 standards by a standard-sample-bracketing technique on an MC-ICP-MS (Nu Instruments Ltd). We have measured the average isotopic fractionation of Mg from six samples of Chl-a from early growth phase and 4 samples from late growth phase, 9 samples of the culture medium and the Cambridge 1 Std, all relative to the DSM3 Std. We demonstrate for the first time that there is a clearly resolved depletion in the heavy isotopes of Mg in Chl-a relative to the culture medium (Δ^{26}Mg =-0.61‰; Δ^{25}Mg =-0.30‰). The heavy isotope depletion observed may be caused by chelation effects during the biosynthesis of Chl-a. We are now evaluating two hypotheses about the cause of the fractionation. One hypothesis is that the insertion step induces a fractionation via the Mg- chelatase enzyme. The second is that transport into the cell, such as via an ion channel, causes the fractionation. In either case, no difference between Chl-a and Chl-b is anticipated. Experiments and field studies are underway to examine these ideas. References Black, J., Yin, Q.-Z., Casey, W.H., 2006. Geochim. Cosmochim. Acta, 70, 4072-4079.

The in vitro biocompatibility and macrophage phagocytosis of Mg17Al12 phase in Mg-Al-Zn alloys.

PubMed

Liu, Chen; He, Peng; Wan, Peng; Li, Mei; Wang, Kehong; Tan, Lili; Zhang, Yu; Yang, Ke

2015-07-01

Mg alloys are gaining interest for applications as biodegradable medical implant, including Mg-Al-Zn series alloys with good combination of mechanical properties and reasonable corrosion resistance. However, whether the existence of second phase particles in the alloys exerts influence on the biocompatibility is still not clear. A deeper understanding of how the particles regulate specific biological responses is becoming a crucial requirement for their subsequent biomedical application. In this work, the in vitro biocompatibility of Mg17Al12 as a common second phase in biodegradable Mg-Al-Zn alloys was investigated via hemolysis, cytotoxicity, cell proliferation, and cell adhesion tests. Moreover, osteogenic differentiation was evaluated by the extracellular matrix mineralization assay. The Mg17Al12 particles were also prepared to simulate the real situation of second phase in the in vivo environment in order to estimate the cellular response in macrophages to the Mg17Al12 particles. The experimental results indicated that no hemolysis was found and an excellent cytocompatibility was also proved for the Mg17Al12 second phase when co-cultured with L929 cells, MC3T3-E1 cells and BMSCs. Macrophage phagocytosis co-culture test revealed that Mg17Al12 particles exerted no harmful effect on RAW264.7 macrophages and could be phagocytized by the RAW264.7 cells. Furthermore, the possible inflammatory reaction and metabolic way for Mg17Al12 phase were also discussed in detail. © 2014 Wiley Periodicals, Inc.

Maintenance treatment of duodenal ulceration: ranitidine 300 mg at night is better than 150 mg in cigarette smokers.

PubMed Central

Lee, F I; Hardman, M; Jaderberg, M E

1991-01-01

Two hundred patients received either ranitidine 150 mg or 300 mg at night for 18 months to prevent duodenal ulcer relapse. Recurrence rates were lower in patients receiving the higher dose of ranitidine (3.1% v 9.7%, p = 0.78; 6.5% v 16.7%, p = 0.037; and 8.9% v 17.0%, p = 0.121 at six, 12, and 18 months respectively). In patients receiving ranitidine 150 mg, recurrences were significantly more common in smokers than non-smokers after 12 and 18 months, while in patients receiving ranitidine 300 mg recurrence rates were similar in smokers and non-smokers. Ranitidine 300 mg at night abolishes the adverse effect of smoking observed during maintenance treatment with ranitidine 150 mg at night and may therefore be an appropriate maintenance dose for smokers who relapse during standard dose maintenance treatment. PMID:1864532

Surface treatments for controlling corrosion rate of biodegradable Mg and Mg-based alloy implants

PubMed Central

Uddin, M S; Hall, Colin; Murphy, Peter

2015-01-01

Due to their excellent biodegradability characteristics, Mg and Mg-based alloys have become an emerging material in biomedical implants, notably for repair of bone as well as coronary arterial stents. However, the main problem with Mg-based alloys is their rapid corrosion in aggressive environments such as human bodily fluids. Previously, many approaches such as control of alloying materials, composition and surface treatments, have been attempted to regulate the corrosion rate. This article presents a comprehensive review of recent research focusing on surface treatment techniques utilised to control the corrosion rate and surface integrity of Mg-based alloys in both in vitro and in vivo environments. Surface treatments generally involve the controlled deposition of thin film coatings using various coating processes, and mechanical surfacing such as machining, deep rolling or low plasticity burnishing. The aim is to either make a protective thin layer of a material or to change the micro-structure and mechanical properties at the surface and sub-surface levels, which will prevent rapid corrosion and thus delay the degradation of the alloys. We have organised the review of past works on coatings by categorising the coatings into two classes—conversion and deposition coatings—while works on mechanical treatments are reviewed based on the tool-based processes which affect the sub-surface microstructure and mechanical properties of the material. Various types of coatings and their processing techniques under two classes of coating and mechanical treatment approaches have been analysed and discussed to investigate their impact on the corrosion performance, biomechanical integrity, biocompatibility and cell viability. Potential challenges and future directions in designing and developing the improved biodegradable Mg/Mg-based alloy implants were addressed and discussed. The literature reveals that no solutions are yet complete and hence new and innovative approaches

Electrochemical Codeposition of Al-Li-Mg Alloys at Solid Aluminum Electrode from LiCl-KCl-MgCl2 Molten Salt System

NASA Astrophysics Data System (ADS)

Ye, Ke; Zhang, Mi Lin; Chen, Ye; Han, Wei; de Yan, Yong; Cao, Peng

2010-06-01

The electrochemical codeposition of Mg and Li at an aluminium electrode in LiCl-KCl (50:50 wt pct) melts containing different concentrations of MgCl2 at 893 K (620 °C) to form Al-Li-Mg alloys was investigated. Cyclic voltammograms showed that the potential of Li metal deposition at an Al electrode, before the addition of MgCl2, is more positive than that of Li metal deposition at an Mo electrode, which indicated the formation of an Al-Li alloy. The underpotential deposition of magnesium at an aluminium electrode leads to the formation of Al-Mg alloys, and the succeeding underpotential deposition of lithium on predeposited Al-Mg alloys leads to the formation of Al-Li-Mg alloys. Chronopotentiometric measurements indicated that the codeposition of Mg and Li occurs at current densities lower than -0.668 A cm-2 in LiCl-KCl-MgCl2 (8 wt pct) melts at an aluminium electrode. The chronoamperometric studies indicated that the onset potential for the codeposition of Mg and Li is -2.000 V, and the codeposition of Mg and Li at an aluminium electrode is formed into Al-Li-Mg alloys when the applied potentials are more negative than -2.000 V. X-ray diffraction and inductively coupled plasma analysis indicated that Al-Li-Mg alloys with different lithium and magnesium contents were prepared via potentiostatic and galvanostatic electrolysis. The microstructure of typical dual phases of the Al-Li-Mg alloy was characterized by an optical microscope and by scanning electron microscopy. The analysis of energy dispersive spectrometry showed that the elements of Al and Mg distribute homogeneously in the Al-Li-Mg alloy. The lithium and magnesium contents of Al-Li-Mg alloys can be controlled by MgCl2 concentrations and by electrolytic parameters.

Rescue of murine F508del CFTR activity in native intestine by low temperature and proteasome inhibitors.

PubMed

Wilke, Martina; Bot, Alice; Jorna, Huub; Scholte, Bob J; de Jonge, Hugo R

2012-01-01

Most patients with Cystic Fibrosis (CF) carry at least one allele with the F508del mutation, resulting in a CFTR chloride channel protein with a processing, gating and stability defect, but with substantial residual activity when correctly sorted to the apical membranes of epithelial cells. New therapies are therefore aimed at improving the folding and trafficking of F508del CFTR, (CFTR correctors) or at enhancing the open probability of the CFTR chloride channel (CFTR potentiators). Preventing premature breakdown of F508del CFTR is an alternative or additional strategy, which is investigated in this study. We established an ex vivo assay for murine F508del CFTR rescue in native intestinal epithelium that can be used as a pre-clinical test for candidate therapeutics. Overnight incubation of muscle stripped ileum in modified William's E medium at low temperature (26°C), and 4 h or 6 h incubation at 37°C with different proteasome inhibitors (PI: ALLN, MG-132, epoxomicin, PS341/bortezomib) resulted in fifty to hundred percent respectively of the wild type CFTR mediated chloride secretion (forskolin induced short-circuit current). The functional rescue was accompanied by enhanced expression of the murine F508del CFTR protein at the apical surface of intestinal crypts and a gain in the amount of complex-glycosylated CFTR (band C) up to 20% of WT levels. Sustained rescue in the presence of brefeldin A shows the involvement of a post-Golgi compartment in murine F508del CFTR degradation, as was shown earlier for its human counterpart. Our data show that proteasome inhibitors are promising candidate compounds for improving rescue of human F508del CFTR function, in combination with available correctors and potentiators.

Effects of various Mg/Si ratios on microstructure and performance property of Al-Mg-Si alloy cables

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

Xu, Xuexuan

2016-09-15

High quality AA6101 aluminum cables are critical to electrical industry to meet the energy consumption requests. In the present work, the influence of Mg/Si ratios on the electrical conductivity and mechanical properties of AA6101 aluminum alloy was investigated. Wheatstone Bridge method and tensile test were employed to characterize the mechanical properties. X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) were used to understand the morphology of the precipitation and the mechanism of age hardening. It is found that excessive Si benefits high strength and high conductivity while excessive Mg plays a negative role in the strengthmore » and the conductivity of AA6101 cables. Excessive Si elements promote both the precipitating rate and quantity of β″ phase therefore increase the tensile strength. Excessive Si elements also help with decreasing the lattice distortion, which contributes to the enhancement of the conductivity. Excessive Mg elements lead to more dissolved Mg after aging treatment, therefore increase lattice distortion of the matrix and promote the deposit of coarse Mg-enriched secondary phase. - Highlights: •A new available method to improve the mechanical and electrical properties of Al-Mg-Si alloy •Investigation on the role of various Mg/Si ratios in the changes of comprehensive performances •Discussions on the morphology of the precipitation phases and the mechanism of hardening.« less

Relative bioavailability of ondansetron 8-mg oral tablets versus two extemporaneous 16-mg suppositories: formulation and gender differences.

PubMed

Jann, M W; ZumBrunnen, T L; Tenjarla, S N; Ward, E S; Weidler, D J

1998-01-01

To compare the relative bioavailability of two 16-mg extemporaneously prepared suppository formulations with that of an 8-mg commercially available oral tablet. Prospective, crossover bioavailability study. Inpatient clinical research center. Sixteen young, nonsmoking, healthy volunteers. Blood samples were obtained 24 and 48 hours after administration of an 8-mg oral ondansetron tablet and 16-mg suppository, respectively. Two 16-mg suppository formulations were compounded using commercially available Fattibase and Polybase. Ondansetron was well absorbed by both routes of administration. The following pharmacokinetic parameters (mean+/-SEM) were obtained for the 8-mg tablet, 16-mg Fattibase suppository, and 16-mg Polybase suppository, respectively: area under the curve (AUC) in men 154.2+/-21.77, 253.4+/-72.3, 304.8+/-62.2 ng x hr/ml; AUC in women 353.6+/-32.7, 561.6+/-103.6, and 768.7+/-117.9 ng x hr/ml; maximum concentration (Cmax) in men 45.5+/-7.0, 40.6+/-10.4, and 51.2+/-6.7 ng/ml; Cmax in women 51.4+/-.8, 47.1+/-3.9, and 82.9+/-6.6 ng/ml. Times to Cmax (Tmax; mean+/-SEM) for men were 1.5+/-0.3, 4.4+/-0.5, and 2.9+/-0.3 hours; Tmax for women were 1.8+/-0.3, 4.1+/-0.4, and 4.4+/-0.6 hours for the three formulations, respectively. Women had a consistently higher AUC for all three formulations than men (p<0.05). With the exception of the 16-mg Polybase formulation in women, the two suppositories closely approximated the pharmacokinetics of the 8-mg oral tablet. These results suggest that gender may be a significant factor in ondansetron's disposition.

Structurally characterized 1,1,3,3-tetramethylguanidine solvated magnesium aryloxide complexes: [Mg(mu-OEt)(DBP)(H-TMG)]2, [Mg(mu-OBc)(DBP)(H-TMG)]2, [Mg(mu-TMBA)(DBP)(H-TMG)]2, [Mg(mu-DPP)(DBP)(H-TMG)]2, [Mg(BMP)2(H-TMG)2], [Mg(O-2,6-Ph2C6H3)2 (H-TMG)2].

PubMed

Monegan, Jessie D; Bunge, Scott D

2009-04-06

The synthesis and structural characterization of several 1,1,3,3-tetramethylguanidine (H-TMG) solvated magnesium aryloxide complexes are reported. Bu(2)Mg was successfully reacted with H-TMG, HOC(6)H(3)(CMe(3))(2)-2,6 (H-DBP), and either ethanol, a carboxylic acid, or diphenyl phosphate in a 1:1 ratio to yield the corresponding [Mg(mu-L)(DBP)(H-TMG)](2) where L = OCH(2)CH(3) (OEt, 1), O(2)CC(CH(3))(3) (OBc, 2), O(2)C(C(6)H(2)-2,4,6-(CH(3))(3)) (TMBA, 3), or O(2)P(OC(6)H(5))(2) (DPP, 4). Bu(2)Mg was also reacted with two equivalents of H-TMG and HOC(6)H(3)(CMe(3))-2-(CH(3))-6 (BMP) or HO-2,6-Ph(2)C(6)H(3) to yield [Mg(BMP)(2)(H-TMG)(2)] (5) and [Mg(O-2,6-Ph(2)C(6)H(3))(2)(H-TMG)(2)] (6). Compounds 1-6 were characterized by single-crystal X-ray diffraction. Polymerization of l- and rac-lactide with 1 was found to generate polylactide (PLA). A discussion concerning the relevance of compounds 2 - 4 to the structure of Mg-activated phosphatase enzymes is also provided. The bulk powders for all complexes were found to be in agreement with the crystal structures based on elemental analyses, FT-IR spectroscopy, and (1)H, (13)C and (31)P NMR studies.

Distribución del continuo ultravioleta e infrarrojo en estrellas Be

NASA Astrophysics Data System (ADS)

Cruzado, A.; Ringuelet, A.; di Rocco, H.

Estamos interesados en interpretar los excesos de flujo infrarrojo y/o ultravioleta observados en estrellas Be con respecto al de estrellas B normales, así como su posible correlación. Una envoltura rodeando la estrella distingue una estrella Be de una B normal; para explicar las observaciones es necesario entonces tener en cuenta todos los posibles procesos físicos que en ella tienen lugar. Adoptando un modelo atmosférico específico, hemos estudiado el proceso de recombinación dielectrónica de metales como MgII y FeII, teniendo en cuenta la posible influencia de la opacidad del medio en el flujo emitido.

Fast Mg2+ diffusion in Mo3(PO4)3O for Mg batteries.

PubMed

Rong, Ziqin; Xiao, Penghao; Liu, Miao; Huang, Wenxuan; Hannah, Daniel C; Scullin, William; Persson, Kristin A; Ceder, Gerbrand

2017-07-13

In this work, we identify a new potential Mg battery cathode structure Mo 3 (PO 4 ) 3 O, which is predicted to exhibit ultra-fast Mg 2+ diffusion and relatively high voltage based on first-principles density functional theory calculations. Nudged elastic band calculations reveal that the migration barrier of the percolation channel is only ∼80 meV, which is remarkably low, and comparable to the best Li-ion conductors. This low barrier is verified by ab initio molecular dynamics and kinetic Monte Carlo simulations. The voltage and specific energy are predicted to be ∼1.98 V and ∼173 W h kg -1 , respectively. If confirmed by experiments, this material would have the highest known Mg mobility among inorganic compounds.

Microstructure and Phase Evolution in Mg-Gd and Mg-Gd-Nd Alloys With Additions of Zn, Y and Zr

NASA Astrophysics Data System (ADS)

Khawaled, S.; Bamberger, M.; Katsman, A.

Microstructure and phase evolution in Mg-Gd and Mg-Gd-Nd based alloys with additions of Zn, Zr and Y were analyzed in the as-cast, solution treated and aged conditions. Alloys has been investigated after solution treatment at 540°C for 24hr followed by isothermal aging at 175°C up to 32 days by using of Vickers hardness, optical microscopy, scanning electron microscopy equipped with EDS, X-ray diffraction and transmission electron microscopy. It was found that the as-cast alloys contained primary α-Mg matrix, eutecticlike structures, cuboid-like phases and Zr-rich clusters. The homogenized and quenched alloys contained primary α-Mg solid solution, smaller amount of divorced eutectic compounds, enlarged cuboid-like particles and Zr-rich clusters. The eutectic phase was Mg5Gd prototype with the composition Mg5(GdxNd1-x, x≈0.2). The compositions of the cuboid shaped particles are characterized by enlarged amount of Gd and can be written as Mg2(Gd x Y1-x) with x≈0.85 in the Mg-5Gd based alloy, and Gd4(YxNd1-x) with x≈0.5 in the Mg-6Gd-3.7Nd based alloy. The cuboid shaped particles grew during aging and reached 3µm average size. Precipitation of ß″ and ß' phases during aging was observed. Mg-6Gd-3.7Nd based alloy reached a maximum value of microhardness after 16 days of aging; in Mg-Gd based alloy, microhardness increased more slowly and reached a maximum value after 32 days of aging.

Lack of effect of the alpha2C-adrenoceptor Del322-325 polymorphism on inhibition of cyclic AMP production in HEK293 cells.

PubMed

Montgomery, M D; Bylund, D B

2010-02-01

The alpha(2C)-adrenoceptor has multiple functions, including inhibiting release of noradrenaline from presynaptic nerve terminals. A human alpha(2C) polymorphism, Del322-325, a potential risk factor for heart failure, has been reported to exhibit reduced signalling in CHO cells. To further understand the role of the Del322-325 polymorphism on receptor signalling, we attempted to replicate and further study the reduced signalling in HEK293 cells. Human alpha(2C) wild-type (WT) and Del322-325 adrenoceptors were stably transfected into HEK293 cells. Radioligand binding was performed to determine affinities for both receptors. In intact cells, inhibition of forskolin-stimulated cyclic AMP production by WT and Del322-325 clones with a range of receptor densities (200-2320 fmol.mg(-1) protein) was measured following agonist treatment. Noradrenaline, brimonidine and clonidine exhibited similar binding affinities for WT and Del322-325. Brimonidine and clonidine also had similar efficacies and potencies for both receptors for the inhibition of cyclic AMP production at all receptor densities tested. A linear regression analysis comparing efficacy and potency with receptor expression levels showed no differences in slopes between WT and Del322-325. The alpha(2C) WT and Del322-325 adrenoceptors exhibited similar binding properties. Additionally, inhibition of cyclic AMP production by Del322-325 was similar to that of WT over a range of receptor densities. Therefore, in intact HEK293 cells, the alpha(2C)-Del322-325 polymorphism does not exhibit reduced signalling to adenylyl cyclase and may not represent a clinically important phenotype.

Distribution of calcium (Ca) and magnesium (Mg) in the leaves of Brassica rapa under varying exogenous Ca and Mg supply.

PubMed

Rios, Juan Jose; Lochlainn, Seosamh O; Devonshire, Jean; Graham, Neil S; Hammond, John P; King, Graham J; White, Philip J; Kurup, Smita; Broadley, Martin R

2012-05-01

Leafy vegetable Brassica crops are an important source of dietary calcium (Ca) and magnesium (Mg) and represent potential targets for increasing leaf Ca and Mg concentrations through agronomy or breeding. Although the internal distribution of Ca and Mg within leaves affects the accumulation of these elements, such data are not available for Brassica. The aim of this study was to characterize the internal distribution of Ca and Mg in the leaves of a vegetable Brassica and to determine the effects of altered exogenous Ca and Mg supply on this distribution. Brassica rapa ssp. trilocularis 'R-o-18' was grown at four different Ca:Mg treatments for 21 d in a controlled environment. Concentrations of Ca and Mg were determined in fully expanded leaves using inductively coupled plasma-mass spectrometry (ICP-MS). Internal distributions of Ca and Mg were determined in transverse leaf sections at the base and apex of leaves using energy-dispersive X-ray spectroscopy (EDS) with cryo-scanning electron microscopy (cryo-SEM). Leaf Ca and Mg concentrations were greatest in palisade and spongy mesophyll cells, respectively, although this was dependent on exogenous supply. Calcium accumulation in palisade mesophyll cells was enhanced slightly under high Mg supply; in contrast, Mg accumulation in spongy mesophyll cells was not affected by Ca supply. The results are consistent with Arabidopsis thaliana and other Brassicaceae, providing phenotypic evidence that conserved mechanisms regulate leaf Ca and Mg distribution at a cellular scale. The future study of Arabidopsis gene orthologues in mutants of this reference B. rapa genotype will improve our understanding of Ca and Mg homeostasis in plants and may provide a model-to-crop translation pathway for targeted breeding.

Radio-Observaciones del OH EN la Coma del Cometa Halley Desde EL Hemisferio Sur

NASA Astrophysics Data System (ADS)

Silva, A. M.; Bajaja, E.; Morras, R.; Cersosimo, J. C.; Martin, M. C.; Arnal, E. M.; Poppel, W. G. L.; Colomb, F. R.; Mazzaro, J.; Olalde, J. C.; Boriakoff, V.; Mirabel, I. F.

1987-05-01

Se utilizó una antena de 30 metros del Instituto Argentino de Radioastronomía para observaciones diarias Cf ebrero a abril de 1986) de la transición en 1667 MHz ( λ = 18 cm) del OH en la coma del cometa Halley. De las observaciones realizadas se concluye: 1) El número promedio de moléculas de OH en la coma durante 37 días de observación fue de (8.9±3.5)x1034 moléculas, lo que implica una tasa de producción promedio de OH de 1.8x1029 moléculas seg-1 y consecuentemente una pérdida de masa promedio de 17±6 toneladas seg-1 . Este valor está de acuerdo con las mediciones realizadas por las sondas Vega y Giotto. 2) El monitoreo desde el lAR revela la existencia de variaciones bruscas en los flujos de absorción del OH. Estas variaciones son consistentes con los modelos que representan la producción gaseosa a partir de ejecciones y/o desprendimientos discretos de materia congelada del núcleo. 3) Las variaciones en la densidad de flujo son consistentes con las estimaciones de los tiem- pos de vida medios del H2O y del OH en presencia del campo de radiación solar. 4) Se encuentra una correlación entre la intensidad del flujo absorbido y anisotropías en Ia dinamica de la coma.

Avisos de salud sobre el PFOA y PFOS en el agua potable

EPA Pesticide Factsheets

La EPA estableció avisos de salud sobre el ácido perfluorooctanoico (PFOA) y el sulfonato de perfluorooctano (PFOS) para proporcionar información a los operadores de sistemas de agua potable y funcionarios estatales, tribales y locales sobre los riesgos de

Pharmacodynamics of 750 mg and 500 mg doses of levofloxacin against ciprofloxacin-resistant strains of Streptococcus pneumoniae.

PubMed

Lister, Philip D

2002-09-01

An in vitro pharmacokinetic model (IVPM) was used to evaluate the pharmacodynamics of the 750 mg and 500 mg doses of levofloxacin against 4 ciprofloxacin-nonsusceptible Streptococcus pneumoniae. Levofloxacin MICs ranged from 1.4 to 3.2 micro g/ml. Log-phase cultures (5 x 10(7) cfu/ml) were inoculated into the IVPM and exposed to the peak free-drug concentrations of levofloxacin achieved in human serum with each dose. Levofloxacin was dosed at 0 and 24 h, elimination pharmacokinetics were simulated, and viable counts were measured over 30 h. The 750 mg dose was rapidly bactericidal against all 4 strains, achieving eradication within 30 h. Against strains with levofloxacin MICs of 1.4 and 1.8 micro g/ml, the 500 mg dose exhibited pharmacodynamics similar to the 750 mg dose. In contrast, against strains with levofloxacin MICs of 2.6 and 3.2 micro g/ml, viable counts never fell below 10(4) cfu/ml. The rapid killing and eradication of these pneumococci by the 750 mg dose warrant the clinical evaluation of this new dose in the treatment of pneumococcal infections.

Synthesis and characterization of the divalent samarium Zintl-phases SmMg 2Bi 2 and SmMg 2Sb 2

DOE PAGES

Ramirez, D.; Gallagher, A.; Baumbach, R.; ...

2015-08-29

Here, single crystals of LnMg 2Bi 2 (Ln = Yb, Eu, Sm) and SmMg 2Sb 2 were synthesized using Mg-Bi metal and Mg-Sb metal fluxes, respectively. The crystal structures are of the CaAl 2Si 2 type with space group P3 m1 (#164, Z = 1): SmMg 2Bi 2 ( a = 4.7745(1)Å, c = 7.8490(2)Å), EuMg 2Bi 2 ( a = 4.7702(1)Å, c = 7.8457(2) Å), YbMg 2Bi 2 ( a = 4.7317(2)Å, c = 7.6524(3) Å), and SmMg 2Sb 2 ( a = 4.6861(1) Å, c = 7.7192(2) Å). Heat capacity, electrical transport, and magnetization of all bismuth containingmore » phases were measured. The materials behave as “poor metals” with resistivity between 2 and 10 mΩ·cm. Temperature independent Van Vleck paramagnetism is observed in SmMg 2Bi 2 indicative of divalent samarium (Sm 2+) ions.« less

SOLID SOLUTION EFFECTS ON THE THERMAL PROPERTIES IN THE MgAl2O4-MgGa2O4

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

O'Hara, Kelley; Smith, Jeffrey D; Sander, Todd P.

Solid solution eects on thermal conductivity within the MgO-Al2O3-Ga2O3 system were studied. Samples with systematically varied additions of MgGa2O4 to MgAl2O4 were prepared and the laser ash technique was used to determine thermal diusivity at temperatures between 200C and 1300C. Heat capacity as a function of temperature from room temperature to 800C was also determined using dierential scanning calorimetry. Solid solution in the MgAl2O4-MgGa2O4 system decreases the thermal conductivity up to 1000C. At 200C thermal conductivity decreased 24% with a 5 mol% addition of MgGa2O4 to the system. At 1000C the thermal conductivity decreased 13% with a 5 mol% addition.more » Steady state calculations showed a 12.5% decrease in heat ux with 5 mol% MgGa2O4 considered across a 12 inch thickness.« less

Pharmacokinetics, Safety, and Tolerability of a Single 500-mg or 1000-mg Intravenous Dose of Dalbavancin in Healthy Japanese Subjects.

PubMed

Scoble, Patrick J; Owens, Robert C; Puttagunta, Sailaja; Yen, Mark; Dunne, Michael W

2015-12-01

Dalbavancin is a novel, once-weekly glycopeptide antibiotic approved for treatment of acute bacterial skin infections. Given the importance of understanding any pharmacokinetic variability across different patient populations, a double-blind, placebo-controlled study was conducted to evaluate the pharmacokinetics, safety, and tolerability of a single 500-mg and a single 1000-mg intravenous dose of dalbavancin in healthy Japanese subjects. Ten subjects received intravenous dalbavancin 1000 mg, five subjects received intravenous dalbavancin 500 mg, and three subjects received intravenous placebo. After a single infusion of dalbavancin, the maximal plasma concentration (C max) and area under the plasma concentration-time curve (AUC) increased in a proportional manner from 500 mg to 1000 mg (C max: 157 μg/ml and 299 μg/ml; AUClast: 10,850 μg·h/ml and 22,679 μg·h/ml, on the 500-mg and 1000-mg regimens, respectively) with low inter-subject variability. The mean terminal phase half-life (t 1/2) was 204 and 193 h after the 500-mg and 1000-mg dose, respectively. Clearance and volume of distribution were similar for the two dose concentrations. Treatment-emergent adverse events reported were considered to be of mild intensity. There were no relevant changes in laboratory values or vital signs over time in subjects in either treatment group. Overall, dalbavancin 500 mg and dalbavancin 1000 mg, administered as a single 30-min infusion, was well tolerated in this population and resulted in plasma exposures similar to those in non-Asians.

Quaternary BeMgZnO by plasma-enhanced molecular beam epitaxy for BeMgZnO/ZnO heterostructure devices

NASA Astrophysics Data System (ADS)

Ullah, M. B.; Toporkov, M.; Avrutin, V.; Özgür, Ü.; Smith, D. J.; Morkoç, H.

2017-02-01

We investigated the crystal structure, growth kinetics and electrical properties of BeMgZnO/ZnO heterostructures grown by Molecular Beam Epitaxy (MBE). Transmission Electron Microscopy (TEM) studies revealed that incorporation of Mg into the BeZnO solid solution eliminates the high angle grain boundaries that are the major structural defects in ternary BeZnO. The significant improvement of x-ray diffraction intensity from quaternary BeMgZnO alloy compared to ternary BeZnO was attributed to the reduction of lattice strain, which is present in the latter due to the large difference of covalent radii between Be and Zn (1.22 Å for Zn, 0.96 Å for Be). Incorporation of Mg, which has a larger covalent radius of 1.41Å, reduced the strain in BeMgZnO thin films and also enhanced Be incorporation on lattice sites in the wurtzite lattice. The Zn/(Be + Mg) ratio necessary to obtain single-crystal O-polar BeMgZnO on (0001) GaN/sapphire templates was found to increase with increasing substrate temperature:3.9, 6.2, and 8.3 at substrate temperatures of 450°C, 475°C, and 500°C, respectively. Based on analysis of photoluminescence spectra from Be0.03MgyZn0.97-yO and evolution of reflection high-energy electron diffraction patterns observed in situ during the MBE growth, it has been deduced that more negative formation enthalpy of MgO compared to ZnO and the increased surface mobility of Mg adatoms at elevated substrate temperatures give rise to the nucleation of a MgO-rich wurtzite phase at relatively low Zn/(Be + Mg) ratios. We have demonstrated both theoretically and experimentally that the incorporation of Be into the barrier in Zn-polar BeMgZnO/ZnO and O-polar ZnO/BeMgZnO polarization doped heterostructures allows the alignment of piezoelectric polarization vector with that of spontaneous polarization due to the change of strain sign, thus increasing the amount of net polarization. This made it possible to achieve Zn-polar BeMgZnO/ZnO heterostructures grown on Ga

Highly Active Electrolytes for Rechargeable Mg Batteries Based on [Mg2(μ-Cl)2]2+ Cation Complex in Dimethoxyethane

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

Cheng, Yingwen; Stolley, Ryan M.; Han, Kee Sung

2015-01-01

Highly active electrolytes based on a novel [Mg2(μ-Cl)2]2+ cation complex for reversible Mg deposition were developed and analyzed in this work. These electrolytes were formulated in dimethoxyethane through dehalodimerization of non-nucleophilic MgCl2 by reacting with either Mg salts (such as Mg(TFSI)2, TFSI= bis(trifluoromethane)sulfonylimide) or Lewis acid salts (such as AlEtCl2 or AlCl3). The cation complex was identified for the first time as [Mg2(μ-Cl)2(DME)4]2+ (DME=dimethoxyethane) and its molecular structure was characterized by single crystal X-ray diffraction, Raman spectroscopy and NMR. The electrolyte synthesis process was studied and rational approaches for formulating highly active electrolytes were proposed. Through control of the anions,more » electrolytes with efficiency close to 100%, wide electrochemical window (up to 3.5V) and high ionic conductivity (> 6 mS/cm) were obtained. The electrolyte synthesis and understandings developed in this work could bring significant opportunities for rational formulation of electrolytes with the general formula [Mg2(μ-Cl)2(DME)4][anion]x for practical Mg batteries.« less

Enhanced bioactivity of Mg-Nd-Zn-Zr alloy achieved with nanoscale MgF2 surface for vascular stent application.

PubMed

Mao, Lin; Shen, Li; Chen, Jiahui; Wu, Yu; Kwak, Minsuk; Lu, Yao; Xue, Qiong; Pei, Jia; Zhang, Lei; Yuan, Guangyin; Fan, Rong; Ge, Junbo; Ding, Wenjiang

2015-03-11

Magnesium (Mg) alloys have revolutionized the application of temporary load-bearing implants as they meet both engineering and medical requirements. However, rapid degradation of Mg alloys under physiological conditions remains the major obstacle hindering the wider use of Mg-based implants. Here we developed a simple method of preparing a nanoscale MgF2 film on Mg-Nd-Zn-Zr (denoted as JDBM) alloy, aiming to reduce the corrosion rate as well as improve the biological response. The corrosion rate of JDBM alloy exposed to artificial plasma is reduced by ∼20% from 0.337 ± 0.021 to 0.269 ± 0.043 mm·y(-1) due to the protective effect of the MgF2 film with a uniform and dense physical structure. The in vitro cytocompatibility test of MgF2-coated JDBM using human umbilical vein endothelial cells indicates enhanced viability, growth, and proliferation as compared to the naked substrate, and the MgF2 film with a nanoscale flakelike feature of ∼200-300 nm presents a much more favorable environment for endothelial cell adhesion, proliferation, and alignment. Furthermore, the animal experiment via implantation of MgF2-coated JDBM stent to rabbit abdominal aorta confirms excellent tissue compatibility of the well re-endothelialized stent with no sign of thrombogenesis and restenosis in the stented vessel.

Effect of amorphous Mg{sub 50}Ni{sub 50} on hydriding and dehydriding behavior of Mg{sub 2}Ni alloy

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

Guzman, D., E-mail: danny.guzman@uda.cl; Ordonez, S.; Fernandez, J.F.

Composite Mg{sub 2}Ni (25 wt.%) amorphous Mg{sub 50}Ni{sub 50} was prepared by mechanical milling starting with nanocrystalline Mg{sub 2}Ni and amorphous Mg{sub 50}Ni{sub 50} powders, by using a SPEX 8000 D mill. The morphological and microstructural characterization of the powders was performed via scanning electron microscopy and X-ray diffraction. The hydriding characterization of the composite was performed via a solid gas reaction method in a Sievert's-type apparatus at 363 K under an initial hydrogen pressure of 2 MPa. The dehydriding behavior was studied by differential thermogravimetry. On the basis of the results, it is possible to conclude that amorphous Mg{submore » 50}Ni{sub 50} improved the hydriding and dehydriding kinetics of Mg{sub 2}Ni alloy upon cycling. A tentative rationalization of experimental observations is proposed. - Research Highlights: {yields} First study of the hydriding behavior of composite Mg{sub 2}Ni (25 wt.%) amorphous Mg{sub 50}Ni{sub 50}. {yields} Microstructural characterization of composite material using XRD and SEM was obtained. {yields} An improved effect of Mg{sub 50}Ni{sub 50} on the Mg{sub 2}Ni hydriding behavior was verified. {yields} The apparent activation energy for the hydrogen desorption of composite was obtained.« less

Size effects in MgO cube dissolution.

PubMed

Baumann, Stefan O; Schneider, Johannes; Sternig, Andreas; Thomele, Daniel; Stankic, Slavica; Berger, Thomas; Grönbeck, Henrik; Diwald, Oliver

2015-03-10

Stability parameters and dissolution behavior of engineered nanomaterials in aqueous systems are critical to assess their functionality and fate under environmental conditions. Using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, we investigated the stability of cubic MgO particles in water. MgO dissolution proceeding via water dissociation at the oxide surface, disintegration of Mg(2+)-O(2-) surface elements, and their subsequent solvation ultimately leads to precipitation of Mg(OH)2 nanosheets. At a pH ≥ 10, MgO nanocubes with a size distribution below 10 nm quantitatively dissolve within few minutes and convert into Mg(OH)2 nanosheets. This effect is different from MgO cubes originating from magnesium combustion in air. With a size distribution in the range 10 nm ≤ d ≤ 1000 nm they dissolve with a significantly smaller dissolution rate in water. On these particles water induced etching generates (110) faces which, above a certain face area, dissolve at a rate equal to that of (100) planes.1 The delayed solubility of microcrystalline MgO is attributed to surface hydroxide induced self-inhibition effects occurring at the (100) and (110) microplanes. The present work underlines the importance of morphology evolution and surface faceting of engineered nanomaterials particles during their dissolution.

Loss of Endothelial Barrier in Marfan Mice (mgR/mgR) Results in Severe Inflammation after Adenoviral Gene Therapy

PubMed Central

Weymann, Alexander; Arif, Rawa; Weber, Antje; Zaradzki, Marcin; Richter, Karsten; Ensminger, Stephan; Robinson, Peter Nicholas; Wagner, Andreas H.; Karck, Matthias; Kallenbach, Klaus

2016-01-01

Objectives Marfan syndrome is an autosomal dominant inherited disorder of connective tissue. The vascular complications of Marfan syndrome have the biggest impact on life expectancy. The aorta of Marfan patients reveals degradation of elastin layers caused by increased proteolytic activity of matrix metalloproteinases (MMPs). In this study we performed adenoviral gene transfer of human tissue inhibitor of matrix metalloproteinases-1 (hTIMP-1) in aortic grafts of fibrillin-1 deficient Marfan mice (mgR/mgR) in order to reduce elastolysis. Methods We performed heterotopic infrarenal transplantation of the thoracic aorta in female mice (n = 7 per group). Before implantation, mgR/mgR and wild-type aortas (WT, C57BL/6) were transduced ex vivo with an adenoviral vector coding for human TIMP-1 (Ad.hTIMP-1) or β-galactosidase (Ad.β-Gal). As control mgR/mgR and wild-type aortas received no gene therapy. Thirty days after surgery, overexpression of the transgene was assessed by immunohistochemistry (IHC) and collagen in situ zymography. Histologic staining was performed to investigate inflammation, the neointimal index (NI), and elastin breaks. Endothelial barrier function of native not virus-exposed aortas was evaluated by perfusion of fluorescent albumin and examinations of virus-exposed tissue were performed by transmission electron microscopy (TEM). Results IHC and ISZ revealed sufficient expression of the transgene. Severe cellular inflammation and intima hyperplasia were seen only in adenovirus treated mgR/mgR aortas (Ad.β-Gal, Ad.hTIMP-1 NI: 0.23; 0.43), but not in native and Ad.hTIMP-1 treated WT (NI: 0.01; 0.00). Compared to native mgR/mgR and Ad.hTIMP-1 treated WT aorta, the NI is highly significant greater in Ad.hTIMP-1 transduced mgR/mgR aorta (p = 0.001; p = 0.001). As expected, untreated Marfan grafts showed significant more elastolysis compared to WT (p = 0.001). However, elastolysis in Marfan aortas was not reduced by adenoviral overexpression of hTIMP-1

Resetting of Mg isotopes between calcite and dolomite during burial metamorphism: Outlook of Mg isotopes as geothermometer and seawater proxy

NASA Astrophysics Data System (ADS)

Hu, Zhongya; Hu, Wenxuan; Wang, Xiaomin; Lu, Yizhou; Wang, Lichao; Liao, Zhiwei; Li, Weiqiang

2017-07-01

Magnesium isotopes are an emerging tool to study the geological processes recorded in carbonates. Calcite, due to its ubiquitous occurrence and the large Mg isotope fractionation associated with the mineral, has attracted great interests in applications of Mg isotope geochemistry. However, the fidelity of Mg isotopes in geological records of carbonate minerals (e.g., calcite and dolomite) against burial metamorphism remains poorly constrained. Here we report our investigation on the Mg isotope systematics of a dolomitized Middle Triassic Geshan carbonate section in eastern China. Magnesium isotope analysis was complemented by analyses of Sr-C-O isotopic compositions, major and trace element concentrations, and petrographic and mineralogical features. Multiple lines of evidence consistently indicated that post-depositional diagenesis of carbonate minerals occurred to the carbonate rocks. Magnesium isotope compositions of the carbonate rocks closely follow a mixing trend between a high δ26Mg dolomite end member and a low δ26Mg calcite end member, irrespective of sample positions in the section and calcite/dolomite ratio in the samples. By fitting the measured Mg isotope data using a two-end member mixing model, an inter-mineral Δ26Mgdolomite-calcite fractionation of 0.72‰ was obtained. Based on the experimentally derived Mg isotope fractionation factors for dolomite and calcite, a temperature of 150-190 °C was calculated to correspond to the 0.72‰ Δ26Mgdolomite-calcite fractionation. Such temperature range matches with the burial-thermal history of the local strata, making a successful case of Mg isotope geothermometry. Our results indicate that both calcite and dolomite had been re-equilibrated during burial metamorphism, and based on isotope mass balance of Mg, the system was buffered by dolomite in the section. Therefore, burial metamorphism may reset Mg isotope signature of calcite, and Mg isotope compositions in calcite should be dealt with caution in

Effect of amorphous lamella on the crack propagation behavior of crystalline Mg/amorphous Mg-Al nanocomposites

NASA Astrophysics Data System (ADS)

Hai-Yang, Song; Yu-Long, Li

2016-02-01

The effects of amorphous lamella on the crack propagation behavior in crystalline/amorphous (C/A) Mg/Mg-Al nanocomposites under tensile loading are investigated using the molecular dynamics simulation method. The sample with an initial crack of orientation [0001] is considered here. For the nano-monocrystal Mg, the crack growth exhibits brittle cleavage. However, for the C/A Mg/Mg-Al nanocomposites, the ‘double hump’ behavior can be observed in all the stress-strain curves regardless of the amorphous lamella thickness. The results indicate that the amorphous lamella plays a critical role in the crack deformation, and it can effectively resist the crack propagation. The above mentioned crack deformation behaviors are also disclosed and analyzed in the present work. The results here provide a strategy for designing the high-performance hexagonal-close-packed metal and alloy materials. Project supported by the National Natural Science Foundation of China (Grant Nos. 11372256 and 11572259), the 111 Project (Grant No. B07050), the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-12-1046), and the Program for New Scientific and Technological Star of Shaanxi Province, China (Grant No. 2012KJXX-39).

Bioavailability, safety, and pharmacodynamics of delayed-release dexlansoprazole administered as two 30 mg orally disintegrating tablets or one 60 mg capsule.

PubMed

Kukulka, Michael; Nudurupati, Sai; Perez, Maria Claudia

2016-11-01

Dual delayed-release dexlansoprazole is approved for use in adults as a 30 mg orally disintegrating tablet (ODT) or as 30 mg and 60 mg capsules. The pharmacokinetics, pharmacodynamics, and safety profile of two dexlansoprazole 30 mg ODTs were compared with one dexlansoprazole 60 mg capsule in this randomized, phase I, open-label, single-center, multiple-dose, two-period crossover study. Participants were randomized in one of two treatment sequences, each comprised two 5-day treatment periods during which two dexlansoprazole 30 mg ODTs or one 60 mg capsule was administered once daily. Pharmacokinetic parameters and the mean intragastric pH profile for the 24-hour period after dosing on days 1 and 5 were described. Adverse events were monitored during study duration and followed up with a phone call 5-10 days after the last dose of study drug. On day 1, peak observed plasma concentration ( C max ) values were similar between two 30 mg ODTs (1047 ng/ml) and one 60 mg capsule (1164 ng/ml). Systemic exposure, measured by the area under the plasma concentration-time curve (AUC), was approximately 25% lower after ODT administration. On day 5, mean pH after daily doses of two 30 mg ODT or one 60 mg capsule was 4.33 and 4.36, respectively; both regimens maintained intragastric pH above 4.0 for 60% of the 24-hour period. Headache was the most commonly reported adverse event (observed in 19.2% of participants); no adverse events leading to study withdrawal occurred. While systemic exposure (AUC) was 25% lower with ODT, peak concentrations ( C max ) after administration of two dexlansoprazole 30 mg ODTs and one 60 mg capsule were similar. The 24-hour intragastric pH control after administration of two dexlansoprazole 30 mg ODTs was equivalent to one dexlansoprazole 60 mg capsule. Both ODT and capsule were well tolerated.

High-precision Mg isotopic systematics of bulk chondrites

NASA Astrophysics Data System (ADS)

Schiller, Martin; Handler, Monica R.; Baker, Joel A.

2010-08-01

Variations of the mass-independent abundance of 26Mg ( δ26Mg*) and stable Mg ( δ25Mg) isotope composition of chondrites are important because they constrain the homogeneity of 26Al and Mg isotopes in the proto-planetary disc and the validity of the short-lived 26Al-to- 26Mg chronometer applied to meteorites. We present high-precision Mg isotope data and Al/Mg ratios of chondrites representing nearly all major chondrite classes, including a step-leaching experiment on the CM2 chondrite Murchison. δ26Mg* variations in leachates of Murchison representing acid soluble material are ≤ 30 times smaller than reported for neutron-rich isotopes of Ti and Cr and do not reveal resolvable deficits in δ26Mg* (-0.002 to + 0.118‰). Very small variations in δ26Mg* anomalies in bulk chondrites (-0.006 to + 0.019‰) correlate with increasing 27Al/ 24Mg ratios and δ50Ti, reflecting the variable presence of calcium-aluminium-rich inclusions (CAIs) in some types of carbonaceous chondrites. Similarly, release of radiogenic 26Mg produced by 26Al decay from CAI material in the step-leaching of Murchison best explains the high δ26Mg* observed in the last, aggressive, leaching steps of this experiment. Overall, the observed variations in δ26Mg* are small and potential differences beyond that which result from the presence of CAI-like material cannot be detected within the analytical uncertainties of this study (± 0.004‰). The results do not allow radical heterogeneity of 26Al (≥±30%) or measurable Mg nucleosynthetic heterogeneity (≥±0.005‰) to have existed on a planetesimal scale in the proto-planetary disc. Combined with published δ26Mg* data for CAIs, the bulk chondrite data yield a precise initial ( 26Al/ 27Al) 0 = (5.21 ± 0.06) × 10 -5 and δ26Mg* = -0.0340 ± 0.0016‰ for the Solar System. However, it is not possible with the currently available data to determine with certainty whether CAIs and the material from which planetesimals accreted including

Mg2BIV: Narrow Bandgap Thermoelectric Semiconductors

NASA Astrophysics Data System (ADS)

Kim, Il-Ho

2018-05-01

Thermoelectric materials can convert thermal energy directly into electric energy and vice versa. The electricity generation from waste heat via thermoelectric devices can be considered as a new energy source. For instance, automotive exhaust gas and all industrial processes generate an enormous amount of waste heat that can be converted to electricity by using thermoelectric devices. Magnesium compound Mg2BIV (BIV = Si, Ge or Sn) has a favorable combination of physical and chemical properties and can be a good base for the development of new efficient thermoelectrics. Because they possess similar properties to those of group BIV elemental semiconductors, they have been recognized as good candidates for thermoelectric applications. Mg2Si, Mg2Ge and Mg2Sn with an antifluorite structure are narrow bandgap semiconductors with indirect band gaps of 0.77 eV, 0.74 eV, and 0.35 eV, respectively. Mg2BIV has been recognized as a promising material for thermoelectric energy conversion at temperatures ranging from 500 K to 800 K. Compared to other thermoelectric materials operating in the similar temperature range, such as PbTe and filled skutterudites, the important aspects of Mg2BIV are non-toxic and earth-abundant elements. Based on classical thermoelectric theory, the material factor β ( m* / m e)3/2μκ L -1 can be utilized as the criterion for thermoelectric material selection, where m* is the density-of-states effective mass, me is the mass of an electron, μ is the carrier mobility, and κL is the lattice thermal conductivity. The β for magnesium silicides is 14, which is very high compared to 0.8 for iron silicides, 1.4 for manganese silicides, and 2.6 for silicon-germanium alloys. In this paper, basic phenomena of thermoelectricity and transport parameters for thermoelectric materials were briefly introduced, and thermoelectric properties of Mg2BIV synthesized by using a solid-state reaction were reviewed. In addition, various Mg2BIV compounds were discussed

Espectroscopia del Cometa Halley

NASA Astrophysics Data System (ADS)

Naranjo, O.; Fuenmayor, F.; Ferrin, L.; Bulka, P.; Mendoza, C.

1987-05-01

Se reportan observaciones espectroscópicas del cometa Halley. Los espectros fueron tomados usando el espectrógrafo del telescopio reflector de 1 metro del Observatorio Nacional de Venezuela. Se utilizó óptica azul, con una red de difracción de 600 lineas/min, obteniéndose una dispersión de 74.2 A/mm y una resolución de 2.5 A, en el rango espectral de 3500 a 6500 A. Seis placas fueron tomadas con emulsión IIa-O y dos con IIa-D. Los tiempos de exposición fueron entre 10 y 150 minutos. El cometa se encontraba entre 0.70 y 1.04 UA del Sol, y entre 1.28 y 0.73 UA de la Tierra. Las emisiones más prominentes en el espectro, son las del CN, C2, y C3. Otras emisiones detectadas corresponden a CH, NH2 y Na. Los espectros muestran un fuerte continuo, indicando un contenido significativo de polvo. Se detectó mayor intensidad del contínuo, en la dirección anti solar, lo cual es evidencia de la cola de polvo.

Misfit paradox on nucleation potency of MgO and MgAl{sub 2}O{sub 4} for Al

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

Zhang, D.; Wang, L.

MgO and MgAl{sub 2}O{sub 4} are believed to be effective heterogeneous nuclei for Al based alloys due to their small lattice misfits with Al. However, there is a strong evidence to suggest that liquid Al reacts with MgO and MgAl{sub 2}O{sub 4} phases but the heterogeneous nucleation behavior of such phases is rarely discussed. In order to identify the nucleation mechanism of Al, under the interference of the chemical reaction, the heterogeneous nucleation process is systematically investigated through thermal analysis and high resolution transmission electron microscopy (HRTEM). The observed multi-nucleation interfaces (Al/MgO, Al/MgAl{sub 2}O{sub 4} and Al/Al{sub 2}O{sub 3}) andmore » scattered experimental undercooling data indicate an independent multi-phase nucleation process in these systems. - Highlights: •Theoretical lattice misfit doesn’t always disclose nucleation potency. •The nucleation of liquid can be triggered by multi-nucleation interfaces. •An independent multi-agents nucleation was verified in the study.« less

Synthesis and luminescence studies of Tb-doped MgO-MgAl2O4-Mg2SiO4 ceramic for use in radiation dosimetry.

PubMed

Gugliotti, C; Moriya, K; Tatumi, S; Mittani, J

2018-05-01

In the present work, MgO ceramic samples with different terbium concentrations were produced and the Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties analyzed and discussed, aiming the use in radiation dosimetry. The samples were produced using MgO, Mg(NO 3 ) 2 ·6H 2 O, Al 2 O 3 , SiO 2 and Tb(NO 3 ) 3 ·6H 2 O precursors in stoichiometric concentrations with five different terbium concentrations between 0.1 and 0.5 mol% and after, heat-treated at high temperature ~1500 °C. X-ray diffraction measurements on samples showed the formation of MgO as principal phase, and others in low concentration due to MgAl 2 O 4 , Mg 2 SiO 4 and Tb 4 O 7 phases. The TL glow curve of samples showed an intense and well-defined peak having the maximum at ~210 °C and other less intense at ~350 °C. The sample with 0.1 mol% of terbium concentration presented highest luminescence peak when compared to the other samples. The relationship between 210 °C TL peak intensity and dose was linear to doses between 1 and 20 Gy and the minimum detectable dose obtained by interpolation taking into account three times the standard deviation of the zero dose reading, was ~40 μGy. A fading of ~20% during the first 5 hours after irradiation of 210 °C peak was observed. TL emission spectra showed strong emission lines due to Tb 3+ ion. The OSL signal presented a linear behavior to doses between 1 and 10 Gy using 532 nm wavelength stimulation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Mg-isotopic fractionation in the manila clam (Ruditapes philippinarum): New insights into Mg incorporation pathway and calcification process of bivalves

NASA Astrophysics Data System (ADS)

Planchon, Frédéric; Poulain, Céline; Langlet, Denis; Paulet, Yves-Marie; André, Luc

2013-11-01

We estimate the magnesium stable isotopic composition (δ26Mg) of the major compartments involved in the biomineralisation process of euryhaline bivalve, the manila clam Ruditapes philippinarum. Our aim is to identify the fractionation processes associated with Mg uptake and its cycling/transport in the bivalve organism, in order to better assess the controlling factors of the Mg isotopic records in bivalve shells. δ26Mg were determined in seawater, in hemolymph, extrapallial fluid (EPF), soft tissues and aragonitic shell of adult clams collected along the Auray River estuary (Gulf of Morbihan, France) at two sites showing contrasted salinity regimes. The large overall δ26Mg variations (4.16‰) demonstrate that significant mass-dependent Mg isotopic fractionations occur during Mg transfer from seawater to the aragonitic shell. Soft tissues span a range of fractionation factors relative to seawater (Δ26Mgsoft tissue-seawater) of 0.42 ± 0.12‰ to 0.76 ± 0.12‰, and show evidence for biological isotopic fractionation of Mg. Hemolymph and EPF are on average isotopically close to seawater (Δ26Mghemolymph-seawater = -0.20 ± 0.27‰; 2 sd; n = 5 and Δ26MgEPF-seawater = -0.23 ± 0.25‰; 2 sd; n = 5) indicating (1) a predominant seawater origin for Mg in the intercellular medium and (2) a relatively passive transfer route through the bivalve organism into the calcifying fluid. The lightest isotopic composition is found in shell, with δ26Mg ranging from -1.89 ± 0.07‰ to -4.22 ± 0.06‰. This range is the largest in the dataset and is proposed to result from a combination of abiotic and biologically-driven fractionation processes. Abiotic control includes fractionation during precipitation of aragonite and accounts for Δ26Mgaragonite-seawater ≈ 1000 ln αaragonite-seawater = -1.13 ± 0.28‰ at 20 °C based on literature data. Deviations from inorganic precipitate (expressed as Δ26MgPhysiol) appear particularly variable in the clam shell, ranging from 0

Review of Dextromethorphan 20 mg/Quinidine 10 mg (NUEDEXTA(®)) for Pseudobulbar Affect.

PubMed

Pioro, Erik P

2014-06-01

Pseudobulbar affect (PBA) is a dysfunction of emotional expression characterized by involuntary outbursts of crying or laughing disproportionate or unrelated to mood, occurring in patients with various underlying neurologic disorders. This review describes the clinical data supporting dextromethorphan (DM) hydrobromide combined with quinidine sulfate (Q) as treatment of PBA and briefly surveys the ongoing debates concerning the terminology for dysfunction of emotional expression, as well as the ongoing searches for its brain substrates. Until recently, pharmacologic intervention consisted chiefly of off-label antidepressants. In October 2010, however, DM/Q at 20/10 mg twice daily received approval from the United States Food and Drug Administration for PBA in any setting, and in June 2013, dosages of 20/10 and 30/10 mg twice daily (labeled as 15/9 and 23/9 mg, respectively, DM/Q base) received approval from the European Medicines Agency. DM is an uncompetitive N-methyl-d-aspartate (NMDA) glutamate receptor antagonist, a sigma-1 receptor agonist, and a serotonin and norepinephrine reuptake inhibitor. To block DM hepatic metabolism, thereby increasing DM bioavailability, Quinidine, a cytochrome P450 2D6 inhibitor, is coadministered at a dosage well below those for treating cardiac arrhythmia. Three large-scale DM/Q trials have utilized PBA-episode counts and the Center for Neurologic Study-Lability Scale (CNS-LS), a validated PBA rating scale, to measure efficacy. In a 4-week study of patients with PBA in amyotrophic lateral sclerosis (ALS), DM/Q 30/30 mg was superior to its component drugs. A 12-week, double-blind, placebo-controlled study of DM/Q 30/30 mg showed similar efficacy in patients with PBA in multiple sclerosis (MS). A subsequent 12-week study of patients with PBA and ALS or MS showed superiority to placebo for the 20/10 and 30/10 mg doses. Efficacy was maintained during a 12-week, open-label extension (30/10 mg dose), with further improvement of

Comparison of the efficacy and safety of bilastine 20 mg vs desloratadine 5 mg in seasonal allergic rhinitis patients.

PubMed

Bachert, C; Kuna, P; Sanquer, F; Ivan, P; Dimitrov, V; Gorina, M M; van de Heyning, P; Loureiro, A

2009-01-01

Bilastine is a novel, nonsedating H(1)-antihistamine developed for symptomatic treatment of Allergic Rhinitis and Chronic Idiopathic Urticaria. The objective of this study was to compare the efficacy and safety of bilastine 20 mg vs placebo and desloratadine 5 mg in subjects with seasonal allergic rhinitis (SAR). This randomized, double blind, placebo-controlled, parallel-group multicentre study evaluated the effect of 2 weeks' treatment with bilastine 20 mg, desloratadine 5 mg or matched placebo once daily, in 12-70 years old symptomatic SAR patients. All subjects assessed the severity of nasal (obstruction, rhinorrhoea, itching, and sneezing) and nonnasal (ocular itching, tearing, ocular redness, itching of ears and/or palate) symptoms on a predetermined scale to provide a total symptom score (TSS), composed of nasal and nonnasal symptom scores (NSS and NNSS, respectively). The primary efficacy measure was the area under the curve (AUC) for the TSS over the entire treatment period. Bilastine 20 mg significantly reduced the AUC of TSS to a greater degree from baseline compared to placebo (98.4 with bilastine vs 118.4 with placebo; P < 0.001), but not compared to desloratadine 5 mg (100.5). Bilastine 20 mg was not different from desloratadine 5 mg but significantly more effective than placebo in improving the NSS, NNSS, and rhinitis-associated discomfort scores (P < 0.05), and rhinoconjunctivitis quality of life questionnaire total (P < 0.005) and four out of seven individual domain (P < 0.05) scores. The incidence of treatment emergent adverse events was similar for bilastine (20.6%), desloratadine (19.8%), and placebo (18.8%). Bilastine 20 mg once daily was efficacious, safe and not different from desloratadine 5 mg once daily in the treatment of SAR symptoms.

Thermoluminescence responses of photon- and electron-irradiated lithium potassium borate co-doped with Cu+Mg or Ti+Mg.

PubMed

Alajerami, Y S M; Hashim, S; Ramli, A T; Saleh, M A; Saripan, M I; Alzimami, K; Min Ung, Ngie

2013-08-01

New glasses Li2CO3-K2CO3-H3BO3 (LKB) co-doped with CuO and MgO, or with TiO2 and MgO, were synthesized by the chemical quenching technique. The thermoluminescence (TL) responses of LKB:Cu,Mg and LKB:Ti,Mg irradiated with 6 MV photons or 6 MeV electrons were compared in the dose range 0.5-4.0 Gy. The standard commercial dosimeter LiF:Mg,Ti (TLD-100) was used to calibrate the TL reader and as a reference in comparison of the TL properties of the new materials. The dependence of the responses of the new materials on (60)Co dose is linear in the range of 1-1000 Gy. The TL yields of both of the co-doped glasses and TLD-100 are greater for electron irradiation than for photon irradiation. The TL sensitivity of LKB:Ti,Mg is 1.3 times higher than the sensitivity of LKB:Cu,Mg and 12 times less than the sensitivity of TLD-100. The new TL dosimetric materials have low effective atomic numbers, good linearity of the dose responses, excellent signal reproducibility, and a simple glow curve structure. This combination of properties makes them suitable for radiation dosimetry. Copyright © 2013 Elsevier Ltd. All rights reserved.

Comparative performance of a combined injectable contraceptive (50 mg norethisterone enanthate plus 5mg estradiol valerate) and a combined oral contraceptive (0.15 mg levonorgestrel plus 0.03 mg ethinyl estradiol) in adolescents.

PubMed

Molina, Ramiro C; Sandoval, Jorge Z; Montero, Adela V; Oyarzún, Pamela G; Molina, Temístocles G; González, Electra A

2009-02-01

To compare in a regular non-clinical trial experience the efficacy, acceptability, and continuation rates of an injectable contraceptive containing 50 mg norethisterone enanthate plus 5mg estradiol valerate (IC) and an oral contraceptive containing 0.15 mg levonorgestrel plus 0.03 mg ethinyl estradiol (OC), among adolescent users. A total of 251 adolescents ages 14-19 were followed during 12 months. The IC group (124 subjects) was studied for 1044 cycles and the OC group (127 subjects) was studied for 1368 cycles. The users were not assigned in a random selection. Information was collected from clinical records. Groups were compared using Pearson chi-square, odds ratio (95% confidence interval), t-test, and proportion difference test. The IC group had significant differences in baseline social risk, confidence, psychiatric problems, consumption of alcohol, and number of sexual partners. At 12 months, the IC group showed significant decrease in weight and increase in hypermenorrhea. In the OC group, dysmenorrhea decreased, and hypomenorrhea and regular cycles were significantly more frequent. One pregnancy occurred in the OC group (Pearl Index: 0.88). Final continuation rates at 12 months were 41.9% and 37.8% for IC and OC, respectively. The monthly injectable is a recommended contraceptive option for adolescents, especially for those facing psychosocial risk factors.

Structure Characterization and Catalytic Properties of Cr2O3 Doped with MgO Supported on MgF2

NASA Astrophysics Data System (ADS)

Goslar, J.; Wojciechowska, M.; Zieliński, M.; Tomska-Foralewska, I.; Przystajko, W.

2006-08-01

A characterization of double oxide systems containing Cr2O3 doped with MgO and supported on MgF2 was carried out. The catalysts were prepared by impregnation and co-impregnation methods and characterized by the Brunauer-Emmett-Teller method, EPR, and temperature programmed reduction. The results proved the interactions between supported oxides and the presence of spinel-like phase after treatment at 400 ºC. Magnesium oxide clearly influences the catalytic activity as well as selectivity of chromium catalysts supported on MgF2. The MgO-Cr2O3/MgF2 systems were active and selective in the reaction of CO oxidation at the room temperature and in the dehydrogenation of cyclohexene.

F-35 Force Development Evaluation and Weapons School Beddown Environmental Impact Statement

DTIC Science & Technology

2011-05-01

deficiencias encontradas después del despliegue del sistema; ♦ explora medios no materiales (por ejemplo, tácticas) para satisfacer requisitos...del adecuado desempeño del avión en combate al proporcionar entrenamiento, información sobre las capacidades operativas y nuevos requisitos. Además

Speciation of Mg in biogenic calcium carbonates

NASA Astrophysics Data System (ADS)

Farges, F.; Meibom, A.; Flank, A.-M.; Lagarde, P.; Janousch, M.; Stolarski, J.

2009-11-01

A selection of marine biominerals, mostly aragonitic coral skeletons were probed at the Mg K-edge by XANES spectroscopy coupled to μXRF methods and compared to an extensive set of relevant model compounds (silicates, carbonates, oxides and organic). Extensive methodologies are required to better describe the speciation of Mg in those minerals. A combination of ab-initio XANES calculations for defective clusters around Mg in aragonite together with wavelets analyzes of the XANES region are required to robustly interpret the spectra. When using those methodologies, the speciation of Mg ranges from a magnesite-type environment in some scleractinian corals to an organic-type environment. In all environments, the Mg-domains probed appear to be less than 1 nm in size.

Intertextual Sexual Politics: Illness and Desire in Enrique Gomez Carrillo's "Del amor", "del dolor y del vicio" and Aurora Caceres's "La rosa muerta"

ERIC Educational Resources Information Center

LaGreca, Nancy

2012-01-01

This study explores the intertextuality between Aurora Caceres's "La rosa muerta" (1914) and the novel "Del amor, del dolor y del vicio" (1898) by her ex-husband, Enrique Gomez Carrillo. Caceres strategically mentions Gomez Carrillo's novel in "La rosa muerta" to invite a reading of her work in dialogue with his. Both narratives follow the sexual…

Layered double hydroxides as adsorbents and carriers of the herbicide (4-chloro-2-methylphenoxy)acetic acid (MCPA): systems Mg-Al, Mg-Fe and Mg-Al-Fe.

PubMed

Bruna, F; Celis, R; Pavlovic, I; Barriga, C; Cornejo, J; Ulibarri, M A

2009-09-15

Hydrotalcite-like compounds [Mg(3)Al(OH)(8)]Cl x 4H(2)O; [Mg(3)Fe(OH)(8)]Cl x 4H(2)O; [Mg(3)Al(0.5)Fe(0.5)(OH)(8)]Cl x 4H(2)O (LDHs) and calcined product of [Mg(3)Al(OH)(8)]Cl x 4H(2)O, Mg(3)AlO(4.5) (HT500), were studied as potential adsorbents of the herbicide MCPA [(4-chloro-2-methylphenoxy)acetic acid] as a function of pH, contact time and pesticide concentration, and also as support for the slow release of this pesticide, with the aim to reduce the hazardous effects that it can pose to the environment. The information obtained in the adsorption study was used for the preparation of LDH-MCPA complexes. The results showed high and rapid adsorption of MCPA on the adsorbents as well as that MCPA formulations based on LDHs and HT500 as pesticide supports displayed controlled release properties and reduced herbicide leaching in soil columns compared to a standard commercial MCPA formulation. Thereby, we conclude that the LDHs employed in this study can be used not only as adsorbents to remove MCPA from aqueous solutions, but also as supports for the slow release of this highly mobile herbicide, thus controlling its immediate availability and leaching.

Ca Addition Effects on the Microstructure, Tensile and Corrosion Properties of Mg Matrix Alloy Containing 8 wt.% Mg2Si

NASA Astrophysics Data System (ADS)

Lotfpour, M.; Emamy, M.; Dehghanian, C.; Pourbahari, B.

2018-02-01

The microstructure, tensile properties and corrosion behavior of the Mg-8 wt.% Mg2Si-x%Ca alloy have been studied by the use of optical microscopy, scanning electron microscopy equipped with energy-dispersive spectroscopy, x-ray diffraction, standard tensile testing, polarization test and electrochemical impedance spectroscopy (EIS) measurements. Microstructural studies indicated that Ca modifies both primary and eutectic Mg2Si phase. It was found that the average size of primary Mg2Si particles is about 60 μm, which is dropped by about 82% in the alloy containing 0.05 wt.% Ca. By the addition of different Ca contents, Ca-rich intermetallics (i.e., CaSi2 and CaMgSi) were formed. The modification mechanism of adding Ca during solidification was found to be due to the strong effect of CaMgSi phase as a heterogonous nucleation site, apart from CaSi2 which was reported before, for Mg2Si intermetallics. Tensile testing results ascertained that Ca addition enhances both ultimate tensile strength (UTS) and elongation values. The optimum amount of Ca was found to be 0.1 wt.%, which improved UTS and elongation values from about 130 MPa and 2% to 165 MPa and 5.5%, whereas more Ca addition (i.e., 3 wt.%) reduced the tensile properties of the alloy to about 105 MPa and 1.8%, which can be due to the formation of CaMgSi intermetallics with deteriorating needle-like morphology. Polarization and EIS tests also showed that the Mg-3%Si-0.5%Ca alloy pronounces as the best anti-corrosion alloy. Nevertheless, further added Ca (up to 3 wt.%) deteriorated the corrosion resistance due to predominance of worse galvanic coupling effect stemmed from the presence of stronger CaMgSi cathode in comparison with Mg2Si. With higher Ca additions, an adverse effect was seen on corrosion resistance of the Mg-3%Si alloy, as a result of forming a weak film on the alloy specimen surface.

Pinning in high performance MgB2 thin films and bulks: Role of Mg-B-O nano-scale inhomogeneities

NASA Astrophysics Data System (ADS)

Prikhna, Tatiana; Shapovalov, Andrey; Eisterer, Michael; Shaternik, Vladimir; Goldacker, Wilfried; Weber, Harald W.; Moshchil, Viktor; Kozyrev, Artem; Sverdun, Vladimir; Boutko, Viktor; Grechnev, Gennadiy; Gusev, Alexandr; Kovylaev, Valeriy; Shaternik, Anton

2017-02-01

The comparison of nano-crystalline MgB2 oxygen-containing thin film (140 nm) and highly dense bulk materials showed that the critical current density, Jc, depends on the distribution of Mg-B-O nano-scale inhomogeneities. It has been shown that MgB2 bulks with high Jc in low (∼106 A/cm2 in 0-1 T at 10 K) and medium magnetic fields contain MgB0.6-0.8O0.8-0.9 nano-inclusions, where δTc or a combined δTc (dominant) / δl pinning mechanism prevails, while in bulk MgB2 with high Jc in high magnetic fields (Birr(18.5 K) = 15 T, Bc2(0 K) = 42.1 T) MgB1.2-2.7O1.8-2.5 nano-layers are present and δl pinning prevails. The structure of oxygen-containing films with high Jc in low and high magnetic fields (Jc (0 Т) = 1.8 × 107 А/сm2 and Jc (5 Т) = 2 × 106 А/сm2 at 10 К) contains very fine oxygen-enriched Mg-B-O inhomogeneities and δl pinning is realized. The results of DOS calculations in MgB2-xOx cells for x = 0, 0.125, 0.25, 0.5, 1 demonstrate that all compounds are conductors with metal-like behaviour. In the case of ordered oxygen substitution for boron the binding energy, Eb, does not increase sufficiently as compared with that for MgB2, while when oxygen atoms form zigzag chains the calculated Eb is even lower (Eb = -1.15712 Ry).

Computational prediction of Mg-isotope fractionation between aqueous [Mg(OH2)6]2+ and brucite

NASA Astrophysics Data System (ADS)

Colla, Christopher A.; Casey, William H.; Ohlin, C. André

2018-04-01

The fractionation factor in the magnesium-isotope fractionation between aqueous solutions of magnesium and brucite changes sign with increasing temperature, as uncovered by recent experiments. To understand this behavior, the Reduced Partition Function Ratios and isotopic fractionation factors (Δ26/24Mgbrucite-Mg(aq)) are calculated using molecular models of aqueous [Mg(OH2)6]2+ and the mineral brucite at increasing levels of density functional theory. The calculations were carried out on the [Mg(OH2)6]2+·12H2O cluster, along with different Pauling-bond-strength-conserving models of the mineral lattice of brucite. Three conclusions were reached: (i) all levels of theory overestimate bond distances in the aqua ion complex relative to Tutton's salts; (ii) the calculations predict that brucite at 298.15 K is always enriched in the heavy isotope, in contrast with experimental observations; (iii) the temperature dependencies of Wimpenny et al. (2014) and Li et al. (2014) could only be achieved by fixing the bond distances in the [Mg(OH2)6]2+·12H2O cluster to values close to those observed in crystals that trap the hydrated ion.

Enhanced corrosion resistance and cytocompatibility of biodegradable Mg alloys by introduction of Mg(OH)2 particles into poly (L-lactic acid) coating

PubMed Central

Shi, Yong-juan; Pei, Jia; Zhang, Jian; Niu, Jia-lin; Zhang, Hua; Guo, Sheng-rong; Li, Zhong-hua; Yuan, Guang-yin

2017-01-01

A strategy of suppressing the fast degradation behaviour of Mg-based biomaterials by the introduction of one of Mg degradation products Mg(OH)2 was proposed according to the following degradation mechanism, Mg + 2H2O ⇋ Mg(OH)2 + H2↑. Specifically, Mg(OH)2 submicron particles were mixed into poly (L-lactic acid) (PLLA) to synthesize a composite coating onto hydrofluoric acid-pretreated Mg-Nd-Zn-Zr alloy. The in vitro degradation investigations showed that the addition of Mg(OH)2 particles not only slowed down the corrosion of Mg matrix, but also retarded the formation of gas pockets underneath the polymer coating. Correspondingly, cytocompatibility results exhibited significant improvement of proliferation of endothelial cells, and further insights was gained into the mechanisms how the introduction of Mg(OH)2 particles into PLLA coating affected the magnesium alloy degradation and cytocompatibility. The present study provided a promising surface modification strategy to tailor the degradation behaviour of Mg-based biomaterials. PMID:28150751

Cathodoluminescence study of Mg activation in non-polar and semi-polar faces of undoped/Mg-doped GaN core-shell nanorods.

PubMed

Hortelano, V; Martínez, O; Cuscó, R; Artús, L; Jiménez, J

2016-03-04

Spectrally and spatially resolved cathodoluminescence (CL) measurements were carried out at 80 K on undoped/Mg-doped GaN core-shell nanorods grown by selective area growth metalorganic vapor phase epitaxy in order to investigate locally the optical activity of the Mg dopants. A study of the luminescence emission distribution over the different regions of the nanorods is presented. We have investigated the CL fingerprints of the Mg incorporation into the non-polar lateral prismatic facets and the semi-polar facets of the pyramidal tips. The amount of Mg incorporation/activation was varied by using several Mg/Ga flow ratios and post-growth annealing treatment. For lower Mg/Ga flow ratios, the annealed nanorods clearly display a donor-acceptor pair band emission peaking at 3.26-3.27 eV and up to 4 LO phonon replicas, which can be considered as a reliable indicator of effective p-type Mg doping in the nanorod shell. For higher Mg/Ga flow ratios, a substantial enhancement of the yellow luminescence emission as well as several emission subbands are observed, which suggests an increase of disorder and the presence of defects as a consequence of the excess Mg doping.

Cathodoluminescence study of Mg activation in non-polar and semi-polar faces of undoped/Mg-doped GaN core-shell nanorods

NASA Astrophysics Data System (ADS)

Hortelano, V.; Martínez, O.; Cuscó, R.; Artús, L.; Jiménez, J.

2016-03-01

Spectrally and spatially resolved cathodoluminescence (CL) measurements were carried out at 80 K on undoped/Mg-doped GaN core-shell nanorods grown by selective area growth metalorganic vapor phase epitaxy in order to investigate locally the optical activity of the Mg dopants. A study of the luminescence emission distribution over the different regions of the nanorods is presented. We have investigated the CL fingerprints of the Mg incorporation into the non-polar lateral prismatic facets and the semi-polar facets of the pyramidal tips. The amount of Mg incorporation/activation was varied by using several Mg/Ga flow ratios and post-growth annealing treatment. For lower Mg/Ga flow ratios, the annealed nanorods clearly display a donor-acceptor pair band emission peaking at 3.26-3.27 eV and up to 4 LO phonon replicas, which can be considered as a reliable indicator of effective p-type Mg doping in the nanorod shell. For higher Mg/Ga flow ratios, a substantial enhancement of the yellow luminescence emission as well as several emission subbands are observed, which suggests an increase of disorder and the presence of defects as a consequence of the excess Mg doping.

Electrochemical Formation of Mg-Li-Sm Alloys by Codeposition from LiCl-KCl-MgCl2-SmCl3 Molten Salts

NASA Astrophysics Data System (ADS)

Han, Wei; Wang, Fengli; Tian, Yang; Zhang, Milin; Yan, Yongde

2011-12-01

In this article, the electrochemical method of preparing Mg-Li-Sm alloys by codeposition in LiCl-KCl-MgCl2-SmCl3 melts was investigated. Transient electrochemical techniques, such as cyclic voltammetry, chronopotentiometry, and chronoamperometry were used to explore the electrochemical formation of Mg-Li-Sm alloys. Chronopotentiograms demonstrated that the codepositon of Mg, Li, and Sm occurred when current densities were more negative than -0.31 A cm-2. Chronoamperograms indicated that the onset potential for the codeposition of Mg, Li, and Sm was -2.40 V, and the codeposition of Mg, Li, and Sm was formed when the applied potentials were more negative than -2.40 V. The different phases of Mg-Li-Sm alloys were prepared by galvanostatic electrolysis and characterized by X-ray diffraction (XRD), optical microscope (OM), and scanning electron microscopy (SEM). An inductively coupled plasma (ICP) analysis showed that the lithium and samarium contents in Mg-Li-Sm alloys could be controlled by the concentrations of MgCl2 and SmCl3. The results demonstrated that Sm could refine the grains dramatically. When the Sm content was 0.8 wt pct, the grain size was the finest.

Hydrogen storage and phase transformations in Mg-Pd nanoparticles

NASA Astrophysics Data System (ADS)

Callini, E.; Pasquini, L.; Rude, L. H.; Nielsen, T. K.; Jensen, T. R.; Bonetti, E.

2010-10-01

Microstructure refinement and synergic coupling among different phases are currently explored strategies to improve the hydrogen storage properties of traditional materials. In this work, we apply a combination of these methods and synthesize Mg-Pd composite nanoparticles by inert gas condensation of Mg vapors followed by vacuum evaporation of Pd clusters. Irreversible formation of the Mg6Pd intermetallic phase takes place upon vacuum annealing, resulting in Mg/Mg6Pd composite nanoparticles. Their hydrogen storage properties are investigated and connected to the undergoing phase transformations by gas-volumetric techniques and in situ synchrotron radiation powder x-ray diffraction. Mg6Pd transforms reversibly into different Mg-Pd intermetallic compounds upon hydrogen absorption, depending on temperature and pressure. In particular, at 573 K and 1 MPa hydrogen pressure, the metal-hydride transition leads to the formation of Mg3Pd and Mg5Pd2 phases. By increasing the pressure to 5 MPa, the Pd-richer MgPd intermetallic is obtained. Upon hydrogen desorption, the Mg6Pd phase is reversibly recovered. These phase transformations result in a specific hydrogen storage capacity associated with Mg-Pd intermetallics, which attain the maximum value of 3.96 wt % for MgPd and influence both the thermodynamics and kinetics of hydrogen sorption in the composite nanoparticles.

Comparison of the effects of esomeprazole 40 mg, rabeprazole 20 mg, lansoprazole 30 mg, and pantoprazole 40 mg on intragastrıc pH in extensive metabolizer patients with gastroesophageal reflux disease.

PubMed

Çelebi, Altay; Aydın, Dinçer; Kocaman, Orhan; Konduk, Buğra Tolga; Şentürk, Ömer; Hülagü, Sadetin

2016-09-01

Studies on the therapeutic efficacy of proton pump inhibitors (PPIs) in patients with gastroesophageal reflux disease (GERD) have been recently published. In most of these studies, comparison of only two PPIs have been made. There are few studies on the comparison of four or more PPIs. We aimed to compare the acid inhibitory effects of esomeprazole 40 mg, rabeprazole 20 mg, lansoprazole 30 mg, and pantoprazole 40 mg on days 1 and 5 of treatment in patients with GERD, who were extensive metabolizers in regard to the CYP2C19 genotype. Helicobacter pylori-negative with typical symptoms of GERD patients were randomly divided into four treatment groups. Efficacy analysis on days 1 and 5 were performed on the four groups which comprised 10 (esomeprazole), 11 (rabeprazole), 10 (lansoprazole), and 10 (pantoprazole) patients. On day 1 of PPI treatment, the mean percentage of time with intragastric Ph>4 were 54%, 58%, 60%, and 35% for the groups, respectively, and on day 5, these values were 67%, 60%, 68%, and 59%, respectively. Esomeprazole, rabeprazole, and lansoprazole were found to be superior to pantoprazole on the first day of treatment. Pantoprazole is a less potent proton pump inhibitor than the other PPIs tested on the first day of treatment. When the time needed to raise the intragatric pH to over 4 was evaluated, esomeprazole was found to have the most rapid action, followed by lansoprazole and rabeprazole.

Mechanisms for monovalent cation-dependent depletion of intracellular Mg2+:Na(+)-independent Mg2+ pathways in guinea-pig smooth muscle.

PubMed

Nakayama, Shinsuke; Nomura, Hideki; Smith, Lorraine M; Clark, Joseph F; Uetani, Tadayuki; Matsubara, Tatsuaki

2003-09-15

It has been suggested that magnesium deficiency is correlated with many diseases. 31P NMR experiments were carried out in order to investigate the effects of Na+ substitution on Mg2+ depletion in smooth muscle under divalent cation-free conditions. In the taenia of guinea-pig caeci, the intracellular free Mg2+ concentration ([Mg2+]i) was estimated from the chemical shifts of (1) the beta-ATP peak alone and (2) beta- and gamma-ATP peaks. Both estimations indicated that [Mg2+]i decreased only very slowly in Mg(2+)-free, Ca(2+)-free solutions in which Na+ was substituted with large cations such as NMDG (N-methyl-D-glucamine) and choline. Furthermore, the measurements of tension development supported the suggestion of preservation of intracellular Mg2+ with NMDG substitution. Substituting extracellular Na+ with the small cation, Li+, also shifted the beta-ATP peak towards a lower frequency, but the frequency shift was significantly less than that seen upon Na+ substitution with K+. The estimated [Mg2+]i depletion was, however, comparable with that seen after Na+ substitution with K+ using the titration curves of metal-free and Mg(2+)-bound ATP obtained in Li(+)-based model solutions. It was concluded that Mg2+ rapidly decreases only when small cations were the major electrolyte of the extracellular medium. Na+ substitutions with NMDG, choline or Li+ had little effect on intracellular ATP concentration after 100 min treatment.

Role of chemical interaction between MgH2 and TiO2 additive on the hydrogen storage behavior of MgH2

NASA Astrophysics Data System (ADS)

Pukazhselvan, D.; Nasani, Narendar; Sandhya, K. S.; Singh, Budhendra; Bdikin, Igor; Koga, Nobuaki; Fagg, Duncan Paul

2017-10-01

The present study explores how the additive titania chemically reacts with magnesium hydride and influences the dehydrogenation of MgH2. Quantitative X - ray diffraction study of ball milled MgH2 + xTiO2 (x = 0.25, 0.33, 0.5 and 1) suggests that Ti substituted MgO is the main reaction product in all the product powders. Convincing evidence is obtained to conclude that Ti dissolution in MgO makes a dramatic behavioral change to MgO; passive MgO turns as an active in-built catalyst. The analysis correlating the dehydrogenation kinetics, composition of in-situ catalyst and sample durability suggests that effectiveness of Ti substituted MgO (MgxTiyOx+y) as a catalyst for MgH2 depends on the concentration of Ti in MgxTiyOx+y rock salt. These observations are immensely helpful for understanding the hydrogen desorption mechanism of metal oxide additives loaded MgH2 system.

Thermodynamics and Kinetics of Three Mg-H-VN Complexes in Mg:GaN from Combined First-Principles Calculation and Experiment

NASA Astrophysics Data System (ADS)

Lee, Donghwa; Mitchell, Brandon; Fujiwara, Y.; Dierolf, V.

2014-05-01

An understanding of the formation and dissociation process of Mg-H defects in GaN is of paramount importance for high efficient GaN-based solid-state lighting. Through a combination of first-principle calculations and experimental observations, we find the existence of three types of Mg related centers forming different Mg-H-VN complexes in Mg:GaN. Our study shows that the three different arrangements, which differ by the relative position of the H, determine the degree of acceptor passivation by changing their charge state from +3 to +1. The energetic study demonstrates that the relative stability of the defect complexes can vary with the location of the Fermi level, as well as thermal annealing and electron beam irradiation. The inclusion of a VN is shown to produce an additional variance in optical spectra associated with Mg acceptor activation, resulting from changes in the defect configurations and charge states. Our study shows that these three Mg-H-VN complexes are key components for understanding the Mg acceptor activation and passivation processes.

A comparison of amorphous calcium carbonate crystallization in aqueous solutions of MgCl2 and MgSO4: implications for paleo-ocean chemistry

NASA Astrophysics Data System (ADS)

Han, Mei; Zhao, Yanyang; Zhao, Hui; Han, Zuozhen; Yan, Huaxiao; Sun, Bin; Meng, Ruirui; Zhuang, Dingxiang; Li, Dan; Liu, Binwei

2018-04-01

Based on the terminology of "aragonite seas" and "calcite seas", whether different Mg sources could affect the mineralogy of carbonate sediments at the same Mg/Ca ratio was explored, which was expected to provide a qualitative assessment of the chemistry of the paleo-ocean. In this work, amorphous calcium carbonate (ACC) was prepared by direct precipitation in anhydrous ethanol and used as a precursor to study crystallization processes in MgSO4 and MgCl2 solutions having different concentrations at 60 °C (reaction times 240 and 2880 min). Based on the morphology of the aragonite crystals, as well as mineral saturation indices and kinetic analysis of geochemical processes, it was found that these crystals formed with a spherulitic texture in 4 steps. First, ACC crystallized into columnar Mg calcite by nearly oriented attachment. Second, the Mg calcite changed from columnar shapes into smooth dumbbell forms. Third, the Mg calcite transformed into rough dumbbell or cauliflower-shaped aragonite forms by local dissolution and precipitation. Finally, the aragonite transformed further into spherulitic radial and irregular aggregate forms. The increase in Ca2+ in the MgSO4 solutions compared with the MgCl2 solutions indicates the fast dissolution and slow precipitation of ACC in the former solutions. The phase transition was more complete in the 0.005 M MgCl2 solution, whereas Mg calcite crystallized from the 0.005 M MgSO4 solution, indicating that Mg calcite could be formed more easily in an MgSO4 solution. Based on these findings, aragonite and Mg calcite relative to ACC could be used to provide a qualitative assessment of the chemistry of the paleo-ocean. Therefore, calcite seas relative to high-Mg calcite could reflect a low concentration MgSO4 paleo-ocean, while aragonite seas could be related to an MgCl2 or high concentration of MgSO4 paleo-ocean.

Interdiffusion and Intrinsic Diffusion in the Mg-Al System

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

Brennan, Sarah; Bermudez, Katrina; Sohn, Yong Ho

2012-01-01

Solid-to-solid diffusion couples were assembled and annealed to examine the diffusion between pure Mg (99.96%) and Al (99.999%). Diffusion anneals were carried out at 300 , 350 , and 400 C for 720, 360, and 240 hours, respectively. Optical and scanning electron microscopes were utilized to identify the formation of the intermetallic phases, -Al12Mg17 and -Al3Mg2 and absence of the -phase in the diffusion couples. Thicknesses of the -Al12Mg17 and -Al3Mg2 phases were measured and the parabolic growth constants were calculated to determine the activation energies for the growth, 165 and 86 KJ/mole, respectively. Concentration profiles were determined with electronmore » microprobe analysis using pure elemental standards. Composition-dependent interdiffusion coefficients in Mg-solid solution, -Al12Mg17 and - Al3Mg2 and Al-solid solutions were calculated based on the Boltzmann-Matano analysis. Average effective interdiffusion coefficients for each phase were also calculated, and the magnitude was the highest for the -Al3Mg2 phase, followed by -Al12Mg17, Al-solid solution and Mg-solid solution. Intrinsic diffusion coefficients based on Huemann s analysis (e.g., marker plane) were determined for the ~38 at.% Mg in the -Al3Mg2 phase. Activation energies and the pre-exponential factors for the inter- and intrinsic diffusion coefficients were calculated for the temperature range examined. The -Al3Mg2 phase was found to have the lowest activation energies for growth and interdiffusion among all four phases studied. At the marker location in the -Al3Mg2 phase, the intrinsic diffusion of Al was found to be faster than that of Mg. Extrapolations of the impurity diffusion coefficients in the terminal solid solutions were made and compared to the available self- and impurity diffusion data from literature. Thermodynamic factor, tracer diffusion coefficients and atomic mobilities at the marker plane composition were approximated using available literature values of Mg activity in

Clinical acceptability study of micronized purified flavonoid fraction 1000 mg tablets versus 500 mg tablets in patients suffering acute hemorrhoidal disease.

PubMed

Shelygin, Yuri; Krivokapic, Zoran; Frolov, S A; Kostarev, I V; Astashov, V L; Vasiliev, S V; Lakhin, A V; Rodoman, G V; Soloviev, A O; Stoyko, Y M; Khitaryan, A G; Nechay, I A

2016-11-01

To compare the clinical acceptability of micronized purified flavonoid fraction (MPFF) 1000 mg with MPFF 500 mg tablets, administered at the same daily dose in patients suffering non-complicated acute hemorrhoids. MPFF is an established treatment for hemorrhoidal disease. This was a double-blind, multi-center, randomized study. Patients took either MPFF 1000 mg or 500 mg tablets for 7 days (daily dose; 3 g over 4 days followed by 2 g over 3 days). Adverse events were recorded in a patient diary. On day 7, anal pain and bleeding were assessed (visual analog scale [VAS] and Dimitroulopoulos scale, respectively). Patients (162) were randomized to MPFF 1000 mg (79) and MPFF 500 mg (83). No serious adverse events (AEs) occurred; 10 emergent AEs were considered treatment-related (6 for MPFF 1000 mg and 4 for 500 mg). Both regimens were associated with significant reduction in anal pain (VAS); -2.37 cm MPFF 1000 mg (P < 0.001) and -2.17 cm 500 mg (P < 0.001), with a slight trend in favor of MPFF 1000 mg (mean global reduction -2.27 cm, P < 0.001). Bleeding improved significantly in both groups of patients, 56% of patients on MPFF 1000 mg versus 61% on MPFF 500 mg. Bleeding ceased after treatment in 47% patients on MPFF 1000 mg versus 54% on 500 mg. After 7 days of treatment with MPFF at the same daily dose, both regimens reduced anal pain and bleeding. MPFF 1000 mg had a comparable safety profile to MPFF 500 mg, with the advantage of fewer tablets. Key limitations: Safety study.

Comparison of 1 mg and 2 mg overnight dexamethasone suppression tests for the screening of Cushing's syndrome in obese patients.

PubMed

Sahin, Mustafa; Kebapcilar, Levent; Taslipinar, Abdullah; Azal, Omer; Ozgurtas, Taner; Corakci, Ahmet; Akgul, Emin Ozgur; Taslipinar, Mine Yavuz; Yazici, Mahmut; Kutlu, Mustafa

2009-01-01

Obesity is currently a major public health problem and one of the potential underlying causes of obesity in a minority of patients is Cushing's syndrome (CS). Traditionally, the gold standard screening test for CS is 1 mg dexamethasone overnight suppression test. However, it is known that obese subjects have high false positive results with this test. We have therefore compared the 1 mg and 2 mg overnight dexamethasone suppression tests in obese subjects. Patients whose serum cortisol after ODST was >50 nM underwent and a low-dose dexamethasone suppression test (LDDST); 24-hour urine cortisol was collected for basal urinary free cortisol (UFC). For positive results after overnight 1-mg dexamethasone suppression test we also performed the overnight 2-mg dexamethasone suppression test. We prospectively evaluated 100 patients (22 men and 78 women, ranging in age from 17 to 73 years with a body mass index (BMI) >30 kg/m2 who had been referred to our hospital-affiliated endocrine clinic because of simple obesity. Suppression of serum cortisol to <50 nM (1.8 microg/dL) after dexamethasone administration was chosen as the cut-off point for normal suppression. Thyroid function tests, lipid profiles, homocysteine, antithyroglobulin, anti-thyroid peroxidase antibody levels, vitamin B12, folate levels, insulin resistance [by homeostasis model assessment (HOMA)] and 1.0 mg postdexamethasone (postdex) suppression cortisol levels were measured. We found an 8% false-positive rate in 1 mg overnight test and 2% in 2 mg overnight test (p=0.001). There was no correlation between the cortisol levels after ODST and other parameters. Our results indicate that the 2 mg overnight dexamethasone suppression test (ODST) is more convenient and accurate than 1-mg ODST as a screening test for excluding CS in subjects with simple obesity.

Interplay of Mg2+, ADP, and ATP in the cytosol and mitochondria: Unravelling the role of Mg2+ in cell respiration

PubMed Central

Gout, Elisabeth; Rébeillé, Fabrice; Douce, Roland; Bligny, Richard

2014-01-01

In animal and plant cells, the ATP/ADP ratio and/or energy charge are generally considered key parameters regulating metabolism and respiration. The major alternative issue of whether the cytosolic and mitochondrial concentrations of ADP and ATP directly mediate cell respiration remains unclear, however. In addition, because only free nucleotides are exchanged by the mitochondrial ADP/ATP carrier, whereas MgADP is the substrate of ATP synthase (EC 3.6.3.14), the cytosolic and mitochondrial Mg2+ concentrations must be considered as well. Here we developed in vivo/in vitro techniques using 31P-NMR spectroscopy to simultaneously measure these key components in subcellular compartments. We show that heterotrophic sycamore (Acer pseudoplatanus L.) cells incubated in various nutrient media contain low, stable cytosolic ADP and Mg2+ concentrations, unlike ATP. ADP is mainly free in the cytosol, but complexed by Mg2+ in the mitochondrial matrix, where [Mg2+] is tenfold higher. In contrast, owing to a much higher affinity for Mg2+, ATP is mostly complexed by Mg2+ in both compartments. Mg2+ starvation used to alter cytosolic and mitochondrial [Mg2+] reversibly increases free nucleotide concentration in the cytosol and matrix, enhances ADP at the expense of ATP, decreases coupled respiration, and stops cell growth. We conclude that the cytosolic ADP concentration, and not ATP, ATP/ADP ratio, or energy charge, controls the respiration of plant cells. The Mg2+ concentration, remarkably constant and low in the cytosol and tenfold higher in the matrix, mediates ADP/ATP exchange between the cytosol and matrix, [MgADP]-dependent mitochondrial ATP synthase activity, and cytosolic free ADP homeostasis. PMID:25313036

Interplay of Mg2+, ADP, and ATP in the cytosol and mitochondria: unravelling the role of Mg2+ in cell respiration.

PubMed

Gout, Elisabeth; Rébeillé, Fabrice; Douce, Roland; Bligny, Richard

2014-10-28

In animal and plant cells, the ATP/ADP ratio and/or energy charge are generally considered key parameters regulating metabolism and respiration. The major alternative issue of whether the cytosolic and mitochondrial concentrations of ADP and ATP directly mediate cell respiration remains unclear, however. In addition, because only free nucleotides are exchanged by the mitochondrial ADP/ATP carrier, whereas MgADP is the substrate of ATP synthase (EC 3.6.3.14), the cytosolic and mitochondrial Mg(2+) concentrations must be considered as well. Here we developed in vivo/in vitro techniques using (31)P-NMR spectroscopy to simultaneously measure these key components in subcellular compartments. We show that heterotrophic sycamore (Acer pseudoplatanus L.) cells incubated in various nutrient media contain low, stable cytosolic ADP and Mg(2+) concentrations, unlike ATP. ADP is mainly free in the cytosol, but complexed by Mg(2+) in the mitochondrial matrix, where [Mg(2+)] is tenfold higher. In contrast, owing to a much higher affinity for Mg(2+), ATP is mostly complexed by Mg(2+) in both compartments. Mg(2+) starvation used to alter cytosolic and mitochondrial [Mg(2+)] reversibly increases free nucleotide concentration in the cytosol and matrix, enhances ADP at the expense of ATP, decreases coupled respiration, and stops cell growth. We conclude that the cytosolic ADP concentration, and not ATP, ATP/ADP ratio, or energy charge, controls the respiration of plant cells. The Mg(2+) concentration, remarkably constant and low in the cytosol and tenfold higher in the matrix, mediates ADP/ATP exchange between the cytosol and matrix, [MgADP]-dependent mitochondrial ATP synthase activity, and cytosolic free ADP homeostasis.

Mg2Sn heterostructures on Si(111) substrate

NASA Astrophysics Data System (ADS)

Dózsa, L.; Galkin, N. G.; Pécz, B.; Osváth, Z.; Zolnai, Zs.; Németh, A.; Galkin, K. N.; Chernev, I. M.; Dotsenko, S. A.

2017-05-01

Thin un-doped and Al doped polycrystalline Mg-stannide films consisting mainly of Mg2Sn semiconductor phase have been grown by deposition of Sn-Mg multilayers on Si(111) p-type wafers at room temperature and annealing at 150 °C. Rutherford backscattering measurement spectroscopy (RBS) were used to determine the amount of Mg and Sn in the structures. Raman spectroscopy has shown the layers contain Mg2Sn phase. Cross sectional transmission electron microscopy (XTEM) measurements have identified Mg2Sn nanocrystallites in hexagonal and cubic phases without epitaxial orientation with respect to the Si(111) substrate. Significant oxygen concentration was found in the layer both by RBS and TEM. The electrical measurements have shown laterally homogeneous conductivity in the grown layer. The undoped Mg2Sn layers show increasing resistivity with increasing temperature indicating the scattering process dominates the resistance of the layers, i.e. large concentration of point defects was generated in the layer during the growth process. The Al doped layer shows increase of the resistance at low temperature caused by freeze out of free carriers in the Al doped Mg2Sn layer. The measurements indicate the necessity of protective layer grown over the Mg2Sn layers, and a short time delay between sample preparation and cross sectionalTEM analysis, since the unprotected layer is degraded by the interaction with the ambient.

The Role of MgCl 2 as a Lewis Base in ROMgCl-MgCl 2 Electrolytes for Magnesium-Ion Batteries

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

Pan, Baofei; Huang, Jinhua; He, Meinan

2016-02-04

A series of strong Lewis acid-free alkoxide/siloxide-based Mg electrolytes were deliberately developed with remarkable oxidative stability up to 3.5 V (vs. Mg/Mg2+). Despite the perception of ROMgCl (R=alkyl, silyl) as a strong base, ROMgCl acts like Lewis acid, whereas the role of MgCl2 in was unambiguously demonstrated as a Lewis base through the identification of the key intermediate using single crystal X-ray crystallography. This Lewis-acid-free strategy should provide a prototype system for further investigation of Mg-ion batteries.

First-principles studies of hydrogen interaction with ultrathin Mg and Mg-based alloy films

NASA Astrophysics Data System (ADS)

Yoon, Mina; Weitering, Hanno H.; Zhang, Zhenyu

2011-01-01

The search for technologically and economically viable storage solutions for hydrogen fuel would benefit greatly from research strategies that involve systematic property tuning of potential storage materials via atomic-level modification. Here, we use first-principles density-functional theory to investigate theoretically the structural and electronic properties of ultrathin Mg films and Mg-based alloy films and their interaction with atomic hydrogen. Additional delocalized charges are distributed over the Mg films upon alloying them with 11.1% of Al or Na atoms. These extra charges contribute to enhance the hydrogen binding strength to the films. We calculated the chemical potential of hydrogen in Mg films for different dopant species and film thickness, and we included the vibrational degrees of freedom. By comparing the chemical potential with that of free hydrogen gas at finite temperature (T) and pressure (P), we construct a hydrogenation phase diagram and identify the conditions for hydrogen absorption or desorption. The formation enthalpies of metal hydrides are greatly increased in thin films, and in stark contrast to its bulk phase, the hydride state can only be stabilized at high P and T (where the chemical potential of free H2 is very high). Metal doping increases the thermodynamic stabilities of the hydride films and thus significantly helps to reduce the required pressure condition for hydrogen absorption from H2 gas. In particular, with Na alloying, hydrogen can be absorbed and/or desorbed at experimentally accessible T and P conditions.

Hysteretic photochromic switching of Eu-Mg defects in GaN links the shallow transient and deep ground states of the Mg acceptor.

PubMed

Singh, A K; O'Donnell, K P; Edwards, P R; Lorenz, K; Kappers, M J; Boćkowski, M

2017-02-03

Although p-type activation of GaN by Mg underpins a mature commercial technology, the nature of the Mg acceptor in GaN is still controversial. Here, we use implanted Eu as a 'spectator ion' to probe the lattice location of Mg in doubly doped GaN(Mg):Eu. Photoluminescence spectroscopy of this material exemplifies hysteretic photochromic switching (HPS) between two configurations, Eu0 and Eu1(Mg), of the same Eu-Mg defect, with a hyperbolic time dependence on 'switchdown' from Eu0 to Eu1(Mg). The sample temperature and the incident light intensity at 355 nm tune the characteristic switching time over several orders of magnitude, from less than a second at 12.5 K, ~100 mW/cm 2 to (an estimated) several hours at 50 K, 1 mW/cm 2 . Linking the distinct Eu-Mg defect configurations with the shallow transient and deep ground states of the Mg acceptor in the Lany-Zunger model, we determine the energy barrier between the states to be 27.7(4) meV, in good agreement with the predictions of theory. The experimental results further suggest that at low temperatures holes in deep ground states are localized on N atoms axially bonded to Mg acceptors.

Determination of the Mg/Mn ratio in foraminiferal coatings: An approach to correct Mg/Ca temperatures for Mn-rich contaminant phases

NASA Astrophysics Data System (ADS)

Hasenfratz, Adam P.; Martínez-García, Alfredo; Jaccard, Samuel L.; Vance, Derek; Wälle, Markus; Greaves, Mervyn; Haug, Gerald H.

2017-01-01

The occurrence of manganese-rich coatings on foraminifera can have a significant effect on their bulk Mg/Ca ratios thereby biasing seawater temperature reconstructions. The removal of this Mn phase requires a reductive cleaning step, but this has been suggested to preferentially dissolve Mg-rich biogenic carbonate, potentially introducing an analytical bias in paleotemperature estimates. In this study, the geochemical composition of foraminifera tests from Mn-rich sediments from the Antarctic Southern Ocean (ODP Site 1094) was investigated using solution-based and laser ablation ICP-MS in order to determine the amount of Mg incorporated into the coatings. The analysis of planktonic and benthic foraminifera revealed a nearly constant Mg/Mn ratio in the Mn coating of ∼0.2 mol/mol. Consequently, the coating Mg/Mn ratio can be used to correct for the Mg incorporated into the Mn phase by using the down core Mn/Ca values of samples that have not been reductively cleaned. The consistency of the coating Mg/Mn ratio obtained in this study, as well as that found in samples from the Panama Basin, suggests that spatial variation of Mg/Mn in foraminiferal Mn overgrowths may be smaller than expected from Mn nodules and Mn-Ca carbonates. However, a site-specific assessment of the Mg/Mn ratio in foraminiferal coatings is recommended to improve the accuracy of the correction.

Índice UV

EPA Pesticide Factsheets

Información general sobre el Índice UV que proporciona un pronóstico del riesgo esperado de sobreexposición a la radiación ultravioleta (UV) del sol. El índice UV va acompañado de recomendaciones para protegerse del sol.

Comparative study of 250 mg/day terbinafine and 100 mg/day itraconazole for the treatment of cutaneous sporotrichosis.

PubMed

Francesconi, Glaucia; Francesconi do Valle, Antonio Carlos; Passos, Sonia Lambert; de Lima Barros, Mônica Bastos; de Almeida Paes, Rodrigo; Curi, André Luiz Land; Liporage, José; Porto, Cássio Ferreira; Galhardo, Maria Clara Gutierrez

2011-05-01

Itraconazole is currently used for the treatment of cutaneous sporotrichosis. Terbinafine at a daily dose of 250 mg has been successfully applied to the treatment of cutaneous sporotrichosis. To compare the efficacy of 250 mg/day terbinafine and 100 mg/day itraconazole for the treatment of cutaneous sporotrichosis. A bidirectional cohort study was conducted on 55 patients receiving 250 mg/day terbinafine and 249 patients receiving 100 mg/day itraconazole. The latter patients were matched for age and clinical form to the terbinafine group at a ratio of 5:1. Sporothrix schenckii was isolated by culture from all patients (age range: 18-70 years), who were submitted to the standard care protocol consisting of clinical and laboratory evaluation and periodic visits. Cure was observed in 51 (92.7%) patients of the terbinafine group and 229 (92%) of the itraconazole group within a similar mean period of time (11.5 and 11.8 weeks, respectively). An increase in the terbinafine dose to 500 mg was necessary in two patients due to the lack of a response, and one patient presented recurrence. In the itraconazole group, two patients required a dose increase and three presented recurrence. Adverse events were equally frequent among patients receiving terbinafine (n = 4, 7.3%) and itraconazole (n = 19, 7.6%) and were generally mild without the need for drug discontinuation, except for two patients of the itraconazole group. Terbinafine administered at a daily dose of 250 mg is an effective and well-tolerated option for the treatment of cutaneous sporotrichosis.

Pressure-induced photoluminescence of MgO

NASA Astrophysics Data System (ADS)

Li, Xin; Yuan, Ye; Zhang, Jinbo; Kim, Taehyun; Zhang, Dongzhou; Yang, Ke; Lee, Yongjae; Wang, Lin

2018-05-01

It is reported in this paper that pressure can promote strong photoluminescence (PL) in MgO. The PL measurements of MgO indicate that it has no obvious luminescence at pressures lower than 13 GPa. PL starts to appear upon further compression and reaches a maximum intensity at about 35 GPa. The center of the emission band shows a red shift at lower pressures and turns to a blue shift as pressure exceeds 25 GPa. The PL is preserved upon complete decompression. The defects and micro-strain due to the plastic deformation of MgO are likely responsible for the origin of the luminescence.

Natural abundance (25)Mg solid-state NMR of mg oxyanion systems: a combined experimental and computational study.

PubMed

Cahill, Lindsay S; Hanna, John V; Wong, Alan; Freitas, Jair C C; Yates, Jonathan R; Harris, Robin K; Smith, Mark E

2009-09-28

Solid-state (25)Mg magic angle spinning nuclear magnetic resonance (MAS NMR) data are reported from a range of organic and inorganic magnesium-oxyanion compounds at natural abundance. To constrain the determination of the NMR interaction parameters (delta(iso), chi(Q), eta(Q)) data have been collected at three external magnetic fields (11.7, 14.1 and 18.8 T). Corresponding NMR parameters have also been calculated by using density functional theory (DFT) methods using the GIPAW approach, with good correlations being established between experimental and calculated values of both chi(Q) and delta(iso). These correlations demonstrate that the (25)Mg NMR parameters are very sensitive to the structure, with small changes in the local Mg(2+) environment and the overall hydration state profoundly affecting the observed spectra. The observations suggest that (25)Mg NMR spectroscopy is a potentially potent probe for addressing some key problems in inorganic materials and of metal centres in biologically relevant molecules.

Responder analysis of a randomized comparison of the 13.3 mg/24 h and 9.5 mg/24 h rivastigmine patch.

PubMed

Molinuevo, José L; Frölich, Lutz; Grossberg, George T; Galvin, James E; Cummings, Jeffrey L; Krahnke, Tillmann; Strohmaier, Christine

2015-01-01

OPtimizing Transdermal Exelon In Mild-to-moderate Alzheimer's disease (OPTIMA) was a randomized, double-blind comparison of 13.3 mg/24 h versus 9.5 mg/24 h rivastigmine patch in patients with mild-to-moderate Alzheimer's disease who declined despite open-label treatment with 9.5 mg/24 h patch. Over 48 weeks of double-blind treatment, high-dose patch produced greater functional and cognitive benefits compared with 9.5 mg/24 h patch. Using OPTIMA data, a post-hoc responder analysis was performed to firstly, compare the proportion of patients demonstrating improvement or absence of decline with 13.3 mg/24 h versus 9.5 mg/24 h patch; and secondly, identify predictors of improvement or absence of decline. 'Improvers' were patients who improved on the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) by ≥4 points from baseline, and did not decline on the instrumental domain of the Alzheimer's Disease Cooperative Study-Activities of Daily Living scale (ADCS-IADL). 'Non-decliners' were patients who did not decline on either scale. Overall, 265 patients randomized to 13.3 mg/24 h and 271 to 9.5 mg/24 h patch met the criteria for inclusion in the intention-to-treat population and were included in the analyses. Significantly more patients were 'improvers' with 13.3 mg/24 h compared with 9.5 mg/24 h patch at Weeks 24 (44 (16.6%) versus 19 (7.0%); P < 0.001) and 48 (21 (7.9%) versus 10 (3.7%); P = 0.023). A significantly greater proportion of patients were 'non-decliners' with 13.3 mg/24 h compared with 9.5 mg/24 h patch at Week 24 (71 (26.8%) versus 44 (16.2%); P = 0.002). At Week 48, there was a trend in favor of 13.3 mg/24 h patch. Functional and cognitive assessment scores at double-blind baseline did not consistently predict effects at Weeks 24 or 48. More patients with mild-to-moderate Alzheimer's disease who are titrated to 13.3 mg/24 h rivastigmine patch at time of decline are 'improvers' or 'non-decliners' i

Mg/Ti multilayers: Structural and hydrogen absorption properties

NASA Astrophysics Data System (ADS)

Baldi, A.; Pálsson, G. K.; Gonzalez-Silveira, M.; Schreuders, H.; Slaman, M.; Rector, J. H.; Krishnan, G.; Kooi, B. J.; Walker, G. S.; Fay, M. W.; Hjörvarsson, B.; Wijngaarden, R. J.; Dam, B.; Griessen, R.

2010-06-01

Mg-Ti alloys have uncommon optical and hydrogen absorbing properties, originating from a “spinodal-like” microstructure with a small degree of chemical short-range order in the atomic distribution. In the present study we artificially engineer short-range order by depositing Pd-capped Mg/Ti multilayers with different periodicities. Notwithstanding the large lattice mismatch between Mg and Ti, the as-deposited metallic multilayers show good structural coherence. On exposure to H2 gas a two-step hydrogenation process occurs with the Ti layers forming the hydride before Mg. From in situ measurements of the bilayer thickness Λ at different hydrogen pressures, we observe large out-of-plane expansions of Mg and Ti layers on hydrogenation, indicating strong plastic deformations in the films and a consequent shortening of the coherence length. On unloading at room temperature in air, hydrogen atoms remain trapped in the Ti layers due to kinetic constraints. Such loading/unloading sequence can be explained in terms of the different thermodynamic properties of hydrogen in Mg and Ti, as shown by diffusion calculations on a model multilayered systems. Absorption isotherms measured by hydrogenography can be interpreted as a result of the elastic clamping arising from strongly bonded Mg/Pd and broken Mg/Ti interfaces.

Ground-state properties of neutron-rich Mg isotopes

NASA Astrophysics Data System (ADS)

Watanabe, S.; Minomo, K.; Shimada, M.; Tagami, S.; Kimura, M.; Takechi, M.; Fukuda, M.; Nishimura, D.; Suzuki, T.; Matsumoto, T.; Shimizu, Y. R.; Yahiro, M.

2014-04-01

We analyze recently measured total reaction cross sections for 24-38Mg isotopes incident on 12C targets at 240 MeV/nucleon by using the folding model and antisymmetrized molecular dynamics (AMD). The folding model well reproduces the measured reaction cross sections, when the projectile densities are evaluated by the deformed Woods-Saxon (def-WS) model with AMD deformation. Matter radii of 24-38Mg are then deduced from the measured reaction cross sections by fine tuning the parameters of the def-WS model. The deduced matter radii are largely enhanced by nuclear deformation. Fully microscopic AMD calculations with no free parameter well reproduce the deduced matter radii for 24-36Mg, but still considerably underestimate them for 37,38Mg. The large matter radii suggest that 37,38Mg are candidates for deformed halo nucleus. AMD also reproduces other existing measured ground-state properties (spin parity, total binding energy, and one-neutron separation energy) of Mg isotopes. Neutron-number (N) dependence of deformation parameter is predicted by AMD. Large deformation is seen from 31Mg with N =19 to a drip-line nucleus 40Mg with N =28, indicating that both the N =20 and 28 magicities disappear. N dependence of neutron skin thickness is also predicted by AMD.

A High Pressure Post-Perovskite Phase Transition in NaMgF3--a MgSiO3 Analog Material

NASA Astrophysics Data System (ADS)

Martin, C.; Liu, H.; Crichton, W.; Parise, J. B.

2005-12-01

Since Murakami et al. (2004) identified a perovskite (pv, Pbnm) to post-perovskite (ppv, Cmcm) structural phase transition in MgSiO3, the transition has been reported to occur in many oxides at ultra-high pressures (>60 GPa). The layered ppv structure is rapidly shaping a better understanding of seismic anisotropy in the controversial D" region of the lower mantle. While the ppv unit cell may be derived from indexing of the powder pattern, the structure adopted at high pressure is experimentally ill-constrained due to compromised powder diffraction statistics typically obtained from small sample volumes at extreme conditions in the diamond anvil cell. NaMgF3, a structural analog material to MgSiO3 pv, exhibits a large compressibility and presents the possibility of reducing the pv-ppv transition pressure, allowing for improved powder statistics from a larger sample volume. In accordance with our previous theoretical and experimental evidence (Liu et al., 2005; Parise et al., 2004), we have observed a phase transition in NaMgF3 during two recent independent high pressure trials utilizing monochromatic x-ray diffraction and in-situ laser heating in the diamond anvil cell at pressures as low as 30 GPa. From our analysis thus far, we have found the unit cell of the high pressure phase cannot be indexed according to pv (Pbnm) or close permutations of ppv (Cmcm) unit cells predicted for NaMgF3 or unit cells observed for ppv MgSiO3 and MgGeO3. In addition, we have precluded a breakdown to high pressure phases of NaF and MgF3 as an explanation for the observed data. Upon pressure release, we observe diffraction peaks from the high pressure phase in the absence of pv NaMgF3, suggesting the high pressure structure is quenchable to ambient conditions. The results of the work in progress will be presented at the meeting.

Microwave surface resistance of MgB2

NASA Astrophysics Data System (ADS)

Zhukov, A. A.; Purnell, A.; Miyoshi, Y.; Bugoslavsky, Y.; Lockman, Z.; Berenov, A.; Zhai, H. Y.; Christen, H. M.; Paranthaman, M. P.; Lowndes, D. H.; Jo, M. H.; Blamire, M. G.; Hao, Ling; Gallop, J.; MacManus-Driscoll, J. L.; Cohen, L. F.

2002-04-01

The microwave power and frequency dependence of the surface resistance of MgB2 films and powder samples were studied. Sample quality is relatively easy to identify by the breakdown in the ω2 law for poor-quality samples at all temperatures. The performance of MgB2 at 10 GHz and 21 K was compared directly with that of high-quality YBCO films. The surface resistance of MgB2 was found to be approximately three times higher at low microwave power and showed an onset of nonlinearity at microwave surface fields ten times lower than the YBCO film. It is clear that MgB2 films are not yet optimized for microwave applications.

Pharmacodynamic target attainment analysis against Streptococcus pneumoniae using levofloxacin 500 mg, 750 mg and 1000 mg once daily in plasma (P) and epithelial lining fluid (ELF) of hospitalized patients with community acquired pneumonia (CAP).

PubMed

Noreddin, Ayman M; Marras, Theodore K; Sanders, Kevin; Chan, Charles K N; Hoban, Daryl J; Zhanel, George G

2004-11-01

The pharmacokinetics and pharmacodynamics of levofloxacin in patients with respiratory infections such as community-acquired pneumonia (CAP) are poorly documented. This work aimed at assessing the pharmacodynamic target attainment against Streptococcus pneumoniae using levofloxacin 500 mg, 750 mg and 1000 mg administered once daily in plasma (P) and epithelial lining fluid (ELF) of hospitalized patients with community acquired pneumonia. The pharmacokinetics of levofloxacin in elderly (>/=65 years) compared with younger patients (<65 years) hospitalized with CAP were simulated. Susceptibility data with S. pneumoniae from our ongoing national surveillance study (Canadian Respiratory Organism Susceptibility Study-CROSS) were then used to produce pharmacodynamic indices of AUC(0-24)/MIC(all.) Monte Carlo simulations were then used to analyse target attainment of levofloxacin using doses of 500 mg, 750 mg and 1000 mg once daily to achieve free drug AUC(0-24)/MIC(all) >/= 30-100 versus S. pneumoniae in patients with CAP. Pharmacokinetics of levofloxacin simulated after 500 mg, 750 mg and 1000 mg once daily dosing resulted in levofloxacin volume of distribution: elderly patients = younger patients, while levofloxacin clearance was: elderly patients < younger patients. Levofloxacin t(1/2) values were longer in elderly patients (9.8 +/- 2.5h) than younger patients with CAP (7.4 +/- 2.5h). Free levofloxacin AUC(0-24) as well as AUC(0-24)/MIC(all) for S. pneumoniae were higher in elderly patients than younger patients. Monte Carlo simulation using levofloxacin 500 mg yielded probabilities of achieving free-drug AUC(0-24)/MIC(all) of 30 in P and ELF (95.7% and 98.1%) in elderly and younger patients (72.7% and 80.6%) respectively. Levofloxacin 750 mg and 1000 mg once daily had probability of achieving free-drug AUC(0-24)/MIC(all) of 30 in P/ELF of 98.1%/98.6% and 99.2%/99.0%, respectively, in elderly patients compared with 89.9%/94.1% and 95.2%/96.5%, respectively, for younger

Effect of Si, Mg, and Mg Zn doping on structural properties of a GaN layer grown by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Cho, H. K.; Lee, J. Y.; Kim, K. S.; Yang, G. M.

2001-12-01

We have studied the structural properties of undoped, Si-doped, Mg-doped, and Mg-Zn codoped GaN using high-resolution X-ray diffraction (HRXRD) and transmission electron microscopy. When compared with undoped GaN, the dislocation density at the surface of the GaN layer decreases with Si doping and increases with Mg doping. In addition, we observed a reduction of dislocation density by codoping with Zn atoms in the Mg-doped GaN layer. The full width at half maximum of HRXRD shows that Si doping and Mg-Zn codoping improve the structural quality of the GaN layer as compared with undoped and Mg-doped GaN, respectively.

Global Mapping of Mg-Number Derived from Clementine Data.

NASA Astrophysics Data System (ADS)

Cahill, J. T.; Lucey, P. G.; Gillis, J. J.; Steutel, D.

2004-12-01

The global mapping of the lunar surface using the petrological parameter Mg-number (Mg*) was undertaken because Mg*, or the ratio of Mg to the sum of Mg and Fe on an atomic basis, is an important disciminator in defining and understanding lunar rocks. The dominant lunar rock types, ferroan anorthosites (FAN), high-magnisium suite (HMS), and high-alkali suite (HAS) rocks all vary in Mg* depending upon the petrologic scenario that formed them. Of particular interest are FAN mineralogy and chemistry, which varies from high-Mg# (~70) troctolites to low-Mg# norites (~50) and for some time has been considered to represent a single magma frac-tionation trend. However, recent studies have also shown that the crystallization of FAN rocks may have been more complicated than originally thought. James et al. [1] found that instead of one simple fractionation trend for ferroan anorthosites, there may have been four. Studies by [2], [3], and [4] using Apollo and lunar meteorites for analysis have also eluded to the possibility that FAN rocks may have evolved from a more complex source or process. Therefore a global assessment of lithologies and corresponding Mg* is of great value for lunar petrology. In a remote sensing context, Mg* is the most important control on the spectral properties of lunar mafic silicates. For stoichiometric orthopyroxene and olivine, Mg* is mathematically linked to the Fe content that controls the overall reflectance and intensity of absorption. The changes in band centers and shape that accompany the structural changes as Fe substitutes for Mg along the solid solution series have long been recognized; these changes are highly correlated with Mg*. In clinopyroxene, the strong effect of Ca on structure makes this element important, but Mg* has the dominant effect on reflectance and a comparable effect on spectral shape. In this study, the lunar surface is quantitatively mapped using a theoretical treatment of mineralogic spectra and the effect of

Interstitial Fe in MgO

NASA Astrophysics Data System (ADS)

Mølholt, T. E.; Mantovan, R.; Gunnlaugsson, H. P.; Svane, A.; Masenda, H.; Naidoo, D.; Bharuth-Ram, K.; Fanciulli, M.; Gislason, H. P.; Johnston, K.; Langouche, G.; Ólafsson, S.; Sielemann, R.; Weyer, G.

2014-01-01

Isolated 57Fe atoms were studied in MgO single-crystals by emission Mössbauer spectroscopy following implantation of 57Mn decaying to 57Fe. Four Mössbauer spectral components were found corresponding to different Fe lattice positions and/or charge states. Two components represent Fe atoms substituting Mg as Fe2+ and Fe3+, respectively; a third component is due to Fe in a strongly implantation-induced disturbed region. The fourth component, which is the focus of this paper, can be assigned to Fe at an interstitial site. Comparison of its measured isomer shift with ab initio calculations suggests that the interstitial Fe is located on, or close to, the face of the rock-salt MgO structure. To harmonize such an assignment with the measured near-zero quadrupole interaction a local motion process (cage motion) of the Fe has to be stipulated. The relation of such a local motion as a starting point for long range diffusion is discussed.

Natural ageing responses of duplex structured Mg-Li based alloys

PubMed Central

Li, C. Q.; Xu, D. K.; Wang, B. J.; Sheng, L. Y.; Qiao, Y. X.; Han, E. H.

2017-01-01

Natural ageing responses of duplex structured Mg-6%Li and Mg-6%Li-6%Zn-1.2%Y alloys have been investigated. Microstructural analyses revealed that the precipitation and coarsening process of α-Mg particles could occur in β-Li phases of both two alloys during ageing process. Since a certain amount of Mg atoms in β-Li phases were consumed for the precipitation of abundant tiny MgLiZn particles, the size of α-Mg precipitates in Mg-6%Li-6%Zn-1.2%Y alloy was relatively smaller than that in Mg-6%Li alloy. Micro hardness measurements demonstrated that with the ageing time increasing, the α-Mg phases in Mg-6%Li alloy could have a constant hardness value of 41 HV, but the contained β-Li phases exhibited a slight age-softening response. Compared with the Mg-6%Li alloy, the age-softening response of β-Li phases in Mg-6%Li-6%Zn-1.2%Y alloy was much more profound. Meanwhile, a normal age-hardening response of α-Mg phases was maintained. Tensile results indicated that obvious ageing-softening phenomenon in terms of macro tensile strength occurred in both two alloys. Failure analysis demonstrated that for the Mg-6%Li alloy, cracks were preferentially initiated at α-Mg/β-Li interfaces. For the Mg-6%Li-6%Zn-1.2%Y alloy, cracks occurred at both α-Mg/β-Li interfaces and slip bands in α-Mg and β-Li phases. PMID:28053318

Mechanical properties and corrosion behavior of Mg-HAP composites.

PubMed

Campo, R Del; Savoini, B; Muñoz, A; Monge, M A; Garcés, G

2014-11-01

Mg and Mg-HAP composites containing 5, 10 and 15 wt% of hydroxyapatite have been produced following a powder metallurgy route that consists of mixing raw powders and consolidation by extrusion. The microstructure, texture, mechanical behavior and resistance to corrosion under a PBS solution have been studied. Addition of HAP increases the microhardness of the composites, however the yield strength under compression slightly decreases. Texture analyses reveal a fiber texture for pure Mg that is weakened increasing the HAP fraction. This texture promotes twinning and softening of Mg and Mg-5HAP during the initial deformation stages. Mg-10HAP and Mg-15HAP present a strain-hardening dependence showing no softening. The volume fraction of HAP particles weakens the texture and favors the activation of secondary slip systems. Corrosion experiments in PBS solution have shown that Mg-5HAP exhibits the best resistance to corrosion. Texture and porosity appear to be the main material features controlling the corrosion rates of Mg-HAP composites under the present conditions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dopant radial inhomogeneity in Mg-doped GaN nanowires.

PubMed

Siladie, Alexandra-Madalina; Amichi, Lynda; Mollard, Nicolas; Mouton, Isabelle; Bonef, Bastien; Bougerol, Catherine; Grenier, Adeline; Robin, Eric; Jouneau, Pierre-Henri; Garro, Nuria; Cros, Ana; Daudin, Bruno

2018-06-22

Using atom probe tomography, it is demonstrated that Mg doping of GaN nanowires grown by Molecular Beam Epitaxy results in a marked radial inhomogeneity, namely a higher Mg content in the periphery of the nanowires. This spatial inhomogeneity is attributed to a preferential incorporation of Mg through the m-plane sidewalls of nanowires and is related to the formation of a Mg-rich surface which is stabilized by hydrogen. This is further supported by Raman spectroscopy experiments which give evidence of Mg-H complexes in the doped nanowires. A Mg doping mechanism such as this, specific to nanowires, may lead to higher levels of Mg doping than in layers, boosting the potential interest of nanowires for light emitting diode applications.

Dopant radial inhomogeneity in Mg-doped GaN nanowires

NASA Astrophysics Data System (ADS)

Siladie, Alexandra-Madalina; Amichi, Lynda; Mollard, Nicolas; Mouton, Isabelle; Bonef, Bastien; Bougerol, Catherine; Grenier, Adeline; Robin, Eric; Jouneau, Pierre-Henri; Garro, Nuria; Cros, Ana; Daudin, Bruno

2018-06-01

Using atom probe tomography, it is demonstrated that Mg doping of GaN nanowires grown by Molecular Beam Epitaxy results in a marked radial inhomogeneity, namely a higher Mg content in the periphery of the nanowires. This spatial inhomogeneity is attributed to a preferential incorporation of Mg through the m-plane sidewalls of nanowires and is related to the formation of a Mg-rich surface which is stabilized by hydrogen. This is further supported by Raman spectroscopy experiments which give evidence of Mg-H complexes in the doped nanowires. A Mg doping mechanism such as this, specific to nanowires, may lead to higher levels of Mg doping than in layers, boosting the potential interest of nanowires for light emitting diode applications.

Matter radii of {sup 32-35}Mg

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

Kanungo, R.; Perro, C.; Prochazka, A.

The interaction cross sections of {sup 32-35}Mg at 900A MeV have been measured using the fragment separator at GSI. The deviation from the r{sub 0}A{sup 1/3} trend is slightly larger for {sup 35}Mg, signaling the possible formation of a longer tail in the neutron distribution for {sup 35}Mg. The radii extracted from a Glauber model analysis with Fermi densities are consistent with models predicting the development of neutron skins.

Microstructural Aspects of Localized Corrosion Behavior of Mg Alloys

NASA Astrophysics Data System (ADS)

Chu, Peng-Wei

Combining high specific strength and unique electrochemical properties, magnesium (Mg) alloys are promising lightweight materials for various applications from automotive, consumer electronics, biomedical body implant, to battery electrodes. Engineering solutions such as coatings have enabled the use of Mg alloys, despite their intrinsic low corrosion resistance. Consequently, the fundamental mechanisms responsible for the unique localized corrosion behavior of bare Mg alloys, the associated abnormal hydrogen evolution response, and the relationships between corrosion behavior and alloy microstructure are still unsolved. This thesis aims to uncover the specificities of Mg corrosion and the roles of alloy chemistry and microstructure. To this end, multiscale site-specific microstructure characterization techniques, including in situ optical microscopy, scanning electron microscopy with focused ion beam milling, and transmission electron microscopy, combined with electrochemical analysis and hydrogen evolution rate monitoring, were performed on pure Mg and selected Mg alloys under free corrosion and anodic polarization, revealing key new information on the propagation mode of localized corrosion and the role of alloy microstructures, thereby confirming or disproving the validity of previously proposed corrosion models. Uniform surface corrosion film on Mg alloys immersed in NaCl solution consisted a bi-layered structure, with a porous Mg(OH)2 outer layer on top of a MgO inner layer. Presence of fine scale precipitates in Mg alloys interacted with the corrosion reaction front, reducing the corrosion rate and surface corrosion film thickness. Protruding hemispherical dome-like corrosion products, accompanied by growing hydrogen bubbles, formed on top of the impurity particles in Mg alloys by deposition of Mg(OH)2 via a microgalvanic effect. Localized corrosion on Mg alloys under both free immersion and anodic polarization was found to be governed by a common mechanism

Laser-induced chemiluminescence of NaMg

NASA Astrophysics Data System (ADS)

Benard, D. J.; Michels, H. H.

1982-03-01

An unstructured continuum emission around 670 nm was observed when Mg was added to an optically pumped heat pipe containing Na and K vapor, in good agreement with ab initio calculations of the NaMg potential energy curves. The corresponding excitation spectrum showed that the incident radiation was observed by NaK molecules (X → C transitions).

A randomized, double-blind, placebo-controlled study of acetaminophen 1000 mg versus acetaminophen 650 mg for the treatment of postsurgical dental pain.

PubMed

Qi, Daniel S; May, Lisa G; Zimmerman, Brenda; Peng, Penny; Atillasoy, Evren; Brown, Jean D; Cooper, Stephen A

2012-12-01

Although acetaminophen is one of the oldest and most widely used of all analgesic drugs, the incremental benefit of the 1000-mg dose compared with the 650-mg dose has been questioned. The aim of this study was to assess the relative efficacy of acetaminophen 1000 mg versus acetaminophen 650 mg over a 6-hour period in patients experiencing at least moderate postsurgical dental pain. This single-center, randomized, double-blind, placebo-controlled, single-dose study enrolled patients aged 16 to 50 years who experienced at least moderate pain after surgical removal of impacted third molars. Each patient received either acetaminophen 1000 mg (n = 239), acetaminophen 650 mg (n = 241), or placebo (n = 60) when they had at least moderate pain and a score ≥50 on the 100-mm Visual Analog Scale (VAS) postsurgically. Pain intensity and pain relief were measured over 6 hours (VAS 0-100 mm). All 540 patients (52% female; age range, 16-30 years; 95% white) were included in the efficacy analysis. For the primary efficacy endpoint (weighted sum of the pain intensity difference from baseline [PID] and pain relief [PAR] scores over 6 hours [SPRID6]), acetaminophen 1000 mg demonstrated a 24% improvement compared with acetaminophen 650 mg (529.4 vs 427.3; P = 0.001). In addition, acetaminophen 650 mg was significantly superior compared with placebo (P < 0.001). The weighted sum of PID over 6 hours (SPID6), the weighted total pain relief over 6 hours (TOTPAR6), and the percentage of patients with >50% of the maximum possible TOTPAR6 score were significantly greater for patients treated with acetaminophen 1000 mg compared with those receiving acetaminophen 650 mg (P ≤ 0.006) or placebo (P < 0.001) and for patients treated with acetaminophen 650 mg compared with placebo (P < 0.001). Time to rescue, rescue rates through 4 and 6 hours, and patient global assessment demonstrated similar findings. Patients treated with acetaminophen 1000 mg or 650 mg had a significantly different

Clinical trial: the treatment of gastro-oesophageal reflux disease in primary care--prospective randomized comparison of rabeprazole 20 mg with esomeprazole 20 and 40 mg.

PubMed

Eggleston, A; Katelaris, P H; Nandurkar, S; Thorpe, P; Holtmann, G

2009-05-01

A trial of empirical PPI therapy is usual practice for most patients with symptoms of gastro-oesophageal reflux disease (GERD) in primary care. To determine if the 4-week efficacy of rabeprazole 20 mg for resolving heartburn and regurgitation symptoms is non-inferior to esomeprazole 40 mg or 20 mg. In all, 1392 patients were randomized to rabeprazole 20 mg, esomeprazole 20 mg or 40 mg once daily. Patients, doctors and assessors were blinded. Symptom resolution data were collected on days 0-7 and day-28 using the Patient Assessment of Upper Gastrointestinal Disorders Symptom Severity Index with a shortened version used on days 8-27. Rabeprazole 20 mg was non-inferior to esomeprazole 40 mg for complete resolution of regurgitation and satisfactory resolution of heartburn and regurgitation. For complete heartburn resolution, the efficacy of rabeprazole 20 mg and esomeprazole 40 mg was statistically indistinguishable, although the non-inferiority test was inconclusive. Rabeprazole 20 mg was non-inferior to esomeprazole 20 mg for all outcomes. In uninvestigated GERD patients, rabeprazole 20 mg was non-inferior to esomeprazole 40 mg for complete and satisfactory relief of regurgitation and satisfactory relief of heartburn, and not different for complete resolution of heartburn.

Low-power, high-uniform, and forming-free resistive memory based on Mg-deficient amorphous MgO film with rough surface

NASA Astrophysics Data System (ADS)

Guo, Jiajun; Ren, Shuxia; Wu, Liqian; Kang, Xin; Chen, Wei; Zhao, Xu

2018-03-01

Saving energy and reducing operation parameter fluctuations remain crucial for enabling resistive random access memory (RRAM) to emerge as a universal memory. In this work, we report a resistive memory device based on an amorphous MgO (a-MgO) film that not only exhibits ultralow programming voltage (just 0.22 V) and low power consumption (less than 176.7 μW) but also shows excellent operative uniformity (the coefficient of variation is only 1.7% and 2.2% for SET and RESET voltage, respectively). Moreover, it also shows a forming-free characteristic. Further analysis indicates that these distinctive properties can be attributed to the unstable local structures and the rough surface of the Mg-deficient a-MgO film. These findings show the potential of using a-MgO in high-performance nonvolatile memory applications.

Surface exciton emission of MgO crystals

NASA Astrophysics Data System (ADS)

Kuang, Wen-Jian; Li, Qing; Chen, Yu-Xiang; Hu, Kai; Wang, Ning-Hui; Xing, Fang-Li; Yan, Qun; Sun, Shuai-Shuai; Huang, Yan; Tao, Ye; Tolner, Harm

2013-09-01

MgO crystals have been exposed to vacuum ultraviolet (VUV) radiation from a synchrotron, with energies up to 9 eV, and the emitted light, at wavelengths above 200 nm, was observed. It is concluded that bulk excitons, play an important role in the diffusion of energy inside MgO crystals, resulting in 5.85 eV (212 nm) emission from the MgO terraces of large (0.2-2 µm) MgO : F crystals. In the case of aliovalent impurity doping, then the bulk exciton energy is also transferred to the Vk centres and 5.3 eV (235 nm) light is emitted. Both fluorine and silicon doping appear to promote UV surface emission, acting similarly to an ns2 ion inside MgO, while strong scandium doping is killing the surface emission completely. The 212 nm surface UV emission and the 235 nm bulk UV emission can be excited only at the bandgap edge. Broadband visible light, centred around 400 nm, is also emitted. Contrary to the UV emission, this is not generated when excited at the bandgap edge; instead, we find that it is only excited at sub-bandgap energies, with a maximum at the 5C surface excitation energy of 5.71 eV (217 nm) for the MgO terraces.

Catalytically Enhanced Hydrogen Sorption in Mg-MgH2 by Coupling Vanadium-Based Catalyst and Carbon Nanotubes

PubMed Central

Kadri, Atikah; Jia, Yi; Chen, Zhigang; Yao, Xiangdong

2015-01-01

Mg (MgH2)-based composites, using carbon nanotubes (CNTs) and pre-synthesized vanadium-based complex (VCat) as the catalysts, were prepared by high-energy ball milling technique. The synergistic effect of coupling CNTs and VCat in MgH2 was observed for an ultra-fast absorption rate of 6.50 wt. % of hydrogen per minute and 6.50 wt. % of hydrogen release in 10 min at 200 °C and 300 °C, respectively. The temperature programmed desorption (TPD) results reveal that coupling VCat and CNTs reduces both peak and onset temperatures by more than 60 °C and 114 °C, respectively. In addition, the presence of both VCat and CNTs reduces the enthalpy and entropy of desorption of about 7 kJ/mol H2 and 11 J/mol H2·K, respectively, as compared to those of the commercial MgH2, which ascribe to the decrease of desorption temperature. From the study of the effect of CNTs milling time, it is shown that partially destroyed CNTs (shorter milling time) are better to enhance the hydrogen sorption performance.

Decay of 34Mg

NASA Astrophysics Data System (ADS)

Chaney, Donlad; Benjamin Luna Collaboration

2017-09-01

One of concepts of modern physics that is not understood is the strong nuclear force. One manifestation of this is our lack of understanding of so-called `islands of inversion', which are groups of nuclides which have deformed ground states. It is known that 34Mg is included in this island, and that its decay (34Al) has a mixed ground state configuration. By studying their decays we hoped to discover definitive information about the branching ratios and the half lives of 34Mg and 34Al. In order to accomplish these goals, we studied the gamma radiation from the decays of 34Mg and 34Al. A Magnesium beam was implanted into a strip of mylar tape and transported to the center of an array of scintillators and germanium detectors, which has allowed us to determine the half-lives for the decays, and the branching ratios for the beta decay. My work on this project began with writing scripts to draw histograms with the data, and using those histograms to gather information that would allow me to gate our data on any number of variables and pieces of information. By cutting out bad portions of our data collection runs and gating on the coincidence of beta decays and other gamma rays, I was able to cut out a significant amount background radiation from our data.

Acid-inhibitory effects of vonoprazan 20 mg compared with esomeprazole 20 mg or rabeprazole 10 mg in healthy adult male subjects--a randomised open-label cross-over study.

PubMed

Sakurai, Y; Mori, Y; Okamoto, H; Nishimura, A; Komura, E; Araki, T; Shiramoto, M

2015-09-01

Proton pump inhibitors (PPIs) are widely used for the treatment of acid-related diseases. Vonoprazan is a member of a new class of acid suppressants; potassium-competitive acid blockers. Vonoprazan may thus be an alternative to PPIs. To evaluate efficacy, rapidity and duration of acid-inhibitory effects of vonoprazan vs. two control PPIs, esomeprazole and rabeprazole, in 20 healthy Japanese adult male volunteers with CYP2C19 extensive metaboliser genotype. In this randomised, open-label, two-period cross-over study, vonoprazan 20 mg and esomeprazole 20 mg (Study V vs. E) or rabeprazole 10 mg (Study V vs. R) were orally administered daily for 7 days. Primary pharmacodynamic endpoint was gastric pH over 24 h measured as percentage of time pH ≥3, ≥4 and ≥5 (pH holding time ratios; HTRs) and mean gastric pH. Acid-inhibitory effect (pH4 HTR) of vonoprazan was significantly greater than that of esomeprazole or rabeprazole on both Days 1 and 7; Day 7 difference in pH4 HTR for vonoprazan vs. esomeprazole was 24.6% [95% confidence interval (CI): 16.2-33.1] and for vonoprazan vs. rabeprazole 28.8% [95% CI: 17.2-40.4]. The Day 1 to Day 7 ratio of 24-h pH4 HTRs was >0.8 for vonoprazan, compared with 0.370 for esomeprazole and 0.393 for rabeprazole. Vonoprazan was generally well tolerated. One vonoprazan subject withdrew due to a rash which resolved after discontinuation. This study demonstrated a more rapid and sustained acid-inhibitory effect of vonoprazan 20 mg vs. esomeprazole 20 mg or rabeprazole 10 mg. Therefore, vonoprazan may be a potentially new treatment for acid-related diseases. © 2015 The Authors. Alimentary Pharmacology & Therapeutics published by John Wiley & Sons Ltd.

Información básica sobre la visibilidad

EPA Pesticide Factsheets

La contaminación del aire puede generar bruma la cual tiene un impacto adverso en la visibilidad, la salud y el medioambiente. La bruma se produce cuando la luz del sol encuentra diminutas partículas de contaminación en el aire.

Powder metallurgical low-modulus Ti-Mg alloys for biomedical applications.

PubMed

Liu, Yong; Li, Kaiyang; Luo, Tao; Song, Min; Wu, Hong; Xiao, Jian; Tan, Yanni; Cheng, Ming; Chen, Bing; Niu, Xinrui; Hu, Rong; Li, Xiaohui; Tang, Huiping

2015-11-01

In this work, powder metallurgical (PM) Ti-Mg alloys were prepared using combined techniques of mechanical alloying and spark plasma sintering. The alloys mainly consist of super saturations of Mg in Ti matrix, and some laminar structured Ti- and Mg-rich phases. The PM Ti-Mg alloys contain a homogeneous mixtures of nanocrystalline Mg and Ti phases. The novel microstructures result in unconventional mechanical and biological properties. It has been shown that the PM Ti-Mg alloys have a much lower compression modulus (36-50GPa) compared to other Ti alloys, but still remain a very high compressive strength (1500-1800MPa). In addition, the PM Ti-Mg alloys show good biocompatibility and bioactivity. Mg can dissolve in the simulated body fluids, and induce the formation of the calcium phosphate layer. The compression modulus of PM Ti-Mg alloys decreases with the amount of Mg, while the bioactivity increases. Although the corrosion resistance of Ti-Mg alloys decreases with the content of Mg, the alloys still show good stability in simulated body fluid under electrochemical conditions. The indirect and direct cytotoxicity results show that PM Ti-Mg alloys have a good biocompatibility to NIH-3T3 cells. Therefore, the PM Ti-Mg alloys are promising candidates in biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.

Differential Conductance Measurements of MgB2/I/Pb Heterojunctions and all-MgB2 Junctions

NASA Astrophysics Data System (ADS)

Cusick, David; Eckhardt, Matthew; Dai, Wenqing; Li, Qi; Chen, Ke; Cunnane, Daniel; Zhuang, C. G.; Xi, X. X.; Naito, Michio; Ramos, Roberto

2015-03-01

We present our work characterizing several types of Magnesium Diboride Josephson junctions, including MgB2/I/Pb heterojunctions and all-MgB2 junctions. We will report on the I-V and dI/dV-V data collected at various temperatures using both a cryocooler-based experimental platform between 2 and 20 Kelvin and using a 3He probe platform between 0.3 and 1.0 Kelvin. These were both developed by undergraduates in a liberal arts university. Using high-sampling rates with a 24-bit data acquisition card and access to a broad of range of temperatures, we track and report energy gap distributions and temperature-dependent features of dI/dV peaks of MgB2, comparing these with theoretical predictions. R.C.R. acknowledges support from National Science Foundation Grant # DMR-1206561.

Wound healing effect of bioactive ion released from Mg-smectite.

PubMed

Sasaki, Yu; Sathi, Gulsan Ara; Yamamoto, Osamu

2017-08-01

Bioactive ions like Mg 2+ and Si 4+ have been known as promotion factors of tissue regeneration. In the present work, Mg-smectite, consisting of Mg 2+ and Si 4+ ions, was synthesized by a solution process, and evaluated for the efficiency of the powder on wound healing in rats. White precipitates were obtained by mixing a magnesium chloride hexahydrate solution and a sodium silicate hexahydrate solution at room temperature. The precipitates mixed with a NaOH aqueous solution were subjected to hydrothermal reaction, and finally crystalline Mg-smectite powder was obtained. The crystal and molecular structure of Mg-smectite was identified by X-ray diffractometry (XRD) and Fourier-transform infrared spectroscopy (FT-IR). The synthesized material was determined to be crystalline Mg-smectite. The amount of Mg 2+ and Si 4+ ions released from Mg-smectite in physiological saline was analyzed by inductively coupled plasma mass spectroscopy (ICP-MS). The total amount of Si 4+ ion released from Mg-smectite was greater than that of Mg 2+ ion. To evaluate the wound healing effect of Mg-smectite, Mg-smectite powder was applied to a full-thickness surgical wound reaching the subcutaneous tissue in the rat's abdomen. At 1 and 2weeks, skin tissue was collected and subjected to histological analysis. The results for skin regeneration showed no significant difference in wound size between the control and Mg-smectite group. However, it was found that the neovascularization, collagen deposition, and maturation were notedly accelerated by applying Mg-smectite powder in comparison with the control. Mg-smectite can then be hypothesized to stimulate the regeneration of skin tissue by releasing Mg 2+ and Si 4+ ions. These results suggested that Mg-smectite could offer great potential as a wound dressing material. Copyright © 2017 Elsevier B.V. All rights reserved.

Recovery of SO2 and MgO from By-Products of MgO Wet Flue Gas Desulfurization.

PubMed

Yan, Liyun; Lu, Xiaofeng; Wang, Quanhai; Guo, Qiang

2014-11-01

An industrial demonstration unit using natural gas as a heat source was built to calcine the by-products of MgO wet flue gas desulfurization from power plants; influencing factors on the SO 2 content in calciner gas were comprehensively analyzed; and an advantageous recycling condition of MgO and SO 2 from by-products was summarized. Results showed that the SO 2 content in the calciner gas was increased by more than 10 times under a lower excess air coefficient, a higher feed rate, a lower crystal water in by-products, and a higher feed port position. For the tests conducted under the excess air coefficient above and below one, the effect of the furnace temperature on the SO 2 content in the calciner gas was reversed. Results of activity analysis indicate that particles of MgO generated under the calcination temperature of 900-1,000°C had a high activity. In contrast, due to the slight sintering, MgO generated under the calcination temperature of 1,100°C had a low activity. To recycle SO 2 as well as MgO, a temperature range of 900-927°C for TE103 is proposed. These studies will prompt the desulfurization market diversification, reduce the sulfur's dependence on imports for making sulfuric acid, be meaningful to balance the usage of the natural resource in China, and be regarded as a reference for the development of this technology for other similar developing countries.

The role of Mg in the crystallization of monohydrocalcite

NASA Astrophysics Data System (ADS)

Rodriguez-Blanco, Juan Diego; Shaw, Samuel; Bots, Pieter; Roncal-Herrero, Teresa; Benning, Liane G.

2014-02-01

Monohydrocalcite is a member of the carbonate family which forms in Mg-rich environments at a wide range of Mg/Ca ratios Mg2+aq/Ca2+aq≥0.17<65. Although found in modern sedimentary deposits and as a product of biomineralization, there is a lack of information about its formation mechanisms and about the role of Mg during its crystallization. In this work we have quantitatively assessed the mechanism of crystallization of monohydrocalcite through in situ synchrotron-based small and wide angle X-ray scattering (SAXS/WAXS) and off-line spectroscopic, microscopic and wet chemical analyses. Monohydrocalcite crystallizes via a 4-stage process beginning with highly supersaturated solutions from which a Mg-bearing, amorphous calcium carbonate (ACC) precursor precipitates. This precursor crystallizes to monohydrocalcite via a nucleation-controlled reaction in stage two, while in stage three it is further aged through Ostwald-ripening at a rate of 1.8 ± 0.1 nm/h1/2. In stage four, a secondary Ostwald ripening process (66.3 ± 4.3 nm/h1/2) coincides with the release of Mg from the monohydrocalcite structure and the concomitant formation of minor hydromagnesite. Our data reveal that monohydrocalcite can accommodate significant amounts of Mg in its structure (χMgCO3 = 0.26) and that its Mg content and dehydration temperature are directly proportional to the saturation index for monohydrocalcite (SIMHC) immediately after mixing the stock solutions. However, its crystallite and particle size are inversely proportional to these parameters. At high supersaturations (SIMHC = 3.89) nanometer-sized single crystals of monohydrocalcite form, while at low values (SIMHC = 2.43) the process leads to low-angle branching spherulites. Many carbonates produced during biomineralization form at similar conditions to most synthetic monohydrocalcites, and thus we hypothesize that some calcite or aragonite deposits found in the geologic record that have formed at high Mg/Ca ratios could be

Evolución estelar en sistemas binarios

NASA Astrophysics Data System (ADS)

De Vito, M. A.; Benvenuto, O.

Definición y clasificación de sistemas binarios; descripción del comportamiento del sistema frente a la variación de su masa; binarias de rayos X; transferencia de masa en sistemas binarios masivos aplicado al posible esclarecimiento del progenitor azul de la supernova SN 1987A; comentario acerca de la evolución de enanas blancas de helio de baja masa y su conexión con los sistemas binarios; reseña del trabajo de Kippenhahn y Weigert sobre el cual está basado el código evolutivo desarrollado en la FCAG por el Dr. Benvenuto y sobre el cual se trabajará para poder incluir la evolución de una estrella con pérdida de masa perteneciente a un sistema binario.

Hydrothermal replacement of calcite by Mg-carbonates

NASA Astrophysics Data System (ADS)

Jonas, Laura; Mueller, Thomas; Dohmen, Ralf

2014-05-01

The transport of heat and mass through the Earth's crust is coupled to mineral reactions and the exchange of isotopes and elements between different phases. Carbonate minerals are a major constituent of the Earth's crust and play an important role in different physical, chemical and even biological processes. In this experimental study, the element exchange reaction between calcite (CaCO3) and a Mg-rich fluid phase is investigated under hydrothermal conditions. Single crystals of calcite (2x2x2 mm) react with 1 ml of a 1 M MgCl2 solution at 200° C in a Teflon-lined steel autoclave for different times between one day and four weeks. The reaction leads to the formation of a porous reaction front and the pseudomorphic replacement of calcite by dolomite [CaMg(CO3)2] and magnesite (MgCO3). Scanning electron microscopy revealed that the reaction rim consists of small Mg-carbonate rhombs closely attached to each other, suggesting that the replacement reaction takes place by a dissolution-precipitation mechanism. Typically, the observed reaction front can be divided into two different domains. The outer part of the reaction rim, i.e. from the mineral surface in contact to the fluid inwards, consists of magnesite, whereas the inner part of the rim surrounding the unreacted calcite core consists of Ca-rich dolomite. The formation of a porous microstructure that varies in different parts of the reaction rim is a direct result of the large molar volume change induced by the replacement of calcite by magnesite and dolomite. The developing porosity therefore creates fluid pathways that promote the progress of the reaction front towards the unreacted core of the single crystal. Compositional profiles measured perpendicular to the mineral surface across the reactions rims using electron microprobe (EMPA) further revealed a compositional gradient within the reaction rim with regard to the structure-forming elements Mg and Ca. Here, the amount of Mg incorporated in both product

[Polarization characteristic of Al + MgF2 film at VUV].

PubMed

Liu, Ying; Li, Zhi-gang; Li, Fu-tian

2002-10-01

Polarization characteristic of Al + MgF2 is researched theoretically and experimentally. According to the theory of electromagnetism, the reflectance perpendicular and parallel to the incident plane of Al + MgF2 is calculated in the way of matrix optics. The effect of incident conditions and thickness of MgF2 is considered on the reflectance of Al + MgF2 coatings. The MgF2 not only prevents the oxidation of aluminum but also increases the reflectance of Al + MgF2 by interference. The polarization of Al + MgF2 is analyzed using the concept of ratio of extinction based on above mentioned calculations. The polarization character of Al + MgF2 and single Al coating is compared. The reflectances perpendicular and parallel to the incident plane of Al + MgF2 film are measured at VUV range, using LiF polarizer as a VUV polarizer. So the polarization character of Al + MgF2 is researched experimentally. Both theoretical and experimental results of the polarization character of Al + MgF2 are coincident.

Destabilization of the Mg-H system through elastic constraints.

PubMed

Baldi, A; Gonzalez-Silveira, M; Palmisano, V; Dam, B; Griessen, R

2009-06-05

We tune the thermodynamics of hydrogen absorption in Mg by means of elastic clamping. The loading isotherms measured by hydrogenography show that Mg films covered with Mg-alloy-forming elements, such as Pd and Ni, have hydrogen plateau pressures more than 2 orders of magnitude higher than bulk Mg at the same temperature. An elastic model allows us to interpret the Mg thickness dependence of the hydrogen plateau pressure. Our results suggest an alternative route for the development of new hydrogen storage materials with optimized thermodynamic properties.

Destabilization of the Mg-H System through Elastic Constraints

NASA Astrophysics Data System (ADS)

Baldi, A.; Gonzalez-Silveira, M.; Palmisano, V.; Dam, B.; Griessen, R.

2009-06-01

We tune the thermodynamics of hydrogen absorption in Mg by means of elastic clamping. The loading isotherms measured by hydrogenography show that Mg films covered with Mg-alloy-forming elements, such as Pd and Ni, have hydrogen plateau pressures more than 2 orders of magnitude higher than bulk Mg at the same temperature. An elastic model allows us to interpret the Mg thickness dependence of the hydrogen plateau pressure. Our results suggest an alternative route for the development of new hydrogen storage materials with optimized thermodynamic properties.

Memorias del tercer simposio internacional sobre economía, planificación, y políticas de los incendios forestales: problemas y enfoques comunes

Treesearch

Armando González-Cabán

2009-01-01

Estas memorias resumen el resultado de un simposio diseñado para discutir los problemas actuales que confrontan las agencias con responsabilidad para la proteccion contra incendios forestales a nivel federal y estadual en los EE.UU., al igual que agencias en la comunidad internacional. Los temas discutidos en el simposio incluyen economía del fuego, teoría y modelos...

Misfit dislocation patterns of Mg-Nb interfaces

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

Chen, Youxing; Shao, Shuai; Liu, Xiang-Yang

The role of heterogeneous interfaces in improving mechanical properties of polycrystalline aggregates and laminated composites has been well recognized with interface structure being of fundamental importance in designing composites containing multiple interfaces. In this paper, taking the Mg (hexagonal close-packed (hcp))/Nb (body-centered cubic (bcc)) interface as an example, we develop Mg-Nb interatomic potentials for predicting atomic configurations of Mg/Nb interfaces. We systematically characterize interface dislocations of Mg/Nb interfaces with Nishiyama-Wassermann (NW) and Kurdjumov-Sachs (KS) orientation relationships and propose a generalized procedure of characterizing interface structure by combining atomistic simulation and interface dislocation theory, which is applicable for not only hcp/bccmore » interfaces, but also other systems with complicated interface dislocation configurations.Here, in Mg/Nb, interface dislocation networks of two types of interfaces are significantly different although they originate from partial dislocations of similar character: the NW interface is composed of three sets of partial dislocations, while the KS interface is composed of four sets of interface dislocations - three sets of partial dislocations and one set of full dislocations that forms from the reaction of two close partial dislocations.« less

Acceptability of an Embodied Conversational Agent-based Computer Application for Hispanic Women

PubMed Central

Wells, Kristen J.; Vázquez-Otero, Coralia; Bredice, Marissa; Meade, Cathy D.; Chaet, Alexis; Rivera, Maria I.; Arroyo, Gloria; Proctor, Sara K.; Barnes, Laura E.

2015-01-01

There are few Spanish language interactive, technology-driven health education programs. Objectives of this feasibility study were to: 1) learn more about computer and technology usage among Hispanic women living in a rural community; and 2) evaluate acceptability of the concept of using an embodied conversational agent (ECA) computer application among this population. A survey about computer usage history and interest in computers was administered to a convenience sample of 26 women. A sample video prototype of a hospital discharge ECA was administered followed by questions to gauge opinion about the ECA. Data indicate women exhibited both a high level of computer experience and enthusiasm for the ECA. Feedback from community is essential to ensure equity in state of the art dissemination of health information. Hay algunos programas interactivos en español que usan la tecnología para educar sobre la salud. Los objetivos de este estudio fueron: 1) aprender más sobre el uso de computadoras y tecnología entre mujeres Hispanas que viven en comunidades rurales y 2) evaluar la aceptabilidad del concepto de usar un programa de computadora utilizando un agente de conversación encarnado (ECA) en esta población. Se administro una encuesta sobre el historial de uso y del interés de aprender sobre computadoras fue a 26 mujeres por muestreo de conveniencia. Un ejemplo del prototipo ECA en forma de video de un alta hospitalaria fue administrado y fue seguido por preguntas sobre la opinión que tenían del ECA. Los datos indican que las mujeres mostraron un alto nivel de experiencia con las computadoras y un alto nivel de entusiasmo sobre el ECA. La retroalimentación de la comunidad es esencial para asegurar equidad en la diseminación de información sobre la salud con tecnología de punta. PMID:26671558

Improved efficacy of intramuscular weekly administration of clodronate 200 mg (100 mg twice weekly) compared with 100 mg (once weekly) for increasing bone mineral density in postmenopausal osteoporosis.

PubMed

Frediani, Bruno; Bertoldi, Ilaria; Pierguidi, Serena; Nicosia, Antonella; Picerno, Valentina; Filippou, Georgios; Cantarini, Luca; Galeazzi, Mauro

2013-03-01

Clodronate is a bisphosphonate used for the treatment of postmenopausal osteoporosis and all conditions characterized by excess bone resorption. We have previously reported that intramuscular (IM) therapy with clodronate at a dose of 100 mg/week displays significant effects on bone mineral density (BMD) although a plateau effect is observed after 1 year of treatment. Previous reports indicate that the densitometric effects of bisphosphonates directly correlate with the drug dosage and suggest that using IM clodronate at doses higher than 100 mg/week may result in improved efficacy. However, to the best of our knowledge, this has never been proved. The primary endpoint of the study was the effect on BMD of IM clodronate 100 mg once weekly or 100 mg twice weekly in patients with postmenopausal osteoporosis. The incidence of non-traumatic vertebral fractures and adverse events was also reported. The present study was a randomized, open-label, parallel-group trial conducted between January 2007 and December 2009 in the Osteoporosis and Osteoarticular Instrumental Diagnosis Centre (University of Siena, Siena, Italy). The study involved 60 women, aged 57-78 years, with a history of postmenopausal osteoporosis for more than 5 years. Patients were randomized to receive IM clodronate 100 mg once weekly (Group A, 30 patients) or 100 mg twice weekly (Group B, 30 patients), for 2 years. Significant increases compared with baseline in BMD were observed for both groups at 1 and 2 years, with significantly higher increases for Group B compared with Group A. Group B displayed a BMD increase (± SD) at the lumbar spine of +4.0 % (± 2.1) and +5.9 % (± 2.0) at 1 and 2 year(s), respectively, compared with +2.8 % (± 1.7) and +3.5 % (± 2.2), respectively, observed for Group A. Similarly, Group B showed better performance compared with Group A for BMD increase at the femoral neck, with an observed increase of +3.5 % (± 1.7) and +5.4 % (± 1.8) at 1 and 2 year(s), respectively

Intraoperative ketorolac dose of 15mg versus the standard 30mg on early postoperative pain after spine surgery: A randomized, blinded, non-inferiority trial.

PubMed

Duttchen, Kaylene M; Lo, Andy; Walker, Andrew; McLuckie, Duncan; De Guzman, Cecilia; Roman-Smith, Helen; Davis, Melinda

2017-09-01

The primary aim of this study is to show the non-inferiority of 15mg intraoperative dose of ketorolac as compared to the standard 30mg ketorolac by looking at the visual analog scale pain (VAS) scores 4h after an adult spine surgery. The study design is a prospective randomized non-inferiority clinical trial looking at non-inferiority of intraoperative 15mg ketorolac from the standard 30mg dose. Quaternary care center. 50 adult (18-65years of age) undergoing lumbar decompression spine surgery. Group A received a single intraoperative dose of 15mg ketorolac at the end of surgery and group B received single intraoperative dose of 30mg ketorolac. The primary outcome was the visual analog scale (VAS) pain scores 4h after an adult spine surgery. Secondary measures were morphine usage in the first 8 and 24h postoperatively, numeric rating scores (NRS) up to 24h, sedation, nausea, vomiting, respiratory depression, pruritus and bleeding complications. Intention to treat analysis showed a mean increase in 4h VAS pain score of 7.9mm (95% CI: -4.5mm to 20.4mm) in patients administered 15mg ketorolac. This difference was neither statistically (P=0.207) nor clinically significant (<18mm on VAS scale). A similar increase in the 15mg group was noted through a per protocol analysis, 6.9mm (95% CI: -6.6mm to 20.5mm, P=0.307) greater in the 15mg group. Non-inferiority of 15mg was not confirmed. No significant difference was found in secondary endpoints. Ketorolac 30mg intravenous was not superior to 15mg intravenous for post-operative pain management after spine surgery. However, 15mg failed to meet the pre-specified criteria for non-inferiority to the 30mg dose. Copyright © 2017 Elsevier Inc. All rights reserved.

Efficacy and safety of 10-mg azilsartan compared with 8-mg candesartan cilexetil in Japanese patients with hypertension: a randomized crossover non-inferiority trial.

PubMed

Takahara, Mitsuyoshi; Shiraiwa, Toshihiko; Shindo, Megumi; Arai, Akie; Kusuda, Yuko; Katakami, Naoto; Kaneto, Hideaki; Matsuoka, Taka-Aki; Shimomura, Iichiro

2014-09-01

We investigated whether 10 mg per day of azilsartan, one-half of the normal dosage, would be non-inferior to 8 mg per day of candesartan cilexetil for controlling blood pressure in Japanese patients with hypertension. In this open-label, randomized, crossover trial, 309 hypertensive Japanese adults treated with 8-mg candesartan cilexetil were randomized into two arms and received either 10-mg azilsartan or 8-mg candesartan cilexetil in a crossover manner. The primary efficacy outcome was systolic blood pressure, and the margin of non-inferiority was set to be 2.5 mm Hg. The participants were 67±11 years old, and 180 (58%) were male. The baseline systolic and diastolic blood pressure levels were 127.1±13.2 and 69.7±11.2 mm Hg, respectively. During the study period, the difference in systolic blood pressure between the treatments with 10-mg azilsartan and 8-mg candesartan cilexetil was -1.7 mm Hg, with the two-sided 95% confidence interval (CI) ranged from -3.2 to -0.2 mm Hg. The upper boundary of the 95% CI was below the margin of 2.5 mm Hg, confirming the non-inferiority of 10-mg azilsartan to 8-mg candesartan cilexetil. The difference also reached significance (P=0.037). The corresponding difference in diastolic blood pressure was -1.4 (95% CI: -2.4 to -0.4) mm Hg (P=0.006). Treatment with 10-mg azilsartan was similar to 8-mg candesartan cilexetil in its association with rare adverse events. In conclusion, 10-mg azilsartan was non-inferior to 8-mg candesartan cilexetil for controlling systolic blood pressure in Japanese hypertensive patients already being treated with 8-mg candesartan cilexetil.

33 CFR 80.1118 - Marina Del Rey, CA.

Code of Federal Regulations, 2010 CFR

2010-07-01

... NAVIGATION RULES COLREGS DEMARCATION LINES Pacific Coast § 80.1118 Marina Del Rey, CA. (a) A line drawn from Marina Del Rey Breakwater South Light 1 to Marina Del Rey Light 4. (b) A line drawn from Marina Del Rey... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Marina Del Rey, CA. 80.1118...

33 CFR 80.1118 - Marina Del Rey, CA.

Code of Federal Regulations, 2012 CFR

2012-07-01

... NAVIGATION RULES COLREGS DEMARCATION LINES Pacific Coast § 80.1118 Marina Del Rey, CA. (a) A line drawn from Marina Del Rey Breakwater South Light 1 to Marina Del Rey Light 4. (b) A line drawn from Marina Del Rey... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Marina Del Rey, CA. 80.1118...

33 CFR 80.1118 - Marina Del Rey, CA.

Code of Federal Regulations, 2013 CFR

2013-07-01

... NAVIGATION RULES COLREGS DEMARCATION LINES Pacific Coast § 80.1118 Marina Del Rey, CA. (a) A line drawn from Marina Del Rey Breakwater South Light 1 to Marina Del Rey Light 4. (b) A line drawn from Marina Del Rey... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Marina Del Rey, CA. 80.1118...

33 CFR 80.1118 - Marina Del Rey, CA.

Code of Federal Regulations, 2011 CFR

2011-07-01

... NAVIGATION RULES COLREGS DEMARCATION LINES Pacific Coast § 80.1118 Marina Del Rey, CA. (a) A line drawn from Marina Del Rey Breakwater South Light 1 to Marina Del Rey Light 4. (b) A line drawn from Marina Del Rey... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Marina Del Rey, CA. 80.1118...

33 CFR 80.1118 - Marina Del Rey, CA.

Code of Federal Regulations, 2014 CFR

2014-07-01

... NAVIGATION RULES COLREGS DEMARCATION LINES Pacific Coast § 80.1118 Marina Del Rey, CA. (a) A line drawn from Marina Del Rey Breakwater South Light 1 to Marina Del Rey Light 4. (b) A line drawn from Marina Del Rey... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Marina Del Rey, CA. 80.1118...

BC3 as electrode for Mg ion batteries

NASA Astrophysics Data System (ADS)

Joshi, Rajendra; Barone, Veronica; Peralta, Juan

We propose layered BC3 a novel electrode material for rechargeable magnesium ion batteries. Using dispersion-corrected density functional theory calculations, we show that layered BC3 can intercalate Mg ions between its layers to form the stoichoimetry Mg0.5BC3, which corresponds to a theoretical capacity of 572 mAh/g. We also propose a three step staging mechanism for Mg ion intercalation in BC3 and show that it presents a moderate open circuit voltage in the range of 0.82 to 0.96 V with respect to metallic Mg anode. NSF DMR-1206920, NSF CBET-1335944.

La dinámica demográfica y la desigualdad educativa en Méxicoa

PubMed Central

Giorguli Saucedo, Silvia E.; Vargas Valle, Eunice D.; Ulloa, Viviana Salinas; Hubert, Celia; Potter, Joseph E.

2015-01-01

En este trabajo se presenta una investigación sobre el vínculo entre los procesos educativos y la dinámica demográfica en México. La tradición del pensamiento sobre población y desarrollo ha partido de la hipótesis de que el ritmo de crecimiento poblacional, el tamaño de las familias y la migración influyen sobre la acumulación de capital humano entre la población en edades escolares. Se explora aquí la relación del desempeño educativo de los jóvenes entre 14 y 23 años y la razón de dependencia juvenil, la fecundidad adolescente y la migración interna e internacional; para ello se utilizan datos agregados a escala municipal del año 2000. El análisis incluye indicadores de la oferta educativa municipal basados en estadísticas administrativas de la SEP. PMID:26146427

Single and Double Photoionization of Mg

NASA Astrophysics Data System (ADS)

Abdel-Naby, Shahin; Pindzola, M. S.; Colgan, J.

2014-05-01

Single and double photoionization cross sections for Mg are calculated using a time-dependent close-coupling method. The correlation between the two 3 s subshell electrons of Mg is obtained by relaxation of the close-coupled equations in imaginary time. An implicit method is used to propagate the close-coupled equations in real time to obtain single and double ionization cross sections for Mg. Energy and angle triple differential cross sections for double photoionization at equal energy sharing of E1 =E2 = 16 . 4 eV are compared with Elettra experiments and previous theoretical calculations. This work was supported in part by grants from NSF and US DoE. Computational work was carried out at NERSC in Oakland, California, NICS in Knoxville, Tennessee, and OLCF in Oak Ridge, Tennessee.

EFFECT OF Mg AND TEMPERATURE ON Fe-Al ALLOY LAYER IN Fe/(Zn-6%Al-x%Mg) SOLID-LIQUID DIFFUSION COUPLES

NASA Astrophysics Data System (ADS)

Liang, Liu; Liu, Ya-Ling; Liu, Ya; Peng, Hao-Ping; Wang, Jian-Hua; Su, Xu-Ping

Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples were kept at various temperatures for different periods of time to investigate the formation and growth of the Fe-Al alloy layer. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) were used to study the constituents and morphology of the Fe-Al alloy layer. It was found that the Fe2Al5Znx phase layer forms close to the iron sheet and the FeAl3Znx phase layer forms near the side of the melted Zn-6%Al-3%Mg in diffusion couples. When the Fe/(Zn-6%Al-3%Mg) diffusion couple is kept at 510∘C for more than 15min, a continuous Fe-Al alloy layer is formed on the interface of the diffusion couple. Among all Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples, the Fe-Al alloy layer on the interface of the Fe/(Zn-6% Al-3% Mg) diffusion couple is the thinnest. The Fe-Al alloy layer forms only when the diffusion temperature is above 475∘. These results show that the Fe-Al alloy layer in Fe/(Zn-6%Al-x%Mg) solid-liquid diffusion couples is composed of Fe2Al5Znx and FeAl3Znx phase layers. Increasing the diffusing temperature and time period would promote the formation and growth of the Fe-Al alloy layer. When the Mg content in the Fe/(Zn-6%Al-x%Mg) diffusion couples is 3%, the growth of the Fe-Al alloy layer is inhibited. These results may explain why there is no obvious Fe-Al alloy layer formed on the interface of steel with a Zn-6%Al-3%Mg coating.

Interface engineering of high-Mg-content MgZnO/BeO/Si for p-n heterojunction solar-blind ultraviolet photodetectors

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

Liang, H. L.; Mei, Z. X.; Zhang, Q. H.

2011-05-30

High-quality wurtzite MgZnO film was deposited on Si(111) substrate via a delicate interface engineering using BeO, by which solar-blind ultraviolet photodetectors were fabricated on the n-MgZnO(0001)/p-Si(111) heterojunction. A thin Be layer was deposited on clean Si surface with subsequent in situ oxidation processes, which provides an excellent template for high-Mg-content MgZnO growth. The interface controlling significantly improves the device performance, as the photodetector demonstrates a sharp cutoff wavelength at 280 nm, consistent with the optical band gap of the epilayer. Our experimental results promise potential applications of this technique in integration of solar-blind ultraviolet optoelectronic device with Si microelectronic technologies.

Investigation on AlP as the heterogeneous nucleus of Mg2Si in Al-Mg2Si alloys by experimental observation and first-principles calculation

NASA Astrophysics Data System (ADS)

Sun, Jiayue; Li, Chong; Liu, Xiangfa; Yu, Liming; Li, Huijun; Liu, Yongchang

2018-03-01

The microstructural evolution of primary Mg2Si in Al-20%Mg2Si with Al-3%P master alloy was observed by scanning electron microscope. And the interfacial properties of AlP/Mg2Si interface were investigated using first-principles calculations. The calculation results show that AlP(1 0 0)/Mg2Si(2 1 1) and AlP(3 3 1)/Mg2Si(1 1 0) interfaces can form steadily. P-terminated AlP(1 0 0)/Mg2Si(2 1 1) interface with the largest work of adhesion (4.13 J/m2) is theoretically the most stable. The interfacial electronic structure reveals that there are covalent Si-Al, Si-P and Mg-P bonds existing between AlP and Mg2Si slabs. Due to the AlP particles as effective heterogeneous nucleus of Mg2Si, primary Mg2Si particles change from dendrite to octahedron/truncated octahedron, and their sizes decrease to ∼20 μm.

Incorporation of Mg, Sr, Ba, U, and B in High-Mg Calcite Benthic Foraminifers Cultured Under Controlled pCO2

NASA Astrophysics Data System (ADS)

Not, C.; Thibodeau, B.; Yokoyama, Y.

2018-01-01

Measurement of elemental ratios (E/Ca) has been performed in two symbiont-bearing species of high-Mg calcite benthic foraminifers (hyaline, Baculogypsina sphaerulata and porcelaneous, Amphisorus hemprichii), cultured under five pCO2 levels, representing preindustrial, modern, and three predicted future values. E/Ca ratios were analyzed by Laser Ablation coupled with Inductively Coupled Plasma Mass Spectrometer (LA-ICP-MS). We measured several E/Ca, such as Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, and B/Ca simultaneously. We observed that high-Mg calcite benthic foraminifers possess higher E/Ca than low-Mg calcite foraminifers, irrespective of their calcification mode (hyaline or porcelaneous). In both modes of calcification, Mg, Sr, Ba, U, and B incorporation could be controlled by Rayleigh fractionation. However, more data are needed to validate and quantify the relative importance of this process and closely investigate the presence/absence of other mechanism. Therefore, it highlights the need for a multielemental approach when looking at trace element incorporation. Finally, no significant relationship was observed between the different ratios and the pCO2 of the water, suggesting that none of the Mg/Ca, Sr/Ca, Ba/Ca, U/Ca, and B/Ca is sensitive to bottom water pCO2 or pH for these species.

Recovery of SO2 and MgO from By-Products of MgO Wet Flue Gas Desulfurization

PubMed Central

Yan, Liyun; Lu, Xiaofeng; Wang, Quanhai; Guo, Qiang

2014-01-01

Abstract An industrial demonstration unit using natural gas as a heat source was built to calcine the by-products of MgO wet flue gas desulfurization from power plants; influencing factors on the SO2 content in calciner gas were comprehensively analyzed; and an advantageous recycling condition of MgO and SO2 from by-products was summarized. Results showed that the SO2 content in the calciner gas was increased by more than 10 times under a lower excess air coefficient, a higher feed rate, a lower crystal water in by-products, and a higher feed port position. For the tests conducted under the excess air coefficient above and below one, the effect of the furnace temperature on the SO2 content in the calciner gas was reversed. Results of activity analysis indicate that particles of MgO generated under the calcination temperature of 900–1,000°C had a high activity. In contrast, due to the slight sintering, MgO generated under the calcination temperature of 1,100°C had a low activity. To recycle SO2 as well as MgO, a temperature range of 900–927°C for TE103 is proposed. These studies will prompt the desulfurization market diversification, reduce the sulfur's dependence on imports for making sulfuric acid, be meaningful to balance the usage of the natural resource in China, and be regarded as a reference for the development of this technology for other similar developing countries. PMID:25371652

Pharmacokinetic characterization of three novel 4-mg nicotine lozenges
.

PubMed

Sukhija, Manpreet; Srivastava, Reena; Kaushik, Aditya

2018-03-01

Nicotine replacement therapy (NRT) increases the probability of smoking cessation. This study was conducted to determine if three prototype 4-mg nicotine lozenges produced locally in India were bioequivalent to a globally marketed reference product, Nicorette® 4-mg nicotine lozenge. Healthy adult smokers (N = 39) were treated with three prototype 4-mg nicotine lozenges in comparison with a reference 4-mg lozenge in this single-center, randomized, open-label, single-dose, 4-way crossover study. Pharmacokinetic sampling was obtained to test for bioequivalence using maximal plasma concentration (Cmax) and extent of absorption (AUC0-t). Secondarily, AUC;0-∞, time to maximal plasma concentration (tmax), half-life (T1/2), elimination rate constant (Kel), and safety of the prototype lozenges versus the reference lozenge were compared. Each prototype 4-mg nicotine lozenge was found to be bioequivalent to the reference 4-mg nicotine lozenge based on the ratio of geometric means and 90% confidence intervals for Cmax, AUC0-t, and AUC;0-∞. Although tmax; was significantly longer for prototype III, all four lozenges achieved maximum plasma nicotine concentrations at a median of 1.5 hours. The safety profiles of the three prototype 4-mg lozenges did not differ from that of the 4-mg reference product. Each prototype 4-mg nicotine lozenge was bioequivalent to the reference 4-mg nicotine lozenge and was well tolerated. Furthermore, as these bioequivalent prototypes differed in in-vitro dissolution profiles, these data suggest that performance from the in -vitro method deployed is not a firm predictor of pharmacokinetic behavior.
.

Mg doping of GaN by molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Lieten, R. R.; Motsnyi, V.; Zhang, L.; Cheng, K.; Leys, M.; Degroote, S.; Buchowicz, G.; Dubon, O.; Borghs, G.

2011-04-01

We present a systematic study on the influence of growth conditions on the incorporation and activation of Mg in GaN layers grown by plasma-assisted molecular beam epitaxy. We show that high quality p-type GaN layers can be obtained on GaN-on-silicon templates. The Mg incorporation and the electrical properties have been investigated as a function of growth temperature, Ga : N flux ratio and Mg : Ga flux ratio. It was found that the incorporation of Mg and the electrical properties are highly sensitive to the Ga : N flux ratio. The highest hole mobility and lowest resistivity were achieved for slightly Ga-rich conditions. In addition to an optimal Ga : N ratio, an optimum Mg : Ga flux ratio was also observed at around 1%. We observed a clear Mg flux window for p-type doping of GaN : 0.31% < Mg : Ga < 5.0%. A lowest resistivity of 0.98 Ω cm was obtained for optimized growth conditions. The p-type GaN layer then showed a hole concentration of 4.3 × 1017 cm-3 and a mobility of 15 cm2 V-1 s-1. Temperature-dependent Hall effect measurements indicate an acceptor depth in these samples of 100 meV for a hole concentration of 5.5 × 1017 cm-3. The corresponding Mg concentration is 5 × 1019 cm-3, indicating approximately 1% activation at room temperature. In addition to continuous growth of Mg-doped GaN layers we also investigated different modulated growth procedures. We show that a modulated growth procedure has only limited influence on Mg doping at a growth temperature of 800 °C or higher. This result is thus in contrast to previously reported GaN : Mg doping at much lower growth temperatures of 500 °C.

Manual del McVCO 1999

USGS Publications Warehouse

McChesney, P.J.

1999-01-01

El McVCO es un generador de frecuencias basado en un microcontrolador que reemplaza al oscilador controlado por voltaje (VCO) utilizado en telemetría analógica de datos sísmicas. Acepta señales de baja potencia desde un sismómetro y produce una señal subportadora modulada en frecuencia adecuada para enlaces telefónicos o vía radio a un lugar remoto de recolección de datos. La frecuencia de la subportadora y la ganancia pueden ser seleccionadas mediante un interruptor. Tiene la opción de poder operar con dos canales para la observación con ganancia alta y baja. El McVCO fue diseñado con el propósito de mejorar la telemetría analógica de las señales dentro de la Pacific Northwest Seismograph Network (PNSN) (Red Sismográfica del Noroeste del Pacífico). Su desarrollo recibió el respaldo del Programa de Geofísica de la Universidad de Washington y del "Volcano Hazards and Earthquake Hazards programs of the United States Geological Survey (USGS) (Programa de Investigaciones de Riesgos Volcánicos y Programa de Investigaciones de Riesgos Sísmicos de los EEUU). Cientos de instrumentos se han construido e instalado. Además de utilizarlo el PNSN, el McVCO es usado por el Observatorio Vulcanológico de Alaska para monitorear los volcanes aleutianos y por el USGS Volcano Disaster Assistance Program (Programa de Ayuda en las Catástrofes Volcánicas del USGS) para responder a crisis volcánicas en otros países. Este manual cubre el funcionamiento del McVCO, es una referencia técnica para aquellos que necesitan saber con más detalle cómo funciona el McVCO, y cubre una serie de temas que requieren un trato explícito o que derivan del despliegue del instrumento.

Codoping characteristics of Zn with Mg in GaN

NASA Astrophysics Data System (ADS)

Kim, K. S.; Han, M. S.; Yang, G. M.; Youn, C. J.; Lee, H. J.; Cho, H. K.; Lee, J. Y.

2000-08-01

The doping characteristics of Mg-Zn codoped GaN films grown by metalorganic chemical vapor deposition are investigated. By means of the concept of Mg-Zn codoping technique, we have grown p-GaN showing a low electrical resistivity (0.72 Ω cm) and a high hole concentration (8.5×1017cm-3) without structural degradation of the film. It is thought that the codoping of Zn atoms with Mg raises the Mg activation ratio by reducing the hydrogen solubility in p-GaN. In addition, the measured specific contact resistance of Mg-Zn codoped GaN film is 5.0×10-4 Ω cm2, which is one order of magnitude lower than that of Mg doped only GaN film (1.9×10-3 Ω cm2).

ASCEND-8: A Randomized Phase 1 Study of Ceritinib, 450 mg or 600 mg, Taken with a Low-Fat Meal versus 750 mg in Fasted State in Patients with Anaplastic Lymphoma Kinase (ALK)-Rearranged Metastatic Non-Small Cell Lung Cancer (NSCLC).

PubMed

Cho, Byoung Chul; Kim, Dong-Wan; Bearz, Alessandra; Laurie, Scott A; McKeage, Mark; Borra, Gloria; Park, Keunchil; Kim, Sang-We; Ghosn, Marwan; Ardizzoni, Andrea; Maiello, Evaristo; Greystoke, Alastair; Yu, Richard; Osborne, Karen; Gu, Wen; Scott, Jeffrey W; Passos, Vanessa Q; Lau, Yvonne Y; Wrona, Anna

2017-09-01

Ceritinib, 750 mg fasted, is approved for treatment of patients with ALK receptor tyrosine kinase gene (ALK)-rearranged (ALK-positive) NSCLC previously treated with crizotinib. Part 1 of the ASCEND-8 study determined whether administering ceritinib, 450 mg or 600 mg, with a low-fat meal may enhance gastrointestinal (GI) tolerability versus 750 mg fasted in patients with ALK-positive NSCLC while maintaining similar exposure. ASCEND-8 is a multicenter, randomized, open-label, phase 1 study. Part 1 investigated the steady-state pharmacokinetics (PK) and safety of ceritinib, 450 mg or 600 mg, taken with a low-fat meal versus 750 mg fasted in patients with advanced ALK-positive NSCLC who were either treatment naive or pretreated with chemotherapy and/or crizotinib. Part 2 will assess efficacy and safety of ceritinib in treatment-naive patients. As of June 16, 2016, 137 patients were randomized (450 mg fed [n = 44], 600 mg fed [n = 47], and 750 mg fasted [n = 46]); 135 patients received ceritinib. Median follow-up duration was 4.14 months. At steady state, relative to 750 mg fasted, 450 mg with food demonstrated comparable PK as assessed by maximum (peak) concentration of drug in plasma and area under the plasma concentration-time curve from time zero to 24 hours, whereas 600 mg with food demonstrated approximately 25% higher PK. Relative to 750 mg fasted, 450 mg with food was associated with a lower proportion of patients with GI toxicities, mostly grade 1 (diarrhea [43.2%], nausea [29.5%], and vomiting [18.2%]); there were no grade 3 or 4 events, study drug discontinuations, or serious AEs due to GI toxicities. Ceritinib, 450 mg with food, had similar exposure and a more favorable GI safety profile than ceritinib, 750 mg in fasted patients with ALK-positive NSCLC. Copyright © 2017 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.

Melting relations in the system FeCO3-MgCO3 and thermodynamic modelling of Fe-Mg carbonate melts

NASA Astrophysics Data System (ADS)

Kang, Nathan; Schmidt, Max W.; Poli, Stefano; Connolly, James A. D.; Franzolin, Ettore

2016-09-01

To constrain the thermodynamics and melting relations of the siderite-magnesite (FeCO3-MgCO3) system, 27 piston cylinder experiments were conducted at 3.5 GPa and 1170-1575 °C. Fe-rich compositions were also investigated with 13 multi-anvil experiments at 10, 13.6 and 20 GPa, 1500-1890 °C. At 3.5 GPa, the solid solution siderite-magnesite coexists with melt over a compositional range of X Mg (=Mg/(Mg + Fetot)) = 0.38-1.0, while at ≥10 GPa solid solution appears to be complete. At 3.5 GPa, the system is pseudo-binary because of the limited stability of siderite or liquid FeCO3, Fe-rich carbonates decomposing at subsolidus conditions to magnetite-magnesioferrite solid solution, graphite and CO2. Similar reactions also occur with liquid FeCO3 resulting in melt species with ferric iron components, but the decomposition of the liquid decreases in importance with pressure. At 3.5 GPa, the metastable melting temperature of pure siderite is located at 1264 °C, whereas pure magnesite melts at 1629 °C. The melting loop is non-ideal on the Fe side where the dissociation reaction resulting in Fe3+ in the melt depresses melting temperatures and causes a minimum. Over the pressure range of 3.5-20 GPa, this minimum is 20-35 °C lower than the (metastable) siderite melting temperature. By merging all present and previous experimental data, standard state (298.15 K, 1 bar) thermodynamic properties of the magnesite melt (MgCO3L) end member are calculated and the properties of (Fe,Mg)CO3 melt fit by a regular solution model with an interaction parameter of -7600 J/mol. The solution model reproduces the asymmetric melting loop and predicts the thermal minimum at 1240 °C near the siderite side at X Mg = 0.2 (3.5 GPa). The solution model is applicable to pressures reaching to the bottom of the upper mantle and allows calculation of phase relations in the FeO-MgO-O2-C system.

Shallow versus deep nature of Mg acceptors in nitride semiconductors

NASA Astrophysics Data System (ADS)

Lyons, John; Janotti, Anderson; van de Walle, Chris G.

2012-02-01

Although Mg doping is the only known method for achieving p-type conductivity in nitride semiconductors, Mg is not a perfect acceptor. Hydrogen is known to passivate the Mg acceptor, necessitating a post-growth anneal for acceptor activation. Furthermore, the acceptor ionization energy of Mg is relatively large (200 meV) in GaN, thus only a few percent of Mg acceptors are ionized at room temperature. Surprisingly, despite the importance of this impurity, open questions remain regarding the nature of the acceptor. Optical and magnetic resonance measurements on Mg-doped GaN indicate intriguing and complex behavior that depends on the growth, doping level, and thermal treatment of the samples. Motivated by these studies, we have revisited this topic by performing first-principles calculations based on a hybrid functional. We investigate the electrical and optical properties of the isolated Mg acceptor and its complexes with hydrogen in GaN, InN, and AlN. With the help of these advanced techniques we explain the deep or shallow nature of the Mg acceptor and its relation to optical signals often seen in Mg-doped GaN. We also explore the properties of the Mg acceptor in InN and AlN, allowing predictions of the behavior of the Mg dopant in ternary nitride alloys.

High Spin States in ^24Mg

NASA Astrophysics Data System (ADS)

Schwartz, J.; Lister, C. J.; Wuosmaa, A.; Betts, R. R.; Blumenthal, D.; Carpenter, M. P.; Davids, C. N.; Fischer, S. M.; Hackman, G.; Janssens, R. V. F.

1996-05-01

The ^12C(^16O,α)^24Mg reaction was used at 51.5MeV to populate high angular momentum states in ^24Mg. Gamma-rays de-exciting high spin states were detected in a 20 detector spectrometer (the AYE-ball) triggered by the ANL Fragment Mass Analyser (FMA). Channel selection, through detection of ^24Mg nuclei with the appropriate time of flight, was excellent. All the known decays from high spin states were seen in a few hours, with the exception of the 5.04 MeV γ-decay of the J^π=9^- state at 16.904 MeV footnote A.E.Smith et al., Phys. Lett. \\underlineB176, (1986)292. which could not be confirmed. The potential of the technique for studying the radiative decay of states with very high spin in light nuclei will be discussed.

The unexpected discovery of the Mg(HMDS) 2 /MgCl 2 complex as a magnesium electrolyte for rechargeable magnesium batteries

DOE PAGES

Liao, Chen; Sa, Niya; Key, Baris; ...

2015-02-02

We developed a unique class of non-Grignard, aluminum-free magnesium electrolytes based on a simple mixture of magnesium compounds: magnesium hexamethyldisilazide (Mg(HMDS) 2) and magnesium chloride (MgCl 2).

Transport characteristics of a ZnMgO/ZnO hetero junction and the effect of temperature and Mg content

NASA Astrophysics Data System (ADS)

Uslu, Salih; Yarar, Zeki

2017-02-01

The Ensemble Monte Carlo method is used to calculate the transport characteristics of two dimensional electron gas (2DEG) at a ZnMgO/ZnO hetero structure. The spontaneous and piezoelectric polarizations are considered and there is no intentional doping in either material. Numerical Schrödinger and Poisson equations are solved self consistently to obtain the scattering rates of various scattering mechanisms. The density of carriers, each energy sub bands, potential profile and corresponding wave functions are obtained from the self consistent calculations. The self consistent sub band wave functions of acoustic and optic phonon scattering and interface roughness scattering are used in Monte Carlo method to obtain transport characteristics at ZnMgO/ZnO junction. Two dimensional electron gas confined to ZnMgO/ZnO hetero structure is studied and the effect of temperature and Mg content are investigated.

Results of a phase IIa study of VX-809, an investigational CFTR corrector compound, in subjects with cystic fibrosis homozygous for the F508del-CFTR mutation.

PubMed

Clancy, J P; Rowe, Steven M; Accurso, Frank J; Aitken, Moira L; Amin, Raouf S; Ashlock, Melissa A; Ballmann, Manfred; Boyle, Michael P; Bronsveld, Inez; Campbell, Preston W; De Boeck, Kris; Donaldson, Scott H; Dorkin, Henry L; Dunitz, Jordan M; Durie, Peter R; Jain, Manu; Leonard, Anissa; McCoy, Karen S; Moss, Richard B; Pilewski, Joseph M; Rosenbluth, Daniel B; Rubenstein, Ronald C; Schechter, Michael S; Botfield, Martyn; Ordoñez, Claudia L; Spencer-Green, George T; Vernillet, Laurent; Wisseh, Steve; Yen, Karl; Konstan, Michael W

2012-01-01

VX-809, a cystic fibrosis transmembrane conductance regulator (CFTR) modulator, has been shown to increase the cell surface density of functional F508del-CFTR in vitro. A randomised, double-blind, placebo-controlled study evaluated the safety, tolerability and pharmacodynamics of VX-809 in adult patients with cystic fibrosis (n=89) who were homozygous for the F508del-CFTR mutation. Subjects were randomised to one of four VX-809 28 day dose groups (25, 50, 100 and 200 mg) or matching placebo. The type and incidence of adverse events were similar among VX-809- and placebo-treated subjects. Respiratory events were the most commonly reported and led to discontinuation by one subject in each active treatment arm. Pharmacokinetic data supported a once-daily oral dosing regimen. Pharmacodynamic data suggested that VX-809 improved CFTR function in at least one organ (sweat gland). VX-809 reduced elevated sweat chloride values in a dose-dependent manner (p=0.0013) that was statistically significant in the 100 and 200 mg dose groups. There was no statistically significant improvement in CFTR function in the nasal epithelium as measured by nasal potential difference, nor were there statistically significant changes in lung function or patient-reported outcomes. No maturation of immature F508del-CFTR was detected in the subgroup that provided rectal biopsy specimens. In this study, VX-809 had a similar adverse event profile to placebo for 28 days in F508del-CFTR homozygous patients, and demonstrated biological activity with positive impact on CFTR function in the sweat gland. Additional data are needed to determine how improvements detected in CFTR function secondary to VX-809 in the sweat gland relate to those measurable in the respiratory tract and to long-term measures of clinical benefit. NCT00865904.

Comprehensive structural and chemical (CO2, Fe/Fe Mg, H2O) investigations of Mg-Fe cordierite with micro Raman spectroscopy

NASA Astrophysics Data System (ADS)

Haefeker, U.; Kaindl, R.; Tropper, P.

2012-04-01

The Mg-Fe silicate cordierite with the idealized formula (Fe, Mg)2Al4Si5O18 occurs as a hexagonal and an orthorhombic polymorph with disordered/ordered Al-Si distribution on the tetrahedral sites. Most of the natural cordierites are fully ordered. Six-membered rings of (Si,Al)O4 are piled in the direction of the crystallographic c-axis and form channels, laterally and vertically linked by additional (Al, Si) tetrahedrons. Mg and Fe in varying fractions occupy the octahedrally coordinated M-sites. CO2 and H2O (and other volatiles) can be incorporated into the structural channels, thus cordierite can be used for paleofluid reconstruction. The vibration energies of incorporated volatiles, their interaction with the lattice and variations of certain lattice-vibration energies caused by the Mg-Fe exchange can be determined with Raman spectroscopy, allowing chemical quantifications and structural investigations. A method for the semi-quantitative determination of CO2-contents of natural cordierites by Kaindl et al. (2006) was optimized and enhanced by Haefeker et al. (2007). CO2 contents can be measured in single crystals and thin sections with an error of ± 0.05 - 0.09 wt.-%. Based on the Mg-Fe exchange with garnet, cordierite can be used as a geothermobarometer. Recent investigations of synthetic Mg-Fe cordierites with XFe = 0 - 1 have shown a linear downshift of six selected lattice peaks between 100 and 1250 cm-1 with the Mg-Fe contents. Correlation diagrams allow an estimation of the Mg-Fe contents in synthetic and natural samples. The experimental data are in good agreement with the results of quantum-mechanical calculations of the Raman spectra of Mg- and Fe cordierite (Kaindl et al., 2011) allowing the assignment of the peaks to specific vibrations of tetrahedral and octahedral sites. Natural Mg-Fe cordierites are mainly orthorhombic with a fully ordered Al/Si distribution on the tetrahedral sites. However, the disordered hexagonal polymorph is observed in many

Na(7)Mg(13)Nd(PO(4))(12).

PubMed

Jerbi, Hasna; Hidouri, Mourad; Mongi, Ben Amara

2012-06-01

Investigations of the quasi-ternary system Na(3)PO(4)-Mg(3)(PO(4))(2)-NdPO(4) allowed us to obtain the new phosphate hepta-sodium trideca-magnesium neodymium dodeca-kis-phosphate, Na(7)Mg(13)Nd(PO(4))(12), by applying a flux method. The crystal structure is isotypic with that of the previously reported Na(7)Mg(13)Ln(PO(4))(12) (Ln = Eu, La) compounds. It consists of a complex three-dimensional framework built up from an NdO(8) polyhedron (m symmetry), an MO(6) octa-hedron statistically occupied by M = Mg and Na, and eight MgO(x) (x = 5, 6) polyhedra (four with site symmetry m), linked either directely by sharing corners, edges and faces, or by one of the eight unique PO(4) tetra-hedra through common corners. Two of the PO(4) tetra-hedra are statisticaly disordered over a mirror plane. The whole structure can be described as resutling from an assembly of two types of structural units, viz [Mg(4)MP(4)O(22)](∞) (2) layers extending parallel to (100) and stacked along [100], and [Mg(4)NdP(4)O(36)](∞) (1) undulating chains running along the [010] direction. The six different Na(+) cations (five with site symmetry m and one with 0.5 occupancy) are situated in six distinct cavities delimited by the framework. The structure was refined from data of a racemic twin.

Ácaros del mango

USDA-ARS?s Scientific Manuscript database

Los ácaros constituyen un grupo abundante y diverso que ocupa diferentes hábitats en árboles frutales y la estructura y disposición del follaje y ramas del mango, contribuyen significativamente a que se presente gran diversidad de ácaros benéficos y dañinos asociados a esta especie frutal. En Colomb...

Microstructure of hydrogenated Mg2Ni studied by SANS

NASA Astrophysics Data System (ADS)

Mori, K.; Sugiyama, M.; Iwase, K.; Kawabe, S.; Onodera, Y.; Itoh, K.; Otomo, T.; Fukunaga, T.

2010-10-01

X-ray powder diffraction (XRD) and small-angle neutron scattering (SANS) experiments were carried out for the hydrogenated and duterated Mg2Ni, respectively. According to the results of XRD experiments, both of them coexisted with unhydrogenated (or undeuterated) Mg2Ni in the hydrogen absorbing cycle. Furthermore, in the SANS experiments, a slope of SANS curve, I(Q), was roughly evaluated by using the following power law: I(Q) propto Q-m, where Q is the magnitude of the scattering vector, and m can be equated with a fractal dimensionality, DS (= 6 - m). In conclusion, the hydrogenated and duterated Mg2Ni showed DS~ 3 and ~ 2, respectively. The significant difference between DS's can be understood by considering the scattering length densities, ρ, of Mg2Ni, Mg2NiH4, and Mg2NiD4.

The anodic surface film and hydrogen evolution on Mg

DOE PAGES

Song, Guang -Ling; Unocic, Kinga A.

2015-06-04

This paper clarifies that the inner and outer layers of the anodic film consist of a nano/micro-porous MgO+Mg(OH) 2 mixture. The film becomes thicker and more porous with increasing potential. It can rupture when potential is too positive in a non-corrosive Mg(OH) 2 solution. Hydrogen evolution becomes more intensive as polarization potential increases, particularly when the potential at the film-covered Mg surface is close to or more positive than the hydrogen equilibrium potential, suggesting that an “anodic hydrogen evolution” (AHE) reaction occurs on the substrate Mg in film pores, and the significantly intensified AHE causes film rupture at high potential.

Multifunctional MgO Layer in Perovskite Solar Cells.

PubMed

Guo, Xudong; Dong, Haopeng; Li, Wenzhe; Li, Nan; Wang, Liduo

2015-06-08

A multifunctional magnesium oxide (MgO) layer was successfully introduced into perovskite solar cells (PSCs) to enhance their performance. MgO was coated onto the surface of mesoporous TiO(2) by the decomposition of magnesium acetate and, therefore, could block contact between the perovskite and TiO(2). X-ray photoelectron spectroscopy and infrared spectroscopy showed that the amount of H(2)O/hydroxyl absorbed on the TiO(2) decreased after MgO modification. The UV/Vis absorption spectra of the perovskite with MgO modification revealed an enhanced photoelectric performance compared with that of unmodified perovskite after UV illumination. In addition to the photocurrent, the photovoltage and fill factor also showed an enhancement after modification, which resulted in an increase in the overall efficiency of the cell from 9.6 to 13.9 %. Electrochemical impedance spectroscopy (EIS) confirmed that MgO acts as an insulating layer to reduce charge recombination. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Phase 2 Trial of Oral Solithromycin 1200 mg or 1000 mg as Single-Dose Oral Therapy for Uncomplicated Gonorrhea.

PubMed

Hook, Edward W; Golden, Matthew; Jamieson, Brian D; Dixon, Paula B; Harbison, Hanne S; Lowens, Sylvan; Fernandes, Prabhavathi

2015-10-01

Progressive resistance to antimicrobial agents has reduced options for gonorrhea therapy worldwide. Solithromycin (CEM-101) is a novel oral fluoroketolide antimicrobial with substantial in vitro activity against Neisseria gonorrhoeae. We conducted a phase 2 trial of 2 oral doses of solithromycin (1200 and 1000 mg) for treatment of uncomplicated gonorrhea. A total of 59 participants were enrolled and treated in this trial; 28 participants received 1200 mg of solithromycin and 31 received 1000 mg. Forty-six (78%) participants had positive cultures for N. gonorrhoeae at the time of enrollment: 24 of the 28 persons (86%) who received 1200 mg of oral solithromycin, and 22 of 31 (71%) who received 1000 mg. In addition, 8 participants had positive pharyngeal gonococcal cultures, and 4 had positive rectal cultures. All patients with positive cultures for N. gonorrhoeae were cured at all sites of infection. Chlamydia trachomatis and Mycoplasma genitalium coinfections were evaluated using nucleic acid amplification tests and were negative at 1 week of follow-up in 9 of 11 (82%) participants positive for C. trachomatis and 7 of 10 (70%) participants positive for M. genitalium. Mild dose-related gastrointestinal side effects (nausea, loose stools, vomiting) were common but did not limit therapy. Oral single-dose solithromycin, in doses of 1000 mg and 1200 mg, was 100% effective for treatment of culture-proven gonorrhea at genital, oral, and rectal sites of infection and is a promising new agent for gonorrhea treatment. NCT01591447. © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Residual effect of zolpidem 10 mg and zopiclone 7.5 mg versus flunitrazepam 1 mg and placebo on driving performance and ocular saccades.

PubMed

Bocca, M L; Le Doze, F; Etard, O; Pottier, M; L'Hoste, J; Denise, P

1999-04-01

Studies report contradictory results concerning the residual effects of zolpidem and zopiclone. Moreover, residual effects of these compounds on healthy subjects have not yet been simultaneously assessed. The present study with healthy subjects investigated the residual effects of zolpidem 10 mg and zopiclone 7.5 mg on driving performance and on ocular saccade and compared them to those under flunitrazepam 1 mg and placebo. The study involved 16 subjects divided into two groups, a 9:00 a.m. group and a 11:00 a.m. group, in a balanced, double-blind, cross-over design. In the 9:00 a.m. group, zolpidem had no residual effects while zopiclone and flunitrazepam both impaired driving performance (P < 0.001 for both) and increased saccadic latency (P < 0.005; P = 0.052, respectively). Zopiclone impaired driving performance 5 times less than did flunitrazepam. In the 11:00 a.m. group, zolpidem and zopiclone had no residual effects, while flunitrazepam increased saccadic latency (P = 0.065) but did not impair driving performance. Zopiclone and flunitrazepam had residual effects in the first part of the morning, whereas zolpidem had no residual effects. The hierarchical character of the effects of the molecules differed according to the test administered. This is probably linked more to drug-induced specific alterations than to different sensitivities of the tests.

Acid-suppressive efficacy of a reduced dosage of rabeprazole: comparison of 10 mg twice daily rabeprazole with 20 mg twice daily rabeprazole, 30 mg twice daily lansoprazole, and 20 mg twice daily omeprazole by 24-hr intragastric pH-metry.

PubMed

Shimatani, Tomohiko; Inoue, Masaki; Kuroiwa, Tomoko; Xu, Jing; Tazuma, Susumu; Horikawa, Yoko; Nakamura, Masuo

2005-07-01

Rabeprazole achieves more potent acid suppression than other proton pump inhibitors. Therefore it is administered at reduced as well as high dosages in eradication therapy for Helicobacter pylori; however, there is incomplete assessment of the efficacy of a reduced dosage of rabeprazole as might be employed in therapy. In this study, we evaluated acid-suppressive efficacy of a reduced dosage of rabeprazole on day 7 by 24-hr pH-metry in 10 healthy male cytochrome P-450 2C19 extensive metabolizers without Helicobacterpylori infection and compared the results with those of high dosages of rabeprazole, lansoprazole, and omeprazole. Median intragastric pH value, pH >3 holding time ratio (pH>3HT), pH>4HT, pH>5HT, pH>6HT, and pH>7HT for 24 hr with rabeprazole, 10 mg twice daily, were not significantly different from those of rabeprazole, 20 mg twice daily, lansoprazole, 30 mg twice daily, and omeprazole, 20 mg twice daily. In conclusion, for acid-suppressive efficacy, a reduced dosage of rabeprazole is comparable to high dosages of rabeprazole, lansoprazole, and omeprazole.

Fabrication of Single Crystal MgO Capsules

NASA Technical Reports Server (NTRS)

Danielson, Lisa

2012-01-01

A method has been developed for machining MgO crystal blocks into forms for containing metallic and silicate liquids at temperatures up to 2,400 C, and pressures up to at least 320 kilobars. Possible custom shapes include tubes, rods, insulators, capsules, and guides. Key differences in this innovative method include drilling along the crystallographic zone axes, use of a vibration minimizing material to secure the workpiece, and constant flushing of material swarf with a cooling medium/lubricant (water). A single crystal MgO block is cut into a section .5 mm thick, 1 cm on a side, using a low-speed saw with a 0.004 blade. The cut is made parallel to the direction of cleavage. The block may be cut to any thickness to achieve the desired length of the piece. To minimize drilling vibrations, the MgO block is mounted on a piece of adhesive putty in a vise. The putty wad cradles the bottom half of the entire block. Diamond coring tools are used to drill the MgO to the desired custom shape, with water used to wet and wash the surface of swarf. Compressed air may also be used to remove swarf during breaks in drilling. The MgO workpiece must be kept cool at all times with water. After all the swarf is rinsed off, the piece is left to dry overnight. If the workpiece is still attached to the base of the MgO block after drilling, it may be cut off by using a diamond cutoff wheel on a rotary hand tool or by using a low-speed saw.

High-pressure melting of MgSiO3.

PubMed

Belonoshko, A B; Skorodumova, N V; Rosengren, A; Ahuja, R; Johansson, B; Burakovsky, L; Preston, D L

2005-05-20

The melting curve of MgSiO(3) perovskite has been determined by means of ab initio molecular dynamics complemented by effective pair potentials, and a new phenomenological model of melting. Using first principles ground state calculations, we find that the MgSiO(3) perovskite phase transforms into post perovskite at pressures above 100 GPa, in agreement with recent theoretical and experimental studies. We find that the melting curve of MgSiO(3), being very steep at pressures below 60 GPa, rapidly flattens on increasing pressure. The experimental controversy on the melting of the MgSiO(3) perovskite at high pressures is resolved, confirming the data by Zerr and Boehler.

Deep-Ultraviolet Luminescence of Rocksalt-Structured Mg x Zn1-x O (x > 0.5) Films on MgO Substrates

NASA Astrophysics Data System (ADS)

Kaneko, Kentaro; Tsumura, Keiichi; Ishii, Kyohei; Onuma, Takayoshi; Honda, Tohru; Fujita, Shizuo

2018-04-01

Rocksalt-structured Mg x Zn1-x O films with Mg composition x of 0.47, 0.57, and 0.64 were grown on (100)-oriented MgO substrates using mist chemical vapor deposition. Cathodoluminescence measurements showed deep ultraviolet (DUV) emission peaking at 4.88 eV (254 nm), 5.15 eV (241 nm), and 5.21 eV (238 nm), respectively, at 12 K. The peak energies were lower than the band gap energies by ca. 1 eV, suggesting that the deep ultraviolet (DUV) emission may be recognized as near band edge luminescence but is associated with impurities, defects, or band fluctuations. The use of carbon-free precursors in the growth is suggested to eliminate carbon impurities and to improve the optical properties of Mg x Zn1-x O.

Comparison of golimumab 100-mg monotherapy to golimumab 50 mg plus methotrexate in patients with rheumatoid arthritis: Results from a multicenter, cohort study.

PubMed

Yonemoto, Yukio; Okamura, Koichi; Takeuchi, Kimihiko; Ayabe, Keio; Kaneko, Tetsuya; Matsushita, Masatoshi; Tamura, Yasuyuki; Iso, Takenobu; Okura, Chisa; Otsuka, Keiko; Inoue, Hiroshi; Takagishi, Kenji

2016-01-01

The aim of this study was to compare the efficacy and safety of golimumab (GLM) 50 mg + methotrexate (MTX) combination therapy and GLM 100 mg monotherapy in patients with rheumatoid arthritis (RA). The subjects were 115 RA patients (92 females and 23 males; median (range) age, 64 (17-87) years; median (range) disease duration, 8 (0.6-48) years) started on GLM. Eighty-three patients received GLM 50 mg/4 weeks + MTX (C group; median (range) MTX dosage 8 (2-16) mg/week), and 32 patients received GLM 100 mg/4 weeks (M group). Serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), matrix metalloproteinase-3, disease activity score (DAS) 28-ESR, DAS28-CRP, simplified disease activity index, and clinical disease activity index were evaluated 4, 12, and 24 weeks after starting GLM. There were no significant differences in disease activity, adverse events, and drug continuation rates at 24 weeks between the groups. The DAS28-ESR remission rate was 34% in the C group and 26% in the M group. GLM 100 mg monotherapy improved disease activity as well as GLM 50 mg + MTX combination therapy. GLM 100 mg monotherapy appears to have a sufficient therapeutic effect in RA patients who cannot take MTX.

Extended-release dexmethylphenidate 30 mg/d versus 20 mg/d: duration of attention, behavior, and performance benefits in children with attention-deficit/hyperactivity disorder.

PubMed

Silva, Raul R; Brams, Matthew; McCague, Kevin; Pestreich, Linda; Muniz, Rafael

2013-01-01

This study aimed to compare the effects of dexmethylphenidate (D-MPH) extended-release (ER) 30 mg and D-MPH-ER 20 mg on attention, behavior, and performance in children with attention-deficit/hyperactivity disorder. In a randomized, double-blind, 3-period-by-3-treatment, crossover study, children aged 6 to 12 years with attention-deficit/hyperactivity disorder stabilized on methylphenidate (40-60 mg/d) or D-MPH (20-30 mg/d) received D-MPH-ER 20 mg/d, 30 mg/d, and placebo for 7 days each (final dose of each treatment period administered in a laboratory classroom). Swanson, Kotkin, Agler, M-Flynn, and Pelham (SKAMP) Combined (Attention and Deportment) rating scale and Permanent Product Measure of Performance (PERMP) math test assessments were conducted at baseline and 3, 6, 9, 10, 11, and 12 hours postdose. A total of 165 children (94 boys; mean age, 9.6 years) were randomized (162 included in intent-to-treat analyses). Significant improvements were noted for D-MPH-ER 30 mg over D-MPH-ER 20 mg at various late time points on the SKAMP scales (Combined scores at 9, 10, 11, and 12 hours postdose; Attention scores at 10, 11, and 12 hours postdose; deportment scores at 9 and 12 hours postdose). The PERMP math test-attempted and -correct scores (change from predose) were significantly higher with D-MPH-ER 30 mg than with D-MPH-ER 20 mg at 10, 11, and 12 hours postdose. Both D-MPH-ER doses were superior to placebo at all time points. D-MPH-ER 30 mg was superior to D-MPH-ER 20 mg at later time points in the day, suggesting that higher doses of D-MPH-ER may be more effective later in the day.

Impact of interface manipulation of oxide on electrical transport properties and low-frequency noise in MgO/NiFe/MgO heterojunctions

NASA Astrophysics Data System (ADS)

Li, Jian-wei; Zhao, Chong-jun; Feng, Chun; Zhou, Zhongfu; Yu, Guang-hua

2015-08-01

Low-frequency noise and magnetoresistance in sputtered-deposited Ta(5 nm)/MgO (3 nm)/NiFe(10 nm)/MgO(3 nm)/Ta(3 nm) films have been measured as a function of different annealing times at 400°C. These measurements did not change synchronously with annealing time. A significant increase in magnetoresistance is observed for short annealing times (of the order of minutes) and is correlated with a relatively small reduction in 1/f noise. In contrast, a significant reduction in 1/f noise is observed for long annealing times (of the order of hours) accompanied by a small change in magnetoresistance. After annealing for 2 hours, the 1/f noise decreases by three orders of magnitude. Transmission electron microscopy and slow positron annihilation results implicate the cause being micro-structural changes in the MgO layers and interfaces following different annealing times. The internal vacancies in the MgO layers gather into vacancy clusters to reduce the defect density after short annealing times, whereas the MgO/NiFe and the NiFe/MgO interfaces improve significantly after long annealing times with the amorphous MgO layers gradually crystallizing following the release of interfacial stress.

Impact of interface manipulation of oxide on electrical transport properties and low-frequency noise in MgO/NiFe/MgO heterojunctions

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

Li, Jian-wei; School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083; Zhao, Chong-jun

2015-08-15

Low-frequency noise and magnetoresistance in sputtered-deposited Ta(5 nm)/MgO (3 nm)/NiFe(10 nm)/MgO(3 nm)/Ta(3 nm) films have been measured as a function of different annealing times at 400°C. These measurements did not change synchronously with annealing time. A significant increase in magnetoresistance is observed for short annealing times (of the order of minutes) and is correlated with a relatively small reduction in 1/f noise. In contrast, a significant reduction in 1/f noise is observed for long annealing times (of the order of hours) accompanied by a small change in magnetoresistance. After annealing for 2 hours, the 1/f noise decreases by three ordersmore » of magnitude. Transmission electron microscopy and slow positron annihilation results implicate the cause being micro-structural changes in the MgO layers and interfaces following different annealing times. The internal vacancies in the MgO layers gather into vacancy clusters to reduce the defect density after short annealing times, whereas the MgO/NiFe and the NiFe/MgO interfaces improve significantly after long annealing times with the amorphous MgO layers gradually crystallizing following the release of interfacial stress.« less

Thermoelectric power of PrMg3

NASA Astrophysics Data System (ADS)

Isikawa, Yosikazu; Somiya, Kazuya; Koyanagi, Huruto; Mizushima, Toshio; Kuwai, Tomohiko; Tayama, Takashi

2010-01-01

PrMg3 is supposed to be one of the strongly correlated electron systems originated from the hybridization between the Pr 4f and conduction electrons, because the gigantic electronic specific heat coefficient C/T was observed at low temperatures. However, a typical behaviour of - ln T dependence was not observed in the temperature dependence of the electrical resistivity. The thermoelectric power S is a powerful tool to investigate the density of states at the Fermi energy. We measured carefully the thermoelectric power of PrMg3 in the temperature range between 2 and 300 K. S is extremely small, ranged within ±1 μV/K over the whole temperature. The value of S/T at low temperature limit was also significantly smaller than expected from the specific heat results. We therefore conclude that the density of state at the Fermi level is not enhanced in PrMg3.

Randomized clinical trial of dexketoprofen/tramadol 25 mg/75 mg in moderate-to-severe pain after total hip arthroplasty

PubMed Central

McQuay, H. J.; Moore, R. A.; Berta, A.; Gainutdinovs, O.; Fülesdi, B.; Porvaneckas, N.; Petronis, S.; Mitkovic, M.; Bucsi, L.; Samson, L.; Zegunis, V.; Ankin, M. L.; Bertolotti, M.; Pizà-Vallespir, B.; Cuadripani, S.; Contini, M. P.; Nizzardo, A.

2016-01-01

Background. The aim was to evaluate the analgesic efficacy and safety of the dexketoprofen/tramadol 25 mg/75 mg fixed-dose combination vs dexketoprofen (25 mg) and tramadol (100 mg) in moderate-to-severe acute pain after total hip arthroplasty. Methods. This was a randomized, double-blind, parallel-group study in patients experiencing pain of at least moderate intensity on the day after surgery, compared with placebo at first administration to validate the pain model. The study drug was administered orally every 8 h throughout a 5 day period. Rescue medication, metamizole 500 mg, was available during the treatment period. The evaluation of efficacy was based on patient assessments of pain intensity and pain relief. The primary end point was the mean sum of the pain intensity difference values throughout the first 8 h (SPID8). Results. Overall, 641 patients, mean age 62 (range 29–80) yr, were analysed; mean (sd) values of SPID8 were 247 (157) for dexketoprofen/tramadol, 209 (155) for dexketoprofen, 205 (146) for tramadol, and 151 (159) for placebo. The primary analysis confirmed the superiority of the combination over dexketoprofen 25 mg (P=0.019; 95% confidence interval 6.4–73) and tramadol 100 mg (P=0.012; 95% confidence interval 9.5–76). The single components were superior to placebo (P<0.05), confirming model sensitivity. Most secondary analyses supported the superiority of the combination. The incidence of adverse drug reactions was low and similar among active treatment groups. Conclusion. The efficacy results confirmed the superiority of dexketoprofen/tramadol over its single components, even at higher doses (tramadol), with a safety profile fully in line with that previously known for these agents in monotherapy. Clinical trial registration. EudraCT 2012-004548-31 (https://www.clinicaltrialsregister.eu/ctr-search/search?query=eudract_number:2012-004548-31); ClinicalTrials.gov NCT01902134 (https://www.clinicaltrials.gov/ct2/show/NCT01902134?term

Randomized clinical trial of dexketoprofen/tramadol 25 mg/75 mg in moderate-to-severe pain after total hip arthroplasty.

PubMed

McQuay, H J; Moore, R A; Berta, A; Gainutdinovs, O; Fülesdi, B; Porvaneckas, N; Petronis, S; Mitkovic, M; Bucsi, L; Samson, L; Zegunis, V; Ankin, M L; Bertolotti, M; Pizà-Vallespir, B; Cuadripani, S; Contini, M P; Nizzardo, A

2016-02-01

The aim was to evaluate the analgesic efficacy and safety of the dexketoprofen/tramadol 25 mg/75 mg fixed-dose combination vs dexketoprofen (25 mg) and tramadol (100 mg) in moderate-to-severe acute pain after total hip arthroplasty. This was a randomized, double-blind, parallel-group study in patients experiencing pain of at least moderate intensity on the day after surgery, compared with placebo at first administration to validate the pain model. The study drug was administered orally every 8 h throughout a 5 day period. Rescue medication, metamizole 500 mg, was available during the treatment period. The evaluation of efficacy was based on patient assessments of pain intensity and pain relief. The primary end point was the mean sum of the pain intensity difference values throughout the first 8 h (SPID8). Overall, 641 patients, mean age 62 (range 29-80) yr, were analysed; mean (sd) values of SPID8 were 247 (157) for dexketoprofen/tramadol, 209 (155) for dexketoprofen, 205 (146) for tramadol, and 151 (159) for placebo. The primary analysis confirmed the superiority of the combination over dexketoprofen 25 mg (P=0.019; 95% confidence interval 6.4-73) and tramadol 100 mg (P=0.012; 95% confidence interval 9.5-76). The single components were superior to placebo (P<0.05), confirming model sensitivity. Most secondary analyses supported the superiority of the combination. The incidence of adverse drug reactions was low and similar among active treatment groups. The efficacy results confirmed the superiority of dexketoprofen/tramadol over its single components, even at higher doses (tramadol), with a safety profile fully in line with that previously known for these agents in monotherapy. EudraCT 2012-004548-31 (https://www.clinicaltrialsregister.eu/ctr-search/search?query=eudract_number:2012-004548-31);ClinicalTrials.gov NCT01902134 (https://www.clinicaltrials.gov/ct2/show/NCT01902134?term=NCT01902134&rank=1). © The Author 2016. Published by Oxford University Press on

[In Process Citation].

PubMed

Caravalí-Meza, Nuris Yohana; Jiménez-Cruz, Arturo; Bacardí-Gascón, Montserrat

2016-03-25

Antecedentes: se ha reportado una asociación entre el aumento del consumo de bebidas azucaradas y varias enfermedades metabólicas. Objetivo: evaluar el efecto del consumo de bebidas azucaradas sobre la obesidad en un periodo de 12 meses en mexicanos de 15 a 19 años. Métodos: el diseño del estudio fue prospectivo, con 12 meses de seguimiento. Se midieron el peso, la talla y la circunferencia de cintura (CC), y se calculó el puntaje z de índice de masa corporal (IMC). Se aplicó un cuestionario sobre consumo de 19 bebidas. Para evaluar la predicción del aumento de IMC y de CC como resultado del consumo de bebidas, se utilizó análisis de regresión logística binomial. Resultados: al final del estudio se evaluó al 89% (1.344). El promedio de edad fue de 15 años, 55% fueron mujeres. La prevalencia de sobre- peso y obesidad al final del estudio fue del 33%. Al final del estudio, un 25% de los participantes consumían más de 50 g de azúcar proveniente de las bebidas. Quienes consumieron 50 g de azúcar o más al día presentaron mayor riesgo de aumentar la CC ≥ 2 cm (RR = 1,19, IC 95%, 1,03-1,39, p = 0,02). Quienes mantuvieron el consumo de bebidas azucaradas durante 12 meses, al compararlo con los que disminuyeron el consumo a 10 g/día, presentaron 71% más probabilidades de aumentar a un puntaje de IMC ≥ 2 (RR = 1,71, IC 95%, 1,03-2,86, p = 0,039). Conclusión: el alto consumo de bebidas azucaradas aumentó las probabilidades de aumentar de peso y de circunferencia de cintura.

Study on biodegradation of the second phase Mg17Al12 in Mg-Al-Zn alloys: in vitro experiment and thermodynamic calculation.

PubMed

Liu, Chen; Yang, Huazhe; Wan, Peng; Wang, Kehong; Tan, Lili; Yang, Ke

2014-02-01

The in vitro biodegradation behavior of Mg17Al12 as a second phase in Mg-Al-Zn alloys was investigated via electrochemical measurement and immersion test. The Hank's solutions with neutral and acidic pH values were adopted as electrolytes to simulate the in vivo environment during normal and inflammatory response process. Furthermore, the local orbital density functional theory approach was employed to study the thermodynamical stability of Mg17Al12 phase. All the results proved the occurrence of pitting corrosion process with crackings for Mg17Al12 phase in Hank's solution, but with a much lower degradation rate compared with both AZ31 alloy and pure magnesium. Furthermore, a preliminary explanation on the biodegradation behaviors of Mg17Al12 phase was proposed. © 2013.

Effect of Mg incorporation on solution-processed kesterite solar cells

NASA Astrophysics Data System (ADS)

Caballero, Raquel; Haass, Stefan G.; Andres, Christian; Arques, Laia; Oliva, Florian; Izquierdo-Roca, Victor; Romanyuk, Yaroslav E.

2018-01-01

The introduction of the alkaline-earth element Mg into Cu2ZnSn(S,Se)4 (CTZSSe) is explored in view of potential photovoltaic applications. Cu2Zn1-xMgxSn(S,Se)4 absorber layers with variable Mg content x=0…1 are deposited using the solution approach with dimethyl sulfoxide solvent followed by annealing in selenium atmosphere. For heavy Mg alloying with x = 0.55…1 the phase separation into Cu2SnSe3, MgSe2, MgSe and SnSe2 occurs in agreement with literature predictions. A lower Mg content of x=0.04 results in the kesterite phase as confirmed by XRD and Raman spectroscopy. A photoluminescence maximum is red-shifted by 0.02 eV as compared to the band-gap and a carrier concentration NCV of 1 x 1016 cm-3 is measured for a Mg-containing kesterite solar cell device. Raman spectroscopy indicates that structural defects can be reduced in Mg-containing absorbers as compared to the Mg-free reference samples, however the best device efficiency of 7.2% for a Mg-containing cell measured in this study is lower than those frequently reported for the conventional Na doping.

Characterization of Mg-containing hydroxyapatites synthesized by combustion method

NASA Astrophysics Data System (ADS)

Kaygili, Omer; Keser, Serhat; Bulut, Niyazi; Ates, Tankut

2018-05-01

In the present paper, Mg-substituted hydroxyapatites with the morphology, composed of the stacked plate- and rod-like structures, were prepared at the temperature of 600 °C by combustion method using glycerine as a fuel. A significant decrease in the crystallite size values calculated for both Scherrer and Williamson-Hall methods is found. The crystallinity, lattice parameter of a, stress and anisotropic energy density values decreased by adding of Mg, whereas the lattice strain increased. The amount of HAp phase decreases with increasing amount of Mg and the β-tricalcium phosphate content increases. Mg incorporation the apatitic structure was detected. Depending on the increase in Mg content, Ca-deficiency was observed.

Selective antibacterial effects of mixed ZnMgO nanoparticles

NASA Astrophysics Data System (ADS)

Vidic, Jasmina; Stankic, Slavica; Haque, Francia; Ciric, Danica; Le Goffic, Ronan; Vidy, Aurore; Jupille, Jacques; Delmas, Bernard

2013-05-01

Antibiotic resistance has impelled the research for new agents that can inhibit bacterial growth without showing cytotoxic effects on humans and other species. We describe the synthesis and physicochemical characterization of nanostructured ZnMgO whose antibacterial activity was compared to its pure nano-ZnO and nano-MgO counterparts. Among the three oxides, ZnO nanocrystals—with the length of tetrapod legs about 100 nm and the diameter about 10 nm—were found to be the most effective antibacterial agents since both Gram-positive ( B. subtilis) and Gram-negative ( E. coli) bacteria were completely eradicated at concentration of 1 mg/mL. MgO nanocubes (the mean cube size 50 nm) only partially inhibited bacterial growth, whereas ZnMgO nanoparticles (sizes corresponding to pure particles) revealed high specific antibacterial activity to Gram-positive bacteria at this concentration. Transmission electron microscopy analysis showed that B. subtilis cells were damaged after contact with nano-ZnMgO, causing cell contents to leak out. Our preliminary toxicological study pointed out that nano-ZnO is toxic when applied to human HeLa cells, while nano-MgO and the mixed oxide did not induce any cell damage. Overall, our results suggested that nanostructured ZnMgO, may reconcile efficient antibacterial efficiency while being a safe new therapeutic for bacterial infections.

Stabilization of Reactive MgO Surfaces by Ni Doping

NASA Astrophysics Data System (ADS)

Mazheika, Aliaksei; Levchenko, Sergey V.

Ni-MgO solid solutions are promising materials for catalytic reduction of CO2 and dry reforming of CH4. To explain the catalytic activity, an ab initio study of Ni-substitutional defects in MgO (NiMg) has been performed. At first, the validation of the theory level was done. We compared results of CCSD(T) embedded-cluster calculations of NiMg formation energies and adsorption energies of CO, CO2 and H2 on them to the HSE(α) hybrid DFT functional with the fraction of the exact exchange α varied between 0 and 1. HSE(0.3) was found to be the best compromise in this study. Our periodic HSE(0.3) calculations show that NiMg defects are most stable at corner sites, followed by steps, and are least stable at (001) terraces. Thus, Ni-doping stabilizes stepped MgO surfaces. The dissociative adsorption of H2 on the terrace is found to be endothermic (+ 1 . 1 eV), whereas on (110) surface with NiMg it is highly exothermic (- 1 . 6 eV). Adsorbed CO2 is also significantly stabilized (- 0 . 6 vs. - 2 . 2 eV). These findings explain recent microcalorimetry measurements of H2 and CO2 adsorption at doped Ni-MgO samples. partially supported by UniCat (Deutsche Forschungsgemeinschaft).

Microstructures and Mechanical Study of Mg Alloy Foam Based on Mg-Zn-Ca-CaCO3 System

NASA Astrophysics Data System (ADS)

Erryani, A.; Pramuji, F.; Annur, D.; Amal, M. I.; Kartika, I.

2017-05-01

Magnesium alloy, a material that has potential to use some applications such as aerospace components, computer parts, and mobile phones. Magnesium alloy can also be a popular candidate as an orthopedic implant material for biodegradability, non-toxicity, and mechanical and physical properties that are excellent. Magnesium, one of the main macro elements required for the proper functioning of the human organism, is used to test the materials for biodegradable implants. The main objective of this study was to find out the microstructure, and mechanical characteristics of the Mg-Ca-Zn-CaCO3 alloy as porous implant materials are biodegradable. The presence of CaCO3 on the alloy functions as a foaming agent expected to produce gas bubbles during manufacturing process taken place that will form pores in the alloy. Mg-Ca-Zn-CaCO3 alloy was made by powder metallurgy method with three variations of composition (96Mg-Ca-3Zn-CaCO3, 91Mg-Ca-3Zn-5CaCO3, and 86Mg-Ca-3Zn-10CaCO3 wt%). Milling process was by using a shaker mill for 2 hours to produce a powder size distribution which was more homogeneous. The mixed powder was uniaxially pressed at a pressure of 100 MPa for 2 minutes and 200 MPa for 3 minutes into green compacts with dimensions of 10 mm in diameter and 10 mm in length. The sintering process was carried out at 650°C with a variation of holding time of 10 and 15 hours, and then the specimens were cooled down at room temperature. Microstructural analysis was performed by using X-Ray diffraction technique and Scanning electron microscopy equipped with an energy disperse spectrometry (EDS). The mechanical characteristics were analyzed by using Universal Testing Machine. The density and porosity of specimen were further measured by using Archimedes method. The results show that the optimum microstructure and mechanical characteristics are the holding time of 10 hours. The value of compression was 208.398 N/mm2, the density was 1.63 g/cc and a porosity was 18% on the

Investigation of the hemostatic effect of a transdermal patch containing 0.55 mg ethinyl estradiol and 2.1 mg gestodene compared with a monophasic oral contraceptive containing 0.03 mg ethinyl estradiol and 0.15 mg levonorgestrel: an open-label, randomized, crossover study.

PubMed

Junge, Wolfgang; Heger-Mahn, Doris; Trummer, Dietmar; Merz, Martin

2013-09-01

Transdermal delivery of contraceptives offers several advantages over combined oral contraceptives (COCs), including effective absorption and the provision of relatively constant serum concentrations. Ethinyl estradiol (EE) and the progestin gestodene are well-absorbed through the skin and, therefore, well-suited for use in a transdermal contraceptive patch. The objective of this study was to investigate the impact of a once-weekly transparent, transdermal patch delivering low doses of EE and gestodene equivalent to a COC containing 0.02 mg EE and 0.06 mg gestodene on hemostasis parameters compared with a monophasic COC containing 0.03 mg EE and 0.15 mg levonorgestrel. In this single-center, open-label, randomized, crossover study, 30 women (aged 18-35 years) received three cycles of each treatment, separated by a two-cycle washout period. The primary outcome measure was the absolute change from baseline in prothrombin fragments 1 + 2 and D-dimer. For both treatments, prothrombin fragments 1 + 2 remained stable during the first treatment period, and increased only slightly in the second period (mean absolute change 0.025 and 0.028 nmol/L in the novel Bayer patch and COC groups, respectively). Increases in D-dimer were observed in both periods (mean absolute change 107.0 ± 147.2 ng/L for the novel Bayer patch and 113.7 ± 159.0 ng/L for the COC). There were no statistically significant treatment differences in prothrombin 1 + 2 or D-dimer (p = 0.667 and p = 0.884, respectively) and no statistically significant treatment sequence or period effects. A COC containing 0.03 mg EE and 0.15 mg levonorgestrel and the novel Bayer patch have comparable influence on hemostatic endpoints. Both treatments were well-tolerated by subjects.

Torres del Paine National Park

NASA Image and Video Library

2017-12-08

Grinding glaciers and granite peaks mingle in Chile’s Torres del Paine National Park. The Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this summertime image of the park on January 21, 2013. This image shows just a portion of the park, including Grey Glacier and the mountain range of Cordillera del Paine. The rivers of glacial ice in Torres del Paine National Park grind over bedrock, turning some of that rock to dust. Many of the glaciers terminate in freshwater lakes, which are rich with glacial flour that colors them brown to turquoise. Skinny rivers connect some of the lakes to each other (image upper and lower right). Cordillera del Paine rises between some of the wide glacial valleys. The compact mountain range is a combination of soaring peaks and small glaciers, most notably the Torres del Paine (Towers of Paine), three closely spaced peaks emblematic of the mountain range and the larger park. By human standards, the mountains of Cordillera del Paine are quite old. But compared to the Rocky Mountains (70 million years old), and the Appalachians (about 480 million years), the Cordillera del Paine are very young—only about 12 million years old. A study published in 2008 described how scientists used zircon crystals to estimate the age of Cordillera del Paine. The authors concluded that the mountain range was built in three pulses, creating a granite laccolith, or dome-shaped feature, more than 2,000 meters (7,000 feet) thick. NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using Advanced Land Imager data from the NASA EO-1 team. Caption by Michon Scott. Instrument: EO-1 - ALI View more info: earthobservatory.nasa.gov/IOTD/view.php?id=80266 Credit: NASA Earth Observatory NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA�

Properties of thymidylate synthetase from Ehrlich ascites carcinoma cells. Effect of Mg2/ and MgATP2-.

PubMed

Jastreboff, M; Kedzierska, B; Rode, W

1982-01-15

Ehrlich ascites carcinoma thymidylate synthetase was purified to electrophoretic homogeneity by affinity chromatography on 10-formyl-5,8-dideazofolate-ethyl-Sepharose. Electrophoretic analysis of the formation of the enzyme-5-fluorodeoxyuridylate-5,10-methylenetetrahydrofolate complexes showed the presence of two binding sites for 5-fluorodeoxyuridylate on the enzyme molecule. Molecular weight of the native enzyme was found to be 78,5000, whereas that of its monomer was 38, 500. The apparent Michaelis constants for dUMP and (+/-)-L-5,10-methylenetetrahydrofolate were 1.3 +/- 0.4 and 32.2 +/- 0.7 micrometers respectively. Phosphate acted as a weak inhibitor, competitive toward dUMP. The enzyme reaction exhibited a temperature-dependent change of activation energy, reflected in the binding affinity of dUMP, with a transitional temperature of 35.8 degrees. Both Mg2+ and MgATP2- were strong activators of the enzyme, MgATP2- being more effective.

Superconducting MgB2 wires with vanadium diffusion barrier

NASA Astrophysics Data System (ADS)

Hušek, I.; Kováč, P.; Melišek, T.; Kulich, M.; Rosová, A.; Kopera, L.; Szundiová, B.

2017-10-01

Single-core MgB2 wires with a vanadium barrier and Cu stabilization have been made by the in situ powder-in-tube (PIT) and internal magnesium diffusion (IMD) into boron processes. Heat treatment of PIT wires was done at the temperature range of 650 °C-850 °C/30 min. Critical currents of differently treated MgB2/V/Cu wires have been measured and related with the structure of MgB2. It was found that critical current density of MgB2/V wire annealed above 700 °C decreases rapidly. The obtained results clearly show that vanadium is a well formable metal and can be applied as an effective diffusion barrier for MgB2 wires heat-treated at temperatures ≤700 °C. This temperature limit is well applicable for MgB2 wires with high current densities made by PIT and also by the IMD process.

Reducing Mg Acceptor Activation-Energy in Al0.83Ga0.17N Disorder Alloy Substituted by Nanoscale (AlN)5/(GaN)1 Superlattice Using MgGa δ-Doping: Mg Local-Structure Effect

NASA Astrophysics Data System (ADS)

Zhong, Hong-Xia; Shi, Jun-Jie; Zhang, Min; Jiang, Xin-He; Huang, Pu; Ding, Yi-Min

2014-10-01

Improving p-type doping efficiency in Al-rich AlGaN alloys is a worldwide problem for the realization of AlGaN-based deep ultraviolet optoelectronic devices. In order to solve this problem, we calculate Mg acceptor activation energy and investigate its relationship with Mg local structure in nanoscale (AlN)5/(GaN)1 superlattice (SL), a substitution for Al0.83Ga0.17N disorder alloy, using first-principles calculations. A universal picture to reduce acceptor activation energy in wide-gap semiconductors is given for the first time. By reducing the volume of the acceptor local structure slightly, its activation energy can be decreased remarkably. Our results show that Mg acceptor activation energy can be reduced significantly from 0.44 eV in Al0.83Ga0.17N disorder alloy to 0.26 eV, very close to the Mg acceptor activation energy in GaN, and a high hole concentration in the order of 1019 cm-3 can be obtained in (AlN)5/(GaN)1 SL by MgGa δ-doping owing to GaN-monolayer modulation. We thus open up a new way to reduce Mg acceptor activation energy and increase hole concentration in Al-rich AlGaN.

Reducing Mg Acceptor Activation-Energy in Al0.83Ga0.17N Disorder Alloy Substituted by Nanoscale (AlN)5/(GaN)1 Superlattice Using MgGa δ-Doping: Mg Local-Structure Effect

PubMed Central

Zhong, Hong-xia; Shi, Jun-jie; Zhang, Min; Jiang, Xin-he; Huang, Pu; Ding, Yi-min

2014-01-01

Improving p-type doping efficiency in Al-rich AlGaN alloys is a worldwide problem for the realization of AlGaN-based deep ultraviolet optoelectronic devices. In order to solve this problem, we calculate Mg acceptor activation energy and investigate its relationship with Mg local structure in nanoscale (AlN)5/(GaN)1 superlattice (SL), a substitution for Al0.83Ga0.17N disorder alloy, using first-principles calculations. A universal picture to reduce acceptor activation energy in wide-gap semiconductors is given for the first time. By reducing the volume of the acceptor local structure slightly, its activation energy can be decreased remarkably. Our results show that Mg acceptor activation energy can be reduced significantly from 0.44 eV in Al0.83Ga0.17N disorder alloy to 0.26 eV, very close to the Mg acceptor activation energy in GaN, and a high hole concentration in the order of 1019 cm−3 can be obtained in (AlN)5/(GaN)1 SL by MgGa δ-doping owing to GaN-monolayer modulation. We thus open up a new way to reduce Mg acceptor activation energy and increase hole concentration in Al-rich AlGaN. PMID:25338639

Reducing Mg acceptor activation-energy in Al(0.83)Ga(0.17)N disorder alloy substituted by nanoscale (AlN)₅/(GaN)₁ superlattice using Mg(Ga) δ-doping: Mg local-structure effect.

PubMed

Zhong, Hong-xia; Shi, Jun-jie; Zhang, Min; Jiang, Xin-he; Huang, Pu; Ding, Yi-min

2014-10-23

Improving p-type doping efficiency in Al-rich AlGaN alloys is a worldwide problem for the realization of AlGaN-based deep ultraviolet optoelectronic devices. In order to solve this problem, we calculate Mg acceptor activation energy and investigate its relationship with Mg local structure in nanoscale (AlN)5/(GaN)1 superlattice (SL), a substitution for Al(0.83)Ga(0.17)N disorder alloy, using first-principles calculations. A universal picture to reduce acceptor activation energy in wide-gap semiconductors is given for the first time. By reducing the volume of the acceptor local structure slightly, its activation energy can be decreased remarkably. Our results show that Mg acceptor activation energy can be reduced significantly from 0.44 eV in Al(0.83)Ga(0.17)N disorder alloy to 0.26 eV, very close to the Mg acceptor activation energy in GaN, and a high hole concentration in the order of 10(19) cm(-3) can be obtained in (AlN)5/(GaN)1 SL by Mg(Ga) δ-doping owing to GaN-monolayer modulation. We thus open up a new way to reduce Mg acceptor activation energy and increase hole concentration in Al-rich AlGaN.

Magnesium uptake characteristics in Arabidopsis revealed by 28Mg tracer studies.

PubMed

Ogura, Takaaki; Kobayashi, Natsuko I; Suzuki, Hisashi; Iwata, Ren; Nakanishi, Tomoko M; Tanoi, Keitaro

2018-06-07

The Mg 2+ uptake system in Arabidopsis roots is Gd 3+ - and Fe 2+ -sensitive, and responds to a changing Mg 2+ concentration within 1 h with the participation of AtMRS2 transporters. Magnesium (Mg 2+ ) absorption and the mechanism regulating its activity have not been clarified yet. To address these issues, it is necessary to reveal the characteristics of Mg 2+ uptake in roots. Therefore, we first investigated the Mg 2+ uptake characteristics in roots of 1-week-old Arabidopsis plants using 28 Mg. The Mg 2+ uptake system in roots was up-regulated within 1 h in response to the low Mg 2+ condition. This induction was inhibited in Arabidopsis "mitochondrial RNA splicing 2/magnesium transport" mutants atmrs2-4/atmgt6 and atmrs2-7/atmgt7, while the expression of AtMRS2-4/AtMGT6 and AtMRS2-7/AtMGT7 genes in the Arabidopsis wild-type was not responsive to Mg 2+ conditions. In addition, the Mg deficiency-induced Mg 2+ uptake system was shut-down within 5 min when Mg 2+ was resupplied to the environment. An inhibition study showed that the constitutive mechanism functioning in Mg 2+ uptake under Mg 2+ sufficient conditions was sensitive to a number of divalent and trivalent cations, particularly Gd 3+ and Fe 2+ , but not to K + .

Depth-dependent and surface damages in MgAl 2O 4 and MgO irradiated with energetic iodine ions

NASA Astrophysics Data System (ADS)

Aruga, T.; Katano, Y.; Ohmichi, T.; Okayasu, S.; Kazumata, Y.; Jitsukawa, S.

2002-11-01

Samples of polycrystalline ceramics of MgAl 2O 4 irradiated at the ambient temperature with 85 MeV I 7+ iodine ions to doses up to 1×10 19 m -2 is observed to be amorphized up to depths around 6 μm from the ion-incident surface for a dose of 1.2×10 19 m -2, through a cross-sectional transmission electron microscopy. A step height of 1 μm is formed across the border between the masked and irradiated regions of the surface. The height of the step is observed to increase sharply from the irradiated area towards the edge at the border, forming a peak as tall as 1.5 μm. A glossy, silver-gray film with a thickness less than 0.1 μm is unexpectedly observed to have formed on the surface of samples of MgAl 2O 4 and MgO, in about 3.5 years aging after the irradiation to 1.2×10 19 m -2, being left untouched in the air. The film is easily peeled off along grain boundaries and found to be amorphous from the electron diffraction pattern. The film from MgAl 2O 4 sample contains Al, Mg and Si. Silicon, which is one of impurities, is found to be enriched noticeably at the surface.

Magnetotransport properties of spin-valve structures with Mg spacer layers

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

Martinez-Boubeta, C., E-mail: cboubeta@gmail.com; Ferrante, Y.; Graduate School of Excellence, Materials Science in Mainz, 55128 Mainz

2015-01-19

A theoretical prediction by Wang et al. [Phys. Rev. B 82, 054405 (2010)] suggests the preferential transmission of majority-spin states with Δ{sub 1} symmetry across a magnesium interlayer in Fe/Mg/MgO/Fe based magnetic tunnel junctions. Here, we report experiments to probe this question in CoFe/Mg/CoFe structures. We find that the strength of the interlayer coupling decays exponentially with increasing the spacer thickness, however, a non-monotonic variation of the magnetoresistance as a function of the Mg layer is observed. These data may help revisit the role of the insertion of a Mg interface layer in MgO-based devices.

Dry cryomagnetic system with MgB2 coil

NASA Astrophysics Data System (ADS)

Abin, D. A.; Mineev, N. A.; Osipov, M. A.; Pokrovskii, S. V.; Rudnev, I. A.

2017-12-01

MgB2 may be the future superconducting wire material for industrial magnets due to it’s higher operation temperature and potentially lower cost than low temperature superconductors (LTS) have. We designed a compact cryomagnetic system with the use of MgB2. The possibility of creating a magnet with a central field of 5 T from a commercial MgB2 wire by the “react and wound” method was investigated. The magnetic system is cooled by a cryocooler through a copper bus. The magnet has a warm bore diameter of 4 cm. The design of a magnet consisting of three concentric solenoids is proposed: an internal one of high-temperature superconductor (HTS), an average of MgB2, and an external of NbTi. The operating current of the system is 100 A. Two pairs of current leads are used. A separate pair of current leads for power supplying NbTi coil allows testing of MgB2 and HTS coils in an external field. The load curves for each of the magnets are calculated.

Production of Mg and Al Auger electrons by noble gas ion bombardment of Mg and Al surfaces

NASA Technical Reports Server (NTRS)

Ferrante, J.; Pepper, S. V.

1976-01-01

Relative production efficiencies of Mg and Al Auger electrons by He, Ne, Ar, Kr, and Xe ion bombardment are reported as a function of ion energy for energies not exceeding 3 keV. The experimental apparatus employed consisted of a LEED-Auger system equipped with an ion gun and a four-grid retarding-potential analyzer. It is found that: (1) the shape of the ion-excited Auger signal was independent of the rare gas and quite symmetric; (2) the Al signal was about an order of magnitude smaller than the Mg signal for a given bombarding species and ion-gun voltage; (3) no signal was observed for He(+) bombardment under any of the experimental conditions; (4) signal strengths were independent of temperature and ion dose; (5) the Auger production efficiencies differed by no more than a factor of two among the different gases - except for He(+) - on a given metal; (6) all the signal strengths increased with increasing ion-gun voltage, with no maximum exhibited; and (7) the apparent threshold energy for the Al signal was higher than that for the Mg signal. The differences between the results for the two metals are attributed to the fact that the Al 2p orbital lies deeper in energy and closer to the nucleus than the corresponding Mg orbital.

Mg-hydrogen interaction in AlGaN alloys

NASA Astrophysics Data System (ADS)

Zvanut, M. E.; Sunay, Ustun R.; Dashdorj, J.; Willoughby, W. R.; Allerman, A. A.

2012-03-01

It is well known that hydrogen passivation of Mg in Mg-doped GaN reduces free hole concentrations. While there are numerous studies of passivation of Mg in GaN, little work has been reported concerning passivation rates in AlGaN alloys. We investigated the hydrogen interaction with Mg in nitrides by measuring the intensity of the electron paramagnetic resonance (EPR) signal associated with the acceptor. The samples were isothermally annealed in sequential steps ranging from 5 min - 6.6 h between 300 and 700 oC in H2:N2 (7%: 92%) or pure N2. The signal intensity decreased during the H2N2 anneal and was revived by the N2 anneal as expected; however, the rate at which the intensity changed was shown to depend on Al concentration. In addition, while all signals were quenched at 700 oC in H2:N2, a 750 oC N2 anneal reactivated only about 30% of the Mg in the alloys and 80% of the intensity in the GaN film. These data suggest that the rate of passivation and activation of Mg by hydrogen is dependent on the concentration of Al in the AlxGa-1xN layer. The EPR annealing data could prove to be beneficial in improving p-type optimization in AlGaN alloys.

Randomised clinical trial: daily pantoprazole magnesium 40 mg vs. esomeprazole 40 mg for gastro-oesophageal reflux disease, assessed by endoscopy and symptoms.

PubMed

Moraes-Filho, J P; Pedroso, M; Quigley, E M M

2014-01-01

Pantoprazole magnesium (pantoprazole-Mg) may display extended inhibition of the proton pump with the potential for improved clinical efficacy in gastro-oesophageal reflux disease (GERD). To compare the efficacy of pantoprazole-Mg and esomeprazole in GERD. Gastro-oesophageal reflux disease (Los Angeles grades A-D) patients were randomised to 4 weeks of treatment with pantoprazole-Mg (n = 290) or esomeprazole (n = 288), both 40 mg once daily, in this multicentre (14 Brazilian sites in 9 cities), double-blind study, with an additional 4 weeks' treatment in nonresponding patients. Severity of oesophagitis (at endoscopy) and GERD-related symptoms (ReQuest-GI) were assessed. The primary end point was the proportion of patients in complete remission (ReQuest-GI score <1.73 plus endoscopic healing) at week 4. Complete remission occurred in 61% of patients in each treatment group at 4 weeks (primary endpoint) and in 81% and 79% of patients in the pantoprazole-Mg and esomeprazole groups at 8 weeks, with no significant differences. Mucosal healing rates were high and not significantly different. At 8 weeks, symptom relief with pantoprazole-Mg was significantly greater than that with esomeprazole (91.6% vs. 86.0%, P = 0.0370) because of continued improvement in symptoms with pantoprazole-Mg from week 4 to week 8 (P = 0.0206). Pantoprazole-Mg 40 mg was at least as effective as esomeprazole 40 mg for complete remission and the mucosal healing rate was high. Symptom relief with pantoprazole-Mg continued to improve from 4 to 8 weeks and was greater than that with esomeprazole at week 8, suggesting an extended period of treatment effect (ClinicalTrials.gov identifier: NCT01132638). © 2013 John Wiley & Sons Ltd.

Investigation of Mg(OH)2 nanoparticles as an antibacterial agent

NASA Astrophysics Data System (ADS)

Dong, Chunxu; Cairney, John; Sun, Qunhui; Maddan, Orville Lee; He, Gaohong; Deng, Yulin

2010-08-01

Our experimental results of using Mg(OH)2 nanoparticles as an antibacterial agent are reported in this study. The antibacterial behavior of Mg(OH)2 nanoparticles in liquid culture and in paper sheets was investigated. The colony forming units (CFU) counting and the headspace gas chromatography (HS-GC) measurement were used to determine the cell viability. Results indicate that Mg(OH)2 nanoparticles are effective antibacterial agent against Escherichia coli ( E. coli) and Burkholderia phytofirmans, and the OH- and Mg2+ ions in Mg(OH)2 water suspension were found not to be the reason for killing the bacteria. Mg(OH)2 nanoparticles could be added directly to wood pulp to make paper sheets, whose antibacterial efficiency increased with the increase of the nanoparticle amount. The possible mechanism of antibacterial effect of Mg(OH)2 nanoparticles is discussed.

Mechanical Properties and Tensile Failure Analysis of Novel Bio-absorbable Mg-Zn-Cu and Mg-Zn-Se Alloys for Endovascular Applications

PubMed Central

Persaud-Sharma, Dharam; Budiansky, Noah; McGoron, Anthony J.

2013-01-01

In this paper, the mechanical properties and tensile failure mechanism of two novel bio-absorbable as-cast Mg-Zn-Se and Mg-Zn-Cu alloys for endovascular medical applications are characterized. Alloys were manufactured using an ARC melting process and tested as-cast with compositions of Mg-Zn-Se and Mg-Zn-Cu, being 98/1/1 wt.% respectively. Nanoindentation testing conducted at room temperature was used to characterize the elastic modulus (E) and surface hardness (H) for both the bare alloys and the air formed oxide layer. As compared to currently available shape memory alloys and degradable as-cast alloys, these experimental alloys possess superior as-cast mechanical properties that can increase their biocompatibility, degradation kinetics, and the potential for medical device creation. PMID:23543822

Single-Dose and Multiple-Dose Pharmacokinetics of Nicotine 6 mg Gum.

PubMed

Hansson, Anna; Rasmussen, Thomas; Kraiczi, Holger

2017-04-01

Under-dosing is a recognized problem with current nicotine replacement therapy (NRT). Therefore, a new 6mg nicotine gum has been developed. To compare the nicotine uptake from the 6mg gum versus currently available NRT products, two pharmacokinetic studies were performed. In one randomized crossover study, 44 healthy adult smokers received single doses of 6, 4, and 2mg nicotine gum, and 4mg nicotine lozenge on separate occasions. In a separate randomized crossover multiple-dose study over 11 hours, 50 healthy adult smokers received one 6mg gum every hour and 90 minutes, respectively, one 4mg gum every hour, and one 4mg lozenge every hour. In both studies, blood samples were collected over 12 hours to determine single-dose and multiple-dose pharmacokinetic variables. In the single-dose study, the amount of nicotine released from the 2, 4, and 6mg gums (1.44, 3.36, and 4.94mg) as well as the resulting maximum concentration and area under the curve (5.9, 10.1, and 13.8ng/mL, and 17.1, 30.7, 46.2ng/mL × h, respectively) increased with dose. The maximum concentration and area under the curve of the 6mg gum were 44% and 30% greater, respectively, than those for 4mg lozenge. Upon hourly administration, the steady-state average plasma nicotine concentration with 6mg gum (37.4ng/mL) was significantly higher than those for 4mg lozenge (28.3ng/mL) and 4mg gum (27.1ng/mL). Nicotine delivery via the 6mg gum results in higher plasma nicotine concentrations after a single dose and at steady state than with currently available oral NRT. Under-dosing is a recognized problem with current NRT. Therefore, a new 6mg nicotine gum has been developed. Our studies show that upon single-dose and multiple-dose administration, the 6mg gum releases and delivers more nicotine to the systemic circulation than 2mg gum, 4mg gum, and 4mg lozenge. Thus, each 6mg nicotine gum provides a higher degree of nicotine substitution and/or lasts for a longer period of time than currently available nicotine

[Not Available].

PubMed

Fernández Castillo, Rafael; Cañadas de la Fuente, Gustavo R; Cañadas de la Fuente, Guillermo A; De la Fuente Solana, Emilia Inmaculada; Esteban de la Rosa, Rafael José; Bravo Soto, Juan

2016-07-19

Introducción: la obesidad y el sobrepeso presentan efectos adversos sobre la salud, lo que contribuye a la aparición de enfermedades metabólicas y cardiovasculares que ponen en peligro la integridad del injerto.Objetivo: investigar la influencia del IMC pretrasplante renal sobre el funcionamiento del injerto renal al año de trasplante mediante el estudio de cuatro métodos distintos de medir la filtración glomerular.Material y métodos: en este trabajo se ha seguido a 1.336 pacientes de ambos sexos trasplantados renales; se les realizaron mediciones pretrasplante y postrasplante de parámetros bioquímicos, mediciones antropométricas y función renal mediante medidas de filtrado glomerular.Resultados: a mayor índice de masa corporal pretrasplante se produce una disminución del filtrado glomerular medido por cuatro métodos distintos, así como mayor porcentaje de rechazos.Conclusiones: un IMC elevado pretrasplante contribuye a la disfunción del injerto, a una disminución del filtrado glomerular y a complicaciones del injerto en el primer año postrasplante.

Dexketoprofen/tramadol 25 mg/75 mg: randomised double-blind trial in moderate-to-severe acute pain after abdominal hysterectomy.

PubMed

Moore, R A; McQuay, H J; Tomaszewski, J; Raba, G; Tutunaru, D; Lietuviete, N; Galad, J; Hagymasy, L; Melka, D; Kotarski, J; Rechberger, T; Fülesdi, B; Nizzardo, A; Guerrero-Bayón, C; Cuadripani, S; Pizà-Vallespir, B; Bertolotti, M

2016-01-22

Dexketoprofen trometamol plus tramadol hydrochloride is a new oral combination of two analgesics, which have different mechanisms of action for the treatment of moderate to severe acute pain. Randomised, double-blind, parallel, placebo and active-controlled, single and multiple-dose study to evaluate the analgesic efficacy and safety of dexketoprofen/tramadol 25 mg/75 mg in comparison with the single agents (dexketoprofen 25 mg and tramadol 100 mg) in moderate to severe acute pain after abdominal hysterectomy. Patients received seven consecutive doses of study drug within a 3-day period, each dose separated by an 8-hour interval. A placebo arm was included during the single-dose phase to validate the pain model. Efficacy assessments included pain intensity, pain relief, patient global evaluation and use of rescue medication. The primary endpoint was the mean sum of pain intensity differences over the first 8 h (SPID8). The efficacy analysis included 606 patients, with a mean age of 48 years (range 25-73). The study results confirmed the superiority of the combination over the single agents in terms of the primary endpoint (p <0.001). Secondary endpoints were generally supportive of the superiority of the combination for both single and multiple doses. Most common adverse drug reactions (ADRs) were nausea (4.6%) and vomiting (2.3%). All other ADRs were experienced by less than 2% of patients. The study results provided robust evidence of the superiority of dexketoprofen/tramadol 25 mg/75 mg over the single components in the management of moderate to severe acute pain, as confirmed by the single-dose efficacy, repeated-dose sustained effect and good safety profile observed. EU Clinical Trials Register (EudraCT number 2012-004545-32, registered 04 October 2012); Clinicaltrials.gov ( NCT01904149, registered 17 July 2013).

Clinical Evaluation of the Oral Contraceptive Use of Norethindrone 5 mg. plus Mestranol 0.075 mg

PubMed Central

Board, John A.

1965-01-01

Norethindrone 5 mg. plus mestranol 0.075 mg., taken daily from menstrual cycle day five through day 24, was used as an oral contraceptive agent in 1248 cycles by 132 clinic patients. One hundred and one patients used this method for six months or more. There were no unplanned pregnancies. Breakthrough bleeding occurred in 38 cycles (3.0% of all cycles). In 25% of 1201 cycles the duration of menstrual flow was shorter than that which had been considered usual for the individual patient involved, and the most common weight change was a gain of 6 to 10 lb. PMID:14272499

Kurt Gödels Brünner Verwandte

NASA Astrophysics Data System (ADS)

Müller, Dora

2007-11-01

The author of this memoir Dora Müller (born 1920) belongs - as well as Kurt Gödel-to the German minority playing an important role in the past life of Brno. The marriage of his son included her among the Gödels collaterals. She was chemist, but also pianist, historician, participant of antinacist movement and iniciator of Czech-German understanding after war. Following her personal experiences, remembrances of Gödels relatives and documental materials, she evokes the atmosphere of broader family milieu of Kurt Gödel.

Comparison of the efficacy of rabeprazole 10 mg and omeprazole 20 mg for the healing rapidity of peptic ulcer diseases.

PubMed

Ji, Sangwon; Kim, Hyun Soo; Kim, Jae Woo; Jee, Myeong Kwan; Park, Kwang Wha; Uh, Young; Lee, Dong Ki; Song, Jae Suk; Baik, Soon Koo; Kwon, Sang Ok

2006-09-01

Rabeprazole has been known to inhibit H(+)/K(+)-ATPase more rapidly than omeprazole, the prototype proton pump inhibitor (PPI). The aim of this study was to demonstrate equivalence between low-dose rabeprazole 10 mg and omeprazole 20 mg for the healing rapidity of active peptic ulcer and for improvement of symptoms. Also, the effect of CYP2C19 genotypes on ulcer healing rapidity was investigated. A total of 112 patients with active peptic ulcer were randomized to receive either rabeprazole 10 mg q.d. or omeprazole 20 mg q.d. for 6 weeks. The remaining ratios (%) and complete healing of the ulcer were determined by endoscopy at 1 week and 6 weeks of treatment. The severity of ulcer pain was also investigated during treatment. CYP2C19 genotype was determined by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The remaining ratio of peptic ulcers after 1 week and the complete healing rate after 6 weeks in the rabeprazole versus omeprazole group were 45.5% versus 50.3% (P = 0.475) and 80.6% versus 87.0% (P = 0.423), respectively. CYP2C19 genotypes had no effect on the remaining ratio of peptic ulcers after 1 week and the healing rate of peptic ulcers after 6 weeks in both groups. The proportions of patients with symptom improvement or resolution were comparable between the two groups. Low-dose rabeprazole 10 mg has a similar efficacy for the healing rapidity of active peptic ulcer disease and symptom improvement compared with standard-dose omeprazole 20 mg.

Highly exothermic and superhydrophobic Mg/fluorocarbon core/shell nanoenergetic arrays.

PubMed

Zhou, Xiang; Xu, Daguo; Yang, Guangcheng; Zhang, Qiaobao; Shen, Jinpeng; Lu, Jian; Zhang, Kaili

2014-07-09

Mg/fluorocarbon core/shell nanoenergetic arrays are prepared onto silicon substrate, with Mg nanorods as the core and fluorocarbon as the shell. Mg nanorods are deposited by the glancing angle deposition technique, and the fluorocarbon layer is then prepared as a shell to encase the Mg nanorods by the magnetron sputtering deposition process. Scanning electron microscopy and transmission electron microscopy show the core/shell structure of the Mg/fluorocarbon arrays. X-ray energy-dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy are used to characterize the structural composition of the Mg/fluorocarbon. It is found that the as-prepared fluorocarbon layer consists of shorter molecular chains compared to that of bulk polytetrafluoroethylene, which is proven beneficial to the low onset reaction temperature of Mg/fluorocarbon. Water contact angle test demonstrates the superhydrophobicity of the Mg/fluorocarbon arrays, and a static contact angle as high as 162° is achieved. Thermal analysis shows that the Mg/fluorocarbon material exhibits a very low onset reaction temperature of about 270 °C as well as an ultrahigh heat of reaction approaching 9 kJ/g. A preliminary combustion test reveals rapid combustion wave propagation, and a convective mechanism is adopted to explain the combustion behaviors.

Luminescence properties of ZnxMg1-xSe layers

NASA Astrophysics Data System (ADS)

Bala, Waclaw; Firszt, Franciszek; Dzik, Janusz; Gapinski, Adam; Glowacki, Grzegorz

1995-10-01

This work deals with the study of luminescence properties of ZnxMg1-xSe layers prepared by different methods. ZnxMg1-xSe mixed crystal layers were obtained by: (a) thermal diffusion of Mg metal in the temperature range 1050 K - 1200 K into ZnSe single crystal grown by Bridgman method, and (b) epitaxial growth on (001) GaAs and (111) ZnTe substrates by MBE using elemental Zn, Se and Mg sources. The luminescence spectra of ZnxMg1-xSe layers grown on (001) GaAs and (111) ZnTe substrates are dominated by narrow blue and violet emission bands with maxima positioned at about 3.05 - 3.28 eV, 2.88 - 3.04 eV, and 2.81 - 2.705 eV.

Room temperature ferromagnetism in Mg-doped ZnO nanoparticles

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

Singh, Jaspal, E-mail: jaspal0314@gmail.com; Vashihth, A.; Gill, Pritampal Singh

Zn{sub 1-x}Mg{sub x}O (x = 0, 0,10) nanoparticles were successfully synthesized using sol-gel method. X-ray diffraction (XRD) confirms that the synthesized nanoparticles possess wurtzite phase having hexagonal structure. Morphological analysis was carried out using transmission electron microscopy (TEM) which depicts the spherical morphology of ZnO nanoparticles. Energy dispersive spectroscopy (EDS) showed the presence of Mg in ZnO nanoparticles. Electron spin resonance (ESR) signal was found to be decreasing with increasing of Mg-doping concentration. The room temperature ferromagnetism was observed in undoped and Mg-doped ZnO nanoparticles. The increase of Mg-doping concentration resulted in decrease of saturation magnetization value which could bemore » attributed to decrease of oxygen vacancies present in host nanoparticles.« less

High-performance MgB2 superconducting wires for use under liquid-helium-free conditions fabricated using an internal Mg diffusion process

NASA Astrophysics Data System (ADS)

Ye, ShuJun; Song, Minghui; Matsumoto, Akiyoshi; Togano, Kazumasa; Takeguchi, Masaki; Ohmura, Takahito; Kumakura, Hiroaki

2013-12-01

MgB2 has a superconducting transition temperature (Tc) of 39 K, which is much higher than that for practical metallic superconductors. Thus, it is hoped that MgB2 can not only replace metallic superconductors, but can be used under liquid-helium-free conditions, for example, at temperatures of 10-20 K that can easily be achieved using cryocooling systems. However, to date, the reported critical current density (Jc) for MgB2 wires is not high enough for large-scale applications in liquid-helium-free conditions. In the present study, successful fabrication of high-performance MgB2 superconducting wires was carried out using an internal Mg diffusion (IMD) process, involving a p-dimethylbenzene (C8H10) pre-treatment of carbon-coated B powder with nanometer-sized particles. The resulting wires exhibited the highest ever Jc of 1.2 × 105 A cm-2 at 4.2 K and 10 T, and an engineering critical current density (Je) of about 1 × 104 A cm-2. Not only in 4.2 K, but also in 10 K, the Jc values for the wires fabricated in the present study are in fact higher than that for Nb-Ti wires at 4.2 K for the magnetic fields at which the measurements were carried out. At 20 K and 5 T, the Jc and Je were about 7.6 × 105 A cm-2 and 5.3 × 103 A cm-2, respectively, which are the highest values reported for MgB2 wires to date. The results of a detailed microstructural analysis suggested that the main reason for the superior electrical performance was the high density of the MgB2 layer rather than just the small grain size, and that the critical current could be further increased by suitable control of the microstructure. These high-performance IMD-processed MgB2 wires are thus promising superconductors for applications such as magnetic resonance imaging and maglev trains that can operate under liquid-helium-free conditions.

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

NASA Astrophysics Data System (ADS)

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

2015-04-01

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

The creatine kinase response to eccentric exercise with atorvastatin 10 mg or 80 mg.

PubMed

Kearns, Amy K; Bilbie, Cherie L; Clarkson, Priscilla M; White, C Michael; Sewright, Kim A; O'Fallon, Kevin S; Gadarla, Mamatha; Thompson, Paul D

2008-09-01

Hydroxy-methyl-glutaryl co-enzyme A (HMG-CoA) reductase inhibitors or statins are well tolerated by most patients, but can produce a variety of skeletal muscle problems including myalgia, creatine kinase (CK) elevations and clinically important rhabdomyolysis. We have previously demonstrated that the CK response to downhill walking is greater in statin compared to placebo treated subjects. This study examined the CK response to downhill walking in subjects treated with low and high dose of atorvastatin. 79 subjects with LDL cholesterol>100mg/dL were randomly assigned to atorvastatin 10mg (N=42) or 80 mg (N=37) for 5 weeks. Subjects performed a downhill walking exercise during the fifth week of treatment. Leg muscle soreness, plasma CK and CK-MB levels were measured daily for 4 days following the exercise. CK, CK-MB and muscle soreness increased above pre-exercise levels in all subjects after the exercise. There were no differences in the CK, CK-MB or soreness response between the high and low dose treatment groups at any time point. The downhill walking model of muscle injury does not distinguish between high and low dose atorvastatin therapy either because this test is insensitive to differences among statin doses or because there is no difference in muscle injury between these two drug doses with this statin. Clinicians should be aware, however, that exercise can increase CK levels with even low dose statin therapy.

Vacancy Defects as Compensating Centers in Mg-Doped GaN

NASA Astrophysics Data System (ADS)

Hautakangas, S.; Oila, J.; Alatalo, M.; Saarinen, K.; Liszkay, L.; Seghier, D.; Gislason, H. P.

2003-04-01

We apply positron annihilation spectroscopy to identify VN-MgGa complexes as native defects in Mg-doped GaN. These defects dissociate in postgrowth annealings at 500 800 °C. We conclude that VN-MgGa complexes contribute to the electrical compensation of Mg as well as the activation of p-type conductivity in the annealing. The observation of VN-MgGa complexes confirms that vacancy defects in either the N or Ga sublattice are abundant in GaN at any position of the Fermi level during growth, as predicted previously by theoretical calculations.

The novel c.247_249delTTC (p.F83del) GJB2 mutation in a family with prelingual sensorineural deafness.

PubMed

Petersen, Michael B; Grigoriadou, Maria; Koutroumpe, Maria; Kokotas, Haris

2012-07-01

Non-syndromic hearing loss is one of the most common hereditary determined diseases in human, and the disease is a genetically heterogeneous disorder. Mutations in the GJB2 gene, encoding connexin 26 (Cx26), are a major cause of non-syndromic recessive hearing impairment in many countries and are largely dependent on ethnic groups. Due to the high frequency of the c.35delG GJB2 mutation in the Greek population, we have previously suggested that Greek patients with sensorineural, non-syndromic deafness should be tested for the c.35delG mutation and the coding region of the GJB2 gene should be sequenced in c.35delG heterozygotes. Here we present on the clinical and molecular genetic evaluation of a family suffering from prelingual, sensorineural, non-syndromic deafness. A novel c.247_249delTTC (p.F83del) GJB2 mutation was detected in compound heterozygosity with the c.35delG GJB2 mutation in the proband and was later confirmed in the father, while the mother was homozygous for the c.35delG GJB2 mutation. We conclude that compound heterozygosity of the novel c.247_249delTTC (p.F83del) and the c.35delG mutations in the GJB2 gene was the cause of deafness in the proband and his father. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Improved Mg-based alloys for hydrogen storage

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

Sapru, K.; Ming, L.; Stetson, N.T.

1998-08-01

The overall objective of this on-going work is to develop low temperature alloys capable of reversibly storing at least 3 wt.% hydrogen, allowing greater than for 2 wt.% at the system level which is required by most applications. Surface modification of Mg can be used to improve its H-sorption kinetics. The authors show here that the same Mg-transition metal-based multi-component alloy when prepared by melt-spinning results in a more homogeneous materials with a higher plateau pressure as compared to preparing the material by mechanical grinding. They have also shown that mechanically alloyed Mg{sub 50}Al{sub 45}Zn{sub 5} results in a samplemore » having a higher plateau pressure.« less

Behaviour of Fe4O5-Mg2Fe2O5 solid solutions and their relation to coexisting Mg-Fe silicates and oxide phases

NASA Astrophysics Data System (ADS)

Uenver-Thiele, Laura; Woodland, Alan B.; Miyajima, Nobuyoshi; Ballaran, Tiziana Boffa; Frost, Daniel J.

2018-03-01

Experiments at high pressures and temperatures were carried out (1) to investigate the crystal-chemical behaviour of Fe4O5-Mg2Fe2O5 solid solutions and (2) to explore the phase relations involving (Mg,Fe)2Fe2O5 (denoted as O5-phase) and Mg-Fe silicates. Multi-anvil experiments were performed at 11-20 GPa and 1100-1600 °C using different starting compositions including two that were Si-bearing. In Si-free experiments the O5-phase coexists with Fe2O3, hp-(Mg,Fe)Fe2O4, (Mg,Fe)3Fe4O9 or an unquenchable phase of different stoichiometry. Si-bearing experiments yielded phase assemblages consisting of the O5-phase together with olivine, wadsleyite or ringwoodite, majoritic garnet or Fe3+-bearing phase B. However, (Mg,Fe)2Fe2O5 does not incorporate Si. Electron microprobe analyses revealed that phase B incorporates significant amounts of Fe2+ and Fe3+ (at least 1.0 cations Fe per formula unit). Fe-L2,3-edge energy-loss near-edge structure spectra confirm the presence of ferric iron [Fe3+/Fetot = 0.41(4)] and indicate substitution according to the following charge-balanced exchange: [4]Si4+ + [6]Mg2+ = 2Fe3+. The ability to accommodate Fe2+ and Fe3+ makes this potential "water-storing" mineral interesting since such substitutions should enlarge its stability field. The thermodynamic properties of Mg2Fe2O5 have been refined, yielding H°1bar,298 = - 1981.5 kJ mol- 1. Solid solution is complete across the Fe4O5-Mg2Fe2O5 binary. Molar volume decreases essentially linearly with increasing Mg content, consistent with ideal mixing behaviour. The partitioning of Mg and Fe2+ with silicates indicates that (Mg,Fe)2Fe2O5 has a strong preference for Fe2+. Modelling of partitioning with olivine is consistent with the O5-phase exhibiting ideal mixing behaviour. Mg-Fe2+ partitioning between (Mg,Fe)2Fe2O5 and ringwoodite or wadsleyite is influenced by the presence of Fe3+ and OH incorporation in the silicate phases.

Low free drug concentration prevents inhibition of F508del CFTR functional expression by the potentiator VX-770 (ivacaftor).

PubMed

Matthes, Elizabeth; Goepp, Julie; Carlile, Graeme W; Luo, Yishan; Dejgaard, Kurt; Billet, Arnaud; Robert, Renaud; Thomas, David Y; Hanrahan, John W

2016-02-01

The most common cystic fibrosis (CF) mutation F508del inhibits the gating and surface expression of CFTR, a plasma membrane anion channel. Optimal pharmacotherapies will probably require both a 'potentiator' to increase channel open probability and a 'corrector' that improves folding and trafficking of the mutant protein and its stability at the cell surface. Interaction between CF drugs has been reported but remains poorly understood. CF bronchial epithelial cells were exposed to the corrector VX-809 (lumacaftor) and potentiator VX-770 (ivacaftor) individually or in combination. Functional expression of CFTR was assayed as the forskolin-stimulated short-circuit current (Isc ) across airway epithelial monolayers expressing F508del CFTR. The potentiated Isc response during forskolin stimulation was increased sixfold after pretreatment with VX-809 alone and reached ~11% that measured across non-CF monolayers. VX-770 (100 nM) and genistein (50 μM) caused similar levels of potentiation, which were not additive and were abolished by the CFTR inhibitor CFTRinh -172. The unbound fraction of VX-770 in plasma was 0.13 ± 0.04%, which together with previous measurements in patients given 250 mg p.o. twice daily, suggests a peak free plasma concentration of 1.5-8.5 nM. Chronic exposure to high VX-770 concentrations (>1 μM) inhibited functional correction by VX-809 but not in the presence of physiological protein levels (20-40 mg·mL(-1) ). Chronic exposure to a low concentration of VX-770 (100 nM) together with VX-809 (1 μM) also did not reduce the forskolin-stimulated Isc , relative to cells chronically exposed to VX-809 alone, provided it was assayed acutely using the same, clinically relevant concentration of potentiator. Chronic exposure to clinically relevant concentrations of VX-770 did not reduce F508del CFTR function. Therapeutic benefit of VX-770 + VX-809 (Orkambi) is probably limited by the efficacy of VX-809 rather than by inhibition by VX-770. © 2015

Electronic structure of scandium-doped MgB2

NASA Astrophysics Data System (ADS)

de La Peña, Omar; Agrestini, Stefano

2005-03-01

Recently has been reported the synthesis of a new superconducting alloy based on MgB2, where Mg is partially substituted with Sc. In order to analyze the effect of Sc doping on the structural and superconducting properties of Mg1-xScxB2, we have performed a detailed study of the electronic structure for this new diboride. The calculations have been done using the first-principles LAPW method, within the supercell approach for modeling the doping. In this work we report results for the electronic band structure, Fermi surface, and density of states. The effect of the Sc-d orbitals on the structural and electronic properties of Mg1-xScxB2 is analyzed. Increasing the Sc concentration (x) the σ-band is gradually filled, because Sc have one valence electron more than Mg. Interestingly, the analysis of the band structure shows that even for ScB2 the top of the σ-band remain above the Fermi level, nevertheless the σ-band presents high dispersion and has an important contribution of d states. In this way, in addition to the band filling effect, Sc doping gradually reduces the two-dimensional character of the σ- band in Mg1-xScxB2 as a result of increasing the sp(B)-d(Sc) hybridization. This research was partially supported by Consejo Nacional de Ciencia y Tecnolog'ia (CONACYT, M'exico) under Grant. No. 43830-F

Magnesium phthalocyanine(MgPc) thin films as nanomaterials

NASA Astrophysics Data System (ADS)

Puri, Munish; Bedi, R. K.; Prakash, G. V.

2006-05-01

MgPc is a promising candidate for photovoltaic applications. It can be easily synthesized and is non-toxic to the envioronment. It is a self assembly molecule developed from deep-blue-green pigment. It exhibits a characteristic structural self organization which is reflected in an efficient energy migration in the form of extinction transport. MgPc relates to the similarity with chlorophyll. In the present work thin films of MgPc have been prepared on glass substrate under strict vacuum conditions(10 Â6 torr), thickness of few nanometers. Absorption spectra in Visible and IR regions have been observed which is good for fabrication of Photovoltaic cells and Nanostructures for Photodynamic Cancer Therapy. Appreciable amount of cytotoxicity can be observed while using MgPc as photosensitizers which is a promising PDT agent. The films thus prepared have been studied for their electrical and optical characterizations. Investigations have been made from different stacking positions of molecular MgPc thin films for studying their self-assembling nature that can be useful for their applications as Molecular-Recognition in Drug delivery and sensors which is one of the key features of Nanotechnology.

Safety and efficacy of levofloxacin 750 mg for 2 weeks or 3 weeks compared with levofloxacin 500 mg for 4 weeks in treating chronic bacterial prostatitis.

PubMed

Paglia, Margaret; Peterson, Janet; Fisher, Alan C; Qin, Zhihai; Nicholson, Susan C; Kahn, James B

2010-06-01

To compare the safety and efficacy of levofloxacin 750 mg QD for 2 weeks or levofloxacin 750 mg QD for 3 weeks to levofloxacin 500 mg QD for 4 weeks in treating chronic bacterial prostatitis (CBP). This was a randomized, multicenter, double-blind, noninferiority study. The primary efficacy end point was investigator assessment of clinical success in the modified intent-to-treat (mITT) population at post-therapy. National Institutes of Health-Chronic Prostatitis Symptom Index (NIH-CPSI) scores were utilized to evaluate subject-reported responses post-therapy. A total of 241 subjects were enrolled. At post-therapy (test of cure [TOC]), clinical success rates for levofloxacin-treated subjects (750 mg QD for 3 weeks [64.9%, 48/74]) were noninferior to 500 mg QD for 4 weeks (69.3%, 52/75: 95% CI, -19.5%, 10.6%). Success rates with levofloxacin 750 mg QD for 2 weeks (63.0%, 46/73) were not noninferior to therapy with levofloxacin 500 mg QD for 4 weeks (95% CI, -21.5%, 8.9%) at TOC. At 3 and 6 months post-therapy, clinical success rates were clinically higher for the 500-mg, 4-week treatment group, and statistical analysis demonstrated both groups were not noninferior to standard therapy with levofloxacin 500 mg (95% CI, -32.5%, -0.6% for both 750-mg groups at 6 months). NIH-CPSI scores showed similar trends. Overall, adverse event (AE) rates were similar for the three treatment groups; however, discontinuation of therapy due to AEs was higher with the 750-mg dose (p = 0.02, and p = 0.13 for 750 mg, 2 weeks and 750 mg, 3 weeks versus 500 mg for 4 weeks, respectively). The main limitation of this study was that no bacterial cultures were required. Higher doses for shorter durations were determined to be no worse than standard therapy with levofloxacin 500 mg for a longer duration at the TOC visit. However, at the 6-month follow-up visit, the levofloxacin 750-mg dose administered for either 2 weeks or 3 weeks was inferior to the standard therapy, suggesting that a longer

Phosphorus recovery from biogas fermentation liquid by Ca-Mg loaded biochar.

PubMed

Fang, Ci; Zhang, Tao; Li, Ping; Jiang, Rongfeng; Wu, Shubiao; Nie, Haiyu; Wang, Yingcai

2015-03-01

Shortage in phosphorus (P) resources and P wastewater pollution is considered as a serious problem worldwide. The application of modified biochar for P recovery from wastewater and reuse of recovered P as agricultural fertilizer is a preferred process. This work aims to develop a calcium and magnesium loaded biochar (Ca-Mg/biochar) application for P recovery from biogas fermentation liquid. The physico-chemical characterization, adsorption efficiency, adsorption selectivity, and postsorption availability of Ca-Mg/biochar were investigated. The synthesized Ca-Mg/biochar was rich in organic functional groups and in CaO and MgO nanoparticles. With the increase in synthesis temperature, the yield decreased, C content increased, H content decreased, N content remained the same basically, and BET surface area increased. The P adsorption of Ca-Mg/biochar could be accelerated by nano-CaO and nano-MgO particles and reached equilibrium after 360min. The process was endothermic, spontaneous, and showed an increase in the disorder of the solid-liquid interface. Moreover, it could be fitted by the Freundlich model. The maximum P adsorption amounts were 294.22, 315.33, and 326.63mg/g. The P adsorption selectivity of Ca-Mg/biochar could not be significantly influenced by the typical pH level of biogas fermentation liquid. The nano-CaO and nano-MgO particles of Ca-Mg/biochar could reduce the negative interaction effects of coexisting ions. The P releasing amounts of postsorption Ca-Mg/biochar were in the order of Ca-Mg/B600>Ca-Mg/B450>Ca-Mg/B300. Results revealed that postsorption Ca-Mg/biochar can continually release P and is more suitable for an acid environment. Copyright © 2014. Published by Elsevier B.V.

Improving properties of Mg with Al–Cu additions

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

Rashad, Muhammad, E-mail: rashadphy87@gmail.com; National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044; Pan, Fusheng, E-mail: fspan@cqu.edu.cn

The present work reports improvement in tensile properties of the Mg matrix reinforced with micron-sized copper–aluminum particulate hybrids. The Al–Cu particulate hybrids were incorporated into the Mg matrix through powder metallurgy method. The synthesized alloys exhibited homogeneously dispersed Mg{sub 2}Cu particles in the matrix, therefore leading to a 110% increase in yield strength (221 MPa) and a 72% enhancement in ultimate tensile strength (284 MPa) by addition of 1.0 wt.%Al–0.6 wt.%Cu particle hybrids. Optical microscopy, scanning election microscopy, transmission electron microscopy and X-ray diffraction were used to investigate the microstructure and intermetallic phases of the synthesized alloys. - Highlights: •more » Mg matrix is reinforced with Al–Cu particulate hybrids. • Powder metallurgic method is used to fabricate the alloys. • Tensile strength and ductility were increased simultaneously.« less

Crystal structures of the new ternary stannides La3Mg4-xSn2+x and LaMg3-xSn2

NASA Astrophysics Data System (ADS)

Solokha, P.; De Negri, S.; Minetti, R.; Proserpio, D. M.; Saccone, A.

2016-01-01

Synthesis and structural characterization of the two new lanthanum-magnesium-stannides La3Mg4-xSn2+x (0.12≤x≤0.40) and LaMg3-xSn2 (0.33≤x≤0.78) are reported. The crystal structures of these intermetallics were determined by single crystal X-ray diffraction analysis and confirmed by Rietveld refinement of powder X-ray diffraction patterns of the corresponding samples. The La3Mg4-xSn2+x phase crystallizes in the hexagonal Zr3Cu4Si2 structure type (P6bar2m, hP9, Z=3, x=0.12(1), a=7.7974(7), c=4.8384(4) Å), which represents an ordered derivative of the hP9-ZrNiAl prototype, ubiquitous among equiatomic intermetallics. The LaMg3-xSn2 phase is the second representative of the trigonal LaMg3-xGe2 type, which is a superstructure of the LaLi3Sb2 structure type (P3bar1c, hP34-0.12, Z=6, x=0.35(1), a=8.3222(9), c=14.9546(16) Å). The scheme describing the symmetry reduction/coloring with respect to the parent type is reported here with the purpose to discuss the LaMg3-xSn2 off-stoichiometry from the geometrical point of view. Structural relationships between the La-Mg-Sn ternary phases, including the already known equiatomic LaMgSn compound (oP12-TiNiSi), are presented in the framework of the AlB2-related compounds family and discussed with the aid of group-subgroup relations in the Bärnighausen formalism.

Estudio del CH interestelar

NASA Astrophysics Data System (ADS)

Olano, C.; Lemarchand, G.; Sanz, A. J.; Bava, J. A.

El objetivo principal de este proyecto consiste en el estudio de la distribución y abundancia del CH en nubes interestelares a través de la observación de las líneas hiperfinas del CH en 3,3 GHz. El CH es una molécula de amplia distribución en el espacio interestelar y una de las pocas especies que han sido observadas tanto con técnicas de radio como ópticas. Desde el punto de vista tecnológico se ha desarrollado un cabezal de receptor que permitirá la realización de observaciones polarimétricas en la frecuencia de 3,3 GHz, con una temperatura del sistema de 60 K y un ancho de banda de 140 MHz, y que será instalado en el foco primario de la antena parabólica del IAR. El cabezal del receptor es capaz de detectar señales polarizadas, separando las componentes de polarización circular derecha e izquierda. Para tal fin el cabezal consta de dos ramas receptoras que amplificarán la señal y la trasladarán a una frecuencia más baja (frecuencia intermedia), permitiendo de esa forma un mejor transporte de la señal a la sala de control para su posterior procesamiento. El receptor además de tener características polarimétricas, podrá ser usado en el continuo y en la línea, utilizando las ventajas observacionales y de procesamiento de señal que actualmente posee el IAR.

Synthesis and structural study of Ti-rich Mg-Ti hydrides

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

Asano, Kohta; Kim, Hyunjeong; Sakaki, Kouji

2014-02-26

Mg xTi 1-x (x = 0.15, 0.25, 0.35) alloys were synthesized by means of ball milling. Under a hydrogen pressure of 8 MPa at 423 K these Mg–Ti alloys formed a hydride phase with a face centered cubic (FCC) structure. The hydride for x = 0.25 consisted of single Mg 0.25Ti 0.75H 1.62 FCC phase but TiH 2 and MgH 2 phases were also formed in the hydrides for x = 0.15 and 0.35, respectively. X-ray diffraction patterns and the atomic pair distribution function indicated that numbers of stacking faults were introduced. There was no sign of segregation between Mgmore » and Ti in Mg 0.25Ti 0.75H 1.62. Electronic structure of Mg 0.25Ti 0.75H 1.62 was different from those of MgH 2 and TiH 2, which was demonstrated by 1H nuclear magnetic resonance. This strongly suggested that stable Mg–Ti hydride phase was formed in the metal composition of Mg 0.25Ti 0.75 without disproportion into MgH 2 and TiH 2.« less

High-pressure phases of Mg2Si from first principles

NASA Astrophysics Data System (ADS)

Huan, Tran Doan; Tuoc, Vu Ngoc; Le, Nam Ba; Minh, Nguyen Viet; Woods, Lilia M.

2016-03-01

First-principles calculations are presented to resolve the possible pressure-dependent phases of Mg2Si . Although previous reports show that Mg2Si is characterized by the cubic antifluorite F m 3 ¯m structure at low pressures, the situation at higher pressures is less clear with many contradicting results. Here we utilize several methods to examine the stability, electron, phonon, and transport properties of this material as a function of pressure and temperature. We find that Mg2Si is thermodynamically stable at low and high pressures. Between 6 and 24 GPa, Mg2Si can transform into Mg9Si5 , a defected compound, and vice versa, without energy cost. Perhaps this result is related to the aforementioned inconsistency in the structures reported for Mg2Si within this pressure range. Focusing solely on Mg2Si , we find a new monoclinic C 2 /m structure of Mg2Si , which is stable at high pressures within thermodynamical considerations. The calculated electrical conductivity and Seebeck coefficient taking into account results from the electronic structure calculations help us understand better how transport can be affected in this material by modulating pressure and temperature.

Extraction of Mg(OH)2 from Mg silicate minerals with NaOH assisted with H2O: implications for CO2 capture from exhaust flue gas.

PubMed

Madeddu, Silvia; Priestnall, Michael; Godoy, Erik; Kumar, R Vasant; Raymahasay, Sugat; Evans, Michael; Wang, Ruofan; Manenye, Seabelo; Kinoshita, Hajime

2015-01-01

The utilisation of Mg(OH)2 to capture exhaust CO2 has been hindered by the limited availability of brucite, the Mg(OH)2 mineral in natural deposits. Our previous study demonstrated that Mg(OH)2 can be obtained from dunite, an ultramafic rock composed of Mg silicate minerals, in highly concentrated NaOH aqueous systems. However, the large quantity of NaOH consumed was considered an obstacle for the implementation of the technology. In the present study, Mg(OH)2 was extracted from dunite reacted in solid systems with NaOH assisted with H2O. The consumption of NaOH was reduced by 97% with respect to the NaOH aqueous systems, maintaining a comparable yield of Mg(OH)2 extraction, i.e. 64.8-66%. The capture of CO2 from a CO2-N2 gas mixture was tested at ambient conditions using a Mg(OH)2 aqueous slurry. Mg(OH)2 almost fully dissolved and reacted with dissolved CO2 by forming Mg(HCO3)2 which remained in equilibrium storing the CO2 in the aqueous solution. The CO2 balance of the process was assessed from the emissions derived from the power consumption for NaOH production and Mg(OH)2 extraction together with the CO2 captured by Mg(OH)2 derived from dunite. The process resulted as carbon neutral when dunite is reacted at 250 °C for durations of 1 and 3 hours and CO2 is captured as Mg(HCO3)2.

WIPP Magnesium Oxide (MgO) - Planned Change Request

EPA Pesticide Factsheets

On April 10, 2006, the DOE submitted a planned change request pertaining to the amount of MgO emplaced in the WIPP repository. MgO is an engineered barrier that DOE included as part of the original WIPP Certification Decision.

Clinical Acceptability Of Trimetazidine Modified-Release 80 mg Once Daily Versus Trimetazidine Modified-Release 35 mg Twice Daily In Stable Angina Pectoris.

PubMed

Pozdnyakov, Yuri M

2018-06-01

Trimetazidine (TMZ) is an anti-ischemic metabolic agent that has been shown to be efficacious in angina treatment, both in monotherapy and in combination. A new formulation of TMZ modified-release (MR) 80 mg was developed, which is to be taken once daily (od), instead of twice daily (bid) for the currently available TMZ MR 35 mg, with the aim of simplifying the medication regimen. The present study was an international, multicenter, randomized, double-blind, parallel-group phase III study with a 12-week treatment period. The safety of TMZ MR 80 mg once daily was assessed compared to TMZ MR 35 mg twice daily, in patients previously treated successfully by the latter. Emergent adverse events (EAEs), biological parameters, vital signs, 12-lead resting ECG (electrocardiogram) and Canadian Cardiovascular Society (CCS) classification were recorded. One-hundred and sixty-five patients previously diagnosed with stable angina pectoris on treatment were randomized to receive either TMZ MR 80 mg od or TMZ MR 35 mg bid. In the TMZ MR 80 mg group, fewer patients had ≥ 1 EAE (17.1 vs. 22.9% in the TMZ MR 35 mg group). Serious EAEs were reported by three patients in each group. No EAE required dose modification, withdrawal, or temporary interruption of study treatments. Vital signs, 12-lead ECG, and laboratory parameters did not change. No worsening in CCS classes was observed with either treatment. TMZ MR 80 mg od and TMZ MR 35 mg bid have similar safety profiles. This new once-daily formulation could improve patient compliance with therapy, thereby enhancing clinical benefit. ISRCTN registry, ISRCTN 84362208. Institut de Recherches Internationales Servier and Servier, Moscow, Russian Federation. Plain language summary available for this article.

Investigating the behaviour of Mg isotopes during the formation of clay minerals

NASA Astrophysics Data System (ADS)

Wimpenny, Joshua; Colla, Christopher A.; Yin, Qing-Zhu; Rustad, James R.; Casey, William H.

2014-03-01

We present elemental and isotopic data detailing how the Mg isotope system behaves in natural and experimentally synthesized clay minerals. We show that the bulk Mg isotopic composition (δ26Mg) of a set of natural illite, montmorillonite and kaolinite spans a 2‰ range, and that their isotopic composition depends strongly on a balance between the relative proportions of structural and exchangeable Mg. After acid leaching, these natural clays become relatively enriched in isotopically heavy Mg by between 0.2‰ and 1.6‰. Results of exchange experiments indicate that the Mg that has adsorbed to interlayer spaces and surface charged sites is relatively enriched in isotopically light Mg compared to the residual clay. The isotopic composition of this exchangeable Mg (-1.49‰ to -2.03‰) is characteristic of the isotopic composition of Mg found in many natural waters. Further experiments with an isotopically characterized MgCl2 solution shows that the clay minerals adsorb this exchangeable Mg with little or no isotopic fractionation, although we cannot discount the possibility that the uptake of exchangeable Mg does so with a slight preference for 24Mg. To characterize the behaviour of Mg isotopes during clay mineral formation we synthesized brucite (Mg(OH)2), which we consider to be a good analogue for the incorporation of Mg into the octahedral sheet of Mg-rich clay minerals or into the brucitic layer of clays such as chlorite. In our experiment the brucite mineral becomes enriched in the heavy isotopes of Mg while the corresponding solution is always relatively enriched in isotopically light Mg. The system reaches a steady state after 10 days with a final fractionation factor (αsolid-solution) of 1.0005 at near-neutral pH. This result is consistent with the general consensus that secondary clay minerals preferentially take up isotopically heavy Mg during their formation. However our results also show that exchangeable Mg is an important component within bulk

CsMgPO4

PubMed Central

Strutynska, Nataliya Yu.; Zatovsky, Igor V.; Baumer, Vyacheslav N.; Slobodyanik, Nikolay S.

2009-01-01

Caesium magnesium orthophosphate is built up from MgO4 and PO4 tetra­hedra (both with . m. symmetry) linked together by corners, forming a three-dimensional framework. The Cs atoms have .m. site symmetry and are located in hexa­gonal channels running along the a- and b-axis directions. PMID:21583294

Simultaneous estimation of intracellular free Mg2+ and pH by use of a new pH-dependent dissociation constant of MgATP.

PubMed

Nakayama, Shinsuke; Nomura, Hideki; Smith, Lorraine M; Clark, Joseph F

2002-06-01

In the present technical note for 31P-NMR, we used a new pH-dependent dissociation constant of MgATP, and re-estimated changes in the intracellular free Mg2+ concentration and pH from the chemical shifts of beta- and gamma-ATP during Na+-removal in smooth muscle. We confirmed the role of Na+ - Mg2+ exchange.

Electrochemical synthesis of superconductive MgB 2 from molten salts

NASA Astrophysics Data System (ADS)

Yoshii, Kenji; Abe, Hideki

2003-05-01

We have found that superconductive MgB2 can be electrochemically synthesized from molten salts. The electrolysis was performed in an Ar flow at 600 °C on fused mixtures composed of MgCl2, MgB2O4, Na2B2O4 and alkali halides such as KCl, NaCl, and LiCl. Superconductivity was observed for a wide variety of electrolytes. It was also found that the magnetic and electrical transport properties are the most improved for samples prepared from MgCl2-NaCl-KCl-MgB2O4 electrolytes.

The Microstructure and Tensile Properties of a Newly Developed Mg-Al/Mg3Sb2 In Situ Composite in As-Cast and Extruded Conditions

NASA Astrophysics Data System (ADS)

Montajabnia, A.; Pourbahari, B.; Emamy, M.

2018-04-01

The microstructures and tensile properties of Mg-x wt%Al-y wt%Sb alloys have been studied where x/y ratio was 1 and Sb(Al) contents were 5, 10, 15 and 20 wt%, respectively. The results indicated that by increasing Sb(Al) content, not only the crystals of primary Mg3Sb2 alter from small flake-like particles to polygonal or needle-like morphology, but also the eutectic structure changes from semi-continuous network in Mg-5Al-5Sb to continuous network in Mg-20Sb-20Al alloy. The results obtained from thermal analysis revealed different peaks related to the formation of Mg3Sb2 as primary phase and eutectic structure containing Mg17Al12 + Al3Mg2 intermetallic phases. Further results also revealed that Sb(Al) additions change the solidification performance of the material by depressing the Mg3Sb2 nucleation temperature, reducing solidification range and widening eutectic area. Tensile testing results showed that with the increase in Sb (Al) content, ultimate tensile strength (UTS) and elongation values of the alloys are decreased in as-cast condition. But, significant improvement in the UTS and elongation values of the extruded specimens was attributed to the severe fragmentation of intermetallic phases and well distributed fine particles in the matrix which provided proper obstacles for dislocation motion. It was interesting to note that the fracture behavior of intermetallic particles was found to be different, while Mg3Sb2 was ductile, intermetallic compounds in eutectic regions were brittle.

Myasthenia Gravis (MG): Medical Management

MedlinePlus

... Search MDA.org Close Myasthenia Gravis (MG) Medical Management Many drugs and procedures are available for treating ... on prepubescent children. For more about myasthenia gravis management, see: Managing Myasthenia Keeping Your Focus: Eye Care ...

Características del viento en estrellas Be derivadas del perfil Hα

NASA Astrophysics Data System (ADS)

Rohrmann, R.; Cidale, L.

El estudio teórico de perfiles Hα y su variabilidad en estrellas Be ha sido frecuentemente desarrollado en base a modelos de envolturas circunestelares inhomogéneas, donde la geometría del material es responsable de la forma del perfil dependiendo de la dirección de observación. Nosotros damos una interpretación alternativa y proponemos que la mayoría de las propiedades de esta línea tienen origen en la base de un viento estelar y de una estructura cromosférica anexa a la fotósfera. Encontramos que típicos perfiles Hα en Be, como son los llamados pole-on y winebottle, pueden ser reproducidos cualitativamente sin recurrir a la existencia de una envoltura asimétrica. Analizamos como la línea Hα permite identificar la posible estructura del viento en la región donde éste se inicia.

Tierra del Fuego, Argentina, South America

NASA Technical Reports Server (NTRS)

1991-01-01

The Mitre Peninsula is the easternmost tip of Tierra del Fuego, Argentina, (54.5S, 65.5W). Early winter snow can be seen on this south tip of the Andes Mountains. These same mountains continue underwater to Antarctica. The Strait of Magellan, separating the South American mainland from Tierra del Fuego is off the scene to the north and west, but the Strait of LeMaire, separating Tierra del Fuego from the Isla de los Estados can be seen.

Effect of Extrusion Parameters on Texture and Microstructure Evolution of Extruded Mg-1 pctMn and Mg-1 pctMn-Sr Alloys

NASA Astrophysics Data System (ADS)

Borkar, Hemant; Pekguleryuz, Mihriban

2015-01-01

Three Mg alloys Mg-1 pctMn (M1), Mg-1 pctMn-1.3 pctSr, and Mg-1 pctMn-2.1 pctSr were subjected to two different extrusion temperatures and two different extrusion speeds in lab-scale extrusion. The extrusion temperatures of 573 K and 673 K (300 °C and 400 °C) and two ram speeds of 4 and 8 mm/s were used at constant extrusion ratio of 7. M1 exhibited strong basal texture after extrusion at 673 K (400 °C) at higher speed. At 573 K (300 °C), recrystallization in all alloys takes place completely or partially by continuous dynamic recrystallization mechanism, while particle stimulated nucleation (PSN) occurs in all M1-Sr alloys at both extrusion temperatures and speeds. At 673 K (400 °C), grain boundary bulging is the only recrystallization mechanism in alloy M1, while it occurs in combination with PSN in M1-Sr alloys. The effect of texture weakening by PSN is more significant in M1-Sr alloys extruded at 573 K (400 °C). The plant extrusion trials were carried out on Mg-1 pctMn, Mg-1 pctMn-0.3 pctSr, and Mg-1 pctMn-2.1 pctSr at 623 K (350 °C) with different speeds than in lab-scale extrusion. M1 alloy exhibited strong basal texture at both speeds, while Sr additions of 0.3 and 2.1 pct promoted similar amount of texture weakening.

Comparison of the adverse event profiles of levofloxacin 500 mg and 750 mg in clinical trials for the treatment of respiratory infections.

PubMed

Khashab, Mohammed M; Xiang, Jim; Kahn, James B

2006-10-01

To compare safety data with levofloxacin 500 mg and 750 mg from clinical trials for the treatment of respiratory infections. We compared adverse event data for levofloxacin 500 mg and 750 mg from clinical trials in acute bacterial sinusitis, acute bacterial exacerbation of chronic bronchitis, and community-acquired pneumonia. Adverse events occurring after the initiation of therapy were classified as treatment-emergent adverse events (TEAE); drug-related adverse events (DRAE) were TEAE assessed by the clinical investigator as definitely/very likely or probably related to levofloxacin therapy. Overall, the safety profile of the two doses was similar but not identical. TEAE occurred in 49.0% (1601/3268) of those treated with 500 mg and in 45.5% (519/1141) of those treated with 750 mg (p = 0.042); the corresponding rates of DRAE were 7.6% (248/3268) and 8.0% (91/1141) (p = 0.699). There was no statistically significant difference in terms of overall TEAE and DRAE rates within each of the three infectious conditions, but there were in specific events, all of which are expected with levofloxacin therapy. The limitations of this analysis include that it utilized a subset of available safety data, that it includes data only from clinical trials, and that we report primarily on events occurring in > or = 2% of patients. Given similar adverse event profiles and the advantages of higher dose therapy, including shorter courses of therapy and potential impact on preventing resistance, clinicians should consider utilizing the 750 mg dose of levofloxacin when choosing between dosage strengths for treatment of indicated infections.

Hydrogen incorporation in high hole density GaN:Mg

NASA Astrophysics Data System (ADS)

Zvanut, M. E.; Uprety, Y.; Dashdorj, J.; Moseley, M.; Doolittle, W. Alan

2011-03-01

We investigate hydrogen passivation in heavily doped p-type GaN using electron paramagnetic resonance (EPR) spectroscopy. Samples include both conventionally grown GaN (1019 cm-3 Mg, 1017 cm-3 holes) and films grown by metal modulation epitaxy (MME), which yielded higher Mg (1- 4 x 1020 cm-3) and hole (1- 40 x 1018 cm-3) densities than found in conventionally grown GaN. The Mg acceptor signal is monitored throughout 30 minute annealing steps in N2 :H2 (92%:7%)) and subsequently pure N2 . N2 :H2 heat treatments of the lower hole density films begin to reduce the Mg EPR intensity at 750 o C, but quench the signal in high hole density films at 600 o C. Revival of the signal by subsequent N2 annealing occurs at 800 o C for the low hole density material and 600 o C in MME GaN. The present work highlights chemical differences between heavily Mg doped and lower doped films; however, it is unclear whether the difference is due to changes in hydrogen-Mg complex formation or hydrogen diffusion. The work at UAB is supported by the NSF.

Investigation of Al Coated Mg for Biomedical Applications

NASA Astrophysics Data System (ADS)

Elmrabet, Nabila; Roe, Martin; Neate, Nigel; Grant, David M.; Brown, Paul D.

The corrosion resistant properties of 1-2 μm thick Al coatings deposited by radio frequency magnetron sputtering on polished Mg surfaces, within Ar and Ar/H2 environments, have been appraised. The coatings were heat-treated at 300°C for 5 h to induce the formation of bioinert Al2O3, and samples were corroded within phosphate buffered saline solution at 37°C to mimic the biological environment. Both the as-deposited and heat-treated coatings were found to delay the onset of corrosion, but showed higher initial corrosion rates, once established, as compared with polished Mg surfaces. Slightly improved performance of the coatings was achieved through the addition of H2 to the system which acted to inhibit Al-Mg alloying and MgO formation. However, localized accelerated corrosion associated with substrate polishing damage emphasized the need for improved process control and coating uniformity.

Reflection polarizers for the vacuum ultraviolet using Al + MgF2 mirrors and an MgF2 plate

NASA Technical Reports Server (NTRS)

Hass, G.; Hunter, W. R.

1978-01-01

Consideration is given to the design and operation of a three-mirror reflecting polarizer where one of the reflecting surfaces is an MgF2 plate, the other surfaces are Al + MgF2 coatings, and one reflection occurs at or near the true Brewster angle. It is found that the polarizer is most efficient in the 1200-2000 A wavelength region, and that by optimum selection of the angle of incidence on the MgF2 plate, polarization values of 100 and over are yielded from 900 to 3000 A. The polarizer may be used at wavelengths as short as 500 A, although it is observed that at such wavelengths the polarization value decreases to about 10. It is noted that all reflecting polarizers operating in the vacuum ultraviolet wavelength may manifest changing characteristics as their mirrors become contaminated, and that polarization must therefore be occasionally remeasured.

Publications on Aerospace Medicine of Dr. H. J. /Von Beckh (1941 - 1987)

DTIC Science & Technology

1986-12-31

Ciclo de Conferencias sobre Medicina A~ro-espacial coincidiendo con el XVII. Congreso Internacional Astronautico. Inspeccion General de Sanidad del...Astronautica (Medical Problems of Astronautics). Sexta Con- 14 NADC 86147 -60 ferencia del Ciclo 1952 de la Sociedad Argentina Interplanetaria...del ciclo 1953 de ia Sociedad Argentina Interplanetaria. Auditorium of the Department of Physiology, Medical School. University of Buenos Aires. 20 Aug

Estudio de la influencia de la refrigeracion con aire de forma natural e inducida en el comportamiento de instalaciones fotovoltaicas

NASA Astrophysics Data System (ADS)

Mazon Hernandez, Rocio

panels are analysed to compare and select the best configuration. The presented research provides a deep knowledge of how they work as well as information and results for an improvement in future designs of building integrated photovoltaic systems. Este estudio se centra en analizar la influencia negativa de la temperatura en la produccion electrica de paneles fotovoltaicos al estar emplazados sobre cubierta de acero, como sucede en naves industriales y sobre un invernadero. Se estudian diferentes configuraciones que permitan refrigerar los paneles, reduciendo su temperatura y mejorar su rendimiento. Para abordar este problema, se han construido dos instalaciones experimentales, fieles a plantas solares en funcionamiento. Una instalacion engloba dos paneles fotovoltaicos sobre estructura fija al suelo. Uno de los paneles esta integrado sobre una superficie paralela y metalica. Entre ambas superficies existe un espacio que posibilita circular aire, permitiendo refrigerar el panel por conveccion natural, o conveccion forzada impulsando el aire con un ventilador. El otro panel, libre por su cara posterior y se ha considerado de referencia. Se ha estudiado el comportamiento del panel integrado sobre cubierta para diferentes secciones de aire y velocidades inducidas, comparandolo con el panel de referencia. Se ha desarrollado un modelo experimental que nos permite determinar la temperatura del panel en funcion de las variables que influyen en su refrigeracion. Adicionalmente, se han analizado los datos de una planta solar en funcionamiento, con paneles de igual caracteristicas, obteniendo correlaciones entre la temperatura del panel y las variables electricas y comparandolos con las obtenidas en la instalacion experimental. La segunda instalacion experimental reproduce parte de una instalacion solar sobre un invernadero, formada por cuatro paneles fotovoltaicos colocados sobre el plastico del invernadero, existiendo un canal divergente entre ambas superficies. Se estudia la

XPS studies of MgO based magnetic tunnel junction structures

NASA Astrophysics Data System (ADS)

Read, John; Mather, Phil; Tan, Eileen; Buhrman, Robert

2006-03-01

The very high tunneling magnetoresistance (TMR) obtained in MgO magnetic tunnel junctions (MTJ)^(1,2) motivates the investigation of the electronic properties of the MgO barrier layer and the study of the ferromagnetic metal - MgO interface chemistry. Such large TMR values are predicted by theory due to the high degree of order apparent in the barrier and electrode materials. However, as grown ultra-thin MgO films generally contain defects that can influence electron transport properties through the creation of low energy states within the bulk MgO band-gap. We will report the results of x-ray photoelectron spectroscopy (XPS) studies of (001) textured ultra-thin MgO layers that are prepared by RF magnetron sputtering and electron beam evaporation on ordered ferromagnetic electrodes and in ordered MTJ structures with and without post growth vacuum annealing. XPS spectra for both MgO deposition techniques clearly indicate a surface oxygen species that is likely bound by defects in the oxide^(3) in half-formed junctions and improvements in MgO quality after counter electrode deposition. We will discuss our results regarding the chemical properties of the oxide and its interfaces directed towards possibly providing guidance to engineer improved MgO MTJ devices. [1] S.S.P. Parkin et. al., Nature Materials, 3, 862 (2004). [2] S. Yuasa et. al., Nature Materials, 3, 868 (2004). [3] E. Tan et. al. , Phys. Rev. B. , 71, 161401 (2005).

Incorporation of Mg in Free-Standing HVPE GaN Substrates

NASA Astrophysics Data System (ADS)

Zvanut, M. E.; Dashdorj, J.; Freitas, J. A.; Glaser, E. R.; Willoughby, W. R.; Leach, J. H.; Udwary, K.

2016-06-01

Mg, the only effective p-type dopant for nitrides, is well studied in thin films due to the important role of the impurity in light-emitting diodes and high-power electronics. However, there are few reports of Mg in thick free-standing GaN substrates. Here, we demonstrate successful incorporation of Mg into GaN grown by hydride vapor-phase epitaxy (HVPE) using metallic Mg as the doping source. The concentration of Mg obtained from four separate growth runs ranged between 1016 cm-3 and 1019 cm-3. Raman spectroscopy and x-ray diffraction revealed that Mg did not induce stress or perturb the crystalline quality of the HVPE GaN substrates. Photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopies were performed to investigate the types of point defects in the crystals. The near-band-edge excitonic and shallow donor-shallow acceptor radiative recombination processes involving shallow Mg acceptors were prominent in the PL spectrum of a sample doped to 3 × 1018 cm-3, while the EPR signal was also thought to represent a shallow Mg acceptor. Detection of this signal reflects minimization of nonuniform strain obtained in the thick free-standing HVPE GaN compared with heteroepitaxial thin films.

A novel approach for arsenic adsorbents regeneration using MgO.

PubMed

Tresintsi, Sofia; Simeonidis, Konstantinos; Katsikini, Maria; Paloura, Eleni C; Bantsis, Georgios; Mitrakas, Manassis

2014-01-30

An integrated procedure for the regeneration of iron oxy-hydroxide arsenic adsorbents by granulated MgO is proposed in this study. A continuous recirculation configuration, with a NaOH solution flowing sequentially through the saturated adsorbent (leaching step) and the MgO (adsorption step) column beds, was optimized by utilizing the high arsenic adsorption efficiency of MgO at strong alkaline environments. Experimental results indicated that the total amount of leached arsenic was captured by MgO whereas the regenerated iron oxy-hydroxide recovered around 80% of its removal capacity upon reuse. The improved adsorption capacity of MgO for As(V), which is maximized at pH 10, is explained by the intermediate hydration to Mg(OH)2 and the following As(V) oxy-anions adsorption on its surface through the formation of monodentate inner sphere complexes, as it is deduced from the AsK-edge X-ray absorption fine structure (EXAFS) analysis. In addition to the economical-benefits, corresponding tests proved that the solid wastes of this process, namely spent MgO/Mg(OH)2, can be environmentally safely disposed as stable additives in cement products, while the alkaline solution is completely detoxified and can be recycled to the regeneration task. Copyright © 2013 Elsevier B.V. All rights reserved.

Hydrogen kinetics studies of MgH2-FeTi composites

NASA Astrophysics Data System (ADS)

Meena, Priyanka; Jangir, Mukesh; Singh, Ramvir; Sharma, V. K.; Jain, I. P.

2018-05-01

MgH2 + x wt% FeTi (x=10, 25, 50) nano composites were ball milled to get nano structured material and characterized for structural, morphological and thermal properties. XRD of the milled samples revealed the formation of MgH2, FeTi, Fe2Ti and H0.06FeTi phases. Morphological studies by SEM were undertaken to investigate the effect of hydrogenation of nanostructure alloy. EDX confirmed elemental composition of the as-prepared alloy. TGA studies showed higher desorption temperature for milled MgH2 compared to x wt% FeTi added MgH2. Activation energy for hydrogen desorption was found to be -177.90, -215.69, -162.46 and -87.93 kJ/mol for milled MgH2 and Mg2+x wt% FeTi (10, 25, 50), showing 89.97 kJ/ mol reduction in activation energy for 50 wt% alloy additives resulting in improved hydrogen storage capacity. DSC investigations were carried out to investigate the effect of alloy on hydrogen absorption behavior of MgH2.

Molecular mechanism of Mg2+-dependent gating in CorA

NASA Astrophysics Data System (ADS)

Dalmas, Olivier; Sompornpisut, Pornthep; Bezanilla, Francisco; Perozo, Eduardo

2014-04-01

CorA is the major transport system responsible for Mg2+ uptake in bacteria and can functionally substitute for its homologue Mrs2p in the yeast inner mitochondrial membrane. Although several CorA crystal structures are available, the molecular mechanism of Mg2+ uptake remains to be established. Here we use electron paramagnetic resonance spectroscopy, electrophysiology and molecular dynamic simulations to show that CorA is regulated by cytoplasmic Mg2+ acting as a ligand and elucidate the basic conformational rearrangements responsible for Mg2+-dependent gating. Mg2+ unbinding at the divalent cation sensor triggers a conformational change that leads to the inward motion of the stalk helix, which propagates to the pore-forming transmembrane helix TM1. Helical tilting and rotation in TM1 generates an iris-like motion that increases the diameter of the permeation pathway, triggering ion conduction. This work establishes the molecular basis of a Mg2+-driven negative feedback loop in CorA as the key physiological event controlling Mg2+ uptake and homeostasis in prokaryotes.

[Comparison of 1 mg/body and 3 mg/body of intravenous granisetron for the prevention of chemotherapy-induced nausea and vomiting and adverse events in hematological malignancy patients].