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Sample records for del mg sobre

  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. 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

  7. 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

  8. 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

  9. 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.

  10. 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

  11. 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.

    2015-01-01

    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.

  12. 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

  13. 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

  14. 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

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. [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. PMID:23541879

  20. 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

  1. 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

  2. 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.

  3. Mg(+)-ligand binding energies

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Ab initio calculations are used to optimize the structures and determine the binding energies of Mg(+) to a series of ligands. Mg(+) bonds electrostatically with benzene, acetone, H2, CO, and NH3 and a self-consistent-field treatment gives a good description of the bonding. The bonding in MgCN(+) and MgCH3(+) is largely covalent and a correlated treatment is required.

  4. 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

  5. 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.

  6. 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

  7. 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…

  8. 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.

  9. 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., (translator); 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.

  10. 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.

  11. Subdivision of the Mg-suite noritic rocks into Mg-gabbronorites and Mg-norites

    NASA Technical Reports Server (NTRS)

    James, O. B.; Flohr, M. K.

    1983-01-01

    Mg-suite noritic rocks can be divided into two groups, the Mg-gabbronorites and the Mg-norites. The rocks of these groups differ in ratios of high-Ca pyroxene to total pyroxene, compositions of pyroxene and plagioclase, assemblages of Ti-, Nb-, and Zr-bearing minerals, compositions of chrome spinel, bulk-rock Ti/Sm and Sc/Sm, and measured ages. The two groups probably crystallized from different types of parent magmas. Two hypotheses are offered for the differences in composition of the parent magmas. One hypothesis ascribes the differences to compositional heterogeneity of the mantle source areas. The other hypothesis ascribes the differences to variations in extent of partial melting of the mantle source regions and variations in extent of assimilation of the anorthosite and the highly differentiated residual liquid that were produced during the primordial lunar differentiation.

  12. 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.

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. Bacterial Mg2+ Homeostasis, Transport, and Virulence

    PubMed Central

    Hollands, Kerry; Kriner, Michelle A.; Lee, Eun-Jin; Park, Sun-Yang; Pontes, Mauricio H.

    2014-01-01

    Organisms must maintain physiological levels of Mg2+ because this divalent cation is critical for the stabilization of membranes and ribosomes, the neutralization of nucleic acids, and as a cofactor in a variety of enzymatic reactions. In this review, we describe the mechanisms that bacteria utilize to sense the levels of Mg2+ both outside and inside the cytoplasm. We examine how bacteria achieve Mg2+ homeostasis by adjusting the expression and activity of Mg2+ transporters, and by changing the composition of their cell envelope. We discuss the connections that exist between Mg2+ sensing, Mg2+ transport and bacterial virulence. Additionally, we explore the logic behind the fact that bacterial genomes encode multiple Mg2+ transporters and distinct sensing systems for cytoplasmic and extracytoplasmic Mg2+. These analyses may be applicable to the homeostatic control of other cations. PMID:24079267

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. X-ray photoelectron spectroscopy studies of MgB 2 for valence state of Mg

    NASA Astrophysics Data System (ADS)

    A. Talapatra; Bandyopadhyay, S. K.; Sen, Pintu; Barat, P.; Mukherjee, S.; Mukherjee, M.

    2005-03-01

    Core level X-ray photoelectron spectroscopy (XPS) studies have been carried out on polycrystalline MgB 2 pellets over the whole binding energy range with a view to having an idea of the charge state of magnesium (Mg). We observe three distinct peaks in Mg 2p spectra at 49.3 eV (trace), 51.3 eV (major) and 54.0 eV (trace), corresponding to metallic Mg, MgB 2 and MgCO 3 or, divalent Mg species, respectively. Similar trend has been noticed in Mg 2s spectra. The binding energy of Mg in MgB 2 is lower than that corresponding to Mg(2+), indicative of the fact that the charge state of Mg in MgB 2 is less than (2+). Lowering of the formal charge of Mg promotes the σ → π electron transfer in boron (B) giving rise to holes on the top of the σ-band which are involved in coupling with B E 2g phonons for superconductivity. Through this charge transfer, Mg plays a positive role in hole superconductivity. B 1s spectra consist of three peaks corresponding to MgB 2, boron and B 2O 3. There is also evidence of MgO due to surface oxidation as seen from O 1s spectra.

  6. 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.

  7. 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.

  8. 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

  9. The potential energy curves of HeBe, HeMg and BeMg

    NASA Astrophysics Data System (ADS)

    Chiles, Richard A.; Dykstra, Clifford E.

    1982-01-01

    Correlated calculations have been performed on the potential curves of mixed dimers of He, Be and Mg He interacts weakly with all partners. BeMg appears to be intermediate in well-depth to Be 2 and Mg 2 and has electronic structure features similar to Be 2 but different from Mg 2.

  10. Mechanical Properties of Mg2Si/Mg Composites via Powder Metallurgy Process

    NASA Astrophysics Data System (ADS)

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

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

  11. 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

  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 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

  13. Antibacterial biodegradable Mg-Ag alloys.

    PubMed

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

    2013-01-01

    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. PMID:23771512

  14. Hydrogen storage systems from waste Mg alloys

    NASA Astrophysics Data System (ADS)

    Pistidda, C.; Bergemann, N.; Wurr, J.; Rzeszutek, A.; Møller, K. T.; Hansen, B. R. S.; Garroni, S.; Horstmann, C.; Milanese, C.; Girella, A.; Metz, O.; Taube, K.; Jensen, T. R.; Thomas, D.; Liermann, H. P.; Klassen, T.; Dornheim, M.

    2014-12-01

    The production cost of materials for hydrogen storage is one of the major issues to be addressed in order to consider them suitable for large scale applications. In the last decades several authors reported on the hydrogen sorption properties of Mg and Mg-based systems. In this work magnesium industrial wastes of AZ91 alloy and Mg-10 wt.% Gd alloy are used for the production of hydrogen storage materials. The hydrogen sorption properties of the alloys were investigated by means of volumetric technique, in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and calorimetric methods. The measured reversible hydrogen storage capacity for the alloys AZ91 and Mg-10 wt.% Gd are 4.2 and 5.8 wt.%, respectively. For the Mg-10 wt.% Gd alloy, the hydrogenated product was also successfully used as starting reactant for the synthesis of Mg(NH2)2 and as MgH2 substitute in the Reactive Hydride Composite (RHC) 2LiBH4 + MgH2. The results of this work demonstrate the concrete possibility to use Mg alloy wastes for hydrogen storage purposes.

  15. 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.

  16. 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.

  17. Twinning-mediated formability in Mg alloys

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

  18. 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

  19. Role of MgO impurity on the superconducting properties of MgB2

    NASA Astrophysics Data System (ADS)

    Singh, Dharmendra Kumar; Tiwari, Brajesh; Jha, Rajveer; Kishan, H.; Awana, V. P. S.

    2014-10-01

    We address the effect of MgO impurity on the superconducting properties of MgB2. The synthesis of MgB2 is very crucial because of sensitivity of Mg to oxidation which may lead to MgO as a secondary phase. Rietveld refinement was performed to determine the quantitative volume fraction of MgO in the samples synthesized by two different techniques. Both the samples were subjected to magnetization measurements under dc and a.c. applied magnetic fields and the observed results were compared as a function of temperature. Paramagnetic Meissner effect has been observed in a sample of MgB2 having more amount of MgO (with Tc = 37.1 K) whereas the pure sample MgB2 having minor quantity of MgO shows diamagnetic Meissner effect with Tc = 38.8 K. M-H measurements at 10 K reveal a slight difference in irreversibility field which is due to MgO impurity along with wide transition observed from ac magnetic susceptibility measurements. The magnetotransport measurements ρ(T) using ρN = 90%, 50% and 10% criterion on pure sample of MgB2 has been used to determine the upper critical field whereas the sample having large quantity of MgO does not allow these measurements due to its high resistance.

  20. 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.

  1. Effect of ambient Mg/Ca ratio on Mg fractionation in calcareous marine invertebrates: A record of the oceanic Mg/Ca ratio over the Phanerozoic

    NASA Astrophysics Data System (ADS)

    Ries, Justin B.

    2004-11-01

    The Mg/Ca ratio of seawater has changed significantly over the Phanerozoic, primarily as a function of the rate of ocean-crust production. Echinoids, crabs, shrimps, and calcareous serpulid worms grown in artificial seawaters encompassing the range of Mg/Ca ratios that existed throughout the Phanerozoic exhibit a direct nonlinear relationship between skeletal and ambient Mg/Ca. Specimens grown in seawater with the lowest Mg/Ca (˜1) changed their mineralogy to low-Mg calcite (<4 mol% MgCO3), suggesting that these high-Mg calcareous organisms would have produced low-Mg calcite in the Cretaceous, when oceanic Mg/Ca was lowest (˜1). These results support the empirical evidence that the skeletal chemistry of calcareous organisms has varied significantly over the Phanerozoic as a function of the Mg/Ca of seawater, and that the Mg/Ca of unaltered fossils of such organisms may be a record of oceanic Mg/Ca throughout the Phanerozoic. Mg fractionation algorithms, which relate skeletal Mg/Ca, seawater Mg/Ca, and temperature, were derived from these and other experiments. They can be used to estimate paleoceanic Mg/ Ca ratios and temperatures from fossil skeletal Mg/Ca of the organisms evaluated. Pale oceanic Mg/Ca ratios, recalculated by using the echinoderm Mg fractionation algorithm from published fossil echinoid Mg/Ca, crinoid Mg/Ca, and paleotemperature data, are consistent with other estimates and models of oceanic Mg/Ca over the Phanerozoic.

  2. 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.

  3. Valsartan 160 mg/Amlodipine 5 mg Combination Therapy versus Amlodipine 10 mg in Hypertensive Patients with Inadequate Response to Amlodipine 5 mg Monotherapy

    PubMed Central

    Sung, Jidong; Jeong, Jin-Ok; Kwon, Sung Uk; Won, Kyung Heon; Kim, Byung Jin; Cho, Byung Ryul; Kim, Myeong-Kon; Lee, Sahng; Kim, Hak Jin; Lim, Seong-Hoon; Park, Seung Woo

    2016-01-01

    Background and Objectives When monotherapy is inadequate for blood pressure control, the next step is either to continue monotherapy in increased doses or to add another antihypertensive agent. However, direct comparison of double-dose monotherapy versus combination therapy has rarely been done. The objective of this study is to compare 10 mg of amlodipine with an amlodipine/valsartan 5/160 mg combination in patients whose blood pressure control is inadequate with amlodipine 5 mg. Subjects and Methods This study was conducted as a multicenter, open-label, randomized controlled trial. Men and women aged 20-80 who were diagnosed as having hypertension, who had been on amlodipine 5 mg monotherapy for at least 4 weeks, and whose daytime mean systolic blood pressure (SBP) ≥135 mmHg or diastolic blood pressure (DBP) ≥85 mmHg on 24-hour ambulatory blood pressure monitoring (ABPM) were randomized to amlodipine (A) 10 mg or amlodipine/valsartan (AV) 5/160 mg group. Follow-up 24-hour ABPM was done at 8 weeks after randomization. Results Baseline clinical characteristics did not differ between the 2 groups. Ambulatory blood pressure reduction was significantly greater in the AV group compared with the A group (daytime mean SBP change: -14±11 vs. -9±9 mmHg, p<0.001, 24-hour mean SBP change: -13±10 vs. -8±8 mmHg, p<0.0001). Drug-related adverse events also did not differ significantly (A:AV, 6.5 vs. 4.5 %, p=0.56). Conclusion Amlodipine/valsartan 5/160 mg combination was more efficacious than amlodipine 10 mg in hypertensive patients in whom monotherapy of amlodipine 5 mg had failed. PMID:27014353

  4. 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.

  5. 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. PMID:26838918

  6. 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.

  7. 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.

    2016-07-01

    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.

  8. 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.

  9. MgO Solubility in Steelmaking Slags

    NASA Astrophysics Data System (ADS)

    Tayeb, Mohammed A.; Assis, Andre N.; Sridhar, Seetharaman; Fruehan, Richard J.

    2015-04-01

    A predominantly liquid and MgO-saturated slag is preferred in EAF and BOF steelmaking. Fully liquid slag provides a better environment for faster mass transfer due to lower bulk viscosities and larger liquid slag volume and these help dephosphorization and desulfurization. Also, an MgO-saturated slag would be preferable in order to increase the lifetime of furnace refractory lining by reducing the extent of dissolution. This article will demonstrate the factors that would influence MgO saturation, which includes FeO, CaO, P2O5, and Al2O3 contents and temperature. In addition, this paper comments on the applicability and accuracy of FactSage prediction, which are compared to laboratory experiments. The results indicate that FactSage may underestimate MgO solubility by up to 2.5 wt pct at higher basicities while there is reasonable agreement with current measurements at lower basicities.

  10. 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.

  11. 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.

  12. Mifepristone 5 mg versus 10 mg for emergency contraception: double-blind randomized clinical trial

    PubMed Central

    Carbonell, Josep Lluis; Garcia, Ramon; Gonzalez, Adriana; Breto, Andres; Sanchez, Carlos

    2015-01-01

    Purpose To estimate the efficacy and safety of 5 mg and 10 mg mifepristone for emergency contraception up to 144 hours after unprotected coitus. Methods This double-blind randomized clinical trial was carried out at Eusebio Hernandez Hospital (Havana, Cuba). A total of 2,418 women who requested emergency contraception after unprotected coitus received either 5 mg or 10 mg mifepristone. The variables for assessing efficacy were the pregnancies that occurred and the fraction of pregnancies that were prevented. Other variables assessed were the side effects of mifepristone, vaginal bleeding, and changes in the date of the following menstruation. Results There were 15/1,206 (1.2%) and 9/1,212 (0.7%) pregnancies in the 5 mg and 10 mg group, respectively (P=0.107). There were 88% and 93% prevented pregnancies in the 5 mg and un ≥7 days was experienced by 4.9% and 11.0% of subjects in the 5 mg and 10 mg group, respectively (P=0.001). There was a significant high failure rate for women weighing >75 kg in the 5 mg group. Conclusion It would be advisable to use the 10 mg dose of mifepristone for emergency contraception as there was a trend suggesting that the failure rate of the larger dose was lower. PMID:25624773

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

    Magnesium/silicon carbide (Mg/SiC) has the potential to be the best-performing reflective multilayer coating 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. 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.

  14. 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

  15. The study of MgB2/BN/MgB2 trilayer films

    NASA Astrophysics Data System (ADS)

    Hu, Hui; Feng, Qingrong; Wang, Yue; Zhang, Yan

    2015-12-01

    MgB2/BN/MgB2 trilayer films have been fabricated by using hybrid physical-chemical vapor deposition (HPCVD) method for the MgB2 layers and chemical vapor deposition (CVD) method for the BN layers in the same reactor. The films are studied by X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD) and magnetization measurements. These test outcomes indicate the trilayer films are grown without deteriorating the superconductivity of MgB2 films. Our results show that it is feasible to grow MgB2/BN/MgB2 trilayer films in the same reactor sequentially, which has the advantage of reducing contamination during the growth. This therefore opens the door for fabricating all-MgB2 Josephson junctions by using the BN film as the insulating layer.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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.

  2. 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.

  3. Electronic states of MgO: Spectroscopy, predissociation, and cold atomic Mg and O production

    SciTech Connect

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

    2010-10-14

    We used multiconfigurational methods and a large basis set to compute the potential energy curves of the valence and valence-Rydberg electronic states of MgO molecule. New bound electronic states are found. Using these highly correlated wave functions, we evaluated their mutual spin-orbit couplings and transition moment integrals. For the bound electronic states of MgO, we deduced an accurate set of spectroscopic constants that agree remarkably well with experimental results. Moreover, our potentials, transition moments, and spin-orbit coupling evolutions are incorporated into Fermi golden rule calculations to deduce the radiative lifetimes of MgO(B {sup 1}{Sigma}{sup +}) rovibrational levels and the natural lifetimes of MgO(A {sup 1}{Pi}) vibrational levels, where a good agreement is found with experimental values. Finally, we suggest new routes for the production of cold Mg and O atoms and cold MgO molecules.

  4. 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.

  5. 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

  6. Spontaneous polarization driven Mg concentration profile reconstruction in MgZnO/ZnO heterostructures

    SciTech Connect

    Imasaka, K.; Falson, J.; Kozuka, Y. Kawasaki, M.; Tsukazaki, A.

    2014-06-16

    Atomic reconstruction at the interface of MgZnO and ZnO in molecular beam epitaxy grown heterostructures is investigated. Using secondary ion mass spectroscopy, we experimentally find that Mg atomic reconstruction depends on the polarity of the interface; it is not observed in n-type interfaces (MgZnO on Zn-polar ZnO) owing to electron accumulation, while in p-type interfaces (ZnO on Zn-polar MgZnO), Mg drastically redistributes into the ZnO layer. Combined with self-consistent calculation of band profiles and carrier distributions, we reveal that the observed Mg reconstruction is not due to thermal diffusion but consequences in order to avoid hole accumulation. This tendency implies inherent significant asymmetry of energy scales of atomic and electronic reconstructions between n-type and p-type interfaces.

  7. 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

  8. Influence of RCS on Al-3Mg and Al-3Mg-0.25Sc alloys

    NASA Astrophysics Data System (ADS)

    Bhovi, Prabhakar M.; Venkateswarlu, K.

    2016-02-01

    An influence of repetitive corrugation and straightening (RCS) was studied on Al-3Mg and Al-3Mg-0.25Sc alloys up to eight passes. Each pass consist of a corrugation and followed by straightening. This has resulted in introducing large plastic strain in sample, and thus led to formation of sub-micron grain sizes with high angle grain boundaries. These sub grain formation was eventually resulted in improved mechanical properties. The average grain size of Al-3Mg-0.25Sc alloy after 8 passes yielded to ∼0.6pm. Microhardness, strength properties were evaluated and it suggests that RCS was responsible for high hardness values as compared to the as cast samples. The microhardness values after RCS were 105 HV and 130 HV for Al-3Mg and Al-3Mg-0.25Sc alloys, respectively. Similarly, ∼ 40% improvement in tensile strength from 240 MPa to 370 MPa was observed for Al- 3Mg-0.25Sc alloy after RCS process.Al-3Mg and Al-3Mg-0.25Scalloys exhibited maximum strength of 220 MPa and 370 MPa, respectively. It is concluded that RCS process has a strong influence on Al- 3Mg and Al-3Mg-0.25Sc alloys for obtaining improved mechanical properties and grain refinement. In addition to RCS process and presence of AESc precipitates in Al-3Mg-0.25Sc alloy had a significant role in grain refinement and improved mechanical properties as compared to Al-3Mg alloy.

  9. Excited states in ^22Mg and the ^21Na(p,γ)^22Mg reaction

    NASA Astrophysics Data System (ADS)

    Jewett, C.; Chipps, K.; Greife, U.; Bishop, S.; D'Auria, J.; Lamey, M.; Trinczek, M.; Hutcheon, D.; Ottewell, D.; Olin, A.; Buchmann, L.; Rogers, J.; Pearson, J.; Engel, S.; Gigliotti, D.; Ruiz, C.; Ruprecht, G.; Vockenhuber, C.; Gross, C.; Radford, D.; Yu, C.-H.; Blackmon, J.; Bardayan, D.; Smith, M. S.; Kozub, R.

    2004-10-01

    In explosive astrophysical scenarios like novae or x-ray bursts, the ^21Na(p,γ)^22Mg reaction is believed to play an important role. The proton capture proceeds predominantly via isolated excited states in the ^22Mg nucleus. This talk will present results from a search for excited states in ^22Mg via the ^12C + ^12C reaction measured at HRIBF (ORNL) and from a direct measurement of ^21Na(p,γ)^22Mg with a radioactive ion beam at ISAC (TRIUMF).

  10. 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. PMID:26636472

  11. 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.

  12. 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)

  13. 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.

  14. Mg2+-sensing mechanism of Mg2+ transporter MgtE probed by molecular dynamics study

    PubMed Central

    Ishitani, Ryuichiro; Sugita, Yuji; Dohmae, Naoshi; Furuya, Noritaka; Hattori, Motoyuki; Nureki, Osamu

    2008-01-01

    Proper regulation of the intracellular ion concentration is essential to maintain life and is achieved by ion transporters that transport their substrates across the membrane in a strictly regulated manner. MgtE is a Mg2+ transporter that may function in the homeostasis of the intracellular Mg2+ concentration. A recent crystallographic study revealed that its cytosolic domain undergoes a Mg2+-dependent structural change, which is proposed to gate the ion-conducting pore passing through the transmembrane domain. However, the dynamics of Mg2+ sensing, i.e., how MgtE responds to the change in the intracellular Mg2+ concentration, remained elusive. Here we performed molecular dynamics simulations of the MgtE cytosolic domain. The simulations successfully reproduced the structural changes of the cytosolic domain upon binding or releasing Mg2+, as well as the ion selectivity. These results suggested the roles of the N and CBS domains in the cytosolic domain and their respective Mg2+ binding sites. Combined with the current crystal structures, we propose an atomically detailed model of Mg2+ sensing by MgtE. PMID:18832160

  15. New FCC Mg-Zr and Mg-Zr-ti deuterides obtained by reactive milling

    NASA Astrophysics Data System (ADS)

    Guzik, Matylda N.; Deledda, Stefano; Sørby, Magnus H.; Yartys, Volodymyr A.; Hauback, Bjørn C.

    2015-03-01

    Results for binary Mg-Zr and ternary Mg-Zr-Ti mixtures ball milled at room temperature under reactive deuterium atmosphere (5.6-6.7 MPa) are reported. X-ray and neutron powder diffraction combined with Rietveld refinements show that two new cubic phases were formed during milling. Mg0.40Zr0.60D1.78 and Mg0.40Zr0.26Ti0.34D1.98 crystallize with disordered face centered cubic metal atom arrangements. Results of differential scanning calorimetry and termogravimetric measurements demonstrate that both deuterides desorb deuterium at lower temperatures than MgD2, ZrD2 or TiD2; 528 and 575 K in the Mg-Zr-D and Mg-Zr-Ti-D system, respectively. Interestingly, Mg0.40Zr0.26Ti0.34D1.98 stores deuterium reversibly at 673 K and 10 MPa of D2.

  16. Role of MgCo compound on the sorption properties of the Mg-Co milled mixtures

    NASA Astrophysics Data System (ADS)

    Verón, M. G.; Gennari, F. C.; Meyer, G. O.

    The influence of MgCo on the reaction paths during hydriding and dehydriding processes of Mg-Co mixtures was studied using a combined HP-DSC and XRD approach. Mg-Co mixtures with different compositions were mechanically milled under argon to prepare Mg-Co nanocomposites and then submitted to thermal treatment at 300 °C for 5 days to induce MgCo formation. The local Mg-Co composition in the milled and milled-heated samples determines the nature of the phases obtained after hydriding/dehydriding cycling. The formation of Mg 6Co 2H 11, Mg 2CoH 5 and MgH 2 hydrides occurs after the first hydriding stage of the 2Mg-Co and Mg-Co milled mixtures due to kinetic restrictions. On the contrary, Mg-Co milled-heated mixture exhibits the selective formation of Mg 2CoH 5 during first hydriding via two-step reaction. In the first one, MgCo disproportion to MgH 2 and Co takes place simultaneously with Mg hydriding (<200 °C). The second step involves MgCo hydriding to Mg 2CoH 5 through MgH 2 as intermediate phase (>200 °C). Dehydriding reaction is enhanced by dispersion of Co into Mg-matrix, which reduces more than 100 °C the hydrogen desorption temperature when compared with the Mg-Co milled sample without previous heating.

  17. Single crystal growth of MgB 2 by evaporating Mg-flux method

    NASA Astrophysics Data System (ADS)

    Du, Wei; Xu, Huizhong; Zhang, Hongbin; Xu, Dong; Wang, Xinqiang; Hou, Xianqin; Wu, Yongzhong; Jiang, Fuyi; Qin, Lianjie

    2006-04-01

    Well hexagonal plate-shaped single crystal of magnesium diboride (MgB 2) with the size of 100 μm has been grown at ambient pressure by evaporating Mg-flux method which is a new practice to grow MgB 2 single crystal. The superconducting transition of as-prepared crystals was measured to be at about 33.7 K by superconducting quantum interference device (dc-SQUID) magnetometer. The X-ray powder diffraction (XRD) confirmed the MgB 2 phase, and the electron diffraction patterns measured by using high-resolution transmission electron microscope (HRTEM) confirmed the structure of MgB 2 single crystal. The single crystal images were observed by scanning electron microscope (SEM) and metallographic microscope (MM). The micromechanism of crystal growth is also proposed through the investigations of SEM and MM.

  18. Growth of MgO on multi-layered graphene and Mg in PVA matrix

    NASA Astrophysics Data System (ADS)

    Marka, Sandeep K.; Mohiddon, Md. Ahamad; Prasad, Muvva D.; Srikanth, Vadali V. S. S.

    2015-07-01

    An easy and low temperature in-situ growth of MgO micro-rods on multi-layered graphene (MLG) in poly vinyl alcohol (PVA) matrix is elucidated. MLG decked with nanosized fragments of MgO and PVA are used as the starting materials to form MgO micro-rods (width = ∼1 μm and length = ∼4 μm) and MLG filled PVA composite film. Simple solution mixing, spin coating and simple drying processes are used to obtain the PVA composite. The growth mechanism of MgO micro-rods and the role of PVA in the growth of MgO micro-rods are explained on the basis of the observed morphological, structural and phase characteristics and a further controlled synthesis experiment, respectively.

  19. 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…

  20. 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…

  1. Il problema del litio.

    NASA Astrophysics Data System (ADS)

    D'Antona, F.

    1995-03-01

    Contents: 1. Introduzione. 2. La nucleosintesi del Big Bang. 3. Il litio nelle stelle di popolazione II. 4. I modelli stellari standard. 5. Il litio negli ammassi aperti. 6. Meccanismi di distruzione "non standard". 7. I modelli non-standard applicati alla popolazione II. 8. L'evoluzione Galattica del litio. 9. Quali stelle producono litio? 10. Il litio come elemento chiave per dare un nome agli oggetti stellari più minuscoli. 11. Conclusioni.

  2. A first-principles study of the thermodynamic and electronic properties of Mg and MgH2 nanowires.

    PubMed

    Wu, Xinxing; Zhang, Ruiqi; Yang, Jinlong

    2016-07-28

    In this article, we studied the thermodynamic and electronic properties of Mg and MgH2 nanowires with different diameters, and elucidated why MgH2 nanowires are good hydrogen storage materials through first-principles calculations. Previous experiments have shown that the orientation relationship between Mg and MgH2 nanowires is the Mg[0001] direction parallel to the MgH2[110] direction. In our calculations, Mg nanowires oriented along the [0001] direction and MgH2 nanowires oriented along the [110] direction were built from bulk Mg and MgH2 crystals, respectively. We found that as the diameters of Mg and MgH2 nanowires decrease, Mg and MgH2 nanowires become more unstable, and the hydrogen desorption energies and temperatures of MgH2 nanowires decrease. That is, the thinner the MgH2 nanowires get, the more dramatically hydrogen desorption temperatures (Td) will decrease. Meanwhile, we also found that when the diameters of MgH2 nanowires are larger than 1.94 nm, the Td almost maintain the same value at about 440 K, only about 40 K lower than that of bulk MgH2 crystal; if the diameters are less than 1.94 nm, the Td reduce very quickly. In particular, compared with bulk MgH2 crystal, the Td of the thinnest MgH2 nanowire with a diameter of 0.63 nm can be reduced by 164 K. In addition, the electronic structure calculations showed that Mg nanowires are metals, while MgH2 nanowires are semiconductors. In particular, our results showed that the electronic structures of MgH2 nanowires are influenced by the surface effect and quantum size effect. That is to say, the band gaps of MgH2 nanowires are controlled by surface electronic states and the size of MgH2 nanowires. PMID:27376680

  3. Espectroscopia del Cometa Halley

    NASA Astrophysics Data System (ADS)

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

    1987-05-01

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

  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. A preliminary study for novel use of two Mg alloys (WE43 and Mg3Gd).

    PubMed

    Guo, Yu; Liu, Weiwei; Ma, Shanshan; Wang, Jia; Zou, Jingting; Liu, Zhenzhen; Zhao, Jinghui; Zhou, Yanmin

    2016-05-01

    In this study, two types of magnesium alloys (WE43 and Mg3Gd) were compared with Heal-All membrane (a biodegradable membrane used in guided bone regeneration) in vitro to determine whether the alloys could be used as biodegradable membranes. Degradation behavior was assessed using immersion testing with simulated body fluid (SBF). Microstructural characteristics before and after immersion were evaluated through scanning electron microscopy, and degradation products were analyzed with energy dispersive spectrometry (EDS). To evaluate the biocompatibility of the three types of materials, we performed cytotoxicity, adhesion, and mineralization tests using human osteoblast-like MG63 cells. Immersion testing results showed no significant difference in degradation rate between WE43 and Mg3Gd alloys. However, both Mg alloys corroded faster than the Heal-All membrane, with pitting corrosion as the main corrosion mode for the alloys. Degradation products mainly included P- and Ca-containing apatites on the surface of WE43 and Mg3Gd, whereas these apatites were rarely detected on the surface of the Heal-All membrane. All three type of materials exhibited good biocompatibility. In the mineralization experiment, the alkaline phosphatase (ALP) activity of 10 % Mg3Gd extract was significantly higher than the extracts of the two other materials and the negative control. This study highlighted the potential of these Mg-REE alloys for uses in bone regeneration and further studies and refinements are obviously required. PMID:26968757

  6. Hydroxyl Motion in Mg(OH)2

    NASA Astrophysics Data System (ADS)

    Itoh, Yutaka; Isobe, Masahiko

    2015-11-01

    We report on pulsed 1H NMR studies of the hydroxyl OH groups in magnesium hydroxide Mg(OH)2 at 77-355 K at 42.5772 MHz. The Fourier-transformed NMR spectra show the superposition of broad and narrow components. The broad NMR spectrum is assigned to dipole-coupled protons on a rigid lattice in the bulk Mg(OH)2, while the narrow NMR spectrum is assigned to extrinsic protons, e.g., conduction protons facilitated by lattice defects. We found a monotonically decreasing linewidth of the broad NMR spectrum on heating. The monotonic decrease in the linewidth is associated with hopping protons around a threefold axis (rotational hydroxyl protons).

  7. Experimental Mg IX photorecombination rate coefficient

    NASA Astrophysics Data System (ADS)

    Schippers, S.; Schnell, M.; Brandau, C.; Kieslich, S.; Müller, A.; Wolf, A.

    2004-07-01

    The rate coefficient for radiative and dielectronic recombination of beryllium-like magnesium ions was measured with high resolution at the Heidelberg heavy-ion storage ring TSR. In the electron-ion collision energy range 0-207 eV resonances due to 2s -> 2p (Δ N = 0) and 2s -> 3l (Δ N=1) core excitations were detected. At low energies below 0.15 eV the recombination rate coefficient is dominated by strong 1s2 (2s 2p 3P) 7l resonances with the strongest one occuring at an energy of only 21 meV. These resonances decisively influence the Mg IX recombination rate coefficient in a low temperature plasma. The experimentally derived Mg IX dielectronic recombination rate coefficient (±15% systematical uncertainty) is compared with the recommendation by Mazzotta et al. (1998, A&AS, 133, 403) and the recent calculations by Gu (2003, ApJ, 590, 1131) and by Colgan et al. (2003, A&A, 412, 597). These results deviate from the experimental rate coefficient by 130%, 82% and 25%, respectively, at the temperature where the fractional abundance of Mg IX is expected to peak in a photoionized plasma. At this temperature a theoretical uncertainty in the 1s2 (2s 2p 3P) 7l resonance positions of only 100 meV would translate into an uncertainty of the plasma rate coefficient of almost a factor 3. This finding emphasizes that an accurate theoretical calculation of the Mg IX recombination rate coefficient from first principles is challenging.

  8. 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

  9. 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.

  10. Roaming dynamics in the MgH + H→Mg + H 2 reaction: Quantum dynamics calculations

    NASA Astrophysics Data System (ADS)

    Takayanagi, Toshiyuki; Tanaka, Tomokazu

    2011-03-01

    Reaction mechanisms of the MgH + H→Mg + H 2 reaction have been investigated using quantum reactive scattering methods on a global ab initio potential energy surface. There exist two microscopic mechanisms in the dynamics of this reaction. One is a direct hydrogen abstraction reaction and the other proceeds via initial formation of a HMgH complex in the deep potential well. The result of the present quantum dynamics calculations suggests that the HMgH complex formed in the reaction mainly decays into the Mg + H 2 channel via a 'roaming mechanism' without going through the saddle point region.

  11. NEXAFS Study of Air Oxidation for Mg Nanoparticle Thin Film

    NASA Astrophysics Data System (ADS)

    Ogawa, S.; Murakami, S.; Shirai, K.; Nakanishi, K.; Ohta, T.; Yagi, S.

    2013-03-01

    The air oxidation reaction of Mg nanoparticle thin film has been investigated by Mg K-edge NEXAFS technique. It is revealed that MgO is formed on the Mg nanoparticle surfaces at the early stage of the air oxidation for Mg nanoparticle thin film. The simulation of NEXAFS spectrum using standard spectra indicates the existence of complex magnesium carbonates (x(MgCO3).yMg(OH2).z(H2O)) in addition to MgO at the early stage of the air oxidation.

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

    PubMed Central

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

    2016-01-01

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

  13. 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. PMID:25905428

  14. A thermokinetic model for Mg-Si couple formation in Al-Mg-Si alloys

    NASA Astrophysics Data System (ADS)

    Svoboda, J.; Shan, Y. V.; Kozeschnik, E.; Fischer, F. D.

    2016-03-01

    Mg-Si couples formed from atomic Mg and Si represent the first step in Mg-Si cluster formation in a dilute Al-Mg-Si system. Based on the thermodynamic extremal principle, a kinetic model for Mg-Si couple formation is developed. The model utilizes the trapping concept for the calculation of Gibbs energy of the non-equilibrium system and provides a generalized (multiplicative) form of the Oriani equation for description of the equilibrium state. The dissipation in the system accounts for diffusion of both Mg and Si atoms in the lattice. The model is compared with the classical Lidiard and Howard equilibrium theory. Some demonstrative examples are presented. Finally the model is applied to an experimentally studied system. Good quantitative agreement with quenching experiments is obtained, if, simultaneously, the impact of excess quenched-in vacancies and their gradual annihilation in the system, which has been already treated in a previous paper, are accounted for. The model is generally applicable for any couple (and pair) formation.

  15. 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.

  16. Theoretical Investigation of the Electronic Structure and Spectra of Mg(2+)He and Mg(+)He.

    PubMed

    Bejaoui, M; Dhiflaoui, J; Mabrouk, N; El Ouelhazi, R; Berriche, H

    2016-02-11

    The ground and many excited states of the Mg(+)He van der Waals molecular system have been explored using a one-electron pseudopotential approach. In this approach, effective potentials are used to consider the Mg(2+) core and the electron-He effects. Furthermore, a core-core interaction is included. This has reduced the number of active electrons of the Mg(+)He, to be considered in the calculation, to a single valence electron. This has permitted to use extended Gaussian basis sets for Mg and He. Therefore, the potentianl energy and dipole moments calculations are carried out at the Hartree-Fock level of theory, and the spin-orbit effect is included using a semiclassical approach. The core-core interaction for the Mg(2+)He ground state is included using accurate CCSD(T) calculations. The spectroscopic constants of the Mg(+)He electronic states are extracted and compared with the existing theoretical works, where very good agreement is observed. Moreover, the transition dipole function has been determined for a large and dense grid of internuclear distances including the spin-orbit effect. PMID:26783874

  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. The Atomization Energy of Mg4

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    The atomization energy of Mg4 is determined using the MP2 and CCSD(T) levels of theory. Basis set incompleteness, basis set extrapolation, and core-valence effects are discussed. Our best atomization energy, including the zero-point energy and scalar relativistic effects, is 24.6+/-1.6 kcal per mol. Our computed and extrapolated values are compared with previous results, where it is observed that our extrapolated MP2 value is good agreement with the MP2-R12 value. The CCSD(T) and MP2 core effects are found to have the opposite signs.

  19. Dipole transition strengths in Mg26

    NASA Astrophysics Data System (ADS)

    Schwengner, R.; Wagner, A.; Fujita, Y.; Rusev, G.; Erhard, M.; de Frenne, D.; Grosse, E.; Junghans, A. R.; Kosev, K.; Schilling, K. D.

    2009-03-01

    Excited states with Jπ=1+ and 1- in Mg26 were studied in a photon-scattering experiment using bremsstrahlung produced by an electron beam of 13.0 MeV kinetic energy provided by the superconducting electron linear accelerator ELBE. We determined the transition strengths from the 1+ and 1- states to the ground state as well as to low-lying excited states. In addition, we observed a J=1 state at 11.154 MeV, above the neutron-separation energy of 11.093 MeV, and determined its partial γ decay width for the first time.

  20. 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.

  1. 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…

  2. 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,…

  3. 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.

  4. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  6. Highly reversible Mg insertion in nanostructured Bi for Mg ion batteries.

    PubMed

    Shao, Yuyan; Gu, Meng; Li, Xiaolin; Nie, Zimin; Zuo, Pengjian; Li, Guosheng; Liu, Tianbiao; Xiao, Jie; Cheng, Yingwen; Wang, Chongmin; Zhang, Ji-Guang; Liu, Jun

    2014-01-01

    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. This paper reports 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/cm(3)Bi), excellent stability, and high Coulombic efficiency (95% initial and very close to 100% afterward). 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 Mg(2+). 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 its properties. PMID:24279987

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. Neural depolarization triggers Mg2+ influx in rat hippocampal neurons.

    PubMed

    Yamanaka, R; Shindo, Y; Karube, T; Hotta, K; Suzuki, K; Oka, K

    2015-12-01

    Homeostasis of magnesium ion (Mg(2+)) plays key roles in healthy neuronal functions, and deficiency of Mg(2+) is involved in various neuronal diseases. In neurons, we have reported that excitotoxicity induced by excitatory neurotransmitter glutamate increases intracellular Mg(2+) concentration ([Mg(2+)]i). However, it has not been revealed whether neuronal activity under physiological condition modulates [Mg(2+)]i. The aim of this study is to explore the direct relationship between neural activity and [Mg(2+)]i dynamics. In rat primary-dissociated hippocampal neurons, the [Mg(2+)]i and [Ca(2+)]i dynamics were simultaneously visualized with a highly selective fluorescent Mg(2+) probe, KMG-104, and a fluorescent Ca(2+) probe, Fura Red, respectively. [Mg(2+)]i increase concomitant with neural activity by direct current stimulation was observed in neurons plated on an indium-tin oxide (ITO) glass electrode, which enables fluorescent imaging during neural stimulation. The neural activity-dependent [Mg(2+)]i increase was also detected in neurons whose excitability was enhanced by the treatment of a voltage-gated K(+) channel blocker, tetraethylammonium (TEA) at the timings of spontaneous Ca(2+) increase. Furthermore, the [Mg(2+)]i increase was abolished in Mg(2+)-free extracellular medium, indicating [Mg(2+)]i increase is due to Mg(2+) influx induced by neural activity. The direct neuronal depolarization by veratridine, a Na(+) channel opener, induced [Mg(2+)]i increase, and this [Mg(2+)]i increase was suppressed by the pretreatment of a non-specific Mg(2+) channel inhibitor, 2-aminoethoxydiphenyl borate (2-APB). Overall, activity-dependent [Mg(2+)]i increase results from Mg(2+) influx through 2-APB-sensitive channels in rat hippocampal neurons. PMID:26455951

  13. 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

  14. PLD growth of multilayered MgO/Ag(001)/MgO photocathode

    NASA Astrophysics Data System (ADS)

    Velazquez, Daniel; Yusof, Zikri; Spentzouris, Linda; Terry, Jeff

    2014-03-01

    Films of of Ag, MgO and multilayers of these were grown via pulsed laser deposition on clean Si(111) 7x7 substrates. The films were studied using reflection high-energy electron diffraction, Kelvin probe and ellipsometry. Information about crystalline and atomic structure as well as surface condition, work function and film thickness was obtained using these techniques. Deposition at various substrate temperatures and partial oxygen pressures was performed in order to understand the parameter settings that lead to higher quality crystalline films. Epitaxial films of Ag(111) were found to grow at an optimal substrate temperature of 256 °C (fig 1.). The superstructure Ag(111) √3 x √3 occurs when deposition takes place at a substrate temperature of 620 °C. In addition, MgO films were found to grow with small grain size on both, Si(111) 7x7 and Ag(111)/Si(111) at room temperature with a partial oxygen pressure of 5x10-5 Torr (fig. 2). Highly-oriented, polycrystalline growth of MgO films is evidenced by their RHEED pattern. In addition, the obliquely-shaped diffraction spots indicate the growth of secondary phase precipitates, most likely due to oxygen deficit. Measurements of the work function of these multilayers indicate that the Ag(111) work function (4.75 eV) is sharply suppressed with the first few MgO shots and has a quasi-linear increase for the first few monolayers (fig. 3). As the thickness of MgO increases (a few nanometers) the work function drops again and stabilizes at the level of MgO (~ 4.2 eV).

  15. On nanoparticle surface growth: MgO nanoparticle formation during a Mg particle combustion

    NASA Astrophysics Data System (ADS)

    Altman, Igor S.; Agranovski, Igor E.; Choi, Mansoo

    2004-06-01

    It is demonstrated that formation of MgO nanoparticles during a Mg particle combustion occurs in the vapor adsorption regime and the particle coagulation and coalescence do not play any significant role in the process in question. Analysis of the particle size distributions shows that the rate of the nanoparticle condensation growth strongly depends on the actual particle size. The revealed dependence of the growth rate upon the size is consistent with the exponential law recently predicted. This finding can shed light on the long-standing general problem of gas-phase nanotechnology—the origin of lognormal size distribution behavior of generated nanoparticles.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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. PMID:26038847

  1. Superplasticity in a thermomechanically processed High-Mg, Al-Mg alloy

    NASA Astrophysics Data System (ADS)

    McNelley, T. R.; Lee, E. W.; Mills, M. E.

    1986-06-01

    Superplastic elongations in excess of 400 pct have been observed in tension testing at 573 K (300 °C) and strain rate έ = 2 × 10-3 s-1 for a thermomechanically processed Al-10.2 pct Mg-0.52 pct Mn alloy. The thermomechanical processing consists of solution treatment and hot working, followed by extensive warm rolling at 573 K (300 °C), a temperature below the solvus for Mg in the alloy. This processing results in a fine subgrain structure in conjunction with refined and homogeneously distributed β(Al8Mg5) and MnAl6 precipitates. This structure does not statically recrystallize when annealed at 573 K (300 °C) but appears to recrystallize continuously during deformation at such a temperature and the resulting fine grain structure deforms with minimal cavitation. At temperatures above the Mg-solvus, e.g., 673 K (400 °C), recrystallization and growth occur readily resulting in rela tively coarser structures which deform superplastically but with extensive grain boundary sliding and cavitation.

  2. 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.

  3. 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.

  4. Effects of MgO and Mg(OH)2 on Phase Formation and Properties of MgTiO3 Microwave Dielectric Ceramics

    NASA Astrophysics Data System (ADS)

    Liou, Yi-Cheng; Yang, Song-Ling; Chu, Sheng-Yuan

    2015-04-01

    This study investigates the effects of MgO and Mg(OH)2 on the phase formation and properties of MgTiO3 ceramics prepared via a reaction-sintering process. A mixture of raw materials was sintered into MgTiO3 ceramics by bypassing calcination and subsequent pulverization stages. The second phase MgTi2O5 forms in pellets with added MgO (MT) and disappears in pellets with added Mg(OH)2 (MHT). Abnormal grain growth is observed in MHT due to different reactions during the heating process. Microwave dielectric properties ɛ r = 18.5-19.2, Q × f = 53,300-76,300 GHz and τ f = -58.7 to -53.2 ppm/°C are measured for MT. ɛ r = 15.3-15.9, Q × f = 118,800-144,400 GHz and τ f = -52.8 to -49.8 ppm/°C are measured for MHT. The lower ɛ r for MHT is caused by a lower density. Q × f increases and τ f shifts to less negative values when Mg(OH)2 is used instead of MgO. The reaction-sintering process is then a simple and effective method to produce MgTiO3 ceramics for applications in microwave dielectric resonators.

  5. Report on the sintering and properties of MgO and MgO-5% TiC

    SciTech Connect

    Bengisu, M.; Inal, O.T.

    1992-07-01

    Sintering of technical grade MgO yields higher fractional densities compared to pure MgO. TiC reacts with MgO under sintering of MgO-TiC composites in air, yielding Mg{sub 2}TiO{sub 4} and CO or CO{sub 2}. This can be suppressed in vacuum by plasma sintering. Plasma sintering of MgO at 1300 C and short times does not produce satisfactory results. 5 vol% TiC increases the sinterability of MgO during conventional air sintering; larger additions (50 vol%) decrease sinterability due to macropores formed by gaseous reaction product. Microwave sintering of MgO is possible. Mechanical properties of MgO are improved by additions of small amounts of TiC to starting powders.

  6. A Fundamental Study on the [(μ-Cl)3Mg2(THF)6]+ Dimer Electrolytes for Rechargeable Mg Batteries

    SciTech Connect

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

    2015-01-01

    We present a fundamental study on [(μ-Cl)3Mg2(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]+. 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.

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

    DOE PAGESBeta

    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

  8. 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

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

    PubMed

    Gallagher, James R; Boldrin, Paul; Combes, Gary B; Ozkaya, Don; Enache, Dan I; Ellis, Peter R; Kelly, Gordon; Claridge, John B; Rosseinsky, Matthew J

    2016-02-28

    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

  10. 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

  11. 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.

  12. 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.

  13. Rotational band structure in 32Mg

    NASA Astrophysics Data System (ADS)

    Crawford, H. L.; Fallon, P.; Macchiavelli, A. O.; Poves, A.; Bader, V. M.; Bazin, D.; Bowry, M.; Campbell, C. M.; Carpenter, M. P.; Clark, R. M.; Cromaz, M.; Gade, A.; Ideguchi, E.; Iwasaki, H.; Langer, C.; Lee, I. Y.; Loelius, C.; Lunderberg, E.; Morse, C.; Richard, A. L.; Rissanen, J.; Smalley, D.; Stroberg, S. R.; Weisshaar, D.; Whitmore, K.; Wiens, A.; Williams, S. J.; Wimmer, K.; Yamamato, T.

    2016-03-01

    There is significant evidence supporting the existence of deformed ground states within the neutron-rich N ≈20 neon, sodium, and magnesium isotopes that make up what is commonly called the "island of inversion." However, the rotational band structures, which are a characteristic fingerprint of a rigid nonspherical shape, have yet to be observed. In this work, we report on a measurement and analysis of the yrast (lowest lying) rotational band in 32Mg up to spin I =6+ produced in a two-step projectile fragmentation reaction and observed using the state-of-the-art γ -ray tracking detector array, GRETINA (γ -ray energy tracking in-beam nuclear array). Large-scale shell-model calculations using the SDPF-U-MIX effective interaction show excellent agreement with the new data. Moreover, a theoretical analysis of the spectrum of rotational states as a function of the pairing gap, together with cranked-shell-model calculations, provides intriguing evidence for a reduction in pairing correlations with increased angular momentum, also in line with the shell-model results.

  14. Rotational Band Structure in 32Mg

    NASA Astrophysics Data System (ADS)

    Crawford, Heather; NSCL E11029 Collaboration Team

    2016-03-01

    There is significant evidence supporting the existence of deformed ground states within the neutron-rich N =20 neon, sodium, and magnesium isotopes that make up what is commonly called the ``Island of Inversion''. However, rotational band structures, a characteristic fingerprint of a rigid non-spherical shape, have yet to be observed. We report on a measurement and analysis of the yrast (lowest lying) rotational band in 32Mg up to spin I = 6+, produced in a two-step projectile fragmentation reaction and observed using the state-of-the-art γ-ray tracking detector array, GRETINA. Large-scale shell model calculations using the SDPF-U-MIX effective interaction show excellent agreement with the new data. Moreover, a theoretical analysis of the spectrum of rotational states as a function of the pairing gap, together with cranked shell model calculations, provides intriguing evidence for a reduction in pairing correlations with increased angular momentum, also in line with the shell-model results. This material is based upon work supported by the U.S. DOE, Office of Science, NP Office under Contract No. DE-AC02-05CH11231 (LBNL). GRETINA was funded by the U.S. DOE Office of Science. Operation of the array at NSCL was supported by NSF.

  15. Fabrication of decorated MgO crystalline fibers

    SciTech Connect

    Chen, Y.J.; Li, J.B.; Han, Y.S.; Yang, X.Z.; Dai, J.H

    2003-02-20

    By depositing Mg vapor generated via carbothermal reduction on boron powder in the presence of different additives, dumbbell-like MgO nanofibers, NaCl particle-decorated MgO nanofibers and camphor tree stalk-like MgO fibers were produced. SEM, TEM and EDS analysis showed that the additives of Si and NaCl deposited in the sites of stacking faults in fiber, which resulted in the growth of different morphologies of decorated fibers.

  16. Transition of interface oxide layer from porous Mg(OH)2 to dense MgO induced by polyaniline and corrosion resistance of Mg alloy therefrom

    NASA Astrophysics Data System (ADS)

    Luo, Yizhong; Sun, Yang; Lv, Jinlong; Wang, Xianhong; Li, Ji; Wang, Fosong

    2015-02-01

    The feasibility of polyaniline emeraldine base (EB) for enhancing long-term corrosion resistance of magnesium alloy (AZ91D Mg alloy) was confirmed, since the complex impedance of Mg alloy protected by EB/epoxy resin (ER) composite coating with 10 wt% EB loading maintained around 2 GΩ cm2 even after 80 day exposure in 0.5 M NaCl solution, while that of pure ER coated analogue decreased to 0.17 MΩ cm2 only after 31 days. The improvement in corrosion resistance was attributed to the transition of interface layer from porous Mg(OH)2 dominated one underneath pure ER coating to dense MgO dominated one underneath EB/ER coating, induced by the redox interaction of EB with Mg alloy. When the EB loading in EB/ER coating increased from 0 to 10 wt%, the relative XPS peak area ratio of MgO to Mg(OH)2 increased from 0.78 to 1.18, indicating that EB behaved as effective corrosion inhibitor causing the transformation of oxide layer from porous Mg(OH)2 to dense MgO.

  17. 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

  18. Mg-lattice associations in red coralline algae

    NASA Astrophysics Data System (ADS)

    Kamenos, N. A.; Cusack, M.; Huthwelker, T.; Lagarde, P.; Scheibling, R. E.

    2009-04-01

    Recent investigations have shown red coralline algae to record ambient temperature in their calcite skeletons. Temperature recorded by variation in Mg concentrations within algal growth bands has sub-annual resolution and high accuracy. The conversion of Mg concentration to temperature is based on the assumption of Ca replacement by Mg within the algal calcite skeleton at higher temperatures. While Mg-temperature relationships in coralline algae have been calibrated for some species, the location of Mg within the calcite lattice remains unknown. Critically, if Mg is not a lattice component but associated with organic components this could lead to erroneous temperature records. Before coralline algae are used in large scale climate reconstructions it is therefore important to determine the location of Mg. Synchrotron Mg-X-ray absorbance near edge structure (XANES) indicates that Mg is associated with the calcite lattice in Lithothamnion glaciale (contemporary free-living, contemporary encrusting and sub-fossil free-living) and Phymatolithon calcareum (contemporary free-living) coralline algae. Mg is deposited within the calcite lattice in all seasons ( L. glaciale & P. calcareum) and thallus areas ( P. calcareum). These results suggest L. glaciale and P. calcareum are robust Mg-palaeotemperature proxies. We suggest that similar confirmation be obtained for Mg associations in other species of red coralline algae aiding our understanding of their role in climate reconstruction at large spatial scales.

  19. Mg-lattice associations in red coralline algae

    NASA Astrophysics Data System (ADS)

    Kamenos, N. A.; Cusack, M.,; Huthwelker, T.; Lagarde, P.; Scheibling, R. E.

    2009-04-01

    Recent investigations have shown red coralline algae to record ambient temperature in their calcite skeletons. Temperature recorded by variation in Mg concentrations within algal growth bands has sub-annual resolution and high accuracy. The conversion of Mg concentration to temperature is based on the assumption of Ca replacement by Mg within the algal calcite skeleton at higher temperatures. While Mg-temperature relationships in coralline algae have been calibrated for some species, the location of Mg within the calcite lattice remains unknown. Critically, if Mg is not a lattice component but associated with organic components this could lead to erroneous temperature records. Before coralline algae are used in large scale climate reconstructions it is therefore important to determine the location of Mg. Synchrotron Mg-X-ray absorbance near edge structure (XANES) indicates that Mg is associated with the calcite lattice in Lithothamnion glaciale (contemporary free-living, contemporary encrusting and sub-fossil free-living) and Phymatolithon calcareum (contemporary free-living) coralline algae. Mg is deposited within the calcite lattice in all seasons (L. glaciale & P. calcareum) and thallus areas (P. calcareum). These results suggest L. glaciale and P. calcareum are robust Mg-palaeotemperature proxies. We suggest that similar confirmation be obtained for Mg associations in other species of red coralline algae aiding our understanding of their role in climate reconstruction at large spatial scales.

  20. Osteopenic effects of MgSO4 in multiple pregnancies.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To describe the effects of prolonged maternal treatment with MgSO4 in infants who were products of multiple pregnancies. Case series of infants presenting with osteopenia secondary to MgSO4 administration for preterm labor. Ten premature infants with hypermagnesemia (4.5+/-0.2 mg/dl), hypocalcemia (...

  1. 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.

  2. 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.

  3. 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}.

  4. 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.

  5. 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.

  6. 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.

  7. Formation and stability of hollow MgO nanoshells.

    PubMed

    Krishnan, Gopi; Palasantzas, G; Kooi, B J

    2010-07-01

    High temperature annealing of gas phase synthesized Mg nanoparticles surrounded by an MgO shell leads to formation of hollow MgO nanoshells due to the evaporation assisted Kirkendall effect. Under electron beam exposure in TEM, the (220) MgO facets reduce their high surface energy by forming cube facets, which is followed by nanoshell size reduction and collapse within a few minutes. However, in ambient conditions the nanoshells remain stable for significant periods of time and further degrade by becoming filled with carbon while lossing any MgO identity. Finally, in moderate low vacuum they remained stable for months indicating promise for applications. PMID:21128428

  8. 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.

  9. The Strength of the Spatially Interconnected Eutectic Network in HPDC Mg-La, Mg-Nd, and Mg-La-Nd Alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Bao; Gavras, Serge; Nagasekhar, Anumalasetty V.; Cáceres, Carlos Horacio; Easton, Mark A.

    2014-09-01

    3D numerical images of the intergranular percolating eutectic of two binary alloys, Mg-0.62 at. pctLa and Mg-0.60 at. pctNd, created using dual beam FIB tomography, were incorporated into an FEM code to model their tensile behavior. Due to its high volume fraction (29.9 pct), the behavior of the Mg-La network was akin to that of a stretch-dominated micro-truss structure, whereas the Mg-Nd's, with a relatively low volume fraction (7.5 pct), mimicked that of a bending-dominated structure. The 3D network contributed some 37 MPa to the strength of the Mg-La alloy casting, whereas it only added about 1.4 MPa to the Mg-Nd's. The model predictions based on the binary alloys were verified using cast-to-shape specimens of the Mg-La and two ternary Mg-La-Nd alloys, subjected to a flash-annealing aiming at breaking up the continuity of the 3D network, while preserving the rest of the microstructure unchanged. The flash-annealed specimens exhibited a decrease in strength that matched closely the computed values. Implications regarding alloy design involving the eutectic network and solid solution hardening of more complex alloys are discussed.

  10. Mg segregation in Mg-rich Mg-Ni switchable mirror studied by Rutherford backscattering, elastic recoil detection analysis, and nuclear reaction analysis

    SciTech Connect

    Sekiba, D.; Horikoshi, M.; Abe, S.; Ishii, S.

    2009-12-01

    Pd/Mg{sub 3.3}Ni films were prepared by dc sputtering deposition on three different substrates of glass, diamondlike carbon/Si, and Si. Hydrogenation and dehydrogenation cycles were performed on these samples simultaneously. The optical switching property due to the hydrogenation and dehydrogenation was monitored by the transmission of laser light via the glass substrate. The switching ability was totally lost after 120 cycles. We made comparative study of the composition change between the new (as-deposited) and old (after 120 switching cycles) samples by Rutherford backscattering (RBS), elastic recoil detection analysis (ERDA), and nuclear reaction analysis (NRA). From the RBS results we found out the segregation of a Mg layer between the Pd cap layer and the rest of the Mg-Ni layer. At the Pd/Mg interface in the old sample, thin MgO layer formed probably during the dehydrogenation process with O{sub 2}. ERDA showed that there is much hydrogen in the old sample. NRA displayed the depth profiles of hydrogen distribution in the old sample. It is revealed that much hydrogen is accumulated at the interface between the Pd cap layer and the segregated Mg layer. It can be concluded that the formations of oxide and hydride of the segregated Mg layer are the main reasons for the degradation of the Mg{sub 3.3}Ni switchable mirror.

  11. The Mg isotopic composition of Cenozoic seawater - evidence for a link between Mg-clays, seawater Mg/Ca, and climate

    NASA Astrophysics Data System (ADS)

    Higgins, John A.; Schrag, Daniel P.

    2015-04-01

    Cooling of Earth's climate over the Cenozoic has been accompanied by large changes in the magnesium and calcium content of seawater whose origins remain enigmatic. The processes that control these changes affect the magnesium isotopic composition of seawater, rendering it a useful tool for elucidating the processes that control seawater chemistry on geologic timescales. Here we present a Cenozoic magnesium isotope record of carbonate sediments and use a numerical model of seawater chemistry and the carbon cycle to test hypotheses for the covariation between Cenozoic seawater chemistry and climate. Records are consistent with a 2-3× increase in seawater Mg/Ca and little change in the Mg isotopic composition of seawater. These observations are best explained by a change in the cycling of Mg-silicates. We propose that Mg/Ca changes were caused by a reduction in removal of Mg from seawater in low-temperature marine clays, though an increase in the weathering of Mg-silicates cannot be excluded. We attribute the reduction in the Mg sink in marine clays to changes in ocean temperature, directly linking the major element chemistry of seawater to global climate and providing a novel explanation for the covariation of seawater Mg/Ca and climate over the Cenozoic.

  12. 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).

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. Structural and optical properties of ZnMgO nanostructures formed by Mg in-diffused ZnO nanowires

    SciTech Connect

    Pan, C.-J.; Hsu, H.-C.; Cheng, H.-M.; Wu, C.-Y.; Hsieh, W.-F.

    2007-04-15

    ZnMgO nanostructures with wurtzite phase were prepared by thermal diffusion of Mg into the ZnO nanowires. As ZnO light-emitting devices have been operated by using ZnMgO layers as energy barrier layers to confine the carriers, it is essential to realize the characterization of ZnMgO particularly. In this work, the Mg content in Zn{sub 1} {sub -x} Mg {sub x} O alloy determined by X-ray diffraction (XRD) and photoluminescence (PL) shows a good coincidence. The variation of lattice constant and the blueshift of near-band-edge emission indicate that Zn{sup 2+} ions are successfully substituted by Mg{sup 2+} ions in the ZnO lattice. In Raman-scattering studies, the change of E {sub 2}(high) phonon line shape in ZnO:Mg nanostructures reveals the microscopic substitutional disorder. In addition to the host phonons of ZnO, two additional bands around 383 and 510 cm{sup -1} are presumably attributed to the Mg-related vibrational modes. - Graphical abstract: We reported the synthesis of the ZnMgO nanostructures prepared by a simple vapor transport method. Magnesium-related anomalous modes are observed by Raman spectra for the first time in ZnMgO system.

  19. Formation and Thermodynamics of Mg-Al-Ti-O Complex Inclusions in Mg-Al-Ti-Deoxidized Steel

    NASA Astrophysics Data System (ADS)

    Ren, Ying; Zhang, Lifeng; Yang, Wen; Duan, Haojian

    2014-12-01

    The formation of Mg-Al-Ti-O complex inclusions in steel was investigated by laboratory experiments and thermodynamic calculation. The composition evolutions of Mg-Al-Ti-O inclusions in steel with different contents of [Al], [Mg], and [Ti] were discussed. Mg-Al-Ti-O complex inclusion with high TiOx content was liquid at 1873 K (1600 °C), indicating MgAl2O4 spinel inclusions can be modified to low melting temperature ones by combining TiOx component. The stability diagram of Al-Mg-Ti-O system inclusions in the molten steel at 1873 K (1600 °C) was calculated, considering many kinds of oxide inclusions such as MgO, Al2O3, TiOx, MgTi2O4, MgAl2O4, Al2TiO5, and liquid inclusion. The thermodynamic calculations are in good agreement with experimental results, which can predict the formation of Al-Mg-Ti-O complex inclusions in molten steel with a large concentration range of [Al], [Mg], and [Ti].

  20. 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

  1. MgO platelets and high critical field in MgB2 thin films doped with carbon from methane

    NASA Astrophysics Data System (ADS)

    Zhu, Y.; Hunte, F.; Zhuang, C. G.; Feng, Q. R.; Gan, Z. Z.; Xi, X. X.; Larbalestier, D. C.; Voyles, P. M.

    2009-12-01

    We report that C-doped MgB2 thin films deposited by hybrid physical-chemical vapor deposition (HPCVD) using CH4 as the carbon source have Hc2(0 K)~60 T, similar to that of HPCVD films obtained using (MeCp)2Mg for the carbon. Using transmission electron microscopy, we show that in the films doped using CH4 there is a MgB2C2 layer on top of the MgB2 film, which does not degrade the MgB2 connectivity or Jc. We also find a high density of coherent MgO nanoplatelets in the MgB2 which create strain fields which may give rise to strong π-band scattering and the very high Hc2.

  2. 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.

  3. 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).

  4. 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.

  5. 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.

  6. Mg Isotope Fractionation During Hydrothermal Ultramafic Rock Alteration

    NASA Astrophysics Data System (ADS)

    Beinlich, A.; Mavromatis, V.; Austrheim, H.; Oelkers, E. H.

    2013-12-01

    Both riverine and ocean waters are enriched in 24Mg compared to the homogenous chondritic Mg isotopic composition of the Earth's mantle requiring a fractionation step that is generally attributed to low temperature continental crust weathering [1,2,3]. Here we present new observations on the Mg isotope fractionation during hydrothermal alteration of ultramafic rocks from three different localities in Norway, the Linnajavri Ultramafic Complex (LUC), the Feragen Ultramafic Body (FUB), and the Solund Sedimentary Basin (SSB). Mineral separates of coexisting olivine and serpentine from serpentinized peridotite samples from the FUB and SSB exhibit invariant Mg isotope ratios suggesting that serpentinization does not fractionate Mg isotopes. In contrast, antigorite carbonation at the LUC resulted in significant inter-mineral Mg isotope fractionation among the antigorite, magnesite, and talc. The carbonation of the natural samples is constrained by O isotope thermometry at ~275 °C [4] and hence closes the temperature gap between previous investigations of the natural distribution of Mg isotopes during surface weathering and magmatic processes. Textures, mass-balance, and reaction path considerations indicate that antigorite carbonation conserved Mg and Si. The precursor antigorite has an isotopic composition of δ26Mg (DSM3)=-0.11×0.05 ‰, whereas the talc is enriched in 26Mg with mean δ26Mg=0.17×0.08 ‰ and the magnesite is depleted in 26Mg with mean δ26Mg=-0.95×0.15 ‰. This hydrothermal fractionation has significant implications for the Mg isotopic compositions of natural surface waters. Our results suggest that carbonation reactions beneath off-axis low temperature hydrothermal vent sites may exert an important control on the Mg isotope ratio in ocean water. As carbonate minerals dissolve significantly faster than silicate minerals [5,6], the chemical weathering of carbonated ultramafic and by analogy mafic rocks on the continents will yield isotopically

  7. 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.

  8. Dihydroxyprogesterone acetophenide 150 mg + estradiol enantate 10 mg as monthly injectable contraceptives.

    PubMed

    Jarquín González, J D; Elda de Aguirre, L; Rodríguez, C; Abrego de Aguilar, M; Carrillo, F; León, D A; Lima, M; Trigueros, S; Acosta, R

    1996-09-01

    A survey among users and health personnel participating in the Salvadorian Social Security Institute (ISSS) Family Planning Program revealed interest in including a monthly preparation for injection as a contraceptive method offered by this Institution. The formulation containing dihydroxyprogesterone acetophenide (DHPA) 150 mg + estradiol enantate (E2EN) 10 mg was chosen for conducting an open and prospective study of efficacy and tolerability. Between January 1992 and March 1994, 7054 women were treated with this product for a total of 60010 months. A sample composed of 4505 women treated at this Institution confirmed that average users are young, have one or two children, do not show a particular geographical distribution and choose the monthly injection instead of oral contraceptives as the first contraceptive method or for the puerperium. The study formulation showed a high efficacy (Pearl Index: 0.018) and tolerability (general withdrawal rate throughout the study: 27.09%). The most frequent adverse events included bleeding disorders, headache and mastalgia; their incidence decreased spontaneously from the sixth month (3.9%), reaching 0% after two years. Treatment was discontinued due to adverse events in 3.47% of women. No significant bodyweight or systolic and diastolic blood pressure alterations were observed. Based on these results, the monthly injectable contraceptive was included in the basic product list at ISSS. PMID:8910663

  9. Ácaros del mango

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  11. Magnetoresistance and electronic structure of granular films with MgO or MgF2 matrices

    NASA Astrophysics Data System (ADS)

    Fujiwara, Y.; Matsuda, H.; Sato, K.; Jimbo, M.; Kobayashi, T.

    2011-01-01

    The magneto-transport properties and electronic structures of FeCo-MgO, FeCoB-MgO, FeCo-MgF2 and FeCoB-MgF2 granular films were investigated. From the X-ray photoelectron spectroscopy (XPS) measurements, it was recognized that the oxide layer formed on the surface of granules in FeCo-MgO. Especially Fe oxides were preferentially formed. By using (Fe50Co50)80B20, the formation of Fe oxides on the granule surface was suppressed since B was oxidized instead of Fe. The MR ratio of FeCoB-MgO was approximately 2%. By using MgF2 matrix, the surface states of granules were drastically improved. XPS measurements indicated that an amount of metallic Fe in FeCoB-MgF2 increased compared with FeCoB-MgO. Reflecting the improvement of surface states of granules, a large MR ratio of approximately 6 % was obtained in FeCoB-MgF2.

  12. A high resolution atlas of Mg II profiles

    NASA Technical Reports Server (NTRS)

    Ewald, R.; Nichols-Bohlin, Joy Y.; Kondo, Yoji

    1990-01-01

    An atlas of high dispersion Mg II profiles for standard stars of spectral types B0 through G9 is presented. The atlas contains plots of the Mg II profiles for approximately 65 stars and associated equivalent width measurements for both absorption and emission components, and the subordinate lines. The atlas is used to investigate systematic behavior of the Mg II profiles and correlation of the behavior with spectral classification.

  13. Proximity Effect in Nb/Mg/CoFe Trilayers.

    NASA Astrophysics Data System (ADS)

    Choi, Seong Kook; Kwon, Jun Hyung; Char, Kookrin

    2007-03-01

    We have fabricated the Nb/Mg bilayer and Nb/Mg/CoFe trilayer samples by varying Mg layer thickness and measured their superconducting transition temperature Tc electrically using the 4-prove method. Mg normal layer was used to investigate the effect of its small atomic number, since we have observed previously the largely different behavior when Au, Cu and Al were used. When the Al layer was used, a very unusual behavior was found. Because of chemical interaction between Nb and Mg, the Tc transition curves did not show sharp Tc transition. In order to prevent this interaction, we inserted 2 nm thick Al layer between Nb and Mg. In the case of Nb/Al(2nm)/Mg, we observed Tc behavior consistent with a conventional SN theory. In the case of Nb/Al(2nm)/Mg/CoFe with fixed thicknesses of Nb and CoFe layer, the Tc values exhibited two distinct behavior as the thickness of Mg increased. The Tc value of S/N/F trialyer increased rapidly until the Mg thickness reached a few nm. As Mg thickness increased further to 200 nm, the Tc value of S/N/F decreased again, following closely those of the S/N data. Overall, the Mg data basically followed those of Al data, suggesting that the low atomic number of the normal layer is important in observing the unusual proximity effect in SNF trilayers. Our analysis of the interface effect using an Usadel picture will be presented.

  14. Defect structure of ultrafine MgB{sub 2} nanoparticles

    SciTech Connect

    Bateni, Ali; Somer, Mehmet E-mail: msomer@ku.edu.tr; Repp, Sergej; Erdem, Emre E-mail: msomer@ku.edu.tr; Thomann, Ralf; Acar, Selçuk

    2014-11-17

    Defect structure of MgB{sub 2} bulk and ultrafine particles, synthesized by solid state reaction route, have been investigated mainly by the aid of X-band electron paramagnetic resonance spectrometer. Two different amorphous Boron (B) precursors were used for the synthesis of MgB{sub 2}, namely, boron 95 (purity 95%–97%, <1.5 μm) and nanoboron (purity >98.5%, <250 nm), which revealed bulk and nanosized MgB{sub 2}, respectively. Scanning and transmission electron microscopy analysis demonstrate uniform and ultrafine morphology for nanosized MgB{sub 2} in comparison with bulk MgB{sub 2}. Powder X-ray diffraction data show that the concentration of the by-product MgO is significantly reduced when nanoboron is employed as precursor. It is observed that a significant average particle size reduction for MgB{sub 2} can be achieved only by using B particles of micron or nano size. The origin and the role of defect centers were also investigated and the results proved that at nanoscale MgB{sub 2} material contains Mg vacancies. Such vacancies influence the connectivity and the conductivity properties which are crucial for the superconductivity applications.

  15. 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.

  16. Superconducting gap parameters of MgB 2 obtained on MgB 2/Ag and MgB 2/In junctions

    NASA Astrophysics Data System (ADS)

    Plecenik, A.; Beňačka, Š.; Kúš, P.; Grajcar, M.

    2002-03-01

    MgB 2 superconducting wires with the critical temperature Tc approaching 40 K were used for the preparation of MgB 2/Ag and MgB 2/In junctions. The differential conductance vs. voltage characteristics of N-S junctions exhibit a clear contribution of the Andreev reflection. Using a modified BTK theory for s-wave superconductors two order parameters Δdirty≈4 meV and Δ3D≈2.6 meV were determined from the temperature dependencies. Surprisingly, the larger order parameter Δdirty vanishes at a lower temperature T c dirty≈20 K compared with the smaller one Δ3D with Tc≈38 K. Both the magnitudes of the order parameters and their critical temperatures are in good agreement with theoretical calculations of electron-phonon coupling in MgB 2 carried out by Liu et al. [cond-mat/0103570 (2001)].

  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. Solidification Pathways of Alloys in the Mg-Rich Corner of the Mg-Al-Ba Ternary System

    NASA Astrophysics Data System (ADS)

    Bryan, Zachary L.; Hooper, Ryan J.; Henderson, Hunter B.; Manuel, Michele V.

    2015-04-01

    An experimental investigation of the solidification reactions and microstructures of alloys in the Mg-rich corner of the Mg-Al-Ba ternary system has been conducted. Four distinct exothermic reactions involving the formation of α-Mg, Mg17Ba2, Mg17Al12, and a fourth phase designated as τ were observed and their onset temperatures were recorded as functions of composition. Using compositional and microstructural analysis, the Mg17Ba2 intermetallic was found to have significant solubility of Al, up to 20 at. pct. The solidification pathways of the investigated alloys involved both a Class I and Class II equilibrium reaction. A flow block diagram that outlines the observed solidification reactions is presented and discussed in reference to cast microstructures.

  19. Effect of sterilization process on surface characteristics and biocompatibility of pure Mg and MgCa alloys.

    PubMed

    Liu, X L; Zhou, W R; Wu, Y H; Cheng, Y; Zheng, Y F

    2013-10-01

    The aim of this work was to investigate the effect of various sterilization methods on surface characteristics and biocompatibility of MgCa alloy, with pure Mg as a comparison, including steam autoclave sterilization (SA), ethylene oxide steam sterilization (EO), glutaraldehyde sterilization (GD), dry heat sterilization (DH) and Co60 γ ray radiation sterilization (R) technologies. The surface characterizations were performed by environmental scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, water contact angle and surface free energy measurement, whereas the cytotoxicity and hemocompatibility were evaluated by cellular adhesive experiment, platelet adhesion and hemolysis test. The results showed that the five sterilization processes caused more changes on the surface of MgCa alloy than that on the surface of pure Mg. The GD sterilization caused the most obvious changes on the surface of the pure Mg, and the SA sterilization made the largest alteration on the MgCa alloy surface. The GD and DH sterilization processes could cause increases on surface free energy for both pure Mg and MgCa alloys, while the other three sterilization processes reduced the surface free energy. The DH and GD sterilization processes caused the least alteration on the cell adhesion on pure Mg surface, whereas the EO sterilization performed the greatest impact on the cell adhesion on the Mg-Ca alloy surface. The hemolysis percentage of pure Mg and MgCa alloys were reduced by SA sterilization, meanwhile the other four sterilization processes increased their hemolysis percentages significantly, especially for the EO sterilization. PMID:23910326

  20. Growth of high Mg content wurtzite MgZnO epitaxial films via pulsed metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Alema, Fikadu; Ledyaev, Oleg; Miller, Ross; Beletsky, Valeria; Osinsky, Andrei; Schoenfeld, Winston V.

    2016-02-01

    We report on the growth of high Mg content, high quality, wurtzite MgxZn1-xO (MgZnO) epitaxial films using a pulsed metal organic chemical vapor deposition (PMOCVD) method. Series of MgZnO films with variable Mg concentration were deposited on bare and AlN coated sapphire substrates. The band gap of the films estimated using UV-visible transmission spectra ranges from 3.24 eV to 4.49 eV, corresponding to fraction of Mg between x=0.0 and x=0.51, as determined by Rutherford backscattering spectroscopy. The cathodoluminescence (CL) measurement has shown a blue-shift in the peak position of MgZnO with an increasing Mg content. No multi-absorption edges and CL band splitting were observed, suggesting the absence of phase segregation in the as grown films. The crystal structure and phase purity of the films were also confirmed by XRD analysis. Hall effect measurement in van der Pauw configuration was employed to evaluate the electrical properties of the films. With a rise in Mg incorporation into the ZnO lattice, the films became very resistive, consistent with the widening of the band gap. The AFM measurement on the films has shown a decreasing surface roughness with an Mg content. To the best of our knowledge, the current result shows the highest Mg content (x=0.51), high quality, wurtzite MgZnO epitaxial film ever grown by MOCVD. The high Mg incorporation without phase separation is believed to be due to the non-equilibrium behavior of the PMOCVD in which the kinetic processes dominate the thermodynamic one.

  1. 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.

  2. Shape and size of crystalline MgO particles formed by the decomposition of Mg(OH)/sub 2/

    SciTech Connect

    Dahmen,; Kim, M.G.; Searcy, A.W.

    1988-08-01

    Decomposition of Mg(OH)/sub 2/ at 300/sup 0/ to 400/sup 0/C yields MgO crystals with often unequal edge lengths which, from counting of crystal planes in high-resolution transmission electron micrographs, range from 0.8 to 2.4 nm, in agreement with conclusions of Moodie and Warble. Optical diffractograms and electron diffraction patterns yield concordant results. An origin for discordant X-ray diffraction estimates of particle size for MgO produced from Mg(OH)/sub 2/ in the same temperature range is suggested.

  3. High-precision Mg isotopic systematics of bulk chondrites

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

  4. 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.

  5. Optical properties and electronic band structure of BiMg2PO6, BiMg2VO6, BiMg2VO6:Pr3+ and BiMg2VO6:Eu3+

    NASA Astrophysics Data System (ADS)

    Barros, A.; Deloncle, R.; Deschamp, J.; Boutinaud, P.; Chadeyron, G.; Mahiou, R.; Cavalli, E.; Brik, M. G.

    2014-08-01

    The luminescence properties of the yellow pigment BiMg2VO6 are revisited and those of BiMg2PO6, BiMg2VO6:Pr3+ and BiMg2VO6:Eu3+ are described. It is shown that the undoped systems exhibit broad band emission in the green or orange spectral regions, but only upon UV or near UV excitation. In contradiction with a previous report, we found that the blue, host absorbed, photons are lost non-radiatively and do not contribute to the luminescence processes in BiMg2VO6. To understand these experimental results, the optical properties of BiMg2VO6 and BiMg2PO6 are theoretically analysed on the basis of electronic structure diagrams calculated by the DFT method. It is found that the optical transitions are mostly localised within [VO4]3- units or non-regular Bi3+ ions and occur in the UV or near UV regions. The luminescence of the trivalent lanthanide dopants is weak (Eu3+) or unobserved (Pr3+) in BiMg2VO6 which is explained by inefficient energy migration in the host lattice to the impurity sites.

  6. 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.

  7. Nanostructured Layered Cathode for Rechargeable Mg-Ion Batteries.

    PubMed

    Tepavcevic, Sanja; Liu, Yuzi; Zhou, Dehua; Lai, Barry; Maser, Jorg; Zuo, Xiaobing; Chan, Henry; Král, Petr; Johnson, Christopher S; Stamenkovic, Vojislav; Markovic, Nenad M; Rajh, Tijana

    2015-08-25

    Nanostructured bilayered V2O5 was electrochemically deposited within a carbon nanofoam conductive support. As-prepared electrochemically synthesized bilayered V2O5 incorporates structural water and hydroxyl groups, which effectively stabilizes the interlayers and provides coordinative preference to the Mg(2+) cation in reversible cycling. This open-framework electrode shows reversible intercalation/deintercalation of Mg(2+) ions in common electrolytes such as acetonitrile. Using a scanning transmission electron microscope we demonstrate that Mg(2+) ions can be effectively intercalated into the interlayer spacing of nanostructured V2O5, enabling electrochemical magnesiation against a Mg anode with a specific capacity of 240 mAh/g. We employ HRTEM and X-ray fluorescence (XRF) imaging to understand the role of environment in the intercalation processes. A rebuilt full cell was tested by employing a high-energy ball-milled Sn alloy anode in acetonitrile with Mg(ClO4)2 salt. XRF microscopy reveals effective insertion of Mg ions throughout the V2O5 structure during discharge and removal of Mg ions during electrode charging, in agreement with the electrode capacity. We show using XANES and XRF microscopy that reversible Mg intercalation is limited by the anode capacity. PMID:26169073

  8. Size effects in MgO cube dissolution.

    PubMed

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

    2015-03-10

    Stability parameters and dissolution behavior of engineered nanomaterials in aqueous systems are critical to assess their functionality and fate under environmental conditions. Using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction, we investigated the stability of cubic MgO particles in water. MgO dissolution proceeding via water dissociation at the oxide surface, disintegration of Mg(2+)-O(2-) surface elements, and their subsequent solvation ultimately leads to precipitation of Mg(OH)2 nanosheets. At a pH ≥ 10, MgO nanocubes with a size distribution below 10 nm quantitatively dissolve within few minutes and convert into Mg(OH)2 nanosheets. This effect is different from MgO cubes originating from magnesium combustion in air. With a size distribution in the range 10 nm ≤ d ≤ 1000 nm they dissolve with a significantly smaller dissolution rate in water. On these particles water induced etching generates (110) faces which, above a certain face area, dissolve at a rate equal to that of (100) planes.1 The delayed solubility of microcrystalline MgO is attributed to surface hydroxide induced self-inhibition effects occurring at the (100) and (110) microplanes. The present work underlines the importance of morphology evolution and surface faceting of engineered nanomaterials particles during their dissolution. PMID:25668706

  9. 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.

  10. The anodic surface film and hydrogen evolution on Mg

    DOE PAGESBeta

    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.

  11. Preparation of MgB2 superconducting tapes using electrophoresis

    NASA Astrophysics Data System (ADS)

    Xu, J. D.; Wang, S. F.; Zhou, Y. B.; Zhou, Y. L.; Chen, Z. H.; Cui, D. F.; Lu, H. B.; He, M.; Dai, S. Y.; Yang, G. Z.

    2002-08-01

    Superconducting MgB2/Ta tapes with a critical temperature of 34 K have been prepared successfully by ex situ annealing of electrophoresis-grown boron in the presence of Mg vapour at 920 °C. Scanning electron microscopy was used to examine the surface morphology of the MgB2/Ta tapes, and well-formed MgB2 crystals with sizes up to 2 μm were observed. The x-ray diffraction patterns showed randomly orientated growth of MgB2 phase in the tapes. Estimates using hysteresis loops and the Bean model give a value of 6.8 × 105 A cm-2 for the critical current density.

  12. 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.

  13. Oxygen Segregation and Ordering in MgB2

    NASA Astrophysics Data System (ADS)

    Idrobo, Juan; Klie, Robert; Browning, Nigel D.

    2002-03-01

    Polycrystalline MgB2 has been studied by atomic resolution scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS). We find that within the detection limits of the techniques, there is no oxygen within the bulk of the grains, but significant oxygen segregated to the grain boundaries. The majority of the grain boundaries contain ordered crystalline MgB_2-xOx and amorphous BOy phases smaller than the coherence length, explaining the high conductivity of the material. Other kinds of grain boundaries containing larger areas of MgO sandwiched between BOy layers were also found. Furthermore, coherent Mg(B,O) precipitates can be formed within the bulk of the MgB2 grains. We will discuss the formation mechanisms of these secondary phases, the presence of oxygen ordering within the precipitates and the effect of the oxide precipitates on the bulk transport properties.

  14. 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

  15. 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

  16. 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.

  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. Effect of Synthesized MgNi4Y Catalyst on Hydrogen Desorption Properties of Milled MgH2

    NASA Astrophysics Data System (ADS)

    ChitsazKhoyi, Leila; Raygan, Shahram; Pourabdoli, Mehdi

    2015-03-01

    It has been reported that ball milling and adding catalyst can improve hydrogen desorption properties of MgH2. In this study, simultaneous effect of adding catalyst and ball milling on hydrogen desorption properties of MgH2 was studied. Mechanical alloying and heat treatment methods were used to synthesize MgNi4Y intermetallic as a catalyst. In this regard, pure Mg, Ni, and Y elemental powders were ball milled in different conditions and then heat treated at 1073 K (800 °C) for 4 hours. XRD and FESEM methods were used to investigate properties of the samples. It was found that, after 10 hours of ball milling and then heat treating at 1073 K (800 °C), MgNi4Y intermetallic was formed almost completely. The results of Sievert tests showed that as-received MgH2 did not release any significant amount of hydrogen at 623 K (350 °C). But, after ball milling for 10 hours, 0.8 wt pct hydrogen was released from MgH2 at 623 K (350 °C) in 40 minutes. Adding 10 wt pct catalyst via ball milling to MgH2 led to releasing 3.5 wt pct hydrogen in the same conditions. In addition, increasing ball milling time from 10 to 65 hours increased the amount of released hydrogen from 51 to 85 pct of theoretical hydrogen desorption value and improved kinetic of desorption process.

  19. 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

  20. Synthesis, crystal growth and structure of Mg containing {beta}-rhombohedral boron: MgB{sub 17.4}

    SciTech Connect

    Adasch, Volker; Hess, Kai-Uwe; Vojteer, Natascha; Hillebrecht, Harald . E-mail: harald.hillebrecht@ac.uni-freiburg.de

    2006-09-15

    For the first time, single crystals of Mg containing {beta}-rhombohedral boron MgB{sub 17.4} were synthesised from the elements in a Mg/Cu melt at 1600deg. C. The crystal structure determined by the refinement of single crystal data (space group R-3m, a=10.991(2)A, c=24.161(4)A, 890 reflections, 123 variables, R{sub 1}(F)=0.049, wR{sub 2}(I)=0.122) improves and modifies the former structure model derived from earlier investigations on powder samples. Mg is located on four different positions with partial occupation. While the occupation of the sites D (53.3%), E (91%) and F (7.2%) is already known from other boron-rich borides related to {beta}-rhombohedral boron, the occupation of the fourth position (18h, 6.7%) is observed for the first time. Two boron positions show partial occupation. The summation reveals the composition MgB{sub 17.4} and Mg{sub 5.85}B{sub 101.9}, respectively, confirmed by WDX measurements. The single crystals of MgB{sub 17.4} show the highest Mg content ever found. Preliminary measurements indicate no superconductivity.

  1. 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.

  2. 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

  3. Possibility of a 2D SiC monolayer formation on Mg(0001) and MgO(111) substrates

    NASA Astrophysics Data System (ADS)

    Kuzubov, A. A.; Eliseeva, N. S.; Krasnov, P. O.; Tomilin, F. N.; Fedorov, A. S.; Tolstaya, A. V.

    2013-08-01

    The geometrical characteristics of a 2D SiC monolayer on Mg(0001) and MgO(111) plates regarded as potential materials for growing two-dimensional silicon carbide were studied. The most favorable positions of the atoms of 2D SiC on the substrates were determined. In the 2D SiC/Mg(0001) system, unlike in 2D SiC/MgO(111), the deviation of the carbon atom from the silicon carbide monolayer was insignificant (0.08 Å). Consequently, magnesium can be used as a substrate for growing two-dimensional silicon carbide. The use of MgO(111) is not recommended because of a significant distortion of the 2D SiC surface.

  4. 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.

  5. Synthesis and crystal structure of MgB{sub 12}

    SciTech Connect

    Adasch, Volker; Hess, Kai-Uwe; Vojteer, Natascha; Hillebrecht, Harald . E-mail: harald.hillebrecht@ac.uni-freiburg.de

    2006-09-15

    Single crystals of MgB{sub 12} were synthesized from the elements in a Mg/Cu melt at 1600deg. C. MgB{sub 12} crystallizes orthorhombic in space group Pnma with a=16.632(3)A, b=17.803(4)A and c=10.396(2)A. The crystal structure (Z=30, 5796 reflections, 510 variables, R{sub 1}(F)=0.049, wR{sub 2}(I)=0.134) consists of a three dimensional net of B{sub 12} icosahedra and B{sub 21} units in a ratio 2:1. The B{sub 21} units are observed for the first time in a solid compound. Mg is on positions with partial occupation. The summation reveals the composition MgB{sub 12.35} or Mg{sub 0.97}B{sub 12} , respectively. This is in good agreement with the value of MgB{sub 11.25} as expected by electronic reasons to stabilize the boron polyhedra B{sub 12}{sup 2-} and B{sub 21}{sup 4-}.

  6. Electrochromism of Mg-Ni hydride switchable mirrors

    NASA Astrophysics Data System (ADS)

    Isidorsson, Jan; Giebels, I. A. M. E.; Di Vece, M.; Griessen, Ronald

    2001-11-01

    Switchable mirrors have so far been made of rare-earth and rare-earth-magnesium based metal-hydrides. In this investigation we study Mg-Ni-hydrides, which have been shown by Richardson et al. to exhibit switchable properties similar to those of the rare-earth hydrides. Cyclic voltammetry on MgzNiHx samples with 0.8 less than z less than 3.7 shows that addition of one Mg atom per Mg2Ni gives the best ab/desorption kinetics for hydrogen. X- ray diffraction reveals a structural change as hydrogen is absorbed. The metal-insulator transition is confirmed with simultaneous resistivity measurements. A pressure- composition isotherm of Mg2NiHx is also determined electrochemically. Optical spectrometry during gas loading gives an optical band gap of 1.6 eV for Mg2NiH4. This gap increases with increasing Mg content in a way similar to that of the Mg-doped rare-earth hydrides.

  7. 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.

  8. Structural and magnetic properties of Mg substituted Co nanoferrites

    NASA Astrophysics Data System (ADS)

    Sharma, Jyoti; Sharma, Neha; Yadav, Premlata; Parashar, Jyoti; Jadoun, Priya; Saxena, V. K.; Bhatnagar, D.; Sharma, K. B.

    2016-05-01

    The structural and magnetic properties of magnesium substituted cobalt nano ferrites CoxMg1-xFe2O4 (x= 0.2, 0.4 and 1.0) have been investigated. The structural characterization has been done by X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). The magnetic studies indicate that the samples show ferromagnetic behaviour at room temperature as well as at low temperature. The magnetization decreases with Mg content in both the cases due to the less magnetic nature of Mg ions than that of the Co ions.

  9. 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.

  10. 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.