WorldWideScience

Sample records for opciones si tiene

  1. Livres et pratique de la lecture chez les chrétiens (Syrie, Liban) XVIIe - XVIIIe siècles

    OpenAIRE

    Bernard Heyberger

    2009-01-01

    L'idée humaniste que l'homme ne peut faire son Salut sans savoir lire pénètre la société chrétienne arabe et grecque à partir du XVIIe siècle. Elle s'accompagne de la diffusion des productions imprimées européennes, ainsi que d'une renaissance locale du manuscrit. Le livre devient un objet convoité, vendu, acheté, offert, dont la possession peut être un signe de reconnaissance sociale, et la marque de relations privilégiées avec les "Francs".L'Église catholique quant à elle, exerce aussi son ...

  2. Las opciones reales como metodologia alternativa en la evaluacion de proyectos de inversion

    National Research Council Canada - National Science Library

    Tamara Ayus, Armando Lenin; Aristizabal Velasquez, Raul Enrique

    2012-01-01

    Este trabajo busca ampliar la aplicabilidad de la metodologia de valoracion de proyectos de inversion por medio de opciones reales como un elemento fundamental al momento de tomar una decision de si...

  3. Opciones de compra y opciones de venta e Ibex 35

    OpenAIRE

    Zalba García, Ainara

    2014-01-01

    El presente trabajo ha perseguido dar una explicación ordenada y clarificadora de los contratos financieros de opciones, así como analizar sus elementos principales y sus diferentes clases. Para llegar aquí se ha trabajado en primer lugar el marco en que se sitúan así como el mercado en el que se encuentran reguladas. Nos ha parecido necesario abordar primero el estudio del contrato de opción en derecho civil para luego poder entender mejor el marco legal en que estos contratos financieros se...

  4. Valuación de opciones de tipo de cambio asumiendo distribuciones a-estables

    Directory of Open Access Journals (Sweden)

    Román Rodríguez Aguilar

    2013-01-01

    Full Text Available Este trabajo tiene por objetivo presentar la valuación de opciones europeas a través del método probabilista utilizando distribuciones α-estables como una alternativa de valuación de opciones en el mercado mexicano. El uso de estas distribuciones para la modelación de series financieras permite superar la principal debilidad de la valuación clásica que supone normalidad al captar los efectos de las colas pesadas y la asimetría propias de las series financieras. Uno de los principales resultados que se encontró se refiere a los diferenciales en la valuación de opciones entre ambos modelos y el efecto de los parámetros de la distribución en los precios; para mostrar esta diferencia, se realiza la valuación de una opción de compra y una opción de venta sobre el tipo de cambio peso-dólar. De igual forma se calcularon las medidas de sensibilidad básicas de las opciones (delta, gama y rho y se analizó el efecto del parámetro de estabilidad α en la volatilidad implícita de las opciones al asumir la valuación α-estable como el precio de mercado.

  5. Wen Tien Ke

    Directory of Open Access Journals (Sweden)

    Qiang Lei

    2017-06-01

    Full Text Available Based on enormous first-hand data as diaries, memoirs, newspapers, archival materials, books, and journals, this article tries to clarify some important aspects concerning Wen Tien Ke(Ko (文殿閣 such as when it established, how its inner structure worked and what its major businesses covered. By doing so, the author tells the story of the Wen Tien Ke: how it had witnessed the vicissitudes of its time and its own, how it had contributed to the cultural exchange and communication between China and the West through its daily business activities such as rare book retails, and reprint of books on various aspects of China in English and other languages written by distinguished western sinologists. In all, this article makes efforts to explore the publishing history of Wen Tien Ke from 1934 to 1950s. [Article content in Chinese

  6. No High School Diploma? You've Got Options! = No tienes un diploma de la escuela preparatoria? Tienes opciones!

    Science.gov (United States)

    EdSource, 2006

    2006-01-01

    If a student completes high school but is unable to graduate, there are still options. The student can still get a high school diploma whether he or she dropped out, failed the California High School Exit Exam, or did not have enough course credits. As many know, a high school diploma is a passport to a more interesting and better paying job.…

  7. Histoire officielle et mémoires en conflit dans le Sud du Mont-Liban : les affrontements druzo-chrétiens du xixe siècle

    Directory of Open Access Journals (Sweden)

    Dima de Clerck

    2014-09-01

    Full Text Available L’espace libanais est caractérisé par l’absence d’une mémoire collective nationale au profit de plusieurs mémoires sociales portées par les différents groupes identitaires confessionnels et élaborées en fonction des relations conflictuelles ou conviviales qu’ils entretenaient entre eux. Ces mémoires rivalisent entre elles et avec une autre mémoire, construite à partir du début du xxe siècle par des tenants de la coexistence et hissée au rang d’histoire officielle, dans une vaine tentative de promouvoir une vision fédératrice de l’histoire du pays. Les mémoires élaborées autour des affrontements druzo-chrétiens du xixe siècle sont particulièrement illustratives de cette disjonction. Le fait que ce moment fondateur de la question du Liban, soit le produit d’un conflit sanglant est presque passé sous silence dans l’histoire officielle. Un sondage des mémoires communautaires chrétienne et druze pour la période 1820-61 permet de saisir comment ces mémoires vives, elles-mêmes en conflit, ont sapé l’histoire officielle, rendant compte d’un échec des historiens de la coexistence à imposer un récit censuré et pudique comme base d’une mémoire historique commune.

  8. Reseña de: Caselli, Elisa, Antijudaïsme, pouvoir politique et administration de la justice. Juifs, chrétiens et converts dans l’ espace jurisdictionnel de la Chancillería de Valladolid (XVe-XVIe siècles.Villeneuve d’Ascq...

    Directory of Open Access Journals (Sweden)

    Enrique Cantera Montenegro

    2017-05-01

    Full Text Available Caselli, Elisa, Antijudaïsme, pouvoir politique et administration de la justice. Juifs, chrétiens et converts dans l’ espace jurisdictionnel de la Chancillería de Valladolid (XVe-XVIe siècles. Villeneuve d’Ascq Cedex. Atelier National de Reproduction des Thèses, 2016. 396 págs. isbn: 978-2-7295-8891-5.

  9. Modelo estocástico multivariado para valuar opciones financieras

    OpenAIRE

    Fuentes de Maria C., Marco A.

    1998-01-01

    La presente tesis expone un modelo multivariado estocástico para el proceso de precios de activos financieros, en particular, acciones, con el propósito de utilizarlo para la valuación de opciones.

  10. Opciones estrategicas de desarrollo organizacional hacia la sostenibilidad

    National Research Council Canada - National Science Library

    Keller, Patricia Ingrid

    2012-01-01

    ... dificiles de abordar en la practica. Por eso, para el presente trabajo se investigaron las estrategias posibles, identificando aquellas opciones que permiten lograr integrar las dimensiones de la sostenibilidad al desarrollo...

  11. Modelo estocástico multivariado para valuar opciones financieras

    OpenAIRE

    Fuentes de Maria C., Marco A.

    1998-01-01

    La presente tesis expone un modelo multivariado estocástico para el proceso de precios de activos financieros, en particular, acciones, con el propósito de utilizarlo para la valuación de opciones.

  12. Valoración de opciones de compra y venta del quintal de soya en el mercado ecuatoriano

    OpenAIRE

    2009-01-01

    El presente trabajo desarrolla las diferentes herramientas financieras llamadas “Los Instrumentos Derivados Financieros” en especial las Opciones. El sector productivo en el Ecuador está expuesto a diferentes tipos de riesgos. El presente trabajo está enfocado a mejorar la comercialización y asegurar el precio de compra y venta del quintal de soya en el Ecuador. El riesgo de variación en el precio de materias primas que tiene un productor o consumidor y la variación de precios de los product...

  13. Valoración de opciones de compra y venta del quintal de soya en el mercado ecuatoriano

    OpenAIRE

    Zambrano Chávez, Washington Xavier; Sandoya Sánchez, Fernando

    2009-01-01

    El presente trabajo desarrolla las diferentes herramientas financieras llamadas “Los Instrumentos Derivados Financieros” en especial las Opciones. El sector productivo en el Ecuador está expuesto a diferentes tipos de riesgos. El presente trabajo está enfocado a mejorar la comercialización y asegurar el precio de compra y venta del quintal de soya en el Ecuador. El riesgo de variación en el precio de materias primas que tiene un productor o consumidor y la variación de precios de los product...

  14. Milpa y capitalismo: opciones para los campesinos mayas yucatecos contemporáneos

    Directory of Open Access Journals (Sweden)

    Manuel Martín Castillo

    2016-07-01

    Full Text Available La mayoría de los mayas yucatecos contemporáneos vive en la pobreza. El eje de su economía y cultura es la agricultura de milpa, que los jóvenes no encuentran atractiva como opción económica. La teoría económica convencional explica la pobreza por la escasez de capital, el uso de tecnologías obsoletas y la baja productividad. Aunque se concibe como un sistema productivo arcaico, la milpa tiene características para explorar opciones de vinculación entre las economías campesina y capitalista, para mejorar las condiciones de vida de los campesinos y contribuir al desarrollo de su cultura en el actual contexto de globalización económica.

  15. Valuación financiera de proyectos de inversión en nuevas tecnologías con opciones reales

    Directory of Open Access Journals (Sweden)

    Francisco Antonio Álvarez Echeverría

    2012-01-01

    Full Text Available La valuación financiera de proyectos de inversión que involucran nuevas tecnologías requiere de cierto grado de flexibilidad en la implementación de estrategias futuras de negocio como son la expansión, contracción, posposición y abandono del proyecto; asimismo, incorporar la creciente incertidumbre que presentan las nuevas tecnologías a través de tasas de descuento que tengan una dinámica estocástica y que pueden ser simuladas con diversos modelos de tasas de interés como el de Vasicek y CIR que permiten hacer escenarios alternos para evaluar un proyecto de inversión. En este trabajo se desarrolla y aplica la metodología de opciones reales para la adopción de una tecnología del tipo Wi-Fi; para ello se considera una opción real de expansión con el objeto de estimar los flujos de efectivo esperados, así como la rentabilidad del proyecto dentro de un intervalo de tiempo determinado en comparación con la técnica tradicional del valor presente neto (VPN. La tasa de descuento utilizada en la valuación se desprende de la estructura de plazos estimada mediante los modelos Vasicek (1977 y CIR (1985. Los resultados de la valuación reflejan que desde el tercer periodo los flujos de efectivo con opciones reales son positivos, mientras que el VPN lo hace hasta el séptimo periodo, situación que incrementa la probabilidad de tener un VPN negativo que rechace el proyecto, a pesar de que éste tiene viabilidad financiera, si incorporamos el valor de la flexibilidad en el proyecto, el cual no es cuantificado por las técnicas tradicional como el VPN; por lo tanto, se debe complementar el análisis incluyendo una opción real.

  16. Valuación de opciones asiáticas versus opciones europeas con tasa de interés

    Directory of Open Access Journals (Sweden)

    Ambrosio Ortiz Ramírez

    2016-01-01

    Full Text Available Este trabajo propone una metodología para obtener el precio de una opción asiática con subyacente promedio mediante simulación Monte Carlo. Se supone que la tasa de interés es conducida por un proceso de reversión a la media de tipo Vasicek y CIR con parámetros calibrados por máxima verosimilitud. La simulación incluye el remuestreo cuadrático, el cual reduce el uso de recursos computacionales; en particular, el método mejora la generación de la matriz de varianza-covarianza. La metodología propuesta se aplica en la valuación de opciones sobre el precio de AMXL. Los resultados muestran que al comparar los precios de opciones europeas —tanto simulados como con los publicados por MexDer— con sus contrapartes asiáticas, los precios de opciones asiáticas son menores en el caso de opciones de compra y de venta dentro del dinero. P ara opciones de venta, los precios simulados fueron menores en todos los casos. Asimismo se encontró que la diferencia se incrementa conforme el plazo al vencimiento de la opción aumenta.

  17. El arrendamiento financiero y valuación de opciones reales

    National Research Council Canada - National Science Library

    Gastón Silverio Milanesi

    2016-01-01

    El trabajo estudia diferentes opciones reales simples y compuestas contenidas en los contratos de leasing, bajo una metodología que combina el método de préstamo equivalente (MPE) y opciones reales...

  18. Modelos de valoración de opciones sobre títulos de renta fija: aplicación al mercado colombiano1

    Directory of Open Access Journals (Sweden)

    Luis Guillermo Herrera Cardona

    2013-01-01

    Full Text Available Este documento tiene como propósito evaluar la aplicabilidad del modelo de tasa de interés de Vasicek (1977 para la valorar opciones call y put sobre un título de renta fija colombiano. Para el desarrollo de esta aplicación, se efectúan estimaciones econométricas con procesos autorregresivos y de volatilidad necesarias para encontrar los parámetros de entrada del modelo. En el avance del trabajo se encuentra que este no arroja resultados satisfactorios para las opciones sobre bonos colombianos, debido al alto valor de las primas. Sin embargo, ajustando el modelo con parámetros basados en criterios empíricos, se obtienen cifras más consistentes.

  19. À propos du lexique juridique en ancien français avant le 13e siècle : la Règle de saint Benoît et le Perceval de Chrétien de Troyes

    Directory of Open Access Journals (Sweden)

    Schauwecker Yela

    2012-07-01

    Full Text Available La plus ancienne traduction de la {em Règle} de saint Benoît en franc{c}ais, rédigée en dialecte picard-wallon, date de la première moitié ou du milieu du {sc xii}$^{m e}$~siècle. On veut montrer que son auteur, pour qui le changement de langue, n'est pas le premier objectif s'efforce de transférer le texte de son milieu originel de l'Antiquité tardive dans le monde chevaleresque-féodal du {sc xii}$^{m e}$~siècle. Même sans nécessité apparente, quand il a eu à sa disposition l'équivalent du mot employé dans la {em Regula}, il substitue aux mots latins des termes juridiques et féodaux franc{c}ais. par Son texte, en tant que document de droit pour les moines, devient ainsi une source de vocabulaire juridique franc{c}ais avant le {sc xiii}$^{m e}$~siècle, c'est-à-dire dans un temps où les documents juridiques en langue vulgaire sont extrêmement rares. Cela est dû au fait que la justice, dans le Nord, fondée sur des coutumes, utilisait la langue vernaculaire à l'oral. La terminologie juridique franc{c}aise est bien enracinée dans la langue courante de l'époque~: leur insertion dans les Lais et les Chansons de geste en fait preuve. Mais cette terminologie est souvent méconnue par la lexicographie traditionnelle de l'ancien franc{c}ais, en raison des contextes littéraires et figurés. par

  20. El arrendamiento financiero y valuación de opciones reales

    OpenAIRE

    Gastón Silverio Milanesi

    2016-01-01

    El trabajo estudia diferentes opciones reales simples y compuestas contenidas en los contratos de leasing, bajo una metodología que combina el método de préstamo equivalente (MPE) y opciones reales. Primero se presenta formalmente el MPE y el modelo binomial para valorar las opciones del contrato. Seguida- mente se analiza el valor al vencimiento de las opciones del leasing clasificadas en: a) simple: de compra, de cancelar anticipadamente, de renovación y excluyente de renovación-compra, y b...

  1. de opciones a la administración de portafolios.

    Directory of Open Access Journals (Sweden)

    Julián Benavides F.

    2002-01-01

    Full Text Available El artículo revisa la teoría de opciones y propone un método para la implementación del «Portfolio Insurance » basado en el modelo binomial, el cual es evaluado en oposición al modelo de Black-Scholes. Usando datos reales y simulados se encuentra que el método de Black-Scholes se desempeña mejor en condiciones «inestables »; el modelo binomial, en cambio, obtiene mejores resultados con tendencias definidas en los precios de las acciones (crecientes, decrecientes o estables durante un período extendido.

  2. OPCIONES ESTRATÉGICAS DE DESARROLLO ORGANIZACIONAL HACIA LA SOSTENIBILIDAD

    Directory of Open Access Journals (Sweden)

    Patricia Ingrid,Keller

    2012-06-01

    Full Text Available La implementación de estrategias empresariales que construyen valor a lo largo de la cadena productiva de bienes y servicios y simultáneamente contribuyen a la sostenibilidad es uno de los temas más difíciles de abordar en la práctica. Por eso, para el presente trabajo se investigaron las estrategias posibles, identificando aquellas opciones que permiten lograr integrar las dimensiones de la sostenibilidad al desarrollo organizacional desde una perspectiva sistémica, así como sus posibilidades y limitaciones. Las actividades características de las cinco opciones posibles – control de riesgos, construcción de imagen y reputación, productividad y eficiencia, innovación y desarrollo de mercados – pueden implementarse de forma pura, combinada o sucesiva. De esta manera se pueden construir ventajas competitivas en el marco de la sostenibilidad, lo cual permite a la empresa lograr mayores posibilidades de éxito, no solo en el corto, sino también a mediano y largo plazo.

  3. El arrendamiento financiero y valuación de opciones reales

    Directory of Open Access Journals (Sweden)

    Gastón Silverio Milanesi

    2016-01-01

    Full Text Available El trabajo estudia diferentes opciones reales simples y compuestas contenidas en los contratos de leasing, bajo una metodología que combina el método de préstamo equivalente (MPE y opciones reales. Primero se presenta formalmente el MPE y el modelo binomial para valorar las opciones del contrato. Seguida- mente se analiza el valor al vencimiento de las opciones del leasing clasificadas en: a simple: de compra, de cancelar anticipadamente, de renovación y excluyente de renovación-compra, y b compuesta: a riesgo (venture ; canon atado a intensidad de uso (percentage y de pago diferido. Utilizando diferentes casos son valuadas las opciones combinando el modelo binomial y el MPE, estimando valor expandido y valor el valor de la opción sobre el valor. Finalmente se presentan las principales conclusiones.

  4. Tien Shan Geohazards Database: Earthquakes and landslides

    Science.gov (United States)

    Havenith, H. B.; Strom, A.; Torgoev, I.; Torgoev, A.; Lamair, L.; Ischuk, A.; Abdrakhmatov, K.

    2015-11-01

    In this paper we present new and review already existing landslide and earthquake data for a large part of the Tien Shan, Central Asia. For the same area, only partial databases for sub-regions have been presented previously. They were compiled and new data were added to fill the gaps between the databases. Major new inputs are products of the Central Asia Seismic Risk Initiative (CASRI): a tentative digital map of active faults (even with indication of characteristic or possible maximum magnitude) and the earthquake catalogue of Central Asia until 2009 that was now updated with USGS data (to May 2014). The new compiled landslide inventory contains existing records of 1600 previously mapped mass movements and more than 1800 new landslide data. Considering presently available seismo-tectonic and landslide data, a target region of 1200 km (E-W) by 600 km (N-S) was defined for the production of more or less continuous geohazards information. This target region includes the entire Kyrgyz Tien Shan, the South-Western Tien Shan in Tajikistan, the Fergana Basin (Kyrgyzstan, Tajikistan and Uzbekistan) as well as the Western part in Uzbekistan, the North-Easternmost part in Kazakhstan and a small part of the Eastern Chinese Tien Shan (for the zones outside Kyrgyzstan and Tajikistan, only limited information was available and compiled). On the basis of the new landslide inventory and the updated earthquake catalogue, the link between landslide and earthquake activity is analysed. First, size-frequency relationships are studied for both types of geohazards, in terms of Gutenberg-Richter Law for the earthquakes and in terms of probability density function for the landslides. For several regions and major earthquake events, case histories are presented to outline further the close connection between earthquake and landslide hazards in the Tien Shan. From this study, we concluded first that a major hazard component is still now insufficiently known for both types of geohazards

  5. Procesos estocásticos en la valuación de proyectos de inversión, opciones reales, árboles binomiales, simulación bootstrap y simulación Monte Carlo: flexibilidad en la toma de decisiones

    Directory of Open Access Journals (Sweden)

    Fernando Cruz Aranda

    2012-01-01

    Full Text Available En este trabajo se incorporan procesos estocásticos en la valuación de proyectos de inversión utilizando opciones reales, lo que está vinculado al valor de la flexibilidad administrativa; es decir, utilizar la opción con el objeto de tomar decisiones estratégicas acordes con el entorno económico de la empresa. Se valúa un proyecto tomando en cuenta la opción real según la cual se tiene la flexibilidad de abandonar el proyecto si el entorno de ésta lo requiere. En la valoración del proyecto se consideran los flujos de efectivo de la empresa y las simulaciones bootstrap, histórica y Monte Carlo que se llevan a cabo en ellos. Asimismo, se analizan y calculan los flujos de efectivo considerando árboles binomiales para, finalmente, determinar el valor de la opción real y la viabilidad del proyecto de inversión de la empresa.

  6. Valuación de opciones simples y complejas contenidas en arrendamientos financieros

    OpenAIRE

    2016-01-01

    El valor de los contratos de arrendamiento es una función del valor presente de los cánones más las opciones reales operativas. Sin embargo, el método del préstamo equivalente (MPE), con amplia aplicación en la valuación de arrendamientos, falla porque no incorpora las opciones contenidas en el contrato. De esta forma, el presente trabajo propone un modelo de valuación combinando el MPE y el enfoque binomial para valuar opciones reales. Para lograr lo anterior, se realiza el planteamiento mat...

  7. Brasil, opciones estratégicas de una potencia emergente para afirmar su liderazgo mundial

    Directory of Open Access Journals (Sweden)

    Gisela da Silva Guevara

    2011-11-01

    Full Text Available Desde el siglo XIX Brasil fue adaptando sus estrategias de soft power (poder blando con la meta de afirmar su poderío político y económico en América Latina y en el mundo, en contraposición a otros poderes hegemónicos regionales y mundiales. Sin embargo, sus rivalidades con potencias regionales, como Argentina o Venezuela y, con Estados Unidos, a nivel regional y mundial, nunca llevaron al coloso suramericano a optar por confrontaciones bélicas. Sus estrategias y opciones de política exterior tuvieron siempre en mira la consolidación del país por vía no violenta y a largo plazo. El presente artículo debate la pregunta-problema de si la nación suramericana podrá seguir la línea de poder blando que ha respetado, por siglos, desde su independencia, o será tentada a privilegiar el hard power para lograr, finalmente, ser reconocida como gran potencia en el siglo XXI.

  8. Valores críticos para la evaluación de una empresa que inicia (START-UP) con opciones reales de crecimiento.

    OpenAIRE

    Cobián Romero, Lizbeth

    2012-01-01

    Una empresa innovadora que inicia en el mercado es conocida en la literatura como Start-Up; esté tipo de firmas al ser evaluadas con los métodos tradicionales (tasa interna de retorno, TIR; valor actual neto, VAN y relación benéfico-costo, B/C) son generalmente rechazadas debido a que no cuentan con información económico-financiera suficiente. El objetivo de éste trabajo fue determinar si la incorporación de las metodologías Opciones Reales y Valores Críticos a la evaluación tradicional a...

  9. Diferencias cualitativas entre experiencias tutoriales para opciones de aprendizaje universitario

    Directory of Open Access Journals (Sweden)

    Ángel J. LÁZARO MARTÍNEZ

    2008-01-01

    Full Text Available Se analiza la tutoría como elemento básico de la excelencia educativa, resaltando su carácter nuclear en todo proceso formativo institucionalizado. Se constata la relación entre los procesos educativos, la orientación y la tutoría, desde el nuevo enfoque de la auténtica orientación. En el contexto universitario se debaten sus competencias, destacando que, desde sus orígenes, la tutoría ha constituido el sentido de la función y el quehacer de la finalidad y optimización de la formación universitaria, tanto en la búsqueda del saber como en la pretensión de aplicación social. Esta situación aboca en el análisis de las opciones de la acción tutorial en la Universidad, sus modalidades y sus posibilidades de intervención, y se plantean, de forma más concreta, recogiendo las experiencias destacables en el ámbito universitario, las estrategias organizativas y de desarrollo en aulas y situaciones individualizadas.

  10. Valoración probabilística versus borrosa, opciones reales y el modelo binomial. Aplicación para proyectos de inversión en condiciones de ambigüedad

    Directory of Open Access Journals (Sweden)

    Gastón Silverio Milanesi

    2014-01-01

    Full Text Available El trabajo tiene por objeto exponer la metodología, las ventajas y las debilidades del modelo binomial borroso de valoración de opciones reales como complemento del modelo binomial probabilístico. Para lograr lo anterior primero se presentan los modelos de opciones reales clasificados en probabilístico y borroso; luego se desarrolla el modelo binomial borroso incorporando: el método Marketed Asset Disclai- mer (MAD, rejillas binomiales borrosas y el índice pesimismo-optimismo, para estimar el valor esperado de las opciones del proyecto (VEOP. Se ilustra con un caso comparando los resultados obtenidos con el modelo borroso y el probabilístico. Finalmente se concluye que, en situaciones de falta de información (ambigüedad, la lógica borrosa es un complemento del modelo probabilístico para determinar el valor de la flexibilidad estratégica. © 2012 Universidad ICESI. Publicado por Elsevier España, S.L. Todos los derechos reservados.

  11. PARA MEDIR LA FLEXIBILIDAD SE DEBEN USAR OPCIONES REALES: UNA VISIÓN GLOBAL

    Directory of Open Access Journals (Sweden)

    Oscar Daniel Mejía Carvajal

    2003-01-01

    Full Text Available Recientemente se ha sentido que los modelos tradicionales de flujo de caja discontinuo (DCF no explican completamente las opciones administrativas de la firma, así como tampoco la flexibilidad y las posibles variantes en sus operaciones. Actualmente la teoría y el desarrollo del modelo de opciones están siendo aplicados para la valoración de derechos de conversión y de suscripción de bonos y acciones, contratos de colocación de valores, seguros, deuda y patrimonio de una firma, hipotecas, deudas subordinadas, contratos de exploración petrolera, etc. Una opción provee al tenedor el derecho de comprar o vender una cantidad fijada de un activo subyacente a un precio fijado de antemano (llamado strike o precio de ejercicio, antes o en la fecha de expiración de la opción. Los árboles de decisión (teoría de juegos constituyen una alternativa para evaluar la flexibilidad asociada con las decisiones de inversión. No obstante, la metodología de opciones reales es rigurosamente más correcta; tanto las opciones reales como los árboles de decisión capturan la flexibilidad, sin embargo las opciones reales son ajustadas por el riesgo.

  12. Valuación de opciones simples y complejas contenidas en arrendamientos financieros

    Directory of Open Access Journals (Sweden)

    Gastón Silverio Milanesi

    2016-01-01

    Full Text Available El valor de los contratos de arrendamiento es una función del valor presente de los cánones más las opciones reales operativas. Sin embargo, el método del préstamo equivalente (MPE, con amplia aplicación en la valuación de arrendamientos, falla porque no incorpora las opciones contenidas en el contrato. De esta forma, el presente trabajo propone un modelo de valuación combinando el MPE y el enfoque binomial para valuar opciones reales. Para lograr lo anterior, se realiza el planteamiento matemático y su aplicación para opciones simples (compra, cancelación anticipada, renovación y compuestas (venture leasing, leasing a porcentaje, pago diferido, pago diferido y compra, demostrando la habilidad del modelo para calcular el valor actual expandido del contrato, como la suma del valor actual de pagos y opciones operativas.

  13. ¿CUÁNTOS SIGNIFICADOS TIENE UN PRODUCTO?

    Directory of Open Access Journals (Sweden)

    Jose Antonio Paris

    2014-06-01

    Full Text Available El marketing esencial se basa en la determinación de los significados en la mente del consumidor y de los códigos en la mente del mercado. Para poder sustentar esto se han creado metodologías como las técnicas de afloramiento de significado y las técnicas proyectivas entre otras. Pero, el nuevo problema que surge de esta conceptualización teórica es si vamos a poner al significado en la base del plan de marketing, la pregunta es ¿cuántos significados se deben determinar? Por lo que sabemos cada cultura tiene sus propias significaciones y los significados también cambian con el tiempo incluso lo hacen contextualmente. Lo cual hace aún más complejo el dilema presentado como título de este artículo. En se presentan los argumentos teóricos que sustentan uno de los descubrimientos más importantes del marketing esencial que sostenemos: en general para cada producto o servicio hay cuatro significados dominantes.

  14. Opciones reales para las fusiones y adquisiciones de empresas: Bimbo y Weston Foods

    OpenAIRE

    Rodríguez Hernández, Velda Liliana; Universidad Nacional Autónoma de México-UNAM; Cruz Salazar, Rafael; Universidad Nacional Autónoma de México-UNAM

    2014-01-01

    Este trabajo propone la utilización de la metodología de Opciones reales al proceso de valuación financiera de las inversiones estratégicas en las fusiones y adquisiciones por parte de las empresas globales mexicanas. Demuestra mediante un ejemplo concreto la conveniencia de su utilización en el análisis de la factibilidad de compra de la empresa americana - canadiense Weston Foods por parte de la empresa multinacional mexicana Bimbo, modelando la compra en el marco de la teoría de opciones r...

  15. Opciones de políticas para la paliación de la pobreza

    OpenAIRE

    1997-01-01

    (Disponible en idioma inglés únicamente) Este trabajo se fundamenta en investigaciones anteriores para desarrollar una metodología que simplifique la identificación de las mejores opciones de políticas para paliar la pobreza en un país dado. Cuando se puede dividir una población en subgrupos según alguna característica fácilmente identificable, se puede entender el problema del alivio de la pobreza mediante un mecanismo dirigido a sectores específicos como una elección entre tres opciones: i)...

  16. Los instrumentos de financiación de la empresa analizados como opciones

    OpenAIRE

    Mascareñas Pérez-Íñigo, Juan

    1998-01-01

    En este trabajo se analiza los principales componentes de la estructura de capital de la empresa a través de la metodología de las opciones. Algunos de ellos son una opción en sí mismos como los warrants (o certificados de opción), otros llevan incorporadas opciones como son los denominados títulos híbridos entre los que destacaremos las obligaciones convertibles y las obligaciones amortizables anticipadamente; por último analizaremos a las propias acciones ordinarias y a las obligaciones a t...

  17. Codesarrollo: la opcion institucional para el vinculo migracion y desarrollo

    National Research Council Canada - National Science Library

    Gomez Johnson, Cristina

    2007-01-01

    .... Para hacer visible esta evolucion y su efectividad, se menciona el caso mexicano, cuya experiencia demuestra que el vinculo entre la migracion y el desarrollo es posible, aunque unicamente si las iniciativas surgen de los propios migrantes y sus comunidades.

  18. Strategi Perekrutan Prospek di Multi Level Marketing TIENS Kota Medan

    OpenAIRE

    Vellayati, Naila

    2013-01-01

    This research entitled prospects recruitment strategy in multi level marketing of TIENS, Medan. This research’s aim is to recognize the recruiting strategy of the prospects and boundaries in recruiting the prospects in multi level marketing of TIENS, Medan. The research methodology that being used is descriptive method in which only describes a situation or event systematically and neither seeks nor explains the relationships, also neither hypotheses test nor make predictions. In a more st...

  19. Real options as an alternative methodology to assess investment projects Las opciones reales como metodología alternativa en la evaluación de proyectos de inversión

    Directory of Open Access Journals (Sweden)

    Raúl Enrique Aristizábal Velásquez

    2012-12-01

    Full Text Available This paper aims to broaden the applicability of the assessment methodology of investment projects through real options as a key element for investment decision making. Traditional project valuation methodologies are described and their gaps, which special characteristic is uncertainty, are presented. A parallel between financial and real options that could be used for valuation is made, using the binomial tree method. Finally, a case study in the construction sector shows a project valuation using expand and waiting options.Este trabajo busca ampliar la aplicabilidad de la metodología de valoración de proyectos de inversión por medio de opciones reales como un elemento fundamental al momento de tomar una decisión de si se debe invertir o no. Se hace un recorrido por las técnicas tradicionales para valorar un proyecto de inversión y se plantean los vacíos que estos dejan, con respecto a proyectos en los que su principal característica es la incertidumbre. Se realiza un paralelo entre las opciones financieras y las opciones reales que per- mita valorar, utilizando la metodología de los árboles binomiales. Por último, se elabora un caso del que se plantea valorar una opción de espera y una opción de expandir de manera conjunta en el sector de la construcción.

  20. Valoración de opciones de compra y venta del quintal de café en el mercado ecuatoriano

    OpenAIRE

    2009-01-01

    El presente trabajo realizado se considera como una guía para las próximas generaciones con el marco teórico y ejercicios prácticos para los diferentes métodos de valoración de las opciones, así como también las diferencias entre los tipos de opciones que hoy por hoy existen en el mercado y cómo interpretar los resultados obtenidos mediante el software utilizado para el calculo del valor de las opciones de compra y venta mediante la formula de Black-Scholes. Con todo lo aplicado en la pr...

  1. Gamificación y docencia: lo que la universidad tiene que aprender de los videojuegos

    OpenAIRE

    Cortizo Pérez, José Carlos; Carrero García, Francisco Manuel; Monsalve Piqueras, Borja; Velasco Collado, Andrés; Díaz del Dedo, Luis Ignacio; Pérez Martín, Joaquín

    2011-01-01

    La Gamificación en un anglicismo, que proviene del inglés “gamification”, y que tiene que ver con la aplicación de conceptos que encontramos habitualmente en los videojuegos, u otro tipo de actividades lúdicas, como los videojuegos. Si bien la gamificación ya se está aplicando con éxito en algunas áreas tan diversas como el márketing, los recursos humanos, o incluso la gestión de relaciones con los clientes, o incluso a la formación de altos directivos, apenas se han planteado ...

  2. DECISIONES DE INVERSIÓN A TRAVÉS DE OPCIONES REALES

    Directory of Open Access Journals (Sweden)

    ANA MARÍA CALLE FERNÁNDEZ

    2009-01-01

    Full Text Available Dadas las limitaciones que presentan los métodos tradicionales de valoración de inversiones, y su dificultad para adaptarse a entornos cambiantes, se explora el método de opciones reales, el cual considera los intangibles y la flexibilidad operativa como elementos que pueden alterar la decisión de realizar un proyecto. El presente artículo da una mirada general a las opciones reales, sus conceptos, modelos, tipología, y presenta al final una aplicación al sector de la construcción. Se concluye que los métodos basados en opciones reales son más adecuados para la evaluación de proyectos, dada su flexibilidad e inclusión de elementos intangibles; comsin embargo, se resalta cómo el éxito de la valoración depende en buena medida de los supuestos e información disponible para realizarla.

  3. INVESTIGATION OF CRUSTAL MOTION IN THE TIEN SHAN USING INSAR

    Energy Technology Data Exchange (ETDEWEB)

    Mellors, R J

    2011-02-25

    The northern Tien Shan of Central Asia is an area of active mid-continent deformation. Although far from a plate boundary, this region has experienced 5 earthquakes larger than magnitude 7 in the past century and includes one event that may as be as large as Mw 8.0. Previous studies based on GPS measurements indicate on the order of 23 mm/yr of shortening across the entire Tien Shan and up to 15 mm/year in the northern Tien Shan (Figure 1). The seismic moment release rate appears comparable with the geodetic measured slip, at least to first order, suggesting that geodetic rates can be considered a proxy for accumulation rates of stress for seismic hazard estimation. Interferometric synthetic aperture radar may provide a means to make detailed spatial measurements and hence in identifying block boundaries and assisting in seismic hazard. Therefore, we hoped to define block boundaries by direct measurement and by identifying and resolving earthquake slip. Due to political instability in Kyrgzystan, the existing seismic network has not performed as well as required to precisely determine earthquake hypocenters in remote areas and hence InSAR is highly useful. In this paper we present the result of three earthquake studies and show that InSAR is useful for refining locations of teleseismically located earthquakes. ALOS PALSAR data is used to investigate crustal motion in the Tien Shan mountains of Central Asia. As part of the work, considerable software development was undertaken to process PALSAR data. This software has been made freely available. Two damaging earthquakes have been imaged in the Tien Shan and the locations provided by ALOS InSAR have helped to refine seismological velocity models. A third earthquake south of Kyrgyzstan was also imaged. The use of InSAR data and especially L band is therefore very useful in providing groundtruth for earthquake locations.

  4. Interacciones radiculares en sistemas agroforestales: mecanismos y opciones de manejo

    Directory of Open Access Journals (Sweden)

    F. Casanova

    2007-01-01

    Full Text Available Los sistemas agroforestales (SAF son una forma de uso de la tierra en donde las leñosas interactúan con los cultivos y/o animales, con la finalidad de diversificar y optimizar la producción de manera sostenida. Sin embargo, estos sistemas tienen limitantes originados por una combinación inadecuada de las diferentes especies, lo que resulta en competencia entre ellas. Las características radiculares de las especies leñosas tienen un papel importante en el éxito de los SAF, ya que indican modificaciones que pudieran existir entre especies asociadas. Por tanto, el objetivo de esta revisión es analizar la importancia de las interacciones radiculares, los criterios para el manejo con base en las características morfológicas y patrones de crecimiento entre especies y su impacto en los SAF. La incorporación de especies arbóreas dentro de los cultivos requiere de objetivos claros; es decir, conocer el papel que desempeñarían dentro del sistema. No es redituable utilizar especies arbóreas que no poseen cierto valor o producto, ya que la competencia entre los árboles y los cultivos es solamente admisible si es compensada a través de porlas ventajas con relación a los aumentos en la productividad de sistema. Son deseables aquellas especies arbóreas cuyas raíces sean agresivas con relación a los sistemas radiculares del cultivo asociado, y que manifiesten un crecimiento lateral profundo y/o posean una alta plasticidad. Una opción para reducir la competencia radicular es la regulación del espaciamiento y/o distribución de las diversas especies asociadas, así como la aplicación de prácticas de manejo. Los patrones de la actividad radicular de las plantas difieren entre especies, su conocimiento puede ayudar a evitar competencia excesiva y pérdidas de nutrientes en SAF con la asignación óptima del espacio y recursos disponibles.

  5. Opciones no protésicas en el tratamiento de la artrosis de tobillo

    Directory of Open Access Journals (Sweden)

    DR. U. Giovanni Carcuro

    2014-09-01

    Full Text Available La artrosis de tobillo es una patología poco frecuente, tiene una incidencia nueve veces menor que la rodilla o la cadera a pesar de relación entre mayor carga y menor superficie de esta. La mayor parte son de causa secundaria, posterior a un trauma o a cambios en la biomecánica de la misma a diferencia de otras articulaciones como cadera o rodilla que su principal causa es idiopática o primaria. Causas menos frecuentes son las artropatías inflamatorias, hemocromatosis o artropatía neuropática. Es un problema creciente en la atención de salud en todo el mundo, con un 1% de prevalencia de artrosis sintomática en población adulta. El tobillo es la articulación que mayor carga recibe en cuanto a superficie se refiere, aproximadamente 500 N. La superficie articular mide 350 mm2 aproximadamente, mientras que la cadera 1100 mm2 y la rodilla 1120 mm2. Soporta hasta 5 veces el peso corporal durante la marcha. Cambios en la distribución de la carga durante la marcha podrían tener un efecto beneficioso en la lubricación y nutrición del cartílago. El cartílago articular es de 1a 1,7 mm comparado con el grosor de cartílago de la rodilla es de 1 a 6 mm. El tobillo con una gran congruencia articular presenta un cartílago más fino que es capaz de equilibrar mejor las cargas. Para el tratamiento de esta patología existen diferentes alternativas, tanto no quirúrgicas como quirúrgicas, y estas últimas se dividen en aquellas que preservan la articulación y las que no. Entre las alternativas no quirúrgicas esta la modificación de estilos de vida. Pacientes con IMC > 25 tienen un riesgo 1,5 veces mayor para el desarrollo de artrosis de pie y tobillo, siendo factor potencialmente mo-dificable, mejorando la eficacia de todas las otras opciones terapéuticas, conservadoras y quirúrgicas. Las actividades de la vida diaria que aumentan el estrés en la articulación del tobillo, así como los deportes de impacto, deben evitarse y

  6. Tratamiento del ojo seco: sus opciones Treatment of the dry eye: its options

    Directory of Open Access Journals (Sweden)

    Marta Herrera Soto

    2002-12-01

    Full Text Available Se realiza una revisión bibliográfica del tratamiento del ojo seco debido a la frecuencia con que aparece esta entidad; se exponen las diferentes opciones terapéuticas para el conocimiento de todos y su objetivo es ofrecer a los nuevos oftalmólogos una panorámica ampliada para su tratamientoA bibliograpic review of the treatment of the dry eye is made due to its frequency. The different therapeutic options are explained so that everybody knows them. It is aimed at offering the new ophthalmologists a wider view for its treatment

  7. Opciones terapéuticas en la sinovitis en pacientes afectos de hemofilia: sinoviortesis

    OpenAIRE

    Querol Giner, María Magdalena

    2016-01-01

    OPCIONES TERAPÉUTICAS EN LA SINOVITIS EN PACIENTES AFECTOS DE HEMOFILIA: SINOVIORTESIS TESIS DOCTORAL Presentada por: María Magdalena Querol Giner Dirigida por los profesores: Dr. D. Antonio Iradi Casal Dra. Dª Sofía Pérez Alenda Dr. D. Felipe Querol Fuentes Valencia, 2016 INTRODUCCIÓN: La hemofilia es una enfermedad de carácter genético ligada al cromosoma X, esto representa su transmisión por parte de la mujer y su padecimiento en el hombre. Es una alteració...

  8. Modificaciones en la gestión del espectro: opciones y situación actual

    OpenAIRE

    Feijoo Gonzalez, Claudio Antonio; Gómez Barroso, José Luis; Mochón, Asunción

    2011-01-01

    El objetivo de este artículo es presentar las opciones que están considerándose (incluso ya aplicándose) para la reforma de los mecanismos de gestión del espectro radioeléctrico y evaluar su conveniencia y oportunidad. En concreto, se describen y valoran los tres cambios más profundos en este posible cambio de modelo: autorización del mercado secundario, utilización de la subasta para la asignación primaria y liberalización plena del uso del espectro. El proceso ya en marcha de introducción d...

  9. El uso de opciones reales para la valuación de proyectos innovadores

    OpenAIRE

    Grassetti, Virginia; García Fronti, Javier

    2012-01-01

    El análisis se divide en tres secciones, en la primera se abordan los métodos de valuación de proyectos de inversión propuestos por la Teoría Neoclasista, reflejando sus limitaciones para adaptarse al mercado de tecnologías innovadoras. Luego, se presenta un enfoque de las Opciones Reales como la alternativa que mejor se adapta a las características propias de este nuevo mercado. Por último, se plantea un modelo sencillo que permite analizar las cuestiones más fundamentales de estas metodolog...

  10. Métodos numéricos para la valoración de opciones

    OpenAIRE

    Jiménez Terradillos, Vanessa

    2013-01-01

    El objetivo de este trabajo de fin de grado es dar una introducción elemental al uso de métodos en diferencias finitas para la resolución numérica de las ecuaciones en derivadas parciales que aparecen en la modelización de los derivados financieros, en particular de los contratos de opciones. La teoría moderna de las Finanzas Matemáticas se inicia con los artículos de F. Black, M. Scholes [1] y R.C. Merton [7]. Desde entonces y en paralelo con la teoría, el comercio de opci...

  11. Opciones reales : una propuesta para valorar centros públicos de investigación agraria

    OpenAIRE

    Vedovoto, Graciela; Prior Jiménez, Diego

    2015-01-01

    Las decisiones de inversión en investigación y desarrollo (I+D) son importantes para el éxito de las organizaciones, sobre todo para los centros públicos de investigación. Este trabajo evalúa un proyecto de I+D (mejora genética de semillas) utilizando un método tradicional, el Valor Actual Neto, así como el uso de las opciones reales. Asimismo, se utiliza la Teoría del Excedente Económico y simulaciones de Monte Carlo para estimar los beneficios sociales. Los resultados indican que el enfoque...

  12. Surge-type glaciers in the Tien Shan (Central Asia)

    Science.gov (United States)

    Mukherjee, Kriti; Bolch, Tobias

    2016-04-01

    Surge-type glaciers in High Mountain Asia are mostly observed in Karakoram and Pamir. However, few surge-type glaciers also exist in the Tien Shan, but have not comprehensively studied in detail in the recent literature. We identified surge-type glaciers in the Tien Shan either from available literature or by manual interpretation using available satellite images (such as Corona, Hexagon, Landsat, SPOT, IRS) for the period 1960 to 2014. We identified 39 possible surge-type glaciers, showing typical characteristics like looped moraines. Twenty-two of them rapidly advanced during different periods or a surge was clearly described in the literature. For the remaining possible surge-type glaciers either the advance, in terms of time and length, were not mentioned in detail in the literature, or the glaciers have remained either stable or retreated during the entire period of our study. Most of the surge-type glaciers cluster in the Inner Tien Shan (especially in the Ak-Shiirak rage) and the Central Tien Shan, are in size and are facing North, West or North West. Pronounced surge events were observed for North Inylchek and Samoilowitsch glaciers, both of which are located in the Central Tien Shan. Samoilowitsch Glacier retreated by more than 3 km between 1960 (length ~8.9 km) and 1992 (~5.8 km), advanced by almost 3 km until 2006 and slightly retreated thereafter. The most pronounced advance occurred between 2000 and 2002. DEM differencing (based on SRTM3 data and stereo Hexagon and Cartosat-1 data) revealed a significant thickening in the middle reaches (reservoir area) of the glacier between 1973 and 2000 while the surface significantly lowered in the middle and upper parts of the glacier between 2000 and 2006. Hence, the ice mass was transferred to the lower reaches (receiving area) and caused the advance with a maximum thickening of more than 80 m. The ~30 km long North Inylchek Glacier retreated since 1943 and showed a very rapid advance of ~3.5 km especially in

  13. Options for rural electrification in Mexico; Opcion para la electrificacion de pequenas comunidades rurales en Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez Vera, Jorge [Luz y Fuerza del Centro, S. A., Mexico, D. F. (Mexico)

    1993-12-31

    The paper summarizes the results obtained in the study carried out in communities of the Hidalgo State, localized in remote and of difficult access sites. In the study 19 different options, which are technically and economically feasible, from the stand point of commercialization and electrification of the same. The performance of these systems was evaluated with respect to their capability to satisfy 12 technical goals and 5 social-economical, as well as their environmental impact. An hybrid system based on photovoltaic cells, diesel or gasoline generator and a wind-power generator, we think is the recommended option for this type of communities. [Espanol] Este trabajo sintetiza los resultados de un estudio llevado a cabo en comunidades del estado de Hidalgo, localizadas en lugares remotos y de dificil acceso. En el estudio se analizaron 19 diferentes opciones que son factibles tecnica y comercialmente hablando para la electrificacion de las mismas. El comportamiento de estos sistemas fue evaluado con respecto a su capacidad para satisfacer 12 objetivos tecnicos y 5 socioeconomicos, asi como su impacto ambiental. Un sistema hibrido a base de celdas fotovoltaicas, generador a diesel o gasolina y generador eolico, creemos que es la opcion recomendada para este tipo de comunidades.

  14. Opciones tipo barrera sobre la tasa de cambio Peso/Dólar

    Directory of Open Access Journals (Sweden)

    Ángela María Pérez Muñoz

    2007-12-01

    Full Text Available Este artículo es derivado de la investigación titulada Opciones tipo barrera sobretasa de cambio. Se realizó un examen de diversas metodologías existentes parala valoración y medición de los riesgos de las opciones tipo barrera europeas. Larevisión se centró, principalmente, en los métodos numéricos. Las SimulacionesMontecarlo constituyen una metodología para valorar y calcular las coberturas deopciones que dependen de la ruta seguida por los precios del activo subyacentedurante su vida útil. Los resultados generados corroboran que ellas convergensatisfactoriamente en la formulación analítica cuando ésta se ajusta a unaobservación discreta de los precios del activo subyacente. Tales resultados seajustan más cuando se aplica el Método de Control de Varianza de Variables Antitéticas a las Simulaciones Montecarlo. 

  15. Design procedure for ritchey-chrétien corrector.

    Science.gov (United States)

    Howell, B J

    1969-03-01

    A four-lens corrector system to remove residual aberrations in a Ritchey-Chrétien telescope was selected as the means of studying the relative effectiveness of two design methods: a ray deviation error function and third order aberration theory. At several stages in the design, very significant improvements were made by switching from ray deviation results to aberration theory and then back to ray deviation design. The goal, a 300-cm focal length, f/10 diffraction-limited 1.2 degrees flat field telescope for white light, was achieved. Lens data and system performance, including computed spot diagrams, are given for eight versions.

  16. Spectral Analysis of Broadband Seismic Array Data, Tien Shan

    Science.gov (United States)

    Shamshy, S.; Pavlis, G. L.

    2003-12-01

    We used a spectral analysis method to examine amplitude variations of body waves recorded in the Tien Shan region of central Asia. We used broadband data from the Kyrgyz Network (KNET), Kazakhstan Network (KZNET), and from a set of temporary, PASSCAL stations operated from 1997-2000 we refer to as the Ghengis array. A spectral ratio method similar to that used by Wilson and Pavlis (2000) was employed, but with station AAK used as a reference instead of the array median. Spectral ratios were estimated for all teleseismic events and a larger, intermediate depth events from the Hindu-Kush region for all three-components of ground motion and total signal strength on all components. Results are visualized by maps of amplitude for various frequency bands and through the 4-D animation method introduced by Wilson and Pavlis (2000). Data from Hindu-Kush events showed amplitude variations as much as a factor of 100 across the study area with a strong frequency dependence. The largest variations were at the highest frequencies observed near 15 Hz. Stations in the northwestern part of the Tien Shan array show little variation in amplitude relative to the reference station, AAK. In the central and eastern part of the array, the amplitude estimates are significantly smaller at all frequencies. In contrast, for stations in the western Tien Shan near the Talas-Fergana Fault, and the southern Tien Shan near the Tarim Basin, the amplitude values become much larger than the reference site. The teleseismic data show a different pattern and show a somewhat smaller, overall amplitude variation at comparable frequencies. The northern part of the array again shows small variations relative to the reference stations. There are some amplifications in the southern stations of the array, especially in the Tarim Basin. The higher frequency observations that show large amplifications at stations in the Tarim Basin are readily explained by site effects due to the thick deposits of sediments

  17. Les transformations du jeûne chez les chrétiens d'Orient

    Directory of Open Access Journals (Sweden)

    Bernard Heyberger

    2006-11-01

    Full Text Available Dans le christianisme, les règles du jeûne et de l’abstinence sont extrêmement complexes, dans leur rythme annuel et dans leurs prescriptions alimentaires, ce qui les distingue nettement de la pratique musulmane. C’est peut-être davantage dans l’anthropologie sous-jacente qu’on pourrait déterminer des conceptions communes aux deux religions. Ces règles se sont élaborées progressivement, entre le ive et le xiiie siècle, différenciant les Églises orientales de l’Église romaine, mais introduisant aussi des distinctions entre Églises orientales rivales. Il est assez difficile de se former une opinion claire sur les prescriptions et sur leur application concrète dans chaque groupe de chrétiens.À partir du xviie siècle, les Églises orientales se voient interrogées à propos de leurs pratiques en matière de jeûne et d’abstinence par les missionnaires et les érudits latins, et sommées de définir des règles strictes et définitives. En même temps, l’introduction des références du catholicisme latin fait perdre le sens du jeûne comme oeuvre collective, au profit d’une ascèse personnelle et intériorisée, centrée sur la pratique des sacrements. Les transformations du jeûne deviennent alors symptôme de la « modernisation » en cours chez les chrétiens orientaux.

  18. Opciones reales, valuación financiera de proyectos y estrategias de negocios. Aplicaciones al caso mexicano

    Directory of Open Access Journals (Sweden)

    Francisco Venegas Martínez

    2006-01-01

    Full Text Available En este trabajo la metodología de opciones reales se presenta como un instrumento indispensable para que los consejos de administración de las empresas tomen decisiones respecto a proyectos de inversión o estrategias de negocios cuando existe la flexibilidad (opcionalidad de tomar en el futuro nuevas decisiones relacionadas con extender, contraer, posponer, enmendar o abandonar un proyecto o estrategia. Al respecto, el presente trabajo realiza una revisión de las diferentes fórmulas analíticas que aparecen en la bibliografía para valuar la opcionalidad de estrategias en el supuesto de que el valor presente de los flujos de efectivo esperados sigue una distribución log normal o bien mediante el uso de métodos de árboles binomiales. En particular, se trata el caso de la toma de decisiones de venta o cierre de una empresa cuando el valor de mercado de sus títulos (de capital y deuda excede el valor presente de los flujos de efectivo esperados o el valor presente de estos flujos es menor que cierto valor de recuperación. En este contexto se analiza el caso de una empresa mexicana de servicios satelitales de comunicación. Asimismo, se aplica la metodología de opciones reales a proyectos carreteros de inversión; específicamente se examina el caso del proyecto de construcción del primer tramo de la autopista Toluca-Atlacomulco según los supuestos de volatilidad constante y estocástica. Es también importante destacar que esta investigación se centra en: i la valuación de opciones reales americanas de abandono; ii valuación de opciones reales compuestas; iii valuación de opciones reales con volatilidad extendiendo el modelo de Hull y White (1987.

  19. Opciones de fijación de precios bajo procesos telegráficos.

    Directory of Open Access Journals (Sweden)

    Nikita Ratanov

    2010-05-01

    Full Text Available En este artículo introducimos un nuevo modelo del mercado financiero basado en movimientos aleatorios en tiempo continuo con alternación de velocidades constantes y saltos, que ocurren con cambios de velocidad. Este modelo está libre de arbitraje, dado que la dirección del salto va de acuerdo a las direcciones de la velocidad del movimiento aleatorio subyacente, de una forma adecuada a las tasas de interés. Adicionalmente, suponemos que las tasas de interés dependen del estado del mercado. Las estrategias replicables son construidas detalladamente y se obtienen las fórmulas de forma cerrada para los precios de las opciones.

  20. Modelos de valorización de opciones europeas en tiempo continuo

    Directory of Open Access Journals (Sweden)

    Villamil Jaime

    2006-08-01

    Full Text Available El clásico modelo de valoración de opciones europeas de Black y Scholes (1973 supone que los retornos logarítmicos de un activo financiero se distribuyen normalmente, no obstante varios estudios empíricos muestran, primero, que esta distribución puede ser asimétrica y tener “colas pesadas” y, segundo, que la varianza del precio del activo no es finita. Este artículo presenta la implementación numérica de tres modelos alternativos: elasticidad constante de la varianza (1976, jump-diffusion (1976 y volatilidad estocástica (1987.

  1. Tien 'stuks wintergezigten in Tartarijen op doek geschilderd' - Chinese exportwinterlandschappen in Museum Volkenkunde

    NARCIS (Netherlands)

    Poel, van der R.H.M.

    2011-01-01

    Onderzoek naar de herkomst van tien zeldzame Chinese exportwinterlandschappen in Rijksmuseum Volkenkunde in Leiden. Daarnaast worden de tien eind-18e, begin-19e-eeuwse hybride Chinese olieverfschilderingen nader beschouwd vanuit iconografisch oogpunt, compositie, technische toepassingen en materiaal

  2. Actes et passions des martyrs chrétiens des premiers siècles

    OpenAIRE

    Vinel, Françoise

    2015-01-01

    Vingt-sept œuvres, brèves pour la plupart, sont regroupées dans ce volume et classées chronologiquement selon les différentes périodes de persécution. Dans une abondante littérature hagiographique, P. Maraval a choisi ceux des récits qui sont reconnus pour leur fondement historique. Il retraduit la plupart à nouveaux frais, sur la base des éditions disponibles, les plus récentes (par ex. la nouvelle édition du Martyre de Polycarpe par J. Leemans, Louvain 2007 ou la Passion d’Irénée, évêque de...

  3. ¿Qué opinión tiene el sector turístico sobre los cruceros?

    OpenAIRE

    Castillo Manzano, José I.; López Valpuesta, Lourdes; Alanis Inurria, Francisco José

    2014-01-01

    Frente al debate sobre si el impacto económico del turismo de cruceros es real o está sobreestimado, este trabajo se centra en analizar la percepción que tiene el propio sector turístico de las ciudades que acogen cruceros sobre dicho impacto. Para ello se cuenta con una muestra de 371 gerentes de establecimientos turísticos del hinterland de dos puertos españoles de cruceros. La metodología está basada en regresiones ordered logit y multinomial logit. Las conclusiones confirma...

  4. Alcoholic fermentation: an option for renewable energy production from agricultural residues; Fermentacion alcoholica: una opcion para la produccion de energia renovable a partir de desechos agricolas

    Energy Technology Data Exchange (ETDEWEB)

    Vazquez, H. J [Universidad Autonoma Metropolitana (Mexico)]. E-mail: hjv@correo.azc.uam.mx; Dacosta, O [Oficina de Consejo, Desarrollo y Transferencia Tecnologica, Dijon (Francia)]. E-mail: statfor@yahoo.com

    2007-10-15

    Biotechnology offers several options for generating renewable energy. One of these technologies consists on producing bioethanol by fermentation. Bioethanol is mainly used to prepare fuel for motor vehicles. This paper presents a proposal to produce such as fuels with a hundred liters experimental fermentation pilot unit. Results derived from essays are similar, in terms of yield and productivity, to those presented by other systems, if we take into account that our unit works under non sterile conditions, which represents significant energy savings. This technology does not require specialized knowledge for its construction and it would accessible to groups of Mexican farmers. [Spanish] La biotecnologia ofrece diversas opciones para la generacion de energias renovables. Una de ellas es la produccion de bioetanol, el cual se obtiene mediante fermentacion. El bioetanol se usa en la preparacion de carburantes para vehiculos automotores. En este articulo se presenta una propuesta para la obtencion de este combustible mediante una unidad de fermentacion piloto experimental de 100 litros. Los resultados de nuestros ensayos, en rendimiento y productividad, son similares a los de otros laboratorios si se considera que esta unidad piloto funciona en condiciones no esteriles, lo que representa como ventaja un ahorro de energia no despreciable. Ademas, la tecnologia no requiere conocimientos especializados para su realizacion y estaria al alcance de grupos campesinos mexicanos.

  5. Hydrological regime of Lake Adygine, Tien Shan, Kyrgyzstan

    Science.gov (United States)

    Falátková, Kristýna; Šobr, Miroslav; Kocum, Jan; Janský, Bohumír

    2014-05-01

    Glacier retreat in high mountain areas around the world is considered one of the major geosciences research topics of last decades. This process may result in formation and further development of glacial lakes that are often unstable and pose a threat to downstream valleys. The studied area is situated at the end of a tributary valley on the northern side of Kyrgyz range, about 40 km south of the capital - Bishkek. Glaciers of Central Tien Shan are considered very sensitive indicators of climate change. The studied lake is part of a system of young lakes situated near the front of a retreating glacier therefore it ranks among potentially dangerous ones. The area is closely observed, terrain research including bathymetric, geophysical, geodetic measurements was carried out during last ten years. The lake level and its dependence on the changing climatic conditions in the area have been monitored in detail at this location since August 2007. Data from two meteorological stations are used to explain lake water level fluctuations, especially during ablation season when the lake is drained by a surface channel. The hydrological regime of the lake is compared with a regime of glacial streams, individual factors that affect it are described and possible trends and uncertainties that arise from it are analysed. The lake is also drained by subsurface channels, and as the water level declines over the cold part of a year, their capacity is studied and compared among years. The main aim of the study is to explain any deviations or changes found in the hydrological regime of the lake and to decide whether their cause could mean a decreased stability of the lake dam. Part of the dam is made up of moraine with buried ice and as the lake is drained by subsurface channels, their capacity can be changed due to moraine subsidence when the ice melts. This may lead either to sudden enlargement of channels' capacity or to their blockage, both of which could cause lake outburst.

  6. El enfoque de las opciones estratégicas de los actores en el estudio de las relaciones laborales

    Directory of Open Access Journals (Sweden)

    Carmen Marina López Pino

    2003-06-01

    Full Text Available El interés fundamental de este artículo es esclarecer la propuesta analítica desarrollada por el MIT (Massachussetts Institute of Technology, inspirada en el concepto de "opciones estratégicas" para el estudio de las relaciones laborales. De manera introductoria se plantea la problemática de las relaciones laborales actuales y los hallazgos fundamentales de las diferentes investigaciones del equipo del MIT. En segunda instancia se realiza una breve presentación del enfoque de sistemas de Dunlop que este equipo de investigadores busca superar. Seguidamente se exponen los principales conceptos y premisas del enfoque de las opciones estratégicas de los actores. Y, por último, se presentan brevemente algunas de las debilidades de dicha propuesta.

  7. Remuneración de directivos mediante opciones sobre acciones: Aspectos económicos y éticos.

    OpenAIRE

    Argandoña, Antonio

    2000-01-01

    La remuneración de directivos mediante opciones sobre acciones («stock options») se ha convertido en una práctica cada vez más frecuente, que ha levantado polémicas de naturaleza económica y también ética. En este documento se explican los caracteres de las opciones sobre acciones, su utilización en los planes de captación, retención y motivación de directivos y los efectos esperados de las mismas, incluyendo algunas consideraciones sobre aspectos de carácter ético, como la licitud del objeti...

  8. Aplicación de las opciones reales en la toma de decisiones en los mercados de electricidad

    Directory of Open Access Journals (Sweden)

    Felipe Isaza Cuervo

    2014-01-01

    Full Text Available Las decisiones estratégicas en los mercados de electricidad están sujetas a un alto riesgo e incertidumbre; en consecuencia, las opciones reales aparecen como una alternativa para la toma de decisiones en dichos mercados. En el presente artículo se realiza una revisión de literatura analizando y clasificando aplicacio- nes de opciones reales sobre decisiones de inversión, operación, y de políticas y programas energéticos. Además se presenta un ejemplo sintético de aplicación teórico utilizando un modelo binomial para incor- porar energía eólica en vez de térmica de acuerdo con la volatilidad de los precios del carbón. Se concluye que las opciones reales permiten tomar mejores decisiones que los métodos tradicionales, pues capturan a través de sus múltiples modelos las diferentes incertidumbres propias de estos mercados.

  9. Aplicación de las opciones reales en la toma de decisiones en los mercados de electricidad

    Directory of Open Access Journals (Sweden)

    Felipe Isaza Cuervo

    2014-10-01

    Full Text Available Las decisiones estratégicas en los mercados de electricidad están sujetas a un alto riesgo e incertidumbre; en consecuencia, las opciones reales aparecen como una alternativa para la toma de decisiones en dichos mercados. En el presente artículo se realiza una revisión de literatura analizando y clasificando aplicaciones de opciones reales sobre decisiones de inversión, operación, y de políticas y programas energéticos. Además se presenta un ejemplo sintético de aplicación teórico utilizando un modelo binomial para incorporar energía eólica en vez de térmica de acuerdo con la volatilidad de los precios del carbón. Se concluye que las opciones reales permiten tomar mejores decisiones que los métodos tradicionales, pues capturan a través de sus múltiples modelos las diferentes incertidumbres propias de estos mercados.

  10. Valuación de opciones sobre subyacentes con rendimientos a-estables

    Directory of Open Access Journals (Sweden)

    José Antonio Climent Hernández

    2013-01-01

    Full Text Available En este trabajo se analiza el modelo log-estable para valuación de opciones europeas; se estiman los parámetros de la distribución de la tasa de depreciación del tipo de cambio peso-dólar a través de los siguientes métodos: 1 máxima verosimilitud, 2 tabulación por cuantiles de las distribuciones estables y 3 regresión sobre la función característica de la muestra; se realiza un análisis cualitativo para mostrar la calidad en el ajuste de la distribución del rendimiento; a través de un análisis cuantitativo se elige la mejor estimación de los parámetros estables y se compara el modelo log-estable ortogonal de McCulloch (2003 con el modelo log-normal de Black y Scholes (1973 y un vector de precios del MexDer; finalmente, se demuestra que el modelo log-estable presenta ventajas sobre el modelo log-normal.

  11. Respuestas y opciones de los productores de subsistencia a las señales de política pública ambiental: un enfoque de análisis multisectorial

    Directory of Open Access Journals (Sweden)

    Javier Becerril García

    2010-01-01

    Full Text Available El objetivo del presente trabajo es evaluar -en el marco de la política ambiental del gobierno mexicano y su contribución al alivio de la pobreza- el impacto que tiene sobre la economía de una comunidad rural yucateca la promoción del uso del maíz para la producción de bioetanol. Los resultados de la simulación, realizada con base en un modelo de multiplicadores contables que toma como punto de partida una Matriz de Contabilidad Social, demuestran que los efectos de un aumento en la demanda del cereal sobre el pib de la economía de subsistencia y en los ingresos de los hogares son mínimos. El estudio propone incentivar la demanda de artesanías o la producción de miel en la localidad, como alternativas de desarrollo sustentable. Las dos opciones tienen impactos significativos en el pib y en la reducción de la pobreza.

  12. Comparación entre algoritmo de ciclos y modelos de regime-switching, con aplicación a estrategias de inversión en derivados (opciones de venta)

    OpenAIRE

    2014-01-01

    En el presente trabajo revisamos los principios de una popular estrategia de inversión basada en opciones financieras, en especial las opciones de venta (puts), y testeamos de manera estadística una estrategia de inversión basada en la compra venta de opciones de venta sobre un índice en el mercado de capitales estadounidense, replicando el comportamiento de una empresa de seguro, que en este caso ofrecería cobertura a la baja del índice de mercado. Con la venta de opciones se ofrece cobertur...

  13. Energetic sustainability: Challenges and options in Mexico; Sustentabilidad energetica: Retos y opciones en Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Rosas Flores, Dionicio; Sheinbaum Pardo, Claudia [Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico)

    2000-07-01

    In this report present a general overview of energy trends and objectives of policy for Mexico, in the context of sustainable development. The work is divided in two main parts: the first one presents trends in energy use and potential, energy sector reform, social and economics indicators and revision of efficiency and renewable energy. The second part discusses options and instruments of energy politics for the country in regard of the sustainable development. The energy is central to concerns of sustainable development, affecting economic; the local and global environment, and social problems as poverty, population, health and education. Mexico should promote political energy that permit the fulfillment the energy requirements while developing strategies that help to alleviate the social problems and productivity, based on lesser environmental impacts. [Spanish] Este reporte presenta una vision sobre las tendencias energeticas de Mexico y plantea prioridades y objetivos de politica para el pais, en el contexto de desarrollo sustentable. El trabajo muestra dos partes principales: la primera seccion presenta tendencias en el uso de energia, potenciales energeticos e indicadores economicos y sociales, ademas de una revision de eficiencias y politicas de energias renovables. La segunda parte discute opciones, instrumentos y restricciones en el contexto del desarrollo energetico sustentable en el pais. La energia es un elemento central en el desarrollo ya que esta relacionado con la economia, el ambiente local y global y aspectos sociales como pobreza, poblacion, salud y educacion. Esto obliga en Mexico a promover politicas que permitan la cobertura de los requerimientos energeticos, las cuales deben desarrollarse de manera conjunta con estrategias, para ayudar a disminuir los problemas, productivos y sociales con menores impactos ambientales.

  14. Opciones no protésicas en el tratamiento de la artrosis de tobillo

    OpenAIRE

    Giovanni Carcuro, U.; Sergio Eckholt, G.; Rodrigo Millán, P.

    2014-01-01

    La artrosis de tobillo es una patología poco frecuente, tiene una incidencia nueve veces menor que la rodilla o la cadera a pesar de relación entre mayor carga y menor superficie de esta. La mayor parte son de causa secundaria, posterior a un trauma o a cambios en la biomecánica de la misma a diferencia de otras articulaciones como cadera o rodilla que su principal causa es idiopática o primaria. Causas menos frecuentes son las artropatías inflamatorias, hemocromatosis o artropatía neuropátic...

  15. Una propuesta para la valuación de opciones financieras: La Fórmula de Primer Acercamiento

    Directory of Open Access Journals (Sweden)

    Adolfo Martinez Huerta

    2002-01-01

    Full Text Available Para coadyuvar a determinados estudiantes y participantes de derivados financieros de nuestro país, en el entendimiento de las principales fórmulas de valuación de opciones como la Black - Scholes o la Binomial, se presenta una fórmula de valuación, llamada de Primer Acercamiento, para cuya deducción se utilizan conocimientos básicos en finanzas y que bajo determinadas condiciones esta fórmula se puede considerar como un caso particular de la Fórmula Binomial

  16. Opciones socio técnicas en la formación de campus virtuales en universidades argentinas

    OpenAIRE

    Luciana Guido; Mariana Versino

    2010-01-01

    Hoy en día, aproximadamente 65% de las universidades argentinas cuentan con un campus virtual. Este trabajoanaliza las estrategias desplegadas en los procesos de selección de diferentes opciones tecnológicas para la construcciónde campus virtuales en universidades nacionales argentinas. Se presenta la heterogeneidad de elementosoperantes a la hora de tomar decisiones acerca del tipo de plataforma utilizada (distribución “libre”, “propietaria” odesarrollo propio) en función de los diferentes “...

  17. Opciones reales aplicadas en redes integradas de servicios de salud empleando diferentes métodos de estimación de la volatilidad

    Directory of Open Access Journals (Sweden)

    Germán González-Echeverri

    2015-07-01

    Full Text Available El objetivo de este artículo es evaluar la posibilidad de expansión de una red integrada de servicios de salud mediante el uso de valoración por opciones reales. Para estimar el parámetro de volatilidad se estudian cuatro metodologías, dos de ellas son usadas en opciones reales las cuales se refieren a: Market Asset Disclaimer y Market Approach. Adicionalmente, las otras dos metodologías propuestas son empleadas en opciones financieras, las cuales son: volatilidad implícita del modelo de Merton y volatilidad implícita mediante Newton-Raphson. Los resultados muestran que la volatilidad estimada mediante las metodologías propuestas es similar a la obtenida por la metodología tradicional de Market Asset Disclaimer. La principal contribución de este artículo consiste en la construcción de la sonrisa de la volatilidad para opciones reales, que es fácil de implementar.

  18. Opciones reales aplicadas en redes integradas de servicios de salud empleando diferentes métodos de estimación de la volatilidad

    Directory of Open Access Journals (Sweden)

    Germán González-Echeverri

    2015-01-01

    Full Text Available El objetivo de este artículo es evaluar la posibilidad de expansión de una red integrada de servicios de salud mediante el uso de valoración por opciones reales. Para estimar el parámetro de volatilidad se estu- dian cuatro metodologías, dos de ellas son usadas en opciones reales las cuales se refieren a: Market Asset Disclaimer y Market Approach . Adicionalmente, las otras dos metodologías propuestas son empleadas en opciones financieras, las cuales son: volatilidad implícita del modelo de Merton y volatilidad implícita mediante Newton-Raphson. Los resultados muestran que la volatilidad estimada mediante las metodo- logías propuestas es similar a la obtenida por la metodología tradicional de Market Asset Disclaimer . La principal contribución de este artículo consiste en la construcción de la sonrisa de la volatilidad para opciones reales, que es fácil de implementar.

  19. Cenozoic episodic uplift and kinematic evolution between the Pamir and Southwestern Tien Shan

    Science.gov (United States)

    Liu, Dongliang; Li, Haibing; Sun, Zhiming; Cao, Yong; Wang, Leizhen; Pan, Jiawei; Han, Liang; Ye, Xiaozhou

    2017-08-01

    The Pamir Salient and Southwestern Tien Shan belong to two different systems, which collided due to the continuous northward drift of the Indian Plate during the Cenozoic, resulting in a shortening of 300 km. The uplift history and kinematic evolution of the Pamir-Southwestern Tien Shan remain unclear. In this study, we chose the 2025 m-thick Pakabulake formation in the East Wuqia section, at the southern-most margin of the Southwestern Tien Shan system, to obtain a high-resolution magnetostratigraphic record spanning 16.61 Ma to 9.78 Ma. Based on its high sedimentation rate, stable ca. E-W paleocurrents and stable magnetic susceptibility values, the nearby Southwestern Tien Shan was inferred to have undergone stable uplift during this period of sedimentation. Combining our results with the previous low-temperature thermochronology, magnetostratigraphy and re-calculated block rotations, we conclude that four episodic uplift events occurred in the Pamir-Southwestern Tien Shan during the Cenozoic, at times of 50-40 Ma, 35-16 Ma, 11-7 Ma and < 5 Ma, and that the first episodic uplift only occurred in the Pamir Salient. In addition, the Pamir Salient underwent a tectonic transformation from entire- to a half-oroclinal bending rotation during the Miocene, caused by activity along the Karakorum Fault and Kashgar-Yecheng Transfer System.

  20. ¿Nada en biología tiene sentidosi no es a la luz de la evolución?

    OpenAIRE

    Julio Alejandro Castro Moreno

    2013-01-01

    Se critica la pertinencia de la famosa frase de Dobzhansky "Nada tiene sentido en biología si no es a la luz de la evolución", la cual denominamos como el Dogma Central de la Síntesis Evolutiva (DCSE). En la primera sección se explica el origen del DCSE y se retoman los puntos centrales del artículo en el que Dobzhansky lo propuso. En el segundo apartado se desarrollan tres puntos: se hace una reflexión sobre cómo el trabajo científico de dicho autor pone en aprietos la idea de Mayr acerca de...

  1. Valor en riesgo para un portafolio con opciones financieras Value at risk for a financial portfolio with options

    Directory of Open Access Journals (Sweden)

    Carlos Alexánder Grajales Correa

    2010-07-01

    Full Text Available En este artículo se presentan y aplican diferentes formulaciones matemáticas, exactas y aproximadas, para el cálculo del valor en riesgo (VaR de algunos portafolios con activos financieros, haciendo especial énfasis en aquellos que contienen opciones financieras. El uso y pertinencia de tales formulaciones es analizado según las características e hipótesis que se tengan de los portafolios construidos, para lo cual se analizan en detalle la volatilidad y el percentil de la distribución de los cambios en el valor del portafolio, al igual que la volatilidad estocástica en un horizonte de tiempo dado. Para éste fin, se consideran los métodos de varianzas y covarianzas, simulación histórica y simulación Monte Carlo, desde una perspectiva formal y ampliada a portafolios que contienen opciones financieras, estableciendo algoritmos alternativos de cálculo y comparaciones entre los resultados.This article presents and applies different mathematical, exact and approximated formulations to estimate value at risk of some portfolios with financial assets, emphasizing on those which contain financial options. The use and appropriateness of such formulations is analyzed base don characteristics and hypothesis of constructed portfolios. With this purpose, volatility and distribution percentile of changes in the value of the portfolio are analyzed. Stochastic volatity at a given time is also analyzed. With this purpose, variances, and co-variance methods. Historic simulation and Monte Carlo simulation from a formal and extended perspective to portfolios containing financial options are taken into consideration, establishing alternative of calculation and comparison between the results.

  2. Opciones socio técnicas en la formación de campus virtuales en universidades argentinas

    Directory of Open Access Journals (Sweden)

    Luciana Guido

    2010-09-01

    Full Text Available Hoy en día, aproximadamente 65% de las universidades argentinas cuentan con un campus virtual. Este trabajoanaliza las estrategias desplegadas en los procesos de selección de diferentes opciones tecnológicas para la construcciónde campus virtuales en universidades nacionales argentinas. Se presenta la heterogeneidad de elementosoperantes a la hora de tomar decisiones acerca del tipo de plataforma utilizada (distribución “libre”, “propietaria” odesarrollo propio en función de los diferentes “modelos” de universidades y las definiciones sobre la innovación educativasustentada en la “virtualidad”. Se seleccionaron ocho casos de universidades nacionales basados en una muestrarepresentativa, en relación con el tipo de tecnología utilizada y con las características propias de cada universidad encuanto a sus proyectos fundacionales y sus propuestas “virtuales”. El estudio se centra en el análisis de fuentes deinformación secundaria (documentos institucionales de archivo, prensa nacional y local, resoluciones y normativa,sitios Web de las universidades y 30 entrevistas realizadas durante el periodo 2006-2008 a los gestores universitariosy empresas que prestan servicios a las iniciativas analizadas. La selección de las plataformas adoptadas muestra quelas opciones tecnológicas no se fundan solamente en cuestiones “estrictamente técnicas”, sino que también involucranaspectos organizacionales, cognitivos y culturales de las universidades analizadas.

  3. El Análisis de Proyectos de Inversión por la Víade las Opciones

    Directory of Open Access Journals (Sweden)

    Manrique Hernández Ramírez

    2013-02-01

    Full Text Available El método del Valor Actual Neto (VAN asume que los proyectos son ahora o nunca, que las inversiones son reversibles o que no se pueden demorar. Por esto las desestima, al no reconocer el valor de las opciones implícitas. La técnica conocida como opciones reales es mejor que el VAN debido a que sí reconoce el valor de la flexibilidad. La incorporación de la flexibilidad operativa en el análisis de inversiones reconoce el hecho de que no existen, en la mayoría de los casos, rutas fijas donde no puedan existir cambios de planes o ajustes en la marcha y que, por el contrario, mucho del valor de los proyectos se crea, precisamente, ajustando éstos a través del tiempo, conforme se va recibiendo nueva información del entorno.   ABSTRACT The NPV assumes that all projects should be done now or never, that investments are reversible or can’t be delayed; that is why it undervalues them as it does not recognize the value of implicit options. The technique known as real options is better than the NPV because it recognizes the value of flexibility. Incorporating operational flexibility in investment analysis addresses the fact that in most cases there are not fixed routes in which cannot be change of plans or adjustments under way and that on the contrary much of the value of the projects is created by precisely adjusting them through time as much new information from the environment is obtained.

  4. Basin evolution in a folding lithosphere: Altai-Sayan and Tien Shan belts in Central Asia

    NARCIS (Netherlands)

    Delvaux, D.; Cloetingh, S.; Beekman, F.; Sokoutis, D.; Burov, E.; Buslov, M.M.; Abdrakhmatov, K.E.

    2013-01-01

    Central Asia is a classical example for continental lithospheric folding. In particular, the Altay–Sayan belt in South-Siberia and the Kyrgyz Tien Shan display a special mode of lithospheric deformation, involving decoupled lithospheric mantle folding and upper crustal folding and faulting. Both are

  5. Empirical Relationship between particulate matter and Aerosol Optical Depth over Northern Tien-Shan, Central Asia

    Science.gov (United States)

    Measurements were obtained at two sites in northern Tien-Shan in Central Asia during a 1-year period beginning July 2008 to examine the statistical relationship between aerosol optical depth (AOD) and of fine [PM2.5, particles less than 2.5 μm aerodynamic diameter (AD)] and coars...

  6. Da Chrétien de Troyes a Shakespeare («The tragedy of King Richard the Third», a. I, sc. 2

    Directory of Open Access Journals (Sweden)

    Alfonso D'Agostino

    2015-07-01

    Full Text Available L’articolo si propone di considerare le somiglianze fra alcune vicende antico-francesi (l’Yvain di Chrétien de Troyes e il fabliau anonimo De celle que se fist foutre sur la fosse son mari con una scena del Riccardo III di Shakespeare. Anche se non si può dire che il dramma inglese dipenda dai testi narrativi oitanici, esso sviluppa lo stesso motivo della vedova consolata e una serie di motivi secondarî, di immagini (il sangue, il diavolo, la seduzione e di espressioni letterarie in modo sintomaticamente affine. The paper aims to evaluate similarities between some Old-French narratives (Chrétien de Troyes’ Yvain and the anonymous fabliau De celle que se fist foutre sur la fosse son mari and a scene from Shakespeare’s Richard III. Although we cannot affirm that Shakespeare’s play derives from the French narratives, it develops the same theme of “comforted widow” along with a series of secondary themes, of images (the blood, the devil, the seduction and literary expressions in a symptomatically, very similar way.

  7. FLEXIBILIDAD ESTRATÉGICA, TEORÍA DE OPCIONES REALES Y CONVERGENCIA CON EL VALOR ACTUAL NETO EMPLEANDO PROBABILIDADES “DEL MUNDO REAL” Y COEFICIENTES EQUIVALENTES CIERTOS.

    Directory of Open Access Journals (Sweden)

    Gastón Silverio Milanesi

    2011-10-01

    Full Text Available El trabajo presenta un modelo para valuar decisiones de inversión aplicando la Teoría de Opciones Reales. Propone el uso de probabilidades “del mundo real” en contraposición a los clásicos coeficientes equivalentes ciertos. El método describe y traduce “con un mayor grado de intuición”, la anatomía del riesgo correspondiente a la flexibilidad estratégica del activo. Adicionalmente, la estimación de coeficientes no emplea el tipo sin riesgo. En cambio emplea tasas estimadas a través de los tradicionales modelos de equilibrio, modelos que incorporan momentos de orden superior, o simples ajustes ad-hoc sobre la tasa. Finalmente demuestra la convergencia entre la Teoría de Opciones Reales y el Valor Actual Neto.

  8. Valuación de opciones arcoíris sobre canastas de activos bajo procesos de difusión con saltos

    Directory of Open Access Journals (Sweden)

    Adriana Zambrano Reyes

    2016-01-01

    Full Text Available En este trabajo se estudia la valuación de opciones sobre el máximo o el mínimo (precio o rendimiento de 2 activos riesgosos, conocidas como opciones arcoíris. Se extiende la valuación de estos contratos al caso en que los activos presentan difusiones combinadas con saltos. Los parámetros de los procesos de saltos son estocásticos, y específicamente el tama ̃ no del salto sigue una distribución normal, lo cual hace necesario recurrir a los procesos de Lévy. Se desarrolla una metodología numérica con MATLAB para valuar una opción cesta (o canasta de venta, y un put sobre el máximo y en el mínimo de 2 activos riesgosos; los resultados se pueden extender para el caso de n activos.

  9. Opciones reales: una propuesta para valorar proyectos de I+D en centros públicos de investigación agraria

    Directory of Open Access Journals (Sweden)

    Graciela Luzia Vedovoto

    2015-01-01

    Full Text Available Las decisiones de inversión en investigación y desarrollo (I+D son importantes para el éxito de las organizaciones, sobre todo para los centros públicos de investigación. Este trabajo evalúa un proyecto de I+D (mejora genética de semillas utilizando un método tradicional, el Valor Actual Neto, así como el uso de las opciones reales. Asimismo, se utiliza la Teoría del Excedente Económico y simulaciones de Monte Carlo para estimar los beneficios sociales. Los resultados indican que el enfoque de las opciones reales es muy adecuado para el análisis de proyectos en centros públicos de I+D.

  10. Calculo y comparacion de la prima de un reaseguro de salud usando el modelo de opciones de Black-Scholes y el modelo actuarial

    Directory of Open Access Journals (Sweden)

    Luis Eduardo Giron

    2015-12-01

    Full Text Available La presente investigación pretende calcular y comparar la prima de un reaseguro  usando el modelo de opciones de Black-Scholes y el modelo clásico actuarial tradicional. El período de análisis va desde enero de 2011 hasta diciembre de 2012. Los resultados obtenidos muestran que el modelo de Black-Scholes, que se utiliza normalmente para valorar opciones financieras, puede ser también usado para la estimación de primas de reaseguros de salud; y que la prima neta estimada a partir de este modelo se aproxima a las establecidas por el método actuarial, excepto cuando el deducible del reaseguro es muy alto (por encima de $200.000.000.

  11. Application of Global Positioning Measurements to Continental Collision in the Pamir-Tien Shan Region, Central Asia and GPS Survey of the Western Tien Shan

    Science.gov (United States)

    Hamburger, Michael W.; Reilinger, Robert E.; Hager, Bradford H.; Molnar, Peter

    1997-01-01

    In this report, we summarize what we have accomplished with five years of funding from NASA under its DOSE program, and with a comparable level of funding from NSF. We describe the development of a GPS network in the Tien Shan of Kyrgyzstan and Kazakhstan of the former Soviet Union, the analysis of data, and the main results. This discussion presents the state of the current network, which has grown significantly since the termination of our DOSE grants, with continued support both from NSF through its continental dynamics program and from NASA's SENH program. Although grants from NASA's DOSE program did not support this growth not directly, it did so indirectly by building the infrastructure that has enabled further expansion in an area where otherwise there would be only a small GPS presence. We note how the network has grown over time, but the emphasis of this discussion is on the quantity and quality of measurements that we have made.

  12. Valuación con opciones reales de proyectos con flujos correlacionados con fundamentales económicos y con saltos extremos Viabilidad del caso COMERCI UCB

    Directory of Open Access Journals (Sweden)

    Sergio Mendoza Sandoval

    2014-01-01

    Full Text Available Este trabajo extiende el método de flujos de efectivo desconta - dos para valuar proyectos de inversión a través de la incorpo - ración de opciones reales. Se supone que los flujos de efectivo generados por la empresa están correlacionados con fundamen - tales macroeconómicos, particularmente con la tasa de interés; asimismo, se supone que presentan saltos cuyo tamaño está dado por una distribución de valores extremos. Estos flujos son vistos como un portafolio de opciones reales, que surgen de un proceso de optimización dinámica estocástica donde el inversionista (el empresario busca maximizar su utilidad total descontada, sujeto a la riqueza que posee. Esta riqueza incluye el proyecto de inversión, un bono libre de riesgo de incumpli - miento y un conjunto de opciones reales asociadas al proyecto.

  13. Source processes of strong earthquakes in the North Tien-Shan region

    Science.gov (United States)

    Kulikova, G.; Krueger, F.

    2013-12-01

    Tien-Shan region attracts attention of scientists worldwide due to its complexity and tectonic uniqueness. A series of very strong destructive earthquakes occurred in Tien-Shan at the turn of XIX and XX centuries. Such large intraplate earthquakes are rare in seismology, which increases the interest in the Tien-Shan region. The presented study focuses on the source processes of large earthquakes in Tien-Shan. The amount of seismic data is limited for those early times. In 1889, when a major earthquake has occurred in Tien-Shan, seismic instruments were installed in very few locations in the world and these analog records did not survive till nowadays. Although around a hundred seismic stations were operating at the beginning of XIX century worldwide, it is not always possible to get high quality analog seismograms. Digitizing seismograms is a very important step in the work with analog seismic records. While working with historical seismic records one has to take into account all the aspects and uncertainties of manual digitizing and the lack of accurate timing and instrument characteristics. In this study, we develop an easy-to-handle and fast digitization program on the basis of already existing software which allows to speed up digitizing process and to account for all the recoding system uncertainties. Owing to the lack of absolute timing for the historical earthquakes (due to the absence of a universal clock at that time), we used time differences between P and S phases to relocate the earthquakes in North Tien-Shan and the body-wave amplitudes to estimate their magnitudes. Combining our results with geological data, five earthquakes in North Tien-Shan were precisely relocated. The digitizing of records can introduce steps into the seismograms which makes restitution (removal of instrument response) undesirable. To avoid the restitution, we simulated historic seismograph recordings with given values for damping and free period of the respective instrument and

  14. Las flores del desierto. Opciones de vida en pueblos de la región central de Sonora

    Directory of Open Access Journals (Sweden)

    Ma. Amalia Gracia

    2014-01-01

    Full Text Available Aunque la búsqueda de las localidades rurales por generar opciones de vida se observa en el esfuerzo de algunos pobladores, en México la política pública se restringe a ofrecer garantías sociales; le deja al mercado la creación de alternativas económicas, que no alcanzan para producir desarrollo local y regional. El presente artículo reflexiona sobre esto, a partir de una iniciativa de trabajo asociativo surgida hace más de seis años en pueblos de la región central del norte de Sonora, y muestra cómo se resuelven temporal y dinámicamente las tensiones entre prácticas de cooperación y reciprocidad y las de intercambio con el mercado utilizando postulados teóricos de distintas disciplinas, retomadas por las propuestas de economía solidaria. El caso ilustra las dificultades, riqueza y potencialidad de iniciativas como ésta, y la importancia del apoyo gubernamental en localidades a las que la baja capacidad económica y la generalización del narcotráfico las vuelve frágiles para contrarrestar procesos profundos de despoblamiento.

  15. ¿Qué tienes en la cara, eso se quita?

    Directory of Open Access Journals (Sweden)

    Jimmy Arévalo Romero

    2013-10-01

    Full Text Available El presente texto es un ensayo preparado por estudiantes de Medicina que tiene origen en su experiencia personal, ya que trata del padecimiento del acné en lo adolescencia, en él quieren concienciar a lo comunidad en general sobre las consecuencias psicológicas que genera el padecimiento del acné en el adolescente, y estimular a las personas a contribuir al desarrollo de estos jóvenes en la sociedad.

  16. Building Forecast Maps Of Water Quality For Main Rivers And Canals In Tien Giang Province, Vietnam

    Directory of Open Access Journals (Sweden)

    Anh Duc Pham

    2015-09-01

    Full Text Available This study aims to enhance the mapping of forecast for water quality assessment in Mekong Delta provinces. The data from 32 sites from main rivers and canals in an area of around 2,482 km2 in Tien Giang Province, Vietnam, were used for calculation and mapping. The ArcGIS 9.3 software, Inverse Distance Weighting (IDW interpolation method, hydrologic data, and water quality parameters in March (2010-2014 were applied to build the maps showing 2020 water quality predictions for main rivers and canals in Tien Giang Province. The estimation was based on the Water Quality Index (WQI with 6 parameters such as pH, total suspended solid (TSS, dissolved oxygen (DO, biochemical oxygen demand (BOD, total nitrogen (T_N, and coliform. The results showed that water quality in the studied area in dry season will not be improved by the year 2020. The finding could be a scientific reference for the selection of effective approaches to improve water quality in main rivers and canals in Tien Giang Province.

  17. EL MÉTODO DE DIFERENCIAS FINITAS EN EVALUACIÓN DE OPCIONES REALES THE FINITE DIFFERENCE METHOD IN REAL OPTIONS VALUATION

    Directory of Open Access Journals (Sweden)

    Sebastián Otero G

    2008-06-01

    Full Text Available Una respuesta a las falencias de los métodos tradicionales de evaluación de proyectos de inversión corresponde a la metodología de "Opciones Reales" que proviene del análisis de opciones sobre instrumentos financieros desarrollado en la década de los 70. Esta técnica, aplicada inicialmente a activos no financieros o reales, ha sido aplicada con singular éxito en la evaluación de proyectos de inversión y se presenta como una alternativa a los métodos de evaluación tradicionales, pues incluye tanto los aspectos estratégicos como de la teoría financiera. La variación fundamental que experimenta la evaluación de proyectos de inversión mediante opciones reales con respecto a la realizada mediante los métodos tradicionales es la incorporación de la incertidumbre y la flexibilidad como elementos que agregan valor al proyecto. En el presente este trabajo se realiza un recorrido del estado del arte en lo que respecta a la teoría de opciones reales para la evaluación de proyectos de inversión mediante diferencias finitas. Se describe la importancia de los componentes económicos y estratégicos a la hora de evaluar proyectos de inversión ante escenarios de incertidumbre, analizando las características de esta metodología, destacando sus virtudes y defectos e identificándose su aplicabilidad en la evaluación de proyectos de inversión. Finalmente se realiza una implementación del método de diferencias finitas implícitas (DFI para la evaluación de un caso real que cuenta con las opciones de esperar, abandonar, contraer, expandir y cambiar a mejor uso alternativo, evaluándose para todas las opciones y combinaciones de opciones posibles. Los resultados fueron comparados con la metodología tradicional (VAN y el árbol binomial con transformada logarítmica (ABTL. Ambas metodologías (DFI y ABTL entregan valores equivalentes, siendo ambos superiores a los obtenidos mediante la metodología tradicional (VAN, diferencia que

  18. Large Igneous Provinces of the Central Asia: data on geochronology, geochemistry and petrology of the Tien Shan and Junggar basaltic complexes

    Science.gov (United States)

    Simonov, V.; Mikolaichuk, A.

    2012-04-01

    spot like Hawaiian islands or island Bouvet (South Atlantic). Mesozoic-Cenozoic - multichannel (cluster) mantle alkaline magmatism. On the basis of data on melt inclusions in minerals from Tien Shan Cretaceous-Paleogene basalts a sharp change of magmatic system temperature from 1245° to 1110° is established at transition from olivine formation to clinopyroxene crystallization with falling TiO2, Al2O3, FeO and MgO in melts against a background of SiO2 growth. High contents of carbon dioxide in melt inclusions are determined. The fluid pressure in the melt, calculated from CO2-containing inclusions, varies from 4 to 8.4 kbar at 1220-1250°. Such enrichment of magma by carbon dioxide had rendered a great influence on the environment during eruption of melts.

  19. Three new species of Macrobiotus (Eutardigrada, Macrobiotidae, tenuis-group from Tien Shan (Kirghizia and Spitsbergen

    Directory of Open Access Journals (Sweden)

    Denis V. TUMANOV

    2007-09-01

    Full Text Available Illustrated descriptions of Macrobiotus danilovi sp. n., Macrobiotus tenuiformis sp. n. from Tien Shan (Kirghizia and Macrobiotus voronkovi sp. n. from Spitsbergen are given. These new species belong to the tenuis-group of the genus Macrobiotus. Members of the tenius-group have claws with a particularly long and thin common tract with a prominent frontal appendage at the base. Macrobiotus danilovi and M. tenuiformis differ from all known species of this group in the structure of their buccal armature. Macrobiotus voronkovi differs from all known species of the tenuis-group in its combination of features in adult animals and in the egg shell.

  20. Miseria y violencia en El Coronel no tiene quien le escriba

    OpenAIRE

    Gloria Escobar Soriano

    1999-01-01

    El trabajo describe la marginación y la pobreza de un sector de la sociedad colombiana en El Coronel no tiene quien le escriba, la célebre novela de Gabriel García Márquez. Mientras el Coronel espera la llegada de la carta, su hijo Agustín, ha muerto por sus actividades revolucionarias. El y su mujer enferma viven en una casa hipotecada y comen de las migajas que le sobran al gallo. El grado de injusticia y violencia política que se respira en el ambiente aumentan la crisis económica del Coro...

  1. Timing and process of river and lake terrace formation in the Kyrgyz Tien Shan

    Science.gov (United States)

    Burgette, Reed J.; Weldon, Ray J.; Abdrakhmatov, Kanatbek Ye.; Ormukov, Cholponbek; Owen, Lewis A.; Thompson, Stephen C.

    2017-03-01

    Well-preserved flights of river and lake terraces traverse an actively deforming rangefront, and form a link between glaciated mountains and a large intermontane lake in the Issyk-Kul basin of the Kyrgyz Tien Shan. We investigated the history and geometry of these lake and river terraces using geologic mapping, surveying, and radiocarbon and terrestrial cosmogenic nuclide dating. A prominent late Pleistocene highstand of the lake occurred over at least the period of 43-25 ka, followed by a period of deep regression and subsequent rise of the lake to the modern sill level in the late Holocene. Major aggradation of the most prominent latest Quaternary river terrace along the Ak-Terek and Barskaun rivers likely started at ∼70-60 ka, coincident to the local last glacial maximum in this region. In contrast to some models of aggradation and incision, the rivers appear to have stayed near the top of the fill for >20 ka, incising subtly below the top of this fill by ∼37 ka, locally. Deep incision likely did not occur until the peak deglaciation in the latest Pleistocene. Older dated terrace surfaces are consistent with one major terrace-forming event per glacial, constant deformation and incision rates, and typical fluvial gradients lower than the modern incising streams. The dating confirms regional terrace correlations for the most prominent late Quaternary terraces, but correlating higher terraces is complicated by spatially varying uplift rates and preferential terrace preservation between basins in the Tien Shan.

  2. Salud Tiene Sabor: a model for healthier restaurants in a Latino community.

    Science.gov (United States)

    Nevarez, Carmen R; Lafleur, Mariah S; Schwarte, Liz U; Rodin, Beth; de Silva, Pri; Samuels, Sarah E

    2013-03-01

    The prevalence of overweight and obesity in children has risen nationally in recent decades, and is exceptionally high in low-income communities of color such as South Los Angeles CA. Independently owned restaurants participating in the Salud Tiene Sabor program at ethnic foods marketplace Mercado La Paloma in South Los Angeles are responding to the childhood obesity crisis by posting calories for menu items and providing nutrition information to patrons. To evaluate whether menu labeling and nutrition information at point of purchase have an influence on availability of healthy food options, patron awareness of calorie information, and restaurant owners' support of the program. A case-study design using mixed methods included restaurant owner and stakeholder interviews, patron surveys, and environmental assessments. Data were collected using originally designed tools, and analyzed in 2009-2011. Healthy eating options were available at the Mercado La Paloma; restaurant owners and the larger community supported the Salud Tiene Sabor program; 33% of patrons reported calorie information-influenced purchase decisions. Owners of independent restaurants have an important role in improving access to healthy foods in low-income, Latino communities. Copyright © 2013 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

  3. Restauración del diente endodonciado. Diagnóstico y Opciones Terapéuticas

    OpenAIRE

    Suárez-Rivaya, Javier; Ripollés de Ramón, Maria José; Pradíes Ramiro, Guillermo

    2006-01-01

    La reconstrucción de un diente endodonciado, implica distintos factores como el grado de destrucción, la valoración del estado periodontal, la situación en la arcada, el material de reconstrucción ideal, etc. Este trabajo tiene como principal objetivo, basándose en la experiencia clínica y en la revisión bibliográfica realizada, aportar unas pautas de actuación protocolizada, de manera que puedan ser de utilidad en la toma de decisiones sobre el diagnóstico, pronóstico y el tratamiento del...

  4. La cultura para la paz en colombia: retos y opciones desde una perspectiva psico-jurídica

    OpenAIRE

    Sánchez Cardona, Mariela

    2012-01-01

    Este artículo se pretende plantear los retos y la viabilidad que tiene Colombia en el desarrollo y fortalecimiento de una Cultura para la Paz. Bajo esta perspectiva se enfatiza que la responsabilidad del Estado debe ir más allá del planteamiento de normas en el tema de la Paz, ya que también debe intervenir, en la implementación de estrategias de paz y en el control de la calidad de los procesos de la educación para la paz en la sociedad en general. Para llevar a...

  5. Un modelo de optimización estocástica para la valuación de una franquicia: un enfoque de opciones reales

    OpenAIRE

    2009-01-01

    Este trabajo extiende el método tradicional de valuación de franquicias basado en el flujo descontado de efectivo al enfoque de opciones reales, las cuales surgen de manera natural como resultado de un proceso de optimización estocástico donde el franquiciante busca maximizar su utilidad descontada por su costo de capital sujeto a la riqueza que posee. Esta riqueza incluye los costos de deuda y los costos adicionales a pagar por concepto de regalías. Se examina como es afectado el valor de la...

  6. Evaluación de opciones y planificación de un servicio de rehabilitación visual y baja visión

    OpenAIRE

    Gónzalez Costa, Ana

    2013-01-01

    Nuestro objetivo es realizar de forma profesional, la realización de un servicio de rehabilitación visual. Se nos plantean distintas opciones entres las que vamos a analiza tres claramente diferenciadas de realización del servicio: 1. Servicio de rehabilitación visual y baja visión dependiente de una óptica 2. Servicio de rehabilitación visual y baja visión como profesional independiente sin localización 3. Servicio de rehabilitación visual y baja visión independiente con localizació...

  7. Valorización de la naturaleza y el territorio. Opciones teóricas-metodológicas para pensar otras territorialidades posibles

    OpenAIRE

    Silvia Valiente; Alejandro Schweitzer

    2016-01-01

    RESUMEN El objetivo de este artículo consiste en pensar otras territorialidades posibles a partir de considerar las distintas valorizaciones de la naturaleza y del territorio desde determinadas opciones teóricas. Estas sonla perspectiva decolonial, la ecología política y la ecología de los saberes, próximas entre sí en lo que respecta a su posicionamiento ético-político. Además comparten las críticas a la ciencia moderna en lo que refiere a la simplificación de la realidad, el conocimiento ab...

  8. Una aplicación de la matemática financiera: valuación de opciones reales con flexibilidad e incertidumbre

    OpenAIRE

    Mallo, Paulino E.; Artola, María Antonia; Morettini, Mariano; Galante, Marcelo Javier; Pascual, Mariano Enrique; Busetto, Adrián Raúl; Zanfrillo, Alicia Inés

    2005-01-01

    Con la finalidad de aportar herramientas a los docentes de nuestra asignatura que les permita trasmitir a los alumnos su importancia, al considerársela como matemática aplicada en otras ramas del conocimiento, presentamos este tema contable relacionado con la valuación de opciones reales. Esta temática se presenta como uno de los campos más propicios para la investigación dada la continua necesidad de obtener mejores métodos de valuación de activos, principalmente, cuando no existe una cotiza...

  9. Efecto del número de opciones de respuesta sobre las propiedades psicométricas de los cuestionarios de personalidad

    OpenAIRE

    2006-01-01

    ¿Cuántas opciones de respuesta hay que utilizar para responder un cuestionario de personalidad? Durante más de ochenta años, numerosas investigaciones previas han examinado este tópico sin lograr alcanzar un consenso. El presente trabajo se aborda esta cuestión de forma exhaustiva.MÉTODO:Se aplican dos escalas de personalidad [(Orientación Negativa hacia los Problemas (NPO) del Social Problem Solving Inventory-Revised (SPSI-R) y la escala Satisfacción con la Vida (SWLS)], cada una a una muest...

  10. Opciones reales: una propuesta para valorar proyectos de I+D en centros públicos de investigación agraria

    OpenAIRE

    Graciela Luzia Vedovoto; Diego Prior

    2015-01-01

    Las decisiones de inversión en investigación y desarrollo (I+D) son importantes para el éxito de las organizaciones, sobre todo para los centros públicos de investigación. Este trabajo evalúa un proyecto de I+D (mejora genética de semillas) utilizando un método tradicional, el Valor Actual Neto, así como el uso de las opciones reales. Asimismo, se utiliza la Teoría del Excedente Económico y simulaciones de Monte Carlo para estimar los beneficios sociales. Los resultados indican que el enfoque...

  11. Source parameters for 11 earthquakes in the Tien Shan, central Asia, determined by P and SH waveform inversion

    Science.gov (United States)

    Nelson, Michael R.; Mccaffrey, Robert; Molnar, Peter

    1987-01-01

    The style and the distribution of faulting occurring today in the Tien Shan region were studied, by digitizing long-period World-Wide Standard Seismograph Network P and SH waveforms of 11 of the largest Tien Shan earthquakes between 1965 and 1982 and then using a least squares inversion routine to constrain their fault plane solutions and depths. The results of the examination indicate that north-south shortening is presently occurring in the Tien Shan, with the formation of basement uplifts flanked by moderately dipping thrust faults. The present-day tectonics of the Tien Shan seem to be analogous to those of the Rocky Mountains in Colorado, Wyoming, and Utah during the Laramide orogeny in Late Cretaceous and Early Tertiary time.

  12. Meso-Cenozoic tectonics of the Central Kyrgyz Tien Shan (Central Asia), based on apatite fission track thermochronology.

    OpenAIRE

    Glorie, Stijn

    2008-01-01

    Apatite fission track thermochronology on the Kyrgyz Tien Shan basement revealed a polyphased thermal history of the study-area. We interpret the Mesozoic and Cenozoic cooling-events as periods of tectonic reactivation.

  13. Climatic vs. Seismic Controlled Rockglacier Advances in Northern Tien Shan - Insights from Lichenometry

    Science.gov (United States)

    Rosenwinkel, S.; Korup, O.; Landgraf, A.; Dzhumabaeva, A.

    2014-12-01

    Glaciers and permafrost landforms in high mountain areas are of major importance for storing and providing fresh water for the surroundings, especially in arid or semi-arid areas as Central Asia. Rockglaciers have been traditionally used as landform proxies of the distribution of alpine permafrost. In the northern Tien Shan mountains, the most distinct lobes of >200 rockglaciers that we mapped from satellite imagery occur at minimum elevations between 2500 and 3700 m. However, individual and particularly low-lying lobes extend down to well below 3000 m, and seem difficult to reconcile with regional paleoclimatic fluctuations. To support ground based and satellite imagery estimates on rockglacier advances (1 to 10 m/yr) and to gain information on their morphological characteristics, we present results of terrestrial LiDAR measurements on six rockglaciers in four steep mountain valleys in the Kyrgyz and Kazakh Tien Shan. Having the ability to destabilize, and thus provide massive sediment input from hillslopes, we hypothesize that strong earthquakes may also have influenced the formation or advance of some of the region's rockglaciers. This hypothesis is based on the observation that the tectonically active area was affected by a series of major earthquakes in the late 19th and earliest 20th centuries, which have subsequently triggered numerous landslides and rock falls. Using lichenometry, we aim to resolve age patterns on lobes of different rockglaciers located both, in the vicinity and distal from large young historic earthquakes. This method has been used successfully to reconstruct glaciation histories, and paleoseismicity. To gain information about and to compare advance histories of the rockglaciers from the relative ages of their lobes, we compiled a dataset of several thousand lichen diameter measurements of different species (e.g., Rhizocarpon geographicum, Aspicilia tianshanica, Lecanora muralis, and Xanthoria elegans). Results show that lichen age

  14. Pierre Maraval, Constantin le Grand. Empereur romain, empereur chrétien (306-337)

    OpenAIRE

    Vinel, Françoise

    2015-01-01

    Pierre Maraval (PM) a déjà publié une biographie de Théodose (Théodose le Grand. Le pouvoir et la foi, Paris, 2009) et son intérêt pour l’empereur Constantin a déjà donné lieu à plusieurs ouvrages (Eusèbe de Césarée, La théologie politique de l’Empire chrétien. Louanges de Constantin, traduction annotée, Paris, Cerf, 2001 ; La véritable histoire de Constantin, traduction de textes choisis, Les Belles Lettres, Paris, 2010 ; Constantin Discours et Lettres, traduction annotée, Les Belles Lettres...

  15. Glacial Retreat and Associated Glacial Lake Hazards in the High Tien Shan

    Science.gov (United States)

    Smith, T. T.

    2013-12-01

    A number of studies have identified glacial retreat throughout the greater Himalayan region over the past few decades, but the Karakorum region remains an anomaly with large stagnating or advancing glaciers. The glacial behavior in the Tien Shan is still unclear, as few studies have investigated mass balances in the region. This study focuses on the highest peaks of the Tien Shan mountain range, in the region of Jengish Chokusu along the Kyrgyzstan-China-Kazakhstan border. In a first step, a 30-year time series of Landsat imagery (n=27) and ASTER imagery (n=10) was developed to track glacial growth and retreat in the region. Using a combination of spectral and topographic information, glacial outlines are automatically delineated. As several important glaciers in the study region contain medium to high levels of debris cover, our algorithm also improves upon current methods of detecting debris-covered glaciers by using topography, distance weighting methods, river networks, and additional spectral data. Linked to glacial retreat are glacial lake outburst floods (GLOFs) that have become increasingly common in High Mountain Asia over the last few decades. As glaciers retreat, their melt water is often trapped by weakly bonded moraines. These moraines have been known to fail due to overtopping caused by surge waves created by avalanches, rockslides, or glacial calving. A suite of studies throughout High Mountain Asia have used remotely-sensed data to monitor the formation and growth of glacial lakes. In a second step of the work, lake-area changes over the past 15 years were tracked monthly and seasonally using dense Landsat/ASTER coverage (n=30) with an automatic procedure based on spectral and topographic information. Previous work has identified GLOFs as a significant process for infrastructural damage in the southern Tien Shan/northern Pamir, as well as in the better studied Himalaya region. Lake identification and quantification of lake-growth rates is a valuable

  16. Miseria y violencia en El Coronel no tiene quien le escriba

    Directory of Open Access Journals (Sweden)

    Gloria Escobar Soriano

    1999-02-01

    Full Text Available El trabajo describe la marginación y la pobreza de un sector de la sociedad colombiana en El Coronel no tiene quien le escriba, la célebre novela de Gabriel García Márquez. Mientras el Coronel espera la llegada de la carta, su hijo Agustín, ha muerto por sus actividades revolucionarias. El y su mujer enferma viven en una casa hipotecada y comen de las migajas que le sobran al gallo. El grado de injusticia y violencia política que se respira en el ambiente aumentan la crisis económica del Coronel y generan en él una resistencia pasiva que recobra cuando se niega a vender el gallo y decide esperar la fecha de la pelea.

  17. La alucinación verbal tiene la estructura de la holofrase

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    Arturo de la Pava Ossa

    2009-05-01

    Full Text Available ¿En qué sentido la alucinaciónauditiva tiene la estructura dela holofrase? La holofrase es lainterjección, dice Lacan en 1958.En 1964, plantea que cuando enel primer par significante no hayintervalo, se solidifica, “se holofrasea”;a lo que añade que algo delmismo orden ocurre en la psicosis.Esta afirmación aporta elementospara pensar que la alucinación esuna holofrase y cómo a partir deella el psicótico construye su delirioparanoico.Palabras clave: holofrase, interjección,alucinación, discurso, funciónfálica.

  18. Using isotope methods to study alpine headwater regions in the Northern Caucasus and Tien Shan

    Science.gov (United States)

    Rets, Ekaterina; Chizhova, Julia N.; Loshakova, Nadezhda; Tokarev, Igor; Kireeva, Maria B.; Budantseva, Nadine A.; Vasil'chuk, Yurij K.; Frolova, Natalia; Popovnin, Viktor; Toropov, Pavel; Terskaya, Elena; Smirnov, Andrew M.; Belozerov, Egor; Karashova, Maria

    2017-09-01

    High mountain areas provide water resources for a large share of the world's population. The ongoing deglaciation of these areas is resulting in great instability of mountainous headwater regions, which could significantly affect water supply and intensify dangerous hydrological processes. The hydrological processes in mountains are still poorly understood due to the complexity of the natural conditions, great spatial variation and a lack of observation. A knowledge of flow-forming processes in alpine areas is essential to predict future possible trends in hydrological conditions and to calculate river runoff characteristics. The goal of this study is to gain detailed field data on various components of natural hydrological processes in the alpine areas of the North Caucasus and Central Tien Shan, and to investigate the possibility that the isotopic method can reveal important regularities of river flow formation in these regions. The study is based on field observations in representative alpine river basins in the North Caucasus (the Dzhankuat river basin) and the Central Tien Shan (the Chon-Kyzyl-Suu river basin) during 2013-2015. A mixing-model approach was used to conduct river hydrograph separation. Isotope methods were used to estimate the contribution of different nourishment sources in total runoff and its regime. d18O, dD and mineralization were used as indicators. Two equation systems for the study sites were derived: in terms of water routing and runoff genesis. The Dzhankuat and Chon-Kyzyl-Suu river hydrographs were separated into 4 components: liquid precipitation/meltwaters, surface routed/subsurface routed waters.

  19. Escenarios Monte Carlo para estrategias con expectativas de baja volatilidad cambiante mediante opciones europeas de compra y venta / Monte Carlo scenarios for strategies with expectations of changing low volatility using European call and put options

    OpenAIRE

    2015-01-01

    En este trabajo se generan estrategias especulativas en volatilidad con opciones europeas sobre veintiún componentes del Índice de Precios y Cotizaciones (IPC) y sobre este mismo índice, bajo el supuesto de que la volatilidad del activo subyacente es conducida por un proceso GARCH-M (1,1) calibrado con datos históricos, el precio de la opción se obtiene por simulación Monte Carlo. Con las estrategias de volatilidad construidas con los precios de las opciones simuladas se determinó que la estr...

  20. VALORACIÓN DE PROYECTOS DE ENERGÍA TÉRMICA BAJO CONDICIONES DE INCERTIDUMBRE A TRAVÉS DE OPCIONES REALES

    Directory of Open Access Journals (Sweden)

    Mónica A. Arango Arango

    2013-12-01

    Full Text Available Este trabajo valora una planta a base de carbón para la generación de energía térmica en un país latinoamericano considerando sus opciones reales. El trabajo presenta, en primer lugar, el comportamiento probabilístico de cada una de las variables que afectan la viabilidad financiera del proyecto. Para ello, se proponen modelos ARIMA-GARCH que permiten pronosticar las medias y la volatilidad de las variables que determinan el flujo de caja. Debido a la alta volatilidad en los precios de la energía y al incremento del precio internacional del carbón en los últimos años, se espera que estos proyectos no sean viables financieramente. Sin embargo, al considerar las opciones reales de expansión, de abandono y de continuar puede dar como resultado escenarios en los cuales esta tecnología sea competitiva. Los resultados obtenidos sugieren disminución de los riesgos de pérdida e incremento del valor del proyecto.

  1. Reconstruction of glacial lake outburst floods in northern Tien Shan: Implications for hazard assessment

    Science.gov (United States)

    Zaginaev, V.; Ballesteros-Cánovas, J. A.; Erokhin, S.; Matov, E.; Petrakov, D.; Stoffel, M.

    2016-09-01

    Glacier lake outburst floods (GLOFs) and related debris flows are among the most significant natural threats in the Tien Shan Mountains of Kyrgyzstan and have even caused the loss of life and damage to infrastructure in its capital Bishkek. An improved understanding of the occurrence of this process is essential so as to be able to design reliable disaster risk reduction strategies, even more so in view of ongoing climate change and scenarios of future evolutions. Here, we apply a dendrogeomorphic approach to reconstruct past debris-flow activity on the Aksay cone (Ala-Archa valley, Kyrgyz range), where outbursting glacier lakes and intense rainfalls have triggered huge debris flows over the past decades. A total of 96 Picea abies (L.) Karst. trees growing on the cone and along the main channel have been selected based on the evidence of past debris-flow damage in their trunks; these trees were then sampled using increment borers. The dating of past events was based on the assessment of growth disturbances (GD) in the tree-ring records and included the detection of injuries, tangential rows of traumatic resin ducts, reaction wood, and abrupt growth changes. In total, 320 GD were identified in the tree-ring samples. In combination with aerial imagery and geomorphic recognition in the field, reactions in trees and their position on the cone have allowed reconstruction of the main spatial patterns of past events on the Aksay cone. Our findings suggest that at least 27 debris flows have occurred on the site between 1877 and 2015 and point to the occurrence of at least 17 events that were not documented prior to this study. We also observe high process activity during the 1950s and 1960s, with major events on the cone in 1950, 1966, and 1968, coinciding with phases of slight glacier advance. The spatial analyses of events also point to two different spatial patterns, suggesting that quite dissimilar magnitudes probably occurred during glacier lake outburst floods and

  2. Morphogenetic features of soils in the Cat Tien National Park, southern Vietnam

    Science.gov (United States)

    Khokhlova, O. S.; Myakshina, T. N.; Kuznetsov, A. N.; Gubin, S. V.

    2017-02-01

    Morphogenetic features of soils on the selected plots in the Cat Tien National Park in southern Vietnam have been studied with the use of a set of morphological, analytical, and instrumental methods. The lithological factor and topographic position play the leading role in the development of the particular genetic soil features. The soils can be subdivided into four groups according to these factors. The soils developing from volcanic deposits with a predominance of tephra can be classified as thin clayey brown tropical soils (Dystric Skeletic Rhodic Cambisols (Clayic)), and the soils developed from less weathered colluvial derivatives of basalts with some admixture of tephra can be classified as dark-humus clayey tropical soils (Skeletic Greyzemic Umbrisols (Clayic)). Very poor soils developed from the eluvium of argillites are classified as thin weakly developed clayey tropical soils (Dystric Regosols (Clayic)). The soils forming from the alluvial sediments of different textures are classified as alluvial loamy sandy soils (Dystric Fluvisols (Arenic, Drainic)) and as alluvial clay loamy soils (Eutric Fluvisols (Episiltic, Endoclayic)).

  3. [Termites (Isoptera) in forest ecosystems of Cat Tien National Park (Southern Vietnam)].

    Science.gov (United States)

    Beliaeva, N V; Tiunov, A V

    2010-01-01

    The species composition and termite community populations were studied and the total land termites biomass was estimated in five forest habitats of Cat Tien National Park, Southern Vietnam. Twenty-four species of two families, Rhinotermitidae (1 species) and Termitidae (23 species), the predominant representatives of the subfamily Macrotermitinae, were found in mounds and in soil samples. On the test plots the density of termite mounds averaged 68 per hectare, primarily the mounds of three Macrotermes species. Destructive sampling allowed estimation of the caste composition and total community biomass based on six termite mounds of the prevailing species (Globitermes sulphureus, Microcerotermes burmanicus, Macrotermes carbonarius, M. gilvus, M. malaccensis, and Hypotermes obscuriceps). The total number of termites in the nests ranged from 65 000 to 3 150 000 individuals with the total biomass ranging from 185 to 2440 g live weight. The total abundance of nesting Macrotermes species alone could conservatively be estimated as 2.5 million individuals and 20.5 kg live weight per hectare. The number of soil- and litter-feeding termites averaged for the test plots was estimated at about 60 ind./m2. Four species dominating on the test plots (M. carbonarius, M. gilvus, M. malaccensis, and H. obscuriceps) belong to active tree litter feeders.

  4. Development of Petrov glacial-lake system (Tien Shan and outburst risk assessment

    Directory of Open Access Journals (Sweden)

    I. A. Torgoev

    2013-01-01

    Full Text Available Global climate warming causes an intensive melting and retreat of glaciers in the Tien Shan mountains. Melting water of glaciers causes overfilling of high mountain lakes. The increase of the surface and volume of the Petrov Lake accompanied with the decrease of stability of the dam represents an extremely dangerous situation that can produce a natural disaster. Failure can happen due to erosion, a buildup of water pressure, an earthquake or if a large enough portion of a glacier breaks off and massively displaces the waters in a glacial lake at its base. In case of the lake dam rupture, flooding of a disposal site of highly toxic tailing from the gold mine Kumtor is a threat. If this happens, the toxic waste containing cyanides would contaminate a large area in the Naryn (Syrdarya river basin. Even if the flooding of the disposal site does not occur, the damage after lake dam fracture will be immense due to the glacial lake outburst flood may be a devastating mudslide. In order to prevent or reduce the risk of this event we recommend performing engineering surveys for the development and implementation of the project for the controlled reduction of water level in the Blue Bay of the Petrov Lake to a safe volume.

  5. Asimetría y curtosis en el modelo binomial para valorar opciones reales: caso de aplicación para empresas de base tecnológica

    Directory of Open Access Journals (Sweden)

    Gastón Silverio Milanesi

    2013-01-01

    Full Text Available El trabajo propone un modelo de valoración de opciones reales con base en el modelo binomial utilizando la transformación de Edgeworth (Rubinstein, 1998 para incorporar momentos estocásticos de orden superior, especialmente para ciertos tipos de organizaciones, como empresas de base tecnológica, donde no se dispone de cartera de activos financieros gemelos, comparables de mercado y procesos estocásticos no gaussianos. Primero, se presenta el desarrollo formal del modelo, luego su aplicación sobre la valuación de spin-off tecnológico universitario, sensibilizando asimetría-curtosis y exponiendo el impacto en el valor del proyecto. Finalmente, se concluye sobre limitaciones y ventajas de la propuesta de valoración que resume la simplicidad del modelo binomial e incorporando momentos de orden superior en subyacentes con procesos no normales.

  6. Asimetría y curtosis en el modelo binomial para valorar opciones reales: caso de aplicación para empresas de base tecnológica

    Directory of Open Access Journals (Sweden)

    Gastón Silverio Milanesi

    2013-07-01

    Full Text Available El trabajo propone un modelo de valoración de opciones reales con base en el modelo binomial utilizando la transformación de Edgeworth (Rubinstein, 1998 para incorporar momentos estocásticos de orden supe- rior, especialmente para ciertos tipos de organizaciones, como empresas de base tecnológica, donde no se dispone de cartera de activos financieros gemelos, comparables de mercado y procesos estocásticos no gaussianos. Primero, se presenta el desarrollo formal del modelo, luego su aplicación sobre la valuación de spin-off tecnológico universitario, sensibilizando asimetría-curtosis y exponiendo el impacto en el valor del proyecto. Finalmente, se concluye sobre limitaciones y ventajas de la propuesta de valoración que resume la simplicidad del modelo binomial e incorporando momentos de orden superior en subyacentes con pro- cesos no normales.

  7. Towards an improved glacier monitoring program in the Kyrgyz Tien Shan and Pamir Mountains

    Science.gov (United States)

    Barandun, Martina; Huss, Matthias; Azisov, Erlan; Gafurov, Abror; Vorogushyn, Sergiy; Usubaliev, Ryskul; Kronenberg, Marlene; Hoelzle, Martin

    2014-05-01

    The monitoring of glacier mass balance in remote regions is important to understand the response of glaciers to climate change. The coverage of monitored glaciers in Central Asia has been very limited for the past 15 years; however the necessity of enhanced understanding regarding glacier dynamics and long term evolution in this particular region is crucial. Moisture availability importantly determines glacier response. Glaciers located in the Northern Tien Shan and Pamir Mountains are likely not to be directly influenced by monsoon such as most monitored Peri-Himalayan glaciers. However, not only scientific reasons make glacier monitoring to be of great relevance, also the link to political and socio-economic constraints on water scarcity carries high importance. First steps towards the establishment of a new glacier monitoring network were performed in 2010/2011 and since then modernization and extension of the monitoring strategies are continuously aspired. Close cooperation of international and local scientists build the basis of the program. Today four glaciers located in the Kyrgyz Tien Shan (Golubin Glacier, Suek Zapadniy Glacier, Glacier No. 354) and the North-Western Pamir (Abramov Glacier) are regularly monitored. The network is planned to be extended in the next years to cover selected glaciers in Uzbekistan and Tajikistan. Further, we intend to develop new approaches to remotely monitor sub-seasonal glacier mass balance at a regional scale. In-situ mass balance measurements are taken at all four glaciers continuously in late summer. Automatic weather stations installed at Abramov Glacier in 2011 and at Golubin Glacier in 2013 deliver daily meteorological data allowing the application of a simple mass balance model driven with local precipitation and temperature data. Model calibration is performed using glaciological measurements and results are validated with snowline observations based on remote imagery. Automatic cameras at Abramov Glacier take

  8. Climate change and glacier retreat in northern Tien Shan (Kazakhstan/Kyrgyzstan) using remote sensing data

    Science.gov (United States)

    Bolch, Tobias

    2007-03-01

    This paper presents an analysis of precipitation and temperature trends and a GIS-supported investigation of the related glacier change in the mountain ridges Zailiyskiy and Kungey Alatau, which represent an important part of the northern Tien Shan. The recent glacier coverage was delineated in a semi-automated way using a TM4/TM5 ratio image of a Landsat ETM Scene from the year 1999 and a merged ASTER/SRTM3-DEM. The extent of these glaciers is compared to that of the glaciers in the Soviet Glacier Inventory [UdSSR, Academica Nauk (1966 to 1983). Katalog Lednikov SSSR (in Russian), Gidrometeoizdat. Leningrad], which represents the situation in study area in approx. 1955. Regionalization of temperature and precipitation as well as solar radiation calculation was conducted in order to determine the climate situation at the glaciers. Trend and correlation analysis for the period from 1879 to 2000 at 16 climate stations showed a temperature increase, which have become pronounced since the 1950s. Another strong increase occurred at the beginning of the 1970s and since around 1980, the temperatures have generally stayed at this high level. The trend coefficient was about 0.8 K/100a for the period 1900 to 2000 and about 2.0 K/100a on average for the second half of the last century. The increase was about two times higher than the global average in northern Tien Shan from 1950 until 2000, where the increase was mainly due to temperature rise in autumn and winter. The increase is less pronounced in the mountainous areas, but still obvious. However, the higher temperature increase at the lower stations, located for the most part in cities or larger settlements, may be due in part to increased urbanization. For precipitation, there was a small increase on average, but no clear trend. On the average, the decrease in glacier extent was more than 32% between 1955 and 1999 in the investigated valleys of Zailiyskiy and Kungey Alatau. The glacier retreat was not homogeneous, but

  9. Metallogeny and geodynamics of the Aktiuz Boordu Mining District, Northern Tien Shan, Kyrgyzstan

    Science.gov (United States)

    Djenchuraeva, R. D.; Borisov, F. I.; Pak, N. T.; Malyukova, N. N.

    2008-03-01

    The Aktiuz-Boordu Mining District is located in the Northern Tien Shan in the eastern part of Kyrgyzstan. The region is characterized by nappe-folding structures and comprises strongly deformed Precambrian and Lower Paleozoic sedimentary, volcano-sedimentary, and metamorphic sequences. Metamorphic rocks are represented by crystalline schists, para- and orthogneisses, marble, migmatite, amphibolite and eclogite lenses. These rocks are thought to be the oldest in the Northern Tien Shan. The 2780-Ma Aktiuz complex has a total thickness of 2800-2900 m. Available U-Pb zircon age data for the Kemin Group migmatites yield ages of 2200 ± 50 Ma. Based upon their geological setting, multistage metamorphism and isotopic ages of retrograde metamorphism (1.1-1.9 Ga), these rocks reach a few kilometers in thickness and are subdivided into Archaean and Paleoproterozoic. The Archaean and Paleoproterozoic basement metamorphic rocks contain mineralization of various ages and types, including porphyry Cu, Au-sulphide, Au-Bi, barite, epithermal base metal and Au-Ag, REE and rare-metals. Two ore fields have been identified within the Aktiuz-Boordu Mining District, they are: (1) Taldybulak-Boordu, with Au, base metal, and porphyry Cu systems; (2) Aktiuz, with REE, rare- and base-metal deposits. Within the Paleozoic Taldybulak-Boordu volcanic structure, deposits and occurrences of Au are present at Taldybulak Levoberezhny, Chimbulak Zapadny, Karamoko and Kuranjailyau; of Pb at Boordu, Taldybulak Stary, Chimbulak Vostochny and Chimbulak Zapadny; of Mo at Karabulak, and of Cu at Berkut-Kashka. Almost all are found along the periphery of deeply eroded volcanoes. Rock types in the Taldybulak-Boordu ore field mainly comprise chlorite-amphibole and amphibole schists, amphibolites, and migmatites of the Paleoproterozoic Kuperlisay suite. The younger Paleoproterozoic Kokbulak and Kapchigay suites are represented by mica schists and granite gneisses, which are separated from the Kuperlisay suite

  10. Contabilización de Contratos de Futuros, Opciones, Forwards y Swaps (Accounting treatment for future, options, forwards and swap contracts

    Directory of Open Access Journals (Sweden)

    Vernor Mesén Figueroa

    2012-12-01

    Full Text Available Un entorno cada vez más dinámico y evolutivo ha dado paso al surgimiento y, por ende, al uso cada vez más frecuente de instrumentos financieros cuya flexibilidad y capacidad de ajuste a las condiciones de mercado permitan a las personas y empresas lograr sus objetivos de operación, inversión y financiamiento. En el contexto antes descrito, los contratos de futuros, opciones, forwards y swaps representan mecanismos cuyas características operativas permiten a sus tenedores el logro de objetivos alternativos tales como la cobertura eficaz de diferentes tipos de riesgos o la obtención de ganancias o pérdidas derivadas de la especulación. El presente artículo pretende reseñar, en forma breve, los mecanismos de operación de los contratos de futuros, opciones, forwards y swaps, para luego enfatizar en los criterios de contabilización que toda entidad o intermediario financiero debe seguir para reconocer los efectos que dichos tipos de contratos tienen sobre su posición financiera, resultados de operación y flujos de efectivo.   ABSTRACT A rapidly changing and evolving environment has given rise and increased the use of financial tools whose flexibility and adjusting capabilities to variable market conditions allow individuals and companies to achieve their operating, investment and financial goals. Within this framework, contracts for futures, options, forwards and swaps provide mechanisms with operating characteristics that allow their tenants to achieve alternative objectives such as the effective coverage of different risks or the attaining of profits or losses as a result of speculation. This article attempts to resume the operating mechanisms of futures, options, forwards and swap contracts and then concentrates into the accounting criteria that must be followed by financial intermediaries or entities to recognize the effects such contracts have on their financial position, operational results and cash flow.

  11. Segmented ruptures during intracontinental earthquakes: Kyrgyz Range, N-Tien Shan

    Science.gov (United States)

    Landgraf, Angela; Patyniak, Magda; Dzhumabaeva, Atyrgul; Abdrakhmatov, Kanatbek; Arrowsmith, J. Ramon; Strecker, Manfred R.

    2016-04-01

    In the late 19th and early 20th centuries, the northern Tien Shan of Kyrgyzstan and Kazakhstan was affected by a series of major M 6.9 to ~8 earthquakes. Ruptures affected either range fronts or range interiors. During these events (AD1885 Belovodskoe; AD1887 Verny; AD1889 Chilik; AD1911 Chon-Kemin; and AD1938 Kemino-Chu), neighboring faults ruptured and caused severe damage in the area of the Kyrgyz capital Bishkek and the former Kazakh capital Almaty (previously also called Alma-Ata or Verny), which were located in the epicentral areas. As recurrence intervals along single faults in this region are on the order of hundreds to thousands of years, such a sequence of earthquakes is not known in the remaining historic record. Earlier events may thus be recorded in long-term geomorphic archives. Through a combination of high-resolution offset measurements in the field, cosmogenic nuclide and luminescence dating of Quaternary landforms, stratigraphic analysis, and paleoseismological trenching, we evaluate the Quaternary deformation and analyze the paleoseismic history of neighboring fault systems along the Kyrgyz range mountain front. Our study sites are located close to the Kyrgyz capital Bishkek and include the epicentral area of the M6.9 Belovodskoe event of AD1885, but also the region west of it, which was not affected by this remarkable earthquake sequence. To date, the paleoseismic and historical seismic records for the Kyrgyz range indicate segmented ruptures that hardly exceed magnitude seven. Based on scaling relationships, however, the linked fault systems would be capable of generating M 8-events, similar to the long segmented ruptures observed in the mountain interior farther east during the late nineteenth and early twentieth centuries. The available observations, thus, point to incomplete fault ruptures along the mountain front, rather than earthquakes failing along a full rupture length.

  12. Seismic triggering of landslides, Part A: Field evidence from the Northern Tien Shan

    Directory of Open Access Journals (Sweden)

    H.-B. Havenith

    2003-01-01

    Full Text Available Landslides triggered by strong earthquakes often caused most of the global damage and most of all casualties related to the events, such as shown by the M = 7.7 Peru earthquake in 1970, by the M = 7.6 El Salvador earthquake in 2001 or by the M = 7.4 Khait (Tajikistan earthquake in 1949. The obvious impact of a landslide on the population is directly related to its movement. Yet, prediction of future failure potential and hence future risk to population is necessary in order to avoid further catastrophes and involves the analyses of the origin of seismic instability. The seismic landslide potential is mainly determined by the interaction between the regional seismic hazard and local geological conditions. At a local scale, seismic factors interfering with geological conditions can produce site-specific ground motions. The influence of such Site Effects on instability is the principal topic of this paper, which is divided into two parts, A and B. The present Part A is concerned with the correlation of field data with observed instability phenomena. Field data were obtained on mainly three landslide sites in the Northern Tien Shan Mountains in Kyrgyzstan, Central Asia. Geophysical prospecting, earthquake recordings, geological observation, trenching and geotechnical tests were the main investigation tools. The collected information gives an insight in the geological background of the slope failure and allows us to roughly infer failure mechanisms from field evidence. A detailed analysis of the susceptibility of a mechanism to specific geological conditions will be shown in Part B.

  13. New complex EAS installation of the Tien Shan mountain cosmic ray station

    Science.gov (United States)

    Chubenko, A. P.; Shepetov, A. L.; Antonova, V. P.; Beisembayev, R. U.; Borisov, A. S.; Dalkarov, O. D.; Kryakunova, O. N.; Mukashev, K. M.; Mukhamedshin, R. A.; Nam, R. A.; Nikolaevsky, N. F.; Pavlyuchenko, V. P.; Piscal, V. V.; Puchkov, V. S.; Ryabov, V. A.; Sadykov, T. Kh.; Saduev, N. O.; Salikhov, N. M.; Shaulov, S. B.; Stepanov, A. V.; Vildanov, N. G.; Vildanova, L. I.; Vildanova, M. I.; Zastrozhnova, N. N.; Zhukov, V. V.

    2016-10-01

    In this paper we present a description of the new complex installation for the study of extensive air showers which was created at the Tien Shan mountain cosmic ray station, as well as the results of the test measurements made there in 2014-2016. At present, the system for registration of electromagnetic shower component consists of ∼100 detector points built on the basis of plastic scintillator plates with the sensitive area of 0.25 m2 and 1 m2, spread equidistantly over ∼104m2 space. The dynamic range of scintillation amplitude measurements is currently about (3 - 7) ·104, and there is a prospect of it being extended up to ∼106. The direction of shower arrival is defined by signal delays from a number of the scintillators placed cross-wise at the periphery of the detector system. For the investigation of nuclear active shower components a multi-tier 55 m2 ionization-neutron calorimeter with a sum absorber thickness of ∼1000 g/cm2, typical spatial resolution of the order of 10 cm, and dynamic range of ionization measurement channel about ∼105 was created. Also, the use of saturation-free neutron detectors is anticipated for registration of the high- and low-energy hadron components in the region of shower core. A complex of underground detectors is designed for the study of muonic and penetrative nuclear-active components of the shower. The full stack of data acquisition, detector calibration, and shower parameters restoration procedures are now completed, and the newly obtained shower size spectrum and lateral distribution of shower particles occur in agreement with conventional data. Future studies in the field of 1014 -1017 eV cosmic ray physics to be held at the new shower installation are discussed.

  14. Association between atmospheric circulation patterns and firn-ice core records from the Inilchek glacierized area, central Tien Shan, Asia

    Science.gov (United States)

    Aizen, V.B.; Aizen, E.M.; Melack, J.M.; Kreutz, K.J.; Cecil, L.D.

    2004-01-01

    Glacioclimatological research in the central Tien Shan was performed in the summers of 1998 and 1999 on the South Inilchek Glacier at 5100-5460 m. A 14.36 m firn-ice core and snow samples were collected and used for stratigraphic, isotopic, and chemical analyses. The firn-ice core and snow records were related to snow pit measurements at an event scale and to meteorological data and synoptic indices of atmospheric circulation at annual and seasonal scales. Linear relationships between the seasonal air temperature and seasonal isotopic composition in accumulated precipitation were established. Changes in the ??18O air temperature relationship, in major ion concentration and in the ratios between chemical species, were used to identify different sources of moisture and investigate changes in atmospheric circulation patterns. Precipitation over the central Tien Shan is characterized by the lowest ionic content among the Tien Shan glaciers and indicates its mainly marine origin. In seasons of minimum precipitation, autumn and winter, water vapor was derived from the and and semiarid regions in central Eurasia and contributed annual maximal solute content to snow accumulation in Tien Shan. The lowest content of major ions was observed in spring and summer layers, which represent maximum seasonal accumulation when moisture originates over the Atlantic Ocean and Mediterranean and Black Seas. Copyright 2004 by the American Geophysical Union.

  15. Revisión metodológica a las herramientas de evaluación financiera de proyectos de inversión: opciones reales, flujos de caja descontados, simulación de Montecarlo y árboles de decisión

    OpenAIRE

    Maya Toro, Lina María

    2014-01-01

    Las herramientas con las que tradicionalmente han contado los gerentes de proyecto para llevar a cabo su evaluación financiera, tienden a omitir información importante de oportunidades dentro y sobre el proyecto mismo, como opciones de abandonar o reducir el alcance u opciones de detener temporalmente su desarrollo -- La valoración de estas alternativas se enmarca en la teoría de opciones reales, la cual en años recientes ha encontrado espacios de aplicación en sectores como la minerí...

  16. Autonomous geodynamics of the Pamir-Tien Shan junction zone from seismology data

    Science.gov (United States)

    Lukk, A. A.; Shevchenko, V. I.; Leonova, V. G.

    2015-11-01

    The geodynamics of the Tajik Depression, the junction zone of the Pamirs and Tien Shan, is typically considered in the context of plate tectonic concept, which implies intense subhorizontal compression of the zone resulting from the subduction of the Indian and Eurasian lithospheric plates. This convergence has been reliably confirmed by the GPS measurements. However, the joint analysis of the geological structure, seismicity, and geodimeter measurements conducted during a few years at the Garm geodynamical testing site of the Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, demonstrates a widening of the Tajik Depression instead of its shortening, as should be expected from the subhorizontal compression predominant in the present-day stress-state of this region. This conclusion, together with the data from the other regions, suggests that, along with the plate tectonic mechanisms, there are also other, local, autonomous drivers that contribute to the tectogenesis of this region. Besides, the probable existence of these autonomous sources within the Tajik Depression directly follows from the seismology data. Among them is the crustal spreading within the depression suggested by the seismotectonic displacements in the focal mechanisms of the earthquakes. These displacements are directed in different azimuths off the axial's most subsided part of the depression at a depth of 20-30 km. Above this region the distribution of seismotectonic deformations (STD) is chaotic. This pattern of deformation is barely accounted for by a simple model of subhorizontal compression of the Earth's crust in the region. In our opinion, these features of the seismotectonic deformation in the crust within the studied part of the Tajik Depression is probably associated with the gain in the volume of the rocks due to the inflow of the additional material, which is supplied from the bottom crust or upper mantle by the deep fluids. This increase in the rock volume

  17. Response of thunderstorm activity in data of neutron monitoring at Tien Shan

    Science.gov (United States)

    Antonova, Valentina; Kryukov, Sergey; Lutsenko, Vadim

    2015-04-01

    We present results of the study of data of the monitoring of high-energy and thermal neutrons at Tien Shan at different stages of thunderstorm activity. The data of the neutron monitoring were used taking into account the barometric effect. The intensity of the neutron component of cosmic rays is recorded in seven energy ranges. The electric field has values of ~ 100 V/m under fair weather conditions. Standard deviation of minute values of the neutron monitor data at the high altitude station does not exceed 0.5-0.6 %. Found that the standard deviation of the data during thunderstorms always exceeds these values. We selected events during the passage of thunderstorm clouds over the high altitude station without lightning discharges or with a small number of them. It was found that the particle rate of the neutron monitor changes in antiphase with the electric field changes. Atmospheric electric field of positive polarity decreases the count rate of the neutron monitor, and negative polarity - increases. Change of the count rate occurs at values of electric field ≥ 10-15 kV/m and reaches 2 %. The neutron monitor at the high-altitude station has the ability to measure the energy of recorded particles through determination of their multiplicity. We experimentally established that the sensitivity of the detected particles to change in Ez increases with decreasing their energy. The upper energy threshold of sensitivity of neutrons to change electric field is ~10 GeV. The physical mechanism of effect is based on lead nucleus capture of soft negative muons with the subsequent generation of neutrons. It is known that 7% of the neutron monitor count rate caused by negative muons. Absence of this effect in thermal neutrons data confirms the conclusion since the main difference of the thermal neutrons detector from the neutron monitor is the absence of the lead. In the active phase of a thunderstorm in the formed thundercloud the picture of distribution of charges is

  18. ¿Nada en biología tiene sentidosi no es a la luz de la evolución?

    Directory of Open Access Journals (Sweden)

    Julio Alejandro Castro Moreno

    2013-01-01

    Full Text Available Se critica la pertinencia de la famosa frase de Dobzhansky "Nada tiene sentido en biología si no es a la luz de la evolución", la cual denominamos como el Dogma Central de la Síntesis Evolutiva (DCSE. En la primera sección se explica el origen del DCSE y se retoman los puntos centrales del artículo en el que Dobzhansky lo propuso. En el segundo apartado se desarrollan tres puntos: se hace una reflexión sobre cómo el trabajo científico de dicho autor pone en aprietos la idea de Mayr acerca de que existen "dos biologías"; se cuestiona en qué medida es factible sostener que la columna vertebral de la biología es la evolución; y se plantean algunas implicaciones del DCSE en la filosofía y en la didáctica de la biología. En las conclusiones se argumenta por qué el DCSE debe ser abandonado de una vez por todas.

  19. Surface rupture of the 1911 Kebin (Chon-Kemin) earthquake, Northern Tien Shan, Kyrgyzstan

    Science.gov (United States)

    Arrowsmith, J. R.; Crosby, C. J.; Korjenkov, A. M.; Mamyrov, E.; Povolotskaya, I.

    2005-12-01

    The 1911 Ms 8.2 Kebin (Chon-Kemin) earthquake in the Northern Tien Shan, Kyrgyzstan is one of the largest historic intraplate reverse-faulting events. Documentation of slip distribution and fault geometry for major historic earthquakes, such as the Chon-Kemin event, provide important data on their source physics and seismotectonics. These data also provide insight into mechanical interaction with other large regional earthquakes, notably the 1887 Ms 7.3 Verny and 1889 Ms 8.3 Chilik events. Through detailed aerial photo mapping, examination of historic data (Bogdonovich et al., 1914), and two seasons of fieldwork, we mapped the entire 200 km of the1911 rupture and associated off-fault deformation and mass movements at > 1:50,000. At the 1911 events western end, the south dipping Djel Aryk section closely follows the range front at the southern edge of the Djel Aryk Valley. Mapping by Bogdonovich et al. indicates 1.5 km of rupture west of the Chu River in 1911 but 10-20 m high fault scarps further west in the Djel Aryk Valley indicate late Pleistocene paleoseismic activity. The Lower Chon-Kemin section stretches from the Chon-Kemin gorge to Chundi-Su. The fault dips steeply south and offset landforms indicate a left-lateral slip component. Vertical 1911 displacements are 1-3 m. Most of this portion of the 1911 rupture is located 500-1500 m above the Chon-Kemin Valley on the northern flank of the Kungei-Alatau Range. Bogdonovich et al. do not report 1911 rupture between Dyure River and Chundi-Su despite clear 10-30 m tall scarps offsetting Holocene landforms. The lack of mapped ground rupture in this area in 1911 suggests either a failure of the Bogdonovich team to reach this section of fault or that the earthquake failed to rupture here, despite clearly having done so prehistorically. The Upper Chon-Kemin section comprises steeply dipping to vertical discontinuous fractures located on steep slopes above the valley floor. Bogdonovich et al. report discontinuous

  20. Simulación financiera aplicada a la valoración del riesgo de crédito con el modelo de opciones Simulación financiera aplicada a la valoración del riesgo de crédito con el modelo de opciones

    Directory of Open Access Journals (Sweden)

    Juan P. Durán Ortiz

    2006-12-01

    Full Text Available El presente documento muestra cómo la simulación financiera puede ser una buenaalternativa para valorar el riesgo de contraparte de una opción real con el Modelode Merton, en contraposición del modelo de Black-Scholes introducido por Hull,Nelken y White en el año 2004 para el mismo caso de estudio.Para tal fin, se revisan los conceptos básicos de opción financiera, se presenta elmodelo de Black-Scholes para la valoración de opciones europeas sobre accioneshaciendo especial énfasis en los supuestos y las limitaciones que implica éste parael caso colombiano; se introduce la analogía entre opciones reales y opcionesfinancieras, que permite medir el riesgo de crédito en las oportunidades deinversión; se explica el modelo de Merton y, por último, se propone la simulaciónfinanciera como una metodología más general y potente para cuantificar el riesgocrediticio con el modelo de opciones, haciendo a su vez una aplicación sobre unproyecto de Inversión en “Crystal Ball”.This paper presents financial simulation as the best alternative for valuating credit risk with the Merton Model on a real option. We propose this in contrast to the Black and Scholes model introduced by Hull, Nelken and White in 2004 for the same case study.To demonstrate this, we begin by reviewing the basic concepts of a financial option. Then we present the Black-Scholes model for the valuation of European options with special emphasis on the assumptions and the limitations that this possibility implies. We introduce the analogy between real options and financial options that allows the measurement of credit risk on investment opportunities. We explain the Merton model, and finally, we propose financial simulation as a general and powerful methodology to quantify credit risk in the Merton model, including an application on an investment project with “Crystal Ball”.

  1. Adaptación al cambio climático y la variabilidad: algunas opciones de respuesta para la producción agrícola en Uruguay Adaptation to climatic change and variability: some response options to agricultural production in Uruguay

    Directory of Open Access Journals (Sweden)

    Agustín Giménez

    2012-06-01

    Full Text Available Adaptación al cambio climático y la variabilidad: "algunas opciones de respuesta para la producción agrícola en Uruguay". Como se señala en varios informes del Panel Intergubernamental sobre Cambio Climático (IPCC, 2007a; IPCC, 2007b, la comunidad científica internacional expresa que el aumento en la concentración de gases de efecto invernadero tiene como resultado cambios en la variabilidad climática diaria, estacional, interanual y a lo largo de decenios. La variabilidad climática y la ocurrencia de eventos extremos (heladas, granizos, sequías resulta en perjuicios muy importantes para el sector agropecuario y frecuentemente el sector requiere de varios años para recuperarse económica y financieramente de los daños ocasionados. La unidad de agroclima y sistemas de información (GRAS del Instituto Nacional de Investigación Agropecuaria (INIA de Uruguay en conjunto con el Banco Mundial (BM y la Universidad de Cornell (UC de los Estados Unidos de América, finalizaron en el año 2009 el proyecto "Vulnerabilidad al cambio climático en los sistemas de producción agrícola en América Latina y el Caribe: "desarrollo de respuestas y estrategias", (Giménez y Lanfranco, 2009. El objetivo de la propuesta fue formular un plan de acción con recomendaciones para el desarrollo de respuestas y estrategias con el fin de contribuir a una mejor adaptación a los impactos de la variabilidad climática y la ocurrencia de eventos climáticos extremos en los sistemas de producción agrícola de Uruguay. Como resultado del trabajo, se identificaron y priorizaron 3 opciones de respuesta: sistema de información y soporte para la toma de decisiones; gestión del agua; y seguros y otros instrumentos financieros para la gestión de riesgos.Adaptation to climatic change and variability: "some response options to agricultural production in Uruguay". Like is mentioned in several reports of Intergovernmental Panel about Climatic Change (IPCC, 2007a; IPCC

  2. Opciones de tratamiento prótésico en niños con oligodoncias por displasia ectodérmica hidrótica

    Directory of Open Access Journals (Sweden)

    Kirenia Pieri Silva

    2014-06-01

    Full Text Available La reposición de los dientes no solamente influye en la adecuada alimentación y fonética, sino que también mejora la sonrisa y la apariencia personal, además del aspecto positivo que produce en el estado de salud psicológico y emocional de los niños afectados. Se presentan tres casos clínicos de niños con oligodoncias asociadas a displasia ectodérmica hidrótica, atendidos en la consulta de prótesis de la Clínica Estomatológica de Especialidades de Cienfuegos. Fueron rehabilitados con prótesis parcial removible acrílica, sobredentadura y prótesis parcial fija, respectivamente. Estas constituyen opciones de tratamiento efectivas, que solucionan el problema estético y funcional de los pacientes, y por tanto, mejoran su calidad de vida.

  3. Las relaciones laborales vistas a través de la teoría de las Opciones Estratégicas de los Actores

    Directory of Open Access Journals (Sweden)

    Carmen Marina López Pino

    2003-01-01

    Full Text Available El presente artículo desentraña el marco analítico de la teoría de las “Opciones Estratégicas de los Actores”, propuesta teórica del equipo del M.I.T. (Massachussets Institute of Tecnology para la explicación y comprensión de las relaciones laborales. Para lo cual aborda primero el enfoque de Dunlop, enfoque del que parte este grupo, y segundo, los conceptos básicos de este marco analítico como son: estrategia, instituciones y entorno. Finalmente, se destaca algunas de sus falencias, y se concluye que, no obstante los vacíos encontrados en las investigaciones del equipo del M.I.T., el marco analítico propuesto por este grupo es un instrumento adecuado, tanto teórico como metodológico, para abordar las relaciones laborales, y debería ser considerado en más investigaciones para contribuir con ello a la formulación de una teoría de las relaciones laborales más sólida y fundamentada.

  4. Valoración de patentes farmacéuticas a través de opciones reales: equivalentes de certeza y función de utilidad

    Directory of Open Access Journals (Sweden)

    Julián Pareja Vasseur

    2016-01-01

    Full Text Available El objetivo de esta investigación es proponer e incentivar el uso de las opciones reales a través de equivalentes de certeza y funciones de utilidad como metodología alternativa para valorar una patente. La incertidumbre y la flexibilidad en la toma de decisiones durante las diferentes etapas de la misma, al igual que las particularidades del inversionista, son elementos esenciales de la metodología que se propone utilizar para encontrar el equivalente de certeza que proporcione al inversor un abanico de resultados, los cuales dependen de la actitud de este frente al riesgo. Se adaptó este método a un caso de estudio sobre patentes f armacéuticas de Serono International S. A. para valorar la opción de abandono. Finalmente, se encuentra que el modelo propuesto permite representar las preferencias de inversionistas no diversificados en mercados incompletos y sus diferentes actitudes frente al riesgo. Se propone aplicar en futuras investigaciones otro tipo de funciones de utilidad con la finalidad de comparar resultados.

  5. Search for Sources of Primary Cosmic Rays at Energies Above 0.1 Pev at Tien Shan

    CERN Document Server

    Benko, J; Nikolsky, S I; Nesterova, N M; Romakhin, V A; Chubenko, A P; Shepetov, A L; Somogyi, A; Varga, A

    2005-01-01

    Analysis of the experimental data of joint Russian - Hungrian research was carried out at Tien Shan station on the search of sources of primary cosmic rays (PCR) at energies 0.1-1.0 PeV. Maps of extensive air shower arrival directions were presented where the standard deviation of mean event numbers in equatorial co-ordinates exceeded a definite value. The excess of EAS number was observed from an Galaxy object - the SN remnant and some other directions. The young pulsar PSR 0656+14 located near the centre of this object.

  6. ¿El sentido del humor, tiene sentido en el aula? / Does Sense of the Humor Make Sense in the Classroom?

    Directory of Open Access Journals (Sweden)

    Freddy Antonio González Ynfante

    2011-11-01

    Full Text Available Recibido 09 de junio de 2011 • Aceptado 24 de octubre de 2011 • Corregido 27 de setiembre de 2011 Resumen. El presente ensayo tiene como finalidad reflexionar sobre la importancia del humor pedagógico como estrategia de enseñanza aprendizaje en el aula; esto, tomando en cuenta la problemática de desmotivación y aburrimiento que sucede normalmente en la clase. Para plantear si “el enseñar contento y el aprender con alegría” pueden aumentar la eficacia en el proceso de enseñanza-aprendizaje, se abordará cómo, a pesar de las múltiples ventajas que puede aportar el humor en las aulas, se omite su empleo por la existencia de ciertos prejuicios y temores. La idea no es que los docentes hagan el papel de comediantes o payasos, sino la de mediar y acercar la clase de manera pedagógica y didáctica a través del uso del humor, y sobre esto reflexionaba Platón (1992, cuando planteaba que muchas veces ayudaba una broma, en donde la seriedad oponía resistencia. Abstract. This paper studies the importance of humor as a teaching strategy in the classroom, considering the usual lack of motivation and boredom. To analyze whether the “happy teaching and happy learning” may increase effectiveness in the teaching-learning process, the author will discuss how, despite the many benefits it may bring, humor is not used in the classroom due to prejudices and fears. The idea is not for teachers to play the role of a comedian or a clown, but to intervene and get closer to the group with a teaching, didactic purpose through humor. Plato (1992 thought about this; he used to say that sometimes a joke may help, where seriousness put up resistance.

  7. Dios conoce todo a priori, tiene un intelecto puro e intuitivo. La determinación kantiana de los predicados psicológicos de Dios por vía especulativa

    Directory of Open Access Journals (Sweden)

    Laura Alejandra Pelegrin

    2016-08-01

    Full Text Available Kant afirma que Dios conoce todo a priori, que tiene un intelecto intuitivo y puro; pero el sistema crítico enseña que este aspecto de la divinidad no es cognoscible por nosotros. Entonces, ¿cómo determinar los atributos del intelecto divino si Dios mismo no puede ser objeto de conocimiento? Algunos sostienen que este modo de concebir este atributo divino debe ser comprendido a partir de las convicciones reli-giosas del filósofo. Por el contrario, mostraremos que este peculiar modo de concebir el intelecto de Dios está fundado en un argumento que Kant expone in extensoen las Lecciones de teología filosófica.

  8. Optimization and risk analyses for rule curves of reservoir operation: application to Tien-Hua-Hu Reservoir in Taiwan.

    Science.gov (United States)

    Kuo, J T; Hsu, N S; Chiu, S K

    2006-01-01

    Tien-Hua-Hu Reservoir is currently under planning by the Water Resources Agency, Taiwan to meet the increasing water demands of central Taiwan arising from rapid growth of domestic water supply, and high-tech industrial parks. This study develops a simulation model for the ten-day period reservoir operation to calculate the ten-day water shortage index under varying rule curves. A genetic algorithm is coupled to the simulation model to find the optimal rule curves using the minimum ten-day water shortage index as an objective function. This study generates many sets of synthetic streamflows for risk, reliability, resiliency, and vulnerability analyses of reservoir operation. ARMA and disaggregation models are developed and applied to the synthetic streamflow generation. The optimal rule curves obtained from this study perform better in the ten-day shortage index when compared to the originally designed rule curves from a previous study. The optimal rule curves are also superior to the originally designed rule curves in terms of vulnerability. However, in terms of reliability and resiliency, the optimal rule curves are inferior to the those originally designed. Results from this study have provided in general a set of improved rule curves for operation of the Tien-Hua-Hu Reservoir. Furthermore, results from reliability, resiliency and vulnerability analyses offer much useful information for decision making in reservoir operation.

  9. Folded Lithospheric Basins in Central Asia: Altai-Sayan and Tien Shan basins in a folding lithosphere

    Science.gov (United States)

    Delvaux, Damien; Cloetingh, Sierd; Beekman, Fred; Sokoutis, Dimitrios; Burov, Evguenii; Buslov, Misha; Abdrakhmatov, Kanatbeck

    2014-05-01

    Central Asia is a classic example for continental lithospheric folding. In particular, the Altay-Sayan belt in South-Siberia and the Kyrgyz Tien Shan display a special mode of lithospheric deformation, involving decoupled lithospheric mantle folding and upper crustal folding and faulting. A review of the paleostress data and tectono-stratigraphic evolution of the Kurai-Chuya basin in Siberian Altai, Zaisan basin in Kazakh South Altai and Issyk-Kul basin in Kyrgyz Tien Shan suggests that these basins were initiated in an extensional context and later inverted by a combination of fault-controlled deformation and flexural folding. They deformed by a combination of lithospheric buckling inducing surface tilting, uplift and subsidence, together with upper crustal fault-controlled deformation. They are good examples of Folded Lithospheric Basins (FLB) which typically form in a buckling lithosphere. Their characteristic basin fill and symmetry, inner structure, folding wavelength and amplitude, thermal regime and time frame are examined in relation to basement structure, stress field, strain rate, timing of deformation, and compared to existing modelling results. Both regions of active lithospheric folding have a heterogeneous crust with a long history of accretion-collision, subsequently reactivated as a far-field effect of the Indian-Eurasian collision. Thanks to the youthfulness of the tectonic deformation in this region (peak deformation in late Pliocene - early Pleistocene), the surface expression of lithospheric deformation is well documented by the surface topography and superficial tectonic structures.

  10. Concentration and composition of dust particles in surface snow at Urumqi Glacier No. 1, Eastern Tien Shan

    Science.gov (United States)

    Wu, Guangjian; Zhang, Xuelei; Zhang, Chenglong; Gao, Shaopeng; Li, Zhongqin; Wang, Feiteng; Wang, Wenbin

    2010-10-01

    Major, trace, and rare earth elements (REE) were determined by inductively coupled plasma-mass spectrometer (ICP-MS) for dust particles that were extracted from fresh surface snow samples collected weekly or biweekly between March 2006 and January 2008 at Urumqi Glacier No. 1 (UG1) in Eastern Tien Shan, Central Asia. The UG1 dust shows average Fe/Al ratios of 0.7, Ca/Al ratios of 0.35, La/Th ratios of 2.62, Th/U ratios of 3.31, an Eu anomaly of 0.63, and L/HREE ratios of 7.87. Seasonal variation is significant in dust concentration, but is not observed in dust composition, which remains rather uniform throughout the sampling period. The compositional homogeneity suggests that dust materials in UG1 are well mixed from their possible source areas. Fine materials from the Junggar Basin, and to a less extend from Tarim Basin, more closely resemble UG1 dust properties in their REE composition than do the local moraines, indicating that the dust in UG1 snow mainly comes from mid- to long-range source areas. The HYSPLIT model results suggest that the Westerlies, Arctic air masses and local winds are the main circulations for dust transport to Eastern Tien Shan.

  11. Enfoque de opciones reales para la valoración financiera de marcas Real Options Approach to Financial Valuation of Brands

    Directory of Open Access Journals (Sweden)

    Yessica González Londoño

    2012-12-01

    Full Text Available Los activos intangibles, especialmente las marcas, son parte fundamental del valor de mercado de las compañías, pues representan su ventaja competitiva; sin embargo, la Contabilidad y las Finanzas se enfrentan ante un reto difícil al momento de valorarlos. Los métodos de medición de intangibles en la literatura revisada se caracterizan por ser limitados y subjetivos, e incluso presentan algunos errores conceptuales, encontrándose su utilidad principal en el campo de la gestión. Este artículo propone una metodología para la valoración financiera de marcas a partir de una extensión de la aplicación de opciones reales compuestas de las patentes, aprovechando las similitudes en su construcción. Su aplicación se ilustra mediante la valoración de la marca de una compañía aseguradora.Intangible assets are an important component of the market value of a company, particularly in brands which represent the competitive advantage of the company; however, both Accounting and Finance face a great challenge when trying to value them. The methods which have been proposed by the literature appear to be subjective, limited, and based on some theoretical errors. Their use is mainly circumscribed to the management of intangibles. This paper proposes a methodology for the financial valuation of brands based on the application of a compound real option model to a patent valuation, acknowledging the similarities in their construction. Later, an application to an insurance company is presented.

  12. Encuentros y Desencuentros entre el Norte y el Sur: Realidades y Opciones alrededor de la Antropología y el Género

    Directory of Open Access Journals (Sweden)

    Tovar, Patricia

    2005-12-01

    Full Text Available I start out with the idea that the challenges and the difficulties that science and academy present to women vary according to the discipline, social class and national origin. I then move into a personal reflection of the experience of a Colombian anthropologist in the United States. The aim is to expose and analyze the perceptions, representations and obstacles that women from the south face in the scientific community of the north, and the limited recognition that they have received historically in relation to their colleagues, that are not from the Third World. In addition to discussing structural difficulties, the article shows the barriers, inconveniences, and daily wounds, that in the long run, produce bigger injuries and affect professional careers. The options and survival strategies that women have in their efforts to become scientists are also presented.

    Se parte de la idea de que los retos y las dificultades que la ciencia y la academia presentan a las mujeres varían según la disciplina, la clase social y el origen nacional, para hacer una reflexión, a partir de una experiencia personal de una colombiana tratando de salir a flote en la antropología de los Estados Unidos. Con esto se exponen y analizan las percepciones, representaciones e impedimentos que tienen las mujeres del sur en la comunidad científica del norte y el muy limitado reconocimiento que históricamente han obtenido en comparación de sus colegas que no tienen origen en el Tercer Mundo. Se discuten no sólo las dificultades estructurales, sino las contrariedades, los impedimentos y las lesiones cotidianas, que producen mella y afectan el desempeño profesional y se presentan también las opciones y las estrategias utilizadas para sobrevivir en este esfuerzo.

  13. Dolarización, caja de conversión o tipo de cambio flexible. ¿Opciones para América Latina hoy?

    Directory of Open Access Journals (Sweden)

    Esmeralda Villegas

    2002-01-01

    Full Text Available El objetivo del presente artículo es el de describir las diferentes opciones de regímenes cambiarios para los mercados emergentes de América Latina; que van desde el tipo de cambio fijo, al flexible; con sus variantes como son la Caja de Conversión y la dolarización de la economía, en el contexto actual caracterizado por situaciones de persistente volatilidad de capital y crisis cambiaria. Se concluye que existen hoy más argumentos en contra de establecer durante mucho tiempo regímenes de tipo de cambio fijo, no solamente debido a las distorsiones y costos de la sobrevaluación de la moneda nacional, sino también por los costos que entraña su abandono, asimismo habría que sopesar los argumentos en contra de una excesiva flexibilidad que devendría en volatilidad del tipo de cambio; para ello cabe dar un espacio a que la autoridad pública intervenga, dando con su intervención una señal del tipo de cambio real que se considera conveniente, y reafirmar la importancia de desalentar los flujos de capitales externos especulativos. Se destaca con respecto a la proposición de la Caja de Conversión o de la Dolarización que son alternativas que privilegian la estabilidad monetaria, sacrificando otros objetivos macroeconómicos como el de la producción, el comercio, el empleo. Por lo cual es necesario actuar sobre determinantes fundamentales como son la disciplina fiscal, el avance en las reformas económicas; impulsando el progreso tecnológico que consiste en hacer más eficiente los procesos productivos a través de la inversión en tecnologías de punta.

  14. La falta de financiacion publica hipoteca el futuro del acelerador de protones valenciano. La Universidad de Valencia tiene avanzado el diseno de este dispositivo de alta tecnologia

    CERN Multimedia

    Jatvia, J M

    2002-01-01

    "La Universidad de Valencia tiene avanzado el diseno de un acelerador lineal de protones, cuya culminacion depende del compromiso del Consell en sufragar la plantilla que necesitaria el centro para estar operativo" (1 page).

  15. Dynamics of Intra-Continental Convergence Between the Western Tarim Basin and Central Tien Shan Constrained by Centroid Moment Tensors of Regional Earthquakes

    Science.gov (United States)

    Huang, Guo-chin Dino; Roecker, Steven W.; Levin, Vadim; Wang, Haitao; Li, Zhihai

    2016-11-01

    Among the outstanding tectonic questions regarding the convergence between the Tien Shan and Tarim basin in northwestern China are the manner in which deformation is accommodated within their lithospheres, and the extent that the Tarim lithosphere underthrusts the Tien Shan. In particular, the amount and type of deformation within the Tarim basin is poorly understood. It is also uncertain if the convergence between the Tarim and the Tien Shan takes place mainly along a discrete boundary, or if the Tarim lithosphere simply indents into the Kazach shield, forming the Tien Shan through crustal thickening accommodated by a distributed series of thrust faults. In this study we use hypocenters from published earthquake catalogs and waveforms recorded by regional seismic networks to determine earthquake source parameters through regional centroid moment tensor inversion. The entire dataset consists of 160 earthquakes that occurred between 1969 and 2009 and with moment magnitudes between 3.5 and 7 distributed throughout the central Tien Shan and northwestern Tarim Basin. The estimated focal depths of these earthquakes range from the near-surface to about 44 km. Focal mechanisms throughout much of the Tien Shan indicate active deformation accommodated by thrust faults from at least the upper crust to 30 km depth. South of the Tien Shan, the Jia-shi earthquake sequence within the Tarim basin suggests that both crustal shortening and localized flexure are part of a complicated process involving rotational convergence. Inside the Tarim basin, two earthquakes with thrust faulting mechanisms near the crust-mantle boundary beneath the Bachu uplift imply a brittle rheology of the lower crust. High-angle thrust events occur broadly across the Tien Shan, suggesting that the Tarim lithosphere as a whole is strong and indents into the Kazach shield to create the mountain range.

  16. Chromosomal Q-heterochromatin regions in native highlanders of Pamir and Tien-Shan and in newcomers.

    Science.gov (United States)

    Ibraimov, A I; Kurmanova, G U; Ginsburg, E Kh; Aksenovich, T I; Aksenrod, E I

    1990-01-01

    The variability of human chromosomal Q-heterochromatin regions (Q-HR) was studied in 385 newcomers well adapted to the extreme environmental conditions of Pamir and Tien-Shan, as well as in 284 representatives of the native population of these regions. Newcomers were found to represent a highly homogeneous group as regards all the quantitative characteristics of Q-HR variability, but at the same time they differed significantly from both native residents and individuals of similar nationality (Russians) living permanently at low altitude. Differences between these three groups in the amount of Q-HRs in their genome are discussed as evidence in favour of the hypothesis of the possible selective value of chromosomal Q-heterochromatin material in human adaptation to extreme environmental high-altitude conditions.

  17. Zones of the origin of seismic centers in the Pamir-Tien Shan sector of High Asia

    Science.gov (United States)

    Gatinsky, Yu. G.; Prokhorova, T. V.; Rundquist, D. V.

    2017-08-01

    The zones of the origin of seismic centers within highly seismic areas of the Pamirs and Tien Shan are established. The majority of catastrophic earthquakes coincide with them in this part of High Asia. Their establishment is based on the distribution of the most intensive epicenters and the maximal volumes of the seismic energy together with its calculation and forecasting of the possible manifestations of high seismicity. The investigation of the deep structure of these zones allows us to determine the connection of the seismicity with geophysical field anomalies and some factors of the deep and near surface lithosphere and crust structure, which influence the present-day geodynamics. The results of our research enable us to appreciate the level of the seismic danger in different parts of the region investigated.

  18. Repeated large-magnitude earthquakes in a tectonically active, low-strain continental interior: The northern Tien Shan, Kyrgyzstan

    Science.gov (United States)

    Landgraf, A.; Dzhumabaeva, A.; Abdrakhmatov, K. E.; Strecker, M. R.; Macaulay, E. A.; Arrowsmith, Jr.; Sudhaus, H.; Preusser, F.; Rugel, G.; Merchel, S.

    2016-05-01

    The northern Tien Shan of Kyrgyzstan and Kazakhstan has been affected by a series of major earthquakes in the late 19th and early 20th centuries. To assess the significance of such a pulse of strain release in a continental interior, it is important to analyze and quantify strain release over multiple time scales. We have undertaken paleoseismological investigations at two geomorphically distinct sites (Panfilovkoe and Rot Front) near the Kyrgyz capital Bishkek. Although located near the historic epicenters, both sites were not affected by these earthquakes. Trenching was accompanied by dating stratigraphy and offset surfaces using luminescence, radiocarbon, and 10Be terrestrial cosmogenic nuclide methods. At Rot Front, trenching of a small scarp did not reveal evidence for surface rupture during the last 5000 years. The scarp rather resembles an extensive debris-flow lobe. At Panfilovkoe, we estimate a Late Pleistocene minimum slip rate of 0.2 ± 0.1 mm/a, averaged over at least two, probably three earthquake cycles. Dip-slip reverse motion along segmented, moderately steep faults resulted in hanging wall collapse scarps during different events. The most recent earthquake occurred around 3.6 ± 1.3 kyr ago (1σ), with dip-slip offsets between 1.2 and 1.4 m. We calculate a probabilistic paleomagnitude to be between 6.7 and 7.2, which is in agreement with regional data from the Kyrgyz range. The morphotectonic signals in the northern Tien Shan are a prime example of deformation in a tectonically active intracontinental mountain belt and as such can help understand the longer-term coevolution of topography and seismogenic processes in similar structural settings worldwide.

  19. Glacier area and mass changes since 1964 in the Ala Archa Valley, Kyrgyz Ala-Too, northern Tien Shan

    Directory of Open Access Journals (Sweden)

    T. Bolch

    2015-01-01

    Full Text Available Glaciers are an important source of fresh water for Central Asia as they release water during the summer months when precipitation is low and water demand highest. Many studies address glacier area changes but only changes in glacier mass can be directly linked to climate and runoff. Despite the importance, investigations of glacier mass changes have been restricted to only a few glaciers in the Tien Shan until now. Geodetic mass balance measurements are suitable to complement and extend existing in-situ measurements. In this study, both area and mass changes of the ~40 km² glacier ice in the Ala Archa Valley, Kyrgyz Tien Shan, were investigated using 1964 and 1971 stereo Corona, 2012 stereo ASTER, the SRTM digital terrain model and other optical data such as Landsat ETM+ or Rapid Eye. In addition, ice thickness was modeled taking the basal shear stress and the glacier surface topography into account. The results indicate an area loss of 18.3±5.0% from 1964 until 2010 with continuous shrinkage in all investigated periods. The glacier’s mass balance was −0.45±0.27 m w.e. a−1 for the period 1964–1999 and −0.42±0.66 m w.e. a−1 for 1999–2012. Golubin Glacier showed a possible slight mass gain for 1964– 1971 and a decelerated mass loss for the 1999–2012 period. This is in good agreement with existing in-situ measurements exiting from 1962 until 1994 and since 2010. The overall ice volume was estimated to be 1.56±0.47 km³ of ice in the year 2000. Hence, the entire ice would be lost by 2100 if the mass loss would continue at the same rate

  20. Estudio Cinemático Comparativo de Tres Opciones de Tratamiento Conservador en el Manejo de los Trastornos de la Marcha de Niños con Equinismo Idiopático

    OpenAIRE

    Lerma Lara, Sergio

    2016-01-01

    Tesis Doctoral leída en la Universidad Rey Juan Carlos de Madrid en 2016. Directores de la Tesis: Carlos Goicoechea García y Tomás Epeldegui Torre El equinismo idiopático es una alteración de la marcha pediátrica caracterizada por la realización de una excesiva flexión plantar del tobillo durante la marcha. No hay consenso en la literatura acerca de la mejor oferta terapéutica, coexistiendo opciones conservadoras y quirúrgicas en la práctica clínica. El objetivo de este t...

  1. Opciones estratégicas de asociación entre política y religión: modelos de legitimación confesional en la política del Medio Oriente

    OpenAIRE

    De Angelis, Martín Federico

    2010-01-01

    Este ensayo indaga sobre las posibles opciones estratégicas de asociación entre Política y Religión. Tomando casos de Medio Oriente, se presentan distintos modelos de vinculación entre posturas ofensivas o defensivas y sus combinaciones con posturas religiosas o seculares. Dichas combinaciones entre política y religión serán contrastadas contra ejemplos históricos. La intención última del trabajo reside en, formular modelos de relación Política-Religión como versátiles recursos estratégicos....

  2. Implementación del modelo de opciones reales para la valoración de proyectos en el complejo inmobiliario los Delfines Golf & Country Club del grupo Barceló

    OpenAIRE

    Castro Gutiérrez, Edward

    2011-01-01

    Tesis de maestría -- Universidad de Costa Rica. Posgrado en Administración y Dirección de Empresas. Maestría Profesional en Administración y Dirección de Empresas, 2011. Sede del Pacífico. El objetivo general consiste en evaluar la planeación y valoración de proyectos mediante el uso del modelo de opciones reales en el complejo inmobiliario Los Delfines Golf & Country Club del Grupo Barceló de forma que se sustente una propuesta de implementación y se logre determinar la suficiencia del mo...

  3. Opciones reales como respuesta ante la valoración con flujo de caja libre en situaciones de incertidumbre: Caso de la compra de maquinaria en una empresa colombiana de consumo masivo

    OpenAIRE

    Donato Valdés, Nathalie; Forero Díaz, Nicolás

    2017-01-01

    El alto grado de incertidumbre de la economía actual impone retos y riesgos a las finanzas corporativas de cualquier compañía -- Encontrar alternativas que permitan la flexibilización de los modelos de evaluación de proyectos empresariales se constituye, en este sentido, en una de sus máximas tareas -- Una de estas alternativas es el método de valoración por Opciones Reales -- El presente estudio aplica dicho método a un proyecto de inversión en innovación tomando el caso de la compra de una ...

  4. Valorización de la naturaleza y el territorio. Opciones teóricas-metodológicas para pensar otras territorialidades posibles

    Directory of Open Access Journals (Sweden)

    Silvia Valiente

    2016-06-01

    Full Text Available RESUMEN El objetivo de este artículo consiste en pensar otras territorialidades posibles a partir de considerar las distintas valorizaciones de la naturaleza y del territorio desde determinadas opciones teóricas. Estas sonla perspectiva decolonial, la ecología política y la ecología de los saberes, próximas entre sí en lo que respecta a su posicionamiento ético-político. Además comparten las críticas a la ciencia moderna en lo que refiere a la simplificación de la realidad, el conocimiento abstracto y normalizado. Toman distancia del pensamiento conservador, el que sólo se interesaba por preservar el orden y explicar las continuidades espacio-temporales. De igual modo toma distancia de la jerarquía de saberes o epistemicidios heredados de la modernidad. Proponen el conocimiento situado, el arte de la argumentación para la comprensión, el conocimiento en términos dialógicos, como opción metodológica. Desde estas aportaciones transdiciplinares actuales proponemos en este trabajo pensar las posibilidades que las mismas ofrecen para el reconocimiento y abordaje de otras territorialidades posibles, en el marco de las investigaciones en marcha vinculadas al modelo neoextractivo minero en Argentina. ABSTRACT The aim of this article is to think about other possible territorialities from considering the different appreciations of nature and the territory from certain theoretical options. These are the decolonial perspective, political ecology and ecology of knowledge, close to each other with respect to its ethical-political positioning. They also share criticism of modern science as regards simplification of reality, abstract and standardized knowledge. They take away the conservative thought, which was only interested in preserving order and explain the spatio-temporal continuities. Similarly it takes away from the hierarchy of knowledge or inherited epistemicidios of modernity. Propose situated knowledge, the art of argumentation

  5. Sistemas Integrados de energías con fuentes renovables, requisitos y opciones. Integrated systems of energy with renewable sources, requirements and options

    Directory of Open Access Journals (Sweden)

    Antonio Sarmiento Sera

    2015-04-01

    Full Text Available En el presente reporte se consideró una instalación conectada a la red eléctrica en la isla de Cuba. Se tenía el interés de introducir un determinado % de energía a partir de fuentes renovables, y se poseía un determinado potencial de energía eólica y fotovoltaica. Se analizaron los requisitos y opciones energéticas, se realizaron simulaciones de alternativas con el programa HOMER y se concluyó con la determinación de las condiciones o potenciales de las fuentes renovables para la recomendación de cada opción energética, y se presentaron los resultados de forma gráfica y fácil comprensión. Se ofreció un análisis de las posibilidades reales que en el ámbito de una localidad, pueden aprovecharse en función de diversificar de manera sostenible, el esquema energético comunitario  con la utilización de las fuentes renovables de energía, utilizando la variante que desde el punto económico y ambiental resulte de más conveniencia.  In this report was considered an electric net connected installation in the island of Cuba. It had the interest of introducing a certain % of energy starting from renewable sources, and a certain potential of wind and photovoltaic energy was possessed. The requirements and energy options were analyzed, and it were carried out simulations of alternative with the HOMER program and it was concluded with the determination of the conditions or potentials of the renewable sources for the recommendation of each energy option, and the results were presented in graphic way and easy understanding. It was offered an analysis of the real possibilities in the environment of a town. It can take advantage in function of diversifying from a sustainable way, with the community energy outline using the renewable sources of energy, and taking the variant of more convenience from the economic and environmental point of view.

  6. Three-dimensional velocity structure and earthquake locations beneath the northern Tien Shan of Kyrgyzstan, central Asia

    Science.gov (United States)

    Ghose, Sujoy; Hamburger, Michael W.; Virieux, Jean

    1998-02-01

    We used the arrival times of local earthquakes and quarry blasts recorded by the Kyrgyzstan Broadband Network (KNET) to obtain three-dimensional (3-D) P and S wave velocity models of the upper crust beneath an actively deforming mountain front and its associated foreland in the Kyrgyz Tien Shan. The continuous velocity models, described by cubic B spline interpolation of the squared slowness over a regular 3-D grid, were computed by simultaneous inversion of hypocenter and medium parameters. Exact ray tracing was done in the smooth 3-D medium by shooting rays from the sources to the stations by an analytical perturbation method based on the paraxial ray theory. The deduced large, sparse, linear system was solved using the damped, iterative, least squares algorithm LSQR. The stability and resolution of the result was qualitatively tested by two synthetic tests: the spike test and the checkerboard resolution test. We found that the models are well resolved up to a depth of ˜27 km for most parts of our image domain. The P and S wave velocity models are consistent with each other and provide evidence for marked heterogeneity in the upper crustal structure beneath the northern Tien Shan. At shallower depths (<7 km) the sediment-filled foreland is imaged as a relatively lower velocity feature compared to the mountains, which are cored by crystalline basement rocks. In contrast, at midcrustal depths the mountains are underlain by relatively lower velocity materials compared to the foreland. A distinct contrast in velocity structure is also observed between the eastern and western parts of the Kyrgyz Range at midcrustal depths, with the presence of relatively higher velocities toward the east. The seismicity is concentrated near the traces of major active faults and extends deeper beneath the foreland compared to the mountains. The regional compression in the Tien Shan is accommodated along a series of high-angle reverse faults distributed throughout the orogenic system

  7. The Jurassic to Paleogene detrital record of the Central Asian Orogenic Belt: results from the Kyrgyz Tien Shan

    Science.gov (United States)

    De Pelsmaeker, Elien; Jolivet, Marc; Dransart Laborde, Amandine; Robin, Cécile; Zhimulev, Fedor; Poujol, Marc; Nachtergaele, Simon; Glorie, Stijn; De Clercq, Shana; Batalev, Vladislav; De Grave, Johan

    2017-04-01

    The Central Asian Orogenic Belt (CAOB) represents one of the largest Phanerozoic accretionary orogens in the world, pinched between North China - Tarim, Kazakhstan and the Siberian craton. It stretches from the Pamir in the southwest, over the Tien Shan, Junggar, Altai and Sayan mountain ranges to the Baikal rift in the northeast. The basement of the CAOB exists of various tectonic units that were assembled during several Paleozoic collision-accretion events. By the Permian, the accretionary tectonics in the CAOB culminated as all major composing units were joined. After final construction in the Late Paleozoic, the CAOB was subjected to several phases of Mesozoic deformation and was again reactivated in the Late Cenozoic as distant effect of the India-Eurasia collision. The Meso-Cenozoic reactivation episodes occurred in an intracontinental setting, related to tectonic far-field effects originating at the Eurasian margins. Subsequently intracontinental orogens, such as Tien Shan, were built superimposed on the inherited basement architecture and the erosion products of their exhuming mountain ranges accumulated in sedimentary basins. New sedimentological and detrital zircon U-Pb (LA-ICP-MS) results from several Jurassic to Paleogene sedimentary sections in Kyrgyzstan provide new insights in the Mesozoic - early Cenozoic geodynamic evolution and related basin-range interactions of the Kyrgyz Tien Shan. Studied sedimentary sections are located in the Fergana and Yarkand-Fergana basins to the west of the Talas-Fergana Fault (TFF) and in the Issyk-Kul and Ming-Kush-Kökömeren basins to the east of the TFF. The U-Pb ages of the post-Precambrian zircon grains found in 18 Jurassic to Paleogene sandstones, can be generally divided into four groups: Caledonian (470-390 Ma), Hercynian (315-260 Ma), Triassic (250-210 Ma) and Jurassic (190-160 Ma) ages. The differences in sedimentation pattern and detrital zircon U-Pb age components suggest that the TFF played an important

  8. Desarrollo de un modelo de valoración de concesiones de autopistas basado en la teoría de opciones reales, validación mediante el análisis de series históricas de datos de concesiones en servicio

    OpenAIRE

    Lara Galera, Antonio Lorenzo

    2006-01-01

    Esta tesis doctoral se inscribe en una línea de investigación de análisis de inversiones en condiciones de incertidumbre, considerando la existencia de opciones reales. En particular, se desarrolla un modelo de valoración de concesiones de autopistas utilizando el método de las opciones reales, que permite complementar los métodos clásicos de valoración de inversiones, incorporando el valor derivado de la flexibilidad gerencial, operativa y administrativa presente en estos proyectos. Se aport...

  9. Upper Paleozoic tectonics in the Tien Shan (Central Asian Orogenic Belt): insight from new structural data (Kyrgyzstan)

    Science.gov (United States)

    Jourdon, Anthony; Petit, Carole; Rolland, Yann; Loury, Chloé; Bellahsen, Nicolas; Guillot, Stéphane; Ganino, Clément

    2016-04-01

    Due to successive block accretions, the polarity of structures and tectonic evolution of the Central Asian Orogenic Belt (CAOB) are still a matter of debate. There are several conflicting models about the polarity of subduction during the Paleozoic, the number of microplates and oceanic basins and the timing of tectonic events in Kyrgyz and Chinese Tien Shan. In this study, we propose new structural maps and cross-sections of Middle and South Kyrgyz Tien Shan (MTS and STS respectively). These cross-sections highlight an overall dextral strike-slip shear zone in the MTS and a north verging structure related to south-dipping subduction in the STS. These structures are Carboniferous in age and sealed by Mesozoic and Cenozoic deposits. In detail, the STS exhibits two deformation phases. The first one is characterized by coeval top-to-the north thrusting and top-to-the-South normal shearing at the boundaries of large continental unit that underwent High-Pressure (Eclogite facies) metamorphism. We ascribe this phase to the exhumation of underthrusted passive margin units of the MTS. The second one corresponds to a top to the North nappe stacking that we link to the last collisional events between the MTS and the Tarim block. Later on, during the Late Carboniferous, a major deformation stage is characterized by the deformation of the MTS and its thrusting over the NTS. This deformation occurred on a large dextral shear zone between the NTS and the MTS known as Song-Kul Zone or Nikolaiev Line as a "side effect" of the Tarim/MTS collision. Based on these observations, we propose a new interpretation of the tectonic evolution of the CAOB. The resulting model comprises the underthrusting of the MTS-Kazakh platform beneath the Tarim and its exhumation followed by the folding, shortening and thickening of the internal metamorphic units during the last collisional events which partitioned the deformation between the STS and the MTS. Finally, the docking of the large Tarim Craton

  10. Une catastrophe glorieuse : le martyre des premiers chrétiens du Japon, Nagasaki, 1597

    Directory of Open Access Journals (Sweden)

    Clotilde Jacquelard

    2011-11-01

    Full Text Available Le naufrage du galion San Felipe dans le port de Urado (Shikoku, Japon en octobre 1596 fut le déclencheur d’un désastre missionnaire : le martyre de vingt-six chrétiens, franciscains espagnols et chrétiens japonais, à Nagasaki, le 5 février 1597. Cet article s’attache à examiner la relation dialectique entre les deux événements par l’étude de deux discours missionnaires franciscains hagiographiques. Il s’agit tout d’abord de rappeler la lecture providentialiste du temps à travers la perception de présages matériels et spirituels de la part des acteurs, puis de montrer que ces évènements paroxystiques révèlent en même temps qu’ils résolvent – temporairement – des tensions et des crises latentes, résultat de la confrontation entre plusieurs communautés culturelles comme la japonaise, l’espagnole et la portugaise, autour de prétentions géopolitiques, commerciales et religieuses dans cette zone de frontière de l’antiméridien du Pacifique nord.El naufragio del galeón San Felipe en el puerto de Urado (Shikoku, Japón en octubre de 1596 desembocó en un desastre misionero : el martirio de veintiséis cristianos, franciscanos españoles y cristianos japoneses, en Nagasaki, el 5 de febrero de 1597. Este artículo quiere examinar la relación dialéctica entre ambos acontecimientos, mediante el estudio de dos discursos misioneros franciscanos hagiográficos. Se trata de recordar primero la lectura providencialista de la época a través de la percepción de presagios tanto materiales como espirituales por parte de los actores, y mostrar luego que estos acontecimientos paroxísticos revelan, al mismo tiempo que resuelven –temporalmente– tensiones y crisis latentes, resultados de la confrontación de varias comunidades culturales como la japonesa, la española y la portuguesa, en torno a pretensiones geopolíticas, comerciales y religiosas en la zona fronteriza del antimeridiano del Pacífico norte.

  11. Comparison of drought-sensitive tree-ring records from the Tien Shan of Kyrgyzstan and Xinjiang (China during the last six centuries

    Directory of Open Access Journals (Sweden)

    Hui-Qin Wang

    2017-03-01

    Full Text Available In this study, tree-ring width data of Schrenk spruce (Picea schrenkiana from the upper timberline of the Tien Shan (Kyrgyzstan were analyzed to investigate the effect of climate change. Growth–climate response analyses revealed that the tree rings of spruce at the upper timberline of the Tien Shan also can provide hydrometeorological (precipitation and streamflow signals. Tree-ring records from both Kyrgyzstan and Xinjiang exhibited similar tree-growth variability at both annual and decadal time scales during the common period 1457–2009. In Xinjiang and Kyrgyzstan, tree growth was reduced during the Little Ice Age (LIA; however, the timing and magnitude of LIA differ between the two regions. During 1470–1660, the two chronologies diverged, and this phenomenon is considered to be caused by a different response to the harsh climate of the LIA. In this study, the tree-ring width series from the upper tree line of the Tien Shan is negatively associated with temperature. As opposed to previous studies, the tree-ring width series from the upper timberline of the Tien Shan appears to respond well to hydrometeorological factors. Therefore, we highlight the need for more detailed ecophysiological response studies for spruce trees at the upper timberline of the Tien Shan, in particular, with regard to the role of water availability and temperature during the growth season.

  12. Spatial-temporal structure of seismicity of the North Tien Shan and its changeunder effect of high energy electromagnetic pulses

    Directory of Open Access Journals (Sweden)

    N. V. Tarasova

    2004-06-01

    Full Text Available The effect of high-energy electromagnetic pulses emitted by a magnetohydrodynamic generator used as a source for deep electrical sounding of the crust on spatial-temporal structure of seismicity of the North Tien Shan is explored. Five-six years periodicity of changes in spatial distribution of seismicity was revealed. The effect of electromagnetic pulses increases the stability of the spatial distribution of seismicity over time and simultaneously speeds up cycles of its transformations, which develop on stabilization background. Increasing of seismic energy release after electromagnetic impacts is observed basically in most active zones. Periodic variation of efficiency of earthquakes triggering on the distance to the MHD-generator was detected. It was shown that electromagnetic pulses give rise to an appreciable increase in the rate of local earthquakes, occurring around 2-6 days after the pulses. Total earthquakes energy released after start-ups was by 2.03·1015 J greater than the energy released before them. At the same time, the total energy transmitted by the MHD-generator was 1.1·109 J, i.e. six orders of magnitude smaller. Consequently, the electromagnetic pulses initiated the release of the energy that had been stored in the crust due to activity of natural tectonic processes in the form of comparatively small earthquakes, which leads to an additional release of tectonic stresses.

  13. Seasonal drainage of supraglacial lakes on debris-covered glaciers in the Tien Shan Mountains, Central Asia

    Science.gov (United States)

    Narama, Chiyuki; Daiyrov, Mirlan; Tadono, Takeo; Yamamoto, Minako; Kääb, Andreas; Morita, Reira; Ukita, Jinro

    2017-06-01

    Using field surveys in 2013, 2014, and 2016 plus satellite data from the 1999-2015 period, we analyze the seasonal drainage cycle of supraglacial lakes on seven debris-covered glaciers in the central Tien Shan. We characterize this cycle by the number of lakes and their water levels. The cycle of the Southern Inylchek Glacier starts to increase in the beginning of April, reaches a maximum in May-June, and decreases sharply in June-July. The increase in April to June comes from an inflow of meltwater from snow and ice, and the subsequent decrease arises from a greater connectivity to the englacial drainage network. For the Southern Inylchek Glacier, 94% of the supraglacial lakes that exist and appear during 2013-2015 drain during all three years, indicating that most lakes could connect to the englacial drainage network for three years. Concerning the water level, lakes in close proximity and with the same base-level tend to synchronize their seasonal water levels through the englacial channels. Although the maximum water level of the three-year, field-measured lake is about the same from 2014 through 2016, the date of maximum water level varies between mid-May and mid-June. During this period, the lifetime and size of the supraglacial lakes are controlled by the timing of their connectivity to the englacial drainage network.

  14. Seasonal deuterium excess in a Tien Shan ice core: Influence of moisture transport and recycling in Central Asia

    Science.gov (United States)

    Kreutz, K.J.; Wake, C.P.; Aizen, V.B.; DeWayne, Cecil L.; Synal, H.-A.

    2003-01-01

    Stable water isotope (??18O, ??D) data from a high elevation (5100 masl) ice core recovered from the Tien Shan Mountains, Kyrgyzstan, display a seasonal cycle in deuterium excess (d = ??D - 8*??18O) related to changes in the regional hydrologic cycle during 1994-2000. While there is a strong correlation (r2 = 0.98) between ??18O and ??D in the ice core samples, the regression slope (6.9) and mean d value (23.0) are significantly different than the global meteoric water line values. The resulting time-series ice core d profile contains distinct winter maxima and summer minima, with a yearly d amplitude of ???15-20???. Local-scale processes that may affect d values preserved in the ice core are not consistent with the observed seasonal variability. Data from Central Asian monitoring sites in the Global Network of Isotopes in Precipitation (GNIP) have similar seasonal d changes. We suggest that regional-scale hydrological conditions, including seasonal changes in moisture source, transport, and recycling in the Caspian/Aral Sea region, are responsible for the observed spatial and temporal d variability.

  15. Source parameters of the major historical earthquakes in the Tien-Shan region from the late 19th to the early 20th century.

    Science.gov (United States)

    Kulikova, Galina; Krüger, Frank

    2016-04-01

    The Tien-Shan is one of the largest mountain belts in the world. Its deformation is dominated by intermontane basins bounded by active thrust and reverse faulting. The Tien-Shan mountain belt is characterized by a very high rate of seismicity along its margins as well as within the Tien-Shan interior. The study area of the here presented work, the western part of the Tien-Shan region, is currently seismically active with small and moderate sized earthquakes. However, at the end of 19th beginning of 20th century, this region was struck by a remarkable series of large magnitude (M>7) earthquakes, two of them reached magnitude 8. These large earthquakes occurred before the global digital seismic network was installed and therefore were recorded only by analog seismic instruments. The processing of the analog is complicated especially due to the digitization of the records - a very time-consuming and delicate part. Therefore a special set of techniques is developed and modern methods are adapted for the digitized instrumental data analysis. Here presented study evaluates the impact of large magnitude M>7.0 earthquakes, in the Tien-Shan region, on the overall regional tectonics. It also investigates the accuracy of previously estimated source parameters for those earthquakes, which were mainly based on macroseismic observations, and re-estimate them based on the instrumental data. Ten strongest and most interesting historical earthquakes in Tien-Shan region are analyzed with in presented work. With the developed techniques, the source parameters of these major earthquakes are determined and their impact on the regional tectonics was investigated. The large magnitudes of the earthquakes are confirmed by instrumental data. The focal mechanisms of these earthquakes were determined providing evidence for responsible faults or fault systems.

  16. Rotifers from Thuy Tien lake and Nhu Y river in central Vietnam, with a description of Ploesoma asiaticum new species (Rotifera: Monogononta

    Directory of Open Access Journals (Sweden)

    Mau Trinh Dang

    2013-08-01

    Full Text Available We surveyed Thuy Tien lake and Nhu Y river, Thua Thien Hue province, Vietnam, for rotifers from March to August 2010, and additionally in February 2012 in Thuy Tien lake. A total of 98 species-level taxa are identified, belonging to 31 genera and 21 families. Of there, 52 are first records for Vietnam, Filinia minuta (Smirnov, 1928 is new to the Oriental region and Ploesoma asiaticum n. sp. is new to science. These results increase the rotifer record for Vietnam from 122 to 174 taxa. In addition to describing the new taxon, we provide comparative illustrations including trophi scanning electron microscopy photographs of Ploesoma hudsoni (Imhof 1891.

  17. Tirant, Yvain i Lancelot, presoners d'amor : L'amor com a connector entre els herois de Chrétien de Troyes i Joanot Martorell

    OpenAIRE

    Crespo Naranjo, Eva

    2013-01-01

    Estudi de tipus comparatiu entre l'amor que experimenten els herois de Chrétien de Troyes i Tirant lo Blanc, i que ens porta a descobrir les hipertextualitats existents referents al tema amorós entre aquestes novel·les separades per 300 anys. Estudio de tipo comparativo entre el amor que experimentan los héroes de Chrétien de Troyes y Tirante el Blanco, y que nos lleva a descubrir las hipertextualidades existentes referentes al tema amoroso entre estas novelas separadas por 300 años. Ba...

  18. Un modelo de opciones barreras para estimar las probabilidades de fracasos financieros de empresas. Barrier options model for estimate firm´s probabilities for financial distress

    Directory of Open Access Journals (Sweden)

    Gastón S. Milanesi

    2016-11-01

    Full Text Available Resumen Asimilar el valor del patrimonio como una opción de compra sobre los activos permitió desarrollar un conjunto de modelos dinámicos para predecir fracasos financieros empresariales. No obstante, el concepto presenta una importante debilidad: la relación directa y positiva entre valor del capital (prima y el nivel de volatilidad del activo subyacente. El razonamiento anterior indica que a mayor riesgo de la firma mayor debe ser su valor, lo que conduce a una lógica inconsistente para estimar probabilidades de fracasos financieros. Las opciones denominadas “exóticas barreras” constituyen un modelo alternativo para predecir dificultades financieras y su estructura se ajusta mejor a la relación valor-volatilidad en las empresas. El trabajo propone un modelo de opción barrera “operativo”, ya que simplifica la estimación de las inobservables variables: valor y riesgo del activo. Primero, se desarrolló formalmente los modelos de opción de compra simple y opción barrera para valorar el patrimonio de la firma y la estimación de probabilidades de fracaso financiero. Con un caso hipotético, se propuso un ejercicio de sensibilidad sobre volatilidades y plazos. Similar ejercicio se aplicó a dos firmas de capitales argentinos con diferentes grados de endeudamiento, gracias al cual se confirmó la consistencia entre volatilidad-valor-probabilidad de fracasos financieros del modelo propuesto. Finalmente se exponen las principales conclusiones.     Abstract Assimilation of the capital value as a call option over firm’s assets allows to develop a group of dynamic models to predict corporate financial distress. However, the concept shows an important weakness: the direct and positive relationship between the capital value (call with the level of underlying’s volatility. This reasoning indicates that the higher the risk is, the higher the value must be for the firm, leading to a weak rationality, in particular to estimate

  19. How much water will glaciers in the Chon Kemin valley (Tien Shan mountains, Kyrgyzstan) provide in the future?

    Science.gov (United States)

    Sorg, Annina; Huss, Matthias; Stoffel, Markus

    2013-04-01

    Climate-driven changes in glacier-fed streamflow regimes have direct implications on freshwater supply, irrigation and hydropower potential. Reliable information on current and future glaciation and runoff is thus crucial for water allocation. In summer-dry regions like Central Asia, glaciers play an important role in streamflow regimes, as meltwater from glaciers is released when other sources such as snowmelt are depleted. This situation is well reflected by the Chon Kemin River, an important tributary to the Chu River providing Kyrgyzstan's capital Bishkek with freshwater. Today, glaciers cover around 8% of the Chon Kemin valley (118 of 1'438 km2) and 30% of the headwater catchment (49 of 165 km2), but these glaciers in the low-altitude northern periphery of the Tien Shan mountains are melting particularly fast. Glacier shrinkage has considerable impacts on the seasonal and overall availability of water: In a first instance, shrinking glaciers supply ample quantities of water in the form of increased glacial runoff, but reduced glacier volume will ultimately result in a decrease in both glacier-fed and total runoff, if no other sources can offset reduced glacier melt. Although crucial for efficient water planning, it is largely unknown if the Tien Shan rivers have already passed this tipping point ("peak water"), or, if not yet, when this will happen. In our study, we assess past and future runoff changes in the Chon Kemin River to elucidate the timing of "peak water" and to quantify water availability in coming summers, when precipitation is expected to be even more scarce than today. Meteorological and hydrological data suggest that total runoff has increased in the past decades, particularly during summer and fall, probably as a result of increasing glacial meltwater. Annual fluctuations in precipitation and runoff have shown an asynchronous behavior in a first phase (1936 until early 1960s), but have then changed to a synchronous pattern (early 1960s until

  20. Regional based modeling approach for rainfall-induced debris flows in the continental-climatic Northern Tien Shan (SE Kazakhstan)

    Science.gov (United States)

    Fischer, Thomas; Küfmann, Carola; Haas, Florian; Baume, Otfried; Becht, Michael

    2013-04-01

    The high mountain systems of Central Asia (Hindukush, Pamir and Tien Shan) are dominated by continental-climatic conditions. Nevertheless, westerly maritime air circulation and convective rainfalls during the summer season result in high rainfall intensities. In combination with a high availability of unconsolidated material rainfall triggered debris flows are prominent and intensive geomorphologic processes in these mountain areas. The presented study aims to figure out a regional based modeling approach for rainfall-induced debris flow processes based on combination of a disposition model for debris flow starting zones with process-flow models. The investigation area has a size of about 700 square kilometers and is situated in the Northern Tien Shan mountains in SE Kazakhstan (investigation areas: valleys of Prochadnaja, Big Almatinka, Little Almatinka and Left Talgar). The area is characterized by mountain forest zone, alpine meadows and high-alpine glaciated areas with the highest peaks at 4500m. In a first step the disposition (point of process triggering) of actual debris flows was analyzed. Due to different triggering mechanisms, the processes were divided into channel-type and slope-type debris flows. Detailed mapping of actual debris flows initiation areas and a GIS-based geostatistical disposition analysis are used to identify the main geofactor-variables and geofactor combinations which enhance the triggering of rainfall-induced debris flows. It can be shown that both, longtime variable geofactors (such as local geomorphology and hydrology) plays a significant role for triggering debris flows, as well as mid- and short time variable geofactors. Especially actual permafrost distribution and degradation plus glacier retreat comes into the focus of interest. This is most notably for rainfall induced slope-type debris flows which primarily are triggered in the discontinuous and continuous permafrost areas eroding younger unconsolidated material from actual

  1. Late Devonian palaeomagnetism of the North Tien Shan, Kyrgyzstan: can secular variation vary on a short timescale?

    Science.gov (United States)

    Bazhenov, Mikhail L.; Van der Voo, Rob; Levashova, Natalia M.; Dominguez, Ada R.

    2013-05-01

    We studied more than 80 lava flows from a ˜600-m-thick pile of Upper Devonian (Frasnian) basalts and andesites of the Aral Formation in the North Tien Shan (Kyrgyzstan, Central Asia). With the aid of stepwise thermal demagnetization, a high-temperature, dual-polarity component was reliably isolated from most flows. The primary origin of the high-temperature component is demonstrated by positive reversal, conglomerate and fold tests. The most prominent and intriguing feature of this Late Devonian data set involves a clear distinction in angular dispersion between the lower and upper parts of the studied section. A rather low concentration parameter (k = 13) and several directional anomalies characterize the lower section; in contrast, a much better grouping (k = 46) and a lack of directional outliers is observed for the dual-polarity vectors from the upper flow sequence of the formation. We analysed different mechanisms to account for this directional pattern and found that it is possible in just two ways. One is to assume that secular variation (SV) in the upper sequence is strongly underrepresented, and it is a coincidence that the mean directions of both polarities are statistically antipodal, and the corresponding concentration parameters are statistically equal. The other explanation is to hypothesize that the magnitude of SV can vary several-fold at the same palaeolatitude and over time intervals estimated as 105-106 yr. This is in sharp contrast with other models of SV, where this magnitude has been assumed to be rather time-independent (for a given latitude). Our hypothesis accounts for the observed irregularities in palaeomagnetic data, but makes attempts to establish a correlation between SV and other parameters (geographic latitude, reversal frequency, age, etc.) more difficult. We are aware, however, that more data are needed to refute or confirm it.

  2. A twentieth century major soluble ion record of dust and anthropogenic pollutants from Inilchek Glacier, Tien Shan

    Science.gov (United States)

    Grigholm, B.; Mayewski, P. A.; Aizen, V.; Kreutz, K.; Aizen, E.; Kang, S.; Maasch, K. A.; Sneed, S. B.

    2017-02-01

    Using a high-resolution ( 18 samples/year) major soluble ion record (Na+, K+, Mg2+, Ca2+, Cl-, NO3-, and SO42-) covering the period 1908-1995 A.D. from the Inilchek Glacier, Tien Shan, Kyrgyzstan, we provide a detailed climate and environmental proxy record for the region. Chemical concentrations, empirical orthogonal function analyses, and noncrustal excess calculations are used to identify natural and potential anthropogenic depositional trends. Dominant dust proxy species (i.e., Ca2+) reveal highest concentrations during the 1950s-1970s, with declining decadal trends through the end of the record. These trends likely reflect decreases in central Asian dust storm activity post-1950, which has been associated with coupled atmospheric circulation variability and anthropogenic activities. Comparison between Ca2+ and ERA-Interim (1979-1995) climate reanalysis data indicates a strong relationship to spring (March-May) geopotential height patterns in northwest China and southern Siberia associated with the Siberian High. Noncrustal contribution (excess) estimates of NO3-, K+, SO42-, and Cl- concentrations suggest discernable anthropogenic inputs began between the 1950s and 1970s, increased into the middle/late 1980s, and declined in the 1990s. Excess trends coincide with Former Soviet Union consumption, production, and emission of fossil fuels and fertilizers, reflecting the rapid growth of agriculture and industry, as well as economic declines in the middle to late 1980s/early 1990s. Excess-Cl- trends reflect timings that coincide with the construction of the Pavlodar Chemical Plant and the military production of Cl2 in Kazakhstan. NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory back trajectory frequency analysis suggests eastern Uzbekistan (e.g., Fergana Valley), Kyrgyzstan, and southern Kazakhstan as the primary pollutant sources to the study region.

  3. The Hunt for Surface Rupture From the 1889 Ms 8.3 Chilik Earthquake, Northern Tien Shan, Kyrgyzstan and Kazakhstan

    Science.gov (United States)

    Crosby, C. J.; Arrowsmith, J. R.; Korjenkov, A. M.; Guralnik, B.; Mamyrov, E.; Povolotskaya, I. E.

    2007-12-01

    The 1889 Ms 8.3 Chilik earthquake in the Northern Tien Shan Mountains of Kyrgyzstan and Kazakhstan is one of the largest historic intraplate reverse-faulting events. Documentation of slip distribution and fault geometry for major historic earthquakes, such as the Chilik event, provide important data on their source physics, seismotectonics, and hazard. These data also provide insight into potential mechanical interaction with other large regional earthquakes, notably the 1887 Ms 7.3 Verny and 1911 Ms 8.2 Kebin (Chon Kemin) events. Despite the importance of the Chilik event, very little is known about the earthquake's epicenter and the presence of associated ground rupture. Isoseismal's from historic shaking intensity data gathered immediately following the event were used to estimate the event magnitude and suggest an epicentral location in the northern foothills of the Kungey Ala-too range, 80-100 kilometers east-southeast of Almaty. Researchers who have visited this area report no evidence of ground rupture, suggesting that the event either did not rupture the ground surface or that the isoseismal data do not provide a sufficiently focused estimate of epicentral location. We have reanalyzed the shaking intensity data to update the estimate of the epicentral location. During June 2007 field work and in review of aerial photography, we observed extensive east-west trending and morphologically youthful km-long and 1-5 m high fault scarps on the eastern crest of the Kungey Ala-Too Range along the Kygyz-Kazak border north of Tyup. Contemporary reports of the 1911 Kebin earthquake did not document these structures, despite the thorough investigation of rupture to the west and northwest. The scarp lengths and their offsets indicate that they did not form in the M6.6 1978 Djalanash Tyup earthquake. Although located to the south of the isoseismal epicenter for the Chilik earthquake, the scarps observed near the range crest must be considered as possible candidates for

  4. Identification and monitoring of potentially dangerous glacial lakes in northern Tien Shan (Kazakhstan/Kyrgyzstan) using geoinformation techniques

    Science.gov (United States)

    Bolch, Tobias; Pradhan, Biswajeet; Peters, Juliane; Buchroithner, Manfred

    2010-05-01

    Like in many other parts of the world, the glaciers in northern Tien Shan are receding and the permafrost is thawing and concomitant glacial lakes are developing. Outbursts of these glacial lakes pose severe hazards for the society. Over the last decade, several outbursts in this seismically active region are documented. Multi-temporal space imageries are an ideal means to study and monitor glaciers and glacial lakes over larger areas. Morphometric analyses and modelling approaches allow the estimation of the potential danger of glacial lake outburst floods (GLOFs). In this paper, we present a comprehensive approach to identify glaciers and the potentially dangerous glacial lakes based on multi-temporal space imagery from 1972 (Corona KH-4B), 1973 (Landsat MSS), 1991 (Landsat TM), 1999 (Landsat ETM+), 2000/2001/ (ASTER) 2005, and 2008 (Landsat TM) as well as morphometric analysis and modelling. The identification and monitoring of glacial lakes were carried out automatically using image ratioing and the Normalized Difference Water Index (except for the panchromatic Corona images). The results were evaluated and, if necessary, manually edited. The probability of the growth of a glacial lake was estimated by analysing glacier changes, glacier motion, and slope analysis. A permafrost model based on morphometric parameters, solar radiation and regionalised temperature conditions aided us to asses the effect of probable permafrost thawing. A GIS-based model was applied in order to simulate the possible downstream impact of a lake outburst. The findings of our studies indicate a continuous glacier recession with an increasing number and area of glacial lakes. This possibly leads into a higher risk of a glacial lake outburst. Finally, the lakes are classified according to their outburst probability and their downstream impact.

  5. Si/SiGe MMIC's

    Science.gov (United States)

    Luy, Johann-Friedrich; Strohm, Karl M.; Sasse, Hans-Eckard; Schueppen, Andreas; Buechler, Josef; Wollitzer, Michael; Gruhle, Andreas; Schaeffler, Friedrich; Guettich, Ulrich; Klaassen, Andreas

    1995-04-01

    Silicon-based millimeter-wave integrated circuits (SIMMWIC's) can provide new solutions for near range sensor and communication applications in the frequency range above 50 GHz. This paper gives a survey on the state-of-the-art performance of this technology and on first applications. The key devices are IMPATT diodes for mm-wave power generation and detection in the self-oscillating mixer mode, p-i-n diodes for use in switches and phase shifters, and Schottky diodes in detector and mixer circuits. The silicon/silicon germanium heterobipolar transistor (SiGe HBT) with f(sub max) values of more than 90 GHz is now used for low-noise oscillators at Ka-band frequencies. First system applications are discussed.

  6. Los orígenes del grial en la literatura medieval: de Chrétien de Troyes a Robert de Boron

    Directory of Open Access Journals (Sweden)

    Mario Martín Botero

    2010-12-01

    Full Text Available Este artículo muestra el origen literario del tema del Grial en la literatura medieval francesa, abordando dos textos esenciales para el surgimiento y consolidación de la “literatura del Grial”: Le Conte du Graal de Chrétien de Troyes y Le Roman de l’Estoire dou Graal de Robert de Boron. Los autores de estas obras establecen las bases para el desarrollo de toda una temática que gira alrededor del Grial a partir del siglo XII hasta nuestros días. El artículo muestra cómo de un objeto apenas sagrado en el texto de Chrétien de Troyes se pasa a una reliquia de la sangre de Cristo en la versión de Robert de Boron.This paper studies the literary origin of the Grail legend in medieval French literature, taking into account two important romances: Le Conte du Graal by Chrétien de Troyes and Le Roman de l’Estoire dou Graal by Robert de Boron. In these two texts the authors established the basis for the development of a new subject matter around the mysterious object called “Grail” from the Middle Ages to the present times. It will also be shown how an object, not totally sacred in Chrétien de Troyes, becomes a relic related with Jesus’s blood in Robert de Boron.

  7. Marketing olfativo : ¿qué olor tienes en mente? = Olfactive marketing : what smell have you in mind?

    OpenAIRE

    2013-01-01

    El marketing olfativo se basa en una ciencia moderna, derivada del marketing sensorial y del neuromarketing, que utiliza aromas específicos con el fin de influir en los comportamientos del consumidor y aumentar los beneficios empresariales. Así mismo se emplea en entornos laborales para incrementar la productividad y el rendimiento de los empleados. Si en países como Estados Unidos, Canadá o Japón es una técnica muy empleada, en España se encuentra aún en una fase inicial, por lo que se trata...

  8. 与Si工艺兼容的Si/SiGe/Si HBT研究%The Study of Si/SiGe/Si HBT and Its Compatibility with Si Process

    Institute of Scientific and Technical Information of China (English)

    廖小平

    2001-01-01

    我们对Si/SiGe/Si HBT及其Si兼容工艺进行了研究,在研究了一些关键的单项工艺的基础上,提出了五个高速Si/SiGe/Si HBT结构和一个低噪声Si/SiGe/Si HBT结构,并已研制成功台面结构Si/SiGe/Si HBT和低噪声Si/SiGe/Si HBT,为进一步高指标的Si/SiGe/Si HBT的研究建立了基础.

  9. The 1911 Chon-Kemin (M 8.3) earthquake in the Tien-Shan region*: preliminary investigation results by means of historical data.

    Science.gov (United States)

    Kulikova, G.; Krüger, F.

    2012-04-01

    For many years the Tien-Shan region* attracts attention of geophysicists and geologists due to complexity and uniqueness of its tectonics. At the turn of the XIX. to the XX. century several destructive earthquakes have occurred in the region with estimated magnitudes between 7 and 8 and two of them even exceeding the magnitude of 8. Our main goal is to investigate the deformation processes responsible for this significant earthquake sequence and the possible interrelation between the single events. Here we present preliminary results of the Chon-Kemin earthquake as an example. On 3rd January 1911 the M 8.3 Chon-Kemin earthquake hit the Tien-Shan region. It is the strongest event in the history of Tien-Shan region for which instrumental recordings are available and one of the strongest intracontinental earthquakes in XX. century. Historical analog data were collected from different seismic archives in European and non-European countries. The data from 20 seismic station were collected, mostly stations at that time had only horizontal components although there are some vertical recordings as well. Preprocessing the analog data brings several difficulties, e.g. limited information on instrument characteristics. Digitization is the most time-consuming part among preprocessing. The quality of seismograms is not always good enough this is why it was necessary to combine different methods of data processing. Since at that time localizations have been done on the base of intensity distributions, the epicenter is poorly determined. Several localizations, differed in the value of up to 80 km, are available. The surface rupture was also estimated in previous studies (about 200 km) and the deformation on the surface can be still observed nowadays, which gives opportunity to calibrate new localization comparing it to the geological data. Thus, we located the earthquake epicenter and determined the magnitude again based on the digitized seismograms. From first motion body wave

  10. Jeux et enjeux d’écriture chez Chrétien de Troyes: l’exemple de «Cligès»

    Directory of Open Access Journals (Sweden)

    Ida Lucia Machado

    2011-10-01

    Full Text Available Neste artigo, nos propomos descrever a estética da trama irônica presente na escritura de Chrétien de Troyes, tomando por base seu romance Cligès. A destacar algumas estratégias passíveis de criar o fenômeno irônico, estaremos também mostrando o poder de sedução que emana desta escritura.Nous nous proposons, dans cet artible, de décrire l’esthétique du jeu ironique chez Chrétien de Troyes, em puisant dans son roman Cligès. Enn dégageant qulques unes dês stratégies susceptibles de créer le phénomène ironique, nous montrerons, à la fois, le pouvoir de séduction qui emane de cette écriture.

  11. Determinants of Biogas Adoption in Manure Management of Vietnamese Household Pig Production : A Case Study in Tien Lu District, Hung Yen Province

    OpenAIRE

    Ly, Nguyen Thi; Nanseki, Teruaki; Chomei, Yosuke

    2015-01-01

    Although biogas technology is one of the useful ways managing the animal manure to reduce environmental problems in rural area, many Vietnamese households that produce pigs still do not apply biogas digesters. This study aim to investigate the main factors contributing to biogas adoption in household pig production based on primary data collected in Tien Lu district, Hung Yen province in Vietnam and the use of Logit regression. The empirical results highlighted that socioeconomic characterist...

  12. Images du mal ou images maléfiques? Les images populaires du Diable chez les chrétiens du Ghana

    NARCIS (Netherlands)

    Meyer, B.

    2008-01-01

    Cet article, qui se concentre sur les images du mal, explore l’écart entre les modes de vision induits d’une part par l’exposition « All About Evil » au Royal Tropical Museum d’Amsterdam, et d’autre part par le cadre chrétien dans lequel apparaissent d’ordinaire les objets ainsi exposés. Tandis que

  13. Interface structure between epitaxial NiSi2 and Si

    Institute of Scientific and Technical Information of China (English)

    Wei-Long Liu; Wen-Jauh Chen; Ting-Kan Tsai; Hsun-Heng Tsai; Shu-Huei Hsieh

    2006-01-01

    The interface structure between the Si and NiSi2 epitaxially grown on the ((-1)12) Si substrate was studied using high resolution transmission electron microscopy and computer image simulation. The results showed that the interface between Si and NiSi2 epitaxially grown on the ((-1)12) Si substrate has six different types: type A NiSi2 ((-1)11 )/( (-1)11 ) Si, type A NiSi2 (001)/(001) Si, type B NiSi2 (1(-1)(-1))/(1(-1)1) Si, type B NiSi2 ((-1)12)/(1(-1)2) Si, type B NiSi2 (2(-2)1)/(001) Si, and type B NiSi2 (1(-1)(4))/( 1(-1)0 ) Si. And there are one or more different atomic structures for one type of interface.

  14. 射频 Si/SiGe/Si HBT的研究%Studies on RF Si/SiGe/Si HBT

    Institute of Scientific and Technical Information of China (English)

    廖小平; 殷刚毅

    2003-01-01

    Si/SiGe/Si HBT与Si工艺兼容的研究基础上,对射频Si/SiGe/Si HBT的射频特性和制备工艺进行了研究,分析了与器件结构有关的关键参数寄生电容和寄生电阻与Si/SiGe/Si HBT的特征频率fT和最高振荡频率fmax的关系,成功地制备了fT为2.5 GHz、fmax为2.3 GHz的射频Si/SiGe/Si HBT,为具有更好的射频性能的Si/SiGe/Si HBT的研究建立了基础.

  15. Ideal climatic variables for the present-day geometry of the Gregoriev Glacier, Inner Tien Shan, Kyrgyzstan, derived from GPS data and energy-mass balance measurements

    Directory of Open Access Journals (Sweden)

    K. Fujita

    2011-03-01

    Full Text Available We conducted 2 yr (2005–2007 of in situ meteorological and glaciological observations on the Gregoriev Glacier, a flat-top glacier within the Inner Tien Shan, Kyrgyzstan. Differential GPS surveys reveal a vertical surface deletion at the summit of the glacier. Based on snow density data and an energy-mass balance model, we estimate that the annual precipitation and summer mean temperature required to maintain the glacier in the modern state are 289 mm and −3.85 °C at the glacier summit (4600 m above sea level, a.s.l., respectively. The good agreement between the long-term estimated and observed precipitation at a nearby station in the Tien Shan (292 mm at 3614 m a.s.l. for the period 1930–2002 suggests that the glacier dynamics have been regulated by the long-term average accumulation. The glacier mass-balance, reconstructed based on meteorological data from the Tien Shan station for the past 80 yr, explains the observed fluctuations in glacier extent, particularly the negative mass balance in the 1990s.

  16. ¿Tanta importancia tiene pasar por alto la arteria umbilical única?: Comentarios a partir de una sentencia judicial

    Directory of Open Access Journals (Sweden)

    A. Ortega Pérez

    2004-07-01

    Full Text Available El Tribunal Supremo ha condenado a varios obstetras por informar que el cordón umbilical tenía los tres vasos, desactivando así la búsqueda de enfermedades fetales que la arteria umbilical única (AUU habría desencadenado. La condena será éticamente correcta si la AUU está realmente asociada a tales enfermedades. En la población general se detecta un caso de AUU en cada 320 fetos estudiados ecográficamente. En el 68 % de esas detecciones se tratará de un hallazgo aislado, pero aún así aumenta el riesgo de parto prematuro, de peso bajo y de mortalidad perinatal. Por otra parte, el 17 % de estos fetos tendrán, además de la arteria única, cromosomopatías y el 31 % malformaciones anatómicas. Concluyendo, la AUU es realmente un marcador cardinal de riesgo de trastornos fetales, que debe buscarse activamente durante el seguimiento ecográfico del embarazo.

  17. Estatinas, una nueva opcion terapéutica en diversos tipos de enfermedades Statines, a new therapeutical option for many diseases

    Directory of Open Access Journals (Sweden)

    Loipa Galán Martínez

    2009-12-01

    Full Text Available Las estatinas al inhibir la enzima 3-hidroxi-3-metilglutaril-coenzima A reductasa, reducen la producción de colesterol y además, previenen la formación de compuestos isoprenoides no esteroidales, que actúan como acoplamientos lipídicos para la modificación postraslacional de varias proteínas, involucradas en diferentes procesos celulares. El bloqueo del proceso de isoprenilación dado por el tratamiento con estatinas también tiene efectos biológicos sobre funciones celulares que van más allá de la disminución en la síntesis de colesterol: estos son los llamados efectos pleiotrópicos que se relacionan principlamente con la función vascular, incluyendo la mejora de la hipertrofia y la insuficiencia cardíaca congestiva y la hipertrofia vascular, tienen propiedades antiinflamatorias, inhiben la proliferación de células cancerígenas, son inmunomoduladores, mejoran la disfunción endotelial y reducen los daños de la isquemia-reperfusión. Esta revisión describe los efectos pleiotrópicos de las estatinas y los mecanismos moleculares a través de los cuales ejercen diferentes funciones biológicas.Statins inhibiting the enzyme 3-hydroxy-3-methylglutaril- coenzyme A reductase decrease the cholesterol production and besides, to prevent the non-steroidal isoprenoids compounds acting like lipid couplings for post-translation modification of some proteins involved in different cellular processes. The isoprenilation process blockade given by statins treatment hass too biological effects on cellular functions beyond the decrease in cholesterol synthesis: these are the so called pleiotropic effects mainly related to vascular function, including an improvement of hypertrophy and its congestive cardiac insufficiency and vascular hypertrophy and have anti-inflammatory properties, inhibiting the cancerous cells proliferation, immunomodulation, improving the endothelial dysfunction and reducing the ischemia-reperfusion damages. This review

  18. Efecto del dopado con Si sobre la estructura de defectos en sistemas heteroepitaxiales GaN/AlN/Si(111

    Directory of Open Access Journals (Sweden)

    Sánchez, A. M.

    2000-08-01

    Full Text Available The Si doping effect on the defect structure in GaN epilayers grown by molecular beam epitaxy on Si(111 substrates using AlN buffer layers has been studied. Transmission electron microscopy and related techniques have been used to carry out the structural characterization. The Si doping affects both the subgrain size and misorientation in GaN epilayer mosaic structure. The Si doping also leads to an increase of the planar defect density, as well as a decrease of the threading dislocation density. The enlargement of the subgrain tilt and the planar defect density explain the reduction of the dislocation density reaching the GaN free surface.

    En el presente artículo se lleva a cabo el análisis del efecto que el dopado con Si tiene sobre la estructura de defectos en epicapas de GaN crecidas por epitaxia de haces moleculares sobre sustratos de Si (111 utilizando capas amortiguadoras de AlN. La caracterización estructural se llevó a cabo mediante microscopía electrónica de transmisión convencional y de alta resolución. El dopado con Si afecta a la desorientación y tamaño de los subgranos que constituyen la estructura mosaico de la epicapa de GaN. El dopado con Si provoca un aumento en la densidad de defectos planares, así como una disminución en la densidad de dislocaciones de propagación. El incremento en el grado de desorientación de inclinación, así como en la densidad de defectos planares que se produce conforme aumenta el dopado con Si explican la disminución en la densidad de dislocaciones que alcanzan la superficie libre de GaN.

  19. 先秦儒家天论思想的兴起、内容与理论功能%Rise,Content and Theoretical Function of Pre-Qin Tien Theory

    Institute of Scientific and Technical Information of China (English)

    朱璐

    2011-01-01

    With the decline of the Zhou empire,Confucian Tien theory began to rise.Kinds of mood,such as suspect,complain towards Tien became popular among the public.Mencius amended the Tien theory metaphysically,he demonstrated the ultimate good of Tien from the perspective of moral subjectivity,connected the Tien with human beings,proposed the idea of Tien Nobility;Master Xun indicated the naturally producing function of Tien and believed that movement of Tien has its own constant regularity.Tien does not decide and control the human affairs.While in the mean time,Tien endows the human being with basic instinct,like love,anger,hates and happiness,therefore we need rites,institutions,moral education to normalize ourselves.%周王权衰弱之后,民间疑天、怨天、问天思潮相继发生,儒家论天思潮由此兴起.孟子对"天"进行了形而上的改造,贯通"天"与"人性",提出了"天爵"理念,认为"天"赋予人"仁义忠信"四爵,从而论证了"天"作为"至善"的道德本体意义;荀子指出"天"生养万物的自然功能,认为"天行有常",并不干预主宰人事,但天赋人喜怒爱恶的本性,需要礼仪制度、伦理教化来规范人事。

  20. Privacy and Yin Si

    Institute of Scientific and Technical Information of China (English)

    胡迪

    2007-01-01

    <正>“Privacy” is translated as yin si in Chinese.Traditionally,in the Chinese mind,yin si is associated with something that is closed or unfair.If someone is said to have yin si,meddlers(好事者) will be attracted to pry(打探) into his or her affairs.So people always state that they don’t have yin si.

  1. Electroluminescence of Si Nanocrystal-Doped SiO2

    Institute of Scientific and Technical Information of China (English)

    CHEN Dan; XIE Zhi-Qiang; WU Qian; ZHAO You-Yuan; LU Ming

    2007-01-01

    @@ We perform a comparative study on the electroluminescence (EL) and photoluminescence (PL) of Si nanocrystaldoped SiO2 (nc-Si:SiO2) and SiO2, and clarify whether the contribution from Si nanocrystals in the EL of nc-Si:SiO2 truly exists. The results unambiguously indicate the presence of EL of Si nanocrystals. The difference of peak positions between the EL and PL spectra are discussed. It is found that the normal method of passivation to enhance the PL of Si nanocrystals is not equally effective for the EL, hence new methods need to be explored to promote the EL of Si nanocrystals.

  2. Spatial variability of recent glacier area changes in the Tien Shan Mountains, Central Asia, using Corona (~ 1970), Landsat (~ 2000), and ALOS (~ 2007) satellite data

    Science.gov (United States)

    Narama, Chiyuki; Kääb, Andreas; Duishonakunov, Murataly; Abdrakhmatov, Kanatbek

    2010-03-01

    Geographic variability of the recent changes of glacier coverage in the Tien Shan Mountains, Central Asia, is assessed using Corona KH-4B satellite photographs for 1968-1971, Landsat 7 ETM+data for 1999-2002, and ALOS/PRISM and AVNIR data for 2006-2008. The four mountain regions investigated (Pskem, Ili-Kungöy, At-Bashy, and SE-Fergana) cover several distributed glacierized areas in the Tien Shan Mountain system, a region that is affected by highly variable local precipitation regimes. Over the 30 years investigated between ~ 1970 and ~ 2000, glacier area decreased by 19% in the Pskem region, 12% in the Ili-Kungöy region, 12% in the At-Bashy region, and 9% in the SE-Fergana region. In the last 7 years (~ 2000 to ~ 2007), glacier area shrank by 5% in the Pskem region, 4% in the Ili-Kungöy region, 4% in the At-Bashy region, and 0% in the SE-Fergana region. Glacier behavior has varied markedly in these regions. The most dramatic glacier shrinkage has occurred in the outer ranges of the Tien Shan Mountains. Recent glacier area loss has resulted from rising summer temperatures. Regional differences of glacier-area changes related to local climate conditions, to the altitudinal distribution of glacier areas, and to the relative proportion of glaciers in different size classes. The observed accelerated glacier shrinkage is expected to have two impacts on the more populated outer ranges: 1) water shortages during summer and 2) increased threat from glacier hazards such as glacier lake outburst floods (GLOFs) and ice avalanches.

  3. VALUACIÓN DE OPCIONES EUROPEAS SOBRE AMX-L, WALMEX-V Y GMEXICO-B. Calibración de parámetros de volatilidad estocástica con funciones cuadráticas de pérdida

    Directory of Open Access Journals (Sweden)

    Ambrosio Ortiz-Ramírez

    2014-01-01

    Full Text Available Esta investigación propone una metodología para estimar los parámetros del modelo de volatilidad estocástica de Heston (1993 por medio de funciones cuadráticas de pérdida, las cuales minimizan el error entre precios de mercado y precios teóricos. Para ello se plantean tres clases de funciones de pérdida, de las cuales dos están asociadas a precios y otra a volatilidades implícitas. La metodología propuesta se aplica a un conjunto de precios de opciones sobre AMX-L, WALMEX-V y GMEXICO-B. Los resultados indican que para opciones de compra sobre AMX-L se generan volatilidades implícitas consistentes con las observadas con base en el criterio de la raíz de la pérdida del error cuadrático medio, mientras que para opciones de compra sobre WALMEX-V y GMEXICO-B se generan volatilidades implícitas consistentes con las observadas con base en el criterio de la raíz de la pérdida relativa del error cuadrático medio.

  4. Los enigmas del Grial. En torno a la polémica sobre la unidad de El Cuento del Grial de Chrétien de Troyes

    Directory of Open Access Journals (Sweden)

    Victoria Cirlot

    2014-12-01

    Full Text Available Relectura de la polémica acerca de la unidad del último roman de Chrétien de Troyes, Li Contes del Graal que tuvo lugar a finales de los años cincuenta entre Martín de Riquer, Jean Frappier y Erich Köhler. Más de cincuenta años después se trata de valorar las aportaciones que dicha polémica supuso para la filología románica y, en concreto, para la valoración de la última obra del escritor de la Champaña.

  5. Search of primary cosmic rays sources at 5x10**13 - 5x10**14 eV with Tien Shan CHRONOTRON - KLARA array

    CERN Document Server

    Gudkova, E N

    2015-01-01

    The primary cosmic ray sources are searched by means of CHRONOTRON - KLARA separate array of the P.N. Lebedev Physical Institute Tien Shan station. It was done on the base of 35 millions observed PCR extensive air showers from 5x10**13 to 5x10**14 eV energies. The data analysis was carried on the method of the direct selection of local areas in equatorial coordinates where the deviation of event numbers exceeded the definite value from normal Gaussian standard. These directions are compared with other arrays observed results and with coordinates of astrophysical sources.

  6. ¿La recepción de remesas tiene efectos sobre la inclusión financiera en México?

    OpenAIRE

    Juan José Li Ng; Juan Carlos Sánchez Salinas; Consuelo del Carmen Hoyo Martínez; Telésforo Ramírez García

    2015-01-01

    Los resultados indican que la recepción de remesas tiene efectos en aumentar la inclusión financiera de las personas receptoras sólo en variables que están altamente relacionadas al acto y causas de recibir remesas (uso de sucursales bancarias y apertura de cuenta de ahorro para administrar este recurso). El efecto negativo en la probabilidad de contar con algún seguro o de usar cajeros automáticos, pese a que en las estimaciones se usaron variables de control, indican que pueden ser personas...

  7. The Dzhungarian fault: Late Quaternary tectonics and slip rate of a major right-lateral strike-slip fault in the northern Tien Shan region

    OpenAIRE

    Campbell, G. E.; Walker, R T; Abdrakhmatov, K.; Schwenninger, J.L.; Jackson, J.; Elliott, J R; Copley, A

    2013-01-01

    This is the final version of the article, originally published in the Journal of Geophysical Research: Solid Earth. It is also available from Wiley at http://onlinelibrary.wiley.com/doi/10.1002/jgrb.50367/abstract. © 2013. American Geophysical Union The Dzhungarian strike-slip fault of Central Asia is one of a series of long, NW-SE right-lateral strike-slip faults that are characteristic of the northern Tien Shan region and extends over 300 km from the high mountains into the Kazakh Pl...

  8. Le statut linguistique des pronoms du créole haïtien et du français : une étude de corpus1

    Directory of Open Access Journals (Sweden)

    Barriere Isabelle

    2016-01-01

    Full Text Available Le statut syntaxique et phonologique des pronoms en créole haïtien et en français a fait l’objet de débats. Les analyses linguistiques classiques du français formulées dans la tradition générative ont proposé une distinction entre les pronoms forts et les pronoms faibles ou ‘clitiques’. Tandis que les pronoms forts se comportent comme des syntagmes nominaux (SN, les clitiques diffèrent de ceux-ci de par leur distribution syntaxique. Ces premières analyses se fondent sur des jugements de grammaticalité et certaines de ces analyses ont été remises en question lorsque des corpus de parole spontanée ont été mis a la disposition des chercheurs et ont permis des analyses quantitatives et phonologiques. La présente étude comparative a pour objectif l’analyse des pronoms personnels du français et du créole haïtien et se fondent sur l’analyse de corpus CHILDES (Demuth & Tremblay, 2008; MacWhinney, 2000 pour le français et un nouveau corpus que nous avons enregistré et transcrit pour le créole haïtien. Les analyses portent sur la distribution syntaxique des pronoms sujets et objets et sur leurs réductions phonologiques. Ces deux sources d’information nous permettent de conclure aux statuts contrastifs des pronoms en créole haïtien qui arborent toutes les caractéristiques des pronoms forts en ce qui concerne leur distribution syntaxique tandis qu’au niveau phonologique ils peuvent être réduits et se comportent donc comme des clitiques phonologiques. En revanche le français comprend des pronoms forts et des pronoms faibles/clitiques qui se distinguent de part leurs trait phonologiques et leur distribution syntaxique.

  9. Si/SiO2和Si/SiNx/SiO2超晶格的能带结构%Band structure of Si/SiO2 and Si/SiNx/SiO2 superlattices

    Institute of Scientific and Technical Information of China (English)

    魏屹; 董成军; 徐明

    2010-01-01

    利用Kronig-Penney模型从理论上计算了Si/SiO2和Si/Si/SiNx/SiO2多层膜结构中量子阱的能带结构,进一步分析了各亚层薄膜厚度对能带结构和有效质量的影响.结果发现,适当减少亚层的厚度都能使得纳米Si薄膜的带隙发生明显宽化.在Si/SiO2超晶格中,Si量子阱层带隙能量随着Si层厚度的变化符合EPLL(eV)=1.6+0.7/d2关系,与我们的计算结果十分吻合.在Si/SiNdSiO2超晶格系统中,可以通过控制各亚层厚度,尤其是Si和SiNx层厚度,均能够有效地控制发光.

  10. Paleo-Climate and Glaciological Reconstruction in Central Asia through the Collection and Analysis of Ice Cores and Instrumental Data from the Tien Shan

    Energy Technology Data Exchange (ETDEWEB)

    Vladimir Aizen; Donald Bren; Karl Kreutz; Cameron Wake

    2001-05-30

    While the majority of ice core investigations have been undertaken in the polar regions, a few ice cores recovered from carefully selected high altitude/mid-to-low latitude glaciers have also provided valuable records of climate variability in these regions. A regional array of high resolution, multi-parameter ice core records developed from temperate and tropical regions of the globe can be used to document regional climate and environmental change in the latitudes which are home to the vase majority of the Earth's human population. In addition, these records can be directly compared with ice core records available from the polar regions and can therefore expand our understanding of inter-hemispheric dynamics of past climate changes. The main objectives of our paleoclimate research in the Tien Shan mountains of middle Asia combine the development of detailed paleoenvironmental records via the physical and chemical analysis of ice cores with the analysis of modern meteorological and hydrological data. The first step in this research was the collection of ice cores from the accumulation zone of the Inylchek Glacier and the collection of meteorological data from a variety of stations throughout the Tien Shan. The research effort described in this report was part of a collaborative effort with the United State Geological Survey's (USGS) Global Environmental Research Program which began studying radionuclide deposition in mid-latitude glaciers in 1995.

  11. Determination of ice thickness, subice topography and ice volume at Glacier No. 1 in Tien Shan, China by ground penetrating radar

    Institute of Scientific and Technical Information of China (English)

    孙波; 张鹏; 焦克勤; 邓新生; 温家洪

    2003-01-01

    We describe a radio-echo sounding (RES) survey for the determination of ice thickness, subglacial topography and ice volume of Glacier No. 1, in Tien Shah,China, using ground-penetrating radar (GPR). Radar data were collected with 100-MHz antennas that were spaced at 4 m with a step size of 8 m. The images produced from radar survey clearly show the continuity of bedrock echoes and the undulation features of the bedrock surface. Radar results show that the maximum ice thickness of Glacier No. 1 is 133 m, the thickness of the east branch of Glacier No. 1 averages at 58.77 m while that of the west branch of Glacier No. 1 averages at 44.84 m. Calculation on ice volume indicates that the ice volume of the east branch of Glacier No. 1 is 51.87 × 106 m3 and that of the west branch of Glacier No. 1 is 20.21 × 106 m3. The amplitude of the undulation of the bedrock surface topography revealed by radar profiles is larger than that of the glacier surface topography, indicating that the surface relief does not directly depend on that of the bedrock undulation in Glacier No. 1, in Tien Shan.

  12. Aperiodic SiSn/Si multilayers for thermoelectric applications

    Science.gov (United States)

    Tonkikh, A. A.; Zakharov, N. D.; Eisenschmidt, C.; Leipner, H. S.; Werner, P.

    2014-04-01

    We report on novel defect-free SiSn/Si heterostructures grown pseudomorphically on Si(001) substrates using temperature-modulated molecular beam epitaxy. This approach results in a sustainable epitaxial growth for SiSn/Si multilayers. Transmission electron microscopy and electron diffraction manifest that SiSn layers possess a diamond lattice structure. X-ray diffraction reveals up to 9.5 at% Sn in the crystal lattice of SiSn layers.

  13. Region-wide glacier mass budgets and area changes for the Central Tien Shan between ~ 1975 and 1999 using Hexagon KH-9 imagery

    Science.gov (United States)

    Pieczonka, Tino; Bolch, Tobias

    2015-05-01

    The meltwater released by the glaciers in the Central Tien Shan feeds in particular the Tarim River which is the main artery for the oases at the northern margin of the Taklamakan desert. The correct assessment of the contribution of the glaciers' meltwater to the total runoff is hampered by the lack of long-term measurements of glacier mass budgets. Digital terrain models (DTMs) for the different regions in the Central Tien Shan were generated based on ~ 1975 KH-9 Hexagon imagery and compared to the SRTM3 DTM acquired in February 2000. Moreover, glacier area changes for the period ~ 1975-2008 have been measured by means of multi-temporal optical satellite imagery. The geodetic mass budget estimates for a glacierized area of 5000 km2 revealed increasing mass loss east to west and from the inner to the outer ranges. Highest mass loss accompanied by the most pronounced glacier retreat was found for the Ak-Shirak massif with a region-wide mass balance of - 0.51 ± 0.36 m w.e. a- 1 and a rate of area change of - 0.27 ± 0.15% a- 1, whilst moderate mass loss was observed for the Inylchek (0.20 ± 0.44 m w.e. a- 1) and Tomur area (0.33 ± 0.30 m w.e. a- 1) despite partly debris cover. These latter regions also revealed the lowest glacier shrinkage within the entire Central Tien Shan. The total glacier mass loss of 0.35 ± 0.34 m w.e. a- 1 is, however, within the global average whilst the glacier area shrinkage is comparatively low. On average, the investigated glacierized area of ~ 6600 km2 shrank by 0.11 ± 0.15% a- 1 only. We could also identify several surge-type glaciers. The results are consistent with in-situ mass balance measurements for Karabatkak Glacier and previously published results of the Ak-Shirak range proving the suitability of declassified imagery for glacier change investigations. The contribution to the runoff of Aksu River, the largest tributary of the Tarim River, due to glacier imbalance has been determined at ~ 20% for the 1975-2000 period.

  14. A 'college of astrology and medicine'? Charles V, Gervais Chrétien, and the scientific manuscripts of Maître Gervais's College.

    Science.gov (United States)

    Boudet, Jean-Patrice

    2010-06-01

    Considered an institution mainly devoted to astrology and medicine by Simon de Phares and by some historians who believe that he was reliable, the college founded in 1371 by Charles V's first physician, Gervais Chrétien, was in fact primarily dedicated to theological students. It was not before 1377 that there were created there two bursaries for scholares regis, specialising in 'licit mathematical sciences', and two medical fellowships. Yet the influence of the activity of these fellows seems to have been rather moderate and-as far as we can learn from the material still extant, notably from manuscripts that belonged to Maître Gervais' College and to some of its members-this institution was devoted much more to theological studies than to medicine and the quadrivium.

  15. Effect of the muon component of cosmic rays on the results of hadron experiments with the big ionization calorimeter (BIC) of the Tien Shan station

    Energy Technology Data Exchange (ETDEWEB)

    Bogdanov, A. G., E-mail: AGBogdanov@mephi.ru; Kokoulin, R. P.; Petrukhin, A. A.; Shalabaeva, A. V. [Moscow Engineering Physics Institute (State University) (Russian Federation); Yakovlev, V. I. [Russian Academy of Sciences, Lebedev Institute of Physics (Russian Federation)

    2008-01-15

    A full-scale simulation of the response of the big ionization calorimeter (BIC) at the Tien Shan station to the passage of single protons and muons was performed on the basis of the GEANT4 package in order to estimate the contribution of the muon cosmic-ray component to the generation of unusual events (such as Anti-Centauros), which were recorded by this facility, and to the imitation of the long-flying component, which changes the shape of the average cascade curve. A comparison of the results of this simulation with experimental data reveals that the appearance of Anti-Centauros may be reasonably explained by the contribution of multiple interactions of single muons, but that muon events are insufficient for explaining the change in the shape of the cascade curve (in particular, the emergence of a second maximum).

  16. Search for EAS radio-emission at the Tien-Shan shower installation at a height of 3340 m above sea level

    Science.gov (United States)

    Beisenova, A.; Boos, E.; Haungs, A.; Sadykov, T.; Salihov, N.; Shepetov, A.; Tautayev, Y.; Vildanova, L.; Zhukov, V.

    2017-06-01

    The complex EAS installation of the Tien Shan mountain cosmic ray station which is situated at a height of 3340 m above sea level includes the scintillation and Cherenkov detectors of charged shower particles, an ionization calorimeter and a set of neutron detectors for registering the hadronic component of the shower, and a number of underground detectors of the penetrative EAS component. Now it is intended to expand this installation with a promising method for detecting the radio-emission generated by the particles of the developing shower. The facility for radio-emission detection consists of a three crossed dipole antennae, one being set vertically, and another two - mutually perpendicularly in a horizontal plane, all of them being connected to a three-channel radio-frequency amplifier of German production. By the passage of an extensive air shower, which is defined by a scintillation shower detector system, the output signal of antenna amplifier is digitized by a fast multichannel DT5720 ADC of Italian production, and kept within computer memory. The further analysis of the detected signal anticipates its operation according to a special algorithm and a search for the pulse of radio-emission from the shower. A functional test of the radio-installation is made with artificial signals which imitate those of the shower, and with the use of a N1996A type wave analyzer of Agilent Technologies production. We present preliminary results on the registration of extensive air shower emission at the Tien Shan installation which were collected during test measurements held in Summer 2016.

  17. Integrating satellite imagery and geostatistics of point samples for monitoring spatio-temporal changes of total suspended solids in bay waters: application to Tien Yen Bay (Northern Vietnam)

    Institute of Scientific and Technical Information of China (English)

    Nguyen Thi Thu HA; Katsuaki KOIKE

    2011-01-01

    High concentrations of total suspended solids (TSS)in coastal and bay areas strongly affect water quality and aquatic ecosystems.Frequent monitoring of spatiotemporal changes of TSS distribution in such areas is indispensable for understanding sediment fluxes and water cycles,and to preserve ecosystem health.This study aimed to identify appropriate and sufficient tools for assessing changes in TSS distribution in Tien Yen Bay in Northem Vietnam,a typical closed bay,which was selected as the study area because of its rich biodiversity.Initially,a physical based model using the reflectance at the sea surface was developed for estimating TSS concentrations from satellite image data,and a model with an exponential function was identified as suitable for the estimation.This model was fitted appropriately to provide a relationship between reflectance from the MODIS/Terra band 1(visible red)after the atmospheric correction and the in situ TSS concentrations at 40 points.Ordinary kriging was then shown to be effective in improving the spatial resolution of the MODIS/Terra image-based estimation of the TSS concentration at a 250 m interval,because it could detect TSS variation in detail,in particular in the local estuaries.TSS distributions derived from 12 MODIS/Terra images from November 2009 to October 2010 clarified seasonal changes in TSS during one year.TSS concentrations were high during summer and lower during fall and winter.Such trends were conformable with the hydrodynamics in Tien Yen Bay.Consequently,the proposed method was more effective for TSS estimation than traditional methods using satellite image data only.

  18. Macroscopic Fault Structure of the 1911 Mw8.1 Chon Kemin Earthquake (Tien Shan, Kyrgyzstan) from Combined Seismic Imaging, Palaeo-Seismological Investigations and Historial Seismicity

    Science.gov (United States)

    Haberland, C. A.; Sonnemann, T.; Landgraf, A.; Ryberg, T.; Kulikova, G.; Krueger, F.; Dzhumabaeva, A.; Abdrakhmatov, K.; Abdybachaev, U.; Orunbaev, S.; Rosenwinkel, S.; Sharshebaev, A.

    2014-12-01

    Earthquakes in low-strain regions and their driving forces are still sparsely studied and understood, and constitute serious first-order research questions. Data acquisition concerning paleo-earthquakes, related hazards, and tectonic activity beyond historical records plays an important role. Such information can be obtained with tools from tectonic geomorphology, geophysics, historic seismicity, and paleo-seismology that should span a variety of time and length scales. The Chon-Kemin Valley in the northern Tien Shan (Kyrgyzstan) is a small, intermontane basin of unknown origin framed by a network of active faults. In the year 1911, the Chon-Kemin earthquake (Mw=8.1) activated fault structures of about 200 km length which also ruptured the surface along the Chon-Kemin Valley and caused numerous landslides and rock avalanches of up to several tens of millions of cubic meters in volume. The Chon-Kemin earthquake was one of a series of strong seismic events that affected the northern Tien Shan between 1885 and 1938. A seismic survey across the Chon-Kemin Valley was conducted to investigate the subsurface velocity structure of the valley and its surrounding faults. Tomographic inversion techniques were applied to first-arrival traveltimes of refracted P waves, and the seismic data were screened for reflection signatures. Additionally, the region was analyzed through paleo-seismological trenching. Tomographic and reflection images identified a shallow basin structure bounded by a set of thrust faults in the south only which - in part - correlate with the surface trace of the rupture. The deformation seems to be distributed in time and space across several sub-parallel fault strands. Synthesis of historical (analog) recordings of this earthquake provide new insights into the source mechanisms and processes.

  19. Prose Writer Si Yu

    Institute of Scientific and Technical Information of China (English)

    1996-01-01

    SI Yu, pen name of Zhan Shaojuan, is well known through her prose works. During the recent more than ten years, Chinese prose writing has developed rapidly, from its previous level to the present flourishing conditions. Si Yu is a distinguished woman writer, whose creative prose alternately displays either

  20. Opciones de conservación y liquidación de los bienes del deudor en el derecho uruguayo vigente: el caso de las sociedades anónimas

    Directory of Open Access Journals (Sweden)

    Eva Holz

    2014-03-01

    Full Text Available Incuestionablemente, del punto de vista empresarial, y los efectos de obtener el mayor valor posible en la realización de los activos de la sociedad anónima deudora en el procedimiento concursal, objetivo que precisamente satisface el interés de todos los acreedores- beneficiarios últimos del resultado de la liquidación -, la flexibilidad en las vías alternativas de realización activo es crucial. A partir de esa afirmación, qué opciones de liquidación son admisibles para nuestra vetusta legislación vigente (ley 2.230 de junio de 1893 y simultáneamente protegen a un eventual adquirente de la acción de los acreedores de la sociedad deudora? Desde ya anticipamos nuestra conclusión, en el sentido de que existen otras vías alternativas a la del remate para la liquidación de los bienes del deudor. Analicemos algunas, descartando desde ya todas aquellas vías que implican la adquisición de activos y pasivos, como podría ser la compraventa de acciones. De lege ferenda, el proyecto de ley de Declaración Judicial del Concurso y Reorganización Empresarial que cuenta con media sanción parlamentaria, determina con claridad que cualquiera sea el procedimiento de realización de los activos del deudor, el adquirente de los mismos no podrá ser perseguido por ninguna especie de acreedor de aquél

  1. Electroluminescence from Si/SiO2 films deposited on p-Si substrates

    Institute of Scientific and Technical Information of China (English)

    马书懿; 萧勇; 陈辉

    2002-01-01

    The structure of Au/Si/SiO2/p-Si has been fabricated using the magnetron sputtering technique. It has a verygood rectifying behaviour. Visible electroluminescence (EL) has been observed from the Au/Si/SiO2/p-Si structureat a forward bias of 5V or larger. A broad band with one peak around 650-660 nm appears in all the EL spectra ofthe structure. The effects of the thickness of the Si layer in the Si/SiO2 films and of the input electrical power on ELspectra are studied systematically.

  2. Influence of Si on Interfacial Combination of SiCp/Al-Mg-Si Composite

    Institute of Scientific and Technical Information of China (English)

    Han Jianmin; Li Ronghua; Li Mingwei; Cui Shihai; Li Weijing; Wang Jinhua

    2004-01-01

    The scanning electron microscopy (SEM) analysis results of Si distribution in the interface between SiC reinforcements and aluminum matrix of a stir casting SiCp/Al-Mg-Si composite were presented. Results show that there is Si precipitation deposit on the interface of the composite and Si connects with SiC reinforcements in one side and connects with aluminum matrix in the other side. Si phase plays as a connecting bridge, which contributes to the interfacial combination of SiCp/Al composite.

  3. La mujer tiene la palabra

    OpenAIRE

    Thomas, Florence

    2001-01-01

    Muchas mujeres, amigas o desconocidas, y algunos hombres me solicitan con insistencia el conjunto de columnas que he publicado en E l Tiempo y me preguntan por mis pequeños ensayos inéditos o los que han aparecido en revistas nacionales que no siempre son fáciles de conseguir. Por eso decidí reunir casi la totalidad de estos artículos en el presente libro. Los textos fueron ordenados en siete grandes temas: el amor, las mujeres, los hombres, la guerra, homosexualismos, Betty y nostalgias. C...

  4. Cambio en la clasificación macroscópica de la apendicitis. ¿Tiene algún impacto? Estudio retrospectivo en un Hospital Universitario Pediátrico

    Directory of Open Access Journals (Sweden)

    Sergio David Castañeda-Espinosa

    2015-04-01

    Full Text Available Antecedentes. La definición actual de apendicitis diferencia la aguda en apéndices no perforados y perforados. Esta clasificación describe los apéndices perforados como aquellos con la presencia de un orificio visible en el apéndice o la presencia de un fecalito libre en la cavidad y ha cambiado el manejo postoperatorio actual. Objetivo. Determinar si el cambio en la definición macroscópica de la apendicitis aguda tiene alguna influencia en la duración de la estancia hospitalaria y la tasa de complicaciones dado el cambio en el manejo antibiótico postoperatorio. Materiales y métodos. Se llevó a cabo un rastreo de aquellos pacientes llevados a cirugía con diagnóstico de apendicitis aguda durante el primer semestre del año 2009 y el segundo semestre del año 2011 en la Fundación HOMI. Se excluyeron los pacientes llevados a laparoscopia diagnóstica por estudio del dolor abdominal, apendicectomias incidentales y los pacientes manejados en el protocolo de apendicectomía de Intervalo. Resultados. Se observó una disminución en el número de días de hospitalización/año y en el número de dosis de antibiótico/año y reducción en el número de complicaciones, lo cual demuestra que la clasificación y el protocolo de manejo actual no se correlacionan con un aumento en el número de complicaciones y se asocia con menores costos. Conclusión. El cambio en la clasificación macroscópica y el aportar la nueva definición sobre apendicitis perforada ha logrado disminuir la estancia hospitalaria y la cantidad de antibióticos utilizados sin una repercusión significativa en la tasa de complicaciones.

  5. Inventory and state of activity of rockglaciers in the Ile and Kungöy Ranges of Northern Tien Shan from satellite SAR interferometry

    Science.gov (United States)

    Strozzi, Tazio; Caduff, Rafael; Kääb, Andreas; Bolch, Tobias

    2017-04-01

    The best visual expression of mountain permafrost are rockglaciers, which, in contrast to the permafrost itself, can be mapped and monitored directly using remotely sensed data. Studies carried out in various parts of the European Alps have shown surface acceleration of rockglaciers and even destabilization of several such landforms over the two last decades, potentially related to the changing permafrost creep conditions. Changes in rockglacier motion are therefore believed to be the most indicative short- to medium-term response of rockglaciers to environmental changes and thus an indicator of mountain permafrost conditions in general. The ESA DUE GlobPermafrost project develops, validates and implements EO products to support research communities and international organizations in their work on better understanding permafrost characteristics and dynamics. Within this project we are building up a worldwide long-term monitoring network of active rockglacier motion investigated using remote sensing techniques. All sites are analysed through a uniform set of data and methods, and results are thus comparable. In order to quantify the rate of movement and the relative changes over time we consider two remote sensing methods: (i) matching of repeat optical data and (ii) satellite radar interferometry. In this contribution, we focus on the potential of recent high spatial resolution SAR data for the analysis of periglacial processes in mountain environments with special attention to the Ile and Kungöy Ranges of Northern Tien Shan at the border between Kazakhstan and Kyrgyzstan, an area which contains a high number of large and comparably fast (> 1m/yr) rockglaciers and is of interest as dry-season water resource and source of natural hazards. As demonstrated in the past with investigations conducted in the Swiss Alps, the visual analysis of differential SAR interferograms can be employed for the rough estimation of the surface deformation rates of rockglaciers and

  6. Impacts of climate change on river discharge in the northern Tien Shan: Results from the long-term observations and modelling

    Science.gov (United States)

    Shahgedanova, Maria; Afzal, Muhammad; Usmanova, Zamira; Kapitsa, Vasilii; Mayr, Elisabeth; Hagg, Wilfried; Severskiy, Igor; Zhumabayev, Dauren

    2017-04-01

    The study presents results of investigation of the observed and projected changes in discharge of seven snow- and glacier-nourished rivers of the northern Tien Shan (south-eastern Kazakhstan). The observed trends were assessed using the long-term (40-60 years) homogeneous daily records of discharge from the gauging stations located in the mountains and unaffected by human activities including water abstraction. Positive trends in discharge were registered at most sites between the 1950s and 2010s with the strongest increase in summer and autumn particularly in 2000-2010s in line with the positive temperature trends. The observed increase was most prominent in the catchments with a higher proportion of glacierized area. At the Ulken Almatinka and Kishi Almatinka rivers, where 16% and 12% of the catchment areas are glacierized, positive trends in summer and autumn discharge exceeded 1% per year. The strongest increase was observed in September indicating that melting period extends in the early autumn. In September-November, the number of days with extreme discharge values, defined as daily values exceeding 95th percentile (calculated for each meteorological season), increased at all rivers. Future changes in discharge were modelled using HBV-ETH hydrological model and four climate change scenarios derived using regional climate model PRECIS with 25 km spatial resolution driven by HadGEM GCM for RCP 2.6 and RCP 8.5 scenarios and HadCM3Q0 and ECHAM5 GCM for A1B scenario. A range of glacier change scenarios was considered. All climate experiments project increase in temperature with the strongest warming projected by the HadGEM-driven simulation for RCP 8.5 scenario and HadCM3Q0-driven simulation for A1B scenario. The projected changes in precipitation varied between models and seasons, however, most experiments did not show significant trends in precipitation within the studied catchments. The exception is a simulation driven by HadGEM GCM for 8.5 RCP scenario which

  7. Title of abstract - Different approaches to the determining of 3-d P and S wave velocity structures of the crust beneath Northern Tien Shan

    Science.gov (United States)

    Kryukova, O.

    2003-04-01

    The seismic images of the crust beneath Northern Tien Shan (NTS) are obtained with using of different sets of data and several algorithms for solution of local earthquake tomography problem. The NTS is a very interesting region from geophysical point if view due to high seismic activity caused by interplate collision: Tien Shan and Kazakh. A rectangular region under investigation is constrained by lines 41.90o N - 43.40o N and 73.50o E- 76.50o E. 14661 P and 14436 S wave arrival times recorded 12 seismic stations of the Kyrgyzstan Broadband Network (KNET) from local earthquake in 1991-1999 years are used. In addition, data from 267 local earthquake recorded over a period of about 20 years by a regional arrays of 93 seismographs in NTS are involved in inversions. 1-d optimal velocity models and stations delays are estimated with help of program VELEST (E.Kissling, 1995). Block parameterization of model and ray tracing described by Thurber and Ellsworth (1980) are used for determination of 3-d velocity structure and relocation of events as one of the approaches (programs S.Roecker Sphypit90 and Sphrel3d). Other approach consists in application linear or cubic B spline interpolation of velocity function and ray tracing Um and Thurber (1987) for the solution of forward problem (program C.Thurber et al. Simulps and own program). The data resolution analysis and statistical analysis of models was carried out. Calculated P wave tomographic models were compared with tomographic models S.Roecker et al. (1993), S.Ghose et al. (1998) and T.Sabitova (1996). The main result is the confirmation of existence of different seismic velocity structure beneath Kyrgyz Range and Chu Basin. Using various sets of date and methods for reconstruction velocity model is effective in reveal of more reliable velocity heterogeneities in the domain of research. The author is grateful to dr. I. Kitov for help and to dr. I.Sanina for useful discussion.

  8. Introduction of atomic H into Si3N4/SiO2/Si stacks

    Institute of Scientific and Technical Information of China (English)

    JIN Hao; WEBER K.J.; LI Weitang; BLAKERS A.W.

    2006-01-01

    Atomic H generated by a plasma NH3 source at 400 ℃ was demonstrated to passivate dehydrogenated Si3N4/SiO2/Si stacks effectively by bonding with defectsin the Si3N4 film and at the Si-SiO2 interface. A subsequent anneal in N2 after atomic H reintroduction was demonstrated to further improve passivation of the Si-SiO2 interface. Isothermal and isochronal anneals in N2 were carried out in order to determine the optimized annealing conditions.

  9. Electronic Structure of Si1-xIVx/Si Superlattices on Si(001)

    Institute of Scientific and Technical Information of China (English)

    CHEN Jie; L(U) Tie-Yu; HUANG Mei-Chun

    2007-01-01

    We have preformed systematical ab initio studies of the structural and electronic properties of short-period Si1-xIVx/Si (x = 0.125, 0.25, 0.5,IV=Ge, Sn) superlattices (SLs) grown along the [001] direction on bulk Si. The present calculations reveal that the Si0.875 Ge0.125/Si, Si0.75 Ge0.25/Si and Si0.875Sn0.125/Si axe the Γ-point direct bandgap semiconductors. The technological importance lies in the expectation that the direct gap Si1-xIVx/Si SLs may be used as components in integrated optoelectronic devices, in conjunction with the already well-established and highly advanced silicon technology.

  10. Photoelectric properties of n-SiC/n-Si heterojunctions

    Directory of Open Access Journals (Sweden)

    Semenov A. V.

    2012-10-01

    Full Text Available Photovoltaic effect in isotype heterotructure formed by nanocrystalline silicon carbide films on single crystal n-Si substrates (n-SiC/n-Si heterojunction was studied. The films were produced by direct ionic deposition method. The model that takes into account the quantum wells and potential barriers caused by band offsets was proposed to explain the current-voltage characteristics and photovoltaic properties of the heterostructure n-SiC/n-Si.

  11. [Soil microarthropods and macrofauna in monsoon tropical forests of Cat Tien and Bi Dup-Nui Ba National Parks, Southern Vietnam].

    Science.gov (United States)

    Anichkin, A E; Beliaeva, N V; Dovgobrod, I G; Shveenkova, Iu B; Tiunov, A V

    2007-01-01

    The abundance, biomass, vertical distribution, and taxonomic composition of soil invertebrates (springtails, macrofauna, and termites) were studied in forest formations differing in edaphic and climatic conditions: lowland forests dominated by Lagerstroeomia spp. or Dipterocarpus spp. in the Cat Tien National Park and in a mountain pine (Pinus kesiya) forest on the Da Lat Plateau, southern Vietnam. In the lowland forests, springtails had a relatively low density (10000-12000 ind./m2), but their diversity was high (41-43 species in each forest). The density of large soil invertebrates (without ants and termites) reached 500-700 ind./m2 at a biomass of approximately 30 g/m2 (with earthworms accounting for up to 230 ind./m2 and 19-28 g/m2). Among termites, species of the genera Macrotermes and Odontotermes were dominant. Their total biomass in some areas exceeded 15-20 g/m2. In the mountain pine forest, the total biomass of soil macrofauna was approximately 11 g/m2, the abundance and diversity of springtails were low (7500 ind./m2, 28 species), and wood-destroying species of the genera Schedorhinotermes sp. and Coptotermes sp. dominated among termites.

  12. Elimination of Cancer Stem-Like “Side Population” Cells in Hepatoma Cell Lines by Chinese Herbal Mixture “Tien-Hsien Liquid”

    Directory of Open Access Journals (Sweden)

    Chih-Jung Yao

    2012-01-01

    Full Text Available There are increasing pieces of evidence suggesting that the recurrence of cancer may result from a small subpopulation of cancer stem cells, which are resistant to the conventional chemotherapy and radiotherapy. We investigated the effects of Chinese herbal mixture Tien-Hsien Liquid (THL on the cancer stem-like side population (SP cells isolated from human hepatoma cells. After sorting and subsequent culture, the SP cells from Huh7 hepatoma cells appear to have higher clonogenicity and mRNA expressions of stemness genes such as SMO, ABCG2, CD133, β-catenin, and Oct-4 than those of non-SP cells. At dose of 2 mg/mL, THL reduced the proportion of SP cells in HepG2, Hep3B, and Huh7 cells from 1.33% to 0.49%, 1.55% to 0.43%, and 1.69% to 0.27%, respectively. The viability and colony formation of Huh7 SP cells were effectively suppressed by THL dose-dependently, accompanied with the inhibition of stemness genes, e.g., ABCG2, CD133, and SMO. The tumorigenicity of THL-treated Huh7 SP cells in NOD/SCID mice was also diminished. Moreover, combination with THL could synergize the effect of doxorubicin against Huh7 SP cells. Our data indicate that THL may act as a cancer stem cell targeting therapeutics and be regarded as complementary and integrative medicine in the treatment of hepatoma.

  13. Targeting PML-RARα and Oncogenic Signaling Pathways by Chinese Herbal Mixture Tien-Hsien Liquid in Acute Promyelocytic Leukemia NB4 Cells

    Directory of Open Access Journals (Sweden)

    Chih-Jung Yao

    2011-01-01

    Full Text Available Tien-Hsien Liquid (THL is a Chinese herbal mixture that has been used worldwide as complementary treatment for cancer patients in the past decade. Recently, THL has been shown to induce apoptosis in various types of solid tumor cells in vitro. However, the underlying molecular mechanisms have not yet been well elucidated. In this study, we explored the effects of THL on acute promyelocytic leukemia (APL NB4 cells, which could be effectively treated by some traditional Chinese remedies containing arsenic trioxide. The results showed THL could induce G2/M arrest and apoptosis in NB4 cells. Accordingly, the decrease of cyclin A and B1 were observed in THL-treated cells. The THL-induced apoptosis was accompanied with caspase-3 activation and decrease of PML-RARα fusion protein. Moreover, DNA methyltransferase 1 and oncogenic signaling pathways such as Akt/mTOR, Stat3 and ERK were also down-regulated by THL. By using ethyl acetate extraction and silica gel chromatography, an active fraction of THL named as EAS5 was isolated. At about 0.5–1% of the dose of THL, EAS5 appeared to have most of THL-induced multiple molecular targeting effects in NB4 cells. Based on the findings of these multi-targeting effects, THL might be regarding as a complementary and alternative therapeutic agent for refractory APL.

  14. Interfacial reaction of eutectic AuSi solder with Si (100) and Si (111) surfaces

    Science.gov (United States)

    Jang, Jin-Wook; Hayes, Scott; Lin, Jong-Kai; Frear, Darrel R.

    2004-06-01

    The dissolution behavior of Si (100) and (111) dies by eutectic AuSi solder was investigated. On the Si (100) surface, the dissolution primarily occurred by the formation of craters resulting in a rough surface. The dissolution of the Si (111) resulted in a relatively smooth surface. The morphology of the Si (100) surface during a AuSi soldering reaction exhibited more time-dependent behavior and the etching craters on a Si (100) surface grew larger with time whereas Si (111) did not significantly change. This difference was ascribed to the surface energy differences between Si (111) and (100) surfaces that resulted in the two- and three-dimensional dissolution behaviors, respectively. This difference plays an important role in the formation of voids during the AuSi die bonding. The etching craters on Si (100) act as a AuSi solder sink and the regions surrounded by etch pits tend to become voids. For Si (111), flat surfaces were observed in the voided regions. Cross section analysis showed that no solder reaction occurred in the voided region of the Si (111) surface. This suggests the possibility of the formation of a thin inert layer in a potentially voided region prior to assembly. To achieve void-free die bonding, different parameters must be adjusted to the Si (100) and Si (111) surfaces with the AuSi alloy.

  15. Correlation between Light Emissions from Amorphous-Si:H/SiO2 and nc-Si/SiO2 Multilayers

    Institute of Scientific and Technical Information of China (English)

    MA Zhong-Yuan; HUANG Xin-Fan; CHEN Kun-Ji; FENG Duan; HAN Pei-Gao; LI Wei; CHEN De-Yuan; WEI De-Yuan; QIAN Bo; LI Wei; XU Jun; XU Ling

    2007-01-01

    We investigate the properties of light emission from amorphous-Si:H/SiO2 and nc-Si/SiO2 multilayers (MLs). The size dependence of light emission is well exhibited when the a-Si:H sublayer thickness is thinner than 4nm and the interface states are well passivated by hydrogen. For the nc-Si/SiO2 MLs, the oxygen modified interface states and nanocrystalline silicon play a predominant role in the properties of light emission. It is found that the light emission from nc-Si/SiO2 is in agreement with the model of interface state combining with quantum confinement when the size of nc-Si is smaller than 4 nm. The role of hydrogen and oxygen is discussed in detail.

  16. Los social media actúan como multiplicadores de una marca país si esta tiene una estrategia bien definida. Entrevista a Justo Villafañe

    OpenAIRE

    Santillán-Vásquez, Manuel; Universidad de Lima (Perú)

    2016-01-01

    Villafañe ha realizado el primer estudio de Marca España desde la teoría de la reputación. Para él, una marca es la promesa que una empresa o un país hace a sus stakeholders. Asimismo, propone un abordaje científico y profesional sobre la construcción de una marca país y busca identificar de manera rigurosa la promesa de la marca para contrastarla a la propia identidad de una nación. Su estudio ahonda en la propuesta de valor y la vincula a las expectativas e intereses de los distintos stakeh...

  17. A comparative study of electroluminescence from Ge/SiO2 and Si/SiO2 films

    Institute of Scientific and Technical Information of China (English)

    Ma Shu-Yi; Chen Hui; Xiao Yong; Ma Zi-Jun; Sun Ai-Min

    2004-01-01

    Ge/SiO2 and Si/SiO2 films were deposited using the two-target alternation magnetron sputtering technique. The Au/Ge/SiO2/p-Si and Au/Si/SiO2/p-Si structures were fabricated and their electroluminescence (EL) characteristics were comparatively studied. Both Au/Ge/SiO2/p-Si and Au/Si/SiO2/p-Si structures have rectifying property. All the EL spectra from the two types of the structure have peak positions around 650-660 nm. The EL mechanisms of the structures are discussed.

  18. a-Si/c-Si heterojunction solar cells on SiSiC ceramic substrates

    Institute of Scientific and Technical Information of China (English)

    LI Xudong; XU Ying; CHE Xiaoqi

    2006-01-01

    Silicon thin-film solar cells are considered to be one of the most promising cells in the future for their potential advantages, such as low cost, high efficiency, great stability, simple processing, and none-pollution. In this paper, latest progress on poly-crystalline silicon solar cells on ceramic substrates achieved by our group was reported. Rapid thermal chemical vapor deposition (RTCVD) was used to deposited poly-crystalline silicon thin films, and the grains of as-grown film were enlarged by Zone-melting Recrystallization (ZMR). As a great changein cell's structure, traditional diffused pn homojunction was replaced by a-Si/c-Si heterojunction, which lead is to distinct improvement in cell's efficiency.A conversion efficiency of 3.42% has been achieved on 1cm2 a-Si/c-Si heterojunction solar cell ( Isc =16.93 mA, Voc =310.9 mV, FF =06493, AM =1.5 G,24 ℃), while the cell with diffused homojunction only gotan efficiency of 0.6%. It indicates that a-Si emitter formed at low temperature might be more suitable for thin film cell on ceramics.

  19. Features of Mg2Si Layer Growth in Si/Mg2Si Multilayers

    Directory of Open Access Journals (Sweden)

    L.E. Konotopskyi

    2016-06-01

    Full Text Available Features of magnesium siliced layer growth in Si/Mg2Si multilayers in initial state and after thermal annealing were studied by methods of transmission electron microscopy and X-Ray scattering. As-deposited magnesium silicide layers are amorphous with nanocrystal inclusions of metastable h-Mg2Si. Formation of Mg2Si in hexagonal modification occurs under the influence of stress produced by silicon layers. At T = 723 К Mg2Si layers finished crystallizes in hexagonal modification, with some coarsening of grains. That is accompanied with 7.3 % reduction in period of the Si/Mg2Si multilayer.

  20. Transport and electroluminescence mechanism in Au/(Si/SiO2)/P-Si film

    Institute of Scientific and Technical Information of China (English)

    ZHANG Kai-biao; MA Shu-yi; MA Zi-jun; CHEN Hai-xia

    2006-01-01

    The samples of Au/(Si/SiO2)/p-Si structure were fabricated by using the R.F magnetron sputtering technique.Its carrier transport and electroluminescence mechanism were studied from the I-V curves and EL spectra by using the Configuration Coordinate as a theoretical model.The result indicates that there are two defect centers in SiO2 films.The electron in Au and the hole in p-Si went into SiO2 film by the Fowler-Nordheim tunneling model at a high bias voltage and recombined through these defect centers in SiO2 film.

  1. Photoreflectance Spectroscopy for Study of Si/SiGe/Si Heterostructure

    Institute of Scientific and Technical Information of China (English)

    Liu Zhihong; Chen Changchun; Lin Huiwang; Xiong Xiaoyi; Dou Weizhi; Tsien Pei-Hsin

    2004-01-01

    UHVCVD-grown Si/Si1- xGex/Si heterostructure was investigated by Photoreflectance spectroscopy (PR). The principle of PR used in semiconductor film was thoroughly described. According to the E1 transition energy in the Si1- xGex alloy, the Ge content in SiGe film with constant composition can be accurately characterized. In this study, determine the composition uniformity of larger diameter SiGe epiwafer by PR mapping technique was determined. These results show PR is very promising for Si1- xGex epilayer characterization with constant Ge content and can provide film measurements for production-worthy line monitor.

  2. Argumentación persuasiva y sintaxis en los mensajes publicitarios. Fórmulas con SI*

    OpenAIRE

    Romero-Gualda, M.V. (María Victoria)

    2008-01-01

    Se trata de examinar la argumentación peculiar de los mensajes publicitarios como estrategia encaminada a conseguir el objetivo persuasivo que pretenden éstos. Dada la capacidad de difundir usos que tiene la lengua empleada en los mensajes publicitarios, es relevante el estudio de las fórmulas sintácticas utilizadas con intención argumentativa; en este artículo se examina un tipo repetidamente empleado en los ganchos de anuncios impresos: las fórmulas con la conjunción SI que potencian la cre...

  3. Unas opciones para muestras de la naturaleza

    Science.gov (United States)

    Frank H. Wadsworth

    2009-01-01

    La ciencia, incluso la de Puerto Rico, aprende de muestras, su interpretación y extrapolación a situaciones más extensas. Las muestras de la naturaleza de Puerto Rico: las del suelo, la hojarasca, la sombra, la biomasa, los árboles, las aves, los reptiles y anfibios, o los insectos caracterizan los ecosistemas. [article in Spanish

  4. Oxide layer dissolution in Si/SiO{sub x}/Si wafer bonded structures

    Energy Technology Data Exchange (ETDEWEB)

    Pippel, E.; Werner, P.; Goesele, U. [Max-Planck-Institut fuer Mikrostrukturphysik, Halle (Germany); Vdovin, V. [Institute for Chemical Problems of Microelectronics, Moscow (Russian Federation); Institute of Rare Metals Giredmet, Moscow (Russian Federation); Zakharov, N.

    2009-10-15

    The evolution of the interfaces of hydrophilic-bonded Si wafers and the corresponding low-angle twist boundary have been analysed in relation to thermal annealing and their relative crystallographic orientation. Two orientation relationships were investigated: Si<001>/Si<001> and Si<001>/Si<110>, where the interfaces are separated by thin native SiO2 layers. The interfaces were analysed by TEM and STEM/EELS. It is found that the decomposition rate of the intermediate oxide layer and the formation of a Si-Si bonded interface depend very much on the lattice mismatch and on the twist angle. The velocity of the dissolution of the thin oxide layers and the formation of Si-Si bonds at the bonding interface depend on the orientation relations of the corresponding wafers. The processes of interface fusion and the dissolution of oxide layer are discussed. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  5. The property of Si/SiGe/Si heterostructure during thermal budget characterized by HRXRD

    Institute of Scientific and Technical Information of China (English)

    CHEN Chang-Chun; LIU Zhi-Hong; HUANG Wen-Tao; DOU Wei-Zhi; ZHANG Wei; TSIEN Pei-Hsin; ZHU De-Zhang

    2003-01-01

    Si/SiGe/Si heterostructures grown by ultra-high-vacuum chemical vapor deposition (UHVCVD) werecharacterized by Rutherford backscattering/Channeling (RBS/C) together with high resolution X ray diffraction(HRXRD). High quality SiGe base layer was obtained. The Si/SiGe/Si heterostructures were subject to conventionalfurnace annealing and rapid thermal annealing with temperature between 750 ℃ and 910 ℃. Both strain and its re-laxation degree in SiGe layer are calculated by HRXRD combined with elastic theory, which are never reported inother literatures. The rapid thermal annealing at elevated temperature between 880 ℃ and 910 ℃ for very short timehad almost no influence on the strain in Si0.84Ge0. 16 epilayer. However, high temperature (900℃) furnace annealingfor 1h prompted the strain in Si0.84Ge0.16 layer to relax.

  6. Si/SiGe/Si HBT的直流特性和低频噪声%Si/SiGe/Si HBT's DC Characterization and Its Low-frequency Noise

    Institute of Scientific and Technical Information of China (English)

    廖小平; 张中平

    2003-01-01

    在对Si/SiGe/Si HBT及其Si兼容工艺的研究基础上,研制成功低噪声Si/SiGe/Si HBT,测试和分析了它的直流特性和低频噪声特性,为具有更好的低噪声性能的Si/SiGe/Si HBT的研究建立了基础.

  7. Surface rupture along the Chon Aksu and Aksu (eastern) segments of the 1911 Kebin (Chon-Kemin) earthquake, Tien Shan, Kyrgyzstan

    Science.gov (United States)

    Arrowsmith, J. R.; Crosby, C. J.; Korjenkov, A. M.; Mamyrov, E.; Povolotskaya, I. E.

    2004-12-01

    The 1911 Ms 8.2 Kebin (Chon-Kemin) earthquake is one of the largest intraplate reverse-faulting events to occur historically. It ruptured a 200 km E-W trending zone in the northern Tien Shan. Description of the characteristics of major historic earthquakes, such as the Chon-Kemin event, provide data on the primary deformation and its initial geomorphic degradation, thus informing paleoseismological investigations. Trace geometry and offset distribution are key parameters for the interpretation of the seismotectonic setting and mechanical interaction with other regional structures. The Chon-Kemin earthquake's relationship to other large regional earthquakes, notably the 1887 Ms 7.3 Verny and 1889 Ms 8.3 Chilik events, indicates a strong interaction between structures in this portion of the Tien Shan. We reconnoitered most of the Chon-Kemin rupture belt and associated mass movements and conclude that many of the 1911 features are still well preserved. We emphasized mapping and description of the easternmost 50 km of the rupture, along the Aksu (easternmost) and Chon-Aksu segments. Moving from east to west, 1-3 m high fault scarps and warped Holocene terraces discontinuously cut the piedmonts north and northeast of the town of Anan'evo. The rupture closely follows the mountain front and enters the range just below the Anan'evo landslide (formed in the earthquake). Scarp heights are 2-4 m. West of the Tegermenty River, the left-stepping rupture is continuous and consists of sub parallel strands in places. Between the Sutubulak and the Aksu River crossing, some of the tallest scarps are present, with heights of 6 - 10 m. The generally north-dipping fault zone has low south dips in the near surface as the thrust has driven the hanging wall over the south-sloping piedmont. This change in dip is likely responsible for the formation of E-W extensional faults in the hanging wall. Given the shallow fault dips and tall scarps in this area, 1911 displacement is probably > 10 m

  8. Mid-twentieth century increases in anthropogenic Pb, Cd and Cu in central Asia set in hemispheric perspective using Tien Shan ice core

    Science.gov (United States)

    Grigholm, B.; Mayewski, P. A.; Aizen, V.; Kreutz, K.; Wake, C. P.; Aizen, E.; Kang, S.; Maasch, K. A.; Handley, M. J.; Sneed, S. B.

    2016-04-01

    High-resolution major and trace element (Al, As, Ca, Cd, Co, Cr, Cu, Fe, Li, Mn, Na, Pb, S, Ti, and V) ice core records from Inilchek glacier (5120 m above sea level) on the northwestern margin of the Tibetan Plateau provide the first multi-decadal ice core record spanning the period 1908-1995 AD in central Tien Shan. The trace element records reveal pronounced temporal baseline trends and concentration maxima characteristic of post-1950 anthropogenic emissions. Examination of Pb, Cd and Cu concentrations, along with non-crustal calculation estimates (i.e. excess (ex) and enrichment factor (EF)), reveal that discernable anthropogenic inputs began during the 1950s and rapidly increased to the late-1970s and early 1980s, by factors up to of 5, 6 and 3, respectively, relative to a 1910-1950 means. Pb, Cd and Cu concentrations between the 1950s-1980s are reflective of large-scale Soviet industrial and agricultural development, including the growth of production and/or consumption of the non-ferrous metals, coal and phosphate fertilizers. NOAA HYSPLIT back-trajectory frequency analysis suggests pollutant sources originating primarily from southern Kazakhstan (e.g. Shymkent and Balkhash) and the Fergana Valley (located in Kazakhstan, Uzbekistan and Kyrgyzstan). Inilchek ice core Pb, Cd and Cu reveals declines during the 1980s concurrent with Soviet economic declines, however, due to the rapid industrial and agricultural growth of western China, Pb, Cd and Cu trends increase during the 1990s reflecting a transition from primarily central Asian sources to emission sources from western China (e.g. Xinjiang Province).

  9. Holocene River Dynamics, Climate Change and Floodwater Farming in the Watersheds of the Pamir and Tien Shan Mountains of Inner Asia

    Science.gov (United States)

    Macklin, M. G.; Panyushkina, I. P.; Toonen, W. H. J.

    2014-12-01

    The Ili, Syr Dayra and Amu Dayra rivers of Inner Asia are emerging as critical areas for the development of irrigation-based agriculture in the ancient world. Following research by Russian archaeologists in the 1970s it is evident that these watersheds had flourishing riverine civilizations comparable to those in Mesopotamia and the Indus Valley. But unlike these areas where the relationship between Holocene river dynamics, climate change and floodwater farming is increasingly underpinned by radiometric dating, the alluvial archaeology of Inner Asia is significantly under researched. To address this, a major multi-disciplinary research program was begun in 2011 centred on the Talgar catchment, a south-bank tributary of the Ili river, southeast Kazakhstan. Building on archaeological excavations and surveys conducted over the past 20 years, we have undertaken one of the most detailed investigations of Holocene people-river environment interactions in Inner Asia. River development has been reconstructed over the last 20,000 years and human settlement histories from the Eneolithic to the Medieval period documented. Periods of Holocene river aggradation and high water levels in Lake Balkhash and Aral Sea correspond with cooler and wetter neoglacial episodes while river entrenchment and floodplain soil development are associated with warmer and drier conditions. Floodwater farming in the Talgar river reached its acme in the late Iron Age (400-200 cal. BC) with more than 60 settlement sites and 550 burial mounds. This corresponds to a period of reduced flood flows, river stability and glacier retreat in the Tien Shan headwaters. A new hydroclimatic-based model for the spatial and temporal dynamics of floodwater farming in the Ili, Syr Dayra and Amu Dayra watersheds is proposed, which explains the large scale expansion (down-river) and contraction (up-river) of settlements since the first use of irrigation in the Neolithic through to the late Medieval period.

  10. Effect of Si/Si1-yCy/Si Barriers on the Characteristics of Si1-xGex/Si Resonant Tunneling Structures

    Institute of Scientific and Technical Information of China (English)

    HAN Ping; CHENG Xue-Mei; Masao Sakuraba; YoungCheon Jeong; Takashi Matsuura; Junichi Murota

    2000-01-01

    P-type double barrier resonant tunneling diodes (RTD) with the single Si0.6Ge0.4 quantum well and double Si0.6 Ge0.4 spacer have been realized by using an ultra clean low-pressure chemical vapor deposition system. The effect of Si1-yCy layer on the characteristics of the devices was shown by comparing the current-voltage (Ⅰ-Ⅴ) characteristics of RTD's of the barriers of Si layers with that of Si/Si1-yCy/Si structures. The peak voltage was gradually increased and the resonant current decreased obviously with increasing C content in the Si/Si1-yCy/Si barriers. The origin of the phenomena above can be attributed to the C related deep acceptor levels in the Si/Si1-yCy/Si barriers. The possible mechanism for the observed Ⅰ-Ⅴcharacteristics was shown more clearly by increasing C content to 3% and changing the thicknesses of Si and Si1-yCy layers in the Si/Si1-yCy/Si barriers.

  11. Relaxed SiGe-on-insulator fabricated by dry oxidation of sandwiched Si/SiGe/Si structure

    Energy Technology Data Exchange (ETDEWEB)

    Di Zengfeng [Research Center of Semiconductor Functional Film Engineering Technology and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Department of Physics and Material Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Zhang Miao [Research Center of Semiconductor Functional Film Engineering Technology and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Liu Weili [Research Center of Semiconductor Functional Film Engineering Technology and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Zhu Ming [Research Center of Semiconductor Functional Film Engineering Technology and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Department of Physics and Material Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China); Lin Chenglu [Research Center of Semiconductor Functional Film Engineering Technology and State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS), Shanghai 200050 (China); Chu, Paul K. [Department of Physics and Material Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)]. E-mail: paul.chu@cityu.edu.hk

    2005-12-05

    An improved technique is demonstrated to fabricate silicon-germanium on insulator (SGOI) starting with a sandwiched structure of Si/SiGe/Si. After oxidation of the sandwiched structure and successive annealing, a relaxed SiGe-on-insulator (SGOI) structure is produced. Our results indicate that the added Si cap layer is advantageous in suppressing Ge loss at the initial stage of SiGe oxidation and the subsequent annealing process homogenizes the Ge fraction. Raman measurements reveal that the strain in the SiGe layer is fully relaxed at high oxidation temperature ({approx}1150 deg. C) without generating any threading dislocations and crosshatch patterns, which generally exist in the relaxed SiGe layer on bulk Si substrate.

  12. ¿Tiene sentido hablar de poshumanismo? Acerca de la relación entre teoría de la comunicación y biopolítica de la información

    Directory of Open Access Journals (Sweden)

    Pablo Esteban Rodríguez

    2011-01-01

    Full Text Available ¿Tiene sentido hablar de poshumanismo? Acerca de la relación entre teoría de la comunicación y biopolítica de la información. Does it make sense to talk about posthumanism? The relationship between communication theory and the biopolitics of information

  13. Endotaxial Si nanolines in Si(001):H

    Science.gov (United States)

    Bianco, F.; Owen, J. H. G.; Köster, S. A.; Mazur, D.; Renner, Ch.; Bowler, D. R.

    2011-07-01

    We present a detailed study of the structural and electronic properties of a self-assembled silicon nanoline embedded in the H-terminated silicon (001) surface, known as the Haiku stripe. The nanoline is a perfectly straight and defect-free endotaxial structure of huge aspect ratio; it can grow micrometer long at a constant width of exactly four Si dimers (1.54 nm). Another remarkable property is its capacity to be exposed to air without suffering any degradation. The nanoline grows independently of any step edges at tunable densities from isolated nanolines to a dense array of nanolines. In addition to these unique structural characteristics, scanning tunneling microscopy and density functional theory reveal a one-dimensional state confined along the Haiku core. This nanoline is a promising candidate for the long-sought-after electronic solid-state one-dimensional model system to explore the fascinating quantum properties emerging in such reduced dimensionality.

  14. ¿El nanocomposite arenado con Corindón Blanco tiene efecto sobre la adhesión y proliferación bacteriana? Estudio in vitro

    OpenAIRE

    Piacentini, Giacomo

    2014-01-01

    Introducción: Los implantes dentales sustituyen a dientes ausentes en el paciente totalmente o parcialmente edéntulo. Las características físico-químicas de las superficies pueden tener influencia sobre la formación de biofilm y la manifestación de patologías peri-implantarias, pero también se ha demostrado que pueden favorecer la re-osteointegración en su tratamiento. El objetivo del presente trabajo es comprobar si la superficie de un disco de material compuesto cerámico-c...

  15. Si-to-Si wafer bonding using evaporated glass

    DEFF Research Database (Denmark)

    Reus, Roger De; Lindahl, M.

    1997-01-01

    Anodic bonding of Si to Si four inch wafers using evaporated glass was performed in air at temperatures ranging from 300°C to 450°C. Although annealing of Si/glass structures around 340°C for 15 minutes eliminates stress, the bonded wafer pairs exhibit compressive stress. Pull testing revealed...

  16. Annealing Behavior of Si1-xGex/Si Heterostructures

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The behavior of Si1-xGex/Si heterostructures under different annealing conditions has been studied. It is found that while RTA treatment diminishes the point defects, it introduces the misfit dislocations into Si1-xGex layers at same time. Higher annealing temperature will result in the propagation of misfit dislocations and then the total destruction of the crystal quality.

  17. Si nanoparticle interfaces in Si/SiO solar cell materials

    DEFF Research Database (Denmark)

    Kilpeläinen, S.; Kujala, J.; Tuomisto, F.

    2013-01-01

    Novel solar cell materials consisting of Si nanoparticles embedded in SiO2 layers have been studied using positron annihilation spectroscopy in Doppler broadening mode and photoluminescence. Two positron-trapping interface states are observed after high temperature annealing at 1100 °C. One...... of the states is attributed to the (SiO2/Si bulk) interface and the other to the interface between the Si nanoparticles and SiO2. A small reduction in positron trapping into these states is observed after annealing the samples in N2 atmosphere with 5% H2. Enhanced photoluminescence is also observed from...

  18. ¿Qué hacer si a mi hijo le derivan a Educación Especial?

    OpenAIRE

    Rodríguez, A. B.

    2016-01-01

    Durante el proceso de escolarización de su hijo con síndrome de Down, la mayoría de las familias escucha que “tiene necesidades educativas especiales”. Son muchas las dudas que asaltan a los padres con relación a este término: ¿A qué se refiere exactamente? ¿Cuándo se puede decir que un alumno tiene necesidades educativas especiales? ¿Qué debemos hacer y cómo actuar si le derivan a un Centro de Educación Especial? La asesora en educación de Down España, Ana Belén Rodríguez Plaza, ofrece en e...

  19. GASIFICACIÓN DE CARBÓN PARA GENERACIÓN DE ENERGÍA ELÉCTRICA: ANÁLISIS CON VALORACIÓN DE OPCIONES REALES COAL GASIFICATION FOR POWER GENERATION: ANALYSIS WITH REAL OPTIONS VALUATION

    Directory of Open Access Journals (Sweden)

    Alejandro Concha A

    2009-12-01

    Full Text Available Se evalúa económicamente la utilización de la tecnología de gasificación de carbón en la generación de energía eléctrica, utilizando información secundaria y el enfoque de valoración de opciones reales mediante árboles binomiales de 2 variables. Se analiza el caso de adaptar una central existente de gas natural de ciclo combinado (NGCC para la utilización de syngas a partir de carbón; en un segundo caso, se evalúa la instalación de una nueva central termoeléctrica de carbón pulverizado (PC o alternativamente una central de gasificación de carbón integrada a ciclo combinado (IGCC. En este último caso, se evalúa la opción de "switching" de combustible. Para los precios de los combustibles se emplean modelos de Movimiento Browniano Geométrico No Homogéneo (IGBM y en ambos casos estudiados se analiza en 2 escenarios de precios, incluyendo análisis de sensibilidad. Respecto al primer caso, la adaptación a syngas de una planta NGCC es conveniente económicamente, teniendo el proyecto una alta sensibilidad respecto a la eficiencia. La sensibilidad a la inversión no es significativa, como tampoco a los gastos de operación. Respecto al segundo caso, la conveniencia económica de la planta IGCC frente a la planta PC no es clara en los escenarios de precios considerados. Pero analizada en diversas combinaciones de precios, la planta IGCC de operación flexible alternando dos combustibles puede lograr ventajas económicas. Respecto a la sensibilidad, se repiten las conclusiones mencionadas para el primer caso.The use of coal gasification technology in the generation of electric power is evaluated economically. Secondary information and valuation of real options approach is used, with two variables binomial lattices. First, the retrofit of an existing natural gas combined cycle plant (NGCC for the utilization of syngas from coal is analyzed; on the second case, an economical evaluation is realized for to compare a new Pulverized

  20. Gallstone ileus: management options and results on a series of 40 patients Íleo biliar: opciones terapéuticas y resultados en una serie de 40 casos

    Directory of Open Access Journals (Sweden)

    D. Martínez Ramos

    2009-02-01

    Full Text Available Introduction: controversy remains about the management of gallstone ileus. While some authors propose enterotomy, others defend the one-stage procedure (simultaneously fistula repair. The objective of the present study was to analyze management options and comparative study their results. Material and methods: retrospective and descriptive study with revision of clinical stories of patients with the diagnosis of gallstone ileus between 1987 and 2008. All the following variables were recorded: dates of hospital admission, surgery and discharge, age, sex, pathological antecedents, preoperative or intraoperative diagnosis, treatment, location of the fistula and location of the obstruction. End-result variables were: postoperative complications, mortality, complications during the follow-up and biliary complications. Results: a total of 40 patients were included of 46,648 admissions. Age, comorbidity, and intraoperative diagnosis were related with poorer short- and long-outcomes. The percentage of postoperative complications was similar for groups with and without fistula repair. Mortality was higher in the group with fistula repair (15vs. 25%. Biliary complications were more frequent in the group without fistula repair (11 vs. 0%. Sex, location of the fistula and location of the obstruction did not be related with the prognosis. Conclusion: one-stage procedure is related with higher mortality rate than enterotomy alone. Nevertheless, fistula repair reduces the number of biliary complications during the follow-up.Introducción: todavía existe gran controversia sobre el mejor tratamiento del íleo biliar. Algunos autores proponen la enterotomía aislada, mientras otros defienden la reparación de la fístula bilioentérica en el mismo acto quirúrgico. El objetivo del presente estudio fue analizar las opciones terapéuticas en estos pacientes y estudiar sus resultados. Material y métodos: estudio retrospectivo y descriptivo, con revisión de las

  1. Resonant Tunnelling and Storage of Electrons in Si Nanocrystals within a-SiNx/nc-Si/a-SiNx Structures

    Institute of Scientific and Technical Information of China (English)

    WANG Xiang; HUANG Jian; ZHANG Xian-Gao; DING Hong-Lin; YU Lin-Wei; HUANG Xin-Fan; LI Wei; XU Jun; CHEN Kun-Ji

    2008-01-01

    @@ The a-SiNx/nanocrystalline silicon (nc-Si)/a-SiNx sandwiched structures with asymmetric double-barrier are fabricated in a plasma enhanced chemical vapour deposition (PECVD) system on p-type Si substrates. The nc-Si layer in thickness 5nm is fabricated from a hydrogen-diluted silane gas by the layer-by-layer deposition technique. The thicknesses of tunnel and control SiNx layers are 3nm and 20nm,respectively. Frequency-dependent capacitance spectroscopy is used to study the electron tunnelling and the storage in the sandwiched structures.Distinct frequency-dependent capacitance peaks due to electrons tunnelling into the nc-Si dots and capacitance-voltage (C- V) hysteresis characteristic due to electrons storage in the nc-Si dots are observed with the same sample.

  2. Geology, mineralization, and fluid inclusion study of the Kuru-Tegerek Au-Cu-Mo skarn deposit in the Middle Tien Shan, Kyrgyzstan

    Science.gov (United States)

    Soloviev, Serguei G.; Kryazhev, Sergey; Dvurechenskaya, Svetlana

    2017-04-01

    The Kuru-Tegerek Cu-Au-Mo deposit is situated in a system of Late Carboniferous subduction-related magmatic arcs of the Middle Tien Shan, which together constitute a metallogenic belt of Cu-Au-Mo (±W) porphyry, with local skarns, deposits. The deposit is related to magnetite-series gabbro-diorite to tonalite intrusion. It contains prograde magnesian and calcic skarns with abundant magnetite, associated with gabbro-diorite, and retrograde skarn with Cu mineralization, formed after intrusion of tonalite. Subsequent propylitic alteration introduced abundant chalcopyrite and pyrrhotite, and native Au culminating in zones overprinting magnetite and garnet skarn. Later quartz-muscovite-carbonate veins, formed after intrusion of late mafic quartz monzogabbro dikes, contain chalcopyrite, pyrite, arsenopyrite and other sulfides and sulfosalts, tellurides, and native Au. The earliest retrograde skarn garnet contains gaseous low-salinity (1.7-3.4 wt.% NaCl eq.) fluid inclusions homogenizing at 460-500 °C into vapor, indicating that the early fluid released from crystallizing magma was a low-density vapor. It was followed by more saline (4.0-5.0 wt.% NaCl eq.), high-temperature (400-440 °C) aqueous fluid, as fluid release from the magma progressed. Boiling of this fluid at temperatures of 420 to 370 °C and a pressure of 350-300 bar produced a low-salinity (0.6-1.2 wt.% NaCl eq.), essentially gaseous, and high-salinity (from 39 to 31 wt.% NaCl eq.) brine, with possible metal (including Cu) partitioning into both gaseous and aqueous-saline phases. Boiling was coeval with sulfide deposition in the retrograde skarn. The latest episode of the retrograde skarn stage included direct separation of saline ( 40-42 wt.% NaCl eq.) fluid from crystallizing magma. The separation of saline ( 40 to 14 wt.% NaCl eq.) fluids from a crystallizing magmatic melt continued during the propylitic stage, when fluid cooling from 370 to 320 °C, together with decreasing fO2, caused Cu and especially

  3. Profilaxis con antibióticos en fracturas de base de cráneo: ¿tiene justificación esa conducta?

    Directory of Open Access Journals (Sweden)

    Justo Luis González González

    1998-08-01

    Full Text Available Se realizó un estudio de 380 pacientes con fractura de la base del cráneo y a 71 de ellos (18,7 % se les administraron antibióticos como profilaxis de la meningoencefalitis y a 309 (81,3 % no se les suministraron estos agentes. Se evaluó la relación entre uso profiláctico o terapéutico de antimicrobianos, localización de la fractura, lesiones asociadas, complicaciones sépticas, edad y sexo, con la aparición de meningoencefalitis. Desarrollaron infección del sistema nervioso central 7 pacientes (1,8 %, 3 de ellos (4,2 % entre los que recibieron profilaxis y 4 (1,3 % entre los que no la recibieron. Se probó que la presencia de meningoencefalitis estaba asociada con el tipo de complicaciones sépticas que además pudieron tener los pacientes, así como al uso de antibióticos como terapéutica de éstas en análisis bivariado, lo que no se corroboró en el multivariado. Se concluye que el empleo de antibióticos profilácticos en estos pacientes no tiene justificación, lo que convierte a esta conducta en una práctica negativa desde el punto de vista médico y económicoA study of 380 patients with basilar skull fracture was performed. 71 (18.7 % of these patients were given antibiotic prophylaxis for meningoencephalitis and 309 (81.3 % were not. The relation of prophylactic or therapeutical use of antimicrobial agents, fracture location, associated injures, septic complications, age and sex to the meningoencephalitis coming out was evaluated. 7 patients (1.8 % developed infections of the central nervous system, 3 (4.2 % had been treated with antibiotics and 4 (1.3 % had not. The bivariate analysis proved that the meningoencephalitis was linked to the type of septic complications that might affect patients as well as the therapeutical use of antibiotics to eliminate them but the multivariate analysis did not demonstrate so. It is concluded that the use of the antibiotic prophylaxis in these patients is not substantiated which turns

  4. Helimagnetic order in bulk MnSi and CoSi/MnSi superlattices

    Science.gov (United States)

    Loh, G. C.; Khoo, K. H.; Gan, C. K.

    2017-01-01

    Skyrmions are nanoscopic whirls of spins that reside in chiral magnets. It is only fairly recent that a plethora of applications for these quasiparticles emerges, especially in data storage. On the other hand, spin spirals are the periodic analogs of skyrmions, and are equally imperative in the course of exploration to enhance our understanding of helimagnetism. In this study, a new infrastructure based on the B20 compound, MnSi is propounded as a hosting material for spin spirals; alternating thin layers of CoSi and MnSi in the superlattice form provides a facile way of varying the properties of the spin spirals across a continuum. Using first-principles calculations based on full-potential linearized augmented plane-wave (FLAPW)-based density functional theory (DFT), the spin order of bulk MnSi, MnSi film, and the CoSi/MnSi superlattice is investigated. Spin dispersion plots as a function of propagation vectors show that the spiral size changes in the presence of CoSi - we find that the size of the spiral is reduced in the superlattice with thin CoSi layers (CoSi:MnSi=1:1 thickness ratio), whilst at a larger CoSi:MnSi=2:1 thickness ratio, the material behaves as a ferromagnet. In a similar fashion, the spin moment and orbital occupancy depend significantly on the thickness of the CoSi layers. However, the exchange interaction between Mn atoms appears to be generally impervious to the presence of CoSi. Succinctly, the CoSi/MnSi superlattice could be an excellent functional material in data storage applications.

  5. Photoluminescence from SiO sub 2 /Si/SiO sub 2 structures

    CERN Document Server

    Photopoulos, P

    2003-01-01

    Si layers were developed on pre-oxidized Si wafers by decomposition of silane in a low pressure chemical vapour deposition reactor. By keeping the deposition time constant (2 min) three sets of samples were fabricated at deposition temperatures equal to 580, 610 and 625 deg C. The deposited Si layers were thinned by high temperature dry oxidation thus forming SiO sub 2 /Si/SiO sub 2 structures. Room temperature photoluminescence (PL) measurements showed that for those samples in which the thickness of the remaining Si layer was greater than approx 6 nm, the spectra exhibited a peak at approx 650 nm. Prolonged oxidations led to the formation of SiO sub 2 /nanocrystalline-Si/SiO sub 2 structures in which the thickness of the remaining nanocrystalline Si (nc-Si) layer was smaller than 3 nm. The PL spectra obtained from these structures were at least ten times stronger compared to the previous ones. The PL peak wavelength exhibited a weak dependence on the nc-Si layer thickness shifting from 800 to 720 nm for nc-...

  6. Strained Si/SiGe MOS transistor model

    Directory of Open Access Journals (Sweden)

    Tatjana Pešić-Brđanin

    2009-06-01

    Full Text Available In this paper we describe a new model of surfacechannel strained-Si/SiGe MOSFET based on the extension of non-quasi-static (NQS circuit model previously derived for bulk-Si devices. Basic equations of the NQS model have been modified to account for the new physical parameters of strained-Si and relaxed-SiGe layers. From the comparisons with measurements, it is shown that a modified NQS MOS including steady-state self heating can accurately predict DC characteristics of Strained Silicon MOSFETs.

  7. Quantum devices using SiGe/Si heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Karunasiri, R.P.G.; Wang, K.L. (Univ. of California, Los Angeles (United States))

    Strained-layer Si{sub 1-x}Ge{sub x}/Si heterostructures have created a great deal of interest due to the potential of integration with the conventional silicon very large scale integrated technology. With the current advances in silicon molecular beam epitaxy (Si-MBE) and other low-temperature epitaxial techniques, many Si{sub 1-x}Ge{sub x}/Si heterojunction devices have been realized. For example, among those realized are avalanche photodiodes, modulation-doped field-effect transistors, heterojunction bipolar transistors, and more recently, resonant tunneling structures, hot-carrier transistors, and quantum well metal-oxide-semiconductor field-effect transistors. In this paper several quantum size effects in strained Si{sub 1-x}Ge{sub x} layers and their potential in device applications will be reviewed. Among those to be discussed are resonant tunneling, miniband transport, and intersubband absorption in Si{sub 1-x}Ge{sub x}/Si superlattice structures, optical properties of monolayer Si{sub m}Ge{sub n} superlattices, and observation of large Stark effect associated with interband transition between quantized states in Si{sub 1-x}Ge{sub x}/Si quantum well structures.

  8. Highly sensitive NIR PtSi/Si-nanostructure detectors

    Science.gov (United States)

    Li, Hua-gao; Guo, Pei; Yuan, An-bo; Long, Fei; Li, Rui-zhi; Li, Ping; Li, Yi

    2016-10-01

    We report a high external quantum efficiency (EQE) photodiode detector with PtSi/Si-nanostructures. Black silicon nanostructures were fabricated by metal-assist chemical etching (MCE), a 2 nm Pt layer was subsequently deposited on black silicon surface by DC magnetron sputtering system, and PtSi/Si-nanostructures were formed in vacuum annealing at 450 oC for 5 min. As the PtSi/Si-nanostructures presented a spiky shape, the absorption of incident light was remarkably enhanced for the repeat reflection and absorption. The breakdown voltage, dark current, threshold voltage and responsivity of the device were investigated to evaluate the performance of the PtSi/Si-nanostructures detector. The threshold voltage and dark currents of the PtSi/Si-nanostructure photodiode tends to be slightly higher than those of the standard diodes. The breakdown voltage remarkably was reduced because of existing avalanche breakdown in PtSi/Si-nanostructures. However, the photodiodes had high response at room temperature in near infrared region. At -5 V reverse bias voltage, the responsivity was 0.72 A/W in 1064 nm wavelength, and the EQE was 83.9%. By increasing the reverse bias voltage, the responsivity increased. At -60 V reverse bias voltage, the responsivity was 3.5 A/W, and the EQE was 407.5%, which means the quantum efficiency of PtSi/Si-nanostructure photodiodes was about 10 times higher than that of a standard diode. Future research includes how to apply this technology to enhance the NIR sensitivity of image sensors, such as Charge Coupled Devices (CCD).

  9. SiC-Si interfacial thermal and mechanical properties of reaction bonded SiC/Si ceramic composites

    Science.gov (United States)

    Hsu, Chun-Yen; Deng, Fei; Karandikar, Prashant; Ni, Chaoying

    Reaction bonded SiC/Si (RBSC) ceramic composites are broadly utilized in military, semiconductor and aerospace industries. RBSC affords advanced specific stiffness, hardness and thermal. Interface is a key region that has to be considered when working with any composites. Both thermal and mechanical behaviors of the RBSC are highly dependent on the SiC-Si interface. The SiC-Si interface had been found to act as a thermal barrier in restricting heat transferring at room temperature and to govern the energy absorption ability of the RBSC. However, up to present, the role of the SiC-Si interface to transport heat at higher temperatures and the interfacial properties in the nanoscale have not been established. This study focuses on these critically important subjects to explore scientific phenomena and underlying mechanisms. The RBSC thermal conductivity with volume percentages of SiC at 80 and 90 vol% was measured up to 1,200 °C, and was found to decrease for both samples with increasing environmental temperature. The RBSC with 90 vol% SiC has a higher thermal conductivity than that of the 80 vol%; however, is still significantly lower than that of the SiC. The interfacial thermal barrier effect was found to decrease at higher temperatures close 1200 °C. A custom-made in-situ tensile testing device which can be accommodated inside a ZEISS Auriga 60 FIB/SEM has been setup successfully. The SiC-Si interfacial bonding strength was measured at 98 MPa. The observation and analysis of crack propagation along the SiC-Si interface was achieved with in-situ TEM.

  10. Radiation-induced plasmons in Si-SiO2

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The first level plasmons of Si in the pure Si state (corresponding to bonding energy (BE) of 116.95 eV) and in the SiO2 state (corresponding to BE of 122.0 eV) of Si-SiO2 prepared by irradiation hard and soft processing were studied with XPS before and after 60Co radiation.The experimental results indicate thatthere was an interface consisting of the two plasmons,this interface was extended by 60Co radiation, the fractions of the plasmon for Si in the Si-SiO2 werechanged with the variation of radiation dosage,the difference of the change in fraction of plasmonsfor the two kinds of samples was that the soft variedfaster than hard, the change of concentrations inplasmons for both hard and soft Si-SiO2 irradiatedin positive bias field were greater than that in bias-free field.The experimental results are explained from the view point of energy absorbed in form of quantization.

  11. Comparison of thermoelectric properties of nanostructured Mg2Si, FeSi2, SiGe, and nanocomposites of SiGe–Mg2Si, SiGe–FeSi2

    Directory of Open Access Journals (Sweden)

    Amin Nozariasbmarz

    2016-10-01

    Full Text Available Thermoelectric properties of nanostructured FeSi2, Mg2Si, and SiGe are compared with their nanocomposites of SiGe–Mg2Si and SiGe–FeSi2. It was found that the addition of silicide nanoinclusions to SiGe alloy maintained or increased the power factor while further reduced the thermal conductivity compared to the nanostructured single-phase SiGe alloy. This resulted in ZT enhancement of Si0.88Ge0.12–FeSi2 by ∼30% over the broad temperature range of 500-950 °C compared to the conventional Si0.80Ge0.20 alloy. The Si0.88Ge0.12–Mg2Si nanocomposite showed constantly increasing ZT versus temperature up to 950 °C (highest measured temperature reaching ZT ∼ 1.3. These results confirm the concept of silicide nanoparticle-in-SiGe-alloy proposed earlier by Mingo et al. [Nano Lett. 9, 711–715 (2009].

  12. Thermal conductivity/diffusivity of SiC-Mullite and SiC-SiC composites

    OpenAIRE

    1987-01-01

    The purposes of this study were to determine as a function of temperature the thermal diffusivity and/or thermal conductivity of SiC-Mullite and SiC-SiC, and to explain the observed behavior in terms of changes in temperature, microstructure, composition, and/or orientation. Materials used in the SiC-Mullite study consisted of single crystal SiC whiskers (prepared from rice hulls or by the vapor-liquid-solid process) dispersed within a polycrystalline mullite matrix. Dur...

  13. Visible photoluminescence related to Si precipitates in Si[sup +]-implanted SiO[sub 2

    Energy Technology Data Exchange (ETDEWEB)

    Shimizu-Iwayama, Tsutomu; Ohshima, Mitsutoshi; Niimi, Tetsuji (Aichi Univ. of Education (Japan). Dept. of Materials Science); Nakao, Setsuo; Saitoh, Kazuo (Government Industrial Research Inst., Nagoya (Japan)); Fujita, Tetsuo (Shizuoka Inst. of Science and Technology (Japan)); Itoh, Noriaki (Nagoya Univ. (Japan). Dept. of Physics)

    1993-08-02

    We have investigated visible photoluminescence from Si[sup +]-implanted SiO[sub 2]. It is found that a luminescence band observed around 2.0 eV in as-implanted specimens disappears on annealing to 500[sup o]C and then a band around 1.7 eV appears on annealing to 1100[sup o]C. We discuss the origin of the luminescence bands in terms of the defects in SiO[sub 2] and the Si nanocrystals grown in SiO[sub 2]. (author).

  14. Estudio cualitativo de las diferencias de género en la elección de opciones académicas en los estudiantes del bachillerato científico-técnico

    Directory of Open Access Journals (Sweden)

    Mª del Carmen RODRÍGUEZ MÉNDEZ

    2016-06-01

    Full Text Available El artículo analiza las causas que ayudan a explicar las diferencias de género en las elecciones académicas a partir de la opinión de los progenitores, docentes y estudiantes. Se ha usado una metodología cualitativa basada en el uso de grupos de discusión. Se organizaron cinco grupos con estudiantes que cursan la modalidad de bachillerato científico-técnico en distintas instituciones de educación secundaria del Principado de Asturias, también se realizaron seis grupos con docentes y dos grupos con progenitores. Los resultados permiten concluir que sigue existiendo un sesgo de género en la elección. La razón fundamental que indican los estudiantes para hacer sus elecciones tiene que ver con lo que hemos denominado la «ideología del gusto innato», pues eligen los estudios porque les gustan o sienten vocación hacia ellos, reforzando los estereotipos de género. El artículo finaliza con unas orientaciones para desarrollar una orientación vocacional no sesgada por razón de género.

  15. The enigmas of The grail. on The ConTroversy over The UniTy of Li Contes deL GraaL of ChréTien de Troyes

    Directory of Open Access Journals (Sweden)

    Victoria Cirlot

    2014-12-01

    Full Text Available This paper presents a review of the controversy about the unity of the last roman of Chrétien de Troyes, Li Contes del Graal which took place in the late fifties between Martí de Riquer, Jean Frappier and Erich Köhler. More than fifty years later, this paper will appraise the contributions that this controversy made to Romance philology, and, in particular, to the assessment of the last work of the Champenian writer.

  16. DESIGN AND FABRICATION OF Si/SiGe PMOSFETs

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Based on theoretical analysis and computer-aided simulation, optimized design prin-ciples for Si/SiGe PMOSFET are given in this paper, which include choice of gate materials, determination of germanium percentage and profile in SiGe channel, optimization of thickness of dioxide and silicon cap layer, and adjustment of threshold voltage.In the light of these principles, a SiGe PMOSFET is designed and fabricated successfully.Measurement indicates that the SiGe PMOSFET's(L=2μ同洒45 mS/mm(300K) and 92 mS/mm(77K) ,while that is 33mS/mm (300K) and 39mS/mm (77K) in Si PMOSFET with the same structure.

  17. DESIGN AND FABRICATION OF Si/SiGe PMOSFETs

    Institute of Scientific and Technical Information of China (English)

    Yang Peifeng; Zhang Jing; Yi Qiang; Fan Zerui; Li Jingchun; Yu Qi; Wang Xiangzhan; Yang Mohua; He Lin; Li Kaicheng; Tan Kaizhou; Liu Daoguang

    2002-01-01

    Based on theoretical analysis and computer-aided simulation, optimized design principles for Si/SiGe PMOSFET are given in this paper, which include choice of gate materials,determination of germanium percentage and profile in SiGe channel, optimization of thickness of dioxide and silicon cap layer, and adjustment of threshold voltage. In the light of these principles,a SiGe PMOSFET is designed and fabricated successfully. Measurement indicates that the SiGe PMOSFET's (L=2μm) transconductance is 45 mS/mm (300K) and 92mS/mm (77K), while that is 33 mS/mm (300K) and 39mS/mm (77K) in Si PMOSFET with the same structure.

  18. Synthesis and characterization of laminated Si/SiC composites

    Directory of Open Access Journals (Sweden)

    Salma M. Naga

    2013-01-01

    Full Text Available Laminated Si/SiC ceramics were synthesized from porous preforms of biogenous carbon impregnated with Si slurry at a temperature of 1500 °C for 2 h. Due to the capillarity infiltration with Si, both intrinsic micro- and macrostructure in the carbon preform were retained within the final ceramics. The SEM micrographs indicate that the final material exhibits a distinguished laminar structure with successive Si/SiC layers. The produced composites show weight gain of ≈5% after heat treatment in air at 1300 °C for 50 h. The produced bodies could be used as high temperature gas filters as indicated from the permeability results.

  19. An efficient Si light-emitting diode based on an n- ZnO/SiO2-Si nanocrystals-SiO2/p-Si heterostructure.

    Science.gov (United States)

    Sun, Edward; Su, Fu-Hsiang; Shih, Ying-Tsang; Tsai, Hung-Ling; Chen, Ching-Huang; Wu, Mong-Kai; Yang, Jer-Ren; Chen, Miin-Jang

    2009-11-04

    Si nanocrystals embedded in a SiO2 matrix and an n-type Al-doped ZnO (ZnO:Al) layer were applied to improve the external quantum efficiency from Si in n- ZnO/SiO2-Si nanocrystals-SiO2/p-Si heterojunction light-emitting diodes (LEDs). The Si nanocrystals were grown by low pressure chemical vapor deposition and the ZnO:Al layer was prepared by atomic layer deposition. The n-type ZnO:Al layer acts as an electron injection layer, a transparent conductive window, and an anti-reflection coating to increase the light extraction efficiency. Owing to the spatial confinement of carriers and surface passivation by the surrounding SiO2, the Si nanocrystals embedded in the SiO2 matrix lead to a significant enhancement of the light emission efficiency from Si. An external quantum efficiency up to 4.3 x 10(-4) at the wavelength corresponding to the indirect bandgap of Si was achieved at room temperature.

  20. "Es la preocupación que nos tiene ahorita traumados". El impacto del cubrimiento sobre la violencia en la prensa escrita

    Directory of Open Access Journals (Sweden)

    Chantal Isabel Lara Guevara

    2013-01-01

    Full Text Available Si bien no es novedad el uso de la violencia en medios de comunicación, sí ha evolucionado la percepción de la cobertura informativa de la violencia, por ello fue importante comprender y describir el impacto del cubrimiento sobre la violencia de los periódicos: El Sol del Bajío, La Prensa, A. M. y Al Día, en ciudadanos mayores de 18 años, y a su vez explorar la apreciación de las personas involucradas en el proceso de edición de los diarios sobre la producción de tal contenido. Para dichos fines se utilizó una metodología cualitativa del análisis del discurso; se obtuvieron respuestas como "hace más agresiva a la gente", entre otras, constatando que el cubrimiento de la violencia genera un impacto de temor y preocupación en la audiencia. Se propone a las empresas editoriales supervisar el manejo y el tratamiento que le dan a la nota roja.

  1. Miscibility of NiSi{sub 2}, FeSi{sub 2} and Cu{sub 3}Si

    Energy Technology Data Exchange (ETDEWEB)

    Langkau, Sabine [IMKM, Universitaet Leipzig, Scharnhorststr. 20, 04275 Leipzig (Germany)], E-mail: Langkau@rz.uni-leipzig.de; Heuer, Matthias [BerlinSolar GmbH, Magnusstrasse 11, 12489 Berlin (Germany); Hoebler, Hans-Joachim; Bente, Klaus; Kloess, Gert [IMKM, Universitaet Leipzig, Scharnhorststr. 20, 04275 Leipzig (Germany)

    2009-04-17

    Ternary and quaternary chemical composition ranges of the phases NiSi{sub 2}, FeSi{sub 2}, Cu{sub 3}Si, NiSi and FeSi were determined using electron-microprobe-measurements. The system NiSi{sub 2}-Cu{sub 3}Si was found to be eutectic and most probably quasi-binary. Furthermore lattice constants of NiSi{sub 2} and Ni{sub 0.62}Fe{sub 0.41}Si{sub 1.98} were determined by means of X-ray diffraction (XRD)

  2. Revisión de los modelos de producción de voz después de una laringectomía total: opciones de calidad de voz

    Directory of Open Access Journals (Sweden)

    Roberto Fernández-Baillo

    2011-12-01

    Full Text Available El paciente laringectomizado es aquel que debido a un proceso cancerígeno ha sido sometido a una intervención quirúrgica cuyo resultado es la extirpación total de la laringe. Como consecuencia de esta operación el paciente sufre una serie de modificaciones anatómicas que conllevan la alteración y/o pérdida de determinadas funciones. Siendo la pérdida de la voz, y por tanto de la comunicación oral, la limitación principal a la que se enfrentan estos pacientes. Es por ello, que el proceso de tratamiento y rehabilitación post-quirúrgico tiene como uno de sus objetivos principales el restablecimiento de la comunicación oral. Para ello se deberá dotar al paciente de una nueva fuente de sonido (neo-glotis, la cual tendrá que suplir o emular la función vibratoria anteriormente realizada por glotis laríngea. El objetivo de este trabajo es analizar desde una perspectiva biomecánica y acústicas los distintos tipos de voces que pueden representar una opción para el paciente laringectomizado. Se pretende mostrar las ventajas y limitaciones de cada modelo de producción, de una forma clara y objetiva, comprensible tanto para el clínico como para el paciente, con el fin de orientar en la toma de decisiones. Finalmente se realiza un análisis acústico de la voz de cuatro pacientes femeninos laringectomizadas. Cada muestra de voz se corresponde con un modelo de producción diferente: laringe artificial, prótesis fonatoria y erigmofonía.

  3. Joining of SiC ceramics and SiC/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Rabin, B.H. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

    1996-08-01

    This project has successfully developed a practical and reliable method for fabricating SiC ceramic-ceramic joints. This joining method will permit the use of SiC-based ceramics in a variety of elevated temperature fossil energy applications. The technique is based on a reaction bonding approach that provides joint interlayers compatible with SiC, and excellent joint mechanical properties at temperatures exceeding 1000{degrees}C. Recent emphasis has been given to technology transfer activities, and several collaborative research efforts are in progress. Investigations are focusing on applying the joining method to sintered {alpha}-SiC and fiber-reinforced SiC/SiC composites for use in applications such as heat exchangers, radiant burners and gas turbine components.

  4. Joining of SiC ceramics and SiC/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Rabin, B.H. [Idaho National Engineering Lab., Idaho Falls, ID (United States)

    1995-08-01

    This project has successfully developed a practical and reliable method for fabricating SiC ceramic-ceramic joints. This joining method has the potential to facilitate the use of SiC-based ceramics in a variety of elevated temperature fossil energy applications. The technique is based on a reaction bonding approach that provides joint interlayers compatible with SiC, and excellent joint mechanical properties at temperatures exceeding 1000{degrees}C. Recent efforts have focused on transferring the joining technology to industry. Several industrial partners have been identified and collaborative research projects are in progress. Investigations are focusing on applying the joining method to sintered a-SiC and fiber-reinforced SiC/SiC composites for use in applications such as heat exchangers, radiant burners and gas turbine components.

  5. Methods of radiation effects evaluation of SiC/SiC composite and SiC fibers

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    This report covers material presented at the IEA/Jupiter Joint International Workshop on SiC/SiC Composites for Fusion structural Applications held in conjunction with ICFRM-8, Sendai, Japan, Oct. 23--24, 1997. Several methods for radiation effects evaluation of SiC fibers and fiber-reinforced SiC/SiC composite are presented.

  6. Al versus Si competition in FeSiAl alloys

    Energy Technology Data Exchange (ETDEWEB)

    Legarra, E. [Dpto. Electricidad y Electronica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco (UPV/EHU), CP 644, 48080 Bilbao (Spain)], E-mail: estibaliz.legarra@ehu.es; Apinaniz, E. [Dpto. Fisica Aplicada I, Escuela de Ingenieria Tecnica Superior, Universidad del Pais Vasco, Alameda de Urquijo s/n 48013 Bilbao (Spain); Plazaola, F. [Dpto. Electricidad y Electronica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco (UPV/EHU), CP 644, 48080 Bilbao (Spain); Jimenez, J.A. [Centro Nacional de Investigaciones Metalurgicas (CENIM), Avda. Gregorio del amo 8, 28040 Madrid (Spain); Pierna, A.R. [Chemical Engineering and Environmental Department, UPV/EHU, Box 1379, 20008 San Sebastian (Spain)

    2008-10-15

    In FeSiAl alloys, when Si substitutes for Al, important changes take place in the magnetism as well as in the structural properties. Alloys in the two composition series Fe{sub 75}Al{sub 25-x}Si{sub x} (x=0, 7.5, 12.5, 17.5, 25) and Fe{sub 70}Al{sub 30-x}Si{sub x} (x=0, 9, 15, 21, 30) were prepared by induction melting; afterwards they were crushed and then annealed in order to recover the DO{sub 3} stable phase. The deformed FeAl samples show larger lattice parameters than the ordered ones; however, this difference ({delta}a) decreases when Si substitutes for Al until it becomes zero (i.e. until the ordered samples and the deformed ones have the same lattice parameters). This trend is the same for both sample series and does not depend on the Fe content of the alloy. However, the magnetization has a different behaviour depending on the Fe content. For deformed Fe{sub 75}Al{sub 25-x}Si{sub x} alloys the saturation magnetization decreases with increasing Si content while for Fe{sub 70}Al{sub 30-x}Si{sub x} deformed alloys the saturation magnetization has a plateau in which the saturation magnetization values do not vary.

  7. SI and Non-SI Units of Concentration: A Truce?

    Science.gov (United States)

    Rich, Ronald L.

    1986-01-01

    Questions the current usage of the International System of Units (called SI units) in representing chemical notation and terminology. Suggests several additions to the system that relate to concentrations. Outlines new symbols for distinguishing between "concentration" and "molality." Includes tables to illustrate the proposed SI units. (TW)

  8. Informe sintético del Componente “Sodas” del “Sistema de Gestión Ambiental Integral (SiGAI) en la Universidad de Costa Rica”, en su eje medular sobre Gestión Ambiental Integral para los Centros de alimentación.

    OpenAIRE

    Torrealba Suárez, Isa M.; Salazar, Gerlin; Alfaro-Mora, Gainer; Astorga, Yamileth

    2012-01-01

    Corresponde al proyecto "Sistema de gestión ambiental integral (SiGAI) para la Universidad de Costa Rica" En este documento se sintetiza como ha sido la labor de gestión ambiental forjada a través del SiGAI en los centros de la alimentación de la Universidad de Costa Rica. Si bien se tiene una perspectiva histórica, se enfocan principalmente los avances logrados en el periodo feb/2011 a abril/2012. Desde el 2007 el componente de "gestión ambiental integral (GAI) en las sodas" es un ej...

  9. Synthesis and structural property of Si nanosheets connected to Si nanowires using MnCl{sub 2}/Si powder source

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Erchao [Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Ueki, Akiko [Toyota Central R& D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Meng, Xiang [Graduate School of Science and Technology, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Suzuki, Hiroaki [Graduate School of Engineering, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan); Itahara, Hiroshi [Toyota Central R& D Labs., Inc., 41-1 Yokomichi, Nagakute, Aichi 480-1192 (Japan); Tatsuoka, Hirokazu, E-mail: tatsuoka.hirokazu@shizuoka.ac.jp [Graduate School of Integrated Science and Technology, Shizuoka University, 3-5-1 Johuku, Naka-ku, Hamamatsu, Shizuoka 432-8561 (Japan)

    2016-08-15

    Graphical abstract: Si nanosheets connected to Si nanowires synthesized using a MnCl{sub 2}/Si powder source with an Au catalyst avoid the use of air-sensitive SiH{sub 4} or SiCl{sub 4}. It was evident from these structural features of the nanosheets (leaf blade) with nanowires (petiole) that the nanosheets were formed by the twin-plane reentrant-edge mechanism. The feature of the observed lattice fringes of the Si(111) nanosheets was clearly explained by the interference with the extra diffraction spots that arose due to the reciprocal lattice streaking effect. - Highlights: • New Si nanosheets connected to Si nanowires were synthesized using MnCl{sub 2}/Si powders. • The synthesis method has benefits in terms of avoiding air sensitive SiH{sub 4} or SiCl{sub 4}. • Structural property and electron diffraction of the Si nanosheets were clarified. • Odd lattice fringes of the Si nanosheets observed by HRTEM were clearly explained. - Abstract: Si nanosheets connected to Si nanowires were synthesized using a MnCl{sub 2}/Si powder source with an Au catalyst. The synthesis method has benefits in terms of avoiding conventionally used air-sensitive SiH{sub 4} or SiCl{sub 4}. The existence of the Si nanosheets connected to the Si<111> nanowires, like sprouts or leaves with petioles, was observed, and the surface of the nanosheets was Si{111}. The nanosheets were grown in the growth direction of <211> perpendicular to that of the Si nanowires. It was evident from these structural features of the nanosheets that the nanosheets were formed by the twin-plane reentrant-edge mechanism. The feature of the observed lattice fringes, which do not appear for Si bulk crystals, of the Si(111) nanosheets obtained by high resolution transmission electron microscopy was clearly explained due to the extra diffraction spots that arose by the reciprocal lattice streaking effect.

  10. Towards a new High Resolution Orthophoto Mosaic Circa 1976 for the Northern Eurasia: Assessing the Potential of Declassified Hexagon KH-9 Images (Tien Shan Region, Central Asia Case Study)

    Science.gov (United States)

    Surazakov, A.; Aizen, V.; Aizen, E.

    2008-12-01

    Repeated satellite-based inventories of land-cover and land-use, such as Global Landsat Orthorectified data collection (28.5-57 m resolution), are crucial for understanding dynamics of terrestrial ecosystems. However, accurate estimation of dynamics of certain natural and man-made phenomena (mountain glaciers, lakes, urban and agricultural areas) often requires higher resolution remote sensed datasets (with resolution below 10-20 m). In the Northern Eurasia, such datasets are often too expensive or unavailable for a regional study (for example SPOT, TK-350, aerial photography) or span only the last decade (for example Landsat ETM, ASTER, IRS, ALOS/PRISM). This study estimates accuracy and potential of historical Hexagon KH-9 images for generation of a high resolution orthorectified product circa 1976 on a regional scale. The Hexagon KH-9 images were declassified by the U.S. Government in 2002. Although the KH-9 dataset coverage is global, it is particularly rich over the Northern Eurasia where multiple repeat images were acquired for the U.S. Defense Mapping Agency. Using a set of KH-9 images we generated a high quality orthorectified mosaic for the area of Tien Shan mountain system (about 550,000 km2) with resolution of 6-9 m and horizontal accuracy about 9 m. The panchromatic orthophoto mosaic is a unique dataset that for the first time portrays the remote region with such detail and, at the same time, extends the retrospective for more than three decades. The mosaic enabled creation of a glacier inventory for the Tien Shan mountains circa 1976. The Tien Shan case study demonstrated that Hexagon KH-9 images can be used for generation of a land-cover/land-use inventory circa 1976 on regional scales and with high spatial resolution.

  11. A note on the Sumerian expression SI-ge4-de3/dam

    Directory of Open Access Journals (Sweden)

    Widell, Magnus

    2002-12-01

    Full Text Available The expression SI-ge4-dam/de3 appears in some of the loan documents of the Ur III period where it was used to establish the interest rate or the loan fee. In addition, it is sometimes preceded by ki-ba 'in its/this place/ground' or, in some cases, ma2 -a 'in the boat'. The regular verb SI.g was closely related, perhaps even synonymous with, the reduplication verb ḡar/ḡa2-ḡa2 'to put' or 'to place'. While it may be concluded that SI-ge4-dam/de3 had nothing to do with the verb si 'to fill' or gi4 'to return', the correct analysis of the expression remains somewhat uncertain. The article proposes that the SI should be read se and understood as a phonetic writing for the regular verb se3.g 'to put', 'to place'. The combination of the verb with the ki-ba may suggest that a more parochial form of keeping products existed side by side with the large centralized granaries and storehouses of the city.La expresión SI-ge4-dam/de3 aparece en algunos contratos de préstamo del período de Ur III, donde se empleaba para determinar el interés de dicho préstamo. Por otra parte, este término se hallaba a veces precedido de ki-ba 'en su/este lugar/suelo', y en algunos casos por ma2 -a 'en la barca'. El verbo regular SI.g está muy relacionado (quizás es incluso sinónimo con el verbo de la clase de la reduplicación ḡar/ḡa2-ḡa2 'poner' o 'colocar'. Mientras que puede concluirse que SI-ge4-dam/de3 no tiene nada que ver con el verbo si 'llenar', ni con gi4 'regresar, devolver', el análisis correcto de la expresión sigue siendo, de algún modo, incierto. En el artículo se propone que SI puede leerse como se , entendiéndolo como una escritura fonética del verbo regular se3.g 'poner', 'colocar'. La combinación del verbo con ki-ba podría indicar que, junto a los grandes graneros y almacenes centrales de la ciudad, había un modo distinto y más modesto de conservar los productos.

  12. Biomorphous SiSiC/Al-Si ceramic composites manufactured by squeeze casting: microstructure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Zollfrank, C.; Travitzky, N.; Sieber, H.; Greil, P. [Department of Materials Science, Glass and Ceramics, University of Erlangen-Nuernberg (Germany); Selchert, T. [Advanced Ceramics Group, Technical University of Hamburg-Harburg (Germany)

    2005-08-01

    SiSiC/Al-Si composites were fabricated by pressure-assisted infiltration of an Al-Si alloy into porous biocarbon preforms derived from the rattan palm. Al-Si alloy was found in the pore channels of the biomorphous SiSiC preform, whereas SiC and carbon were present in the struts. The formation of a detrimental Al{sub 4}C{sub 3}-phase was not observed in the composites. A bending strength of 200 MPa was measured. The fractured surfaces showed pull-out of the Al-alloy. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  13. Improvement of parameters in a-Si(p)/c-Si(n)/a-Si(n) solar cells

    Science.gov (United States)

    Moustafa Bouzaki, Mohammed; Aillerie, Michel; Ould Saad Hamady, Sidi; Chadel, Meriem; Benyoucef, Boumediene

    2016-10-01

    We analyzed and discussed the influence of thickness and doping concentration of the different layers in a-Si(p)/c-Si(n)/a-Si(n) photovoltaic (PV) cells with the aim of increasing its efficiency while decreasing its global cost. Compared to the efficiency of a standard marketed PV cell, elaborated with a ZnO transparent conductive oxide (TCO) layer but without Back Surface Field (BSF) layer, an optimization of the thickness and dopant concentration of both the emitter a-Si(p) and absorber c-Si(n) layers will gain about 3% in the global efficiency of the cell. The results also reveal that with introduction of the third layer, i.e. the BSF layer, the efficiency always achieves values above 20% and all other parameters of the cell, such as the open-circuit voltage, the short-circuit current and the fill-factor, are strongly affected by the thickness and dopant concentration of the layers. The values of all parameters are given and discussed in the paper. Thereby, the simulation results give for an optimized a-Si(p)/c-Si(n)/a-Si(n) PV cells the possibility to decrease the thickness of the absorber layer down to 50 μm which is lower than in the state-of-the-art. This structure of the cell achieves suitable properties for high efficiency, cost-effectiveness and reliable heterojunction (HJ) solar cell applications.

  14. Fabrication and Mechanical Properties of SiCw(p/SiC-Si Composites by Liquid Si Infiltration using Pyrolysed Rice Husks and SiC Powders as Precursors

    Directory of Open Access Journals (Sweden)

    Dan Zhu

    2014-03-01

    Full Text Available Dense silicon carbide (SiC matrix composites with SiC whiskers and particles as reinforcement were prepared by infiltrating molten Si at 1550 °C into porous preforms composed of pyrolysed rice husks (RHs and extra added SiC powder in different ratios. The Vickers hardness of the composites showed an increase from 18.6 to 21.3 GPa when the amount of SiC added in the preforms was 20% (w/w, and then decreased to 17.3 GPa with the increase of SiC added in the preforms up to 80% (w/w. The values of flexural strength of the composites initially decreased when 20% (w/w SiC was added in the preform and then increased to 587 MPa when the SiC concentration reached 80% (w/w. The refinement of SiC particle sizes and the improvement of the microstructure in particle distribution of the composites due to the addition of external SiC played an effective role in improving the mechanical properties of the composites.

  15. Fabrication and evaluation of propagation loss of Si/SiGe/Si photonic-wire waveguides for Si based optical modulator

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Younghyun, E-mail: yhkim@mosfet.t.u-tokyo.ac.jp [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Takenaka, Mitsuru [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Osada, Takenori; Hata, Masahiko [Sumitomo Chemical Co. Ltd., 6 Kitahara, Tsukuba, Ibaraki 300-3294 (Japan); Takagi, Shinichi [Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan)

    2014-04-30

    We have characterized photonic-wire waveguides with Si/SiGe/Si heterostructure ribs for Si-based optical modulators. The Si (80 nm)/Si{sub 0.72}Ge{sub 0.28} (40 nm) layers grown on Si-on-insulator by molecular beam epitaxy for optical modulators were evaluated by in-situ reflection high-energy electron diffraction, atomic force microscope, X-ray diffraction and Raman spectroscopy, exhibiting that the fully-strained highly-crystalline SiGe layer was obtained. We have evaluated the propagation loss of the Si/strained SiGe/Si photonic-wire waveguides. The wavelength dependence of the propagation loss exhibits the bandgap narrowing of the strained Si{sub 0.72}Ge{sub 0.28}, while the optical absorption of the strained Si{sub 0.72}Ge{sub 0.28} is not significant for the optical modulator application at 1.55-μm wavelength. - Highlights: • We have characterized photonic-wire waveguides with Si/SiGe/Si heterostructure ribs. • The Si/Si{sub 0.72}Ge{sub 0.28} grown on Si-on-insulator were evaluated to be fully strained. • We have fabricated and evaluated the Si/strained SiGe/Si photonic-wire waveguides. • The wavelength dependence exhibits bandgap narrowing of the strained Si{sub 0.72}Ge{sub 0.28}. • Optical absorption of the SiGe is not significant for optical modulators at 1.55 μm.

  16. Ge-on-Si optoelectronics

    Energy Technology Data Exchange (ETDEWEB)

    Liu Jifeng, E-mail: Jifeng.Liu@Dartmouth.edu [Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 (United States); Camacho-Aguilera, Rodolfo; Bessette, Jonathan T.; Sun, Xiaochen [Microphotonics Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Wang Xiaoxin [Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 (United States); Cai Yan; Kimerling, Lionel C.; Michel, Jurgen [Microphotonics Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2012-02-01

    Electronic-photonic synergy has become an increasingly clear solution to enhance the bandwidth and improve the energy efficiency of information systems. Monolithic integration of optoelectronic devices is the ideal solution for large-scale electronic-photonic synergy. Due to its pseudo-direct gap behavior in optoelectronic properties and compatibility with Si electronics, epitaxial Ge-on-Si has become an attractive solution for monolithic optoelectronics. In this paper we will review recent progress in Ge-on-Si optoelectronics, including photodetectors, electroabsorption modulators, and lasers. The performance of these devices has been enhanced by band-engineering such as tensile strain and n-type doping, which transforms Ge towards a direct gap material. Selective growth reduces defect density and facilitates monolithic integration at the same time. Ge-on-Si photodetectors have approached or exceeded the performance of their III-V counterparts, with bandwidth-efficiency product > 30 GHz for p-i-n photodiodes and bandwidth-gain product > 340 GHz for avalanche photodiodes. Enhanced Franz-Keldysh effect in tensile-strained Ge offers ultralow energy photonic modulation with < 30 fJ/bit energy consumption and > 100 GHz intrinsic bandwidth. Room temperature optically-pumped lasing as well as electroluminescence has also been achieved from the direct gap transition of band-engineered Ge-on-Si waveguides. These results indicate that band-engineered Ge-on-Si is promising to achieve monolithic active optoelectronic devices on a Si platform.

  17. Si Isotopes of Brownleeite

    Science.gov (United States)

    Nakamura-Messenger, K.; Messenger, Scott R.; Ito, M.; Keller, L. P.; Clemett, S. J.; Jones, J. H.; Tatsuoka, H.; Zolensky, M. E.; Tatsuoka, H.

    2010-01-01

    Brownleeite is a manganese silicide, ideally stoichiometric MnSi, not previously observed in nature until its discovery within an interplanetary dust particle (IDP) that likely originated from a comet [1]. Three discrete brownleeite grains in the IDP L2055 I3 (4 microns in size, hereafter IDP I3) were identified with maximum dimensions of 100, 250 and 600 nm and fully analyzed using scanning-transmission electron microscopy (STEM) [1]. One of the grains (100 nm in size) was poikilitically enclosed by low-Fe, Mn-enriched (LIME) olivine. LIME olivine is epitaxial to the brownleeite with the brownleeite (200) parallel to the olivine c* [1]. LIME olivine is an enigmatic phase first reported from chondritic porous IDPs and some unequilibrated ordinary chondrites [ 2], that is commonly observed in chondritic-porous IDPs. Recently, LIME olivine has been also found in comet Wild-2 (Stardust) samples [3], indicating that LIME olivine is a common mineral component of comets. LIME olivine has been proposed to form as a high temperature condensate in the protosolar nebula [2]. Brownleeite grains also likely formed as high-temperature condensates either in the early Solar System or in the outflow of an evolved star or supernova explosion [1]. The isotopic composition of the brownleeite grains may strongly constrain their ultimate source. To test this hypothesis, we performed isotopic analyses of the brownleeite and the associated LIME olivine, using the NASA/JSC NanoSIMS 50L ion microprobe.

  18. Formation of extended defects in SiGe/Si heterostructures with SiGeC intermediate layers

    Energy Technology Data Exchange (ETDEWEB)

    Vdovin, V.I.; Reznik, V.Ya. [Institute for Chemical Problems of Microelectronics, Moscow (Russian Federation); Torack, T.A.; Fei, Lu [MEMC Inc, St Peters, MO (United States); Mil' vidskii, M.G. [Institute of Rare Metals ' Giredmet' , Moscow (Russian Federation); Falster, R. [MEMC Electronic Materials SpA, Novara (Italy)

    2007-07-01

    The generation of misfit dislocations (MDs) and stacking faults (SFs) was studied by TEM and preferential chemical etching in multilayer Si(001)/SiGe/SiGeC(10 nm)/SiGe/Si heterostructures grown by CVD at 650 C. Prior to growth of Si layer, the other part of heterostructure was annealed at 950 C in the growth chamber to get relaxed buffer layers and strained Si layer free of extended defects. We used SiGe alloys with Ge content of 24 at.% and C content of 0.5 at.%. Carbon in the strained SiGe matrix was found to promote high rates of strain relaxation through the nucleation of perfect dislocation loops close to the interface with Si substrate. For Si layer thickness >10 nm, threading dislocations split in these layers under tensile strain to form SFs. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Organic thin film transistors with a SiO2/SiNx/SiO2 composite insulator layer

    Institute of Scientific and Technical Information of China (English)

    Liu Xiang; Liu Hui

    2011-01-01

    We have investigated a SiO2/SiNx/SiO2 composite insulation layer structured gate dielectric for an organic thin film transistor (OTFT) with the purpose of improving the performance of the SiO2 gate insulator.The SiO2/SiNx/SiO2 composite insulation layer was prepared by magnetron sputtering.Compared with the same thickness of a SiO2 insulation layer device,the SiO2/SiNx/SiO2 composite insulation layer is an effective method of fabricating OTFT with improved electric characteristics and decreased leakage current.Electrical parameters such as carrier mobility by field effect measurement have been calculated.The performances of different insulating layer devices have been studied,and the results demonstrate that when the insulation layer thickness increases,the off-state current decreases.

  20. P-type poly-Si prepared by low-temperature aluminum-induced crystallization and doping for solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Yasuhiro; Yu, Zhenrui; Morales-Acevedo, Arturo [CINVESTAV-IPN, Mexico, D.F. (Mexico)

    2000-07-01

    P-type poly-Si thin films prepared by low temperature aluminum-induced crystallization and doping are reported. The starting material was boron-doped a-Si:H prepared by PECVD on glass substrates. Aluminum layers with different thickness were evaporated on a-Si:H surface and conventional thermal annealing was performed at temperatures ranging from 300 to 550 Celsius degrees. XRD, SIMS, and Hall effect measurements were carried out to characterize the annealed Al could be crystallized at temperature as low as 300 Celsius degrees in 60 minutes. This material has high carrier concentration as well as high Hall mobility and can be used as a p-layer of seed layer for thin film poly-Si solar cells. The technique reported here is compatible with PECVD process. [Spanish] Se informa sobre la preparacion de peliculas delgadas tipo P y Poli-Si mediante la cristalizacion inducida de aluminio a baja temperatura y el dopado. El material inicial era de boro dopado y a-Si:H preparado PECVD sobre substratos de vidrio. Se evaporaron capas de aluminio de diferente espesor sobre una superficie de a-Si:H y se llevo a cabo un destemplado termico convencional a temperaturas que varian entre 300 y 500 grados Celsius. Se llevaron a cabo mediciones de XRB, SIMS y del efecto Hall para caracterizar el aluminio destemplado para que pudiera ser cristalizado a temperaturas tan bajas como 300 grados Celsius en 60 minutos. Este material tiene una alta concentracion portadora asi como una alta movilidad Hall y puede usarse como una capa de semilla para celdas solares de pelicula delgada Poli-Si. La tecnica reportada aqui es compatible con el proceso PECVD.

  1. Study of New Way about Si/Si Bonding

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A new set of technique was adopted in bonding Si-Si by using Ge (Ⅳ element),which is used as the substitute for the common hydrophilic method. The bond layer has no holes, and the edge bond-rate amounts to above 98%, and the bond strength is above 2156 Pa. By doping the same kind of dopant with low-resistance in Ge, the stress compensation was realized.

  2. Formation of microtubes from strained SiGe/Si heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Qin, H [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Shaji, N [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Merrill, N E [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Kim, H S [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Toonen, R C [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Blick, R H [Laboratory of Molecular-scale Engineering, Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706 (United States); Roberts, M M [Department of Materials Science and Engineering, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706 (United States); Savage, D E [Department of Materials Science and Engineering, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706 (United States); Lagally, M G [Department of Materials Science and Engineering, University of Wisconsin-Madison, 1500 Engineering Drive, Madison, WI 53706 (United States); Celler, G [SOITEC USA Inc., 2 Centennial Drive, Peabody, MA 01960 (United States)

    2005-11-15

    We report the formation of micrometre-sized SiGe/Si tubes by releasing strained SiGe/Si bilayers from substrates in a wet chemical-etching process. In order to explore statistical studies of dynamic formation of microtubes, we fabricated arrays of square bilayers. Due to the dynamic change in curvature of the bilayers, and hence the underlying etch channels, the etching process deviates from a transport-controlled regime to one of kinetic controlled. We identified two distinct modes of etching. A slow etching mode is associated with symmetric surface deformation in which the bilayers mostly retain their initial pattern. In the fast mode, bilayers are asymmetrically deformed while large etch channels are induced and etching becomes kinetically controlled. Etch rate dispersion is directly related to the degree of asymmetry in surface deformation. When the dimensions of the bilayers become significantly larger than the curvature radius, kinetic etching dominates. During the formation of tubes, SiGe/Si bilayers strongly interact with the liquid environment of etchant and solvent. Assisted by the surface tension of evaporating liquids, the tubes are drawn near the substrate and eventually fixed to it because of van der Waals forces. Our study illuminates the dynamic etching and curling processes involved with and provides insight on how a uniform etch rate and consistent curling directions can be maintained.

  3. Formation of microtubes from strained SiGe/Si heterostructures

    Science.gov (United States)

    Qin, H.; Shaji, N.; Merrill, N. E.; Kim, H. S.; Toonen, R. C.; Blick, R. H.; Roberts, M. M.; Savage, D. E.; Lagally, M. G.; Celler, G.

    2005-11-01

    We report the formation of micrometre-sized SiGe/Si tubes by releasing strained SiGe/Si bilayers from substrates in a wet chemical-etching process. In order to explore statistical studies of dynamic formation of microtubes, we fabricated arrays of square bilayers. Due to the dynamic change in curvature of the bilayers, and hence the underlying etch channels, the etching process deviates from a transport-controlled regime to one of kinetic controlled. We identified two distinct modes of etching. A slow etching mode is associated with symmetric surface deformation in which the bilayers mostly retain their initial pattern. In the fast mode, bilayers are asymmetrically deformed while large etch channels are induced and etching becomes kinetically controlled. Etch rate dispersion is directly related to the degree of asymmetry in surface deformation. When the dimensions of the bilayers become significantly larger than the curvature radius, kinetic etching dominates. During the formation of tubes, SiGe/Si bilayers strongly interact with the liquid environment of etchant and solvent. Assisted by the surface tension of evaporating liquids, the tubes are drawn near the substrate and eventually fixed to it because of van der Waals forces. Our study illuminates the dynamic etching and curling processes involved with and provides insight on how a uniform etch rate and consistent curling directions can be maintained.

  4. The origin of blue photoluminescence from nc-Si/SiO2 multilayers

    Institute of Scientific and Technical Information of China (English)

    Ma Zhong-Yuan; Xu Ling; Huang Xin-Fan; Chen Kun-Ji; Feng Duan; Guo Si-Hua; Chen De-Yuan; Wei De-Yuan; Yao Yao; Zhou Jiang; Huang Rui; Li Wei; Xu Jun

    2008-01-01

    Intensive blue photoluminescence (PL) was observed at room temperature from the nanocrystalline-Si/SiO2 (ncSi/SiO2) multilayers (MLs) obtained by thermal annealing of SiO/SiO2 MLs for the first time.By controlling the size of nc-Si formed in SiO sublayer from 3.5 to 1.5 nm,the PL peak blueshifts from 457 to 411 nm.Combining the analysis of TEM,Raman and absorption measurement,this paper attributes the blue PL to multiple luminescent centres at the interface of nc-Si and SiO2.

  5. SiC/Si's CRYSTALLOGRAPHIC ORIENTATION RELATIONSHIP IN SiCp/Al-Si COMPOSITES%SiCp/Al-Si复合材料中SiC/Si的晶体学位向关系

    Institute of Scientific and Technical Information of China (English)

    隋贤栋; 罗承萍; 欧阳柳章; 骆灼旋

    2000-01-01

    用TEM研究了离心铸造和挤压铸造的SiCp/ZL109复合材料,发现Si优先在SiC表面上形核、长大,并形成大量"界面Si"及SiC/Si界面.SiC与Si之间不存在固定的晶体学位向关系,但存在(1101)sic//(111)si,[1120]sic∥[112]si优先出现的位向关系,而(0001)sic∥(111)si不是优先出现的位向关系.

  6. Dimensionless Units in the SI

    CERN Document Server

    Mohr, Peter J

    2014-01-01

    The International System of Units (SI) is supposed to be coherent. That is, when a combination of units is replaced by an equivalent unit, there is no additional numerical factor. Here we consider dimensionless units as defined in the SI, {\\it e.g.} angular units like radians or steradians and counting units like radioactive decays or molecules. We show that an incoherence may arise when different units of this type are replaced by a single dimensionless unit, the unit "one", and suggest how to properly include such units into the SI in order to remove the incoherence. In particular, we argue that the radian is the appropriate coherent unit for angles and that hertz is not a coherent unit in the SI. We also discuss how including angular and counting units affects the fundamental constants.

  7. THE STRUCTURE OF LIQUID LI-SI ALLOYS

    NARCIS (Netherlands)

    DEJONG, PHK; VERKERK, P; VANDERLUGT, W; DEGRAAF, LA

    1993-01-01

    The reverse Monte Carlo method is used to analyse neutron diffraction data on liquid Li65Si35. A well defined Si-Si partial pair correlation function is obtained with strong indications for covalent Si-Si bonds. It is also clear that most of the Si4 stars and Si5 rings occurring in solid Li12Si7 hav

  8. SEMICONDUCTOR MATERIALS Photoelectric conversion characteristics of ZnO/SiC/Si heterojunctions

    Science.gov (United States)

    Xiaopeng, Wu; Xiaoqing, Chen; Lijie, Sun; Shun, Mao; Zhuxi, Fu

    2010-10-01

    A series of n-ZnO/n-SiC/p-Si and n-ZnO/p-Si heterojunctions were prepared by DC sputtering. Their structural properties, I—V curves, photovoltaic effects and photo-response spectra were studied. The photoelectric conversion characteristics of n-ZnO/n-SiC/p-Si and n-ZnO/p-Si heterojunctions were investigated. It is found that the photoelectric conversion efficiency of the n-ZnO/n-SiC/p-Si heterojunction is about four times higher than that of the n-ZnO/p-Si heterojunction. The photovoltaic response spectrum indicated that the photoresponse curve of n-ZnO/n-SiC/p-Si increased more strongly than that of n-ZnO/p-Si with the wavelength increasing. It shows that the photoresponse of n-ZnO/p-Si can be enhanced when inserting a 3C-SiC layer between ZnO and Si. There is one inflexion in the photocurrent response curve of the n-ZnO/p-Si heterojunction and two inflexions in that of the n-ZnO/n-SiC/p-Si heterojunction. It is clear that the 3C-SiC plays an important role in the photoelectric conversion of the n-ZnO/n-SiC/p-Si heterojunction.

  9. SiC-SiC and C-SiC Honeycomb for Advanced Flight Structures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed project builds upon the work done in Phase I with the development of a C-SiC CMC honeycomb material that was successfully tested for mechanical...

  10. Ionic S(N)i-Si Nucleophilic Substitution in N-Methylaniline-Induced Si-Si Bond Cleavages of Si2Cl6.

    Science.gov (United States)

    Zhang, Jie; Xie, Ju; Lee, Myong Euy; Zhang, Lin; Zuo, Yujing; Feng, Shengyu

    2016-03-24

    N-Methylaniline-induced Si-Si bond cleavage of Si2Cl6 has been theoretically studied. All calculations were performed by using DFT at the MPWB1K/6-311++G(3df,2p)//MPWB1K/6-31+G(d,p) levels. An ionic SN i-Si nucleophilic substitution mechanism, which is a newly found nucleophilic substitution in silicon-containing compounds, is proposed in the N-methylaniline-induced Si-Si bond cleavage in Si2Cl6. Unlike general S(N)i-Si nucleophilic substitutions that go through a pentacoordinated silicon transition state, ionic nucleophilic substitution goes through a tetracoordinated silicon transition state, in which the Si-Si bond is broken and siliconium ions are formed. Special cleavage of the Si-Si bond is presumably due to the good bonding strength between Si and N atoms, which leads to polarization of the Si-Si bond and eventually to heterolytic cleavage. Calculation results show that, in excess N-methylaniline, the final products of the reaction, including (NMePh)(3-n) SiHCl(n) (n=0-2) and (NMePh)(4-n) SiCl(n) (n=2-3), are the Si-Si cleavage products of Si2Cl6 and the corresponding amination products of the former. The ionic S(N)i-Si nucleophilic substitution mechanism can also be employed to describe the amination of chlorosilane by N-methylaniline. The suggested mechanisms are consistent with experimental data.

  11. An Introduction to the New SI

    Science.gov (United States)

    Knotts, Sandra; Mohr, Peter J.; Phillips, William D.

    2017-01-01

    Plans are under way to redefine the International System of Units (SI) around 2018. The new SI specifies the values of certain physical constants to define units. This article explains the new SI in order to provide a resource for high school teachers as well as for advanced students already familiar with the pre-2018 SI.

  12. An Introduction to the New SI

    Science.gov (United States)

    Knotts, Sandra; Mohr, Peter J.; Phillips, William D.

    2017-01-01

    Plans are under way to redefine the International System of Units (SI) around 2018. The new SI specifies the values of certain physical constants to define units. This article explains the new SI in order to provide a resource for high school teachers as well as for advanced students already familiar with the pre-2018 SI.

  13. Escolhas Associadas ao Automóvel por Homens e por Mulheres: confluência ou divergência? Choices associated with automobiles for Men and Women: convergence or divergence? Opciones relacionadas con el Automóvil por Hombres y por Mujeres: ¿convergencia o divergencia?

    Directory of Open Access Journals (Sweden)

    LICHT, René Henrique Götz

    2009-03-01

    revealed there are more similarities than differences between choices associated to the automobile by men and choices associated to the automobile by women. The similarity between the choices suggests that the representations, the meanings and values assigned to the car by men and women are similar and thus the strategy of product differentiation does not apply to the automotive industry.RESUMENEl aumento del poder de compra de las mujeres llevó a las empresas a adoptar estrategias de diferenciación de los productos y a producir productos específicos para el público femenino. La industria automovilística no es inmune a este fenómeno, pues las mujeres concentran aproximadamente la mitad de las ventas de automóviles en el país. Considerando las diferencias de consumo e de comportamiento entre mujeres y hombres se plantea la siguiente cuestión: ¿hay diferencias en las opciones relacionadas con el automóvil entre hombres y mujeres? Se presentaron ante los participantes algunos ítems que forman parte de la vida diaria de las personas y que ellas valorizan; se solicitó a los participantes que escogiesen y asociasen estos ítems al automóvil. El análisis de los resultados reveló que había más similitudes que diferencias entre las opciones relacionadas con el automóvil por parte de los hombres y las opciones relacionadas al automóvil por parte de las mujeres. La similitud entre las opciones indica que las representaciones, los significados y valores atribuidos al automóvil por hombres y mujeres son similares y por lo tanto, la estrategia de diferenciación de productos no se aplica a la industria automovilística.

  14. Revealing heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys.

    Science.gov (United States)

    Li, Jiehua; Hage, Fredrik S; Liu, Xiangfa; Ramasse, Quentin; Schumacher, Peter

    2016-04-28

    The heterogeneous nucleation of primary Si and eutectic Si can be attributed to the presence of AlP. Although P, in the form of AlP particles, is usually observed in the centre of primary Si, there is still a lack of detailed investigations on the distribution of P within primary Si and eutectic Si in hypereutectic Al-Si alloys at the atomic scale. Here, we report an atomic-scale experimental investigation on the distribution of P in hypereutectic Al-Si alloys. P, in the form of AlP particles, was observed in the centre of primary Si. However, no significant amount of P was detected within primary Si, eutectic Si and the Al matrix. Instead, P was observed at the interface between the Al matrix and eutectic Si, strongly indicating that P, in the form of AlP particles (or AlP 'patch' dependent on the P concentration), may have nucleated on the surface of the Al matrix and thereby enhanced the heterogeneous nucleation of eutectic Si. The present investigation reveals some novel insights into heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys and can be used to further develop heterogeneous nucleation mechanisms based on adsorption.

  15. Quantum wells based on Si/SiO{sub x} stacks for nanostructured absorbers

    Energy Technology Data Exchange (ETDEWEB)

    Berghoff, B.; Suckow, S.; Roelver, R.; Spangenberg, B.; Kurz, H. [Institute of Semiconductor Electronics, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen (Germany); Sologubenko, A.; Mayer, J. [Central Facility for Electron Microscopy, RWTH Aachen University, Ahornstr. 55, 52074 Aachen (Germany); Ernst Ruska Centre for Microscopy and Spectroscopy with Electrons, Research Centre Juelich, 52426 Juelich (Germany)

    2010-11-15

    We report on electrical transport and quantum confinement in thermally annealed Si/SiO{sub x} multiple quantum well (QW) stacks. Results are correlated with the morphology of the stacks. High temperature annealing of Si/SiO{sub x} stacks leads to precipitation of excess Si from the SiO{sub x} layers, which enhances the degree of crystallization and increases the grain sizes in the Si QWs compared to the conventional Si/SiO{sub 2} system. Moreover, the excess Si forms highly conductive pathways between adjacent Si QWs that are separated by ultrathin silicon oxide barriers. This results in an increase of conductivity by up to 10 orders of magnitude compared to the tunneling dominated transport in Si/SiO{sub 2} stacks. The stacks exhibit a distinct quantum confinement as confirmed by photoluminescence measurements. (author)

  16. Si/SiGe/Si HBT直流特性的可靠性%Reliability of DC characteristics in mesa Si/SiGe/Si HBT

    Institute of Scientific and Technical Information of China (English)

    崔福现; 张万荣

    2003-01-01

    对单台面SiGe HBT在E-B结反偏应力下直流特性的可靠性进行了研究.研究结果表明,随应力时间的增加,开启电压增加,直流电流增益下降,特别是在低E-B正偏电压时下降明显;而交流电流增益退化缓慢.

  17. Construction and characterization of spherical Si solar cells combined with SiC electric power inverter

    Science.gov (United States)

    Oku, Takeo; Matsumoto, Taisuke; Hiramatsu, Kouichi; Yasuda, Masashi; Shimono, Akio; Takeda, Yoshikazu; Murozono, Mikio

    2015-02-01

    Spherical silicon (Si) photovoltaic solar cell systems combined with an electric power inverter using silicon carbide (SiC) field-effect transistor (FET) were constructed and characterized, which were compared with an ordinary Si-based converter. The SiC-FET devices were introduced in the direct current-alternating current (DC-AC) converter, which was connected with the solar panels. The spherical Si solar cells were used as the power sources, and the spherical Si panels are lighter and more flexible compared with the ordinary flat Si solar panels. Conversion efficiencies of the spherical Si solar cells were improved by using the SiC-FET.

  18. Circumferential tensile test method for mechanical property evaluation of SiC/SiC tube

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Ju-Hyeon, E-mail: 15096018@mmm.muroran-it.ac.jp [Graduate School, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); Kishimoto, Hirotatsu [Graduate School, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); OASIS, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); Park, Joon-soo [OASIS, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); Nakazato, Naofumi [Graduate School, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan); Kohyama, Akira [OASIS, Muroran Institute of Technology, 27-1, Muroran, Hokkaido (Japan)

    2016-11-01

    Highlights: • NITE SiC/SiC cooling channel system to be a candidate of divertor system in future. • Hoop strength is one of the important factors for a tube. • This research studies the relationship between deformation and strain of SiC/SiC tube. - Abstract: SiC fiber reinforced/SiC matrix (SiC/SiC) composite is expected to be a candidate material for the first-wall, components in the blanket and divertor of fusion reactors in future. In such components, SiC/SiC composites need to be formed to be various shapes. SiC/SiC tubes has been expected to be employed for blanket and divertor after DEMO reactor, but there is not established mechanical investigation technique. Recent progress of SiC/SiC processing techniques is likely to realize strong, having gas tightness SiC/SiC tubes which will contribute for the development of fusion reactors. This research studies the relationship between deformation and strain of SiC/SiC tube using a circumferential tensile test method to establish a mechanical property investigation method of SiC/SiC tubes.

  19. Estudio de la reactividad entre aleaciones de aluminio y partículas de SiC

    Directory of Open Access Journals (Sweden)

    Ureña, A.

    2000-04-01

    Full Text Available The SiC reinforcement particles react with the molten aluminium to form Al4C3 that is brittle and sensitive to the the humidity. This reaction degrades the properties of the SiC reinforced aluminium matrix composites. The extend of the reaction in the Al/SiC interface depends on the fabrication parameters such as the temperature, residence time, atmosphere and chemical composition of the aluminium matrix and the reinforcement. Systematic studies on the reactivity between the SiC particles and molten aluminium alloys have been performed, analysing the effect of the presence of a SiO2 layer, which was formed by oxidation on the ceramic particles before their incorporation into the melt, as a protective barrier for preventing the attack of the SiC. As well, the effect of the metal matrix composition on the interfacial reactivity has been studied employing different aluminium alloys: AA1070 (99,7% Al, A-319.0 (Al-6Si-3Cu and A-332.0 (Al-11Si-1,5Cu. The composites were prepared by mixture of SiC particles (30 % vol. %, cold pressure and fusion at 900 ºC, varying the residence time in the furnace, which simulated a cast fabrication process. The results are compared with those obtained for a metal matrix composite (AA2014/SiC/13p.

    Las partículas de refuerzo de SiC reaccionan con el aluminio fundido y forman Al4C3 que es frágil y sensible al contacto con la humedad, lo que degrada las propiedades de los materiales compuestos constituidos por ambos componentes. La reacción en la intercara Al/SiC depende de varios parámetros de fabricación como temperatura, tiempo de residencia, atmósfera y composición química, tanto de la matriz de aluminio como del refuerzo de SiC. Se han realizado estudios sistemáticos de reactividad entre partículas de SiC y aluminio fundido, analizando el efecto que tiene la formación de una capa de SiO2 por oxidación de las partículas cerámicas, antes de su incorporación en el fundido, como barrera protectora

  20. Reactive diffusion bonding of SiCp/Al composites by insert layers of mixed Al-Si and Al-Si-SiC powders

    Institute of Scientific and Technical Information of China (English)

    Jihua Huang; Yueling Dong; Yun Wan; Jiangang Zhang; Hua Zhang

    2005-01-01

    Mixed Al-Si and Al-Si-SiC powders were employed as insert layers to reactive diffusion bond SiCp/6063 MMC (metal matrix composites). The results show that SiCp/6063 MMC joints bonded by the insert layer of the mixed Al-Si powder have a dense joining layer with a typical hypoeutectic microstructure. Using the mixed Al-Si-SiC powder as the insert layer, SiCp/6063 MMC can be reactive diffusion bonded by a composite joint. Because of the SiC segregation, however, there are a number of porous zones in the joining layer, which results in the bad shear strength of the joints reactive diffusion bonded by the insert layer of the mixed Al-SiSiC powder, even lower than that of the joints reactive diffusion bonded by the insert layer of the mixed Al-Si powder. Ti and Mg added in the insert layers obviously improve the strength of the joints reactive diffusion bonded by the insert layer of the mixed AlSi-SiC powder, especially, Mg has a more obvious effect.

  1. Field evaluation of spatial repellency of metofluthrin-impregnated latticework plastic strips against Aedes aegypti (L.) and analysis of environmental factors affecting its efficacy in My Tho City, Tien Giang, Vietnam.

    Science.gov (United States)

    Kawada, Hitoshi; Iwasaki, Tomonori; LE Loan, Luu; Tien, Tran Khanh; Mai, Nguyen Thi Nhu; Shono, Yoshinori; Katayama, Yasuyuki; Takagi, Masahiro

    2006-12-01

    Spatial repellency of metofluthrin-impregnated polyethylene latticework plastic strips against Aedes aegypti mosquitoes was evaluated. Analysis of environmental factors affecting the efficacy of these strips, such as room temperature, humidity, and house structure, was performed in a residential area in My Tho City, Tien Giang Province, Vietnam. Treatment with the strips at the rate of 1 strip per 2.6-5.52 m(2) (approximately 600 mg per 2.6-5.52 m(2)) reduced the collection of Ae. aegypti resting inside the houses for at least eight weeks. Multiple regression analysis indicated that both increase in the average room temperature and decrease in the area of openings in the rooms that were treated with the strips positively affected the spatial repellency of metofluthrin.

  2. Odd Bed-fellows: British Christians and Communists in the Struggle for Peace D’étranges compagnons : chrétiens et communistes britanniques dans la lutte pour la paix

    Directory of Open Access Journals (Sweden)

    Jeremy Tranmer

    2011-04-01

    Full Text Available Au début des années 1950, le doyen de l’archevêché de Cantorbéry œuvra au sein du mouvement pour la paix et participa à des activités organisées par le parti communiste britannique. En 1983, le prêtre catholique Bruce Kent, leader de la Campagne pour le Désarmement Nucléaire, loua l’engagement des communistes britanniques en faveur de la paix. Cet article cherche à examiner pourquoi et comment chrétiens et communistes surmontèrent leurs différences et coopérèrent dans la lutte contre l’arme nucléaire.

  3. Testamento vital, conocimiento y opinión que sobre él tiene una población de asistentes a unas jornadas sobre la enfermedad de Alzheimer

    Directory of Open Access Journals (Sweden)

    José Carlos Bermejo Higuera

    Full Text Available Objetivo: recoger conocimiento, opinión, sentimientos e intenciones que sobre el testamento vital tiene una población perteneciente al ámbito de la enfermedad de Alzheimer. Diseño: estudio descriptivo transversal mediante encuesta auto cumplimentada. Participantes: 370 asistentes a las Jornadas sobre Alzheimer organizadas en un centro de atención sociosanitaria de la Comunidad de Madrid. Conclusiones: los participantes están a favor del testamento vital con amplia intención de formalizarlo. Se observa una evolución en el interés por el documento, pero para incrementar la formalización entendemos que es necesario el trabajo hacia la creación de espacios para la reflexión sobre el testamento vital.

  4. Si{endash}N linkage in ultrabright, ultrasmall Si nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Rogozhina, E.; Belomoin, G.; Smith, A.; Abuhassan, L.; Barry, N.; Akcakir, O.; Braun, P. V.; Nayfeh, M. H.

    2001-06-04

    Ultrabright ultrasmall ({similar_to}1 nm) blue luminescent Si{sub 29} nanoparticles are chlorinated by reaction with Cl{sub 2} gas. A Si{endash}N linkage is formed by the reaction of the chlorinated particles with the functional amine group in butylamine. Fourier transform infrared spectroscopy and x-ray photospectroscopy measurements confirm the N linkage and the presence of the butyl group, while emission, excitation, and autocorrelation femtosecond optical spectroscopy show that, after the linkage formation, the particles with the ultrabright blue luminescent remain, but with a redshift of 40 nm. {copyright} 2001 American Institute of Physics.

  5. Room-temperature formation of Pt$_3$Si/Pt$_2$Si films on poly-Si substrates

    CERN Document Server

    Dubkov, V P; Chizh, K V; Yuryev, V A

    2016-01-01

    We propose a way of formation of thin bilayer Pt$_3$Si/Pt$_2$Si films at room temperature on poly-Si substrates by Pt magnetron sputtering and wet etching, obtain such film, investigate its structure and phase composition and estimate the thickness of its layers. We verify by direct x-ray photoelectron-spectroscopic measurements our previous observation of the Pt$_2$Si layer formaton between Pt and poly-Si films as a result of Pt magnetron sputtering at room temperature. This layer likely appears due to high enough temperature of Pt ions in the magnetron plasma sufficient for chemical reaction of the silicide film formation on the Si surface. The Pt$_3$Si layer likely forms from the Pt--Pt$_3$Si layer (Pt$_{95}$Si$_5$), which arises under Pt film during the magnetron sputtering, as a result of Pt removal by wet etching.

  6. Analyses of the As doping of SiO{sub 2}/Si/SiO{sub 2} nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Ruffino, Francesco; Miritello, Maria [CNR-IMM MATIS, via S. Sofia 64, 95123 Catania (Italy); Tomasello, Mario Vincenzo [Scuola Superiore di Catania, via San Nullo 5/i, 95123 Catania (Italy); De Bastiani, Riccardo; Grimaldi, Maria Grazia [Dipartimento di Fisica ed Astronomia, Universita di Catania, via S. Sofia 64, 95123 Catania (Italy); CNR-IMM MATIS, via S. Sofia 64, 95123 Catania (Italy); Nicotra, Giuseppe; Spinella, Corrado [Consiglio Nazionale delle Ricerche-Istituto per la Microelettronica e Microsistemi (CNR-IMM), VIII Strada 5, 95121 Catania (Italy)

    2011-03-15

    We illustrate the behaviour of As when it is confined, by the implantation technique, in a SiO{sub 2}(70nm)/Si(30nm)/SiO{sub 2}(70nm) multilayer and its spatial redistribution when annealing processes are performed. By Rutherford backscattering spectrometry and Z-contrast transmission electron microscopy we found an As accumulation at the Si/SiO{sub 2} interfaces and at the Si grain boundaries with no segregation of the As in the Si layer. Such an effect is in agreement with a model that assumes a traps distribution in the Si in the first 2-3 nm above the SiO{sub 2}/Si interfaces and along the Si grain boundaries. The traps concentration at the Si/SiO{sub 2} interfaces was estimated in 10{sup 14} traps/cm{sup 2}. The outlined results can open perspectives on the doping properties of As in Si nanocrystals, whose applications in nanoelectronics and optoelectronics are widely investigated (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  7. Improved Accuracy of Chlorophyll-a Concentration Estimates from MODIS Imagery Using a Two-Band Ratio Algorithm and Geostatistics: As Applied to the Monitoring of Eutrophication Processes over Tien Yen Bay (Northern Vietnam

    Directory of Open Access Journals (Sweden)

    Nguyen Thi Thu Ha

    2013-12-01

    Full Text Available Sea eutrophication is a natural process of water enrichment caused by increased nutrient loading that severely affects coastal ecosystems by decreasing water quality. The degree of eutrophication can be assessed by chlorophyll-a concentration. This study aims to develop a remote sensing method suitable for estimating chlorophyll-a concentrations in tropical coastal waters with abundant phytoplankton using Moderate Resolution Imaging Spectroradiometer (MODIS/Terra imagery and to improve the spatial resolution of MODIS/Terra-based estimation from 1 km to 100 m by geostatistics. A model based on the ratio of green and blue band reflectance (rGBr is proposed considering the bio-optical property of chlorophyll-a. Tien Yen Bay in northern Vietnam, a typical phytoplankton-rich coastal area, was selected as a case study site. The superiority of rGBr over two existing representative models, based on the blue-green band ratio and the red-near infrared band ratio, was demonstrated by a high correlation of the estimated chlorophyll-a concentrations at 40 sites with values measured in situ. Ordinary kriging was then shown to be highly capable of predicting the concentration for regions of the image covered by clouds and, thus, without sea surface data. Resultant space-time maps of concentrations over a year clarified that Tien Yen Bay is characterized by natural eutrophic waters, because the average of chlorophyll-a concentrations exceeded 10 mg/m3 in the summer. The temporal changes of chlorophyll-a concentrations were consistent with average monthly air temperatures and precipitation. Consequently, a combination of rGBr and ordinary kriging can effectively monitor water quality in tropical shallow waters.

  8. De la chair imbibée de foi : la viande comme marqueur de la frontière entre chrétiens et musulmans en Éthiopie

    Directory of Open Access Journals (Sweden)

    Éloi Ficquet

    2006-05-01

    Full Text Available Jamais en Éthiopie un chrétien et un musulman ne mangent de viande ensemble. Consommer de la viande qui n’a pas été consacrée à sa propre foi est appréhendé comme un acte hautement sacrilège équivalent à une apostasie. Cet interdit doit être compris dans une perspective comparative large sur les pratiques et les débats qui restreignent la commensalité de la viande entre les chrétiens et les musulmans. Les usages éthiopiens ont accentué cette question pour en faire un interdit puissant, marqueur d’une frontière interreligieuse. Comme toute frontière, cette « frontière carnée » a été le lieu de confrontations, d’aménagements et de transgressions dont les effets ont contribué à la construction de l’espace national éthiopien contemporain.Christians and Muslims in Ethiopia never eat meat together. Consuming meat that was not consecrated to one’s faith is seen as a highly sacrilegious act equal to apostasy. This interdict must be understood in comparative perspective that looks at the restrictions regarding the sharing of meat between Christians and Muslims. Ethiopian customs have emphasized this issue to turn it into a powerful interdict, tracing an inter-religious boundary. Like any boundary, this “dietary boundary” has been the site of confrontations, readjustments and transgressions whose effects have contributed to the building of a contemporary Ethiopian national space.

  9. Thickness effect on the formation of SiC nanoparticles in sandwiched Si/C/Si and C/Si multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Chung, C.K., E-mail: ckchung@mail.ncku.edu.t [Department of Mechanical Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan, 701, Taiwan (China); Wu, B.H.; Chen, T.S.; Peng, C.C.; Lai, C.W. [Department of Mechanical Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan, 701, Taiwan (China)

    2009-08-31

    The effect of carbon (C) and amorphous silicon (a-Si) thicknesses on the formation of SiC nanoparticles (np-SiC) in sandwiched Si/C/Si and C/Si multilayers on Si(100) substrates were investigated using ultra-high-vacuum ion beam sputtering system and vacuum thermal annealing at 500, 700, 900 {sup o}C for 1.0 h. Three-layer a-Si/C/a-Si structures with thicknesses of 50/200/50 nm and 75/150/75 nm and a two-layer C/a-Si structure of 200/50 nm were examined in this study. The size and density of np-SiC were strongly influenced by the annealing temperature, a-Si thickness and layer number. Many np-SiC appeared at 900 {sup o}C at a density order about 10{sup 8} cm{sup -2} in both three-layer structures while no particles formed in the two-layer structure. The thick a-Si structure (75/150/75 nm) produces a particle density approximately 1.8 times higher than thin structure (50/200/50 nm). This implies that thick a-Si structure had a lower activation energy of SiC formation compared to the thin a-Si structure. Few particles were found at 700 {sup o}C and no particles at 500 {sup o}C in both three-layer structures. The np-SiC formation is a thermally activated reaction. The higher temperature leads to higher particle density. A mechanism of np-SiC formation in thermodynamic and kinetic viewpoints is proposed.

  10. Mo-Si alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Heatherly, L.; Wright, J.L. [Oak Ridge National Lab., TN (United States)

    1996-06-01

    The objective of this task is to develop new-generation corrosion-resistant Mo-Si intermetallic alloys as hot components in advanced fossil energy conversion and combustion systems. The initial effort is devoted to Mo{sub 5}-Si{sub 3}-base (MSB) alloys containing boron additions. Three MSB alloys based on Mo-10.5Si-1.1B (wt %), weighing 1500 g were prepared by hot pressing of elemental and alloy powders at temperatures to 1600{degrees}C in vacuum. Microporosities and glassy-phase (probably silicate phases) formations are identified as the major concerns for preparation of MSB alloys by powder metallurgy. Suggestions are made to alleviate the problems of material processing.

  11. HV/CVD Grown Relaxed SiGe Buffer Layers for SiGe HMOSFETs

    Institute of Scientific and Technical Information of China (English)

    黄文韬; 罗广礼; 史进; 邓宁; 陈培毅; 钱佩信

    2003-01-01

    High-vacuum/chemical-vapor deposition (HV/CVD) system was used to grow relaxed SiGe buffer layers on Si substrates. Several methods were then used to analyze the quality of the SiGe films. X-ray diffraction and Raman spectroscopy showed that the upper layer was almost fully relaxed. Second ion mass spectroscopy showed that the Ge compositions were step-graded. Transmission electron microscopy showed that the misfit dislocations were restrained to the graded SiGe layers. Tests of the electrical properties of tensile-strained Si on relaxed SiGe buffer layers showed that their transconductances were higher than that of Si devices. These results verify the high quality of the relaxed SiGe buffer layer. The calculated critical layer thicknesses of the graded Si1-xGex layer on Si substrate and a Si layer on the relaxed SiGe buffer layer agree well with experimental results.

  12. High thermal conductivity SiC/SiC composites for fusion applications -- 2

    Energy Technology Data Exchange (ETDEWEB)

    Kowbel, W.; Tsou, K.T.; Withers, J.C. [MER Corp., Tucson, AZ (United States); Youngblood, G.E. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    This report covers material presented at the IEA/Jupiter Joint International Workshop on SiC/SiC Composites for Fusion Structural Applications held in conjunction with ICFRM-8, Sendai, Japan, Oct. 23--24, 1997. An unirradiated SiC/SiC composite made with MER-developed CVR SiC fiber and a hybrid PIP/CVI SiC matrix exhibited room temperature transverse thermal conductivity of 45 W/mK. An unirradiated SiC/SiC composite made from C/C composite totally CVR-converted to a SiC/SiC composite exhibited transverse thermal conductivity values of 75 and 35 W/mK at 25 and 1000 C, respectively. Both types of SiC/SiC composites exhibited non-brittle failure in flexure testing.

  13. Progress of Si-based Optoelectronic Devices

    Institute of Scientific and Technical Information of China (English)

    PENG Ying-cai; FU Guang-sheng; WANG Ying-long; SHANG Yong

    2004-01-01

    Si-based optoelectronics is becoming a very active research area due to its potential applications to optical communications. One of the major goals of this study is to realize ali-Si optoelectronic integrated circuit. This is due to the fact that Si- based optoelectronic technology can be compatible with Si microelectronic technology. If Si-based optoelectronic devices and integrated circuits can be achieved,it will lead to a new informational technological revolution. In the article, the current developments of this exciting field are mainly reviewed in the recent years. The involved contents are the realization of various Si-based optoelectronic devices, such as light-emitting diodes,optical waveguides devices, Si photonic bandgap crystals,and Si laser,etc. Finally, the developed tendency of all-Si optoelectronic integrated technology are predicted in the near future.

  14. Honda Civic Mugen Si Sedan

    Institute of Scientific and Technical Information of China (English)

    Prometheus

    2007-01-01

    美国本田汽车公司宣布08款本田Civic Mugen,SiSedan将于10月中旬正式亮相。这辆Civic Mugen Si Sedan配备有一个高性能的悬挂系统、锻造的铝质车轮、空气动力挠流体的设计式样和一个跑车化调校排气系统,新车搭载1998cc i-VTEC直四自然吸气引擎,

  15. Analysis of Si/SiGe Heterostructure Solar Cell

    Directory of Open Access Journals (Sweden)

    Ashish Kumar Singh

    2014-01-01

    Full Text Available Sunlight is the largest source of carbon-neutral energy. Large amount of energy, about 4.3 × 1020 J/hr (Lewis, 2005, is radiated because of nuclear fusion reaction by sun, but it is unfortunate that it is not exploited to its maximum level. Various photovoltaic researches are ongoing to find low cost, and highly efficient solar cell to fulfil looming energy crisis around the globe. Thin film solar cell along with enhanced absorption property will be the best, so combination of SiGe alloy is considered. The paper presented here consists of a numerical model of Si/Si1-xGex heterostructure solar cell. The research has investigated characteristics such as short circuit current density (Jsc, generation rate (G, absorption coefficient (α, and open circuit voltage (Voc with optimal Ge concentration. The addition of Ge content to Si layer will affect the property of material and can be calculated with the use of Vegard’s law. Due to this, short circuit current density increases.

  16. Morphology Analysis of Si Island Arrays on Si(001)

    Science.gov (United States)

    González-González, A.; Alonso, M.; Navarro, E.; Sacedón, J. L.; Ruiz, A.

    2010-12-01

    The formation of nanometer-scale islands is an important issue for bottom-up-based schemes in novel electronic, optoelectronic and magnetoelectronic devices technology. In this work, we present a detailed atomic force microscopy analysis of Si island arrays grown by molecular beam epitaxy. Recent reports have shown that self-assembled distributions of fourfold pyramid-like islands develop in 5-nm thick Si layers grown at substrate temperatures of 650 and 750°C on HF-prepared Si(001) substrates. Looking for wielding control and understanding the phenomena involved in this surface nanostructuring, we develop and apply a formalism that allows for processing large area AFM topographic images in a shot, obtaining surface orientation maps with specific information on facets population. The procedure reveals some noticeable features of these Si island arrays, e.g. a clear anisotropy of the in-plane local slope distributions. Total island volume analysis also indicates mass transport from the substrate surface to the 3D islands, a process presumably related to the presence of trenches around some of the pyramids. Results are discussed within the framework of similar island arrays in homoepitaxial and heteroepitaxial semiconductor systems.

  17. Acute koolmonoxide-intoxicatie bij tien personen

    NARCIS (Netherlands)

    de Vries I; Hegger C; Joore JCA; Savelkoul TJF; Meulenbelt J

    1992-01-01

    January 1992 ten persons (all adults, seven women and three men) were admitted to the special unit for calamities of the Intensive Care and Clinical Toxicology department of the University Hospital Utrecht with symptoms of an acute carbon monixide intoxication. All persons were exployees of the sam

  18. Oman tien rullaajat : Joensuulainen skeittiporukka 1990-luvulla

    OpenAIRE

    Tanskanen, Janne

    2011-01-01

    Tämä tutkimus käsittelee 1990-luvun joensuulaista skeittariryhmää ja sitä, kuinka ryhmään kuuluneet jälkeenpäin ovat kokeneet skeittikulttuurin vaikuttaneen heidän elämäänsä ja mikä tässä kulttuurissa oli heille tärkeää. Tarkastelen rullalautailukulttuuria alakulttuurina ja vastakulttuurina. Alakulttuurin osalta käsittelen muun muassa ryhmän pukeutumista, tyyliä ja kuunneltua musiikkia. Vastakulttuurin näkökulmasta pyrin tarkastelemaan skeittikulttuurin ideologisia puolia, kuten suhtautumis...

  19. Een speld in tien miljoen hooibergen

    CERN Multimedia

    Minkema, Martin

    2008-01-01

    Deeply under the ground in Geneva, thousands of scientists work with a giant particle accelerator. A discovery machine which will brew particles as from this summer and perhaps even create mini black holes.

  20. Tien eeue leksikografie: Van woordelys tot woordeboek

    Directory of Open Access Journals (Sweden)

    Wouter C. van Wyk

    1985-01-01

    Full Text Available Ten centuries of lexicography: From vocabulary list to dictionary The aim of the article is to illuminate the development in the lexicography of Biblical Hebrew through ten centuries from the first vocabularly list to a dictionary based on linguistic, comparative Semitic and encyclopedic principles. The writer treats several stages through the Middle Ages, the Reformation period, the Enlightenment and the Twentieth century up to a contemporary project of South African scholars working on a new Semantic Hebrew 'wordbook'. The conclusion in the article is that the nature of a specific dictionary or vocabularly list, for example philological, theological or linguistic, serves particular, legitimate needs.

  1. Acute koolmonoxide-intoxicatie bij tien personen

    NARCIS (Netherlands)

    de Vries I; Hegger C; Joore JCA; Savelkoul TJF; Meulenbelt J

    1992-01-01

    January 1992 ten persons (all adults, seven women and three men) were admitted to the special unit for calamities of the Intensive Care and Clinical Toxicology department of the University Hospital Utrecht with symptoms of an acute carbon monixide intoxication. All persons were exployees of the

  2. Laser annealing of sputter-deposited -SiC and -SiCN films

    Indian Academy of Sciences (India)

    M A Fraga; M Massi; I C Oliveira; F D Origo; W Miyakawa

    2011-12-01

    This work describes the laser annealing of -SiC and -SiCN films deposited on (100) Si and quartz substrates by RF magnetron sputtering. Two samples of -SiCN thin films were produced under different N2/Ar flow ratios. Rutherford backscattering spectroscopy (RBS), Raman analysis and Fourier transform infrared spectrometry (FTIR) techniques were used to investigate the composition and bonding structure of as-deposited and laser annealed SiC and SiCN films.

  3. Investigation of an a-Si/c-Si interface on a c-Si(P) substrate by simulation

    Institute of Scientific and Technical Information of China (English)

    Wang Jianqiang; Gao Hua; Zhang Jian; Meng Fanying; Ye Qinghao

    2012-01-01

    We investigate the recombination mechanism in an a-Si/c-Si interface,and analyze the key factors that influence the interface passivation quality,such as Qs,δp/δn and Dit.The polarity of the dielectric film is very important to the illustration level dependent passivation quality; when nδn =pδp and the defect level Et equal to Ei (c-Si),the defect states are the most effective recombination center,AFORS-HET simulation and analysis indicate that emitter doping and a-Si/c-Si band offset modulation are effective in depleting or accumulating one charged carrier.Interface states (Dit) severely deteriorate Voc compared with Jsc for a-Si/c-Si HJ cell performance when Dit is over 1 × 1010 cm-2.eV-1.For a c-Si(P)/a-Si(P+) structure,ΦBSF in c-Si and Φo in a-Si have different performances in optimization contact resistance and c-Si(P)/a-Si(P+) interface recombination.

  4. Are hepatocellular carcinoma surveillance programs effective at improving the therapeutic options?: ¿mejoran las opciones terapéuticas de estos pacientes? Eficacia de los programas de cribado de hepatocarcinoma

    Directory of Open Access Journals (Sweden)

    E. Zapata

    2010-08-01

    Full Text Available Aim: to evaluate whether the current surveillance programs (ultrasonography and alpha-fetoprotein testing every six months are successful in detecting patients in the early stages. Material and methods: the health records of all patients diagnosed with hepatocellular carcinoma in Donostia Hospital between 2003 and 2005 were reviewed retrospectively. Eighty-five patients (11 women and 74 men were included in the study and demographic data, risk factors and clinical data were obtained. Patients were split into two groups according to whether or not they had been included in a surveillance program. Results: seventy per cent of patients of the surveillance group is diagnosed in early stage opposite to 26.7% of patients in no surveillance group (p Objetivo: determinar si la utilización en nuestro medio del programa de cribado de HCC establecido -alfa-fetoproteína (AFP y ecografia semestral- en pacientes con hepatopatía crónica permite detectar pacientes en estadios precoces de la enfermedad. Material y métodos: Diseño experimental: estudio retrospectivo. Criterios diagnósticos de HCC: 2 o más técnicas de imagen con lesión hipervascular mayor de 2 cm o 1 técnica de imagen con lesión hipervascular mayor de 2 cm asociado a AFP mayor de 400 ng/ml. Pacientes: 85 pacientes diagnosticados de HCC en el Hospital Donostia entre los años 2003 y 2005. Datos analizados: información demográfica (sexo, edad, factores de riesgo (alcohol, virus de hepatitis, hemocromatosis, otras enfermedades asociadas, e información clínica (etiología de la hepatopatía, estadio de Child-Pugh, determinación de AFP, hallazgos radiológicos, criterios de resecabilidad, tratamiento recibido, evolución. Se divide la muestra en dos grupos según hubieran seguido o no un programa de cribado. Resultados: el 70% de los pacientes del grupo de cribado se diagnostican en estadio precoz frente al 26,7% del grupo de no cribado (p < 0,05. Trece pacientes no pueden recibir

  5. Microwave joining of SiC

    Energy Technology Data Exchange (ETDEWEB)

    Silberglitt, R.; Ahmad, I.; Tian, Y.L. [FM Technologies, Inc., Fairfax, VA (United States)] [and others

    1997-04-01

    The purpose of this work is to optimize the properties of SiC-SiC joints made using microwave energy. The current focus is on identification of the most effective joining methods for scale-up to large tube assemblies, including joining using SiC produced in situ from chemical precursors. During FY 1996, a new microwave applicator was designed, fabricated and tested that provides the capability for vacuum baking of the specimens and insulation and for processing under inert environment. This applicator was used to join continuous fiber-reinforced (CFCC) SiC/SiC composites using a polymer precursor to form a SiC interlayer in situ.

  6. Microscopic and macroscopic characterization of the charging effects in SiC/Si nanocrystals/SiC sandwiched structures.

    Science.gov (United States)

    Xu, Jie; Xu, Jun; Wang, Yuefei; Cao, Yunqing; Li, Wei; Yu, Linwei; Chen, Kunji

    2014-02-07

    Microscopic charge injection into the SiC/Si nanocrystals/SiC sandwiched structures through a biased conductive AFM tip is subsequently characterized by both electrostatic force microscopy and Kelvin probe force microscopy (KPFM). The charge injection and retention characteristics are found to be affected by not only the band offset at the Si nanocrystals/SiC interface but also the doping type of the Si substrate. On the other hand, capacitance-voltage (C-V) measurements investigate the macroscopic charging effect of the sandwiched structures with a thicker SiC capping layer, where the charges are injected from the Si substrates. The calculated macroscopic charging density is 3-4 times that of the microscopic one, and the possible reason is the underestimation of the microscopic charging density caused by the averaging effect and detection delay in the KPFM measurements.

  7. Three carbon pairs in Si

    Energy Technology Data Exchange (ETDEWEB)

    Docaj, A. [Physics Department, Texas Tech University, Lubbock, TX 79409-1051 (United States); Estreicher, S.K., E-mail: Stefan.Estreicher@ttu.edu [Physics Department, Texas Tech University, Lubbock, TX 79409-1051 (United States)

    2012-08-01

    Carbon impurities in Si are common in floating-zone and cast-Si materials. The simplest and most discussed carbon complex is the interstitial-substitutional C{sub i}C{sub s} pair, which readily forms when self-interstitials are present in the material. This pair has three possible configurations, each of which is electrically active. The less common C{sub s}C{sub s} pair has been studied in irradiated material but has also recently been seen in as-grown C-rich cast-Si, which is commonly used to fabricate solar cells. The third pair consists of two interstitial C atoms: C{sub i}C{sub i}. Although its formation probability is low for several reasons, the C{sub i}C{sub i} pair is very stable and electrically inactive. In this contribution, we report preliminary results of first-principles calculations of these three C pairs in Si. The structures, binding energies, vibrational spectra, and electrical activity are predicted.

  8. Using SI Units in Astronomy

    Science.gov (United States)

    Dodd, Richard

    2011-12-01

    1. Introduction; 2. An introduction to SI units; 3. Dimensional analysis; 4. Unit of angular measure (radian); 5. Unit of time (second); 6. Unit of length (metre); 7. Unit of mass (kilogram); 8. Unit of luminous intensity (candela); 9. Unit of thermodynamic temperature (kelvin); 10. Unit of electric current (ampere); 11. Unit of amount of substance (mole); 12. Astronomical taxonomy; Index.

  9. The impact resistance of SiC and other mechanical properties of SiC and Si3N4

    Science.gov (United States)

    Bradt, R. C.

    1984-01-01

    Studies focused on the impact and mechanical behavior of SiC and Si3N4 at high temperatures are summarized. Instrumented Charpy impact testing is analyzed by a compliance method and related to strength; slow crack growth is related to processing, and creep is discussed. The transient nature of flaw populations during oxidation under load is emphasized for both SiC and Si3N4.

  10. The HFIR 14J irradiation SiC/SiC composite and SiC fiber collaboration

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States); Kohyama, Akira; Katoh, Yutai [Kyoto Univ., Uji, Kyoto (Japan); Hasegawa, Akira [Tohoku Univ., Aramaki, Sendai (Japan); Snead, L. [Oak Ridge National Lab., TN (United States); Scholz, R.

    1998-09-01

    A short introduction with references establishes the current status of research and development of SiC{sub f}/SiC composites for fusion energy systems with respect to several key issues. The SiC fiber and composite specimen types selected for the JUPITER 14J irradiation experiment are presented together with the rationale for their selection.

  11. Effect of Ti and Si interlayer materials on the joining of SiC ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Yang Il; Park, Jung Hwan; Kim, Hyun Gil; Park, Dong Jun; Park, Jeong Yong; Kim, Weon Ju [LWR Fuel Technology Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-08-15

    SiC-based ceramic composites are currently being considered for use in fuel cladding tubes in light-water reactors. The joining of SiC ceramics in a hermetic seal is required for the development of ceramic-based fuel cladding tubes. In this study, SiC monoliths were diffusion bonded using a Ti foil interlayer and additional Si powder. In the joining process, a very low uniaxial pressure of ∼0.1 MPa was applied, so the process is applicable for joining thin-walled long tubes. The joining strength depended strongly on the type of SiC material. Reaction-bonded SiC (RB-SiC) showed a higher joining strength than sintered SiC because the diffusion reaction of Si was promoted in the former. The joining strength of sintered SiC was increased by the addition of Si at the Ti interlayer to play the role of the free Si in RB-SiC. The maximum joint strength obtained under torsional stress was ∼100 MPa. The joint interface consisted of TiSi{sub 2}, Ti{sub 3}SiC{sub 2}, and SiC phases formed by a diffusion reaction of Ti and Si.

  12. Superior solid solubility of MnSiO3 in CaSiO3 perovskite

    Science.gov (United States)

    Li, Lin; Nagai, Takaya; Seto, Yusuke; Fujino, Kiyoshi; Kawano, Jun; Itoh, Shoich

    2015-02-01

    The silicate perovskite phase relation between CaSiO3 and MnSiO3 was investigated at 35-52 GPa and at 1,800 K using laser-heated diamond anvil cells combined with angle-dispersive synchrotron X-ray diffraction and energy-dispersive X-ray spectroscopic chemical analyses with scanning or transmission electron microscopy. We found that MnSiO3 can be incorporated into CaSiO3 perovskite up to 55, and 20 mol % of CaSiO3 is soluble in MnSiO3 perovskite. The range of 55-80 mol % of MnSiO3 in the CaSiO3-MnSiO3 perovskite system could be immiscible. We also observed that the two perovskite structured phases of the Mn-bearing CaSiO3 and the Ca-bearing MnSiO3 coexisted at these conditions. The Mn-bearing CaSiO3 perovskite has non-cubic symmetry and the Ca-bearing MnSiO3 perovskite has an orthorhombic structure with space group Pbnm. All the perovskite structured phases in the CaSiO3-MnSiO3 system convert to the amorphous phase during pressure release. MnSiO3 is the first chemical component confirmed to show such a superior solid solubility in CaSiO3 perovskite.

  13. VALORACIÓN DEL RIESGO FINANCIERO (CFAR EN LAS EPS A TRAVÉS DE OPCIONES REALES: UNA APLICACIÓN AL NIVEL DE ATENCIÓN IV Financial Risk Valuation (CFARin EPS's through Real Options: An Application at the IV Assistance Level

    Directory of Open Access Journals (Sweden)

    Mónica A. Arango Arango

    2011-12-01

    Full Text Available El número de pacientes tratados por insuficiencia renal en Colombia es cada vez mayor; por esta razón conocer los costos asociados a esta enfermedad es una necesidad manifiesta de las Entidades Promotoras de Salud con el fin de garantizar la estabilidad del Sistema de Seguridad Social en Salud. Este trabajo evalúa financieramente, mediante opciones reales, la posibilidad de hacer un trasplante de riñón en un paciente bajo tratamiento de insuficiencia renal y el Flujo de Caja en Riesgo al tener en cuenta esta opción. Se encontró que al hacer un análisis periódico de los costos asociados a continuar con el tratamiento, existen casos en los que es más eficiente hacer el trasplante, disminuyendo el valor presente de las erogaciones del paciente, mejorando el flujo de caja en riesgo y controlando los gastos futuros de la entidad que lo atiende.Number of patients treated for renal failure in Colombia is increasingly high; for this reason, knowing the costs associated to this disease is a clear need for Health Promoting Entities with the purpose of assuring stability of the Health Social Security System. Through real options, this article is a financial evaluation of the possibility of conducting a kidney transplant in a patient being under a renal failure treatment and the cash flow at risk when having this as an option. It was found that when a periodical analysis of costs associated to continuation of treatment is made, there are cases where transplant is a more efficient option to be executed since the present value of the patient's expenses is decreased, thus improving the cash flow at risk and controlling future expenses of the entity treating the patient.

  14. Binomial tree for option valuation process derived from stochastic autonomous differential equation Árboles binomiales para la valoración de opciones sobre procesos derivados de la ecuación diferencial estocástica autónoma

    Directory of Open Access Journals (Sweden)

    Freddy Marín-Sánchez

    2010-12-01

    Full Text Available In this paper we propose a multiplicative generalized binomial trees recombination associated with the autonomous equation in terms of the initial condition and the product of non-constant upwards and downwards jumps from the discretized process. We present a formal technique for finding the dynamic transition probabilities involving the first two moments of the solution to the differential equation, which incorporate the factor of growth and volatility in terms of the parameters and the underlying process along its branching. Some experimental numerical results are shown for European option pricing for lognormal process and the processes of mean reversion with additive noise and proportional noise for different expiration dates.En este trabajo se propone una recombinación en árboles binomiales multiplicativageneralizada para la ecuación autónoma, en términos de la condición inicial y del producto entre saltos no constantes hacia arriba y hacia abajo delproceso discretizado. Se presenta de manera formal una técnica para encontrarlas probabilidades de transición dinámicas considerando los dos primeros momentos del proceso solución de la ecuación diferencial, los cuales incorporanel factor de crecimiento y la volatilidad en términos de los parámetrosy del proceso subyacente a lo largo de su ramificación. Se muestran algunosresultados numéricos experimentales de valoración de opciones Europeas parael proceso log–normal y para los procesos de reversión a la media con ruidoaditivo y ruido proporcional para diferentes fechas de expiración.

  15. Effective passivation of Si surfaces by plasma deposited SiOx/a-SiNx:H stacks

    Science.gov (United States)

    Dingemans, G.; Mandoc, M. M.; Bordihn, S.; van de Sanden, M. C. M.; Kessels, W. M. M.

    2011-05-01

    Very low surface recombination velocities field-effect passivation was absent for a reference stack comprising thermally grown SiO2. The results indicate that hydrogenation of interface states played a key role in the passivation and remained effective up to annealing temperatures >800 °C.

  16. An inside job for siRNAs.

    Science.gov (United States)

    Golden, Daniel E; Gerbasi, Vincent R; Sontheimer, Erik J

    2008-08-08

    Among the three main categories of small silencing RNAs in insects and mammals-siRNAs, miRNAs, and piRNAs-siRNAs were thought to arise primarily from exogenous sources, whereas miRNAs and piRNAs arise from endogenous loci. Recent work in flies and mice reveals several classes of endogenous siRNAs (endo-siRNAs) that contribute to functions previously reserved for miRNAs and piRNAs, including gene regulation and transposon suppression.

  17. Microwave joining of SiC

    Energy Technology Data Exchange (ETDEWEB)

    Silberglitt, R.; Ahmad, I. [FM Technologies, Inc., Fairfax, VA (United States); Black, W.M. [George Mason Univ., Fairfax, VA (United States)] [and others

    1995-05-01

    The purpose of this work is to optimize the properties of SiC-SiC joints made using microwave energy. The current focus is on optimization of time-temperature profiles, production of SiC from chemical precursors, and design of new applicators for joining of long tubes.

  18. An introduction to the New SI

    CERN Document Server

    Knotts, Sandra; Phillips, William D

    2015-01-01

    Plans are underway to redefine the International System of Units (SI) around 2018. The New SI specifies the values of certain physical constants to define units. This article explains the New SI in a way that could be used to present it to high-school physics classes.

  19. Emission efficiency limit of Si nanocrystals

    NARCIS (Netherlands)

    Limpens, R.; Luxembourg, S.L.; Weeber, A.W.; Gregorkiewicz, T.

    2016-01-01

    One of the important obstacles on the way to application of Si nanocrystals for development of practical devices is their typically low emissivity. In this study we explore the limits of external quantum yield of photoluminescence of solid-state dispersions of Si nanocrystals in SiO2. By making use

  20. 3C-SiC nanocrystal growth on 10° miscut Si(001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Deokar, Geetanjali, E-mail: gitudeo@gmail.com [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); D' Angelo, Marie; Demaille, Dominique [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); Cavellin, Catherine Deville [INSP, UPMC, CNRS UMR 7588, 4 place Jussieu, Paris F-75005 (France); Faculté des Sciences et Technologie UPEC, 61 av. De Gaulle, Créteil F-94010 (France)

    2014-04-01

    The growth of 3C-SiC nano-crystal (NC) on 10° miscut Si(001) substrate by CO{sub 2} thermal treatment is investigated by scanning and high resolution transmission electron microscopies. The vicinal Si(001) surface was thermally oxidized prior to the annealing at 1100 °C under CO{sub 2} atmosphere. The influence of the atomic steps at the vicinal SiO{sub 2}/Si interface on the SiC NC growth is studied by comparison with the results obtained for fundamental Si(001) substrates in the same conditions. For Si miscut substrate, a substantial enhancement in the density of the SiC NCs and a tendency of preferential alignment of them along the atomic step edges is observed. The SiC/Si interface is abrupt, without any steps and epitaxial growth with full relaxation of 3C-SiC occurs by domain matching epitaxy. The CO{sub 2} pressure and annealing time effect on NC growth is analyzed. The as-prepared SiC NCs can be engineered further for potential application in optoelectronic devices and/or as a seed for homoepitaxial SiC or heteroepitaxial GaN film growth. - Highlights: • Synthesis of 3C-SiC nanocrystals epitaxied on miscut-Si using a simple technique • Evidence of domain matching epitaxy at the SiC/Si interface • SiC growth proceeds along the (001) plane of host Si. • Substantial enhancement of the SiC nanocrystal density due to the miscut • Effect of the process parameters (CO{sub 2} pressure and annealing duration)

  1. Laser cladding of Al-Si/SiC composite coatings : Microstructure and abrasive wear behavior

    NARCIS (Netherlands)

    Anandkumar, R.; Almeida, A.; Vilar, R.; Ocelik, V.; De Hosson, J.Th.M.

    2007-01-01

    Surface coatings of an Al-Si-SiC composite were produced on UNS A03560 cast Al-alloy substrates by laser cladding using a mixture of powders of Al-12 wt.% Si alloy and SiC. The microstructure of the coatings depends considerably on the processing parameters. For a specific energy of 26 MJ/m2 the

  2. Microstructure and wear studies of laser clad Al-Si/SiC(p) composite coatings

    NARCIS (Netherlands)

    Anandkumar, R.; Almeida, A.; Colaco, R.; Vilar, R.; Ocelik, V.; De Hosson, J. Th. M.

    2007-01-01

    Coatings of a composite material consisting of an Al-Si matrix reinforced with SiC particles were produced by laser cladding on UNS A03560 cast Al-alloy substrates from mixtures of powders of Al-12 wt.% Si alloy and SiC. The influence of the processing parameters on the microstructure and abrasive

  3. Ultrasound assisted siRNA delivery using PEG-siPlex loaded microbubbles.

    Science.gov (United States)

    Vandenbroucke, Roosmarijn E; Lentacker, Ine; Demeester, Joseph; De Smedt, Stefaan C; Sanders, Niek N

    2008-03-20

    Short interfering RNA (siRNA) attracts much attention for the treatment of various diseases. However, its delivery, especially via systemic routes, remains a challenge. Indeed, naked siRNAs are rapidly degraded, while complexed siRNAs massively aggregate in the blood or are captured by macrophages. Although this can be circumvented by PEGylation, we found that PEGylation had a strong negative effect on the gene silencing efficiency of siRNA-liposome complexes (siPlexes). Recently, ultrasound combined with microbubbles has been used to deliver naked siRNA but the gene silencing efficiency is rather low and very high amounts of siRNA are required. To overcome the negative effects of PEGylation and to enhance the efficiency of ultrasound assisted siRNA delivery, we coupled PEGylated siPlexes (PEG-siPlexes) to microbubbles. Ultrasound radiation of these microbubbles resulted in massive release of unaltered PEG-siPlexes. Interestingly, PEG-siPlexes loaded on microbubbles were able to enter cells after exposure to ultrasound, in contrast to free PEG-siPlexes, which were not able to enter cells rapidly. Furthermore, these PEG-siPlex loaded microbubbles induced, in the presence of ultrasound, much higher gene silencing than free PEG-siPlexes. Additionally, the PEG-siPlex loaded microbubbles only silenced the expression of genes in the presence of ultrasound, which allows space and time controlled gene silencing.

  4. Microstructure and wear studies of laser clad Al-Si/SiC(p) composite coatings

    NARCIS (Netherlands)

    Anandkumar, R.; Almeida, A.; Colaco, R.; Vilar, R.; Ocelik, V.; De Hosson, J. Th. M.

    2007-01-01

    Coatings of a composite material consisting of an Al-Si matrix reinforced with SiC particles were produced by laser cladding on UNS A03560 cast Al-alloy substrates from mixtures of powders of Al-12 wt.% Si alloy and SiC. The influence of the processing parameters on the microstructure and abrasive w

  5. Laser cladding of Al-Si/SiC composite coatings : Microstructure and abrasive wear behavior

    NARCIS (Netherlands)

    Anandkumar, R.; Almeida, A.; Vilar, R.; Ocelik, V.; De Hosson, J.Th.M.

    2007-01-01

    Surface coatings of an Al-Si-SiC composite were produced on UNS A03560 cast Al-alloy substrates by laser cladding using a mixture of powders of Al-12 wt.% Si alloy and SiC. The microstructure of the coatings depends considerably on the processing parameters. For a specific energy of 26 MJ/m2 the mic

  6. SiO adsorption on a p(2 × 2) reconstructed Si(1 0 0) surface

    NARCIS (Netherlands)

    Violanda, M.; Rudolph, H.

    2009-01-01

    We have investigated the adsorption mechanism of SiO molecule incident on a clean Si(1 0 0) p(2 × 2) reconstructed surface using density functional theory based methods. Stable adsorption geometries of SiO on Si surface, as well as their corresponding activation and adsorption energies are identifie

  7. MoSi2 oxidation resistance coatings for Mo5Si3/MoSi2 composites

    Institute of Scientific and Technical Information of China (English)

    YAN Jianhui; XU Hongmei; ZHANG Houan; TANG Siwen

    2009-01-01

    In order to improve the oxidation resistance properties of 30 at.% Mo5Si3/MoSi2 composite at high temperature in air, a molybdenum disili-tide coating was prepared on its surface by a molten salt technology. XRD and SEM analysis showed that only tetragonal MoSi2 phase ex-isted in the coating after being siliconized for 5 h at 900℃. The oxidation film formed on the uncoated sample was not dense, so that oxygen diffused easily through it. The volatilization of MoO3 resulted in the oxidation film separating from the substrate. The MoSi2coating was proved to be an effective method to prevent 30 at.% MosSi3/MoSi2 composites from being oxidized at 1200℃. A dense glassy SiO2 film was formed on the MoSi2 coating surface, which acted as a barrier layer for the diffusion of oxygen atoms to the substrate. The 30at.% Mo5Si3/MoSi2 composites with a MoSi2 coating showed much better oxidation resistance at high temperature.

  8. Abrupt GaP/Si hetero-interface using bistepped Si buffer

    Energy Technology Data Exchange (ETDEWEB)

    Ping Wang, Y., E-mail: yanping.wang@insa-rennes.fr; Kuyyalil, J.; Nguyen Thanh, T.; Almosni, S.; Bernard, R.; Tremblay, R.; Da Silva, M.; Létoublon, A.; Rohel, T.; Tavernier, K.; Le Corre, A.; Cornet, C.; Durand, O. [UMR FOTON, CNRS, INSA Rennes, Rennes F-35708 (France); Stodolna, J.; Ponchet, A. [CEMES-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, BP 94347, 31055 Toulouse Cedex 04 (France); Bahri, M.; Largeau, L.; Patriarche, G. [Laboratoire de Photonique et Nanostructures, CNRS UPR 20, Route de Nozay, Marcoussis 91460 (France); Magen, C. [LMA, INA-ARAID, and Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50018 Zaragoza (Spain)

    2015-11-09

    We evidence the influence of the quality of the starting Si surface on the III-V/Si interface abruptness and on the formation of defects during the growth of III-V/Si heterogeneous crystal, using high resolution transmission electron microscopy and scanning transmission electron microscopy. GaP layers were grown by molecular beam epitaxy on vicinal Si (001). The strong effect of the Si substrate chemical preparation is first demonstrated by studying structural properties of both Si homoepitaxial layer and GaP/Si heterostructure. It is then shown that choosing adequate chemical preparation conditions and subsequent III-V regrowth conditions enables the quasi-suppression of micro-twins in the epilayer. Finally, the abruptness of GaP/Si interface is found to be very sensitive to the Si chemical preparation and is improved by the use of a bistepped Si buffer prior to III-V overgrowth.

  9. Safety and Efficacy of Tien-Hsien Liquid Practical in Patients with Refractory Metastatic Breast Cancer: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group, Phase IIa Trial

    Directory of Open Access Journals (Sweden)

    Wen-Hung Kuo

    2012-01-01

    Full Text Available To evaluate the safety and efficacy of Tien-Hsien Liquid Practical (THL-P, a Chinese herbal mixture, in patients with refractory metastatic breast cancer, we performed a randomized, double-blind, placebo-controlled, parallel-group, phase IIa pilot trial. Patients were randomly assigned to either receive THL-P or matching placebo and followed up every 4 weeks for 24 weeks. The primary endpoint was changes in the global health status/quality of life (GHS/QOL scale. The secondary endpoints were changes in functional and symptom scales, immunomodulating effects, and adverse events. Sixty-three patients were enrolled between June 2009 and June 2011. The intent-to-treat population included 28 patients in the THL-P group and 11 patients in the placebo group. Compared to the placebo group, the THL-P group had significant improvement from baseline to last visit in GHS/QOL (41.7 versus −33.3; P<0.05, CD3, CD4/CD8, CD19, CD16+56 positive cells (P<0.05, and higher levels of physical, role, emotional, and cognitive functioning, as well as decreased fatigue and systemic side effects. Treatment-related adverse events were mild constipation and localized itching, and no serious adverse events were reported. THL-P appears to be a safe alternative adjuvant treatment for patients with refractory metastatic breast cancer, as it effectively improves QOL and palliates cancer-related symptoms.

  10. Columnar growth of CoSi2 on Si(111), Si(100) and Si(110) by molecular beam epitaxy

    Science.gov (United States)

    Fathauer, R. W.; Nieh, C. W.; Xiao, Q. F.; Hashimoto, Shin

    1990-01-01

    Codeposition of silicon and cobalt on heated silicon substrates in ratios several times the silicide stoichiometry is found to result in epitaxial columns of CoSi2 surrounded by a matrix of epitaxial silicon. For (111)-oriented wafers, nearly cylindrical columns are formed, where both columns and surrounding silicon are defect free, as deduced from transmission electron microscopy. Independent control of the column diameter and separation is possible, and diameters of 27-135 nm have been demonstrated.

  11. Si Scott溜冰鞋

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Vauxhall Ice Skate公司特别邀请Si Scott为Vauxhall Ice Skate event活动设计了一款造型奇特的溜冰鞋:鞋身以轿车模样出现下面则是冰刀,再加上设计师的非凡创意涂鸦,令溜冰鞋充满童趣。

  12. Nanoporosity of Si (100) bars

    Science.gov (United States)

    Novikov, S. N.; Timoshenkov, S. P.; Minaev, V. S.; Goryunova, E. P.; Gerasimenko, N. N.; Smirnov, D. I.

    2016-09-01

    Si(100) samples cut from a typical bar (100 mm in diameter) prepared using industrial technology are studied. Measurements of the electron work function (EWF) show that the size effects in these samples (a reduction in thickness along with a sample's area and the EWF) detected earlier were due to nanostructure porosity that was buried by the technological treatment of a bar's surface. This hidden nanoporosity is assumed to be a manifestation of the secondary crystal structure.

  13. Lattice dislocation in Si nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Omar, M.S., E-mail: dr_m_s_omar@yahoo.co [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq); Taha, H.T. [Department of Physics, College of Science, University of Salahaddin, Arbil, Iraqi Kurdistan (Iraq)

    2009-12-15

    Modified formulas were used to calculate lattice thermal expansion, specific heat and Bulk modulus for Si nanowires with diameters of 115, 56, 37 and 22 nm. From these values and Gruneisen parameter taken from reference, mean lattice volumes were found to be as 20.03 A{sup 3} for the bulk and 23.63, 29.91, 34.69 and 40.46 A{sup 3} for Si nanowire diameters mentioned above, respectively. Their mean bonding length was calculated to be as 0.235 nm for the bulk and 0.248, 0.269, 0.282 and 0.297 nm for the nanowires diameter mentioned above, respectively. By dividing the nanowires diameter on the mean bonding length, number of layers per each nanowire size was found to be as 230, 104, 65 and 37 for the diameters mentioned above, respectively. Lattice dislocations in 22 nm diameter wire were found to be from 0.00324 nm for the 1st central lattice to 0.2579 nm for the last surface lattice. Such dislocation was smaller for larger wire diameters. Dislocation concentration found to change in Si nanowires according to the proportionalities of surface thickness to nanowire radius ratios.

  14. Current–voltage studies on -FeSi2/Si heterojunction

    Indian Academy of Sciences (India)

    A Datta; S Kal; S Basu

    2000-08-01

    – characteristics of both -FeSi2/n-Si and -FeSi2/p-Si were studied at room temperature. The junctions were formed by depositing Fe on Si selectively followed by thermal annealing and some samples were later treated by pulsed laser. Temperature of thermal annealing and diode area were also varied. – studies on all these samples were done and ideality factors were computed. Results obtained were interpreted.

  15. Effect of Si interface surface roughness to the tunneling current of the Si/Si{sub 1-x}Ge{sub x}/Si heterojunction bipolar transistor

    Energy Technology Data Exchange (ETDEWEB)

    Hasanah, Lilik, E-mail: lilikhasanah@upi.edu; Suhendi, Endi; Tayubi, Yuyu Rahmat; Yuwono, Heru [Department of Physics Education, Universitas Pendidikan Indonesia, Jl. Setiabudhi 229 Bandung 40154 (Indonesia); Nandiyanto, Asep Bayu Dani [Department Kimia, Universitas Pendidikan Indonesia, Jl. Setiabudhi 229 Bandung 40154 (Indonesia); Murakami, Hideki [Graduate School of Advanced Sciences of Matter, Hiroshima University, Higashi-Hiroshima 739-8527 (Japan); Khairrurijal [Physics of Electronic Materials Research Division, Institut Teknologi Bandung, Bandung 40132 (Indonesia)

    2016-02-08

    In this work we discuss the surface roughness of Si interface impact to the tunneling current of the Si/Si{sub 1-x}Ge{sub x}/Si heterojunction bipolar transistor. The Si interface surface roughness can be analyzed from electrical characteristics through the transversal electron velocity obtained as fitting parameter factor. The results showed that surface roughness increase as Ge content of virtual substrate increase This model can be used to investigate the effect of Ge content of the virtual substrate to the interface surface condition through current-voltage characteristic.

  16. Active Oxidation of SiC

    Science.gov (United States)

    Jacobson, Nathan S.; Myers,Dwight L.; Harder, Bryan J.

    2011-01-01

    The high temperature oxidation of silicon carbide occurs in either a passive or active mode, depending on temperature and oxygen potential. Passive oxidation forms a protective oxide film which limits attack of the SiC:SiC(s) + 3/2 O2(g) = SiO2(s) + CO(g.) Active oxidation forms a volatile oxide and leads to extensive attack of the SiC: SiC(s) + O2(g) = SiO(g) + CO(g). The transition points and rates of active oxidation are a major issue. Previous studies are reviewed and the leading theories of passive/active transitions summarized. Comparisons are made to the active/passive transitions in pure Si, which are relatively well-understood. Critical questions remain about the difference between the active-to-passive transition and passive-to-active transition. For Si, Wagner [2] points out that the active-to-passive transition is governed by the criterion for a stable Si/SiO2 equilibria and the passive-to-active transition is governed by the decomposition of the SiO2 film. This suggests a significant oxygen potential difference between these two transitions and our experiments confirm this. For Si, the initial stages of active oxidation are characterized by the formation of SiO(g) and further oxidation to SiO2(s) as micron-sized rods, with a distinctive morphology. SiC shows significant differences. The active-to-passive and the passive-to-active transitions are close. The SiO2 rods only appear as the passive film breaks down. These differences are explained in terms of the reactions at the SiC/SiO2 interface. In order to understand the breakdown of the passive film, pre-oxidation experiments are conducted. These involve forming dense protective scales of 0.5, 1, and 2 microns and then subjecting the samples with these scales to a known active oxidation environment. Microstructural studies show that SiC/SiO2 interfacial reactions lead to a breakdown of the scale with a distinct morphology.

  17. Complexation of Si in Hydrothermal Systems

    Institute of Scientific and Technical Information of China (English)

    樊文苓; 王声远; 田弋夫; 陈紫新

    2001-01-01

    The Au-SiO2 and Sn-SiO2 complexes have been experimentally calibrated at varying temperature, silica concentration and pH:Au+ + H3SiO4-=AuH3SiO4 lgK = - 1. 65436 + 9611.21/TSn4 + + 4H3SiO4-=Sn(H3SiO4)4 lgK200℃ = 42.73Compared with Au-Cl, Au-HS and Sn-OH complexes, AuH3SiO4 and Sn(H3SiO4)4 complexes can be recognized as the dominant transport forms in Si-bearing solutions under pH and Eh con ditions of general interest. The decrease of SiO2 concentration and oxygen fugacity would re verse the direction of dissolution-complexing reactions, resulting in the precipitation of gold and silica, as well as cassiterite and silica. This study illustrates the significance of SiO2-complexa tion in hydrothermal solutions for gold, tin and other metallizations.

  18. Comparison of the thermal stabilities of NiSi films in Ni/Si, Ni/Pd/Si and Ni/Pt/Si systems

    CERN Document Server

    Wang, R N

    2003-01-01

    The effects of different interlayer materials (Pd and Pt) deposited between Ni films and Si substrates on the NiSi thermal stability are discussed. Ni sub 0 sub . sub 9 sub 4 sub 3 Pd sub 0 sub . sub 0 sub 5 sub 7 Si and Ni sub 0 sub . sub 9 sub 4 sub 5 Pt sub 0 sub . sub 0 sub 5 sub 5 Si solid solutions were formed when the samples were annealed at high temperatures and the lattice parameters of Ni sub 0 sub . sub 9 sub 4 sub 3 Pd sub 0 sub . sub 0 sub 5 sub 7 Si were calculated according to Vegard's law. The NiSi thermal stability was enhanced by interposing a Pd or Pt interlayer, and the sample with the Pt interlayer had the highest NiSi thermal stability among all the samples studied. This is attributed to the reduction of the interface energy between NiSi and Si substrates and the decrease of the driving force for the nucleation of NiSi sub 2 , induced by formation of the NiSi(200) preferred orientation and the solid solution respectively.

  19. Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Liu Jian

    2009-01-01

    Full Text Available Abstract Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondary nanostructures of SiO2 nanowires are highly dense grown on the primary Cd4SiS6 core-SiO2 sheath nanowires and formed hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.

  20. Theoretic Study on Band Structure of Si/SiNx Multilayer Film%Si/SiNx多层膜能带结构的理论研究

    Institute of Scientific and Technical Information of China (English)

    徐明; 魏屹; 何贤模; 芦伟

    2010-01-01

    利用Kronig-Penney模型计算了Si/SiNx多层膜结构中Si亚层的能带结构.结果表明,无论是减少Si或Si/SiNx亚层的厚度都将导致Si层的带隙发生宽化,计算结果与实验值符合较好.进而还发现,当Si层厚度减小时,Si/SiNx多层膜结构中载流子(电子和空穴)的有效质量均减小,有利于对载流子复合发光的控制.计算结果对实验上研究发光可控的Si/SiNx多层膜结构有重要指导意义.

  1. Differential cross sections measurement of 28Si(p,p/γ)28Si and 29Si(p,p/γ)29Si reactions for PIGE applications

    Science.gov (United States)

    Jokar, A.; Kakuee, O.; Lamehi-Rachti, M.

    2016-03-01

    Differential cross sections for gamma-ray emission from the 28Si(p,p/γ)28Si (Eγ = 1779 keV) and the 29Si(p,p/γ)29Si (Eγ = 1273 keV) nuclear reactions were measured in the energy range of 2.0-3.2 MeV and 2.0-3.0 MeV, respectively. The thin Si targets were prepared by evaporating natural SiO onto self-supporting Ag films. The gamma-rays and backscattered protons were detected simultaneously. An HPGe detector placed at an angle of 90° with respect to beam direction was employed to collect gamma-rays while an ion implanted Si detector placed at a scattering angle of 165° was used to detect backscattered protons. The great advantage of this work is that differential cross sections were obtained with a procedure irrespective of absolute value of the collected beam charge.

  2. Enhancement of the Si p-n diode NIR photoresponse by embedding [beta]-FeSi2 nanocrystallites

    National Research Council Canada - National Science Library

    A V Shevlyagin; D L Goroshko; E A Chusovitin; K N Galkin; N G Galkin; A K Gutakovskii

    2015-01-01

    ...+ -Si/p-Si/β-FeSi2 nanocrystallites/n-Si(111) diode structure was fabricated. Transmission electron microscopy data confirmed a well-defined multilayered structure with embedded nanocrystallites of two typical sizes...

  3. Relación entre la percepción del clima laboral que tiene el personal de enfermería y el cuidado humano que brinda a la paciente en la unidad de cuidados intensivos materno, del instituto nacional materno perinatal, Lima, 2014.

    OpenAIRE

    Espinoza de la Sota, Irene Beatriz

    2015-01-01

    El presente trabajo de investigación tiene como objetivo determinar la relación entre la percepción del clima laboral que tiene el personal de enfermería y el cuidado humano que brinda a la paciente de la Unidad de Cuidados Intensivos Materno del Instituto Nacional Materno Perinatal, lima 2014, el estudio es de diseño no experimental correlacional y transversal, la población estuvo constituida por el personal de enfermería que fueron 28, quienes trabajan en la Unidad de Cuidados Intensivos M...

  4. Deformation effects in the 28Si + 12C and 28Si + 28Si reactions

    Indian Academy of Sciences (India)

    C Bhattacharya; M Rousseau; C Beck; V Rauch; R M Freeman; R Nouicer; F Haas; O Dorvaux; K Eddahbi; P Papka; O Stezwski; S Szilner; D Mahboub; A Szanto De Toledo; A Hachem; E Martin; S J Sanders

    2001-07-01

    The possible occurrence of highly deformed configurations is investigated in the 40Ca and 56Ni di-nuclear systems as formed in the 28Si + 12C, 28Si reactions by using the properties of emitted light charged particles. Inclusive as well as exclusive data of the heavy fragments and their associated light charged particles have been collected by using the ICARE charged particle multidetector array. The data are analysed by Monte Carlo CASCADE statistical-model calculations using a consistent set of parameters with spin-dependent level densities. Significant deformation effects at high spin are observed as well as an unexpected large 8Be cluster emission of a binary nature.

  5. Corrosion properties of amorphous Mo-Si-N and nanolayered Mo-Si-Nn/SiC coatings

    Energy Technology Data Exchange (ETDEWEB)

    Torri, P.; Mahiout, A.; Koskinen, J.; Hirvonen, J.P.; Johansson, L.S.

    2000-02-01

    Corrosion properties of sputter deposited MoSi{sub 2}, SiC, Mo-Si-N (MoSi{sub 2.2}N{sub 2.5}) and nanolayered Mo-Si-N/SiC coatings on Fe37 low carbon steel have been studied using electrochemical polarization measurements in 1 N H{sub 2}SO{sub 4} solution. A decrease in both critical current density for passivation and minimum current in passive state was observed in annealed nanolayered Mo-Si-N/SiC coating compared to each of its constituents alone as single layer coating. On contrary to MoSi{sub 2} coating, only slight increase in critical current density was observed in Mo-Si-N coated sample after annealing. Molybdenum disilicide source material has good thermal and electrical conductivity, which allows effective dc-magnetron sputter deposition. Therefore this is a relatively simple method to produce amorphous coatings which have a high crystallization temperature and promising properties for corrosion applications.

  6. An Isotope Study of Hydrogenation of poly-Si/SiOx Passivated Contacts for Si Solar Cells: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Schnabel, Manuel; Nemeth, William; van de Loo, Bas, W.H.; Macco, Bart; Kessels, Wilhelmus, M.M.; Stradins, Paul; Young, David, L.

    2017-06-26

    For many years, the record Si solar cell efficiency stood at 25.0%. Only recently have several companies and institutes managed to produce more efficient cells, using passivated contacts of made doped poly-Si or a-Si:H and a passivating intrinsic interlayer in all cases. Common to these designs is the need to passivate the layer stack with hydrogen. In this contribution, we perform a systematic study of passivated contact passivation by hydrogen, using poly-Si/SiOx passivated contacts on n-Cz-Si, and ALD Al2O3 followed by a forming gas anneal (FGA) as the hydrogen source. We study p-type and n-type passivated contacts with implied Voc exceeding 690 and 720 mV, respectively, and perform either the ALD step or the FGA with deuterium instead of hydrogen in order to separate the two processes via SIMS. By examining the deuterium concentration at the SiOx in both types of samples, we demonstrate that the FGA supplies negligible hydrogen species to the SiOx, regardless of whether the FGA is hydrogenated or deuterated. Instead, it supplies the thermal energy needed for hydrogen species in the Al2O3 to diffuse there. Furthermore, the concentration of hydrogen species at the SiOx can saturate while implied Voc continues to increase, showing that the energy from the FGA is also required for hydrogen species already at the SiOx to find recombination-active defects to passivate.

  7. GeSn/Si Avalanche Photodetectors on Si substrates

    Science.gov (United States)

    2016-09-16

    Photodetectors on Si substrates Report Title In this project, firstly, the material growth of GeSn by chemical vapor deposition (CVD) system has been...between GeSn and other market dominating IR detectors in short-IR wavelength (First time reported the D* of a GeSn detector in the world). The D* of...Standard Form 298 (Rev 8/98) Prescribed by ANSI Std. Z39.18 Final Report W911NF-13-1-0196 64461-EL-DRP.43 479-575-7265 a. REPORT 14. ABSTRACT 16

  8. Fiber/matrix interfaces for SiC/SiC composites: Multilayer SiC coatings

    Energy Technology Data Exchange (ETDEWEB)

    Halverson, H.; Curtin, W.A. [Virginia Polytechnic Institute and State Univ., Blacksburg, VA (United States)

    1996-08-01

    Tensile tests have been performed on composites of CVI SiC matrix reinforced with 2-d Nicalon fiber cloth, with either pyrolitic carbon or multilayer CVD SiC coatings [Hypertherm High-Temperature Composites Inc., Huntington Beach, CA.] on the fibers. To investigate the role played by the different interfaces, several types of measurements are made on each sample: (i) unload-reload hysteresis loops, and (ii) acoustic emission. The pyrolitic carbon and multilayer SiC coated materials are remarkably similar in overall mechanical responses. These results demonstrate that low-modulus, or compliant, interface coatings are not necessary for good composite performance, and that complex, hierarchical coating structures may possibly yield enhanced high-temperature performance. Analysis of the unload/reload hysteresis loops also indicates that the usual {open_quotes}proportional limit{close_quotes} stress is actually slightly below the stress at which the 0{degrees} load-bearing fibers/matrix interfaces slide and are exposed to atmosphere.

  9. Three-dimensional crossbar arrays of self-rectifying Si/SiO2/Si memristors

    Science.gov (United States)

    Li, Can; Han, Lili; Jiang, Hao; Jang, Moon-Hyung; Lin, Peng; Wu, Qing; Barnell, Mark; Yang, J. Joshua; Xin, Huolin L.; Xia, Qiangfei

    2017-06-01

    Memristors are promising building blocks for the next-generation memory and neuromorphic computing systems. Most memristors use materials that are incompatible with the silicon dominant complementary metal-oxide-semiconductor technology, and require external selectors in order for large memristor arrays to function properly. Here we demonstrate a fully foundry-compatible, all-silicon-based and self-rectifying memristor that negates the need for external selectors in large arrays. With a p-Si/SiO2/n-Si structure, our memristor exhibits repeatable unipolar resistance switching behaviour (105 rectifying ratio, 104 ON/OFF) and excellent retention at 300 °C. We further build three-dimensinal crossbar arrays (up to five layers of 100 nm memristors) using fluid-supported silicon membranes, and experimentally confirm the successful suppression of both intra- and inter-layer sneak path currents through the built-in diodes. The current work opens up opportunities for low-cost mass production of three-dimensional memristor arrays on large silicon and flexible substrates without increasing circuit complexity.

  10. High-efficiency si/polymer hybrid solar cells based on synergistic surface texturing of Si nanowires on pyramids.

    Science.gov (United States)

    He, Lining; Lai, Donny; Wang, Hao; Jiang, Changyun; Rusli

    2012-06-11

    An efficient Si/PEDOT:PSS hybrid solar cell using synergistic surface texturing of Si nanowires (SiNWs) on pyramids is demonstrated. A power conversion efficiency (PCE) of 9.9% is achieved from the cells using the SiNW/pyramid binary structure, which is much higher than similar cells based on planar Si, pyramid-textured Si, and SiNWs. The PCE is the highest reported to-date for hybrid cells based on Si nanostructures and PEDOT.

  11. Simulation analysis of the effects of a back surface field on a p-a-Si:H/n-c-Si/n+-a-Si:H heterojunction solar cell

    Institute of Scientific and Technical Information of China (English)

    Hu Yuehui; Zhang Xiangwen; Qu Minghao; Wang Lifu; Zeng Tao; Xie Yaojiang

    2009-01-01

    In order to investigate the effects of a back surface field (BSF) on the performance of a p-doped amorphous silicon (p-a-Si:H)/n-doped crystalline silicon (n-c-Si) solar cell, a heterojunction solar cell with a p-a-Si:H/nc-Si/n+-a-Si:H structure was designed. An n+-a-Si:H film was deposited on the back of an n-c-Si wafer as the BSF.The photovoltaic performance of p-a-Si:H/n-c-Si/n+-a-Si:H solar cells were simulated. It was shown that the BSF of the p-a-Si:H/n-c-Si/n+-a-Si:H solar cells could effectively inhibit the decrease of the cell performance caused by interface states.

  12. High-performance a -Si/c-Si heterojunction photoelectrodes for photoelectrochemical oxygen and hydrogen evolution

    KAUST Repository

    Wang, Hsin Ping

    2015-05-13

    Amorphous Si (a-Si)/crystalline Si (c-Si) heterojunction (SiHJ) can serve as highly efficient and robust photoelectrodes for solar fuel generation. Low carrier recombination in the photoelectrodes leads to high photocurrents and photovoltages. The SiHJ was designed and fabricated into both photoanode and photocathode with high oxygen and hydrogen evolution efficiency, respectively, by simply coating of a thin layer of catalytic materials. The SiHJ photoanode with sol-gel NiOx as the catalyst shows a current density of 21.48 mA/cm2 at the equilibrium water oxidation potential. The SiHJ photocathode with 2 nm sputter-coated Pt catalyst displays excellent hydrogen evolution performance with an onset potential of 0.640 V and a solar to hydrogen conversion efficiency of 13.26%, which is the highest ever reported for Si-based photocathodes. © 2015 American Chemical Society.

  13. Microstructures and Properties of Ti-Coated SiCp Reinforced Al-Si Alloy Composites

    Science.gov (United States)

    Feng, Yan; Ren, Junpeng; Dong, Cuige; Wang, Richu

    2016-12-01

    A double-layer structure of Ti coating was plated on the surface of SiC particles using a diffusion method in a vacuum reactor, which is a new method to fabricate a Ti-coating layer on the SiC particles. The phase structure of Ti coating on the surface of SiC particles was composed inside of Ti5Si3 and outside of TiC investigated by x-ray diffraction. The Ti5Si3 and TiC double-layer structure realizes the tight chemical bonding between SiC particles and the Ti coating, and significantly promotes the wettability between the aluminum matrix and the Ti-coated SiC particles. The Ti-coated SiCp-reinforced Al-Si composites are prepared by a powder metallurgy method, and express excellent relative densities, desirable mechanical properties and frictional wear resistance.

  14. Phase transformation in SiOx/SiO₂ multilayers for optoelectronics and microelectronics applications.

    Science.gov (United States)

    Roussel, M; Talbot, E; Pratibha Nalini, R; Gourbilleau, F; Pareige, P

    2013-09-01

    Due to the quantum confinement, silicon nanoclusters (Si-ncs) embedded in a dielectric matrix are of prime interest for new optoelectronics and microelectronics applications. In this context, SiO(x)/SiO₂ multilayers have been prepared by magnetron sputtering and subsequently annealed to induce phase separation and Si clusters growth. The aim of this paper is to study phase separation processes and formation of nanoclusters in SiO(x)/SiO₂ multilayers by atom probe tomography. Influences of the silicon supersaturation, annealing temperature and SiO(x) and SiO₂ layer thicknesses on the final microstructure have been investigated. It is shown that supersaturation directly determines phase separation regime between nucleation/classical growth and spinodal decomposition. Annealing temperature controls size of the particles and interface with the surrounding matrix. Layer thicknesses directly control Si-nc shapes from spherical to spinodal-like structures.

  15. Propagation of misfit dislocations from buffer/Si interface into Si

    Science.gov (United States)

    Liliental-Weber, Zuzanna [El Sobrante, CA; Maltez, Rogerio Luis [Porto Alegre, BR; Morkoc, Hadis [Richmond, VA; Xie, Jinqiao [Raleigh, VA

    2011-08-30

    Misfit dislocations are redirected from the buffer/Si interface and propagated to the Si substrate due to the formation of bubbles in the substrate. The buffer layer growth process is generally a thermal process that also accomplishes annealing of the Si substrate so that bubbles of the implanted ion species are formed in the Si at an appropriate distance from the buffer/Si interface so that the bubbles will not migrate to the Si surface during annealing, but are close enough to the interface so that a strain field around the bubbles will be sensed by dislocations at the buffer/Si interface and dislocations are attracted by the strain field caused by the bubbles and move into the Si substrate instead of into the buffer epi-layer. Fabrication of improved integrated devices based on GaN and Si, such as continuous wave (CW) lasers and light emitting diodes, at reduced cost is thereby enabled.

  16. From Si wafers to cheap and efficient Si electrodes for Li-ion batteries

    Science.gov (United States)

    Gauthier, Magali; Reyter, David; Mazouzi, Driss; Moreau, Philippe; Guyomard, Dominique; Lestriez, Bernard; Roué, Lionel

    2014-06-01

    High-energy ball milling is used to recycle Si wafers to produce Si powders for negative electrodes of Li-ion batteries. The resulting Si powder consists in micrometric Si agglomerates made of cold-welded submicrometric nanocrystalline Si particles. Silicon-based composite electrodes prepared with ball-milled Si wafer can achieve more than 900 cycles with a capacity of 1200 mAh g-1 of Si (880 mAh g-1 of electrode) and a coulombic efficiency higher than 99%. This excellent electrochemical performance lies in the use of nanostructured Si produced by ball milling, the electrode formulation in a pH 3 buffer solution with CMC as binder and the use of FEC/VC additives in the electrolyte. This work opens the way to an economically attractive recycling of Si wastes.

  17. Fusion of Si28+Si28,30: Different trends at sub-barrier energies

    Science.gov (United States)

    Montagnoli, G.; Stefanini, A. M.; Esbensen, H.; Jiang, C. L.; Corradi, L.; Courtin, S.; Fioretto, E.; Grebosz, J.; Haas, F.; Jia, H. M.; Mazzocco, M.; Michelagnoli, C.; Mijatović, T.; Montanari, D.; Parascandolo, C.; Scarlassara, F.; Strano, E.; Szilner, S.; Torresi, D.

    2014-10-01

    Background: The fusion excitation function of the system Si28+Si28 at energies near and below the Coulomb barrier is known only down to ≃15 mb. This precludes any information on both coupling effects on sub-barrier cross sections and the possible appearance of hindrance. For Si28+Si30 even if the fusion cross section is measured down to ≃50 μb, the evidence of hindrance is marginal. Both systems have positive fusion Q values. While Si28 has a deformed oblate shape, Si30 is spherical. Purpose: We investigate 1. the possible influence of the different structure of the two Si isotopes on the fusion excitation functions in the deep sub-barrier region and 2. whether hindrance exists in the Si+Si systems and whether it is strong enough to generate an S-factor maximum, thus allowing a comparison with lighter heavy-ion systems of astrophysical interest. Methods: Si28 beams from the XTU Tandem accelerator of the INFN Laboratori Nazionali di Legnaro were used. The setup was based on an electrostatic beam separator, and fusion evaporation residues (ER) were detected at very forward angles. Angular distributions of ER were measured. Results: Fusion cross sections of Si28+Si28 have been obtained down to ≃600 nb. The slope of the excitation function has a clear irregularity below the barrier, but no indication of a S-factor maximum is found. For Si28+Si30 the previous data have been confirmed and two smaller cross sections have been measured down to ≃4 μb. The trend of the S-factor reinforces the previous weak evidence of hindrance. Conclusions: The sub-barrier cross sections for Si28+Si28 are overestimated by coupled-channels calculations based on a standard Woods-Saxon potential, except for the lowest energies. Calculations using the M3Y+repulsion potential are adjusted to fit the Si28+Si28 and the existing Si30+Si30 data. An additional weak imaginary potential (probably simulating the effect of the oblate Si28 deformation) is required to fit the low-energy trend of

  18. Electrical Performance of Electron Irradiated SiGe HBT and Si BJT

    Institute of Scientific and Technical Information of China (English)

    Wentao HUANG; Jilin WANG; Zhinong LIU; Peiyi CHEN; Peihsin TSIEN; Xiangti MENG

    2004-01-01

    The change of electrical performances of 1 MeV electron irradiated silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) and Si bipolar junction transistor (BJT) was studied. After electron irradiation, both the collector current IC and the base current IB changed a little, and the current gainβ decreased a little for SiGe HBT. The higher the electron irradiation fluence was, the lower the IC decreased. For conventional Si BJT, IC and IB increased as well asβ decreased much larger than SiGe HBT under the same fluence. The contribution of IB was more important to the degradation ofβ for both SiGeHBT and Si BJT. It was shown that SiGe HBT had a larger anti-radiation threshold and better anti-radiation performance than Si BJT. The mechanism of electrical performance changes induced by irradiation was preliminarily discussed.

  19. Nonisovalent Si-III-V and Si-II-VI alloys: Covalent, ionic, and mixed phases

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Joongoo; Park, Ji-Sang; Stradins, Pauls; Wei, Su-Huai

    2017-07-01

    Nonequilibrium growth of Si-III-V or Si-II-VI alloys is a promising approach to obtaining optically more active Si-based materials. We propose a new class of nonisovalent Si2AlP (or Si2ZnS) alloys in which the Al-P (or Zn-S) atomic chains are as densely packed as possible in the host Si matrix. As a hybrid of the lattice-matched parent phases, Si2AlP (or Si2ZnS) provides an ideal material system with tunable local chemical orders around Si atoms within the same composition and structural motif. Here, using first-principles hybrid functional calculations, we discuss how the local chemical orders affect the electronic and optical properties of the nonisovalent alloys.

  20. Study of indentation induced cracks in MoSi2-reaction bonded SiC ceramics

    Indian Academy of Sciences (India)

    O P Chakrabarti; P K Das; S Mondal

    2001-04-01

    MoSi2–RBSC composite samples were prepared by infiltration of Si–2 at.% Mo melt into a preform of commercial SiC and petroleum coke powder. The infiltrated sample had a density > 92% of the theoretical density (TD) and microstructurally contained SiC, MoSi2, residual Si and unreacted C. The material was tested for indentation fracture toughness at room temperature with a Vicker’s indenter and KIC was found to be 4.42 MPa√m which is around 39% higher than the conventional RBSC material. Enhancement in indentation fracture toughness is explained in terms of bowing of propagating cracks through MoSi2/SiC interface which is under high thermal stress arising from the thermal expansion mismatch between MoSi2 and SiC.

  1. Switching Performance Evaluation of Commercial SiC Power Devices (SiC JFET and SiC MOSFET) in Relation to the Gate Driver Complexity

    DEFF Research Database (Denmark)

    Pittini, Riccardo; Zhang, Zhe; Andersen, Michael A. E.

    2013-01-01

    and JFETs. The recent introduction of SiC MOSFET has proved that it is possible to have highly performing SiC devices with a minimum gate driver complexity; this made SiC power devices even more attractive despite their device cost. This paper presents an analysis based on experimental results...... of the switching losses of various commercially available Si and SiC power devices rated at 1200 V (Si IGBTs, SiC JFETs and SiC MOSFETs). The comparison evaluates the reduction of the switching losses which is achievable with the introduction of SiC power devices; this includes analysis and considerations...

  2. Fabrication and characterization of Ti3SiC2–SiC nanocomposite by in situ reaction synthesis of TiC/Si/Al powders

    Indian Academy of Sciences (India)

    Baoyan Liang; Mingzhi Wang; Xiaopu Li; Yunchao Mu

    2011-12-01

    The microstructure and mechanical properties of Ti3SiC2–SiC nanocomposite fabricated by in situ hot pressing (HP) synthesis process were studied. The results show that dense Ti3SiC2–SiC composite contained minor TiSi2 obtained by hot sintering at 1350°C for 1 h. The average grain size of Ti3SiC2 was 4 m in length, and the size of SiC grains is about 100 nm. With its fine microstructure, the Ti3SiC2–SiC nanocomposite shows good mechanical properties.

  3. Si3N4/SiC nanocomposite powder from a preceramic polymeric network based on poly(methylsilane as the SiC precursor

    Directory of Open Access Journals (Sweden)

    Maurício F. Gozzi

    2001-01-01

    Full Text Available Si3N4/SiC nanocomposite powders were obtained from a preceramic polymeric network based on poly(methylsilane as the in situ quasi-stoichiometric SiC source. These powders were constituted of nanosized SiC particles homogeneously distributed in the Si3N4 particulate matrix. beta-SiC whiskers were grown at 1400 °C in the pores of the matrix. At 1600 °C, the alpha -> beta Si3N4 phase transition took place, but no elemental silicon from Si3N4 decomposition was detected, evidencing the protective effect of the SiC phase.

  4. Interfacial stability of CoSi2/Si structures grown by molecular beam epitaxy

    Science.gov (United States)

    George, T.; Fathauer, R. W.

    1992-01-01

    The stability of CoSi2/Si interfaces was examined in this study using columnar silicide structures grown on (111) Si substrates. In the first set of experiments, Co and Si were codeposited using MBE at 800 C and the resulting columnar silicide layer was capped by epitaxial Si. Deposition of Co on the surface of the Si capping layer at 800 C results in the growth of the buried silicide columns. The buried columns grow by subsurface diffusion of the deposited Co, suppressing the formation of surface islands of CoSi2. The column sidewalls appear to be less stable than the top and bottom interfaces, resulting in preferential lateral growth and ultimately in the coalescence of the columns to form a continuous buried CoSi2 layer. In the second set of experiments, annealing of a 250 nm-thick buried columnar layer at 1000 C under a 100 nm-thick Si capping layer results in the formation of a surface layer of CoSi2 with a reduction in the sizes of the CoSi2 columns. For a sample having a thicker Si capping layer the annealing leads to Ostwald ripening producing buried equiaxed columns. The high CoSi2/Si interfacial strain could provide the driving force for the observed behavior of the buried columns under high-temperature annealing.

  5. Photoluminescence and structural properties of Si/SiC core–shell nanowires growth by HWCVD

    Energy Technology Data Exchange (ETDEWEB)

    Nazarudin, Nur Fatin Farhanah Binti; Mohd Noor, Nurul Jannah Binti; Rahman, Saadah Abdul; Goh, Boon Tong, E-mail: boontong77@yahoo.com

    2015-01-15

    Si/SiC core–shell nanowires grown by hot-wire chemical vapor deposition were studied. Ni nanoparticles act as metal nano-templates to catalyze the growth of these core–shell nanowires. These nanowires were grown at different deposition pressures of 0.5 and 1 mbar. The nanowires showed a tapered-like morphology at deposition pressure 0.5 mbar. Increase in pressure to 1 mbar leads to a formation of agglomerated grains at the root of the nanowires. The results show that these nanowires consisted of crystalline Si core and amorphous SiC shell nanowires. Increase in pressure enhanced the formation of SiC phase in the shell of the nanowires. On the other hand, the formation of the agglomerated grains attributed to an increasing of the SiC phase at higher deposition pressure. The presence of Si and SiC nano-crystallites embedded within an amorphous matrix exhibited a room temperature PL emission in the range of 400–1000 nm. The effects of the deposition pressure on the optical and structural properties of the nanowires are also discussed. - Highlights: • Growth of Si/SiC core–shell nanowires by HWCVD. • The nanowires consisted of crystalline Si core and amorphous SiC shell. • Metal nano-templates catalyzed the growth of Si core nanowires. • Increase in deposition pressure enhanced the SiC phase. • The presence of nano-crystallites exhibited a room temperature PL.

  6. Resonance Raman mapping as a tool to monitor and manipulate Si nanocrystals in Si-SiO{sub 2} nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Rani, Ekta; Ingale, Alka A., E-mail: alka@rrcat.gov.in [Laser Physics Applications Section, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Homi Bhabha National Institute, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Chaturvedi, A. [Laser Material Processing Division, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Joshi, M. P.; Kukreja, L. M. [Homi Bhabha National Institute, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India); Laser Material Processing Division, Raja Ramanna Centre for Advanced Technology, Indore-452013 (India)

    2015-10-19

    Specially designed laser heating experiment along with Raman mapping on Si-SiO{sub 2} nanocomposites elucidates the contribution of core and surface/interface in the intermediate frequency range (511–514 cm{sup −1}) Si phonons. The contribution of core to surface/interface increases with the size of Si nanocrystal, which itself increases on laser irradiation. Further, it is found that resonance Raman is crucial to the observance of surface/interface phonons and wavelength dependent Raman mapping can be corroborated with band edges observed in absorption spectra. This understanding can be gainfully used to manipulate and characterize Si-SiO{sub 2} nanocomposite, simultaneously for photovoltaic device applications.

  7. Airborne Emissions from Si/FeSi Production

    Science.gov (United States)

    Kero, Ida; Grådahl, Svend; Tranell, Gabriella

    2017-02-01

    The management of airborne emissions from silicon and ferrosilicon production is, in many ways, similar to the management of airborne emissions from other metallurgical industries, but certain challenges are highly branch-specific, for example the dust types generated and the management of NO X emissions by furnace design and operation. A major difficulty in the mission to reduce emissions is that information about emission types and sources as well as abatement and measurement methods is often scarce, incomplete and scattered. The sheer diversity and complexity of the subject presents a hurdle, especially for new professionals in the field. This article focuses on the airborne emissions from Si and FeSi production, including greenhouse gases, nitrogen oxides, airborne particulate matter also known as dust, polyaromatic hydrocarbons and heavy metals. The aim is to summarize current knowledge in a state-of-the-art overview intended to introduce fresh industry engineers and academic researchers to the technological aspects relevant to the reduction of airborne emissions.

  8. Impact Resistance of Uncoated SiC/SiC Composites

    Science.gov (United States)

    Bhatt, Ramakrishna T.; Choi, Sung R.; Cosgriff, Laura M.; Fox, Dennis S.; Lee, Kang N.

    2008-01-01

    Two-dimensional woven SiC/SiC composites fabricated by melt infiltration method were impact tested at room temperature and at 1316 C in air using 1.59-mm diameter steel-ball projectiles at velocities ranging from 115 to 400 m/s. The extent of substrate damage with increasing projectile velocity was imaged and analyzed using optical and scanning electron microscopy, and non-destructive evaluation (NDE) methods such as pulsed thermography, and computed tomography. The impacted specimens were tensile tested at room temperature to determine their residual mechanical properties. Results indicate that at 115 m/s projectile velocity, the composite showed no noticeable surface or internal damage and retained its as-fabricated mechanical properties. As the projectile velocity increased above this value, the internal damage increased and mechanical properties degraded: At velocities >300 m/s, the projectile penetrated through the composite, but the composite retained approx.50% of the ultimate tensile strength of the as-fabricated composite and exhibited non-brittle failure. Predominant internal damages are delamination of fiber plies, fiber fracture and matrix shearing.

  9. Airborne Emissions from Si/FeSi Production

    Science.gov (United States)

    Kero, Ida; Grådahl, Svend; Tranell, Gabriella

    2016-10-01

    The management of airborne emissions from silicon and ferrosilicon production is, in many ways, similar to the management of airborne emissions from other metallurgical industries, but certain challenges are highly branch-specific, for example the dust types generated and the management of NO X emissions by furnace design and operation. A major difficulty in the mission to reduce emissions is that information about emission types and sources as well as abatement and measurement methods is often scarce, incomplete and scattered. The sheer diversity and complexity of the subject presents a hurdle, especially for new professionals in the field. This article focuses on the airborne emissions from Si and FeSi production, including greenhouse gases, nitrogen oxides, airborne particulate matter also known as dust, polyaromatic hydrocarbons and heavy metals. The aim is to summarize current knowledge in a state-of-the-art overview intended to introduce fresh industry engineers and academic researchers to the technological aspects relevant to the reduction of airborne emissions.

  10. Evaluation of photovoltaic properties of nanocrystalline-FeSi2/Si heterojunctions

    Science.gov (United States)

    Shaban, Mahmoud; Bayoumi, Amr M.; Farouk, Doaa; Saleh, Mohamed B.; Yoshitake, Tsuyoshi

    2016-09-01

    In this paper, an application of nanocrystalline iron disilicide (NC-FeSi2) combined with nanocrystalline-Si (NC-Si) in a heterostructured solar cell is introduced and numerically evaluated in detail. The proposed cell structure is studied based on an experimental investigation of photovoltaic properties of NC-FeSi2/crystalline-Si heterojunctions, composed of unintentionally-doped NC-FeSi2 thin film grown on Si substrate. Photoresponse measurement of NC-FeSi2/crystalline-Si heterojunction confirmed ability of NC-FeSi2 to absorb NIR light and to generate photocarriers. However, collection of these carriers was not so efficient and a radical improvement in design of the device is required. Therefore, a modified device structure, comprising of NC-FeSi2 layer sandwiched between two heavily-doped p- and n-type NC-Si, is suggested and numerically evaluated. Simulation results showed that the proposed structure would exhibit a relatively high conversion efficiency of 25%, due to an improvement in collection efficiency of photogenerated carriers in the NC-FeSi2 and NC-Si layers. To attain such efficiency, defect densities in NC-FeSi2 and NC-Si layers should be kept less than 1014 and 1016 cm-3 eV-1, respectively. Remarkable optical and electrical properties of NC-FeSi2, employed in the proposed structure, facilitate improving device quantum efficiency spectrum providing significant spectrum extension into the near-infrared region beyond Si bandgap.

  11. Charted Choices 2013-2017. An analysis of ten election programmes. Effects on the economy and the environment; Keuzes in Kaart 2013-2017. Een analyse van tien verkiezingsprogramma's. Effecten op economie en milieu

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2010-05-15

    At the request of ten political parties, the Netherlands Bureau for Economic Policy Analysis (CPB) and PBL Netherlands Environmental Assessment Agency have mapped out the effects of the respective election platforms on the economy and the environment. The analysis shows that each of the proposed policy measures included in the platforms has both advantages and disadvantages. The platforms thus reflect the diverse choices that have been made by the parties. The publication presents the impact of party programs on public finances, purchasing power and employment. Also included in the publication are analyses in the field of mobility, energy and climate, nature, education, housing and healthcare [Dutch] De verkiezingsprogramma's 2012 laten zien welke keuzes politieke partijen maken voor de jaren 2013-2017. De programma's tonen aan dat er echt iets te kiezen valt voor de komende kabinetsperiode. Hoe gaan we na de economische crisis de overheidsfinancien weer op orde brengen en hoe snel? Verhogen we de AOW-leeftijd en beperken we de aftrek van de hypotheekrente, of juist niet? Hoe verminderen we de filedruk? Willen we klimaatverandering aanpakken en zo ja, hoe dan? Is het de moeite waarde om meer geld uit te geven aan onderwijs of innovatie? Hoeveel trekken we uit voor natuur? Hoe kunnen we de woningmarkt beter laten functioneren? Hoe gaan we om met de stijging van de kosten van de zorg? In de aanloop naar de verkiezingen van 12 september 2012 hebben tien politieke partijen - VVD, PvdA, PVV, CDA, SP, D66, GroenLinks, ChristenUnie, SGP, DPK - gevraagd om een analyse van hun verkiezingsprogramma's. Het CPB heeft de economische effecten geanalyseerd, het PBL de effecten op milieu.

  12. In-Plane Si Nanowire Growth Mechanism in Absence of External Si Flux.

    Science.gov (United States)

    Curiotto, Stefano; Leroy, Frédéric; Cheynis, Fabien; Müller, Pierre

    2015-07-01

    We report on a new mechanism of nanowire formation: during Au deposition on Si(110) substrates, Au-Si droplets grow, move spontaneously, and fabricate a Si nanowire behind them in the absence of Si external flux. Nanowires are formed by Si dissolved from the substrate at the advancing front of the droplets and transported backward to the crystallization front. The droplet shape is determined by the Si etching anisotropy. The nanowire formation can be tuned by changing experimental parameters like substrate temperature and Au deposition rate.

  13. Si/SiO2/p-Si结构的电学特性

    Institute of Scientific and Technical Information of China (English)

    马自军; 马书懿

    2008-01-01

    用射频磁控溅射法在p-Si衬底上制备了Si/SiO2薄膜,利用Au/(Si/SiO2)/p-Si结构的I-V特性曲线对其电学特性进行了分析.结果表明,样品具有很好的整流作用,起整流作用的势垒存在于(Si/SiO2)/p-Si界面附近.

  14. Hydrogen Passivation Effect on Enhanced Luminescence from Nanocrystalline Si/SiO2 Multilayers

    Institute of Scientific and Technical Information of China (English)

    XIA Zheng-Yue; HAN Pei-Gao; XU Jun; CHEN De-Yuan; WEI De-Yuan; MA Zhong-Yuan; CHEN Kun-Ji; XU Ling; HUANG Xin-Fan

    2007-01-01

    Nanocrystalline Si/SiO2 multilayers are prepared by thermally annealing amorphous Si/SiO2 stacked structures.The photoluminescence intensity is obviously enhanced after hydrogen passivation at various temperatures. It is suggested that the hydrogen trapping and detrapping processes at different temperatures strongly influence the passivation effect. Direct experimental evidence is given by electron spin resonance spectra that hydrogen effectively reduces the nonradiative defect states existing in the Si nanocrystas/SiO2 system which enhances the radiative recombination probability. The luminescence characteristic shows its stability after hydrogen passivation even after aging eight months.

  15. 非晶硅/晶体硅(a-Si/c-Si)异质结%Property Investigation of a-Si/c-Si Hetero-Junction Structure

    Institute of Scientific and Technical Information of China (English)

    汪建强; 高华; 张剑; 张松; 李晨; 叶庆好; 孟凡英

    2011-01-01

    通过对非晶硅/晶体硅(a-Si/c-Si)异质结能带不连续、发射结掺杂以及界面态密度进行分析,研究它们对a-Si/c-Si异质结的界面特性,以及a-Si(N+)/c-Si(P)结构电池性能的影响.研究发现,能带不连续以及a-Si发射结高掺杂有利于实现界面复合机制由以悬挂键复合主导的复合机制向由少数载流子复合占主导的SRH(Shockly-Read-Hall)复合机制转变,有效降低界面复合速率.AFORS-HET软件模拟显示:在c-Si(P)衬底掺杂浓度为1.6×1016cm-3时,a-Si(N+)发射结掺杂浓度大于1.5×1020cm-3是获得高电池效率的必要条件;与短路电流密度相比,开路电压受a-Si/c-Si界面态密度影响更明显.%T his paper investigated the influence ot a-hi/c-bi band ottset, amorphous silicon emitter doping concentration and interface defects density on interface property of a-Si/c-Si structure. Band offset in a-Si(N+ )/c-Si(P) hetero-junction and a-Si emitter high level doping is very useful for the transformation of recombination mechanism from dangling bond to SRH (Shockly-Read-Hall). AFORS-HET simulation indicates that a-Si(N+ ) emitter doping level of over 1. 5X1020 cm~3 on c-Si(P) is an indispensable condition for achieving high efficiency. Comparing with density of short circuit current, open circuit voltage of a-Si/c-Si structure cell is much more susceptible to interface defect density.

  16. Epitaxy of Si1- x C x via ultrahigh-vacuum chemical vapor deposition using Si2H6, Si3H8, or Si4H10 as Si precursors

    Science.gov (United States)

    Koo, Sangmo; Jang, Hyunchul; Ko, Dae-Hong

    2017-09-01

    In this study, disilane (Si2H6), trisilane (Si3H8), and tetrasilane (Si4H10) were used as Si precursors for the growth of Si1- x C x epilayers, and the growth properties of the layers were compared. The use of a higher-order silane significantly increased the growth rates of the Si1- x C x epilayers at a processing temperature of 650 °C. In addition, a higher growth rate realized by using a higher-order silane promoted an increase in the substitutional carbon concentration in the Si1- x C x epilayers owing to the additional injection of a C-source gas (SiH3CH3) and the incorporation of C atoms into substitutional sites. The differences in growth properties between Si precursors were explained on the basis of reaction mechanisms.

  17. Magnetron-sputter epitaxy of {beta}-FeSi{sub 2}(220)/Si(111) and {beta}-FeSi{sub 2}(431)/Si(001) thin films at elevated temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Liu Hongfei; Tan Chengcheh; Chi Dongzhi [Institute of Materials Research and Engineering (IMRE), A-STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore)

    2012-07-15

    {beta}-FeSi{sub 2} thin films have been grown on Si(111) and Si(001) substrates by magnetron-sputter epitaxy at 700 Degree-Sign C. On Si(111), the growth is consistent with the commonly observed orientation of [001]{beta}-FeSi{sub 2}(220)//[1-10]Si(111) having three variants, in-plane rotated 120 Degree-Sign with respect to one another. However, on Si(001), under the same growth conditions, the growth is dominated by [-111]{beta}-FeSi{sub 2}(431)//[110]Si(001) with four variants, which is hitherto unknown for growing {beta}-FeSi{sub 2}. Photoelectron spectra reveal negligible differences in the valance-band and Fe2p core-level between {beta}-FeSi{sub 2} grown on Si(111) and Si(001) but an apparent increased Si-oxidization on the surface of {beta}-FeSi{sub 2}/Si(001). This phenomenon is discussed and attributed to the Si-surface termination effect, which also suggests that the Si/Fe ratio on the surface of {beta}-FeSi{sub 2}(431)/Si(001) is larger than that on the surface of {beta}-FeSi{sub 2}(220)/Si(111).

  18. SiC nanowires: material and devices

    Science.gov (United States)

    Zekentes, K.; Rogdakis, K.

    2011-04-01

    SiC nanowires are of high interest since they combine the physical properties of SiC with those induced by their low dimensionality. For this reason, a large number of scientific studies have been dedicated to their fabrication and characterization as well as to their application in devices. SiC nanowires' growth involving different growth mechanisms and configurations was the main theme for the large majority of these studies. Various physical characterization methods have been employed for evaluating SiC nanowire quality. SiC nanowires with narrow-diameter (channel material. On the other hand, the grown nanowires are suitable for field-emission applications and to be used as reinforcing material in composite structures as well as for increasing the hydrophobicity of Si surfaces. All these aspects are examined in detail in different sections of this paper.

  19. Polarization memory effect in the photoluminescence of nc-Si-SiOx light-emitting structures.

    Science.gov (United States)

    Michailovska, Katerina; Indutnyi, Ivan; Shepeliavyi, Petro; Sopinskyy, Mykola

    2016-12-01

    The polarization memory (PM) effect in the photoluminescence (PL) of the porous nc-Si-SiOx light-emitting structures, containing nanoparticles of silicon (nc-Si) in the oxide matrix and passivated in a solution of hydrofluoric acid (HF), has been investigated. The studied nc-Si-SiOx structures were produced by evaporation of Si monoxide (SiO) powder in vacuum and oblique deposition on Si wafer, and then the deposited silicon oxide (SiOx) films were annealed in the vacuum at 975 °C to grow nc-Si. It was found that the PM effect in the PL is observed only after passivation of nanostructures: during etching in HF solution, the initial symmetric nc-Si becomes asymmetric elongated. It was also found that in investigated nanostructures, there is a defined orientational dependence of the PL polarization degree (ρ) in the sample plane which correlates with the orientation of SiOx nanocolumns, forming the structure of the porous layer. The increase of the ρ values in the long-wavelength spectral range with time of HF treatment can be associated with increasing of the anisotropy of large Si nanoparticles. The PM effect for this spectral interval can be described by the dielectric model. In the short-wavelength spectral range, the dependence of the ρ values agrees qualitatively with the quantum confinement effect.

  20. Polarization memory effect in the photoluminescence of nc-Si-SiOx light-emitting structures

    Science.gov (United States)

    Michailovska, Katerina; Indutnyi, Ivan; Shepeliavyi, Petro; Sopinskyy, Mykola

    2016-06-01

    The polarization memory (PM) effect in the photoluminescence (PL) of the porous nc-Si-SiOx light-emitting structures, containing nanoparticles of silicon (nc-Si) in the oxide matrix and passivated in a solution of hydrofluoric acid (HF), has been investigated. The studied nc-Si-SiOx structures were produced by evaporation of Si monoxide (SiO) powder in vacuum and oblique deposition on Si wafer, and then the deposited silicon oxide (SiOx) films were annealed in the vacuum at 975 °C to grow nc-Si. It was found that the PM effect in the PL is observed only after passivation of nanostructures: during etching in HF solution, the initial symmetric nc-Si becomes asymmetric elongated. It was also found that in investigated nanostructures, there is a defined orientational dependence of the PL polarization degree ( ρ) in the sample plane which correlates with the orientation of SiOx nanocolumns, forming the structure of the porous layer. The increase of the ρ values in the long-wavelength spectral range with time of HF treatment can be associated with increasing of the anisotropy of large Si nanoparticles. The PM effect for this spectral interval can be described by the dielectric model. In the short-wavelength spectral range, the dependence of the ρ values agrees qualitatively with the quantum confinement effect.

  1. Study on in-situ Mg2Si/Al-Si composites with different compositions

    Institute of Scientific and Technical Information of China (English)

    Jing Qingxiu; Zhang Caixia; Huang Xiaodong

    2009-01-01

    Effects of chemical composition and heat treatment on microstructures and mechanical properties of in-situ Mg2Si/Al-Si composites were investigated. It was found that, in the microstructure of an Al-5.7wt% Mg2Si composite with 8.2wt% extra Si, the binary eutectic Mg2Si locates at the grain boundaries with an undeveloped Chinese script-like morphology, and the primary α-Al is formed into a cell structure due to the selective modification effect of the modifiers of mischmetal and Strontium salt; whereas in the composite with a near Al-Mg2Si eutectic composition and little extra Si content, the intercrescence eutectic Mg2Si formed with the binary eutectic a-Al grows into integrated Chinese script-like shape. As Si content increases, the eutectic Mg2Si dendrite becomes coarser in morphology but less in volum e fraction. Hardness and tensile strength of the cast Mg2Si/Al-Si composites do not increase with increasing of Mg content, but they are related to the size and morphology of the eutectic and primary Mg2Si phases. Heat treatment with optimal parameters is an effective way to improve the properties of the in-situ composites.

  2. siRNA的应用

    Institute of Scientific and Technical Information of China (English)

    孟立根; 马清河; 王安忠; 秦俊文

    2004-01-01

    RNAi(RNA interference,RNA阻断)当初是在研究绦虫C elegans时观测到的一种现象。当将双链的RNA(double stranded RNA;dsRNA)导人体内后,与这种双链RNA相同性较高的mRNA将被特异性地抑制或者消除。除了绦虫之外,RNAi已被作为一种研究基因功能的有效工具,广泛运用于植物、真菌、线虫、果蝇以及哺乳动物,并获得了好的效果。近来使用短链(21~23碱基对)siRNA(short interfering RNA)也获得了同样的效果。siRNA与传统RNA干涉技术相比具有极大的优越

  3. SiLix-C Nanocomposites

    Science.gov (United States)

    Henry, Francois

    2015-01-01

    For this Phase II project, Superior Graphite Co., in collaboration with the Georgia Institute of Technology and Streamline Nanotechnologies, Inc., developed, explored the properties of, and demonstrated the enhanced capabilities of novel nanostructured SiLix-C anodes. These anodes can retain high capacity at a rapid 2-hour discharge rate and at 0 C when used in Li-ion batteries. In Phase I, these advanced anode materials had specific capacity in excess of 1,000 mAh/g, minimal irreversible capacity losses, and stable performance for 20 cycles at C/1. The goals in Phase II were to develop and apply a variety of novel nanomaterials, fine-tune the properties of composite particles at the nanoscale, optimize the composition of the anodes, and select appropriate binder and electrolytes. In order to achieve a breakthrough in power characteristics of Li-ion batteries, the team developed new nanostructured SiLix-C anode materials to offer up to 1,200 mAh/g at C/2 at 0 C.

  4. Chemical compatibility issues associated with use of SiC/SiC in advanced reactor concepts

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, Dane F. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-09-01

    Silicon carbide/silicon carbide (SiC/SiC) composites are of interest for components that will experience high radiation fields in the High Temperature Gas Cooled Reactor (HTGR), the Very High Temperature Reactor (VHTR), the Sodium Fast Reactor (SFR), or the Fluoride-cooled High-temperature Reactor (FHR). In all of the reactor systems considered, reactions of SiC/SiC composites with the constituents of the coolant determine suitability of materials of construction. The material of interest is nuclear grade SiC/SiC composites, which consist of a SiC matrix [high-purity, chemical vapor deposition (CVD) SiC or liquid phase-sintered SiC that is crystalline beta-phase SiC containing small amounts of alumina-yttria impurity], a pyrolytic carbon interphase, and somewhat impure yet crystalline beta-phase SiC fibers. The interphase and fiber components may or may not be exposed, at least initially, to the reactor coolant. The chemical compatibility of SiC/SiC composites in the three reactor environments is highly dependent on thermodynamic stability with the pure coolant, and on reactions with impurities present in the environment including any ingress of oxygen and moisture. In general, there is a dearth of information on the performance of SiC in these environments. While there is little to no excess Si present in the new SiC/SiC composites, the reaction of Si with O2 cannot be ignored, especially for the FHR, in which environment the product, SiO2, can be readily removed by the fluoride salt. In all systems, reaction of the carbon interphase layer with oxygen is possible especially under abnormal conditions such as loss of coolant (resulting in increased temperature), and air and/ or steam ingress. A global outline of an approach to resolving SiC/SiC chemical compatibility concerns with the environments of the three reactors is presented along with ideas to quickly determine the baseline compatibility performance of SiC/SiC.

  5. Graphene/Si-nanowire heterostructure molecular sensors

    Science.gov (United States)

    Kim, Jungkil; Oh, Si Duk; Kim, Ju Hwan; Shin, Dong Hee; Kim, Sung; Choi, Suk-Ho

    2014-06-01

    Wafer-scale graphene/Si-nanowire (Si-NW) array heterostructures for molecular sensing have been fabricated by vertically contacting single-layer graphene with high-density Si NWs. Graphene is grown in large scale by chemical vapour deposition and Si NWs are vertically aligned by metal-assisted chemical etching of Si wafer. Graphene plays a key role in preventing tips of vertical Si NWs from being bundled, thereby making Si NWs stand on Si wafer separately from each other under graphene, a critical structural feature for the uniform Schottky-type junction between Si NWs and graphene. The molecular sensors respond very sensitively to gas molecules by showing 37 and 1280% resistance changes within 3.5/0.15 and 12/0.15 s response/recovery times under O2 and H2 exposures in air, respectively, highest performances ever reported. These results together with the sensor responses in vacuum are discussed based on the surface-transfer doping mechanism.

  6. Si isotope homogeneity of the solar nebula

    Energy Technology Data Exchange (ETDEWEB)

    Pringle, Emily A.; Savage, Paul S.; Moynier, Frédéric [Department of Earth and Planetary Sciences and McDonnell Center for the Space Sciences, Washington University in St. Louis, One Brookings Drive, St. Louis, MO 63130 (United States); Jackson, Matthew G. [Department of Earth Science, University of California, Santa Barbara, CA 93109 (United States); Barrat, Jean-Alix, E-mail: eapringle@wustl.edu, E-mail: savage@levee.wustl.edu, E-mail: pringle@ipgp.fr, E-mail: moynier@ipgp.fr, E-mail: jackson@geol.ucsb.edu, E-mail: Jean-Alix.Barrat@univ-brest.fr [Université Européenne de Bretagne, Université de Brest, CNRS UMR 6538 (Domaines Océaniques), I.U.E.M., Place Nicolas Copernic, F-29280 Plouzané Cedex (France)

    2013-12-20

    The presence or absence of variations in the mass-independent abundances of Si isotopes in bulk meteorites provides important clues concerning the evolution of the early solar system. No Si isotopic anomalies have been found within the level of analytical precision of 15 ppm in {sup 29}Si/{sup 28}Si across a wide range of inner solar system materials, including terrestrial basalts, chondrites, and achondrites. A possible exception is the angrites, which may exhibit small excesses of {sup 29}Si. However, the general absence of anomalies suggests that primitive meteorites and differentiated planetesimals formed in a reservoir that was isotopically homogenous with respect to Si. Furthermore, the lack of resolvable anomalies in the calcium-aluminum-rich inclusion measured here suggests that any nucleosynthetic anomalies in Si isotopes were erased through mixing in the solar nebula prior to the formation of refractory solids. The homogeneity exhibited by Si isotopes may have implications for the distribution of Mg isotopes in the solar nebula. Based on supernova nucleosynthetic yield calculations, the expected magnitude of heavy-isotope overabundance is larger for Si than for Mg, suggesting that any potential Mg heterogeneity, if present, exists below the 15 ppm level.

  7. The Si/Si_3N4 Interface and Si/Si_3N4 Submicron Mesa: A Multi-million Atom Molecular Dynamics Study

    Science.gov (United States)

    Bachlechner, Martina E.; Omeltchenko, Andrey; Nakano, Aiichiro; Kalia, Rajiv K.; Vashishta, Priya; Ebbsjö, Ingvar; Madhukar, Anupam

    1998-03-01

    Using molecular dynamics simulations on parallel computers, the interface structure, stress distribution, crack propagation and fracture in a Si_3N4 film on Si substrate are studied. Bulk Si is described by Stillinger-Weber potential and Si_3N4 is represented by a combination of two- and three-body covalent interactions. At the interface, the charge transfer is taken from LCAO electronic structure calculations (G.-L. Zhao and M.E. Bachlechner, Europhys. Lett. 36, 287 (1997)). Results for structural correlations at the interface and 3D stress distribution for the submicron mesa are presented.

  8. SiD Letter of Intent

    Energy Technology Data Exchange (ETDEWEB)

    Aihara, H., (Ed.); Burrows, P., (Ed.); Oreglia, M., (Ed.); Berger, E.L.; Guarino, V.; Repond, J.; Weerts, H.; Xia, L.; Zhang, J.; /Argonne, HEP; Zhang, Q.; /Argonne, HEP /Beijing, Inst. High Energy Phys.; Srivastava, A.; /Birla Inst. Tech. Sci.; Butler, J.M.; /Boston U.; Goldstein, Joel; Velthuis, J.; /Bristol U.; Radeka, V.; /Brookhaven; Zhu, R.-Y.; /Caltech.; Lutz, P.; /DAPNIA, Saclay; de Roeck, A.; Elsener, K.; Gaddi, A.; Gerwig, H.; /CERN /Cornell U., LNS /Ewha Women' s U., Seoul /Fermilab /Gent U. /Darmstadt, GSI /Imperial Coll., London /Barcelona, Inst. Microelectron. /KLTE-ATOMKI /Valencia U., IFIC /Cantabria Inst. of Phys. /Louis Pasteur U., Strasbourg I /Durham U., IPPP /Kansas State U. /Kyungpook Natl. U. /Annecy, LAPP /LLNL, Livermore /Louisiana Tech. U. /Paris U., VI-VII /Paris U., VI-VII /Munich, Max Planck Inst. /MIT, LNS /Chicago, CBC /Moscow State U. /Nanjing U. /Northern Illinois U. /Obninsk State Nucl. Eng. U. /Paris U., VI-VII /Strasbourg, IPHC /Prague, Inst. Phys. /Princeton U. /Purdue U. /Rutherford /SLAC /SUNY, Stony Brook /Barcelona U. /Bonn U. /UC, Davis /UC, Santa Cruz /Chicago U. /Colorado U. /Delhi U. /Hawaii U. /Helsinki U. /Indiana U. /Iowa U. /Massachusetts U., Amherst /Melbourne U. /Michigan U. /Minnesota U. /Mississippi U. /Montenegro U. /New Mexico U. /Notre Dame U. /Oregon U. /Oxford U. /Ramon Llull U., Barcelona /Rochester U. /Santiago de Compostela U., IGFAE /Hefei, CUST /Texas U., Arlington /Texas U., Dallas /Tokyo U. /Washington U., Seattle /Wisconsin U., Madison /Wayne State U. /Yale U. /Yonsei U.

    2012-04-11

    This document presents the current status of the Silicon Detector (SiD) effort to develop an optimized design for an experiment at the International Linear Collider. It presents detailed discussions of each of SiD's various subsystems, an overview of the full GEANT4 description of SiD, the status of newly developed tracking and calorimeter reconstruction algorithms, studies of subsystem performance based on these tools, results of physics benchmarking analyses, an estimate of the cost of the detector, and an assessment of the detector R and D needed to provide the technical basis for an optimised SiD.

  9. Si3N4-SiC材料的氧化性能研究%Study on Oxidation Performance of Si3N4-SiC

    Institute of Scientific and Technical Information of China (English)

    李杰

    2009-01-01

    通过对不同Si3N4含量、不同温度下Si3N4-SiC材料的氧化实验,分析氧化后的氧化增重率,得出Si3N4含量越高,材料氧化越严重;氧化温度越高,材料氧化越严重;且氧化增重率与氧化时间呈直线-抛物线规律.

  10. One-dimensional Si nanolines in hydrogenated Si(001)

    Science.gov (United States)

    François, Bianco; Köster, Sigrun A.; Owen, James G. H.; Renner, Christoph; Bowler, David R.

    2012-02-01

    We present a detailed study of the structural and electronic properties of a self-assembled silicon nanoline embedded in the H-terminated silicon (001) surface, known as the Haiku stripe. The nanoline is a perfectly straight and defect free endotaxial structure of huge aspect ratio; it can grow micrometre long at a constant width of exactly four Si dimers (1.54 nm). Another remarkable property is its capacity to be exposed to air without suffering any degradation. The nanoline grows independently of any step edges at tunable densities, from isolated nanolines to a dense array of nanolines. In addition to these unique structural characteristics, scanning tunnelling microscopy and density functional theory reveal a one-dimensional state confined along the Haiku core. This nanoline is a promising candidate for the long sought after electronic solid-state one-dimensional model system to explore the fascinating quantum properties emerging in such reduced dimensionality. Phys. Rev. B, 84, 035328 (2011)

  11. Thermogravimetric and microscopic analysis of SiC/SiC materials with advanced interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Windisch, C.F. Jr.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States); Snead, L.L. [Oak Ridge National Lab., TN (United States)

    1997-04-01

    The chemical stability of SiC/SiC composites with fiber/matrix interfaces consisting of multilayers of SiC/SiC and porous SiC have been evaluated using a thermal gravimetric analyzer (TGA). Previous evaluations of SiC/SiC composites with carbon interfacial layers demonstrated the layers are not chemically stable at goal use temperatures of 800-1100{degrees}C and O{sub 2} concentrations greater than about 1 ppm. No measureable mass change was observed for multilayer and porous SiC interfaces at 800-1100{degrees}C and O{sub 2} concentrations of 100 ppm to air; however, the total amount of oxidizable carbon is on the order of the sensitivity of the TGA. Further studies are in progress to evaluate the stability of these materials.

  12. Nature of visible luminescence of co-sputtered Si-SiO{sub x} systems

    Energy Technology Data Exchange (ETDEWEB)

    Torchynska, T.; Becerril Espinoza, F.G.; Goldstein, Y.; Savir, E.; Jedrzejewski, J.; Khomenkova, L.; Korsunska, N.; Yukhimchuk, V

    2003-12-31

    Photoluminescence (PL) spectra and Raman scattering spectra of Si-SiO{sub x} systems, prepared by radio frequency magnetron sputtering method and thermal annealed at 1150 deg. C for creation of Si nano-crystallites, were investigated as a function of Si content and Si nano-crystallite sizes. It was shown that the PL spectrum of such systems consists of several bands with peak positions at 1.32-1.34, 1.42-1.58, 1.77, 2.05 and 2.30 eV. The dependencies of these PL band parameters on concentration and size of Si nano-crystallites in the Si-SiO{sub x} system have been investigated and analyzed. The nature of radiative optical transitions for all PL bands is discussed.

  13. Optimization of Waveguide Structure for Tunable Optical Switch in Si/SiGe System

    Institute of Scientific and Technical Information of China (English)

    Seongjae Boo; Won-Taek Han

    2003-01-01

    A new electro-optical device using Si/SiGe-system with two parallel ridge waveguides is proposed for optical switching and the optimization of the structure for a single mode operation is investigated.

  14. Recycling of Al-Si die casting scraps for solar Si feedstock

    Science.gov (United States)

    Seo, Kum-Hee; Jeon, Je-Beom; Youn, Ji-Won; Kim, Suk Jun; Kim, Ki-Young

    2016-05-01

    Recycling of aluminum die-casting scraps for solar-grade silicon (SOG-Si) feedstock was performed successfully. 3 N purity Si was extracted from A383 die-casting scrap by using the combined process of solvent refining and an advanced centrifugal separation technique. The efficiency of separating Si from scrap alloys depended on both impurity level of scraps and the starting temperature of centrifugation. Impurities in melt and processing temperature governed the microstructure of the primary Si. The purity of Si extracted from the scrap melt was 99.963%, which was comparable to that of Si extracted from a commercial Al-30 wt% Si alloy, 99.980%. The initial purity of the scrap was 2.2% lower than that of the commercial alloy. This result confirmed that die-casting scrap is a potential source of high-purity Si for solar cells.

  15. Fabrication and characteristics of the nc-Si/c-Si heterojunction MAGFET

    Institute of Scientific and Technical Information of China (English)

    Zhao Xiaofeng; Wen Dianzhong

    2009-01-01

    A MAGFET using an nc-Si/c-Si heterojunction as source and drain was fabricated by CMOS technology, using two ohm-contact electrodes as Hall outputs on double sides of the channel situated 0.7L from the source. The experimental results show that when V_(DS) = -7.0 V, the magnetic sensitivity of the single nc-Si/c-Si heterojunction magnetic metal oxide semiconductor field effect transistor (MAGFET) with an L : W ratio of 2 : 1 is 21.26 mV/T,and that with an L : W ratio of 4 : 1 is 13.88 mV/T. When the outputs of double nc-Si/c-Si heterojunction MAGFETs with an L : W ratio of 4 : 1 are in series, their magnetic sensitivity is 22.74 mV/T, which is an improvement of about 64% compared with that of a single nc-Si/c-Si heterojunction MAGFET.

  16. 26Si Excited States via One-Neutron Removal from 27Si Using Radioactive Beam

    Science.gov (United States)

    Chen, J.; Chen, A. A.; Amthor, A. M.; Bazin, D.; Becerril, A. D.; Gade, A.; Galaviz, D.; Glasmacher, T.; Kahl, D.; Lorusso, G.; Matos, M.; Ouellet, C. V.; Pereira, J.; Schatz, H.; Smith, K. M.; Wales, B.; Weisshaar, D.; Zegers, R. G. T.

    2013-03-01

    A measurement of the p(27Si, d)26Si reaction has been performed to study levels of 26Si, with connections to the stellar 25Al(p, γ)26Si reaction rate. A beam of adioactive 27Si of energy 84.3 MeV/A was impinged on a polypropylene foil (CH2) of 180 mg/cm2 in thickness. De-excitation γ-rays were detected with a highly-segmented germanium detector array, in coincidence with the 26Si recoils. Our results are an independent measurement of states used in the energy calibration of other experiments on 26Si structure. They also suggest that the spin-parity of the Ex(26Si) = 6454 keV (Er = 940 keV) state should be 4+ instead of the previously adopted assignment of 0+.

  17. W-Mo-Si/SiC Oxidation Protective Coating for Carbon/Carbon Composites

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A W-Mo-Si/SiC double-layer oxidation protective coating for carbon/carbon (C/C) composites was prepared by a two-step pack cementation technique. XRD (X-ray diffraction) and SEM (scanning electron microscopy)results show that the coating obtained by the first step pack cementation was a thin inner buffer layer of SiC with some cracks and pores, and a new phase of (WxMo1-x)Si2 appeared after the second step pack cementation. Oxidation test shows that, after oxidation in air at 1773 K for 175 h and thermal cycling between 1773 K and room temperature for 18 times, the weight loss of the W-Mo-Si/SiC coated C/C composites was only 2.06%. The oxidation protective failure of the W-Mo-Si/SiC coating was attributed to the formation of some penetrable cracks in the coating.

  18. Behaviour of Oxygen-Implanted and Hydrogen-Implanted SiGe/Si Heterostructures

    Institute of Scientific and Technical Information of China (English)

    安正华; 张苗; 门传玲; 沈勤我; 林梓鑫; 李开成; 林成鲁

    2002-01-01

    For SiGe-on-insulator fabrication, a l00nm SiGe tilm with uniform germanium composition was grown on a Si(l00) substrate using a molecular beam epitaxy system without a graded SiGe buffer layer. The samples were implanted by oxygen ions at an energy of 45kev and a dose of 3 × 1017 cm-2, and annealed for five hours at 1250°C in flowing (Ar + 5% 02) atmosphere with a l00nm oxide protective layer. The result indicates that a buried oxide layer was successfully formed at the interface of SiGe and Si on the substrate. Furthermore,hydrogen was implanted into SiGe at the energy of 62keV and the dose of 6 × 1016 cm-2 to perform a blistering study, which confirmed the feasibility of H-induced layer splitting in SiGe layer.

  19. Characterization of ultrathin SiO 2/Si interface grown by low temperature plasma oxidation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Ultrathin SiO 2 layers on Si (100) wafers were prepared by plasma oxidation at a low temperature (250℃). The analyses of X-ray photoelectron spectroscopy (XPS) and TEM reveal that the chemical composition of the oxide layer is stoichiometric SiO 2 and the SiO 2/Si interface is abrupt. The thickness of the ultrathin oxide layer obtained from XPS, capacitance-voltage (C-V) and ellipsometry measurements indicate a nonlinear time dependence. The high frequency C-V characterization of MOS structure shows that the fixed charge density in SiO 2 film is about 10 11 cm -2 . It is also shown that the strength of breakdown electrical field of SiO 2 film with 6 nm thickness is of the order of 10 6 Vcm -1 . These properties of the ultrathin SiO 2 layer ensure its application in silicon quantum devices.

  20. Characterization of SiC-SiC composites for accident tolerant fuel cladding

    Science.gov (United States)

    Deck, C. P.; Jacobsen, G. M.; Sheeder, J.; Gutierrez, O.; Zhang, J.; Stone, J.; Khalifa, H. E.; Back, C. A.

    2015-11-01

    Silicon carbide (SiC) is being investigated for accident tolerant fuel cladding applications due to its high temperature strength, exceptional stability under irradiation, and reduced oxidation compared to Zircaloy under accident conditions. An engineered cladding design combining monolithic SiC and SiC-SiC composite layers could offer a tough, hermetic structure to provide improved performance and safety, with a failure rate comparable to current Zircaloy cladding. Modeling and design efforts require a thorough understanding of the properties and structure of SiC-based cladding. Furthermore, both fabrication and characterization of long, thin-walled SiC-SiC tubes to meet application requirements are challenging. In this work, mechanical and thermal properties of unirradiated, as-fabricated SiC-based cladding structures were measured, and permeability and dimensional control were assessed. In order to account for the tubular geometry of the cladding designs, development and modification of several characterization methods were required.

  1. Passivation of surface-nanostructured f-SiC and porous SiC

    DEFF Research Database (Denmark)

    Ou, Haiyan; Lu, Weifang; Ou, Yiyu

    The further enhancement of photoluminescence from nanostructured fluorescent silicon carbide (f-SiC) and porous SiC by using atomic layer deposited (ALD) Al2O3 is studied in this paper.......The further enhancement of photoluminescence from nanostructured fluorescent silicon carbide (f-SiC) and porous SiC by using atomic layer deposited (ALD) Al2O3 is studied in this paper....

  2. Fabrication and Properties of Ti3SiC2/SiC Composites

    Institute of Scientific and Technical Information of China (English)

    YIN Hongfeng; FAN Qiang; REN Yun; ZHANG Junzhan

    2008-01-01

    Ti3SiC2/SiC composites were fabricated by reactive hot pressing method. Effects of hot pressing temperature, the content and panicle size of SiC on phase composition, densification, mechanical properties and behavior of stress-strain of the composites were investigated. The results showed that:(1)Hot-pressing temperature influenced the phase composition of Ti3SiC2/SiC composites. The flexural strength and fracture toughness of composites increased with hot pressing temperature.(2)It became more difficult for the composites to densify when the content of SiC in composites increased. It need be sintered at higher temperature to get denser composite. The flexural strength and fracture toughness of composites increased when the content of SiC added in composites increased. However, when the content of SiC reached 50 wt%, the flexural strength and fracture toughness of composites decreased due to high content of pore in composites.(3)When the content of SiC was same, Ti3SiC2/SiC composites were denser while the particle size of SiC added in composites is 12.8μm compared with the composites that the particle size of SiC added is 3μm.The flexural strength and fracture toughness of composites increased with the increase of particle size of SiC added in composites.(4)Ti3SiC2/SiC composites were non-brittle fracture at room temperature.

  3. Minimum bar size for flexure testing of irradiated SiC/SiC composite

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Jones, R.H. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    This report covers material presented at the IEA/Jupiter Joint International Workshop on SiC/SiC Composites for Fusion structural Applications held in conjunction with ICFRM-8, Sendai, Japan, Oct. 23-24, 1997. The minimum bar size for 4-point flexure testing of SiC/SiC composite recommended by PNNL for irradiation effects studies is 30 {times} 6 {times} 2 mm{sup 3} with a span-to-depth ratio of 10/1.

  4. C-V and DLTS studies of radiation induced Si-SiO2 interface defects

    Science.gov (United States)

    Capan, I.; Janicki, V.; Jacimovic, R.; Pivac, B.

    2012-07-01

    Interface traps at the Si-SiO2 interface have been and will be an important performance limit in many (future) semiconductor devices. In this paper, we present a study of fast neutron radiation induced changes in the density of Si-SiO2 interface-related defects. Interface related defects (Pb centers) are detected before and upon the irradiation. The density of interface-related defects is increasing with the fast neutron fluence.

  5. An efficient Si light-emitting diode based on an n- ZnO/SiO{sub 2}-Si nanocrystals-SiO{sub 2}/p-Si heterostructure

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Edward; Su, Fu-Hsiang; Shih, Ying-Tsang; Tsai, Hung-Ling; Chen, Ching-Huang; Wu, Mong-Kai; Yang, Jer-Ren; Chen, Miin-Jang, E-mail: mjchen@ntu.edu.t [Department of Materials Science and Engineering, National Taiwan University, Taipei, Taiwan (China)

    2009-11-04

    Si nanocrystals embedded in a SiO{sub 2} matrix and an n-type Al-doped ZnO (ZnO:Al) layer were applied to improve the external quantum efficiency from Si in n- ZnO/SiO{sub 2}-Si nanocrystals-SiO{sub 2}/p-Si heterojunction light-emitting diodes (LEDs). The Si nanocrystals were grown by low pressure chemical vapor deposition and the ZnO:Al layer was prepared by atomic layer deposition. The n-type ZnO:Al layer acts as an electron injection layer, a transparent conductive window, and an anti-reflection coating to increase the light extraction efficiency. Owing to the spatial confinement of carriers and surface passivation by the surrounding SiO{sub 2}, the Si nanocrystals embedded in the SiO{sub 2} matrix lead to a significant enhancement of the light emission efficiency from Si. An external quantum efficiency up to 4.3 x 10{sup -4} at the wavelength corresponding to the indirect bandgap of Si was achieved at room temperature.

  6. Electroluminescence and Photoluminescence from Scored Si-Rich SiO2 Film/p-Si Structure

    Institute of Scientific and Technical Information of China (English)

    冉广照; 孙永科; 陈源; 戴伦; 崔晓明; 张伯蕊; 乔永平; 马振昌; 宗婉华; 秦国刚

    2003-01-01

    Electroluminescence (EL) is observed from the Au/Si-rich SiO2 film/p-Si diodes, in which the Si-rich SiO2 films are scored deliberately by a diamond tip. The EL intensity of the scored diode annealed at 800°C is about 6times of that of the unscored counterpart. The EL spectrum of the unscored diode could be decomposed into two Gaussian luminescence bands with peaks at about 1.83 and 2.23 eV, while for the EL spectrum of the scored diode, an additional Gaussian band at about 3.0eV appears, and the 1.83-eV peak increases significantly in intensity. The photoluminescence (PL) spectrum of an unscored Si-rich SiO2 film has only one band peaking at about 1.48eV, whereas the PL spectrum of the scored one has two bands at about 1.48 and 1.97eV. We consider that the high-density defect regions produced by the scoring provide new luminescence centres and become some types of nonradiative centres in the Si oxide layer, which thus result in changes of the EL and PL spectra.

  7. Electroluminescence and Photoluminescence from Scored Si-Rich SiO2 Film/p-Si Structure

    Science.gov (United States)

    Ran, Guang-Zhao; Sun, Yong-Ke; Chen, Yuan; Dai, Lun; Cui, Xiao-Ming; Zhang, Bo-Rui; Qiao, Yong-Ping; Ma, Zhen-Chang; Zong, Wan-Hua; Qin, Guo-Gang

    2003-02-01

    Electroluminescence (EL) is observed from the Au/Si-rich SiO2 film/p-Si diodes, in which the Si-rich SiO2 films are scored deliberately by a diamond tip. The EL intensity of the scored diode annealed at 800°C is about 6 times of that of the unscored counterpart. The EL spectrum of the unscored diode could be decomposed into two Gaussian luminescence bands with peaks at about 1.83 and 2.23 eV, while for the EL spectrum of the scored diode, an additional Gaussian band at about 3.0 eV appears, and the 1.83-eV peak increases significantly in intensity. The photoluminescence (PL) spectrum of an unscored Si-rich SiO2 film has only one band peaking at about 1.48 eV, whereas the PL spectrum of the scored one has two bands at about 1.48 and 1.97 eV. We consider that the high-density defect regions produced by the scoring provide new luminescence centres and become some types of nonradiative centres in the Si oxide layer, which thus result in changes of the EL and PL spectra.

  8. Patología meniscal: opciones terapéuticas

    OpenAIRE

    Fernández, E

    2015-01-01

    La cirugía de la patología meniscal es uno de los procedimientos más frecuentes en la cirugía ortopédica. Los estudios de los últimos años han supuesto una modificación de los tratamientos y planteamientos antes las roturas meniscales. La sutura meniscal, con el tratamiento de lesiones concomitantes, como las lesiones del ligamento cruzado anterior o lesiones condrales , han mejorado los resultados clínicos. Pero, al mismo tiempo, surgen problemas derivados de la meniscectomía, en...

  9. Interacciones radiculares en sistemas agroforestales: mecanismos y opciones de manejo

    National Research Council Canada - National Science Library

    Casanova, F; Ramirez, L; Solorio, F

    2007-01-01

    Los sistemas agroforestales (SAF) son una forma de uso de la tierra en donde las lenosas interactuan con los cultivos y/o animales, con la finalidad de diversificar y optimizar la produccion de manera sostenida...

  10. Microwave Sintering of MoSi2 and SiC/MoSi2 Nanocomposite Ceramics%微波烧结制备MoSi2及SiC/MoSi纳米复合陶瓷

    Institute of Scientific and Technical Information of China (English)

    刘长虹; 艾云龙; 何文

    2012-01-01

    MoSi2 and SiC/MoSi2 nanocomposite ceramics were prepared by microwave sintering. Hybrid heating using SiC as preheating material and reasonable design of heat preservation system realized the fast elevation of temperature of MoSi2 on the low temperature stage, and enhanced the temperature uniformity of MoSi2. The density and mechanical properties tests showed that under the sintering parameters of 1 400℃ and holding 60 min, the properties of pure MoSi2 sample achieved relative density of 93.4% , fracture toughness 4.5 MPa·m1/2, Vickers hardness 10.53 GPa, and bending strength 186 MPa. All the mechanical properties of 10vol. % SiC -MoSi2 were superior to that of pure MoSi2, though the relative density decreased to 90.3%. The temperature of microwave sintering MoSi2 and SiC/ MoSi2 samples decreased 200℃ lower than hot-pressing sintering temperature (1 650℃ ) , but the mechanical properties are actually enhanced greatly, in particular MoSi2sample. Fracture surfaces indicated that compared to hot-pressing sintered samples,the microwave sintered samples presented refined grain size, fine and uniform pore. However the effect of grain refinement of microwave sintering to SiC/MoSi2 is weaken compared to pure MoSi2 sample.%采用微波烧结法制备了MoSi2和10vol% SiC/MoSi2纳米复合陶瓷.通过SiC预加热体的混合式加热法和合理的保温结构设计,实现了MoSi2低温阶段的快速升温,提高了温度均匀性.密度和力学性能测试结果表明,1450℃保温60 min烧结工艺下,MoSi2试样的相对密度达到93.4%,断裂韧度4.5 MPa·ml/2,维氏硬度为10.53 GPa,弯曲强度为186 MPa.10vol% SiC/MoSi2试样尽管相对密度下降为90.3%,但各项力学性能均优于MoSi2试样.相比1650℃热压烧结,微波烧结温度降低了200℃,MoSi2和SiC/MoSi2试样致密性有所下降,但力学性能有较大提高,尤其是MoSi2试样.断口扫描分析表明,微波烧结试样相对热压烧结试样基体晶粒更细,孔隙细

  11. Anticipating Central Asian Water Stress: Variation in River Flow Dependency on Melt Waters from Alpine to Plains in the Remote Tien Shan Range, Kyrgyzstan Using a Rapid Hydro Assessment Methodology

    Science.gov (United States)

    Hill, A. F.; Wilson, A. M.; Williams, M. W.

    2016-12-01

    The future of mountain water resources in High Asia is of high interest to water managers, development organizations and policy makers given large populations downstream reliant on snow and ice sourced river flow. Together with historical and cultural divides among ex-Soviet republics, a lack of central water management following the Soviet break-up has led to water stress as trans-boundary waters weave through and along borders. New upstream hydropower development, a thirsty downstream agricultural sector and a shrinking Aral Sea has led to increasing tension in the region. Despite these pressures and in contrast to eastern High Asia's Himalayan basins (Ganges, Brahmaputra), little attention has been given to western High Asia draining the Pamir and Tien Shan ranges (Syr Darya and Amu Darya basins) to better understand the hydrology of this vast and remote area. Difficult access and challenging terrain exacerbate challenges to working in this remote mountain region. As part of the Contributions to High Asia Runoff from Ice and Snow (CHARIS) project, we asked how does river flow source water composition change over an alpine-to-plains domain of Kyrgyzstan's Naryn River in the Syr Darya basin? In addition, what may the future hold for river flow in Central Asia given the differing responses of snow and ice to climate changes? Utilizing a Rapid Hydrologic Assessment methodology including a suite of pre-field mapping techniques we collected in situ water chemistry data at targeted, remote mountain sites over 450km of the Naryn River over an elevation gradient from glacial headwaters to the lower lying areas - places where people, hydropower and agriculture utilize water. Chemical and isotope tracers were used to separate stream flow to understand relative dependency on melt waters as the river moves downstream from glaciers and snow covered areas. This case study demonstrates a technique to acquire field data over large scales in remote regions that facilitates

  12. De la dédiasporisation des jeunes Haïtiens à New-York On De-diasporization of Second-generation Haitians in New York City

    Directory of Open Access Journals (Sweden)

    Stéphanie Melyon-Reinette

    2012-05-01

    Full Text Available Les facteurs répulsifs de l’émigration haïtienne ont complètement changé depuis les années 1950 qui marquèrent le début de ce mouvement avec le régime duvaliériste. Les entités géopolitiques et sociopolitiques qui en résultent évoluent, elles aussi, proportionnellement et rationnellement aux motivations des individus en partance. Ainsi, les exilés forcés rêvaient de retrouver leur chère Haïti, les nouveaux primo-arrivants sont des individus qui cherchent à se ré-enraciner dans un terreau aux airs d’ailleurs. Le diasporique est-il un individu dont l’identité est figée ? Dans cet article, une étude statistique simple cherche à démontrer l’évolution des mentalités des jeunes Haïtiens à travers un questionnement des identités et des orientations culturelles. Des dynamiques se font jour montrant que la diaspora est fluctuante comme les identités et les cultures qui la composent.The Push factors of Haitian emigration have completely changed since the late 1950s which marked the beginning of this movement with the Duvalier regime. The geopolitical and sociopolitical entities which result from it are changing as well, in proportion and accordance with the motivations of the people who leave. Thus, the forced exiles dreamt of going back to their dearest Haiti, the latest newly-arrived immigrants are individuals who desire to re-root into a land that sounds like “elsewhere”. Must the diasporic individual’s identity be stable? In this article, a simple survey seeks to shed light on the changing mentalities of young Haitians, examining their identities and cultural choices.  Emerging trends show that diaspora is a flow, not unlike the identities and the cultures of which it is composed.

  13. El fin de la situación de transitoriedad: la Ley Orgánica 15/1999, de 13 de diciembre, de Protección de Datos de Carácter Personal ya tiene desarrollo reglamentario

    Directory of Open Access Journals (Sweden)

    Mònica Vilasau

    2008-09-01

    Full Text Available El 19 de abril del 2008 entró en vigor el Reglamento 1720/2007, de 21 de diciembre, que desarrolla la Ley Orgánica de Protección de Datos (LOPD. Este texto había sido muy esperado por los aplicadores del derecho, por las empresas de consultoría y de seguridad, por sectores del marketing y publicidad, por empresas dedicadas a la solvencia patrimonial y crédito y, en un grado menor, por los consumidores y usuarios. La norma responde a la necesidad de dotar la Ley Orgánica sobre la materia del correspondiente desarrollo reglamentario y dar respuesta a las nuevas necesidades de la sociedad de la información constantemente en evolución. En el Reglamento de la LOPD se regula el otorgamiento del consentimiento por silencio positivo, el otorgamiento del consentimiento de los menores, se sistematiza el ejercicio de los derechos por parte del afectado, se regulan detalladamente los ficheros de marketing y publicidad, los de solvencia patrimonial y crédito, se dota la figura del encargado de un estatuto jurídico, se proporciona un nuevo marco a las medidas de seguridad y se sistematizan los procedimientos tramitados por la Agencia Española de Protección de Datos. El texto aprobado, evidentemente, no complacerá a todo el mundo, la existencia de múltiples instancias involucradas (estatales y autonómicas y de múltiples agentes con diferentes perspectivas hace que las soluciones proporcionadas no se ajusten a los ideales de todos los implicados.Sin embargo, el nuevo reglamento es un paso adelante en la consolidación del derecho a la protección de datos de carácter personal, aporta mayor seguridad jurídica y flexibilización y se tiene que ver como una oportunidad de crear una nueva cultura de protección de datos integrada en el tratamiento de la información de una forma global.

  14. Polycrystalline SiC as source material for the growth of fluorescent SiC layers

    DEFF Research Database (Denmark)

    Kaiser, M.; Hupfer, T.; Jokubavicus, V.;

    2013-01-01

    Polycrystalline doped SiC act as source for fluorescent SiC. We have studied the growth of individual grains with different polytypes in the source material. We show an evolution and orientation of grains of different polytypes in polycrystalline SiC ingots grown by the Physical Vapor Transport...

  15. Thermal Stability of siRNA Modulates Aptamer- conjugated siRNA Inhibition

    Directory of Open Access Journals (Sweden)

    Alexey Berezhnoy

    2012-01-01

    Full Text Available Oligonucleotide aptamer-mediated in vivo cell targeting of small interfering RNAs (siRNAs is emerging as a useful approach to enhance the efficacy and reduce the adverse effects resulting from siRNA-mediated genetic interference. A current main impediment in aptamer-mediated siRNA targeting is that the activity of the siRNA is often compromised when conjugated to an aptamer, often requiring labor intensive and time consuming design and testing of multiple configurations to identify a conjugate in which the siRNA activity has not been significantly reduced. Here, we show that the thermal stability of the siRNA is an important parameter of siRNA activity in its conjugated form, and that siRNAs with lower melting temperature (Tm are not or are minimally affected when conjugated to the 3′ end of 2′F-pyrimidine-modified aptamers. In addition, the configuration of the aptamer-siRNA conjugate retains activity comparable with the free siRNA duplex when the passenger strand is co-transcribed with the aptamer and 3′ overhangs on the passenger strand are removed. The approach described in this paper significantly reduces the time and effort necessary to screening siRNA sequences that retain biological activity upon aptamer conjugation, facilitating the process of identifying candidate aptamer-siRNA conjugates suitable for in vivo testing.

  16. Microstructure and abrasive wear studies of laser clad Al-Si/SiC composite coatings

    NARCIS (Netherlands)

    Anandkumar, R.; Colaco, R.; Ocelik, V.; De Hosson, J. Th. M.; Vilar, R.; Gyulai, J; Szabo, PJ

    2007-01-01

    Surface coatings of Al-Si/SiC metal-matrix composites were deposited on Al-7 wt. % Si alloy substrates by laser cladding. The microstructure of the coatings was characterized by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The microstructure of the coating mate

  17. The effect of biaxial strain on impurity diffusion in Si and SiGe

    DEFF Research Database (Denmark)

    Larsen, Arne Nylandsted; Zangenberg, Nikolaj; Fage-Pedersen, Jacob

    2005-01-01

    Results from diffusion studies of different impurities in biaxially strained Si and Si"1"-"xGe"x for low x-values will be presented. The structures are all molecular-beam epitaxy (MBE) grown on strain-relaxed Si"1"-"xGe"x layers, and the impurity profiles are introduced during growth. We have...

  18. Enhanced electroluminescence from nanocrystallite Si based MOSLED by interfacial Si nanopyramids

    Institute of Scientific and Technical Information of China (English)

    Gong-Ru Lin

    2007-01-01

    The interfacial Si nano-pyramid-enhanced electroluminescence (EL) of an ITO/SiOx/p-Si/Al metal-oxidesemiconductor (MOS) diode with turn-on voltage of 50 V, threshold current of 1.23 mA/cm2, output power of 16 nW, and lifetime of 10 h is reported.

  19. About the International System of Units (SI) Part III. SI Table

    Science.gov (United States)

    Aubrecht, Gordon J., II; French, Anthony P.; Iona, Mario

    2012-01-01

    Before discussing more details of SI, we will summarize the essentials in a few tables that can serve as ready references. If a unit isn't listed in Tables I-IV, it is not part of SI or specifically allowed for use with SI. The units and symbols that are sufficient for most everyday applications are given in bold.

  20. Computer aided cooling curve analysis for Al-5Si and Al-11Si alloys

    African Journals Online (AJOL)

    user

    Aluminium-Silicon (Al-Si) alloys are considered as the most important cast .... of MA1, the melt was stirred gently with zircon coated iron rod and was held for 5 min. ..... and mechanical properties of Al-7Si and Al-7Si-2.5Cu cast alloys, Materials ...

  1. Preparation of Si3N4–SiC composites by microwave route

    Indian Academy of Sciences (India)

    M Panneerselvam; K J Rao

    2002-12-01

    Si3N4–SiC composites have been microwave sintered using -Si3N4 and -SiC as starting materials. Si3N4 rich compositions (95 and 90 vol.% Si3N4) have been sintered above 96% of theoretical density without using any sintering additives in 40 min. A monotonic decrease in relative density is observed with increase in SiC proportion in the composite. Decrease in relative density has manifested in the reduction of fracture toughness and microhardness values of the composite with increase in SiC content although the good sintering of matrix Si3N4 limits the decrease of fracture toughness. Highest value of fracture toughness of 6.1 MPa m1/2 is observed in 10 vol.% SiC composite. Crack propagation appears to be transgranular in the Si3N4 matrix and the toughening of the composites is through crack deflection around hard SiC particles in addition to its debonding from the matrix.

  2. Thermochemical instability effects in SiC-based fibers and SiC{sub f}/SiC composites

    Energy Technology Data Exchange (ETDEWEB)

    Youngblood, G.E.; Henager, C.H.; Jones, R.H. [Pacific Northwest National Laboratory, Richland, WA (United States)

    1997-08-01

    Thermochemical instability in irradiated SiC-based fibers with an amorphous silicon oxycarbide phase leads to shrinkage and mass loss. SiC{sub f}/SiC composites made with these fibers also exhibit mass loss as well as severe mechanical property degradation when irradiated at 800{degrees}C, a temperature much below the generally accepted 1100{degrees}C threshold for thermomechanical degradation alone. The mass loss is due to an internal oxidation mechanism within these fibers which likely degrades the carbon interphase as well as the fibers in SiC{sub f}/SiC composites even in so-called {open_quotes}inert{close_quotes} gas environments. Furthermore, the mechanism must be accelerated by the irradiation environment.

  3. Silane photoabsorption spectra near the Si 2p thresholds: the geometry of Si 2p excited SiH4

    Institute of Scientific and Technical Information of China (English)

    张卫华; 许如清; 李家明

    2003-01-01

    Based on the multiple-scattering self-consistent-field method, we have studied the photoabsorption spectra near the Si 2p thresholds of silane. According to our calculations, the clear assignments of the inner-shell photoabsorption spectra are provided. In comparison with the high-resolution experimental spectra, the geometric structure of the Si 2p-excited SiH4** is recommended to be of a C2v symmetry. More specifically, the Si 2p-excited Si4** have two bond lengths of 2.50 a.u. and another two bond lengths of 2.77 a.u., and the corresponding two bond angles are 104.0° and 112.5° respectively.

  4. Tunneling magnetoresistance in Si nanowires

    Science.gov (United States)

    Montes, E.; Rungger, I.; Sanvito, S.; Schwingenschlögl, U.

    2016-11-01

    We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green’s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

  5. Tunneling magnetoresistance in Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2016-11-09

    We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green\\'s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

  6. Metastability of a-SiOx:H thin films for c-Si surface passivation

    Science.gov (United States)

    Serenelli, L.; Martini, L.; Imbimbo, L.; Asquini, R.; Menchini, F.; Izzi, M.; Tucci, M.

    2017-01-01

    The adoption of a-SiOx:H films obtained by PECVD in heterojunction solar cells is a key to further increase their efficiency, because of its transparency in the UV with respect to the commonly used a-Si:H. At the same time this layer must guarantee high surface passivation of the c-Si to be suitable in high efficiency solar cell manufacturing. On the other hand the application of amorphous materials like a-Si:H and SiNx on the cell frontside expose them to the mostly energetic part of the sun spectrum, leading to a metastability of their passivation properties. Moreover as for amorphous silicon, thermal annealing procedures are considered as valuable steps to enhance and stabilize thin film properties, when performed at opportune temperature. In this work we explored the reliability of a-SiOx:H thin film layers surface passivation on c-Si substrates under UV exposition, in combination with thermal annealing steps. Both p- and n-type doped c-Si substrates were considered. To understand the effect of UV light soaking we monitored the minority carriers lifetime and Sisbnd H and Sisbnd O bonding, by FTIR spectra, after different exposure times to light coming from a deuterium lamp, filtered to UV-A region, and focused on the sample to obtain a power density of 50 μW/cm2. We found a certain lifetime decrease after UV light soaking in both p- and n-type c-Si passivated wafers according to a a-SiOx:H/c-Si/a-SiOx:H structure. The role of a thermal annealing, which usually enhances the as-deposited SiOx passivation properties, was furthermore considered. In particular we monitored the UV light soaking effect on c-Si wafers after a-SiOx:H coating by PECVD and after a thermal annealing treatment at 300 °C for 30 min, having selected these conditions on the basis of the study of the effect due to different temperatures and durations. We correlated the lifetime evolution and the metastability effect of thermal annealing to the a-SiOx:H/c-Si interface considering the evolution

  7. Experimental PDT: studies on new Si-phthalocyanines and Si-naphthalocyanines in Cremophor emulsions

    Science.gov (United States)

    Shopova, Maria; Mantareva, Vanya; Woehrle, Dieter; Mueller, Silke

    1996-12-01

    In the present work the following silicon (IV) - phthalocyanines and -naphthalocyanines bearing methoxyethylene glycol or methoxypolyethylene glycol covalently bound at the silicon are investigated: SiPc[OCH2CH2OCH3]2 (SiPc1), SiNc[OCH2CH2OCH3]2 (SiNc), SiPc[(OCH2CH2)nOCH3] with n approximately 115 (SiPc2). The phototherapeutic effect was shown at Lewis lung carcinoma implanted in mice. SiPc2 is monomeric soluble in water whereas the other two compounds aggregated in this solvent. Therefore these compounds were dissolved monomer in in aqueous Cremophor solution before in vivo administration. Laser irradiation was applied 7 days after implantation and 24 h after drug administration at the following wavelength (eta) ext: 672 nm for SiPc1 and SiPc2, 782 nm for SiNc. In all cases a fluence rate of 370 mW/cm2 at fluence of 360 J/cm2 was used. The assessment criteria for the tumor response were the changes in the mean tumor diameter with time, regrowth delay and average survival time (AST). According to the first parameter the most promising result was obtained after treatment with SiPc1. For example the mean tumor diameter increases as follows: SiPc1 less than SiPc2 less than SiNc very much less than control group without photosensitizer. The regrowth delay showed the same trend. however, for AST another dependence was observed. AST was the longest for SiPc2 (26 days) and shortest for SiNc (22 days). Compared to the control group (without sensitizer and irradiation) the AST was 9 days longer after SiPc2 treatment. Comparing SiPc1 and SiPc2 the chain length of the substituents does not influence the phototherapeutic properties. The detected therapeutic results probably are connected with the long wavelength absorption of the photosensitizers. The relatively lower affectivity of SiNc may be due to a lower degree of tumor accumulation as it was observed in our preliminary pharmacokinetic studies. It is also possible that the shorter AST after treatment with SiNc is

  8. Lateral boron distribution in polycrystalline SiC source materials

    DEFF Research Database (Denmark)

    Linnarsson, M. K.; Kaiser, M.; Liljedahl, R.

    2013-01-01

    Polycrystalline SiC containing boron and nitrogen are used in growth of fluorescent SiC for white LEDs. Two types of doped polycrystalline SiC have been studied in detail with secondary ion mass spectrometry: sintered SiC and poly-SiC prepared by sublimation in a physical vapor transport setup...

  9. Synthesis of Hybrid SiC/SiO2 Nanoparticles and Their Polymer Nanocomposites

    Science.gov (United States)

    Hassan, Tarig A.; Rangari, Vijaya K.; Baker, Fredric; Jeelani, Shaik

    2013-04-01

    In the present investigation, silicon carbide (β-SiC) nanoparticles ( 30 nm) were coated on silicon dioxide (SiO2) nanoparticles ( 200 nm) using sonochemical method. The resultant hybrid nanoparticles were then infused into SC-15 epoxy resin to enhance the thermal and mechanical properties of SC-15 epoxy for structural application. To fabricate an epoxy-based nanocomposite containing SiC/SiO2 hybrid nanoparticles, we have opted a two-step process. In the first step, the silica nanoparticles were coated with SiC nanoparticles using high intensity ultrasonic irradiation. In a second step, 1 wt.% of as-prepared SiC/SiO2 particles were dispersed in epoxy part-A (diglycidylether of bisphenol A) using a high intensity ultrasound for 30 min at 5°C. The part-B (cycloaliphatic amine hardener) of the epoxy was then mixed with part-A-SiC/SiO2 mixture using a high-speed mechanical stirrer for 10 min. The SiC/SiO2/epoxy resin mixture was cured at room temperature for 24 h. The SiC nanoparticles coating on SiO2 was characterized using X-ray diffraction (XRD) and high resolution transmission electron microscope (TEM). The as-prepared nanocomposite samples were characterized using thermo gravimetric analysis (TGA) and differential scanning calorimeter (DSC). Compression tests have been carried out for both nanocomposite and neat epoxy systems. The results indicated that 1 wt.% (SiC) + (SiO2) loading derived improvements in both thermal and mechanical properties when compared to the neat epoxy system.

  10. Optical properties of passivated Si nanocrystals and SiO{sub {ital x}} nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Dinh, L.N. [Department of Applied Science, University of California, Davis/Livermore, California (United States)]|[Chemistry and Materials Science Department, University of California, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Chase, L.L.; Balooch, M.; Siekhaus, W.J. [Chemistry and Materials Science Department, University of California, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Wooten, F. [Department of Applied Science, University of California, Davis/Livermore, California 94550 (United States)

    1996-08-01

    Thin films of Si nanoclusters passivated with oxygen or hydrogen, with an average size of a few nanometers, have been synthesized by thermal vaporization of Si in an Ar buffer gas, followed by subsequent exposure to oxygen or atomic hydrogen. High-resolution transmission electron microscopy and x-ray diffraction revealed that these nanoclusters were crystalline. However, during synthesis, if oxygen was the buffer gas, a network of amorphous Si oxide nanostructures (an-SiO{sub {ital x}}) with occasional embedded Si dots was formed. All samples showed strong infrared and/or visible photoluminescence (PL) with varying decay times from nanoseconds to microseconds depending on synthesis conditions. Absorption in the Si cores for surface passivated Si nano- crystals (nc-Si), but mainly in oxygen related defect centers for an-SiO{sub {ital x}}, was observed by photoluminescence excitation spectroscopy. The visible components of PL spectra were noted to blueshift and broaden as the size of the nc-Si was reduced. There were differences in PL spectra for hydrogen and oxygen passivated nc-Si. Many common PL properties between oxygen passivated nc-Si and an-SiO{sub {ital x}} were observed. Our data can be explained by a model involving absorption between quantum confined states in the Si cores and emission for which the decay times are very sensitive to surface and/or interface states. The emission could involve a simple band-to-band recombination mechanism within the Si cores. The combined evidence of all of our experimental results suggests, however, that emission between surface or interface states is a more likely mechanism. {copyright} {ital 1996 The American Physical Society.}

  11. Optical properties of passivated Si nanocrystals and SiOx nanostructures

    Science.gov (United States)

    Dinh, L. N.; Chase, L. L.; Balooch, M.; Siekhaus, W. J.; Wooten, F.

    1996-08-01

    Thin films of Si nanoclusters passivated with oxygen or hydrogen, with an average size of a few nanometers, have been synthesized by thermal vaporization of Si in an Ar buffer gas, followed by subsequent exposure to oxygen or atomic hydrogen. High-resolution transmission electron microscopy and x-ray diffraction revealed that these nanoclusters were crystalline. However, during synthesis, if oxygen was the buffer gas, a network of amorphous Si oxide nanostructures (an-SiOx) with occasional embedded Si dots was formed. All samples showed strong infrared and/or visible photoluminescence (PL) with varying decay times from nanoseconds to microseconds depending on synthesis conditions. Absorption in the Si cores for surface passivated Si nano- crystals (nc-Si), but mainly in oxygen related defect centers for an-SiOx, was observed by photoluminescence excitation spectroscopy. The visible components of PL spectra were noted to blueshift and broaden as the size of the nc-Si was reduced. There were differences in PL spectra for hydrogen and oxygen passivated nc-Si. Many common PL properties between oxygen passivated nc-Si and an-SiOx were observed. Our data can be explained by a model involving absorption between quantum confined states in the Si cores and emission for which the decay times are very sensitive to surface and/or interface states. The emission could involve a simple band-to-band recombination mechanism within the Si cores. The combined evidence of all of our experimental results suggests, however, that emission between surface or interface states is a more likely mechanism.

  12. Next Generation, Si-Compatible Materials and Devices in the Si-Ge-Sn System

    Science.gov (United States)

    2015-10-09

    performed extensive growth studies aimed to create entire new families of Ge1-x-ySixSny materials on industrially compatible group IV platforms ( Si , Ge and...AFRL-AFOSR-VA-TR-2016-0044 Next generation, Si -compatible materials and devices in the Si -Ge-Sn system John Kouvetakis ARIZONA STATE UNIVERSITY Final...4. TITLE AND SUBTITLE Next generation, Si -compatible materials and devices in the Si -Ge-Sn system 5a. CONTRACT NUMBER FA9550-12-1-0208 5b. GRANT

  13. Deep levels, transport and THz emission properties of SiGe/Si quantum-well structures

    Institute of Scientific and Technical Information of China (English)

    I.; V.; ANTONOVA; M.; S.; KAGAN; E.; P.; NEUSTROEV; S.; A.; SMAGULOVA

    2009-01-01

    Recharging of quantum confinement levels in SiGe quantum wells (QW) was studied by charge deep-level transient spectroscopy (Q-DLTS) for Si/SiGe/Si structures with different Ge contents in the SiGe layer. A peak with activation energy varying in the range from 0 to 100 meV in different tempera-ture intervals was observed in Q-DLTS spectra. Activation energies extracted from Q-DLTS measure-mens are in good agreement with energies of quantum confinement levels in the QW.

  14. High Efficiency Hybrid Solar Cells Using Nanocrystalline Si Quantum Dots and Si Nanowires.

    Science.gov (United States)

    Dutta, Mrinal; Thirugnanam, Lavanya; Trinh, Pham Van; Fukata, Naoki

    2015-07-28

    We report on an efficient hybrid Si nanocrystal quantum dot modified radial p-n junction thinner Si solar cell that utilizes the advantages of effective exciton collection by energy transfer from nanocrystal-Si (nc-Si) quantum dots to underlying radial p-n junction Si nanowire arrays with excellent carrier separation and propagation via the built-in electric fields of radial p-n junctions. Minimization of recombination, optical, and spectrum losses in this hybrid structure led to a high cell efficiency of 12.9%.

  15. Evaluation of CVI SiC/SiC Composites for High Temperature Applications

    Science.gov (United States)

    Kiser, D.; Almansour, A.; Smith, C.; Gorican, D.; Phillips, R.; Bhatt, R.; McCue, T.

    2017-01-01

    Silicon carbide fiber reinforced silicon carbide (SiC/SiC) composites are candidate materials for various high temperature turbine engine applications because of their high specific strength and good creep resistance at temperatures of 1400 C (2552 F) and higher. Chemical vapor infiltration (CVI) SiC/SiC ceramic matrix composites (CMC) incorporating Sylramic-iBN SiC fiber were evaluated via fast fracture tensile tests (acoustic emission damage characterization to assess cracking behavior), tensile creep testing, and microscopy. The results of this testing and observed material behavior degradation mechanisms are reviewed.

  16. DLC-Si protective coatings for polycarbonates

    Directory of Open Access Journals (Sweden)

    Damasceno J.C.

    2003-01-01

    Full Text Available In this work, a-C:H:Si (DLC-Si films were produced onto crystalline silicon and polycarbonate substrates by the rf-PACVD technique from gaseous mixtures of CH4 + SiH4 and C2H2 + SiH4. The effects of self-bias and gas composition upon mechanical and optical properties of the films were investigated. Micro-hardness, residual stress, surface roughness and refractive index measurements were employed for characterization. By incorporating low concentrations of silicon and by exploring the more favorable conditions for the rf-PACVD deposition technique, highly adherent DLC-Si thin films were produced with reduced internal stresses (lower than 1 GPa, high hardness (around 20 GPa and high deposition rates (up to 10 µm/h. Results that show the technological viability of this material for application as protective coatings for polycarbonates are also discussed.

  17. Biomorphic SiC from lotus root

    Institute of Scientific and Technical Information of China (English)

    Qing Wang; Donghua Wang; Guoqiang Jin; Yingyong Wang; Xiangyun

    2009-01-01

    Biomorphic silicon carbide (bioSiC) with macro-channels and alveolate micropores was prepared by spon-taneous infiltration of melted silicon into a carbon template derived from lotus root at 1600 ℃. The carbon template and purified bioSiC samples were characterized by X-ray diffraction, scanning electron microscopy, camera and mercury intrusion. The results suggest that the bioSiC mainly consists of β-SiC and perfectly replicates the shape and microstructure of the carbon template. The bioSiC has a mean pore diameter of 91.1 μm and a porosity of 50.1%, both similar to those of the carbon template, 92.3 μm and 50.7%, respectively.

  18. PLGA microspheres encapsulating siRNA.

    Science.gov (United States)

    De Rosa, Giuseppe; Salzano, Giuseppina

    2015-01-01

    The therapeutic use of small interfering RNA (siRNA) represents a new and powerful approach to suppress the expression of pathologically genes. However, biopharmaceutical drawbacks, such as short half-life, poor cellular uptake, and unspecific distribution into the body, hamper the development of siRNA-based therapeutics. Poly(lactide-co-glycolide), (PLGA) microspheres can be a useful tool to overcome these issues. siRNA can be encapsulated into the PLGA microspheres, which protects the loaded nucleic acid against the enzymatic degradation. Moreover, PLGA microspheres can be injected directly into the action site, where the siRNA can be released in controlled manner, thus avoiding the need of frequent invasive administrations. The complete biodegradability of PLGA to monomers easily metabolized by the body, and its approval by FDA and EMA for parenteral administration, assure the safety of this copolymer and do not require the removal of the device after the complete drug release. In chapter, a basic protocol for the preparation of PLGA microspheres encapsulating siRNA is described. This protocol is based on a double emulsion/solvent evaporation technique, a well known and easy to reproduce method. This specific protocol has been developed to encapsulate a siRNA anti-TNFα in PLGA microspheres, and it has been designed and optimized to achieve high siRNA encapsulation efficiency and slow siRNA release in vitro. However, it can be extended also to other siRNA as well as other RNA or DNA-based oligonucleotides (miRNA, antisense, decoy, etc.). Depending on the applications, chemical modifications of the backbone and site-specific modification within the siRNA sequences could be required.

  19. Effects of SiC amount on phase compositions and properties of Ti3SiC2-based composites

    Institute of Scientific and Technical Information of China (English)

    蔡艳芝; 殷小玮; 尹洪峰

    2015-01-01

    The phase compositions and properties of Ti3SiC2-based composites with SiC addition of 5%−30% in mass fraction fabricated by in-situ reaction and hot pressing sintering were studied. SiC addition effectively prevented TiC synthesis but facilitated SiC synthesis. The Ti3SiC2/TiC−SiC composite had better oxidation resistance when SiC added quantity reached 20% but poorer oxidation resistance with SiC addition under 15%than Ti3SiC2/TiC composite at higher temperatures. There were more than half of the original SiC and a few Ti3SiC2 remaining in Ti3SiC2/TiC−SiC with 20% SiC addition, but all constituents in Ti3Si2/TiC composite were oxidized after 12 h in air at 1500 °C. The oxidation scale thickness of TS30, 1505.78μm, was near a half of that of T, 2715μm, at 1500 °C for 20 h. Ti3SiC2/TiC composite had a flexural strength of 474 MPa, which was surpassed by Ti3SiC2/TiC−SiC composites when SiC added amount reached 15%. The strength reached the peak of 518 MPa at 20%SiC added amount.

  20. Investigation on The Properties of Fe-Si3N4 Bonded SiC Composite

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yong; FENG Di; PENG Dayan

    2005-01-01

    The mechanical properties of pressureless sintering Fe-Si3N4 bonded SiC and Si3 N4 bonded SiC with same manufacture process have been compared in this paper.The oxidizing mechanism of Fe-Si3 N4 bonded SiC ceramic matrix composite has been investigated especially through TG-DSC (thermo gravimetric analysis-differential scanning calorimeter) experiment. During oxidation procedure the main reaction is the oxidation of SiC and Si3N4, SiO2 which form protecting film to prevent further oxidizing. And residual iron in the samples become Fe2 O3 and Fe3O4, the oxidation kinetics at 1100 ~ 1300℃ of re-Si3 N4 bonded SiC has been studied especially. The weight gain per unit area at initial stage changes according to beeline rule, in the middle according to conic, and in the last oxidation period follows parabola rule.

  1. Fabrication and measurement of devices in Si/SiGe nanomembranes

    Science.gov (United States)

    Mohr, Robert

    Silicon/silicon-germanium (Si/SiGe) heterostructures are useful as hosts for gated quantum dots. The quality of the as-grown Si/SiGe heterostructure has a large impact on the final quality of the quantum dot as a qubit host. For many years, quantum dots have been fab- ricated on strain-graded heterostructures. Commonly used strain-graded heterostructures inevitably develop plastic defects that lead to interface roughness, crosshatch, and mosaic tilt. All of these factors are sources of disorder in Si/SiGe quantum electronics. In this dissertation, I report the fabrication of Hall bars and gated quantum dots on heterostructures grown on fully elastically relaxed SiGe nanomembranes, rather than strain-graded heterostructures. I report measurements of Hall bars demonstrating the creation of two-dimensional electron gases in these structures. I report the fabrication procedures used to create pairs of Hall bars and quantum dots on individual membranes. In addition, I explain a general process flow for the creation of Si/SiGe quantum devices. I focus especially on an ion-implantation technique I implemented for the fabrication of Hall bars and quantum dots in Si/SiGe heterostructures without modulation doping layers.

  2. Effects of SiC on Properties of Cu-SiC Metal Matrix Composites

    Science.gov (United States)

    Efe, G. Celebi; Altinsoy, I.; Ipek, M.; Zeytin, S.; Bindal, C.

    2011-12-01

    This paper was focused on the effects of particle size and distribution on some properties of the SiC particle reinforced Cu composites. Copper powder produced by cementation method was reinforced with SiC particles having 1 and 30 μm particle size and sintered at 700 °C. SEM studies showed that SiC particles dispersed in copper matrix homogenously. The presence of Cu and SiC components in composites were verified by XRD analysis technique. The relative densities of Cu-SiC composites determined by Archimedes' principle are ranged from 96.2% to 90.9% for SiC with 1 μm particle size, 97.0 to 95.0 for SiC with 30 μm particle size. Measured hardness of sintered compacts varied from 130 to 155 HVN for SiC having 1 μm particle size, 188 to 229 HVN for SiC having 1 μm particle size. Maximum electrical conductivity of test materials was obtained as 80.0% IACS (International annealed copper standard) for SiC with 1 μm particle size and 83.0% IACS for SiC with 30 μm particle size.

  3. Influence of Si content and heat treatment on microstructure of Al-Fe-Si alloys

    Institute of Scientific and Technical Information of China (English)

    Zhao Yuhua; Wang Xiubin; Liu Yulin; Wang Chao

    2014-01-01

    The effect of Si addition and heat treatment on the Al-5wt.%Fe al oy has been investigated by OM, SEM-EDS and XRD. The results show that the Si plays a significant role in refining the primary Al3Fe phase. It was found that the addition of 3.0wt.% Si made the al oy present the finest and wel -distributed primary Al3Fe phase, but the Al3Fe phase almost disappeared when 5wt.% Si was added. With further increase in the Si content, some Fe-rich phases appeared in the inter-grains and coarsened. In addition, the heat treatments exert a significant impact on the microstructural evolution of the Al-5wt.%Fe-5wt.%Si al oy. After heat treatment for 28 hours at 590 ºC, the coarse platelet or blocky Fe-rich phase in Al-5wt.%Fe-5wt.%Si al oys was granulated; the phase transformation from metastable platelet Al3FeSi and blocky Al8Fe2Si to stable Al5FeSi had occurred. With the extension of heat treatment, the Si phase coarsened gradual y.

  4. Improving Passivation Process of Si Nanocrystals Embedded in SiO2 Using Metal Ion Implantation

    Directory of Open Access Journals (Sweden)

    Jhovani Bornacelli

    2013-01-01

    Full Text Available We studied the photoluminescence (PL of Si nanocrystals (Si-NCs embedded in SiO2 obtained by ion implantation at MeV energy. The Si-NCs are formed at high depth (1-2 μm inside the SiO2 achieving a robust and better protected system. After metal ion implantation (Ag or Au, and a subsequent thermal annealing at 600°C under hydrogen-containing atmosphere, the PL signal exhibits a noticeable increase. The ion metal implantation was done at energies such that its distribution inside the silica does not overlap with the previously implanted Si ion . Under proper annealing Ag or Au nanoparticles (NPs could be nucleated, and the PL signal from Si-NCs could increase due to plasmonic interactions. However, the ion-metal-implantation-induced damage can enhance the amount of hydrogen, or nitrogen, that diffuses into the SiO2 matrix. As a result, the surface defects on Si-NCs can be better passivated, and consequently, the PL of the system is intensified. We have selected different atmospheres (air, H2/N2 and Ar to study the relevance of these annealing gases on the final PL from Si-NCs after metal ion implantation. Studies of PL and time-resolved PL indicate that passivation process of surface defects on Si-NCs is more effective when it is assisted by ion metal implantation.

  5. 2D SiC/SiC composite for flow channel insert (FCI) application

    Energy Technology Data Exchange (ETDEWEB)

    Yu Haijiao [Key Laboratory of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, 47 Yanwachi Street, Changsha 410073 (China); Zhou Xingui, E-mail: zhouxinguilmy@163.com [Key Laboratory of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, 47 Yanwachi Street, Changsha 410073 (China); Wang Honglei; Zhao Shuang [Key Laboratory of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, 47 Yanwachi Street, Changsha 410073 (China); Wu Yican; Huang Qunying; Zhu Zhiqiang [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Huang Zelan [Chongyi Zhangyuan Tungsten Co. Ltd., Chongyi 341300 (China)

    2010-12-15

    Two-dimensional (2D) silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) composite suiting for flow channel insert (FCI) application was successfully fabricated by stacking molding-precursor impregnation and pyrolysis (PIP) process. Plain-woven KD-I SiC fiber fabric was used as the reinforcement. SiC coating was deposited as the fiber/matrix interphase layer by chemical vapor deposition (CVD) technique. Mechanical, thermal and electrical properties of the 2D SiC/SiC composite were investigated. The results show that mechanical properties and through thickness thermal conductivity of the 2D KD-I/PIP SiC composite well meet the FCI application requirements; meanwhile, it seems that the electrical conductivity requirement will also be satisfied with a series of improvements.

  6. Synthesis of nickel catalyzed Si/SiC core-shell nanowires by HWCVD

    Science.gov (United States)

    Tong Goh, Boon; Abdul Rahman, Saadah

    2014-12-01

    Si/SiC core-shell nanowires grown on glass substrates by hot-wire chemical vapor deposition were studied. Nickel was used as a catalyst to initiate the growth of these core-shell nanowires and the nanowires were grown at different deposition pressures of 0.5 and 1 mbar. The core of the nanowire was found to be a single crystalline Si. The shell of the nanowire consisted of Si nano-crystallites embedded within an amorphous SiC matrix which was attributed to a radial growth of columnar structures. The Si and SiC nano-crystallites embedded within an amorphous matrix exhibited room-temperature photoluminescence emissions in the range of 400 nm-1 μm. A vapor-solid-solid growth mechanism of these core-shell nanowires is proposed. The effects of the deposition pressure on the properties of the core-shell nanowires are also discussed.

  7. A low temperature processed Si-quantum-dot poly-Si TFT nonvolatile memory device

    Institute of Scientific and Technical Information of China (English)

    Sun Wei

    2013-01-01

    This paper reports on a successful demonstration of poly-Si TFT nonvolatile memory with a much reduced thermal-budget.The TFT uses uniform Si quantum-dots (size ~10 nm and density ~1011 cm-2) asstorage media,obtained via LPCVD by flashing SiH4/H2 at 580 ℃ for 15 s on a Si3N4 surface.The poly-Si grain-enlargement step was shifted after source/drain formation.The NiSix-silicided source/drain enables a fast lateral-recrystallization,and thus grain-enlargement can be accomplished by a much reduced thermal-cycle (i.e.,550 ℃/4 h).The excellent memory characteristics suggest that the proposed poly-Si TFT Si quantum-dot memory and associated processes are promising for use in wider TFT applications,such as system-on-glass.

  8. Quantum Confinement Effects in Strained SiGe/Si Multiple Quantum Wells

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Strained SiGe/Si multiple quantum wells (MQWs) were grown by cold-wall ultrahigh vacuum chemical vapor deposition (UHV/CVD). Photoluminescence measurement was performed to study the exciton energies of strained Si0.84 Ge0.16/Si MQWs with SiGe well widths ranging from 4.2nm to 25.4nm. The confinement energy of 43meV is found in the Si0.84Ge0.16/Si MQWs with well width of 4.2nm. The confinement energy was calculated by solving the problem of a particle confined in a single finite rectangular poteintial well using one band effect mass model. Experimental and theoretical confinement energies are in good agreement

  9. Ge nanocrystals embedded in ultrathin Si3N4 multilayers with SiO2 barriers

    Science.gov (United States)

    Bahariqushchi, R.; Gundogdu, Sinan; Aydinli, A.

    2017-04-01

    Multilayers of germanium nanocrystals (NCs) embedded in thin films of silicon nitride matrix separated with SiO2 barriers have been fabricated using plasma enhanced chemical vapor deposition (PECVD). SiGeN/SiO2 alternating bilayers have been grown on quartz and Si substrates followed by post annealing in Ar ambient from 600 to 900 °C. High resolution transmission electron microscopy (HRTEM) as well as Raman spectroscopy show good crystallinity of Ge confined to SiGeN layers in samples annealed at 900 °C. Strong compressive stress for SiGeN/SiO2 structures were observed through Raman spectroscopy. Size, as well as NC-NC distance were controlled along the growth direction for multilayer samples by varying the thickness of bilayers. Visible photoluminescence (PL) at 2.3 and 3.1 eV with NC size dependent intensity is observed and possible origin of PL is discussed.

  10. Transport properties of double-gate SiO{sub 2}-Si-SiO{sub 2} quantum well

    Energy Technology Data Exchange (ETDEWEB)

    Prunnila, Mika; Ahopelto, Jouni [VTT Information Technology, Microelectronics, P.O. Box 1208, 02044 VTT (Finland); Sakaki, Hiroyuki [University of Tokyo, Institute of Industrial Science, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8503 (Japan)

    2005-05-01

    We report on fabrication and low temperature transport properties of double-gate SiO{sub 2}-Si-SiO{sub 2} quantum well with a 16.5 nm thick Si layer. The device is fabricated on a silicon-on-insulator substrate utilizing wafer bonding, which enables us to use heavily doped back gate. Transport properties of the device are characterized by low field Hall and high field magnetotransport measurements at 4.2 K and at 0.38 K, respectively. Top (back) Si-SiO{sub 2} interface peak mobility of 1.9 m{sup 2}/Vs (1.0 m{sup 2}/Vs) is measured at 4.2 K. When both gates have a (large) positive bias the Hall carrier density is observed to fall below the value of the expected total carrier density, which is interpreted to arise from the occupancy of the second sub-band in the Si well. This is confirmed by the high field magnetotransport measurements. In quantizing magnetic fields the longitudinal resistivity minima show Landau level filling factor behavior which is typical for weakly coupled bi-layers. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Quantitative analysis of hydrogen in SiO2/SiN/SiO2 stacks using atom probe tomography

    Directory of Open Access Journals (Sweden)

    Yorinobu Kunimune

    2016-04-01

    Full Text Available We have demonstrated that it is possible to reproducibly quantify hydrogen concentration in the SiN layer of a SiO2/SiN/SiO2 (ONO stack structure using ultraviolet laser-assisted atom probe tomography (APT. The concentration of hydrogen atoms detected using APT increased gradually during the analysis, which could be explained by the effect of hydrogen adsorption from residual gas in the vacuum chamber onto the specimen surface. The amount of adsorbed hydrogen in the SiN layer was estimated by analyzing another SiN layer with an extremely low hydrogen concentration (<0.2 at. %. Thus, by subtracting the concentration of adsorbed hydrogen, the actual hydrogen concentration in the SiN layer was quantified as approximately 1.0 at. %. This result was consistent with that obtained by elastic recoil detection analysis (ERDA, which confirmed the accuracy of the APT quantification. The present results indicate that APT enables the imaging of the three-dimensional distribution of hydrogen atoms in actual devices at a sub-nanometer scale.

  12. Study for obtaining a suppressor device of transients using the Al/SRO/Si structure; Estudio para la obtencion de un dispositivo supresor de transitorios utilizando la estructura Al/SRO/Si

    Energy Technology Data Exchange (ETDEWEB)

    Marin Ramos, Heriberto

    1999-06-01

    transitorios de voltaje. En este trabajo se presenta la estructura Aluminio/Oxido rico en Silicio/Silicio como otra opcion en el campo de los dispositivos supresores de transitorios. Algunos dispositivos utilizados en la supresion de transitorios de voltaje son: varistores de oxido de zinc, varistores de carburo de silicio, celdas de selenio, diodos zener, etcetera. La estructura AI/SRO/Si presenta propiedades conductoras debido a la presencia de exceso de silicio en la pelicula de SRO. Variando la razon de gases reaccionantes (Ro=N{sub 2}O/SiH{sub 4}) durante el crecimiento de la pelicula de Oxido Rico en Silicio (SRO, por sus siglas en ingles), se puede variar la conductividad del material. El SRO resulta de mucha importancia para el dispositivo supresor de transitorios que se pretende obtener en el presente trabajo debido a su comportamiento no-ohmico. El dispositivo AI/SRO/Si se comporta de varias maneras dependiendo de las caracteristicas del SRO y del sustrato de silicio. Se ha encontrado que uno de estos comportamientos es como un supresor de transitorios de voltaje. Verificando su comportamiento como supresor de transitorios, se estudiaron los efectos del espesor de la pelicula, del area y del exceso de silicio del dispositivo, para lo cual se obtuvo la caracteristica I-V, y la obtencion de algunos parametros en c.d. En el presente trabajo el SRO se obtuvo mediante LPCVD (Low Pressure Chemical Vapor Deposition), inicialmente se realizo una caracterizacion C-V para obtener parametros indicativos del exceso de silicio, tales como: permitividad de la pelicula de SRO. Tambien se obtuvo el indice de refraccion, el cual es un parametro indicativo de la presencia de exceso de silicio. Una vez teniendo la certeza de la presencia de exceso de silicio se procedio a obtener la caracteristica I-V de la estructura AI/SRO/Si como dispositivo. Se analizo el comportamiento de la estructura AI/SRO/Si con diferentes parametros, tales como: Ro, espesor de SOR, areas.

  13. Effect of PECVD SiNx/SiOyNx-Si interface property on surface passivation of silicon wafer

    Science.gov (United States)

    Jia, Xiao-Jie; Zhou, Chun-Lan; Zhu, Jun-Jie; Zhou, Su; Wang, Wen-Jing

    2016-12-01

    It is studied in this paper that the electrical characteristics of the interface between SiOyNx/SiNx stack and silicon wafer affect silicon surface passivation. The effects of precursor flow ratio and deposition temperature of the SiOyNx layer on interface parameters, such as interface state density Dit and fixed charge Qf, and the surface passivation quality of silicon are observed. Capacitance-voltage measurements reveal that inserting a thin SiOyNx layer between the SiNx and the silicon wafer can suppress Qf in the film and Dit at the interface. The positive Qf and Dit and a high surface recombination velocity in stacks are observed to increase with the introduced oxygen and minimal hydrogen in the SiOyNx film increasing. Prepared by deposition at a low temperature and a low ratio of N2O/SiH4 flow rate, the SiOyNx/SiNx stacks result in a low effective surface recombination velocity (Seff) of 6 cm/s on a p-type 1 Ω·cm-5 Ω·cm FZ silicon wafer. The positive relationship between Seff and Dit suggests that the saturation of the interface defect is the main passivation mechanism although the field-effect passivation provided by the fixed charges also make a contribution to it. Project supported by the National High Technology Research and Development Program of China (Grant No. 2015AA050302) and the National Natural Science Foundation of China (Grant No. 61306076).

  14. Estudio por espectroscopía infrarroja de la reacción de obtención de geles de borosilicato con diferentes relaciones Si/B

    Directory of Open Access Journals (Sweden)

    Peña-Alonso, R.

    2005-12-01

    Full Text Available Borosilicate gels with different Si/B ratio have been prepared by the sol-gel method. Such gels were obtained by hydrolysis and further condensation of TEOS (tetraethylorthosilicate and TEB (triethylborate alkoxides in acidic aqueous media. The evolution of the Si-O-Si bonds during the sol-gel condensation was dependent on the concentration of boron. Infrared spectroscopy suggested that boron plays an important role on the formation of the siloxane bonds from the hydrolysed TEOS. Thus, the cross-linking of Si-O-Si bonds decreased and the condensation of linear structures increased when the amount of TEB was higher than 10 wt.%. Moreover, it has been observed that this behaviour is directly related with the increase of gelling time in the sols containing significant amount of boron.

    Se ha llevado a cabo el estudio de la formación de diferentes geles de borosilicato preparados mediante la reacción sol-gel de hidrólisis y condensación de los alcóxidos TEOS (tetraetilortosilicato y TEB (trietilborato en diferentes proporciones Si/B y en medio acuoso acidulado. La formación de los enlaces Si-O-Si que tiene lugar durante la condensación la reacción sol-gel depende de la cantidad de boro añadido a los diferentes soles. Así, la espectroscopia infrarroja ha puesto de manifiesto que el boro juega un papel determinante en la formación de los enlaces siloxano a partir del TEOS hidrolizado, observándose que el entrecruzamiento de los enlaces Si-O-Si disminuye con el empleo de cantidades de TEB superiores al 10% en peso a la vez que aumenta la condensación en forma de estructuras lineales de los mismos. Además, se pone de manifiesto que este comportamiento está relacionado con el aumento de los tiempos de gelificación observados para altas adiciones de boro.

  15. p-n Junction Diodes Fabricated on Si-Si/Ge Heteroepitaxial Films

    Science.gov (United States)

    Das, K.; Mazumder, M. D. A.; Hall, H.; Alterovitz, Samuel A. (Technical Monitor)

    2000-01-01

    A set of photolithographic masks was designed for the fabrication of diodes in the Si-Si/Ge material system. Fabrication was performed on samples obtained from two different wafers: (1) a complete HBT structure with an n (Si emitter), p (Si/Ge base), and an n/n+ (Si collector/sub-collector) deposited epitaxially (MBE) on a high resistivity p-Si substrate, (2) an HBT structure where epitaxial growth was terminated after the p-type base (Si/Ge) layer deposition. Two different process runs were attempted for the fabrication of Si-Si/Ge (n-p) and Si/Ge-Si (p-n) junction diodes formed between the emitter-base and base-collector layers, respectively, of the Si-Si/Ge-Si HBT structure. One of the processes employed a plasma etching step to expose the p-layer in the structure (1) and to expose the e-layer in structure (2). The Contact metallization used for these diodes was a Cu-based metallization scheme that was developed during the first year of the grant. The plasma-etched base-collector diodes on structure (2) exhibited well-behaved diode-like characteristics. However, the plasma-etched emitter-base diodes demonstrated back-to-back diode characteristics. These back-to back characteristics were probably due to complete etching of the base-layer, yielding a p-n-p diode. The deep implantation process yielded rectifying diodes with asymmetric forward and reverse characteristics. The ideality factor of these diodes were between 1.6 -2.1, indicating that the quality of the MBE grown epitaxial films was not sufficiently high, and also incomplete annealing of the implantation damage. Further study will be conducted on CVD grown films, which are expected to have higher epitaxial quality.

  16. Abiologic silicon isotope fractionation between aqueous Si and Fe(III)-Si gel in simulated Archean seawater: Implications for Si isotope records in Precambrian sedimentary rocks

    Science.gov (United States)

    Zheng, Xin-Yuan; Beard, Brian L.; Reddy, Thiruchelvi R.; Roden, Eric E.; Johnson, Clark M.

    2016-08-01

    Precambrian Si-rich sedimentary rocks, including cherts and banded iron formations (BIFs), record a >7‰ spread in 30Si/28Si ratios (δ30Si values), yet interpretation of this large variability has been hindered by the paucity of data on Si isotope exchange kinetics and equilibrium fractionation factors in systems that are pertinent to Precambrian marine conditions. Using the three-isotope method and an enriched 29Si tracer, a series of experiments were conducted to constrain Si isotope exchange kinetics and fractionation factors between amorphous Fe(III)-Si gel, a likely precursor to Precambrian jaspers and BIFs, and aqueous Si in artificial Archean seawater under anoxic conditions. Experiments were conducted at room temperature, and in the presence and absence of aqueous Fe(II) (Fe(II)aq). Results of this study demonstrate that Si solubility is significantly lower for Fe-Si gel than that of amorphous Si, indicating that seawater Si concentrations in the Precambrian may have been lower than previous estimates. The experiments reached ˜70-90% Si isotope exchange after a period of 53-126 days, and the highest extents of exchange were obtained where Fe(II)aq was present, suggesting that Fe(II)-Fe(III) electron-transfer and atom-exchange reactions catalyze Si isotope exchange through breakage of Fe-Si bonds. All experiments except one showed little change in the instantaneous solid-aqueous Si isotope fractionation factor with time, allowing extraction of equilibrium Si isotope fractionation factors through extrapolation to 100% isotope exchange. The equilibrium 30Si/28Si fractionation between Fe(III)-Si gel and aqueous Si (Δ30Sigel-aqueous) is -2.30 ± 0.25‰ (2σ) in the absence of Fe(II)aq. In the case where Fe(II)aq was present, which resulted in addition of ˜10% Fe(II) in the final solid, creating a mixed Fe(II)-Fe(III) Si gel, the equilibrium fractionation between Fe(II)-Fe(III)-Si gel and aqueous Si (Δ30Sigel-aqueous) is -3.23 ± 0.37‰ (2σ). Equilibrium

  17. Rapid synthesis of MoSi2-Si3N4 nanocomposite via reaction milling of Si and Mo powder mixture

    Institute of Scientific and Technical Information of China (English)

    Majid Abdellahi; Alireza Amereh; Hamed Bahmanpou; and Behzad Sharafati

    2013-01-01

    The nanocomposite of MoSi2-Si3N4 (molybdenum disilicide-silicon nitride) was synthesized by reaction milling of the Mo and Si powder mixture. Changing the processing parameters led to the formation of diff erent products such asα-andβ-MoSi2, Si3N4, Mo2N, and Mo5Si3 at various milling times. A thermodynamic appraisal showed that the milling of Mo32Si68 powder mixture was associated with highly exothermic mechanically induced self-sustaining reaction (MSR) between Mo and Si. The MSR took place around 5 h of milling led to the formation ofα-MoSi2 and the reaction between Si and N2 to produce Si3N4 under a nitrogen pressure of 1 MPa. By increasing the nitrogen pressure to 5 MPa, more heat is released, resulting in the dissociation of Si3N4 and the transformation ofα-MoSi2 toβ-MoSi2. Heat treatment was also performed on the milled samples and led to the formation of Mo2N and the transformation ofα-MoSi2 toβ-MoSi2 at the milling times of 10 and 40 h, respectively.

  18. X-Ray Photoelectron Spectroscopy and Reflection High Energy Electron Diffraction of Epitaxial Growth SiC on Si(100) Using C60 and Si

    Institute of Scientific and Technical Information of China (English)

    LIU Yan-Fang; LIU Jin-Feng; XU Peng-Shou; PAN Hai-Bin

    2007-01-01

    The formation of silicon carbide upon deposition of C60 and Si on Si(100) surface at 850 ℃ is studied via x-ray photoelectron spectroscopy and reflection high energy electron diffraction (RHEED). The C 1s, O 1s and Si 2p core-level spectra and the RHEED patterns indicate the formation of 3C-SiC.

  19. Effect of hydrogen on passivation quality of SiN{sub x}/Si-rich SiN{sub x} stacked layers deposited by catalytic chemical vapor deposition on c-Si wafers

    Energy Technology Data Exchange (ETDEWEB)

    Thi, Trinh Cham, E-mail: s1240009@jaist.ac.jp; Koyama, Koichi; Ohdaira, Keisuke; Matsumura, Hideki

    2015-01-30

    We investigate the role of hydrogen content and fixed charges of catalytic chemical vapor deposited (Cat-CVD) SiN{sub x}/Si-rich SiN{sub x} stacked layers on the quality of crystalline silicon (c-Si) surface passivation. Calculated density of fixed charges is on the order of 10{sup 12} cm{sup −2}, which is high enough for effective field effect passivation. Hydrogen content in the films is also found to contribute significantly to improvement in passivation quality of the stacked layers. Furthermore, Si-rich SiN{sub x} films deposited with H{sub 2} dilution show better passivation quality of SiN{sub x}/Si-rich SiN{sub x} stacked layers than those prepared without H{sub 2} dilution. Effective minority carrier lifetime (τ{sub eff}) in c-Si passivated by SiN{sub x}/Si-rich SiN{sub x} stacked layers is as high as 5.1 ms when H{sub 2} is added during Si-rich SiN{sub x} deposition, which is much higher than the case of using Si-rich SiN{sub x} films prepared without H{sub 2} dilution showing τ{sub eff} of 3.3 ms. - Highlights: • Passivation mechanism of Si-rich SiN{sub x}/SiN{sub x} stacked layers is investigated. • H atoms play important role in passivation quality of the stacked layer. • Addition of H{sub 2} gas during Si-rich SiN{sub x} film deposition greatly enhances effective minority carrier lifetime (τ{sub eff}). • For a Si-rich SiN{sub x} film with refractive index of 2.92, τ{sub eff} improves from 3.3 to 5.1 ms by H{sub 2} addition.

  20. p-Cu2O/SiO x /n-SiC/n-Si memory diode fabricated with room-temperature-sputtered n-SiC and SiO x

    Science.gov (United States)

    Yamashita, Atsushi; Tsukamoto, Takahiro; Suda, Yoshiyuki

    2016-12-01

    We investigated low-temperature fabrication processes for our previously proposed pn memory diode with a p-Cu2O/SiC x O y /n-SiC/n-Si structure having resistive nonvolatile memory and rectifying behaviors suitable for a cross-point memory array with the highest theoretical density. In previous fabrication processes, n-SiC was formed by sputtering at 1113 K, and SiC x O y and p-Cu2O were formed by the thermal oxidation of n-SiC and Cu at 1073 and 473 K, respectively. In this study, we propose a pn memory diode with a p-Cu2O/SiO x /n-SiC/n-Si structure, where n-SiC and SiO x layers are deposited by sputtering at room temperature. The proposed processes enable the fabrication of the pn memory diode at temperatures of not more than 473 K, which is used for the formation of p-Cu2O. This memory diode exhibits good nonvolatile memory and rectifying characteristics. These proposed low-temperature fabrication processes are expected to expand the range of fabrication processes applicable to current LSI fabrication processes.