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  1. Contribución al flujo infrarrojo de las estrellas Be de la recombinación dielectrónica del MgII

    NASA Astrophysics Data System (ADS)

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

    Para evaluar la contribución del proceso de recombinación dielectrónica del átomo de MgII al exceso de flujo infrarrojo observado en las estrellas Be, calculamos la energía emitida en las líneas originadas por este proceso. Se evaluaron los efectos de las condiciones físicas del medio, como la temperatura electrónica y la densidad electrónica, sobre el flujo emitido. Se consideró también la influencia de una posible opacidad.

  2. Informe del NCI y los CDC sobre el tabaco sin humo

    Cancer.gov

    El primer informe sobre el consumo mundial del tabaco sin humo y sus consecuencias en la salud pública reveló que más de 300 millones de personas en al menos 70 países usan estos productos dañinos.

  3. Informe Anual a la Nación sobre el Estado del Cáncer con una sección especial sobre la prevalencia d

    Cancer.gov

    El Informe Anual a la Nación sobre el Estado del Cáncer (1975 a 2010), mostró un descenso más acelerado que en años anteriores de los índices de mortalidad por cáncer de pulmón. También contiene una sección especial que destaca los efectos significativos

  4. Informe Anual a la Nación sobre el Estado del Cáncer, 1975 a 2012

    Cancer.gov

    El Informe Anual a la Nación sobre el Estado del Cáncer, 1975 a 2012, es una actualización de los índices de casos nuevos, muertes y tendencias de los cánceres más comunes en los Estados Unidos.

  5. El Informe a la Nación sobre el Estado del Cáncer, 1975-2012

    Cancer.gov

    El Informe a la Nación sobre el Estado del Cáncer (1975-2012) indica que continuó la baja de tasas de mortalidad de todos los cánceres juntos, así como de la mayoría de los cánceres en hombres y mujeres de todos los grupos raciales y étnicos principales.

  6. Sobre las soluciones acotadas del problema instantáneo de dos cuerpos

    NASA Astrophysics Data System (ADS)

    Altavista, C.

    La demostración se basa en el hecho de que las integrales del problema de los N-cuerpos admiten componentes en el campo complejo según las raíces n-ésimas de la unidad. Definida la matriz unitaria correspondiente, la fórmula de Cayley permite transformar la matriz unitaria en una matriz hermitiana. Utilizando como parámetros los cosenos direccionales de un sistema de coordenadas orbitales referidos a un sistema de referencia fijo, puede construirse, utilizando el operador hermitiano antes definido, una forma cuadrática cuyas raíces mínima y máxima definen las cotas respectivas de los movimientos de los mencionados cosenos direccionales.

  7. 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

  8. Educación sobre sexualidad y prevención del VIH: un diagnóstico para América Latina y el Caribe

    PubMed Central

    DeMaria, Lisa M.; Galárraga, Omar; Campero, Lourdes; Walker, Dilys M.

    2016-01-01

    RESUMEN Objetivo Mostrar, a través de un diagnóstico en América Latina y el Caribe, el panorama legislativo y curricular sobre sexualidad y prevención contra el virus de inmunodeficiencia humana (VIH) en el ámbito escolar, contrastándolo con los comportamientos sexuales reportados en encuestas demográficas y de salud. Métodos En mayo de 2008 se realizó, con el apoyo del Fondo de Población de las Naciones Unidas (UNFPA), una encuesta a informantes clave en 34 países de la Región. El cuestionario autoaplicado solicitó información sustantiva de agentes de las diferentes partes interesadas, como ministerios de educación y de salud, sobre los programas de prevención contra el VIH/Sida que se están aplicando en las escuelas. Resultados Respondieron a la encuesta 27 países que representan 95,5% de la población objetivo (6 a 18 años de edad). La mayoría de los países informó tener al menos un libro de texto o un capítulo específico para enseñar los temas de educación sobre sexualidad y prevención del VIH. En la escuela secundaria se cubren la mayor parte de los temas pertinentes relevantes para la educación sobre sexualidad, pero no todos. Por ejemplo, el problema de la discriminación por orientación o preferencia sexual no se incluye en los programas escolares. Conclusiones El material educativo sobre sexualidad debe ser revisado y actualizado periódicamente de modo que refleje los avances en los temas y en la forma de tratar los contenidos. En cada país el currículo debe abordar el tema del respeto a la diversidad sobre orientación, preferencia e identidad sexuales, y en particular el manejo apropiado de la educación para prevenir infecciones de transmisión sexual (ITS) en hombres que tienen sexo con hombres. Los esfuerzos de evaluación de la efectividad de los programas deben contemplar desenlaces tales como marcadores biológicos (incidencia y prevalencia de ITS y embarazo) y no únicamente indicadores de conocimiento y

  9. La utilizacion de los mapas conceptuales en la ensenanza de biologia y su efecto sobre el dominio del proceso de fotosintesis en los estudiantes universitarios

    NASA Astrophysics Data System (ADS)

    Gonzalez Rivera, Maria M.

    Se investigo el efecto de los mapas conceptuales sobre el dominio del proceso de fotosintesis en estudiantes universitarios. La investigacion utilizo dos estrategias: mapas conceptuales individuales y mapas conceptuales colaborativos, con el fin de investigar si existen diferencias significativas en el dominio del proceso de fotosintesis. El analisis de los datos incluyo aspectos cualitativos y cuantitativos. Se desprende del estudio que el 80% de los estudiantes describen la utilizacion de los mapas conceptuales como una experiencia beneficiosa. El 70% de los estudiantes expreso que los mapas conceptuales son utiles en el aprendizaje del proceso de fotosintesis y el 61% indico que facilitan la comprension de los conceptos. Los hallazgos mas importantes del analisis cuantitativo indican que los estudiantes que utilizaron los mapas conceptuales mejoraron significativamente su desempeno en la posprueba global. Se utilizo la prueba Mann-Whitney para investigar si existian diferencias significativas en la posprueba y preprueba global, el valor de W = 1945.0, para un valor p de 0.00, lo cual establece diferencias significativas. Para determinar si existian diferencias significativas entre la posprueba y preprueba del grupo individual, se realizo la prueba nuevamente. El valor de W correspondio a 490.5, que es significativo, con un valor p de 0.00. Se concluye que existen diferencias significativas entre la ejecucion de la posprueba y preprueba del grupo individual. Los datos proveen suficiente evidencia para sostener que los estudiantes que utilizaron la estrategia de mapas conceptuales individuales mejoraron el dominio del proceso de fotosintesis significativamente. Se realizo nuevamente la prueba para los resultados de posprueba y preprueba del grupo colaborativo. El valor de W correspondio a 446 con un valor p de 0.00. Se concluyo que existen diferencias significativas entre la ejecucion de la posprueba y preprueba del grupo colaborativo. Finalmente, se efectuo una

  10. Cambios históricos en el aporte terrígeno de la cuenca del Río de la Plata sobre la plataforma interna Uruguaya

    NASA Astrophysics Data System (ADS)

    Marrero, Analía; Tudurí, Adriana; Pérez, Laura; Cuña, Caroline; Muniz, Pablo; Lopes Figueira, Rubens; Michaelovitch de Mahiques, Michel; Alves de Lima Ferreira, Paulo; Pittauerová, Daniela; Hanebuth, Till; García Rodríguez, Felipe

    2014-12-01

    B 13813-4. También se determinó una mayor acumulación de sedimentos a través del tiempo en el cinturón de barro del Río de la Plata (plataforma continental adyacente), comparado con aquel registrado en la Barra del Indio (límite entre zona intermedia y externa del estuario). Estas diferencias podrían estar relacionadas con la influencia del Río de la Plata, el cual genera un ambiente altamente dinámico sobre la Barra del Indio y un ambiente más estable sobre el cinturón de barro en la plataforma continental.

  11. Informe sobre el avance del proyecto de determinaciones de V sen i para todas las estrellas B más brillantes que 6.5 mag.

    NASA Astrophysics Data System (ADS)

    Abt, H.; Levato, H.

    Se ha finalizado con la determinación de V sen i para todas las estrellas B más brillantes que 6.5 mag y al norte de -30 grados de declinación. Esta muestra involucra casi 1000 estrellas. Las observaciones fueron realizadas desde KPNO. Mientras tanto, se ha completado desde CASLEO la observación de 350 estrellas B más brillantes que 6.5 mag. al sur de -30 grados. Además de la determinación de la rotación axial se determinan, en los casos posibles, los anchos equivalentes de las líneas 4471 Ådel He I y 4481 Ådel Mg II.

  12. 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.

  13. 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. PMID:20830214

  14. 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

  15. 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.

  16. 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

  17. Distinción Empírica Entre Engagement y Trabajolismo en Enfermeras Hospitalarias de Japón: Efecto Sobre la Calidad del Sueño y el Desempeño Laboral

    PubMed Central

    Kubota, Kazumi; Shimazu, Akihito; Kawakami, Norito; Takahashi, Masaya; Nakata, Akinori; Schaufeli, Wilmar B.

    2016-01-01

    Objetivo El objetivo de este estudio es demostrar la distinción entre engagement y trabajolismo, estudiando su relación con la calidad del sueño y el desempeño laboral. Método Un total de 447 enfermeras de 3 hospitales de Japón fueron entrevistadas mediante un cuestionario autoadministrado que incluía la escala Utrecht (UWES, Utrecht Work Engagement Scale), la Escala de Adicción al Trabajo Holandesa (DUWAS, Dutch Workaholism Scale), preguntas sobre la calidad del sueño (7 ítems) con respecto a (1) dificultad para conciliar el sueño, (2) dificultad para mantener el sueño, (3) despertar temprano por la mañana, (4) dormirse o tomar siestas durante el día, (5) somnolencia diurna excesiva en el trabajo, (6) dificultad para despertarse por la mañana, y (7) despertar cansado en la mañana, y el Cuestionario sobre Salud y Desempeño (CSD) de la Organización Mundial de la Salud. Resultados Los modelos de ecuaciones estructurales demostraron que el engagement se relaciona positivamente con la calidad del sueño y el rendimiento laboral, mientras que el trabajolismo tiene una relación negativa con la calidad del sueño y el desempeño laboral. Conclusión Los resultados indican que el engagement y el trabajolismo son conceptualmente diferentes. El primero tiene una connotación positiva, mientras que el segundo se asocia de manera negativa al bienestar (buena calidad del sueño y buen rendimiento en el trabajo). PMID:26752805

  18. 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.

  19. 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

  20. Líneas Vitales: Programas y servicios del NCI

    Cancer.gov

    Artículos y videos sobre los programas y servicios del Instituto Nacional del Cáncer de la serie educativa Líneas Vitales del NCI, la cual está dirigida especialmente a poblaciones multiculturales.

  1. Instantánea del linfoma

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el linfoma; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  2. Instantánea del melanoma

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el melanoma; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  3. Instantánea del sarcoma

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el sarcoma; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  4. Instantánea del mieloma

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el mieloma; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  5. Instantánea del cáncer colorrectal

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer colorrectal; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  6. Instantánea del sarcoma de Kaposi

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el sarcoma de Kaposi; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  7. Control del cáncer y salud mundial: noticia del Instituto Nacional del Cáncer (NCI)

    Cancer.gov

    En combinación con una reunión de alto nivel de las Naciones Unidas sobre enfermedades no transmisibles en países en vías de desarrollo, el doctor Harold Varmus, director del NCI, y el doctor Ted L. Trimble, del NCI, han publicado un comentario en Science

  8. Instantánea de los cánceres de cerebro y del sistema nervioso central

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre los cánceres de cerebro y del sistema nervioso central; así como ejemplos de actividades del NCI y adelantos en la investigación de estos tipos de cáncer.

  9. Instantánea del cáncer de páncreas

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de páncreas; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  10. Instantánea del cáncer de pulmón

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de pulmón; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  11. Instantánea del cáncer de seno (mama)

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de seno (mama); así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  12. Instantánea del cáncer de tiroides

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de tiroides; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  13. Instantánea del cáncer de cuello uterino

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de cuello uterino; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  14. Instantánea del cáncer de próstata

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de próstata; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  15. Instantánea del cáncer de estómago

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de estómago; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  16. Instantánea del cáncer de esófago

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de esófago; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  17. Instantánea del cáncer de ovario

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de ovario; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  18. Instantánea del cáncer de endometrio

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de endometrio; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  19. Instantánea del cáncer de vejiga

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de vejiga; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  20. Instantánea del cáncer de riñón

    Cancer.gov

    Información sobre las tendencias de incidencia, mortalidad y financiamiento del NCI sobre el cáncer de riñón; así como ejemplos de actividades del NCI y adelantos en la investigación de este tipo de cáncer.

  1. Role of Mg interlayers in Fe/Mg/MgO/Fe and Fe/Mg/MgO/Mg/Fe magnetic tunnel junctions

    SciTech Connect

    Wang, Y.; Zhang, J.; Zhang, Xiaoguang; Cheng, Hai-Ping; Han, Prof. X. F.

    2010-01-01

    -Fe(001)/Mg/MgO/Fe- and -Fe(001)/Mg/MgO/Mg/Fe- magnetic tunnel junctions (MTJs) with Mg interlayers are studied by first-principles calculation. An important role of the Mg interlayer is identified to be preserving the preferential transmission of the majority-spin states with \\Delta_1 symmetry, which dominate the spin-dependent electron transport of MTJs with MgO barrier. One layer of Mg at the electrode/barrier interface does not decrease the tunneling magnetoresistance (TMR) ratio nearly as much as one layer of oxide. At certain Mg thickness case the TMR could be strongly influenced by the resonance tunneling states in minority-spin channel, these states are mainly raised from the quantum-well states formed in the Mg interlayer and coupled with interfacial resonance states which are very sensitive to the interface structures.

  2. [The Spanish AIDS Study Group and Spanish National AIDS Plan (GESIDA/Secretaría del Plan Nacional sobre el Sida) recommendations for the treatment of tuberculosis in HIV-infected individuals (Updated January 2013)].

    PubMed

    Rivero, Antonio; Pulido, Federico; Caylá, Joan; Iribarren, José A; Miró, José M; Moreno, Santiago; Pérez-Camacho, Inés

    2013-12-01

    This consensus document was prepared by an expert panel of the Grupo de Estudio de Sida (GESIDA [Spanish AIDS Study Group]) and the Plan Nacional sobre el Sida (PNS [Spanish National AIDS Plan]). The document updates current guidelines on the treatment of tuberculosis (TB) in HIV-infected individuals contained in the guidelines on the treatment of opportunistic infections published by GESIDA and PNS in 2008. The document aims to facilitate the management and treatment of HIV-infected patients with TB in Spain, and includes specific sections and recommendations on the treatment of drug-sensitive TB, multidrug-resistant TB, and extensively drug-resistant TB, in this population. The consensus guidelines also make recommendations on the treatment of HIV-infected patients with TB in special situations, such as chronic liver disease, pregnancy, kidney failure, and transplantation. Recommendations are made on the timing and initial regimens of antiretroviral therapy in patients with TB, and on immune reconstitution syndrome in HIV-infected patients with TB who are receiving antiretroviral therapy. The document does not cover the diagnosis of TB, diagnosis/treatment of latent TB, or treatment of TB in children. The quality of the evidence was evaluated and the recommendations graded using the approach of the Grading of Recommendations Assessment, Development and Evaluation Working Group.

  3. 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

  4. Learning about the Sky from the Environment: An Experience Working Along One Year with Students of Elementary Education. (Spanish Title: Aprendiendo sobre EL Cielo Desde el Entorno: Una Experiencia Trabajando Durante un Año Junto a Estudiantes del Primario.) Aprendendo sobre o Céu a Partir do Entorno: Uma Experiência de Trabalho ao Longo de um Ano com Alunos de Ensino Fundamental

    NASA Astrophysics Data System (ADS)

    Longhini, Marcos Daniel; Gomide, Hanny Angeles

    2014-12-01

    Research developed with 95 students of the 6th year of elementary education in a public school of Uberlândia, Minas Gerais. It was a continuous work from February to December 2013, which led the students to participate in activities of observation of the environment, specifically the sky, analyzing the changes occurred. We focused on the study of variations in temperature, rainfall, day length, variations in the size of the shadows and changes in the aspect of the Moon. Our focus of analysis targeted the discussion of the knowledge that these students had about the topics indicated and as they entered the stage during the implementation of the proposal. The results showed a limited perception that students have of their environment, however, lately expanded due to the undertaken activities, especially in relation to the Moon. Working with systematic measure procedures reveals the careful handling of data so that they become understandable to students, and working with the shadows points towards the students first understand how shadows are formed, and then apply this knowledge to Astronomy. Finally, we conclude that the lived process consisted of an initial step of a work that should be encouraged for the subsequent years of training of these students. Proyecto de investigación desarrollado con 95 alumnos del sexto año de primaria en una escuela pública de Uberlândia, Minas Gerais. Fue un trabajo continuo, de febrero a diciembre de 2013, que llevó a los estudiantes a participar en actividades de observación de su entorno, entre ellas, el cielo, analizando los cambios ocurridos. Nos centramos en el estudio de las variaciones en la temperatura, las precipitaciones, la duración del día, las variaciones en el tamaño de las sombras y los cambios en los aspectos de la Luna. Nuestro foco de análisis se centró en discutir el conocimiento que estos estudiantes tenían sobre los temas indicados al inicio y término de la propuesta. Los resultados mostraron una

  5. Observaciones del CH interestelar y el continuo en 3,3 GHz

    NASA Astrophysics Data System (ADS)

    Olano, C. A.; Combi, J. A.; Pöppel, W.; Benaglia, P.; Sanz, A. J.; Bava, J. A.

    Se informa sobre el proyecto que se lleva a cabo en el IAR con el propósito de observar las líneas hiperfinas del estado fundamental del CH y el continuo en la banda de 3,3 GHz. El nuevo receptor construído en nuestro laboratorio para tal fin se instaló sobre uno de los radiotelescopios, funcionando conjuntamente con los sistemas de procesamiento actuales del IAR. Los resultados de las primeras observaciones, realizadas tanto en las líneas espectrales como en el continuo sobre fuentes conocidas, fueron satisfactorios.

  6. Porous Mg thin films for Mg-air batteries.

    PubMed

    Xin, Gongbiao; Wang, Xiaojuan; Wang, Chongyun; Zheng, Jie; Li, Xingguo

    2013-12-28

    An alkaline primary Mg-air battery made from a porous Mg thin film displayed superior discharge performances, including a flat discharge plateau, a high open-circuit voltage of 1.41 V and a large discharge capacity of 821 mAh g(-1), suggesting that the electrochemical performances of Mg-air batteries can be improved by controlling the Mg anode morphology. PMID:24158667

  7. 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.

  8. Questions about Brain Development = Preguntas sobre el desarrollo del cerebro.

    ERIC Educational Resources Information Center

    Southeastern Regional Vision for Education (SERVE), Tallahassee, FL.

    Noting that new research shows that a baby's earliest years shape how he or she grows later in life, this brochure, in English- and Spanish-language versions, provides brief answers to some important questions parents may have about their baby's brain. The questions answered are: (1) "Why is brain development a popular subject lately?; (2) "What…

  9. Calcio y la prevención del cáncer

    Cancer.gov

    Hoja informativa que resume los resultados de estudios sobre el calcio y la prevención del cáncer. Incluye información sobre las recomendaciones dietéticas para calcio y la cantidad de calcio en los alimentos y en complementos de calcio.

  10. Control del dolor: Apoyo para las personas con cáncer

    Cancer.gov

    Contiene información sobre las medicinas contra el dolor para pacientes con cáncer, los planes para controlarlo, cómo hablar con su equipo de atención médica sobre el dolor que usted siente y qué hacer para controlar los efectos físicos y emocionales del

  11. Comportamiento del Helio en estrellas químicamente peculiares

    NASA Astrophysics Data System (ADS)

    Malaroda, S. M.; López García, Z.; Leone, F.; Catalano, F.

    Las estrellas químicamente peculiares (CP) se caracterizan por tener deficiencias y sobreabundancias de algunos elementos químicos de hasta 106 veces la abundancia solar. Además presentan variaciones en las líneas espectrales. Se piensa que ello se debe a que los campos magnéticos presentes en este tipo de estrellas son principalmente dipolares, con un eje de simetría diferente del eje de rotación. La distribución de los elementos sobreabundantes y deficientes no es homogénea sobre la superficie estelar y las variaciones observadas serían una consecuencia directa de la rotación estelar. Entre los elementos con abundancia anómala se encuentra el Helio, cuyas líneas tienen intensidades que no son consistentes con una abundancia normal, que no puede ser determinada del modo usual, o sea, considerando una atmósfera con composición solar. Con el fin de determinar la abundancia de este elemento, se inició un estudio de estrellas anómalas de Helio, Hew y He strong. Además se determinarán las abundancias de otros elementos anómalos como ser el Si, Cr, Mg, Mn y Fe. Las mismas se determinan del modo tradicional, o sea: a) medida de los anchos equivalentes de las líneas de los distintos elementos analizados; b) adopción de la temperatura efectiva, gravedad y abundancia del Helio; c) cálculo del modelo de atmósfera d) comparación con las observaciones y reinicio de un proceso iterativo hasta lograr un acuerdo entre todos los parámetros analizados. Las observaciones se llevaron a cabo en el Complejo Astronómico El Leoncito. Se observaron setenta y ocho estrellas anómalas de Helio. En este momento se está procediendo a calcular las abundancias correspondientes a los distintos elementos químicos. Para ello se hace uso de los modelos de Kurucz, ATLAS9. Los cálculos NLTE de las líneas de Helio se llevan a cabo con el programa MULTI y se compararán con los realizados con el programa WIDTH9 de Kurucz (LTE), con el objeto de resaltar la importancia de

  12. PREVALENCE AND FACTORS ASSOCIATED WITH VITAMIN B12 DEFICIENCY IN ELDERLY FROM VIÇOSA/MG, BRASIL.

    PubMed

    Oliveira Martinho, Karina; Luiz Araújo Tinôco, Adelson; Queiroz Ribeiro, Andréia

    2015-11-01

    La prevalencia de deficiencia nutricional de vitamina B12 aumenta con la edad y es especialmente común en la población mayor. El objetivo de este estudio consistió en determinar su prevalencia y los factores asociados a esta carencia en mayores no institucionalizados de Viçosa, Estado de Minas Gerais, Brasil. Métodos: estudio poblacional interseccional, realizado para identificar la prevalencia y los factores asociados a deficiencia de vitamina B12 entre la población de mayores en Viçosa (MG). Los datos fueron recopilados desde agosto de 2011 hasta junio de 2012 mediante una encuesta en los hogares y pruebas hematológicas y bioquímicas realizadas en 340 mayores. Resultados: la prevalencia de deficiencia de vitamina B12 en este grupo fue del 17,4% (95% CI, 13,4% - 21,4%). La deficiencia cognitiva se presenta como un factor importante relacionado con la deficiencia de vitamina B12. Conclusiones: el informe actual contribuye a los estudios que destacan ciertos factores que podrían afectar al rendimiento de las personas mayores en su proceso de envejecimiento natural, especialmente cuando estos factores están asociados con deficiencia cognitiva y dan lugar a una discapacidad significativa así como pérdida de calidad de vida. Así, los resultados aquí presentados han servido para aportar un conocimiento más comprensivo sobre la relación entre deficiencia de B12 y su impacto sobre este grupo de población. También han demostrado su relevancia de cara a la planificación de programas e iniciativas de salud pública centrados en este grupo de población.

  13. Substitution of Mn for Mg in MgB_2*

    NASA Astrophysics Data System (ADS)

    Fitzpatrick, Michael D.; Johnston, David C.; Miller, Lance L.; Hill, Julienne M.

    2002-03-01

    The study of solid solutions in which the Mg in MgB2 is partially replaced by magnetic 3d or 4f atoms can potentially reveal important information on the superconducting state of MgB_2. As an end-member of the hypothetical Mg_1-xMn_xB2 system, MnB2 is isostructural with MgB2 and is an antiferromagnet below TN = 760 K which becomes canted at 157 K. A previous study by Moritomo et al.[1] examined the structure and properties of multi-phase samples with 0.01<= x<= 0.15. We attempted to obtain single-phase samples with x<= 0.25 by reacting the constituent elements in sealed Ta tubes and/or using prereacted MnBx synthesized using an arc furnace. The results of x-ray diffraction and magnetization measurements on those samples will be presented. * Supported by the USDOE under contract no. W-7405-Eng-82. [1] "Mn-substitution effects on MgB2 superconductor", Y.Moritomo et al. J. Phys. Soc. Japan b70, 1889 (2001).; “Effects of transition metal doping in MgB2 superconductor", Y. Moritomo at al. arXiv:cond-mat/0104568.

  14. Coulomb excitation of 31Mg

    NASA Astrophysics Data System (ADS)

    Seidlitz, M.; Mücher, D.; Reiter, P.; Bildstein, V.; Blazhev, A.; Bree, N.; Bruyneel, B.; Cederkäll, J.; Clement, E.; Davinson, T.; Van Duppen, P.; Ekström, A.; Finke, F.; Fraile, L. M.; Geibel, K.; Gernhäuser, R.; Hess, H.; Holler, A.; Huyse, M.; Ivanov, O.; Jolie, J.; Kalkühler, M.; Kotthaus, T.; Krücken, R.; Lutter, R.; Piselli, E.; Scheit, H.; Stefanescu, I.; Van de Walle, J.; Voulot, D.; Warr, N.; Wenander, F.; Wiens, A.

    2011-06-01

    The ground state properties of 31Mg indicate a change of nuclear shape at N = 19 with a deformed Jπ = 1 /2+ intruder state as a ground state, implying that 31Mg is part of the "island of inversion". The collective properties of excited states were the subject of a Coulomb excitation experiment at REX-ISOLDE, CERN, employing a radioactive 31Mg beam. De-excitation γ-rays were detected by the MINIBALL γ-spectrometer in coincidence with scattered particles in a segmented Si-detector. The level scheme of 31Mg was extended. Spin and parity assignment of the 945 keV state yielded 5 /2+ and its de-excitation is dominated by a strong collective M1 transition. Comparison of the transition probabilities of 30,31,32Mg establishes that for the N = 19 magnesium isotope not only the ground state but also excited states are largely dominated by a deformed pf intruder configuration.

  15. 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.

  16. Vigilando la Calidad del Agua de los Grandes Rios de la Nacion: El Programa NASQAN del Rio Grande (Rio Bravo del Norte)

    USGS Publications Warehouse

    Lurry, Dee L.; Reutter, David C.; Wells, Frank C.; Rivera, M.C.; Munoz, A.

    1998-01-01

    La Oficina del Estudio Geologico de los Estados Unidos (U.S. Geological Survey, 0 USGS) ha monitoreado la calidad del agua de la cuenca del Rio Grande (Rio Bravo del Norte) desde 1995 como parte de la rediseiiada Red Nacional para Contabilizar la Calidad del Agua de los Rios (National Stream Quality Accounting Network, o NASOAN) (Hooper and others, 1997). EI programa NASOAN fue diseiiado para caracterizar las concentraciones y el transporte de sedimento y constituyentes quimicos seleccionados, encontrados en los grandes rios de los Estados Unidos - incluyendo el Misisipi, el Colorado y el Columbia, ademas del Rio Grande. En estas cuatro cuencas, el USGS opera actualmente (1998) una red de 40 puntos de muestreo pertenecientes a NASOAN, con un enfasis en cuantificar el flujo en masa (la cantidad de material que pasa por la estacion, expresado en toneladas por dial para cada constituyente. Aplicacando un enfoque consistente, basado en la cuantificacion de flujos en la cuenca del Rio Grande, el programa NASOAN esta generando la informacion necesaria para identificar fuentes regionales de diversos contaminantes, incluyendo sustancias qui micas agricolas y trazas elementos en la cuenca. EI efecto de las grandes reservas en el Rio Grande se puede observar segun los flujos de constituyentes discurren a 10 largo del rio. EI analisis de los flujos de constituyentes a escala de la cuenca proveera los medios para evaluar la influencia de la actividad humana sobre las condiciones de calidad del agua del Rio Grande.

  17. Estudio multifrecuencia del medio interestelar cercano a HD 192281

    NASA Astrophysics Data System (ADS)

    Arnal, E. M.; Cappa, C.; Cichowolski, S.; Pineault, S.; St-Louis, N.

    Una de las causas que modifica la estructura y dinámica del medio interestelar es la acción que los vientos de las estrellas de gran masa ejercen sobre el mismo. En este trabajo, mediante el uso de datos interferométricos obtenidos en la banda de radio en la transición de 21-cm del Hidrógeno neutro y de imágenes de la emisión de continuo en las bandas de 408 y 1420 MHz, de imágenes HIRES del satélite IRAS en 60 y 100 micrones, y de observaciones de continuo obtenidas con radiotelescopios de disco simple en 2695, 4850 y 8350 MHz se ha realizado un estudio multifrecuencia de los efectos que los vientos estelares de HD 192281, una estrella de tipo espectral O5 Vn((f))p, han tenido sobre el medio interestelar que rodea a la misma.

  18. Comunicado de prensa del Informe Anual sobre el Estado del Cáncer 2015

    Cancer.gov

    Por primera vez, los investigadores han usado datos a nivel nacional para determinar la incidencia de los cuatro subtipos moleculares principales de cáncer de seno (mama) por edad, raza y grupo étnico, nivel de pobreza y varios otros factores. El informe

  19. Spin assignments of 22Mg states through a 24Mg(p,t)22Mg measurement

    SciTech Connect

    Chae, K. Y.; Jones, K. L.; Moazen, Brian; Pittman, S. T.; Bardayan, Daniel W; Blackmon, Jeff C; Liang, J Felix; Smith, Michael Scott; Chipps, K.; Hatarik, Robert; O'Malley, Patrick; Pain, Steven D; Kozub, R. L.; Matei, Catalin; Nesaraja, Caroline D

    2009-01-01

    The {sup 18}Ne({alpha},p){sup 21}Na reaction plays a crucial role in the ({alpha},p) process, which leads to the rapid proton capture process in X-ray bursts. The reaction rate depends upon properties of {sup 22}Mg levels above the {alpha} threshold at 8.14 MeV. Despite recent studies of these levels, only the excitation energies are known for most with no constraints on the spins. We have studied the {sup 24}Mg(p,t){sup 22}Mg reaction at the Oak Ridge National Laboratory (ORNL) Holifield Radioactive Ion Beam Facility (HRIBF), and by measuring the angular distributions of outgoing tritons, we provide the first experimental constraints on the spins of astrophysically-important {sup 18}Ne({alpha},p){sup 21}Na resonances.

  20. Memories of Astronomy Education in Brazil: Clippings from the Discourses of Interviewed Researchers on the Subject. (Spanish Title: Memorias de la Educación en Astronomía en Brasil: Recortes de los Discursos de Investigadores Entrevistados Acerca del Tema ) Memórias da Educação em Astronomia no Brasil: Recortes a Partir das Falas de Pesquisadores Entrevistados sobre o Tema

    NASA Astrophysics Data System (ADS)

    Iachel, Gustavo; Nardi, Roberto

    2014-12-01

    This paper presents a historical retrospective concerning data from a research in Astronomy Education in Brazil, after 1973. It was organized on the basis of the speech analysis of national researchers considered references in this field by their peers. Furthermore, it was elaborated on the basis of other studies from the areas of Science Education, Physics and Astronomy. This historical overview was developed in order to facilitate understanding of the contexts in which the interviewed researchers have developed professionally. Moreover, we attempted to recover the memory of the growing field of research in Astronomy Education in the country. We believe that the history presented can help those trying to understand the past in an attempt to resolve current and future demands. Se presenta en este artículo una retrospectiva histórica referente a datos provenientes de la investigación en enseñanza de la astronomía en el Brasil, después de 1973, organizada sobre la base del análisis de los discursos de los investigadores nacionales considerados referencias en este campo, y también en la lectura de las publicaciones en las áreas de Enseñanza de las Ciencias, Física y Astronomía. Este repaso histórico se desarrolló con el fin de facilitar la comprensión de los contextos en los que los investigadores entrevistados se han desarrollado profesionalmente. Por otra parte, se intentó recuperar la memoria del creciente campo de la investigación en Educación en Astronomía en el país. Creemos que el relato presentado puede contribuir a quien trata de comprender el pasado, en un intento de resolver las demandas actuales y futuras. Relata-se neste artigo uma retrospectiva histórica referente a dados provenientes de pesquisa em Educação em Astronomia no país, pós 1973, organizada com base na análise das falas de pesquisadores considerados referências nacionais nesse campo, como também na leitura de publicações das áreas de ensino de Ciências, F

  1. Providing Meaningful Learning for Students of the Sixth Grade of Middle School: a Study on the Moon Phases. (Breton Title: Propiciando Aprendizagem Significativa Para Alunos do Sexto Ano do Ensino Fundamental: um Estudo sobre as Fases da Lua.) Propiciando el Aprendizaje Significativo Para Alumnos del Sexto Nivel de la Educación General Básica: un Estudio sobre Las Fases de la Luna

    NASA Astrophysics Data System (ADS)

    Darroz, Luiz Marcelo; Samudio Pérez, Carlos Ariel; da Rosa, Cleci Werner; Heineck, Renato

    2012-07-01

    We relate in this article a didactic experience studying the moon phases with a group of middle school students of a private school of the municipality of Passo Fundo, RS. Based on David Ausubel's Meaningful Learning Theory, we have sought to develop a proposal following a didactic model which simulates the phases of the Moon, as based on the previous conceptions of the students. The signs of learning were evidenced by means of memory registries of the activity. From the obtained results we believe that the proposal achieved its goals, since the students were able to identify, differentiate and transfer the phenomenon of the moon phases to new contexts. Thus, it is concluded that a methodology focused on a meaningful content for the students is fundamental to the construction and genuine grasping of what is being learned. Neste artigo, relata-se uma experiência didática de estudo das fases da Lua com uma turma do 6° ano do Ensino Fundamental, de uma escola privada do município de Passo Fundo, RS. Tendo como fundamentação teórica a Teoria da Aprendizagem Significativa de David Ausubel, buscou-se desenvolver a proposta a partir de um modelo didático que simula as fases da Lua e com base nas concepções prévias dos estudantes. Os indícios da aprendizagem foram constatados através de registros de memórias da atividade. Pelos resultados apresentados, acredita-se que a proposta alcançou seus objetivos, uma vez que os estudantes conseguiram identificar, diferenciar e transferir o fenômeno das fases da Lua para novos contextos. Assim, conclui-se que uma metodologia com enfoque em um conteúdo significativo ao estudante é fundamental para a construção e compreensão genuína do que está sendo aprendido. En este artículo se relata una experiencia didáctica de estudio de las fases de la Luna con una clase de 6º año de la educación general básica de una escuela privada del municipio de Passo Fundo, RS. Teniendo como fundamentación teórica la Teor

  2. The Arabidopsis Mg Transporter, MRS2-4, is Essential for Mg Homeostasis Under Both Low and High Mg Conditions.

    PubMed

    Oda, Koshiro; Kamiya, Takehiro; Shikanai, Yusuke; Shigenobu, Shuji; Yamaguchi, Katsushi; Fujiwara, Toru

    2016-04-01

    Magnesium (Mg) is an essential macronutrient, functioning as both a cofactor of many enzymes and as a component of Chl. Mg is abundant in plants; however, further investigation of the Mg transporters involved in Mg uptake and distribution is needed. Here, we isolated an Arabidopsis thaliana mutant sensitive to high calcium (Ca) conditions without Mg supplementation. The causal gene of the mutant encodes MRS2-4, an Mg transporter.MRS2-4 single mutants exhibited growth defects under low Mg conditions, whereas an MRS2-4 and MRS2-7 double mutant exhibited growth defects even under normal Mg concentrations. Under normal Mg conditions, the Mg concentration of the MRS2-4 mutant was lower than that of the wild type. The transcriptome profiles of mrs2-4-1 mutants under normal conditions were similar to those of wild-type plants grown under low Mg conditions. In addition, both mrs2-4 and mrs2-7 mutants were sensitive to high levels of Mg. These results indicate that both MRS2-4 and MRS2-7 are essential for Mg homeostasis, even under normal and high Mg conditions. MRS2-4-green fluorescent protein (GFP) was mainly detected in the endoplasmic reticulum. These results indicate that these two MRS2 transporter genes are essential for the ability to adapt to a wide range of environmental Mg concentrations. PMID:26748081

  3. Phase transformation of Mg-Fe alloys

    SciTech Connect

    Yoneda, Yasuhiro; Abe, Hiroshi; Ohshima, Takeshi; Uchida, Hirohisa

    2010-05-15

    An Mg-Fe alloy system prepared through mechanical alloying (MA) was structurally analyzed. MA can produce single-phase bcc alloys using Mg concentrations up to about 15 mol %. Use of conventional average structure analysis and x-ray pair-distribution function method enabled the long-range and short-range order structures of the Mg-Fe alloys to be bridged. The substituted Mg atoms were randomly arranged in the low-Mg composition but started to have an order structure. The partially ordered Mg-Fe alloy undergoes an austenitic (cubic) to martensitic (orthorhombic) phase change, as increasing Mg composition.

  4. Sobre | Smokefree Español

    Cancer.gov

    Espanol.smokefree.gov ofrece apoyo y recursos para norteamericanos que hablan español y quieren dejar de fumar. Este sitio en la red fue creada por la División de Investigación para el Control del Tabaco del Instituto Nacional del Cáncer.

  5. First-principles study of Mg(0001)/MgO(1-11) interfaces

    NASA Astrophysics Data System (ADS)

    Song, Hong-Quan; Zhao, Ming; Li, Jian-Guo

    2016-06-01

    By means of first-principles density-functional calculations, we studied the surface energy of a nonstoichiometric MgO(1-11) slab, the interfacial energy and interfacial bonding characteristics of Mg-terminated and O-terminated Mg/MgO(1-11) interfaces with three stacking-site (TOP, HCP and FCC sites) models, and the effect of the thickness of Mg films on the O-terminated MgO(1-11) surface. The results indicate that the surface energies of the nonstoichiometric MgO(1-11) slab and interfacial energies of Mg/Mg(1-11) interface depend on Mg chemical potential. We found that the Mg-terminated MgO(1-11) surface is more stable than the O-terminated MgO(1-11) surface at high Mg chemical potential, and Mg/MgO(1-11) with FCC stacking-site model is the most stable configuration in the Mg/MgO(1-11) interfaces. The results of the electronic structure reveals that the interfacial bonding of Mg-terminated interface with FCC site model mainly consists of metallic bond and of the O-terminated interface with FCC site model is mainly ionic with a small degree of σ-type covalent bond. Although the interfacial energy of Mg-terminated Mg/MgO interface with FCC stacking-site model is slightly higher than that of O-terminated Mg/MgO interface, the molten Mg would epitaxially grow on the FCC sites of the Mg-terminated MgO(1-11) surface because of the high evaporation pressure of Mg at high temperature.

  6. Highly (100) oriented MgO growth on thin Mg layer in MTJ structure

    NASA Astrophysics Data System (ADS)

    Jimbo, K.; Nakagawa, S.

    2011-01-01

    In order to apply Stress Assisted Magnetization Reversal (SAMR) method to perpendicular magnetoresistive random access memory (p-MRAM) with magnetic tunnel junction (MTJ) using MgO (001) oriented barrier layer, multilayer of Ta/ Terfenol-D/ Mg/ MgO and Ta/ Terfenol-D/ MgO were prepared. While the MgO layer, deposited directly on the Terfenol-D layer, did not show (100) orientatin, very thin metallic Mg layer, deposited prior to the MgO deposition, was effective to attain MgO (100) orientation. The crystalline orientation was very weak without Mg, however, the multilayer with Mg showed very strong MgO(100) peak and the MgO orientation was shifted depending on the Mg thickness.

  7. Aspectos generales de los exámenes de detección del cáncer (PDQ®)—Versión para profesionales de salud

    Cancer.gov

    Información sobre la medición de la eficacia de las pruebas de detección del cáncer y la evaluación de la solidez de las pruebas obtenidas en estudios de investigación de detección del cáncer.

  8. Aspectos generales de los exámenes de detección del cáncer (PDQ®)—Versión para pacientes

    Cancer.gov

    Información sobre la medición de la eficacia de los exámenes de detección del cáncer y la evaluación de la solidez de las pruebas obtenidas en estudios de investigación de detección del cáncer.

  9. Fabrication and superconducting properties of internal Mg diffusion processed MgB2 wires using MgB4 precursors

    NASA Astrophysics Data System (ADS)

    Xu, Da; Wang, Dongliang; Yao, Chao; Zhang, Xianping; Ma, Yanwei; Oguro, Hidetoshi; Awaji, Satoshi; Watanabe, Kazuo

    2016-10-01

    Monofilament MgB2/Nb/Monel wires were fabricated using three different MgB4 precursors by an internal Mg diffusion (IMD) process. The wire geometry and heat-treatment conditions were optimized in order to improve the critical current density (J c) of the MgB2 wire. The influences of the quality of MgB4 powders, such as the particle size and MgO impurity, on the microstructure and superconducting properties of the wires were discussed. Although there were small amounts of voids, unreacted MgB4 particles and MgO impurity existed in the superconducting layers, and the transport layer J c of the wire with the MgB4 precursor reached 3.0 × 104 A cm-2 at 4.2 K and 10 T, which was comparable to that of IMD-processed wires fabricated using boron precursors. Both the non-barrier J c and engineering J c of MgB2 wire made using a MgB4 precursor were enhanced due to the improved grain connectivity and the enlarged fill factor.

  10. A Facile Approach Using MgCl2 to Formulate High Performance Mg2+ Electrolytes for Rechargeable Mg Batteries

    SciTech Connect

    Liu, Tianbiao L.; Shao, Yuyan; Li, Guosheng; Gu, Meng; Hu, Jian Z.; Xu, Suochang; Nie, Zimin; Chen, Xilin; Wang, Chong M.; Liu, Jun

    2014-01-01

    Rechargeable Mg batteries have been regarded as a viable battery technology for grid scale energy storage and transportation applications. However, the limited performance of Mg2+ electrolytes has been a primary technical hurdle to develop high energy density rechargeable Mg batteries. In this study, MgCl2 is demonstrated as a non-nucleophilic and cheap Mg2+ source in combining with Al Lewis acids (AlCl3, AlPh3 and AlEtCl2) to formulate a series of Mg2+ electrolytes characteristic of high oxidation stability (up to 3.4 V vs Mg), sulfur compatibility and electrochemical reversibility (up to 100% coulombic efficiency). Three electrolyte systems (MgCl2-AlCl3, MgCl2-AlPh3, and MgCl2-AlEtCl2) were prepared free of purification and fully characterized by multinuclear NMR (27Al{1H} and 25Mg{1H}) spectroscopies, single crystal X-ray diffraction, and electrochemical analysis. The reaction mechanism of MgCl2 and the Al Lewis acids in THF is discussed to highlight the formation of the electrochemically active [(µ-Cl)3Mg2(THF)6]+ monocation in these electrolytes. We are grateful for the financial support from the Pacific Northwest National Laboratory (PNNL)-Laboratory Directed Research and Development (LDRD) program for developing magnesium battery technology. The XRD and SEM data were collected at the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at PNNL. PNNL is a multiprogram laboratory operated by Battelle Memorial Institute for the Department of Energy under Contract DE-AC05-76RL01830.

  11. Polymeric gamma-MgCl2 Nanoribbons

    SciTech Connect

    Vittadello,M.; Stallworth, P.; Alamgir, F.; Suarez, S.; Abbrent, S.; Drain, C.; Di Noto, V.; Greenbaum, S.

    2006-01-01

    {delta}-MgCl{sub 2} has relevant applications in the field of electrochemical energy storage and Ziegler-Natta catalysis. Here, we clarify the short-range structural peculiarities that make the disordered phase {delta}-MgCl{sub 2} extremely chemically active relative to the higher lattice energy phases, {alpha}-MgCl{sub 2} and {beta}-MgCl{sub 2}. X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and nuclear magnetic resonance (NMR) results are included. These findings, demonstrate the existence of [MgCl{sub 2}]{sub n} nanoribbons and active nanosurfaces in {delta}-MgCl{sub 2} and provide new insight about the nature of the bonding in the allotropic forms of MgCl{sub 2}.

  12. Experiencias sobre el impacto del Programa de Formación en Ética de la Investigación Biomédica y Psicosocial en el ámbito de la salud mental y la investigación conductual.

    PubMed

    Barrios, Liliana Mondragón

    2012-01-01

    El propósito de este trabajo es presentar el impacto y la integración que los conocimientos adquiridos en el Programa Internacional de Formación en Ética de la Investigación Biomédica y Psicosocial de la Universidad de Chile han tenido en mi experiencia profesional, en el ámbito de la investigación psicosocial en un Instituto de Salud de México. Para este objetivo, expondré tres áreas en las cuales se ha podido evidenciar tal impacto: trabajo en los comités de ética, desarrollo de programas de académicos en bioética e investigación y publicación sobre ética y bioética. El motivo que me llevó a incursionar en el Programa fue que su enseñanza vincula la investigación psicosocial con la ética y la bioética, lo cual me permitió dirigir este tipo de reflexión hacia problemas como violencia, suicidio, adicciones, depresión y salud mental, y a nuevos campos como los estudios comunitarios, con poblaciones en riesgo o vulnerables, en los cuales las diversas implicaciones son difíciles de indagar.

  13. Experiencias sobre el impacto del Programa de Formación en Ética de la Investigación Biomédica y Psicosocial en el ámbito de la salud mental y la investigación conductual.

    PubMed

    Barrios, Liliana Mondragón

    2012-01-01

    El propósito de este trabajo es presentar el impacto y la integración que los conocimientos adquiridos en el Programa Internacional de Formación en Ética de la Investigación Biomédica y Psicosocial de la Universidad de Chile han tenido en mi experiencia profesional, en el ámbito de la investigación psicosocial en un Instituto de Salud de México. Para este objetivo, expondré tres áreas en las cuales se ha podido evidenciar tal impacto: trabajo en los comités de ética, desarrollo de programas de académicos en bioética e investigación y publicación sobre ética y bioética. El motivo que me llevó a incursionar en el Programa fue que su enseñanza vincula la investigación psicosocial con la ética y la bioética, lo cual me permitió dirigir este tipo de reflexión hacia problemas como violencia, suicidio, adicciones, depresión y salud mental, y a nuevos campos como los estudios comunitarios, con poblaciones en riesgo o vulnerables, en los cuales las diversas implicaciones son difíciles de indagar. PMID:22754085

  14. Experiencias sobre el impacto del Programa de Formación en Ética de la Investigación Biomédica y Psicosocial en el ámbito de la salud mental y la investigación conductual

    PubMed Central

    Barrios, Liliana Mondragón

    2012-01-01

    El propósito de este trabajo es presentar el impacto y la integración que los conocimientos adquiridos en el Programa Internacional de Formación en Ética de la Investigación Biomédica y Psicosocial de la Universidad de Chile han tenido en mi experiencia profesional, en el ámbito de la investigación psicosocial en un Instituto de Salud de México. Para este objetivo, expondré tres áreas en las cuales se ha podido evidenciar tal impacto: trabajo en los comités de ética, desarrollo de programas de académicos en bioética e investigación y publicación sobre ética y bioética. El motivo que me llevó a incursionar en el Programa fue que su enseñanza vincula la investigación psicosocial con la ética y la bioética, lo cual me permitió dirigir este tipo de reflexión hacia problemas como violencia, suicidio, adicciones, depresión y salud mental, y a nuevos campos como los estudios comunitarios, con poblaciones en riesgo o vulnerables, en los cuales las diversas implicaciones son difíciles de indagar. PMID:22754085

  15. Inventario mundial de la calidad del carbon mineral (WoCQI) [The world coal quality inventory (WoCQI)

    USGS Publications Warehouse

    Finkelman, R.B.; Lovern, V.S.

    2001-01-01

    Los oficiales encargados de la politica comercial de cada pais requieren informacion clara y precisa sobre el recurso del carbon mineral, particularmente sobre sus propiedades y caracteristicas, para tomar decisiones bien fundamentadas con respecto al mejor uso de los recursos naturales, necesidades de importacion y oportunidades de exportacion, objetivos de politica interna y externa, oportunidades de transferencia tecnologica, posibilidades de inversion externa, estudios ambientales y de salud, y asuntos relacionados con el uso de productos secundarios y su disposicion.

  16. 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.

  17. Transformation of Mg-bearing amorphous calcium carbonate to Mg-calcite - In situ monitoring

    NASA Astrophysics Data System (ADS)

    Purgstaller, Bettina; Mavromatis, Vasileios; Immenhauser, Adrian; Dietzel, Martin

    2016-02-01

    The formation of Mg-bearing calcite via an amorphous precursor is a poorly understood process that is of relevance for biogenic and abiogenic carbonate precipitation. In order to gain an improved insight on the controls of Mg incorporation in calcite formed via an Mg-rich amorphous calcium carbonate (Mg-ACC) precursor, the precipitation of Mg-ACC and its transformation to Mg-calcite was monitored by in situ Raman spectroscopy. The experiments were performed at 25.0 ± 0.03 °C and pH 8.3 ± 0.1 and revealed two distinct pathways of Mg-calcite formation: (i) At initial aqueous Mg/Ca molar ratios ⩽ 1:6, Mg-calcite formation occurs via direct precipitation from solution. (ii) Conversely, at higher initial Mg/Ca molar ratios, Mg-calcite forms via an intermediate Mg-rich ACC phase. In the latter case, the final product is a calcite with up to 20 mol% Mg. This Mg content is significant higher than that of the Mg-rich ACC precursor phase. Thus, a strong net uptake of Mg ions from the solution into the crystalline precipitate throughout and also subsequent to ACC transformation is postulated. Moreover, the temporal evolution of the geochemical composition of the reactive solution and the Mg-ACC has no significant effect on the obtained "solubility product" of Mg-ACC. The enrichment of Mg in calcite throughout and subsequent to Mg-ACC transformation is likely affected by the high aqueous Mg/Ca ratio and carbonate alkalinity concentrations in the reactive solution. The experimental results have a bearing on the formation mechanism of Mg-rich calcites in marine early diagenetic environments, where high carbonate alkalinity concentrations are the rule rather than the exception, and on the insufficiently investigated inorganic component of biomineralisation pathways in many calcite secreting organisms.

  18. Mg Isotopic Compositions of Modern Marine Carbonates

    NASA Astrophysics Data System (ADS)

    Krogstad, E.; Bizzarro, M.; Hemming, N.

    2003-12-01

    We have used a MC-ICP-MS to measure the isotopic composition of magnesium in a number of samples of modern marine carbonate. Due to the large mass difference between 26Mg and 24Mg (similar to that between 13C and 12C), there is potential for mass fractionation during geologic and biologic processes that may make this isotope system useful for geochemical studies. These samples are from the study of Hemming and Hanson (1992, GCA 56: 537-543). The carbonate minerals analyzed include aragonite, low-Mg calcite, and high-Mg calcite. The samples include corals, echinoderms, ooids, etc., from subtropical to Antarctic settings. Mg purification was accomplished by ion-exchange chromatography, using Bio-Rad AG50W-X12 resin on which greater than 99 percent recovery of Mg is achieved. Samples were introduced into the MC-ICP-MS (VG Axiom) using a Cetac MCN-6000 nebuliser. We use a standard-sample-standard bracketing technique, and samples are analysed at least three times. For lab standards we find that the reproducibility on the 26Mg/24Mg to be about ñ 0.12 permil (2 s.d.). We monitored our separated samples for Na and Ca, as we have found that high Ca/Mg and Na/Mg produce variable magnesium isotopic fractionation during mass spectrometry due to as yet unclear matrix effects. We have normalized our results to our measured values for seawater. We observed a d26Mg(s.w.) range of -1.4 to -2.4 permil in our modern carbonate samples relative to present day seawater. Due to the long residence time of Mg in the oceans (ca. 50 my), this must be due to kinetic or biologic effects. Our d25Mg(s.w.) variations as a function of d26Mg(s.w.) plot along the terrestrial fractionation trend. With an average d26Mg(s.w.) of ca. +0.5 permil in all samples of mantle lithologies and mantle-derived igneous rocks (Bizzarro et al., Goldschmidt abs., 2003), we can assume that the Mg isotopic composition of Earth's river water lies between ca. -2.4 and +0.5 permil (relative to seawater). The actual

  19. Antibacterial biodegradable Mg-Ag alloys.

    PubMed

    Tie, D; Feyerabend, F; Müller, W D; Schade, R; Liefeith, K; Kainer, K U; Willumeit, R

    2013-06-16

    The use of magnesium alloys as degradable metals for biomedical applications is a topic of ongoing research and the demand for multifunctional materials is increasing. Hence, binary Mg-Ag alloys were designed as implant materials to combine the favourable properties of magnesium with the well-known antibacterial property of silver. In this study, three Mg-Ag alloys, Mg2Ag, Mg4Ag and Mg6Ag that contain 1.87 %, 3.82 % and 6.00 % silver by weight, respectively, were cast and processed with solution (T4) and aging (T6) heat treatment. The metallurgical analysis and phase identification showed that all alloys contained Mg4Ag as the dominant β phase. After heat treatment, the mechanical properties of all Mg-Ag alloys were significantly improved and the corrosion rate was also significantly reduced, due to presence of silver. Mg(OH)₂ and MgO present the main magnesium corrosion products, while AgCl was found as the corresponding primary silver corrosion product. Immersion tests, under cell culture conditions, demonstrated that the silver content did not significantly shift the pH and magnesium ion release. In vitro tests, with both primary osteoblasts and cell lines (MG63, RAW 264.7), revealed that Mg-Ag alloys show negligible cytotoxicity and sound cytocompatibility. Antibacterial assays, performed in a dynamic bioreactor system, proved that the alloys reduce the viability of two common pathogenic bacteria, Staphylococcus aureus (DSMZ 20231) and Staphylococcus epidermidis (DSMZ 3269), and the results showed that the killing rate of the alloys against tested bacteria exceeded 90%. In summary, biodegradable Mg-Ag alloys are cytocompatible materials with adjustable mechanical and corrosion properties and show promising antibacterial activity, which indicates their potential as antibacterial biodegradable implant materials.

  20. Mg Isotopes of USGS Igneous Rock Standards

    NASA Astrophysics Data System (ADS)

    Huang, F.; Glessner, J. J.; Lundstrom, C. C.

    2008-12-01

    Magnesium has three stable isotopes, 24Mg, 25Mg, and 26Mg with abundances of 78.99%, 10.00%, and 11.01%, respectively. It is one of the most abundant elements in the crust and mantle. As advancements of analytical techniques using MC-ICP-MS have dramatically advanced our ability to measure isotope ratios of Mg with greater precision, Mg isotopes can now be applied to study a variety of fundamental geological processes, such as continental crust weathering, chemical diffusion, and chondrule formation. Therefore the need for well characterized Mg isotope ratios for geological materials is increasingly important. Routine measurement of readily-available USGS rock standards is a viable way for inter-lab comparison to show the quality of data. However, the Mg isotope data for USGS standards reported in the literature are limited and inconsistent. USGS standards reported by different MC-ICP-MS labs have a range of Mg isotopic data outside of the normal external error of 0.1‰ (2σ). Mg isotopes of USGS igneous rock standards (dunite, DTS-1; basalts, BCR-1, BCR-2, BHVO-1; and andesite, AGV-1) were measured by a sample-standard bracketing method using a low resolution MC-ICP- MS (Nu-Plasma HR). The method has a large tolerance of matrix bias with Na/Mg and Al/Mg > 100% only changing the δ26Mg by less than 0.1‰. Dilution effects do not cause significant error (< 0.1‰) until the concentration difference between standard and sample is greater than 25%. The isobaric interference of CN+ on 26Mg was avoided by measuring Mg signal on the low mass shoulder. Only purified samples with excellent yields (>99.5%) and acceptable concentrations of matrix (mainly Na, Al, Ca, and Fe) are included in these results. Duplicate analyses of independently processed standards yielded the following results (δ26MgDSM-3 (‰)): BCR-2 (-0.306±0.144, - 0.290±0.116, -0.283±0.048, -0.288±0.057), BCR-1 (-0.399±0.079, -0.346±0.046), AGV-1 (-0.295±0.110, -0.307±0.086, -0.339±0.068), BHVO-1

  1. [Fluorescent probes for intracellular Mg2+ measurement].

    PubMed

    Komatsu, Hirokazu; Suzuki, Yoshio; Suzuki, Koji

    2004-08-01

    Recently, fluorescent probes are widely used as tools for dynamical measurement of ion distributions and concentrations in cells. They are highly sensitive, and offer imaging by the use of fluorescent microscopy in easily and less cell damaging way. This paper discusses the selectivity and optical character of the three novel Mg(2+) fluorescent probes. KMG-20AM offers ratiometric quantative measurement of Mg(2+), KMG-104 provides high-sensitive qualitative analysis and 3-D measurement. With those improved Mg(2+) fluorescent probes, the physiological and pathological role of Mg(2+) are going to be more and more clear. PMID:15577092

  2. Coherent interface structures and intergrain Josephson coupling in dense MgO/Mg2Si/MgB2 nanocomposites

    NASA Astrophysics Data System (ADS)

    Ueno, Katsuya; Nagashima, Yukihito; Seto, Yusuke; Matsumoto, Megumi; Sakurai, Takahiro; Ohta, Hitoshi; Takahashi, Kazuyuki; Uchino, Takashi

    2016-07-01

    Many efforts are under way to control the structure of heterointerfaces in nanostructured composite materials for designing functionality and engineering application. However, the fabrication of high-quality heterointerfaces is challenging because the crystal/crystal interface is usually the most defective part of the nanocomposite materials. In this work, we show that fully dense insulator (MgO)/semiconductor(Mg2Si)/superconductor(MgB2) nanocomposites with atomically smooth and continuous interfaces, including epitaxial-like MgO/Mg2Si interfaces, are obtained by solid phase reaction between metallic magnesium and a borosilicate glass. The resulting nanocomposites exhibit a semiconductor-superconducting transition at 36 K owing to the MgB2 nanograins surrounded by the MgO/Mg2Si matrix. This transition is followed by the intergrain phase-lock transition at ˜24 K due to the construction of Josephson-coupled network, eventually leading to a near-zero resistance state at 17 K. The method not only provides a simple process to fabricate dense nanocomposites with high-quality interfaces, but also enables to investigate the electric and magnetic properties of embedded superconducting nanograins with good intergrain coupling.

  3. The puzzle of {sup 32}Mg

    SciTech Connect

    Fortune, H. T.

    2011-08-15

    An analysis of results of the {sup 30}Mg(t,p) {sup 32}Mg reaction demonstrates that the ground state is the normal state and the excited 0{sup +} state is the intruder, contrary to popular belief. Additional experiments are suggested.

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

    NASA Astrophysics Data System (ADS)

    Kozioł-Rachwał, Anna; Nozaki, Takayuki; Zayets, Vadym; Kubota, Hitoshi; Fukushima, Akio; Yuasa, Shinji; Suzuki, Yoshishige

    2016-08-01

    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 in 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.

  5. Twinning-mediated formability in Mg alloys

    PubMed Central

    Suh, Byeong-Chan; Kim, Jae H.; Hwang, Ji Hyun; Shim, Myeong-Shik; Kim, Nack J.

    2016-01-01

    Mg alloys are promising candidates for automotive applications due to their low density and high specific strength. However, their widespread applications have not been realized mainly because of poor formability at room temperature, arising from limited number of active deformation systems and strong basal texture. It has been recently shown that Mg-Zn-Ca alloys have excellent stretch formability, which has been ascribed to their weak basal texture. However, the distribution of basal poles is orthotropic, which might result in anisotropy during deformation and have adverse effect on formability. Here, we show that tension twinning is mainly responsible for enhanced formability of Mg-Zn-Ca alloys. We found that tension twinning is quite active during both uniaxial deformation and biaxial deformation of Mg-Zn-Ca alloy even under the stress conditions unfavourable for the formation of tensile twins. Our results provide new insights into the development of Mg alloys having high formability. PMID:26926655

  6. Preparation and characterization of Mg nanoparticles

    SciTech Connect

    Song Meirong; Chen Miao Zhang Zhijun

    2008-05-15

    In this paper, Mg nanoparticles were prepared in tetrahydrofuran via lithium reduction of the corresponding Mg salt. X-ray diffraction and scanning electron microscope investigations confirm the formation of hexagonal phase Mg particles with an average size of 300 nm. X-ray photoelectron spectrometer analysis indicates that the as-prepared Mg nanoparticles are covered with a protecting layer consisting of residue solvents, naphthalene and Mg(OH){sub 2}, which slows down further oxidation under ambient conditions. Thermal analysis shows that the rapid oxidation and nitridation processes of the particles take place at around 500 deg. C and 553 deg. C, respectively. Furthermore, the addition of a small amount of magnesium nanoparticles remarkably catalyzes the decomposition process of ammonium perchlorate by lowering the decomposition temperature and enhancing its heat output.

  7. La reconstrucción del seno después de una mastectomía

    Cancer.gov

    Hoja informativa que describe la reconstrucción del seno (mama) después de una mastectomía. Contiene información sobre las opciones quirúrgicas, los cuidados de seguimiento y los exámenes de detección del cáncer de seno después de la reconstrucción.

  8. UHV and Ambient Pressure XPS: Potentials for Mg, MgO, and Mg(OH)2 Surface Analysis

    NASA Astrophysics Data System (ADS)

    Head, Ashley R.; Schnadt, Joachim

    2016-10-01

    The surface sensitivity of x-ray photoelectron spectroscopy (XPS) has positioned the technique as a routine analysis tool for chemical and electronic structure information. Samples ranging from ideal model systems to industrial materials can be analyzed. Instrumentational developments in the past two decades have popularized ambient pressure XPS, with pressures in the tens of mbar now commonplace. Here, we briefly review the technique, including a discussion of developments that allow data collection at higher pressures. We illustrate the information XPS can provide by using examples from the literature, including MgO studies. We hope to illustrate the possibilities of ambient pressure XPS to Mg, MgO, and Mg(OH)2 systems, both in fundamental and applied studies.

  9. Diffusion of Ca and Mg in Calcite

    SciTech Connect

    Cygan, R.T.; Fisler, D.K.

    1999-02-10

    The self-diffusion of Ca and the tracer diffusion of Mg in calcite have been experimentally measured using isotopic tracers of {sup 25}Mg and {sup 44}Ca. Natural single crystals of calcite were coated with a thermally-sputtered oxide thin film and then annealed in a CO{sub 2} gas at one atmosphere total pressure and temperatures from 550 to 800 C. Diffusion coefficient values were derived from the depth profiles obtained by ion microprobe analysis. The resultant activation energies for Mg tracer diffusion and Ca self-diffusion are respectively: E{sub a}(Mg) = 284 {+-} 74 kJ/mol and E{sub a}(Ca) = 271 {+-} 80 kJ/mol. For the temperature ranges in these experiments, the diffusion of Mg is faster than Ca. The results are generally consistent in magnitude with divalent cation diffusion rates obtained in previous studies and provide a means of interpreting the thermal histories of carbonate minerals, the mechanism of dolomitization, and other diffusion-controlled processes. The results indicate that cation diffusion in calcite is relatively slow and cations are the rate-limiting diffusing species for the deformation of calcite and carbonate rocks. Application of the calcite-dolomite geothermometer to metamorphic assemblages will be constrained by cation diffusion and cooling rates. The direct measurement of Mg tracer diffusion in calcite indicates that dolomitization is unlikely to be accomplished by Mg diffusion in the solid state but by a recrystallization process.

  10. 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. PMID:19265212

  11. 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.

  12. Comparative analysis of Mg-dependent and Mg-independent HCO3(-) ATPases.

    PubMed

    Dzneladze, S; Tsakadze, L; Leladze, M; Nozadze, E; Arutinova, N; Shioshvili, L; Chkadua, G

    2015-02-01

    The comparative analysis between two enzymes, Mg-dependent and Mg-independent HCO3(-) ATPases, were studied in synaptosomal and microsomal membrane fractions of albino rat brain, using the method of kinetic analysis of the multi-sited enzyme systems. Therefore, it can be inferred that Mg-dependent HCO3(-) ATPase belongs to the group of "P-type" transporting ATPases. Mg-independent HCO3(-) ATPase with its kinetic properties may be attributed to the group of "Ecto" ATPases.

  13. 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.

  14. In vitro and in vivo comparison of binary Mg alloys and pure Mg.

    PubMed

    Myrissa, Anastasia; Agha, Nezha Ahmad; Lu, Yiyi; Martinelli, Elisabeth; Eichler, Johannes; Szakács, Gábor; Kleinhans, Claudia; Willumeit-Römer, Regine; Schäfer, Ute; Weinberg, Annelie-Martina

    2016-04-01

    Biodegradable materials are under investigation due to their promising properties for biomedical applications as implant material. In the present study, two binary magnesium (Mg) alloys (Mg2Ag and Mg10Gd) and pure Mg (99.99%) were used in order to compare the degradation performance of the materials in in vitro to in vivo conditions. In vitro analysis of cell distribution and viability was performed on discs of pure Mg, Mg2Ag and Mg10Gd. The results verified viable pre-osteoblast cells on all three alloys and no obvious toxic effect within the first two weeks. The degradation rates in in vitro and in vivo conditions (Sprague-Dawley® rats) showed that the degradation rates differ especially in the 1st week of the experiments. While in vitro Mg2Ag displayed the fastest degradation rate, in vivo, Mg10Gd revealed the highest degradation rate. After four weeks of in vitro immersion tests, the degradation rate of Mg2Ag was significantly reduced and approached the values of pure Mg and Mg10Gd. Interestingly, after 4 weeks the estimated in vitro degradation rates approximate in vivo values. Our systematic experiment indicates that a correlation between in vitro and in vivo observations still has some limitations that have to be considered in order to perform representative in vitro experiments that display the in vivo situation.

  15. The Mg impurity in nitride alloys

    SciTech Connect

    Zvanut, M. E.; Willoughby, W. R.; Sunay, U. R.; Koleske, D. D.; Allerman, A. A.; Wang, Ke; Araki, Tsutomu; Nanishi, Yasushi

    2014-02-21

    Although several magnetic resonance studies address the Mg acceptor in GaN, there are few reports on Mg doping in the alloys, where hole production depends strongly on the Al or In content. Our electron paramagnetic resonance (EPR) measurements of the p-type alloys suggest that the Mg impurity retains the axial symmetry, characteristic of a p-type dopant in both alloys; however, In and Al produce additional, different characteristics of the acceptor. In InGaN, the behavior is consistent with a lowering of the acceptor level and increasing hole density as In concentration increases. For AlGaN, the amount of neutral Mg decreases with increasing Al content, which is attributed to different kinetics of hydrogen diffusion thought to occur in samples with higher Al mole fraction.

  16. Formation of Mg{sub 2}Ni with enhanced kinetics: Using MgH{sub 2} instead of Mg as a starting material

    SciTech Connect

    Zhao Bin; Fang Fang; Sun Dalin; Zhang Qingan; Wei Shiqiang; Cao Fenglei; Sun Huai; Ouyang Liuzhang; Zhu Min

    2012-08-15

    At a temperature over the decomposition point (375 Degree-Sign C) of MgH{sub 2}, the formation of Mg{sub 2}Ni is greatly enhanced from the 2MgH{sub 2}+Ni system, as compared to the 2Mg+Ni system. In support of this finding, in-situ observation of X-ray absorption fine structure of the two systems indicates that Mg---Ni bonds form faster in the 2MgH{sub 2}+Ni system than in the 2Mg+Ni system. Furthermore, theoretical modeling also shows that Mg atoms are readily released from MgH{sub 2} using much less energy and thus are more available to react with Ni once the dehydrogenation of MgH{sub 2} occurs, as compared to normal Mg. - Graphical Abstract: The formation of Mg{sub 2}Ni is greatly enhanced by using MgH{sub 2} instead of Mg at a temperature higher than the MgH{sub 2} decomposition point. Highlights: Black-Right-Pointing-Pointer A new and efficient synthesis of Mg-based compounds at a reduced temperature. Black-Right-Pointing-Pointer Mg{sub 2}Ni formation is enhanced by using MgH{sub 2} instead of Mg as a starting material. Black-Right-Pointing-Pointer XAFS results show that Mg---Ni bonds are formed faster in 4MgH{sub 2}+Ni than in 4Mg+Ni. Black-Right-Pointing-Pointer DFT calculations show that Mg atoms are released from MgH{sub 2} more readily than from Mg. Black-Right-Pointing-Pointer Mg formed by MgH{sub 2} dehydrogenation is more available to react with Ni than normal Mg.

  17. Estudio multifrecuencia del medio interestelar cercano a HD 192281

    NASA Astrophysics Data System (ADS)

    Arnal, E. M.; Cappa, C. E.; Cichowolski, S.; Pineault, S.; St-Louis, N.

    Una de las causas que modifica la estructura y dinámica del medio interestelar es la acción que los vientos de las estrellas de gran masa ejercen sobre el mismo. En este trabajo, mediante el uso de datos interferométricos obtenidos en la banda de radio en la transición de λ˜21-cm del hidrógeno neutro y de imágenes de la emisión de continuo en las bandas de 408 y 1420 MHz, de imágenes HIRES del satélite IRAS en 60 y 100μm, y de observaciones de continuo obtenidas con radiotelescopios de disco simple en 2695, 4850 y 8350 MHz se ha realizado un estudio multifrecuencia de los efectos que los vientos estelares de HD 192281, una estrella de tipo espectral O5,Vn((f))p, han tenido sobre el medio interestelar que rodea a la misma.

  18. Mg/Ca of Continental Ostracode Shells

    NASA Astrophysics Data System (ADS)

    Ito, E.; Forester, R. M.; Marco-Barba, J.; Mezquita, F.

    2007-12-01

    Marine ionic chemistry is thought to remain constant. This, together with the belief that marine calcifiers partition Mg/Ca in a systematic manner as functions of temperature (and Mg/Ca) of water forms the basis of the Mg/Ca thermometer. In continental settings both of these assumptions are usually not true. Continental waters contain a wide variety of solutes in absolute and relative ion concentrations. Hence, waters with identical Mg/Ca may have very different concentrations of Mg and Ca and very different anions. Here we use two examples to focus on the effects of ion chemistry on Mg/Ca partitioning in continental ostracode shells and we ignore the complexities of solute evolution, which can change Mg/Ca over timescales of minutes to millennia. Palacios-Fest and Dettman (2001) conducted a monthly study of ,Cypridopsis vidua at El Yeso Lake in Sonora, Mexico. They established a relation between temperature and average shell Mg/Ca using regression analyses on averaged data. When their Mg/Ca-temperature relation is applied to monthly ,C. vidua data from Page Pond near Cleveland, Ohio, water temperatures of -8 to -1°C are obtained. The observed Mg/Ca ranges for El Yeso Lake (0.31 to 0.46) and Page Pond (0.33 to 0.46) are similar, as are their specific conductivities (700 to 850μS for El Yeso Lake; 400 to 600μS for Page Pond). However, [Ca] is 140-260 mg/L for El Yeso, but only 70-90 mg/L for Page Pond. Page Pond data, in fact, shows a good temperature shell Mg/Ca relation for .C. vidua, but the relation is different from that at El Yeso. Hence, shell Mg/Ca is a multi-valued, family of curves function of temperature and Mg/Ca of water that depends on the [Mg] and [Ca] values in water and perhaps other factors. Our second example comes from sites near Valencia, Spain and involves shell data for ,Cyprideis torosa, an estuarine ostracode that is tolerant of a wide range of salinity and can live in continental waters as long as the carbonate alkalinity to Ca ratio is

  19. Diffusion behavior and distribution regulation of MgO in MgO-bearing pellets

    NASA Astrophysics Data System (ADS)

    Gao, Qiang-jian; Shen, Yan-song; Wei, Guo; Jiang, Xin; Shen, Feng-man

    2016-09-01

    In this paper, the diffusion behavior between MgO and Fe2O3 (the main iron oxide in pellets) is investigated using a diffusion couple method. In addition, the distribution regulation of MgO in MgO-bearing pellets is analyzed via pelletizing experiments. The results illustrate that MgO is prone to diffuse into Fe2O3 in the form of solid solution; the diffusion rate considered here is 13.64 µm·min-1. Most MgO content distributes in the iron phase instead of the slag phase. The MF phase {(Mg1-x Fex)O·Fe2O3, x ≤ 1} is generated in the MgO-bearing pellets. However, the distribution of MgO in the radial direction of the pellets is inconsistent. The solid solution portion of MgO in the MF phase is larger in the outer layer of the pellets than in the inner layer. In this work, the approximate chemical composition of the MF phase in the outer layer of the pellets is {(Mg0.35-0.77·Fe0.65-0.23) O·Fe2O3} and in the inner layer is {(Mg0.13-0.45·Fe0.87-0.55) O·Fe2O3}.

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

    SciTech Connect

    Soufli, Regina; Fernandez-Perea, Monica; Baker, Sherry L.; Robinson, Jeff C.; Alameda, Jennifer; Walton, Christopher C.

    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.

  1. Mg deficiency affects leaf Mg remobilization and the proteome in Brassica napus.

    PubMed

    Billard, Vincent; Maillard, Anne; Coquet, Laurent; Jouenne, Thierry; Cruz, Florence; Garcia-Mina, José-Maria; Yvin, Jean-Claude; Ourry, Alain; Etienne, Philippe

    2016-10-01

    In order to cope with variable mineral nutrient availability, higher plants have developed numerous strategies including the remobilization of nutrients from source to sink tissues. However, such processes remain relatively unknown for magnesium (Mg), which is the third most important cation in plant tissues. Using Mg depletion of Brassica napus, we have demonstrated that Mg is remobilized from old leaves to young shoot tissues. Moreover, this study showed that Mg depletion induces modification of nutrient uptake, especially Zn and Mn. Finally, comparative proteomic analysis of old leaves (source of Mg) revealed amongst other results that some proteins requiring Mg for their functionality (isocitrate dehydrogenase for example) were up-regulated. Moreover, down-regulation of proteases suggested that mobilization of Mg from old leaves was not associated with senescence. PMID:27362297

  2. Fourier transform infrared emission spectra of MgH and MgD

    NASA Astrophysics Data System (ADS)

    Shayesteh, A.; Appadoo, D. R. T.; Gordon, I.; Le Roy, R. J.; Bernath, P. F.

    2004-06-01

    High resolution Fourier transform infrared emission spectra of MgH and MgD have been recorded. The molecules were generated in an emission source that combines an electrical discharge with a high temperature furnace. Several vibration-rotation bands were observed for all six isotopomers in the X 2Σ+ ground electronic state: v=1→0 to 4→3 for 24MgH, v=1→0 to 3→2 for 25MgH and 26MgH, v=1→0 to 5→4 for 24MgD, v=1→0 to 4→3 for 25MgD and 26MgD. The new data were combined with the previous ground state data, obtained from diode laser vibration-rotation measurements and pure rotation spectra, and spectroscopic constants were determined for the v=0 to 4 levels of 24MgH and the v=0 to 5 levels of 24MgD. In addition, Dunham constants and Born-Oppenheimer breakdown correction parameters were obtained in a combined fit of the six isotopomers. The equilibrium vibrational constants (ωe) for 24MgH and 24MgD were found to be 1492.776(7) cm-1 and 1077.298(5) cm-1, respectively, while the equilibrium rotational constants (Be) are 5.825 523(8) cm-1 and 3.034 344(4) cm-1. The associated equilibrium bond distances (re) were determined to be 1.729 721(1) Å for 24MgH and 1.729 157(1) Å for 24MgD.

  3. 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.

  4. Preguntas y respuestas acerca del Estudio del

    Cancer.gov

    El Estudio del Tamoxifeno y Raloxifeno (STAR, por sus siglas en ingls) es un estudio clnico (un estudio de investigacin conducido con voluntarios) diseado para ver cómo el medicamento raloxifeno (Evista) se compara con el medicamento tamoxifeno (Nolvadex)

  5. Mg/Ca and δ18O in the calcite of benthic foraminifera: does size matter?

    NASA Astrophysics Data System (ADS)

    de Nooijer, Lennart; Bijma, Jelle; -Jan Reichart, Gert; Hathorne, Ed

    2010-05-01

    Mg/Ca and del-18O are popular proxies for past sea water temperatures, ice volume and, together, salinity. The biological control that foraminifera have over calcification results in precipitation of calcium carbonate that has an isotope and element composition that is very different from those of inorganically precipitated calcium carbonates. Indications for an effect of ontogeny (i.e. size of a specimen) on the fractionation of oxygen isotopes are contradictory, while for the incorporation of most (trace) elements, data are lacking. The causes of size-based variability in element incorporation and isotope fractionation need to be understood and quantified in order to reliably use them as paleoproxies. In this study, we present Mg/Ca and oxygen isotope data from cultured specimens of the benthic foraminifer Ammonia tepida. When asexual reproduction takes place in this species, 50-300 genetically identical juveniles (i.e. clones) are produced. These juveniles are cultured at constant temperature, carbonate chemistry, salinity, etc to determine inter- and intra-specimen variability in Mg/Ca, Ba/Ca and Sr/Ca. From the same groups of clones, del-18O was determined from specimens with different sizes. Results show that the variability differs greatly between the analysed elements (e.g. relatively constant for Sr and Ba, variable for Mg) and isotopes, underscoring the need for a biological understanding of foraminiferal calcification pathways.

  6. Análisis del antígeno prostático específico (PSA)

    Cancer.gov

    Hoja informativa sobre la prueba del antígeno prostático específico (PSA) y los exámenes selectivos de detección para el cáncer de próstata, y clarifica los beneficios y limitaciones de dicha prueba.

  7. 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

  8. 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.

  9. "Safe" Coulomb excitation of 30Mg.

    PubMed

    Niedermaier, O; Scheit, H; Bildstein, V; Boie, H; Fitting, J; von Hahn, R; Köck, F; Lauer, M; Pal, U K; Podlech, H; Repnow, R; Schwalm, D; Alvarez, C; Ames, F; Bollen, G; Emhofer, S; Habs, D; Kester, O; Lutter, R; Rudolph, K; Pasini, M; Thirolf, P G; Wolf, B H; Eberth, J; Gersch, G; Hess, H; Reiter, P; Thelen, O; Warr, N; Weisshaar, D; Aksouh, F; Van den Bergh, P; Van Duppen, P; Huyse, M; Ivanov, O; Mayet, P; Van de Walle, J; Aystö, J; Butler, P A; Cederkäll, J; Delahaye, P; Fynbo, H O U; Fraile, L M; Forstner, O; Franchoo, S; Köster, U; Nilsson, T; Oinonen, M; Sieber, T; Wenander, F; Pantea, M; Richter, A; Schrieder, G; Simon, H; Behrens, T; Gernhäuser, R; Kröll, T; Krücken, R; Münch, M; Davinson, T; Gerl, J; Huber, G; Hurst, A; Iwanicki, J; Jonson, B; Lieb, P; Liljeby, L; Schempp, A; Scherillo, A; Schmidt, P; Walter, G

    2005-05-01

    We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient gamma spectrometer MINIBALL. Using 30Mg ions accelerated to an energy of 2.25 MeV/u together with a thin (nat)Ni target, Coulomb excitation of the first excited 2+ states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation gamma-ray yields the B(E2;0(+)gs-->2(+)1) value of 30Mg was determined to be 241(31)e2 fm4. Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope 30Mg resides outside the "island of inversion."

  10. Unraveling the role of Mg(++) in osteoarthritis.

    PubMed

    Li, Yaqiang; Yue, Jiaji; Yang, Chunxi

    2016-02-15

    Mg(++) is widely involved in human physiological processes that may play key roles in the generation and progression of diseases. Osteoarthritis (OA) is a complex joint disorder characterized by articular cartilage degradation, abnormal mineralization and inflammation. Magnesium deficiency is considered to be a major risk factor for OA development and progression. Magnesium deficiency is active in several pathways that have been implicated in OA, including increased inflammatory mediators, cartilage damage, defective chondrocyte biosynthesis, aberrant calcification and a weakened effect of analgesics. Abundant in vitro and in vivo evidence in animal models now suggests that the nutritional supplementation or local infiltration of Mg(++) represent effective therapies for OA. The goal of this review is to summarize the current understanding of the role of Mg(++) in OA with particular emphasis on the related molecular mechanisms involved in OA progression. PMID:26800786

  11. Efficient hydrogen storage with the combination of lightweight Mg/MgH2 and nanostructures.

    PubMed

    Cheng, Fangyi; Tao, Zhanliang; Liang, Jing; Chen, Jun

    2012-07-28

    Efficient hydrogen storage plays a key role in realizing the incoming hydrogen economy. However, it still remains a great challenge to develop hydrogen storage media with high capacity, favourable thermodynamics, fast kinetics, controllable reversibility, long cycle life, low cost and high safety. To achieve this goal, the combination of lightweight materials and nanostructures should offer great opportunities. In this article, we review recent advances in the field of chemical hydrogen storage that couples lightweight materials and nanostructures, focusing on Mg/MgH(2)-based systems. Selective theoretical and experimental studies on Mg/MgH(2) nanostructures are overviewed, with the emphasis on illustrating the influences of nanostructures on the hydrogenation/dehydrogenation mechanisms and hydrogen storage properties such as capacity, thermodynamics and kinetics. In particular, theoretical studies have shown that the thermodynamics of Mg/MgH(2) clusters below 2 nm change more prominently as particle size decreases. PMID:22715459

  12. 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.

  13. Interdiffusion in the Mg-Al system and Intrinsic Diffusion in (Al3Mg2) Phase

    SciTech Connect

    Brennan, Sarah; Bermudez, Katrina; Kulkarni, Nagraj S; Sohn, Yong Ho

    2011-01-01

    Increasing use and development of lightweight Mg-alloys have led to the desire for more fundamental research in and understanding of Mg-based systems. As a strengthening component, Al is one of the most important and common alloying elements for Mg-alloys. In this study, solid-to-solid diffusion couple techniques were employed to examine the interdiffusion between pure Mg and Al. Diffusion anneals were carried out at 300 , 350 , and 400 C for 720, 360, and 240 hours, respectively. Optical and scanning electron microscopies (SEM) were employed to observe the formation of the intermetallics -Al12Mg17 and -Al3Mg2, but not -phase. Concentration profiles were determined using X-ray energy dispersive spectroscopy (XEDS). The growth constants and activation energies were determined for each intermetallic phase.

  14. Superconductivity in MgPtSi: An orthorhombic variant of MgB2

    NASA Astrophysics Data System (ADS)

    Kudo, Kazutaka; Fujimura, Kazunori; Onari, Seiichiro; Ota, Hiromi; Nohara, Minoru

    2015-05-01

    A ternary compound, MgPtSi, was synthesized by solid-state reaction. An examination of the compound by powder x-ray diffraction revealed that it crystallizes in the orthorhombic TiNiSi-type structure with the P n m a space group. The structure comprises alternately stacked layers of Mg and PtSi honeycomb network, which is reminiscent of MgB2, and the buckling of the honeycomb network causes orthorhombic distortion. Electrical and magnetic studies revealed that MgPtSi exhibited superconductivity with a transition temperature of 2.5 K. However, its isostructural compounds, namely, MgRhSi and MgIrSi, were not found to exhibit superconductivity.

  15. Excited intruder states in {sup 32}Mg

    SciTech Connect

    Tripathi, Vandana; Tabor, S. L.; Bender, P.; Hoffman, C. R.; Lee, Sangjin; Pepper, K.; Perry, M.; Utsuno, Y.; Otsuka, T.; Mantica, P. F.; Pinter, J. S.; Stoker, J. B.; Cook, J. M.; Pereira, J.; Weisshaar, D.

    2008-03-15

    The low energy level structure of N=20 {sup 32}Mg obtained via {beta}-delayed {gamma} spectroscopy is reported. The level structure of {sup 32}Mg is found to be completely dominated by intruders. An inversion between the 1p-1h and 3p-3h states is observed for the negative parity states, similar to the 0p-0h and 2p-2h inversion for the positive parity states in these N{approx}20 nuclei. The intruder excited states, both positive and negative parity, are reasonably explained by Monte Carlo shell model calculations, which suggest a shrinking N=20 shell gap with decreasing Z.

  16. El Conocimiento Ocupacional y del Yo para los Grupos Especiales. Monografias sobre el Conocimiento Ocupacional y del Yo.

    ERIC Educational Resources Information Center

    Hoyt, Kenneth B.

    This Spanish translation of ED 132 428 includes the three papers representing Office of Education attempts to face the need for improving delivery of career education to special portions of the population. New additions are brief sections on basic definitions and additional considerations of the significance of work. The first paper, on career…

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

    PubMed

    See, Kimberly A; Chapman, Karena W; Zhu, Lingyang; Wiaderek, Kamila M; Borkiewicz, Olaf J; Barile, Christopher J; Chupas, Peter J; Gewirth, Andrew A

    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, (27)Al and (35)Cl nuclear magnetic resonance spectroscopy, and pair distribution function analysis, we explore the 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.

  18. Seminario Tecnico Regional Sobre Alternativas de Educacion Basica de Adultos en el Marco de la REDALF del Proyecto Principal de Educacion en America Latina y el Caribe (Colonia Tovar, Venezuela, 29 de Septiembre al 3 de Octubre, 1986). Documento Final. (Regional Seminar on Alternatives for Basic Adult Education in the REDALF Project for Education in Latin America and the Caribbean (Colonia Tovar, Venezuela, September 29-October 3, 1986). Final Document.)

    ERIC Educational Resources Information Center

    United Nations Educational, Scientific, and Cultural Organization, Santiago (Chile). Regional Office for Education in Latin America and the Caribbean.

    The final report of a conference concerning adult basic education de Adultos en el Marco de la REDALF del related to innovative projects in adult education in nine countries. A wide spectrum of issues related to adult basic education, curriculum, methodology, evaluation, and research are analyzed in the context of educational planning. Among the…

  19. Measurement of lifetimes in 23Mg

    NASA Astrophysics Data System (ADS)

    Kirsebom, O. S.; Bender, P.; Cheeseman, A.; Christian, G.; Churchman, R.; Cross, D. S.; Davids, B.; Evitts, L. J.; Fallis, J.; Galinski, N.; Garnsworthy, A. B.; Hackman, G.; Lighthall, J.; Ketelhut, S.; Machule, P.; Miller, D.; Nielsen, S. T.; Nobs, C. R.; Pearson, C. J.; Rajabali, M. M.; Radich, A. J.; Rojas, A.; Ruiz, C.; Sanetullaev, A.; Unsworth, C. D.; Wrede, C.

    2016-02-01

    Several lifetimes in 23Mg have been determined for the first time using the Doppler-shift attenuation method. A Monte Carlo simulation code has been written to model the γ -ray line shape. An upper limit of τ <12 fs at the 95% C.L. has been obtained for the astrophysically important 7787 keV state.

  20. Thermodynamic data of Mg-chloritoid

    NASA Astrophysics Data System (ADS)

    Grevel, K.-D.; Navrotsky, A.; Kahl, W.-A.; Majzlan, J.; Lathe, C.

    2003-04-01

    Calorimetric and P-V-T data for synthetic Mg-chloritoid (MgAl2SiO5(OH)2) have been obtained. The enthalpy of drop-solution was measured by high-temperature oxide melt calorimetry in two laboratories (UC Davis, California, and Ruhr-University Bochum, Germany) using lead borate (2 PbO\\cdotB2O3) at T = 700 oC as solvent. The resulting values were used to calculate the enthalpy of formation from the elements; they range from -3552.7 ± 4.9 kJ mol-1 to -3555.4±6.1 kJ mol-1. Some preliminary heat capacity measurements of MgAl2SiO5(OH)2 have shown that a Berman and Brown (1985) type four-term equation based on the Neumann-Kopp rule represents the heat capacity over the entire temperature range to within the experimental uncertainty. The P-V-T behaviour of Mg-chloritoid has been determined under high pressures and high temperatures up to 8.5 GPa and 800 oC using a MAX 80 cubic anvil high-pressure apparatus. The samples were mixed with vaseline to ensure hydrostatic pressure transmitting conditions, NaCl served as an internal standard for pressure calibration. By fitting a Birch-Murnaghan EOS to the data, the bulk modulus was determined as 131.0 ± 2.4 GPa, (K' = 4), VT,0 = 456.58 Å3 exp [int(0.30±0.02) × 10-4 dT], (partialKT/partialT)P = -0.023±0.007 GPa K-1. The thermodynamic data obtained for Mg-chloritoid are consistent with phase equilibrium data reported in the literature. The best agreement was obtained with ΔfH0298 (Mg-chloritoid) = -3557.5 kJ mol-1, and S0298 (Mg-chloritoid) = 131.7 J K-1mol-1.

  1. 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.

  2. Dust in MG II Absorption Systems

    NASA Astrophysics Data System (ADS)

    Malhotra, S.

    The dust absorption feature at 2175 AA is detected in a composite spectrum of Mg II absorbers. The composite absorber spectrum is obtained by taking the geometric mean of 92 quasar spectra after aligning them in the rest-frame of 96 absorbers. By aligning the spectra according to absorber redshifts we reinforce the spectral features of the absorbers, and smooth over possible bumps and wiggles in the emission spectra. The width of the observed absorption feature is 200-300 AA (FWHM), or 0.4-0.6 microns^{-1} and the central wavelength is 2240 AA. The Galactic dust feature has a central wavelength of 2176 AA and FWHM = 0.8-1.25 microns^{-1}. Simulations show that this discrepancy between the properties of the 2175 AA feature in Mg II absorbers and Galactic ISM can be mostly explained by the different methods used to measure them (cf. Malhotra 1997).

  3. Effects of atorvastatin 20 mg, rosuvastatin 10 mg, and atorvastatin/ezetimibe 5 mg/5 mg on lipoproteins and glucose metabolism.

    PubMed

    Her, Ae-Young; Kim, Jong-Youn; Kang, Seok-Min; Choi, Donghoon; Jang, Yangsoo; Chung, Namsik; Manabe, Ichiro; Lee, Sang-Hak

    2010-06-01

    The aim of this study was to compare the effects of 3 different statin regimens that have equivalent low-density lipoprotein cholesterol (LDL-C) lowering efficacy on the apolipoprotein B/A1 ratio and glucose metabolism. After a 4-week dietary lead-in, 90 hypercholeserolemic patients were randomly assigned to 1 of 3 treatment groups for 8 weeks: atorvastatin 20 mg, rosuvastatin 10 mg, or atorvastatin/ezetimibe 5 mg/5 mg. At drug treatment week 8, we compared the percentage changes in lipid parameters, apolipoprotein B/A1 ratio, hemoglobin A1c, and homeostasis model assessment-insulin resistance (HOMA-IR) from baseline. Seventy-six patients completed the study and the percentage changes in LDL-C were comparable among the groups. However, the percentage reduction in the apolipoprotein B/A1 ratio was significantly greater in the rosuvastatin group (-47% +/- 14%, P = .04) and the combination group (-46% +/- 8%, P = .05) than in the atorvastatin group (-39% +/- 11%). The percentage increase in hemoglobin A1c was small but significantly greater in the atorvastatin group compared to the combination group (3.0% +/- 5.2% and -0.4% +/- 4.0%, P = .03). The effect of rosuvastatin on hemoglobin A1c was not different from those of the other 2 regimens. The effects of 3 statin regimens were similar on HOMA-IR. In conclusion, 3 statin regimens have differential effect on apolipoprotein B/A1 and glycemic control after comparable LDL-C reduction.

  4. Highly Reversible Mg Insertion in Nanostructured Bi for Mg Ion Batteries

    SciTech Connect

    Shao, Yuyan; Gu, Meng; Li, Xiaolin; Nie, Zimin; Zuo, Pengjian; Li, Guosheng; Liu, Tianbiao L.; Xiao, Jie; Cheng, Yingwen; Wang, Chong M.; Zhang, Jiguang; Liu, Jun

    2014-01-08

    Rechargeable magnesium batteries have attracted wide attention for energy storage. Currently, most studies focus on Mg metal as the anode, but this approach is still limited by the properties of the electrolyte and poor control of the Mg plating/stripping processes.1,2 Here we report the synthesis and application of Bi nanotubes as a high performance anode material for rechargeable Mg ion batteries. The nanostructured Bi anode delivers a high reversible specific capacity (350 mAh/gBi, or 3430 mAh/cm3 Bi), excellent stability, and high columbic efficiency (95 % initial and very close to 100% afterwards). The good performance is attributed to the unique properties of in-situ formed, interconnected nanoporous bismuth. Such nanostructures can effectively accommodate the large volume change without losing electric contact and significantly reduce diffusion length for Mg2+. Significantly, the nanostructured Bi anode can be used with conventional electrolytes which will open new opportunities to study Mg ion battery chemistry and further improve the properties. The performance and the stability of a full cell Mg ion battery have been demonstrated with conventional electrolytes. This work suggests that other high energy density alloy compounds may also be considered for Mg-ion chemistry for high capacity electrode materials.

  5. 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.

  6. The significance of Mg in prebiotic geochemistry

    PubMed Central

    Holm, N G

    2012-01-01

    Magnesium plays a special role in biochemistry because of its ability to coordinate six oxygen atoms efficiently in its first coordination shell. Such oxygen atoms may be part of one or two charged oxyanions, which means that Mg2+ can, for instance, tie together two different phosphate groups that are located at distance from each other in a macromolecule, and in this way be responsible for the folding of molecules like RNA. This property of Mg2+ also helps the stabilization of diphosphate and triphosphate groups of nucleotides, as well as promoting the condensation of orthophosphate to oligophosphates, like pyrophosphate and trimetaphosphate. Borates, on the other hand, are known to promote the formation of nucleobases and carbohydrates, ribose in particular, which is yet another constituent of nucleotides. The oldest borate minerals that we find on Earth today are magnesium borates. Dissolved borate stabilizes pentose sugars by forming complexes with cis-hydroxyl groups. In the furanose form of ribose, the preferential binding occurs to the 2 and 3 carbon, leaving the 5 carbon free for phosphorylation. The central role of Mg2+ in the function of ribozymes and its ‘archaic’ position in ribosomes, and the fact that magnesium generally has coordination properties different from other cations, suggests that the inorganic chemistry of magnesium had a key position in the first chemical processes leading to the origin and early evolution of life. PMID:22429303

  7. Interstitial Fe in MgO

    SciTech Connect

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

    2014-01-14

    Isolated {sup 57}Fe atoms were studied in MgO single-crystals by emission Mössbauer spectroscopy following implantation of {sup 57}Mn decaying to {sup 57}Fe. Four Mössbauer spectral components were found corresponding to different Fe lattice positions and/or charge states. Two components represent Fe atoms substituting Mg as Fe{sup 2+} and Fe{sup 3+}, 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.

  8. Influence of Mg component and pressure on magnetic ordering of (Mg,Fe)O

    NASA Astrophysics Data System (ADS)

    Fujii, A.; Kondo, T.; Taniguchi, T.

    2012-12-01

    (Mg,Fe)O is the second most abundant phase in the Earth's lower mantle. Knowing the fundamental properties of (Mg,Fe)O is important to understand the Earth's materials. The relation between rhombohedral distortion and antiferromagnetic ordering in FeO have been discussed, as an end member of (Mg,Fe)O. However, it does not fully understand for (Mg,Fe)O yet because its structural transition pressure is influenced by Mg component and stress condition [e.g. Zhuravlev et al., 2007]. We should also account compositional dependence on Néel temperature [Woods and Fine, 1969; Fujii et al., 2011] and spin glass-like behavior [Abbas and Hicks, 1990; Jing et al., 1993]. In this study, we investigated the compositional dependence of magnetic ordering at ambient pressure, and pressure dependence of Néel temperature up to 1.27 GPa. Superconducting Quantum Interference Device (SQUID, MPMS-7, Quantum design) was used for all magnetic measurements. We measured the temperature dependence of susceptibilities cooling with in zero field (ZFC) and in a field (FC) at ambient pressure and observed splitting between susceptibility of ZFC and FC. We confirmed that the smaller compositional dependence on Néel temperature in (Mg1-XFeX)O (X ≤ 0.60) [Fujii et al., 2011] may be explained by spin-glass transition. The transition temperature of (Mg0.40Fe0.60)O is 82 K and is close to 76 K that observed in (Mg0.23Fe0.77)0.92O [Abbas and Hicks, 1990]. The spin-glass like behavior does not affect on the Néel temperature of (Mg1-XFeX)O (X ≥ 0.70) suggested by previous work [Fujii et al., 2011] because spin-glass transition temperature would not exceed 82 K. We also measured the pressure dependence of Néel temperature of (Mg0.30Fe0.70)O, (Mg0.25Fe0.75)O and (Mg0.20Fe0.80)O using a piston cylinder type pressure cell. We calibrated pressure by superconducting transition of tin. Néel temperature of (Mg,Fe)O were increased with increasing pressure except for some measurements under non

  9. Speech and Language Disorders. Fact Sheet = Trastornos del Habla y Lenguaje. Hojas Informativas Sobre Discapacidades.

    ERIC Educational Resources Information Center

    National Information Center for Children and Youth with Disabilities, Washington, DC.

    This fact sheet on speech and language disorders is presented in English and Spanish. It provides information on the definition of speech and language disorders and possible causes; the incidence (about one in ten people); and characteristics of delayed communication, speech disorders, and language disorders. It notes educational implications,…

  10. Bibliografia sobre el "bilinguismo" del Paraguay (A Bibliography on Bilingualism in Paraguay)

    ERIC Educational Resources Information Center

    Melia, Bartomeu

    1974-01-01

    This bibliography of ninety-five entries ranging in publication date from 1847 to 1947 brings together information from areas of history, literature, sociology, anthropology, sociolinguistics, descriptive linguistics, folk-lore and language planning, the central criterion being the relationship of these areas specifically to the bilingual…

  11. Multiparticle-multihole states in 31Mg and 33Mg: A critical evaluation

    NASA Astrophysics Data System (ADS)

    Neyens, Gerda

    2011-12-01

    The experiments that provide information about the level structure of the “island of inversion” isotopes 31Mg and 33Mg are reviewed. Since the model-independent measurement of their ground-state spins was done, much experimental data can be reinterpreted, and spins and parities can be assigned to their excited states. Both experimental level schemes are found in very good agreement with calculations based on antisymmetrized molecular dynamics combined with the generator coordinate method. These calculations predict that both ground states are dominated by 2ℏω neutron excitations (more than 85% of the wave function). In the case of 33Mg, the energy of the 1ℏω and 3ℏω levels are calculated about 400 keV too high with respect to the ground state, while in 31Mg the 1ℏω levels are calculated only 200 keV too high. New key experiments are suggested.

  12. Mg intercalation in layered and spinel host crystal structures for Mg batteries.

    PubMed

    Emly, Alexandra; Van der Ven, Anton

    2015-05-01

    We investigate electrochemical properties of Mg in layered and spinel intercalation compounds from first-principles using TiS2 as a model system. Our calculations predict that Mg(x)TiS2 in both the layered and spinel crystal structures exhibits sloping voltage profiles with steps at stoichiometric compositions due to Mg-vacancy ordering. Mg ions are predicted to occupy the octahedral sites in both layered and spinel TiS2 with diffusion mediated by hops between octahedral sites that pass through adjacent tetrahedral sites. Predicted migration barriers are substantially higher than typical Li-migration barriers in intercalation compounds. The migration barriers are shown to be very sensitive to lattice parameters of the host crystal structure. We also discuss the possible role of rehybridization between the transition metal and the anion in affecting migration barriers.

  13. Laser cooling of MgCl and MgBr in theoretical approach

    SciTech Connect

    Wan, Mingjie; Shao, Juxiang; Huang, Duohui; Yang, Junsheng; Cao, Qilong; Jin, Chengguo; Wang, Fanhou; Gao, Yufeng

    2015-07-14

    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 laser 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.

  14. Laser cooling of MgCl and MgBr in theoretical approach

    NASA Astrophysics Data System (ADS)

    Wan, Mingjie; Shao, Juxiang; Gao, Yufeng; Huang, Duohui; Yang, Junsheng; Cao, Qilong; Jin, Chengguo; Wang, Fanhou

    2015-07-01

    Ab initio calculations for three low-lying electronic states (X2Σ+, A2Π, and 22Π) 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 f00 for A2Π3/2,1/2 (υ' = 0) → X2Σ+1/2 (υ″ = 0) are determined for both MgCl and MgBr molecules. Suitable radiative lifetimes τ of A2Π3/2,1/2 (υ' = 0) states for rapid laser cooling are also obtained. The proposed laser drives A2Π3/2 (υ' = 0) → X2Σ+1/2 (υ″ = 0) transition by using three wavelengths (main pump laser λ00; two repumping lasers λ10 and λ21). These results indicate the probability of laser cooling MgCl and MgBr molecules.

  15. On the dissociation energy of Mg2

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Bauschlicher, Charles W., Jr.; Pettersson, Lars G. M.; Mclean, A. D.; Liu, Bowen

    1990-01-01

    The bonding in the X 1Sigma(+)g state of Mg2 is investigated using near-complete valence one-particle Slater and Gaussian basis sets containing up to h functions. It is shown that the four-electron complete CI limit can be approached using a sequence of either second-order CI (SOCI) or interacting correlated fragment (ICF) calculations. At the valence level, the best estimate of the dissociation energy D(e) was 464/cm. This is a lower limit and is probably within 5/cm of the complete basis value.

  16. -MgO Melt by Super Gravity

    NASA Astrophysics Data System (ADS)

    Li, Juncheng; Guo, Zhancheng; Gao, Jintao; Li, Jingwei

    2014-08-01

    Perovskite phase was successfully separated from CaO-TiO2-SiO2-Al2O3-MgO melt by super gravity. Under the hypothesis that the titanium exists in the slag in terms of TiO2, with the gravity coefficient G = 600, time t = 5 minutes, and temperature T = 1563 K (1290 °C), the mass fraction of TiO2 in the concentrate is up to 52.94 pct, while that of the tailing is just 5.88 pct. The recovery ratio of Ti in the concentrate is up to 81.28 pct by centrifugal separation.

  17. 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.

  18. Variable Stars from the MG-1 Catalog

    NASA Astrophysics Data System (ADS)

    Flurchick, K. M.; Griego, Ben; Culver, Roger B.

    2014-06-01

    This work describes the recent efforts at North Carolina A&T(NCAT) mining the MG catalogs for variable stars. NCAT is a node in both the GNAT network and the SKYNET collaboration which forms the basis of the collaboration including access to instruments. The initial data analysis to obtain the light curves (LC) for MG-1 has been performed and a number of candidate variable stars have been identified including brown dwarf stars, eclipsing binaries and long period variable stars.Many of the identified candidate variable stars are now the subject of coordinated multi-site follow-on observations to elucidate the details of the variability. The coordinated observing includes researchers in Australia, Arizona, Colorado and North Carolina. As a node in both the GNAT network and the SKYNET collaboration NCAT has access to a number of instruments. Much of the observational work is performed using the SKYNET node in Chile.For the North Carolina work reported here, the observational work and initial LC generation is performed using telescopes and applications from the SKYNET program. In this work the instrumentation, the LC analysis and status of the coordinated follow-on observations arepresented.

  19. 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.

  20. Exámenes de detección del cáncer de próstata (PDQ®)—Versión para pacientes

    Cancer.gov

    Resumen de información revisada por expertos acerca de los factores que pueden influir en el desarrollo del cáncer de próstata y sobre la investigación dirigida a la prevención de esta enfermedad.

  1. The Del Rio ataxite, Texas

    NASA Technical Reports Server (NTRS)

    Henderson, E. P.; King, E. A.

    1977-01-01

    Basic data are presented on the Del Rio, Nordheim, and Monahans ataxites found in Texas. Results are reported for bulk-chemistry analysis, metallographic observations, and electron-microprobe analysis of the Del Rio meteorite. It is shown that Del Rio is distinctly different from the other two ataxites in terms of nickel, phosphorous, and carbon content, and is composed of at least three coarse grains in different crystallographic orientations. All the kamacite in Del Rio is found to have transformation structures that are probable shock products, and minor inclusions of daubreelite, schreibersite, and troilite are observed. It is concluded that Del Rio was apparently mildly shocked prior to its fall.

  2. Toward Understanding the Roaming Mechanism in H + MgH → Mg + HH Reaction.

    PubMed

    Mauguière, Frédéric A L; Collins, Peter; Stamatiadis, Stamatis; Li, Anyang; Ezra, Gregory S; Farantos, Stavros C; Kramer, Zeb C; Carpenter, Barry K; Wiggins, Stephen; Guo, Hua

    2016-07-14

    The roaming mechanism in the reaction H + MgH →Mg + HH is investigated by classical and quantum dynamics employing an accurate ab initio three-dimensional 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 space 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. 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. PMID:26918375

  3. 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.

  4. Atomistically informed solute drag in Al Mg

    NASA Astrophysics Data System (ADS)

    Zhang, F.; Curtin, W. A.

    2008-07-01

    Solute drag in solute-strengthened alloys, caused by diffusion of solute atoms around moving dislocations, controls the stress at deformation rates and temperatures useful for plastic forming processes. In the technologically important Al-Mg alloys, the solute drag stresses predicted by classical theories are much larger than experiments, which is resolved in general by eliminating the singularity of the dislocation core via Peierls-Nabarro-type models. Here, the drag stress versus dislocation velocity is computed numerically using a realistic dislocation core structure obtained from an atomistic model to investigate the role of the core and obtain quantitative stresses for comparison with experiment. The model solves a discrete diffusion equation in a reference frame moving with the dislocation, with input solute enthalpies and diffusion activation barriers in the core computed by or estimated from atomistic studies. At low dislocation velocities, the solute drag stress is controlled by bulk solute diffusion because the core diffusion occurs too quickly. In this regime, the drag stress can be obtained using a Peierls-Nabarro model with a core spreading parameter tuned to best match the atomistic models. At intermediate velocities, both bulk and core diffusion can contribute to the drag, leading to a complex stress-velocity relationship showing two peaks in stress. At high velocities, the drag stress is controlled solely by diffusion within and across the core. Like the continuum models, the drag stress is nearly linear in solute concentration. The Orowan relationship is used to connect dislocation velocity to deformation strain rate. Accounting for the dependence of mobile dislocation density on stress, the simulations are in good agreement with experiments on Al-Mg alloys over a range of concentrations and temperatures.

  5. Role of dopants in LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P detectors

    SciTech Connect

    Mohammadi, Kh. Moussavi Zarandi, A.; Afarideh, H.; Shahmaleki, S.

    2013-06-15

    In this study, electronic structure of LiF crystal doped with Mg,Cu,P impurities was studied with WIEN2k code on the basis of FPLAPW+lo method. Results show that in Mg-doped LiF composition, an electronic trap was created with impurity concentration of 1.56% and 3.125%. In this condition, the electronic trap with increasing the percentage of the impurities up to 4.687% is annihilated. It was found, that by doping of Mg and Cu or P simultaneously, a hole-trap is created in valence band. It was realized that in LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P, Cu impurity and Li atom, have a key role in creation of levels which lead to create electronic and hole traps. Mg impurity and F atom, only have a role in creation of electronic traps. In addition, P impurity has a main role in creation of the electronic and hole traps in LiF:Mg,Cu,P. The activation energy of electronic and hole trap in LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P crystalline lattice were obtained as 0.3 and 5.5 eV, 0.92 and 3.4 eV and 0.75 and 3.1 eV, respectively. - Graphical abstract: Figure (a) and (b) shows changes in electronic structure and band gap energy of LiF crystal due to presence of Mg and Cu, Mg and P ions respectively. - Highlights: • Electronic structure of LiF, LiF:Mg,Cu, LiF:Mg,P and LiF:Mg,Cu,P materials were studied with WIEN2K code. • In LiF:Mg,Cu and LiF:Mg,Cu,P, Li atom and Cu impurity have a key role in creation of levels. • F atom and Mg impurity only have a role in creation of electronic traps. • In LiF:Mg,Cu,P, P impurity has a main role in creation of electronic and hole traps.

  6. Phase transition and optoelectronic properties of MgH2

    NASA Astrophysics Data System (ADS)

    Nayak, Vikas; Verma, U. P.

    2016-05-01

    In this article, structural and electronic properties of MgH2 have been studied. The aim behind this study was to find out the ground state crystal structure of MgH2. For the purpose, density functional theory (DFT)-based full-potential linearized augmented plane wave (FP-LAPW) calculations have been performed in three different space groups: P42/mnm (α-MgH2), Pa3 (β-MgH2) and Pbcn (γ-MgH2). It has been found that the ground state structure of MgH2 is α-MgH2. The present study shows that α-MgH2 transforms into γ-MgH2 at a pressure of 0.41 GPa. After further increase in pressure, γ-MgH2 transforms into β-MgH2 at a pressure of 3.67 GPa. The obtained results are in good agreement with previously reported experimental data. In all the studied phases, the behavior of MgH2 is insulating and its optical conductivity is around 6.0 eV. The α-MgH2 and γ-MgH2 are anisotropic materials while β-MgH2 is isotropic in nature.

  7. Results from d(30Mg, p)31Mg at Rex-Isolde

    NASA Astrophysics Data System (ADS)

    Bildstein, V.

    2013-03-01

    In this proceedings the preliminary results of a d(30Mg, p)31Mg experiment at REXISOLDE are presented. The experiment was performed using the new T-REX setup for transfer reactions in inverse kinematics. The angular distribution of protons was measured for the second excited state at 221 keV in coincidence with de-excitation γ-rays. The comparison of the angular distribution with DWBA calculations for different transferred orbital momenta, identifies the state for the first time as an l = 1 state.

  8. Porous composite materials ZrO2(MgO)-MgO for osteoimplantology

    NASA Astrophysics Data System (ADS)

    Buyakov, Ales; Litvinova, Larisa; Shupletsova, Valeria; Kulbakin, Denis; Kulkov, Sergey

    2016-08-01

    The pore structure and phase composition of ceramic composite material ZrO2(Mg)-MgO at different sintering temperatures were studied. The main mechanical characteristics of the material were determined and it was shown that they are close to the characteristics of natural bone tissues. It was shown that material structure has a positive effect on the pre-osteoblast cells proliferation. In-vitro studies of pre-osteoblast cells, cultivation on material surface showed a good cell adhesion, proliferation and differentiation of MMSC by osteogenic type.

  9. The influence of MgH2 on the assessment of electrochemical data to predict the degradation rate of Mg and Mg alloys.

    PubMed

    Mueller, Wolf-Dieter; Hornberger, Helga

    2014-06-26

    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.

  10. 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

  11. Nevado del Huila, Columbia

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Nevado del Huila Volcano in Colombia is actually a volcanic chain running north to south, capped by a glacier. With peaks ranging in height from 2,600 to 5,780 meters (8,530 to 18,960 feet), Nevado del Huila is a stratovolcano composed of alternating layers of hardened lava, solidified ash, and volcanic rocks. Its first recorded eruption occurred in the mid-sixteenth century. The long-dormant volcano erupted again in mid-April 2007. A few months before the eruption, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite captured this image of Nevado del Huila, on February 23, 2007. In this image, the bright white area just east of the central summit is ice. Immediately west of the summit are bare rocks, appearing as blue-gray. West of those rocks, white reappears, but this patch of white results from clouds hovering in the nearby valley. In the east, the colors turn to brown (indicating bare rock) and bright green (indicating vegetation). ASTER photographed Nevado del Huila near the end of a long phase of quietude. On April 17, 2007, local authorities recorded seismic activity associated with rock fracturing on the volcano's central summit, according to the ReliefWeb Website. Activity intensified the following day with an eruption and mudflows, forcing thousands of nearby residents to evacuate. As the Associated Press reported, the eruption caused avalanches and floods that wiped away both houses and bridges. It marked the volcano's first recorded eruption since the Spanish colonized the area five centuries earlier. NASA image created by Jesse Allen, using data provided courtesy of the NASA/GSFC/MITI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.

  12. ZnO/(ZnMg)O single quantum wells with high Mg content graded barriers

    SciTech Connect

    Laumer, Bernhard; Schuster, Fabian; Wassner, Thomas A.; Stutzmann, Martin; Rohnke, Marcus; Schoermann, Joerg; Eickhoff, Martin

    2012-06-01

    ZnO/Zn{sub 1-x}Mg{sub x}O single quantum wells (SQWs) were grown by plasma-assisted molecular beam epitaxy on c-plane sapphire substrates. Compositional grading allows the application of optimized growth conditions for the fabrication of Zn{sub 1-x}Mg{sub x}O barriers with high crystalline quality and a maximum Mg content of x = 0.23. High resolution x-ray diffraction reveals partial relaxation of the graded barriers. Due to exciton localization, the SQW emission is found to consist of contributions from donor-bound and free excitons. While for narrow SQWs with well width d{sub W}{<=}2.5nm, the observed increase of the exciton binding energy is caused by quantum confinement, the drop of the photoluminescence emission below the ZnO bulk value found for wide SQWs is attributed to the quantum-confined Stark effect. For a Mg content of x = 0.23, a built-in electric field of 630 kV/cm is extracted, giving rise to a decrease of the exciton binding energy and rapid thermal quenching of the SQW emission characterized by an activation energy of (24 {+-} 4) meV for d{sub W} = 8.3 nm.

  13. Mg2+ coordinating dynamics in Mg:ATP fueled motor proteins

    NASA Astrophysics Data System (ADS)

    Bojovschi, A.; Liu, Ming S.; Sadus, Richard J.

    2014-03-01

    The coordination of Mg2+ with the triphosphate group of adenosine triphosphate (ATP) in motor proteins is investigated using data mining and molecular dynamics. The possible coordination structures available from crystal data for actin, myosin, RNA polymerase, DNA polymerase, DNA helicase, and F1-ATPase are verified and investigated further by molecular dynamics. Coordination states are evaluated using structural analysis and quantified by radial distribution functions, coordination numbers, and pair interaction energy calculations. The results reveal a diverse range of both transitory and stable coordination arrangements between Mg2+ and ATP. The two most stable coordinating states occur when Mg2+ coordinates two or three oxygens from the triphosphate group of ATP. Evidence for five-site coordination is also reported involving water in addition to the triphosphate group. The stable states correspond to a pair interaction energy of either ˜-2750 kJ/mol or -3500 kJ/mol. The role of water molecules in the hydration shell surrounding Mg2+ is also reported.

  14. Rupatadine 20 mg and 40 mg are Effective in Reducing the Symptoms of Chronic Cold Urticaria.

    PubMed

    Abajian, Marina; Curto-Barredo, Laia; Krause, Karoline; Santamaria, Eva; Izquierdo, Iñaki; Church, Martin K; Maurer, Marcus; Giménez-Arnau, Ana

    2016-01-01

    Chronic cold urticaria (ColdU) is a rare disease characterized by mast cell-mediated wheals and angioedema following cold exposure. Second-generation H1-antihistamines, such as rupatadine, are the recommended first-line therapy. As of yet, the effects of rupatadine up-dosing on development of ColdU symptom have only been partially characterized. Two-centre, randomized, double-blind, 3-way crossover, placebo-controlled study in patients with a confirmed ColdU was designed to assess the effects of up-dosing of rupatadine. A total of 23 patients were randomized to receive placebo, rupatadine 20 mg/day, and rupatadine 40 mg/day for 1 week. The primary outcome was change in critical temperature thresholds and critical stimulation time thresholds after treatment. Secondary endpoints included assessment of safety and tolerability of rupatadine. Both 20 and 40 mg rupatadine were highly effective in reducing critical temperature thresholds (p < 0.001) and critical stimulation time thresholds (p < 0.001). In conclusion, rupatadine 20 and 40 mg significantly reduced the development of chronic cold urticaria symptom without an increase in adverse effects.

  15. Microstructural formation in a hypereutectic Mg-Si alloy

    SciTech Connect

    Pan Yichuan . E-mail: riverpan@mail.sdu.edu.cn; Liu Xiangfa; Yang Hua

    2005-09-15

    In the present work, the microstructure of an ingot metallurgy hypereutectic Mg-8 wt.% Si alloy was studied using electron probe microanalysis (EPMA) and the solidification process was discussed. The components of the alloy are Mg{sub 2}Si and Mg. The solidified microstructure of the alloy contains three constituents: Mg{sub 2}Si primary dendrites that are surrounded by Mg sub-primary particles and the Mg-Mg{sub 2}Si eutectic. The primary Mg{sub 2}Si dendrites have a secondary dendrite arm spacing d {sub 2} of approximately 17 {mu}m or show polygonal morphologies with a mean size of 30 {mu}m. An Mg phase appearing as halos surround the Mg{sub 2}Si constituents. The Mg-Mg{sub 2}Si eutectic has a regular morphology of rod-like Mg{sub 2}Si distributed in a continuous matrix of Mg having an interphase spacing r of approximately 0.8 {mu}m.

  16. Mg intercalation into Ti2C building block

    NASA Astrophysics Data System (ADS)

    Yu, Xue-fang; Cheng, Jianbo; Liu, Zhenbo; Li, Qingzhong; Li, Wenzuo; Yang, Xin; Xiao, Bo

    2015-06-01

    Generally, intercalation occurs when foreign atoms intercalate into multi-layer structures, while adsorption occurs when foreign atoms interact with monolayer structures or surfaces. We performed an investigation on the Mg intercalation into Ti2C building block (MXene) from first-principles simulation. We found that Mg can favorably intercalate into MXene, forming the stable compound Ti2MgC, which corresponds to the stage I in the Li intercalation into graphite. Based on the evaluation of the average cell potential and the energy barrier of Mg diffusion for the most energetically stable structure, our results suggest that Ti2MgC is a potential anode for Mg ion batteries.

  17. Sunspot umbral oscillations in Mg II k

    NASA Technical Reports Server (NTRS)

    Gurman, Joseph B.

    1987-01-01

    Time series observations of the profile of the Mg II k line 2795.52 A have been obtained in five sunspots with the Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission. The three sunspots with umbrae larger than the 3 x 3 arcsec pixel size show significant oscillations in integrated line intensity and line centroid, with frequencies in the range 5.29-7.55 mHz (periods of 132-190 s). The frequencies of significant peaks in average umbral power spectra agree well with the frequencies of the three lowest-frequency transmission peaks predicted by a model of resonant transmission of acoustic waves. If radiative delays are unimportant, and the line centroid can be interpreted straightforwardly as a Doppler shift, the measured velocity-intensity phase differences indicate the superposition of upward-propagating and downward-propagating waves in the umbral chromosphere; this is further evidence for the resonant transmission model. A single, quiet sun time series of k core profiles yields power spectra and a phase difference consistent with the existence of a chromospheric p-mode.

  18. Structural and electronic properties of Mg and Mg-Nb co-doped TiO2 (101) anatase surface

    NASA Astrophysics Data System (ADS)

    Sasani, Alireza; Baktash, Ardeshir; Mirabbaszadeh, Kavoos; Khoshnevisan, Bahram

    2016-10-01

    In this paper, by using density functional theory, Mg and Nb-Mg co-doping of TiO2 anatase (101) surfaces are studied. By studying the formation energy of the defects and the bond length distribution of the surface, it is shown that Mg defects tend to stay as far as possible to induce least possible lattice distortion while Nb and Mg defects stay close to each other to cause less stress to the surface. By investigating band structure of the surface and changes stemmed from the defects, potential effects of Mg and Mg-Nb co-doping of TiO2 surface on dye-sensitized solar cells are investigated. In this study, it is shown that the Nb-Mg co-doping could increase JSC of the surface while slightly decreasing VOC compared to Mg doped surface, which might result in an increase in efficiency of the DSSCs compared to Nb or Mg doped surfaces.

  19. The effect of Mg location on Co-Mg-Ru/γ-Al2O3 Fischer–Tropsch catalysts

    PubMed Central

    Combes, Gary B.; Ozkaya, Don; Enache, Dan I.; Ellis, Peter R.; Kelly, Gordon; Rosseinsky, Matthew J.

    2016-01-01

    The effectiveness of Mg as a promoter of Co-Ru/γ-Al2O3 Fischer–Tropsch catalysts depends on how and when the Mg is added. When the Mg is impregnated into the support before the Co and Ru addition, some Mg is incorporated into the support in the form of MgxAl2O3+x if the material is calcined at 550°C or 800°C after the impregnation, while the remainder is present as amorphous MgO/MgCO3 phases. After subsequent Co-Ru impregnation MgxCo3−xO4 is formed which decomposes on reduction, leading to Co(0) particles intimately mixed with Mg, as shown by high-resolution transmission electron microscopy. The process of impregnating Co into an Mg-modified support results in dissolution of the amorphous Mg, and it is this Mg which is then incorporated into MgxCo3−xO4. Acid washing or higher temperature calcination after Mg impregnation can remove most of this amorphous Mg, resulting in lower values of x in MgxCo3−xO4. Catalytic testing of these materials reveals that Mg incorporation into the Co oxide phase is severely detrimental to the site-time yield, while Mg incorporation into the support may provide some enhancement of activity at high temperature. PMID:26755760

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

    DOE PAGES

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

    2015-01-05

    We present a fundamental study on [(μ-Cl)3 Mg2 (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 MgCl2 and an Al Lewis acid. Solvated MgCl2 in the electrolyte was confirmed by Raman spectroscopy. The experimental results establish the previously proposed dimerization equilibrium of solvated [MgCl]+ and MgCl2 with [(μ-Cl)3Mg2(THF)6]+.more » 25Mg{1H} NMR, 27Al{1H} NMR and electrochemical analysis on chloration reaction of [(μ-Cl)3Mg2(THF)6]AlPh3Cl 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 Mg2+ and Cl- ion transports of the Mg dimer electrolytes in rechargeable Mg batteries.« less

  1. Mg Isotopes of the Late Permian Evaporites, New Mexico, USA

    NASA Astrophysics Data System (ADS)

    Feng, C.; Gao, C. H.; Chang, S. C.

    2015-12-01

    Mg isotope holds promise to decipher the evaporative environment of evaporites. High-precision Mg isotope compositions of the late Permian langbeinites have been measured by using MC-ICPMS. The equilibrium Mg isotope fractionation factor between langbeinite and aqueous Mg2+ solutions has been determined using quantum chemistry calculations. All computations are employed at B3LYP/6-311++G(2d,2p) level and solvation effects are treated by solvent model ("water-droplet" approach), mineral structures are constructed using volume variable cluster models (VVCM). The Mg isotope compositions of the langbeinite samples, whose total formation thickness ranges up to 100 meters, are extremely isotopically lighter than that of modern seawater and relatively homogeneous (δ26MgDSM3 is from -4.12±0.03‰ to -3.81±0.07‰ v.s. -0.83‰ of modern seawater). The computed equilibrium Mg isotope fractionation factors between langbeinite and aqueous Mg2+ solutions are -2.73‰, -2.66‰ and -2.53‰ at 25, 30 and 40 ℃, respectively. These significant equilibrium fractionation factors indicate that a huge equilibrium Mg isotope fractionation between langbeinite and its parent brine can happen during langbeinite depositions, and langbeinites are enriched in isotopically light 24Mg comparing to the brine. Using the computed fractionation factors to simulate a Rayleigh fractionation process of langbeinite Mg precipitation, we find that a significant Mg isotope difference between langbeinite and its growing brine (seawater) is indeed present but the Mg isotope composition of langbeinite merely increase monotonically in a closed system. Because of that, the homogenous Mg isotope compositions of such a thick evaporite sequence suggest a disequlibrium effect rather than an equilibrium Mg isotope fractionation behavior during its formation. Combined with its prevailing Mg-bearing character, the homogenous Mg isotope compositions reveal that this the late Permian langbeinite sequence has

  2. Alterations of ionized Mg2+ in human blood after exercise.

    PubMed

    Mooren, Frank C; Golf, S W; Lechtermann, A; Völker, K

    2005-07-29

    Magnesium (Mg) is the second most abundant intracellular cation with modulating properties in a number of metabolic processes, e.g. in glycolysis, and intracellular signalling processes, e.g. regulation of ion channels and transporters. There are conflicting data available about the regulation of Mg in blood cells during exercise. Moreover, there are no data available about changes of the metabolic important fraction of ionized Mg(2+) both in blood and in blood cells during exercise. The present study investigated the changes of ionized Mg(2+) and total Mg concentration in different compartments after a stepwise treadmill ergometer test. Intracellular ionized Mg(2+) of thrombocytes and erythrocytes was determined by the magnesium sensitive fluorescent dyes mag-fura-2 and Mag-Green using fluorescence spectroscopy and flow cytometry, respectively. Ionized Mg(2+) in blood/serum was measured by an ion-sensitive microelectrode. Total cellular and serum Mg concentration were investigated using atomic absorbance spectroscopy and photometry, respectively. The present results shown that at the end of the ergometer test, ionized Mg(2+) in both blood and serum and total serum Mg decreased. In contrast, intracellular concentration of ionized Mg increased in both thrombocytes and erythrocytes. Total intracellular Mg was unchanged making a Mg(2+) shift between the intra- and extracellular compartment unlikely. The present study therefore demonstrated opposite changes of the ratio [ionized Mg(2+)]/[total Mg] in the intracellular and the extracellular compartment after anaerobic exercise. In in vitro experiments, similar changes of ionized Mg(2+) in both compartments could be mimicked by application of weak acids like propionic and lactic acid. It is concluded changes in the fraction of ionized Mg(2+) should be high enough to influence intracellular signalling and metabolic processes.

  3. Photodissociation spectroscopy of the Mg{sup +}-acetic acid complex

    SciTech Connect

    Abate, Yohannes; Kleiber, P. D.

    2006-11-14

    We have studied the structure and photodissociation of Mg{sup +}-acetic acid clusters. Ab initio calculations suggest four relatively strongly bound ground state isomers for the [MgC{sub 2}H{sub 4}O{sub 2}]{sup +} complex. These isomers include the cis and trans forms of the Mg{sup +}-acetic acid association complex with Mg{sup +} bonded to the carbonyl O atom of acetic acid, the Mg{sup +}-acetic acid association complex with Mg{sup +} bonded to the hydroxyl O atom of acetic acid, or to a Mg{sup +}-ethenediol association complex. Photodissociation through the Mg{sup +}-based 3p<-3s absorption bands in the near UV leads to direct (nonreactive) and reactive dissociation products: Mg{sup +}, MgOH{sup +}, Mg(H{sub 2}O){sup +}, CH{sub 3}CO{sup +}, and MgCH{sub 3}{sup +}. At low energies the dominant reactive quenching pathway is through dehydration to Mg(H{sub 2}O){sup +}, but additional reaction channels involving C-H and C-C bond activation are also open at higher energies.

  4. Texture and microstructure in co-sputtered Mg-M-O (M = Mg, Al, Cr, Ti, Zr, and Y) films

    NASA Astrophysics Data System (ADS)

    Saraiva, M.; Depla, D.

    2012-05-01

    Mg-M-O solid solution films (M = Mg, Al, Cr, Ti, Zr, and Y) with various M contents are grown employing reactive co-sputtering by varying the target-to-substrate distance. It is shown that all films are biaxially aligned. When the two cathodes are equipped with the same target material (Mg), the in-plane alignment is determined by the cathode closest to the substrate, i.e., by the largest material flux. In the case of nearly equal material fluxes from the two cathodes, double in-plane orientation is observed. This is also the case for the Mg-Al-O and Mg-Cr-O films, while the Mg-Ti-O, Mg-Zr-O and Mg-Y-O films exhibit single in-plane orientation. Pole figures indicate that the grains in Mg-M-O (M different than Mg) are titled; in the Mg-Al-O, Mg-Cr-O, and Mg-Ti-O films, the grains tilt towards the Al, Cr, and Ti metal flux, respectively, while the grain tilt of the Mg-Zr-O and Mg-Y-O films is found to be towards the Mg metal flux. Furthermore, SEM cross-sectional images of the Mg-M-O films reveal columnar microstructure with columns tilted to the same direction as the grains. A mechanism which is based on the cation radius change upon the incorporation of an M atom in the MgO lattice is proposed to explain the tilting.

  5. The possibility of forming a sacrificial anode coating for Mg

    SciTech Connect

    Dudney, Nancy J; Li, Juchuan; Sacci, Robert L; Thomson, Jeffery K

    2014-01-01

    Mg is the most active engineering metal, and is often used as a sacrificial anode/coating to protect other engineering metals from corrosion attack. So far no sacrificial anode coating has been developed or considered for Mg. This study explores the possibility of forming a sacrificial coating for Mg. A lithiated carbon coating and a metaphosphated coating are applied on the Mg surface, respectively, and their open-circuit-potentials are measured in saturated Mg(OH)2 solution. They exhibit more negative potentials than bare Mg. SEM reveals that the metaphosphated coating offers more effective and uniform protection for Mg than the lithiated carbon coating. These preliminary results indicate that development of a sacrificial anode coating for Mg is indeed possible.

  6. LOW Mg/Si PLANETARY HOST STARS AND THEIR Mg-DEPLETED TERRESTRIAL PLANETS

    SciTech Connect

    Carter-Bond, Jade C.; O'Brien, David P.; Delgado Mena, Elisa; Israelian, Garik; Gonzalez Hernandez, Jonay I.; Santos, Nuno C.

    2012-03-15

    Simulations have shown that a diverse range of extrasolar terrestrial planet bulk compositions are likely to exist based on the observed variations in host star elemental abundances. Based on recent studies, it is expected that a significant proportion of host stars may have Mg/Si ratios below 1. Here we examine this previously neglected group of systems. Planets simulated as forming within these systems are found to be Mg-depleted (compared to Earth), consisting of silicate species such as pyroxene and various feldspars. Planetary carbon abundances also vary in accordance with the host star C/O ratio. The predicted abundances are in keeping with observations of polluted white dwarfs, lending validity to this approach. Further studies are required to determine the full planetary impacts of the bulk compositions predicted here.

  7. Room-temperature perpendicular magnetic anisotropy of MgO/Fe/MgO ultrathin films

    SciTech Connect

    Kozioł-Rachwał, A.; Ślęzak, T.; Przewoźnik, J.; Skowroński, W.; Stobiecki, T.; Wilgocka-Ślęzak, D.; Qin, Q. H.; Dijken, S. van; Korecki, J.

    2013-12-14

    We used the anomalous Hall effect to study the magnetic properties of MgO/Fe(t)/MgO(001) structures in which the Fe thickness t ranged from 4 Å to 14 Å. For the iron deposited at 140 K, we obtained perpendicular magnetization at room temperature below the critical thickness of t{sub c} = (9 ± 1) Å. In the vicinity of t{sub c}, the easy magnetization axis switched from an out-of-plane orientation to an in-plane orientation, and the observed spin-reorientation transition was considered in terms of the competition among different anisotropies. The perpendicular magnetization direction was attributed to magnetoelastic anisotropy. Finally, the temperature-dependent spin-reorientation transition was analyzed for Fe thicknesses close to t{sub c}.

  8. Concepciones y concepciones alternativas de estudiantes universitarios/as de biologia y futuros maestros/as de Ciencia de escuela secundaria sobre la teoria de evolucion biologica por seleccion natural

    NASA Astrophysics Data System (ADS)

    Morales Ramos, Egda M.

    La teoria de evolucion biologica (TEB) por seleccion natural es uno de los conceptos unificadores mas importantes del curriculo de Biologia. En Puerto Rico se han hecho pocas investigaciones que abunden sobre las concepciones y concepciones alternativas (CA) que tienen los estudiantes universitarios/as de Biologia y los maestros/as de Ciencia del nivel secundario sobre esta teoria. La politica publica educativa actual establece mediante documentos normativos como los Estandares de contenido y Expectativas de grado del Programa de Ciencias [Puerto Rico Core Standards] la ensenanza de esta teoria. Sin embargo, no se encontraron preguntas sobre la seleccion natural en los ejercicios de practica provistos por el Departamento de Educacion para las pruebas estandarizadas lo cual puede influir para que no se ensene adecuadamente. Las preguntas de investigacion fueron 1. ¿Cuales son las concepciones y concepciones alternativas de estudiantes universitarios/as y de los futuros maestros y maestras de Ciencia sobre la TEB? 2. ¿Cuales conceptos que seleccionan los estudiantes universitarios/as y los futuros maestros y maestras de Ciencia sobre la TEB coinciden con lo aceptado como valido por la comunidad cientifica? y 3. ¿Como comparan las respuestas de la prueba original. v. Entendiendo el cambio biologico que mide concepciones y CA sobre la TEB por seleccion natural, con las de la traducida al idioma espanol? Se utilizo el metodo cuantitativo con un diseno de investigacion transversal por encuesta. La tecnica principal para recopilar los datos fue una prueba con doce items, que formo parte de un instrumento para el cual se recopilaron diversas fuentes de evidencia acerca de su validez. Las muestras estuvieron formadas por 69 estudiantes de Ciencias Naturales y por 16 estudiantes futuros maestros y maestras del nivel secundario de la UPR-RP. Se utilizaron estadisticas descriptivas, analisis de Ji cuadrado y se calcularon los coeficientes alfa de Cronbach y de Spearman

  9. Impact of Mg Content on (Mg,Zn)O Native Point Defects

    NASA Astrophysics Data System (ADS)

    Ball, Molly; Restrepo, Oscar; Brillson, Leonard; Windl, Wolfgang; Department of Material Science; Engineering Collaboration; Department of Physics Collaboration

    2015-03-01

    The two most thermodynamically stable defects in ZnO are oxygen vacancies (VO) and zinc vacancies (VZn) . These native point defects are electrically charged and can contribute to free carrier densities. Experiment shows that Mg addition to ZnO significantly changes native defect densities. To better understand this dramatic decrease in VZn and VO-related defects with increasing Mg content up to x =0.44 and the subsequent increase, we performed density functional theory (DFT) calculations using PAW potentials within PBE using VASP. The results showed to be very sensitive to DFT method used and chemical-potential calculation. For the latter, the literature shows that one can assume that the oxygen chemical potential equals that of the atoms in the oxygen molecules at a given surrounding partial oxygen pressure. However, one can also postulate that the total defect concentrations conserve the stoichiometry, or limiting potentials from elemental equilibrium phases can be used. The experimentally observed dependence helped identify the correct way to reproduce the experimental dependence of formation energy on Mg concentration, which will be discussed in detail in this presentation.

  10. 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. PMID:27058131

  11. Atlas del Genoma del Cáncer: Antecedentes

    Cancer.gov

    El Atlas del Genoma del Cáncer es una iniciativa de los Institutos Nacionales de la Salud (NIH) para crear mapas multidimensionales completos de los cambios genómicos clave en los tipos y subtipos principales de cáncer.

  12. Dehydrogenation kinetics of air-exposed MgH2/Mg2Cu and MgH2/MgCu2 studied with in situ X-ray powder diffraction

    NASA Astrophysics Data System (ADS)

    Andreasen, A.; Sørensen, M. B.; Burkarl, R.; Møller, B.; Molenbroek, A. M.; Pedersen, A. S.; Vegge, T.; Jensen, T. R.

    2006-02-01

    The dehydrogenation kinetics of air exposed samples of MgH2/Mg2Cu and MgH2/MgCu2 have been studied with in situ time resolved X-ray powder diffraction. The X-ray setup enabled the recording of full diffraction patterns within 150 s, thereby allowing the study of structural changes combined with simultaneous extraction of kinetic parameters. Phase fractions as a function of time and temperature were derived from series of consecutive diffraction patterns by numerical integration of selected diffraction peaks. The apparent activation energy for the dehydrogenation of the MgH2/Mg2Cu, and MgH2/MgCu2 sample was found to be 108 kJ/mol and 160 kJ/mol, respectively. Furthermore, substantially improved dehydrogenation kinetics of MgH2 and resistance towards oxidation of Mg due to the presence of Mg2Cu/MgCu2 are discussed in relation to previous work.

  13. Solid Solution Effects on the MgAl2O4-MgGa2O4 System

    SciTech Connect

    O'Hara, Kelley; Smith, Jeffrey D; Hemrick, James Gordon

    2009-01-01

    Phase relations between two spinel compounds (MgAl2O4 and MgGa2O4) were studied. Stoichiometric MgAl2O4 was formed in the laboratory through a coprecipitation method. Complete solid solution formation int eh MgAl2O4-MgGa2O4 systems was confirmed through X-ray diffraction analysis. Solid solution between MgAl2O4-MgGa2O4 decreases thermal conductivity at all temperatures up to 900oC. At 200oC with 10 mol% additoin of MgGa2O4 thermal conductivity decreases approximately 25%, and at 900oC there was still an 8% decrease. Additionally, preliminary studies show that porosity between 5% and 10% does not have an appreciable effect on the thermal conductivity in this study.

  14. The dependence of Raman scattering on Mg concentration in Mg-doped GaN grown by MBE

    NASA Astrophysics Data System (ADS)

    Flynn, Chris; Lee, William

    2014-04-01

    Magnesium-doped GaN (GaN:Mg) films having Mg concentrations in the range 5 × 1018-5 × 1020 cm-3 were fabricated by molecular beam epitaxy. Raman spectroscopy was employed to study the effects of Mg incorporation on the positions of the E2 and A1(LO) lines identifiable in the Raman spectra. For Mg concentrations in excess of 2 × 1019 cm-3, increases in the Mg concentration shift both lines to higher wave numbers. The shifts of the Raman lines reveal a trend towards compressive stress induced by incorporation of Mg into the GaN films. The observed correlation between the Mg concentration and the Raman line positions establish Raman spectroscopy as a useful tool for optimizing growth of Mg-doped GaN.

  15. Inter-mineral Mg isotope fractionation during hydrothermal ultramafic rock alteration - Implications for the global Mg-cycle

    NASA Astrophysics Data System (ADS)

    Beinlich, Andreas; Mavromatis, Vasileios; Austrheim, Håkon; Oelkers, Eric H.

    2014-04-01

    Both riverine and ocean waters are enriched in 24Mg compared to the homogeneous chondritic Mg isotopic composition of the Earth's mantle requiring a fractionation step that is generally attributed to low temperature continental crust weathering. Here we present new observations that indicate that this 24Mg enrichment of surface waters may originate from Mg isotope fractionation during the hydrothermal alteration of primary silicate minerals. Mineral separates of hydrothermally altered ultramafic rocks were collected from three different localities in Norway. Coexisting olivine and serpentine exhibit invariant Mg isotope ratios suggesting that serpentinization does not fractionate Mg isotopes. In contrast, carbonation results in significant inter-mineral Mg isotope fractionation between the antigorite, magnesite, and talc. The carbonation of the natural samples is constrained by O isotope thermometry at ∼275 °C and hence closes the temperature gap between previous investigations of the natural distribution of Mg isotopes during surface weathering and magmatic processes. The precursor antigorite has an isotopic composition of δ26Mg (DSM-3)=-0.11±0.05‰, whereas the talc is enriched in 26Mg with mean δMg26=0.17±0.08‰ and the magnesite is depleted in 26Mg with mean δMg26=-0.95±0.15‰. As carbonate minerals dissolve faster than silicate minerals, the chemical weathering of carbonated ultramafic and by analogy mafic rocks on the continents will yield isotopically lighter Mg to natural surface waters consistent with field observations. Moreover, the Mg fractionation observed in this study suggests that sub-seafloor hydrothermal carbonation may be a significant contribution to the Mg isotopic composition of ocean water.

  16. Study of some Mg-based ferrites as humidity sensors

    NASA Astrophysics Data System (ADS)

    Rezlescu, N.; Rezlescu, E.; Doroftei, C.; Popa, P. D.

    2005-01-01

    The micostructure and humidity sensitivity of MgFe2O4 + CaO, Mg0.5Cu0.5Fe1.8Ga0.2O4, Mg0.5Zn0.5Fe2O4 + KCl and MgMn0.2Fe1.8O4 ferrites were investigated. We have found that the humidity sensitivity largely depends on composition, crystallite size, surface area and porosity. The best results concerning humidity sensitivity were obtained for MgMn0.2Fe1.8O4 ferrite.

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

    SciTech Connect

    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 thin 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.

  18. A Computational Investigation of Precipitates in Mg-RE Alloys With Applications To Mg-X Systems

    NASA Astrophysics Data System (ADS)

    Issa, Ahmed

    Increasing fuel efficiency in transportation vehicles is a major policy goal for both government and auto and aerospace manufacturers. Lightweight structural materials, such as magnesium alloys, hold great promise in enabling such fuel efficiency gains. Understanding the controlling factors in Mg alloy strengthening is crucial for the rational design of structurally strong and inexpensive Mg alloys. In this work, we seek to understand the energetic underpinnings giving rise to a class of remarkably strong Mg alloys: Mg-RE systems. We use first-principles methods to efficiently explore seventeen Mg-RE systems, drawing out broad patterns and distilling our knowledge into simple design rules for Mg alloys. We begin by investigating the controlling factors for the Mg-strengthening prismatic plate precipitates in Mg-RE systems, discovering the critical role of strain in such systems. We then proceed to investigate the surprising role of interfacial energies in determining the course of the Mg-RE precipitation reactions. Using strain and interfacial energies, we construct a phase-field model which accurately depicts the precipitate morphology as a function of time and size in a Mg-Nd system. Finally, we combine our gained insights to implement a computational alloy design scheme on a large portion of the periodic table where we seek Mg-strengthening solutes. Our work advances the understanding of strengthening in Mg alloys and lays the groundwork for full scale computational alloy design.

  19. Diffusion Couple Investigation of the Mg-Zn System

    SciTech Connect

    Brennan, Sarah; Bermudez, Katrina; Sohn, Yong Ho; Kulkarni, Nagraj S

    2012-01-01

    Phase layer growth and interdiffusion in the binary Mg-Zn system was investigated utilizing solid-to-solid diffusion couples annealed at 295 , 315 and 325 C for 21, 7 and 5 days, respectively. The diffusion microstructure was examined by scanning electron microscopy and concentration profiles were determined using X-ray energy dispersive spectroscopy and electron microprobe analysis. The Mg solid solution, Mg2Zn11, MgZn2 and Mg2Zn3 in all three couples were observed in addition to the high temperature, Mg51Zn20 phase at 325 C. The MgZn2 phase was observed to grow the thickest layer, followed by the Mg2Zn3 and the Mg2Zn11 phases. Activation energies for the parabolic growth were calculated to be 105 kJ/mol and 207 kJ/mol for the Mg2Zn3 and MgZn2, respectively. Relevant interdiffusion coefficients were calculated for the phases present by analyses of concentration profiles. This study was sponsored by the US Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program (DE-AC05-00OR22725).

  20. Physiological characterization of Mg deficiency in Arabidopsis thaliana.

    PubMed

    Hermans, Christian; Verbruggen, Nathalie

    2005-08-01

    Although the symptoms of magnesium deficiency are well documented in plants, the primary physiological effects of low Mg availability remain largely unknown. This paper describes the physiological responses of Mg starvation in Arabidopsis thaliana. Growth characteristics, Mg and sugar concentration, and photochemical performance were measured at regular intervals during the induction of Mg deficiency. These data show that Mg deficiency increased the sugar concentration and altered sucrose export from young source leaves before any noticeable effect on photosynthetic activity was seen. The decline in photosynthetic activity might be elicited by increased leaf sugar concentrations. Transcript levels of Cab2 (encoding a chlorophyll a/b protein) were lower in Mg-deficient plants before any obvious decrease in the chlorophyll concentration. These transcriptional data suggest that the reduction of chlorophyll is a response to sugar levels, rather than a lack of Mg atoms for chelating chlorophyll. PMID:15983014

  1. Mechanical Properties of High Strength Al-Mg Alloy Sheet

    NASA Astrophysics Data System (ADS)

    Choi, Bong-Jae; Hong, Kyung-Eui; Kim, Young-Jig

    The aim of this research is to develop the high strength Al alloy sheet for the automotive body. For the fabrication Al-Mg alloy sheet, the composition of alloying elements was designed by the properties database and CALPHAD (Calculation Phase Diagram) approach which can predict the phases during solidification using thermodynamic database. Al-Mg alloys were designed using CALPHAD approach according to the high content of Mg with minor alloying elements. After phase predictions by CALPHAD, designed Al-Mg alloys were manufactured. Addition of Mg in Al melts were protected by dry air/Sulphur hexafluoride (SF6) mixture gas which can control the severe Mg ignition and oxidation. After rolling procedure of manufactured Al-Mg alloys, mechanical properties were examined with the variation of the heat treatment conditions.

  2. Energy band bowing parameter in MgZnO alloys

    SciTech Connect

    Wang, Xu; Saito, Katsuhiko; Tanaka, Tooru; Nishio, Mitsuhiro; Guo, Qixin; Nagaoka, Takashi; Arita, Makoto

    2015-07-13

    We report on bandgap bowing parameters for wurtzite and cubic MgZnO alloys from a study of high quality and single phase films in all Mg content range. The Mg contents in the MgZnO films were accurately determined using the energy dispersive spectrometer and X-ray photoelectron spectroscopy (XPS). The measurement of bandgap energies by examining the onset of inelastic energy loss in core-level atomic spectra from XPS is proved to be valid for determining the bandgap of MgZnO films. The dependence of the energy bandgap on Mg content is found to deviate downwards from linearity. Fitting of the bandgap data resulted in two bowing parameters of 2.01 ± 0.04 eV and 1.48 ± 0.11 eV corresponding to wurtzite and cubic MgZnO films, respectively.

  3. Impacto del Seguro Popular en el gasto catastrófico y de bolsillo en el México rural y urbano, 2005–2008

    PubMed Central

    Sosa-Rubí, Sandra G; Salinas-Rodríguez, Aarón; Galárraga, Omar

    2016-01-01

    Objetivo Estimar el efecto del Seguro Popular (SP) sobre la incidencia del gasto catastrófico en salud (GCS) y sobre el gasto de bolsillo en salud (GBS) en el mediano plazo. Material y métodos Con base en la Encuesta de Evaluación del Seguro Popular (2005–2008), se analizaron los resultados del efecto del SP en la cohorte rural para dos años de seguimiento (2006 y 2008) y en la cohorte urbana para un año (2008). Resultados A nivel conglomerado no se detectaron efectos del SP. A nivel hogar se encontró que el SP tiene un efecto protector en el GCS y en el GBS en consulta externa y hospitalización en zonas rurales; y efectos significativos en la reducción de GBS en consulta externa en zonas urbanas. Conclusiones El SP se muestra como un programa efectivo para proteger a los hogares contra gastos de bolsillo por motivos de salud en el mediano plazo. PMID:22282205

  4. 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).

  5. Mg isotope fractionation during calcite precipitation: An experimental study

    NASA Astrophysics Data System (ADS)

    Saulnier, Ségolène; Rollion-Bard, Claire; Vigier, Nathalie; Chaussidon, Marc

    2012-08-01

    Experimental precipitations of calcite and other carbonate minerals were performed under various conditions of pH, temperature and solution Mg/Ca to determine the Mg partition coefficient and Mg isotope fractionation. Fifteen experiments were performed at pH ranging from 7.41 ± 0.07 to 8.51 ± 0.39, temperature ranging from 16.2 ± 0.7 to 26.5 ± 0.3 °C and Mg/Casolution ranging from 0.11 to 0.52 mol/mol. The apparent Mg partition coefficient between calcite and solution (DMg) spans a large range of values from 0.018 ± 0.014 to 0.15 ± 0.11 and carbonate Mg isotope fractionation (Δ26Mg) ranges from -2.53 ± 0.25‰ to -1.33 ± 0.14‰ and does not correlate with either pH or temperature. The range in DMg and Δ26Mg suggests non-equilibrium partitioning controlled by the processes of calcite growth, i.e. mixing between calcite grown at equilibrium and fluid inclusions, and entrapment of a surface Mg-rich calcite layer in isotopic equilibrium with the solution. The equilibrium Mg isotope fractionation between inorganic calcite and solution is estimated to be -2.13 ± 0.24‰. Additional Mg elemental and isotopic fractionations are observed to occur during biogenic formation of calcite due to variable removal of Mg by the organisms (high-Mg calcite corals, foraminifera) of seawater Mg from their calcification medium.

  6. Mg isotopic composition of carbonate: insight from speleothem formation

    NASA Astrophysics Data System (ADS)

    Galy, Albert; Bar-Matthews, Miryam; Halicz, Ludwik; O'Nions, R. Keith

    2002-07-01

    Simultaneous high-precision measurement of 24Mg, 25Mg and 26Mg isotopic compositions were made by multiple collector inductively coupled mass spectrometry (MC-ICP-MS) relative to the international standard SRM980. Data are presented on low-Mg calcite speleothems and their associated host rocks and waters from four caves, one in the French Alps and three in Israel, covering various climate conditions. In addition, data are presented on three dolostones and three limestones from the Himalaya. The overall variation is 4.13‰ and 2.14‰ in δ 26Mg and δ 25Mg, respectively. This is 35 times the uncertainty of the measurements and clearly demonstrates that the terrestrial isotopic composition of Mg is not unique. Each speleothem shows a characteristic range of δ 26Mg values that are attributed to the isotopic composition of the local water. Differences between the isotopic composition of Mg in the water dripping from stalactites and that of the modern speleothem are interpreted as being due to Mg isotopic fractionation during carbonate precipitation in the temperature range of 4-18°C. The low-Mg calcite is enriched in light isotopes by 1.35‰/AMU and the dependence on temperature has been found to be less than 0.02‰/AMU/°C. Despite various geological settings, the δ 26Mg of the studied dolostones is 2.0±1.2‰ higher than the δ 26Mg of the limestones. All together, these results suggest a strong mineralogical control and a weak temperature effect on the Mg isotopic composition of carbonate.

  7. Transformation of echinoid Mg calcite skeletons by heating

    NASA Astrophysics Data System (ADS)

    Dickson, J. A. D.

    2001-02-01

    Interambularcral plates of echinoid Heterocentrotus trigonarius, composed of Mg calcite 1 (≈14 mol% MgCO 3), were heated in three timed series of experiments at 300°C. Dried plate fragments and fragments with added water were heated separately in pressurized bombs. X-ray powder diffractometry, unit cell dimensions, and phase compositions are used to monitor reaction progress. After 10 h heating in the bombs dolomite (43.5 mol% MgCO 3) and Mg calcite appear (4-7 mol% MgCO 3); by 20 h all Mg calcite 1 is consumed, and at 120 h dolomite composition has evolved to ≈47 mol% MgCO 3 and calcite to ≈2 mol% MgCO 3. Whole plates heated at 300°C in an open muffle furnace develop dolomite (≈42 mol% MgCO 3) and Mg calcite 2 (≈6 mol% MgCO 3) after 10 h and remain compositionally invariant throughout subsequent heating to 620 h. Limited skeletal water catalyzes the early reaction but escapes from the open furnace and consequently reaction ceases after ≈10 h. The experimentally produced dolomite has relative Mg-Ca ordering of 75% to 79%. The stabilization of echinoid Mg calcite by heating at 300°C to a mixture of dolomite and calcite occurs through a dissolution/precipitation reaction. The alteration fabric produced within the stereom consists of irregularly shaped, branched dolomite crystals > 5 μm homoaxially set in a calcite 2 (bomb) or Mg calcite 2 (furnace) matrix. Round and tubular pores 1 to 5 μm are randomly distributed throughout this fabric. The stereom pore system remains intact during furnace heating but is destroyed during heating in bombs. The texture of experimentally stabilized echinoid skeletons is different from that of fossil echinoderms that are composed of microrhomic dolomite homoaxially set in a single calcite crystal.

  8. Solubility of MgO in MgCl{sub 2}-NaCl-NaF melts

    SciTech Connect

    Mediaas, H.; Vinstad, J.E.; Oestvold, T.

    1996-10-01

    The solubility of MgO in MgCl{sub 2}-NaCl-NaF melts has been measured for melts with varying NaF concentration for x{sub MgCl{sub 2}} = 0.10 and 0.63 and for x{sub MgCl{sub 2}}/x{sub NaCl} = 1.70. Melt samples have been analyzed by carbothermal reduction (Leco TC-436) for total oxide content. The oxide content in the binary melt MgCl{sub 2}-NaCl was also analyzed by Iodometric titration. The results indicate two different oxide-containing species, denoted MgOCl and MgOF, in the solidified samples withdrawn from the melt. The latter appears only in fluoride-containing melts, but may, however, also contain chloride ions. The oxide solubility is increasing with increasing concentration of Mg{sup 2+} in both MgCl{sub 2}-NaCl and MgCl{sub 2}-NaCl-NaF melts. The solubility of MgO is always higher in fluoride containing melts at the same Mg{sup 2+} concentration. In the systems concentrated in MgCl{sub 2}, the increase in oxide solubility as function of x{sub NaF} is more pronounced than what is predicted from a simple model calculation. The increase is much smaller in the x{sub NaF} < 0.2 range for small MgCl{sub 2} contents than predicted from the same model calculation. The introduction of 1.7 mol% NaF to an industrial electrolyte does not seem to change the oxide solubility significantly. In such an electrolyte, where x{sub MgCl{sub 2}} {approx_equal} 0.1, the data gives a constant oxide solubility around 10 ppm O up to 5 mol% NaF.

  9. Experimental calibration of Mg isotope fractionation between aragonite and seawater

    NASA Astrophysics Data System (ADS)

    Wang, Zhengrong; Hu, Ping; Gaetani, Glenn; Liu, Chao; Saenger, Casey; Cohen, Anne; Hart, Stanley

    2013-02-01

    The detectable magnesium (Mg) isotope fractionation between biogenic aragonite (including aragonitic corals, bivalves, scaphopod, and sclerosponges) and seawater can potentially be applied to reconstruct sea surface temperature (SST) in the past. To calibrate this thermometer, eight sets of inorganic precipitation experiments ('free-drift') in seawater (Mg/Ca = 5 or 10) have been carried out at 25-55 °C over a range of degassing rate. A cleaning procedure was adopted to remove Mg contamination by sea salt, surface absorbed Mg and silicate dust as nucleation centers. The Mg isotope fractionation between cleaned aragonite and seawater-like aqueous solution varies insignificantly with Mg/Ca ratios and Mg isotope compositions of the initial solution, and the CO2-degassing rate (0-75 cc/min), but decreases noticeably with increasing temperatures having a temperature sensitivity of ˜0.008-0.01‰/°C in the following form: Δ≈1000lnα=1.67(±0.36)-0.82(±0.11)×{1000}/{T} where αaragonite-seawater is the fractionation factor, and T is the absolute temperature in Kelvin. It is consistent with equilibrium fractionation between Mg2+ aquo-complex and magnesite predicted by one theoretical calculation. Qualitative comparison among Mg-bearing carbonates based on Mg-O bond strengths show the relative sequence of 26Mg enrichment is aragonite > dolomite > magnesite > calcite. Thus, the surprising agreement indicates either the calculation overestimated Mg fractionation between magnesite and fluid, or both theoretical calculation and our calibration represent Mg isotope fractionation between MgCO30-H2O cluster and Mg2+ aquo complexes. Comparison of our calibration with the Mg isotope fractionation between biogenic aragonite and seawater suggests Mg and oxygen isotope fractionations of some biogenic aragonites (e.g., Porites sp. corals) agree with our calibration within analytical uncertainty, whereas others deviate significantly, indicating biological and/or kinetic isotope

  10. Interdiffusion and Intrinsic Diffusion in the Mg-Al System

    SciTech Connect

    Brennan, Sarah; Bermudez, Katrina; Sohn, Yong Ho; Kulkarni, Nagraj S

    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 electron 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 the -Al

  11. Dual-color ultraviolet photodetector based on mixed-phase-MgZnO/i-MgO/p-Si double heterojunction

    NASA Astrophysics Data System (ADS)

    Xie, X. H.; Zhang, Z. Z.; Shan, C. X.; Chen, H. Y.; Shen, D. Z.

    2012-08-01

    We report a dual-color ultraviolet (UV) photodetector based on mixed-phase-MgZnO/i-MgO/p-Si double heterojunction. The device exhibits distinct dominant responses at solar blind (250 nm) and visible blind (around 330 nm) UV regions under different reverse biases. By using the energy band diagram of the structure, it is found that the bias-tunable two-color detection is originated from different valence band offset between cubic MgZnO/MgO and hexagonal MgZnO/MgO. Meanwhile, due to the large conduction band offset at the Si/MgO interface, the visible-light photoresponse from Si substrate is suppressed.

  12. 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.

  13. Clustering effects in 48Cr composite nuclei produced via the 24Mg+24Mg reaction

    NASA Astrophysics Data System (ADS)

    Di Nitto, A.; Vardaci, E.; Brondi, A.; La Rana, G.; Cinausero, M.; Gelli, N.; Moro, R.; Nadtochy, P. N.; Prete, G.; Vanzanella, A.

    2016-04-01

    The nuclear properties of 48Cr composite α -like nuclei produced at 60 MeV of excitation energy via the 24Mg+24Mg reaction were investigated. This excitation energy corresponds to a resonance with a narrow width (170 keV) observed in the elastic and inelastic channels, which was interpreted as a highly deformed state. To gain insight on the deformation of this state exclusive measurements of light charged particles were carried out with 8 π LP apparatus at Laboratori Nazionali di Legnaro and compared to statistical model predictions. The measured of α -particle energy spectra, α -evaporation residues, α -α , and α -α -α correlations indicate the limitation of the rotating liquid drop model in describing the nuclear shape of the compound nucleus along the decay cascade. To reproduce the full set of experimental data very elongated nuclear shapes had to be considered, with an axis ratio 3 :1 at the resonance angular momentum. This large deformation is consistent with previous findings for α -like nuclei and with the predictions of the cranked cluster model.

  14. 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.

  15. 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.

  16. Cardiovascular effect of dental anesthesia with articaine (40 mg with epinefrine 0,5 mg % and 40 mg with epinefrine 1 mg%) versus mepivacaine (30mg and 20 mg with epinefrine 1 mg%) in medically compromised cardiac patients: A cross-over, randomized, single blinded study

    PubMed Central

    Torres-Lagares, Daniel; Serrera-Figallo, María Á.; Corcuera-Flores, José R.; Machuca-Portillo, Carmen; Castillo-Oyagüe, Raquel; Gutiérrez-Pérez, José L.

    2012-01-01

    Objectives: The aim of the present study is to compare cardiovascular safety profiles of two dental anesthetics: articaine versus two standard mepivacaine solutions used during etiological periodontal treatment in cardiovascular patients. Study Design: Using a cross-over study design, ten cardiovascular patients were randomly assigned to dental treatment with 1.8mL of a local anesthetic injected on each quadrant of the mouth: Articaine (40mg with Epinephrine 0.5mg % and 40mg with Epinephrine 1mg %) or Mepivacaine (30mg and 20mg with Epinephrine 1mg %). A computer programme enabled continuous longitudinal data collection: O2 saturation, blood pressure (BP) and heart rate (HR). Results: No severe clinical side effects were observed. During the treatment period, we observed statistically significant differences as regards HR between injections with and without adrenalin (p< 0.039) and as regards systolic (p< 0.046) and diastolic (p < 0.046) blood pressure during the stabilization period. In both cases, the parameters under study increase. Age, gender, jaw treated, treatment duration and the rest of cardiovascular variables did not affect the results. None of the patients underwent ischemic alterations or any other complication derived from the treatment or the anesthesia. Conclusions: According to the results of our study, dental anesthetics with standard concentrations of Epinephrine seem to alter HR and BP. Although no cardiac ischemic alterations or any other cardiovascular complications have been observed, we must be cautious with the administration of anesthetics containing vasoconstrictors in patients with cardiovascular diseases. Key words:Dental anesthesia, cardiovascular diseases, chronic periodontitis, drug toxicity. PMID:22322521

  17. Los ojos de la NASA sobre la Tierra

    NASA Video Gallery

    La NASA cuenta con más de una decena de satélites que estudian la Tierra. Conoce la información que recaban los satélites, junto con Gilberto Colón, asistente especial del subdirector del Centro de...

  18. Yeast DEL assay detects clastogens.

    PubMed

    Kirpnick, Zhanna; Homiski, Michael; Rubitski, Elizabeth; Repnevskaya, Marina; Howlett, Niall; Aubrecht, Jiri; Schiestl, Robert H

    2005-04-01

    Chromosomal rearrangements, including DNA deletions are involved in carcinogenesis. The deletion (DEL) assay scoring for DNA deletions in the yeast Saccharomyces cerevisiae is able to detect a wide range of carcinogens. Among approximately 60 compounds of known carcinogenic activity, the DEL assay detected 86% correctly whereas the Ames Salmonella assay detected only 30% correctly [R.J. Brennan, R.H. Schiestl, Detecting carcinogens with the yeast DEL assay, Methods Mol. Biol. 262 (2004) 111-124]. Since the DEL assay is highly inducible by DNA double strand breaks, this study examined the utility of the DEL assay for detecting clastogens. Ten model compounds, with varied mechanisms of genotoxicity, were examined for their effect on the frequency of DNA deletions with the DEL assay. The compounds tested were: actinomycin D, camptothecin, methotrexate and 5-fluorodeoxyuridine, which are anticancer agents, noscapine and furosemide are therapeutics, acridine, methyl acrylate and resorcinol are industrial chemicals and diazinon is an insecticide. The in vitro micronucleus assay (IVMN) in CHO cells, a commonly used tool for detection of clastogens, was performed on the same compounds and the results of the two assays were compared. The results of our study show that there is 70% concordance in the presence of metabolic activation (rat liver S9) and 80% concordance in the absence of metabolic activation between the DEL assay and the standard in vitro micronucleus assay. The lack of cytotoxicity observed for four of the ten compounds examined indicates limited diffusion of lipophilic compounds across the yeast cell wall. Thus, the development of a more permeable yeast tester strain is expected to greatly improve concordance of the DEL assay with the IVMN assay. The yeast DEL assay is inexpensive, amenable to automation and requires less expertise to perform than the IVMN. Thus, it has a strong potential as a robust, fast and economical screen for detecting clastogens in

  19. Preparation and characterisation of Ru doped MgB2

    NASA Astrophysics Data System (ADS)

    Grivel, J.-C.; Holte, O. J.

    2013-12-01

    Samples with Mg1-xRuxB2 nominal stoichiometry were prepared by sintering at 800 °C. The critical transition temperature decreases up to a substitution level of x ≈ 0.015. A maximum solubility limit slightly in excess of 1 at.% Ru for Mg is confirmed by energy dispersive spectroscopy measurements. From and beyond this limit, an unidentified phase appears in the X-ray diffraction patterns. Interestingly, the lattice parameters of the MgB2 phase are constant up to x = 0.015, but start to decrease for higher Ru contents. This feature could be related to the fact that a Mg-Ru impurity phase results in a Mg-deficient (Mg,Ru)B2 matrix.

  20. A novel Drosophila mitochondrial carrier protein acts as a Mg(2+) exporter in fine-tuning mitochondrial Mg(2+) homeostasis.

    PubMed

    Cui, Yixian; Zhao, Shanke; Wang, Xudong; Zhou, Bing

    2016-01-01

    The homeostasis of magnesium (Mg(2+)), an abundant divalent cation indispensable for many biological processes including mitochondrial functions, is underexplored. In yeast, the mitochondrial Mg(2+) homeostasis is accurately controlled through the combined effects of importers, Mrs2 and Lpe10, and an exporter, Mme1. However, little is known about this Mg(2+) homeostatic process in multicellular organisms. Here, we identified the first mitochondrial Mg(2+) transporter in Drosophila, the orthologue of yeast Mme1, dMme1, by homologous comparison and functional complementation. dMme1 can mediate the exportation of mitochondrial Mg(2+) when heterologously expressed in yeast. Altering the expression of dMme1, although only resulting in about a 10% change in mitochondrial Mg(2+) levels in either direction, led to a significant survival reduction in Drosophila. Furthermore, the reduced survival resulting from dMme1 expression changes could be completely rescued by feeding the dMME1-RNAi flies Mg(2+)-restricted food or the dMME1-over-expressing flies the Mg(2+)-supplemented diet. Our studies therefore identified the first Drosophila mitochondrial Mg(2+) exporter, which is involved in the precise control of mitochondrial Mg(2+) homeostasis to ensure an optimal state for survival.

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

    PubMed Central

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

    2012-01-01

    Background and Aims 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. Methods 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). Key Results 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. Conclusions 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. PMID:22362665

  2. Magnetic lenses using different MgB2 bulk superconductors

    NASA Astrophysics Data System (ADS)

    Zhang, Z. Y.; Choi, S.; Matsumoto, S.; Teranishi, R.; Giunchi, G.; Figini Albisetti, A.; Kiyoshi, T.

    2012-02-01

    A magnetic lens allows the concentration of magnetic fields using the diamagnetism of superconductors. The important features of the magnetic lens are a tapered inner diameter from which the magnetic flux is extruded and a slit to suppress the circumference current that shields the magnetic flux. This concept was experimentally confirmed through the use of GdBaCuO bulks and a stack of NbTi/Nb/Cu sheets. We refer to this arrangement as a magnetic lens. The Mg-reactive liquid infiltration (Mg-RLI) process developed by Edison SpA is suitable for the production of large and high-density MgB2 bulks. Three MgB2 bulk magnetic lenses, each with a different microstructure, were fabricated following the Mg-RLI process. The properties of the MgB2 magnetic lenses were measured in a cryocooler system as well as in liquid helium. The results confirmed that the MgB2 bulk magnetic lenses could concentrate a magnetic field and that their field concentration properties were greatly affected by the temperature and the external field. In addition, the microstructure of the MgB2 bulk also had an influence on the magnetic properties at different external fields. The results indicated that the MgB2 lens might be utilized as a field amplifier in intermediate fields.

  3. A determination of Mg(+)-ligand binding energies

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry

    1991-01-01

    Theoretical calculations employing large basis sets and including correlation are carried out for Mg(+) with methanol, water, and formaldehyde. For Mg(+) with ethanol and acetaldehyde, the trends in the binding energies are studied at the self-consistent-field level. The predictions for the binding energy of Mg(+) to methanol and water of 41 + or - 5 and 36 + or - 5 kcal/mol, respectively, are much less than the experimental upper bounds, of 61 + or - 5 and 60 + or - 5 kcal mol, determined by using photodissociation techniques. The theoretical results are inconsistent with the onset of Mg(+) production observed in the photodissociation experiments, as the smallest absorptions are calculated at about 80 kcal/mol for both Mg(+)-CH3OH and Mg(+)-H2O, and these transitions are to bound excited states. The binding energy for Mg(+) with formaldehyde is predicted to be similar to Mg(+)-H2O. The relative binding energies are in reasonable agreement with experiment. The binding energy of a second water molecule to Mg(+) is predicted to be similar to the first. This suggests that the reduced reaction rate observed for the second ligand is not a consequence of a significantly smaller binding energy, at least for the smaller ligards such as those considered in this work.

  4. Boron isotope effect in superconducting MgB2.

    PubMed

    Bud'ko, S L; Lapertot, G; Petrovic, C; Cunningham, C E; Anderson, N; Canfield, P C

    2001-02-26

    We report the preparation method of and boron isotope effect for MgB2, a new binary intermetallic superconductor with a remarkably high superconducting transition temperature T(c)(10B) = 40.2 K. Measurements of both temperature dependent magnetization and specific heat reveal a 1.0 K shift in T(c) between Mg11B2 and Mg10B2. Whereas such a high transition temperature might imply exotic coupling mechanisms, the boron isotope effect in MgB2 is consistent with the material being a phonon-mediated BCS superconductor.

  5. Synthesis of MgB 2 film by electrochemical process

    NASA Astrophysics Data System (ADS)

    Sakurai, Hiroshi; Kuramochi, Takashi; Furuya, Yudai; Oike, Hiromi; Kato, Tadashi; Hoshi, Kazushi

    2008-07-01

    In order to synthesize MgB2 films, electrolysis is performed in an electrolyte comprising a fused mixture of B2O3, KCl and MgCl2 in a molar ratio of B2O3:KCl:MgCl2 = x:3.5:5. The results of the Meissner effects and X-ray diffraction measurements indicate the formation of MgB2 films on graphite and Si substrates. The superconducting critical temperature depends on both the synthesis temperature of the electrolysis and the amount of B2O3 in the electrolyte.

  6. Mg-Zr-Sr alloys as biodegradable implant materials.

    PubMed

    Li, Yuncang; Wen, Cuie; Mushahary, Dolly; Sravanthi, Ragamouni; Harishankar, Nemani; Pande, Gopal; Hodgson, Peter

    2012-08-01

    Novel Mg-Zr-Sr alloys have recently been developed for use as biodegradable implant materials. The Mg-Zr-Sr alloys were prepared by diluting Mg-Zr and Mg-Sr master alloys with pure Mg. The impact of Zr and Sr on the mechanical and biological properties has been thoroughly examined. The microstructures and mechanical properties of the alloys were characterized using optical microscopy, X-ray diffraction and compressive tests. The corrosion resistance was evaluated by electrochemical analysis and hydrogen evolution measurement. The in vitro biocompatibility was assessed using osteoblast-like SaOS2 cells and MTS and haemolysis tests. In vivo bone formation and biodegradability were studied in a rabbit model. The results indicated that both Zr and Sr are excellent candidates for Mg alloying elements in manufacturing biodegradable Mg alloy implants. Zr addition refined the grain size, improved the ductility, smoothed the grain boundaries and enhanced the corrosion resistance of Mg alloys. Sr addition led to an increase in compressive strength, better in vitro biocompatibility, and significantly higher bone formation in vivo. This study demonstrated that Mg-xZr-ySr alloys with x and y ≤5 wt.% would make excellent biodegradable implant materials for load-bearing applications.

  7. Mg and Mg alloys: how comparable are in vitro and in vivo corrosion rates? A review.

    PubMed

    Martinez Sanchez, Adela Helvia; Luthringer, Bérengère J C; Feyerabend, Frank; Willumeit, Regine

    2015-02-01

    Due to their biodegradability, magnesium and magnesium-based alloys could represent the third generation of biomaterials. However, their mechanical properties and time of degradation have to match the needs of applications. Several approaches, such as choice of alloying elements or tailored microstructure, are employed to tailor corrosion behaviour. Due to the high electrochemical activity of Mg, numerous environmental factors (e.g. temperature and surrounding ion composition) influence its corrosion behaviour, making it unpredictable. Nevertheless, the need of reliable in vitro model(s) to predict in vivo implant degradation is increasing. In an attempt to find a correlation between in vitro and vivo corrosion rates, this review presents a systematic literature survey, as well as an attempt to correlate the different results.

  8. Albedo polarimétrico de asteroides del grupo Hungaria

    NASA Astrophysics Data System (ADS)

    Gil-Hutton, R.; Benavidez, P.

    La región del cinturón de asteroides en donde se encuentra el grupo de los Hungarias (a= 1.79 a 1.98 UA, i=15 a 40 grados) es la única zona donde es común encontrar objetos de tipo taxonómico E, caracterizados por altos albedos, colores relativamente neutros y espectros sin detalles. Este tipo de asteroides está relacionado espectralmente con ciertos meteoritos (aubritas) que indican la existencia de episodios de gran calentamiento que ocurrieron durante la formación del Sistema Solar. Como el espectro de los asteroides de tipo E es idéntico a los de tipo M y P, la única forma de clasificar un asteroide en alguno de estos tres tipos taxonómicos es mediante el albedo. En este trabajo se presentan resultados preliminares sobre la determinación polarimétrica de albedos para objetos de este grupo utilizando el polarímetro CASPROF de CASLEO.

  9. 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

  10. Case Study: del Amo Bioventing

    EPA Science Inventory

    The attached presentation discusses the fundamentals of bioventing in the vadose zone. The basics of bioventing are presented. The experience to date with the del Amo Superfund Site is presented as a case study.

  11. Scleractinian Fossil Corals as Archives of Seawater δ26Mg

    NASA Astrophysics Data System (ADS)

    Gothmann, A. O.; Higgins, J. A.; Adkins, J. F.; Stolarski, J.; Bender, M. L.

    2014-12-01

    The recovery of environmental signatures from coral skeletons is often made difficult by 'vital effects', which cause skeletal chemistry to deviate from the expected composition of aragonite in equilibrium with seawater. Recent studies show that Mg isotopes in scleractinian corals are subject to vital effects, which appear as a departure of the δ26Mg coral temperature dependence from that of inorganic aragonite [1]. However, different from the case for Mg/Ca or δ44Ca in coral, the magnitude of the observed Mg-isotope vital effect is small (on the order of 0.1 ‰ or less). In addition, measurements of different species of modern coral show similar fractionations, suggesting that coral δ26Mg is not species dependent [2]. Together, these observations indicate that corals should faithfully record the seawater Mg-isotope composition, and that vital effects will not bias reconstructions. We measured Mg isotopes in a set of extremely well-preserved fossil scleractinian corals, ranging in age from Jurassic through Recent, to reconstruct past seawater δ26Mg. Well-preserved fossil corals of similar age show a range in δ26Mg of ~0.2 ‰, pointing to the presence of vital effects. However, our results show little variability in the δ26Mg of fossil corals across different geologic ages, suggesting that seawater δ26Mg has remained relatively constant throughout the Cenozoic and Mesozoic. This pattern has implications for our understanding of the mechanisms driving secular variations in seawater Mg/Ca. In particular, our data imply that dolomitization rates have not changed enough during the Mesozoic and Cenozoic to account for secular variations in seawater Mg/Ca. Our coral δ26Mg record agrees with a Cenozoic record from bulk foraminifera, further supporting the faithfulness of the coral archive. However, both of these records disagree with a third Cenozoic Mg-isotope record, derived from species-specific planktic forams [3]. [1] Saenger, C. et al. (2014) Chem. Geol

  12. HIV suppression with stavudine 30 mg versus 40 mg in adults over 60 kg on antiretroviral therapy in South Africa.

    PubMed

    Hoffmann, Christopher J; Charalambous, Salome; Fielding, Katherine L; Innes, Craig; Chaisson, Richard E; Grant, Alison D; Churchyard, Gavin J

    2009-08-24

    In 2007, the WHO recommended a maximum stavudine dose of 30 mg. We compared virologic suppression among patients weighing more than 60 kg and receiving stavudine 30 mg (n = 110) versus 40 mg (n = 508) in community HIV clinics in South Africa, before and after guidelines changed. At 6 months, HIV RNA less than 400 copies/ml was achieved in 79% and 81% receiving 30 and 40 mg stavudine, respectively (chi2, P = 0.6). In regression modeling, including baseline HIV RNA and nonnucleoside reverse transcriptase inhibitor agent, stavudine dose remained unassociated with suppression.

  13. Spin and charge transport in double-junction Fe/MgO/GaAs/MgO/Fe heterostructures

    SciTech Connect

    Wolski, S. Szczepański, T.; Dugaev, V. K.; Barnaś, J.; Landgraf, B.; Slobodskyy, T.; Hansen, W.

    2015-01-28

    We present theoretical and experimental results on tunneling current in single Fe/MgO/GaAs and double Fe/MgO/GaAs/MgO/Fe tunnel junctions. The charge and spin currents are calculated as a function of external voltage for different sets of parameters characterizing the semiconducting GaAs layer. Transport characteristics of a single Fe/MgO/GaAs junction reveal typical diode as well as spin diode features. The results of numerical calculations are compared with current-voltage characteristics measured experimentally for double tunnel junction structures, and a satisfactory agreement of the theoretical and experimental results has been achieved.

  14. 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.

  15. The acute effects of amisulpride (50 mg and 200 mg) and haloperidol (2 mg) on cognitive function in healthy elderly volunteers.

    PubMed

    Legangneux, E; McEwen, J; Wesnes, K A; Bergougnan, L; Miget, N; Canal, M; L'Heritier, C; Pinquier, J L; Rosenzweig, P

    2000-06-01

    In this double-blind, placebo controlled, four-way cross-over trial in 16 healthy elderly volunteers, the acute effects of haloperidol 2 mg, amisulpride 50 mg and 200 mg, were assessed on a range of tests of cognitive function. On each study day, cognitive performance was assessed prior to dosing and at 2, 4, 6, 9, 12 and 24 h after dosing with the following tests from the Cognitive Drug Research computerized assessment system: simple reaction time, digit vigilance task, choice reaction time, visual tracking, Critical Flicker Fusion, body sway, numeric working memory, immediate and delayed word recall, word recognition and self-ratings of mood and alertness. Haloperidol showed a general tendency to impair performance, and although this did not reach significance compared to placebo, for two tasks there were significant impairments with haloperidol compared to amisulpride. Amisulpride 50 mg and 200 mg, was not associated with impairment. In fact, there was some suggestion of improvement over placebo on three measures. The timings of assessment were appropriate for the study compounds. Furthermore, in a recent study in which a smaller number of elderly volunteers was tested on the same cognitive assessment system, a clear profile of acute impairments of haloperidol 3 mg, was identified. This indicates that haloperidol 2 mg, is not a sufficient dose to affect cognitive function in the elderly, supporting the general absence of effects with this dose in the young. Thus, the general absence of cognitive impairments with amisulpride at the doses used in this study suggests that this compound does not impair cognitive function in the elderly. PMID:10890311

  16. Masses of 17,18,19,20Mg

    NASA Astrophysics Data System (ADS)

    Fortune, H. T.

    2016-10-01

    A previous simple parametrization of mirror energy differences in pairs of nuclei consisting of a p -shell core plus two s d -shell nucleons is applied to a series of mirrors that contain s d -shell nucleons in the core. Results for Mg,2019 agree with experiment and with a potential model. Predictions are made for 2 p separation energies of Mg,1817.

  17. Projectile deformation effects in the breakup of 37Mg

    NASA Astrophysics Data System (ADS)

    Shubhchintak; Chatterjee, R.; Shyam, R.

    2016-05-01

    We study the breakup of 37Mg on Pb at 244MeV/u with the recently developed extended theory of Coulomb breakup within the postform finite range distorted wave Born approximation that includes deformation of the projectile. Comparing our calculated cross section with the available Coulomb breakup data we determine the possible ground state configuration of 37Mg.

  18. Mg-based compounds for hydrogen and energy storage

    NASA Astrophysics Data System (ADS)

    Crivello, J.-C.; Denys, R. V.; Dornheim, M.; Felderhoff, M.; Grant, D. M.; Huot, J.; Jensen, T. R.; de Jongh, P.; Latroche, M.; Walker, G. S.; Webb, C. J.; Yartys, V. A.

    2016-02-01

    Magnesium-based alloys attract significant interest as cost-efficient hydrogen storage materials allowing the combination of high gravimetric storage capacity of hydrogen with fast rates of hydrogen uptake and release and pronounced destabilization of the metal-hydrogen bonding in comparison with binary Mg-H systems. In this review, various groups of magnesium compounds are considered, including (1) RE-Mg-Ni hydrides (RE = La, Pr, Nd); (2) Mg alloys with p-elements (X = Si, Ge, Sn, and Al); and (3) magnesium alloys with d-elements (Ti, Fe, Co, Ni, Cu, Zn, Pd). The hydrogenation-disproportionation-desorption-recombination process in the Mg-based alloys (LaMg12, LaMg11Ni) and unusually high-pressure hydrides synthesized at pressures exceeding 100 MPa (MgNi2H3) and stabilized by Ni-H bonding are also discussed. The paper reviews interrelations between the properties of the Mg-based hydrides and p- T conditions of the metal-hydrogen interactions, chemical composition of the initial alloys, their crystal structures, and microstructural state.

  19. Oxidation and growth of Mg thin films on Ru(001)

    NASA Astrophysics Data System (ADS)

    Huang, H. H.; Jiang, X.; Siew, H. L.; Chin, W. S.; Sim, W. S.; Xu, G. Q.

    1999-08-01

    The oxidation and growth of ultra-thin Mg films on a Ru(001) substrate have been studied using X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS) in the temperature range of 300-1500 K. Our results suggest that the growth of Mg thin films follows a layer-by-layer mode. Upon oxygen adsorption at 300 K, two O 1s peaks were detected on the Mg film. The peak at 532.2-532.6 eV could be attributed to either dioxygen or partially reduced species (O δ-, δ<2), whereas that at 530.1-530.6 eV is due to lattice oxygen in MgO. Annealing of the oxidized film to 800 K causes the conversion of the dioxygen or partially reduced species to the oxide state. Thermal desorption peaks of MgO were directly detected at 1000-1127 and 1350-1380 K, respectively. However, initial evaporation of Mg atoms onto an oxygen pre-adsorbed surface yields a fully oxidized MgO. Further Mg deposition results in the formation of a partially oxidized film with the observation of an O 1s peak at 532.2 eV.

  20. Informe trata el descenso del cáncer y los tumores cerebrales

    Cancer.gov

    Los índices de mortalidad en los Estados Unidos de todos los cánceres en hombres y mujeres siguieron bajando entre 2003 y 2007, que es el período más reciente del que se disponen datos, según el último Informe Anual a la Nación sobre el Estado del Cáncer. El informe encuentra también que el índice general combinado de nuevos diagnósticos de cáncer en hombres y mujeres decreció un promedio un poco menos de 1% por año en el mismo período.

  1. Magnetic properties of epitaxial discontinuous Fe/MgO multilayers.

    PubMed

    García-García, A; Pardo, J A; Strichovanec, P; Magén, C; Vovk, A; De Teresa, J M; Kakazei, G N; Pogorelov, Yu G; Golub, V; Salyuk, O; Morellón, L; Algarabel, P A; Ibarra, M R

    2012-09-01

    We report magnetic, dynamic and transport properties of discontinuous metal-insulator multilayers Fe/MgO grown on amorphous Corning glass and single-crystalline MgO (001) substrates. The films of structure Substrate/MgO (3 nm)/[Fe (0.6 nm)/MgO (3.0 nm)] x 10 were prepared in ultra-high vacuum conditions using Pulsed Laser Deposition. It was shown that conditions of epitaxial growth are favorable for MgO substrates. As a result a substantial increase of tunneling magnetoresistance caused by spin-filtering effect was observed and reasonably theoretically explained. The value of TMR - 9.2% at room temperature in 18 kOe magnetic field is three times higher comparing to that for the samples grown on Corning glass substrates. PMID:23035505

  2. Defect complexes in Li-doped MgO

    NASA Astrophysics Data System (ADS)

    Richter, N. A.; Stavale, F.; Levchenko, S. V.; Nilius, N.; Freund, H.-J.; Scheffler, M.

    2015-05-01

    Magnesium oxide (MgO) is used in a variety of industrial applications due to its low cost and structural stability. In heterogeneous catalysis, MgO and Li-doped MgO have been studied as catalysts for the oxidative coupling of methane. In this work, we analyze the structure and stability of defect complexes comprising Li dopants and oxygen vacancies in MgO, combining scanning tunneling microscopy, photon-emission experiments, and density-functional theory computations. The experimental results strongly indicate that after annealing Li-doped MgO to temperatures of 600 K and higher, Li evaporates from the surface, but Li defects, such as substitutional defects, interstitials, or defect complexes comprising Li remain in the bulk. Our calculations show that bulk defect complexes containing F2 + color centers, that have donated their two electrons to two adjacent Li defects, are the most stable configurations at realistic pressure and temperature conditions.

  3. The anodic surface film and hydrogen evolution on Mg

    SciTech Connect

    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.

  4. Model for nonprotective oxidation of Al-Mg alloys

    SciTech Connect

    Zayan, M.H. )

    1990-12-01

    The oxidation of Al-5Mg alloy has been studied at 550 C in dry air. Morphological details of the MgO layers which develop on this alloy during high-temperature oxidation have been studied by scanning electron microscopy (SEM). A localized detachment of the protective, adherent MgO layer was found, which is caused by voids formed by vacancy condensation at the metal-oxide interface. The source of these vacancies was the outward diffusion of Mg though the oxide layer. Continuing growth of these voids was responsible for cracking of oxide ridges and nodules, as well as the growth of new MgO having a cauliflower morphology. A model describing the process of the outward diffusion is given.

  5. Preparation and characterisation of Os doped MgB2

    NASA Astrophysics Data System (ADS)

    Grivel, J.-C.; Namazkar, S.; Alexiou, A.; Holte, O. J.

    2014-12-01

    Polycrystalline samples with Mg1-xOsxB2.04 nominal stoichiometry were made by reacting elemental powders at 800 °C under argon atmosphere. Based on XRD diffraction patterns, EDS analysis and magnetisation measurements, it is found that Os can replace up to about 1 at.% Mg in the MgB2 lattice. Beyond this doping level, unreacted Os and Mg-rich Mg-Os impurity phases are formed. The a-axis parameter contracts upon doping while the superconducting transition temperature decreases at a rate of 2.1 K/at.% Os substitution. At 10 K, Os doping induces an improvement of the normalised critical current density under applied magnetic fields in excess of 0.5 T, indicating a modest enhancement of flux pinning in this range.

  6. 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.

  7. Mg Isotope Fractionation Between E. coli and Growth Medium

    NASA Astrophysics Data System (ADS)

    Basset, R.; Lemelle, L.; Albalat, E.; Telouk, P.; Albarède, F.

    2008-12-01

    Magnesium is a major element in both microbial cells and minerals, immune to redox conditions and atmospheric interactions. In organic cells, Mg can be associated with membranes, with cytoplasm (either as an isolated ion or bound to proteins). Its isotope composition can be used to constrain the contribution of organic material to carbonate fluxes and the overall cycle of this element in the exogenous environment [1, 2]. Cells of DH5α E. coli strain were grown in Luria Broth medium and the Mg isotope fractionation between the cells and their growth medium determined after calcination in Pt crucibles, chemical purification by cation exchange chemistry in HCl medium [3] and isotopic analysis on a Nu HR MC-ICPMS. The yield is better than 96%. The Mg contents of 2.19 ± 0.08 mg per g DW in cells and 0.117 ± 0.001 mg per g DW in Luria Broth medium are consistent with literature data [4]. About half of the Mg initially present in the LB medium is taken up by the growing cells. At high cellular concentrations (OD600 = 3.5), cells are enriched in 26Mg by 0.97 ± 0.14 ‰ with respect to the culture medium. Although E. coli may not be a good proxy for oceanic plankton, such a substantial fractionation of Mg isotopes suggests that incorporation of even a few percent organic matter into oceanic oozes depletes oceanic Mg in its heavy isotopes and therefore accounts for the isotopic difference between riverine and marine Mg. [1] Drever, The Sea 5 (1974) 337-357 [2] Tipper et al., EPSL 250 (2006) 241-253 [3] Chang et al., JAAS 18 (2003) 296-301 [4] Outten et al., Science 292 (2001), 2488-2492

  8. In vitro degradation and electrochemical corrosion evaluations of microarc oxidized pure Mg, Mg-Ca and Mg-Ca-Zn alloys for biomedical applications.

    PubMed

    Pan, Yaokun; He, Siyu; Wang, Diangang; Huang, Danlan; Zheng, Tingting; Wang, Siqi; Dong, Pan; Chen, Chuanzhong

    2015-02-01

    Calcium phosphate (CaP) ceramic coatings were fabricated on pure magnesium (Mg) and self-designed Mg-0.6Ca, Mg-0.55Ca-1.74Zn alloys by microarc oxidation (MAO). The coating formation, growth and biomineralization mechanisms were discussed. The coating degradability and bioactivity were evaluated by immersion tests in trishydroxymethyl-aminomethane hydrochloric acid (Tris-HCl) buffer and simulated body fluid (SBF) solutions, respectively. The coatings and corrosion products were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) and fourier transform infrared spectrometer (FT-IR). The electrochemical workstation was used to investigate the electrochemical corrosion behaviors of substrates and coatings. Results showed that Mg-0.55Ca-1.74Zn alloy exhibits the highest mechanical strength and electrochemical corrosion resistance among the three alloys. The MAO-coated Mg-0.55Ca-1.74Zn alloy has the potential to be served as a biodegradable implant.

  9. 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

  10. Effect of Mg content on the bioactivity and biocompatibility of Mg-substituted fluorapatite nanopowders fabricated via mechanical activation.

    PubMed

    Kheradmandfard, M; Fathi, M H; Ansari, F; Ahmadi, T

    2016-11-01

    The aim of this work was preparation, characterization, bioactivity and biocompatibility evaluation of Mg-substituted fluorapatite (Mg-FA) nanopowders. Mg-FA nanopowders with a chemical composition of Ca10-xMgx(PO4)6F2, with x=0, 0.5, 1, and 2 were prepared by mechanically activated method. The in vitro bioactivity was investigated by soaking the powders in simulated body fluid (SBF) for various time periods to analyze the nucleation and growth of bone-like apatite on the surface of the samples. Cell viability and cell attachment were studied by MTT assay. Results indicated that the bioactivity of all of samples with different Mg content was improved compared with the pure FA. However, the mechanism of bioactivity is different and depends on the amount of Mg substitution. Finally, cell culture suggested that the addition of Mg(2+) has no adverse effect and Mg-FA samples have good biocompatibility. The Mg-FA material shows potential in satisfying the requirements of biomedical applications. PMID:27524005

  11. Reactions of Mg and Mg2 with SO2 in low-temperature matrices: association or insertion?

    PubMed

    Liu, Xing; Xing, Xiaopeng; Zhao, Jie; Wang, Xuefeng

    2015-01-29

    Laser-ablated magnesium species were codeposited with SO2 in excess argon or neon on the substrate at 4 K. The reactions mainly produced Mg(η(2)-O2S), Mg(η(2)-O2S)2, Mg2(η(2)-O2S), OMg2(η(2)-SO), and Mg(η(2)-SO) complexes, which were identified by isotopic substitutions and density functional frequency calculations (B3LYP and BPW91). In addition, the collected infrared spectra suggest that the single Mg atoms could react with SO2 to form the Mg(η(2)-O2S) complex on annealing, which further reacts with SO2 to produce the Mg(η(2)-O2S)2 complex on irradiation. In contrast, the reactions of magnesium dimers lead to cleavage of the S═O bond in SO2 on irradiating. Structural and bonding characteristics of these generated complexes, which shed light on the different performances of single Mg atom and its dimer in their reactions with small molecules, are discussed.

  12. Laser cladding of a Mg based Mg-Gd-Y-Zr alloy with Al-Si powders

    NASA Astrophysics Data System (ADS)

    Chen, Erlei; Zhang, Kemin; Zou, Jianxin

    2016-03-01

    In the present work, a Mg based Mg-Gd-Y-Zr alloy was subjected to laser cladding with Al-Si powders at different laser scanning speeds in order to improve its surface properties. It is observed that the laser clad layer mainly contains Mg2Si, Mg17Al12 and Al2(Gd,Y) phases distributed in the Mg matrix. The depth of the laser clad layer increases with decreasing the scanning speed. The clad layer has graded microstructures and compositions. Both the volume fraction and size of Mg2Si, Mg17Al12 and Al2(Gd,Y) phases decreases with the increasing depth. Due to the formation of these hardening phases, the hardness of clad layer reached a maximum value of HV440 when the laser scanning speed is 2 mm/s, more than 5 times of the substrate (HV75). Besides, the corrosion properties of the untreated and laser treated samples were all measured in a NaCl (3.5 wt.%) aqueous solution. The corrosion potential was increased from -1.77 V for the untreated alloy to -1.13 V for the laser clad alloy with scanning rate of 2 mm/s, while the corrosion current density was reduced from 2.10 × 10-5 A cm-2 to 1.64 × 10-6 A cm-2. The results show that laser cladding is an efficient method to improve surface properties of Mg-Rare earth alloys.

  13. Demixing Instability in Dense Molten MgSiO3 and the Phase Diagram of MgO

    NASA Astrophysics Data System (ADS)

    Boates, Brian; Bonev, Stanimir A.

    2013-03-01

    The phase diagrams of MgSiO3 and MgO are studied from first-principles theory for pressures and temperatures up to 600 GPa and 20 000 K. Through the evaluation of finite-temperature Gibbs free energies, using density-functional theory within the generalized gradient approximation as well as with hybrid exchange-correlation functionals, we find evidence for a vast pressure-temperature regime where molten MgSiO3 decomposes into liquid SiO2 and solid MgO, with a volume change of approximately 1.2%. The demixing transition is driven by the crystallization of MgO—the reaction only occurs below the high-pressure MgO melting curve. The predicted transition pressure at 10 000 K is in close proximity to an anomaly reported in recent laser-driven shock experiments of MgSiO3. We also present new results for the high-pressure melting curve of MgO and its B1-B2 solid phase transition, with a triple point at 364 GPa and 12 000 K.

  14. Simulating GTP:Mg and GDP:Mg with a simple force field: a structural and thermodynamic analysis.

    PubMed

    Simonson, Thomas; Satpati, Priyadarshi

    2013-04-01

    Di- and tri-phosphate nucleotides are essential cofactors for many proteins, usually in an Mg(2+) -bound form. Proteins like GTPases often detect the difference between NDP and NTP and respond by changing conformations. To study such complexes, simple, fixed charge force fields have been used, which allow long simulations and precise free energy calculations. The preference for NTP or NDP binding depends on many factors, including ligand structure and Mg(2+) coordination and the changes they undergo upon binding. Here, we use a simple force field to examine two Mg(2+) coordination modes for the unbound GDP and GTP: direct, or "Inner Sphere" (IS) coordination by one or more phosphate oxygens and indirect, "Outer Sphere" (OS) coordination involving one or more bridging waters. We compare GTP: and GDP:Mg binding with OS and IS coordination; combining the results with experimental data then indicates that GTP prefers the latter. We also examine different kinds of IS coordination and their sensitivity to a key force field parameter: the optimal Mg:oxygen van der Waals distance Rmin . Increasing Rmin improves the Mg:oxygen distances, the GTP: and GDP:Mg binding affinities, and the fraction of GTP:Mg with β + γ phosphate coordination, but does not improve or change the GTP/GDP affinity difference, which remains much larger than experiment. It has no effect on the free energy of GDP binding to a GTPase.

  15. Reactions of Mg and Mg2 with SO2 in low-temperature matrices: association or insertion?

    PubMed

    Liu, Xing; Xing, Xiaopeng; Zhao, Jie; Wang, Xuefeng

    2015-01-29

    Laser-ablated magnesium species were codeposited with SO2 in excess argon or neon on the substrate at 4 K. The reactions mainly produced Mg(η(2)-O2S), Mg(η(2)-O2S)2, Mg2(η(2)-O2S), OMg2(η(2)-SO), and Mg(η(2)-SO) complexes, which were identified by isotopic substitutions and density functional frequency calculations (B3LYP and BPW91). In addition, the collected infrared spectra suggest that the single Mg atoms could react with SO2 to form the Mg(η(2)-O2S) complex on annealing, which further reacts with SO2 to produce the Mg(η(2)-O2S)2 complex on irradiation. In contrast, the reactions of magnesium dimers lead to cleavage of the S═O bond in SO2 on irradiating. Structural and bonding characteristics of these generated complexes, which shed light on the different performances of single Mg atom and its dimer in their reactions with small molecules, are discussed. PMID:25521504

  16. The formation of MgH(2) nanowires during the hydrogenation of Ti-doped Mg film.

    PubMed

    He, Yuping; Liu, Yongjun; Zhao, Yiping

    2008-11-19

    A unique diffusion barrier structure, consisting of layers of a Ti nanorod array and Ti film, has been fabricated on Si substrate for a subsequent 2 at.% Ti-doped Mg film deposition using a combinational technique of multilayer growth, co-deposition and dynamic shadowing growth. The hydrogenation of the Ti-doped Mg film on such a barrier structure shows that the barrier can prevent direct Mg-Si contact and suppress the formation of Mg(2)Si alloy in a high-temperature process. When this film has been hydrogenated at temperatures T≤300 °C for approximately 150 h, tetragonal single-crystal MgH(2) nanowires are formed on the surface of the Ti-doped Mg film. The hydrogenation time and temperature are the two main factors for the nanowire formation. The doping of Ti also plays a significant role. This result reveals that complicated dynamic processes could occur during the hydrogenation of Ti-doped Mg film when Mg(2)Si formation can be eliminated by an effective diffusion barrier layer.

  17. Structural, electronic and bonding properties of antifluorite crystals of Be2C, BeMgC and Mg2C

    NASA Astrophysics Data System (ADS)

    Joshi, K. B.; Trivedi, D. K.; Paliwal, U.; Galav, K. L.

    2016-05-01

    Structure prediction methods are coupled with the first-principles linear combination of atomic orbitals method to propose the crystal parameters and bulk modulus of antifluorite BeMgC. The binary antifluorite methanides Be2C, Mg2C are also studied. Electronic structure calculations and Mulliken population analyses (MPA) are performed to unravel bands dispersion and bonding properties. The values of the indirect band gap Γ → X for Be2C, Mg2C and BeMgC, in order, are 2.90, 2.05 and 1.86 eV. The calculated energies of a few occupied bands in Be2C are in very good agreement with the available experimental data. The application of pressure causes change in the band gap of three carbides. The Γ-Γ, Γ-X and Γ-K band gaps exhibit different trends with pressure. Effective charges on the basis of MPA in the three compounds are {(B{e}+1.095)}2{C}-2.19, {(M{g}+1.615)}2{C}-3.23 and B{e}+1.12M{g}+1.682{C}-2.802. It signifies covalent bonding in Be2C, ionic in Mg2C, and intermediate in the BeMgC.

  18. Magnetic characterization of CoFeB /MgO and CoFe /MgO interfaces

    NASA Astrophysics Data System (ADS)

    Negusse, Ezana; Lussier, A.; Dvorak, J.; Idzerda, Y. U.; Shinde, S. R.; Nagamine, Y.; Furukawa, S.; Tsunekawa, K.; Djayaprawira, D. D.

    2007-02-01

    The use of CoFeB ferromagnetic electrodes in place of CoFe has been shown to significantly increase the tunneling magnetoresistance (TMR) of MgO based magnetic tunnel junctions (MTJs). By using soft x-ray scattering techniques, we show that the behavior of the magnetic moments located at the CoFe-MgO interface are drastically different from the rest of the CoFe film, whereas the magnetic response of the CoFeB-MgO interfacial moments is coherent with the film's bulk. Our results support the view that the high TMR values observed in MgO based MTJs with CoFeB electrodes are due to the uniform magnetic response of the entire CoFeB electrode including the MgO interfacial moments.

  19. Strengthening of Al and Al-Mg alloy wires by melt inoculation with Al/MgB2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Florián-Algarín, David; Marrero, Raúl; Padilla, Alexandra; Suárez, Oscar Marcelo

    2015-12-01

    This study hinges on the feasibility of strengthening Al and Al-Mg wires by adding Al nanocomposite pellets containing MgB2 nanoparticles into the melt upon fabrication. These MgB2 nanoparticles were obtained by fragmentation using a high-energy ball mill, and were, afterward, mechanically alloyed with pure aluminum. The resulting MgB2/Al nanocomposite pellets were sintered at 260°C to be subsequently added into molten aluminum and an Al-Mg alloy melt. Cold rolling intercalated with stepwise annealing allowed the fabrication of 1 mm diameter wires with a final area reduction of 96%. Mechanical and physical properties of the treated wire specimens were compared to those of similarly processed pure aluminum wire. The ultimate tensile strength of the treated wires increased approximately double fold with respect to untreated wires at the expense of some loss in electrical conductivity.

  20. Superconductivity in dense MgB2 wires.

    PubMed

    Canfield, P C; Finnemore, D K; Bud'ko, S L; Ostenson, J E; Lapertot, G; Cunningham, C E; Petrovic, C

    2001-03-12

    MgB2 becomes superconducting just below 40 K. Whereas porous polycrystalline samples of MgB2 can be synthesized from boron powders, in this Letter we demonstrate that dense wires of MgB2 can be prepared by exposing boron filaments to Mg vapor. The resulting wires have a diameter of 160 microm, are better than 80% dense, and manifest the full chi = -1/4pi shielding in the superconducting state. Temperature-dependent resistivity measurements indicate that MgB2 is a highly conducting metal in the normal state with rho(40 K) = 0.38 microOmega cm. By using this value, an electronic mean-free path, l approximately 600 A can be estimated, indicating that MgB2 wires are well within the clean limit. Tc, Hc2(T), and Jc data indicate that MgB2 manifests comparable or better superconducting properties in dense wire form than it manifests as a sintered pellet.

  1. Characterization of Mg2+ Distributions around RNA in Solution

    PubMed Central

    2016-01-01

    Binding of metal ions is an important factor governing the folding and dynamics of RNA. Shielding of charges in the polyanionic backbone allows RNA to adopt a diverse range of folded structures that give rise to their many functions within the cell. Some RNA sequences fold only in the presence of Mg2+, which may be bound via direct interactions or occupy the more diffuse “ion atmosphere” around the RNA. To understand the driving forces for RNA folding, it is important to be able to fully characterize the distribution of metal ions around the RNA. In this work, a combined Grand Canonical Monte Carlo-Molecular Dynamics (GCMC-MD) method is applied to characterize Mg2+ distributions around folded RNA structures. The GCMC-MD approach identifies known inner- and outer-shell Mg2+ coordination, while also predicting new regions occupied by Mg2+ that are not observed in crystal structures but that may be relevant in solution, including the case of the Mg2+ riboswitch, for which alternate Mg2+ binding sites may have implications for its function. This work represents a significant step forward in establishing a structural and thermodynamic description of RNA–Mg2+ interactions and their role in RNA structure and function.

  2. 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.

  3. Elemental maps in human allantochorial placental vessels cells: 2. MgCl2 and MgSO4 effects.

    PubMed

    Michelet-Habchi, Claire; Barberet, Philippe; Dutta, Raj Kumar; Moretto, Philippe; Guiet-Bara, Andrée; Bara, Michel

    2003-09-01

    Extracellular magnesium salts are known to interfere with ionic channels in the cellular membranes. The membrane potential, a regulator of vascular tone, is a function of the physiological activities of ionic channels (particularly, K+ and Ca2+ channels in these cells). These channels regulate the ionic distribution into these cells. Micro-Particule Induced X-ray Emission (PIXE) analysis was applied to determine the ionic composition of vascular smooth muscle cells (VSMC) and of vascular endothelial cells (VEC) in the placental human allantochorial vessels in a physiological medium (Hanks' solution) modified by the addition of 2 mM MgCl2 or 2 mM MgSO4 which block the calcium-sensitive K+ channels (K(Ca)), the ATP-sensitive K+ channels (K(ATP)) and the voltage-sensitive K+ (K(df)) and Ca2+ channels. In VSMC (media layer), the addition of MgCl2 induced no modification of the K, Cl, P, S and Ca concentrations but increased the Na and Mg concentrations and the addition of MgSO4 only significantly increased the Mg concentration, the other ion concentrations remaining constant. In endothelium (VEC), MgCl2 or MgSO4 addition implicated the same observations as in VSMC. These results confirmed the blockage of K(df), K(Ca), K(ATP) and Ca channels in VSMC and VEC by magnesium salts, the relationship between Mg2+ ions and internal Na and demonstrated the possible intervention of a Na+/Mg2+ exchanger.

  4. A Redetermination of the Dissociation Energy of MgO(+)

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Partridge, Harry

    1994-01-01

    In 1986, we reported a dissociation energy (D(sub 0) of 2.31 eV for the X(sup 2)Pi ground state of MgO(+). This value was determined by computing the dissociation energy to the Mg(2+) + O(-) limit and adjusting the value to the Mg(+) + O limit using the experimental Ionization Potential (IP) of Mg(+) and the Electron Affinity (EA) of O. The success of this method relies on the assumption that there is little covalent contribution to the bonding. The very small (0.04 eV) correlation contribution to the binding energy was taken as corroboration for the validity of this approach. Our earlier theoretical value was estimated to be accurate to at least 0.2 eV. It is in excellent agreement with the subsequent value of 2.30 +/- 0.13 eV determined by Freiser and co-workers from photodissociation experiments. It is also consistent with the upper (less than 3.1 eV) and lower (greater than 1.1 eV) bounds determined by Rowe obtained by studying the reactions of Mg(+) with 03 and NO2. However, it is inconsistent with an upper bound of 1.7 eV reported by Kappes and Staley based on their failure to observe MgO(+) in the reaction of Mg(+) with N2O. The picture became somewhat clouded, however, by the recent guided-ion beam mass spectrometric studies of Dalleska and Armentrout. Their initial analysis of the reaction data for Mg(+) + O2 lead to a bond dissociation energy of 2.92 +/- 0.25 eV, which is considerably larger than the value of 2.47 +/- 0.06 eV deduced from their studies of the Mg(+)+NO2 reaction.

  5. Superconductivity of Metallic Boron in MgB2

    NASA Astrophysics Data System (ADS)

    Kortus, J.; Mazin, I. I.; Belashchenko, K. D.; Antropov, V. P.; Boyer, L. L.

    2001-05-01

    Boron in MgB2 forms stacks of honeycomb layers with magnesium as a space filler. Band structure calculations indicate that Mg is substantially ionized, and the bands at the Fermi level derive mainly from B orbitals. Strong bonding with an ionic component and considerable metallic density of states yield a sizable electron-phonon coupling. Together with high phonon frequencies, which we estimate via zone-center frozen phonon calculations to be between 300 and 700 cm-1, this produces a high critical temperature, consistent with recent experiments. Thus MgB2 can be viewed as an analog of the long sought, but still hypothetical, superconducting metallic hydrogen.

  6. Matter radii of {sup 32-35}Mg

    SciTech Connect

    Kanungo, R.; Perro, C.; Prochazka, A.; Farinon, F.; Knoebel, R.; Horiuchi, W.; Nociforo, C.; Aumann, T.; Geissel, H.; Gerl, J.; Kindler, B.; Lommel, B.; Mahata, K.; Scheidenberger, C.; Weick, H.; Winkler, M.; Boutin, D.; Lenske, H.; Cortina-Gil, D.; Davids, B.

    2011-02-15

    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.

  7. Mg II 2800 A emission in late type stars

    NASA Technical Reports Server (NTRS)

    Doherty, L. R.

    1972-01-01

    The largest body of data on ultraviolet spectra of late-type stars now available is the series of scans made with the long wavelength spectrometer onboard OAO-2. Some features of selected scans from this series and estimates of Mg II emission fluxes were reported earlier. Since that time, the effects of sky background, scattered light and variable instrumental sensitivity have become better understood. Additional stars are used to define more clearly the transition from Mg II 2800 A absorption to emission with advancing spectral type, and additional scans of alpha Sco provide a better estimate of Mg II emission strength for this supergiant in OAO observations.

  8. Superconductivity of metallic boron in MgB2.

    PubMed

    Kortus, J; Mazin, I I; Belashchenko, K D; Antropov, V P; Boyer, L L

    2001-05-14

    Boron in MgB2 forms stacks of honeycomb layers with magnesium as a space filler. Band structure calculations indicate that Mg is substantially ionized, and the bands at the Fermi level derive mainly from B orbitals. Strong bonding with an ionic component and considerable metallic density of states yield a sizable electron-phonon coupling. Together with high phonon frequencies, which we estimate via zone-center frozen phonon calculations to be between 300 and 700 cm(-1), this produces a high critical temperature, consistent with recent experiments. Thus MgB2 can be viewed as an analog of the long sought, but still hypothetical, superconducting metallic hydrogen.

  9. PROPERTIES OF DEFECTS AND IMPLANTS IN Mg+ IMPLANTED SILICON CARBIDE

    SciTech Connect

    Jiang, Weilin; Zhu, Zihua; Varga, Tamas; Bowden, Mark E.; Manandhar, Sandeep; Roosendaal, Timothy J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2013-09-25

    As a candidate material for fusion reactor designs, silicon carbide (SiC) under high-energy neutron irradiation undergoes atomic displacement damage and transmutation reactions that create magnesium as one of the major metallic products. The presence of Mg and lattice disorder in SiC is expected to affect structural stability and degrade thermo-mechanical properties that could limit SiC lifetime for service. We have initiated a combined experimental and computational study that uses Mg+ ion implantation and multiscale modeling to investigate the structural and chemical effects in Mg implanted SiC and explore possible property degradation mechanisms.

  10. Phase stability in the Cd-Mg system

    SciTech Connect

    Asta, M.; McCormack, R.; de Fontaine, D.

    1993-12-31

    This paper reports on results of a theoretical study of solid-state phase equilibria and short-range order in Cd-Mg alloys. Results of first-principles linear muffin-tin orbital method total-energy calculations for seven hcp-based superstructures have been combined with cluster-variation-method calculations of thermodynamic properties in order to compute the Cd-Mg phase diagram. Effect on the calculated phase diagram of contributions to the alloy free energy arising from atomic vibrations and structural relaxations are assessed using available experimental information for ordered and disordered alloys in the Cd-Mg system.

  11. Electronic structure of Mg: From monolayers to bulk

    SciTech Connect

    Schiller, F.; Laubschat, C.; Heber, M.; Servedio, V.D.P.

    2004-09-15

    The structure of thin Mg films epitaxially grown onto a W(110) crystal was analyzed by low energy electron and Auger electron diffraction verifying a growth of bulk Mg. Normal-emission angle-resolved photoemission spectra of the growing films reveal quantum well states on both sides of a surface state. These states result from electron confinement in the Mg layer and are used to derive the electronic structure perpendicular to the surface. Off-normal, the electronic structure is dominated by the parabolic dispersion of surface states forming circles around the {gamma}-points and ellipses around the M-points in the Fermi surface cuts.

  12. Calculation of Mg(+)-ligand relative binding energies

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Bauschlicher, Charles W., Jr.

    1992-01-01

    The calculated relative binding energies of 16 organic molecules to Mg(+) are compared with experimental results where available. The geometries of the ligands and the Mg(+)-ligand complexes arc optimized at the self-consistent field level using a 6-31G* basis set. The Mg(+) binding energies are evaluated using second-order perturbation theory and basis sets of triple-sigma quality augmented with two sets of polarization functions. This level of theory is calibrated against higher levels of theory for selected systems. The computed binding energies are accurate to about 2 kcal/mol.

  13. Mg isotope fractionation between inorganic aragonite and aqueous solution

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Zhang, S.; Hu, P.

    2012-12-01

    Recent studies showed δ26Mg values of some species of Scleractinian corals, and aragonitic sponges and Scaphopod are inconsistent with the Mg isotope fractionation calibrated previously between inorganic aragonite and seawater. In this study, we explored Mg isotope fractionation between aragonite and aqueous solution under various experimental conditions, including salinity (mostly in fresh water), Mg/Ca ratio (3-5 in molar), Ca concentration (400-1500 ppm), temperature (25-55oC) and duration of experiments (3-21 days). Precipitation experiments were conducted using 'free-drift' method. The starting solution was made by mixing an appropriate amount of reagent-grade NaHCO3, CaCl2 and MgCl2 in deionized water, flushed with CO2 gas. The mixed solution was filtered after these reagents completely dissolved before any experiment, and then passively-degassed in a water bath kept at a constant temperature. Over the course of the experiments, pH and alkalinity of the aqueous solution were closely monitored. At the end of the experiment, the precipitates were cleaned, characterized by SEM and checked by XRD. The solution and precipitates were treated by acid. The supernatant was passed through two chromatographic columns to extract pure Mg, and measured for their δ26Mg values. In each case, a leaching procedure is employed to clean aragonite before their isotopic compositions were measured. Our preliminary results show that the Mg isotope fractionation between aragonite and solution varies with Ca concentration at a given Mg/Ca ratio, i.e., aragonite are strongly depleted in 26Mg in solution with high and low Ca concentration (e.g., Ca = 400ppm and 2000 ppm), but less depleted in solutions with intermediate Ca concentration (e.g., Ca= 1000 ppm). At a given Ca and Mg/Ca, the fractionation factor is temperature-dependent, defining linear relationship with 1/T (T is temperature in Kelvin) with temperature sensitivity of ~ 0.01‰/oC. These results seem to suggest a kinetic

  14. Control of carbonate alkalinity on Mg incorporation in calcite: Insights on the occurrence of high Mg calcites in diagenetic environments

    NASA Astrophysics Data System (ADS)

    Purgstaller, Bettina; Mavromatis, Vasileios; Dietzel, Martin

    2015-04-01

    High Mg calcites (HMC), with up to 25 mol % of Mg, are common features in early diagenetic environments and are frequently associated with bio-induced anaerobic oxidation of methane (AOM). Such archives hold valuable information about the biogeochemical processes occurring in sedimentary environments in the geological past. Despite the frequency AOM-induced HMC observed in marine diagenetic settings and their potential role in dolomitization, only a minor number of experimental studies has been devoted on deciphering their formation conditions. Thus, in order to improve our understanding on the formation mechanism of HMC induced by elevated carbonate ion concentrations, we precipitated HMC by computer controlled titration of a (Mg,Ca)Cl2 solution at different Mg/Ca ratios into a NaHCO3 solution under precisely defined physicochemical conditions (T = 25.00 ±0.03°C; pH = 8.3 ±0.1). The formation of carbonates was monitored at a high temporal resolution using in situ Raman spectroscopy as well as by continuous sampling and analyzing of precipitates and reactive solutions. We identified two distinct mechanisms of HMC formation. In solutions with molar Mg/Ca ratios ≤ 1/8 calcium carbonate was precipitated as crystalline phases directly from homogeneous solution. In contrast, higher Mg/Ca ratios induced the formation of Mg-rich ACC (up to 10 mol % of Mg), which was subsequently transformed to HMC with up 20 mol % of Mg. Our experimental results highlight that the finally formed HMC has a higher Mg content than the ACC precursor phase. Considering experimental data for Mg containing ACC transformation to crystalline calcium carbonate from literature, the continuous enrichment of Mg in the precipitate throughout transformation of amorphous to crystalline CaCO3 most likely occurs due to the high carbonate alkalinity (DIC about 0.1 M) of our reactive solutions. The Mg incorporation into calcite lattice seems to be favored by intensive supply of carbonate ions as

  15. El libro del Relogio del Palacio de las Horas

    NASA Astrophysics Data System (ADS)

    Morales, J. D.

    2009-08-01

    This paper resume the investigation entitled ``El libro del Relogio del Palacio de las Horas''. That consist in an edition of the original text of the book of the Clock of the Palace of the Hours from the Books of the knowledge of Astronomy of Alfonso X (Manuscript 156, Complutense University). And a description of the astronomical functionality of the Clock of the Palace of the Hours. It includes a geometric description of the positional astronomy on which the operation of the Palace is based.

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

    SciTech Connect

    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 5-10nm 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 rodlike, triangular, and plate-like shapes were also observed.

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

    SciTech Connect

    Tran, P.X.; Howard, B.H.; Martello, D.V.; Soong, Y.; Chyu, M.K.

    2008-01-01

    laser ablation of magnesium in deionized water (OW), solutions of OW and sodium dodecyl sulfate (50S) 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 alterationj 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 OW or OW~SOS solutions. Ablation in OW yielded particles of fiber-like shapes having a diameter of about 5-lOnm and length as long as 150nm. Materials produced in DW-SOS solutions were composed of various size and shape particles, Some had rough surfaces with irregular shapes. Small particles were about 20-30nm and larger particles were about 120 nm. Particles with rod-like, triangular, and plate-like shapes were also observed.

  18. A novel process for fabricating Mg{sub 2}Ni

    SciTech Connect

    Guthrie, S.E.; Thomas, G.J.

    1998-05-01

    The alloy, Mg{sub 2}Ni, has a number of desirable properties for use as a lightweight reversible hydride for hydrogen storage applications. It has relatively good storage capacity (3.6 wt.% H{sub 2} as Mg{sub 2}NiH{sub 4}) and a higher plateau pressure and lower operating temperature than MgH{sub 2}. A novel low temperature (<300 C) process is reported that does not require melting of the alloy constituents to achieve a single phase alloy of Mg{sub 2}Ni. The process results in smaller particle dimensions without sacrifice in product yield and eliminates the need for post processing to achieve homogenization and particle sizing. It can also be implemented in-situ in storage vessels to greatly simplify fabrication while providing more material predictability during the activation process. The process is described and the hydride properties of the product are reported and compared to conventionally formed alloys.

  19. Drug-induced alterations in Mg2+ homoeostasis.

    PubMed

    Lameris, Anke L; Monnens, Leo A; Bindels, René J; Hoenderop, Joost G J

    2012-07-01

    Magnesium (Mg2+) balance is tightly regulated by the concerted actions of the intestine, bone and kidneys. This balance can be disturbed by a broad variety of drugs. Diuretics, modulators of the EGFR (epidermal growth factor receptor), proton pump inhibitors, antimicrobials, calcineurin inhibitors and cytostatics may all cause hypomagnesaemia, potentially leading to tetany, seizures and cardiac arrhythmias. Conversely, high doses of Mg2+ salts, frequently administered as an antacid or a laxative, may lead to hypermagnesaemia causing various cardiovascular and neuromuscular abnormalities. A better understanding of the molecular mechanisms underlying the adverse effects of these medications on Mg2+ balance will indicate ways of prevention and treatment of these adverse effects and could potentially provide more insight into Mg2+ homoeostasis.

  20. Spark Plasma Sintering of MgO-Strengthened Aluminum

    NASA Astrophysics Data System (ADS)

    Ben-Haroush, M.; Dikovsky, G.; Kalabukhov, S.; Aizenshtein, M.; Hayun, S.

    2016-02-01

    The effects of MgO as a sintering additive, sintering duration, and post-heat treatment on mechanical properties and microstructure of spark plasma-sintered aluminum powders were investigated. The sinterability of aluminum with or without MgO was found to be sensitive to the aluminum average particle size, meaning the amount of native oxide within the raw aluminum powders. The fracture mode changes gradually from a brittle mode (after short SPS), through a mixed brittle-ductile fracture mode (after long SPS), ending with the pure ductile form (short SPS followed by heat treatment). Maxima flexural strength and elongation were found in samples with particles size of about 44 μm and the addition of 2 wt.% MgO after short SPS process followed by an additional heat treatment. The addition of MgO may contribute to perforation of the aluminum native oxide and enhance aluminum diffusion during the heat treatment.

  1. Simultaneous Determination of Si and Mg Isotopic Composition in Meteorites

    NASA Astrophysics Data System (ADS)

    Sikdar, J.; Rai, V. K.

    2016-08-01

    This paper utilizes simultaneous Si and Mg isotopic analyses of different classes of bulk meteorites including CC, OC, EC and HED with aim to understand the cause of enrichment of heavy Si in Bulk Silicate Earth relative to chondrites.

  2. Laser-Ultrasonic Inspection of MG/AL Castings

    SciTech Connect

    Blouin, Alain; Levesque, Daniel; Monchalin, Jean-Pierre; Baril, Eric; Fischersworring-Bunk, Andreas

    2005-04-09

    Laser-ultrasonics is used to assess the metallurgical bond between Mg/Al materials in die-cast Magnesium/Aluminum composite. The acoustic impedances of Mg, Al and air are such that the amplitude of ultrasonic echoes reflected back from a void is many times larger than the amplitude of those reflected back from a well-bonded interface. In addition, the polarity of echoes from a void is inverted compared to that from a well-bonded interface. Laser-ultrasonic F-SAFT is also used for imaging tilted Mg/Al interfaces. Experimental setup, signal processing and results for detecting voids in the Mg/Al interface of cast parts are presented.

  3. ZnCdMgSe-Based Semiconductors for Intersubband Devices

    SciTech Connect

    Tamargo, Maria C.

    2008-11-13

    This paper presents a review of recent results on the application of ZnCdMgSe-based wide bandgap II-VI compounds to intersubband devices such as quantum cascade lasers and quantum well infrared photodetectors operating in the mid-infrared region. The conduction band offset of ZnCdSe/ZnCdMgSe quantum well structures was determined from contactless electroreflectance measurements to be as high as 1.12 eV. FT-IR was used to measure intersubband absorption in multi-quantum well structures in the mid-IR range. Electroluminescence at 4.8 {mu}m was observed from a quantum cascade emitter structure made from these materials. Preliminary results are also presented on self assembled quantum dots of CdSe on ZnCdMgSe, and novel quantum well structures with metastable binary MgSe barriers.

  4. Bending strain tolerance of MgB2 superconducting wires

    NASA Astrophysics Data System (ADS)

    Kováč, P.; Hušek, I.; Melišek, T.; Kulich, M.; Kopera, L.

    2016-04-01

    This work describes the strain tolerance of MgB2 superconductors subjected to variable bending stresses. Bending of MgB2 wire was done at room temperature in different modes: (i) direct bending of straight annealed samples to variable diameters and by (ii) indirect bending by straightening of bent and annealed samples. I c-bending strain characteristics of samples made by in situ PIT and by the internal magnesium diffusion (IMD) process were measured at 4.2 K. The results show a good agreement between the direct and indirect bending mode, which allows easier estimation of limits important for the winding process of MgB2 superconductors with brittle filaments. A comparison of MgB2 wires made by in situ PIT and IMD processes showed improved strain tolerance for IMD due to better grain connectivity the low annealing temperature, which does not appear to reduce the mechanical strength of sheath material.

  5. Improving properties of Mg with Al–Cu additions

    SciTech Connect

    Rashad, Muhammad; Pan, Fusheng; Asif, Muhammad; Hussain, Shahid; Saleem, Muhammad

    2014-09-15

    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: • 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.

  6. Dissolution control of Mg by cellulose acetate-polyelectrolyte membranes.

    PubMed

    Yliniemi, Kirsi; Wilson, Benjamin P; Singer, Ferdinand; Höhn, Sarah; Kontturi, Eero; Virtanen, Sannakaisa

    2014-12-24

    Cellulose acetate (CA)-based membranes are used for Mg dissolution control: the permeability of the membrane is adjusted by additions of the polyelectrolyte, poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA). Spin-coated films were characterized with FT-IR, and once exposed to an aqueous solution the film distends and starts acting as a membrane which controls the flow of ions and H2 gas. Electrochemical measurements (linear sweep voltammograms, open-circuit potential, and polarization) show that by altering the CA:PDMAEMA ratio the dissolution rate of Mg can be controlled. Such a control over Mg dissolution is crucial if Mg is to be considered as a viable, temporary biomedical implant material. Furthermore, the accumulation of corrosion products between the membrane and the sample diminishes the undesirable effects of high local pH and H2 formation which takes place during the corrosion process.

  7. Photoluminescence properties of Mg-doped InN nanowires

    SciTech Connect

    Zhao, Songrui; Liu, Xuedong; Mi, Zetian

    2013-11-11

    In this work, photoluminescence (PL) properties of nearly defect-free Mg-doped InN nanowires were investigated in detail. The low-doped sample exhibits two PL emission peaks up to 152 K, which can be ascribed to the band-to-band recombination and the Mg-acceptor energy level related recombination, respectively. For the high-doped sample, the Mg-acceptor energy level related transition dominates. Detailed power dependent PL studies further indicate that the Mg-acceptor energy level related PL emission is due to the donor-acceptor pair recombination process, which subsequently evolves into the free-to-acceptor recombination with increasing temperature.

  8. Nucleosynthesis in AGB stars: Observation of Mg-25 and Mg-26 in IRC+10216 and possible detection of Al-26

    NASA Technical Reports Server (NTRS)

    Guelin, M.; Forestini, M.; Valiron, P.; Ziurys, L. M.; Anderson, M. A.; Cernicharo, J.; Kahane, C.

    1995-01-01

    We report the detection in the circumstellar envelope IRC+10216 of millimeter lines of the rare isotopomers (25)MgNC and (26)MgNC, as well as of a line at 234433 MHz, which could be the J= 7-6 transition of (26)AlF (an alternate, although less likely identified would be the J= 9-8 transition of NaF). The derived Mg-24:Mg-25:Mg-26 isotopic abundance ratios (78 : 11+/- 1 : 11 +/-1) are consistent with the solar system values (79.0:10.0:11.0), following Anders & Grevesse 1989). According to new calculations of evolutionary models of 3 solar mass and 5 solar mass asymptotic giant branch (AGB) stars, these ratios and the previously measured N, O and Si isotopic ratios imply that the central star had an initial mass 3 solar mass (less than or equal to M(sub *, ini) less than 5 solar mass and has already experienced many 3rd dredge-up events. From this, it can be predicted that the Al-26/Al-27 isotopics ratio lies between 0.01 and 0.08; in fact, the value derived in the case that U234433 arises from (26)AlF is Al-26/Al-27 = 0.04. The identification of the (25)MgNC and (26)MgNC lines was made possible by ab-initio quantum mechanical calculations of the molecule geometrical structure. It was confirmed through millimeter-wave laboratory measurements. The quantum mechanical calculations are briefly described and the laboratory results presented in some detail. The rotation constants B, D, H and the spin-rotation constant gamma of (25)MgNC and (26)MgNC are determined from a fit of laboratory and astronomical data.

  9. ELECTRON-ION RECOMBINATION OF Mg{sup 6+} FORMING Mg{sup 5+} AND OF Mg{sup 7+} FORMING Mg{sup 6+}: LABORATORY MEASUREMENTS AND THEORETICAL CALCULATIONS

    SciTech Connect

    Lestinsky, M.; Hahn, M.; Novotny, O.; Savin, D. W.; Badnell, N. R.; Bernhardt, D.; Mueller, A.; Schippers, S.; Bing, D.; Grieser, M.; Hoffmann, J.; Jordon-Thaden, B.; Krantz, C.; Orlov, D. A.; Repnow, R.; Shornikov, A.; Wolf, A.

    2012-10-10

    We have measured electron-ion recombination for C-like Mg{sup 6+} forming Mg{sup 5+}, and for B-like Mg{sup 7+} forming Mg{sup 6+}. These studies were performed using a merged electron-ion beam arrangement at the TSR heavy ion storage ring located in Heidelberg, Germany. Both primary ions have metastable levels with significant lifetimes. Using a simple cascade model we estimate the population fractions in these metastable levels. For the Mg{sup 6+} results, we find that the majority of the stored ions are in a metastable level, while for Mg{sup 7+} the metastable fraction is insignificant. We present the Mg{sup 6+} merged beams recombination rate coefficient for DR via N = 2 {yields} N' = 2 core electron excitations ({Delta}N = 0 DR) and for Mg{sup 7+} via 2 {yields} 2 and 2 {yields} 3 core excitations. Taking the estimated metastable populations into account, we compare our results to state-of-the-art multiconfiguration Breit-Pauli theoretical calculations. Significant differences are found at low energies where theory is known to be unreliable. Moreover, for both ions we observe a discrepancy between experiment and theory for {Delta}N = 0 DR involving capture into high-n Rydberg levels and where the stabilization is primarily due to a radiative transition of the excited core electron. This is consistent with previous DR experiments on M-shell iron ions which were performed at TSR. The large metastable content of the Mg{sup 6+} ion beam precludes generating a plasma recombination rate coefficient (PRRC). However, this is not an issue for Mg{sup 7+} and we present an experimentally derived Mg{sup 7+} PRRC for plasma temperatures from 400 K to 10{sup 7} K with an estimated uncertainty of less than 27% at a 90% confidence level. We also provide a fit to our experimentally derived PRRC for use in plasma modeling codes.

  10. High Resolution Laser Spectroscopy of Mg12C12CD, Mg13C13CH and Mg12C_4H

    NASA Astrophysics Data System (ADS)

    Forthomme, D.; Linton, C.; Tokaryk, D. W.; Adam, A. G.; Granger, A. D.

    2010-06-01

    Carbon and magnesium are abundant elements in the interstellar medium, so it is possible that carbon chain molecules containing a magnesium atom may exist in this environment. With this in mind, radical molecules of the form MgC2nH (n = 1,2,3) have been frequent subjects of both experimental and theoretical studies In this presentation we will discuss our high-resolution experiments of the ~A2Π-~X2Σ+ transitions in the isotopologues Mg12C12CD and Mg13C13CH, which complement our earlier investigation of this spectrum in Mg12C12CH^b. The data permit us to determine the lengths of individual bonds to high precision. In addition, we have expanded on previous studies of the ~A2Π-~X2Σ+ transition of Mg12C_4H, conducted at medium resolution. The parameters obtained from our high-resolution spectra are compared with those obtained from theoretical structure calculations. H. Ding, C. Apetrei, L. Chacaga, J. P. Maier, Astrophys. J. 677 (2008) 348-352 D. W. Tokaryk, A. G. Adam, W. S. Hopkins, J. Mol. Spectrosc. 230 (2005) 54-61 D. E. Woon, Chem. Phys. Lett. 274 (1997) 299-305 C. A. Thompson and L. Andrews, J. Am. Chem. Soc. 118 (1996) 10242-10249 X. Guo, J. Zhang, J. Li, L. Jiang, J. Zhang, Chem. Phys 360 (2009) 27-31 E. Chasovskikh, E. B. Jochnowitz, J. P. Maier, J. Phys. Chem. A. 112 (2008) 8686-8689.

  11. Single and double photoionization of Be and Mg

    NASA Astrophysics Data System (ADS)

    Pindzola, M. S.; Ballance, C. P.; Abdel-Naby, Sh A.; Robicheaux, F.; Armstrong, G. S. J.; Colgan, J.

    2013-02-01

    A new version of the time-dependent close-coupling method is used to calculate the single and double photoionization of the Be and Mg atoms. Total cross sections are calculated using an implicit time propagator with a core orthogonalization method on a variable radial mesh. The double to single photoionization cross section ratios are found to be in good agreement with experiment for both Be and Mg.

  12. On Interpreting the Photoelectron Spectra of MgO

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Partridge, Harry; Arnold, James (Technical Monitor)

    2001-01-01

    The (sup 2)Sigma(+) and (sup 2)Pi states of MgO(-) and the (sup 1)Sigma(+), (sup 1)Pi, and (sup 3)Pi states of MgO are studied using the averaged coupled-pair functional (ACPF) approach. The computed spectroscopic constants are in good agreement with the available experimental data. The computed Franck-Condon factors and photodetachment overlaps are compared with experiment.

  13. 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

  14. The upper critical field in doped MgCNi 3

    NASA Astrophysics Data System (ADS)

    Andrzejewski, Bartłomiej; Klimczuk, Tomasz; Cava, Robert J.

    2007-09-01

    The upper critical field (Hc2) in the doped and undoped intermetallic superconductor MgCNi3 is studied. In MgCNi3-xMx (M = Ru, Fe), Hc2 decreases monotonically as x increases. In the case of Fe doping, Hc2 changes most dramatically: from 10.7 T at x = 0 to 7.9 T at x = 0.015, which might be caused by the fact that the 3d electrons in Fe break superconducting Cooper-pairs. Although, doping carbon on the boron site in Mg(B1-xCx)2 has a substantial effect on the upper critical field, here we report that for MgC1-xBxNi3, boron substitution slightly increases Hc2 for the lowest B doping level, x = 0.04, only. For x > 0.04 the upper critical field decreases slowly as x increases. The initial slope of Hc2(T) in MgC0.96B0.04Ni3 is nearly the same as that of pure MgCNi3.

  15. Time to reconsider dabigatran 110 mg in the USA.

    PubMed

    Hernandez, Inmaculada

    2015-10-01

    Unlike other international regulatory agencies, the US FDA did not approve the dabigatran 110 mg dose for the prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation. Such decision was based on the review of the results from the RE-LY trial, after which the US FDA concluded there was no subgroup of patients for whom dabigatran 110 mg was not inferior to dabigatran 150 mg. Recently, observational studies based on US data have found that the safety profile of dabigatran differs between subgroups, considerably more than what was suggested in clinical trials. In addition, post hoc analyses of the RE-LY trial support the use of dabigatran 110 mg in high-risk patients, as recommended by the European label. Based on this new evidence, the US FDA should reconsider the approval of the dabigatran 110 mg dose. The availability of dabigatran 110 mg may be especially favorable for groups of patients for whom dabigatran has been associated with higher risk of bleeding than warfarin, which represent a high proportion of the patients recommended for oral anticoagulation. In addition, the approval of this intermediate strength would increase prescribers' and patients' flexibility in the choice of oral anticoagulant.

  16. Recycling practices of spent MgO-C refractories

    SciTech Connect

    Kwong, Kyei-Sing; Bennett, James P.

    2002-10-01

    The recycling options of spent MgO-C refractories from an electrical arc furnace (EAF) have been evaluated. The economic, quality of spent refractories and products made from it, the ease of implementation of a recycling practice and the interest of steel melt shops were considered. It was decided that the best option of most EAF shops would be to recycle spent MgO-C refractory as a foaming slag conditioner because of their MgO content. Crushed MgO-C spent refractories can be reused directly back into an EAF without complex and costly beneficiation. Even though this practice is simple, it is critical to know the optimum amount of MgO in the slag to achieve the best foaming quality. A computer model was designed to find the optimum MgO amount. This modeling also helps the melt shop extend refractory service life, increase the energy efficiency, increase productivity, and decrease the amount of slag. Issues related to the refractory recycling will be discussed.

  17. 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

  18. Inhibition of DNA ejection from bacteriophage by Mg+2 counterions

    NASA Astrophysics Data System (ADS)

    Lee, Sell; Tran, C. V.; Nguyen, T. T.

    2011-03-01

    The problem of inhibiting viral DNA ejection from bacteriophages by multivalent counterions, specifically Mg+2 counterions, is studied. Experimentally, it is known that MgSO4 salt has a strong and nonmonotonic effect on the amount of DNA ejected. There exists an optimal concentration at which the minimum amount of DNA is ejected from the virus. At lower or higher concentrations, more DNA is ejected from the capsid. We propose that this phenomenon is the result of DNA overcharging by Mg+2 multivalent counterions. As Mg+2 concentration increases from zero, the net charge of DNA changes from negative to positive. The optimal inhibition corresponds to the Mg+2 concentration where DNA is neutral. At lower/higher concentrations, DNA genome is charged. It prefers to be in solution to lower its electrostatic self-energy, which consequently leads to an increase in DNA ejection. By fitting our theory to available experimental data, the strength of DNA-DNA short range attraction energies, mediated by Mg+2, is found to be -0.004 kBT per nucleotide base. This and other fitted parameters agree well with known values from other experiments and computer simulations. The parameters are also in agreement qualitatively with values for tri- and tetravalent counterions.

  19. Inhibition of DNA ejection from bacteriophage by Mg^+2 counterions

    NASA Astrophysics Data System (ADS)

    Lee, Seil; Tran, Cathy V.; Nguyen, Toan T.

    2009-03-01

    The problem of inhibiting viral DNA ejection from bacteriophages by multivalent counterions, especially Mg^+2 counterions, is studied. Experimentally, it is known that MgSO4 salt has a strong and non-monotonic effect on the amount of DNA ejected. There exists an optimal concentration at which the least DNA is ejected from the virus. At lower or higher concentrations, more DNA is ejected from the capsid. We propose that this phenomenon is the result of DNA overcharging by Mg^+2 multivalent counterions. As Mg^+2 concentration increases from zero, DNA net charge changes from negative to positive. The optimal inhibition corresponds to the Mg^+2 concentration where DNA is neutral. At lower/higher concentrations, DNA genome is charged. It prefers to be in solution to lower its electrostatic self-energy, which consequently leads to an increase in DNA ejection. Our theory fits experimental data well. The strength of DNA-DNA short range attraction, mediated by Mg^+2, is found to be -0.003 kBT per nucleotide base.

  20. In vitro degradation of pure Mg in response to glucose

    PubMed Central

    Zeng, Rong-Chang; Li, Xiao-Ting; Li, Shuo-Qi; Zhang, Fen; Han, En-Hou

    2015-01-01

    Magnesium and its alloys are promising biodegradable biomaterials but are still challenging to be used in person with high levels of blood glucose or diabetes. To date, the influence of glucose on magnesium degradation has not yet been elucidated, this issue requires more attention. Herein, we present pure Mg exhibiting different corrosion responses to saline and Hank’s solutions with different glucose contents, and the degradation mechanism of pure Mg in the saline solution with glucose in comparison with mannitol as a control. On one hand, the corrosion rate of pure Mg increases with the glucose concentration in saline solutions. Glucose rapidly transforms into gluconic acid, which attacks the oxides of the metal and decreases the pH of the solution; it also promotes the absorption of chloride ions on the Mg surface and consequently accelerates corrosion. On the other hand, better corrosion resistance is obtained with increasing glucose content in Hank’s solution due to the fact that glucose coordinates Ca2+ ions in Hank’s solution and thus improves the formation of Ca-P compounds on the pure Mg surface. This finding will open up new avenues for research on the biodegradation of bio-Mg materials in general, which could yield many new and interesting results. PMID:26264413

  1. In vitro degradation of pure Mg in response to glucose

    NASA Astrophysics Data System (ADS)

    Zeng, Rong-Chang; Li, Xiao-Ting; Li, Shuo-Qi; Zhang, Fen; Han, En-Hou

    2015-08-01

    Magnesium and its alloys are promising biodegradable biomaterials but are still challenging to be used in person with high levels of blood glucose or diabetes. To date, the influence of glucose on magnesium degradation has not yet been elucidated, this issue requires more attention. Herein, we present pure Mg exhibiting different corrosion responses to saline and Hank’s solutions with different glucose contents, and the degradation mechanism of pure Mg in the saline solution with glucose in comparison with mannitol as a control. On one hand, the corrosion rate of pure Mg increases with the glucose concentration in saline solutions. Glucose rapidly transforms into gluconic acid, which attacks the oxides of the metal and decreases the pH of the solution; it also promotes the absorption of chloride ions on the Mg surface and consequently accelerates corrosion. On the other hand, better corrosion resistance is obtained with increasing glucose content in Hank’s solution due to the fact that glucose coordinates Ca2+ ions in Hank’s solution and thus improves the formation of Ca-P compounds on the pure Mg surface. This finding will open up new avenues for research on the biodegradation of bio-Mg materials in general, which could yield many new and interesting results.

  2. Electronic structure of the [MgO3]+ cation

    NASA Astrophysics Data System (ADS)

    Ben Houria, A.; Yazidi, O.; Jaidane, N.; Senent, M. L.; Hochlaf, M.

    2012-01-01

    Accurate ab initio calculations are performed to investigate the stable isomers of [MgO3]+ and its lowest electronic states at both molecular and asymptotic regions. The calculations are done using large basis sets and configuration interaction methods including the complete active space self-consistent field, the internally contracted multi-reference configuration interaction, the standard coupled cluster (RCCSD(T)) approaches and the newly implemented explicitly correlated coupled cluster method (RCCSD(T)-F12). The presence of three stable forms is predicted: a cyclic global minimum c-MgO3+, which is followed by a quasi-linear isomer, l2-MgO3+. A third isomer of Cs symmetry (l1-MgO3+) is also found. Moreover, we computed the one-dimensional cuts of the six-dimensional potential energy surfaces of the lowest doublet and quartet electronic states of [MgO3]+ along the RMgO and ROO stretching coordinates covering both the molecular and the asymptotic regions. These curves are used later for discussing the metastability of this cation and to propose plausible mechanisms for the Mg+ + O3 atmospherically important ion-molecule reaction and related reactive channels.

  3. 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.

  4. On the Incidence and Kinematics of Strong Mg II Absorbers

    NASA Astrophysics Data System (ADS)

    Prochter, Gabriel E.; Prochaska, Jason X.; Burles, Scott M.

    2006-03-01

    We present the results of two complementary investigations into the nature of strong (rest equivalent width, Wr>1.0 Å) Mg II absorption systems at high redshift. The first line of questioning examines the complete Sloan Digital Sky Survey Data Release 3 set of quasar spectra to determine the evolution of the incidence of strong Mg II absorption. This search resulted in 7421 confirmed Mg II systems of Wr>1.0 Å, yielding a >95% complete statistical sample of 4835 absorbers (systems detected in S/N>7 spectral regions) spanning a redshift range 0.35Mg(X), is characterized by a roughly constant value at z>0.8, indicating that the product of the number density and gas cross section of halos hosting strong Mg II is unevolving at these redshifts. In contrast, one observes a decline in lMg(X) at z<0.8, which we interpret as a decrease in the gas cross section to strong Mg II absorption and therefore a decline in the physical processes relevant to strong Mg II absorption. Perhaps uncoincidentally, this evolution roughly tracks the global evolution of the star formation rate density. Dividing the systems in Wr subsamples, the lMg(X) curves show similar shape with lower normalization at higher Wr values and a more pronounced decrease in lMg(X) at z<0.8 for larger Wr systems. We also present the results of a search for strong Mg II absorption in a set of 91 high-resolution quasar spectra collected on the ESI and HIRES spectrographs. These data allow us to investigate the kinematics of such systems at 0.81.0 Å were discovered. These systems are characterized by the presence of numerous components spread over an average velocity width of Δv~200 km s-1. Also, absorption due to more highly ionized species (e.g., Al III, C IV, Si IV) tends to display kinematic profiles similar to the corresponding Mg II and Fe II absorption. We consider all of these

  5. A SIMS Calibration of Benthic Foraminiferal Mg/Ca

    NASA Astrophysics Data System (ADS)

    Curry, W. B.; Marchitto, T. M.

    2005-12-01

    Using a suite of multi-core tops, we have produced a calibration of C. pachyderma Mg/Ca versus temperature spanning the temperature range of 5 to 18 °C. The core tops are located along the Florida margin south of Dry Tortugas (KNR166), along the Bahamas west of Andros Island and Great Bahama Bank (KNR166), and along the southeastern margin of Brazil (KNR159). Water depths range from about 200 to 800 m for the Florida Straits multi-cores and 400 to 800 m for the Brazil margin multi-cores. Five of the KNR166 core tops contain post-1950 bomb radiocarbon with Fmodern> 1; several others have bomb radiocarbon mixed in with pre-bomb sediments to give ages less than 0 BP. Core top ages are generally older for the KNR159 multi-cores, but each is from a location with a well documented Holocene section. Sedimentation rates for KNR166 multi-cores vary from 10 to 100 cm kyr-1; for KNR159 multi-cores, sedimentation rates vary from 5 to 10 cm kyr-1. Elemental ratios were determined by Secondary Ionization Mass Spectrometry (SIMS) using a Cameca IMS 3f ion probe calibrated for Mg/Ca and Sr/Ca using two standards which were independently measured using ICP-MS. Using SIMS, the external precision of the calibration standards averages ±3.5% (1σ RSD) for Mg/Ca and ± 1.7% (1σ RSD) for Sr/Ca. SIMS elemental measurements were performed on one to three individual C. pachyderma tests in each core top; more than 30 tests have been measured from 18 multi-core tops. Mg/Ca variability within C. pachyderma tests averages ± 20% (1σ RSD) with a small but significant trend toward higher variability at higher Mg/Ca. Higher Mg/Ca is observed in warmer waters, but the Mg/Ca values are generally lower (at comparable warm temperatures) than observed in previous calibration studies. At temperatures below 8 °C, C. pachyderma Mg/Ca values are less than 2 mmole/mole. At temperatures warmer than 15 °C, C. pachyderma Mg/Ca values exceed 3 mmole/mole. The slope of Mg/Ca versus temperature (~0.14 mmole

  6. 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

  7. Effect of sonotrode material on grain refining of Mg-3Al and Mg-9Al alloys by ultrasonic melt treatment

    NASA Astrophysics Data System (ADS)

    Youn, Jeong IL; Lee, Young Ki; Jig Kim, Young; Park, Jeong Wook

    2016-07-01

    The new process, nucleation enhanced ultrasonic melt treatment (NEUMT), was proposed to increase the refining efficiency through heterogeneous nucleation by using the sonotrode which has been only concerned with the medium to transfer the ultrasonic energy. In the processing, the metal atoms and/or clusters eroded from the sonotrode were supplied and were simultaneously mixed uniformly into the melt by the ultrasound. These particles act as potential nuclei and refine the structure. The process was applied to assess grain refinement of Mg alloys, especially Mg-3Al and Mg-9Al. The refining efficiency was affected by the sonotrode material, and Ti was very effective in this process by the formation of proper intermetallic compound in the Mg alloy melt. The intermetallic compound was searched by the calculation of plane disregistry of the crystallographic orientation, and Al3Ti was suggested to be the heterogeneous nuclei.

  8. In Vitro Degradation Behavior of Ternary Mg-Zn-Se and Mg-Zn-Cu Alloys as Biomaterials

    PubMed Central

    Persaud-Sharma, Dharam; Budiansky, Noah

    2013-01-01

    In this study, the corrosion behavior of Mg-Zn-Se and Mg-Zn-Cu alloys was investigated to evaluate their corrosion behavior related to use as implantable biomaterials. The corrosion behavior of these alloys and a commercially available Mg-Zn alloy were examined using static solution electrochemical testing, dynamic solution gravimetric testing, ion leaching testing, and microscopic evaluation. Fluctuations in the pH of the Dulbecco’s Modified Eagles Medium (DMEM) used for the gravimetric and ion leaching immersion testing were also recorded over the 30-day duration to assess whether the media conditions induced by the alloy degradation would permit for cellular survival. Weight loss experimentation and electrochemical tests revealed the Mg-Zn-Cu alloy to have the greatest corrosion rate. PMID:24465245

  9. 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

  10. 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

  11. 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

  12. 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

  13. Corrosion inhibition of powder metallurgy Mg by fluoride treatments.

    PubMed

    Pereda, M D; Alonso, C; Burgos-Asperilla, L; del Valle, J A; Ruano, O A; Perez, P; Fernández Lorenzo de Mele, M A

    2010-05-01

    Pure Mg has been proposed as a potential degradable biomaterial to avoid both the disadvantages of non-degradable internal fixation implants and the use of alloying elements that may be toxic. However, it shows excessively high corrosion rate and insufficient yield strength. The effects of reinforcing Mg by a powder metallurgy (PM) route and the application of biocompatible corrosion inhibitors (immersion in 0.1 and 1M KF solution treatments, 0.1M FST and 1M FST, respectively) were analyzed in order to improve Mg mechanical and corrosion resistance, respectively. Open circuit potential measurements, polarization techniques (PT), scanning electrochemical microscopy (SECM) and electrochemical impedance spectroscopy (EIS) were performed to evaluate its corrosion behavior. SECM showed that the local current of attacked areas decreased during the F(-) treatments. The corrosion inhibitory action of 0.1M FST and 1M FST in phosphate buffered solution was assessed by PT and EIS. Under the experimental conditions assayed, 0.1M FST revealed better performance. X-ray photoelectron spectroscopy, energy dispersive X-ray and X-ray diffraction analyses of Mg(PM) with 0.1M FST showed the presence of KMgF(3) crystals on the surface while a MgF(2) film was detected for 1M FST. After fluoride inhibition treatments, promising results were observed for Mg(PM) as degradable metallic biomaterial due to its higher yield strength and lower initial corrosion rate than untreated Mg, as well as a progressive loss of the protective characteristics of the F(-)-containing film which ensures the gradual degradation process.

  14. Nanoscale order in ZnSe:(Mg, O)

    SciTech Connect

    Elyukhin, Vyacheslav A.

    2014-02-21

    Self-assembling of 1O4Mg identical tetrahedral clusters resulting in the nanoscale order in ZnSe:(Mg, O) is presented. Co-doping transforms ZnSe into Mg{sub x}Zn{sub 1−x}O{sub y}Se{sub 1−y} alloy of MgO, MgSe, ZnO and ZnSe. The decrease of a sum of the enthalpies of the constituent compounds and diminution of the strain energy are the causes of this phenomenon. The self-assembling conditions are obtained from the free energy minimum when magnesium and oxygen are in the dilute and ultra dilute limits, correspondingly. The occurrence of 1O4Mg clusters and completion of self-assembling when all oxygen atoms are in clusters are results of the continuous phase transitions. The self-assembling occurrence temperature does not depend on the oxygen content and it is a function of magnesium concentration. Mg{sub x}Zn{sub 1−x}O{sub y}Se{sub 1−y} with all oxygen atoms in clusters can be obtained in temperature ranges from T = 206 °C (x = 0.001, y = 1×10{sup −4}) to T = 456 °C (x = 0.01, y = 1×10{sup −4}) and from T = 237 °C (x = 0.001, y = 1×10{sup −6}) to T = 462 °C (x = 0.01, y = 1×10{sup −6})

  15. Contributions of Mycorrhizal Trees to Mg Isotopic Variations in Weathering

    NASA Astrophysics Data System (ADS)

    Bryce, J. G.; Hobbie, E. A.; Blichert-Toft, J.; Colpaert, J.; Hoff, C.; Prado, M. F.; Pettitt, E.; Telouk, P.

    2013-12-01

    Although it is well established that organisms contribute significantly to the weathering process and to the distribution of elements within continental environments, the degree to which biota actively drive weathering versus the degree to which organisms benefit from nutrients released during largely inorganic weathering processes remains shrouded in mystery. Furthermore, the relative influence of different organisms on key emerging isotopic systems, especially Mg, remains poorly understood. To address these questions, we have carried out a series of Mg isotopic investigations on semi-hydroponically cultured trees (pine, Pinus sylvestris and sugar maple, Acer saccharum) grown with appropriate mycorrhizal symbionts (ectomycorrhizal, Suillus, or arbuscular, Glomus, respectively) in different geologic substrates (carbonate and granitic) under low nutrient supply. Plant tissues and eluting solutions across these biogeochemical experiments were studied for elemental abundances and Mg isotopic signatures. Eluting solutions were most distinctive from the abiotic control for those trees grown in granite-bearing cultures, an observation we attribute to biotite weathering. Foliar and root tissues recorded distinctive isotopic compositions (e.g., differences up to 0.6 ‰ δ26/24Mg) in both the pines and sugar maples. Foliar δ26/24Mg varied amongst the trees grown in the different experiments: compared to the substrate, ectomycorrhizal pine had more depleted Mg isotopic signatures in foliage than nonmycorrhizal pine and arbuscular mycorrhizal sugar maple. Taken together our results indicate that ectomycorrhizal symbioses contribute to Mg isotopic variations during weathering and that this effect may be more pronounced in soils forming over biotite-bearing terrains.

  16. MG132 reverse the malignant characteristics of hypopharyngeal cancer.

    PubMed

    Ma, Juke; Yu, Liang; Tian, Jiajun; Mu, Yakui; Lv, Zhenghua; Zou, Jidong; Li, Jianfeng; Wang, Haibo; Xu, Wei

    2014-06-01

    In order to reverse the malignant characteristics of hypopharyngeal cancer, the proteasome inhibitor MG132 was introduced into FaDu/T cells and the mechanisms underlying its effects were investigated. The multi-drug resistance (MDR) sensitivities of FaDu/T and FaDu/T-MG132 cancer cells to several chemotherapeutics were investigated by a 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT) assay. Apoptosis was measured by staining cells with Annexin V and propidium iodide (PI) double staining. Reverse transcription-polymerase chain reaction and western blot analysis were conducted to detect mRNA and corresponding protein levels of the MDR- and apoptosis-related genes P-glycoprotein (P-gp), caspase-3, Bcl-2 and Bax. The nuclear protein of nuclear factor κ-light-chain-enhancer of activated B cells. (NF-κB) and p53 were also investigated via western blot analysis. Compared with FaDu/T cells, the drug resistance of FaDu/T + MG132 cells to cisplatin (DDP), 5-fluorouracil (5-FU), doxorubicin (Dox) and vincristine (VCR) decreased. With increased expression of caspase-3 and Bax and decreased expression of Bcl-2, the anti-apoptotic ability markedly decreased in FaDu/T + MG132 cells. P-gp and NF-κB significantly decreased; however, p53 increased in FaDu/T + MG132 cells. These results suggested that the proteasome inhibitor MG132 reversed the malignant characteristics of FaDu/T by enhancing apoptosis and inhibiting P-gp. MG132 was also able to inhibit the nuclear translocation of NF-κB and increase the expression of p53. PMID:24691740

  17. Vacunas contra los virus del papiloma humano

    Cancer.gov

    Una hoja informativa acerca de las vacunas contra los virus del papiloma humano (VPH) para prevenir infecciones con ciertos tipos de VPH, los cuales son la causa principal del cáncer de cuello del útero o cérvix.

  18. Atropine or glycopyrrolate with neostigmine 5 mg: a comparative dose-response study.

    PubMed Central

    Salem, M G; Ahearn, R S

    1986-01-01

    One hundred and fifteen patients, separated into 4 groups, received neostigmine 5 mg with either atropine 1.2 mg or 1.8 mg, or glycopyrrolate 0.6 mg or 0.9 mg. Those receiving 0.9 mg glycopyrrolate had insignificant changes in heart rate in the immediate postreversal period. It is recommended that when glycopyrrolate is used with 5 mg neostigmine, the optimum dose is 0.9 mg. PMID:3944815

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

    SciTech Connect

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

    2014-12-07

    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.

  20. Experimental 25Mg and 13C NMR and Computational Modeling Studies of Amorphous Mg-Ca Carbonates

    NASA Astrophysics Data System (ADS)

    Singer, J. W.; Yazaydin, A. O.; Kirkpatrick, R. J.; Saharay, M.; Bowers, G. M.

    2012-12-01

    Nuclear magnetic resonance (NMR) spectroscopy of synthetic Mg-Ca amorphous carbonates (AMC-ACC) provides direct, element specific structural information about these complicated phases. The 13C, 25Mg, and 43Ca resonances are typically broad and span the chemical shift ranges of all the crystalline polymorphs in the Ca-Mg-CO3-H2O system. In a fashion similar to our previous analysis of 43Ca NMR results for ACC,1 here we integrate new experimental 13C and 25Mg spectra obtained at 20T for samples with Mg/(Ca+Mg) ratios from x=0 to x=1 with quantum chemical calculations of the NMR parameters of the crystalline phases using CASTEP calculations, simulations of the spectra using the SIMPSON software, and classical molecular dynamics calculations. XRD and 13C NMR results are in general agreement with the one-phase/two-phase model of ACC-AMC derived from thermochemical work by others.2 13C-NMR spectra of amorphous materials having intermediate compositions can not be completely fit by mechanical mixing of ACC and AMC end members—requiring a degree of Ca/Mg solid solution. Amorphous samples in two-phase region crystallize to assemblages of dolomite-like (x~0.5) and hydromagnesite-like (x~1) defective structures, but we also observe aragonite co-nucleation in the presence of excess water, indicative of a more complex evolution. While 43Ca NMR of X-ray amorphous materials shows featureless, symmetric, Gaussian line shapes, the large quadrupole moment of 25Mg gives rise to superposition of several quadrupolar line shapes representing different local structural environments. Singularities of static Mg spectra are best explained by local environments similar to nequehonite, hydromagnesite, and landsfordite. The spectra can not exclude minor contributions from anhydrous phases dolomite, huntite, and magnesite. Additional sites having very large quadrupolar coupling and/or site asymmetry are not explained by any known reference phases. CITATIONS (1) Singer, J. W.; Yazaydin, A. O

  1. Surface morphology of a die-cast Mg alloy

    NASA Astrophysics Data System (ADS)

    Unigovski, Ya. B.; Gutman, E. M.

    1999-12-01

    We have studied the microstructure, phase composition and morphology of the intermetallic β-phase in the surface layer of the most widespread magnesium alloy AZ91D (Mg-9 wt.% Al-1 wt.% Zn) used in pressure die casting. Auger electron spectroscopy (AES), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and optical microscopy have been applied. The surface of the AZ91D Mg alloy consists of an oxide-metallic film with a thickness of about 0.15 micron containing Mg and Al oxides. Prolonged aging in air at 200°C promotes an increase in the MgO/Al 2O 3 ratio from 9±2 to 14±2. The aluminum concentration gradient in the surface layer is rather significant. The external layer of as-cast specimens contains up to 32 at.% Al, whereas α-Mg grains in the bulk contain, on the average, about 5 at.% Al. Aging leads to a substantial increase in the surface concentration of aluminum at the expense of the acceleration of its diffusion and the intensification of supersaturated solid solution decomposition. During creep tests at elevated temperatures the morphology of the β-phase is significantly affected by strain and, to a lesser extent, by the casting temperature.

  2. Grain Size Hardening Effects in Mg-Gd Solid Solutions

    NASA Astrophysics Data System (ADS)

    Nagarajan, Devarajan; Cáceres, Carlos H.; Griffiths, John R.

    2016-11-01

    Pure Mg and alloys with 0.4, 1.3, and 3.8 at. pct Gd were cast with grain sizes between 700 and 35 µm and tested in tension and compression after solid solution heat treatment and quenching. The grain structure of the castings was random, that is, there was no preferred orientation, unlike the situation in extrusions and forgings usually reported in the literature. The results are compared to earlier work on Mg-Zn alloys. A tension-compression asymmetry in which the yield strength in compression is less than in tension was observed in pure Mg but was reversed for the concentrated alloys. The Hall-Petch stress intensity factor, k, first increased then decreased with the amount of Gd in solution. It is noted that defining the friction stress by extrapolating the data to infinite grain size should be treated with caution in Mg and its alloys: nevertheless, a rationale involving solid solution softening/hardening and twinning is offered for the observed values of the friction stress. The reversion of the tension-compression asymmetry is explained by the operation of { {10bar{1}1} } (contraction) twinning in the concentrated alloys in place of { {10bar{1}2} } (extension) twinning in pure Mg and the dilute alloys. It is argued that the activation of { {10bar{1}1} } twinning in the more concentrated alloys accounts for their lower k-value.

  3. Magnesium balances and /sup 28/Mg studies in man

    SciTech Connect

    Spencer, H.; Schwartz, R.; Osis, D.

    1988-01-01

    The intestinal absorption of magnesium was determined under strictly controlled dietary conditions in patients with normal renal function and also in patients with chronic renal failure. The average net absorption of magnesium of patients with normal renal function, expressed as percent of the magnesium intake, was 48.5%, while that of patients with chronic renal failure was significantly lower, 17%. Increasing the calcium intake from a low calcium intake of 200 mg/day to different higher intake levels up to 2000 mg/day did not change the magnesium balance nor the net absorption of magnesium of both types of patients. The lack of effect of the higher calcium intake on the absorption of magnesium was confirmed in /sup 28/Mg studies in which an oral dose of /sup 28/Mg, as the chloride, was given. The excretion of the absorbed magnesium into the intestine, the endogenous fecal magnesium, was low. Also, increasing the phosphorus intake up to 2000 mg/day in subjects with normal renal function did not affect the magnesium balance, regardless of the calcium intake.

  4. MAGNESIUM PRECIPITATION AND DIFUSSION IN Mg+ ION IMPLANTED SILICON CARBIDE

    SciTech Connect

    Jiang, Weilin; Jung, Hee Joon; Kovarik, Libor; Wang, Zhaoying; Roosendaal, Timothy J.; Zhu, Zihua; Edwards, Danny J.; Hu, Shenyang Y.; Henager, Charles H.; Kurtz, Richard J.; Wang, Yongqiang

    2015-03-02

    As a candidate material for fusion reactor applications, silicon carbide (SiC) undergoes transmutation reactions under high-energy neutron irradiation with magnesium as the major metallic transmutant; the others include aluminum, beryllium and phosphorus in addition to helium and hydrogen gaseous species. Calculations by Sawan et al. predict that at a dose of ~100 dpa (displacements per atom), there is ~0.5 at.% Mg generated in SiC. The impact of these transmutants on SiC structural stability is currently unknown. This study uses ion implantation to introduce Mg into SiC. Multiaxial ion-channeling analysis of the as-produced damage state indicates a lower dechanneling yield observed along the <100> axis. The microstructure of the annealed sample was examined using high-resolution scanning transmission electron microscopy. The results show a high concentration of likely non-faulted tetrahedral voids and possible stacking fault tetrahedra near the damage peak. In addition to lattice distortion, dislocations and intrinsic and extrinsic stacking faults are also observed. Magnesium in 3C–SiC prefers to substitute for Si and it forms precipitates of cubic Mg2Si and tetragonal MgC2. The diffusion coefficient of Mg in 3C–SiC single crystal at 1573 K has been determined to be 3.8 ± 0.4E-19 m2/s.

  5. Multifunctional MgO Layer in Perovskite Solar Cells.

    PubMed

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

    2015-06-01

    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. PMID:25851999

  6. Multifunctional MgO Layer in Perovskite Solar Cells.

    PubMed

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

    2015-06-01

    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.

  7. Grain Size Hardening Effects in Mg-Gd Solid Solutions

    NASA Astrophysics Data System (ADS)

    Nagarajan, Devarajan; Cáceres, Carlos H.; Griffiths, John R.

    2016-08-01

    Pure Mg and alloys with 0.4, 1.3, and 3.8 at. pct Gd were cast with grain sizes between 700 and 35 µm and tested in tension and compression after solid solution heat treatment and quenching. The grain structure of the castings was random, that is, there was no preferred orientation, unlike the situation in extrusions and forgings usually reported in the literature. The results are compared to earlier work on Mg-Zn alloys. A tension-compression asymmetry in which the yield strength in compression is less than in tension was observed in pure Mg but was reversed for the concentrated alloys. The Hall-Petch stress intensity factor, k, first increased then decreased with the amount of Gd in solution. It is noted that defining the friction stress by extrapolating the data to infinite grain size should be treated with caution in Mg and its alloys: nevertheless, a rationale involving solid solution softening/hardening and twinning is offered for the observed values of the friction stress. The reversion of the tension-compression asymmetry is explained by the operation of {10bar{1}1} (contraction) twinning in the concentrated alloys in place of {10bar{1}2} (extension) twinning in pure Mg and the dilute alloys. It is argued that the activation of {10bar{1}1} twinning in the more concentrated alloys accounts for their lower k-value.

  8. La influencia del medio interestelar sobre la evolución del remanente de supernova (RSN) G53.6-2.2

    NASA Astrophysics Data System (ADS)

    Giacani, E. B.; Dubner, G.; Cappa, C.; Testori, J. C.

    G53.6-2.2 is a supernova remnant with an unusual morphology: in the radio band the overall shape can be described as two shells that overlap on the NW side of the remnant. The X-ray emission fills the source and peaks in the region where the radio rings overlap; while in the optical range the emission consists of filaments that correlate with portions of radio rings that overlap in the NW. The aim of the present project is to investigate the neutral hydrogen distribution around the remnant in search for signatures that allow to disclose the role of the surrounding gas in conditioning the observed morphology.

  9. CVD synthesis of graphene nanoplates on MgO support

    NASA Astrophysics Data System (ADS)

    Jugade, Ravin M.; Sharma, Shalini; Gokhale, Suresh

    2014-06-01

    Synthesis of graphene directly on MgO has been carried out and the structural properties of the obtained material have been investigated. Few-layered graphene was produced by simple thermal decomposition of methane over MgO powder at 950 °C in a CVD reactor. The samples were purified by 10 N HNO3 treatment, and studied by TEM, Raman spectroscopy, EDAX and SEM. TEM clearly indicated the formation of graphene. EDAX showed that the purified sample contained only carbon and no traces of MgO. The characteristic Raman features of graphene were also seen as D-band at 1316 cm-1, G-band at 1602 cm-1, and a small 2D-band at 2700 cm-1 in the Raman spectra. The strong D-band suggests that the graphene possess large number of boundary defects. The small 2D-band indicates the formation of few-layered graphene.

  10. The MG-RAST Metagenomics Database and Portal in 2015

    SciTech Connect

    Wilke, Andreas; Bischof, Jared; Gerlach, Wolfgang; Glass, Elizabeth; Harrison, Travis; Keegan, Kevin; Paczian, Tobias; Trimble, William L.; Bagchi, Saurabh; Grama, Ananth; Chaterji, Somali; Meyer, Folker

    2015-12-09

    MG-RAST (http://metagenomics.anl.gov) is an opensubmission data portal for processing, analyzing, sharing and disseminating metagenomic datasets. Currently, the system hosts over 200 000 datasets and is continuously updated. The volume of submissions has increased 4-fold over the past 24 months, now averaging 4 terabasepairs per month. In addition to several new features, we report changes to the analysis workflow and the technologies used to scale the pipeline up to the required throughput levels. Lastly, to show possible uses for the data from MG-RAST, we present several examples integrating data and analyses from MG-RAST into popular third-party analysis tools or sequence alignment tools.

  11. The MG-RAST Metagenomics Database and Portal in 2015

    DOE PAGES

    Wilke, Andreas; Bischof, Jared; Gerlach, Wolfgang; Glass, Elizabeth; Harrison, Travis; Keegan, Kevin; Paczian, Tobias; Trimble, William L.; Bagchi, Saurabh; Grama, Ananth; et al

    2015-12-09

    MG-RAST (http://metagenomics.anl.gov) is an opensubmission data portal for processing, analyzing, sharing and disseminating metagenomic datasets. Currently, the system hosts over 200 000 datasets and is continuously updated. The volume of submissions has increased 4-fold over the past 24 months, now averaging 4 terabasepairs per month. In addition to several new features, we report changes to the analysis workflow and the technologies used to scale the pipeline up to the required throughput levels. Lastly, to show possible uses for the data from MG-RAST, we present several examples integrating data and analyses from MG-RAST into popular third-party analysis tools or sequence alignmentmore » tools.« less

  12. Experimental study of MgB{sub 2} decomposition

    SciTech Connect

    Fan, Z. Y.; Hinks, D. G.; Newman, N.; Rowell, J. M.

    2001-07-02

    The thermal stability of MgB{sub 2} has been studied experimentally to determine the role of thermodynamic and kinetic barriers in the decomposition process. The MgB{sub 2} decomposition rate approaches one monolayer per second at 650 C and has an activation energy of 2.0 eV. The evaporation coefficient is inferred to be {approx}10{sup -4}, indicating that this process is kinetically limited. These values were inferred from in situ measurements using a quartz crystal microbalance and a residual gas analyzer, in conjunction with ex situ measurements of redeposited material by Rutherford backscattering spectroscopy and secondary ion mass spectroscopy. The presence of a large kinetic barrier to decomposition indicates that the synthesis of MgB{sub 2} thin films conditions may be possible with vacuum processing, albeit within a narrow window in the reactive growth conditions.

  13. Beta-delayed proton emission from 20Mg

    NASA Astrophysics Data System (ADS)

    Lund, M. V.; Andreyev, A.; Borge, M. J. G.; Cederkäll, J.; De Witte, H.; Fraile, L. M.; Fynbo, H. O. U.; Greenlees, P. T.; Harkness-Brennan, L. J.; Howard, A. M.; Huyse, M.; Jonson, B.; Judson, D. S.; Kirsebom, O. S.; Konki, J.; Kurcewicz, J.; Lazarus, I.; Lica, R.; Lindberg, S.; Madurga, M.; Marginean, N.; Marginean, R.; Marroquin, I.; Mihai, C.; Munch, M.; Nacher, E.; Negret, A.; Nilsson, T.; Page, R. D.; Pascu, S.; Perea, A.; Pucknell, V.; Rahkila, P.; Rapisarda, E.; Riisager, K.; Rotaru, F.; Sotty, C.; Stanoiu, M.; Tengblad, O.; Turturica, A.; Van Duppen, P.; Vedia, V.; Wadsworth, R.; Warr, N.

    2016-10-01

    Beta-delayed proton emission from 20 Mg has been measured at ISOLDE, CERN, with the ISOLDE Decay Station (IDS) setup including both charged-particle and gamma-ray detection capabilities. A total of 27 delayed proton branches were measured including seven so far unobserved. An updated decay scheme, including three new resonances above the proton separation energy in 20 Na and more precise resonance energies, is presented. Beta-decay feeding to two resonances above the Isobaric Analogue State (IAS) in 20 Na is observed. This may allow studies of the 4032.9(2.4)keV resonance in 19 Ne through the beta decay of 20 Mg, which is important for the astrophysically relevant reaction 15O( α, γ)19Ne . Beta-delayed protons were used to obtain a more precise value for the half-life of 20 Mg, 91.4(1.0)ms.

  14. Hydrothermal synthesis of Mg-Al hydrotalcites by urea hydrolysis

    SciTech Connect

    Rao, M. Mohan . E-mail: mandapati@iict.res.in; Reddy, B. Ramachandra; Jayalakshmi, M.; Jaya, V. Swarna; Sridhar, B.

    2005-02-15

    We report a simple method to prepare hydrotalcites involving both urea hydrolysis and hydrothermal synthetic conditions. Out of a series of Mg/Al ratios tried, pure hydrotalcite like phase was obtained for Mg/Al ratios of 1:1 and 2:1. Unlike in conventional co-precipitation method we succeeded in preparing Mg/Al ratio of 1:1 by this route. The high temperature (180 deg. C) applied and pressure developed in the autoclave during the synthesis might have altered the topochemical transformation. The materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, thermo gravimetric and differential thermal analysis and transmission electron microscopy.

  15. Improved Mg-based alloys for hydrogen storage

    SciTech Connect

    Sapru, K.; Ming, L.; Stetson, N.T.; Evans, J.

    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 sample having a higher plateau pressure.

  16. Selection of novel Mg(2+)-dependent self-cleaving ribozymes.

    PubMed Central

    Williams, K P; Ciafré, S; Tocchini-Valentini, G P

    1995-01-01

    Four RNA motifs are known that catalyse site-specific cleavage in the presence of Mg2+ ions, all discovered in natural RNAs. In a single in vitro selection experiment we have isolated representatives of five novel classes of Mg(2+)-dependent ribozymes. Small versions of three of these showed that a very simple internal loop type of secondary structure is responsible for the activity. One of these was synthesized in a bimolecular form, and compared directly with the hammerhead ribozyme; for the new ribozyme, the cleavage step of the reaction is much faster than the spontaneous rate of phosphodiester bond cleavage, yet substantially slower than that for the hammerhead. The results suggest that many more Mg(2+)-dependent self-cleaving RNA sequences can be found. Images PMID:7556098

  17. Surface segregation of Ba in MgO

    NASA Astrophysics Data System (ADS)

    Cotter, M.; Campbell, S.; Cao, L. L.; Egdell, R. G.; Mackrodt, W. C.

    1989-02-01

    Surface segregation of Ba in doped polycrystalline and single crystal MgO has been studied by XPS. There is little variation in surface coverage of Ba over a range of bulk doping levels from 7 to 7000 ppm in ceramic pellets equilibrated at 1630 K. This remarkable behaviour is shown to be consistent with surface coverage calculated from heats of segregation derived from ionic model simulations of the surface if due account is taken of the strong variation of the segregation energy with coverage. The coverage of Ba on a MgO(001) single crystal surface doped by indiffusion of Ba deposited onto the crystal from a getter source can be made similar to that of the polycrystalline material. The Ba-segregated MgO(001) surface exhibits a complex LEED pattern.

  18. Metagenomes from Argonne's MG-RAST Metagenomics Analysis Server

    DOE Data Explorer

    MG-RAST has a large number of datasets that researchers have deposited for public use. As of July, 2014, the number of metagenomes represented by MG-RAST numbered more than 18,500, and the number of available sequences was more than 75 million! The public can browse the collection several different ways, and researchers can login to deposit new data. Researchers have the choice of keeping a dataset private so that it is viewable only by them when logged in, or they can choose to make a dataset public at any time with a simple click of a link. MG-RAST was launched in 2007 by the Mathematics and Computer Science Division at Argonne National Laboratory (ANL). It is part of the toolkit available to the Terragenomics project, which seeks to do a comprehensive metagenomics study of U.S. soil. The Terragenomics project page is located at http://www.mcs.anl.gov/research/projects/terragenomics/.

  19. EBSD analysis of MgB2 bulk superconductors

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Schmauch, J.; Inoue, K.; Muralidhar, M.; Berger, K.; Noudem, J.

    2016-04-01

    The grain orientation, the texture and the grain boundary misorientations are important parameters for the understanding of the magnetic properties of the bulk MgB2 samples intended for super-magnet applications. Such data can be provided by electron backscatter diffraction (EBSD) analysis. However, as the grain size (GS) of the MgB2 bulks is preferably in the 100-200 nm range, the common EBSD technique working in reflection operates properly only on highly dense samples. In order to achieve a reasonably good Kikuchi pattern quality on all samples, we apply here the newly developed transmission EBSD (t-EBSD) technique to several bulk MgB2 samples. This method requires the preparation of TEM slices by means of focused ion-beam milling, which are then analyzed within the SEM, operating with a specific sample holder. We present several EBSD mappings of samples prepared with different techniques and at various reaction temperatures.

  20. The MG-RAST metagenomics database and portal in 2015

    PubMed Central

    Wilke, Andreas; Bischof, Jared; Gerlach, Wolfgang; Glass, Elizabeth; Harrison, Travis; Keegan, Kevin P.; Paczian, Tobias; Trimble, William L.; Bagchi, Saurabh; Grama, Ananth; Chaterji, Somali; Meyer, Folker

    2016-01-01

    MG-RAST (http://metagenomics.anl.gov) is an open-submission data portal for processing, analyzing, sharing and disseminating metagenomic datasets. The system currently hosts over 200 000 datasets and is continuously updated. The volume of submissions has increased 4-fold over the past 24 months, now averaging 4 terabasepairs per month. In addition to several new features, we report changes to the analysis workflow and the technologies used to scale the pipeline up to the required throughput levels. To show possible uses for the data from MG-RAST, we present several examples integrating data and analyses from MG-RAST into popular third-party analysis tools or sequence alignment tools. PMID:26656948

  1. The corrosivity and passivity of sputtered Mg-Ti alloys

    SciTech Connect

    Song, Guang -Ling; Unocic, Kinga A.; Meyer, III, Harry M.; Cakmak, Ercan; Brady, Michael P.; Gannon, Paul E.; Himmer, Phil; Andrews, Quinn

    2015-11-30

    Our study explored the possibility of forming a “stainless” Mg–Ti alloy. The electrochemical behavior of magnetron-sputtered Mg–Ti alloys was measured in a NaCl solution, and the surface films on the alloys were examined by XPS, SEM and TEM. Increased corrosion resistance was observed with increased Ti content in the sputtered Mg–Ti alloys, but passive-like behavior was not reached until the Ti level (atomic %) was higher than the Mg level. Moreover, the surface film that formed on sputtered Mg–Ti based alloys in NaCl solution was thick, discontinuous and non-protective, whereas a thin, continuous and protective Mg and Ti oxide film was formed on a sputtered Ti–Mg based alloy.

  2. Interpretation of Na-K-Mg relations in geothermal waters

    USGS Publications Warehouse

    Fournier, R.O.

    1990-01-01

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

  3. The corrosivity and passivity of sputtered Mg-Ti alloys

    DOE PAGES

    Song, Guang -Ling; Unocic, Kinga A.; Meyer, III, Harry M.; Cakmak, Ercan; Brady, Michael P.; Gannon, Paul E.; Himmer, Phil; Andrews, Quinn

    2015-11-30

    Our study explored the possibility of forming a “stainless” Mg–Ti alloy. The electrochemical behavior of magnetron-sputtered Mg–Ti alloys was measured in a NaCl solution, and the surface films on the alloys were examined by XPS, SEM and TEM. Increased corrosion resistance was observed with increased Ti content in the sputtered Mg–Ti alloys, but passive-like behavior was not reached until the Ti level (atomic %) was higher than the Mg level. Moreover, the surface film that formed on sputtered Mg–Ti based alloys in NaCl solution was thick, discontinuous and non-protective, whereas a thin, continuous and protective Mg and Ti oxide filmmore » was formed on a sputtered Ti–Mg based alloy.« less

  4. The MG-RAST metagenomics database and portal in 2015.

    PubMed

    Wilke, Andreas; Bischof, Jared; Gerlach, Wolfgang; Glass, Elizabeth; Harrison, Travis; Keegan, Kevin P; Paczian, Tobias; Trimble, William L; Bagchi, Saurabh; Grama, Ananth; Chaterji, Somali; Meyer, Folker

    2016-01-01

    MG-RAST (http://metagenomics.anl.gov) is an open-submission data portal for processing, analyzing, sharing and disseminating metagenomic datasets. The system currently hosts over 200,000 datasets and is continuously updated. The volume of submissions has increased 4-fold over the past 24 months, now averaging 4 terabasepairs per month. In addition to several new features, we report changes to the analysis workflow and the technologies used to scale the pipeline up to the required throughput levels. To show possible uses for the data from MG-RAST, we present several examples integrating data and analyses from MG-RAST into popular third-party analysis tools or sequence alignment tools.

  5. The Mg II h and k lines in Vega

    NASA Technical Reports Server (NTRS)

    Ferrero, R. F.; Gouttebroze, P.; Kondo, Y.

    1983-01-01

    High resolution h (2802.7 A) and k (2795.5 A) lines Mg II obtained for the star Vega (Alpha Lyr, A0V) with Copernicus satellite and a balloon-borne ultraviolet stellar spectrometer (BUSS) are interpreted by means of theoretical NLTE line profiles in the frame work of complete (CR) and partial (PR) redistribution hypothesis. The PR profiles are remarkably coincident with the observed ones for a magnesium abundance Mg/H = 0.00001 and a projected rotation velocity v sin i = 17 km/s. LTE and NLTE atmospheric models with a temperature plateau or with temperature rises (depending on whether the atmosphere is in radiative equilibrium or not) are used to account for the possible presence of a chromosphere on Vega. The possible presence of an interstellar Mg II absorption line superimposed on the stellar ones is also discussed.

  6. A DNA enzyme with Mg(2+)-Dependent RNA Phosphoesterase Activity

    NASA Technical Reports Server (NTRS)

    Breaker, Ronald R.; Joyce, Gerald F.

    1995-01-01

    Previously we demonstrated that DNA can act as an enzyme in the Pb(2+)-dependent cleavage of an RNA phosphoester. This is a facile reaction, with an uncatalyzed rate for a typical RNA phosphoester of approx. 10(exp -4)/ min in the presence of 1 mM Pb(OAc)2 at pH 7.0 and 23 C. The Mg(2+) - dependent reaction is more difficult, with an uncatalyzed rate of approx. 10(exp -7)/ min under comparable conditions. Mg(2+) - dependent cleavage has special relevance to biology because it is compatible with intracellular conditions. Using in vitro selection, we sought to develop a family of phosphoester-cleaving DNA enzymes that operate in the presence of various divalent metals, focusing particularly on the Mg(2+) - dependent reaction. Results: We generated a population of greater than 10(exp 13) DNAs containing 40 random nucleotides and carried out repeated rounds of selective amplification, enriching for molecules that cleave a target RNA phosphoester in the presence of 1 mM Mg(2+), Mn(2+), Zn(2+) or Pb(2+). Examination of individual clones from the Mg(2+) lineage after the sixth round revealed a catalytic motif comprised of a three-stem junction.This motif was partially randomized and subjected to seven additional rounds of selective amplification, yielding catalysts with a rate of 0.01/ min. The optimized DNA catalyst was divided into separate substrate and enzyme domains and shown to have a similar level of activity under multiple turnover conditions. Conclusions: We have generated a Mg(2+) - dependent DNA enzyme that cleaves a target RNA phosphoester with a catalytic rate approx. 10(exp 5) - fold greater than that of the uncatalyzed reaction. This activity is compatible with intracellular conditions, raising the possibility that DNA enzymes might be made to operate in vivo.

  7. 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.

  8. Aging of magnetic properties in MgO films

    SciTech Connect

    Balcells, Ll.; Konstantinovic, Z.; Martinez, B.; Beltran, J. I.; Martinez-Boubeta, C.; Arbiol, J.

    2010-12-20

    In this work we report on the magnetic behavior of MgO thin films prepared by sputtering. A severe aging process of the ferromagnetic properties is detected in magnetic samples exposed to ambient atmosphere. However, ferromagnetism can be successively switched on again by annealing samples in vacuum. We suggest this behavior reflects the key role played by defects in stabilizing ferromagnetism in MgO films and is likely to be closely related to the hydrogen-driven instability of V-type centers in this material.

  9. Divorced Eutectic Solidification of Mg-Al Alloys

    NASA Astrophysics Data System (ADS)

    Monas, Alexander; Shchyglo, Oleg; Kim, Se-Jong; Yim, Chang Dong; Höche, Daniel; Steinbach, Ingo

    2015-08-01

    We present simulations of the nucleation and equiaxed dendritic growth of the primary hexagonal close-packed -Mg phase followed by the nucleation of the -phase in interdendritic regions. A zoomed-in region of a melt channel under eutectic conditions is investigated and compared with experiments. The presented simulations allow prediction of the final properties of an alloy based on process parameters. The obtained results give insight into the solidification processes governing the microstructure formation of Mg-Al alloys, allowing their targeted design for different applications.

  10. Superconducting properties of MgB2 from first principles.

    PubMed

    Floris, A; Profeta, G; Lathiotakis, N N; Lüders, M; Marques, M A L; Franchini, C; Gross, E K U; Continenza, A; Massidda, S

    2005-01-28

    Solid MgB(2) has rather interesting and technologically important properties, such as a very high superconducting transition temperature. Focusing on this compound, we report the first nontrivial application of a novel density-functional-type theory for superconductors, recently proposed by the authors. Without invoking any adjustable parameters, we obtain the transition temperature, the gaps, and the specific heat of MgB(2) in very good agreement with experiment. Moreover, our calculations show how the Coulomb interaction acts differently on sigma and pi states, thereby stabilizing the observed superconducting phase.

  11. NMR structure of hypothetical protein MG354 from Mycoplasmagenitalium

    SciTech Connect

    Pelton, Jeffrey G.; Shi, Jianxia; Yokotoa, Hisao; Kim, Rosalind; Wemmer, David E.

    2005-04-12

    Mycoplasma genitalium (Mg) and M. pneumoniae (Mp) are human pathogens with two of the smallest genomes sequenced to date ({approx} 480 and 680 genes, respectively). The Berkeley Structural Genomics Center is determining representative structures for gene products in these organisms, helping to understand the set of protein folds needed to sustain this minimal organism. The protein coded by gene MG354 (gi3844938) from M. genitalium has a relatively unique sequence, related only to MPN530 from M. pneumoniae (68% identity, coverage 99%) and MGA{_}0870 from the avian pathogen M. gallisepticum (23% identity, coverage 94%), has no homologue with a determined structure, and no functional annotations.

  12. Foram Farming in the Mid-Continent: Culturing Low-Mg Benthic Foraminifera to Calibrate the Mg/Ca Paleothermometer

    NASA Astrophysics Data System (ADS)

    Jennings, D.; Hasiuk, F.; Thomas, E.; Varekamp, J. C.

    2014-12-01

    The initiation of Cenozoic continental ice sheets and the history of their growth/decay is difficult to reconstruct because of the mixed effects of polar ice volume and temperature on benthic foraminiferal oxygen isotope values. Coupled measurements of foraminiferal δ18O and Mg/Ca are a promising tool to unlock the history of past continental glaciation by calculating the oxygen isotopic composition of paleo-seawater. This method has been applied on Quaternary timescales with success, but uncertainty about secular changes in seawater Mg/Ca and potential changes in carbonate saturation have produced varying results with deeper time data. Currently, no experimentally-calibrated model explains how the Mg/Ca of low-Mg calcite, such as secreted by benthic foraminifera, responds to variations in seawater temperature and Mg/Ca. Our "Foram Farm" is a culture system for low-Mg calcite benthic foraminifera, composed of a colony and an experimental line. Currently, the colony hosts several species of rotaliids, miliolids, and buliminids obtained from Qatar, the Dominican Republic, Scotland, and Long Island Sound, USA. In addition, two tanks contain "live sand," a mixture of sandy material and seawater obtained from tropical reefs, and commonly used to condition hobbyist saltwater aquaria. This sand contains foraminifera and numerous other microorganisms. "Live sand" could be a source for cheap and easy to obtain test subjects. The foram farm gives access to a constant supply and variety of test subjects for the experimental line, which consists of several analytical refrigerators with varying temperatures. Each refrigerator houses petri dishes where forams are grown in water with varying Mg/Ca compositions. Elphidium excavatum, a well-researched, eurytopic taxon, will be the first to be cultured in the experimental line. After growing under experimental conditions, specimens will be analyzed using LA-ICP-MS, in order to model effects of seawater T and Mg/Ca on foram Mg

  13. New quaternary semiconductor Cu2MgSnS4 and Cu2MgSnSe4 for photovoltaics

    NASA Astrophysics Data System (ADS)

    Tse, Kinfai; Zhong, Guohua; Zhang, Yiou; Li, Xiaoguang; Yang, Chunlei; Zhu, Junyi; Zeng, Zhi; Zhang, Zhenyu; Xiao, Xudong

    Element substitution of Zn by Mg and Ca is attempted to overcome the problem of potential fluctuation in Cu2ZnSnS4 and Cu2ZnSnSe4 (CZTSSe) due to prevalence of CuZn + ZnCu defect complex. Through density function theory calculation with hybrid functional, we have shown that Cu2MgSnS4 and Cu2MgSnSe4 (CMTSSe) are stable with respect to secondary phases considered under suitable chemical potential. Stannite CMTSSe is thermodynamically more favorable over the kesterite structure. The alternating Cu and Mg/Sn cation layer of stannite structure may suppress the formation of MgCu antisite due to large stress induced. The electronic and optical properties of CMTSSe are similar to that of CZTSSe with comparable absorption coefficient at the band-edge suggests CMTSSe to be a promising photovoltaic material. The work was supported by the National Major Science Research Program of China under Grant No. 2012CB933700, the Natural Science Foundation of China (Grant Nos. 61274093, 61574157, 11274335, 11504398, 51302303, and 51474132), and the Shenzhen Basic Resear.

  14. 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).

  15. 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

  16. Noncontact atomic force and Kelvin probe force microscopy on MgO(100) and MgO(100)-supported Ba

    NASA Astrophysics Data System (ADS)

    Pang, Chi Lun; Sasahara, Akira; Onishi, Hiroshi

    2016-08-01

    Atomically-flat MgO(100) surfaces were prepared by sputtering and annealing. Noncontact atomic force microscopy (NC-AFM) and Kelvin probe force microscopy (KPFM) were used to characterize the MgO(100) surfaces. The NC-AFM images revealed the presence of point defects on an atomically-resolved surface. The surface potential at these point defects, as well as features such as step edges and deposited Ba nanoparticles were mapped using KPFM. The Kelvin images show that the surface potential increases at the point defects and at the step edges. On the other hand, a decrease in the potential was found over Ba nanoparticles which can be explained by electron charge transfer from the Ba to the MgO.

  17. Positron lifetime studies of decomposition in 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) alloys

    SciTech Connect

    Dlubek, G. |; Lademann, P.; Krause, H.; Krause, S.; Unger, R.

    1998-09-04

    In the current paper, the decomposition behavior of the engineering alloys 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) is studied using positron lifetime measurements. Positrons probe open volume defects such as vacancies and dislocations. However, they may also be used to investigate coherent zones and incoherent precipitates. In order to understand the rather complicated precipitation sequences and the response of positrons to different type of precipitates occurring in 2024 and 7010 alloys, binary and ternary laboratory alloys were also investigated under the same experimental conditions as the engineering alloys. The interpretations of the results are based on experiences of the group from extensive positron studies of laboratory alloys such as Al-Zn, Al-Zn-Mg, Al-Cu, and further Al alloys (see also the review (4)). Their collected results are shown as lifetimes and curve-shape parameters S of the electron-positron momentum distribution curves characteristic for different precipitates in Al alloys.

  18. Tunneling conductance studies in the ion-beam sputtered CoFe/Mg/MgO/NiFe magnetic tunnel junctions

    SciTech Connect

    Singh, Braj Bhusan; Chaudhary, Sujeet

    2013-06-03

    Magnetic tunnel junctions consisting of CoFe(10 nm)/Mg(1 nm)/MgO(3.5 nm)/NiFe(10 nm) are grown at room temperature using dual ion beam sputtering via in-situ shadow masking. The effective barrier thickness and average barrier height are estimated to be 3.5 nm (2.9 nm) and 0.69 eV (1.09 eV) at 290 K (70 K), respectively. The tunnel magnetoresistance value of 0.2 % and 2.3 % was observed at 290 K and 60 K, respectively. The temperature dependence of tunneling conductance revealed the presence of localized states present within the forbidden gap of the MgO barrier leading to finite inelastic spin independent tunneling contributions, which degrade the TMR value.

  19. 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.

  20. Estudios sobre Educacion, 2002 (Studies on Education, 2002).

    ERIC Educational Resources Information Center

    Estudios sobre Educacion, 2002

    2002-01-01

    This scholarly journal deals with the study of education. Articles in this second issue are: "La Vertebracion Academica de la Formacion Inicial del Profesorado" (The Academic Backbone of the Initial Formation of Teachers) (Jose M. Esteve); "Deficiencia Visual en el Nino" (Visual Deficiency in the Young Child) (Feli Peralta; Juan Narbona); "The…

  1. Phase stability of fine-grained (Mg,Y)-PSZ

    SciTech Connect

    Meschke, F.; Claussen, N.; Portu, G. De; Roedel, J.

    1995-07-01

    A fine-grained zirconia, which has been costabilized with yttria magnesia, has been prepared. Its stability during subeutectoid annealing at 1,100 C, and its hydrothermal stability during hydrothermal treatment at 180 C, have been determined and they are compared to those of Y-TZP and Mg-PSZ materials.

  2. High pressure phase diagram of MgO

    NASA Astrophysics Data System (ADS)

    French, Martin; Cebulla, Daniel; Redmer, Ronald

    2015-06-01

    In order to improve the understanding of the interior of super-Earths (planets in the range of 1-10 Earth masses) and other exoplanets, ab inito calculations for the planetary materials and the equation of state (EOS) and phase diagram of planetary materials are needed. A typical representative is MgO, which is an abundant material in the Earth's mantle and is also expected to be important for the mantle of exoplanets as well as for the rocky cores of gas giants such as Jupiter. Using ab initio molecular dynamic simulations, we have determined the phase diagram for MgO up to 20000 K and 1.5 TPa. In particular, the transition from the solid to the molten salt has been studied using diffusion analyses and pair distribution functions. The transition from the B1 to the B2 structure in solid MgO is determined by calculating the respective free enthalpies. The phase diagram of MgO is constructed based on accurate EOS data. We compare with results from (decaying) shock and ramp compression experiments and theoretical calculations for the B1-B2 and the liquid-solid transition line.

  3. A Bayesian, multivariate calibration for Globigerinoides ruber Mg/Ca

    NASA Astrophysics Data System (ADS)

    Khider, D.; Huerta, G.; Jackson, C.; Stott, L. D.; Emile-Geay, J.

    2015-09-01

    The use of Mg/Ca in marine carbonates as a paleothermometer has been challenged by observations that implicate salinity as a contributing influence on Mg incorporation into biotic calcite and that dissolution at the sea-floor alters the original Mg/Ca. Yet, these factors have not yet been incorporated into a single calibration model. We introduce a new Bayesian calibration for Globigerinoides ruber Mg/Ca based on 186 globally distributed core top samples, which explicitly takes into account the effect of temperature, salinity, and dissolution on this proxy. Our reported temperature, salinity, and dissolution (here expressed as deep-water ΔCO32-) sensitivities are (±2σ) 8.7±0.9%/°C, 3.9±1.2%/psu, and 3.3±1.3%/μmol.kg-1 below a critical threshold of 21 μmol/kg in good agreement with previous culturing and core-top studies. We then perform a sensitivity experiment on a published record from the western tropical Pacific to investigate the bias introduced by these secondary influences on the interpretation of past temperature variability. This experiment highlights the potential for misinterpretations of past oceanographic changes when the secondary influences of salinity and dissolution are not accounted for. Multiproxy approaches could potentially help deconvolve the contributing influences but this awaits better characterization of the spatio-temporal relationship between salinity and δ18Osw over millennial and orbital timescales.

  4. Permanent magnet with MgB2 bulk superconductor

    NASA Astrophysics Data System (ADS)

    Yamamoto, Akiyasu; Ishihara, Atsushi; Tomita, Masaru; Kishio, Kohji

    2014-07-01

    Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB2) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron. Magnetic hysteresis loop of the MgB2 permanent bulk magnet was detrmined. Because MgB2 is a simple-binary-line compound that does not contain rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making MgB2 bulks promising for the next generation of Tesla-class permanent-magnet applications.

  5. The CorA Mg2+ Transporter Is a Homotetramer

    SciTech Connect

    Warren, Mary A.; Kucharski, Lisa M.; Veenstra, Alexander; Shi, Liang; Grulich, Paul F.; Maguire, Michael E.

    2004-07-01

    Salmonella enterica serovar Typhimurium has three transport systems mediating influx of Mg2+: CorA, MgtA, and MgtB (6, 7, 22, 24). The CorA system is encoded by the corA gene that constitutively expresses a 37-kDa integral membrane protein (19).

  6. Permanent magnet with MgB{sub 2} bulk superconductor

    SciTech Connect

    Yamamoto, Akiyasu; Ishihara, Atsushi; Tomita, Masaru; Kishio, Kohji

    2014-07-21

    Superconductors with persistent zero-resistance currents serve as permanent magnets for high-field applications requiring a strong and stable magnetic field, such as magnetic resonance imaging. The recent global helium shortage has quickened research into high-temperature superconductors (HTSs)—materials that can be used without conventional liquid-helium cooling to 4.2 K. Herein, we demonstrate that 40-K-class metallic HTS magnesium diboride (MgB{sub 2}) makes an excellent permanent bulk magnet, maintaining 3 T at 20 K for 1 week with an extremely high stability (<0.1 ppm/h). The magnetic field trapped in this magnet is uniformly distributed, as for single-crystalline neodymium-iron-boron. Magnetic hysteresis loop of the MgB{sub 2} permanent bulk magnet was determined. Because MgB{sub 2} is a simple-binary-line compound that does not contain rare-earth metals, polycrystalline bulk material can be industrially fabricated at low cost and with high yield to serve as strong magnets that are compatible with conventional compact cryocoolers, making MgB{sub 2} bulks promising for the next generation of Tesla-class permanent-magnet applications.

  7. PD/MG BIMETALLIC CORROSION CELLS FOR DECHLORINATING PCBS

    EPA Science Inventory

    Two dissimilar metals immersed in a conducting solution develop different corrosion potentials forming a bimetallic corrosion cell. Enhanced corrosion of an active metal like Mg combined with catalytic hydrogenation properties of a noble metal like Pd in such bimetallic cells can...

  8. STORAGE RING MEASUREMENT OF ELECTRON IMPACT IONIZATION FOR Mg{sup 7+} FORMING Mg{sup 8+}

    SciTech Connect

    Hahn, M.; Lestinsky, M.; Novotny, O.; Savin, D. W.; Bernhardt, D.; Mueller, A.; Schippers, S.; Wolf, A.

    2010-04-01

    We report electron impact ionization cross section measurements for Mg{sup 7+} forming Mg{sup 8+} at center of mass energies from approximately 200 eV to 2000 eV. The experimental work was performed using the heavy-ion storage ring TSR located at the Max-Planck-Institut fuer Kernphysik in Heidelberg, Germany. We find good agreement with distorted wave calculations using both the GIPPER code of the Los Alamos Atomic Physics Code suite and using the Flexible Atomic Code.

  9. Reaction mechanisms in {sup 24}Mg+{sup 12}C and {sup 32}S+{sup 24}Mg

    SciTech Connect

    Beck, C.; Sanchez i Zafra, A.; Papka, P.; Thummerer, S.; Azaiez, F.; Courtin, S.; Curien, D.; Dorvaux, O.; Lebhertz, D.; Nourreddine, A.; Rousseau, M.; Oertzen, W. von; Gebauer, B.; Kokalova, Tz.; Wheldon, C.; De Angelis, G.; Gadea, A.; Lenzi, S.; Napoli, D. R.; Szilner, S.

    2009-03-04

    The occurrence of 'exotic' shapes in light N = Z{alpha}-like nuclei is investigated for {sup 24}Mg+{sup 12}C and {sup 32}S+{sup 24}Mg. Various approaches of superdeformed and hyperdeformed bands associated with quasimolecular resonant structures with low spin are presented. For both reactions, exclusive data were collected with the Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the VIVITRON Tandem facility of Strasbourg. Specific structures with large deformation were selectively populated in binary reactions and their associated {gamma}-decays studied. The analysis of the binary and ternary reaction channels is discussed.

  10. PIGE related differential cross-section measurements of the 25Mg(p,p‧γ)25Mg reaction

    NASA Astrophysics Data System (ADS)

    Preketes-Sigalas, K.; Lagoyannis, A.; Axiotis, M.; Becker, H. W.; Foteinou, V.; Harissopulos, S.; Kokkoris, M.; Provatas, G.

    2016-11-01

    The differential cross sections of the 25Mg(p,p‧γ)25Mg reaction, critical for the quantitative determination of magnesium in complex matrices using the PIGE technique, were measured at two (2) angles, 55° and 90°, and at proton energies from 2420 to 4550 keV, by detecting the 390, 585 and 975 keV γ-rays emitted. The experimental setup consisted of two 100% relative efficiency HPGe detectors. The results are compared to those already present in literature and an attempt is made to explain the existing discrepancies. The obtained results from the present work are validated via thick-target measurements.

  11. Four treatment failures of pharyngeal gonorrhoea with ceftriaxone (500 mg) or cefotaxime (500 mg), Sweden, 2013 and 2014.

    PubMed

    Golparian, D; Ohlsson, Ak; Janson, H; Lidbrink, P; Richtner, T; Ekelund, O; Fredlund, H; Unemo, M

    2014-07-31

    We describe four cases in Sweden of verified treatment failures of pharyngeal gonorrhoea with ceftriaxone (500 mg; n=3) or cefotaxime (500 mg; n=1) monotherapy. All the ceftriaxone treatment failures were caused by the internationally spreading multidrug-resistant gonococcal NG-MAST genogroup 1407 clone. Increased awareness of treatment failures is crucial particularly when antimicrobial monotherapy is used. Frequent test of cure and appropriate verification/falsification of suspected treatment failures, as well as implementation of recommended dual antimicrobial therapy are imperative.

  12. Mg2(Si,Sn)-based thermoelectric materials and devices

    NASA Astrophysics Data System (ADS)

    Gao, Peng

    Thermoelectric effects are phenomena found in materials that can achieve direct conversion between heat flow and electricity. One important application of thermoelectric effects is thermoelectric generators, which can generate electricity when a temperature gradient is applied. Thermoelectric generators make use of various sources of heat and it is considered a promising solution for waste heat recovery. The conversion efficiency of thermoelectric generators depends on the materials used in the devices. Significant improvement in the performance of thermoelectric materials has been made in the past few decades. However, most of the good thermoelectric materials being investigated have limitations, such as the high materials cost, high materials density and toxicity of the constituent elements. The Mg2(Si,Sn)-based materials studied in this work are promising candidates for thermoelectric generators in the mid-temperature range and have drawn increasing research interest in recent years because these materials are high performance thermoelectrics that are low cost, low-density and non-toxic. In this work, systematic studies were performed on the Mg2(Si,Sn) thermoelectric materials. Thermal phase stability was studied for different compositions of Mg2Si1-xSnx and Mg2Si0.4Sn 0.6 was used as base material for further optimization. Both n-type and p-type samples were obtained by doping the materials with different elements. Peak ZT ˜ 1.5 for the n-type and ZT ˜ 0.7 for the p-type materials were obtained, both of which are among the best reported results so far. Experimental work was also done to study the techniques to develop the Mg2Si 0.4Sn0.6 materials into working devices. Different electrode materials were tested in bonding experiment for this compound, and copper was found to be the best electrode material for Mg2Si 0.4Sn0.6. Preliminary work was done to demonstrate the possibility of fabricating a Mg2Si0.4Sn0.6-based thermoelectric generator and the result is

  13. Signal-to-Noise Characteristics of Solar MG II Indices

    NASA Astrophysics Data System (ADS)

    Crane, P. C.; Floyd, L. E.

    1999-05-01

    Knowledge of the variations in solar ultraviolet irradiances is essential to understanding both the Sun and the behavior of the Earth's upper atmosphere. Since the solar ultraviolet radiation is absorbed by the atmosphere, the requisite measurements must be done from space. Reliable, approximately daily measurements of solar ultraviolet irradiances have been made since November 1978 by a variety of instruments (Numbus-7 SBUV, NOAA-9 and NOAA-11 SBUV/2, UARS SUSIM and SOLSTICE, and ERS-2 GOME). To overcome differences in spectral coverage and resolution and the challenges involved in the long-term calibrations of the instruments, a solar index suitable for use as a proxy for the solar ultraviolet (i.e., 100-400 nm) irradiances has been sought. The most popular indices for this purpose are the several Mg II indices based upon the Mg II k and h doublet near 280 nm; starting with the core-to-wing index developed by Heath and Schlesinger (J. Geophys. Res. 91, 8672, 1986) for the Nimbus-7 SBUV, they are calculated by taking the ratio of adjacent parts of the Mg II feature: one originating in the upper chromosphere that exhibits solar ultraviolet variations and the other, in the upper photosphere which is insensitive to solar variations. Because the ratio is of irradiances at nearby wavelengths, the Mg II indices mostly are not affected by temporal and spectral variations in the instrument responses. While there is an ongoing effort to combine the available Mg II indices into a single 20-year time series (i.e., Viereck and Puga, J. Geophys. Res., in press), we are investigating an alternate approach. We report here on the first step in that study: the characterization of the signal and noise properties of the several Mg II indices available. We use Fourier analysis to determine the amplitudes of a common signal (the 27-day variations) and of the high-frequency, day-to-day errors. Ultimately, the corresponding signal-to-noise ratios may be used to derive statistical

  14. 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.

  15. 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.

  16. Unusually large spin polarization and magnetoresistance in a FeMg8-FeMg8 superatomic dimer.

    PubMed

    Zhu, Lin; Qian, Meichun; Khanna, Shiv N

    2013-08-14

    Electronic transport across a FeMg8 magnetic superatom and its dimer has been investigated using a density functional theory combined with Keldysh nonequilibrium Green's-function formalism. For a single cluster, our studies for the cluster supported in various orientations on a Au(100) surface show that the transport is sensitive to the contact geometry. Investigations covering the cases where the axes of Mg square antiprism are 45°, perpendicular, and parallel to the transport direction, show that the equilibrium conductance, transferred charge, and current polarizations can all change significantly with orientation. Our studies on the transport across a magnetic superatom dimer FeMg8-FeMg8 focus on the effect of electrode contact distance and the support. The calculated I-V curves show negative differential resistance behavior at larger electrode-cluster contact distances. Further, the equilibrium conductance in ferromagnetic state shows an unusually high spin polarization that is about 81.48% for specific contact distance, and a large magnetoresistance ratio exceeding 500% is also found. The results show that the superatom assemblies can provide unusual transport characteristics, and that the spin polarization and magnetoresistance can be controlled via the contact geometry.

  17. 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.

  18. Randomised clinical trial comparing melatonin 3 mg, amitriptyline 25 mg and placebo for migraine prevention

    PubMed Central

    Gonçalves, Andre Leite; Martini Ferreira, Adriana; Ribeiro, Reinaldo Teixeira; Zukerman, Eliova; Cipolla-Neto, José; Peres, Mario Fernando Prieto

    2016-01-01

    Introduction Melatonin has been studied in headache disorders. Amitriptyline is efficacious for migraine prevention, but its unfavourable side effect profile limits its use. Methods A randomised, double-blind, placebo-controlled study was carried out. Men and women, aged 18–65 years, with migraine with or without aura, experiencing 2–8 attacks per month, were enrolled. After a 4-week baseline phase, 196 participants were randomised to placebo, amitriptyline 25 mg or melatonin 3 mg, and 178 took a study medication and were followed for 3 months (12 weeks). The primary outcome was the number of migraine headache days per month at baseline versus last month. Secondary end points were responder rate, migraine intensity, duration and analgesic use. Tolerability was also compared between groups. Results Mean headache frequency reduction was 2.7 migraine headache days in the melatonin group, 2.2 for amitriptyline and 1.1 for placebo. Melatonin significantly reduced headache frequency compared with placebo (p=0.009), but not to amitriptyline (p=0.19). Melatonin was superior to amitriptyline in the percentage of patients with a greater than 50% reduction in migraine frequency. Melatonin was better tolerated than amitriptyline. Weight loss was found in the melatonin group, a slight weight gain in placebo and significantly for amitriptyline users. Conclusions Melatonin 3 mg is better than placebo for migraine prevention, more tolerable than amitriptyline and as effective as amitriptyline 25 mg. PMID:27165014

  19. Single dose oral amoxycillin 3 g with either 125 mg or 250 mg clavulanic acid to treat uncomplicated anogenital gonorrhoea.

    PubMed Central

    Lawrence, A G; Shanson, D C

    1985-01-01

    A single supervised oral dose of amoxycillin 3 g combined with clavulanic acid 125 mg as a suspension (Augmentin 3.125G) plus probenecid 1 g, cured 97 of 100 assessable patients who had uncomplicated anogenital gonorrhoea. Thirteen of the 100 patients were infected with penicillinase producing strains of Neisseria gonorrhoeae (PPNG) and 11 (85%) of these patients were cured, including one infected with a PPNG strain that was also resistant to spectinomycin. Another group of 93 assessable patients was treated with ampicillin 3 g plus probenecid 1 g, and only 85 (91%) patients were cured. Of the eight treatment failures in this group, five were found to be infected with PPNG strains. In a second study 144 assessable patients were treated with amoxycillin 3 g combined with clavulanic acid 250 mg, (Augmentin 3.250G) plus probenecid 1 g, and a 97% cure rate was again obtained. Five of seven (71%) patients infected with PPNG strains were cured. Although both Augmentin regimens were effective for treating gonorrhoea caused by PPNG and non-PPNG strains, side effects were noted in more patients treated with 250 mg clavulanic acid (24%) than with 125 mg clavulanic acid (5%). In addition, a similar cure rate was obtained in the three primary sites of infection, the urethra, cervix, and rectum. PMID:4007860

  20. Pd/MgO: Catalyst characterization and phenol hydrogenation activity

    SciTech Connect

    Claus, P.; Berndt, H.; Mohr, C.; Radnik, J.; Shin, E.J.; Keane, M.A.

    2000-05-15

    The gas-phase hydrogenation of phenol has been studied over a 1% w/w Pd/MgO catalyst prepared by impregnation of MgO with (NH{sub 4}){sub 2}PdCl{sub 6}. The catalyst precursor was activated by precalcination in air at 473 K followed by reduction in hydrogen at 573 K. Temperature-programmed reduction/desorption has revealed the presence of ammonium carbonate and/or ammonium hydrogen carbonate on the active surface in addition to a metallic palladium component. Whereas the latter was not detectable by X-ray diffraction due to the high metal dispersion, transmission electron microscopy revealed that the mean palladium particle diameter is 1.3 {+-} 0.2 nm, which corresponds to a palladium dispersion of D{sub Pd} = 71%. Impregnation followed by calcination is shown to transform MgO to Mg(OH){sub 2} while the additional reduction step generates a surface phase that is composed of both needle-like Periclase MgO and Mg(OH){sub 2}. X-ray photoelectron spectrometric analyses of the activated catalyst has established the presence of zero-valent palladium which appears to be electron rich as a result of metal-support interaction; a degree of palladium charging is also evident as well as residual surface chlorine. The effects on fractional phenol conversion and reaction selectivity of varying such process variables as reaction time, temperature, and phenol molar feed rate are considered and the possibility of thermodynamic limitations is addressed. Hydrogenation was observed to proceed in a stepwise fashion with cyclohexanone as the partially hydrogenated product and cyclohexanol as the fully hydrogenated product. The catalyst delivered a 96% selectivity with respect to cyclohexanone production at 423 K but the cyclohexanone yield decreased at higher temperatures as conversion declined and cyclohexanol was increasingly preferred. Conversion and selectivity were both stable with prolonged catalyst use, i.e., time on stream in excess of 55 h.

  1. 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 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.

  2. 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

  3. Improved hydrogen storage kinetics of the Li-Mg-N-H system by addition of Mg(BH4)2.

    PubMed

    Pan, Hongge; Shi, Songbo; Liu, Yongfeng; Li, Bo; Yang, Yanjing; Gao, Mingxia

    2013-03-21

    A Mg(BH(4))(2)-added Mg(NH(2))(2)-2LiH system was prepared by ball milling the corresponding chemicals. The hydrogen storage properties of the Mg(NH(2))(2)-2LiH-xMg(BH(4))(2) (x = 0, 0.1, 0.2, 0.3) samples and the role played by Mg(BH(4))(2) were systematically investigated. The results show that the onset and peak temperatures for hydrogen desorption from the Mg(BH(4))(2)-added Mg(NH(2))(2)-2LiH sample shifted to lower temperatures. In particular, the Mg(NH(2))(2)-2LiH-0.1Mg(BH(4))(2) sample could reversibly absorb ~4.5 wt% of hydrogen in the temperature range of 120-150 °C, which is superior to the pristine sample. During ball milling, a metathesis reaction between Mg(BH(4))(2) and LiH readily occurred to form LiBH(4) and MgH(2) and subsequently, the newly formed MgH(2) reacted with Mg(NH(2))(2) to generate MgNH. Upon heating, the presence of LiBH(4) not only decreased the recrystallization temperature of Mg(NH(2))(2) but also reacted with LiNH(2) to form the Li(4)(BH(4))(NH(2))(3) intermediate, which weakens the N-H bonding and enhances the ion conductivity. Meanwhile, MgNH may act as the nucleation center for the dehydrogenation product of Li(2)MgN(2)H(2) due to the structural similarity. Thus, the in situ formed LiBH(4) and MgNH provide a synergetic effect to improve the hydrogen storage performances of the Mg(NH(2))(2)-2LiH system. PMID:23178338

  4. Fabrication of MgB2 superconducting wires with a hybrid method combining internal-Mg-diffusion and powder-in-tube processes

    NASA Astrophysics Data System (ADS)

    Ye, ShuJun; Matsumoto, Akiyoshi; Togano, Kazumasa; Zhang, YunChao; Ohmura, Takahito; Kumakura, Hiroaki

    2014-05-01

    We have previously reported that the addition of Mg powder to the B powder layer (B layer) of internal-Mg-diffusion (IMD)-processed MgB2 wires can decrease the amount of unreacted B particles, and hence increase the critical current density (Jc). As the amount of Mg powder is increased, the diameter of the central Mg rod must be reduced in order to maintain an overall Mg:B molar ratio of 1:2, corresponding to stoichiometric MgB2. If this ratio is achieved by the Mg powder alone, then the required diameter of the Mg rod is zero, which means that the IMD process becomes the powder-in-tube (PIT) process. A hybrid process intermediate between the IMD and PIT processes is proposed as a new approach for fabricating MgB2 wires. In the present study, the critical current and microstructure of MgB2 wires fabricated using this method are investigated. It is found that the method yields a higher engineering critical current density (Je, = Jc × MgB2 area fraction, where the MgB2 area fraction corresponds to the ratio of the MgB2 cross-sectional area to the total cross-sectional area of the wire) than that for either the IMD or the PIT method. Compared with the IMD method, the MgB2 layer thickness (the thickness of the MgB2 layer in the transverse cross section) is increased and the diameter of the central hole is decreased, thus increasing the MgB2 area fraction The proposed method also achieves a much higher MgB2 layer density, and thus a much higher Jc, than is possible using the PIT method. The combination of these factors leads to the enhanced Je value of MgB2 wires.

  5. Lattice instability in the AlMgB14 structure

    NASA Astrophysics Data System (ADS)

    Wan, L. F.; Beckman, S. P.

    2014-04-01

    The lattice dynamics of the AlMgB14 structure is characterized by phonon vibrational modes that are calculated from first-principles methods. The stoichiometric composition of AlMgB14 is found to have three soft phonon modes, which have displacements associated with metal atoms vibrating against the B lattice. This lattice instability is believed to be associated with the occupation of electronic states in the conduction bands. The off-stoichiometric occupation sweeps the Fermi level from the conduction band into the gap, and as a result the observed soft phonon modes are driven away. Based on a simple electron counting scheme, as also discussed by Mori [39], it is observed that stable XYB14 compounds have between 15 and 16 electrons contributed to the B-lattice from the metal species.

  6. Two-band superconductivity in MgB{sub 2}.

    SciTech Connect

    Iavarone, M.; Karapetrov, G.; Koshelev, A. E.; Kwok, W.-K.; Crabtree, G. W.; Hinks, D. G.; Materials Science Division

    2002-10-28

    The study of the anisotropic superconductor MgB2 using a combination of scanning tunneling microscopy and spectroscopy reveals two distinct energy gaps at {Delta}{sub 1}=2.3 meV and {Delta}{sub 2}=7.1 meV at 4.2 K. Different spectral weights of the partial superconducting density of states are a reflection of different tunneling directions in this multiband system. Temperature evolution of the tunneling spectra follows the BCS scenario with both gaps vanishing at the bulk T{sub c}. The data confirm the importance of Fermi-surface sheet dependent superconductivity in MgB{sub 2} proposed in the multigap model by Liu et al.

  7. Superior hydrogen absorption and desorption behavior of Mg thin films

    NASA Astrophysics Data System (ADS)

    Qu, Jianglan; Wang, Yuntao; Xie, Lei; Zheng, Jie; Liu, Yang; Li, Xingguo

    Pd-capped Mg films prepared by magnetron sputtering achieved complete dehydrogenation in air at room temperature and behaved as favorable gasochromic switchable mirrors. Their cyclic hydrogen absorption and desorption kinetics in air were investigated by using the Bruggeman effective medium approximation. The overall activation energy was 80 kJ mol -1, while the reaction orders controlling desorption were deduced to be n = 2 at 328 K and n = 1 at lower temperatures by analyzing the transmittance data. The hydrogen diffusion coefficient and the corresponding activation energy were calculated by electrochemical measurements. Mg thin films exhibited the smaller activation energy and remarkable diffusion kinetics at room temperature which implied potential applications in smart windows.

  8. High-resolution photoemission study of MgB2.

    PubMed

    Takahashi, T; Sato, T; Souma, S; Muranaka, T; Akimitsu, J

    2001-05-21

    We have performed high-resolution photoemission spectroscopy on MgB2 and observed opening of a superconducting gap with a narrow coherent peak. We found that the superconducting gap is s like with the gap value ( Delta) of 4.5+/-0.3 meV at 15 K. The temperature dependence (15-40 K) of the gap value follows well the BCS form, suggesting that 2Delta/k(B)T(c) at T = 0 is about 3. No pseudogap behavior is observed in the normal state. The present results strongly suggest that MgB2 is categorized into a phonon-mediated BCS superconductor in the weak-coupling regime.

  9. Evidence for two superconducting gaps in MgB2.

    PubMed

    Chen, X K; Konstantinovic, M J; Irwin, J C; Lawrie, D D; Franck, J P

    2001-10-01

    We have measured the Raman spectra of polycrystalline MgB2 from 25 to 1200 cm(-1). A superconductivity-induced redistribution in the electronic Raman continuum was observed. Two pair-breaking peaks appear in the spectra, suggesting the presence of two superconducting gaps. The measured spectra were analyzed using a quasi-two-dimensional model in which two s-wave superconducting gaps open on two sheets of Fermi surface. For the gap values we have obtained Delta(1) = 22 cm(-1) ( 2.7 meV) and Delta(2) = 50 cm(-1) ( 6.2 meV). Our results suggest that a conventional phonon-mediated pairing mechanism occurs in the planar boron sigma bands and is responsible for the superconductivity of MgB2.

  10. Heterostructures of Bi-4334 and MgB2 superconductors

    NASA Astrophysics Data System (ADS)

    Padmavathi, M.; Singh, R.

    2016-05-01

    We report the studies on hetero structures of Bi-4334 and MgB2 superconductors. The two superconductors were arranged in the form of bulk multilayers using hydraulic pressure system. X-ray diffraction pattern and dc magnetization studies confirm the presence of both superconducting phases in this try-layer hetero structured sample. The d.c magnetization shows the superconducting onset at 77K and 39K for Bi-4334 and MgB2 phases respectively. Critical current density (Jc) is calculated from hysteresis loop of the sample in both in-plane field and out of plane field configurations. Inverted anisotropy in Jc is observed due to enhancement of ab-plane properties because of multilayer growth process. Morphology of the samples at surface and interface of two superconducting layers is discussed in view of Field emission scanning electron microscopy.

  11. Doublet 2800 MgII in close binary systems

    NASA Technical Reports Server (NTRS)

    Gurzadian, G. A.; Perez, M.

    1991-01-01

    The origin of the intercomponent ultraviolet emission from binary radio stars is discussed following an examination of observed emission parameters. Observations are used to consider four arguments which suggest that the Mg emission originates in the space between the components of the binary and not in the chromosphere. Parameters examined include the ratio of Mg emission to that of other binaries, the direct variation of emission with brightness strength, the derivation and nature of the radial velocity, and comparisons of absolute luminosities. Emission (A) and absorption (B) streams or clouds generate the emission, and the observed wavelength distortions are caused by B. An examination of the nature of the emission yields both qualitative and quantitative criteria, including the notion of weak ionization of the hydrogen atoms in B clouds relative to the ionization in A clouds.

  12. Active Protection of an MgB2 Test Coil

    PubMed Central

    Park, Dong Keun; Hahn, Seungyong; Bascuñán, Juan; Iwasa, Yukikazu

    2011-01-01

    This paper presents results of a study, experimental and computational, of a detect-and-activate-the-heater protection technique applied to a magnesium diboride (MgB2) test coil operated in semi-persistent mode. The test coil with a winding ID of 25 cm and wound with ~500-m long reacted MgB2 wire was operated at 4.2 K immersed in a bath of liquid helium. In this active technique, upon the initiation of a “hot spot” of a length ~10 cm, induced by a “quench heater,” a “protection heater” (PH) of ~600-cm long planted within the test coil is activated. The normal zone created by the PH is large enough to absorb the test coil’s entire initial stored energy and still keeps the peak temperature within the winding below ~260 K. PMID:22081754

  13. 33 CFR 80.1118 - Marina Del Rey, CA.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Marina Del Rey, CA. 80.1118... 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...

  14. 33 CFR 80.1118 - Marina Del Rey, CA.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Marina Del Rey, CA. 80.1118... 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...

  15. 33 CFR 80.1118 - Marina Del Rey, CA.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Marina Del Rey, CA. 80.1118... 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...

  16. 33 CFR 80.1118 - Marina Del Rey, CA.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Marina Del Rey, CA. 80.1118... 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...

  17. 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

  18. Flexible MgO Barrier Magnetic Tunnel Junctions.

    PubMed

    Loong, Li Ming; Lee, Wonho; Qiu, Xuepeng; Yang, Ping; Kawai, Hiroyo; Saeys, Mark; Ahn, Jong-Hyun; Yang, Hyunsoo

    2016-07-01

    Flexible MgO barrier magnetic tunnel junction (MTJ) devices are fabricated using a transfer printing process. The flexible MTJ devices yield significantly enhanced tunneling magnetoresistance of ≈300% and improved abruptness of switching, as residual strain in the MTJ structure is released during the transfer process. This approach could be useful for flexible electronic systems that require high-performance memory components. PMID:27119207

  19. Alpha inelastic scattering and cluster structures in {sup 24}Mg

    SciTech Connect

    Kawabata, T.; Ishiguro, Y.; Nozawa, Y.; Tomida, N.; Yokota, N.; Adachi, T.; Fujiwara, M.; Hatanaka, K.; Tamii, A.; Yasuda, Y.; Zenihiro, J.; Itoh, M.; Takahashi, T.; Yoshida, H. P.; Maeda, Y.; Miyasako, H.; Saito, T.; Matsubara, H.; Sasamoto, Y.; Tokieda, H.

    2011-05-06

    The alpha inelastic scattering from {sup 24}Mg was measured to obtain the isoscalar natural-parity excitation strengths and to search for the {alpha}-condensed states. The multipole decomposition analysis for the measured cross sections was performed. The strength distributions for the {Delta}L = 0-3 were successfully obtained and the possible candidates for the {alpha}-condensed states around the {sup 16}O core were found.

  20. Laboratory measurements for the astrophysical identification of MgH

    SciTech Connect

    Zink, L.R.; Jennings, D.A.; Evenson, K.M.; Leopold, K.R. Minnesota Univ., Minneapolis )

    1990-08-01

    A tunable far-infrared spectrometer has been used to observe the pure rotational spectrum of MgH in a DC discharge of H2 with magnesium. The frequencies of the hyperfine components of the N = 1 - 0 transition are predicted to an estimated accuracy of + or - 350 kHz, which should be sufficient for the astrophysical identification of this species. 6 refs.

  1. MAGIICAT I. THE Mg II ABSORBER-GALAXY CATALOG

    SciTech Connect

    Nielsen, Nikole M.; Churchill, Christopher W.; Kacprzak, Glenn G.; Murphy, Michael T.

    2013-10-20

    We describe the Mg II Absorber-Galaxy Catalog, MAGIICAT, a compilation of 182 spectroscopically identified intermediate redshift (0.07 ≤ z ≤ 1.1) galaxies with measurements of Mg II λλ2796, 2803 absorption from their circumgalactic medium within projected distances of 200 kpc from background quasars. In this work, we present 'isolated' galaxies, which are defined as having no spectroscopically identified galaxy within a projected distance of 100 kpc and a line of sight velocity separation of 500 km s{sup –1}. We standardized all galaxy properties to the ΛCDM cosmology and galaxy luminosities, absolute magnitudes, and rest-frame colors to the B- and K-band on the AB system. We present galaxy properties and rest-frame Mg II equivalent width, W{sub r} (2796), versus galaxy redshift. The well-known anti-correlation between W{sub r} (2796) and quasar-galaxy impact parameter, D, is significant to the 8σ level. The mean color of MAGIICAT galaxies is consistent with an Sbc galaxy for all redshifts. We also present B- and K-band luminosity functions for different W{sub r} (2796) and redshift subsamples: 'weak absorbing' [W{sub r} (2796) < 0.3 Å], 'strong absorbing' [W{sub r} (2796) ≥ 0.3 Å], low redshift (z < (z)), and high redshift (z ≥ (z)), where (z) = 0.359 is the median galaxy redshift. Rest-frame color B – K correlates with M{sub K} at the 8σ level for the whole sample but is driven by the strong absorbing, high-redshift subsample (6σ). Using M{sub K} as a proxy for stellar mass and examining the luminosity functions, we infer that in lower stellar mass galaxies, Mg II absorption is preferentially detected in blue galaxies and the absorption is more likely to be weak.

  2. Effect of Fe and Mg on crystallization in granitic systems

    SciTech Connect

    Naney, M.T.; Swanson, S.E.

    1980-07-01

    Single-step and multistep undercooling experiments using both Fe, Mg-free and Fe, Mg-bearing model granitic compositions were conducted to investigate the influence of mafic components on the crystallization of granitic melts. Crystallization of granite and granodiorite compositions in the system NaAlSi/sub 3/O/sub 8/-KAlSi/sub 3/O/sub 8/-CaAl/sub 2/Si/sub 2/O/sub 8/-SiO/sub 2/-H/sub 2/O produces assemblages containing one or more of the following phases: plagioclase, alkali feldspar, quartz, silicate liquid, and vapor. The observed phase assemblages are generally in good agreement with equilibrium data reported in the literature on the same bulk compositions. With the addition of Fe and Mg to these bulk compositions six new phases participate in the equilibria (orthopyroxene, clinopyroxene, biotite, hornblende,epidote, and magnetite). However, crystalline assemblages produced in phase equilibrium and crystal growth experiments brought to the same final P-T-X/sub H/sub 2/O/ conditions are in general not equivalent. Perhaps the addition of Fe and Mg has caused a breakdown of the Si-O framework in the melt, thereby promoting the more rapid nucleation of the ino- and phyllosilicates rather than the framework silicates. Border zones of granitic plutons, commonly rich in mafic minerals, may result from the more rapid nucleation of mafic phases from the silicate liquid. These zones are thought to develop by early crystallization along the walls of the pluton. Our results suggest the mafic phases should nucleate more quickly than the feldspars and quartz and thus should enrich the early crystallization products in ferromagnesian minerals.

  3. Phase Transitions of MgO Along the Hugoniot (Invited)

    NASA Astrophysics Data System (ADS)

    Root, S.; Shulenburger, L.; Lemke, R. W.; Cochrane, K. R.; Mattsson, T. R.

    2013-12-01

    The formation of terrestrial planets and planetary structure has become of great interest because of recent exoplanet discoveries of super earths. MgO is a major constituent of Earth's mantle, the rocky cores of gas giants such as Jupiter, and likely constitutes the interiors of many exoplanets. The high pressure - high temperature behavior of MgO directly affects equation of state models for planetary structure and formation. In this work, we examine single crystal MgO under shock compression utilizing experimental and density functional theory (DFT) methods to determine phase transformations along the Hugoniot. We perform plate impact experiments using Sandia's Z - facility on MgO up to 11.6 Mbar. The plate impact experiments generate highly accurate Hugoniot state data. The experimental results show the B1 - B2 solid - solid phase transition occurs near 4 Mbar on the Hugoniot. The solid - liquid transition is determined to be near 7 Mbar with a large region of B2-liquid coexistence. Using DFT methods, we also determine melt along the B1 and B2 solid phase boundaries as well as along the Hugoniot. The combined experimental and DFT results have determined the phase boundaries along the Hugoniot, which can be implemented into new planetary and EOS models. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Securities Administration under Contract No. DE-AC04-94AL85000.

  4. Superconductivity in MgB2 irradiated with energetic protons

    NASA Astrophysics Data System (ADS)

    Sandu, Viorel; Craciun, Liviu; Ionescu, Alina Marinela; Aldica, Gheorghe; Miu, Lucica; Kuncser, Andrei

    2016-09-01

    A series of MgB2 samples were irradiated with protons of 11.3 and 13.2 MeV. Magnetization data shows an insignificant reduction of the critical temperatures but a continuous decrease of the Meissner fraction with increasing fluence or energy. All samples show a consistent improvement of the critical current density compared to the virgin sample and an increase of the pinning energy at high fields as resulted from relaxation data.

  5. Enhanced magnetization at the Cr/MgO(001) interface

    SciTech Connect

    Leroy, M.-A.; Bataille, A. M. Ott, F.; Wang, Q.; Fitzsimmons, M. R.; Bertran, F.; Le Fèvre, P.; Taleb-Ibrahimi, A.; Vlad, A.; Coati, A.; Garreau, Y.; Hauet, T.; Andrieu, S.; Gatel, C.

    2015-12-21

    We report on the magnetization at the Cr/MgO interface, which we studied through two complementary techniques: angle-resolved photoemission spectroscopy and polarized neutron reflectivity. We experimentally observe an enhanced interface magnetization at the interface, yet with values much smaller than the ones reported so far by theoretical and experimental studies on Cr(001) surfaces. Our findings cast some doubts on the interpretations on previous works and could be useful in antiferromagnetic spin torque studies.

  6. Characterisation of Mg biodegradable stents produced by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Elmrabet, N.; Botterill, N.; Grant, D. M.; Brown, P. D.

    2015-10-01

    Novel Mg-minitubes for biodegradable stent applications have been produced using PVD magnetron sputtering. The minitubes were characterised, as a function of annealing temperature, using a combination of SEM/EDS, XRD and hardness testing. The as-deposited minitubes exhibited columnar grain structures with high levels of porosity. Slight alteration to the crystal structure from columnar to equiaxed grain growth was demonstrated at elevated temperature, along with increased material densification, hardness and corrosion resistance.

  7. 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.

  8. Theoretical studies on the two-dimensional electron-gas properties of MgZnO/MgO/ZnO heterostructures

    NASA Astrophysics Data System (ADS)

    Park, Seoung-Hwan; Hong, Woo-Pyo; Kim, Jong-Jae

    2016-07-01

    The polarization effects on the two-dimensional electron-gas (2DEG) of the ZnO/MgO/MgZnO heterostructure were theoretically investigated. The carrier confinement in the MgZnO/MgO/ZnO high-electron-mobility transistor (HEMT) structure is shown to be superior to that in the conventional MgZnO/ZnO HEMT structure. The electron density is shown to be very sensitive to the layer thickness and to become a maximum at a layer thickness of 2 nm. Also, the MgZnO/MgO/ZnO HEMT structure shows a larger saturation drain current than the conventional MgZnO/ZnO HEMT structure does. This is mainly due to the increased channel electron density induced by the enhanced polarization charge with the inclusion of the MgO layer.

  9. Vibronic Perturbations in the Electronic Spectrum of MgC

    NASA Astrophysics Data System (ADS)

    Lolur, Phalgun; Dawes, Richard; Heaven, Michael

    2014-06-01

    Accurate studies of the ground and low lying excited triplet pi-states of the covalently bonded alkaline earth metal carbides have been of interest to both theoreticians and experimentalists in the past few decades to understand their bonding. Diatomic beryllium carbide (BeC), which is valence iso-electronic with MgC, was probed by laser ablation and jet cooling techniques producing rotationally resolved data reported in a previous study.[1] Dynamically weighted MRCI calculations were used to construct adiabatic potential energy curves for the ground and the four lowest triplet pi-states up to 50,000 wn. From these, diabatic potentials and couplings were obtained and used to compute vibronic levels for the four interacting states. Here we apply the same methodology to MgC and examine the similarities and differences between the two systems. Results show significantly different bonding characteristics for the pi-states of MgC when compared to BeC. References: 1- B. J. Barker et al. J. Chem. Phys. 137, 214313 (2012).

  10. Automotive Mg Research and Development in North America

    SciTech Connect

    Carpenter, Joseph A.; Jackman, Jennifer; Li, Naiyi; Osborne, Richard J.; Powell, Bob R.; Sklad, Philip S

    2006-01-01

    Expanding world economic prosperity and probable peaking of conventional petroleum production in the coming decades require efforts to increase the efficiency of, and the development of alternatives to, petroleum-based fuels used in automotive transportation. North America has been aggressively pursuing both approaches for over ten years. Mainly as a result of lower prices due to global sourcing, magnesium has recently emerged as a serious candidate for lightweighting, and thus increasing the fuel efficiency of, automotive transportation. Automotive vehicles produced in North America currently use more Mg than vehicles produced elsewhere in the world, but the amounts per vehicle are very small in comparison to other materials such as steel, aluminum and plastics. The reasons, besides price, are primarily a less-developed state of technology for Mg in automotive transportation applications and lack of familiarity by the vehicle manufacturers with the material. This paper reviews some publicly-known, recent, present and future North American research and development activities in Mg for automotive applications.

  11. Grain boundary mobility in anion doped MgO

    NASA Technical Reports Server (NTRS)

    Kapadia, C. M.; Leipold, M. H.

    1973-01-01

    Certain anions OH(-), F(-) and Gl(-) are shown to enhance grain growth in MgO. The magnitude of their effect decreases in the order in which the anions are listed and depends on their location (solid-solution, second phase) in the MgO lattice. As most anions exhibit relatively high vapor pressures at sintering temperatures, they retard densification and invariably promote residual porosity. The role of anions on grain growth rates was studied in relation to their effect on pore mobility and pore removal; the atomic process controlling the actual rates was determined from observed kinetics in conjunction with the microstructural features. With respect to controlling mechanisms, the effects of all anions are not the same. OH(-) and F(-) control behavior through creation of a defect structure and a grain boundary liquid phase while Cl(-) promotes matter transport within pores by evaporation-condensation. Studies on an additional anion, S to the minus 2nd power gave results which were no different from undoped MgO, possibly because of evaporative losses during hot pressing. Hence, the effect of sulphur is negligible or undetermined.

  12. Synthesis and characterization of Mn intercalated Mg-Al hydrotalcite.

    PubMed

    Yang, Chengxue; Liao, Libing; Lv, Guocheng; Wu, Limei; Mei, Lefu; Li, Zhaohui

    2016-10-01

    Mn intercalated hydrotalcite was prepared using a reconstruction method. And Mn intercalation was confirmed by XRD, FTIR, and thermal analyses. The different valences of Mn were present as determined by XPS. Calcination slightly promoted the isomorphic replacement of Mn(2+) and Mn(3+) for Mg(2+) and Al(3+), especially the replacement of Mn(2+) for Mg(2+) and Al(3+), and to some extent, reduced Mn intercalation. Ultrasonic treatment significantly increased Mn intercalation in permanganate form (Mn(7+)), and promoted the replacement of Mn(2+) for Mg(2+) and Al(3+). XRF analysis showed that ultrasonic treatment decreased the unbalanced layer charge of Mn intercalated hydrotalcite, while prolonged calcination increased it. These results may provide guidance on the preparation and application of Mn intercalated hydrotalcite. Extended calcination time and ultrasonic vibration increased the interlayer spacing of hydrotalcite, as a result of reduction in layer charge. As the layer charge was not completely balanced after Mn intercalation, a certain amount of CO3(2-) was re-adsorbed into the interlayer space. Mn-hydrotalcites with different layer charges, different contents of Mn with varying valences are expected to have different performances in the process of adsorption, degradation, and catalysis. PMID:27380016

  13. The electric dipole moment of magnesium deuteride, MgD

    SciTech Connect

    Steimle, Timothy C. Zhang, Ruohan; Wang, Hailing

    2014-06-14

    The (0,0) A{sup 2}Π–X {sup 2}Σ{sup +} band of a cold molecular beam sample of magnesium monodeuteride, MgD, has been recorded field-free and in the presence of a static electric field of up to 11 kV/cm. The lines associated with the lowest rotational levels are detected for the first time. The field-free spectrum was analyzed to produce an improved set of fine structure parameters for the A{sup 2}Π (v = 0) state. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments, μ{sup -vector}{sub el} of 2.567(10)D and 1.31(8)D for A{sup 2}Π (v = 0) and X{sup 2}Σ{sup +}(v = 0) states, respectively. The recommended value for μ{sup -vector}{sub el}(X{sup 2}Σ{sup +} (v = 0)) for MgH, based upon the measured value for MgD, is 1.32(8)D.

  14. Fine-Filament MgB2 Superconductor Wire

    NASA Technical Reports Server (NTRS)

    Cantu, Sherrie

    2015-01-01

    Hyper Tech Research, Inc., has developed fine-filament magnesium diboride (MgB2) superconductor wire for motors and generators used in turboelectric aircraft propulsion systems. In Phase I of the project, Hyper Tech demonstrated that MgB2 multifilament wires (<10 micrometers) could reduce alternating current (AC) losses that occur due to hysteresis, eddy currents, and coupling losses. The company refined a manufacturing method that incorporates a magnesium-infiltration process and provides a tenfold enhancement in critical current density over wire made by a conventional method involving magnesium-boron powder mixtures. Hyper Tech also improved its wire-drawing capability to fabricate fine multifilament strands. In Phase II, the company developed, manufactured, and tested the wire for superconductor and engineering current density and AC losses. Hyper Tech also fabricated MgB2 rotor coil packs for a superconducting generator. The ultimate goal is to enable low-cost, round, lightweight, low-AC-loss superconductors for motor and generator stator coils operating at 25 K in next-generation turboelectric aircraft propulsion systems.

  15. Dipole defects in Al2O3:Mg,Cr.

    PubMed

    Blak, A R; Gobbi, V; Ayres, F

    2002-01-01

    In this work, dipole defects are investigated applying the thermally stimulated depolarisation currents (TSDC) technique. The TSDC spectra of Al2O3 doped with Mg and Cr show two bands centred at 230 K and 250 K, respectively. The maximum intensity of the bands increases linearly with the polarisation field, a typical behaviour of defects with dipole origin. An increase of the band at 250 K with gamma irradiation has been observed and a thermal decrease of the bands for heat treatments between 1000 K and 1400 K. Above this temperature the bands are partially recovered. Impurity neutron activation analysis shows that magnesium. chromium and iron content varies from 15 to 60 ppm. Optical absorption (AO) measurements show a broad band centred in 2.6 eV (21000 cm(-1)) associated with trapped holes localised on an O- ion adjacent to a cation site which is deficient in positive charge. It has been assumed that a substitutional Mg2+ ion occupies the cation site near a trapped hole on one of the six oxygen ions surrounding the magnesium impurity giving rise to the dipole responsible for the observed TSDC bands. Calculations carried out through defect simulation methods confirm that the probability of Al3+ being replaced by Mg2+ is higher than Mn2+, Co2+, Fe2+ and Cr2+. PMID:12382829

  16. The electric dipole moment of magnesium deuteride, MgD

    NASA Astrophysics Data System (ADS)

    Steimle, Timothy C.; Zhang, Ruohan; Wang, Hailing

    2014-06-01

    The (0,0) A2Π-X 2Σ+ band of a cold molecular beam sample of magnesium monodeuteride, MgD, has been recorded field-free and in the presence of a static electric field of up to 11 kV/cm. The lines associated with the lowest rotational levels are detected for the first time. The field-free spectrum was analyzed to produce an improved set of fine structure parameters for the A2Π (v = 0) state. The observed electric field induced splittings and shifts were analyzed to produce permanent electric dipole moments, ěc μ _{el} of 2.567(10)D and 1.31(8)D for A2Π (v = 0) and X2Σ+(v = 0) states, respectively. The recommended value for ěc μ _{el}(X2Σ+ (v = 0)) for MgH, based upon the measured value for MgD, is 1.32(8)D.

  17. Optical properties of MgO irradiated by fast neutrons

    NASA Astrophysics Data System (ADS)

    Okada, M.; Seiyama, T.; Ichihara, C.; Nakagawa, M.

    1985-08-01

    Optical properties of color centers in MgO single crystals irradiated by fission neutrons (Kyoto University Reactor, KUR) and by 14 MeV neutrons (RTNS-II, at Lawrence Livermore National Laboratory, LLNL) have been investigated. The absorption spectra of MgO crystals irradiated by neutrons from the two different sources are similar; exhibited principal bands are 250 nm band consisting of F and F + bands, 352 (F 2 center), 570 and 975 (F 2 center) nm bands. In the samples irradiated by fission neutrons, the absorption intensity of the 570 nm band does not reach a maximum by neutron fluence through which the F and F 2 type bands reach a maximum. These phenomena are remarkable in the impurity-doped samples. A linear increase of the intensity of the 570 nm band with a dose of fast neutrons does not change with impurity contents, and exists in the extensive range examined of fast neutron dose (10 15-10 19 n/cm 2). This fact suggests that the crystalline MgO can be applied as a fluence monitor for fast neutrons with extensive energy.

  18. Synthesis and characterization of Mn intercalated Mg-Al hydrotalcite.

    PubMed

    Yang, Chengxue; Liao, Libing; Lv, Guocheng; Wu, Limei; Mei, Lefu; Li, Zhaohui

    2016-10-01

    Mn intercalated hydrotalcite was prepared using a reconstruction method. And Mn intercalation was confirmed by XRD, FTIR, and thermal analyses. The different valences of Mn were present as determined by XPS. Calcination slightly promoted the isomorphic replacement of Mn(2+) and Mn(3+) for Mg(2+) and Al(3+), especially the replacement of Mn(2+) for Mg(2+) and Al(3+), and to some extent, reduced Mn intercalation. Ultrasonic treatment significantly increased Mn intercalation in permanganate form (Mn(7+)), and promoted the replacement of Mn(2+) for Mg(2+) and Al(3+). XRF analysis showed that ultrasonic treatment decreased the unbalanced layer charge of Mn intercalated hydrotalcite, while prolonged calcination increased it. These results may provide guidance on the preparation and application of Mn intercalated hydrotalcite. Extended calcination time and ultrasonic vibration increased the interlayer spacing of hydrotalcite, as a result of reduction in layer charge. As the layer charge was not completely balanced after Mn intercalation, a certain amount of CO3(2-) was re-adsorbed into the interlayer space. Mn-hydrotalcites with different layer charges, different contents of Mn with varying valences are expected to have different performances in the process of adsorption, degradation, and catalysis.

  19. Mg(PF6)2-Based Electrolyte Systems: Understanding Electrolyte-Electrode Interactions for the Development of Mg-Ion Batteries.

    PubMed

    Keyzer, Evan N; Glass, Hugh F J; Liu, Zigeng; Bayley, Paul M; Dutton, Siân E; Grey, Clare P; Wright, Dominic S

    2016-07-20

    Mg(PF6)2-based electrolytes for Mg-ion batteries have not received the same attention as the analogous LiPF6-based electrolytes used in most Li-ion cells owing to the perception that the PF6(-) anion decomposes on and passivates Mg electrodes. No synthesis of the Mg(PF6)2 salt has been reported, nor have its solutions been studied electrochemically. Here, we report the synthesis of the complex Mg(PF6)2(CH3CN)6 and its solution-state electrochemistry. Solutions of Mg(PF6)2(CH3CN)6 in CH3CN and CH3CN/THF mixtures exhibit high conductivities (up to 28 mS·cm(-1)) and electrochemical stability up to at least 4 V vs Mg on Al electrodes. Contrary to established perceptions, Mg electrodes are observed to remain electrochemically active when cycled in the presence of these Mg(PF6)2-based electrolytes, with no fluoride (i.e., MgF2) formed on the Mg surface. Stainless steel electrodes are found to corrode when cycled in the presence of Mg(PF6)2 solutions, but Al electrodes are passivated. The electrolytes have been used in a prototype Mg battery with a Mg anode and Chevrel (Mo3S4)-phase cathode.

  20. Mg(PF6)2-Based Electrolyte Systems: Understanding Electrolyte-Electrode Interactions for the Development of Mg-Ion Batteries.

    PubMed

    Keyzer, Evan N; Glass, Hugh F J; Liu, Zigeng; Bayley, Paul M; Dutton, Siân E; Grey, Clare P; Wright, Dominic S

    2016-07-20

    Mg(PF6)2-based electrolytes for Mg-ion batteries have not received the same attention as the analogous LiPF6-based electrolytes used in most Li-ion cells owing to the perception that the PF6(-) anion decomposes on and passivates Mg electrodes. No synthesis of the Mg(PF6)2 salt has been reported, nor have its solutions been studied electrochemically. Here, we report the synthesis of the complex Mg(PF6)2(CH3CN)6 and its solution-state electrochemistry. Solutions of Mg(PF6)2(CH3CN)6 in CH3CN and CH3CN/THF mixtures exhibit high conductivities (up to 28 mS·cm(-1)) and electrochemical stability up to at least 4 V vs Mg on Al electrodes. Contrary to established perceptions, Mg electrodes are observed to remain electrochemically active when cycled in the presence of these Mg(PF6)2-based electrolytes, with no fluoride (i.e., MgF2) formed on the Mg surface. Stainless steel electrodes are found to corrode when cycled in the presence of Mg(PF6)2 solutions, but Al electrodes are passivated. The electrolytes have been used in a prototype Mg battery with a Mg anode and Chevrel (Mo3S4)-phase cathode. PMID:27359196

  1. Facile synthesis and regeneration of Mg(BH4)2 by high energy reactive ball milling of MgB2.

    PubMed

    Gupta, Shalabh; Hlova, Ihor Z; Kobayashi, Takeshi; Denys, Roman V; Chen, Fu; Zavaliy, Ihor Y; Pruski, Marek; Pecharsky, Vitalij K

    2013-01-28

    We report direct hydrogenation of MgB(2) in a planetary ball mill. Magnesium borohydride, Mg(BH(4))(2), and various polyhedral borane anion salts have been synthesized at pressures between 50 and 350 bar H(2) without the need for subsequent isothermal hydrogenation at elevated temperature and pressure. The obtained products release ∼4 wt% H(2) below 390 °C, and a major portion of Mg(BH(4))(2) transforms back to MgB(2) at around 300 °C, demonstrating the possibility of reversible hydrogen storage in an Mg(BH(4))(2)-MgB(2) system.

  2. Improving the EUV reflectivity of Mg/SiC multilayers by inserting Zr barrier layers at the SiC-on-Mg interfaces

    NASA Astrophysics Data System (ADS)

    Huang, Shuiping; Ji, Bei; Zhou, Jun; Li, Haochuan; Zhu, Jingtao

    2016-10-01

    In Mg/SiC multilayer deposition, the SiC-on-Mg interfaces were found to be much more diffused than the Mg-on-SiC interfaces. By inserting Zr barrier layers at the SiC-on-Mg interfaces, the diffusion at interface can be suppressed. The Mg/SiC multilayers were deposited by magnetron sputtering method, and were characterized by X-ray reflectometry and reflectometer of National Synchrotron Radiation Laboratory of China, respectively. Results show that 0.5-nm-thick Zr barrier layers can dramatically reduce the interdiffusion at the SiC-on-Mg interfaces.

  3. Comparison of a single end point to determine optimal initial warfarin dosing (5 mg versus 10 mg) for venous thromboembolism.

    PubMed

    Quiroz, Rene; Gerhard-Herman, Marie; Kosowsky, Joshua M; DeSantis, Stacia M; Kucher, Nils; McKean, Sylvia C; Goldhaber, Samuel Z

    2006-08-15

    There remains considerable controversy regarding optimal initial warfarin dosing in patients with acute venous thromboembolism. Therefore, an open-label, randomized trial comparing 2 warfarin initiation nomograms (5 vs 10 mg) was conducted in patients with acute venous thromboembolism. All participants received fondaparinux for > or = 5 days as a "bridge" to warfarin. The primary end point was defined as the number of days necessary to achieve 2 consecutive international normalized ratio laboratory test values > 1.9. A total of 50 patients were enrolled and randomly assigned to each of the treatment arms. The median time to 2 consecutive international normalized ratios was 5 days in the 2 groups. There was no statistical difference in achieving the primary end point using either the 5- or the 10-mg nomogram (p = 0.69). These results should provide clinicians with increased warfarin dosing options in patients presenting with acute venous thromboembolism.

  4. Spin Polarization of Mg-23 in Mg-24 + Au, Cu and Al Collisions at 91 A MeV

    NASA Technical Reports Server (NTRS)

    Matsuta, K.; Fukuda, S.; Izumikawa, T.; Tanigaki, M.; Fukuda, M.; Nakazato, M.; Mihara, M.; Onishi, T.; Yamaguchi, T.; Miyake, T.

    1994-01-01

    Spin polarization of beta-emitting fragment Mg-23(I(sup pi) = 3/2(sup +), T(sub 1/2 = l1.3 s) produced through the projectile fragmentation process in Mg-24 + Au, Cu and Al collisions has been observed at 91 AMeV. General trend in the observed momentum dependence of polarization is reproduced well qualitatively by a simple fragmentation model based on the participant-spectator picture, for heavy and light targets. However the polarization behavior differs from this model in tern of zero crossing momentum, which become prominent in the case of Cu target, where the polarization is not monotone function of the fragment momentum.

  5. High-power high-brightness solar laser approach for renewable Mg recovery from MgO

    NASA Astrophysics Data System (ADS)

    Almeida, Joana; Liang, Dawei

    2014-08-01

    Hydrogen and heat energy from the reaction of magnesium with water can be used for engines and fuel cells. However, at least 4000 K is necessary for magnesium oxide reduction. Ultra high brightness solar-pumped lasers become essential to make this renewable process technology efficient and economically competitive. 2.3 mg/kJ solar laser - induced magnesium production efficiency has been achieved by T. Yabe et al., in 2012, by focusing a 53 W solar laser beam on a mixture of MgO with Si as reducing agent. This result is however far from the 12.1 mg/kJ attained with 2 kW/mm2 CO2 laser beam. To improve substantially the solar laser - induced Mg production efficiency, a simple high-power, high brightness Nd:YAG solar laser pumping approach is proposed. The solar radiation is both collected and concentrated by four Fresnel lenses, and redirected towards a Nd:YAG laser head by four plane folding mirrors. A fused-silica secondary concentrator is used to compress the highly concentrated solar radiation to a laser rod. Optimum pumping conditions and laser resonator parameters are found through ZEMAXand LASCADnumerical analysis. High-record solar laser beam brightness figure of merit - defined as the ratio between laser power and the product of Mx 2 and My 2 - of 10.5 W is numerically achieved, being 5.5 times higher than the previous record and about 1600 times more than that of the most powerful Nd:YAG solar laser. 8340 W/mm2 is numerically achieved at its focal region, which can quadruple the magnesium production efficiency with clean energy.

  6. Evaluation of thermochemical data on Fe-Mg olivine, orthopyroxene, spinel and Ca-Fe-Mg-Al garnet

    SciTech Connect

    Chatterjee, N.

    1987-09-01

    Thermochemical data on Fe-Mg olivine, orthopyroxene, spinel and Ca-Fe-Mg garnet have been tested and reevaluated in reproducing experimental equilibrium data. All data (except of spinel) adjusted in this process lie within the error limits of original calorimetric experiments. For spinel, an enthalpy of -2307.2 kJmol and an entropy of 81.5 Jmol-K has been recommended. Recommended interaction parameters for the spinel-hercynite and forsterite-fayalite solutions are as follows: Spinel: W/sub (spinel-hercynite)/= 9124.0 Jmol. W/sub (hercynite-spinel)/ = 0.0 Jmol. Olivine: W = 4500.0 Jmol for 1 cation. Excess entropies (on 1 cation basis) necessary to reproduce phase equilibria for the pyrope-almandine and almandine-grossular solutions are as follows: Mg-Fe garnet: Wsub(pyrope-almandine) = 11.760 - 0.0016T Jmol-K. Wsub(almandine-pyrope) = -10.146 + 0.0037T Jmol-K. Fe-Ca garnet: W/sup s/ = -16.07 + 0.0126T Jmol-K.

  7. Volatile magnesium octahydrotriborate complexes as potential CVD precursors to MgB2. Synthesis and characterization of Mg(B3H8)2 and its etherates.

    PubMed

    Kim, Do Young; Yang, Yu; Abelson, John R; Girolami, Gregory S

    2007-10-29

    The solid-state reaction of MgBr2 and NaB3H8 at 20 degrees C, followed by sublimation at 80 degrees C and 0.05 Torr, affords Mg(B3H8)2 as a white solid. Similar reactions with MgBr2(Et2O) and MgBr2(Me2O)1.5 afford the crystalline ether adducts Mg(B3H8)2(Et2O)2 and Mg(B3H8)2(Me2O)2, respectively. In contrast, reactions of MgBr2 with NaB3H8, the presence of excess solvent result in the formation of nonvolatile, probably ionic, magnesium compounds of the type [MgLx][B3H8]2. The adducts Mg(B3H8)2(Et2O)2 and Mg(B3H8)2(Me2O)2 are the first crystallographically characterized magnesium complexes of the B3H8- ligand; in both structures, the magnesium center adopts a distorted cis-octahedral geometry with two bidentate B3H8 groups and two Et2O ligands. Owing to their volatility, Mg(B3H8)2(Et2O)2 and Mg(B3H8)2(Me2O)2 are potential precursors for the deposition of MgB2 thin films, although preliminary efforts to employ them as chemical vapor deposition sources produce boron-rich MgBx films instead, with x approximately 7. Finally, the synthesis and structure of Cp2Mg(thf) are described: this mono-thf adduct of Cp2Mg bears two eta5-Cp groups, unlike other Lewis base adducts of Cp2Mg, which contain one eta5-Cp group and one eta1- or eta2-Cp group.

  8. 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

  9. Electron microscopy of Mg/TiO{sub 2} photocatalyst morphology for deep desulfurization of diesel

    SciTech Connect

    Yin, Yee Cia; Kait, Chong Fai Fatimah, Hayyiratul Wilfred, Cecilia

    2015-07-22

    A series of Mg/TiO{sub 2} photocatalysts were prepared and characterized using Field Emission Scanning Electron Microscopy (FESEM) and High-Resolution Transmission Electron Microscopy (HRTEM). The average particle sizes of the photocatalysts were ranging from 25.7 to 35.8 nm. Incorporation of Mg on TiO{sub 2} did not lead to any surface lattice distortion to TiO{sub 2}. HRTEM data indicated the presence of MgO and Mg(OH){sub 2} mixture at low Mg loading while at higher Mg loading, the presence of lamellar Mg-oxyhydroxide intermediates and Mg(OH){sub 2}.

  10. Effect of excess Mg and nano-additives on the superconducting properties of weakly connected bulk MgB2

    NASA Astrophysics Data System (ADS)

    Bhadauria, P. P. S.; Gupta, Anurag; Kishan, Hari; Narlikar, A. V.

    2013-02-01

    Series of ex-situ polycrystalline MgB2 bulk samples, by adding different additives like more of excess Mg (5 wt. %), nanoparticles of Ag (3 wt. %), and SiC (10 wt. %) to a previously optimized composition MgB2 + Mg (5 wt. %), were prepared by solid state synthesis route. Detailed investigations were carried out by XRD, SEM, and thermoelectric power S(T), resistivity ρ(T), and magnetization M(B) at temperatures T = 4.2-300 K and applied fields B = 0-8 T. All the samples typically show low connectivity (i.e., normal state current carrying cross section ˜0.9%-3%). The effect of different additives was different on the critical current density (Jc) of the samples. The Jc, for instance at T = 4.2 K and B = 1 T, varied between 4.8 × 107 and 2.8 × 108 A/m2 for various samples. In comparison to the previously optimized values, the Jc was enhanced by further addition of 5 wt. % Mg and degraded both by nano-SiC and nano-Ag addition. However, many of the other properties of the samples were not much affected. For instance, the samples did not show any change in the superconducting onsets, S(T) and the parallel upper critical field (Bc2|| (T) ˜ 11-13 T at 20 K and 20-21 T at 4.2 K). The Jc(B) dependence also shows similar behavior in all the samples, where the Jc is found to scale as B-1 up to a sample independent crossover field Bcr ˜ 2 T and 1.3 T at T = 4.2 and 20 K, respectively. At higher fields B > Bcr, the Jc(B) curves branch out and decrease rapidly towards zero at a sample dependent characteristic field. We try to understand these results quantitatively in terms of changes in connectivity, pinning, and anisotropy driven percolation. However, all our results and analysis point out that the intra-particle regions stay unaffected and mainly the inter-particle regions get affected by the additives leading to the Jc variation in the weakly connected samples.

  11. Multistage growth of Fe-Mg-carpholite and Fe-Mg-chloritoid, from field evidence to thermodynamic modelling

    NASA Astrophysics Data System (ADS)

    Pourteau, Amaury; Bousquet, Romain; Vidal, Olivier; Plunder, Alexis; Duesterhoeft, Erik; Candan, Osman; Oberhänsli, Roland

    2015-04-01

    We provide new insights into the prograde evolution of HP/LT meta-sedimentary rocks on the basis of detailed petrologic examination, element-partitioning analysis, and thermodynamic modelling of well-preserved Fe-Mg-carpholite- and chloritoid-bearing rocks from the Afyon zone (Anatolia). Study samples, stemming from three different areas of the metamorphic belt, include typical quartz-carpholite veins as well as quartz-free and quartz-bearing phyllites. All samples exhibit multiple stages of carpholite, whereas zoning was until now rarely documented in this type of rocks. We document continuous, and discontinuous compositional (ferro-magnesian substitution) zoning of carpholite (overall XMg = 0.27-0.73) and chloritoid (overall XMg = 0.07-0.30), as well as clear equilibrium, and disequilibrium (i.e. reaction-related) textures involving carpholite and chloritoid, which consistently account for the consistent enrichment in Mg of both minerals through time, and the progressive replacement of carpholite by chloritoid. Mg/Fe distribution coefficients calculated between carpholite and chloritoid vary widely within samples (2.2-20.0). Among this range, only values of 7-11 correlate with equilibrium textures, in agreement with data from the literature. Equilibrium phase diagrams for (NaK)FMASH rock compositions are calculated using a newly modified thermodynamic dataset, including most recent data for carpholite, chloritoid, chlorite, and white mica, as well as further refinements for Fe-carpholite, and both chloritoid end-members, as required to reproduce accurately petrologic observations (phase relations, experimental constraints, Mg/Fe partitioning). Modelling reveals that Mg/Fe partitioning between carpholite and chloritoid is greatly sensitive to temperature, and calls for a future evaluation of possible use as a thermometer, valid for blueschist-facies conditions, which has so far been missing. In addition, calculations show significant effective bulk composition

  12. Estudio muestra importancia de conversaciones tempranas sobre el cuidado en etapa final de la vida

    Cancer.gov

    Artículo sobre la importancia de hablar en forma temprana sobre el cuidado paliativo para asegurar que la atención prestada en la etapa final de la vida sea más acorde con las preferencias de los pacientes.

  13. The magnesium isotope (δ26Mg) signature of dolomites

    NASA Astrophysics Data System (ADS)

    Geske, A.; Goldstein, R. H.; Mavromatis, V.; Richter, D. K.; Buhl, D.; Kluge, T.; John, C. M.; Immenhauser, A.

    2015-01-01

    Dolomite precipitation models and kinetics are debated and complicated due to the complex and temporally fluctuating fluid chemistry and different diagenetic environments. Using well-established isotope systems (δ18O, δ13C, 87Sr/86Sr), fluid inclusions and elemental data, as well as a detailed sedimentological and petrographic data set, we established the precipitation environment and subsequent diagenetic pathways of a series of Proterozoic to Pleistocene syn-depositional marine evaporative (sabkha) dolomites, syn-depositional non-marine evaporative (lacustrine and palustrine) dolomites, altered marine ("mixing zone") dolomites and late diagenetic hydrothermal dolomites. These data form the prerequisite for a systematic investigation of dolomite magnesium isotope ratios (δ26Mgdol). Dolomite δ26Mg ratios documented here range, from -2.49‰ to -0.45‰ (δ26Mgmean = -1.75 ± 1.08‰, n = 42). The isotopically most depleted end member is represented by earliest diagenetic marine evaporative sabkha dolomites (-2.11 ± 0.54‰ 2σ, n = 14). In comparing ancient compositions to modern ones, some of the variation is probably due to alteration. Altered marine (-1.41 ± 0.64‰ 2σ, n = 4), and earliest diagenetic lacustrine and palustrine dolomites (-1.25 ± 0.86‰ 2σ, n = 14) are less negative than sabkha dolomites but not distinct in composition. Various hydrothermal dolomites are characterized by a comparatively wide range of δ26Mg ratios, with values of -1.44 ± 1.33‰ (2σ, n = 10). By using fluid inclusion data and clumped isotope thermometry (Δ47) to represent temperature of precipitation for hydrothermal dolomites, there is no correlation between fluid temperature (∼100 to 180 °C) and dolomite Mg isotope signature (R2 = 0.14); nor is there a correlation between δ26Mgdol and δ18Odol. Magnesium-isotope values of different dolomite types are affected by a complex array of different Mg sources and sinks, dissolution/precipitation and non

  14. Rutherford Backscattering and Channeling Studies of Mg and Fe Diffusion at the Interface of gamma-Fe₂O₃(001)/MgO(001)

    SciTech Connect

    Thevuthasan, Suntharampillai; Jiang, Weilin; McCready, David E.; Chambers, Scott A.

    1999-12-01

    Investigates the crystalline quality of an epitaxially grown gamma-FeO(001) film on Mg/O(001) substrate along with the Mg and Fe inter-diffusion using Rutherford Backscattering and channeling experiments.

  15. OBSERVED VARIABILITY OF THE SOLAR Mg II h SPECTRAL LINE

    SciTech Connect

    Schmit, D.; Pontieu, B. De; Bryans, P.; McIntosh, S.; Leenaarts, J.; Carlsson, M.

    2015-10-01

    The Mg ii h and k doublet are two of the primary spectral lines observed by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These lines are tracers of the magnetic and thermal environment that spans from the photosphere to the upper chromosphere. We use a double-Gaussian model to fit the Mg ii h profile for a full-Sun mosaic data set taken on 2014 August 24. We use the ensemble of high-quality profile fits to conduct a statistical study on the variability of the line profile as it relates the magnetic structure, dynamics, and center-to-limb viewing angle. The average internetwork profile contains a deeply reversed core and is weakly asymmetric at h2. In the internetwork, we find a strong correlation between h3 wavelength and profile asymmetry as well as h1 width and h2 width. The average reversal depth of the h3 core is inversely related to the magnetic field. Plage and sunspots exhibit many profiles that do not contain a reversal. These profiles also occur infrequently in the internetwork. We see indications of magnetically aligned structures in plage and network in statistics associated with the line core, but these structures are not clear or extended in the internetwork. The center-to-limb variations are compared to predictions of semi-empirical model atmospheres. We measure a pronounced limb darkening in the line core that is not predicted by the model. The aim of this work is to provide a comprehensive measurement baseline and preliminary analysis on the observed structure and formation of the Mg ii profiles observed by IRIS.

  16. MG Isotopic Measurement of FIB-Isolated Presolar Silicate Grains

    NASA Technical Reports Server (NTRS)

    Messenger, Scott R.; Nguyen, A.; Ito, M.; Rahman, Z.

    2010-01-01

    The majority of presolar oxide and silicate grains are ascribed to origins in low-mass red giant and asymptotic giant branch (AGB) stars based on their O isotopic ratios. However, a minor population of these grains (< 10%) has O isotopic ratios incompatible with these sources. Two principle alternative sources are higher-than-solar metallicity (Z) stars or, more likely, supernovae (SN) [1-3]. These rare (Group 4) grains [3] are characterized by enrichments in O-18, and typically also enrichments in O-17. An even rarer subset of grains with extremely large enrichments in O-17 and smaller depletions in O-18 were suggested to come from binary star systems [2]. To establish the origins of these isotopically unusual grains, it is necessary to examine isotopic systems in addition to O. Presolar silicates offer several elements diagnostic of their stellar sources and nuclear processes, including O, Si, Mg, Fe and Ca. However, the database for minor element isotopic compositions in silicates is seriously lacking. To date only two silicate grains have been analyzed for Mg [4] or Fe [5]. One major complicating factor is their small size (average 230 nm), which greatly limits the number of measurements that can be performed on any one grain and makes it more difficult to obtain statistically relevant data. This problem is compounded because the grains are identified among isotopically solar silicates, which contribute a diluting signal in isotopic measurements [1]. Thus, relatively small isotopic anomalies are missed due to this dilution effect. By applying focused ion beam (FIB) milling, we obtain undiluted Mg isotopic ratios of isolated rare presolar silicate grains to investigate their sources.

  17. Observed Variability of the Solar Mg II h Spectral Line

    NASA Astrophysics Data System (ADS)

    Schmit, D.; Bryans, P.; De Pontieu, B.; McIntosh, S.; Leenaarts, J.; Carlsson, M.

    2015-10-01

    The Mg ii h&k doublet are two of the primary spectral lines observed by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These lines are tracers of the magnetic and thermal environment that spans from the photosphere to the upper chromosphere. We use a double-Gaussian model to fit the Mg ii h profile for a full-Sun mosaic data set taken on 2014 August 24. We use the ensemble of high-quality profile fits to conduct a statistical study on the variability of the line profile as it relates the magnetic structure, dynamics, and center-to-limb viewing angle. The average internetwork profile contains a deeply reversed core and is weakly asymmetric at h2. In the internetwork, we find a strong correlation between h3 wavelength and profile asymmetry as well as h1 width and h2 width. The average reversal depth of the h3 core is inversely related to the magnetic field. Plage and sunspots exhibit many profiles that do not contain a reversal. These profiles also occur infrequently in the internetwork. We see indications of magnetically aligned structures in plage and network in statistics associated with the line core, but these structures are not clear or extended in the internetwork. The center-to-limb variations are compared to predictions of semi-empirical model atmospheres. We measure a pronounced limb darkening in the line core that is not predicted by the model. The aim of this work is to provide a comprehensive measurement baseline and preliminary analysis on the observed structure and formation of the Mg ii profiles observed by IRIS.

  18. A MgB2 superferric racetrack magnet

    NASA Astrophysics Data System (ADS)

    Musenich, R.; Sorbi, M.; Tavilla, G.; Volpini, G.; Marabotto, R.; Modica, M.; Nardelli, D.

    2008-10-01

    A magnesium diboride, cryogen-free, H-dipole magnet with cold iron yoke was constructed and tested. The racetrack coil, 48 cm long, was wound with 350 m of nickel-clad, copper-MgB2 tape. The iron yoke forms a 2.6 cm gap. The magnet was connected to a cryocooler and tested at different temperatures ranging between 8.5 and 24 K. The maximum current, 263 A, was reached, without training, at 8.5 K. The corresponding field in the gap was 2.35 T.

  19. Neutron irradiation of MgB2 bulk superconductors

    SciTech Connect

    Eisterer, M; Zehetmayer, M; Tonies, S; Weber, H W.; Kambara, M; Babu, N H.; Cardwell, D A.; Greenwood, Lawrence R. )

    2001-12-01

    Sintered samples of MgB2 were irradiated in a fission reactor. Defects in the bulk microstructure are produced during this process mainly by the 10B(n,a7Li) reaction while collisions of fast neutrons with the lattice atoms induce much less damage. Self-shielding effects turn out to be very important and lead to a highly inhomogeneous defect distribution in the irradiated samples. The resulting disorder enhances the normal state resistivity and the upper critical field. The irreversibility line shifts to higher fields at low temperatures and the measured critical current densities increase following irradiation.

  20. Superconductivity in MgB2: clean or dirty?

    PubMed

    Mazin, I I; Andersen, O K; Jepsen, O; Dolgov, O V; Kortus, J; Golubov, A A; Kuz'menko, A B; Van Der Marel, D

    2002-09-01

    A large number of experimental facts and theoretical arguments favor a two-gap model for superconductivity in MgB2. However, this model predicts strong suppression of the critical temperature by interband impurity scattering and, presumably, a strong correlation between the critical temperature and the residual resistivity. No such correlation has been observed. We argue that this fact can be understood if the band disparity of the electronic structure is taken into account, not only in the superconducting state, but also in normal transport.

  1. Two-band superconductivity in MgB2.

    PubMed

    Iavarone, M; Karapetrov, G; Koshelev, A E; Kwok, W K; Crabtree, G W; Hinks, D G; Kang, W N; Choi, Eun-Mi; Kim, Hyun Jung; Kim, Hyeong-Jin; Lee, S I

    2002-10-28

    The study of the anisotropic superconductor MgB2 using a combination of scanning tunneling microscopy and spectroscopy reveals two distinct energy gaps at Delta(1)=2.3 meV and Delta(2)=7.1 meV at 4.2 K. Different spectral weights of the partial superconducting density of states are a reflection of different tunneling directions in this multiband system. Temperature evolution of the tunneling spectra follows the BCS scenario [Phys. Rev. Lett. 3, 552 (1959)

  2. Phonon dispersion and lifetimes in MgB2.

    PubMed

    Shukla, Abhay; Calandra, Matteo; D'Astuto, Matteo; Lazzeri, Michele; Mauri, Francesco; Bellin, Christophe; Krisch, Michael; Karpinski, J; Kazakov, S M; Jun, J; Daghero, D; Parlinski, K

    2003-03-01

    We measure phonon dispersion and linewidth in a single crystal of MgB2 along the Gamma-A, Gamma-M, and A-L directions using inelastic x-ray scattering. We use density functional theory to compute the effect of both electron-phonon coupling and anharmonicity on the linewidth, obtaining excellent agreement with experiment. Anomalous broadening of the E(2g) phonon mode is found all along Gamma-A. The dominant contribution to the linewidth is always the electron-phonon coupling.

  3. The Evolution of ONeMg Cores with MESA

    NASA Astrophysics Data System (ADS)

    Schwab, Josiah; Quataert, Eliot; Bildsten, Lars

    2015-01-01

    We present calculations of the evolution of degenerate cores composed primarily of oxygen, neon, and magnesium which are undergoing compression. We make use of the state-of-the-art MESA stellar evolution code, with updated weak reaction rates from Martinez-Pinedo et al. (2014). We perform a detailed parameter study of the effects a number of quantities, including the accretion rate, magnesium mass fraction, and initial core temperature. We discuss the final fate of these ONeMg cores, focusing on cores formed as a result of the merger of two carbon-oxygen white dwarfs.

  4. Electronic structure and thermoelectric properties of (Mg2X)2 / (Mg2Y)2 (X, Y = Si, Ge, Sn) superlattices from first-principle calculations

    NASA Astrophysics Data System (ADS)

    Guo, San-Dong

    2016-05-01

    To identify thermoelectric materials containing abundant, low-cost and non-toxic elements, we have studied the electronic structures and thermoelectric properties of (Mg2X)2/ (Mg2Y)2 (X, Y = Si, Ge, Sn) superlattices with state-of-the-art first-principles calculations using a modified Becke and Johnson (mBJ) exchange potential. Our results show that (Mg2Ge)2/ (Mg2Sn)2 and (Mg2Si)2/ (Mg2Sn)2 are semi-metals using mBJ plus spin-orbit coupling (mBJ + SOC), while (Mg2Si)2/ (Mg2Ge)2 is predicted to be a direct-gap semiconductor with a mBJ gap value of 0.46 eV and mBJ + SOC gap value of 0.44 eV. Thermoelectric properties are predicted by through solving the Boltzmann transport equations within the constant scattering time approximation. It is found that (Mg2Si)2/ (Mg2Ge)2 has a larger Seebeck coefficient and power factor than (Mg2Ge)2/ (Mg2Sn)2 and (Mg2Si)2/ (Mg2Sn)2 for both p-type and n-type doping. The detrimental influence of SOC on the power factor of p-type (Mg2X)2/ (Mg2Y)2 (X, Y = Si, Ge, Sn) is analyzed as a function of the carrier concentration, but there is a negligible SOC effect for n-type. These results can be explained by the influence of SOC on their valence and conduction bands near the Fermi level.

  5. 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

  6. Microstructure and dielectric tunable properties of Ba0.6Sr0.4TiO3-Mg2SiO4-MgO composite.

    PubMed

    He, Yanyan; Xu, Yebin; Liu, Ting; Zeng, Chunlian; Chen, Wanping

    2010-07-01

    Ba(0.6)Sr(0.4)TiO(3)-Mg(2)SiO(4)-MgO composite ceramics were prepared by a solid-state reaction method and their dielectric tunable characteristics were investigated for the potential application as microwave tunable materials. The addition of Mg(2)SiO(4)-MgO into Ba(0.6)Sr(0.4)TiO(3) forms ferroelectric (Ba(0.6)Sr(0.4)TiO(3))-dielectric (Mg(2)SiO(4)-MgO) composites and shifts the Curie temperature to a lower temperature. The dielectric constant and loss tangent of Ba(0.6)Sr(0.4)TiO(3)-Mg(2)Si(O4)- MgO composites have been decreased and the overall tunability is maintained at a sufficiently high level. The microwave dielectric properties of Ba(0.6)Sr(0.4)TiO(3)-Mg(2)Si(O4)-MgO composites were evaluated. Ba(0.6)Sr(0.4)TiO(3)-Mg(2)SiO(4)-MgO composites have tunability of 9.2 to 10.5% at 100 kHz under 2 kV/mm, indicating that it is a promising candidate material for tunable microwave applications requiring a low dielectric constant.

  7. 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.

  8. Epidemiological surveillance of ovine hydatidosis in Tierra del Fuego, Patagonia Argentina, 1997-1999.

    PubMed

    Zanini, Fabián; Gonzalo, Roberto; Pérez, Héctor; Aparici, Inés; Soto, Ximena; Guerrero, Juvenal; Cerrone, Gloria; Elissondo, Celina

    2006-06-15

    Cystic echinococcosis is the most prevalent zoonosis in Tierra del Fuego province, Argentina, with important economic, productive and public health consequences. The present work was performed to determine the ovine prevalence in Tierra del Fuego, Argentina, as well as to evaluate the quality of diagnostic systems in slaughterhouses. Moreover, genetic analyses to characterize the strain of Echinococcus granulosus involved in the region were done. The first actions to perform a diagnosis of the epidemiological situation of hydatidosis in Tierra del Fuego were done between 1976 and 1977. A canine prevalence of 80% and an ovine prevalence of 55% results were obtained. Since 1979 the control program of Hydatidosis of Tierra del Fuego was implemented. It was based on semiannual canine anthelmintic treatment with praziquantel at dose of 5mg/kg, and complemented with sanitary education and canine and ovine epidemiological surveillance. During May 1997-January 1999: 5,916 sheep coming from 20 farms of the programmatic area were evaluated. In the lamb category, hydatid cysts were not found. In the adults category, 62 infected animals were found (3.2%). The ovine prevalence was 1.1% and there was 100% of coincidence between diagnosis in the slaughterhouse, re-inspection in the laboratory and histopathological study. The marked decrease in the prevalence observed for sheep infection evidenced a destabilization of the biological cycle of the parasite. This could be explained by the application of a control program with uninterrupted systematic actions. Polymerase chain reaction-ribosomal ITS-1 DNA (rDNA) restriction fragment length polymorphism (PCR-RFLP) analysis and partial sequencing of the mitochondrial cytochrome c oxidase subunit 1 (CO1) gene were used to characterize E. granulosus isolates collected from different regions of Tierra del Fuego to determine which genotypes occurred in this region. The results revealed the presence of the G1 genotype (sheep-dog strain

  9. Zn2Mg alkaline phosphatase in an early ptolemeic mummy.

    PubMed

    Kaup, Y; Baumer, U; Koller, J; Hedges, R E; Werner, H; Hartmann, H J; Etspüler, H; Weser, U

    1994-01-01

    Bone samples of a ptolemeic mummy have been employed to study the mode of conservation on the intactness of Zn2Mg alkaline phosphatase in both structure and catalytic activity. A protein of M(r) = 190 +/- 10 kDa being identical to the 200 kDa enzyme of fresh human bones was successfully isolated. Regardless of age 200 kDa protein bands and a distinct subunit at 60 kDa were seen in SDS-PAGE electrophoresis. The 200 kDa band was also monitored by activity staining. The specific activity was 120 mU/mg and 65% of the respective activity obtained in the identical preparation using fresh human tibia or rib. The enzymic activity was inhibited in the presence of 1,10-phenanthroline and L-homoarginine. Radiocarbon dating supported the assignment of the mummy to the early ptolemeic period. Among the many bactericidal and fungicidal components employed for mummification were aromatic alcohols, mono- and sesquiterpenes. Pistachio resin was the major balm resin used. The microbiological sterility of the bone surface was ascertained by independent bacterial and fungal examinations.

  10. Chemically Sensitive Imaging of MgP with STM

    NASA Astrophysics Data System (ADS)

    Yu, Arthur; Li, Shaowei; Czap, Greg; Ho, Wilson

    2014-03-01

    Since its invention, the STM has been limited by its lack of sensitivity to chemical structures in molecules. Recent advances in scanning probe microscopy techniques, such as non-contact AFM and scanning tunneling hydrogen microscopy have enabled imaging of the internal structure and bonding of aromatic molecules such as pentacene and PTCDA. Here, we present a novel method of using the STM to image magnesium porphyrin molecules adsorbed on Au(110) with chemical sensitivity. In our previous study, we have shown that hydrogen molecules weakly adsorb on Au(110), exhibiting both vibrational and rotational IETS spectra. Exploiting the sensitivity of the vibrational and rotational mode energies to the local chemical environment, we perform dI/dV and d2I/dV2 imaging at different bias voltages, highlighting the various parts of the MgP molecule. In particular, we are able to image the positions of the nitrogen atoms in MgP. d2I/dV2 spectral mapping reveals that the origin of the chemical sensitivity comes from an energy shift of the rotational peak as the tip is scanned across the molecule, indicating a changing potential landscape for the H2. Similar d2I/dV2 imaging with a CO terminated tip reveals no chemical sensitivity to nitrogen.

  11. Ab initio simulations of MgO under extreme conditions

    NASA Astrophysics Data System (ADS)

    Cebulla, Daniel; Redmer, Ronald

    2014-04-01

    We determined the phase diagram of magnesium oxide with finite-temperature density functional theory molecular dynamics simulations up to temperatures and pressures as relevant for the deep interior of super-Earths and in rocky cores of giant planets such as Jupiter. The equation of state data, the Hugoniot, and a ramp compression curve are computed and compared to earlier results from diamond anvil cell and (decaying) shock wave experiments. In addition, the dynamical electrical conductivity and the reflectivity along the experimental Hugoniot curve are calculated in order to characterize electronic structure changes under compression. The structural properties of MgO are identified using pair correlation functions and self-diffusion coefficients. The solid-solid coexistence line is calculated by comparing the free enthalpies of the B1 and the B2 phase. The free energy of the solid phases is determined via thermodynamic relations using the ab initio simulation results and phonon calculations in the harmonic approximation. Our results indicate that the solid B2 phase of MgO does not occur in the interior of the Earth but may play an important role in super-Earths and in rocky planetary cores.

  12. Vortex-flux anomalies in MgB 2 polycrystals

    NASA Astrophysics Data System (ADS)

    Goeckner, H. P.; Claus, H.; Kouvel, J. S.

    2005-02-01

    For two MgB 2 polycrystalline samples prepared differently, magnetic hysteresis loops at 4.2 K revealed some striking magnetization ( M) anomalies at low magnetic fields ( H). In one sample, M drops abruptly by an amount that diminishes to zero as the maximum M, reached just before the drop, is reduced below a critical value (by reducing the slowly cycled H). The remanent magnetization ( Mrem), measured as the temperature ( T) was slowly raised from 4.2 K to Tc (39 K), was seen to decrease very rapidly just above 4.2 K and then remain constant up to ∼20 K, where it starts to descend gradually to zero at Tc. A similar set of anomalies was observed with the second sample, but where the hysteretic drop of M is rapid but not abrupt. However, both samples showed that the vortex-flux component of M remains nearly constant over a range of H just before the rapid drop of M, indicating that the vortices in the sample stay fairly constant in number before many of them exit the sample rapidly. For both MgB 2 samples, this whole set of anomalous properties disappears at temperatures above 5 K, where the slow steady descent of Mrem as T increases to Tc indicates that the size distribution of vortex pinning forces extends up to very high values.

  13. Novel Co:MgF2 lidar for aerosol profiler

    NASA Technical Reports Server (NTRS)

    Acharekar, M. A.

    1993-01-01

    Lidars are of great interest because of their unique capabilities in remote sensing applications in sounding of the atmosphere, meteorology, and climatology. In this small business innovative research (SBIR) phase II program, laser sources including Co:MgF2, CTH:YAG, CTH:YSGG, CT:YAG, and Er:Glass were evaluated. Modulator of fused silica and TeO2 materials with Brewster's angle end faces were used with these lasers as acousto-optical (AO) Q-switches. A higher hold-off energy and hence a higher Q-switched energy was obtained by using a high power RF driver. The report provides performance characteristics of these lasers. The tunable (1.75-2.50 microns) Co:MgF2 laser damaged the TeO2 Q-switch cell. However, the CTH:YAG laser operating at 2.09 microns provided output energy of over 300 mJ/p in 50 ns pulse width using the fused silica Q-switch. This Q-switched CTH:YAG laser was used in a breadboard vertical aerosol profiler. A 40 cm diameter telescope, InSb and InGaAs detectors were used in the receiver. The data obtained using this lidar is provided in the report. The data shows that the eye safe lidar using CTH:YAG laser for the vertical aerosol density and range measurements is the viable approach.

  14. Characterization of MgB2 Superconducting Hot Electron Bolometers

    NASA Technical Reports Server (NTRS)

    Cunnane, D.; Kawamura, J. H.; Wolak, M. A.; Acharya, N.; Tan, T.; Xi, X. X.; Karasik, B. S.

    2014-01-01

    Hot-Electron Bolometer (HEB) mixers have proven to be the best tool for high-resolution spectroscopy at the Terahertz frequencies. However, the current state of the art NbN mixers suffer from a small intermediate frequency (IF) bandwidth as well as a low operating temperature. MgB2 is a promising material for HEB mixer technology in view of its high critical temperature and fast thermal relaxation allowing for a large IF bandwidth. In this work, we have fabricated and characterized thin-film (approximately 15 nanometers) MgB2-based spiral antenna-coupled HEB mixers on SiC substrate. We achieved the IF bandwidth greater than 8 gigahertz at 25 degrees Kelvin and the device noise temperature less than 4000 degrees Kelvin at 9 degrees Kelvin using a 600 gigahertz source. Using temperature dependencies of the radiation power dissipated in the device we have identified the optical loss in the integrated microantenna responsible as a cause of the limited sensitivity of the current mixer devices. From the analysis of the current-voltage (IV) characteristics, we have derived the effective thermal conductance of the mixer device and estimated the required local oscillator power in an optimized device to be approximately 1 microwatts.

  15. Low-noise THz MgB2 Josephson mixer

    NASA Astrophysics Data System (ADS)

    Cunnane, Daniel; Kawamura, Jonathan H.; Acharya, Narendra; Wolak, Matthäus A.; Xi, X. X.; Karasik, Boris S.

    2016-09-01

    The potential applications for high frequency operation of the Josephson effect in MgB2 include THz mixers, direct detectors, and digital circuits. Here we report on MgB2 weak links which exhibit the Josephson behavior up to almost 2 THz and using them for low-noise heterodyne detection of THz radiation. The devices are made from epitaxial film grown in the c-axis direction by the hybrid physical-chemical vapor deposition method. The current in the junctions travels parallel to the surface of the film, thus making possible a large contribution of the quasi-two-dimensional σ-gap in transport across the weak link. These devices are connected to a planar spiral antenna with a dielectric substrate lens to facilitate coupling to free-space radiation for use as a detector. The IcRn product of the junction is 5.25 mV, giving confirmation of a large gap parameter. The sensitivity of the mixer was measured from 0.6 THz to 1.9 THz. At a bath temperature of over 20 K, a mixer noise temperature less than 2000 K (DSB) was measured near 0.6 THz.

  16. Multilayer MgB2 superconducting quantum interference filter magnetometers

    NASA Astrophysics Data System (ADS)

    Galan, Elias; Melbourne, Thomas; Davidson, Bruce A.; Xi, X. X.; Chen, Ke

    2016-04-01

    We report two types of all-MgB2 superconductive quantum interference filter (SQIF) magnetometers that can measure absolute magnetic fields with high sensitivity. In one configuration, the SQIFs were made of 20 multilayer nonplanar all-MgB2 superconducting quantum interference devices (SQUIDs) connected in parallel with loop areas ranging in size from 0.4 to 3.6 μm2. These devices are sensitive to magnetic fields parallel to the substrate and show a single antipeak from 3 to 16 K with a maximum transfer function of ˜16 V/T at 3 K and a field noise of ˜110 pT/Hz1/2 above 100 Hz at 10 K. In a second configuration, the SQIFs were made with 16 planar SQUIDs connected in parallel with loop areas ranging in size from 4 μm2 to 25 μm2 and are sensitive to the magnetic fields perpendicular to the substrate. The planar SQIF shows a single antipeak from 10 to 22 K with a maximum transfer function of 7800 V/T at 10 K and a field noise of ˜70 pT/Hz1/2 above 100 Hz at 20 K.

  17. Density Functional Study of Perovskite Superconductor MgCNi3

    NASA Astrophysics Data System (ADS)

    Kumar, Jagdish; Sharma, Devina; Kumar, Ranjan; Awana, V. P. S.; Ahluwalia, P. K.

    2011-12-01

    We here report the first principle density functional study of MgCNi3 which crystallize in cubic perovskite structure having critical transition temperature of 8 K. The interesting aspect of this compound is that in normal state it is non magnetic in nature despite conduction electrons in it are derived from partially filled Ni d states, which typically lead to ferromagnetism in metallic Ni and many Ni-based binary alloys. To investigate the detailed microscopic origin of the non magnetic nature we have done density functional based calculations on this compound. The lattice constant is calculated using minimum energy criteria from total energy versus lattice constant plot. By taking the calculated values of lattice constant we have done the precise calculations on the compound using Full Potential Linear Augmented Plane Wave (FP-LAPW) method implemented in ELK code. The electronic density of states is found spin degenerate that corresponds to a non-magnetic ground state. The density of states (DOS) at Fermi level, N(EF) is dominated by Ni-d states. The sharp peak observed just below Fermi level corresponds to van Hove singularity (vHs). The projected density of states (PDOS) suggests a strong hybridization of Ni-3d and C-2p states which is responsible for the observed non magnetic nature of MgCNi3.

  18. Antibacterial polyelectrolyte-coated Mg alloys for biomedical applications

    NASA Astrophysics Data System (ADS)

    Seraz, Md. S.; Asmatulu, R.; Chen, Z.; Ceylan, M.; Mahapatro, A.; Yang, S. Y.

    2014-04-01

    This study deals with two biomedical subjects: corrosion rates of polyelectrolyte-coated magnesium (Mg) alloys, mainly used for biomedical purposes, and antibacterial properties of these alloys. Thin sheets of Mg alloys were coated with cationic polyelectrolyte chitosan (CHI) and anionic polyelectrolyte carboxymethyl cellulose (CMC) using a layer-by-layer coating method and then embedded with antibacterial agents under vacuum. Electrochemical impedance spectroscopy was employed to analyze these samples in order to detect their corrosion properties at different conditions. In the electrochemical analysis section, a corrosion rate of 72 mille inches per year was found in a salt solution for the sample coated with a 12 phosphonic acid self-assembled monolayer and 9 CHI/CMC multilayers. In the antibacterial tests, gentamicin was used to investigate the effects of the drug embedded with the coated surfaces against the Escherichia coli (E. coli) bacteria. Antibacterial studies were tested using the disk diffusion method. Based on the standard diameter of the zone of inhibition chart, the antibacterial diffusion from the surface strongly inhibited bacterial growth in the regions. The largest recorded diameter of the zone of inhibition was 50 mm for the pre-UV treated and gentamicin-loaded sample, which is more than three times the standard diameter.

  19. Al-26-Mg-26 ages of iron meteorites

    NASA Technical Reports Server (NTRS)

    Herzog, G. F.; Souzis, A. E.; Xue, S.; Klein, J.; Juenemann, D.; Middleton, R.

    1993-01-01

    An exposure age for an iron meteorite can be calculated from measurements of a radioactive nuclide and a stable nuclide that are produced by similar sets of nuclear reactions, provided that the stable nuclide is present with low initial abundance. The standard methods rely on either K-40 (t(sub 1/2) = 1.26 Gy), K-39, and K-41 or on a shorter-lived radionuclide and a stable, noble gas isotope. Widely used pairs of this type include Cl-36/Ar-36 and Al-26/Ne-21. Other pairs that may serve the purpose for iron meteorites contain many stable isotopes besides those of K and the noble gases that are produced partly by cosmic rays. We consider here the calculation of exposure ages, t(sub 26), from measurements of Al-26 (t(sub 1/2) = 0.7 My) and (stable) Mg-26. Ages based on Al-26/Mg-26 ratios, like those based on Cl-36/Ar-36 ratios, are 'buffered' against changes in relative production rates due to shielding because decay of the radioactive nuclide accounts for a good part of the inventory of the stable nuclide.

  20. Preparation of MgH{sub 2} composite with a composition of 40%MgH{sub 2} + 30%LiBH{sub 4} + 30%(2LiBH{sub 4} + MgF{sub 2})

    SciTech Connect

    Hong, Seong-Hyeon; Song, Myoung Youp

    2012-09-15

    Graphical abstract: Hydrogen content vs. desorption time curves for consecutive 1st desorptions of 40 wt%MgH{sub 2} + 30 wt%LiBH{sub 4} + 30 wt%(2LiBH{sub 4} + MgF{sub 2}) at 533–873 K. Highlights: ► Addition of MgF{sub 2} and LiBH{sub 4} with a higher hydrogen storage capacity to MgH{sub 2}. ► Preparation of 40%MgH{sub 2} + 30%LiBH{sub 4} + 30% (2LiBH{sub 4} + MgF{sub 2}) composite. ► Examination of desorption properties of the composite. ► Total desorbed hydrogen quantity for consecutive 1st desorptions of 7.07 wt%. ► Reactions of LiBH{sub 4} → LiH + B + (3/2)H{sub 2}, and 2LiBH{sub 4} + MgF{sub 2} → 2LiF + MgB{sub 2} + 4H{sub 2}. -- Abstract: A mixture of containing two chemical equivalents of lithium borohyride and one equivalent of magnesium fluoride is known to yield hydrogen in an amount of about 7.6 wt% of the mixture when heated to about 150 °C at atmospheric pressure by the following reaction; 2LiBH{sub 4} + MgF{sub 2} = 2LiF + MgB{sub 2} + 4H{sub 2}. In order to increase hydrogen storage capacity of Mg-based materials, a mixture with a composition of 2LiBH{sub 4} + MgF{sub 2} and LiBH{sub 4}with a higher hydrogen storage capacity of 18.4 wt% were added to MgH{sub 2}. MgH{sub 2} composite with a composition of 40 wt%MgH{sub 2} + 30 wt%LiBH{sub 4} + 30 wt%(2LiBH{sub 4} + MgF{sub 2}) was prepared by reactive mechanical grinding. The hydrogen storage properties of the sample were then examined. Hydrogen content vs. desorption time curves for consecutive 1st desorptions of 40 wt%MgH{sub 2} + 30 wt%LiBH{sub 4} + 30 wt%(2LiBH{sub 4} + MgF{sub 2}) at 533–873 K showed that the total desorbed hydrogen quantity for consecutive 1st desorptions is 7.07 wt%.

  1. Sexual asthenia: Tradamixina versus Tadalafil 5 mg daily

    PubMed Central

    2012-01-01

    Background Reduced libido is widely considered the most prominent symptomatic reflection of low testosterone (T) levels in men. Testosterone deficiency (TD) afflicts approximately 30% of men aged 40-79 years. This study seeks to evaluate the effect of a new natural compound “tradamixina “in order to improve male sexual function in elderly men, particularly libido and possible erectile dysfunction, versus administration of tadalafil 5 mg daily. Methods Seventy patients (67.3± 3.7 years) with stable marital relations and affected by reduced libido, with or without erectile dysfunction were recruited. They were randomly separated in 2 groups A-B of 35. Group A was administered twice a day a new compound “Tradamixina” (150 mg of Alga Ecklonia Bicyclis, 396 mg of Tribulus Terrestris and 144 mg of D-Glucosamine and N-Acetyl-D-Glucosamine) for two months, while Group B was administered tadalafil 5 mg daily, for two months. At visit and after 60 days of treatment patients were evaluated by means of detailed medical and sexual history, clinical examination, laboratory investigations (Total and Free T), instrumental examination (NPTR- nocturnal penile tumescence and rigidity test- with Rigiscan). Patients completed a self-administered IIEF questionnaire (The international index of erectile function) and SQoLM questionnaire (Sexual quality of life Questionnarie-Male). The results pre and post treatment were compared by Student t test (p<0.005). Results After 2 months of treatment in group A serum TT levels (230±18 ng/dl vs 671±14 ng/dl ) and FT levels(56± 2.4 pg/ml vs 120± 3.9pg/ml) increased, while in group B serum TT levels (245±12 ng/dl vs 247±15 ng/dl ) and FT levels(53± 0.3 pg/ml vs 55± 0.5pg/ml) increased not statistically significant. The patient’s numbers with negative NPTR improved after treatment in group A and B (15 vs 18 and 13 vs 25 respectively). The IIEF total score in group A increased after treatment with tradamixina (15±1.5 vs 29.77±1

  2. 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**.

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

    PubMed Central

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

    2016-01-01

    Background: 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. Methods: 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. Results: On day 1, peak observed plasma concentration (Cmax) 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. Conclusions: While systemic exposure (AUC) was 25% lower with ODT, peak concentrations (Cmax) 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. PMID:27803732

  4. Thermoelectric properties of n-Type Mg2Si-Mg2Sn solid solutions with different grain sizes

    NASA Astrophysics Data System (ADS)

    Samunin, A. Yu.; Zaitsev, V. K.; Pshenay-Severin, D. A.; Konstantinov, P. P.; Isachenko, G. N.; Fedorov, M. I.; Novikov, S. V.

    2016-08-01

    Influence of the grain sizes on thermoelectric parameters of pressurized solid solutions of the composition Mg2Si0.8Sn0.2 was studied. The Seebeck coefficient, electric conductivity, thermal conductivity, and Hall coefficient were determined. Decreasing the grain size to the nanoscale was found to decrease the mobility at low temperatures and resulted in a peculiar temperature dependence of the electric conductivity, but did not lead to a decrease in the thermo EMF. It was found that the grain size had no effect on the thermoelectric efficiency of the investigated solid solution in the operating temperature range.

  5. Prediction of novel stable compounds in the Mg-Si-O system under exoplanet pressures.

    PubMed

    Niu, Haiyang; Oganov, Artem R; Chen, Xing-Qiu; Li, Dianzhong

    2015-01-01

    The Mg-Si-O system is the major Earth and rocky planet-forming system. Here, through quantum variable-composition evolutionary structure explorations, we have discovered several unexpected stable binary and ternary compounds in the Mg-Si-O system. Besides the well-known SiO2 phases, we have found two extraordinary silicon oxides, SiO3 and SiO, which become stable at pressures above 0.51 TPa and 1.89 TPa, respectively. In the Mg-O system, we have found one new compound, MgO3, which becomes stable at 0.89 TPa. We find that not only the (MgO)x · (SiO2)y compounds, but also two (MgO3)x · (SiO3)y compounds, MgSi3O12 and MgSiO6, have stability fields above 2.41 TPa and 2.95 TPa, respectively. The highly oxidized MgSi3O12 can form in deep mantles of mega-Earths with masses above 20 M⊕ (M⊕:Earth's mass). Furthermore, the dissociation pathways of pPv-MgSiO3 are also clarified, and found to be different at low and high temperatures. The low-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ SiO2 + Mg2SiO4 ⇒ MgO + SiO2, while the high-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ MgO + MgSi2O5 ⇒ MgO + SiO2. Present results are relevant for models of the internal structure of giant exoplanets, and for understanding the high-pressure behavior of materials.

  6. Prediction of novel stable compounds in the Mg-Si-O system under exoplanet pressures.

    PubMed

    Niu, Haiyang; Oganov, Artem R; Chen, Xing-Qiu; Li, Dianzhong

    2015-01-01

    The Mg-Si-O system is the major Earth and rocky planet-forming system. Here, through quantum variable-composition evolutionary structure explorations, we have discovered several unexpected stable binary and ternary compounds in the Mg-Si-O system. Besides the well-known SiO2 phases, we have found two extraordinary silicon oxides, SiO3 and SiO, which become stable at pressures above 0.51 TPa and 1.89 TPa, respectively. In the Mg-O system, we have found one new compound, MgO3, which becomes stable at 0.89 TPa. We find that not only the (MgO)x · (SiO2)y compounds, but also two (MgO3)x · (SiO3)y compounds, MgSi3O12 and MgSiO6, have stability fields above 2.41 TPa and 2.95 TPa, respectively. The highly oxidized MgSi3O12 can form in deep mantles of mega-Earths with masses above 20 M⊕ (M⊕:Earth's mass). Furthermore, the dissociation pathways of pPv-MgSiO3 are also clarified, and found to be different at low and high temperatures. The low-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ SiO2 + Mg2SiO4 ⇒ MgO + SiO2, while the high-temperature pathway is MgSiO3 ⇒ Mg2SiO4 + MgSi2O5 ⇒ MgO + MgSi2O5 ⇒ MgO + SiO2. Present results are relevant for models of the internal structure of giant exoplanets, and for understanding the high-pressure behavior of materials. PMID:26691903

  7. New CeMgCo{sub 4} and Ce{sub 2}MgCo{sub 9} compounds: Hydrogenation properties and crystal structure of hydrides

    SciTech Connect

    Denys, R.V.; Riabov, A.B.; Cerny, R.; Koval'chuk, I.V.; Zavaliy, I.Yu.

    2012-03-15

    Two new ternary intermetallic compounds, CeMgCo{sub 4} (C15b pseudo-Laves phase, MgCu{sub 4}Sn type) and Ce{sub 2}MgCo{sub 9} (substitution derivative of PuNi{sub 3} type) were synthesized by mechanical alloying method. The structural and hydrogenation properties of these compounds were studied by X-ray diffraction and Pressure-Composition-Temperature measurements. Both compounds absorb hydrogen at room temperature and pressures below 10 MPa forming hydrides with maximum compositions CeMgCo{sub 4}H{sub 6} and Ce{sub 2}MgCo{sub 9}H{sub 12}. Single plateau behavior was observed in P-C isotherm during hydrogen absorption/desorption by Ce{sub 2}MgCo{sub 9} alloy. The CeMgCo{sub 4}-H{sub 2} system is characterized by the presence of two absorption/desorption plateaus corresponding to formation of {beta}-CeMgCo{sub 4}H{sub 4} and {gamma}-CeMgCo{sub 4}H{sub 6} hydride phases. The structure of {beta}-hydride CeMgCo{sub 4}H(D){sub 4} was determined from X-ray and neutron powder diffraction data. In this structure initial cubic symmetry of CeMgCo{sub 4} is preserved and hydrogen atoms fill only one type of interstitial sites, triangular MgCo{sub 2} faces. These positions are occupied by 70% and form octahedron around Mg atom with Mg-D bond distances 1.84 A. - Graphical abstract: Crystal structure of the {beta}-CeMgCo{sub 4}D{sub 4.2} deuteride. Octahedra of D-sites around Mg atoms are shown. Highlights: Black-Right-Pointing-Pointer Two new ternary compounds have been synthesized in the Ce-Mg-Co system. Black-Right-Pointing-Pointer Below 100 bar H{sub 2} CeMgCo{sub 4} and Ce{sub 2}MgCo{sub 9} reversibly absorb hydrogen at room temperature. Black-Right-Pointing-Pointer Crystal structure of cubic CeMgCo{sub 4}D{sub 4.2} deuteride has been determined.

  8. The Role of MgCl2 as a Lewis Base in ROMgCl-MgCl2 Electrolytes for Magnesium-Ion Batteries.

    PubMed

    Pan, Baofei; Huang, Jinhua; He, Meinan; Brombosz, Scott M; Vaughey, John T; Zhang, Lu; Burrell, Anthony K; Zhang, Zhengcheng; Liao, Chen

    2016-03-21

    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/Mg(2+)). 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.

  9. Possibility of Mg- and Ca-based intermetallic compounds as new biodegradable implant materials.

    PubMed

    Hagihara, Koji; Fujii, Kenta; Matsugaki, Aira; Nakano, Takayoshi

    2013-10-01

    Mg- or Ca-based intermetallic compounds of Mg2Ca, Mg2Si, Ca2Si and CaMgSi are investigated as possible new candidates for biodegradable implant materials, attempting to improve the degradation behavior compared to Mg and Ca alloys. The reactivity of Ca can be indeed reduced by the formation of compounds with Mg and Si, but its reactivity is still high for applications as an implant material. In contrast, Mg2Si shows a higher corrosion resistance than conventional Mg alloys while retaining biodegradability. In cytotoxicity tests under the severe condition conducted in this study, both pure Mg and Mg2Si showed relatively high cytotoxicity on preosteoblast MC3T3-E1. However, the cell viability cultured in the Mg2Si extract medium was confirmed to be better than that in a pure Mg extract medium in all the conditions investigated with the exception of the 10% extract medium, because of the lower corrosion rate of Mg2Si. The cytotoxicity derived from the Si ion was not significantly detected in the Mg2Si extract medium in the concentration level of ~70 mg/l measured in the present study. For aiming the practical application of Mg2Si as an implant material, however, its brittle nature must be improved.

  10. 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

  11. In vitro biocompatibility of Ti-Mg alloys fabricated by direct current magnetron sputtering.

    PubMed

    Hieda, Junko; Niinomi, Mitsuo; Nakai, Masaaki; Cho, Ken

    2015-09-01

    Ti-xMg (x=17, 33, and 55 mass%) alloy films, which cannot be prepared by conventional melting processes owing to the absence of a solid-solution phase in the phase diagram, were prepared by direct current magnetron sputtering in order to investigate their biocompatibility. Ti and Mg films were also prepared by the same process for comparison. The crystal structures were examined by X-ray diffraction (XRD) analysis and the surfaces were analyzed by X-ray photoelectron spectroscopy. The Ti, Ti-xMg alloy, and Mg films were immersed in a 0.9% NaCl solution at 310 K for 7d to evaluate the dissolution amounts of Ti and Mg. In addition, to evaluate the formation ability of calcium phosphate in vitro, the Ti, Ti-xMg alloy, and Mg films were immersed in Hanks' solution at 310 K for 30 d. Ti and Mg form solid-solution alloys because the peaks attributed to pure Ti and Mg do not appear in the XRD patterns of any of the Ti-xMg alloy films. The surfaces of the Ti-17 Mg alloy and Ti-33 Mg alloy films contain Ti oxides and MgO, whereas MgO is the main component of the surface oxide of the Ti-55 Mg alloy and Mg films. The dissolution amounts of Ti from all films are below or near the detection limit of inductively coupled plasma-optical emission spectroscopy. On the other hand, the Ti-17 Mg alloy, Ti-33 Mg alloy, Ti-55 Mg alloy, and Mg films exhibit Mg dissolution amounts of approximately 2.5, 1.4, 21, and 41 μg/cm(2), respectively. The diffraction peaks attributed to calcium phosphate are present in the XRD patterns of the Ti-33 Mg alloy, Ti-55 Mg alloy, and Mg films after the immersion in Hanks' solution. Spherical calcium phosphate particles precipitate on the surface of the Ti-33 Mg film. However, many cracks are observed in the Ti-55 Mg film, and delamination of the film occurs after the immersion in Hanks' solution. The Mg film is dissolved in Hanks' solution and calcium phosphate particles precipitate on the glass substrate. Consequently, it is revealed that the Ti-33 Mg

  12. Epitaxial orientation of Mg{sub 2}Si(110) thin film on Si(111) substrate

    SciTech Connect

    Wang, Y.; Wang, X. N.; Mei, Z. X.; Du, X. L.; Zou, J.; Jia, J. F.; Xue, Q. K.; Zhang, X. N.; Zhang, Z.

    2007-12-15

    Epitaxial Mg{sub 2}Si(110) thin film has been obtained on Si(111) substrate by thermally enhanced solid-phase reaction of epitaxial Mg film with underlying Si substrate. An epitaxial orientation relationship of Si(111) parallel Mg{sub 2}Si(110) and Si<110> parallel Mg{sub 2}Si<110> has been revealed by transmission electron microscopy. The formation of the unusual epitaxial orientation relationship is attributed to the strain relaxation of Mg{sub 2}Si film in a MgO/Mg{sub 2}Si/Si double heterostructure.

  13. In vitro biocompatibility of Ti-Mg alloys fabricated by direct current magnetron sputtering.

    PubMed

    Hieda, Junko; Niinomi, Mitsuo; Nakai, Masaaki; Cho, Ken

    2015-09-01

    Ti-xMg (x=17, 33, and 55 mass%) alloy films, which cannot be prepared by conventional melting processes owing to the absence of a solid-solution phase in the phase diagram, were prepared by direct current magnetron sputtering in order to investigate their biocompatibility. Ti and Mg films were also prepared by the same process for comparison. The crystal structures were examined by X-ray diffraction (XRD) analysis and the surfaces were analyzed by X-ray photoelectron spectroscopy. The Ti, Ti-xMg alloy, and Mg films were immersed in a 0.9% NaCl solution at 310 K for 7d to evaluate the dissolution amounts of Ti and Mg. In addition, to evaluate the formation ability of calcium phosphate in vitro, the Ti, Ti-xMg alloy, and Mg films were immersed in Hanks' solution at 310 K for 30 d. Ti and Mg form solid-solution alloys because the peaks attributed to pure Ti and Mg do not appear in the XRD patterns of any of the Ti-xMg alloy films. The surfaces of the Ti-17 Mg alloy and Ti-33 Mg alloy films contain Ti oxides and MgO, whereas MgO is the main component of the surface oxide of the Ti-55 Mg alloy and Mg films. The dissolution amounts of Ti from all films are below or near the detection limit of inductively coupled plasma-optical emission spectroscopy. On the other hand, the Ti-17 Mg alloy, Ti-33 Mg alloy, Ti-55 Mg alloy, and Mg films exhibit Mg dissolution amounts of approximately 2.5, 1.4, 21, and 41 μg/cm(2), respectively. The diffraction peaks attributed to calcium phosphate are present in the XRD patterns of the Ti-33 Mg alloy, Ti-55 Mg alloy, and Mg films after the immersion in Hanks' solution. Spherical calcium phosphate particles precipitate on the surface of the Ti-33 Mg film. However, many cracks are observed in the Ti-55 Mg film, and delamination of the film occurs after the immersion in Hanks' solution. The Mg film is dissolved in Hanks' solution and calcium phosphate particles precipitate on the glass substrate. Consequently, it is revealed that the Ti-33 Mg

  14. Methylglyoxal (MG) and cerebro-renal interaction: does long-term orally administered MG cause cognitive impairment in normal Sprague-Dawley rats?

    PubMed

    Watanabe, Kimio; Okada, Kana; Fukabori, Ryoji; Hayashi, Yoshimitsu; Asahi, Koichi; Terawaki, Hiroyuki; Kobayashi, Kazuto; Watanabe, Tsuyoshi; Nakayama, Masaaki

    2014-01-07

    Methylglyoxal (MG), one of the uremic toxins, is a highly reactive alpha-dicarbonyl compound. Recent clinical studies have demonstrated the close associations of cognitive impairment (CI) with plasma MG levels and presence of kidney dysfunction. Therefore, the present study aims to examine whether MG is a direct causative substance for CI development. Eight-week-old male Sprague-Dawley (SD) rats were divided into two groups: control (n = 9) and MG group (n = 10; 0.5% MG in drinking water), and fed a normal diet for 12 months. Cognitive function was evaluated by two behavioral tests (object exploration test and radial-arm maze test) in early (4-6 months of age) and late phase (7-12 months of age). Serum MG was significantly elevated in the MG group (495.8 ± 38.1 vs. 244.8 ± 28.2 nM; p < 0.001) at the end of study. The groups did not differ in cognitive function during the course of study. No time-course differences were found in oxidative stress markers between the two groups, while, antioxidants such as glutathione peroxidase and superoxide dismutase activities were significantly increased in the MG group compared to the control. Long-term MG administration to rats with normal kidney function did not cause CI. A counter-balanced activation of the systemic anti-oxidant system may offset the toxicity of MG in this model. Pathogenetic significance of MG for CI requires further investigation.

  15. Modelling dislocation cores in MgSiO3 perovskite

    NASA Astrophysics Data System (ADS)

    Cordier, P.; Carrez, P.; Gouriet, K.; Kraych, A.

    2012-12-01

    MgSiO3 perovskite is the most abundant mineral of the Earth's lower mantle (i.e. between 700 and 2900 km depth) and accounts for half of Earth's mass. At lower mantle pressures (25-135 GPa) MgSiO3 crystallises in a distorted (orthorhombic) perovskite structure (described in the following using the Pbnm space group). In this structure, SiO6 octahedra are tilted with tilt angles increasing with increasing pressure. Since it is very difficult to perform deformation experiments under the extreme P, T conditions of the lower mantle, little is known about plastic deformation of MgSiO3 perovskite and its slip systems are still a matter of debate. To overcome this difficulty, we model dislocation core structures in this mineral taking into account the influence of pressure. In this study, we focus on dislocation core structures of dislocations with [100] and [010] Burgers vectors (which derive from <110> Burgers vectors of the underlying pseudo-cubic structure). Atomistic calculations are performed using pair-wise potentials as implemented in the LAMMPS code. The choice of potentials was initially validated by comparing generalized stacking fault (GSF) energies to similar calculations performed with the density functional theory (DFT). The core structures of screw dislocations are calculated using two independent methods. The first one is based on Peierls-Nabarro-Galerkin simulations involving GSF as an input. Direct calculations have also bee performed using cluster approach. It turns out that screw dislocations with [100] Burgers vector are characterised by a core mostly spread in the (010) plane. The core exhibits two edge-sharing octahedra in a configuration very similar to that modelled in SrTiO3 cubic perovskite. The structure of [010] screw dislocations is more complex with dissociation into two, non-collinear partial dislocations with a significant non-screw component. Both dislocations exhibit high Peierls stresses. This illustrates the effect of orthorhombic

  16. Epitaxial growth of tungsten layers on MgO(001)

    SciTech Connect

    Zheng, Pengyuan; Ozsdolay, Brian D.; Gall, Daniel

    2015-11-15

    Smooth single crystal W(001) layers were grown on MgO(001) substrates by magnetron sputtering at 900 °C. X-ray diffraction ω–2θ scans, ω-rocking curves, pole figures, and reciprocal space maps indicate a 45°-rotated epitaxial relationship: (001){sub W}‖(001){sub MgO} and [010]{sub W}‖[110]{sub MgO}, and a relaxed lattice constant of 3.167 ± 0.001 nm. A residual in-plane biaxial compressive strain is primarily attributed to differential thermal contraction after growth and decreases from −0.012 ± 0.001 to −0.001 ± 0.001 with increasing layer thickness d = 4.8–390 nm, suggesting relaxation during cooling by misfit dislocation growth through threading dislocation glide. The in-plane x-ray coherence length increases from 3.4 to 33.6 nm for d = 4.8–390 nm, while the out-of-plane x-ray coherence length is identical to the layer thickness for d ≤ 20 nm, but is smaller than d for d ≥ 49.7 nm, indicating local strain variations along the film growth direction. X-ray reflectivity analyses indicate that the root-mean-square surface roughness increases from 0.50 ± 0.05 to 0.95 ± 0.05 nm for d = 4.8–19.9 nm, suggesting a roughness exponent of 0.38, but remains relatively constant for d > 20 nm with a roughness of 1.00 ± 0.05 nm at d = 47.9 nm.

  17. Superior hydrogen desorption kinetics of Mg(NH{sub 2}){sub 2} hollow nanospheres mixed with MgH{sub 2} nanoparticles

    SciTech Connect

    Xie Lei; Li Yaoqi; Yang Rong; Liu Yang; Li Xingguo

    2008-06-09

    Mg{sub 3}N{sub 2} nanocubes were prepared by vaporized bulk magnesium in ammonia atmosphere associated with plasma metal reaction. Then the product transformed to Mg(NH{sub 2}){sub 2} hollow nanospheres after it was reacted with NH{sub 3} based on the Kirkendall effect. The electron microscopy results suggested that the obtained hollow nanospheres were around 100 nm and the shell thickness was about 10 nm. Because of its short distance for Mg{sup 2+} diffusion and large specific surface area for interaction between Mg(NH{sub 2}){sub 2} and MgH{sub 2}, the structure dramatically enhanced the hydrogen desorption kinetics of Mg(NH{sub 2}){sub 2}-2MgH{sub 2}.

  18. Impact of Mg concentration on energy-band-depth profile of Mg-doped InN epilayers analyzed by hard X-ray photoelectron spectroscopy

    SciTech Connect

    Imura, M.; Tsuda, S.; Nagata, T.; Takeda, H.; Liao, M. Y.; Koide, Y.; Yang, A. L.; Yamashita, Y.; Yoshikawa, H.; Kobayashi, K.; Kaneko, M.; Uematsu, N.; Wang, K.; Araki, T.; Nanishi, Y.

    2013-10-14

    The electronic structures of Mg-doped InN (Mg-InN) epilayers with the Mg concentration, [Mg], ranging from 1 × 10{sup 19} to 5 × 10{sup 19} cm{sup −3} were systematically investigated by soft and hard X-ray photoelectron spectroscopies. The angle-resolved results on the core-level and valence band photoelectron spectra as a function of [Mg] revealed that the energy band of Mg-InN showed downward bending due to the n{sup +} surface electron accumulation and p type layers formed in the bulk. With an increase in [Mg], the energy-band changed from monotonic to two-step n{sup +}p homojunction structures. The oxygen concentration rapidly increased at the middle-bulk region (∼4.5 to ∼7.5 nm) from the surface, which was one of the reasons of the transformation of two-step energy band.

  19. Structural characterization of MG and pre-MG states of proteins by MD simulations, NMR, and other techniques.

    PubMed

    Naiyer, Abdullah; Hassan, Md Imtaiyaz; Islam, Asimul; Sundd, Monica; Ahmad, Faizan

    2015-01-01

    Almost all proteins fold via a number of partially structured intermediates such as molten globule (MG) and pre-molten globule states. Understanding the structure of these intermediates at atomic level is often a challenge, as these states are observed under extreme conditions of pH, temperature, and chemical denaturants. Furthermore, several other processes such as chemical modification, site-directed mutagenesis (or point mutation), and cleavage of covalent bond of natural proteins often lead to MG like partially unfolded conformation. However, the dynamic nature of proteins in these states makes them unsuitable for most structure determination at atomic level. Intermediate states studied so far have been characterized mostly by circular dichroism, fluorescence, viscosity, dynamic light scattering measurements, dye binding, infrared techniques, molecular dynamics simulations, etc. There is a limited amount of structural data available on these intermediate states by nuclear magnetic resonance (NMR) and hence there is a need to characterize these states at the molecular level. In this review, we present characterization of equilibrium intermediates by biophysical techniques with special reference to NMR. PMID:25586676

  20. Phonon Density of States in MgB{sub 2}

    SciTech Connect

    Osborn, R.; Goremychkin, E. A.; Kolesnikov, A. I.; Hinks, D. G.

    2001-07-02

    We report inelastic neutron scattering measurements of the phonon density of states in Mg {sup 11}B{sub 2} , which has a superconducting transition at 39.2K. The acoustic phonons extend in energy to 36meV, and there are highly dispersive optic branches peaking at 54, 78, 89, and 97meV. A simple Born{endash}von K{grave a}rm{grave a}n model reproduces the mode energies, and provides an estimate of the electron-phonon coupling of {lambda}{similar_to}0.9 . Furthermore, the estimated boron and magnesium contributions to the isotope effect are in qualitative agreement with experiment. The data confirm that a conventional phonon mechanism, with moderately strong electron-phonon coupling, can explain the observed superconductivity.

  1. Scanning Tunneling Spectroscopy in MgB{sub 2}

    SciTech Connect

    Karapetrov, G.; Iavarone, M.; Kwok, W. K.; Crabtree, G. W.; Hinks, D. G.

    2001-05-07

    We present scanning tunneling microscopy measurements of the surface of superconducting MgB{sub 2} with a critical temperature of 39 K. In zero magnetic field the conductance spectra can be analyzed in terms of the standard BCS theory with a smearing parameter {Gamma} . The value of the superconducting gap is 5 meV at 4.2 K, with no experimentally significant variation across the surface of the sample. The temperature dependence of the gap follows the BCS form, fully consistent with phonon-mediated superconductivity in this novel superconductor. The application of a magnetic field induces strong pair breaking as seen in the conductance spectra in fields up to 6 T.

  2. Al-Mg Isotope Study of Allende 5241

    NASA Technical Reports Server (NTRS)

    Kerekgyarto, A. G.; Jeffcoat, C. R.; Lapen, T. J.; Andreasen, R.; Righter, M.; Ross, D. K.; Simon, J. I.

    2016-01-01

    The defining characteristic of type B1 CAIs is a large (.5- 3mm) concentric melilite mantle [1]. In [2] we presented two isochrons from separate traverses across the melilite mantle of Allende EK 459-5-1. The primary petrographic differences between the traverses was the preservation of strong oscillatory zoning. The traverse that crossed the distinctive oscillatory zone produced a pristine internal isochron, while the other that did not have a strongly preserved oscillatory zone produced a disturbed isochron indicated by more scatter (higher MSWD) and a positive (delta)26Mg* intercept. The implication simply being that the oscillatory zone may represent varying conditions during the mantle formation event. We targeted a similar texture in Allende 5241 using the same methodology in an attempt to achieve similar results.

  3. Diffusion of aluminium in MgO from first principles

    NASA Astrophysics Data System (ADS)

    Ammann, M. W.; Brodholt, J. P.; Dobson, D. P.

    2012-06-01

    We have calculated the diffusivity of aluminium in periclase, MgO, under pressures relevant to deep planetary interiors from first principles. We reconcile differences between experimental migration enthalpies and those obtained with previous theoretical studies by finding a lower energy saddle point for the aluminium atom migration. Previous studies did not recognise a bifurcation at the saddle point. We also explain differences between experimental and theoretical binding enthalpies of an aluminium with a magnesium vacancy. We find that binding enthalpies continuously increase with decreasing aluminium concentrations, such that the difference between experimental and theoretical binding energies can be attributed to differing concentrations. We also find that binding energies increase with pressure as the permittivity decreases. Aluminium therefore not only causes extrinsic vacancy formation but also binds some of them, effectively removing them for magnesium diffusion. We discuss the implications for how other 3+ ions affect diffusion in oxides and silicates.

  4. Bone mineral alterations and Mg content in aging.

    PubMed

    Mongiorgi, R; Gnudi, S; Moroni, A; Bertocchi, G; Galliani, I; Benfenati, L

    1990-07-01

    The authors propose to determine whether the quantity of bone mass reduction linked to aging is accompanied by qualitative modifications of the mineral structure. To this end, 18 samples of cancellous bone from the femoral heads of two groups of patients (Groups A & B), were examined. Group A was made up of 8 old osteopenic patients suffering from fracture of the femur neck (age 62-84). Group B consisted of 10 young non-osteopenic subjects (age 34-53). Through chemical analysis a statistically significant percentage increase in Mg++ was noted in Group A and, by X-Ray diffraction, significant presence of beta-TCP. Mineral structure alterations occur in the process of aging of the skeletal tissue.

  5. Scanning tunneling spectroscopy in MgB2.

    PubMed

    Karapetrov, G; Iavarone, M; Kwok, W K; Crabtree, G W; Hinks, D G

    2001-05-01

    We present scanning tunneling microscopy measurements of the surface of superconducting MgB2 with a critical temperature of 39 K. In zero magnetic field the conductance spectra can be analyzed in terms of the standard BCS theory with a smearing parameter gamma. The value of the superconducting gap is 5 meV at 4.2 K, with no experimentally significant variation across the surface of the sample. The temperature dependence of the gap follows the BCS form, fully consistent with phonon-mediated superconductivity in this novel superconductor. The application of a magnetic field induces strong pair breaking as seen in the conductance spectra in fields up to 6 T.

  6. Bismuth-doped Mg - Al silicate glasses and fibres

    SciTech Connect

    Bufetov, Igor' A; Vel'miskin, V V; Galagan, B I; Denker, B I; Sverchkov, S E; Semjonov, S L; Firstov, Sergei V; Shulman, I L; Dianov, Evgenii M

    2012-09-30

    This paper compares the optical properties of bulk bismuth-doped Mg - Al silicate glasses prepared in an iridium crucible to those of optical fibres prepared by the powder-in-tube method and having a core identical in composition to the glasses. The bulk glasses and fibres are shown to be similar in luminescence properties. The optical loss in the fibres in their IR luminescence band is about one order of magnitude lower than that in the crucible-melted glasses. The level of losses in the fibres and their luminescence properties suggest that such fibres can be made to lase near 1.15 {mu}m. (optical fibres, lasers and amplifiers. properties and applications)

  7. Wastewater treatment in production of MgA zeolite

    SciTech Connect

    Barsukov, V.V.; Akopyants, T.V.; Rudova, S.A.; Shumovskii, A.V.

    1986-09-01

    This paper reports the development of zero-waste technology for treatment of chloride waste formed in the manufacture of MgA microbead zeolite, based on the method and flow plan used in treating similar wastes formed in the manufacture of bead zeolite. The first crystals of sodium chloride appeared at a magnesium chloride concentration of 8-9% by weight. With a magnesium chloride concentration of 35% by weight, at 50 C, the sodium chloride was almost completely precipitated. Under these conditions, the magnesium chloride did not precipitate. Sodium chloride crystals were washed with water in order to obtain a commercial product meeting the requirements of the specification Tu 6-12-33-78. This product is recommended for use in regenerating cation exchange filters in thermal power plants.

  8. Pulse TIG Welding of Two Al-Mg-Si Alloys

    NASA Astrophysics Data System (ADS)

    Manti, Rajesh; Dwivedi, D. K.; Agarwal, A.

    2008-10-01

    This article reports the influence of pulse tungsten inert gas (TIG) welding parameters on the microstructure, hardness and tensile strength of weld joints of two Al-(0.5-0.8%)Si-(0.5-0.6%)Mg alloy (T4) produced by using three pulse frequencies (25, 33, and 50 Hz) and two duty cycles (40 and 50%). It has been observed that the mechanical properties (hardness and tensile strength) are sensitive to microstructure of weld metal, which is appreciably affected by the pulse parameters. Low frequency produced higher strength and hardness than high pulse frequency under identical welding conditions. Weld metal and HAZ were found stronger than the base metal. SEM study showed that the fracture of weldment was mostly brittle type.

  9. Novel electrolyte chemistries for Mg-Ni rechargeable batteries.

    SciTech Connect

    Garcia-Diaz, Brenda; Kane, Marie; Au, Ming

    2010-10-01

    Commercial hybrid electric vehicles (HEV) and battery electric vehicles (BEV) serve as means to reduce the nation's dependence on oil. Current electric vehicles use relatively heavy nickel metal hydride (Ni-MH) rechargeable batteries. Li-ion rechargeable batteries have been developed extensively as the replacement; however, the high cost and safety concerns are still issues to be resolved before large-scale production. In this study, we propose a new highly conductive solid polymer electrolyte for Mg-Ni high electrochemical capacity batteries. The traditional corrosive alkaline aqueous electrolyte (KOH) is replaced with a dry polymer with conductivity on the order of 10{sup -2} S/cm, as measured by impedance spectroscopy. Several potential novel polymer and polymer composite candidates are presented with the best-performing electrolyte results for full cell testing and cycling.

  10. 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.

  11. Aberrant tropoelastin secretion in MG-63 human osteosarcoma cells

    SciTech Connect

    Curtiss, S.W.

    1989-01-01

    The secretion of newly synthesized tropoelastin, the soluble precursor of the extracellular matrix protein elastin, is not well understood. MG-63 human osteosarcoma cells were found by immunoblot analysis to synthesize 62 kD and 64 kD tropoelastins. Media from 63 cells labelled for five hours with ({sup 3}H)-valine contain no detectable tropoelastin, unlike media from other tropoelastin-synthesizing cells. Immunoblots of conditioned media and 1Ox-concentrated conditioned media left on the cells for six days also show an absence of tropoelastin from the cell media. No insoluble elastin is associated with the cell layer, as determined by amino acid analysis and electron microscopy of 18-21 day cell cultures. The absence of tropoelastin from the cell medium and elastin from the extracellular matrix indicates that MG63 cells do not secrete tropoelastin as expected, but accumulate it intracellularly. This accumulation is transient: immunoblots and immunofluorescence microscopy show that cells three days after passage have the highest steady-state levels of tropoelastin per cell, that day 8 cells contain lower but still significant amounts of tropoelastin, and that by day 22 tropoelastin is no longer present in the cell cultures. Cell density is a critical factor in the observed pattern of tropoelastin expression. Cells seeded at ten fold their usual initial density have high tropoelastin levels at one day after passage, sooner than cells seeded normally. Tropoelastin also disappears from high density-seeded cells more quickly and is no longer detectable at day 10. Lysosome-like vesicles containing membranous structures appear by immunoelectron microscopy to be the primary site of intracellular tropoelastin localization.

  12. Sustained efficacy of agomelatine 10 mg, 25 mg, and 25-50 mg on depressive symptoms and functional outcomes in patients with major depressive disorder. A placebo-controlled study over 6 months.

    PubMed

    Kennedy, Sidney H; Avedisova, Alla; Belaïdi, Carole; Picarel-Blanchot, Françoise; de Bodinat, Christian

    2016-02-01

    This randomized placebo-controlled "dose relation study" was conducted in patients who met criteria for major depressive disorder, to evaluate the efficacy and safety of agomelatine during 24 weeks at 3 doses (i) low fixed dosage (10 mg/day, n=100 patients entered the extension period), (ii) fixed dosage (25 mg/day, n=111) and (iii) a flexible dosage with up-titration in case of insufficient improvement at week 2 (25-50 mg/day, n=115) versus placebo (n=85). Mood was evaluated using the Hamilton rating scale for depression (HAM-D17) and Clinical Global Impression (CGI) scale. The functional status was examined with the Sheehan Disability Scale (SDS). At last post-baseline assessment, there were significant placebo-agomelatine differences on mean HAM-D17 total scores in favour of each agomelatine dose regimen (4.51±1.06 points, p<0.0001 at 10 mg; 7.74±1.05 points, p<0.0001 at 25 mg and 7.72±1.05 points, p<0.0001 at 25-50 mg). The response rate according to HAM-D17 was significantly higher in patients taking agomelatine than those taking placebo (difference of 21.8% at 10mg p<0.001; 36.4% and 35.4% respectively at 25 mg and 25-50 mg, p<0.0001). The remitter rate was significantly higher in patients taking agomelatine than those taking placebo (difference of 16.7% at 10 mg p=0.003; 33.8% and 35.4% respectively at 25 mg and 25-50 mg, p<0.0001). The effects of agomelatine were corroborated by CGI scores. Agomelatine improved symptom-related functional impairment on all domains of the SDS scale for the fixed dose 25 mg, and the one step titration 25-50 mg dose regimen. Similar findings were obtained for all measures in the subgroup of severely depressed patients. All dose regimens of agomelatine were well tolerated and no unexpected adverse event was reported. Long term agomelatine treatment improves both mood symptoms and social and occupational functioning of moderately to severely depressed patients. There is a dose effect between 10 mg and higher dose regimens of

  13. Gallium-assisted growth of flute-like MgO nanotubes, Ga2O3-filled MgO nanotubes, and MgO/Ga2O3 co-axial nanotubes.

    PubMed

    Jie, Jiansheng; Wu, Chunyan; Yu, Yongqiang; Wang, Li; Hu, Zhizhong

    2009-02-18

    Flute-like MgO nanotubes were successfully synthesized via a simple thermal evaporation method by using Mg(3)N(2) and Ga(2)O(3) as the source materials. The nanotubes are single-crystal cubic MgO, and have [100] orientation. In contrast to conventional nanotubes with intact walls, the flute-like MgO nanotubes possess a unique porous structure. On the nanotubes there are series of holes aligned along the nanotube length with approximate equidistance. Ga(2)O(3)-filled MgO nanotubes and MgO/Ga(2)O(3) co-axial nanotubes were also found in the product. Further investigation confirms that the inner beta-Ga(2)O(3) has an epitaxial growth relation with the outer MgO nanotube due to their perfect lattice matching. A gallium-assisted growth mechanism was proposed to interpret the growth of the flute-like MgO nanotubes. The thermal expansion and evaporation of the filled liquid gallium in MgO nanotubes are likely responsible for the formation of the hole structures on the side walls.

  14. Effect of different seawater Mg2 + concentrations on calcification in two benthic foraminifers

    PubMed Central

    Mewes, Antje; Langer, Gerald; de Nooijer, Lennart Jan; Bijma, Jelle; Reichart, Gert-Jan

    2014-01-01

    Magnesium, incorporated in foraminiferal calcite (Mg/CaCC), is used intensively to reconstruct past seawater temperatures but, in addition to temperature, the Mg/CaCC of foraminiferal tests also depends on the ratio of Mg and Ca in seawater (Mg/CaSW). The physiological mechanisms responsible for these proxy relationships are still unknown. This culture study investigates the impact of different seawater [Mg2 +] on calcification in two benthic foraminiferal species precipitating contrasting Mg/CaCC: Ammonia aomoriensis, producing low-Mg calcite and Amphistegina lessonii, producing intermediate-Mg calcite. Foraminiferal growth and test thickness were determined and, Mg/Ca was analyzed using Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). Results show that at present-day seawater Mg/CaSW of ~ 5, both species have highest growth rates, reflecting their adaptation to modern seawater element concentrations. Test thickness is not significantly affected by different Mg/CaSW. The relationship between Mg/CaSW and Mg/CaCC shows a distinct positive y-axis intercept, possibly reflecting at least two processes involved in foraminiferal biomineralization. The associated Mg partition (DMg) changes non-linearly with increasing Mg/CaSW, hence suggesting that the DMg is best described by an exponential function approaching an asymptote. PMID:26089590

  15. Solute carrier 41A3 encodes for a mitochondrial Mg2+ efflux system

    PubMed Central

    Mastrototaro, Lucia; Smorodchenko, Alina; Aschenbach, Jörg R.; Kolisek, Martin; Sponder, Gerhard

    2016-01-01

    The important role of magnesium (Mg2+) in normal cellular physiology requires flexible, yet tightly regulated, intracellular Mg2+ homeostasis (IMH). However, only little is known about Mg2+ transporters of subcellular compartments such as mitochondria, despite their obvious importance for the deposition and reposition of intracellular Mg2+ pools. In particular, knowledge about mechanisms responsible for extrusion of Mg2+ from mitochondria is lacking. Based on circumstantial evidence, two possible mechanisms of Mg2+ release from mitochondria were predicted: (1) Mg2+ efflux coupled to ATP translocation via the ATP-Mg/Pi carrier, and (2) Mg2+ efflux via a H+/Mg2+ exchanger. Regardless, the identity of the H+-coupled Mg2+ efflux system is unknown. We demonstrate here that member A3 of solute carrier (SLC) family 41 is a mitochondrial Mg2+ efflux system. Mitochondria of HEK293 cells overexpressing SLC41A3 exhibit a 60% increase in the extrusion of Mg2+ compared with control cells. This efflux mechanism is Na+-dependent and temperature sensitive. Our data identify SLC41A3 as the first mammalian mitochondrial Mg2+ efflux system, which greatly enhances our understanding of intracellular Mg2+ homeostasis. PMID:27302215

  16. 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 :

  17. Properties of YBCO on LaMnO3-capped IBAD MgO-templates without Homo-epitaxial MgO layer.

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Kim, Kyunghoon; Zhang, Yifei; Cantoni, Claudia; Zuev, Yuri L; Goyal, Amit; Thompson, James R; Christen, David K

    2009-01-01

    Previously, it has been well established that in an IBAD architecture for coated conductors, (1) LaMnO3 (LMO) buffer layers are structurally and chemically compatible with an underlying homo-epitaxial MgO layer and (2) high current density YBCO films can be grown on these LMO templates. In the present work, the homo-epi MgO layer has been successfully eliminated and a LMO cap layer was grown directly on the IBAD (MgO) template. The performance of the LMO/IBAD (MgO) samples has been qualified by depositing 1 m-thick YBCO coatings by pulsed laser deposition. Electrical transport measurements of YBCO films on the standard (with homo-epi MgO) and simplified (without homo-epi MgO) IBAD architectures were carried out. The angular dependencies of critical current density (Jc) are similar for both IBAD architectures. XRD measurements indicate good, c-axis aligned YBCO films. Transmission electron microscopy (TEM) images reveal that microstructures of YBCO/LMO/IBAD (MgO) and YBCO/LMO/homo-epi MgO/IBAD (MgO) templates are similar. These results demonstrate the strong potential of using LMO as a single cap layer directly on IBAD (MgO) for the development of a simplified IBAD architecture.

  18. Corrosion-controlling and osteo-compatible Mg ion-integrated phytic acid (Mg-PA) coating on magnesium substrate for biodegradable implants application.

    PubMed

    Chen, Yingqi; Zhao, Sheng; Liu, Bo; Chen, Meiyun; Mao, Jinlong; He, Hairuo; Zhao, Yuancong; Huang, Nan; Wan, Guojiang

    2014-11-26

    Biodegradable, a new revolutionary concept, is shaping the future design of biomedical implants that need to serve only as a temporary scaffold. Magnesium appears to be the most promising biodegradable metal, but challenges remain in its corrosion-controlling and uncertain biocompatibility. In this work, we employ chemical conversion and alternating dip-coating methods to anchor and deposit an Mg ion-integrated phytic acid (Mg-PA) coating on Mg, which is supposed to function both corrosion-controlling and osteo-compatible. It was ascertained that PA molecules were covalently immobilized on a chemically converted Mg(OH)2 base layer, and more PA molecules were deposited subsequently via chelating reactions with the help of additive Mg ions. The covalent immobilization and the Mg ion-supported chelating deposition contribute to a dense and homogeneous protective Mg-PA coating, which guarantees an improved corrosion resistance as well as a reduced degradation rate. Moreover, the Mg-PA coating performed osteo-compatible to promote not only bioactivity of bonelike apatite precipitation, but also induced osteoblast cells adhesion and proliferation. This is ascribed to its nature of PA molecule and the biocompatible Mg ion, both of which mimic partly the compositional structure of bone. Our magnesium ion-integrated PA-coated Mg might bode well for the future of biodegradable bone implant application.

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

    SciTech Connect

    Guzman, D.; Ordonez, S.; Fernandez, J.F.; Sanchez, C.; Serafini, D.; Rojas, P.A.; Aguilar, C.; Tapia, P.

    2011-04-15

    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{sub 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.

  20. Simultaneous desorption behavior of M borohydrides and Mg2FeH6 reactive hydride composites (M = Mg, then Li, Na, K, Ca)

    NASA Astrophysics Data System (ADS)

    Chaudhary, Anna-Lisa; Li, Guanqiao; Matsuo, Motoaki; Orimo, Shin-ichi; Deledda, Stefano; Sørby, Magnus H.; Hauback, Bjørn C.; Pistidda, Claudio; Klassen, Thomas; Dornheim, Martin

    2015-08-01

    Combinations of complex metal borohydrides ball milled with the transition metal complex hydride, Mg2FeH6, are analysed and compared. Initially, the Reactive Hydride Composite (RHC) of Mg2+ cation mixtures of Mg2FeH6 and γ-Mg(BH4)2 is combined in a range of molar ratios and heated to a maximum of 450 °C. For the molar ratio of 6 Mg2FeH6 + Mg(BH4)2, simultaneous desorption of the two hydrides occurred, which resulted in a single event of hydrogen release. This single step desorption occurred at temperatures between those of Mg2FeH6 and γ-Mg(BH4)2. Keeping this anionic ratio constant, the desorption behavior of four other borohydrides, Li-, Na-, K-, and Ca-borohydrides was studied by using materials ball milled with Mg2FeH6 applying the same milling parameters. The mixtures containing Mg-, Li-, and Ca-borohydrides also released hydrogen in a single event. The Mass Spectrometry (MS) results show a double step reaction within a narrow temperature range for both the Na- and K-borohydride mixtures. This phenomenon, observed for the RHC systems at the same anionic ratio with all five light metal borohydride mixtures, can be described as simultaneous hydrogen desorption within a narrow temperature range centered around 300 °C.

  1. Complex transition metal hydrides incorporating ionic hydrogen: thermal decomposition pathway of Na2Mg2FeH8 and Na2Mg2RuH8.

    PubMed

    Humphries, Terry D; Matsuo, Motoaki; Li, Guanqiao; Orimo, Shin-Ichi

    2015-03-28

    Complex transition metal hydrides have potential technological application as hydrogen storage materials, smart windows and sensors. Recent exploration of these materials has revealed that the incorporation of anionic hydrogen into these systems expands the potential number of viable complexes, while varying the countercation allows for optimisation of their thermodynamic stability. In this study, the optimised synthesis of Na2Mg2TH8 (T = Fe, Ru) has been achieved and their thermal decomposition properties studied by ex situ Powder X-ray Diffraction, Gas Chromatography and Pressure-Composition Isotherm measurements. The temperature and pathway of decomposition of these isostructural compounds differs considerably, with Na2Mg2FeH8 proceeding via NaMgH3 in a three-step process, while Na2Mg2RuH8 decomposes via Mg2RuH4 in a two-step process. The first desorption maxima of Na2Mg2FeH8 occurs at ca. 400 °C, while Na2Mg2RuH8 has its first maxima at 420 °C. The enthalpy and entropy of desorption for Na2Mg2TH8 (T = Fe, Ru) has been established by PCI measurements, with the ΔHdes for Na2Mg2FeH8 being 94.5 kJ mol(-1) H2 and 125 kJ mol(-1) H2 for Na2Mg2RuH8. PMID:25732233

  2. Localized Mg-vacancy states in the thermoelectric material Mg2-δSi0.4Sn0.6

    NASA Astrophysics Data System (ADS)

    Zhang, Libin; Xiao, Penghao; Shi, Li; Henkelman, Graeme; Goodenough, John B.; Zhou, Jianshi

    2016-02-01

    Mg2SixSn1-x has been widely studied as a thermoelectric material owing to its high figure-of-merit, low cost, and non-toxicity. However, its electronic structure, particularly when the material contains Mg vacancies, has not been adequately described. The n-type nature of Mg2-δSi0.4Sn0.6 has been a puzzle. Mg deficiency can be present in Mg2SixSn1-x due to Mg evaporation and oxidation. Therefore, an investigation of the role of Mg vacancies is of great interest. In this work, we have prepared a series of samples with various Mg deficiency and Sb doping levels and measured their transport properties. The Seebeck coefficient of these samples all reveals n-type conduction. We propose that Mg vacancies in Mg2-δSixSn1-x create localized hole states inside the band gap instead of simply moving the Fermi-level into the valence band as would be predicted by a rigid band model. Our hypothesis is further confirmed by density-functional theory calculations, which show that the hole states are trapped at Mg vacancies above the valence band. Moreover, this localized hole-states model is used to interpret electrical transport properties. Both the Seebeck coefficient and resistivity of Mg2-δSi0.4Sn0.6 indicate an electron-hopping transport mechanism. In addition, the data suggest that localized band-tail states may exist in the conduction-band edge of Mg2SixSn1-x.

  3. Busulfan 12 mg/kg plus melphalan 140 mg/m2 versus melphalan 200 mg/m2 as conditioning regimens for autologous transplantation in newly diagnosed multiple myeloma patients included in the PETHEMA/GEM2000 study

    PubMed Central

    Lahuerta, Juan José; Mateos, Maria Victoria; Martínez-López, Joaquin; Grande, Carlos; de la Rubia, Javier; Rosiñol, Laura; Sureda, Anna; García-Laraña, José; Díaz-Mediavilla, Joaquín; Hernández-García, Miguel T.; Carrera, Dolores; Besalduch, Joan; de Arriba, Felipe; Oriol, Albert; Escoda, Lourdes; García-Frade, Javier; Rivas-González, Concepción; Alegre, Adrían; Bladé, Joan; San Miguel, Jesús F.

    2010-01-01

    Background The aim of this study was to compare the long-term safety and efficacy of oral busulfan 12 mg/kg plus melphalan 140 mg/m2 and melphalan 200 mg/m2 as conditioning regimens for autologous stem cell transplantation in newly diagnosed patients with multiple myeloma in the GEM2000 study. Design and Methods The first 225 patients received oral busulfan 12 mg/kg plus melphalan 140 mg/m2; because of a high frequency of veno-occlusive disease, the protocol was amended and a further 542 patients received melphalan 200 mg/m2. Results Engraftment and hospitalization times were similar in both groups. Oral busulfan 12 mg/kg plus melphalan 140 mg/m2 resulted in higher transplant-related mortality (8.4% versus 3.5%; P=0.002) due to the increased frequency of veno-occlusive disease in this group. Response rates were similar in both arms. With respective median follow-ups of 72 and 47 months, the median progression-free survival was significantly longer with busulfan plus melphalan (41 versus 31 months; P=0.009), although survival was similar to that in the melphalan 200 mg/m2 group. However, access to novel agents as salvage therapy after relapse/progression was significantly lower for patients receiving busulfan plus melphalan (43%) than for those receiving melphalan 200 mg/m2 (58%; P=0.01). Conclusions Conditioning with oral busulfan 12 mg/kg plus melphalan 140 mg/m2 was associated with longer progression-free survival but equivalent survival to that achieved with melphalan 200 mg/m2 but this should be counterbalanced against the higher frequency of veno-occlusive disease-related deaths. This latter fact together with the limited access to novel salvage therapies in patients conditioned with oral busulfan 12 mg/kg plus melphalan 140 mg/m2 may explain the absence of a survival difference. Oral busulfan was used in the present study; use of the intravenous formulation may reduce toxicity and result in greater efficacy, and warrants further investigation in myeloma

  4. Conversation with Lara about the Earth and Land. (Spanish Title: Conversando con Lara sobre la Tierra y la Teirra.) Conversando com Lara sobre a Terra e a Terra

    NASA Astrophysics Data System (ADS)

    da Conceição Barbosa-Lima, Maria

    2010-12-01

    The present article is the analysis of a conversation between the author and Lara, a four-yearold- girl, enrolled in nursery school, while she makes a drawing of the Earth. It took place outside school environment and without any other person around to avoid interference during the interview. According to Ferreira & Silva (2004), a researcher can only comprehend a child's drawing, or form, by listening to him/her while he/she is creating it. Lara presented the traditional flat drawing, picturing the sky parallel to the ground, as reported by Nardi & Carvalho (1996). However, when asked to draw the World - term used by Butterworth et al. (2002), in order to avoid unnecessary confusion - she represented it by a circle, with herself on the surface. Her drawings led to the conclusion that such girl does not know yet the World in which she lives is the Earth, and probably because of that, within her age and consequent maturity, she accurately differentiates the concepts of land and Earth. El presente artículo analiza una entrevista libre, mientras una niña de 4 años y 4 meses, matriculada en el pregrado, dibuja la Tierra. Esta entrevista se realizó fuera del ambiente escolar y sin otra persona alrededor que pudiera interferir. De acuerdo con Ferreira Silva (2004), para quien investiga es posible conocer realmente lo que un niño o una niña pone en el papel a través de grafismos y/o dibujos si se lo escucha durante el proceso de creación de la escritura con imágenes. La niña, en este caso, representa la Tierra con el tradicional dibujo plano y el "cielo" paralelo al suelo, conforme analizaron Nardi & Carvalho (1996). Pero, cuando se Le solicita dibujar el "Mundo" - palabra empleada en un trabajo de Butterworth et al. (2002), con intención de no provocar "confusiones" innecesarias a sus sujetos de investigación- lo representa de forma circular, poniéndose sobre su superficie. Sus dibujos llevan a concluir que esta niña aún no tiene conocimiento que el mundo

  5. Divacancies and the hydrogenation of Mg-Ti films with short range chemical order

    SciTech Connect

    Leegwater, H.; Schut, H.; Eijt, S. W. H.; Egger, W.; Baldi, A.; Dam, B.

    2010-03-22

    We obtained evidence for the partial chemical segregation of as-deposited and hydrogenated Mg{sub 1-y}Ti{sub y} films (0<=y<=0.30) into nanoscale Ti and Mg domains using positron Doppler-broadening. We exclusively monitor the hydrogenation of Mg domains, owing to the large difference in positron affinity for Mg and Ti. The electron momentum distribution broadens significantly upon transformation to the MgH{sub 2} phase over the whole compositional range. This reveals the similarity of the metal-insulator transition for rutile and fluorite MgH{sub 2}. Positron lifetime studies show the presence of divacancies in the as-deposited and hydrogenated Mg-Ti metal films. In conjunction with the relatively large local lattice relaxations we deduce to be present in fluorite MgH{sub 2}, these may be responsible for the fast hydrogen sorption kinetics in this MgH{sub 2} phase.

  6. 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. PMID:26249586

  7. Erythrocyte intracellular Mg2+ concentration as an index of recognition and memory

    PubMed Central

    Xiong, Wenxiang; Liang, Yaru; Li, Xue; Liu, Guosong; Wang, Zhao

    2016-01-01

    Magnesium (Mg2+) plays an important role in the neural system, and yet scarcely any research has quantitatively analyzed the link between endogenous Mg2+ level and memory. Using our original technique, we measured erythrocyte intracellular ionized Mg2+ concentration (RBC [Mg2+]i), which linearly correlated to recognition and spatial memory in normal aging rats. In the brain, RBC [Mg2+]i significantly correlated to hippocampus extracellular fluid Mg2+ concentration, and further correlated to hippocampal synapse density. Elevation of Mg2+ intake in aged rats demonstrated an association between RBC [Mg2+]i increase and memory recovery. The therapeutic effect of Mg2+ administration was inversely correlated to individual basal RBC [Mg2+]i. In summary, we provide a method to measure RBC [Mg2+]i, an ideal indicator of body Mg2+ level. RBC [Mg2+]i represents rodent memory performance in our study, and might further serve as a potential biomarker for clinical differential diagnosis and precise treatment of Mg2+-deficiency-associated memory decline during aging. PMID:27253451

  8. 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.

  9. Differential responses of the Mg/Ca Ratio in scleractinians to variations in Mg2+ and Ca2+ content of seawater

    NASA Astrophysics Data System (ADS)

    Swart, P. K.; Giri, S.; Adkins, J. F.

    2014-12-01

    Although it is well known that the Mg2+/Ca2+ ratio of seawater has varied throughout the Phanerozoic, there is little information on whether the concentration of Ca2+ has changed in conjunction with Mg2+ or whether these two elements have changed independently. In addition while it has been documented that the Mg/Ca has varied within scleractinian corals during certain time periods, there have been no studies which have verified that changing Mg/Ca ratio in corals corresponds with a similar variation in seawater. Here we report studies using Modern corals which have been grown for an extended period of time (10 weeks) in elevated Ca2+and Mg2+ concentrations. While these studies show that the Mg2+/Ca2+ of the seawater is related to the same ratio in the coral skeleton, the slope of the relationship is dependent upon which of the two cations is altered. When the Ca2+ is increased, thereby decreasing the Mg2+/Ca2+ ratio in seawater, then the ratio within the skeleton decreases by ~0.7 mM/M for every 1 M/M decrease in the Mg2+ / Ca2+ ratio in the external seawater. However, when the Mg2+/Ca2+ ratio is altered by adding Mg2+, then there is an increase is ~2 mM/M for every 1 M/M increase in Mg2+/Ca2+. Assuming that such changes can be replicated by the reverse experiment, i.e. reducing the concentration of Ca2+ and Mg2+, then such a finding offers a solution to resolving whether the Mg/Ca ratio in ancient unaltered corals is responding to a change in Mg2+ or a change in Ca2+ in seawater. For example, the Mg/Ca ratios of unaltered corals from a defined time period might only be possible if the Ca2+ of seawater was altered rather than Mg2+. The reverse might be case for other time periods. Further supporting evidence for this hypothesis will be presented by other elements which exhibited unexpected behavior in response to changing Ca2+ and Mg2+.

  10. Presence of a novel influx pathway for Mg2+ in MDCK cells.

    PubMed

    Quamme, G A; Dai, L J

    1990-09-01

    Basal free Mg2+ concentration was 0.49 +/- 0.03 mM in normal single Madin-Darby canine kidney (MDCK) cells as measured by fluorescence with the aid of mag-fura-2. Accordingly, Mg2+ may enter the cell down a transmembrane electrical gradient. The present study describes some aspects of Mg2+ entry into the established MDCK cell line. MDCK cells were Mg2(+)-depleted (0.26 +/- 0.01 mM) by culturing in Mg2(+)-free media for 16-20 h. Cells were subsequently exposed to 5 mM MgCl2, and intracellular Mg2+ concentration ([Mg2+]i) was monitored with fluorescence. [Mg2+]i returned to normal basal levels, 0.56 +/- 0.05 mM, with a refill rate of 272 +/- 39 nM/s, n = 4. Mg2+ entry was not changed by 5.0 mM external Ca2+ but was completely inhibited with 5.0 mM La3+. Intracellular Ca2+ concentration was not altered by Mg2+ depletion or during Mg2+ repletion. Mg2+ uptake was inhibited by verapamil (0 +/- 27 nM/s, n = 3), was inhibited less so by diltiazem (141 +/- 34 nM/s, n = 3), and was not affected by nifedipine (300 +/- 53 nM/s, n = 6). These inhibitors were fully reversible on removal, and [Mg2+]i returned to normal levels. These data indicate the presence of a unique Mg2+ entry pathway in MDCK cells that may be important in Mg2+ homeostasis. The model of Mg2+ refill into Mg2(+)-depleted cells may be useful in other cell types.

  11. Effect of Mg doping level on the antibacterial activity of (Mg + F)-doped ZnO nanopowders synthesized using a soft chemical route

    NASA Astrophysics Data System (ADS)

    Ravichandran, K.; Snega, S.; Jabena Begum, N.; Christena, L. Rene; Dheivamalar, S.; Swaminathan, K.

    2014-08-01

    ZnO nanopowders simultaneously doped with fluorine (20 at.%) and magnesium (4, 8, 12 and 16 at.%) (ZnO:F:Mg) have been synthesized using an inexpensive simple soft chemical route for the first time. The effect of Mg doping level on certain physical properties and antibacterial activities of ZnO:F:Mg nanopowders has been investigated and reported. XRD studies showed that the products have the hexagonal wurtzite structure of ZnO. Fourier transform infrared spectra authenticate the presence of MgO stretching vibration, which is responsible for the increased antibacterial activity of the synthesized samples. The antibacterial activity of ZnO:F:Mg nanopowders was found to be enhanced with increase in Mg doping level as it causes a reduction in the grain size.

  12. Fabrication of Fully Epitaxial CoFe/MgO/CoFe Magnetic Tunnel Junctions on Ge(001) Substrates via a MgO Interlayer

    NASA Astrophysics Data System (ADS)

    Li, Gui-fang; Taira, Tomoyuki; Liu, Hong-xi; Matsuda, Ken-ichi; Uemura, Tetsuya; Yamamoto, Masafumi

    2012-09-01

    Fully epitaxial magnetic tunnel junctions (MTJs) with Co50Fe50 (CoFe) electrodes and a MgO barrier were fabricated on Ge(001) single-crystal substrates via a MgO interlayer. Microfabricated CoFe/MgO/CoFe MTJs with a 10-nm-thick MgO interlayer showed a high tunnel magnetoresistance (TMR) ratio of 218% at 293 K, which is encouraging for monolithic integration of MTJs and Ge field-effect transistors for constructing future-generation nonvolatile logic circuits featuring ultralow-power consumption. Furthermore, MTJs with even a decreased MgO interlayer thickness of 1.0 nm showed a relatively high TMR ratio of 110% at 293 K, suggesting the promise of heterostructures consisting of MTJ/MgO interlayer/Ge(001) as a key device structure for spin injection into a Ge channel from an MTJ.

  13. Gonadal dysgenesis in del (18p) syndrome

    SciTech Connect

    Telvi, L.; Ion, A.; Fouquet, F.

    1995-07-17

    We report on a girl with syndromal gonadal dysgenesis and a de novo del (18p). Genetic factors controlling gonadal development are located not only on the X chromosome, but also on autosomes. The present case suggests that one of these genes is situated on 18p. We conclude that patients with del (18p) syndrome should be evaluated for gonadal dysgenesis. 16 refs., 3 figs.

  14. Mg3(VO4)2-MgO-ZrO2 nano-catalysts for oxidative dehydrogenation of n-butane.

    PubMed

    Lee, Jong Kwon; Seo, Hyun; Hong, Ung Gi; Yoo, Yeonshick; Cho, Young-Jin; Lee, Jinsuk; Park, Gle; Chang, Hosik; Song, In Kyu

    2014-11-01

    A series of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts with different vanadium content (X = 3.3, 5.3, 7.0, 10.2, and 13.4) were prepared by a single-step citric acid-derived sol-gel method for use in the oxidative dehydrogenation of n-butane to n-butene and 1,3-butadiene. The effect of vanadium content of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts on their physicochemical properties and catalytic activities in the oxidative dehydrogenation of n-butane was investigated. Successful formation of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts was confirmed by XRD, Raman spectroscopy, and ICP-AES analyses. The catalytic performance of X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts strongly depended on vanadium content. All the X-Mg3(VO4)2-MgO-ZrO2 nano-catalysts showed a stable catalytic performance without catalyst deactivation during the reaction. Among the catalysts tested, 7.0-Mg3(VO4)2-MgO-ZrO2 nano-catalyst showed the best catalytic performance in terms of yield for total dehydrogenation products (TDP, n-butene and 1,3-butadiene). TPRO (temperature-programmed reoxidation) experiments were carried out to measure the oxygen capacity of the catalyst. Experimental results revealed that oxygen capacity of the catalyst was closely related to the catalytic performance. Yield for TDP increased with increasing oxygen capacity of the catalyst. PMID:25958621

  15. 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. PMID:26391815

  16. Al-doped MgB2 materials studied using electron paramagnetic resonance and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Bateni, Ali; Erdem, Emre; Repp, Sergej; Weber, Stefan; Somer, Mehmet

    2016-05-01

    Undoped and aluminum (Al) doped magnesium diboride (MgB2) samples were synthesized using a high-temperature solid-state synthesis method. The microscopic defect structures of Al-doped MgB2 samples were systematically investigated using X-ray powder diffraction, Raman spectroscopy, and electron paramagnetic resonance. It was found that Mg-vacancies are responsible for defect-induced peculiarities in MgB2. Above a certain level of Al doping, enhanced conductive properties of MgB2 disappear due to filling of vacancies or trapping of Al in Mg-related vacancy sites.

  17. Functional Mn–Mg{sub k} cation complexes in GaN featured by Raman spectroscopy

    SciTech Connect

    Devillers, T. Bonanni, A.; Leite, D. M. G.; Dias da Silva, J. H.

    2013-11-18

    The evolution of the optical branch in the Raman spectra of (Ga,Mn)N:Mg epitaxial layers as a function of the Mn and Mg concentrations, reveals the interplay between the two dopants. We demonstrate that the various Mn-Mg-induced vibrational modes can be understood in the picture of functional Mn–Mg{sub k} complexes formed when substitutional Mn cations are bound to k substitutional Mg through nitrogen atoms, the number of ligands k being driven by the ratio between the Mg and the Mn concentrations.

  18. MgO buffer layers on rolled nickel or copper as superconductor substrates

    DOEpatents

    Paranthaman, Mariappan; Goyal, Amit; Kroeger, Donald M.; List, III, Frederic A.

    2001-01-01

    Buffer layer architectures are epitaxially deposited on biaxially-textured rolled-Ni and/or Cu substrates for high current conductors, and more particularly buffer layer architectures such as MgO/Ag/Pt/Ni, MgO/Ag/Pd/Ni, MgO/Ag/Ni, MgO/Ag/Pd/Cu, MgO/Ag/Pt/Cu, and MgO/Ag/Cu. Techniques used to deposit these buffer layers include electron beam evaporation, thermal evaporation, rf magnetron sputtering, pulsed laser deposition, metal-organic chemical vapor deposition (MOCVD), combustion CVD, and spray pyrolysis.

  19. Method for making MgO buffer layers on rolled nickel or copper as superconductor substrates

    DOEpatents

    Paranthaman, Mariappan; Goyal, Amit; Kroeger, Donald M.; List, III, Frederic A.

    2002-01-01

    Buffer layer architectures are epitaxially deposited on biaxially-textured rolled-Ni and/or Cu substrates for high current conductors, and more particularly buffer layer architectures such as MgO/Ag/Pt/Ni, MgO/Ag/Pd/Ni, MgO/Ag/Ni, MgO/Ag/Pd/Cu, MgO/Ag/Pt/Cu, and MgO/Ag/Cu. Techniques used to deposit these buffer layers include electron beam evaporation, thermal evaporation, rf magnetron sputtering, pulsed laser deposition, metal-organic chemical vapor deposition (MOCVD), combustion CVD, and spray pyrolysis.

  20. Magnetotransport properties of spin-valve structures with Mg spacer layers

    NASA Astrophysics Data System (ADS)

    Martinez-Boubeta, C.; Ferrante, Y.; Parkin, S. S. P.

    2015-01-01

    A theoretical prediction by Wang et al. [Phys. Rev. B 82, 054405 (2010)] suggests the preferential transmission of majority-spin states with Δ1 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.