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Sample records for cual se forman

  1. Forman curvature for directed networks

    CERN Document Server

    Sreejith, R P; Saucan, Emil; Samal, Areejit

    2016-01-01

    A goal in network science is the geometrical characterization of complex networks. In this direction, we have recently introduced the Forman's discretization of Ricci curvature to the realm of undirected networks. Investigation of Forman curvature in diverse model and real-world undirected networks revealed that this measure captures several aspects of the organization of complex undirected networks. However, many important real-world networks are inherently directed in nature, and the Forman curvature for undirected networks is unsuitable for analysis of such directed networks. Hence, we here extend the Forman curvature for undirected networks to the case of directed networks. The simple mathematical formula for the Forman curvature in directed networks elegantly incorporates node weights, edge weights and edge direction. By applying the Forman curvature for directed networks to a variety of model and real-world directed networks, we show that the measure can be used to characterize the structure of complex ...

  2. Forman curvature for complex networks

    Science.gov (United States)

    Sreejith, R. P.; Mohanraj, Karthikeyan; Jost, Jürgen; Saucan, Emil; Samal, Areejit

    2016-06-01

    We adapt Forman’s discretization of Ricci curvature to the case of undirected networks, both weighted and unweighted, and investigate the measure in a variety of model and real-world networks. We find that most nodes and edges in model and real networks have a negative curvature. Furthermore, the distribution of Forman curvature of nodes and edges is narrow in random and small-world networks, while the distribution is broad in scale-free and real-world networks. In most networks, Forman curvature is found to display significant negative correlation with degree and centrality measures. However, Forman curvature is uncorrelated with clustering coefficient in most networks. Importantly, we find that both model and real networks are vulnerable to targeted deletion of nodes with highly negative Forman curvature. Our results suggest that Forman curvature can be employed to gain novel insights on the organization of complex networks.

  3. Decreto Rectoral No. 1037 : Por el cual se establece la política de creación, funcionamiento y utilización del repositorio institucional

    OpenAIRE

    Knudsen Quevedo, Hans Peter; Universidad del Rosario

    2008-01-01

    Decreto rectoral No. 1037 (28 de octubre de 2008) Este decreto considera que un repositorio institucional (RI) es el conjunto de servicios ofrecidos por una organización con el objeto de gestionar, difundir, y facilitar el acceso a cualquier persona con conexión a Internet, a aquellos documentos electrónicos creados por dicha institución y por aquellas personas que forman parte de ella. Que un repositorio contiene mecanismos para importar, identificar, almacenar, preservar, ...

  4. Ley 160 de 1994 (3 Agosto): Por medio de la cual se crea el Sistema Nacional de Reforma Agraria y Desarrollo Rural Campesino, se establece un subsidio para la adquisición de tierras, se reforma el Instituto Colombiano de la Reforma Agraria y se dictan otras disposiciones. Normas que la reglamentan y desarrollan

    OpenAIRE

    2003-01-01

    Ley por medio de la cual se crea el Sistema Nacional de Reforma Agraria y Desarrolo Rural Campesino, se establece un subsidio para la adquisición de tierras, se reforma el Instituto Colombiano de la Reforma Agraria y se dictan otras disposiciones. Inspirada en el precepto constitucional según el cual es deber del Estado promover el acceso progresivo a la propiedad de la tierra de los trabajadores agrarios y a otros servicios públicos rurales, con el fin de mejorar el ingreso y la calidad ...

  5. The Forman Thesis: 40 Years After

    Science.gov (United States)

    Carson, Cathryn; Kojevnikov, Alexei; Trischler, Helmuth

    Forty years ago, in 1971, Paul Forman published Weimar Culture, Causality, and Quantum Theory, 1918-1927: Adaptation by German Physicists and Mathematicians to a Hostile Intellectual Environment. His landmark study (too long, too thorough and too fundamental to be called simply an article) became immediately famous, and famously controversial. It has remained at the heart of debates about the historical relationship between science and culture ever since. The controversy surrounding the Forman Thesis was practically unavoidable, for Forman's work put forward and placed at the centre of a broader discussion the argument that the cultural values prevalent in a given place and time could influence the results of discipline-bound research, i.e. the very content of scientific knowledge. This idea, if still controversial, has since become commonly used in cultural studies of science, but at the time of its introduction it created uproar as it explicitly contradicted generally accepted and cherished beliefs about science. Yet tectonic shifts were already underway, if not always visible, that would eventually put those very beliefs into question. The Forman study both reflected and forwarded these shifts in our general perspectives on the nature and practice of science. Despite some heated objections to its findings, Forman's work has fundamentally changed directions of research in the history, sociology and philosophy of science and established itself as a classic in this group of fields, sometimes collectively called science studies. In subsequent decades it has been read and discussed in practically every graduate program that trains students in those fields, circulating in numerous copies and translated into many languages, while the original publication in the journal Historical Studies in the Physical Sciences has long become a bibliographic rarity…

  6. /Cu-Al System

    Science.gov (United States)

    Kish, Orel; Froumin, Natalya; Aizenshtein, Michael; Frage, Nachum

    2014-05-01

    Wettability and interfacial interaction of the Ta2O5/Cu-Al system were studied. Pure Cu does not wet the Ta2O5 substrate, and improved spreading is achieved when relatively a high fraction of the active element (~40 at.% Al) was added. The Al2O3 and AlTaO4 phases were observed at the Ta2O5/Cu-Al interface. A thermodynamic evaluation allowed us to suggest that the lack of wetting bellow 40 at.% Al is due to the presence of a native oxide, which covers the drop. The conditions of the native oxide decomposition and the formation of the volatile Al2O suboxide strongly depend on the vacuum level during sessile drop experiments and the composition of the Cu-Al alloy. In our case, Al contents greater than 40% provides thermodynamic conditions for the formation of Al2O (as a result of Al reaction with Al2O3) and the drop spreading. It was suggested that the final contact angle in the Ta2O5/Cu-Al system (50°) is determined by Ta adsorption on the newly formed alumina interlayer.

  7. Calcular cual es el menor número natural en cuyo factorial se encuentra determinado factor primo elevado a determinado exponente

    OpenAIRE

    Navarro Gonzalez, Roberto

    2012-01-01

    Observemos, ante todo, que, eligiendo los datos al azar, el problema no es siempre resoluble. Basta considerar, por ejemplo, que los respectivos exponentes de 7 en 343 = 73 y en 342 han de diferir entre sí en 3 unidades, de modo que no existirá ningún número en cuyo factorial se encuentre 7 elevado a un exponente intermedio

  8. La vivencia de la pre-eclampsia: una dura travesía para la cual no se está preparada

    Directory of Open Access Journals (Sweden)

    Celmira Laza Vásquez

    2014-08-01

    Full Text Available Objetivo: Describir las experiencias vividas por las mujeres con una gestación por preeclampsia severa en el Hospital de San José de la ciudad de Bogotá, Colombia. Método: Estudio cualitativo fenomenológico. Participaron diez mujeres puérperas que presentaron preeclampsia severa y fueron atendidas en el Hospital de San José durante el año 2012. Las participantes fueron seleccionaron mediante un muestreo intencional. El tamaño de la muestra se determinó por el criterio de saturación de la información. La información se recolectó mediante de una entrevista a profundidad y los datos se analizaron mediante la propuesta de Colaizzi. Resultados: La vivencia de la enfermedad dio cuenta de tres grandes categorías. Dos de ellas, la vivencia de la mujer, y con su hijo prematuro, emergieron como travesías que narraron el duro camino recorrido por el binomio madre-hijo desde su hospitalización hasta la recuperación de los dos en el hogar y los diferentes soportes con los que contó. Estas trayectorias estuvieron marcadas por sentimientos de miedo, angustia, incertidumbre; el sufrimiento por los síntomas físicos y el sometimiento a dolorosos procedimientos médicos. La tercera categoría dio cuenta de la falta de preparación de las participantes para enfrentarse a la enfermedad y todo lo que conllevaba. Conclusiones: Es necesario el fortalecimiento de las redes de apoyo primario y el papel de Enfermería como soporte para las gestantes; así como la revisión de las condiciones de hospitalización. La preparación para el impacto emocional y las consecuencias de afrontar una preeclampsia es un aspecto que se pudiera abordar durante el control prenatal.

  9. How to read Simon Forman's casebooks: medicine, astrology, and gender in Elizabethan London.

    Science.gov (United States)

    Kassel, L

    1999-04-01

    Simon Forman's astrological casebooks record thousands of medical consultations. Amidst the wealth of information in these documents, however, it is unclear to what extent Forman relied on the stars for diagnoses and therapies, or how the casebooks reflect the dymanic between Forman and his clients. This article attempts to answer these questions by reading the casebooks alongside Forman's guide to astrological physic. This approach reveals that astrology was paramount in Forman's evaluations and treatments of his patients. According to Forman, in order for him to effect a cure, he had to be trusted. It was particularly difficult to treat women because their health depended on the state of their wombs, and on their sexual activity, subjects about which women were notoriously duplicitous. The task of the astrologer was first to assess whether or not a woman was sexually active, and only then could he make a judgement about her disease. At the same time, in demonstrating an ability to discern whether or not she was being honest about her sexual activities, Forman won her confidence. By accounting for the role of astrology and the dynamics between the patient and the physician, this article provides the framework within which to read one of the most comprehensive records of medical practices in early modern England.

  10. Conference "The Cultural Alchemy of the Exact Sciences : Revisiting the Forman Thesis"

    CERN Document Server

    Kojevnikov, Alexei; Trischler, Helmuth; Weimar culture and quantum mechanics : selected papers by Paul Forman and contemporary perspectives on the Forman thesis

    2011-01-01

    This volume reprints Paul Forman's classic papers on the history of physics in post-World War I Germany and the invention of quantum mechanics. The Forman thesis has become famous as the first argument in favor of the cultural conditioning of scientific knowledge, in particular for its demonstration of the historical connection between the culture of Weimar Germany - known for its irrationality and antiscientism - and the emerging concept of quantum acausality.This volume reprints Paul Forman's classic papers on the history of physics in post-World War I Germany and the invention of quantum mechanics. The Forman thesis has become famous as the first argument in favor of the cultural conditioning of scientific knowledge, in particular for its demonstration of the historical connection between the culture of Weimar Germany - known for its irrationality and antiscientism - and the emerging concept of quantum acausality. At the 2007 international conference in Vancouver, Canada, leading historians of physics disc...

  11. Mechanochemical synthesis of Cu-Al and methyl orange intercalated Cu-Al layered double hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Qu, Jun, E-mail: forsjun@whut.edu.cn [School of Resources and Environmental Engineering, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070 (China); He, Xiaoman; Chen, Min; Hu, Huimin [School of Resources and Environmental Engineering, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070 (China); Zhang, Qiwu, E-mail: zhangqw@whut.edu.cn [School of Resources and Environmental Engineering, Wuhan University of Technology, Luoshi Road 122, Wuhan, Hubei 430070 (China); Liu, Xinzhong [College of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou 350118 China (China)

    2017-04-15

    In this study, a mechanochemical route to synthesize a Cu-Al layered double hydroxide (LDH) and a methyl orange (MO) intercalated one (MO-LDH) was introduced, in which basic cupric carbonate (Cu{sub 2}(OH){sub 2}CO{sub 3}) and aluminum hydroxide (Al(OH){sub 3}) with Cu/Al molar ratio at 2/1 was first dry ground for 2 h and then agitated in water or methyl orange solution for another 4 h to obtain the LDH and MO-LDH products without any heating operation. The prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetry (TG), Differential scanning calorimetry (DSC) and Scanning electron microscopy (SEM). The products showed high crystallinity phase of Cu-Al and MO intercalated Cu-Al LDH with no evident impurities, proving that the craft introduced here was facile and effective. The new idea can be applied in other fields to produce organic-inorganic composites. - Highlights: • A facile mechanochemical route to synthesize Cu-Al and MO intercalated Cu-Al LDH. • The products possesses high crystalline of LDH phase with no impure phases. • The dry milling process induces the element substitution between the raw materials. • The agitation operation helps the grain growth of LDH.

  12. The Feature Films of Milos Forman: A Bibliography of the Literature.

    Science.gov (United States)

    Hooker, Charlotte S.

    This bibliography covers the literature on four of the feature films of Milos Forman: "Black Peter (Peter and Pavla)" (1964), "A Blonde in Love (Loves of a Blond)" (1965), "The Firemen's Ball" (1967), and "Taking Off" (1971). Listed separately by type are materials found in dictionaries, encyclopedias, and…

  13. Perspectiva de Derechos en Programas Universitarios que forman Para la Educación Inicial

    Directory of Open Access Journals (Sweden)

    Nisme Pineda

    2009-01-01

    Full Text Available En las últimas décadas se ha asignado mayor importancia tanto al papel del desarrollo infantil temprano en el desarrollo humano como a los contextos en los cuales éste se da y a la atención a la primera infancia. Esto llevó a pensar en la necesidad de comprender cómo se están formando los docentes y las docentes que se encargan de la atención a la niñez durante los primeros años de vida, reconociendo la tendencia creciente a la inscripción de niños y niñas en las ofertas institucionales a edades cada vez más tempranas, y la necesidad de promover y garantizar los derechos de la infancia. La investigación caracterizó de manera cualitativa los planes curriculares de 34 programas universitarios de pre-grado en Colombia, que buscan la formación de docentes para trabajar con niños y niñas en la primera infancia. El estudio incluyó análisis de documentos, entrevistas con coordinadores de programas, y grupos focales con estudiantes de último semestre y graduados. Los resultados muestran que pocos programas explicitan en sus currículos la perspectiva de derechos de la infancia. Además, prevalecen las miradas tradicionales sobre educación inicial y sobre el papel del entorno en que crecen los niños y niñas. Las metodologías de formación de los programas en general consideran a sus estudiantes como sujetos activos, y en consonancia asumen estrategias pedagógicas y de evaluación activas. La actualización de los programas es constante y busca mejorar la calidad académica, pero no tiene como uno de sus referentes la situación de la infancia en el país.

  14. Strategi Mengenali Motif Khas Kain Tenun Cual Bangka Dengan AHP

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    Hilyah Magdalena

    2016-12-01

    Full Text Available Woven fabric cual Bangka currently used as one of the identity of community pride in Bangka Belitung Islands. The specificity of this fart cual fabric interesting to study because of the motives that have similarities with songket palembang. Woven fabric cual Bangka and Palembang songket cloth looks similar because the same cloth-making techniques - both using techniques sungkit. The purpose of this research is how to recognize a particular motif woven fabric cual fart. This research using Analytical Hierarchy Process ( AHP to classify some specific motifs that exist in woven fabric cual fart. Experts in the field of woven fabric cual is to inform you that the woven fabric cual farts have tabled motif, motifs or patterns, motifs fabric edge, motif gold thread, fabric base material, as well as the specific color. The research involved four experts that the results of the questionnaires is processed by software Expert Choice 2000. The results showed that the main peculiarity of the woven fabric cual fart is in a pattern or motif with a percentage of 31.5, and is the chosen alternative product is songket with a percentage of 25.4.

  15. [Beyond Weimar Culture--the significance of the Forman thesis for a cultural approach to the history of science].

    Science.gov (United States)

    Trischler, Helmuth; Carson, Cathryn; Kojevnikov, Alexei

    2008-12-01

    '"Forman thesis', published in 1971, argued for a historical linkage among the intellectual atmosphere of Weimar Germany, popular revolts against determinism and materialism, and the creation of the revolutionary new theory of quantum mechanics. Paul Forman's long essay on "Weimar Culture" has shaped research agendas in numerous fields, from the history and philosophy of physics to German history to the sociology of scientific knowledge. Despite its status as a classic and its transformative effect, Weimar Culture has always inspired as much critique as assent. In particular in the history of science, cohorts of students and two generations of scholars have debated the Forman thesis as a conceptual tool for linking scientific change with cultural processes. The Forman thesis raises critical questions for both the ongoing debates over cultural approaches to the history of science and the burgeoning newer scholarship on physics in and beyond Weimar Germany. Exploring these implications has been the aim of a transnational project of the three authors of this article which sheds some light on these debates and briefly introduces the following papers of this special issue devoted to Paul Forman and his seminal works in the history of science.

  16. La exportación de un producto de alta calidad depende en gran manera de su procesamiento y tecnología aplicada el Ecuador no tiene historia citrícola como se mencionó, y todos los adelantos que se han conseguido se han hecho en forma apresurada y sin mayores planteamientos técnicos motivo por el cual, es necesarío establecer directrices en torno a “proyectos de cámaras frigoríficas”, estableciendo pautas sobre ubicación, posición de las cámaras, criterios de dimensionamiento, y sobre todo características que debe cumplir la construcción, sin olvidar las características organolépticas del limón en función de las condiciones anotadas anteriormente

    OpenAIRE

    Galarza Hernandez, Alberto; Pazmiño B, Marco

    2009-01-01

    El presente trabajo desarrolla un sistema de Fiscalización a los Depósitos Comerciales Públicos implementando la Inteligencia y la Gestión de Riesgo, lo cual permitirá un nuevo enfoque que modificara el método con que se toman las decisiones y, en consecuencia, la forma en que se desarrollan los trabajos en los diferentes Distritos Aduaneros respecto al ingreso de mercadería a este tipo de régimen aduanero exento temporalmente de sus obligaciones tributarias, mejorando así la eficiencia en la...

  17. "Te Enseño a Jugar": Caracterización de Movimientos Interaccionales y Formas Lingüísticas Mediante las Cuales se Regula la Interacción Lúdica "I Teach You How to Play": Description of the Interactional Movements and Linguistics Forms Used to Regulate Play Interactions

    Directory of Open Access Journals (Sweden)

    Alejandra Stein

    2012-05-01

    Full Text Available El lenguaje regula la actividad humana, incluyendo el juego; simultáneamente, el juego constituye un medio para el desarrollo lingüístico (Katherine Nelson, 1996; Vigotsky, 1988. El juego resulta un contexto privilegiado para los usos regulativos del lenguaje y para el desarrollo del discurso instructivo (Graves, 1992. Se analiza una muestra intencional conformada por 31 situaciones de juego en las que participaron en el hogar 10 niños de 4 años de barrios marginados de Argentina. El análisis cualitativo (Strauss & Corbin, 2002 mostró distintos movimientos interaccionales (modelado, preguntas, comparaciones y formas lingüísticas de regulación de la situación (imperativos, frases verbales de obligación usados por los adultos, que pueden contribuir al desarrollo del discurso instructivo de los niños.Language regulates human activity, including play; simultaneously, play is a means for linguistic development (Katherine Nelson, 1996; Vigotsky, 1988. Play situations are a privileged context for the regulative uses of language and for the development of instructional discourse (Graves, 1992. Within this framework, in this paper a purposive sample that includes 31 play situations is analyzed. In these situations participated 10 4-year-old children from marginalized neighbourhoods in Argentina. The qualitative analysis (Strauss & Corbin, 2002 showed that adults used different interactional movements (modelling, questions, comparisons alongside with linguistic forms of regulating the situation (imperatives, verbal phrases of obligation, all of which can contribute to the development of instructional discourse in children.

  18. Atomic diffusion behavior in Cu-Al explosive welding process

    Science.gov (United States)

    Chen, S. Y.; Wu, Z. W.; Liu, K. X.; Li, X. J.; Luo, N.; Lu, G. X.

    2013-01-01

    A hybrid method is proposed to study atomic diffusion behavior in Cu-Al explosive welding process. The method combines molecular dynamics simulation and classical diffusion theory. Cu-Al explosive welding and scanning electron microscope experiments are done to verify the method. Using the method, we find that the atomic diffusion mostly takes place in the unloading stage of the welding process. The diffusion coefficients are collision velocity-dependent, with higher velocities generating larger coefficients. When there is no transverse velocity, the diffusion coefficient is directly proportional to the longitudinal velocity. With the longitudinal velocity fixed, the diffusion coefficient is proportional to the square of the transverse velocity. The thickness of the diffusion layer is calculated from the simulation result, and it is in good agreement with the experiment result.

  19. Investigation on contact melting of Cu/Al laminated composite

    Directory of Open Access Journals (Sweden)

    Dmitry V. Pronichev

    2016-12-01

    Full Text Available The study presents investigation of chemical composition, microhardness and electrical conductivity of Cu/Al laminated metal composite after heat treatment at temperatures higher than Cu–Al eutectic melting point. The Cu/Al bimetal was obtained via explosion welding. Chemical composition of the material after heat treatments was identified using EDS analysis. Eddy current testing was applied to investigate electrical conductivity of the composite’s components. Strain-hardened zones were identified in the explosion welded composite. The experimental value of electrical conductivity of explosion welded composite was in good coherence with calculated by additivity rule results. Heat treatments resulted in the formation of multiple interlayers which had high microhardness value and had intermetallics in composition. The electrical conductivity of the identified interlayers was significantly lower than of Cu and Al.

  20. Debilidades en los programas que forman docentes en educación matemática percepción de los actores

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    Edwin Chaves Esquivel

    2016-03-01

    Full Text Available Debido a las críticas sobre el bajo rendimiento en matemática a nivel de Enseñanza Media en Costa Rica, donde mucha de la responsabilidad es achacada al docente, surge el cuestionamiento de la calidad del proceso de formación de los docentes de esta disciplina. El presente artículo procura determinar las carencias de los programas académicos que forman profesores en Educación Matemática en el país. Para ellos se consideran las opiniones de estudiantes actuales de estos programas y profesores egresados de los mismos. Se analiza la percepción de 171 estudiantes y 172 docentes obtenida mediante una  encuesta autoadministrada. Existe coherencia en las opiniones de los dos grupos. Coinciden en señalar que la principal fortaleza en estos programas se fundamenta en la formación en matemáticas teóricas y en el razonamiento lógico. Sin embargo, en términos generales, se denota cierto descontento debido una serie de debilidades que, a su criterio, afecta notoriamente el desempeño en el aula. La principal crítica consiste en el divorcio existente entre los cursos de matemática y educación. A su criterio, no existe relación entre estos cursos que les permita promover metodologías de enseñanza en áreas específicas de la matemática. Se ha percibido también una fuerte carencia de componentes históricos, filosóficos y metodológicos de las matemáticas. Además señalan que se denota una carencia de aplicaciones prácticas de los diferentes conceptos matemáticos. Señalan también los encuestados que no se desarrollan estrategias que le permitan participar en procesos serios de investigación en Educación Matemática. Finalmente se indica que no recibe la suficiente capacitación sobre el uso de los recursos tecnológicos más modernos. Estas opiniones consisten en un importante referente para evaluar la labor de las universidades en estos procesos de formación, así como en la conveniencia de futuros procesos de capacitación a

  1. Modelado de estrategias reproductivas en peces que forman agrupaciones de desove

    OpenAIRE

    Sánchez Cárdenas, Rebeca

    2012-01-01

    La biología reproductiva de los peces es diversa en cuanto a características y procesos que usualmente se clasifican conforme a semejanzas. Los modelos resultantes facilitan la vinculación de la reproducción y otros fenómenos biológicos y físicos en situaciones prácticas. El presente trabajo presenta la exploración de los procesos reproductivos de 78 teleósteos con el objetivo de identificar y proponer un modelo la estrategia reproductiva. Las especies fueron seleccionadas por formar agrupaci...

  2. Strength and thermal stability of Cu-Al2O3 composite obtained by internal oxidation

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    Jovanovic, M. T.

    2010-12-01

    Full Text Available The objective of the work is to study the effects of the high-energy milling on strengthening, thermal stability and electrical conductivity of Cu-Al2O3 composite. The prealloyed copper powders, atomized in inert gas and containing 3 wt. % Al, were milled up to 20 h in the planetary ball mill to oxidize in situ aluminium with oxygen from the air. Composite compacts were obtained by hot-pressing in an argon atmosphere at 800 °C for 3 h under the pressure of 35MPa. The microstructural characterization was performed by the optical microscope, scanning electron microscope (SEM, transmission electron microscope (TEM and X-ray diffraction analysis (XRD. The microhardness, electrical conductivity and density measurements were also carried out. The effect of internal oxidation and high-energy milling on strengthening of Cu-Al2O3 composite was significant, The increase of the microhardness of composite compacts (292 HV is almost threefold comparing to compacts processed from the as-received Cu-3 wt. % Al powder (102 HV. The grain size of Cu-Al2O3 compacts processed from 5 and 20 h-milled powders was 75 and 45 nm, respectively. The small increase in the grain size and the small microhardness drop indicate the high thermal stability of Cu-Al2O3 composite during high-temperature exposure at 800 °C.El objetivo del trabajo es el estudio de los efectos de la pulverización con altas energías sobre la resistencia, estabilidad térmica y conductividad eléctrica del compuesto Cu-Al2O3. El polvo pre-aleado de cobre, obtenido a través de la atomización con gas inerte y con un contenido de 3wt. % Al, se molió durante 20 h en el molino planetario de bolas dando lugar a la oxidación in situ del aluminio con el oxígeno del aire. El compuesto compactado se ha obtenido mediante prensado en caliente en atmósfera de argón a 800 °C durante 3 h y a una presión de 35MPa. La caracterización microestructural se hizo a través de microscopia óptica, microscopia

  3. Isla del río Cuale (Puerto Vallarta, Jalisco, México

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    Edmundo Andrade Romo

    2007-01-01

    Full Text Available Los destinos turísticos internacionales experimentan cambios continuos y a velocidades generalmente mayores que en ciudades o poblados no turísticos. Esta evolución urbano-turística resulta un excelente tema de investigación para el estudio del patrimonio cultural local y sus implicaciones socioantropológicas, Puerto Vallarta, Jalisco, uno de los tres destinos turísticos internacionales más importantes de México, no ha sido la excepción. En el presente artículo se advierte como los elementos naturales se transforman en culturales y a través del análisis diacrónico se distinguen los distintos momentos que conforman y explican la identidad local, así como de la elaboración mitológica sobre el origen local. Finalmente se expone la situación actual impactada por el turismo y la percepción social sobre la Isla del río Cuale como el elemento natural-cultural más significativo en la población vallartense.

  4. Qué democracia para cuales mujeres. Abriendo el debate

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    Josefina L. Brown

    2007-01-01

    Full Text Available En este trabajo nos proponemos abordar, conceptual y analíticamente, dos de los ejes principales que atraviesan los asuntos relativos a ciudadanía y mujeres. Esto es el dilema igualdad-desigualdades sociales y el dilema igualdad-diferencia. En una primera parte nos detendremos en el análisis de la democracia realmente existente en Latinoamérica en general pero sobretodo en argentina y en los debates que entorno de la democracia se reavivaron en los noventa. Un hecho paradigmático se ese renacer es la reedición en castellano del libro de Marshall en 1998.- con este telón de fondo esbozamos el panorama especifico de los debates para la ciudadanía plena para las mujeres que tiene a los derechos sexuales y no reproductivos como punto de bisagra en un panorama complejo: mas derechos formales, menos derechos reales; politización del cuerpo de las mujeres.

  5. Uptake of Sc 3+ and La 3+ from aqueous solution using ethylenediaminetetraacetate-intercalated Cu-Al layered double hydroxide reconstructed from Cu-Al oxide

    Science.gov (United States)

    Kameda, Tomohito; Hoshi, Kazuaki; Yoshioka, Toshiaki

    2011-02-01

    A Cu-Al layered double hydroxide intercalated with ethylenediaminetetraacetate (edta·Cu-Al LDH) was prepared by suspending Cu-Al oxide, obtained by the calcination of CO32--intercalated Cu-Al LDH, in edta solution. It was found that the reconstruction of Cu-Al oxide to Cu-Al LDH was promoted with an increase in the temperature and time. The reaction in the pH range of around 8 suggests that Hedta 3- was intercalated in the interlayer of Cu-Al LDH. Edta·Cu-Al LDH was found to take up rare metal ions such as Sc 3+ and La 3+ in an aqueous solution at a pH of around 6-6.5. The uptake of Sc 3+ was caused not only by the chelating function of Hedta 3- in the interlayer but also by the chemical behavior of Cu-Al LDH itself. On the other hand, the uptake of La 3+ was caused only by the chelating function of Hedta 3- in the interlayer. The Hedta 3- in the interlayer of edta·Cu-Al LDH had the potential to form a chelate complex more preferentially with Sc 3+ than with La 3+.

  6. Twenty five years since the first prospective study by Forman et al. (1991) on Helicobacter pylori and stomach cancer risk.

    Science.gov (United States)

    Sitas, Freddy

    2016-04-01

    Stomach cancer is one of the leading causes of cancer death worldwide, despite its incidence and mortality falling in many places. The discovery in 1984 that a bacterial infection with Helicobacter pylori could cause stomach and duodenal ulcers prompted work in its role in causing gastritis, and led to the first prospective study in 1991 by Forman et al., showing that infection with H.pylori increased the risk of stomach cancer in those infected by almost three-fold. Prior to then, it was hypothesized that stomach was caused by poor diets. While diets may still play a role, the falls in stomach cancer incidence have been associated with reductions in population prevalence of H. pylori. Discovery of the link was accelerated by the use of stored sera from other unrelated studies, and the use of serological assays. Since those discoveries the treatment landscape of gastric disorders has changed significantly, with a rapid uptake of antibiotic and proton pump inhibitors (triple) therapies in those who are H. pylori positive. Over time we have seen falls in gastric cancer, peptic and duodenal ulcers and in many of the procedures previously used to cure peptic ulcer disease, such as vagotomies and gastrectomies. Further still, an oral vaccine against H. pylori, first trialled in China, holds much promise of being the third vaccine against a cancer causing infection. If successful this would lead to a further reduction in H. pylori related conditions, and ultimately gastric cancer, an otherwise lethal disease.

  7. Effect of the diameter on Cu-Al post retention Efeito do diâmetro na retenção de pinos de Cu-Al

    Directory of Open Access Journals (Sweden)

    Celso Bernardo de Souza Filho

    2004-09-01

    Full Text Available This study compared the resistance to removal by traction of abraded cylindrical metal cast posts of Cu-Al (Goldent-LA. The posts had constant length (9 mm and three different diameters (0.9, 1.3 and 1.7 mm, and were cemented with zinc phosphate cement. The crowns of 36 sound maxillary canines were sectioned, the roots were immersed in resin blocks and the root canals were endodontically treated. The teeth were divided into three groups to be prepared and standardized with the use of a parallelometer with the following burs: Group 1 - Largo n. 2; Group 2 - Largo n. 4; Group 3 - Largo n. 6. The posts were molded with chemically activated resin and after casting they were abraded and their dimensions were confirmed with a digital caliper. After cementation of the posts in the prepared root canals, the samples were kept at 37ºC in distilled water for 7 days and subsequently submitted to the traction test in a universal testing machine (Instron 4444. The results showed no statistical difference between the groups. Diameter variation (0.9 mm, 1.3 mm and 1.7 mm in abraded cylindrical posts cemented with zinc phosphate did not affect resistance to removal.Este estudo in vitro comparou a resistência à remoção por tração de núcleos metálicos fundidos em liga de Cu-Al (Goldent-LA cilíndricos, jateados, de comprimento constante igual a 9 mm, cimentados com cimento de fosfato de zinco e com três diferentes diâmetros: 0,9 mm, 1,3 mm e 1,7 mm. Trinta e seis caninos superiores hígidos tiveram suas coroas seccionadas, sendo as raízes incluídas em blocos de resina acrílica, e os canais, tratados endodonticamente. Os dentes foram divididos em três grupos para serem preparados e padronizados com o auxílio de um paralelômetro com as seguintes brocas: Grupo 1 - Largo nº 2; Grupo 2 - Largo nº 4; Grupo 3 - Largo nº 6. Os núcleos foram moldados com resina acrílica ativada quimicamente e, após a fundição, foram jateados e tiveram as suas

  8. ANÁLISIS SOCIOECONÓMICO DE LA CUENCA DEL RIO CUALE, JALISCO, MÉXICO: UNA CONTRIBUCIÓN PARA LA DECLARACIÓN DEL ÁREA NATURAL PROTEGIDA RESERVA DE LA BIOSFERA EL CUALE

    Directory of Open Access Journals (Sweden)

    Jorge Téllez López

    2013-06-01

    Full Text Available Durante los meses de enero a mayo de 2013, a través de la metodología propuesta por Alciaturi (2009; se realizó el análisis de los factores socioeconómicos involucrados en la cuenca del rio Cuale, Jalisco, México. Los resultados incluyeron aspectos relacionados con la dinámica demográfica, grado de marginación, nivel educativo, población económicamente activa, principales actividades económicas, comunidades rurales, descripción socioeconómica, potenciales de los recursos naturales, usos y aprovechamientos actuales; así como la situación jurídica de la tenencia de la tierra. El objetivo de esta investigación es conocer cómo estos factores inciden sobre los recursos naturales de la cuenca. Con la finalidad de utilizar esta información para establecer la declaratoria del Área Natural Protegida Reserva de la Biosfera El Cuale, que es una herramienta que puede ayudar a asegurar la conservación de esta zona. Por lo tanto, se han incluido elementos de análisis social, económico y ambiental, puesto que estos factores han resultado determinantes en los procesos que inciden en la deforestación y cambio de uso de suelo.

  9. Kinetic equation for internal oxidation of Cu-Al alloy cylinders

    Institute of Scientific and Technical Information of China (English)

    Kexing Song; Jiandong Xing; Baohong Tian; Ping Liu; Qiming Dong

    2005-01-01

    The kinetics of internal oxidation of Cu-Al alloy cylinders, containing up to 2.214mol% Al, were investigated in the temperature range of 1023 K to 1273 K, and the depth of internal oxidation was measured in the microscopy. A kinetic equation was derived to describe the internal oxidation of Cu-Al alloy cylinders. For the internal oxidation of Cu-Al alloys employed in the synthesis of alumina dispersion strengthened copper, the kinetic equation can be simplified. The derived equation was checked experimentally by means of oxidation depth measurements and the results show that the derived equation is exact enough to describe the kinetics of internal oxidation of Cu-Al alloy cylinders. Based on this equation and the oxidation depth measurements, the permeability of oxygen in solid copper was obtained. Investigation also shows that there is no evidence for preferential diffusion along grain boundaries in the process of internal oxidation.

  10. La interdependencia de contratos que forman un mismo grupo contractual en el derecho francés

    OpenAIRE

    Carlos Pizarro-Wilson

    2010-01-01

    La doctrina, como la jurisprudencia francesa, han recurrido a ingeniosas elucubraciones para justificar la interdependencia  al interior de los grupos de contratos. En este trabajo se exponen las diversas teorías con el objeto de mostrar la carencia de una solución unívoca como fundamento de la indivisibilidad en los grupos y cadenas de contratos. En definitiva, para lograr construir la noción de grupo de contrato se requiere la voluntad de las partes para hacer del otro u otros actos una con...

  11. Effect of the diameter on Cu-Al post retention Efeito do diâmetro na retenção de pinos de Cu-Al

    OpenAIRE

    Celso Bernardo de Souza Filho; Silvana Maria Paulino; Edson Alfredo; Manoel Damião de Sousa Neto; Luiz Pascoal Vansan

    2004-01-01

    This study compared the resistance to removal by traction of abraded cylindrical metal cast posts of Cu-Al (Goldent-LA). The posts had constant length (9 mm) and three different diameters (0.9, 1.3 and 1.7 mm), and were cemented with zinc phosphate cement. The crowns of 36 sound maxillary canines were sectioned, the roots were immersed in resin blocks and the root canals were endodontically treated. The teeth were divided into three groups to be prepared and standardized with the use of a par...

  12. Kinetic Equation for Internal Oxidation of Cu-Al Alloy Spheres

    Institute of Scientific and Technical Information of China (English)

    SONG Kexing; GAO Jianxin; XU Xiaofeng; LI Peiquan; TIAN Baohong; GUO Xiuhua

    2007-01-01

    The kinetics of internal oxidation of Cu-Al alloy spheres, containing up to 2.214% mole fraction Al was investigated in the temperature range 1 023 K to 1 273 K, and the depth of internal oxidation was measured in the microscopy. A kinetic equation was derived to describe the internal oxidation of Cu-Al alloy spheres, which was checked experimentally by means of oxidation depth measurements. The results show that the derived equation is exact enough to describe the kinetics of internal oxidation of Cu-Al alloy spheres.Based on this equation and the oxidation depth measurements, the permeability of oxygen in solid copper has been obtained. Investigation also shows that in the process of internal oxidation, there is no evidence for preferential diffusion along grain boundaries.

  13. La interdependencia de contratos que forman un mismo grupo contractual en el derecho francés

    Directory of Open Access Journals (Sweden)

    Carlos Pizarro-Wilson

    2010-03-01

    Full Text Available La doctrina, como la jurisprudencia francesa, han recurrido a ingeniosas elucubraciones para justificar la interdependencia  al interior de los grupos de contratos. En este trabajo se exponen las diversas teorías con el objeto de mostrar la carencia de una solución unívoca como fundamento de la indivisibilidad en los grupos y cadenas de contratos. En definitiva, para lograr construir la noción de grupo de contrato se requiere la voluntad de las partes para hacer del otro u otros actos una condición de la validez recíproca de cada uno de los elementos que participan en el conjunto contractual. Esta explicación no infringe el principio del efecto relativo de los contratos, sino que plantea una relectura del mismo más acorde con la realidad económica de la contratación.

  14. Mechanical properties of intermetallics formed during thermal aging of Cu-Al ball bonds

    NARCIS (Netherlands)

    Kouters, M.H.M.; Gubbels, G.H.M.; O'Halloran, O.; Rongen, R.; Weltevreden, E.R.

    2011-01-01

    In high power automotive electronics copper wire bonding is regarded as most promising alternative for gold wire bonding in 1st level interconnects and therefore subjected to severe functional requirements. In the Cu-Al ball bond interface the growth of intermetallic compounds may deteriorate the

  15. Elimination of formaldehyde over Cu-Al2O3 catalyst at room temperature.

    Science.gov (United States)

    Zhang, Chang-Bin; Shi, Xiao-Yan; Gao, Hong-Wei; He, Hong

    2005-01-01

    Catalytic elimination of formaldehyde (HCHO) was investigated over Cu-Al2O3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO2 occurs at room temperature, but the adsorption of HCHO occurs on the catalyst surface. With the increase of gas hourly space velocity (GHSV) and inlet HCHO concentration, the time to reach saturation was shortened proportionally. The results of the in situ DRIFTS, Density functional theory calculations and temperature programmed desorption(TPD) showed that HCHO was completely oxidized into HCOOH over Cu-Al2O3 at room temperature. With increasing the temperature in a flow of helium, HCOOH was completely decomposed into CO2 over the catalyst surface, and the deactivated Cu-Al2O3 is regenerated at the same time. In addition, although Cu had no obvious influence on the adsorption of HCHO on Al2O3, Cu dramatically lowered the decomposition temperature of HCOOH into CO2. It was shown that Cu-Al2O3 catalyst had a good ability for the removal of HCHO, and appeared to be promising for its application in destroying HCHO at room temperature.

  16. Facile synthesis of dendritic Cu by electroless reaction of Cu-Al alloys in multiphase solution

    Science.gov (United States)

    Wang, Ying; Liang, Shuhua; Yang, Qing; Wang, Xianhui

    2016-11-01

    Two-dimensional nano- or micro-scale fractal dendritic coppers (FDCs) were synthesized by electroless immersing of Cu-Al alloys in hydrochloric acid solution containing copper chloride without any assistance of template or surfactant. The FDC size increases with the increase of Al content in Cu-Al alloys immersed in CuCl2 + HCl solution. Compared to Cu40Al60 and Cu45Al55 alloys, the FDC shows hierarchical distribution and homogeneous structures using Cu17Al83 alloy as the starting alloy. The growth direction of the FDC is , and all angles between the trunks and branches are 60°. Nanoscale Cu2O was found at the edge of FDC. Interestingly, nanoporous copper (NPC) can also be obtained through Cu17Al83 alloy. Studies showed that the formation of FDC depended on two key factors: the potential difference between CuAl2 intermetallic and α-Al phase of dual-phase Cu-Al alloys; a replacement reaction that usually occurs in multiphase solution. The electrochemical experiment further proved that the multi-branch dendritic structure is very beneficial to the proton transfer in the process of catalyzing methanol.

  17. Mechanical properties of intermetallics formed during thermal aging of Cu-Al ball bonds

    NARCIS (Netherlands)

    Kouters, M.H.M.; Gubbels, G.H.M.; O'Halloran, O.; Rongen, R.; Weltevreden, E.R.

    2011-01-01

    In high power automotive electronics copper wire bonding is regarded as most promising alternative for gold wire bonding in 1st level interconnects and therefore subjected to severe functional requirements. In the Cu-Al ball bond interface the growth of intermetallic compounds may deteriorate the wi

  18. Elimination of formaldehyde over Cu-Al2O3 catalyst at room temperature

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chang-bin; SHI Xiao-yan; GAO Hong-wei; HE Hong

    2005-01-01

    Catalytic elimination of formaldehyde(HCHO) was investigated over Cu-Al2O3 catalyst at room temperature. The results indicated that no oxidation of HCHO into CO2 occurs at room temperature, but the adsorption of HCHO occurs on the catalyst surface.With the increase of gas hourly space velocity (GHSV) and inlet HCHO concentration, the time to reach saturation was shortened proportionally. The results of the in situ DRIFTS, Density functional theory calculations and temperature programmed desorption(TPD)showed that HCHO was completely oxidized into HCOOH over Cu-Al2 O3 at room temperature. With increasing the temperature in a flow of helium, HCOOH was completely decomposed into CO2 over the catalyst surface, and the deactivated Cu-Al2 O3 is regenerated at the same time. In addition, although Cu had no obvious influence on the adsorption of HCHO on Al2 O3, Cu dramatically lowered the decomposition temperature of HCOOH into CO2. It was shown that Cu-Al2 O3 catalyst had a good ability for the removal of HCHO, and appeared to be promising for its application in destroying HCHO at room temperature.

  19. Facile synthesis of dendritic Cu by electroless reaction of Cu-Al alloys in multiphase solution

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Ying; Liang, Shuhua, E-mail: liangxaut@gmail.com; Yang, Qing; Wang, Xianhui

    2016-11-30

    Highlights: • Nano- or micro-scale fractal dendritic copper (FDC) was synthesized by electroless immersing of Cu-Al alloys in CuCl{sub 2} + HCl. • FDC size increases with the increase of Al content in Cu-Al alloys immersed in CuCl{sub 2} + HCl solution. • Nanoscale Cu{sub 2}O was found at the edge of FDC. Nanoporous copper (NPC) can also be obtained by using Cu{sub 17}Al{sub 83} alloy. • The potential difference between CuAl{sub 2} and α-Al phase and the replacement reaction in multiphase solution are key factors. - Abstract: Two-dimensional nano- or micro-scale fractal dendritic coppers (FDCs) were synthesized by electroless immersing of Cu-Al alloys in hydrochloric acid solution containing copper chloride without any assistance of template or surfactant. The FDC size increases with the increase of Al content in Cu-Al alloys immersed in CuCl{sub 2} + HCl solution. Compared to Cu{sub 40}Al{sub 60} and Cu{sub 45}Al{sub 55} alloys, the FDC shows hierarchical distribution and homogeneous structures using Cu{sub 17}Al{sub 83} alloy as the starting alloy. The growth direction of the FDC is <110>, and all angles between the trunks and branches are 60°. Nanoscale Cu{sub 2}O was found at the edge of FDC. Interestingly, nanoporous copper (NPC) can also be obtained through Cu{sub 17}Al{sub 83} alloy. Studies showed that the formation of FDC depended on two key factors: the potential difference between CuAl{sub 2} intermetallic and α-Al phase of dual-phase Cu-Al alloys; a replacement reaction that usually occurs in multiphase solution. The electrochemical experiment further proved that the multi-branch dendritic structure is very beneficial to the proton transfer in the process of catalyzing methanol.

  20. Preparation and Properties of Plasma Spraying Cu-Al2O3 Gradient Coatings

    Institute of Scientific and Technical Information of China (English)

    Ali LEI; Nan DONG; Lajun FENG

    2007-01-01

    In order to overcome the limitations of low adhesion strength and poor thermal-shock resistance of pure ceramic coatings, Cu-Al2O3 gradient coatings were fabricated by plasma spraying. The microstructure and distribution of Cu-Al2O3 gradient coatings were analyzed. The adhesion strength, thermal-shock resistance and porosity of the coatings were tested. The results show that the composition of the gradient coatings has a gradient distribution along the thickness of coatings. As copper has a relatively low melting point and the molten copper has good wettability on the surface of Al2O3, it can be melted sufficiently and could fill the interstices and pores among the spraying particles effectively, thus improves the adhesion strength, thermal shock resistance and reduces the porosity. The adhesion strength of the gradient coating is 15.2 MPa which is two times of that of the double-layer structure coating.

  1. Study of CuAl(100) by using He ion scattering

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, L.; Zur Muhlen, E.; O`Connor, D.J. [Newcastle Univ., NSW (Australia). Dept. of Physics

    1993-12-31

    The clean CuAl (100) surface has been investigated by using He{sup +} ion scattering. The polar scans show that Al atoms randomly replace the Cu atoms but sit (0.15{+-}0.05) Angstroms higher than the Cu atoms. The outmost layer concentration of Al is about (17{+-}3)%. The aluminium concentration on the outmost layer is sensitive to the sample temperature up to 300 deg C. 7 refs., 5 figs.

  2. The structure of Cu-Al films prepared by unbalanced DC magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Musil, J.; Bell, A.J. [Czech Acad. of Sci., Prague (Czech Republic). Inst. of Phys.; Chepera, M.; Zeman, J. [Military Technical Institute, PO Box 574, 602 00 (Czech Republic)

    1997-11-25

    Recently, the formation of nanostructured and amorphous materials has been the focus of intense research owing to interest from a basic scientific point of view and their potential technological value. This paper reports on the variation in, and control of, the structure of Cu-Al films prepared in a state-of-the-art unbalanced DC magnetron sputtering system. The structure is shown to be considerably influenced by ion bombardment during growth with both the energy and ratio of impinging ions: arriving atoms playing dominant roles. In addition, the addition of different quantities of Al to the thin film is shown to have a dramatic impact on the structure. The conditions under which nanocrystalline Cu-Al films can be prepared are given. The films were deposited by the magnetron sputter ion plating (MSIP) process using negative substrate biases up to 1000 V and at different argon pressures down to 0.04 Pa. The structure of the films were determined from XRD analyses. An attempt to correlate obtained XRD spectra with the structure of the film is suggested. The resistivities of the films were measured using the four-point probe method, whilst the content of Al was determined from EDX measurements. (orig.) 15 refs.

  3. A metastable HCP intermetallic phase in Cu-Al bilayer films

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Limei

    2006-07-01

    For the present study, three kinds of layered Cu/Al films have been fabricated. The first kind of samples were multilayered Cu/Al films deposited by sputtering on (001)Si. The individual layer thicknesses were 100 nm, 200 nm and 400 nm, while the total film thickness of 800 nm was kept constant, thus leading to multilayer systems with 8, 4 and 2 layers, respectively. The second type of samples were Cu/Al bilayer films grown on (0001) sapphire by sputtering, with individual layer thicknesses of 400 nm. The third type of samples were bilayer films (100 nm Cu and 100 nm Al) deposited on (0001)sapphire by MBE at room temperature. Applying conventional transmission electron microscopy and X-ray diffraction, different epitaxial growth behaviors were found in these films. All multilayer films from the first type were polycrystalline. The second type of films show a (111) FCC texture and possess intermetallic phases at the interfaces. HRTEM investigations displayed that along [111]FCC, the atomic structure of the interlayer has an ABAB stacking sequence, which is identical with a hexagonal close-packed (HCP) structure in [0001] direction, but not with the ABCABC stacking sequence of Cu and Al in [111]FCC. The lattice parameters of the HCP structure at the interlayer were determined from a model which gave the best agreement between the experimental and simulated images. The parameters are: a=b=0.256 nm, c=0.419 nm, ?=120 , with the space group of P6m2. Furthermore, lattice distortion analysis revealed that the lattice parameters of the HCP phase are increasing from the near-Cu-side to the near-Al-side. The chemical composition of the interlayer was investigated by energy dispersive X-ray spectroscopy (EDS). EDS linescans were performed from pure Al to pure Cu layers. In order to examine the stability of this HCP phase, in-situ heating experiments were performed in the HRTEM at {proportional_to}600 C. Ex-situ heating experiments were performed at different temperatures to

  4. Room temperature fatigue behavior of OFHC copper and CuAl25 specimens of two sizes

    DEFF Research Database (Denmark)

    Singhal, A.; Stubbins, J.F.; Singh, B.N.

    1994-01-01

    requiring an understanding of their fatigue behavior.This paper describes the room temperature fatigue behavior of unirradiated OFHC (oxygen-free high-conductivity) copper and CuAl25 (copper strengthened with a 0.25% atom fraction dispersion of alumina). The response of two fatigue specimen sizes to strain......Copper and its alloys are appealing for application in fusion reactor systems for high heat flux components where high thermal conductivities are critical, for instance, in divertor components. The thermal and mechanical loading of such components will be, at least in part, cyclic in nature, thus...... controlled fatigue loading is examined, and differences in behavior are discussed. Specimens with the smaller size are now being irradiated in several reactors...

  5. Nanomechanical properties and thermal decomposition of Cu-Al2O3 composites for FGM applications

    Directory of Open Access Journals (Sweden)

    Koumoulos Elias P.

    2016-01-01

    Full Text Available It is widely reported that copper-alumina (Cu-Al2O3 nanocomposite materials exhibit high potential for use in structural applications in which enhanced mechanical characteristics are required. The investigation of Cu-Al2O3 nanocomposites which are to form a functionally graded material (FGM structure in terms of nanomechanical/structural integrity and thermal stability is still scarce. In this work, fully characterized nanosized Al2O3 powder has been incorporated in Cu matrix in various compositions (2, 5 and 10 wt.% of Al2O3 content. The produced composites were evaluated in terms of their morphology, structural analysis, thermal behavior, nanomechanical properties and their extent of viscoplasticity. The results reveal that all nanocomposites degrade at elevated temperatures; increased surface mass gain with decreasing Al2O3 content was observed, while no such difference of % mass gain in 5 and 10 wt.% of Al and Al2O3 content in Cu was observed. The increase of Al2O3 wt.% content results in thermal stability enhancement of the nanocomposites. The thermal decomposition process of the material is reduced in the presence of 10 wt.% of Al2O3 content. This result for the matrix decomposition can be explained by a decrease in the diffusion of oxygen and volatile degradation products throughout the composite material due to the incorporation of Al and Al2O3. The Al2O3 powder enhances the overall thermal stability of the system. All samples exhibited significant pile-up of the materials after nanoindentation testing. Increasing the wt.% of Al2O3 content was found to increase the creep deformation of the samples as well as the hardness and elastic modulus values.

  6. Numerical investigation on thermal properties at Cu-Al interface in micro/nano manufacturing

    Science.gov (United States)

    Zhang, Liqiang; Yang, Ping; Chen, Min; Liao, Ningbo

    2012-02-01

    A hybrid model by integrating TTM (two-temperature model) and MD (molecular dynamics) is proposed to investigate the properties on interface of dissimilar materials under thermal flux conditions. This model can describe the electron phonon coupling and phonon scattering at the interface of different metals easily. By comparing the Cu-Cu interface and Cu-Al interface, the atoms of the Cu-Cu interface at different sides tend to move together; while, the atoms displacements of Cu and Al are opposite along the interface, which may cause stress and voids at the interface. Moreover, the propagation mechanisms of nanocracks and the corresponding change of temperature distribution and thermal flux are investigated. The results show that the interfaces of dissimilar materials are prone to crack initiations, leading to delaminations because of the high temperature. All these are useful for understanding the deformation and failure of the interfaces structures. It implies a potential method for design and analysis of interface structure in micro/nano manufacturing.

  7. Señas Mexicano

    Directory of Open Access Journals (Sweden)

    Juan F. García Mejía

    2007-01-01

    Full Text Available En este artículo se muestra un sistema que permite el estudio y práctica del Lenguaje de Señas Mexicano (LMS, el cual es el método de comunicación de las personas que padecen un trastorno de procesamiento auditivo. El sistema propuesto en este artículo consta de un guante de tela instrumentado con sensores de flexión, una etapa de acondicionamiento de señales y una tarjeta de adquisición de datos; que en su conjunto constituyen el Hardware. El software esta formado por un programa de adquisición de datos y una interfaz de usuario, ambos codificados en Visual Basic Net. El sistema propuesto se modela por medio del lenguaje de modelado unificado (UML, ya que Visual Basic es un lenguaje orientado a eventos.

  8. Orientar desde el Ser: algunas aportaciones del programa Orient@cual para la elaboración del proyecto profesional y vital de alumnado de PCPI y CFGM

    Directory of Open Access Journals (Sweden)

    Soledad Romero\\u2010Rodríguez

    2015-01-01

    Full Text Available El trabajo que presentamos se enmarca en el desarrollo del proyecto de investigación “ORIENT@CUAL: elaboración de proyectos profesionales en la formación profesional del sistema educativo. Diseño de un programa y una plataforma virtual de orientación” subvencionado por el Plan Nacional I+D. Aportamos los primeros resultados obtenidos en la evaluación piloto del programa generado en el proyecto. Dicho programa se basa en un enfoque narrativo y sistémico de la orientación en el que el trabajo desde el Ser es el elemento clave. Se presentan los resultados obtenidos a través de entrevistas en profundidad realizadas a 16 estudiantes de PCPI y CFGM de dos IES de la provincia de Sevilla una vez finalizada su participación en el programa. Los resultados apuntan a que el programa contribuye al desarrollo de las competencias implicadas en las diferentes fases de elaboración del proyecto profesional y vital.

  9. SE PREVENINDO?

    Directory of Open Access Journals (Sweden)

    Ana Débora Assis Moura

    2010-01-01

    Full Text Available Este estudio tuvo como objetivo verificar el comportamiento de las prostitutas en relación a la prevención de enfermedades de transmisión sexual y del Síndrome de Inmunodeficiencia Adquirida-SIDA, así como investigar cómo se previenen de esas enfermedades. Se trata de una investigación exploratoria, con enfoque cualitativo, llevada a cabo en la Asociación de las Prostitutas en Ceará, Brazil, en septiembre de 2008, a través de una encuesta con 25 prostitutas. El análisis de los datos se hizo según el análisis de contenido, después de ser agrupados en cuatro categorías: conocimiento sobre las enfermedades de transmisión sexual/SIDA; convivencia con la(s enfermedad(es; prevención de la enfermedad de transmisión sexual/SIDA; y el uso de drogas. Se concluyó que las prostitutas no usan preservativos en todas las relaciones sexuales, por lo tanto, las enfermedades de transmisión sexual representan una realidad; la desinformación sobre la(s enfermedad(es es notable; el consumo de drogas lícitas e ilícitas es frecuente entre ellas, factor que las expone a situaciones más vulnerables con relación al VIH/SIDA.

  10. Study of the optical properties of CuAlS2 thin films prepared by two methods

    Science.gov (United States)

    Ahmad, S. M.

    2017-04-01

    CuAlS2 thin films were successfully deposited on glass substrates using two methods: chemical spray pyrolysis (CSP) and chemical bath deposition (CBD). It was confirmed from the X-ray diffraction (XRD) analysis that CSP films exhibited a polycrystalline nature while amorphous nature was diagnosed for CBD films. Also XRD analysis was utilized to compute grain size, strain and dislocation density. Surface morphology was characterized using scanning electron microscope and photomicroscope images. The optical absorption measurement revealed that the direct allowed electronic transition with band gaps 2.8 eV and 3.0 eV for CBD and CSP methods, respectively. The optical constants, such as extinction coefficient ( k), refractive index ( n), real and imaginary dielectric constants ( ɛ 1, ɛ 2) were discussed. The photoluminescence (PL) spectra of CuAlS2 thin films appeared as a single peak for each of them, and this is attributed to band-to-band transition.

  11. Distribution of distances between dislocations in different types of dislocation substructures in deformed Cu-Al alloys

    Energy Technology Data Exchange (ETDEWEB)

    Trishkina, L., E-mail: trishkina.53@mail.ru; Zboykova, N.; Koneva, N., E-mail: koneva@tsuab.ru; Kozlov, E. [Tomsk State University of Architecture and Building, 2 Solyanaya St., Tomsk, 634003 (Russian Federation); Cherkasova, T. [Tomsk State University of Architecture and Building, 2 Solyanaya St., Tomsk, 634003 (Russian Federation); National Research Tomsk Polytechnic University, 50 Lenin Ave., Tomsk, 634050 (Russian Federation)

    2016-01-15

    The aim of the investigation was the determination of the statistic description of dislocation distribution in each dislocation substructures component forming after different deformation degrees in the Cu-Al alloys. The dislocation structures were investigated by the transmission diffraction electron microscopy method. In the work the statistic description of distance distribution between the dislocations, dislocation barriers and dislocation tangles in the deformed Cu-Al alloys with different concentration of Al and test temperature at the grain size of 100 µm was carried out. It was established that the above parameters influence the dislocation distribution in different types of the dislocation substructures (DSS): dislocation chaos, dislocation networks without disorientation, nondisoriented and disoriented cells, in the walls and inside the cells. The distributions of the distances between dislocations in the investigated alloys for each DSS type formed at certain deformation degrees and various test temperatures were plotted.

  12. Se los por se lo

    Directory of Open Access Journals (Sweden)

    José Luis Rivarola

    1985-12-01

    Full Text Available El sistema de la conjugación "objetiva" plantea interesantesproblemas que fueron tratados en parte por K. Heger (1966 en suestudio comparativo del francés y del español. De la comparaciónse desprende, por ejemplo, que en español hay un cierto número deambigüedades que no permiten establecer un "paradigma tan completo y unívoco" como en el caso del francés. Dentro de estas ambigüedades se encuentran las que propicia el gramema se: "El morfema [gramema] se funciona no sólo como pronombre reflexivo, sinotambién como variante combinatoria del pronombre personal complemento indirecto de la tercera persona.

  13. Señales entre hongos patógenos y plantas hospederas resistentes

    OpenAIRE

    G. Camarena Gutiérrez

    2001-01-01

    Los hongos parásitos obligados obtienen sus nutrimentos de células vivas. Durante su ciclo de vida, se forman tres tipos de estructuras intracelulares (hifa de invasión, haustorio M y haustorio D) y cada uno puede afectar de manera diferente la membrana de la célula huésped que le rodea, también cómo afectar otros componentes celulares. Cada estructura intracelular también previene que se disparen defensas no específicas de la planta por la actividad del hongo, posiblemente interfiriendo el s...

  14. Adsorption and subsequent partial photodegradation of methyl violet 2B on Cu/Al layered double hydroxides

    Energy Technology Data Exchange (ETDEWEB)

    Guzmán-Vargas, Ariel, E-mail: aguzmanv@ipn.mx [Instituto Politécnico Nacional, ESIQIE-SEPI-DIQI, Laboratorio de Investigación en Materiales Porosos, Catálisis Ambiental y Química Fina (LiMpCa-QuF), UPALM Edif. 7 P.B. Zacatenco, GAM, México, D.F.07738 (Mexico); Lima, Enrique [Instituto de Investigaciones en Materiales-UNAM, Circuito exterior s/n, Cd. Universitaria, Del. Coyoacán, México, D.F. 04510 (Mexico); Uriostegui-Ortega, Gisselle A. [Instituto Politécnico Nacional, ESIQIE-SEPI-DIQI, Laboratorio de Investigación en Materiales Porosos, Catálisis Ambiental y Química Fina (LiMpCa-QuF), UPALM Edif. 7 P.B. Zacatenco, GAM, México, D.F.07738 (Mexico); Oliver-Tolentino, Miguel A. [Instituto Politécnico Nacional, Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Calzada Legaria 694, Col. Irrigación, México, D.F. 11500 (Mexico); Rodríguez, Esaú E. [Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional 2580, Col. San Pedro Zacatenco, México, D.F. 07360 (Mexico)

    2016-02-15

    Graphical abstract: - Highlights: • LDH Cu/Al material showed high adsorption capacity. • Adsorption occurs by π–π interactions from the aromatic ring on the surface. • Adsorption mechanism fits to pseudo-second order model. • The photodegradation is due to the ·OH radical formation. - Abstract: Uncalcined Cu/Al LDH was studied as adsorbent and photocatalyst in the adsorption and subsequent photodegradation of methyl violet 2B dye (MV2B). Physicochemical characterization was carried out by XRD, FTIR, UV–vis, including photoactive properties, DSC/TGA and SEM. Kinetic and thermodynamic models showed great affinity and sorption capacity, the maximum adsorption capacity was 361.0 mg g{sup −1} obtained by Langmuir model, in addition, the results showed that the dye was adsorbed on the LDH surface. Photocatalytic activity was evaluated in the MV2B dye photodegradation process, and it was confirmed by the presence ·OH radicals monitored by EPR spin trapping technique, additionally, COD and TOC parameters were measured, {sup 13}C NMR showed differences for the adsorbed and photodegraded samples.

  15. Fabrication of Copper-Rich Cu-Al Alloy Using the Wire-Arc Additive Manufacturing Process

    Science.gov (United States)

    Dong, Bosheng; Pan, Zengxi; Shen, Chen; Ma, Yan; Li, Huijun

    2017-09-01

    An innovative wire-arc additive manufacturing (WAAM) process is used to fabricate Cu-9 at. pct Al on pure copper plates in situ, through separate feeding of pure Cu and Al wires into a molten pool, which is generated by the gas tungsten arc welding (GTAW) process. After overcoming several processing problems, such as opening the deposition molten pool on the extremely high-thermal conductive copper plate and conducting the Al wire into the molten pool with low feed speed, the copper-rich Cu-Al alloy was successfully produced with constant predesigned Al content above the dilution-affected area. Also, in order to homogenize the as-fabricated material and improve the mechanical properties, two further homogenization heat treatments at 1073 K (800 °C) and 1173 K (900 °C) were applied. The material and mechanical properties of as-fabricated and heat-treated samples were compared and analyzed in detail. With increased annealing temperatures, the content of precipitate phases decreased and the samples showed gradual improvements in both strength and ductility with little variation in microstructures. The present research opened a gate for in-situ fabrication of Cu-Al alloy with target chemical composition and full density using the additive manufacturing process.

  16. Preparation and Mechanical Characterization of Cu-Al2O3 Functionally Graded Material for electrical contact applications

    Directory of Open Access Journals (Sweden)

    Abdul Raheem. K. Abid Ali

    2017-07-01

    Full Text Available In this study, five-layered stepwise Cu/Al2O3 as functionally graded materials have been prepared from copper powder with with five percentage of alumina powder as (5 ,10 ,20 ,30 and 40 Wt% by using powder metallurgy technique. Mixing of copper (34.32 µm and alumina (1.439 µm powders for two hours and then several disk sample with dimensions (14mm diameter and 10 thickness have been compacting at different compacting stresses (550, 650 and 750 MPa. However, sintering of specimens for three hours at 850 under vacuum about has been achieved. The Porosity and density before and after sintering have been calculated. X-ray diffraction analysis showed that tests before and after sintering is similar, there is no new phase formed after sintering. Scanning electron microscopy technique is used to characterize the surface of each layer. Hardness test showed slight linear graded microhardness across the layers without any obvious jumps throughout the thickness. Pin on disc method have been used in determining the wear or material removal of prepared FGM samples. In addition, it was examined thermal conductivity and the electrical resistance have been done in preparing samples from composite and functionally graded material. From the experimental results, it is clear that hardness results change in each layer by producing FGM according to the percentage of the harder constituent (i.e. Al2O3 from 53 to 113 Hv. While Thermal conductivity decrease with the increasing addition weight percentage for α-Al2O3. And Electrical resistance increased when alumina content increased for (5% to 40%. Wear rate improved with the increasing additive percentage of alumina from 0.507 for layer 1 to 0.15 for layer five at 15N and 25 min. Smoothly gradual change of the composition in the Cu/Al2O3 FGM can eliminate the microscopic interface, such as a result as that traditional Cu-Al2O3 joint.

  17. Adsorption and subsequent partial photodegradation of methyl violet 2B on Cu/Al layered double hydroxides

    Science.gov (United States)

    Guzmán-Vargas, Ariel; Lima, Enrique; Uriostegui-Ortega, Gisselle A.; Oliver-Tolentino, Miguel A.; Rodríguez, Esaú E.

    2016-02-01

    Uncalcined Cu/Al LDH was studied as adsorbent and photocatalyst in the adsorption and subsequent photodegradation of methyl violet 2B dye (MV2B). Physicochemical characterization was carried out by XRD, FTIR, UV-vis, including photoactive properties, DSC/TGA and SEM. Kinetic and thermodynamic models showed great affinity and sorption capacity, the maximum adsorption capacity was 361.0 mg g-1 obtained by Langmuir model, in addition, the results showed that the dye was adsorbed on the LDH surface. Photocatalytic activity was evaluated in the MV2B dye photodegradation process, and it was confirmed by the presence rad OH radicals monitored by EPR spin trapping technique, additionally, COD and TOC parameters were measured, 13C NMR showed differences for the adsorbed and photodegraded samples.

  18. The activity and selectivity of catalytic peroxide oxidation of chlorophenols over Cu-Al hydrotalcite/clay composite.

    Science.gov (United States)

    Zhou, Shiwei; Gu, Chuantao; Qian, Zhenying; Xu, Jinguang; Xia, Chuanhai

    2011-05-15

    Liquid phase catalytic oxidation of chlorophenols (CPs) was carried out over Cu-Al hydrotalcite/clay composite at ambient temperature and pressure using hydrogen peroxide as oxidant. The results showed that the catalyst had high catalytic activity, with complete oxidation of 4-CP within 40 min at 40 °C. The content and position of chlorine on the aromatic ring had significantly different effects on the oxidation rate of CPs, with the rate sequence of phenol > monochlorophenol (MCP) > dichlorophenol (DCP) > trichlorophenol (TCP), 3-CP > 2-CP > 4-CP, and 3,5-DCP > 3,4-DCP > 2,5-DCP > 2,4-DCP > 2,6-DCP. This was ascribed to the interactions among σ-electron withdrawing conductive effect, π-electron donating conjugative effect, and steric hindrance effect of chlorine. It was evidenced that the catalytic peroxide oxidation of CPs in the first step was selective and rate-limiting, where chlorinated 1,4-benzoquinones formed.

  19. Optimization of the processing parameters during internal oxidation of Cu-Al alloy powders using an artificial neural network

    Energy Technology Data Exchange (ETDEWEB)

    Song Kexing; Xing Jiandong; Dong Qiming; Liu Ping; Tian Baohong; Cao Xianjie

    2005-06-15

    Internal oxidation is a commercial method for producing oxide dispersion strengthened copper (ODS Cu). In this paper, the dilute Cu-Al alloy powders containing 0.26 wt% of Al have been internally oxidized at temperatures (T) from 700 to 1000 deg. C, for holding times (t) up to 10 h. The alumina particle size has been observed and determined by electron microscopy using the two-stage preshadowed carbon replica method. By the use of backpropagation network, the non-linear relationship between internal oxidation process parameters (T,t) and alumina particle size has been established on the base of dealing with the experimental data. The results show that the well-trained backpropagation neural network can predict the alumina particle size during internal oxidation precisely and the prediction values have sufficiently mined the basic domain knowledge of internal oxidation process. Therefore, a new way of optimizing process parameters has been provided by the authors.

  20. Molecular Dynamics Study of Stability of Solid Solutions and Amorphous Phase in the Cu-Al System

    Institute of Scientific and Technical Information of China (English)

    YANG Bin; LAI Wen-Sheng

    2009-01-01

    The relative stability of fcc and bcc solid solutions and amorphous phase with different compositions in the Cu-Al system is studied by molecular dynamics simulations with n-body potentials.For Cu1-xAlx alloys,the calculations show that the fcc solid solution has the lowest energies in the composition region with x<0.32 or x>0.72,while the bcc solid solution has the lowest energies in the central composition range,in agreement with the ball-milling experiments that a single bcc solid solution with 0.30<x< 0.70 is obtained.The evolution of structures in solid solutions and amorphous phase is studied by the coordination number (CN) and bond-length analysis so as to unveil the underlying physics.It is found that the energy sequence among three phases is determined by the competition in energy change originating from the bond length and CNs (or the number of bonds).

  1. Surface-Mechanical Properties of Electrodeposited Cu-Al2O3 Composite Coating and Effects of Processing Parameters

    Science.gov (United States)

    Maharana, H. S.; Ashok, Akarapu; Pal, S.; Basu, A.

    2016-01-01

    Cu/Al2O3 composite coatings were prepared from acidic copper sulfate bath containing ultrafine Al2O3 particles by direct current plating method to increase the surface-mechanical property of Cu for its possible use as electrical contact. Effect of ultrafine Al2O3 particle concentration in electrolyte and deposition current density on the surface-mechanical properties of the coatings was investigated. Coatings were characterized by scanning electron microscopy and X-ray diffraction (XRD) techniques for the purpose of surface morphology and phase study. From XRD data, crystallographic texture of the coating was also analyzed. To study the mechanical properties, microhardness testing, adhesion, and wear test were carried out. Improved hardness of the resultant coatings was observed and was correlated with the wt pct of ultrafine particle in the Cu matrix, matrix structure, and crystallographic orientation. Better wear property of the composite coating was also reported from the wear plot and wear track morphology. Altogether, better coating property was attributed toward finer matrix, hard reinforced phase, and preferred orientation in selected conditions. Electrical conductivity of the coating was affected by grain size and second-phase concentration, and the values obtained were in the usable range required for electrical applications.

  2. Redes neuronales analógicas para la computación paralela masiva de señales en tiempo real

    OpenAIRE

    Cancelo, Gustavo Indalecio Eugenio

    1996-01-01

    En esta tesis se realiza un estudio sobre las posibilidades de la electrónica para modelar unidades y sistemas neuronales. En particular, se proponen implementaciones de redes neuronales analógicas. La primera a nivel microelectrónico, comprende el diseño de una neurona computacional con función de activación gaussiana. Primeramente, se demostrará que las unidades computacionales con función de activación gaussiana forman una base para aproximadores universales de funciones continuas y discon...

  3. Redes neuronales analógicas para la computación paralela masiva de señales en tiempo real

    OpenAIRE

    Cancelo, Gustavo Indalecio Eugenio

    1996-01-01

    En esta tesis se realiza un estudio sobre las posibilidades de la electrónica para modelar unidades y sistemas neuronales. En particular, se proponen implementaciones de redes neuronales analógicas. La primera a nivel microelectrónico, comprende el diseño de una neurona computacional con función de activación gaussiana. Primeramente, se demostrará que las unidades computacionales con función de activación gaussiana forman una base para aproximadores universales de funciones continuas y discon...

  4. Nucleation and Growth of Cu-Al Intermetallics in Al-Modified Sn-Cu and Sn-Ag-Cu Lead-Free Solder Alloys

    Science.gov (United States)

    Reeve, Kathlene N.; Anderson, Iver E.; Handwerker, Carol A.

    2015-03-01

    Lead-free solder alloys Sn-Cu (SC) and Sn-Ag-Cu (SAC) are widely used by the microelectronics industry, but enhanced control of the microstructure is needed to improve solder performance. For such control, nucleation and stability of Cu-Al intermetallic compound (IMC) solidification catalysts were investigated by variation of the Cu (0.7-3.0 wt.%) and Al (0.0-0.4 wt.%) content of SC + Al and SAC + Al alloys, and of SAC + Al ball-grid array (BGA) solder joints. All of the Al-modified alloys produced Cu-Al IMC particles with different morphologies and phases (occasionally non-equilibrium phases). A trend of increasing Cu-Al IMC volume fraction with increasing Al content was established. Because of solidification of non-equilibrium phases in wire alloy structures, differential scanning calorimetry (DSC) experiments revealed delayed, non-equilibrium melting at high temperatures related to quenched-in Cu-Al phases; a final liquidus of 960-1200°C was recorded. During cooling from 1200°C, the DSC samples had the solidification behavior expected from thermodynamic equilibrium calculations. Solidification of the ternary alloys commenced with formation of ternary β and Cu-Al δ phases at 450-550°C; this was followed by β-Sn, and, finally, Cu6Sn5 and Cu-Al γ1. Because of the presence of the retained, high-temperature phases in the alloys, particle size and volume fraction of the room temperature Cu-Al IMC phases were observed to increase when the alloy casting temperature was reduced from 1200°C to 800°C, even though both temperatures are above the calculated liquidus temperature of the alloys. Preliminary electron backscatter diffraction results seemed to show Sn grain refinement in the SAC + Al BGA alloy.

  5. Señales entre hongos patógenos y plantas hospederas resistentes

    Directory of Open Access Journals (Sweden)

    G. Camarena Gutiérrez

    2001-01-01

    Full Text Available Los hongos parásitos obligados obtienen sus nutrimentos de células vivas. Durante su ciclo de vida, se forman tres tipos de estructuras intracelulares (hifa de invasión, haustorio M y haustorio D y cada uno puede afectar de manera diferente la membrana de la célula huésped que le rodea, también cómo afectar otros componentes celulares. Cada estructura intracelular también previene que se disparen defensas no específicas de la planta por la actividad del hongo, posiblemente interfiriendo el sistema de señales más que la expresión de defensa.

  6. La finalidad del presente artículo es establecer la fuerte vinculación que existe entre el conocimiento y los activos intangibles, siendo que estos son los grandes desconocidos en la valoración de las empresas y en el cálculo de las cuentas nacionales, en especial el PIB y la productividad. Fue el investigador Robert Solow, en 1956, uno de los primeros en señalar la importancia del conocimiento en el crecimiento económico, expresando que este es una función de capital, trabajo y conocimiento. Desde la década de 1990 viene creciendo la inquietud sobre la necesidad de analizar y medir los diferentes tipos de activos intangibles para incluirlos, con su justo valor, tanto en las cuentas nacionales como en los estados financieros de las empresas. Pero dichos activos tienen unas características muy especiales, las cuales hacen de su valoración monetaria una difícil tarea. Es impostergable profundizar su análisis y estudio para que no sigan siendo ignorados o minimizados en las prácticas cotidianas de las empresas y los mercados.

    Directory of Open Access Journals (Sweden)

    Leonidas Torres Citraro

    2014-12-01

    Full Text Available La finalidad del presente artículo es establecer la fuerte vinculación que existe entre el conocimiento y los activos intangibles, siendo que estos son los grandes desconocidos en la valoración de las empresas y en el cálculo de las cuentas nacionales, en especial el PIB y la productividad. Fue el investigador Robert Solow, en 1956, uno de los primeros en señalar la importancia del conocimiento en el crecimiento económico, expresando que este es una función de capital, trabajo y conocimiento. Desde la década de 1990 viene creciendo la inquietud sobre la necesidad de analizar y medir los diferentes tipos de activos intangibles para incluirlos, con su justo valor, tanto en las cuentas nacionales como en los estados financieros de las empresas. Pero dichos activos tienen unas características muy especiales, las cuales hacen de su valoración monetaria una difícil tarea. Es impostergable profundizar su análisis y estudio para que no sigan siendo ignorados o minimizados en las prácticas cotidianas de las empresas y los mercados.

  7. LA RESPONSABILIDAD DEL FRANQUICIADOR ANTE TERCEROS CLIENTES DEL FRANQUICIADO: UN ASUNTO FRENTE AL CUAL EL DERECHO COMERCIAL ESTÁ EN MORA

    Directory of Open Access Journals (Sweden)

    Sergio Alberto Rojas Quiñones

    2010-05-01

    Full Text Available La franquicia comercial en Colombia constituye hoy en día un excelente laboratorio de investigación para todos aquellos que desean contar con una caleidoscópica institución cuyo análisis sea factible no sólo desde una perspectiva teórica e iusprivatista, sino práctica, constitucionalista, administrativista y, en general, multifacética en sus diversas presentaciones en la praxis y la academia del derecho. El presente artículo procura contribuir en los avances metodológicos y dogmáticos en torno a esta materia, ocupándose de un asunto pasado por alto en la grandísima mayoría de las investigaciones propias de esta materia y cuya monta no es desdeñable a la luz de los efectos prácticos que puede acarrear: la responsabilidad del franquiciante por el hecho del franquiciado. Con miras a lograr una verdadera profundización de la materia, se procederá a desarrollar con minucia algunos asuntos que se han considerado como fundamentales en esta temática y que, entre otras, darán una visión integral de cómo puede el constituyente de la franquicia verse comprometido por los hechos de su co-contratante, a la luz de la legislación colombiana.

  8. El presente trabajo tiene como objetivo el de modelar matemáticamente la realidad de un sistema específico con el fin de maximizar sus utilidades por medio de una herramienta de la investigación de operaciones como es la programación lineal. el sistema al cual este trabajo hace referencia es un restaurante de servicio rápido perteneciente a una de la mejores cadenas como es mcdonald´s

    OpenAIRE

    Wong Leon, Javier; Barriga Rivera, Alfredo Nicolas

    2009-01-01

    El diseño el reactor de saponificación se hizo sobre la base de códigos internacionales, en donde la saponificación es la división de las grasas. El diseño siempre se lo realizo pensando en los materiales y herramientas existen en nuestro medio. El proyecto se realizo en dos etapas la primera en la cual se diseño mecánicamente el equipo y la segunda en donde se hizo un análisis térmico del mismo.

  9. Band gap engineering of CuAl1-x In x S2 alloys for photovoltaic applications: a first principles study

    Science.gov (United States)

    Kumar, S.; Joshi, Suman; Gupta, S. K.; Auluck, S.

    2016-05-01

    The mixed cation alloys CuAl1-x In x S2 span a band gap range that fits the requirement for solar cell light absorbers. However, the materials properties of CuAl1-x In x S2 are not well known as a function of concentration (x). We have used density functional theory calculations to study the structural and electronic properties of these alloys. The most stable configuration out of all possible configurations in the given supercell was obtained with the site occupancy disorder (SOD) program. We find that (i) the structural properties are reproduced to within less than 1% of the measured values; (ii) the CuAl1-x In x S2 alloys are highly miscible with low formation enthalpies; (iii) the band gap of CuAl1-x In x S2 decreases from 3.3 eV to 1.5 eV as In concentration (x) increases from 0 to 1, and shows a small bowing when calculated with hybrid Heyd-Scuseria-Ernzerhof (HSE06) functionals; (iv) the calculated band offset shows that the band gap decreases with the addition of In, resulting mainly from the valence band upshift.

  10. Preparation of Cu-Al layered double hydroxide intercalated with ethylenediaminetetraacetate by coprecipitation and its uptake of rare earth ions from aqueous solution

    Science.gov (United States)

    Kameda, Tomohito; Hoshi, Kazuaki; Yoshioka, Toshiaki

    2013-03-01

    A Cu-Al layered double hydroxide intercalated with ethylenediaminetetraacetate (edta•Cu-Al LDH) was prepared by the dropwise addition of a Cu-Al nitrate solution to an edta solution at constant pH values of 8.0, 9.0, and 10.0. The edta•Cu-Al LDH had Hedta3- in the interlayer. Furthermore, the preparation at pH 8.0 resulted in the intercalation of Cu(edta)2-. The edta•Cu-Al LDH was found to take up rare earth ions from aqueous solution. The uptake of Sc3+ and Y3+ by edta•Cu-Al LDH was attributed to both the chelating functions of the edta ion in the interlayer and the chemical properties of Cu-Al LDH itself. The uptake of La3+ by edta•Cu-Al LDH was primarily caused by the chelating function of edta ions in the interlayer. The edta ions in the edta•Cu-Al LDH interlayer formed chelate complexes in the order Sc3+ > Y3+ > La3+ due to their relative stabilities, Sc(edta)- > Y(edta)- > La(edta)-. Thus, edta ions retain their chelating function even when intercalated in a Cu-Al LDH interlayer.

  11. Photocatalytic reduction of Cr(VI) on the new hetero-system CuAl2O4/TiO2.

    Science.gov (United States)

    Gherbi, R; Nasrallah, N; Amrane, A; Maachi, R; Trari, M

    2011-02-28

    Visible light driven HCrO(4)(-) reduction was successfully achieved over the new hetero-system CuAl(2)O(4)/TiO(2). The spinel, elaborated by nitrate route, was characterized photo electrochemically. The optical gap was found to be 1.70 eV and the transition is directly allowed. The conduction band (-1.05 V(SCE)) is located below that of TiO(2), more negative than the HCrO(4)(-)/Cr(3+) level (+0.58 V(SCE)) yielding a thermodynamically feasible chromate reduction upon visible illumination. CuAl(2)O(4) is stable against photo corrosion by holes consumption reaction involving salicylic acid which favors the charges separation. There is a direct correlation between the dark adsorption and the photo activity. A reduction of more than 95% of chromate was achieved after 3 h irradiation at pH 2 with an optimal mass ratio (CuAl(2)O(4)/TiO(2)) equal to 1/3. The reduction follows a first order kinetic with a half life of ∼1 h and a quantum yield of 0.11% under polychromatic light. Prolonged illumination was accompanied by a deceleration of the Cr(VI) reduction thanks to the competitive water discharge. The hydrogen evolution, an issue of energetic concern, took place with a rate of 3.75 cm(3) (g catalyst)(-1) h(-1).

  12. Illa se iactet in aula!

    Directory of Open Access Journals (Sweden)

    Bertomeu, María Julia

    2010-06-01

    , con Burke, el verso de Virgilio en inequívoca alusión a barrotes seguramente menos simbólicos: «Illa se iactet in aula Aeolus, et clauso ventorum carcere regnet». Kant respondió en su momento a los unos y a los otros, por separado, y también de consuno, pero siempre desde la convicción, tenazmente mantenida, de la importancia de la teoría filosófica y de una disciplina metodológica, las cuales, aun si «impopulares» al comienzo, consideraba esenciales para una práctica moral y política tan hostil al paternalismo moral como a su contracara, el despotismo político (paternalista.

  13. Study on Sn-Zn Solder Used in Cu-Al Soldering%用于铜铝焊接的锡锌焊料研究

    Institute of Scientific and Technical Information of China (English)

    倪广春; 张浩; 韩敏

    2013-01-01

    Lead-free electronic products led the development of lead-free solder technology. Taking cost factors into account, some copper material has been replaced by aluminum material. When ordinary Sn-Cu and Sn-Ag-Cu solder are used in soldering of Cu-Al, there is the electrochemical corrosion problems. So Sn-Zn solder is used for Cu-Al soldering. However, the joints of Sn-Zn solder are brittle and easy to crack. Focus on problems in Cu-Al soldering joint of electrical and electronic devices, put forward Sn-Zn-X alloy soldering materials, did a large number of experiments, and achieved good results.%电子产品无铅化的推广带动了无铅焊料技术的发展,考虑到成本因素,部分铜材已被铝材取代。普通的锡铜系和锡银铜系焊料在铜铝焊接时,存在电化学腐蚀问题,因此多用锡锌焊料进行焊接。但锡锌焊料的焊点脆,存在易开裂的问题。针对电工电子器件铜铝焊接点存在的问题,提出了Sn一Zn一X多元合金焊接材料,并做了大量实验,取得很好的效果。

  14. Preparation and physical properties of CuAl 1- xMn xO 2 (0 ≤ x ≤ 0.2) delafossites

    Science.gov (United States)

    Töpfer, Jörg; Trari, Mohamed; Doumerc, Jean-Pierre

    2007-03-01

    The formation of a CuAl 1- xMn xO 2 solid solution for a limited range of x values (0 ≤ x ≤ 0.2) is demonstrated. The samples were synthesized by solid state reactions in silica sealed tubes. They crystallize with the 3R delafossite structure (space group R3¯m). Magnetic studies show that Mn 3+ ions are in the HS state and that the predominant interactions are antiferromagnetic. The oxides are semiconductors with an activation energy decreasing with x.

  15. Fabrication of CuAl1-xMxO2 (M = Fe, Cr)/Ni film delafossite compounds using spin coating and their microstructure and dielectric constant

    Science.gov (United States)

    Diantoro, Markus; Yuwita, Pelangi Eka; Olenka, Desyana; Nasikhudin

    2014-09-01

    The discovery of delafossite compound has encouraged more rapid technological developments particularly in transparent electronic devices. Copper oxide-based transparent thin films delafossite semiconductor recently give much attention in the field of optoelectronic technology, after the discovery of p-type CuAlO2. The potential applications of a p-type semiconductor transparent conductive oxides (TCO) have been applied in broad field of optoelectronics. To explore a broad physical properties interms of magnetic conducting subtitution is understudied. In this work we report the fabrication of delafossite film on Ni substrate and their characterization of CuAl1-xMxO2 delafossite compounds doped with Cr3+ and Fe3+ from the raw material of Cu(NO3)2˙3H2O, Al(NO3)3˙9H2O, Fe(NO3)3˙9H2O and Cr(NO3)3˙9H2O. The films were prepared using spin coating through a sol-gel technique at various concentrations of x = 0, 0.03, 0.04, and 0.05 for chromium and x = 0, 0.02, 0.04, 0.06, and 0.08 for iron doped. Crystal and microstructure were characterized by means of Cu-Kα Bragg-Brentano X-RD followed by High Score Plus and SEM-EDAX. The dielectric constants of the films were characterized using LCR meter. It was found that the CuAl1-xMxO2/Ni delafossite films were successfully fabricated. The CuAl1-xFexO2 compound crystallized with lattice parameters of a = b ranged from 2.8603 Å to 2.8675 Å and c ranged from 16.9576 to 17.0763 Å. The increase of the dopant give rise to the increase of the lattice parameters. Since iron has bigger ionic radius (69 pm) than original site of Al3+ with radius of 53 pm the crystal volume lattice also increase. Further analyses of increasing volume of the crystal, as expected, affected to the decreasing of its dielectric constant. The similar trends also shown by Cr3+ doped of CuAl1-xCrxO2 films with smaller effects.

  16. El hombre como señor del tiempo

    OpenAIRE

    Haya, F. (Fernando)

    2008-01-01

    La denominación del ser personal como señor del tiempo significa que la esencia de la persona humana aparece en condición de anteposición esenáal con relación al tiempo. De acuerdo con ella, el ser humano dispone del tiempo en articulación presencial, la cual depende de la distinción real antropológica de esencia y ser. Se incluye el examen metafísico de los valores puros del antes y el después, e intentan resolverse las dificultades en orden al pensar puro del tiempo.

  17. Graphene-oxide-supported CuAl and CoAl layered double hydroxides as enhanced catalysts for carbon-carbon coupling via Ullmann reaction

    Science.gov (United States)

    Ahmed, Nesreen S.; Menzel, Robert; Wang, Yifan; Garcia-Gallastegui, Ainara; Bawaked, Salem M.; Obaid, Abdullah Y.; Basahel, Sulaiman N.; Mokhtar, Mohamed

    2017-02-01

    Two efficient catalyst based on CuAl and CoAl layered double hydroxides (LDHs) supported on graphene oxide (GO) for the carbon-carbon coupling (Classic Ullmann Homocoupling Reaction) are reported. The pure and hybrid materials were synthesised by direct precipitation of the LDH nanoparticles onto GO, followed by a chemical, structural and physical characterisation by electron microscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), surface area measurements and X-ray photoelectron spectroscopy (XPS). The GO-supported and unsupported CuAl-LDH and CoAl-LDH hybrids were tested over the Classic Ullman Homocoupling Reaction of iodobenzene. In the current study CuAl- and CoAl-LDHs have shown excellent yields (91% and 98%, respectively) at very short reaction times (25 min). GO provides a light-weight, charge complementary and two-dimensional material that interacts effectively with the 2D LDHs, in turn enhancing the stability of LDH. After 5 re-use cycles, the catalytic activity of the LDH/GO hybrid is up to 2 times higher than for the unsupported LDH.

  18. Juvenile scleractinian coral mortality at Nuestra Señora del Rosario Archipielago, Colombian Caribbean

    OpenAIRE

    López Londoño, T.; Navas Camacho, R.; Gil-Agudelo, D. L.

    2011-01-01

    Mortalidad de corales escleractínios juveniles en el archipiélago Nuestra Señora del Rosario, Caribe colombiano. En la estación de monitoreo de arrecifes coralinos del SIMAC en isla Tesoro, archipiélago Nuestra Señora del Rosario, se evaluó la mortalidad y se identificaron algunos signos de deterioro en corales escleractínios juveniles (colonias < 2-4 cm). Se marcaron y evaluaron 41 colonias por un período de seis meses (abril-octubre de 2006), de las cuales 31 pertenecieron a esp...

  19. Proyecto de Ley por el Cual se Dicta el Estatuto General de Educacion y Pliego de Modificaciones Propuesto (Bill Establishing a General Statute for Education and Explanation of Proposed Modifications).

    Science.gov (United States)

    Suarez Villa, Diego

    This document contains the 1971 Colombian education bill and suggested bill modifications. The bill states educational objectives and establishes the structure of the national education system, the organization for educational administration, financing procedures, regulations for educational personnel, and the means for implementing the…

  20. Contenha-se, se for capaz

    Directory of Open Access Journals (Sweden)

    Mirna Feitoza Pereira

    2008-11-01

    Full Text Available Em O Instinto da Linguagem, Steven Pinker discorre sobre sua célebre tese: a linguagem não é a mais prodigiosa invenção cultural humana. Ela é uma peça da constituição biológica do cérebro. A linguagem é uma habilidade complexa e especializada, que se desenvolve espontaneamente na criança, sem qualquer esforço consciente ou instrução formal, que se manifesta sem que se perceba sua lógica subjacente, que é qualitativamente a mesma em todo indiví­duo, e que difere de capacidades mais gerais de processamento de informações ou de comportamento inteligente. Para Pinker, a concepção de linguagem como um tipo de instinto transmite a idéia de que as pessoas sabem falar mais ou menos da mesma maneira que as aranhas sabem tecer suas teias. Ele apóia suas idéias em Darwin e Chomsky. Palavras-chave linguagem, gramática universal, evolução Abstract In Language Instinct, Steven Pinker argues about his famous thesis: language is not the most prodigious human cultural invention. It is a distinct piece of the biological constitution of the brain. Language is a complex, specialized skill, which develops spontaneously in the child, without conscious effort or formal instruction. It reveals itself without awareness of its underlying logic, which is qualitatively the same in every individual, and which is distinct from more general abilities of information processing of intelligent behavior. According to Pinker, the conception of language as a kind of instinct conveys the idea that people know how to talk in more or less the same way as spiders know how to spin webs. His thesis is founded in Darwin and Chomsky-s theories. Keywords language, universal grammar, evolution

  1. Experimental determination of interfacial energies for Ag2A1 solid solution in the CuAl2-Ag2Al system

    Institute of Scientific and Technical Information of China (English)

    Ocak Y; Akbulut S; Keslio(g)lu K; Mara(s)ll N; (C)adlrll E; Kaya H

    2009-01-01

    The equilibrated grain boundary groove shapes of solid solution Ag2Al in equilibrium with an Al-Cu-Ag liquid were observed from a quenched sample with a radial heat flow apparatus. The Gibbs-Thomson coefficient,solid-liquid interfacial energy and grain boundary energy of the solid solution Ag2Al have been determined from the observed grain boundary groove shapes. The thermal conductivity of the solid phase and the thermal conductivity ratio of the liquid phase to solid phase for Ag2Al-28.3 at the %CuAl2 alloy at the melting temperature have also been measured with a radial heat flow apparatus and Bridgman type growth apparatus,separately.

  2. The Influence of Al2O3 Powder Morphology on the Properties of Cu-Al2O3 Composites Designed for Functionally Graded Materials (FGM)

    Science.gov (United States)

    Strojny-Nędza, Agata; Pietrzak, Katarzyna; Węglewski, Witold

    2016-08-01

    In order to meet the requirements of an increased efficiency applying to modern devices and in more general terms science and technology, it is necessary to develop new materials. Combining various types of materials (such as metals and ceramics) and developing composite materials seem to be suitable solutions. One of the most interesting materials includes Cu-Al2O3 composite and gradient materials (FGMs). Due to their potential properties, copper-alumina composites could be used in aerospace industry as rocket thrusters and components in aircraft engines. The main challenge posed by copper matrix composites reinforced by aluminum oxide particles is obtaining the uniform structure with no residual porosity (existing within the area of the ceramic phase). In the present paper, Cu-Al2O3 composites (also in a gradient form) with 1, 3, and 5 vol.% of aluminum oxide were fabricated by the hot pressing and spark plasma sintering methods. Two forms of aluminum oxide (αAl2O3 powder and electrocorundum) were used as a reinforcement. Microstructural investigations revealed that near fully dense materials with low porosity and a clear interface between the metal matrix and ceramics were obtained in the case of the SPS method. In this paper, the properties (mechanical, thermal, and tribological) of composite materials were also collected and compared. Technological tests were preceded by finite element method analyses of thermal stresses generated in the gradient structure, and additionally, the role of porosity in the formation process of composite properties was modeled. Based on the said modeling, technological conditions for obtaining FGMs were proposed.

  3. SE-FIT

    Science.gov (United States)

    Chen, Yongkang; Weislogel, Mark; Schaeffer, Ben; Semerjian, Ben; Yang, Lihong; Zimmerli, Gregory

    2012-01-01

    The mathematical theory of capillary surfaces has developed steadily over the centuries, but it was not until the last few decades that new technologies have put a more urgent demand on a substantially more qualitative and quantitative understanding of phenomena relating to capillarity in general. So far, the new theory development successfully predicts the behavior of capillary surfaces for special cases. However, an efficient quantitative mathematical prediction of capillary phenomena related to the shape and stability of geometrically complex equilibrium capillary surfaces remains a significant challenge. As one of many numerical tools, the open-source Surface Evolver (SE) algorithm has played an important role over the last two decades. The current effort was undertaken to provide a front-end to enhance the accessibility of SE for the purposes of design and analysis. Like SE, the new code is open-source and will remain under development for the foreseeable future. The ultimate goal of the current Surface Evolver Fluid Interface Tool (SEFIT) development is to build a fully integrated front-end with a set of graphical user interface (GUI) elements. Such a front-end enables the access to functionalities that are developed along with the GUIs to deal with pre-processing, convergence computation operation, and post-processing. In other words, SE-FIT is not just a GUI front-end, but an integrated environment that can perform sophisticated computational tasks, e.g. importing industry standard file formats and employing parameter sweep functions, which are both lacking in SE, and require minimal interaction by the user. These functions are created using a mixture of Visual Basic and the SE script language. These form the foundation for a high-performance front-end that substantially simplifies use without sacrificing the proven capabilities of SE. The real power of SE-FIT lies in its automated pre-processing, pre-defined geometries, convergence computation operation

  4. EFECTO DE VINAZAS SOBRE HONGOS QUE FORMAN MICORRIZA ARBUSCULAR EN UN MOLISOL DEL VALLE DEL CAUCA, COLOMBIA EFFECT OF VINASSE ON ARBUSCULAR MYCORRHIZAL FUNGI IN A MOLLISOL OF CAUCA VALLEY (COLOMBIA

    Directory of Open Access Journals (Sweden)

    Diana Cristina Velásquez Pomar

    2011-06-01

    Full Text Available La adición de etanol a la gasolina busca disminuir la contaminación ambiental; sin embargo, su producción genera vinaza, un material contaminante en cuerpos de agua. Por su alta concentración de K y potencialidad como fertilizante, los ingenios azucareros del Valle del Cauca (Colombia, adelantan investigaciones dirigidas a mejorar la productividad y efectos en propiedades químicas y físicas del suelo. Son escasas las publicaciones sobre su influencia en propiedades biológicas como hongos formadores de micorriza arbuscular (HMA, componente sensible y estrechamente asociado con la nutrición de las plantas y condiciones físicas del suelo. Con el fin de conocer si algunos componentes de HMA se afectan por vinazas, se sembró maíz blanco (Zea mays L. SV1127 en un Pachic Haplustolls del Valle deficiente en K, bajo condiciones de invernadero. Se utilizó un diseño completamente al azar con 5 tratamientos: testigo absoluto y 4 correspondientes a vinaza: KCl en proporciones de 100:0, 75:25, 50:50 y 0:100. La longitud de micelio externo (LME, micelio externo vivo y activo (MEV, glomalina fácilmente extractable (GFE y glomalina total (GT, fueron estimados a los 36 y 70 días después de siembra. Con excepción de la GFE, las demás variables respondieron significativamente a los tratamientos. Al suplir el K por vía orgánica (vinaza o inorgánica KCl, LME y MEV se incrementaron. El máximo valor para LME fue 10,4 m•g-1, con 100% vinaza. GT fue sensible a la fuente de K utilizada y se deprimió con KCl 100%. Incrementos en la actividad biológica pueden estar relacionados con los efectos de la vinaza sobre LME y MEV. Estudios indican que gradientes de fertilidad pueden afectar la GT, asociados a tasas de descomposición de esta molécula.In order to reduce environmental pollution, a mix of ethanol gasoline has been used; however, the ethanol production generates vinasse, a pollutant in water. Because vinasse has a high concentration of K and

  5. Análisis y procesado de señales multicanal procedentes de sensores industriales

    OpenAIRE

    García Cantalapiedra, Adrián

    2017-01-01

    Este Trabajo de Fin de Máster se centra en el estudio y elaboración de técnicas para facilitar la detección de irregularidades presentes en unas determinadas piezas industriales, a partir de señales temporales adquiridas con diferentes tipos de sensores. Dichas señales presentan correlación en los momentos en los cuales hay eventos a detectar, y por lo tanto buscaremos el beneficio de buscar información multicanal entre las señales disponibles. Una de las principales dificultades a las que...

  6. Photosensitive anisotype n-ZnSe/ p-InSe and n-ZnSe/ p-GaSe heterojunctions

    Science.gov (United States)

    Kudrynskyi, Z. R.; Kovalyuk, Z. D.

    2014-08-01

    Anisotype n-ZnSe/ p-InSe and n-ZnSe/ p-GaSe heterojunctions are obtained for the first time. They are grown on layered crystalline GaSe and InSe substrates by annealing in Zn vapor. It is found that these heterojunctions are sensitive to light in the near-infrared and visible spectral ranges.

  7. A literatura se ensina?

    OpenAIRE

    Cerdeira, Teresa Cristina

    2016-01-01

    Não sei se, na verdade, se ensina literatura. Mas qualquer coisa que se parecer com isto – ensinar literatura – tem que nascer de uma vibração conjunta de quem mostra e de quem vê pela primeira vez. Caminhar junto e descobrir sempre que as malhas do texto são infinitas. Venho portanto falar de sala de aula e de seminário, de circulação de saberes e de desejos, de uma atenção ao corpo sensível do texto que deve impactar, comprometer a linearidade da percepção, desalojar os sentidos prévios, en...

  8. Cuando la ciencia se adorna de colores

    Directory of Open Access Journals (Sweden)

    César Arana

    2013-05-01

    Full Text Available La conservación de la biodiversidad ha dejado de ser un tema de discusión únicamente en círculos científicos e intelectuales, para convertirse en un tema de noticia diaria. Esto ha llevado entre otras cosas a la creación de instrumentos de información para todos los agentes sociales de las áreas geográficas donde se pretende establecer proyectos de explotación de recursos, en particular para las comunidades campesinas e indígenas. La única manera de apreciar y valorar un recurso es conociéndolo, a pesar de ello la información de nuestra mayor riqueza, la biodiversidad, sólo se ha venido restringiendo a las comunicaciones especializadas que circulan en la comunidad científica, dejando de lado a los agentes sociales y políticos de los cuales dependen las decisiones sobre la explotación sustentable de los recursos. Es por esto que publicaciones como la comentada aquí tienen mucha importancia, porque teniendo como principal objetivo la divulgación, no dejan de ser importante fuente de información y herramienta de trabajo para futuros estudios, así como información básica para proyectos de manejo de recursos naturales y ecoturismo.

  9. Étude par spectroscopie d'admittance et MEB de la dégradation électrique des couches minces de CuAlS{2} non dopé déposées sous vide

    Science.gov (United States)

    Helali, N.; Bouricha, B.; Rezig, B.

    1998-07-01

    We have accelerated the ageing of CuAlS2 by the application of a static electrical field for different degradation times. We have investigated the admittance spectroscopy and the scanning electron microscopy to follow and understand the (mass-charge) coupled transport processes produced in the volume and on the surface of these films. The electrical constraint induces, after an incubation phase, an activated decrease of the resistance, followed by a susbstantial increase correlated to the formation of an open circuit. This degradation occurs more rapidly for the films having initially a lower resistance, due to the thermal dissipation which increases considerably the temperature to about 140 °C. Admittance spectra reveal, at low frequencies, a capacitive loop related to the formation of a charge space induced by copper diffusion. Such migration develop induces the formation of copper arborescences, spreading from the cathode towards the anode. The effect of these structures on the properties of the degraded films is discussed in relation to electromigration and associated processes (whiskers, fracture, healing, bridge-building, ...). Also, we have noticed their similarity with fractal phenomena such as electrodeposition and dielectric breakdown. Nous avons accéléré le vieillissement des couches minces de CuAlS2 par l'application d'un champ électrique statique pendant des durées variables. Nous avons fait appel à la spectroscopie d'admittance et la microscopie électronique à balayage, pour suivre et comprendre les processus de transport couplé (masse- charge) qui se produisent en volume et en surface de ces couches. L'effet de la contrainte électrique s'est traduit, après une phase d'incubation, par une décroissance activée de la résistance, suivie d'une phase d'emballement reliée à la formation d'un circuit ouvert. Cette fracturation se manifeste plus rapidement pour les couches ayant initialement une faible résistance, suite à l'effet de la

  10. Effect of two-stage isothermal annealing on microstructure CuAl10Fe5Ni5 bronze with additions of Si, Cr, Mo, W and C

    Directory of Open Access Journals (Sweden)

    B. P. Pisarek

    2011-07-01

    Full Text Available The aim of this study was to investigate the effect of a two-step isothermal annealing respectively at 1000 ̊C for 30 min, then at the range of 900÷450 ̊C increments 50 ̊C on the microstructure CuAl10 Ni5Fe5 bronze with additions of Si, Cr, Mo, W and C, cast into sand moulds. The study concerned the newly developed species, bronze, aluminium-iron-nickel with additions of Si, Cr, Mo, W and C. In order to determine the time and temperature for the characteristic of phase transitions that occur during heat treatment of the test method was used thermal and derivation analysis (TDA. The study was conducted on cylindrical test castings cast in the mould of moulding sand. It was affirmed that one the method TDA can appoint characteristic for phase transformations points about co-ordinates: τ (s, t ( ̊ C, and to plot out curves TTT for the studied bronze with their use. It was also found that there is a fiveisothermalannealingtemperatureranges significantly altering the microstructure of examined bronze.

  11. Thermodynamic properties and mixing thermodynamic parameters of Ba-Al, Mg-Al, Sr-Al and Cu-Al metallic melts

    Institute of Scientific and Technical Information of China (English)

    张鉴

    2004-01-01

    Application of equations of mixing thermodynamic parameters formulated on the basis of the coexistence theory of metallic melts in Ba-Al, Mg-Al, Sr-A1 and Cu-Al melts leads to fruitful results that not only the evaluated mass action concentrations agree well with the measured activities, but also the calculated mixing thermodynamic parameters are quite coincident with the experimental values. Moreover, the calculated mass action concentrations strictly obey the mass action law. The evaluated mixing thermodynamic parameters have very fine regularity: the mixing free energy is composed of standard free formation energies of all compounds and chemical potentials of all structural units at equilibrium; the mixing enthalpy consists of standard formation enthalpies of all compounds; the mixing entropy is composed of standard entropies of all compounds and configuration entropies of all structural units at equilibrium. As the equations of mixing thermodynamic parameters formulated are widely applicable to metallic melts involving compound formation, they can be used as the second practical criterion to determine whether thermodynamic models of metallic melts are correctly formulated.

  12. Desarrollo de Nuevas Reacciones Multicomponente basadas en la activación de isonitrilos. Aplicaciones en biomedicina

    OpenAIRE

    2011-01-01

    Una reacción multicomponente (MCR) se define como un proceso en el cual tres o más reactivos forman un aducto final a través de un único mecanismo. Las MCRs tienen muchas ventajas en comparación con las síntesis clásicas, en las cuales el producto final se obtiene utilizando una secuencia multietapa con formación de un solo enlace en cada paso. En la presente tesis se describen dos nuevas MCRs, desarrolladas a través de una estrategia racional, en la cual un isonitrilo es activado por un agen...

  13. Desarrollo de Nuevas Reacciones Multicomponente basadas en la activación de isonitrilos. Aplicaciones en biomedicina

    OpenAIRE

    Kielland, Nicola

    2011-01-01

    Una reacción multicomponente (MCR) se define como un proceso en el cual tres o más reactivos forman un aducto final a través de un único mecanismo. Las MCRs tienen muchas ventajas en comparación con las síntesis clásicas, en las cuales el producto final se obtiene utilizando una secuencia multietapa con formación de un solo enlace en cada paso. En la presente tesis se describen dos nuevas MCRs, desarrolladas a través de una estrategia racional, en la cual un isonitrilo es activado por un agen...

  14. Pintuco se internacionaliza en el mercado andino.

    Directory of Open Access Journals (Sweden)

    Carlos Enrique Ramírez R.

    2004-01-01

    Full Text Available La historia de la internacionalización de Pintuco está presentada en este trabajo. Es importante resaltar la valiosa información sobre el mercado mundial de pinturas lo cual despierta el interés del lector al mostrar el tamaño del mercado y la importancia económica del mismo. De igual forma, la introducción es muy expedita al señalar cuál es la tendencia de dicho mercado, pues con esto se puede hacer una idea de hacia dónde deberá ir Pintuco y cuáles serán sus principales retos a superar. Luego de dar un vistazo general de lo que son las pinturas y su impacto económico, el artículo continúa con la historia del Grupo Inversiones Mundial (GIM, ente económico que ha triunfado gracias a la tenacidad de sus directivos desde 1921. La estrategia utilizada por la empresa colombiana es explicada a través de los ejemplos de cómo empezó y se desarrolló en Venezuela y Ecuador, principalmente. Y es en esto, en lo que precisamente radica lo más importante del trabajo pues sirve como motivación y como ejemplo a seguir. Las empresas colombianas como Pintuco han entendido que una de las formas de amoldarse a las nuevas tendencias del mundo empresarial es la de competir con calidad, pero no sólo en su propio mercado, sino también en el mercado de origen de su competencia. Hoy en día las fronteras son cada vez más invisibles y eso, más que una amenaza, debería ser un atractivo.

  15. Effect of Annealing Time for Quenching CuAl7Fe5Ni5W2Si2 Bronze on the Microstructure and Mechanical Properties

    Directory of Open Access Journals (Sweden)

    B. P. Pisarek

    2012-04-01

    Full Text Available This paper presents the influence of annealing time 30, 60 and 120 min at 1000°C for quenching CuAl7Fe5Ni5W2Si2 bronze in 10% water solution of NaCl, on the microstructure and mechanical properties. The presented results concern the species newly developed aluminum-iron-nickel bronze, with additions W and Si.In order to determine changes in the microstructure of the hardened bronze metallographic studies were performed on cylindrical samples of diameter 10 mm, on the metallographic microscope with digital image analysis, X-ray phase analysis, EDX point with the digital recording on the computer. Specified percentage of the microstructure of martensite and bainite, participation of proeutectoid α phase in the microstructure, grain size of former β phase, the amount of dissolved κ phase.It was found that in the microstructure of bronze in the cast state, there are a number of intermetallic phases of κ type. At interphase boundaries of primary intermetallic faceted precipitates, especially rich in tungsten (IM_W, nucleate and grow dendritic primary intermetallic κI phases, with chemical composition similar to the type of Fe3Si iron silicide.Dissolved, during the heating, in the β phase are all the intermediate phase included in the microstructure, with the exception of primary intermetallic phases of tungsten and κI. Prolongation of the isothermal annealing causes coagulation and coalescence of primary phases. In microstructure of the bronze after quenching obtained the α phase precipitation on the grain boundary of secondary β phase, coarse bainite and martensite, for all annealing times. With the change of annealing time are changed the relative proportions of individual phases or their systems, in the microstructure. In the microstructure of bronze, hold at temperature of 1000°C for 60 min, after quenching martensitic microstructure was obtained with the primary phases, and the least amount of bainite.

  16. El trabajo domestico se sienta a la mesa: la comida en la configuracion de las relaciones entre empleadores y empleadas en la ciudad de Buenos Aires

    National Research Council Canada - National Science Library

    Gorban, Debora

    2013-01-01

    .... Especificamente, este articulo se propone indagar acerca del lugar que ocupa la comida en el contexto de las interacciones mencionadas, en cuanto elemento a traves del cual se construyen lugares sociales jerarquizados. El trabajo de campo fue realizado en Buenos Aires (Argentina) entre 2010 y 2011, siguiendo una aproximacion de tipo cualitativo.

  17. ZnSe/ZnSeTe Superlattice Nanotips

    Directory of Open Access Journals (Sweden)

    Young SJ

    2010-01-01

    Full Text Available Abstract The authors report the growth of ZnSe/ZnSeTe superlattice nanotips on oxidized Si(100 substrate. It was found the nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. It was also found that photoluminescence intensities observed from the ZnSe/ZnSeTe superlattice nanotips were much larger than that observed from the homogeneous ZnSeTe nanotips. Furthermore, it was found that activation energies for the ZnSe/ZnSeTe superlattice nanotips with well widths of 16, 20, and 24 nm were 76, 46, and 19 meV, respectively.

  18. ZnSe/ZnSeTe Superlattice Nanotips

    Science.gov (United States)

    2010-01-01

    The authors report the growth of ZnSe/ZnSeTe superlattice nanotips on oxidized Si(100) substrate. It was found the nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. It was also found that photoluminescence intensities observed from the ZnSe/ZnSeTe superlattice nanotips were much larger than that observed from the homogeneous ZnSeTe nanotips. Furthermore, it was found that activation energies for the ZnSe/ZnSeTe superlattice nanotips with well widths of 16, 20, and 24 nm were 76, 46, and 19 meV, respectively. PMID:20672085

  19. Interaction of aluminum projectiles with quartz sand in impact experiments: Formation of khatyrkite (CuAl2) and reduction of SiO2 to Si

    Science.gov (United States)

    Hamann, Christopher; Stöffler, Dieter; Reimold, Wolf Uwe

    2016-11-01

    We analyzed the interaction of spherical, 6.36-mm-diameter, Cu-bearing aluminum projectiles with quartz sand targets in hypervelocity impact experiments performed at NASA Ames Vertical Gun Range. Impact velocities and inferred peak shock pressures varied between 5.9 and 6.5 km/s and ∼41 and 48 GPa, respectively. Shocked particles ("impact melt particles") coated with thin crusts of molten projectile material were recovered from the floors of the ca. 33-cm-diameter craters and the respective ejecta blankets. Through petrographic and chemical (optical microscopy, FE-EMPA, SEM-EDX, and XRF) analysis we show that these particles have a layered structure manifested in distinct layers of decreasing shock metamorphism. These can be characterized by the following physical and chemical reactions and alteration products: (i) complete melting and subsequent recrystallization of the projectile, forming a distinct crystallization texture in the fused metal crust; (ii) projectile-target mixing, involving a redox reaction between Cu-bearing Al alloy und SiO2, leading to formation of khatyrkite (CuAl2), Al2O3 melt, euhedral silicon crystals, and spherical droplets of silicon; (iii) melting of quartz to lechatelierite and formation of planar deformation features in relic quartz grains; and (iv) shock lithification of quartz grains with fracturing of grains, grain-boundary melting, planar deformation features, and complete loss of porosity. To our knowledge, this is the first report of khatyrkite formed experimentally in hypervelocity impact experiments. These results have implications for the understanding of a similar redox reaction between Al-Cu metal and siliceous impact melt recently postulated for the Khatyrka CV3 carbonaceous chondrite. Moreover, these results bear on the processes that lead to layers of regolith on the surfaces of planetary bodies without atmospheres, such as asteroids in the main belt (e.g., 4 Vesta), and on the Moon. Specifically, impacts of mm

  20. Plantas Alimenticias que se ofertan en los mercados de la ciudad de León

    OpenAIRE

    Guevara Guevara, Ängelica María; Rueda Pereira, Ricardo M

    2009-01-01

    El propósito de este estudio es conocer las plantas alimenticias que se ofertan en los cuatro mercados de la ciudad de León, Terminal, Estación, Central y mercadito Sutiava, en el periodo comprendido de mayo 2006 a mayo 2007 investiga sobre procedencia, situación de mercadeo y usos de estas plantas. Se realizaron visitas a los diferentes mercados dos veces por mes (inicio y final) para conocer que plantas ingresan y cuales son permanentes en los diferentes meses. La recopilación de datos se h...

  1. ...Arte ostentando los primores es cauteloso engaño del sentido...: Representaciones identatarias de géneros y sexualidades

    Directory of Open Access Journals (Sweden)

    Eliseo R. Colón

    1997-01-01

    Full Text Available Este ensayo abunda sobre un conjunto de categorías culturales mediante las cuales se forman las construcciones identatarias de géneros y sexualidades. El ensayo elabora a partir de la teatralización de estas categorías cómo se pone en riesgo y se desestabiliza el conjunto de categorías oficiales de género y sexualidad.

  2. Fe distribution in GaSe and InSe

    Energy Technology Data Exchange (ETDEWEB)

    Kovalyuk, Z.D.; Feichuk, P.I.; Shcherbak, L.P.; Zbykovskaya, N.I.

    1985-06-01

    In this paper, the authors use tagged atoms to determine the effective coefficients of Fe distribution in GaSe and InSe during crystallization of a doped melt by the Bridgman method. The distribution of Fe in GaSe and InSe was studied with the aid of Fe tagged with the radiosotopes VVFe + VZFe. Doping of the material was combined with the processes of synthesis and crystallization. Equations are presented for the calculation of the real impurity distribution in GaSe and InSe crystals.

  3. ¿Cual esel papel actual de los biopéptidos presentes en los productos lácteos sobre el control de la saciedad?

    OpenAIRE

    Baeza Redondo, Patricia

    2016-01-01

    La leche es el alimento más completo que forma parte, de manera esencial, de nuestra alimentación. Desde que nacemos nos aporta los nutrientes necesarios para el crecimiento, desarrollo, protección y fortalecimiento de nuestro cuerpo. La leche y sus derivados están compuestos por distintas proteínas precursoras de sustancias activas denominadas biopéptidos. Los biopéptidos activos son secuencias de 2 a 20 aminoácidos, que se encuentran encriptados e inactivos dentro de la proteína nativa. Ést...

  4. MECANISMOS MOLECULARES POR LOS CUALES LOS ÁCIDOS GRASOS PODRÍAN INFLUIR EN LA CAPTACIÓN DE GLUCOSA Molecular mechanisms by which free fatty acids might interfere with periferic insuline action

    Directory of Open Access Journals (Sweden)

    Clara Eugenia Pérez

    2005-04-01

    Full Text Available Esta revisión tiene el propósito de actualizar el probable mecanismo molecular que ejercen los ácidos grasos en las células que captan glucosa, bajo el estimulo de la insulina y su posible implicación en la diabetes mellitus tipo 2 en la que suelen asociarse resistencia a la insulina, obesidad y síndrome metabólico. Entre los mecanismos moleculares por los cuales un aumento de los ácidos grasos libres podría producir resistencia a la insulina, se encuentra la disminución de los niveles de xilulosa 5-fosfato que bloquea la glucólisis por inhibición de la fosfofructocinasa, ello conduce a un aumento de los productos finales en la vía de las hexosaminas y a la activación de la proteincinasa C, un conocido activador de inhibidor de la cinasa Kappa Beta que inhibe la fosforilación del receptor del sustrato de insulina en tirosina, bloqueando los transportadores de glucosa. Existen investigaciones que sugieren que los ácidos grasos libres están implicados en la insulino-resistencia pero el mecanismo bioquímico no esta dilucidado del todo, pues no hay un mecanismo integral que los relacione o interconecte para concluir determinantemente cómo los altos niveles de ácidos grasos libres inducen la resistencia a la insulina.Previous research suggests that free fatty acids are implicated in insulin resistance, but the molecular mechanism for it isn't completely elucidated, given the lack of an integrated hypothesis relating all of the proposed mechanisms. At the present time, the causes of insulin resistance, obesity and metabolic syndrome, a common feature in patients with diabetes mellitus are matter of intense study. Among several molecular mechanisms by which the increase in free fatty acids could raise insulin resistance is decrease in xylulose-5-phosphate that leads to an inhibition of phosphofructokinase-2, and consequently to a blockade in glycol sis with a subsequent increase in the final products of the hexosamine pathway and

  5. Electronic states of InSe/GaSe superlattice

    Science.gov (United States)

    Erkoç, Ş.; Allahverdi, K.; Ibrahim, Z.

    1994-06-01

    Analysis of recent publications revealed an increasing interest in epitaxial growth of InSe/GaSe superlattice. Within the effective mass theory we carried out self-consistent calculations of the confined and itinerant electronic states, potential profile and charge density distribution of InSe/GaSe superlattice, where the InSe layers are the well and the GaSe layers the barrier. Calculations were performed for three types of doping: uniform, modulated in the well, and modulated in the barrier. It has been found that the Coulomb interaction in the well and barrier forces the formation of localized states in the barrier region. The possibility of an insulator-metal transition in InSe/GaSe superlattice is predicted for modulation doping in the barrier and for a doping level n = 10 19cm-3. A decrease of the barrier height has been found for modulation doping in the well.

  6. „Amadeusz”. Miloš Forman i Peter Shaffer

    Directory of Open Access Journals (Sweden)

    Małgorzata Choczaj

    2012-01-01

    Full Text Available The study is devoted to Miloš Forman’s film, a story about Mozart’s life, taken from Peter Shaffer’s drama. The author proposes a detailed analysis of Forman’s film as an autonomous work in the production of which the film was a medium. The film was an effect of collaboration between the author of the play and the director. The effect of the work is a film which is an example of a close connection of the form and the content – harmony between picture and music, which becomes almost one of the main characters. Individual compositions of Mozart form a network of motives closely connected with the visual aspect and make its sense deeper according to several rules of showing music as a part of the film medium, such as musical motives, explaining the music by the composer or music which uses media. Connecting the music and the aesthetics of the film make Amadeus a harmonious audio-visual performance.

  7. Miloš Forman esitles kodumaal uut filmi

    Index Scriptorium Estoniae

    2009-01-01

    USAs töötav tšehhi päritolu režissöör esitles Karlovy Vary filmifestivalil oma filmi "Kasulik jalutuskäik", mis on Formani Praha rahvusteatris lavastatud J. Suchy ja J. Slitri muusikali filming

  8. Información, señal, comunidad y contexto: su importancia al tratar con sistemas adaptativos complejos

    OpenAIRE

    Jordi Guzman

    2007-01-01

    El artículo trata de las diferencias entre información y conocimiento, así como de la relevancia del contexto en el aprendizaje, el cual se da dentro de una cultura en competencia por su supervivencia con otras culturas. Estas características definen un sistema adaptativo complejo, que se asemeja a la conducta de las especies que luchan por sobrevivir a los cambios de un entorno en continuo movimiento.

  9. Información, señal, comunidad y contexto: su importancia al tratar con sistemas adaptativos complejos

    Directory of Open Access Journals (Sweden)

    Jordi Guzman

    2007-07-01

    Full Text Available El artículo trata de las diferencias entre información y conocimiento, así como de la relevancia del contexto en el aprendizaje, el cual se da dentro de una cultura en competencia por su supervivencia con otras culturas. Estas características definen un sistema adaptativo complejo, que se asemeja a la conducta de las especies que luchan por sobrevivir a los cambios de un entorno en continuo movimiento.

  10. Fe distribution in GaSe and InSe

    Energy Technology Data Exchange (ETDEWEB)

    Kovalyuk, Z.D.; Fejchuk, P.I.; Shcherbak, L.P.; Zbykovskaya, N.I.

    1985-01-01

    Radiometry was used to determine the effective coefficients of Fe distribution in GaSe and InSe during planar crystallization of melt with 5 x 10/sup 17/-6 x 10/sup 19/ at/cm/sup 3/ initial impurity concentration; concentration dependence of these cofficients was established. Equations for calculation of the real impurity distribution in GaSe and InSe crystals are presented.

  11. Labeling radiopharmaceuticals with Se-75: using Se-75 selenious acid

    Energy Technology Data Exchange (ETDEWEB)

    Sadek, S.A.; Basmadjian, G.P.; Ice, R.D. (Oklahoma Univ., Oklahoma City (USA). Health Sciences Center)

    1982-08-01

    A cheap, easy method of introducing high specific activity Se-75 into radiopharmaceuticals is described. Se-75 selenious acid is reduced with NaBH/sub 4/ producing the nucleophile NaHSe. Using this method, a fatty acid, cholesterol, estrogen and phenethylamine are all labelled with Se-75.

  12. de drogas que se consumen en su medio

    Directory of Open Access Journals (Sweden)

    José F. Enríquez Bielma

    2006-01-01

    Full Text Available Las adicciones son un problema de salud pública. Se estima que en México 3.5 millones de personas entre 12 a los 65 años han consumido algún tipo de drogas. A pesar de los avances en los estudios, se ha dejado de lado el carácter cultural que tiene la adicción. Con este estudio, se deseba conocer qué saben los estudiantes de segundo de secundaria sobre cuáles son las drogas que se consumen en su medio. Se llevó a cabo un estudio observacional con un muestreo aleatorio, con múltiples etapas y proporcional al tamaño en escuelas públicas y privadas. En total se estudiaron 42 escuelas del municipio de León, Gto., México de las cuales el 76.2% lo conformaron las escuelas públicas y el resto las escuelas privadas. Refirieron que conocen que se consumen, en su medio, 11 tipos de drogas. El 88% mencionó a la cocaína en primer lugar, en segundo lugar con un 85% la marihuana, siguiendo las tachas en un 62% y el pegamento en un 49%. En cuanto a los nombres que los estudiantes le dan a las drogas, estos van desde 23 hasta los 4 nombres, siendo la marihuana a la que se le da el mayor número de nombres, seguidos de la cocaína y el éxtasis.

  13. Modelado de generadores eólicos para estudios de estabilidad de pequeña señal

    OpenAIRE

    Barbero, Santiago; Agüero, Jorge Luis; Biteznik, Carlos E.

    2013-01-01

    En este trabajo se muestra que la presencia de generación eólica no afecta sustancialmente la frecuencia y amortiguamiento de las oscilaciones electromecánicas dominantes o de bajo amortiguamiento de los sistemas de energía eléctrica. Como demostración, se presenta un sistema eléctrico compuesto por dos generadores convencionales y un parque eólico sobre el cual se realizan análisis de oscilaciones electromecánicas. Mediante simulaciones temporales realizadas con el programa PSS/E, se evalúa ...

  14. TEST CELLS SE-5 - SE-8 - SE-10 IN THE ENGINE RESEARCH BUILDING ERB AND 117 HIGH ENERGY FUELS LABORAT

    Science.gov (United States)

    1963-01-01

    TEST CELLS SE-5 - SE-8 - SE-10 IN THE ENGINE RESEARCH BUILDING ERB AND 117 HIGH ENERGY FUELS LABORATORY HEFL - TRANSDUCER INSTRUMENTATION CONSOLE SE-10 - TEMPERATURE INSTRUMENTATION CONSOLE SE-10 - MODULE FUEL CELL EXPERIMENT SE-8 -

  15. Implementación de un electrocardiógrafo mostrando la señal cardíaca en una computadora gobernada por software libre (python)

    OpenAIRE

    Cirino Morales, Roberto Carlos; Murillo Castro, Ronny Javier; Yapur Auad, Miguel

    2014-01-01

    El electrocardiograma es la mejor manera de observar el comportamiento del corazón humano y registrar la gran variedad de señales eléctricas que ahí se producen. Este proyecto consiste en implementar un circuito de electrocardiografía, y, mediante comunicación USB enviar los datos a una computadora personal. Para esto se creó una aplicación en Python, mediante el cual se procesan los datos y se los convierte en la señal cardíaca en tiempo real. Python que es un lenguaje de programación fácil ...

  16. Intraband Spectroscopy of GaSe Nanoparticles and InSe/GaSe Nanoparticle Heterojunctions

    Science.gov (United States)

    Kelley, David F.; Tu, Haohua; Chen, Xiang-Bai

    The spectroscopic and dynamical characteristics of electron and hole intraband transitions in several sizes of GaSe nanoparticles have been studied using polarized femtosecond transient absorption spectroscopy. Assignments of the observed absorptions are made in terms of the known GaSe band structure and a model in which the electron and hole states are described by particle-in-a-cylinder states. The results indicate that the transient absorption spectrum is due to a size-independent, z-polarized hole intraband transition, and in the smaller particles, an x,y-polarized electron transition. In InSe/GaSe mixed aggregates, direct electron transfer from InSe to GaSe nanoparticles occurs upon photoexcitation of a charge transfer band. An exciton on GaSe nanoparticles can undergo diffusion and charge separation the an InSe/GaSe heterojunction.

  17. Study of the heterointerfaces InSe on GaSe and GaSe on InSe

    Science.gov (United States)

    Fargues, D.; Brahim-Otsmane, L.; Eddrief, M.; Sébenne, C.; Balkanski, M.

    1993-03-01

    InSe and GaSe thin films are grown on freshly cleaved (00.1) substrates of GaSe and InSe, respectively, by molecular beam epitaxy. They are studied in situ by X-ray photoelectron spectroscopy (XPS) and reflection high energy electron diffraction (RHEED). From the attenuation curves of the XPS substrate core level peaks, the quasi layer-by-layer growth is shown during the first stages of deposition in agreement with RHEED results. But both interfaces are not totally symmetrical. For InSe on GaSe(00.1), the sharpness of the interface is shown and the conditions of growth are well established. For GaSe on InSe(00.1), the sharpness of the interface can also be suggested although it is less clear; this is related to the growth conditions.

  18. PRIMER REGISTRO DE LA NUTRIA NEOTROPICAL LONTRA LONGICAUDIS ANNECTENS (CARNÍVORA, MUSTELIDAE) EN EL RÍO CUALE, PUERTO VALLARTA, JALISCO, MÉXICO: UNA APROXIMACIÓN AL CONOCIMIENTO DE SU DIETA

    OpenAIRE

    M. Á. Rubio-Padilla,; M. C. Rodríguez-Uribe

    2014-01-01

    The first record of the Neotropical otter Lontra longicaudis annectens (Carnivora, Mustelidae) in the Cuale River in the downtown of the city of Puerto Vallarta, Jalisco is presented. Also, relevant information about their diet and a photograph in their natural habitat are included.

  19. Quick photo-Fenton degradation of phenolic compounds by Cu/Al2O3-MCM-41 under visible light irradiation: small particle size, stabilization of copper, easy reducibility of Cu and visible light active material.

    Science.gov (United States)

    Pradhan, Amaresh C; Nanda, Binita; Parida, K M; Das, Mira

    2013-01-14

    The present study reports the photo-Fenton degradation of phenolic compounds (phenol, 2-chloro-4-nitrophenol and 4-chloro-2-nitrophenol) in aqueous solution using mesoporous Cu/Al(2)O(3)-MCM-41 nanocomposite as a heterogeneous photo-Fenton-like catalyst. The in situ incorporation of mesoporous Al(2)O(3) (MA) into the framework of MCM-41 (sol-gel method) forms Al(2)O(3)-MCM-41 and wetness impregnation of Cu(II) on Al(2)O(3)-MCM-41 generates mesoporous Cu/Al(2)O(3)-MCM-41 composite. The effects of pH and H(2)O(2) concentration on degradation of phenol, 2-chloro-4-nitrophenol and 4-chloro-2-nitrophenol are studied. Kinetics analysis shows that the photocatalytic degradation reaction follows a first-order rate equation. Mesoporous 5 Cu/Al(2)O(3)-MCM-41 is found to be an efficient photo-Fenton-like catalyst for the degradation of phenolic compounds. It shows nearly 100% degradation in 45 min at pH 4. The combined effect of small particle size, stabilization of Cu(2+) on the support Al(2)O(3)-MCM-41, ease reducibility of Cu(2+) and visible light activeness are the key factors for quick degradation of phenolic compounds by Cu/Al(2)O(3)-MCM-41.

  20. What are the next steps? Legal perspectives on Mexico's general climate change law; Cuales son los siguientes pasos? Perspectivas juridicas sobre la ley general de cambio climatico de Mexico

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-07-01

    cambio climatico; o la generacion y diseminacion de informacion en la materia, los desarrollos legislativos y regulatorios para respaldar los esfuerzos tendientes a enfrentar el cambio climatico se habian quedado muy atras. Como ejemplos del desarrollo de politicas publicas de corto, largo y mediano plazo y de la cuantificacion de costos podemos mencionar la Estrategia Nacional de Cambio Climatico (2007) y el Programa Especial de Cambio Climatico (2009-2012) (PECC), asi como el estudio: La Economia del Cambio Climatico en Mexico, en el cual se estiman los costos de inaccion frente al cambio climatico. 1 Para ilustrar los desarrollos en la generacion y difusion de informacion pueden consultarse las cuatro Comunicaciones Nacionales sobre Cambio Climatico que Mexico ha presentado ante la Convencion Marco de las Naciones Unidas sobre el Cambio Climatico (CMNUCC), asi como la Quinta Comunicacion en proceso de preparacion. 2 Sin embargo, a nivel nacional, hasta la reciente promulgacion de la Ley General de Cambio Climatico (LGCC), dichos importantes pasos no habian sido respaldados por un esfuerzo igual de ambicioso en el ambito juridico.

  1. Cu/Al管气体火焰钎焊接头特征及热力学分析%Characteristics and thermodynamics analysis of oxyacetylene flame brazing joint of Cu/Al tubes

    Institute of Scientific and Technical Information of China (English)

    罗键; 赵国际; 王向杰; 孙玉

    2011-01-01

    Entropy changes in chemical reaction of Cu/Al intermetallic compounds formation in Cu/Al oxyacetylene flame brazing are calculated, and the tendency of Cu/Al intermetallic compounds form and transform to CuAl2 is analyzed with the method of chemical thermodynamics. The microstructure and characteristics of elements distribution and diffusion of the Cu/Al oxyacetylene flame brazing joint are analyzed by XRD, SEM and EDS. Results show that, under the condition of Cu/Al oxyacetylene flame brazing, the CuAl2 intermetallic compounds formed by the direct reaction of Cu&Al atoms and the sustained reaction of Cu/Al intermetallic compounds with Al atoms. CuAl has relatively strong independent transformation trend. The results of thermodynamics analysis and calculation are consistent with the XRD of joint. Brazing joint can be divided into three feature regions: the a-Al and binary eutectic (α-Al+CuAl2) region is near Al side with the width of about 30 μm; the fine multiple eutectic structure is formed in brazing seam center near Al side with the width of about 150 μm; and the region near Cu substrate with the width of about 120 μm, where Cu diffuses largely and reacts richly with Al and massive CuAl2 is formed like corals.%通过计算Cu/Al管氧乙炔气体火焰钎焊条件下形成金属间化合物的各化学反应的熵变,对Cu/Al金属间化合物的形成及向CuAl2转化的趋势进行了化学热力学分析;结合XRD、SEM、EDS研究了Cu/Al管氧乙炔气体火焰钎焊接头组织与元素分布特征.结果表明,Cu/Al管氧乙炔气体火焰钎焊条件下,接头中脆性金属间化合物CuAl2由Cu、Al原子的直接结合和其他Cu/Al金属间化合物与Al原子的继续反应生成,其中CuAl自主转化趋势较强;热力学计算分析与接头XRD分析结果一致.钎焊接头可分为3个特征区域:靠近Al基体侧形成了宽度约30μm的α-Al与α-Al+CuAl2二元共晶区;钎缝中心偏Al基体一侧形成了宽度约150

  2. Auditoría externa: responsabilidades cuando se trabaja con otros profesionales

    Directory of Open Access Journals (Sweden)

    Padin, María Belén

    2008-11-01

    Full Text Available Cuando un Contador Público es contratado como auditor externo se compromete a emitir un informe en el cual expresará su opinión sobre los estados contables del ente (puede suceder que el auditor finalmente deba abstenerse de opinar, pero esta es una excepción, ya que lo normal es que cuando se requieren los servicios de un auditor se espera que emita un informe. Al aceptar ser designado como auditor externo, el contador público acepta también las responsabilidades que recaen sobre él. Que son inherentes a su desempeño profesional y que están regidas por las normas profesionales dentro de las cuales debe encuadrar su actividad. A lo largo de este trabajo, se estudiará qué responsabilidades recaen sobre el auditor cuando actúa en colaboración con otros profesionales. Los casos específicos que se estudiarán son: 1 responsabilidad por la utilización del trabajo de otro auditor; 2 consideración del trabajo de auditoria interna; y 3 utilización del trabajo de un experto. Para ello se mencionarán las normas internacionales de auditoria (NIA que tratan cada tema en específico, y alguna norma en particular que exista de otro organismo al respecto.

  3. Epitaxial growth of ZnSe and ZnSe/CdSe nanowires on ZnSe

    Energy Technology Data Exchange (ETDEWEB)

    Bellet-Amalric, E.; Bounouar, S.; Kheng, K. [CEA-CNRS-UJF Group, Nanophysique et Semiconducteurs, CEA Grenoble, INAC, 17 rue des Martyrs, 38 054 Grenoble (France); Elouneg-Jamroz, M.; Bougerol, C.; Hertog, M. den; Genuist, Y.; Poizat, J.P.; Andre, R.; Tatarenko, S. [CEA-CNRS-UJF Group, Nanophysique et Semiconducteurs, Institut Neel, BP 166, 38 042 Grenoble (France)

    2010-06-15

    We report the molecular beam epitaxy (MBE) growth of ZnSe nanowires (NWs) on a ZnSe(100) epilayer assisted by gold catalyst. Gold dewetting assists in the formation of nanotrenches along the [0-1-1] direction in the ZnSe buffer layer. Nucleation of the gold catalyst in the trenches leads to the growth of NWs preferentially in directions orthogonal to the trenches. The wires adopt mostly the wurtzite type structure and grow along the c-axis. CdSe quantum dots were inserted in the ZnSe NWs. The CdSe insertions systematically adopt a cubic zinc-blende arrangement with a[111] growth axis, as confirmed by transmission electron microscopy. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Mitos de la mexicanidad en "Chac Mool" de Carlos Fuentes

    OpenAIRE

    Quezada Camberos, Silvia

    2012-01-01

    El concepto de la mexicanidad se ha construido sobre una base de estereotipos, los cuales forman parte del discurso oficial, de la conversación compartida, del imaginario colectivo. Los estereotipos nacionales permiten identificar lo propio y discriminar lo extraño, crean un referente de mexicanidad por medio de figuras que son construidas, reconstruidas y deconstruidas en el tiempo por la acción de diversas herramientas, como el cuento. Roger Bartra (2003) ha encontrado elementos que se repi...

  5. The Effect of Toughening Combined with Microjet Cooling During Quenching (Solution Heat Treatment of Calcium Carbide-modified CuAl10Fe4Ni4 Alloy on its Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Z. Górny

    2013-01-01

    Full Text Available The work presents the results of the experimental research concerning the impact of a heat treatment (toughening of aluminum bronze CuAl10Fe4Ni4 on its mechanical properties. The conditions of the experiments and selected results are described. A detailed description of the effects of individual heat treatment conditions namely low and high temperature aging is also presented in the work.

  6. Enhanced photocatalytic and adsorptive degradation of organic dyes by mesoporous Cu/Al2O3-MCM-41: intra-particle mesoporosity, electron transfer and OH radical generation under visible light.

    Science.gov (United States)

    Pradhan, Amaresh C; Parida, K M; Nanda, Binita

    2011-07-28

    Mesoporous Cu/Al(2)O(3)-MCM-41 composite was synthesized by two step processes; in situ incorporation of high surface area mesoporous Al(2)O(3) (MA) into the framework of MCM-41 (in situ method) followed by impregnation of Cu(II) by incipient wetness method. The interesting thing is that starch was used for the first time as template for the preparation of high surface area MA. To evaluate the structural and electronic properties, these catalysts were characterized by low angle X-ray diffraction (LXRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV-vis DRS, FTIR and photoluminescent (PL) spectra. The various cationic dye such as methylene blue (MB), methyl violet (MV), malachite green (MG) and rhodamine 6G (Rd 6G) of high concentration 500 mg L(-1) were degraded and adsorbed very efficiently (100%) using the 5 Cu/Al(2)O(3)-MCM-41 composite within 30 and 60 min, respectively. The high and quick removal of such concerted cationic organic dyes and also mixed dyes (MB+MV+MG+Rd 6G) by means of photocatalysis/adsorption is basically due to the combined effect three characteristics of synthesized mesoporous 5 Cu/Al(2)O(3)-MCM-41 composite. These characteristics are intra-particle mesoporosity, electron transfer and ˙OH radical generation under solar light.

  7. Control de brazo electrónico usando señales electromiográficas

    Directory of Open Access Journals (Sweden)

    Jorge Andrés García-Pinzón

    2015-05-01

    Full Text Available Los trabajos enfocados en la extracción de patrones en señales electromiográficas (SEMG han venido creciendo debido a sus múltiples aplicaciones. En este artículo se presenta una aplicación en la cual se implementa un sistema electrónico para el registro de las SEMG de la extremidad superior en un sujeto, con el fin de controlar de forma remota un brazo electrónico. Se realizó una etapa de preprocesamiento de las señales registradas, para eliminar información poco relevante, y reconocimiento de zonas de interés; enseguida se extraen los patrones y se clasifican. Las técnicas utilizadas fueron: análisis wavelet (AW, análisis de componentes principales (ACP, transformada de fourier (TF, transformada del coseno discreta (TDC, energía, máquinas de soporte vectorial (MSV o SVM y redes neuronales (RNA. En este artículo se demuestra que la metodología planteada permite realizar un proceso de clasificación con un rendimiento superior al 95%. Se registraron más de 4000 señales.

  8. NEURONTOGENIA DEL RECEPTOR 5-HT2B EN LA PAPILA CALICIFORME DE LA RATA

    OpenAIRE

    Acosta Chávez, Jaime

    2012-01-01

    El sentido del gusto es el encargado de reconocer a las moléculas sápidas contendidas en los alimentos y líquidos que son ingeridos. El primer elemento en el procesamiento de los sabores son un tipo de células especializadas denominadas células gustativas, las cuales se agrupan para formar los corpúsculos, que a su vez forman las papilas gustativas. Las cuales se clasifican atendiendo a su morfología en papilas fungiformes, foliadas y caliciformes. Se ha reportado la presenc...

  9. GENERACIÓN TRAS GENERACIÓN, SE RECOBRAN LOS JUEGOS TRADICIONALES

    Directory of Open Access Journals (Sweden)

    María Morera Castro

    2008-07-01

    Full Text Available Actualmente, las comunidades, barrios y ambientes se encuentran inmersos en una serie de situaciones y problemáticas que han propiciado el deterioro de valores sociales, culturales y espirituales, indispensables para la armonía con uno mismo, el prójimo y el entorno. Los estereotipos se han apoderado de las mentes y los entornos se han reducido a cuatro paredes, llenos de rejas y dispositivos de seguridad. La paz, la fraternidad, y alegría se van, disminuyen. Y es aquí donde la labor social, espiritual y profesional de especialistas en el ámbito recreativo toma fuerza para contribuir con el rescate y la reestructuración de la sociedad. Son los juegos y las rondas tradicionales instrumentos que facilitan las relaciones, contribuyen en el aprendizaje y son una prueba de demostración de habilidades. Forman parte inseparable de la vida de la persona ya que estos son una expresión social y cultural de la adaptación que ha protagonizado el ser humano en relación con su entorno (Maestro, 2005. Además no toma en cuenta la raza, edad, sexo o la condición social; son una fuente generadora de salud, una ayuda para mejorar las destrezas motoras, cognitivas y emocionales; un medio para fomentar la creatividad, despertar la imaginación, desarrollar el sentido del ritmo; su objetivo es el bienestar personal. Son un estímulo para liberar tensiones y energía acumulada, así como para salir de la rutina diaria y un puente para el aprendizaje de sí mismo, del hábitat, de valores, costumbres y tradiciones. A través de este documento las personas podrán encontrar respuesta a cómo se trasmiten los juegos tradicionales, qué los caracteriza, por qué son una herramienta importante en la sociedad actual, con qué y cómo se pueden elaborar y de qué manera se puede contribuir al rescate y conservación de los mismos.

  10. Sample Set (SE): SE12 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE12 Effect of agricultural films for spinach leaf metabolites Investigation of Spi...nacia oleracea leaf metabolites. 2 cultivars (Nihon and Wasesaradaakari), 2 growth conditions (normal film and UV film

  11. Sample Set (SE): SE30 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE30 Comparison of seed metabolites among soybean varieties Investigation of Glycin...e max. green seed metabolites. 3 varieties (Kamogawashichiri, Koitozairai, Tanbakuro) data are examined. Tak

  12. Sample Set (SE): SE26 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE26 Effect of compost for cabbage metabolites Investigation of Brassica oleracea v...ar. capitata YR Seisyun leaf metabolites. 2 growth conditions (with or without 6t compost treatment) and 3 r

  13. Sample Set (SE): SE20 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE20 Arabidopsis thaliana leaf metabolite analysis for a software test Investigatio...es that were investigated to optimize the parameters of PowerGet software for better metabolite annotation i

  14. Sample Set (SE): SE51 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE51 RIKEN tandem mass spectral database (ReSpect) for phytochemicals: A plant-spec...ochemicals was developed and named ReSpect (RIKEN tandem mass spectral database). Of the 3595 metabolites in

  15. Sample Set (SE): SE37 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE37 Medicago truncatula shoot metabolite analysis using stable isotopes Metabolite...formed to estimate the elemental composition with high reliability using the number of stable isotopes incor

  16. Sample Set (SE): SE28 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE28 Comparison of leaf metabolites among developmental stages of Hevea brasiliensi...s Investigation of Hevea brasiliensis leaf metabolites. 4 developmental stages and 6 replicates data are exa

  17. Sample Set (SE): SE48 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE48 Toward better annotation in plant metabolomics: isolation and structure elucidation of 36 special... elucidated the structures of specialized metabolites from rice by using MS/MS and NMR. Thirty-six compounds

  18. Sample Set (SE): SE55 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE55 AtMetExpress development: a phytochemical atlas of arabidopsis development We analyzed phytochem...idopsis produces various phytochemicals in a highly tissue-specific manner, which often accompanies the expr

  19. Sample Set (SE): SE10 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE10 Effect of phosphorus nutrition for cabbage metabolites Investigation of Brassi...ca oleracea var. capitata Hatukoi leaf metabolites. 3 growth conditions (high, low and no phosphorus nutrition

  20. Sample Set (SE): SE14 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE14 Effect of agricultural films for tomato fruit metabolites Investigation of Sol...anum lycopersicum fruit metabolites. 3 growth conditions (covered with normal or UV cut agricultural film or no agricultura

  1. Sample Set (SE): SE16 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE16 Effect of agricultural films for spinach leaf metabolites 2 Investigation of S...pinacia oleracea leaf metabolites. 3 growth conditions (covered with normal or UV cut agricultural film or no agricultura

  2. Sample Set (SE): SE19 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE19 Grobal triacylglycerol analysis in mouse liver and white adipose tissue (WAT) ...rol (TAG) molecular species from complex lipid mixtures of mouse liver and white adipose tissue (WAT) using

  3. Photophysics of GaSe/InSe nanoparticle heterojunctions.

    Science.gov (United States)

    Chen, Xiang-Bai; Kelley, David F

    2006-12-21

    The photophysics of mixed aggregates of GaSe/InSe nanoparticles have been studied using static and time-resolved absorption and emission spectroscopies. The results indicate that the GaSe/InSe interfaces form heterojunctions and exhibit photoinduced direct charge transfer from the GaSe valence band to the InSe conduction band. This results in the electrons and holes being localized separately in these two types of nanoparticles. The energy diagram of the nanoparticle heterojunction can be constructed from the static spectra, known bulk band offsets, and quantum confinement effects. These considerations accurately predict the energy of the observed charge-transfer band. Photoexcitation also produces excitons in the aggregates, away from the heterojunctions. These excitons can undergo diffusion and quench upon reaching a heterojunction. Time-resolved fluorescence kinetics can be modeled to extract an exciton diffusion coefficient. A value of 2.0 nm2/ns is obtained, which is in good agreement with values obtained from previous fluorescence anisotropy decay measurements.

  4. Nacen, se hacen o los hacen: formación de investigadores y cultura organizacional en las universidades

    Directory of Open Access Journals (Sweden)

    José Fernando Serrano A.

    1997-10-01

    Full Text Available Más allá de la descripción de políticas educativas o de ciencia y tecnología sobre formación de investigadores, el tema es un objeto por construir cuando se le aborda desde la investigación social. Esto supone posturas epistemológicas y metodológicas relacionadas con la sociología de la ciencia y los estudios sobre comunidades académicas que definan y deslinden los territorios del “formar” y permitan el desarrollo del conocimiento al respecto. En este texto nos preguntamos por los diversos aspectos que inciden en la creación y preparación de investigadores, con particular énfasis en su relación con la(s cultura(s del contexto organizacional universitario, pues en buena medida es allí donde muchos de ellos se forman y desempeñan.

  5. ¿Es la vejez lo que se dice de ella?

    Directory of Open Access Journals (Sweden)

    Sandra Emma Carmona Valdés

    2013-10-01

    Full Text Available Mucho se ha hablado acerca de los cambios y las transformaciones en diferentes niveles y esferas de la población que han contribuido a la conformación de una nueva sociedad; en donde las modificaciones demográficas, científicas, tecnológicas, médicas, económicas, políticas, sociales y culturales que han ocurrido configuran una nueva forma de ser de los individuos en el México actual. Este panorama de avances médico-científicos y adelantos tecnológicos permite que se envejezca de diferente manera que en épocas anteriores, lo cual, permite a que las personas vivan más años y en mejores condiciones de salud. Sin embargo, la vejez se ha asociado con enfermedad, deterioro y decadencia de los individuos, lo cual, da lugar a una actitud colectiva negativa que se representa por un conjunto de prejuicios, estereotipos y discriminaciones que adquieren las personas conforme avanza su edad. El propósito de esta investigación es discutir los estereotipos y prejuicios que acompañan a la vejez y sus diversas implicaciones tanto individuales, sociales como culturales.

  6. Vetenfinf se ha actualizado recientemente

    Directory of Open Access Journals (Sweden)

    Veterinaria.org

    2008-02-01

    Full Text Available ResumenSe trata de un sitio web alojado en el servidor de Veterinaria.org y mantenido por el Dr. Norberto Fondevila, del Instituto de Virologia CICVyA- INTA Cautelar de Argentina .

  7. Porøse materialer

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan de Place

    2000-01-01

    Dette undervisningsnotat er en samling af noter, der refererer til den indledende del af kurset Materialmekanik og Porøse materailer på Insitut for Bærende Konstruktiner og Materialer (BKM).......Dette undervisningsnotat er en samling af noter, der refererer til den indledende del af kurset Materialmekanik og Porøse materailer på Insitut for Bærende Konstruktiner og Materialer (BKM)....

  8. Que se de diferente modo al gobierno de las Indias, que se van perdiendo muy a prisa. Arbitrismo y administración a principios del siglo XVII

    Directory of Open Access Journals (Sweden)

    Amadori, Arrigo

    2009-12-01

    Full Text Available Although arbitrismo was an important element in seventeenth-century Hispanic political life, Americanist historiography has not paid much attention to their study. This article proposes to underscore the importance of this type of literature through the work of Manuel Gaytan de Torres. It will aim to analyze his thoughts on public administration, American institutional organization, and the principles that should guide professional activities in the arts and crafts, as well as his proposals for the remedy of the complex situation in which the Hispanic world was immersed in the seventeenth century. Gaytan’s works are interesting because they form part of the reform movement that developed under the influence of the royal favourite, Olivares, with whose general programme they have several common points in common.A pesar de que el arbitrismo era un elemento importante de la vida política hispánica del siglo XVII, la historiografía americanista no ha puesto demasiado énfasis en su estudio. Este artículo intenta resaltar la trascendencia de este género a través de la obra del arbitrista Manuel Gaytán de Torres. El objetivo consiste en trazar una aproximación a sus percepciones sobre la administración, la organización institucional americana y los principios que debían informar el ejercicio de los oficios, y a sus propuestas para revertir la compleja situación atravesada por el mundo hispánico en las primeras décadas del siglo XVII. Los escritos de Gaytán poseen un gran interés porque forman parte del movimiento reformista que se desarrolló durante el valimiento del conde-duque de Olivares y comparten bastantes puntos en común con el programa del favorito real.

  9. ?Cuales son las amenazas o peligros volcanicos?

    Science.gov (United States)

    Myers, Bobbie; Brantley, Steven R.; Stauffer, Peter; Hendley, James W.

    2000-01-01

    Los volcanes son capaces de producir numerosos peligros geologicos e hidrologicos. Los cientificos del Servicio Geologico de los EE. UU. (USGS, por sus siglas en ingles) y de otras instituciones alrededor del mundo estan estudiando los peligros de muchos de los centenares de volcanes activos y potencialmente activos del mundo. Estos cientificos vigilan muy de cerca la actividad de algunos de los volcanes mas peligrosos, por lo que estan preparados para alertar a las autoridades y/o a la poblacion en caso de que aumente sustancialmente la probabilidad de que ocurra una erupcion u otro evento peligroso.

  10. On the twinning initiation criterion in Cu-Al alpha single crystals-I. Experimental and numerical analysis of slip and dislocation patterns up to the onset of twinning

    Energy Technology Data Exchange (ETDEWEB)

    Tranchant, F.; Vergnol, J. (Univ. Poitiers, Villetaneuse (France). Lab. de Metallurgie Physique); Franciosi, P. (Univ. Paris-Nord, Villetaneuse (France). CNRS)

    1993-05-01

    Tensile tests on Cu-Al alpha single crystals oriented along the [111] axis have been performed, at room temperature, up to the twinning deformation stage on samples previously prestrained in compression along the [[bar 3]12] transversal axis. For various prestrain amplitudes, the mechanical behavior and the associated crystallographic features have been observed at both dislocation structure and slip and twin activity scales. They have then been analyzed with the help of qualitative numerical simulation obtained from a code specifically written for the single crystal plasticity and based on a dislocation description of (work) hardening.

  11. Calidad total. Trabajo en la periferia versus trabajo en el producto y el proceso: dos enfoques que se complementan

    OpenAIRE

    2010-01-01

    El presente artículo es una primera contribución al estudio de técnicas y metodologías relacionadas con la filosofía y conceptos de calidad total, las cuales, en el manejo que se está dando en el medio empresarial del Valle del Cauca, están siendo ignoradas, minimizadas o referencia das únicamente en forma tangencial.

  12. El paradigma de la ciencia política y la administración pública: retos a los que se enfrentan en el siglo XXI

    OpenAIRE

    Julio César Olvera García

    2009-01-01

    En el presente artículo se plantean los retos a los que se enfrentan dos disciplinas fundamentales para entender el quehacer político y gubernamental, ante una sociedad cada vez más plural y demandante de cara al siglo XXI. Entender a la ciencia política y a la administración pública frente al sistema capitalista en el cual ambas nacen y se desarrollan, entrelaza necesariamente la evolución de la ciencia política en distintas épocas, donde se localiza también el surgimiento de la administraci...

  13. Sample Set (SE): SE27 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE27 Effect of agricultural films for cabbage leaf metabolites Investigation of Bra...ssica oleracea var. capitata YR Tenkuu leaf metabolites. 3 growth conditions (covered with normal or UV cut agricultura...l film or no agricultural film), 3 replicates data are examined. Takeshi Ara 1, Naoki Yamamoto 1,

  14. Sample Set (SE): SE56 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE56 MS/MS spectral tag-based annotation of non-targeted profile of plant secondary...sis, resulting in clarification of the functions of reported genes involved in glycosylation of flavonoids. Thus, non-target

  15. Sample Set (SE): SE50 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available oids We report that flavonoids with radical scavenging activity mitigate against ox...ress. These data confirm the usefulness of flavonoids for enhancing both biotic and abiotic stress tolerance...SE50 Enhancement of oxidative and drought tolerance in arabidopsis by overaccumulation of antioxidant flavon

  16. Sample Set (SE): SE58 [Metabolonote[Archive

    Lifescience Database Archive (English)

    Full Text Available SE58 Exploring matrix effects and quantification performance in metabolomics experiments using artificial...ificial biological gradients is a general and inexpensive tool for calibration that... the peaks but also highlights cases with strong background-dependent signal interference. Analysis of art

  17. Significados y funciones del "se"

    Directory of Open Access Journals (Sweden)

    Lidia Contreras

    2004-06-01

    Full Text Available En este artículo la autora se limita a comentar críticamente lo que la Real Academia Española de la Lengua (cit. Ac. dice en su "Gramática de la lengua española" de 1931 (Madrid, Espasa-Calpe, S. A. con respecto a los diversos tipos de "se" que ella toma en cuenta, comentario que pretende mostrar una mayor diversificación que la establecida en la mencionada obra. (In this article, its author offers a critical commentary of the position taken by The Spanish Royal Academy of Language (RAE in Gramática de la lengua española (1931 on the subject of "Uses of 'se'". The author intends to show a greater variety of uses than those proposed by RAE.

  18. Effect of Cryogenic Treatment on Thermal Diffusion Coefficient of Cu-Al Alloy%深冷处理对Cu-Al合金热扩散系数的影响

    Institute of Scientific and Technical Information of China (English)

    徐红

    2013-01-01

    The thermal diffusion coefficient of Cu-Al alloy before and after cryogenic treatment in the heating temperature range of 25-600 ℃ was measured by thermal constant tester.The effects of cryogenic treatment on the thermal diffusion coefficient of the alloy were investigated through comparing the variation of the thermal diffusion coefficient before and after cryogenic treatment.The results show that the variation trend of the thermal diffusion coefficient of the alloy after cryogenic treatment is the same as before,cryogenic treatment can increase the thermal diffusion coefficient of Cu-Al alloy,and the maximum difference of the thermal diffusion coefficient before and after cryogenic treatment appears at 400 ℃.%采用热常数测试仪测试了深冷处理前后Cu-Al合金在25~600℃的热扩散系数,通过对比深冷处理前后Cu-Al合金热扩散系数的变化,探讨了深冷处理对Cu-Al合金热扩散系数的影响.结果表明:深冷处理前后Cu-Al合金在25~600℃的热扩散系数变化趋势一致,深冷处理能增大Cu-Al合金热扩散系数,在400℃时,两者差值最大.

  19. “CONFIABILIDAD DE LA ESCALA PRIME MD TODAY EN LOS PACIENTES CON TRASTORNO DE SOMATIZACION EN LA CONSULTA EXTERNA DE MEDICINA FAMILIAR.”

    OpenAIRE

    Pérez Rodríguez, Quedma Sarai

    2012-01-01

    En los últimos años se ha visto un incremento importante en la demanda de la consulta externa del médico familiar, principalmente por pacientes recurrentes que solicitan el servicio por múltiples patologías dentro de las cuales destacan síntomas de dolor, síntomas gástricos, artralgias entre otros que forman parte del Trastorno de somatización y del cual de acuerdo al registro de los últimos años en el SIMO de la UMF 80 del IMSS se tienen pocos casos lo que nos hace pensar que es ...

  20. Gestión Automática de Incidentes e Inventarios GAII

    OpenAIRE

    Gibellini, Fabián; Ruhl, Analía Lorena; Di Gionantonio, M. Alejandra; Rapallini, Marcos; Flores, Nora Viviana; Serna, Mónica Mariel

    2013-01-01

    Uno de los problemas que enfrentan los grandes ambientes informáticos es conocer en tiempo real el parque informático del cual dispone, el estado de cada componente, las condiciones en las cuales se encuentran, y si están en reparación o desuso. Actualmente, se han implementado algunas aplicaciones para inventariar los equipos y el software que forman parte del activo informático de diversos organismos. Estas aplicaciones permiten registrar en forma manual las distintas actualizaciones del in...

  1. 时效对铜铝钎焊接头界面化合物和性能的影响%Effects of thermal aging on intermetallic compounds and properties of Cu/Al brazing joint

    Institute of Scientific and Technical Information of China (English)

    姬峰; 薛松柏; 张满; 娄继源; 王水庆

    2012-01-01

    采用Zn-22Al钎料对铜铝异种合金进行了火焰钎焊,并用加速老化试验模拟了其服役环境.研究了时效过程中铜铝钎焊接头界面化合物的形貌变化及其对铜铝钎焊接头电阻率和抗剪强度的影响,并对其生长规律进行了初步计算.结果表明,铜侧界面化合物在250℃恒温时效过程中不断变厚,其生长规律呈抛物线状,且其生长系数约为6.1×10-13cm2/s;当界面化合物的厚度为4.2μm和18.1μm时,铜铝接头的电阻分别为120.3μΩ和132.9μΩ,该界面化合物厚度对电阻率的影响系数为0.25;铜铝接头抗剪强度在时效过程中先有3%的上升,随后逐渐降低至接头初始值的85%.%Cu/Al dissimilar metals were joined with Zn-22Al filler metal by torch-brazing technology and heat treated at constant temperature of 250 ℃ for 0 to 1000 h.To guarantee the reliability of the Cu/Al torch-brazing joints in service requirement,the growth rate of intermetallic compounds on Cu side was calculated and the effects of the intermetallic compound layer on the electrical and mechanical properties have been investigated under various annealing time.It was observed that the width of intermetallic compound increased as the thermal aging proceeded,and the growth rate of the intermetallic compound was 6.1×1013 cm2/s when the aging temperature was 250 ℃.A thicker intermetallic compound layers could degrade the resistivity and shear strength of Cu/Al joints.When the thickness of intermetallic compound was 4.2 μm and 18.1 μm,the electric resistance was 120.3 μΩ and 132.9 μΩ,respectively.Moreover,the shear strength of Cu/Al brazing joint increased by 3% when the aging time was 100 h while the strength decreased by 15% when the Cu/Al joints endured 1000 h thermal aging.

  2. Dealing with Pro Se Patrons

    Science.gov (United States)

    Pettinato, Tammy R.

    2008-01-01

    The problem of the "pro se" patrons (people who are representing themselves in a legal dispute or transaction) has received significant attention in the legal information literature, and many excellent suggestions have been offered to aid law librarians in dealing with this population group. However, these suggestions can be usefully applied in…

  3. Educar mientras se informa : una propuesta de resignificación de la prensa tradicional

    Directory of Open Access Journals (Sweden)

    Nélida María Montoya Ramírez

    2014-01-01

    Full Text Available Este artículo da cuenta de los resultados del estudio de caso cualitativo sobre la estrategia Educar mientras se informa , propuesta alternativa a través de la cual un periódico puede comprometerse con la función social de educar al reestructurar la manera de abordar el acto de informar, entretener y la interacción con sus lectores. Esta estrategia se presenta como una posibilidad de resignificar el lugar de la prensa actual en un contexto digital y audiovisual que interroga sobre la desaparición de este tipo de medio desde sus usos tradicionales. Educar mientras se informa asume este dilema desde un reto comunicativo-educativo en coherencia con una visión de la prensa como texto social en la cual interesa ir más allá de lo informativo y fortalecer los procesos formativos que son posibles con este tipo de recursos. Descriptores: Periodismo educativo, periodismo y educación, medios de comunicación de masas y educación.

  4. Mecanismos de señalización celular que median la tolerancia inmunitaria

    OpenAIRE

    Ana Maria Blasini

    2013-01-01

    La tolerancia inmunitaria es la capacidad del sistema inmunitario de no responder a un antígeno al cual ha estado expuesto previamente. Un conjunto de mecanismos a nivel central y a nivel periférico garantizan que los linfocitos, al encontrar ciertos antígenos, se inactiven o sean eliminados. El sistema inmunitario mantiene un delicado balance entre la tolerancia dirigida por sus antígenos propios y la inmunidad desencadenada por patógenos. La falta de respuesta conduce a estados de inmunodef...

  5. Effect of doping on exciton states in InSe and GaSe lamellar semiconductors. [InSe:Dy; InSe:Ho; GaSe:Sn

    Energy Technology Data Exchange (ETDEWEB)

    Dzhafarova, S.Z.; Ragimova, N.A.; Abutalybov, G.I.; Guseinov, A.M.; Abdinov, A.S. (Inst. of Physics, Azerbaijan Academy of Sciences, Baku (Azerbaijan))

    1991-11-16

    Investigations of exciton luminescence and absorption spectra of InSe (GaSe) lamellar semiconductors doped with different kinds of compounds at T=1.8 K are carried out. It is found that changes in the luminescence intensity of free and bound excitons are due to screening of Coulomb interaction between electron and hole. Increase of free excitons luminescence intensity in InSe crystals activated by holmium ions is attributed to ''healing'' of metal and chalcogenide vacancies and also to interlaminar interaction increase due to exchange interaction of local formations, i.e. holmium ions. (orig.).

  6. ¿Se desindustrializa Brasil?

    Directory of Open Access Journals (Sweden)

    Fernando Mattos

    2014-01-01

    Full Text Available Este estudio pretende retomar algunos temas específicos del debate sobre la desindustrialización en Brasil, así como también, apunta a recordar algunos aspectos del debate teórico-histórico sobre la desindustrialización, presente en la literatura sobre desarrollo económico. En la primera parte, se destacan algunos elementos del referido debate presentes en la literatura especializada, discutiendo aspectos teóricos de la formulación kaldoriana que destacan el papel del crecimiento industrial y de la mudanza estructural en el crecimiento de las economías capitalistas. En la segunda, son organizados y analizados algunos indicadores recientes del desempeño del sector industrial brasileño. Finalmente, se ofrecen algunas breves notas conclusivas.

  7. Precios de los medicamentos: cómo se establecen y cuáles son sus sistemas de control

    Directory of Open Access Journals (Sweden)

    Joan Rovira Forns

    2015-01-01

    Full Text Available El precio es una de las principales barreras de acceso a los medicamentos. Por ello es importante conocer cómo se forman los precios y qué factores determinan su cuantía y también qué formas de intervención y regulación son las más adecuadas teniendo en cuenta sus efectos, tanto sobre el acceso, como sobre la innovación, la producción local y otros posibles objetivos de la política de medicamentos. El análisis económico ha desarrollado un conjunto de modelos de mercado que permiten explicar el comportamiento de los precios, aunque los mercados reales divergen sustancialmente de los modelos teóricos. La regulación de precios está justificada por los llamados “fallos de mercado”; la regulación de precios basada en el costo de producción, la modalidad de control de precios más tradicional, ha caído en desuso a favor de los sistemas de precios de referencia internacionales y por la fijación del precio basada en el valor.

  8. In-situ investigation on the growth of Cu-Al intermetallic comp ounds in Cu wire b onding%Cu/Al引线键合界面金属间化合物生长过程的原位实验研究∗

    Institute of Scientific and Technical Information of China (English)

    杨庆龄; 陈奕仪; 吴幸; 沈国瑞; 孙立涛

    2015-01-01

    According to Moore’s Law, as the feature size of semiconductor devices becoming smaller and smaller, the chip integration degree keeps increasing. In particular, accompanying with the development of high chip integration and unit size reduction, the metal interconnects, i. e. the wire bonding, are becoming a challenging problem. Copper wire is believed to be an excellent metal for wire bonding, instead of gold wire, due to its attractive advantages such as low cost, favorable electrical and thermal conductivities etc. However, the excess Cu/Al intermetallic compounds (IMC) at the interface of copper wire and aluminum pad will increase the contact resistance and reduce bonding strength. This can affect the properties and reliability of devices. Currently, the evolutions of the interfacial microstructures as well as the growth mechanism of Cu/Al IMC at the bonding interface under thermal condition are still unclear. In-situ transmission electron microscope (TEM) has high spatial resolution and strong analysis ability. With fast CCD cameras, TEM can also record the dynamic structure evolution of the sample in real time. Combined with multi-function holders, TEM can also exert diverse fields and loads on the sample and synchronously monitor their structures and component evolutions. Hence, in situ TEM provides an advanced technique to explore the structural evolution and growth mechanism of Cu/Al IMC. In this paper, the growth mechanism of Cu/Al IMC is investigated during the annealing temperature from 50–220◦C based on the in-situ high resolution transmission electron microscopy (in-situ HRTEM). Specifically, the dynamic growth and structural evolution of Cu/Al IMC during annealing are recorded in real time. Results show that the isolated Cu/Al IMC is distributed in the bonding interface before annealing. The main component of IMC is Cu9Al4, whereas the minor one of IMC is CuAl2. After annealing at 50–220 ◦C for 24 h, Cu/Al IMC near the Cu layer is Cu9Al4

  9. El derecho costarricense se actualiza

    OpenAIRE

    Romero-Pérez, Jorge Enrique

    2014-01-01

    Durante muchos años el derecho costarricense se mantuvo estático, tranquilo frente a los cambios sociales, políticos, económicos, religiosos, etc. Parecía que el sistema jurídico era indiferente a la movilidad en las demás estructuras del Sistema Social. Esto, superficialmente, indujo a más de un observador, pétreo, reaccionario y resistente en las transformaciones operadas en el resto de la realidad del país. Sin embargo, tales cambios en las estructuras y en las relaciones globales paulatin...

  10. Buenas piezas. Cuando se siente

    OpenAIRE

    Martínez, Borja; Lo Siento; Molinero Domingo, Silvia

    2016-01-01

    Entrevista a Borja Martínez de Lo Siento Studio. Viajamos a Barcelona para conocer el espacio en el que Lo Siento desarrolla su trabajo. Se trata de un estudio reconocido por los proyectos de identidad gráfica, packaging, diseño editorial y especialmente valorados por la creación de atractivas tipografías. Han recibido varios Laus y Grand Laus, premios organizados por la Asociación de Diseñadores Gráficos y Directores de Arte (ADG-FAD), por ejemplo al álbum The Mill...

  11. Redes de señalización en la producción de biopelículas en bacterias: quorum sensing, di-GMPc y óxido nítrico

    Directory of Open Access Journals (Sweden)

    Alberto Ramírez-Mata

    Full Text Available Las bacterias forman biopelículas de manera ubicua, y esta característica les otorga una flexibilidad que es resultado, en parte, de una matriz compleja construida según las exigencias de las condiciones ambientales. Aunque los estadios de la formación de las biopelículas bacterianas se conocen con detalle, para entender con profundidad la formación de las biopelículas es deseable un conocimiento mayor de los mecanismos de señalización. Las bacterias detectan cambios en la densidad de población por regulación del quórum y condiciones específicas, empleando señales como el di-GMPc y el óxido nítrico. La importancia del conocimiento de estas vías de señalización radica en que controlan una variedad de funciones, como la formación de biopelículas y la movilidad, y proporcionan a las bacterias beneficios en la colonización del hospedador, la defensa contra competidores y los cambios adversos del entorno. Por la trascendencia que revisten estos aspectos, revisamos aquí las redes de regulación y la conexión de la señalización entre quorum sensing, di-GMPc y óxido nítrico.

  12. Modelado e implementación de un sistema de enseñanza de Lenguaje de Señas Mexicano

    OpenAIRE

    Juan F. García Mejía; Luz A. Tinoco Monroy; Germán González Hernández; José A. García Mejía; Judith Moreno Jiménez

    2007-01-01

    En este artículo se muestra un sistema que permite el estudio y práctica del Lenguaje de Señas Mexicano (LMS), el cual es el método de comunicación de las personas que padecen un trastorno de procesamiento auditivo. El sistema propuesto en este artículo consta de un guante de tela instrumentado con sensores de flexión, una etapa de acondicionamiento de señales y una tarjeta de adquisición de datos; que en su conjunto constituyen el Hardware. El software esta ...

  13. Señalética y emoción

    OpenAIRE

    Raiberti, Mónica

    2006-01-01

    Esta presentación surge en el marco del Proyecto de Investigación CAI+D de la Universidad Nacional del Litoral: “Signo icónico y pictogramático en el espacio urbano de la ciudad de Santa Fe”. Dicho proyecto pertenece a la Cátedra Taller B de Diseño de la Comunicación Visual II-IV de la Licenciatura de Diseño de la Comunicación Visual de la Facultad de Arquitectura, Diseño y Urbanismo de la mencionada Universidad. La disciplina desde la cual se enmarca el citado proyecto es la Señalética...

  14. Main: SE2PVGRP1 [PLACE

    Lifescience Database Archive (English)

    Full Text Available SE2PVGRP1 S000101 17-May-1998 (last modified) kehi SE2 (stem element 2) of bean (P.v.) GRP...1.8 gene; part of SE2 element; stem; SE2; GRP; GRP1; bean (Phaseolus vulgaris) TTNNNGTAGCTAGTGTATTTGTAT ...

  15. A transferable force field for CdS-CdSe-PbS-PbSe solid systems

    NARCIS (Netherlands)

    Fan, Zhaochuan; Koster, Rik S.; Wang, Shuaiwei; Fang, Changming; Yalcin, Anil O.; Tichelaar, Frans D.; Zandbergen, Henny W.; van Huis, Marijn A.; Vlugt, Thijs J. H.

    2014-01-01

    A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., "Atomic resolution monitoring of cation exchange in CdSe-PbSe heterona

  16. Se metallomics during lactic fermentation of Se-enriched yogurt.

    Science.gov (United States)

    Palomo, María; Gutiérrez, Ana M; Pérez-Conde, M Concepción; Cámara, Carmen; Madrid, Yolanda

    2014-12-01

    Selenium biotransformation by lactic acid bacteria during the preparation of Se-enriched yogurt was evaluated. The study focused on the distribution of selenium in the aqueous soluble protein fraction and the detection of selenoamino acids. Screening of selenium in Tris-buffer-urea soluble fraction was carried out by sodium dodecyl sulphate polyacrylamide gel electrophoresis after pre-fractionating with asymmetric field flow fractionation using inductively coupled plasma-mass spectrometry as the detector. Selenium-containing fractions were identified by peptide mapping using nano LC-ESI/LTQMS. Proteins such as thioredoxin, glutaredoxin, albumin, β-lactoglobulin, and lactoperoxidase were identified in the selenium-containing fraction. All these proteins were detected in both the control and the selenium-enriched yogurt except chaperones, which were only detected in the control samples. Chaperones are heat-shock proteins expressed in response to elevated temperature or other cellular stresses. Selenium may have an effect on chaperones expression in Lactobacillus. For the amino acids analysis, selenocysteine was the primary seleno-containing species.

  17. Se equivocó el masoreta ¿se equivocaba?

    Directory of Open Access Journals (Sweden)

    Fernández Tejero, Emilia

    2009-12-01

    Full Text Available This article has a didactic purpose; it is not aimed at scholars of the Masora but rather at researchers in closely associated areas. The editions of Hebrew Biblical manuscripts and critical studies that have been published recently are particularly useful tools for those who wish to delve into other areas of research such as the history of the Hebrew Biblical text, its exegesis or the origins of grammar. Here, the author concentrates on the analysis of three issues: variant formulations of a same information; coherence between a text and its Masorah, and the possible discrepancies among sources.

    Este artículo, de carácter didáctico, no está destinado a los estudiosos de la Masora, sino a investigadores de áreas cercanas. Las ediciones de manuscritos y los estudios publicados en los últimos años son instrumentos de gran utilidad para quienes deseen adentrarse en un campo de investigación con repercusión en otras áreas tales como la historia del texto bíblico hebreo, su exégesis o los inicios de la gramática. Se analizan tres cuestiones: distinta formulación para una misma noticia, coherencia entre un texto y su masora y posibles discrepancias entre las fuentes.

  18. PROPUESTA DE UN MODELO PARA EL CONTROL DE GESTIÓN DE LOS SERVICIOS PÚBLICOS MUNICIPALES, MEDIANTE UN SISTEMA DE INFORMACIÓN EN EL MUNICIPIO DE ECATEPEC DE MORELOS, ESTADO DE MÉXICO.

    OpenAIRE

    Patiño Galván, Israel

    2015-01-01

    Los servicios públicos forman parte del bienestar social en México, en especial los servicios públicos municipales (SPM), los cuales en la actualidad adolecen de alternativas que propicien una mejora continua en su control de gestión. La presente propuesta se integró empleando metodologías científicas mixtas como son la metodología cualitativa y cuantitativa, análisis y síntesis entre otras, las cuales guían la correcta estructuración y fundamento de dicha propuesta. El r...

  19. CURETAJE ABIERTO E INJERTO ÓSEO: REPORTE DE CASO

    OpenAIRE

    JUÁREZ JIMÉNEZ, MARINA

    2015-01-01

    En las lesiones endoperiodontales las diferentes interconexiones anatómicas y vasculares entre la pulpa y el periodonto juegan un rol fundamental. Desde el desarrollo del germen dental se forman estructuras como los túbulos dentinarios y conductos principales, secundarios, laterales, entre otros, los cuales son capaces de comunicar las estructuras endodónticas y periodontales y de esta manera permitir un intercambio de sustancias entre ambas, razón por la cual es común que una enfermedad pulp...

  20. ¿Un fin o un medio?: Contexto en el que se decide la reproducción

    Directory of Open Access Journals (Sweden)

    Diva Estela Jaramillo

    Full Text Available Estudio cualitativo que explora el proceso de toma de decisiones en la reproducción. Describe el contexto para dicha decisión. Se entrevistan 17 hombres y 23 mujeres, entre 20 y 35 años, de diferentes estratos sociales, procedencias y niveles educativos, con relación de pareja mayor a un año. Metodológicamente se apoya en la teoría fundada y el interaccionismo simbólico. Los hallazgos muestran diferentes significados de reproducirse y de interpretar las normas de género, los cuales guían las decisiones sobre la descendencia. Cuando las parejas entienden la reproducción como un fin, deciden prepararse y planear el número y el momento de realizarla. Son decisiones dialogadas y concertadas a la luz de sus planes de vida. Cuando entienden reproducirse como un medio para lograr fines individuales, como son, desde lo masculino obtener placer sexual o cuidados, y desde lo femenino, encontrar estabilidad afectiva, emocional y económica para tener unas determinadas condiciones de vida, las decisiones son individuales no negociadas. No se preparan, e interpretan rígidamente las normas de género, lo cual conduce a relaciones de inequidad. La reproducción no es motivo de preocupación y en consecuencia, los hijos aparecen inesperadamente, lo que se convierte en motivo permanente de conflicto entre la pareja.

  1. Control de estabilidad de un robot por medio de señales ultrasónicas

    Directory of Open Access Journals (Sweden)

    Wilmar G. Monsalve

    2010-12-01

    Full Text Available Actualmente son diversos los métodos utilizados para la medición de una inclinación de un cuerpo respecto a una referencia o un marco fijo, pero el problema radica en los costos que estos acarrean, siendo este un factor limitante para el desarrollo científico cuando se dispone de bajos recursos económicos. En Este punto es en donde se hace relevante la investigación y el desarrollo en materia de tecnología llevado a cavo, en este articulo, ya que la finalidad del presente proyecto, consiste en proporcionarle estabilidad a un robot autónomo de un solo eje, para lo cual se hace necesario, la implementación de un sistema de control de inclinación. El sistema de detección de inclinación desarrollado, está basado en el ultrasonido como herramienta principal de medición de distancia entre dos puntos equidistantes del eje central de la plataforma robótica, la cual es inestable por naturaleza. Mediante este nuevo método, se ha logrado establecer magnitudes de inclinación del orden de fracciones de grados, ya que los transductores piezoeléctricos en conjunto con la electrónica implementada, brinda gran precisión en las medidas realizadas.

  2. Aproximación al silencio elocuente de los enunciados: lo que se comunica y no se dice

    Directory of Open Access Journals (Sweden)

    Constanza Moya Pardo

    2012-01-01

    Full Text Available El estudio del silencio muestra otras posibilidades de interacción humana que se creían excluidas al callar. Esta dimensión lacónica del lenguaje posibilita una fenomenología de las formas de expresión que incorpora el mundo de lo implícito y supera el privilegio que ejerce la palabra verbal-explícita en nuestros procesos de comunicación. Muchos de los enunciados de la lengua ocultan otros que les dan sentido. Además de aparecer como privación verbal, como ausencia de habla o artificio de la economía lingüística, el silencio es una manera de pensar y de comunicar. Es el saber compartido, el mundo implícito de los hablantes. Este juego de silencios, mediante el cual transmitimos pensamientos e intenciones sin necesidad de enunciarlos directamente, es posible gracias a habilidades cognitivas de conexión e inferencia, y al conjunto de supuestos compartidos por los miembros que pertenecen a una misma comunidad pragmática y que dominan las reglas de esa gramática del silencio.

  3. Characterization of Cu-exchanged SSZ-13: a comparative FTIR, UV-Vis, and EPR study with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios

    DEFF Research Database (Denmark)

    Giordanino, Filippo; Vennestrøm, Peter N. R.; Lundegaard, Lars Fahl

    2013-01-01

    revealed the presence of different Cu2+ species. New data and discussion are devoted to (i) [Cu–OH]+ species likely balanced by one framework Al atom; (ii) mono(μ-oxo)dicopper [Cu2(μ-O)]2+ dimers observed in Cu-ZSM-5 and Cu-β, but not in Cu-SSZ-13. UV-Vis-NIR spectra of O2 activated samples reveal......Cu-SSZ-13 has been characterized by different spectroscopic techniques and compared with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios and prepared by the same ion exchange procedure. On vacuum activated samples, low temperature FTIR spectroscopy allowed us to appreciate a high...... concentration of reduced copper centres, i.e. isolated Cu+ ions located in different environments, able to form Cu+(N2), Cu+(CO)n (n = 1, 2, 3), and Cu+(NO)n (n = 1, 2) upon interaction with N2, CO and NO probe molecules, respectively. Low temperature FTIR, DRUV-Vis and EPR analysis on O2 activated samples...

  4. Impact of temperature and programming method on the data retention of Cu/Al2O3-based conductive-bridge RAM operated at low-current (10 μA)

    Science.gov (United States)

    Belmonte, A.; Fantini, A.; Redolfi, A.; Houssa, M.; Jurczak, M.; Goux, L.

    2016-11-01

    In this paper we outline the effects on the memory window of the programming method and pulse width and of the temperature, in Cu/Al2O3-based CBRAM targeting a 10-μA current regime. Despite its large median value, the overall HRS/LRS ratio in these devices can be drastically reduced due to the LRS and HRS dispersion and to the instability of the resistive states over time, especially in a low-current regime. For this reason, in this study we adopt a statistical approach, focusing on the tails of the cumulative distribution Function (CDF). We compare different verify-based algorithms to force an initial tail-to-tail (1st percentile of CDF) resistive window, demonstrating that, in order to reduce the total programming time, a complete Write/Erase cycle must be performed at each verify attempt. We also prove that the stability of the programmed LRS/HRS states is strongly influenced by the external temperature and that it is affected by the programming pulse width (PW) used in the algorithm, likely driving the diffusion processes that originate the state degradation. Selecting the appropriate PW, no overlap of the LRS and HRS distributions is observed after 1 week at room temperature.

  5. Characterization of Cu-exchanged SSZ-13: a comparative FTIR, UV-Vis, and EPR study with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios.

    Science.gov (United States)

    Giordanino, Filippo; Vennestrøm, Peter N R; Lundegaard, Lars F; Stappen, Frederick N; Mossin, Susanne; Beato, Pablo; Bordiga, Silvia; Lamberti, Carlo

    2013-09-21

    Cu-SSZ-13 has been characterized by different spectroscopic techniques and compared with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios and prepared by the same ion exchange procedure. On vacuum activated samples, low temperature FTIR spectroscopy allowed us to appreciate a high concentration of reduced copper centres, i.e. isolated Cu(+) ions located in different environments, able to form Cu(+)(N2), Cu(+)(CO)n (n = 1, 2, 3), and Cu(+)(NO)n (n = 1, 2) upon interaction with N2, CO and NO probe molecules, respectively. Low temperature FTIR, DRUV-Vis and EPR analysis on O2 activated samples revealed the presence of different Cu(2+) species. New data and discussion are devoted to (i) [Cu-OH](+) species likely balanced by one framework Al atom; (ii) mono(μ-oxo)dicopper [Cu2(μ-O)](2+) dimers observed in Cu-ZSM-5 and Cu-β, but not in Cu-SSZ-13. UV-Vis-NIR spectra of O2 activated samples reveal an intense and finely structured d-d quadruplet, unique to Cu-SSZ-13, which is persistent under SCR conditions. This differs from the 22,700 cm(-1) band of the mono(μ-oxo)dicopper species of the O2 activated Cu-ZSM-5, which disappears under SCR conditions. The EPR signal intensity sets Cu-β apart from the others.

  6. Electrical and photovoltaic properties of Cu-doped p-GaSe/n-InSe heterojunction

    Science.gov (United States)

    Shigetomi, S.; Ikari, T.

    2000-08-01

    GaSe(Cu)/InSe heterojunctions have been formed by bringing the cleavage surface of undoped n-InSe and Cu-doped p-GaSe into direct contact. Transport and phototransport properties are studied by the measurements of capacitance-voltage, current-voltage, and the spectral response of short-circuit current. Moreover, the efficiency parameters under illumination are estimated by using the open-circuit voltage and short-circuit current. These characteristics of GaSe(Cu)/InSe heterojunctions are compared with those of GaSe(Un)/InSe heterojunctions fabricated by undoped p-GaSe and n-InSe. The series resistance of GaSe(Cu)/InSe heterojunctions is found, the value of which is about 103 times lower than the corresponding value of GaSe(Un)/InSe heterojunctions. A short-circuit current density of 9.0 mA/cm2 and an open-circuit voltage of 0.42 V on GaSe(Cu)/InSe heterojunctions are obtained under illumination of 120 mW/cm2 of a halogen lamp. The short-circuit current of GaSe(Cu)/InSe heterojunctions is about one order of magnitude lager than that of GaSe(Un)/InSe heterojunctions. These experimental results indicate that the low-resistivity of Cu-doped GaSe is effective for the electrical and photovoltaic properties of GaSe/InSe heterojunctions.

  7. El sistema penal debe construirse a partir de las finalidades que se le asignen y del modelo de estado. ¿Cambio de paradigma gracias a la irrupción del racionalismo?

    Directory of Open Access Journals (Sweden)

    Francisco Bernate-Ochoa

    2010-03-01

    Full Text Available La construcción del delito como método lógico no debe entenderse como algo independiente del modelo de Estado en el cual se construye. El sistema penal, sin importar la escuela dogmática que se acoja, estará siempre condicionado por el modelo de Estado que definirá  las pautas  y  los parámetros  del delito.

  8. Reaction kinetics of CuGaSe 2 formation from a GaSe/CuSe bilayer precursor film

    Science.gov (United States)

    Kim, W. K.; Payzant, E. A.; Kim, S.; Speakman, S. A.; Crisalle, O. D.; Anderson, T. J.

    2008-06-01

    The reaction pathway and kinetics of CuGaSe 2 formation were investigated by monitoring the phase evolution of temperature ramp annealed or isothermally soaked bilayer glass/GaSe/CuSe precursor film using time-resolved, in situ high-temperature X-ray diffraction. Bilayer GaSe/CuSe precursor films were deposited on alkali-free thin glass substrates in a migration-enhanced epitaxial deposition system. The initial CuSe phase begins to transform to β-Cu 2-xSe at around 230 °C, followed by CuGaSe 2 formation accompanied by a decrease in the β-Cu 2-xSe peak intensity at around 260 °C. Both the parabolic and Avrami diffusion-controlled reaction models represented the experimental data very well over the entire temperature range (280-370 °C) of the set of isothermal experiments with estimated activation energies of 115(±16) and 124(±19) kJ/mol, respectively. Transmission electron microscopy-energy-dispersive X-ray spectrometry (TEM-EDS) analysis suggests that CuGaSe 2 forms at the interface of the initial GaSe and CuSe layers.

  9. Heteroepitaxy of Layered Compound InSe and InSe/GaSe onto GaAs Substrates

    Science.gov (United States)

    Budiman, Maman; Yamada, Akira; Konagai, Makoto

    1998-07-01

    The van der Waals epitaxy of InSe films was performed on (111)GaAs surface at the growth temperature of 350°C. A spiral trigonal structure was observed on the surface of the InSe films. To improve crystal quality of the InSe films, their orientation control was investigated. The growth rate decreased rapidly as the growth temperature increased and no InSe films were obtained at growth temperatures higher than 480°C. At growth temperatures of 450°C and higher, a double-domain structure was observed, probably due to the coexistence of In4Se3 phase in the films. Therefore, the InSe film was directly grown on c-axis inclined GaSe, and it was revealed that InSe films were more easily grown on GaSe than on (001)GaAs surface, due to the same crystal structure. Furthermore, for fabrication of the quantum well structure, heteroepitaxial growth of GaSe/InSe/GaSe films on (001)GaAs substrate was investigated.

  10. Zn-Al钎料钎焊Cu/Al接头组织和性能%Microstructure and properties of Cu/Al joints brazed with Zn-Al filler metals

    Institute of Scientific and Technical Information of China (English)

    姬峰; 薛松柏; 娄继源; 娄银斌; 王水庆

    2012-01-01

    使用不同成分的Zn-Al钎料对铜铝异种金属进行火焰钎焊,研究其力学性能.利用光学显微镜、扫描电镜和能谱研究不同Zn-Al钎料对Cu/Al钎焊接头钎焊性、力学性能及显微组织的影响.结果表明:随着Al含量的增加,Zn-Al钎料在Cu和Al上的铺展面积逐渐增大.当钎料中Al含量为15%时,Cu/Al接头的抗剪强度达到最大值88 MPa;随着组织的变化,钎缝硬度值呈现HV122到HV515不等的分布.另外,钎缝组织的成分主要为富Zn相和富Al相,但是当钎料中Al含量为2%和15%以上时,靠近Cu侧的界面处会分别形成CuZn3和Al2Cu两种完全不同的金属间化合物.研究Zn-Al钎料中铝含量对Cu/Al接头界面化合物类型的影响.%The mechanical properties and microstructural distribution of the Cu/Al brazing joints formed by torch-brazing with different Zn-Al filler metals were investigated.The microstructure of the Zn-Al alloys was studied by optical microscopy and scanning electron microscopy,and the phase constitution of the Cu/Al joints was analyzed by energy dispersion spectrometry.The results show that the spreading area of the Zn-Al filler metals on the Cu and Al substrates increases as the Al content increases.The mechanical results indicate that the shear strength reaches a peak value of 88 MPa when Al and Cu are brazed with Zn-15Al filler metal.Microhardness levels from HV122 to HV515 were produced in the three brazing seam regions corresponding to various microstructure features.The Zn- and Al-rich phases exist in the middle brazing seam regions.However,two interface layers,CuZn3 and Al2Cu are formed on the Cu side when the Al content in the filler metals is 2% and more than 15%,respectively.The relationship between intermetallic compounds on Cu side and Zn-xAl filler metals was investigated.

  11. Mechanical alloying of Cu/Al plates and preparation of bulk amorphous/nanocrystalline composite by thermoplastic deformation%搅拌摩擦法制备Cu-Al非晶/纳米晶复合材料

    Institute of Scientific and Technical Information of China (English)

    徐红霞; 段辉平; 宋洪海

    2013-01-01

    利用搅拌摩擦技术,使叠放在一起的Cu、Al板材发生强烈的热塑性变形.对搅拌区产物的显微结构分析表明:Cu、Al板材被搅拌破碎并充分混合在一起,Cu、Al元素发生扩散并实现合金化;在搅拌区中有许多尺寸> 1μm的非晶相和非晶/纳米晶复合相,非晶相的基体中含有平均尺寸约为5nm的纳米晶.热塑性变形技术不仅可用于块体金属材料的机械合金化,也可用于制备块体非晶/纳米晶复合材料.%Strong thermoplastic deformation of overlapped Cu and Al plates had been realized by stir friction processing. Transmission electron microscopy investigation on the microstructure of the stirred zone demonstrate that the Cu and Al plates are torn into shreds and well-mixed in the stirred zone. The inter-diffusion between Cu and Al shreds happens, resulting in the mechanical alloying of Cu/Al plates. There are many amorphous phases with size of more than 1 micron and amorphous/nanocrystalline composite phases in the deformation zone. The average size of the nanocrystallines surrounded by amorphous phases, is about 5 nanometers. Experimental results strongly suggest that the thermoplastic deformation technique can not only be used to do mechanical alloying for bulk metallic materials but also to fabricate bulk amorphous/crystalline materials.

  12. Electron and hole dynamics in GaSe nanoparticles and GaSe-InSe nanoparticle heterojunctions.

    Science.gov (United States)

    Kelley, David F.; Tu, Haohua; Mogyorosi, Karoly; Chen, Xiang-Bai

    2006-08-01

    Femtosecond polarized transient absorption results are obtained for InSe and GaSe nanoparticles. The results indicate that the transient absorption spectrum of large GaSe particles is dominated by a size-independent, z-polarized hole intraband transition. The small particle spectra exhibit the same z-polarized hole transition and a much more intense x,y-polarized absorption that is assigned to a charge transfer transition from the conduction band to particle surface (edge) states. The intensity of this transition depends on the momentum state (Γ or M) of the electron, and Γ to M electron momentum relaxation results in a 15 ps absorption decay. These results are used to interpret analogous results obtained for mixed GaSe-InSe nanoparticle aggregates, also in the solution phase. The static absorption spectrum of the mixed aggregates exhibits a strong interparticle charge transfer absorption band at an energy slightly higher than the InSe bandgap. Photoexcitation of this band results in a polarized transient absorption spectrum and transient absorption kinetics characteristic of InSe valence band holes and GaSe conduction band electrons. This result indicates that with small GaSe particles, direct InSe to GaSe electron transfer occurs upon photoexcitation.

  13. Which will be final destination of Spanish photovoltaic Market?. An external vision of opportunities and challenges the Spanish photovoltaic market has to face; Cual sera el destino del mercado fotovoltaico espanol?. Una vision externa sobre las oportunidades y desafios a los que se enfrenta el mercado fotovoltaico en Espana

    Energy Technology Data Exchange (ETDEWEB)

    Mohrstedt, U.

    2009-07-01

    Her Udo Mohrstedt, founder of the German company IBC SOLAR, specialized in photovoltaic supplies, makes an introduction to the current status of Spanish photovoltaic market, comparing it with some other European countries. In this article, he enlists opportunities and challenges for Spanish solar photovoltaic market, to conclude that there are reasons enough to look at the future with optimism. (Author) 6 refs.

  14. La economía de los bienes simbólicos en una organización del Tercer Sector: el poder del desinterés

    OpenAIRE

    Salvadé, Romina

    2014-01-01

    Se desarrollan en el trabajo algunos ejes a partir de los cuales se indagaron los modos de construir legitimidad social en una organización no lucrativa que trabaja en la prevención del cáncer y se encuentra ubicada en Olavarría, Buenos Aires. Tales reflexiones forman parte de las conclusiones de una investigación que da cuenta de la producción del Trabajo Final Integral para la Licenciatura en Comunicación Social. Las organizaciones del Tercer Sector muestran algunas especificidades en su...

  15. Eficacia del entrenamiento excéntrico en tendinopatía aquílea

    OpenAIRE

    Martínez Martínez, Daniel

    2013-01-01

    La tendinopatía aquilea se produce cuando se forman pequeños desgarros en las fibras que conforman el tendón. Independientemente de si la lesión es inflamatoria o degenerativa, o si el asiento de la lesión está en la inserción o en el cuerpo del tendón, un alto porcentaje de personas, hasta un 60%, que presenta una Tendinopatía de Aquiles tiene problemas de apoyo podal o de mala alineación de la extremidad inferior. No se sabe cual es mejor tratamiento para ella. Objetivo...

  16. Importancia de la valoración clínica preoperatoria en cirugía de catarata

    OpenAIRE

    Diley Estrada Ramos

    2015-01-01

    La evaluación preoperatoria del paciente quirúrgico es uno de los eslabones fundamentales de la actividad clínica diaria; puede considerarse como la fase en que la búsqueda y el hallazgo de información, relacionada con el paciente y su entorno, forman un fuerte pilar sobre el cual se sustenta gran parte del perioperatorio. Del análisis y la interpretación que de ella se obtengan, se trazarán las pautas para obtener buenos resultados, orientados a disminuir la morbimortalidad perioperatoria. S...

  17. Efecto que se obtiene en la industria con la automatización del sistema de aire comprimido

    Directory of Open Access Journals (Sweden)

    Jorge Torres Rodríguez

    2016-06-01

    Full Text Available Hoy en día todas las empresas tienen dentro de sus compromisos el cuidado del medio ambiente, por lo cual se tiene como objetivo reducir al mínimo el consumo de energía dentro de sus operaciones. En una empresa de manufacturación los principales equipos que consumen energía son los motores; principalmente los tipos cuadráticos (banda transportadoras, compresores, ventiladores y bombas. El control eficiente de los motores cuadráticos puede llegar a reducir el consumo eléctrico hasta un 20% a 30% en cada uno de estos equipos, lo cual convierte en una inversión rentable a futuro. En el anterior control de los compresores hacían arranques continuos cada cierto tiempo, (dependiendo de la señal del presostato lo cual originaba picos de corriente elevando los Kw/h, esto se debe a que los equipos de puesta en marcha son mediante dispositivos eléctricos y electromecánicos que no pueden controlar la velocidad de cada compresor. La presente investigación tiene como fin el diseño, instalación y puesta en marcha de un sistema de control descentralizado para la generación de aire comprimido. El nuevo sistema propuesto interconectará 4 compresores (2 VDP con arranque variador  de  frecuencia, 2 AD arranque directo. Este regulará la velocidad de 2 de los compresores, con el objetivo principal de ahorrar energía  para la planta y a su vez mejorar el sistema de funcionamiento  de los mismos. Todo el Sistema será controlado por PLC y su proceso será monitoreado en el Intouch (Software de monitoreo del Scada de la planta. Lo cual me generará ahorro en costos de mantenimiento de cada uno de los compresores a utilizar, ahorro de consumo de energía eléctrica y por ende  se contribuye  a cuidar el medio ambiente realizando un uso eficiente de cada uno de los equipos.

  18. Implicaciones funcionales de la señalización purinérgica en la red trabecular

    OpenAIRE

    2005-01-01

    La red trabecular es una estructura situada en la cámara anterior del ojo cuya función es drenar el humor acuoso. Alteraciones en ella pueden producir aumentos de la presión intraocular (IOP) los cuales pueden provocar pérdidas en el campo visual y por lo tanto cegueras parciales o totales (glaucoma).El objetivo de esta tesis doctoral se basa en el estudio de la fisiología de la red trabecular con el fin de tener un mayor conocimiento de sus funciones y así poder entender mejor su papel regul...

  19. ¿Cómo se enfrentan tres culturas corporativas en una joint venture? Caso Intesa-Venezuela

    OpenAIRE

    Margalit Berlin

    2002-01-01

    Este es un estudio de caso realizado en Intesa, una empresa conjunta o joint venture. En Intesa coinciden tres tipos de gerentes, según el tipo de organización de la cual provienen: de Petróleos de Venezuela (PDVSA), del sector privado nacional y del sector multinacional. Mientras los gerentes se adaptan a las culturas corporativas de estos tres sectores, traen ciertas características culturales que los diferencian entre sí. El objetivo de este trabajo es determinar si las diferen...

  20. Teoria de la deteccion de señales (tds y caracteristicas de la memoria transitoria

    Directory of Open Access Journals (Sweden)

    Paul Stephaneck

    1987-01-01

    Full Text Available Seis sujetos fueron sometidos a una tarea de memorización en la cual el sujeto conserva informaciones, recibe nuevos datos durante el intervalo de retención y elimina, al mismo tiempo, algunos aspectos antiguos de su memoria que se volvían inútiles. El material memorizado consistió en objetos abstractos que poseían varios atributos. Fueron establecidas dos condiciones experimentales. Condición V: numerosos atributos de pocos objetos. Condición U: un solo atrio buto de numerosos objetos. Los resultados obtenidos por la aplicación de la Teoría de la Detección de Señales (TDS muestran una leve superioridad del desempeño de los sujetos en la condición U. Reagrupando los datos se puede mostrar que el efecto principal en la degradación de la memoria se debe al número de aspectos conservados en la memoria en el momento de recordar

  1. Influence of the technology of melting and inoculation preliminary alloy AlBe5 on change of concentration of Al and micro-structure of the bronze CuAl10Ni5Fe4

    Directory of Open Access Journals (Sweden)

    B. Pisarek

    2010-04-01

    Full Text Available Examining was the aim of the work: influence of the permanent temperature 1300°C ± 15°C and changing time of isothermal holding in the range 0÷50 minutes on the melting loss of aluminum in the bronze CuAl10Ni5Fe4; the quantity the slag rafining - covering Unitop BA-1 (0÷1,5% on the effectiveness of the protection of liquid bronze before the oxygenation, the quantity of the preliminary alloy - in-oculant AlBe5 (0÷1,0% on the effective compensation melting loss of aluminum and time of isothermal holding on the effect of the in-oculation of the bronze and the comparison of the effectiveness of the inoculation of the bronze in furnace and in the form. Introduced investigations resulted from the study of the new grades of the Cu-Al-Fe-Ni bronze with additions singly or simultaneously Si, Cr, Mo and/or W, to melting which necessary it is for high temperature and comparatively long time isothermal holding indispensable to the occur of the process of diffusive dissolving the high-melting of the bronze components. High temperature and lengthening the time of isothermal holding the liquid bronze in casting furnace the melting loss of Al influences the growth. Addition the slag of covering-refining Unitop BA-1 in the quantity 1,5% the bronze protects before the melting loss of aluminum by the time of isothermal holding in the temperature 1300°C about 15 minutes. Addition of the preliminary alloy AlBe5 in the quantity 0,6% it assures the effective compensation of the aluminum which melting loss undergoes for the studied parameters of the melting. The effect of the inoculation of the bronze together with diminishes the preliminary alloy AlBe5 with lengthening the time of isothermal hold-ing. Because of this, use of the method of introducing the preliminary alloy it is seems good solution on the inoculation of aluminum bronzes directly to form, unsensitive on the time of isothermal holding the bronze.

  2. Low temperature solution-phase growth of ZnSe and ZnSe/CdSe core/shell nanowires

    Science.gov (United States)

    Petchsang, Nattasamon; Shapoval, Liubov; Vietmeyer, Felix; Yu, Yanghai; Hodak, Jose H.; Tang, I.-Ming; Kosel, Thomas H.; Kuno, Masaru

    2011-08-01

    High quality ZnSe nanowires (NWs) and complementary ZnSe/CdSe core/shell species have been synthesized using a recently developed solution-liquid-solid (SLS) growth technique. In particular, bismuth salts as opposed to pre-synthesized Bi or Au/Bi nanoparticles have been used to grow NWs at low temperatures in solution. Resulting wires are characterized using transmission electron microscopy and possess mean ensemble diameters between 15 and 28 nm with accompanying lengths ranging from 4-10 μm. Subsequent solution-based overcoating chemistry results in ZnSe wires covered with CdSe nanocrystals. By varying the shell's growth time, different thicknesses can be obtained and range from 8 to 21 nm. More interestingly, the mean constituent CdSe nanocrystal diameter can be varied and results in size-dependent shell emission spectra.High quality ZnSe nanowires (NWs) and complementary ZnSe/CdSe core/shell species have been synthesized using a recently developed solution-liquid-solid (SLS) growth technique. In particular, bismuth salts as opposed to pre-synthesized Bi or Au/Bi nanoparticles have been used to grow NWs at low temperatures in solution. Resulting wires are characterized using transmission electron microscopy and possess mean ensemble diameters between 15 and 28 nm with accompanying lengths ranging from 4-10 μm. Subsequent solution-based overcoating chemistry results in ZnSe wires covered with CdSe nanocrystals. By varying the shell's growth time, different thicknesses can be obtained and range from 8 to 21 nm. More interestingly, the mean constituent CdSe nanocrystal diameter can be varied and results in size-dependent shell emission spectra. Electronic supplementary information (ESI) available. See DOI: 10.1039/c1nr10176e

  3. ¿Disenso entre pares revisores? No se preocupe, que a fin de cuentas el editor siempre tiene la última palabra

    OpenAIRE

    A. M. Cruz

    2012-01-01

    Todos hemos sometido algún artículo científico a revisión con la idea de que sea publicado en cierta revista. Frecuentemente, los autores experimentan muchas barreras para alcanzar el éxito (lograr la publicación) cuando someten artículos a revisión. Estas barreras dependen de la escritura del artículo en sí mismo, de los sesgos de los pares revisores, de la forma en que se escribe la carta de presentación (cover letter), y de la manera en la cual se implementa una estrategia para ab...

  4. Celebrado el I Encuentro Latinoamericano de Revistas Zootécnicas donde se fundó la Red Latina de Revistas de Zootecnia

    OpenAIRE

    Veterinaria.org

    2008-01-01

    ResumenSe celebró en la Universidad de Córdoba, del 12 al 14 de Diciembre de 2007, el “I Encuentro Latinoamericano de Revistas Zootécnicas”, en el cual se convocó a los responsables de la edición de las revistas más prestigiosas dentro del ámbito científico. En el cartel anunciador, figura el título y fecha del evento y debajo un arco formado por portadas de revistas del sector, entre las que está REDVET, y de fondo un mapa mundi, culminado por los logotipos institucionales de las entidades o...

  5. Turnover of Se in adequately fed chickens using Se-75 as a tracer.

    Science.gov (United States)

    Brandt-Kjelsen, A; Govasmark, E; Haug, A; Salbu, B

    2014-06-01

    Inorganic selenium (Se) in the form of selenite is applied to livestock to avoid Se deficiency. Selenite is, however, an artificial Se source in diets of unsupplemented chickens. It is therefore hypothesized that organic Se sources, such as Se-enriched yeast and wheat, could be a more suitable Se supply in animal nutrition, although information on the transition of Se from organic Se sources in fast-growing chickens is scarce. In this work, chickens were fed a low Se diet (0.27 ± 0.01 mg Se/kg, Se-enriched yeast) until 20 days of age, after which the Se concentration was increased to maximum concentration allowed by the poultry industry in Europe (0.5 p.p.m. Se). At the same time, a daily contribution of carrier-free (75)Se tracer from labelled wheat was administered from day 20 to 27. The chickens showed S and Se homeostasis, as the concentration of S and Se in liver, blood or kidney remained about constant, and steady state of S and Se in the other organs was reached 1 day after the diet shift. The uptake of (75)Se was readily seen in all organs. After 1 week, the depuration of the (75)Se tracer was followed, and biological half-lives and retention in individual organs were determined. The shortest biological half-lives were observed in major metabolic organs, the liver, kidney and pancreas with half-lives close to 4 days. There was a significant (p < 0.05) uptake in lung, brain and muscle that reached steady state when the administration of (75)Se was terminated. The half-life of (75)Se in heart was 9 days and 7 days in blood. The longest half-lives were observed in muscle (12 days), brain and lungs (13 days). All half-lives were shorter than in Se deplete animals.

  6. The reactivity of [PhP(Se)(mu-Se)]2 and (PhP)3Se2 towards acetylenes and cyanamides: X-ray crystal structures of some P-Se-C and P-Se-C-N heterocycles.

    Science.gov (United States)

    Bhattacharyya, Pravat; Slawin, Alexandra M Z; Woollins, J Derek

    2002-06-17

    Several unusual P-Se-C and P-Se-C-N heterocycles are formed by the reaction of [PhP(Se)(mu-Se)]2 or (PhP)3Se2 with alkynes or cyanamides, generated by the fragmentation of the organophosphorus-selenium compound and addition across the C identical to C or C identical to N triple bond of the organic substrate. X-ray crystallographic analysis reveals an unexpected diversity of structural motifs within these heterocyclic systems, including P2SeCN, P2C2Se and PC2Se2 rings.

  7. ON THE FORMATION OF THE MOST MASSIVE STARS IN THE GALAXY

    Directory of Open Access Journals (Sweden)

    R. Galván-Madrid

    2011-01-01

    Full Text Available Presentamos resultados obtenidos con el Submillimeter Array (SMA y el Very Large Array (VLA en regiones de formaci n de estrellas masivas en sus primeras etapas de ionizaci n. Las observaciones de gas ionizado y molecular con resoluci n angular de hasta 0.300 revelan rotaci n, colapso, y flujos eyectados en escalas de parsecs a 15 M se forman por procesos de acreci n similares a los de estrellas de baja masa, pero con ionizaci n considerable. (ii Los n cleos moleculares a partir de los cuales se forman estas estrellas contin an acretando gas de su ambiente. (iii La acreci n a la estrella puede continuar despu s del inicio de la ionizaci n.

  8. Defect studies of ZnSe nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Philipose, U; Saxena, Ankur; Ruda, Harry E [Centre for Nanotechnology, University of Toronto, 170 College Street, Toronto, ON, M5S 3E4 (Canada); Simpson, P J [Department of Physics and Astronomy, University of Western Ontario, London, ON, N6A 3K7 (Canada); Wang, Y Q; Kavanagh, K L [Department of Physics, Simon Fraser University, Burnaby, BC, V5A 1S6 (Canada)

    2008-05-28

    During the synthesis of ZnSe nanowires various point and extended defects can form, leading to observed stacking faults and twinning defects, and strong defect related emission in photoluminescence spectra. In this paper, we report on the development of a simple thermodynamic model for estimating the defect concentration in ZnSe nanowires grown under varying Se vapour pressure and for explaining the results of our experimental findings. Positron annihilation spectroscopy was used successfully for the first time for nanowires and the results support predictions from the defect model as well as agreeing well with our structural and optical characterization results. Under very high Se vapour pressure, Se nodules were observed to form on the sidewalls of the nanowire, indicating that beyond a limit, excess Se will begin to precipitate out of the liquid alloy droplet in the vapour-liquid-solid growth of nanowires.

  9. Excitons, biexcitons, and phonons in ultrathin CdSe/ZnSe quantum structures

    DEFF Research Database (Denmark)

    Gindele, F.; Woggon, Ulrike; Langbein, Wolfgang Werner

    1999-01-01

    The optical properties of CdSe nanostructures grown by migration-enhanced epitaxy of CdSe on ZnSe are studied by time-, energy-, and temperature-dependent photoluminescence and excitation spectroscopy, as well as by polarization-dependent four-wave mixing and two-photon absorption experiments....... The nanostructures consist of a coherently strained Zn1-xCdxSe/ZnSe quantum well with embedded islands of higher Cd content with sizes of a few nanometer due to strain-induced CdSe accumulation. The local increase in CdSe concentration results in a strong localization of the excitonic wave function, in an increase...

  10. Strain Compensation in Single ZnSe/CdSe Quantum Wells: Analytical Model and Experimental Evidence.

    Science.gov (United States)

    Rieger, Torsten; Riedl, Thomas; Neumann, Elmar; Grützmacher, Detlev; Lindner, Jörg K N; Pawlis, Alexander

    2017-03-08

    The lattice mismatch between CdSe and ZnSe is known to limit the thickness of ZnSe/CdSe quantum wells on GaAs (001) substrates to about 2-3 monolayers. We demonstrate that this thickness can be enhanced significantly by using In0.12Ga0.88As pseudo substrates, which generate alternating tensile and compressive strains in the ZnSe/CdSe/ZnSe layers resulting in an efficient strain compensation. This method enables to design CdSe/ZnSe quantum wells with CdSe thicknesses ranging from 1 to 6 monolayers, covering the whole visible spectrum. The strain compensation effect is investigated by high resolution transmission electron microscopy and supported by molecular statics simulations. The model approach with the supporting experimental measurements is sufficiently general to be also applied to other highly mismatched material combinations for the design of advanced strained heterostructures.

  11. The distributed generation in Mexico: Which are the new perspectives associated to the institutional reforms of the electrical sector?; La generacion distribuida en Mexico: Cuales son las nuevas perspectivas asociadas a las reformas institucionales del sector electrico?

    Energy Technology Data Exchange (ETDEWEB)

    Islas Samperio, Jorge [Centro de Investigacion en Energia, Universidad Nacional Autonoma de Mexico, Mexico, D.F. (Mexico); Menanteau, Philippe [Departamento de Economia y Politica de la Energia, Universidad Pierre Mendes France (France)

    2004-06-15

    Historically, the electrical systems were constituted from local networks of small scale that were added together progressively to benefit from the effects of a more abundant demand and of the economies of scale in generation, that authorize the large interconnected systems. This logic at the moment seems to show certain limits, the factors that influence these technologies can vary greatly from one country to another, but nevertheless it is found in different degrees certain constants such as the search for a greater reliability in the electrical supply, the putting into work prevention policies of climatic change or the reforms of the electrical sector. In this work the influence of these factors was examined insisting particularly on the consequences of the opening of the electrical sector, departing from an analysis of the international experience in a first time and later examining the case of Mexico in the context of the present energy situation and the debate of the energy reform. The distributed generation: a new vector of technological opportunities in the electrical sector, the barriers for the diffusion of the distributed generation: the lessons of the international experience, the institutional problematic of the distributed generation within the effective legal framework of Mexico. [Spanish] Historicamente, los sistemas electricos se constituyeron a partir de redes locales de pequena escala que se fueron agregando progresivamente para beneficiarse de los efectos de una demanda mas abundante y de las economias de escala en generacion que autorizan los grandes sistemas interconectados. Esta logica parece actualmente mostrar ciertos limites, los factores que influyen sobre estas tecnologias pueden variar grandemente de un pais al otro, pero se encuentra, sin embargo, a grados diferentes ciertas constantes tales como la busqueda de una confiabilidad mas grande en el aprovisionamiento electrico, la puesta en obra de politicas de prevencion de cambio

  12. Análisis de aprovechamiento de calores residuales de los gases de escape del motor térmico mediante efecto Seebeck en una unión Cu-Al

    OpenAIRE

    Fernández Juncà, Joan

    2014-01-01

    El presente documento pretende estudiar la posibilidad de recuperar parte de la energía térmica expulsada (calor residual) por un motor térmico, en su paso por el sistema de escape. Analizar la viabilidad de poder cargar baterías y/o alimentar sistemas electrónicos del vehículo, a partir del flujo térmico de los gases de escape. Se pretende analizar con detalle el flujo térmico así como los efectos electromagnéticos asumibles en un transformador de una sola espira de sección gene...

  13. 复合活性钎料钎焊Cu与Al2 O3的接头组织及性能%Microstructure and performance of the Cu/Al2O3 joint brazed with active composite filler

    Institute of Scientific and Technical Information of China (English)

    周英豪; 刘多; 雷玉珍; 宋晓国; 冯吉才

    2016-01-01

    为改善紫铜与Al2 O3陶瓷的连接强度,采用纳米-Al2 O3增强的AgCuTi复合钎料( AgCuTip )对紫铜与Al2 O3陶瓷进行了真空钎焊.采用扫描电镜、能谱分析以及剪切试验对钎焊接头微观组织及力学性能进行了分析.钎焊接头典型界面组织为紫铜/扩散层/铜基固溶体+银基固溶体+ Ti2 Cu + Ti3( Cu, Al)3 O/Al2 O3.纳米-Al2 O3的添加抑制了Al2 O3侧反应层的生长,并促进钎缝中形成弥散分布的Ti2Cu相.随着保温时间的延长,铜侧扩散层和Ti3(Cu, Al)3O反应层的厚度逐渐增大.保温时间为20 min时,铜母材向钎料过度溶解,降低了接头性能.当钎焊温度为880°C,保温10 min时,接头抗剪强度最高为82 MPa.纳米颗粒的加入细化了钎缝组织并降低了母材与钎缝热膨胀系数的不匹配,因此提高了接头的连接性能.保温时间可影响界面组织及反应层的厚度,进而影响接头的连接强度.%In order to improve the strength of Cu/Al2 O3 joint, vacuum brazing of copper to Al2 O3 ceramic was performed using nano -Al2O3 strengthened AgCuTi composite filler ( abbreviated as AgCuTip filler ). The microstructure and mechanical performance of the brazed joint were investigated by scanning electron microscope ( SEM ) , energy dispersive spectrometer ( EDS ) and shear strength test. Typical interfacial microstructure of Cu/AgCuTip/Al2O3 brazed joint is Cu/diffusion layer/Cu-based solid solution + Ag-based solid solution+Ti2 Cu +Ti3( Cu, Al) 3 O/Al2 O3 . The addition of nano-Al2 O3 can improve the interfacial microstructure by inhibiting the growth of reaction layer near Al2 O3 ceramic side, and promoting the formation of dispersed Ti2 Cu phase in brazing seam. Moreover, both thickness of diffusion layer and Ti3(Cu, Al)3O reaction layer thickened with an increasing holding time. Excessive dissolution of copper was occurred when holding time reached 20 min, which

  14. Sistema traductor de la lengua de señas colombiana a texto basado en FPGA

    Directory of Open Access Journals (Sweden)

    Juan David Guerrero-Balaguera

    2015-01-01

    Full Text Available Este trabajo presenta el desarrollo de un sistema diseñado para facilitar la comunicación e interacción de personas con discap acidad auditiva severa con las demás personas. El sistema emplea técni cas de visión artificial para el reconocimiento de las señas es táticas de la Lengua de Señas Colombiana (LSC. El sistema tiene cuatro etapa s: Captura de la imagen, preprocesamiento, extracción de características y reconocimiento. La imagen es capturada median te una cámara digital TRDBD5M diseñada para tarjetas de desarr ollo de DE1 y DE2 Altera. En la etapa de preprocesamiento, la seña es extraída del fondo de la imagen mediante el método de segmen tación por umbral; posteriormente, la ima gen segmentada es filtrada us ando una operación morfológica para eliminar el ruido. La etapa de extracción de características está basada en la creación de dos vectores que caracterizan la forma de la mano mediante la que se realiza la seña. La etapa de reconocimiento está constituida por una red n euronal artificial perceptrón multicapa (MLP, la cual actúa co mo clasificador. El sistema fue imp lementado en el dispositivo FPG A Cyclone II EP2C70F896C6 y no requiere el uso de guantes o marcadores visuales para su correcto funcionamiento. Los result ados muestran que el sistema tiene la capacidad para reconocer todas las 23 señas estáticas de la LSC con una taza de reconocimiento del 98.15 %.

  15. Enfermos de amor: ¿Cómo se negocia la identidad en la modernidad colonial?

    Directory of Open Access Journals (Sweden)

    Roberto Pineda Camacho

    1992-05-01

    Full Text Available Los pueblos nativos perciben su historia a través de diversas tramas simbólicas de carácter oral, que condensan su experiencia pasada y presente, y permiten prever algunos de sus posibles caminos "futuros". En este sentido, las "historias de animales" constituyen un marco de referencia privilegiado, no solamente como fábula que transmiten de manera metafórica la experiencia del mundo, sino también en cuanto a que los animales son -fundamentalmente- "destinos humanos", formas de existencia, posibilidades de identidad, a las cuales los hombres pueden acceder, de acuerdo con su comportamiento específico en el mundo.  El presente trabajo se propone explorar aspectos de esta temática, tomando como base de referencia las historias y comportamientos asociados al bugeo o delfín de agua dulce, en el "area huitoto".

  16. Cs3Sm7Se12

    Directory of Open Access Journals (Sweden)

    Christof Schneck

    2012-01-01

    Full Text Available The title compound, tricaesium heptasamarium(III dodecaselenide, is setting a new starting point for realization of the channel structure of the Cs3M7Se12 series, now with M = Sm, Gd–Er. This Cs3Y7Se12-type arrangement is structurally based on the Z-type sesquiselenides M2Se3 adopting the Sc2S3 structure. Thus, the structural set-up of Cs3Sm7Se12 consists of edge- and vertex-connected [SmSe6]9− octahedra [dØ(Sm3+ – Se2− = 2.931 Å], forming a rock-salt-related network [Sm7Se12]3− with channels along [001] that are apt to take up monovalent cations (here Cs+ with coordination numbers of 7 + 1 for one and of 6 for the second cation. The latter cation has a trigonal–prismatic coordination and shows half-occupancy, resulting in an impossible short distance [2.394 (4 Å] between symmetrically coupled Cs+ cations of the same kind. While one Sm atom occupies Wyckoff position 2b with site symmetry ..2/m, all other 11 crystallographically different atoms (namely 2 × Cs, 3 × Sm and 6 × Se are located at Wyckoff positions 4g with site symmetry ..m.

  17. Cs(3)Sm(7)Se(12).

    Science.gov (United States)

    Schneck, Christof; Elbe, Andreas; Schurz, Christian M; Schleid, Thomas

    2012-01-01

    The title compound, tricaesium hepta-samarium(III) dodeca-selenide, is setting a new starting point for realization of the channel structure of the Cs(3)M(7)Se(12) series, now with M = Sm, Gd-Er. This Cs(3)Y(7)Se(12)-type arrangement is structurally based on the Z-type sesquiselenides M(2)Se(3) adopting the Sc(2)S(3) structure. Thus, the structural set-up of Cs(3)Sm(7)Se(12) consists of edge- and vertex-connected [SmSe(6)](9-) octa-hedra [d(Ø)(Sm(3+) - Se(2-)) = 2.931 Å], forming a rock-salt-related network [Sm(7)Se(12)](3-) with channels along [001] that are apt to take up monovalent cations (here Cs(+)) with coordination numbers of 7 + 1 for one and of 6 for the second cation. The latter cation has a trigonal-prismatic coordination and shows half-occupancy, resulting in an impossible short distance [2.394 (4) Å] between symmetrically coupled Cs(+) cations of the same kind. While one Sm atom occupies Wyckoff position 2b with site symmetry ..2/m, all other 11 crystallographically different atoms (namely 2 × Cs, 3 × Sm and 6 × Se) are located at Wyckoff positions 4g with site symmetry ..m.

  18. Doping of CdSe Nanocrystals

    Science.gov (United States)

    Jensen, John

    2003-10-01

    What happens to a nanocrystal when it is doped with electrons? We doped CdSe nanocrystals with potassium metal and sodium biphenyl, potassium and sodium acting as the charge carriers. In order to monitor the properties of the doped nanocrystals we used Electron Spin Resonance and luminescence techniques. In this poster we present findings and problems encountered in doping CdSe nanocrystals.

  19. Preparation of CdSe/ZnSe Core-shell Nanocrystal in One-step Reaction

    Institute of Scientific and Technical Information of China (English)

    FEI Xiao-fang; SHAN Gui-ye; KONG Xiang-gui; WANG Xin; ZENG Qing-hui; ZHANG You-lin

    2005-01-01

    High-quality Zn-doped CdSe core-shell nanocrystals were successfully prepared by incorporating a stoichiometric amount of Zn precursor into the CdSe reaction system, in which the Se precursor was excess and an Se-rich surface was formed. By injecting different amounts of Zn precursor, the core-shell nanocrystals demonstrated by the emission spectra were formed. The obtained Zn-doped CdSe nanocrystals exhibit a photoluminescence efficiency from 30% to 85%, which is comparable to those for the reported CdSe/ZnS, CdSe/CdS in the literature. In particular, a shell ZnSe layer with different thicknesses of ZnSe can be formed in this experiment by only changing the amount of Zn precursor added, which is simple and effective.

  20. One-step synthesis of PbSe-ZnSe composite thin film

    Science.gov (United States)

    2011-01-01

    This study investigates the preparation of PbSe-ZnSe composite thin films by simultaneous hot-wall deposition (HWD) from multiple resources. The XRD result reveals that the solubility limit of Pb in ZnSe is quite narrow, less than 1 mol%, with obvious phase-separation in the composite thin films. A nanoscale elemental mapping of the film containing 5 mol% PbSe indicates that isolated PbSe nanocrystals are dispersed in the ZnSe matrix. The optical absorption edge of the composite thin films shifts toward the low-photon-energy region as the PbSe content increases. The use of a phase-separating PbSe-ZnSe system and HWD techniques enables simple production of the composite package. PMID:21711822

  1. One-step synthesis of PbSe-ZnSe composite thin film

    Directory of Open Access Journals (Sweden)

    Abe Seishi

    2011-01-01

    Full Text Available Abstract This study investigates the preparation of PbSe-ZnSe composite thin films by simultaneous hot-wall deposition (HWD from multiple resources. The XRD result reveals that the solubility limit of Pb in ZnSe is quite narrow, less than 1 mol%, with obvious phase-separation in the composite thin films. A nanoscale elemental mapping of the film containing 5 mol% PbSe indicates that isolated PbSe nanocrystals are dispersed in the ZnSe matrix. The optical absorption edge of the composite thin films shifts toward the low-photon-energy region as the PbSe content increases. The use of a phase-separating PbSe-ZnSe system and HWD techniques enables simple production of the composite package.

  2. Synthesis and characterization of ZnSe:Fe/ZnSe core/shell nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Lin; Zhu, Jianguo, E-mail: yanglin_1028@163.com; Xiao, Dingquan

    2014-04-15

    High-quality ZnSe:Fe/ZnSe core/shell nanocrystals were prepared via a hydrothermal microemulsion technique. Effective surface passivation of monodisperse ZnSe:Fe nanocrystals is achieved by overcoating them with a ZnSe shell. The samples were characterized by means of XRD, EDX, TEM, PSD, XPS, photoluminescence, and Raman spectrum. The results show that the as-synthesized nanocrystals are cubic zinc blende ZnSe structure with high purity and the average particle size of ZnSe:Fe/ZnSe core/shell nanocrystal is larger than that of ZnSe:Fe core. The growth of ZnSe shell causes a small red shift in PL spectra, and then the PL quantum yield (QY) increases from 16% before shell growth to the maximum of 37% after increasing shell thickness up to 1.2 monolayers (ML). Moreover, both transverse optic (TO) and longitudinal optic (LO) phonon modes of ZnSe are shifted toward lower frequency as compared with the reported ones. -- Highlights: • ZnSe:Fe/ZnSe core/shell QDs were prepared by a hydrothermal microemulsion method. • ZnSe shell efficiently passivates surface defects by serving as a physical barrier. • The particle size and PL properties can be turned with the growth of ZnSe shell. • The luminescence efficiency and stability of QDs could be improved in this manner.

  3. Thermodynamic properties of SeS

    Energy Technology Data Exchange (ETDEWEB)

    Huang, M.D.

    1977-12-01

    Mass-spectrometry and Knudsen effusion experiments were used to study the equilibrium partial pressure of SeS formed by reaction of S/sub 2/ and Se/sub 2/ which were produced by thermally decomposing a mixture of In/sub 2/S/sub 3/ and In/sub 2/Se/sub 3/ in a Knudsen effusion cell. The heat of formation of SeS(g) was determined by the second law method to be -0.6 +- 3 kcal/mole. The entropy of formation of SeS(g) was calculated from spectrographic data in Ahmed and Barrow to be 1.5 cal/degree-mole at 298/sup 0/K.

  4. Cs2UPd3Se6

    Directory of Open Access Journals (Sweden)

    George N. Oh

    2011-02-01

    Full Text Available Dicaesium uranium(IV tripalladium(II hexaselenide, Cs2UPd3Se6, crystallizes in the space group Fmmm in the Ba2NaCu3O6 structure type. The asymmetric unit comprises the following atoms with site symmetries as shown: U1 (mm2, Cs1 (222, Cs2 (m2m, Pd1 (.m., Pd2 (2mm, Se1 (m.., and Se2 (1. This layered structure contains six edge-sharing square-planar [PdSe4] units that form a hexagon. These, in turn, edge-share with [USe6] trigonal–prismatic units, forming an extended layer parallel to (010. The layers are stacked along [010]. They are staggered, and are separated by the Cs atoms. The Cs atoms are either coordinated in a square antiprism of Se atoms or are ten-coordinate, with one square face and the opposite face hexagonal.

  5. Planificación de talleres para padres de familia en donde se analice la inteligencia emocional y su importancia para el desarrollo de las habilidades sociales en niños y niñas en edad preescolar

    OpenAIRE

    Madrigal Corrales, María Elena; Garro Jiménez, Yancy Lineth

    2014-01-01

    El presente trabajo se encuentra fundamentado en la necesidad que existe de valorar la inteligencia emocional como una capacidad o habilidad que debe ser estimulada en los niños y niñas desde el ámbito familiar. Para ello, se diseña, bajo la modalidad de taller, una propuesta para padres de familia, basado, principalmente, en un diagnóstico previo realizado en el kinder La Casita del Zapato, el cual se ubica en San Ramón de Alajuela, y el kinder Escuela Santa Rosa Abajo, ubi...

  6. Entendimento do termo de consentimento por pacientes partícipes em pesquisas com fármaco na cardiologia La comprensión del formulario de consentimiento por los pacientes que forman parte de investigaciones con fármaco en la cardiología Informed consent as viewed by patients participating in cardiology drug trial

    Directory of Open Access Journals (Sweden)

    Silmara Meneguin

    2010-01-01

    Informado (FCI es fundamental para que se preserve la ética, sin embargo por su complexidad él puede no comprenderse completamente. En este estudio, evaluamos la comprensión del FCI por parte del paciente. OBJETIVO: Abordamos la cuestión sobre el nivel de comprensión de los pacientes respecto a los estudios basados en el Consentimiento Informado. MÉTODOS: INVITamos a los participantes de investigación clínica fase II, III y IV con fármacos para responder un cuestionario estructurado con 29 cuestiones, tales como: ¿Por qué aceptó participar?¿Leyó el FCI antes de firmarlo?¿Al firmarlo estaba seguro de haberlo entendido? Ochenta individuos (20 mujeres y 60 varones comparecieron, en un total de 106 pacientes. Las variables de cada cuestión se llevaron a cabo por frecuencia de ocurrencia. La comparación entre los promedios entre los grupos se realizó mediante las pruebas t de Student o Wilcoxon; y para asociaciones, el Chi-cuadrado o Razón de Verosimilitud, o prueba exacta de Fisher. RESULTADOS: El promedio de las edades fue de 58,7 ± 9,3 años. De las motivaciones para participar en la investigación, el 66,2% señaló su propio beneficio; un 42,5%, el bien de la ciencia; un 25,0% alegó atender a una petición de su médico; el 50% no comprendió correctamente el FCI; y un 32,9% tampoco leyó el formulario, pero lo firmó. Entre los que recibieron placebo tras la randomización (n = 47, un 66,7% no entendió el significado de este término. Hubo una fuerte correlación entre las personas que no entendían el significado de placebo con la escolaridad (p = 0,02, evidenciando que cuanto menor era el nivel de instrucción, menor era la comprensión. CONCLUSIÓN: EL FCI es poco comprendido por los pacientes y para algunos de ellos la confianza en el médico tuvo impacto en la decisión de participar en el ensayo clínico con fármaco, habiendo también influencia del nivel de instrucción de los sujetos en la comprensión del término "placebo".BACKGROUND: In

  7. Fabricación de material de referencia 72a (aleación Cu-Al) utilizando la técnica de aleación mecánica

    OpenAIRE

    Herrera-Basurto, Raúl; Salas, J A; Martínez, F

    2013-01-01

    Los materiales de referencia empleados para la técnica de discriminación de energía de rayos X (EDE) requieren que su homogeneidad satisfaga los análisis químicos en regiones de aproximadamente 1 a 3 mm de diámetro, condición que la técnica de preparación de aleación mecánica (AM) cumple satisfactoriamente. El material de referencia 72a consiste de una aleación binaria de composición química nominal de Cu – 10 % kg/kg Al. Se preparó el material mezclando la cantidad respectiva de ...

  8. Fabricación de material de referencia 72a (aleación Cu-Al) utilizando la técnica de aleación mecánica

    OpenAIRE

    Herrera-Basurto, Raúl; Salas, J A; Martínez, F.

    2013-01-01

    Los materiales de referencia empleados para la técnica de discriminación de energía de rayos X (EDE) requieren que su homogeneidad satisfaga los análisis químicos en regiones de aproximadamente 1 a 3 mm de diámetro, condición que la técnica de preparación de aleación mecánica (AM) cumple satisfactoriamente. El material de referencia 72a consiste de una aleación binaria de composición química nominal de Cu – 10 % kg/kg Al. Se preparó el material mezclando la cantidad respectiva de ...

  9. "La `historia´ de los señores étnicos de Casabindo y Cochinoca (1540-1662"

    Directory of Open Access Journals (Sweden)

    Silvia Palomeque

    2006-01-01

    Full Text Available La recuperación y el análisis histórico del relato de los ancianos indígenas del pueblo de Casabindo en 1662 sobre la historia de su pueblo y de sus autoridades desde el fin del "tiempo del inca", conforman las preocupaciones centrales de este artículo. Durante su desarrollo se avanza en la inclusión de la historia de este grupo indígena dentro de la historia política y militar del largo y confuso período de la invasión española sobre las poblaciones indígenas de este pueblo en particular y también de los localizados en zonas vecinas, que habitaban los territorios que actualmente forman parte del norte de Argentina, de Chile y del sur de Bolivia. Esta búsqueda de comprensión y de inclusión de los relatos provenientes de los indígenas obliga a recuperar, modificar y reinterpretar los relatos históricos habituales sobre la historia provincial de Jujuy en el período de la conquista definitiva de los españoles sobre esta zona, donde se tendía a recuperar la visión proveniente de sus últimos conquistadores, que podríamos denominarlos como los vecinos de la Gobernación del Tucumán, soslayando la participación de otras huestes y autoridades coloniales como las de los vecinos de Charcas. Un reconocimiento minucioso del accionar de diversas huestes y autoridades coloniales y el ir relacionando la documentación generada con los diversos intereses en pugna, permite comenzar un nuevo tipo de análisis sobre los documentos relativos al accionar de las sociedades indígenas que, hasta el momento, sólo brindaban informaciones que se entendían como contradictorias o que reflejaban un alto grado de desestructuración de las sociedades indígenas.

  10. ¿Cómo en el ejercicio de la práctica de modelación de un sistema de resortes se construyen modelos multilineales?

    OpenAIRE

    Méndez, María Esther Magali; Arrieta, Jaime

    2007-01-01

    Este artículo se desprende de una investigación realizada por Mendez (2006), la cual se desarrolló bajo una visión socioepistemológica y se inscribe en la línea de investigación llamada las prácticas sociales en la emergencia del conocimiento matemático. El objetivo de la investigación fue aportar evidencias sobre cómo los estudiantes del nivel medio superior, construyen lo multilineal en el ejercicio de la modelación de un sistema de resortes. La tesis central que se planteó es que lo multil...

  11. One-step synthesis of PbSe-ZnSe composite thin film

    OpenAIRE

    2011-01-01

    Abstract This study investigates the preparation of PbSe-ZnSe composite thin films by simultaneous hot-wall deposition (HWD) from multiple resources. The XRD result reveals that the solubility limit of Pb in ZnSe is quite narrow, less than 1 mol%, with obvious phase-separation in the composite thin films. A nanoscale elemental mapping of the film containing 5 mol% PbSe indicates that isolated PbSe nanocrystals are dispersed in the ZnSe matrix. The optical absorption edge of the composite thin...

  12. A transferable force field for CdS-CdSe-PbS-PbSe solid systems

    OpenAIRE

    Fan, Zhaochuan; Koster, Rik S.; Wang, Shuaiwei; Fang, Changming; Anil O. Yalcin; Frans D. Tichelaar; Zandbergen, Henny W.; Van Huis, Marijn A.; Vlugt, Thijs J H

    2014-01-01

    A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., "Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth," Nano Lett. 14, 3661-3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and C...

  13. Al/CdSe/GaSe/C resonant tunneling thin film transistors

    Science.gov (United States)

    Qasrawi, A. F.; Kayed, T. S.; Elsayed, Khaled A.

    2017-02-01

    An Al/CdSe/GaSe/C thin film transistor device was prepared by the physical vapor deposition technique at a vacuum pressure of 10-5 mbar. The x-ray diffraction measurements demonstrated the polycrystalline nature of the surface of the device. The dc current-voltage characteristics recorded for the Al/CdSe/C and Al/CdSe/GaSe/C channels displayed a resonant tunneling diode features during the forward and reverse voltage biasing, respectively. In addition, the switching current ratio of the Al/CdSe/C increased from 18.6 to 9.62×103 as a result of the GaSe deposition on the CdSe surface. Moreover, the alternating electrical signal analyses in the frequency range of 1.0 MHz to 1.8 GHz, showed some remarkable properties of negative resistance and negative capacitance spectra of the Al/CdSe/GaSe/C thin film transistors. Two distinct resonance-antiresonance phenomena in the resistance spectra and one in the capacitance spectra were observed at 0.53, 1.04 and 1.40 GHz for the Al/CdSe/C channel, respectively. The respective resonating peak positions of the resistance spectra shift to 0.38 and 0.95 GHz when GaSe is interfaced with CdSe. These features of the thin film transistors are promising for use in high quality microwave filtering circuits and also for use as ultrafast switches.

  14. El camuflaje (1980-2010) como forma de apropiación de otras ilusiones ópticas

    OpenAIRE

    IRACHETA, MARÍA

    2013-01-01

    NOTA 520 8 Esta tesis toma como referencia el estudio de las ilusiones ópticas para profundizar en una de ellas —el camuflaje—, dada su vigencia en la sociedad de la ocultación y la pérdida de identidad del siglo XXI. Se ha observado también que este fenómeno óptico es una de las ilusiones que más absorbe del resto, por lo cual se considera como una de las formas de apropiacionismo tan extendido en el arte actual. Las ilusiones han formado y forman parte del imaginario de la historia del ho...

  15. Los Partidos Políticos y su crisis de representatividad en México.

    OpenAIRE

    2016-01-01

    Existe un sinnúmero de literatura empírica dedicada al estudio de los partidos políticos, en virtud de la cual se afirma que el desempeño de dichas organizaciones de intermediación en los sistemas democráticos contemporáneos, se encuentra en franco declive. Por lo tanto, una nueva mirada a estos actores políticos resulta pertinente, ya que estos forman parte del grupo de instituciones esenciales e imprescindibles para el funcionamiento de la democracia representa...

  16. El camuflaje (1980-2010) como forma de apropiación de otras ilusiones ópticas

    OpenAIRE

    Iracheta, María de

    2013-01-01

    NOTA 520 8 Esta tesis toma como referencia el estudio de las ilusiones ópticas para profundizar en una de ellas —el camuflaje—, dada su vigencia en la sociedad de la ocultación y la pérdida de identidad del siglo XXI. Se ha observado también que este fenómeno óptico es una de las ilusiones que más absorbe del resto, por lo cual se considera como una de las formas de apropiacionismo tan extendido en el arte actual. Las ilusiones han formado y forman parte del imaginario de la historia del ho...

  17. Las bebidas indígenas fermentadas y los patrones de consumo de alcohol de los grupos étnicos

    OpenAIRE

    Luis Berruecos Villalobos

    2007-01-01

    En esta presentación, abordaremos tanto las bebidas tradicionales no comerciales, como las que, inventadas en otras regiones, han llegado a nuestro país y se utilizan de manera frecuente, por lo cual ya forman parte de nuestras tradiciones. Contamos con la información, pero no se incluye por falta de espacio, de los nombres originales, los lugares de producción, su forma de elaboración y el tipo de consumo. Cabe hacer notar que tanto las bebidas alcohólicas como las no alcohólicas tradicional...

  18. Caracterización de hidrogeles de quitosano-alcohol polivinílico obtenidos por radiación gamma

    OpenAIRE

    2006-01-01

    Se han obtenido hidrogeles de quitosano con alcohol polivinílico (PVA) utilizando radiación gamma. Se presenta un análisis preliminar del tipo de interacción entre las cadenas de quitosano y del PVA en estos hidrogeles. El quitosano en solución disminuye rápidamente su peso molecular por efecto de la radiación gamma, mientras que el PVA en solución acuosa forma hidrogeles luego de ser irradiadas a dosis mayores a 5 kGy. Sin embargo, las mezclas de quitosano y PVA forman hidrogeles en los cual...

  19. Adsorción y desorción de fósforo en suelos del área central de la región pampeana

    OpenAIRE

    Silva Rossi, Martín María

    2011-01-01

    Tesis (Doctor en Ciencias Agropecuarias)--UNC- Facultad de Ciencias Agropecuarias, 2011. Luego de la aplicación de una fuente fosfatada al suelo, se producen una serie de reacciones, las cuales generan productos con distinto grado de solubilidad. Compuestos más solubles se forman en reacciones más rápidas que los menos solubles. La capacidad de un suelo de proveer fósforo a los cultivos, depende de la cantidad y velocidad de desorción. Este trabajo s...

  20. Las canastas comunitarias en Ecuador : una apuesta por la salud, la economía y la solidaridad

    Directory of Open Access Journals (Sweden)

    Sandra Garcés Jaramillo

    2013-09-01

    Full Text Available Una canasta comunitaria, o “canasta”, es una organización popular urbana de consumidores (mujeres y hombres, principalmente de los sectores populares del país. Durante el estudio, se ubicaron canastas comunitarias en la Sierra y Costa ecuatoriana, cada una de ellas conformada por grupos de 15 a 400 familias. Es claro que inicialmente las familias que forman parte de las canastas se unen a ellas por los beneficios prácticos y motivos individuales, los cuales son urgentes y tangibles como el ahorro económico, el ahorro de tiempo y el mejoramiento de la salud.

  1. Injection of majority carriers through InSe-GaSe heterojunctions

    Energy Technology Data Exchange (ETDEWEB)

    Bakumenko, V.L.; Tagaev, V.G.

    1982-10-01

    Injection of majority carriers through heterojunction under intensive illumination conditions is discussed. Experimental results of injection of majority carriers through InSe-GaSe heterojunctions have been presented.

  2. Lattice dynamics of a simple GaSe-InSe superlattice

    Science.gov (United States)

    Schwarcz, R.; Kanehisa, M. A.

    1994-11-01

    A simple linear chain model is used to calculate the phonon dispersion curves for a superlattice composed of one layer of GaSe and one layer of InSe alternatively stacked along the c-axis. The resultant acoustic modes are essentially averages of the two constituents. Most optical modes are found to be confined in either GaSe layers of InSe layers. However, some low energy-optical modes have contributions from the two constituents.

  3. Papel de la leptina como señal aferente en la regulación de la homeostasis energética

    Directory of Open Access Journals (Sweden)

    José María Basain Valdés

    Full Text Available La obesidad es una enfermedad crónica caracterizada por un aumento patológico de grasa corporal generado por un desbalance entre los ingresos y los egresos energéticos; este exceso de energía se almacena en el tejido adiposo, el cual no solo almacena lípidos, sino que secreta numerosas hormonas, por lo que constituye el órgano endocrino de mayor tamaño del organismo. A diferencia de otras glándulas endocrinas, su masa es variable y puede aumentar o disminuir progresivamente de tamaño dependiendo de la edad, la ingesta alimentaria, la actividad física, la programación perinatal y la predisposición genética; se destaca dentro de los factores secretados la leptina, la cual participa en la regulación del balance energético y la secreción de gonadotropinas.El objetivo de la presente revisión bibliográfica es describir el papel de la leptina como señal aferente en la regulación de la homeostasis energética, y se destaca su importancia como uno de los mecanismos implicados en la patogénesis de la obesidad.

  4. Structural and optical properties of ZnSe thin films stacked with PbSe submonolayers

    Science.gov (United States)

    Manonmani Parvathi, M.; Arivazhagan, V.; Rajesh, S.

    2014-09-01

    Structural and optical properties of Zinc Selenide (ZnSe) thin films stacked with multiple Lead Selenide (PbSe) submonolayers (ML) were studied. Thermal evaporation was preferred to produce ZnSe-PbSe thin films with the PbSe ML thickness ranges from 2.5 to 10 nm. Polycrystalline nature of the ZnSe was revealed through high resolution X-ray diffractometer measurement. The development of micro strain at the interfaces with increasing PbSe ML thickness was observed. A cross-sectional TEM image shows well-ordered periodicity and reproducibility of the layer thickness. The enhancement of optical absorption of ZnSe was identified upon stacking of PbSe ML. The evidence for quantum confinement in PbSe ML was revealed by the obtained red shift in band gap (2.5-1.8 eV) values as well as photoluminescence emission at 1,071 nm. The presence of tensile strain in the ZnSe layers upon staking of PbSe ML was discussed by the shift in LO phonon modes in Raman spectra.

  5. Thermal transport in monolayer InSe

    Science.gov (United States)

    Nissimagoudar, Arun S.; Ma, Jinlong; Chen, Yani; Li, Wu

    2017-08-01

    Two-dimensional InSe, a recently synthesized semiconductor having a moderate band gap, has gained attention due to its ultra high mobility and high photo-responsivity. In this work, we calculate the lattice thermal conductivity (κ) of monolayer InSe by solving the phonon Boltzmann transport equation (BTE) with first-principles calculated inter atomic force constants. κ of monolayer InSe is isotropic and found to be around 27.6 W m K-1 at room temperature along the in-plane direction. The size dependence of κ shows the size effect can persist up to 20 μm. Further, κ can be reduced to half by tuning the sample size to 300 nm. This low value suggests that κ might be a limiting factor for emerging nanoelectronic applications of monolayer InSe.

  6. The system SnSe-Bi

    Energy Technology Data Exchange (ETDEWEB)

    Alidzhanov, M.A.; Alizade, M.Z.; Aslanov, G.A.; Gurshumov, A.P.; Persakhova, A.Y.

    1986-10-01

    The authors study the system SnSe-Bi on annealed samples by methods of physicochemical analysis; x-ray phase, differential-thermal analysis, microstructural analysis, and measurements of the microhardness. It was established that the eutectic contains five mole % SnSe and melts at 260 C. A bounded region of the SnSe-based solid solutions exist, and the solubility of SnSe in bismuth was not observed. Anomalies in the temperature dependences of the thermo-emf and electrical conductivity of the solid solutions were determined by the phase transformations of tin monoselenide. The nature of the changes in the thermo-emf and the electrical conductivity as a function of the temperature is associated with the changes in the density and effective mass of the charge carriers.

  7. Solving the shape conundrum in $^{70}$Se

    CERN Multimedia

    We propose a multi-step Coulomb-excitation study of $^{70}$Se at HIE-ISOLDE using the $^{208}$Pb( $^{70}$Se, $^{70}$Se*)$^{208}$Pb* reaction at a safe energy of 5.0 MeV/u. We aim at a precise measurement of the $\\left \\langle 2^{+}_{1} \\hspace{0.1cm} || \\hspace{0.1cm}\\hat{E}2 \\hspace{0.1cm} || \\hspace{0.1cm}2^{+}_{ 1} \\right \\rangle$ diagonal matrix element as well as gaining information on additional matrix elements. Such information will shed light onto the shape conundrum of the 2$^{+}_{1}$ state in $^{70}$Se as well as foreseeing the opportunity for a more detailed understanding of the shape-coexistence phenomenon in this region.

  8. Optical anisotropy in GaSe

    Energy Technology Data Exchange (ETDEWEB)

    Seyhan, A.; Karabulut, O.; Akinoglu, B.G.; Aslan, B.; Turan, R. [Department of Physics, Middle East Technical University, 06531, Ankara (Turkey)

    2005-09-01

    Optical anisotropy of the layer semiconductor GaSe has been studied by photoluminescence (PL) and Fourier Transform Infrared Spectroscopy (FTIR). The PL spectra are dominated by two closely positioned emission bands resulting from the free exciton and the bound exciton connected direct band edge of GaSe. Photoluminescence and transmission spectra of GaSe crystals have been measured for two cases in which the propagation vector k is perpendicular (k perpendicular to c) and parallel to the c-axis (k//c). Peak position of the PL emission band and the onset of the transmission have been found to be significantly different for these two cases. This observed anisotropy is related to anisotropic band structure and the selection rules for the optical absorption in layered GaSe. FTIR transmission spectrum is in good agreement with PL results. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Double electron capture searches in $^{74}$Se

    CERN Document Server

    Lehnert, B; Degering, D; Sommer, D; Wagner, L; Zuber, K

    2016-01-01

    A search for various double electron capture modes of $^{74}$Se has been performed using an ultralow background Ge-detector in the Felsenkeller laboratory, Germany. Especially for the potentially resonant transition into the 1204.2 keV excited state of $^{74}$Ge a lower half-life limit of $0.70\\cdot 10^{19}$ yr (90% credibility) has been obtained. Serious concerns are raised about the validity of obtained $^{74}$Se limits in some recent publications.

  10. Amphoteric CdSe nanocrystalline quantum dots.

    Science.gov (United States)

    Islam, Mohammad A

    2008-06-25

    The nanocrystal quantum dot (NQD) charge states strongly influence their electrical transport properties in photovoltaic and electroluminescent devices, optical gains in NQD lasers, and the stability of the dots in thin films. We report a unique electrostatic nature of CdSe NQDs, studied by electrophoretic methods. When we submerged a pair of metal electrodes, in a parallel plate capacitor configuration, into a dilute solution of CdSe NQDs in hexane, and applied a DC voltage across the pair, thin films of CdSe NQDs were deposited on both the positive and the negative electrodes. Extensive characterizations including scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FTIR) and Raman studies revealed that the films on both the positive and the negative electrodes were identical in every respect, clearly indicating that: (1) a fraction (<1%) of the CdSe NQDs in free form in hexane solution are charged and, more importantly, (2) there are equal numbers of positive and negative CdSe NQDs in the hexane solution. Experiments also show that the number of deposited dots is at least an order of magnitude higher than the number of initially charged dots, indicating regeneration. We used simple thermodynamics to explain such amphoteric nature and the charging/regeneration of the CdSe NQDs.

  11. Compression of klockmannite, CuSe

    Science.gov (United States)

    Peiris, Suhithi M.; Pearson, Tania T.; Heinz, Dion L.

    1998-07-01

    Copper selenide (CuSe) was compressed in a diamond anvil cell at room temperature up to a pressure of 52 GPa and studied using energy dispersive x-ray diffraction and Raman spectroscopy. CuSe is nearly isostructural with copper sulfide (CuS), and a previous study indicates that copper sulfide undergoes reversible pressure-induced amorphization at 18 GPa. The intensity of the x-ray diffraction peaks for CuSe decrease slowly, however, they never completely disappear up to a pressure of 52 GPa. The third-order Birch-Murnaghan equation of state fit to the data yields K0=96.9±5.3 GPa and K0'=4.1±0.5. Vinet's universal equation of state yields essentially identical parameters. Raman spectroscopy demonstrates that upon compression, the S-S bond in CuS compresses differently than the Se-Se bond in CuSe, possibly accounting for the different high pressure behavior of these two very similar compounds.

  12. Sb2Se3 under pressure

    Science.gov (United States)

    Efthimiopoulos, Ilias; Zhang, Jiaming; Kucway, Melvin; Park, Changyong; Ewing, Rodney C.; Wang, Yuejian

    2013-01-01

    Selected members of the A2B3 (A = Sb, Bi; B = Se, Te) family are topological insulators. The Sb2Se3 compound does not exhibit any topological properties at ambient conditions; a recent high-pressure study, however, indicated that pressure transforms Sb2Se3 from a band insulator into a topological insulator above ~2 GPa; in addition, three structural transitions were proposed to occur up to 25 GPa. Partly motivated by these results, we have performed x-ray diffraction and Raman spectroscopy investigations on Sb2Se3 under pressure up to 65 GPa. We have identified only one reversible structural transition: the initial Pnma structure transforms into a disordered cubic bcc alloy above 51 GPa. On the other hand, our high-pressure Raman study did not reproduce the previous results; we attribute the discrepancies to the effects of the different pressure transmitting media used in the high-pressure experiments. We discuss the structural behavior of Sb2Se3 within the A2B3 (A = Sb, Bi; B = Se, Te) series. PMID:24045363

  13. Biomineralization of Se Nanoshpere by Bacillus Licheniformis

    Institute of Scientific and Technical Information of China (English)

    Yongqiang Yuan; Jianming Zhu; Congqiang Liu; Shen Yu; Lei Lei

    2015-01-01

    Biological dissimilatory reduction of selenite (SeO32-) to elemental selenium (Se0) is com-mon, but the mineral formation and the biogenic process remain uncertain. In this study, we examined the Se0 formation during the selenite bioreduction by Bacillus licheniformis SeRB-1 through transmis-sion electron microscope (TEM), energy-dispersive spectrometry (EDS) and X-ray absorption fine structure (XAFS) techniques. Results showed that the reduction process occurred mostly during the exponential phase and early stationary phase, whilst the elemental selenium was produced in these pe-riods. From the TEM images and polyacrylamide gel electropheresis, it is known that the Se0 granule formation is a biologically-induced type, and the cell envelopes are the main biomineralization positions, and particles may go through a process from nucleation to crystallization, under the control of mi-crobes. In fact, the minerals are spherical nanoparticles, occurring as a microcrystal or amorphous form. It is vital to recognize which kinds of proteins and/or polysaccharides act as a template to direct nanoparticle nucleation and growth? This should focus for further studies. This study may shed light on the process of formation of Se(0) nanosphere.

  14. Quando a escritura se quebra nas ondas

    Directory of Open Access Journals (Sweden)

    Cleonice Paes Barreto Mourão

    2005-12-01

    Full Text Available Desviando-se da estrutura tradicional do romance, Virginia Woolf, em As ondas, põe em cena seis vozes cujas falas executam um movimento contínuo de retração e distenção – movimento das ondas. As falas não estabelecem diálogo, apenas se tocam para um novo relance, revivem o passado contraído no presente e no futuro, cada uma delas marcada por pontos de intensidade, revivências que se repetem por não poderem ser substituídas. O cenário onde se desenrolam as falas é construído por uma narradora que limita o tempo aopercurso de um dia, sempre à beira-mar. Metáfora maior da escritura, o mar se derrama sobre as falas e aí produz um efeito de liquefação: desmancham-se os vetores do tempo, do espaço e das situações, para deixar na superfície a profusão de palavras que sobrenadam os acontecimentos revivenciados.

  15. Exciton-Phonon Scattering in CdSe/ZnSe Quantum Dots

    Institute of Scientific and Technical Information of China (English)

    张立功; 申德振; 范希武; 吕少哲

    2002-01-01

    A temperature-dependent photoluminescence measurement is performed in CdSe/ZnSe quantum dots with a ZnCdSe quantum well. We deduce the temperature dependence of the exciton linewidth and peak energy of the zero-dimensional exciton in the quantum dots and two-dimensional exciton in the CdSe wetting layer. The experimental data reveal a reduction of homogeneous broadening of the exciton line in the quantum dots in comparison with that in the two-dimensional wetting layer, which indicates the decrease of exciton and optical phonon coupling in the CdSe quantum dots.

  16. Atomistic Model of Physical Ageing in Se-rich As-Se Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Golovchak,R.; Shpotyuk, O.; Kozdras, A.; Bureau, B.; Vlcek, M.; Ganjoo, A.; Jain, H.

    2007-01-01

    Thermal, optical, X-ray excited and magnetic methods were used to develop a microstructural model of physical ageing in Se-rich glasses. The glass composition As10Se90, possessing a typical cross-linked chain structure, was chosen as a model object for the investigations. The effect of physical ageing in this glass was revealed by differential scanning calorimetry, whereas the corresponding changes in its atomic arrangement were studied by extended X-ray absorption fine structure, Raman and solid-state 77Se nuclear magnetic resonance spectroscopy. Straightening-shrinkage processes are shown to be responsible for the physical ageing in this Se-rich As-Se glass.

  17. Ser mujer se aprende, enseña, disfruta y sufre. Telenovela, cultura e identidad de género

    Directory of Open Access Journals (Sweden)

    María Rebeca Padilla de la Torre

    2005-01-01

    Full Text Available En este texto se recuperan los discursos femeninos en torno a la recepción de telenovelas y la construcción de la identidad femenina. Se retoman las teorías y metodologías feministas, así como los aportes desde la psicología, para abordar la identidad de género como un proceso personal y cultural en continua construcción. Las mujeres orientan su interpretación de las telenovelas a partir de sus preocupaciones o conflictos, los cuales se centran en su desarrollo personal, sus relaciones de pareja o su papel de madre, y a la vez, los referentes en los melodramas nutren y amplían su perspectiva y proceso personal de construcción de su identidad de género. La telenovela desempeña un papel lúdico en donde se recrea lo que se desea y asimismo ofrece información valiosa sobre otras posibilidades de vida más allá de la propia cotidianidad.

  18. “Esta religión sobre la cual todos los hombres concuerdan”: la invención de la masonería, una revolución cultural entre religión, ciencia y exilios

    Directory of Open Access Journals (Sweden)

    Dévrig Mollès

    2015-10-01

    Full Text Available La francmasonería despierta un creciente interés en América latina. Sociólogos e historiadores de las religiones, de las relaciones internacionales o de las ciencias, por ejemplo, subrayan regularmente su importancia en los procesos de modernización del siglo XIX. Sin embargo, esta cuestión queda muy mal conocida. Su actualidad no es dudosa: lo enseña por ejemplo el persistente conflicto ideológico con la Iglesia católica. Para alimentar la comprensión y la reflexión sobre estas cuestiones, este texto propone volver a las fuentes. Inventada entre las Islas británicas, Holanda y Francia a la confluencia del siglo XVII y del siglo XVIII, la francmasonería fue la primera expresión de una sociedad civil internacional. ¿Cuál fue la relación entre su creación y la revolución cultural del siglo XVIII, siglo de las Luces, de la ciencia y de la razón? Este texto se fundamenta en fuentes originales y la mejor historiografía producida en Francia, Inglaterra y Escocia desde los años 1970. Después de presentar la actualidad de la cuestión masónica, precisa el contexto de invención de la masonería para luego analizar en qué medida esta invención participó de una revolución cultural cuyo epicentro fue, precisamente, la religión.

  19. Structural Characterization Of CdSe and ZnSe Nanostructures

    Science.gov (United States)

    Bhattacharyya, B.; Kalita, P. K.; Datta, P.

    2010-10-01

    Chemically bath deposited CdSe and ZnSe powder possesses mixed type structures whereas it is hexagonal wurtzite type in thin film form. SEM images of CdSe symmetrically exhibit the growth of spherical, rod and the rose(flower) type microstructures. ZnSe shows fine grain structures. The growth of microstructures in these selenides according to the growth direction along c-axis of hexagonal wurtzite crystal. Photoluminescence shows strong blue luminescence at 414 and 437 nm in CdSe nanoparticles. ZnSe shows strong PL at 650 nm that is attributed to the strong d-native traps. The blue shifted band gap luminescence at 392 nm shows the quantum confinement in ZnSe nanoparticles.

  20. CONOCIMIENTO DE LOS ESTUDIANTES DE SECUNDARIA SOBRE LOS TIPOS DE DROGAS QUE SE CONSUMEN EN SU MEDIO

    Directory of Open Access Journals (Sweden)

    Luis Ignacio Rosiles del Barrio

    2006-06-01

    Full Text Available Las adicciones son un problema de salud pública. Se estima que en México 3.5 millones de personas entre 12 a los 65 años han consumido algún tipo de drogas. A pesar de los avances en los estudios, se ha dejado de lado el carácter cultural que tiene la adicción. Con este estudio, se deseba conocer qué saben los estudiantes de segundo de secundaria sobre cuáles son las drogas que se consumen en su medio. Se llevó a cabo un estudio observacional con un muestreo aleatorio, con múltiples etapas y proporcional al tamaño en escuelas públicas y privadas. En total se estudiaron 42 escuelas del municipio de León, Gto., México de las cuales el 76.2% lo conformaron las escuelas públicas y el resto las escuelas privadas. Refirieron que conocen que se consumen, en su medio, 11 tipos de drogas. El 88% mencionó a la cocaína en primer lugar, en segundo lugar con un 85% la marihuana, siguiendo las tachas en un 62% y el pegamento en un 49%. En cuanto a los nombres que los estudiantes le dan a las drogas, estos van desde 23 hasta los 4 nombres, siendo la marihuana a la que se le da el mayor número de nombres, seguidos de la cocaína y el éxtasis.

  1. Effect of composition on optical properties of GeSe3–Sb2Se3–ZnSe thin films

    Indian Academy of Sciences (India)

    M R Balboul; H M Hosni; M A Soliman; S A Fayek

    2014-10-01

    Optical properties of the chalcogenides GeSe3, Sb2Se3, ZnSe, (GeSe3)80(Sb2Se3)20 and (GeSe3)70 (Sb2Se3)10(ZnSe)20 thin films are investigated. Incorporation of ZnSe into both GeSe3, Sb2Se3 results in amorphous (GeSe3)70(Sb2Se3)10(ZnSe)20 composition. The estimated optical energy gap, g, is found to decrease from 3.06 eV for ZnSe to 1.81 eV for (GeSe3)70(Sb2Se3)10(ZnSe)20. While, the band tail width, e, exhibits an opposite trend. The g behaviour is believed to be associated with cohesive energy, CE, as the incorporation of ZnSe lowers its value. The calculated number of the excess of Se–Se homopolar bonds is found to affect mainly the e values. The refractive index, , is discussed in terms of Wemple–DiDomenico single oscillator dispersion model in the normal dispersion region. The oscillator energy, o, and the dispersion energy, d, are determined for films under investigation.

  2. Paramagnetism in NiSe2

    Science.gov (United States)

    Inoue, Nozomu; Yasuoka, Hiroshi; Ogawa, Shinji

    1980-03-01

    The magnetic properties of a pyrite compound NiSe2 have been investigated by the 77Se NMR, the magnetic susceptibility and the specific heat measurements in the temperature range between 1.6 and 300 K. The electronic specific heat coefficient, γ, is obtained to be (8.5± 1.0) mJ/K2mol. The values of the magnetic susceptibility and the Knight shift are estimated to be 2.17× 10-4 emu/mol and +(1.0± 0.1)%, respectively, both being independent of temperature. The product of the nuclear spin-lattice relaxation time and temperature, T1T, is found to be constant with a value or 240 msec K. From these results, it is concluded that NiSe2 is one of the typical Pauli paramagnets and the usual Korringa relation holds with a relatively small exchange enhancement effect. Discussions of the origin of the hyperfine coupling constant of 77Se are also given in conjunction with the reported result of CoSe2.

  3. MoSe2 / Polyaniline Solar Cells

    Directory of Open Access Journals (Sweden)

    H.S. Patel

    2011-01-01

    Full Text Available Solar cells have been investigated since long for harnessing the solar energy. During this decade, a new direction has come up where in the polymers have been used in the fabrication of solar cells. Polyaniline is one of the polymers which has shown potential for its applications in heterostructure solar cells. This material is being used along with the semiconductors like InSe, TiO2, Si etc. to form the photosensitive interface. In this direction, we report our investigations on the use of Molybdenum diselenide (MoSe2 as photosensitive semiconducting material in MoSe2 / polyaniline solar cells. In this paper, the preparation of MoSe2 / polyaniline solar cells has been reported. Also, the photovoltage → photocurrent characteristics of this structure have been discussed in detail in this paper. The variation of different parameters of MoSe2 / polyaniline solar cells (like open circuit voltage, short circuit current, photoconversion efficiency and fill factor with the intensity of incident illuminations has been reported in this paper. In present case, the photocurrent density was found to be around 250 µA/cm2 with the photovoltage around 8.5 mV (which is low the photoconversion efficiency was found to be around 0.7 % along with the fill factor around 0.33. The efforts have been made to explain the low values of the photoconversion efficiency.

  4. PbSe Nanocrystal Excitonic Solar Cells

    KAUST Repository

    Choi, Joshua J.

    2009-11-11

    We report the design, fabrication, and characterization of colloidal PbSe nanocrystal (NC)-based photovoltaic test structures that exhibit an excitonic solar cell mechanism. Charge extraction from the NC active layer is driven by a photoinduced chemical potential energy gradient at the nanostructured heterojunction. By minimizing perturbation to PbSe NC energy levels and thereby gaining insight into the "intrinsic" photovoltaic properties and charge transfer mechanism of PbSe NC, we show a direct correlation between interfacial energy level offsets and photovoltaic device performance. Size dependent PbSe NC energy levels were determined by cyclic voltammetry and optical spectroscopy and correlated to photovoltaic measurements. Photovoltaic test structures were fabricated from PbSe NC films sandwiched between layers of ZnO nanoparticles and PEDOT:PSS as electron and hole transporting elements, respectively. The device current-voltage characteristics suggest a charge separation mechanism that Is distinct from previously reported Schottky devices and consistent with signatures of excitonic solar cells. Remarkably, despite the limitation of planar junction structure, and without film thickness optimization, the best performing device shows a 1-sun power conversion efficiency of 3.4%, ranking among the highest performing NC-based solar cells reported to date. © 2009 American Chemical Society.

  5. A transferable force field for CdS-CdSe-PbS-PbSe solid systems.

    Science.gov (United States)

    Fan, Zhaochuan; Koster, Rik S; Wang, Shuaiwei; Fang, Changming; Yalcin, Anil O; Tichelaar, Frans D; Zandbergen, Henny W; van Huis, Marijn A; Vlugt, Thijs J H

    2014-12-28

    A transferable force field for the PbSe-CdSe solid system using the partially charged rigid ion model has been successfully developed and was used to study the cation exchange in PbSe-CdSe heteronanocrystals [A. O. Yalcin et al., "Atomic resolution monitoring of cation exchange in CdSe-PbSe heteronanocrystals during epitaxial solid-solid-vapor growth," Nano Lett. 14, 3661-3667 (2014)]. In this work, we extend this force field by including another two important binary semiconductors, PbS and CdS, and provide detailed information on the validation of this force field. The parameterization combines Bader charge analysis, empirical fitting, and ab initio energy surface fitting. When compared with experimental data and density functional theory calculations, it is shown that a wide range of physical properties of bulk PbS, PbSe, CdS, CdSe, and their mixed phases can be accurately reproduced using this force field. The choice of functional forms and parameterization strategy is demonstrated to be rational and effective. This transferable force field can be used in various studies on II-VI and IV-VI semiconductor materials consisting of CdS, CdSe, PbS, and PbSe. Here, we demonstrate the applicability of the force field model by molecular dynamics simulations whereby transformations are initiated by cation exchange.

  6. Incorporation of HNO{sub 3} into GaSe and InSe

    Energy Technology Data Exchange (ETDEWEB)

    Nekrasov, O.V.; Zavrazhnov, A.Yu.; Semenov, V.N. [Voronezh State Univ. (Russian Federation)] [and others

    1994-06-01

    Gallium selenide is a congruently melting compound (T{sub m}=1100 K) with a layered hexagonal crystal structure built from consecutive Se-Ga-Ga-Se slabs. These slabs are bonded by van der Waals forces. In the literature, GaSe crystals are reported to exist in several modifications, among them {epsilon}- and {gamma}-polytypes differing in layer alternation were reliably identified. GaSe is an off-stoichiometric, cation-rich phase with a homogenity range of 47.5 - 49.5 at. % Se (at T=1113 K). The {epsilon}- and {gamma}- polytypes always coexist, and the higher is the Ga content, the stronger is the structural disorder, as evidenced by broadening of lines with non-zero index l in X-ray diffraction patterns of GaSe. Irrespective of preparation conditions, GaSe is a p-type semiconductor with a band gap of 2.03 eV. A high dislocation density (10{sup 9} - 10{sup 11} cm{sup -2}), observed by TEM, is characteristic for these crystals. In many respects, InSe is similar to GaSe. InSe is a narrow-gap semiconductor with N-type conductivity. The homogeneity range of this compound is much narrower than that of GaSe, but it is likewise displaced toward metal-rich compositions. Interlayer incorporation is known to accompany a great variety of reactions, among which the reaction of HNO{sub 3} with GaSe and InSe is of great interest.

  7. Improved photoluminescence quantum yield and stability of CdSe-TOP, CdSe-ODA-TOPO, CdSe/CdS and CdSe/EP nanocomposites

    Science.gov (United States)

    Wei, Shutian; Zhu, Zhilin; Wang, Zhixiao; Wei, Gugangfen; Wang, Pingjian; Li, Hai; Hua, Zhen; Lin, Zhonghai

    2016-07-01

    Size-controllable monodisperse CdSe nanocrystals with different organic capping were prepared based on the hot-injection method. The effective separation of nucleation and growth was achieved by rapidly mixing two highly reactive precursors. As a contrast, we prepared CdSe/CdS nanocrystals (NCs) successfully based on the selective ion layer adsorption and reaction (SILAR) technique. This inorganic capping obtained higher photoluminescence quantum yield (PLQY) of 59.3% compared with organic capping of 40.8%. Furthermore, the CdSe-epoxy resin (EP) composites were prepared by adopting a flexible ex situ method, and showed excellent stability in the ambient environment for one year. So the composites with both high PLQY of nanocrystals and excellent stability are very promising to device application.

  8. Lattice thermal conductivity of LaSe

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wei, E-mail: tolwwt@163.com [School of Physics and Telecommunication Engineering, South China Normal University, 510006 Guangzhou (China); Pan, Zhong-liang; Chen, Jun-fang; He, Qin-yu [School of Physics and Telecommunication Engineering, South China Normal University, 510006 Guangzhou (China); Wang, Teng [School of Computer, South China Normal University, 510631 Guangzhou (China)

    2015-07-15

    The phonon dispersions and phonon density of states of LaSe are obtained, based on density functional perturbation theory and the norm-conserving pseudo-potential method. An anomaly in calculated phonon dispersion curves is presented and interpreted as a Kohn anomaly. The heat capacity of LaSe is calculated then. For the three-phonon process scattering, the lowest non-harmonic cubic terms of the interatomic potential are considered to obtain single-phonon relaxation rate by applying the Fermi's golden rule. For the boundary scattering, the average phonon relaxation time was obtained. Considering two kinds of phonon scattering mechanisms, we obtain the lattice thermal conductivity of LaSe.

  9. Tl2Mo9Se11

    Directory of Open Access Journals (Sweden)

    Patrick Gougeon

    2010-08-01

    Full Text Available The structure of Tl2Mo9Se11, dithallium nonamolybdenum undecaselenide, is isotypic with Tl2Mo9S11 [Potel et al. (1980. Acta Cryst. B36, 1319–1322]. The structural set-up is characterized by a mixture of Mo6Sei8Sea6 and Mo12Sei14Sea6 cluster units in a 1:1 ratio. Both components are interconnected through interunit Mo—Se bonds. The cluster units are centered at Wyckoff positions 3a and 3b (point-group symmetry overline{3}.. The two TlI atoms are situated in the voids of the three-dimensional arrangement. Two of the five independent Se atoms and the Tl atoms lie on sites with 3. symmetry (Wyckoff site 6c.

  10. Los valores postmodernos en la formación ciudadana de los alumnos del Nivel Medio a la luz de la interpretación de los documentos oficiales que se elaboran en el marco del Plan Decenal (1992-2002) para la Educación Dominicana

    OpenAIRE

    Firpo Z, Antonio Luciano

    2013-01-01

    El estudio de la influencia de los valores postmodernos en la educación cívica de los estudiantes de nivel medio de la República Dominicana, conlleva a la reflexión y la interpretación de los autores y textos posmodernos, los cuales abordan el fenómeno de la educación y la cultura; a la luz de la reflexión y comentarios de esos autores se desarrolla una interpretación hermenéutica de algunos documentos oficiales, los cuales resultan muy importantes para el estudio de la educ...

  11. Formation of CuInSe{sub 2} from Cu{sub 2}Se and In{sub 2}Se{sub 3} compounds

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Daigao [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui (China); Wang, Deliang [Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui (China); CAS Key Laboratory of Materials for Energy Conversion, University of Science and Technology of China, Hefei, Anhui (China)

    2011-10-15

    Chalcopyrite {alpha}-CuInSe{sub 2} ({alpha}-CIS) was prepared from mixed powders of Cu{sub 2}Se and In{sub 2}Se{sub 3} by annealing in the Se- and the non-Se environments. The mechanically ground powders were in an overall amorphous state. The mechanical alloying produced Cu{sub 3}Se{sub 2} and CuSe compounds. At relatively low temperature, Cu{sub 3}Se{sub 2} decomposed, Cu{sub 2-x}Se and CuSe formed. The reaction for the formation of {alpha}-CuInSe{sub 2} occurred essentially at a temperature at {proportional_to}350 C in both the Se- and the non-Se environments. In the non-Se environment, reactions occurred by a solid-solid reaction and a certain amount of Se were released from the mixed powder, resulting in poor crystalline {alpha}-CuInSe{sub 2} powders. When annealed in the Se environment, low-melting Se-rich Cu-Se compounds were produced during reaction. The reactions occurred by a liquid-solid reaction above 450 C. Large-grained and good crystalline quality of chalcopyrite CIS with near stoichiometric atomic ratio was obtained above 450 C. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Što se dogodilo gospodinu Davisonu

    Directory of Open Access Journals (Sweden)

    Una Krizmanić Ožegović

    2014-12-01

    Full Text Available Prije svega, dozvolite mi da kažem da svi osjećamo najiskreniju sućut zbog onoga što se dogodilo gospodinu Davidsonu. Naravno, nitko od nas nije mogao ni pomisliti da će sve tako završiti. To ne treba ni napominjati. Mislim, doista ne vjerujem da je bilo tko mogao predvidjeti posljedice onoga što se dogodilo. Daleko od toga da smo sjeli i proveli detaljnu analizu rizika kad smo odlučili djelovati u tome smjeru. Naravno da ne. Riječ je o spontanoj odluci, jednostavno nas je ponio trenutak. No, unatoč nedostatku podrobnije analize, mogu sa sigurnošću reći kako ovakav ishod nitko od nas nije mogao ni zamisliti. Mislim, očito da nije. Jednostavno, mi nismo takvi ljudi, nitko od nas. Mislim da se to podrazumijeva. Mislim da sa sigurnošću mogu reći kako se to uvriježilo među nekim ljudima koje je ovo pogodilo, u odnosu na kasniji tijek događaja. Uključujući i samoga gospodina Davidsona. S obzirom na sve što smo uspjeli zaključiti. Mislim, znate, neki od ljudi kojima se okružio bili su s pravom oprezni, s obzirom na ono što bismo mogli nazvati pristupom. Tako barem ja to, i dandanas, vidim: takav pristup u sadašnjem trenutku ne bi bio dobro prihvaćen, s obzirom na trenutačne okolnosti. Govorim s obzirom i u odnosu na treće strane, u ovome kontekstu. S obzirom da smo držali kako bi se izravan pristup protumačio kao neprimjeren, u odnosu na širi kontekst i povijest i tome slično.

  13. One-pot synthesis of hollow NiSe-CoSe nanoparticles with improved performance for hybrid supercapacitors

    Science.gov (United States)

    Chen, Haichao; Fan, Meiqiang; Li, Chao; Tian, Guanglei; Lv, Chunju; Chen, Da; Shu, Kangying; Jiang, Jianjun

    2016-10-01

    Hollow NiSe-CoSe samples have been synthesized for the first time via a one-pot solvothermal approach. The strategy is robust enough to synthesize NiSe-CoSe nanoparticles with different NiSe to CoSe ratios but with a similar hollow structure. Co ions in the NiSe-CoSe nanoparticles play decisive role for formation of the hollow structure; otherwise, the nanoparticles become solid for the NiSe sample. When used as the positive electroactive materials for energy storage, the NiSe-CoSe samples show excellent electrochemical activity in alkaline electrolyte. Using the synergistic effect between NiSe and CoSe, the electrochemical performance of NiSe-CoSe can be tuned by varying the NiSe to CoSe ratios. The NiSe-CoSe sample with a NiSe to CoSe ratio of 4:2 shows the best electrochemical performance in terms of superior specific capacity, improved rate capability and excellent cycling stability. In addition, the electrochemical performance of NiSe-CoSe sample with a NiSe to CoSe ratio of 4:2 is also evaluated via assembling hybrid supercapacitors with RGO, and the hybrid supercapacitor delivers both high power and energy densities (41.8 Wh kg-1 at 750 W kg-1 and 20.3 Wh kg-1 at 30 kW kg-1).

  14. “Esta religión sobre la cual todos los hombres concuerdan”: la invención de la masonería, una revolución cultural entre religión, ciencia y exilios

    Directory of Open Access Journals (Sweden)

    Dévrig Mollès

    2015-10-01

    Full Text Available Resumen La francmasonería despierta un creciente interés en América latina. Sociólogos e historiadores de las religiones, de las relaciones internacionales o de las ciencias, por ejemplo, subrayan regularmente su importancia en los procesos de modernización del siglo XIX. Sin embargo, esta cuestión queda muy mal conocida. Su actualidad no es dudosa: lo enseña por ejemplo el persistente conflicto ideológico con la Iglesia católica. Para alimentar la comprensión y la reflexión sobre estas cuestiones, este texto propone volver a las fuentes. Inventada entre las Islas británicas, Holanda y Francia a la confluencia del siglo XVII y del siglo XVIII, la francmasonería fue la primera expresión de una sociedad civil internacional. ¿Cuál fue la relación entre su creación y la revolución cultural del siglo XVIII, siglo de las Luces, de la ciencia y de la razón? Este texto se fundamenta en fuentes originales y la mejor historiografía producida en Francia, Inglaterra y Escocia desde los años 1970. Después de presentar la actualidad de la cuestión masónica, precisa el contexto de invención de la masonería para luego analizar en qué medida esta invención participó de una revolución cultural cuyo epicentro fue, precisamente, la religión. Masonería, siglo XVIII, Ilustración, historia cultural Abstract Freemasonry rouses an increasing interest among Latin-American sociologists and historians of the religions, international relationships and sciences, for example. During the last years, they regularly stressed its importance in the processes of cultural and religious modernization, particularly during the 19th century. Nevertheless, this question remains very badly known. Her current importance is not doubtful, like shows us the persistent ideological conflict with the Catholic Church, for example. To provide tools for comprehension and critical thought, this text proposes to return to the sources, very little known in Latin

  15. Growth and structural characterizations of GaSe and GaSe:Cd single crystals

    Science.gov (United States)

    Ashkhasi, Afsoun; Gürbulak, Bekir; Şata, Mehmet; Turgut, Güven; Duman, Songül

    2017-02-01

    GaSe and GaSe:Cd single crystals used in this research were grown by using the Bridgman/Stockbarger method. All of the samples were freshly and gently cleaved with a razor blade from the grown ingots and no further polishing and cleaning treatments were required because of the natural mirror-like cleavage faces. The Samples were cleaved along the cleavage planes (001). The structure and lattice parameters of the undoped GaSe and GaSe:Cd semiconductors have been analyzed using a X-ray diffractometer (XRD), Scanning electron microscopy (SEM) and energy dispersive X-rays (EDX) techniques. It is found that GaSe and GaSe:Cd crystals have hexagonal structure, quite close 2θ peak values. XRD measurements indicate that there is an increase in peak intensities at specific annealing temperatures (500°C). Cd doping causes a significant decrease in the XRD peak intensity.

  16. {InSe}/{GaSe} heterointerfaces prepared by Van der Waals epitaxy

    Science.gov (United States)

    Lang, O.; Klein, A.; Schlaf, R.; Löher, T.; Pettenkofer, C.; Jaegermann, W.; Chevy, A.

    1995-01-01

    Epitaxial films of layered substrates can be prepared onto layered substrates even for large lattice mismatch, when the growth is attempted with the Van der Waals surfaces opposing each other (Van der Waals epitaxy). Thin epitaxial InSe(GaSe) films are prepared onto ultrahigh vacuum (UHV) cleaved GaSe(InSe) Van der Waals (0001) surfaces. The films and the heterointerface are characterized by photoelectron spectroscopy, electron diffraction and scanning tunneling microscopy (STM). High quality and stoichiometric films are obtained by direct InSe(GaSe) evaporation from a Knudsen cell at sample temperatures between 520 and 620 K. Despite a 6% lattice mismatch the deposited films are oriented with their c- and α-axis to the hexagonal substrate. The growth mostly follows the Frank-Van der Merwe mode. This rather ideal growth behaviour is related to the specific properties of the Van der Waals plane which contains no dangling bonds.

  17. Mecanismos de señalización celular que median la tolerancia inmunitaria

    Directory of Open Access Journals (Sweden)

    Ana Maria Blasini

    2013-12-01

    Full Text Available La tolerancia inmunitaria es la capacidad del sistema inmunitario de no responder a un antígeno al cual ha estado expuesto previamente. Un conjunto de mecanismos a nivel central y a nivel periférico garantizan que los linfocitos, al encontrar ciertos antígenos, se inactiven o sean eliminados. El sistema inmunitario mantiene un delicado balance entre la tolerancia dirigida por sus antígenos propios y la inmunidad desencadenada por patógenos. La falta de respuesta conduce a estados de inmunodeficiencia mientras que un exceso de respuesta, o una respuesta inapropiada, resulta en condiciones patofisiológicas como la autoinmunidad. La regulación de la autotolerancia dentro del repertorio de los linfocitos T se ejerce a dos niveles. Primero, el desarrollo y selección de linfocitos T en el timo desplaza el repertorio en contra de la autoreactividad (tolerancia central. En segundo lugar, los linfocitos T maduros sufren un segundo proceso de selección por deleción o por anergia, en órganos linfoides y no linfoides (tolerancia periférica. Además, los linfocitos T reguladores pueden suprimir la activación de aquellos linfocitos T autoreactivos que escapan de la mencionada selección.

  18. El cielo se llena de santos mexicanos

    Directory of Open Access Journals (Sweden)

    Verónica Zárate Toscano

    2005-02-01

    Full Text Available Preliminares A fines del próximo mes de julio, si Dios le conserva la vida y su salud se lo permite, el Papa Juan Pablo II elevará a la categoría de Santo al indio Juan Diego en una ceremonia en la ciudad de México, culminando así un largo, discutido y tortuoso proceso de canonización. Suerte parecida corrió en su momento el criollo Felipe de Jesús; sin embargo, otros miembros de la corte celestial de origen mexicano se han elevado a los altares de manera casi vertiginosa, como es el caso de ...

  19. Dommere og religiøse symboler

    DEFF Research Database (Denmark)

    Holtug, Nils

    2012-01-01

    Om politiske kontroverser, der angår religiøse symboler i det offentlige rum i Danmark, og den måde, hvorpå idéer, der undfanges på den nationalistiske højrefløj......Om politiske kontroverser, der angår religiøse symboler i det offentlige rum i Danmark, og den måde, hvorpå idéer, der undfanges på den nationalistiske højrefløj...

  20. Synthesis of near-infrared-emitting CdTe/CdSe/ZnSe/ZnS heterostructure.

    Science.gov (United States)

    Yang, Ping

    2014-04-01

    Near-infrared-emitting quantum dots (QDs) were fabricated via organic synthesis strategies through constructing CdTe/CdSe/ZnSe/ZnS multishell heterostructure. An effective shell-coating route was developed for multishell growth on CdTe cores. Core/shell growth was monitored by absorption and photoluminescence (PL) spectroscopy and transmission electron microscopy observation. Yellow emitting CdTe cores were coated with a CdSe shell to generate type II structure. This yields core/shell QDs with red photoluminescence. The passivation by the ZnSe shell having a substantially wide bandgap confines the excitons within the CdTe/CdSe interface and isolates them from the solution environment and consequently improves the stability of the heterostructure. An additional ZnS shell was deposited around the outer layer of CdTe/CdSe/ZnSe QDs to form a heterostructure through the reaction between zinc oleate and trioctylphosphine sulfur in the crude CdTe/CdSe/ZnSe solution. By varying CdTe core size and each shell thickness, the PL wavelength of the obtained heterostructure can span from 580 to 770 nm. The PL efficiency is quenched in CdTe QDs in diluted solution but increases substantially up to 24% for CdTe/CdSe core/shell QDs. The PL efficiency of CdTe/CdSe/ZnSe/ZnS QDs with average diameter of 5.4 nm and a PL peak wavelength of 770 nm is 20%.

  1. Se activity and its effect on Cu(In,Ga)Se{sub 2} photovoltaic thin films

    Energy Technology Data Exchange (ETDEWEB)

    Contreras, Miguel A.; Repins, Ingrid; Metzger, Wyatt K.; Romero, Manuel [National Renewable Energy Laboratory, Golden, CO (United States); Abou-Ras, Daniel [Hahn-Meitner-Institut Berlin (Germany)

    2009-05-15

    We study some physical properties of CuIn{sub 1-x}Ga{sub x}Se{sub 2} thin-films fabricated by evaporation from elemental sources under various Selenium environments. Specifically, thin-films were fabricated under growth conditions such as Se deficiency, near stoichiometry and excess Se during coevaporation to investigate the impact of the Se environment on absorber film properties and ultimately the device performance. We determine the chemical activity of Se in the evaporation process has a strong influence on film macrostructure (prefered orientation) and microstructure, particularly at the grain and grain boundary level. It is shown that the optoelectronic properties at grain boundaries are affected by the Se environment used resulting in absorber thin-films with distinctive defect distribution and defect density. Consequently, the performance of the solar cells fabricated from those films is also affected by the Se environment. These effects on solar cell performance and absorber properties are reported in a (i) structural analysis of the CuIn{sub 1-x}Ga{sub x}Se{sub 2}/Mo/glass samples by X-ray and electron backscattering techniques; (ii) optolectronic radiative characteristics of the absorbers by cathode luminescence and photoluminescence studies and (iii) current-voltage, quantum efficiency and capacitance-voltage measurements for the solar cells made from the absorbers fabricated under the pre prescribed Se growth conditions. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Inverse-photoemission spectroscopy of GaSe and InSe

    Science.gov (United States)

    Sporken, R.; Hafsi, R.; Coletti, F.; Debever, J. M.; Thiry, P. A.; Chevy, A.

    1994-04-01

    The lamellar semiconductors GaSe and InSe have been studied with k-resolved inverse-photoemission spectroscopy along two major symmetry directions (Γ¯ K¯ and Γ¯ M¯) of the surface Brillouin zone. Three bands with well-resolved features are observed from which the dispersion of the conduction bands can be determined with good precision. The minimum of the conduction band is found at M¯ in GaSe and at Γ¯ in InSe. These results are compared with theoretical studies using pseudopotential and tight-binding calculations.

  3. Y Se Repite = And It Repeats Itself

    Science.gov (United States)

    Katzew, Adriana

    2010-01-01

    In this article, the author discusses Y Se Repite [And It Repeats Itself], a project she conceptualized due to the growing number of Latino/a Mexican migrant workers in dairy farms in the state of Vermont. In 2006, approximately 2,000 Latinos/as--most of them undocumented Mexican migrant workers--worked throughout the state's dairy farms, yet…

  4. Enriched $^{82}$Se for the LUCIFER experiment

    CERN Document Server

    Beeman, J W; Benetti, P; Cardani, L; Casali, N; Chiesa, D; Clemenza, M; Dafinei, I; Di Domizio, S; Ferroni, F; Gironi, L; Giuliani, A; Gotti, C; Laubenstein, M; Maino, M; Nagorny, S; Nisi, S; Nones, C; Orio, F; Pagnanini, L; Pattavina, L; Pessina, G; Piperno, G; Pirro, S; Previtali, E; Rusconi, C; Schäffner, K; Tomei, C; Vignati, M

    2015-01-01

    The LUCIFER project aims at deploying the first array of enriched scintillating bolometers for the investigation of neutrinoless double-beta decay of $^{82}$Se. The matrix which embeds the source is an array of ZnSe crystals, where enriched $^{82}$Se is used as decay isotope. The radiopurity of the initial components employed for manufacturing crystals, that can be operated as bolometers, is crucial for achieving a null background level in the region of interest for double-beta decay investigations. In this work, we evaluated the radioactive content in 2.5 kg of 96.3% enriched $^{82}$Se metal, measured with a high-purity germanium detector at the Gran Sasso deep underground laboratory. The limits on internal contaminations of primordial decay chain elements of $^{232}$Th, $^{238}$U and $^{235}$U are respectively: $<$61 $\\mu$Bq/kg, $<$110 $\\mu$Bq/kg and $<$74 $\\mu$Bq/kg at 90% C.L.. The extremely low-background conditions in which the measurement was carried out and the high radiopurity of the $^{82}$...

  5. Electroreflectance study of RuSe 2

    Science.gov (United States)

    Huang, Y. S.; Lin, S. S.; Sheu, J. S.; Shen, W. M.; Pollak, Fred H.

    1990-12-01

    We report the first electrolyte-electroreflectance (EER) study of a RuSe 2 single crystal in the photon energy region of 0.9-5.5 eV. The EER spectrum exhibits differential like structure in the vicinity of interband transitions. The transition energies are determined accurately. A probable energy-band structure is constructed.

  6. VerSeDa: vertebrate secretome database

    Science.gov (United States)

    Cortazar, Ana R.; Oguiza, José A.

    2017-01-01

    Based on the current tools, de novo secretome (full set of proteins secreted by an organism) prediction is a time consuming bioinformatic task that requires a multifactorial analysis in order to obtain reliable in silico predictions. Hence, to accelerate this process and offer researchers a reliable repository where secretome information can be obtained for vertebrates and model organisms, we have developed VerSeDa (Vertebrate Secretome Database). This freely available database stores information about proteins that are predicted to be secreted through the classical and non-classical mechanisms, for the wide range of vertebrate species deposited at the NCBI, UCSC and ENSEMBL sites. To our knowledge, VerSeDa is the only state-of-the-art database designed to store secretome data from multiple vertebrate genomes, thus, saving an important amount of time spent in the prediction of protein features that can be retrieved from this repository directly. Database URL: VerSeDa is freely available at http://genomics.cicbiogune.es/VerSeDa/index.php PMID:28365718

  7. Biaxially Oriented CdSe Nanorod

    DEFF Research Database (Denmark)

    Breiby, Dag W.; Chin, Patrick T.K.; Andreasen, Jens Wenzel

    2009-01-01

    The shape, structure, and orientation of rubbing-aligned cadmium selenide (CdSe) nanorods on polymer coated glass substrates have been studied using transmission electron microscopy (TEM) and grazing incidence X-ray scattering combined with computer simulations. The nanorods are found to be of wu...

  8. VerSeDa: vertebrate secretome database.

    Science.gov (United States)

    Cortazar, Ana R; Oguiza, José A; Aransay, Ana M; Lavín, José L

    2017-01-01

    Based on the current tools, de novo secretome (full set of proteins secreted by an organism) prediction is a time consuming bioinformatic task that requires a multifactorial analysis in order to obtain reliable in silico predictions. Hence, to accelerate this process and offer researchers a reliable repository where secretome information can be obtained for vertebrates and model organisms, we have developed VerSeDa (Vertebrate Secretome Database). This freely available database stores information about proteins that are predicted to be secreted through the classical and non-classical mechanisms, for the wide range of vertebrate species deposited at the NCBI, UCSC and ENSEMBL sites. To our knowledge, VerSeDa is the only state-of-the-art database designed to store secretome data from multiple vertebrate genomes, thus, saving an important amount of time spent in the prediction of protein features that can be retrieved from this repository directly. VerSeDa is freely available at http://genomics.cicbiogune.es/VerSeDa/index.php.

  9. Señales en el agua

    Directory of Open Access Journals (Sweden)

    Helcías Martan Góngora

    1964-11-01

    Full Text Available La lluvia fue siempre compañera de la soledad. En su ámbito de música se mueve el pensamiento con monótono ritmo y el alma encuentra su centro de gravedad, mientras dura el imperio de su amada caricia.

  10. No todo lo que cuenta se cuenta

    NARCIS (Netherlands)

    van Rijckevorsel, J.

    2008-01-01

    En este trabajo publicado en "Insurance Economics" Nº 58 (Julio 2008), Jan van Rijckevorsel hace un profundo análisis del uso práctico de las estadísticas de seguros aplicadas a aspectos reales del quehacer institucional del sector, y señala varios campos (como el valor y calificación de la reputaci

  11. Reference: SE2PVGRP1 [PLACE

    Lifescience Database Archive (English)

    Full Text Available ter, domain A of the 35S promoter and the 35S2 promoter. Transgenic Res 4:388-396 (1995) PubMed: 7581519; ... ...SE2PVGRP1 Elmayan T, Tepfer M. Evaluation in tobacco of the organ specificity and strength of the rolD promo

  12. El cristal con que se mira. Comparando dos contextos arqueológicos urbanos a través del material vítreo

    Directory of Open Access Journals (Sweden)

    Aniela Romina Traba

    2011-07-01

    Full Text Available Entre los materiales que se recuperan arqueológicamente en contextos urbanos, el vidrio es uno de los más recurrentes, lo cual evidencia el consumo cada vez más generalizado de estos artículos desde fines del siglo XIX. Este progreso puede explicarse a partir de la masificación de las manufacturas vítreas de origen extranjero, sumado al incipiente desarrollo de la industria local en aquel período. En este trabajo se aplica una metodología de análisis de los artefactos vítreos, como así también algunas propuestas para el abordaje interpretativo a los procesos de formación culturales. Esto se llevará a cabo a partir del estudio de los materiales recuperados en dos sitios de la Ciudad de Buenos Aires: “Rodríguez Visillac” y “Corralón de Floresta”, los cuales representan dos contextos de descarte diferenciales.

  13. Electronic and structural properties of A Al 2Se 4 ( A=Ag, Cu, Cd, Zn) chalcopyrite semiconductors

    Science.gov (United States)

    Mishra, S.; Ganguli, B.

    2011-07-01

    We have studied the structural and electronic properties of defect chalcopyrite semiconductors A Al 2Se 4 ( A=Ag, Cu, Cd, Zn) using density functional theory (DFT) based first principle technique within tight binding linear muffin-tin orbital (TB-LMTO) method. Our calculated structural parameters such as lattice constants a and c, tetragonal distortion ( η=c/2a) are in good agreement with experimental work. Anion displacement parameters, bond lengths and bulk modulus are also calculated. Our band structure calculation suggests that these compounds are direct band gap semiconductors having band gaps 2.40, 2.50, 2.46 and 2.82 eV for A Al 2Se 4 ( A=Ag, Cu, Cd, Zn) respectively. Calculated band gaps are in good agreement with other experimental and theoretical works within LDA limitation. We have made a quantitative estimation of the effect of p- d hybridization and structural distortion on the electronic properties. The reduction in band gap due to p- d hybridization is 19.47%, 21.29%, 0% and 0.7% for A Al 2Se 4 ( A=Ag, Cu, Cd, Zn) respectively. Increment of the band gap due to structural distortion is 11.62%, 2.45%, 2.92% and 9.30% in case of AgAl 2Se 4, CuAl 2Se 4, CdAl 2Se 4 and ZnAl 2Se 4 respectively. We have also discussed the bond nature of all four compounds.

  14. APROXIMACIÓN AL SILENCIO ELOCUENTE DE LOS ENUNCIADOS: LO QUE SE COMUNICA Y NO SE DICE: WHAT IS COMMUNICATED BUT NOT SAID

    Directory of Open Access Journals (Sweden)

    Constanza Moya Pardo

    2012-06-01

    Full Text Available El estudio del silencio muestra otras posibilidades de interacción humana que se creían excluidas al callar. Esta dimensión lacónica del lenguaje posibilita una fenomenología de las formas de expresión que incorpora el mundo de lo implícito y supera el privilegio que ejerce la palabra verbal-explícita en nuestros procesos de comunicación. Muchos de los enunciados de la lengua ocultan otros que les dan sentido. Además de aparecer como privación verbal, como ausencia de habla o artificio de la economía lingüística, el silencio es una manera de pensar y de comunicar. Es el saber compartido, el mundo implícito de los hablantes. Este juego de silencios, mediante el cual transmitimos pensamientos e intenciones sin necesidad de enunciarlos directamente, es posible gracias a habilidades cognitivas de conexión e inferencia, y al conjunto de supuestos compartidos por los miembros que pertenecen a una misma comunidad pragmática y que dominan las reglas de esa gramática del silencio.

  15. Ultra-Fast Synthesis for Ag2Se and CuAgSe Thermoelectric Materials

    Science.gov (United States)

    DUAN, H. Z.; LI, Y. L.; ZHAO, K. P.; QIU, P. F.; SHI, X.; CHEN, L. D.

    2016-10-01

    Ag2Se and CuAgSe have been recently reported as promising thermoelectric materials at room temperature. The traditional melting-annealing-sintering processes are used to grow Ag2Se and CuAgSe materials with the disadvantages of high costs of energy and time. In this work, phase-pure polycrystalline Ag2Se and CuAgSe compounds were synthesized from raw elemental powders directly by manual mixing followed by spark plasma sintering (MM-SPS) in a few minutes. The influence of SPS heating rate on the phase composition, microstructure, and thermoelectric properties, including Seebeck coefficient, electrical conductivity, and thermal conductivity, were investigated. The zTs of 0.8 at 390 K and 0.6 at 450 K are obtained for Ag2Se and CuAgSe, respectively, which is comparable with the values in the materials prepared by the traditional method. Furthermore, this ultrafast sample synthesis can significantly save material synthesis time and thus has the obvious advantage for large-scale production.

  16. Que se vea lo que se oye: a vueltas con los fonemas y las letras

    Directory of Open Access Journals (Sweden)

    Gómez del Estal Villarino, Mario

    2011-03-01

    Full Text Available Partiendo de lo que el refrán “La letra con sangre entra” viene a decir a quien se deje escucharlo, se abre una descripción de las diferencias radicales que se dan entre aprender a hablar y aprender a escribir. La relación entre ambas actividades no se puede entender sin analizar la tan extendida perversión que supone hablar lo que se escribe en vez de escribir lo que se habla. A continuación, se detallan algunos de los síntomas más frecuentes de dicha perversión, caracterizados todos por la intromisión de la conciencia en terrenos donde lo único que hace es estorbar, en especial la pronunciación pedantesca de ciertos finales silábicos o de palabra, como en traNSporte, aBStraKción, óPtico, oBjeto, fúTbol, libertaD, diGno o fraK, así como las distintas deformaciones que sufren las palabras que la ortografía académica prescribe que se escriban con la letra equis.

  17. Interaction induced dephasing of excitons in wide ZnSe/ZnMgSe single quantum wells

    DEFF Research Database (Denmark)

    Wagner, Hans Peter; Schätz, A.; Maier, R.;

    1998-01-01

    The dephasing of excitons in wide ZnSe/Zn0.94Mg0.06Se single quantum wells (SQW) is investigated by spectrally resolved, time integrated four-wave mixing (FWM). Simultaneous excitation of Is center-of-mass quantized heavy-hole and light-hole excition states leads to pronounced quantum beats. Pola...

  18. Dephasing and interaction of excitons CdSe/ZnSe islands

    DEFF Research Database (Denmark)

    Wagner, H. P.; Tranitz, H.-P.; Preis, H.;

    2000-01-01

    The dephasing of excitons in self-organized CdSe/ZnSe islands grown by molecular-beam epitaxy is investigated using spectrally resolved four-wave mixing. A distribution of dephasing times is observed, indicating the existence of localized excitons with different relaxation times at comparable...

  19. Exciton dephasing and biexciton binding in CdSe/ZnSe islands

    DEFF Research Database (Denmark)

    Wagner, Hans Peter; Tranitz, H.-P.; Preis, H;

    1999-01-01

    The dephasing of excitons and the formation of biexcitons in self-organized CdSe/ZnSe islands grown by molecular-beam epitaxy is investigated using spectrally resolved four-wave mixing. A distribution of exciton-exciton scattering efficiencies and dephasing times in the range of 0.5-10 ps...

  20. Dephasing and interaction of excitons CdSe/ZnSe islands

    DEFF Research Database (Denmark)

    Wagner, H. P.; Tranitz, H.-P.; Preis, H.

    2000-01-01

    The dephasing of excitons in self-organized CdSe/ZnSe islands grown by molecular-beam epitaxy is investigated using spectrally resolved four-wave mixing. A distribution of dephasing times is observed, indicating the existence of localized excitons with different relaxation times at comparable...

  1. Speciation of Se and DOC in soil solution and their relation to Se bioavailability.

    NARCIS (Netherlands)

    Weng, L.P.; Vega, F.A.; Supriatin, S.; Bussink, W.; Riemsdijk, van W.H.

    2011-01-01

    A 0.01 M CaCl2 extraction is often used to asses the bioavailability of plant nutrients in soils. However, almost no correlation was found between selenium (Se) in the soil extraction and Se content in grass. The recently developed anion Donnan membrane technique was used to analyze chemical speciat

  2. Optical detectors on GaSe and InSe layered crystals

    Science.gov (United States)

    Kyazym-Zade, A. G.; Agaeva, A. A.; Salmanov, V. M.; Mokhtari, A. G.

    2007-12-01

    Fast uncooled GaSe and InSe detectors that can record ultrashort (10-12 10-9 s) laser pulses in the visual and near-IR ranges are developed. The quick response of the detectors is due to rapid recombination channels with a high capture cross section present in the crystals.

  3. Isothermal currents in InSe, GaSe, and GaS single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Micocci, G.; Rizzo, A.; Tepore, A.; Zuanni, F. (Lecce Univ. (Italy). Ist. di Fisica)

    1983-11-16

    Isothermal current-time measurements are performed on InSe, GaSe, and GaS single crystals. The results reveal the presence of trapping centres and their activation energies and capture cross-sections are determined. The limitations of this method for the determination of trapping parameters in crystals are also discussed.

  4. Ultrafast carrier dynamics in type II ZnSe/CdS/ZnSe nanobarbells.

    Science.gov (United States)

    Hewa-Kasakarage, Nishshanka N; El-Khoury, Patrick Z; Tarnovsky, Alexander N; Kirsanova, Maria; Nemitz, Ian; Nemchinov, Alexander; Zamkov, Mikhail

    2010-04-27

    We employ femtosecond transient absorption spectroscopy to get an insight into ultrafast processes occurring at the interface of type II ZnSe/CdS heterostructured nanocrystals fabricated via colloidal routes and comprising a barbell-like arrangement of ZnSe tips and CdS nanorods. Our study shows that resonant excitation of ZnSe tips results in an unprecedently fast transfer of excited electrons into CdS domains of nanobarbells (ZnSe tips (tau(h)= 95 ps). A qualitative thermodynamic description of observed electron processes within the classical limit of Marcus theory was used to identify a specific charge transfer regime associated with the ultrafast electron injection into CdS. Potential photocatalytic applications of the observed fast separation of carriers along the main axis of ZnSe/CdS barbells are discussed.

  5. 'Cold' crystallization in nanostructurized 80GeSe2-20Ga2Se3 glass.

    Science.gov (United States)

    Klym, Halyna; Ingram, Adam; Shpotyuk, Oleh; Calvez, Laurent; Petracovschi, Elena; Kulyk, Bohdan; Serkiz, Roman; Szatanik, Roman

    2015-01-01

    'Cold' crystallization in 80GeSe2-20Ga2Se3 chalcogenide glass nanostructurized due to thermal annealing at 380°C for 10, 25, 50, 80, and 100 h are probed with X-ray diffraction, atomic force, and scanning electron microscopy, as well as positron annihilation spectroscopy performed in positron annihilation lifetime and Doppler broadening of annihilation line modes. It is shown that changes in defect-related component in the fit of experimental positron lifetime spectra for nanocrystallized glasses testify in favor of structural fragmentation of larger free-volume entities into smaller ones. Nanocrystallites of Ga2Se3 and/or GeGa4Se8 phases and prevalent GeSe2 phase extracted mainly at the surface of thermally treated samples with preceding nucleation and void agglomeration in the initial stage of annealing are characteristic features of cold crystallization.

  6. Ab initio calculations of optical constants of GaSe and InSe layered crystals

    Science.gov (United States)

    Sarkisov, S. Yu.; Kosobutsky, A. V.; Brudnyi, V. N.; Zhuravlev, Yu. N.

    2015-09-01

    The dielectric functions, refractive indices, and extinction coefficients of GaSe and InSe layered crystals have been calculated within the density functional theory. The calculations have been performed for the values of theoretical structural parameters optimized using the exchange-correlation functional, which allows one to take into account the dispersion interactions. It has been found that optical functions are characterized by the most pronounced polarization anisotropy in the range of photon energies of ˜4-7 eV. The frequency dependences for InSe compound in the range up to 4 eV demonstrate the more pronounced anisotropy as compared to GaSe. The results obtained for GaSe crystal agree better with the experimental data as compared to the previous calculations.

  7. Anisotropy in CdSe quantum rods

    Energy Technology Data Exchange (ETDEWEB)

    Li, Liang-shi

    2003-09-01

    The size-dependent optical and electronic properties of semiconductor nanocrystals have drawn much attention in the past decade, and have been very well understood for spherical ones. The advent of the synthetic methods to make rod-like CdSe nanocrystals with wurtzite structure has offered us a new opportunity to study their properties as functions of their shape. This dissertation includes three main parts: synthesis of CdSe nanorods with tightly controlled widths and lengths, their optical and dielectric properties, and their large-scale assembly, all of which are either directly or indirectly caused by the uniaxial crystallographic structure of wurtzite CdSe. The hexagonal wurtzite structure is believed to be the primary reason for the growth of CdSe nanorods. It represents itself in the kinetic stabilization of the rod-like particles over the spherical ones in the presence of phosphonic acids. By varying the composition of the surfactant mixture used for synthesis we have achieved tight control of the widths and lengths of the nanorods. The synthesis of monodisperse CdSe nanorods enables us to systematically study their size-dependent properties. For example, room temperature single particle fluorescence spectroscopy has shown that nanorods emit linearly polarized photoluminescence. Theoretical calculations have shown that it is due to the crossing between the two highest occupied electronic levels with increasing aspect ratio. We also measured the permanent electric dipole moment of the nanorods with transient electric birefringence technique. Experimental results on nanorods with different sizes show that the dipole moment is linear to the particle volume, indicating that it originates from the non-centrosymmetric hexagonal lattice. The elongation of the nanocrystals also results in the anisotropic inter-particle interaction. One of the consequences is the formation of liquid crystalline phases when the nanorods are dispersed in solvent to a high enough

  8. Desarrollo de un sistema de adquisición y procesado de señales electrooculográficas para el diagnóstico de la ataxia

    OpenAIRE

    Gallego Navarrete, David

    2007-01-01

    Accèssit al Premi CETIB 2007 Enginyeria i Societat / Col·legi Oficial d’Enginyers Tècnics Industrials de Barcelona Este proyecto final de carrera consiste en el diseño y construcción de un sistema de adquisición de biopotenciales de bajo coste para captar y visualizar la señal electrooculográfica (EOG) y ser usado en el diagnóstico de la Ataxia SCA2. El objetivo final es tener un sistema hardware de amplificación plenamente funcional a partir del cual podamos capatar la señal del EOG y mos...

  9. ¿POR QUÉ LAS MUJERES NO SE TOMAN EL PAPANICOLAOU? RESPUESTAS ENTREGADAS POR LOS PROFESIONALES DEL PROGRAMA CÁNCER CERVICOUTERINO- AUGE DEL SERVICIO DE SALUD METROPOLITANO SUR ORIENTE

    OpenAIRE

    Urrutia S,María Teresa; Araya G,Alejandra; Poupin B,Lauren

    2010-01-01

    Antecedentes: Los beneficios del test de Papanicolaou (Pap) en reducir la mortalidad de cáncer cervicouterino han sido bien documentados a nivel mundial y nacional. Sin embargo, aún persisten mujeres que no se realizan el Pap rutinariamente. Objetivo: Conocer la percepción que tienen los profesionales de la salud en relación a las causas por las cuales las mujeres no se toman la prueba del Pap. Método: Estudio descriptivo transversal, con una muestra de 59 profesionales del Servicio de Salud ...

  10. Investigación de la biotransformación de Se en tejidos de Phaseolus vulgaris L. mediante espectroscopia de absorción de rayos X Investigación de la biotransformación de Se en tejidos de Phaseolus vulgaris L. mediante espectroscopia de absorción de rayos X

    Directory of Open Access Journals (Sweden)

    Jorge L. Gardea-Torresdey

    2012-02-01

    Full Text Available   In this investigation, selenate toxicity was evaluated in three varieties of Phaseoulus vulgaris L.: Negro, Peruano, and Flor de Mayo, where this last was identified as the most resistant to selenate. In the Flor de Mayo variety, Se in plant tissues was quantified and X-ray absorption spectroscopy (XAS analysis performed in order to determine the potential selenate biotransformation. Root and stem tissues accumulated up to 1 218 mg Se kg-1 and 101 mg Se kg-1, respectively. XAS results indicated that part of the selenate was biotransformed, as in plant tissues selenate as well as selanide forms were identified. According to these results, Flor de Mayo variety can be classified as a Se secondary accumulator. Also, selenate biotransformation was identified. To our knowledge, this is the first time selenate biotransformation using XAS in this plant species is reported.En este trabajo se evaluó la toxicidad del selenato en tres variedades de frijol (Phaseoulus vulgaris L.: Negro, Peruano y Flor de Mayo. La variedad Flor de Mayo se identificó como la más resistente por lo que en ella se cuantificó el selenio y se determinó la biotransformación del selenato mediante espectroscopia de absorción de rayos X (EAX. La raíz y tallo de esta variedad acumularon hasta 1 218 mg Se kg-1 y 101 mg Se kg-1, respectivamente. Los resultados de EAX indicaron que parte del selenato se biotransformó en los tejidos de la planta, en donde se identificaron las formas selenato y selenuro. De acuerdo a estos resultados, esta variedad de P. vulgaris puede ser clasificada como una acumuladora secundaria de selenio; por otro lado se comprobó la biotransformación del selenato usando EAX lo cual, hasta donde sabemos, no ha sido previamente reportada en la literatura.

  11. Discurso, Palabras del señor Presidente de la Academia Nacional de Medicina

    Directory of Open Access Journals (Sweden)

    Gilberto Rueda Pérez

    1998-12-01

    Full Text Available

    Señora Ministra de Salud Doctora María Teresa Forero de Saade, Señor Doctor Jaime Posada Díaz, Presidente del Colegio Máximo de las Academias – Director de la Academia Colombiana de la Lengua, Señor Doctor Roberto de Zubiría Vicepresidente de la Academia Nacional de Medicina, Señor Doctor Hernando Groot Liévano Secretario Perpetuo de la Academia, Señor Doctor Zoilo Cuéllar-Montoya Secretario General de la Academia, Señor Doctor Gonzalo López Escobar Tesorero de la Academia, Señor Doctor José Félix Patiño Presidente Electo de la Academia Nacional de Medicina, Señores Miembros de la Junta Directiva entrante Señores Miembros de la familia del Doctor Patiño Restrepo, Señores Académicos Señoras y Señores invitados.

    Hace cerca de cuatro años recibí de ustedes Señores Académicos el mandato mas trascendental e importante en la vida de un médico: la Presidencia de la Academia Nacional de Medicina, distinción y categoria ésta que por grandiosa, por espléndida y por inmerecida en mi caso, produce en la mente y en la conciencia de quien la recibe poderoso impacto que lo deslumbra y que lo ubica en su pequeñez, en su humildad en su incapacidad para afrontar tamaño desafío y ponderosa y delicada misión.

    Pero simultáneamente lo estimula y lo impulsa en su poder de superación y su deseo de servir, a acometer la tarea y a fijarse metas que, aunque puedan parecer inalcanzables, tracen el derrotero que con teson y con firmeza y con decisión haya de recorrer, para alcanzarlas o al menos aproximarse a ellas.

    Tiene consigo la fuerza impulsora y estimulante de la confianza depositada en el por sus pares al escogerlo. Puede apoyarse cual en bastón sólido y equilibrante, en el discernimiento, en la solidez y en la experiencia acumulada en la Academia a través de los años y en la colaboración y sabio consejo de quienes han de acompañarlo en la Junta Directiva durante su período estatutario.

    Y al

  12. Superconducting gap structure of FeSe.

    Science.gov (United States)

    Jiao, Lin; Huang, Chien-Lung; Rößler, Sahana; Koz, Cevriye; Rößler, Ulrich K; Schwarz, Ulrich; Wirth, Steffen

    2017-03-07

    The microscopic mechanism governing the zero-resistance flow of current in some iron-based, high-temperature superconducting materials is not well understood up to now. A central issue concerning the investigation of these materials is their superconducting gap symmetry and structure. Here we present a combined study of low-temperature specific heat and scanning tunnelling microscopy measurements on single crystalline FeSe. The results reveal the existence of at least two superconducting gaps which can be represented by a phenomenological two-band model. The analysis of the specific heat suggests significant anisotropy in the gap magnitude with deep gap minima. The tunneling spectra display an overall "U"-shaped gap close to the Fermi level away as well as on top of twin boundaries. These results are compatible with the anisotropic nodeless models describing superconductivity in FeSe.

  13. Chemical beam epitaxy of ZnSe

    Science.gov (United States)

    Kolodziejski, Leslie A.

    1990-10-01

    ZnSe, ZnTe, and ZnSe/ZnTe layered quantum well structures have room temperature direct energy bandgaps which span the blue/blue-green optical spectrum. These II-VI semiconductors possess significant technological potential for visible optoelectronic device applications. Both military and commercial applications are envisioned. Blue/blue-green semiconductor injection lasers for underwater to satellite communications, visible flat panel electroluminescent displays, optical disc recording using blue wavelengths to increase the density of recorded information, color laser printers, and short range domestic or industrial communications via polymer fibers are examples of frequently quoted potential markets. The magnitude in U.S. dollars offered by these varied and large commercial markets warrants substantial investment in both research time and funds to push these materials to their ultimate potential for optoelectronic device fabrication testing, and marketing. Substantial effort is currently underway in Japan and Europe with major investment in funds and manpower.

  14. Two-dimensional semiconductor HfSe{sub 2} and MoSe{sub 2}/HfSe{sub 2} van der Waals heterostructures by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Aretouli, K. E.; Tsipas, P.; Tsoutsou, D.; Marquez-Velasco, J.; Xenogiannopoulou, E.; Giamini, S. A.; Vassalou, E.; Kelaidis, N.; Dimoulas, A., E-mail: a.dimoulas@inn.demokritos.gr [Institute of Nanoscience and Nanotechnology, National Center for Scientific Research “Demokritos,” 15310, Aghia Paraskevi, Athens (Greece)

    2015-04-06

    Using molecular beam epitaxy, atomically thin 2D semiconductor HfSe{sub 2} and MoSe{sub 2}/HfSe{sub 2} van der Waals heterostructures are grown on AlN(0001)/Si(111) substrates. Details of the electronic band structure of HfSe{sub 2} are imaged by in-situ angle resolved photoelectron spectroscopy indicating a high quality epitaxial layer. High-resolution surface tunneling microscopy supported by first principles calculations provides evidence of an ordered Se adlayer, which may be responsible for a reduction of the measured workfunction of HfSe{sub 2} compared to theoretical predictions. The latter reduction minimizes the workfunction difference between the HfSe{sub 2} and MoSe{sub 2} layers resulting in a small valence band offset of only 0.13 eV at the MoSe{sub 2}/HfSe{sub 2} heterointerface and a weak type II band alignment.

  15. Forming Glasses from Se and Te

    Directory of Open Access Journals (Sweden)

    Pierre Lucas

    2009-10-01

    Full Text Available Despite being close neighbors on the Periodic Table, selenium and tellurium present a totally different abilities to form glasses. Se is a very good glass former, and gives rise to numerous glass compositions which are popular for their transparency in the infrared range and their stability against crystallization. These glasses can be shaped into sophisticated optical devices such as optical fibers, planar guides or lenses. Nevertheless, their transparencies are limited at about 12 μm (depending on the thickness of the optical systems due to the relatively small mass of the Se element. On the other hand, tellurium is heavier and its use in substitution for Se permits to shift the IR cutoff beyond 20 μm. However, the semimetallic nature of Te limits its glass formation ability and this glass family is known to be unstable and consequently has found application as phase change material in the Digital Versatile Disk (DVD technology. In this paper, after a review of selenide glasses and their applications, it will be shown how, in a recent past, it has been possible to stabilize tellurium glasses by introducing new elements like Ga or I in their compositions.

  16. Patrimonio cultural: lo intangible se hace tangible

    Directory of Open Access Journals (Sweden)

    William Heredia Orjuela

    2004-11-01

    Full Text Available Se presentan tres reflexiones a manera de ensayo, elaboradas por estudiantes de vii semestre de la Facultad de Administración de Empresas Turísticas y Hoteleras. El tema central que engloba los escritos es el de la responsabilidad frente al patrimonio cultural, su valoración y su relación con el turismo. En el ensayo La protección del patrimonio cultural como reflejo del ser humano, la estudiante cecilia hinosTrosa hace un llamado de atención frente al problema del tráfico ilícito de bienes que conlleva la pérdida de testimonios de la cultura humana. El escrito de la estudiante mariel cecilia hernández destaca las bondades de recuperar las tradiciones y de cómo éstas se pueden difundir a través del turismo. Por último, el estudiante William heredia hace una reflexión sobre la tangibilidad de lo intangible, en el ensayo Patrimonio Cultural: lo tangible se hace intangible, donde destaca la declaratoria del Carnaval de Barranquilla como patrimonio oral e intangible de la humanidad.

  17. Thermoelectric properties of SnSe compound

    Energy Technology Data Exchange (ETDEWEB)

    Guan, Xinhong [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, P.O. Box 72, Beijing 100876 (China); Lu, Pengfei, E-mail: photon@bupt.edu.cn [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, P.O. Box 72, Beijing 100876 (China); Wu, Liyuan; Han, Lihong [State Key Laboratory of Information Photonics and Optical Communications, Ministry of Education, Beijing University of Posts and Telecommunications, P.O. Box 72, Beijing 100876 (China); Liu, Gang [School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Song, Yuxin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Wang, Shumin [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 (China); Photonics Laboratory, Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Gothenburg (Sweden)

    2015-09-15

    Highlights: • The electronic and thermoelectric properties of SnSe bulk material are studied. • The ZT can reach as high as 1.87 along yy and 1.6 along zz direction at 800k. • SnSe is an indirect-band material, and SOC has little effect on the band structure. • The high ZT can be attributed to the intrinsically ultralow thermal conductivity. - Abstract: A first-principles study and Boltzmann transport theory have been performed to evaluate the electronic structure and thermoelectric properties of SnSe compound. The energy band structure and density of states are studied in detail. The electronic transport coefficients are then calculated as a function of chemical potential or temperature within the assumption of the constant relaxation time. The figure of merit ZT is obtained with the use of calculated thermoelectric properties and can reach as high as 1.87 along yy and 1.6 along zz direction at 800 K. Our theoretical result agrees well with previous experimental data.

  18. Experience with the SE in Germany

    Directory of Open Access Journals (Sweden)

    Jochem Reichert

    2008-03-01

    Full Text Available A rather significant proportion of the Societas Europaeas (the European Company, or SE formed to date have had German roots. German corporate law has been enriched by an interesting alternative which meanwhile seems to have gained momentum. This contribution focuses on SEs incorporated by German entrepreneurs and provides an interesting account concerning the use of SEs in Germany in practice, such as Allianz, Fresenius, BASF and Porsche. Has the SE been used to circumvent rigid company law provisions or is it a more flexible and effective tool, perhaps, for company mobility? The practical motives behind setting up this company form are also reflected upon. These include: the facilitation of cross-border mergers; transfer of the registered office; the ‘European’ image; a more flexible form of co-determination in large companies (reduction of the number of supervisory board members; avoidance and freezing of co-determination for medium-sized enterprises; the appeal of the one-tier system and its endangerment by German co-determination; and flat and uniform structures for company groups. The author also briefly discusses some of the problems arising from the formation of SEs in Germany. He ultimately concludes that practice has shown that it is possible to work with the legal regime of the SE in Germany, which adds a new company form to those available in that Member State.

  19. Apoptosis neuronal: la diversidad de señales y de tipos celulares

    Directory of Open Access Journals (Sweden)

    Lina Vanessa Becerra

    2009-03-01

    Full Text Available La muerte celular programada es un evento fisiológico durante el desarrollo. En el encéfalo y la médula espinal, este proceso determina el número y la localización de los diferentes tipos celulares. En el sistema nervioso del adulto, la muerte celular programada o apoptosis está más restringida, pero puede jugar un papel determinante en enfermedades crónicas o agudas. Al contrario de otros tejidos en los cuales la apoptosis está documentada ampliamente desde el punto de vista morfológico, en el sistema nervioso central la evidencia en este sentido es escasa. A pesar de esto, existe consenso acerca de la activación de diferentes sistemas de señalización apoptótica. En el presente artículo se intenta resumir las principales vías de señalización apoptótica identificadas en el tejido nervioso. Considerando que las vías apoptóticas son múltiples, los tipos neuronales diversos y especializados y que la respuesta neuronal a la lesión y la supervivencia dependen del contexto de la célula en el tejido (preservación de la conectividad, integridad glial y matriz extracelular, flujo sanguíneo y disponibilidad de factores tróficos, lo que es relevante en el proceso apoptótico en un sector del cerebro puede no serlo en otro.

  20. One-pot synthesis of multicolor MnSe:ZnSe nanocrystals for optical coding.

    Science.gov (United States)

    Wang, Yanbin; Wang, Chunlei; Xu, Shuhong; Shao, Haibao; Jiang, Yuan; Bo, Fan; Wang, Zhuyuan; Cui, Yiping

    2014-02-01

    Though the investigation on controlling the fluorescence properties of nanocrystals (NCs) with single emission has been widely reported, few efforts were spent on adjusting the fluorescence properties of NCs with multiple emission peaks. In this work, we successfully synthesized multicolor MnSe:ZnSe NCs with multiple emission peaks and developed a simple and accurate method to realize photoluminescence (PL) spectra (or color) adjustment. The PL of MnSe:ZnSe NCs has two distinct emission peaks, the trap emission of ZnSe at 475nm and Mn(2+)-induced emission at 585nm. By adjusting the nucleation temperature, the emission color of the NCs can be encoded according to the ratio of the emission intensities at 475 and 585nm. With the nucleation temperature rising from 0 to 70°C, the PL ratio between trap emission and Mn(2+)-induced emission can be consecutively changed from (1, 3) to (1, 0.5). In addition, the trap state is deeply inside the NCs rather than on NCs surface so that the trap emission is stable during environment change. Thus, these MnSe:ZnSe NCs hold great promise as novel single-particle coding labels for biomedical imaging. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. Generation of Se-fortified broccoli as functional food: impact of Se fertilization on S metabolism.

    Science.gov (United States)

    Hsu, Fu-Chen; Wirtz, Markus; Heppel, Simon C; Bogs, Jochen; Krämer, Ute; Khan, Muhammad Sayyar; Bub, Achim; Hell, Rüdiger; Rausch, Thomas

    2011-02-01

    Selenium (Se)-fortified broccoli (Brassica oleracea var. italica) has been proposed as a functional food for cancer prevention, based on its high glucosinolate (GSL) content and capacity for Se accumulation. However, as selenate and sulphate share the initial assimilation route, Se fertilization could interfere with sulphur metabolism and plant growth. Consequently, GSL accumulation could be compromised. To evaluate these potentially adverse effects of Se fertilization, we performed a comprehensive study on sand-grown young broccoli plants (weekly selenate applications of 0.8 µmol plant(-1) via the root) and field-grown adult broccoli plants during head formation (single foliar selenate application: 25.3 or 253 µmol plant(-1) ). The results show that under these conditions, Se application does not affect plant growth, contents of cysteine, glutathione, total GSL, glucoraphanin (major aliphatic GSL) or the expression of BoMYB28 (encoding a functionally confirmed master regulator for aliphatic GSL biosynthesis). Conversely, due to the changed expression of sulphate transporters (BoSULTR1;1, 1;2, 2;1, and 2;2), sulphate and total S contents increased in the shoot of young plants while decreasing in the root. We conclude that broccoli can be fertilized with Se without reduction in GSL content, even with Se accumulation exceeding the level recommended for human consumption.

  2. Análisis y mejora del sistema de recogida de leche de una industria láctea

    OpenAIRE

    Rojas Molina, Isaac

    2005-01-01

    Los departamentos logísticos del sector industrial lácteo tienen en la reducción de costes de transporte una de sus principales fuentes para generar beneficios, objetivo final de toda empresa privada. El siguiente estudio pretende reducir estos costes y mejorar sensiblemente el sistema de recogida de leche, y consta de dos partes principales: • Un análisis de la situación actual de la recogida de leche en una industria láctea, en el cual se describen los procesos que forman la recogida y l...

  3. Anexo 1. Las unidades residenciales de las tres comunidades

    OpenAIRE

    2014-01-01

    En la comunidad de Yanayacu, las 27 casas (de las cuales 5 son plurifamiliares) se organizan en cuatro conjuntos. Dos casas al centro forman un conjunto particular, asociado a la escuela. Grupo de vecindad de Puerto Huamán Primer conjunto Los hermanos y hermanas de un linaje de descendencia paterna, del clan oyo baht, originario de Sucusari, dominado numéricamente por los hombres, permanecen juntos y han integrado sus aliados respectivos (dei bahῖ e ῖye bahῖ). El conjunto (cuatro linajes de d...

  4. Procesos de construcción de saberes relativos a las prácticas de belleza entre mujeres de sectores populares

    OpenAIRE

    Claudia Gabriela Reta

    2017-01-01

    El propósito de este artículo es analizar los procesos de construcción de saberes de belleza y estética corporal entre mujeres en contextos de pobreza y segregación socio-espacial. Para ello se identifican y describen las prácticas realizadas por un grupo de mujeres de una villa de la Ciudad Autónoma de Buenos Aires, Argentina, en el marco de una investigación con perspectiva etnográfica. Los resultados obtenidos demuestran que dichos procesos forman parte de una dinámica a partir de la cual ...

  5. Notas sobre el origen de la diversidad biológica

    OpenAIRE

    Pérez-Urria Carril, Elena

    2007-01-01

    Conocemos moléculas, células, organismos y ecosistemas que forman parte de lo que llamamos "Diversidad Biológica". Pero es importante también conocer el origen de esa diversidad. En ese contexto se entiende la evolución biológica como proceso o fuerza generadora de distintas formas de vida. Pero antes de la "era biológica" existió un mundo prebiótico desde el cual "surgen" los elementos o moléculas que más tarde sustentarán las formas de vida más elementales.

  6. PERCEPCIONES DE ACADEMICOS, DIRECTIVOS Y FUNCIONARIOS SOBRE LA LEGITIMIDAD Y EL LIDERAZGO DE LOS RECTORES DE LAS UNIVERSIDADES PUBLICAS MEXICANAS

    OpenAIRE

    ROMUALDO LÓPEZ ZÁRATE

    2013-01-01

    Los rectores de las universidades públicas forman parte de la estructura de la autoridad institucional. La autoridad que ostentan proviene de varias fuentes, la racional, la tradicional y la carismática, las cuales le dan legitimidad al ejercerla. Un aspecto de la legitimidad se relaciona con la percepción que tiene parte de la comunidad universitaria sobre el desempeño del rector, sobre su liderazgo. Este trabajo pretende incursionar en la percepción que tienen varios sectores de la comunida...

  7. Regulación por proteasas del canal de sodio sensible al amiloride (ENaC)

    OpenAIRE

    Luciano Galizia; Alejandro Ojea; Basilio A. Kotsias

    2011-01-01

    El ENaC es un canal que permite el movimiento de Na+ desde el líquido luminal hacia las células en numerosos epitelios reabsortivos y también en otros tejidos como la placenta. ENaC juega un papel crucial en la homeostasis de los electrolitos y volumen de líquido extracelular. Es regulado por numerosas hormonas, incluyendo la aldosterona y bloqueado por el diurético amiloride. El ENaC está formado por tres subunidades homólogas α, β y γ que forman el poro por el cual se mueven los iones Na+. ...

  8. Reflexión sobre una nueva formación del docente de enfermería para una nueva época: ¿el porqué de una nueva formación docente, y qué hay que cambiar?

    OpenAIRE

    Palencia Esperanza, E.; Gonzalez, M; Evies, A.; Guevara, B.; Mejías, M.

    2006-01-01

    Las Universidades son centros en los cuales se forman individuos con competencias para desempeñarse en la sociedad, por lo que deben contar con un personal docente altamente calificado y con una preparación docente que les permita dar respuesta a las necesidades de la comunidad estudiantil y de la población en general. Para ello, es imprescindible que el personal docente que labora en estas instituciones educativas emplee estrategias de enseñanza que permitan la relación e...

  9. Notas sobre el origen de la diversidad biológica

    OpenAIRE

    2007-01-01

    Conocemos moléculas, células, organismos y ecosistemas que forman parte de lo que llamamos "Diversidad Biológica". Pero es importante también conocer el origen de esa diversidad. En ese contexto se entiende la evolución biológica como proceso o fuerza generadora de distintas formas de vida. Pero antes de la "era biológica" existió un mundo prebiótico desde el cual "surgen" los elementos o moléculas que más tarde sustentarán las formas de vida más elementales.

  10. ¿El retorno del leopardo? Patrimonialismo y crisis post-transición en la República Democrática del Congo | The return of the leopard? Patrimonialism and post-transition crisis in Democratic Republic of Congo

    OpenAIRE

    Vlassenroot, Koen; Raeymaekers, Timothy

    2007-01-01

    El artículo ofrece una interpretación de las razones por las cuales, a pesar del proceso de paz iniciado en el 2003 en la República democrática del Congo, el país se sigue caracterizando por elevados niveles de violencia física y estructural. Una violencia provocada por factores diversos a) la propia intervención internacional que en parte puede al promover acuerdos de poder compartido retribuyendo la violencia armada y b) el proceso de fragmentación de los actores armados que forman compleja...

  11. MERCOSUR y UNASUR: Una aproximación al tratamiento de la movilidad de personas

    OpenAIRE

    Lucila Nejamkis Rubellin

    2017-01-01

    La integración regional constituye un proceso complejo que involucra un conjunto de fenómenos políticos, económicos, culturales y sociales sobre los cuales los estados deben lograr acuerdos a fin de definir políticas coordinadas. El tránsito de personas y la regulación de los flujos migratorios forman parte de estos aspectos que se deben abordar. En los últimos años, los diferentes bloques regionales de América del Sur (MERCOSUR, CAN, UNASUR) han pretendido avanzar en esta dirección. Concepto...

  12. ZnCdSe/ZnSe quantum-dot semiconductor optical amplifiers

    Science.gov (United States)

    Al-Mossawi, Muwaffaq Abdullah

    2017-02-01

    Gain of CdZnSe quantum dot (QD) semiconductor optical amplifiers (SOAs) is studied theoretically using non-Markovian gain model including many-body effects. The calculations are done at three mole fractions. Spontaneous emission and noise figure of the amplifier are studied. The effect of shot noise is included. High gain, polarization independence, and low noise figure are characterize these QD-SOAs. A multi-mode gain appears for Zn0.69Cd0.31Se structure while the structure Zn0.6Cd0.4Se give a low noise.

  13. Optical nonlinearities in GaSe and InSe crystals upon laser excitation

    Science.gov (United States)

    Kyazym-zade, A. G.; Salmanov, V. M.; Guseinov, A. G.; Gasanova, L. G.; Mamedov, R. M.

    2014-04-01

    The nonlinear absorption of light and its temporal evolution in the vicinity of exciton resonance in layered GaSe and InSe crystals under high optical excitation have been experimentally investigated. The decisive factor for the observed temporal dependence of the absorption coefficient and its dependence on the excitation intensity is screening excitons by nonequilibrium-carrier plasma. It is shown that the increase in the transmittance in the absorption-band edge in GaSe with a simultaneous blue shift of the band edge is caused by filling the energy bands under high optical excitation.

  14. Highly luminescent CdSe/ZnSe core-shell quantum dots of one-pot preparation in octadecene

    NARCIS (Netherlands)

    Zeng, Q.; Kong, X.; Zhang, Y.; Zhang, H.

    2008-01-01

    CdSe/ZnSe core-shell quantum dots were synthesized using a new one-pot procedure where the core was prepared in octadecene. A ZnSe shell around a CdSe nanoparticle was formed by the reaction of selenium-richness on the surfaces of CdSe nanoparticles with Zn2+ from the injected zinc stearate precurso

  15. Highly luminescent CdSe/ZnSe core-shell quantum dots of one-pot preparation in octadecene

    NARCIS (Netherlands)

    Zeng, Q.; Kong, X.; Zhang, Y.; Zhang, H.

    2008-01-01

    CdSe/ZnSe core-shell quantum dots were synthesized using a new one-pot procedure where the core was prepared in octadecene. A ZnSe shell around a CdSe nanoparticle was formed by the reaction of selenium-richness on the surfaces of CdSe nanoparticles with Zn2+ from the injected zinc stearate

  16. 77Se nuclear magnetic resonance of topological insulator Bi2Se3

    Science.gov (United States)

    Georgieva, Nataliya M.; Rybicki, Damian; Guehne, Robin; Williams, Grant V. M.; Chong, Shen V.; Kadowaki, Kazuo; Garate, Ion; Haase, Jürgen

    2016-05-01

    Topological insulators constitute a new class of materials with an energy gap in the bulk and peculiar metallic states on the surface. We report on new features resulting from the bulk electronic structure, based on a comprehensive nuclear magnetic resonance (NMR) study of 77Se on Bi2Se3 and Cu0.15Bi2Se3 single crystals. First, we find two resonance lines and show that they originate from the two inequivalent Se lattice sites. Second, we observe unusual field-independent linewidths and attribute them to an unexpectedly strong internuclear coupling mediated by bulk electrons. In order to support this interpretation, we present a model calculation of the indirect internuclear coupling and show that the Bloembergen-Rowland coupling is much stronger than the Ruderman-Kittel-Kasuya-Yosida coupling. Our results call for a revision of earlier NMR studies and add information concerning the bulk electronic properties.

  17. Temperature dependence of excitonic transition in ZnSe/ZnCdSe quantum wells

    Institute of Scientific and Technical Information of China (English)

    GUO Zi-zheng; LIANG Xi-xia; BAN Shi-liang

    2005-01-01

    A theoretical calculation for the temperature dependence of the excitonic transition in ZnSe/ZnCdSe quantum wells is performed. The exciton binding energy is calculated with a variational technique by considering the temperature-dependence parameters. Our results show that the exciton binding energy reduces linearly with temperature increasing. We find that the strain due to lattice mismatch and differential thermal expansion decreases with the temperature increasing.

  18. Hjem og arbejde for hjemløse og arbejdsløse EU medborgere

    DEFF Research Database (Denmark)

    Ravnbøl, Camilla Ida

    2015-01-01

    belyses hvor meget arbejde og hjem betyder for denne gruppe af formelt hjemløse og arbejdsløse EU medborgere. Udgangspunktet er etnografisk materiale, som viser roma kvinder og mænds erfaringer med at opretholde hjemmet i Rumænien, skabe sig et trygt hjem på gaden samt at søge efter arbejde og arbejde med...

  19. Conduction band offset determination between strained CdSe and ZnSe layers using DLTS

    Science.gov (United States)

    Rangel-Kuoppa, Victor-Tapio

    2013-12-01

    The conduction band offset between strained CdSe layers embedded in unintentionally n-type doped ZnSe is measured and reported. Two samples, consisting of thirty Ultra Thin Quantum Wells (UTQWs) of CdSe embedded in ZnSe, grown by Atomic Layer Epitaxy, are used for this study. The thicknesses of the UTQWs are one and three monolayers (MLs) in each sample, respectively. As expected, the sample with one ML UTQWs does not show any energy level in the UTQWs due to the small thickness of the UTQWs, while the thickness of the sample with 3 ML UTQWs is large enough to form an energy level inside the UTQWs. This energy level appears as a majority trap with an activation energy of 223.58 ± 9.54 meV. This corresponds to UTQWs with barrier heights (the conduction band offset) between 742 meV and 784 meV. These values suggest that the band gap misfit between strained CdSe and ZnSe is around 70.5 to 74 % in the conduction band.

  20. Conduction band offset determination between strained CdSe and ZnSe layers using DLTS

    Energy Technology Data Exchange (ETDEWEB)

    Rangel-Kuoppa, Victor-Tapio [Institute of Semiconductor and Solid State Physics, Johannes Kepler Universität, A-4040 Linz (Austria)

    2013-12-04

    The conduction band offset between strained CdSe layers embedded in unintentionally n-type doped ZnSe is measured and reported. Two samples, consisting of thirty Ultra Thin Quantum Wells (UTQWs) of CdSe embedded in ZnSe, grown by Atomic Layer Epitaxy, are used for this study. The thicknesses of the UTQWs are one and three monolayers (MLs) in each sample, respectively. As expected, the sample with one ML UTQWs does not show any energy level in the UTQWs due to the small thickness of the UTQWs, while the thickness of the sample with 3 ML UTQWs is large enough to form an energy level inside the UTQWs. This energy level appears as a majority trap with an activation energy of 223.58 ± 9.54 meV. This corresponds to UTQWs with barrier heights (the conduction band offset) between 742 meV and 784 meV. These values suggest that the band gap misfit between strained CdSe and ZnSe is around 70.5 to 74 % in the conduction band.

  1. Schilddrüse und Schwangerschaft

    Directory of Open Access Journals (Sweden)

    Zettinig G

    2009-01-01

    Full Text Available Kinderwunsch, Schwangerschaft und die Zeit nach einer Geburt sind besondere Lebensabschnitte bei Patientinnen mit Schilddrüsenerkrankungen. Bei jungen Frauen sind Autoimmunerkrankungen der Schilddrüse, die Einfluss auf die Fruchtbarkeit und die intellektuelle und körperliche Entwicklung des Fetus haben können, häufig. Schilddrüsenerkrankungen können sich in dieser Lebensphase auch erstmals manifestieren; besondere Beachtung verdient die Wechselwirkung von β-HCG mit dem TSH-Rezeptor. Diese Übersicht behandelt das aktuelle Management von Patientinnen mit Schilddrüsenerkrankungen bei Kinderwunsch, in der Schwangerschaft und Postpartalperiode.

  2. Patrimonio cultural: lo intangible se hace tangible

    OpenAIRE

    William Heredia Orjuela

    2004-01-01

    Se presentan tres reflexiones a manera de ensayo, elaboradas por estudiantes de vii semestre de la Facultad de Administración de Empresas Turísticas y Hoteleras. El tema central que engloba los escritos es el de la responsabilidad frente al patrimonio cultural, su valoración y su relación con el turismo. En el ensayo La protección del patrimonio cultural como reflejo del ser humano, la estudiante cecilia hinosTrosa hace un llamado de atención frente al problema del tráfico ilícito de bienes q...

  3. Leishmaniasis visceral: senderos que confluyen, se bifurcan

    OpenAIRE

    Oscar Daniel Salomón; Andrea Verónica Mastrángelo; María Soledad Santini; Silvina Ruvinsky; Tomás Orduna; Angel Sinagra; Concepción Luna; Adelina Riarte; Natalia Casas; Paola Amiotti

    2012-01-01

    La leishmaniasis visceral urbana es una zoonosis emergente en Argentina. En América es producida por Leishmania infantum, con el perro como reservorio principal e insectos flebotomíneos como vectores. En este artículo se presenta el conocimiento acumulado a partir de su emergencia y dispersión en el país, por los referentes del Programa Nacional de Leishmaniasis, en el diagnóstico clínico y de laboratorio, tratamiento, biología de vectores, manejo de reservorio, y el conflicto generado con la...

  4. Los guionistas hablan: cómo se crean personajes en la ficción nacional resultados de un estudio cualitativo

    Directory of Open Access Journals (Sweden)

    María Marcos Ramos

    2014-12-01

    Full Text Available Mediante un estudio de corte cualitativo en el que se realiza una entrevista a una muestra de guionistas en activo (n=19 se analiza el proceso de creación y de incorporación de personajes inmigrantes en las principales series y películas nacionales. Gracias al análisis de sus respuestas se pueden conocer los motivos por los cuales los personajes inmigrantes están infrarrepresentados y estereotipados, tal y como han indicado diversas investigaciones (Igartua; Barrios y Ortega, 2012; Marcos; Igartua; Frutos; Barrios; Ortega y Piñeiro, 2014. Del análisis de sus respuestas se puede saber cómo se crean los personajes inmigrantes en la ficción nacional, siendo este el objetivo de este estudio. Entre los resultados más significativos habría que destacar que los guionistas recurren a los estereotipos para crear personajes, especialmente cuando se habla de inmigrantes, además de que estos no son comerciales y su creación depende del género del programa. Sin embargo no ha habido unanimidad en otras cuestiones,como si hay actores inmigrantes, si desempeñan el rol de ignorante en las comedias y el uso de realidad en el proceso de creación.

  5. Vacancy defects in epitaxial thin film CuGaSe2 and CuInSe2

    OpenAIRE

    Korhonen, E.; Kuitunen, K.; Tuomisto, Filip; Urbaniak, A.; Igalson, M.; Larsen, J.; Gutay, L; Siebentritt, S; Tomm, Y.

    2012-01-01

    Epitaxial thin film CuGaSe2 and CuInSe2 samples grown on GaAs substrates with varying [Cu]/[Ga,In] ratios were studied using positron annihilation Doppler-broadening spectroscopy and were compared to bulk crystals. We find both Cu monovacancies and Cu-Se divacancies in CuInSe2, whereas, in CuGaSe2, the only observed vacancy defect is the Cu-Se divacancy. Peer reviewed

  6. Lo que se debe a las cimentaciones

    Directory of Open Access Journals (Sweden)

    Oroviogoicoechea, Alberto

    1975-05-01

    Full Text Available This article describes: the problems that arise when the foundations has to act on soils with low consistency or when very narrow tolerances have to be met; the origin of the above mentioned problems; the requirements that are not really necessary, with suitable examples; the absolute and relative admissible magnitudes of differential settlements in concrete structures, walls, partitions and metal structures; the tolerances for mechanical installations; recommendations for projects and a table that sums up the proposed tolerances for relative foundations.En el artículo se describen: los problemas que surgen cuando la cimentación ha de actuar sobre terrenos poco consistentes o cuando se quieren cumplir tolerancias muy estrechas; de dónde provienen dichos problemas; las exigencias que no son realmente necesarias, con ejemplos apropiados; las magnitudes absolutas y relativas admisibles de asientos diferenciales, en estructuras de hormigón, muros, tabiques y estructuras metálicas; las tolerancias para instalaciones mecánicas; recomendaciones para proyecto, y una tabla que recoge las tolerancias propuestas para asientos relativos.

  7. Resepsies van Catullus se Carmen XLIX

    Directory of Open Access Journals (Sweden)

    J. Swanepoel

    1984-05-01

    Full Text Available Gaius Valerius Catullus (c. 84-c. 54 v.C., die Romeinse digter wat veral bekend is vir sy verse aan sy geliefde Lesbia, het benewens liefdesgedigte ook ’n hele aantal verse geskryf waarin van sy lydgenote figureer. Hierdie gedigie wat aan spesifieke persone gerig is, is wyd uiteenlopend en die toon en strekking daarvan wissel van toegeneentheid en liefde enersyds (vgl. Carmen IX tot felie invektief (Carmina CVIII, XCIII en spot (Carmen LXXXIV andersyds. Die leser kan gewoonlik maklik vasstel of hy in ’n gedig met vriend of vyand te doen liet. Maar daar is een uitsondering, en dit is Catullus se gedig aan die Romeinse staatsman, retor en skrywer, Marcus Tullius Cicero. Hierdie gedig, wat soos die meeste van Catullus se gedigte heel kort en kragtig is, is deur die eeue op uiteenlopende en botsende wyses geinterpreteer. Enersyds word dit beskou as ’n opregte dankbetuiging en lofprysing aan Cicero, terwyl ander lesers dit weer sien as ’n gedig wat ironies bedoel is.

  8. Leishmaniasis visceral: senderos que confluyen, se bifurcan

    Directory of Open Access Journals (Sweden)

    Oscar Daniel Salomón

    2012-01-01

    Full Text Available La leishmaniasis visceral urbana es una zoonosis emergente en Argentina. En América es producida por Leishmania infantum, con el perro como reservorio principal e insectos flebotomíneos como vectores. En este artículo se presenta el conocimiento acumulado a partir de su emergencia y dispersión en el país, por los referentes del Programa Nacional de Leishmaniasis, en el diagnóstico clínico y de laboratorio, tratamiento, biología de vectores, manejo de reservorio, y el conflicto generado con las acciones recomendadas en relación con los perros infectados. La detección temprana y el tratamiento precoz, con estrategias descentralizadas y horizontales, contribuirán a disminuir la morbimortalidad asociada a la leishmaniasis visceral. El control de su transmisión y dispersión requiere de un manejo ambiental integral y la tenencia responsable de perros. Se discuten los intereses y discursos en conflicto generados por la leishmaniasis visceral en el marco de la relación humano-perro, proponiendo la búsqueda de un discurso consensuado de riesgo.

  9. Se il filosofo ha un compito

    Directory of Open Access Journals (Sweden)

    Carmine Di Martino

    2011-01-01

    Full Text Available Il testo muove da una ricognizione dello “stile” complessivo dell’interrogazione filosofica contemporanea: stile decostruttivo, che si risolve in un’illustrazione del limite istitutivo e costitutivo di ogni dire filosofico (e non solo filosofico. In un secondo tempo del suo intervento, l’autore si chiede se una tale comprensione, puramente “negativa”, di quel limite e della validità della parola che ne discende, non sia essa stessa ideologica, e se non sia possibile frequentare una definizione positiva di tale limite, e una possibilità non soltanto autodecostruttiva della parola filosofica “dopo” Nietzsche, Heidegger, Derrida.

  10. Fabrication and characterization of CuInSe{sub 2} thin films from In{sub 2}Se{sub 3} and Cu{sub 2}Se precursors

    Energy Technology Data Exchange (ETDEWEB)

    Song, Jin Soo [Korea Inst. of Energy and Resources, Daeduk (Korea, Republic of); Huh, Gyung Jae; Kwon, Se Han; Ahn, Byung Tae [Korea Advanced Energy Research Inst., Daeduk-Danji (Korea, Republic of). Korea Nuclear Safety Center

    1995-12-01

    CuInSe{sub 2} this films as a light absorber layer were fabricated by vacuum evaporation using In{sub 2}Se{sub 3} and Cu{sub 2}Se precursors and their properties were analyzed. Indium selenide films of 0.5{mu}m thickness were first deposited by vacuum evaporation of In{sub 2}Se{sub 3} on a Corn ing 7059 glass substrate. The films deposited at susceptor temperature of 400 degree showed a flat surface morphology with densely packed grain structure. CuInSe{sub 2} films directly formed by evaporating Cu{sub 2}Se in the pre-deposited In{sub 2}Se{sub 2} films also showed a very flat surface when the susceptor temperature was 700 degree. Cu{sub 2}Se, a second phase in the CuInSe{sub 2} film, was removed by evaporating additional In{sub 2}Se{sub 3} on the CuInSe{sub 2} film at 700 degree. The grain size of 1.2{mu}m thick CuInSe{sub 2} film was about 2{mu}m and the film had a (112) preferred orientation. As the amount of deposited In{sub 2}Se{sub 3} increased, the electrical resistivity of CuInSe{sub 2} films increased because of the decrease of hole concentration. But the optical band gap was almost constant at the value of 1.04 eV. The CuInSe{sub 2} film grown in a Mo/glass substrate had a similar smooth microstructure compared to that on a glass substrate. A solar cell with ZnO/CdS/CuInSe{sub 2}/Mo structure may be realized based on the above CuInSe{sub 2} films. (author). 16 refs., 11 figs.

  11. Política pública de la migración en el Departamento del Valle del Cauca: ¿Cómo se está tratando el tema de la migración internacional, en el Departamento del Valle del Cauca hasta el 2009?

    OpenAIRE

    Lorena López López; Diana Marcela Méndez Figueroa

    2011-01-01

    El presente documento de trabajo se basa en la tesis de grado, presentada en la Universidad Icesi de Cali, bajo el mismo título del presente artículo. El texto aborda la Política Integral Migratoria (PIM) de Colombia y sus implicaciones en el departamento del Valle del Cauca. El documento está dividido en cuatro temas principales. Primero, se presenta el marco teórico, enfocado, particularmente, en el concepto de migración internacional, el cual se analiza desde distintos puntos de vista y au...

  12. Los deberes contractuales de información en materia de contratación a distancia ante la Ley 3/2014, de 27 de marzo, por la que se modifica el Texto Refundido de la Ley de Consumidores y Usuarios

    Directory of Open Access Journals (Sweden)

    Henrry Sosa Olan

    2016-01-01

    Full Text Available Con la transposición de la Directiva de los derechos de los consumidores de 2011 se refuerzan los deberes precontractuales de información y se impone al empresario una serie de requisitos formales en materia de contratación a distancia, los cuales a su vez se dividen en deberes formales relativos a la información precontractual y los requisitos de documentación del contrato. La omisión de estos últimos puede acarrear tanto sanciones civiles como administrativa, como veremos en este trabajo.

  13. Escuela para señoritas, Inglaterra

    Directory of Open Access Journals (Sweden)

    Stillman y Eastwlck-Field, Arquitectos

    1963-02-01

    Full Text Available The object was to design part of a new building which had been seriously damaged during the war, so that the old and new parts would blend into a pleasant whole, with a capacity for 600 girls. The new designs avoid the glass box style of school buildings, and glass walls have been adopted only on the ground floor, thus giving an impression of light and airiness to what used to be a partial basement. Classrooms have been designed in a simple manner, and give the impression of conventional rooms. Simple lines and materials have been chosen throughout. Strong contrasts in the external finish have been avoided, and colours provide a relaxing background to the intensive activities of the students. A constructional feature is the use of prefabricated concrete joists and supports. Outer walls consist of brick panels filling in the space between the visible concrete framework. Ceilings are of insulating boards, and the floors are covered with linoleum. Special attention has been devoted to the hall. In this case the roof is of white gypsum, and the only features are the grills covering the fluorescent lighting. The walls of this hall are of glass, and are covered with heavy velvet curtains. A balcony with hardwood posts adds a simple and friendly feature to the building. The furniture and drapery have been carefully chosen. Camden school has a rigid tradition of individualism and fine education, and the new building has succeeded in maintaining the exclusive quality of the older parts, as well as offering an overall impression of up to date construction.El problema consistía en proyectar un nuevo núcleo para un edificio que había sido seriamente bombardeado durante la guerra, de tal modo que las partes antiguas y nuevas formasen un conjunto agradable y con capacidad para más de 600 chicas. En la nueva construcción se ha evitado el carácter de «cajas de cristal» de las nuevas escuelas ordinarias y se han empleado muros de cristal solamente en la

  14. Estudio drx en materiales catalizadores cu-ni-sio2 para hidrogenación de aceite de soya. desarrollo de estructura cristalina y actividad catalítica

    OpenAIRE

    Cubillos, Gloria I.; Jesús A García; Delgado, Carlos A.; Liliana Giraldo

    2009-01-01

    Para buscar elementos experimentales que soporten la hipótesis según la cual se forman estructuras cristalinas Cu-Ni o eventualmente Cu-Ni-SiO2 en la síntesis de catalizadores para la hidrogenación de aceite de soya, se prepararon mezclas de estos tres materiales a partir de sales de los metales con sílice (aerosil). Se calcinaron a 270oC y se redujeron a 330oC en atmósfera de hidrógeno. En  los materiales reducidos se  estudió el difractógrama de RX en el rango 37 a 53 grados, y se comparó c...

  15. Estudio mediante EIS de la respuesta electroquímica de la aleación AA5083 frente a señales DC anódicas

    Directory of Open Access Journals (Sweden)

    Aballe, A.

    1998-05-01

    Full Text Available Electrochemical Impedance Spectroscopy (EIS has been applied to characterise the behaviour of AA5083 alloy samples under anodic polarisation in a 3.5 % NaCl solution. EIS spectra were obtained at different DC potentials falling within the passivity range characteristic of the anodic polarisation branch of this alloy in the cited corrosive environment. Three different types of electrochemical response, with specific features in the corresponding Nyquist diagrams, were observed within the potential range covered in this study. The different type of spectra have been fitted with equivalent circuits. The evolution of the values of the different elements in the circuits as a function of the applied DC polarisation potential has been established. The analysis of these data has allowed us to determine the ranges of polarisation potentials where the passivation layer remains stable, metastable pits are nucleated or where stable pits grow. Finally, the use of a "Bode Surface Plot" has been proposed to get a better visualization of the evolution of the system with the applied DC potential.

    Se ha llevado a cabo un estudio, mediante Espectroscopia de Impedancia Electroquímica (EIS, del comportamiento de la aleación AA5083 polarizada anódicamente en disolución de NaCl al 3,5 %. Los espectros de impedancia se registraron a distintos potenciales DC, seleccionados de acuerdo con el intervalo de pasividad que aparece en su curva de polarización anódica. En el rango de potenciales estudiado, se han obtenido tres tipos de respuesta electroquímica, cada una con un diagrama de Nyquist característico. Los diagramas obtenidos se han simulado construyendo los correspondientes circuitos equivalentes. La evolución, con la polarización aplicada, de los valores de los elementos que componen cada circuito ha permitido definir el intervalo de potencial en el que la capa pasiva es estable, se forman picaduras metaestables, o se nuclean y crecen picaduras. Por

  16. ¿Cómo se enfrentan tres culturas corporativas en una joint venture? Caso Intesa-Venezuela

    Directory of Open Access Journals (Sweden)

    Margalit Berlin

    2002-01-01

    Full Text Available Este es un estudio de caso realizado en Intesa, una empresa conjunta o joint venture. En Intesa coinciden tres tipos de gerentes, según el tipo de organización de la cual provienen: de Petróleos de Venezuela (PDVSA, del sector privado nacional y del sector multinacional. Mientras los gerentes se adaptan a las culturas corporativas de estos tres sectores, traen ciertas características culturales que los diferencian entre sí. El objetivo de este trabajo es determinar si las diferencias culturales tienen una influencia en la adopción de la cultura que auspicia la empresa. Los resultados de esta investigación coinciden con los encontrados en la literatura sobre la importancia de las condiciones iniciales en las que se forma una joint venture para determinar que una cultura predomine sobre otra. Estas condiciones iniciales son: la ubicación, las instalaciones, el lenguaje utilizado en la firma, los horizontes de carrera. Este estudio muestra un elemento más que contribuye al predominio de una cultura sobre otra. Este depende de las vías que posea cada sector para transmitir su cultura corporativa, algunas son más efectivas que otras. Las menos efectivas son los talleres itinerantes, los boletines, los correos electrónicos mientras las más efectivas son los premios y sanciones que se dan en la organización.

  17. Bio-fortification and isotopic labelling of Se metabolites in onions and carrots following foliar application of Se and 77Se

    DEFF Research Database (Denmark)

    Kápolna, Emese; Laursen, Kristian H.; Husted, Søren;

    2012-01-01

    that foliar application of Se(IV) gave rise to bio-synthesis of a higher fraction of the desired organic Se species and was better tolerated by the plants than Se(VI). Based on these findings onions and carrots were bio-fortified by foliar application of a solution of 77Se(IV) that was enriched to 99.7% as 77...

  18. The Preparation and Properties of DSSC CuAl2O4/TiO2 Photoanodes%染料敏化太阳电池CuAl2O4/TiO2光阳极制备及性能

    Institute of Scientific and Technical Information of China (English)

    胡志强; 刘显卿; 黄德锋; 高宏

    2012-01-01

    采用柠檬酸法制备了尖晶石型纳米晶CuA12O4,将其添加到P25(degussa,TiO2)中,制备成CuAl2O4/TiO2薄膜光阳极,并组装成染料敏化太阳电池(DSSC),对其光电性能进行表征.结果表明:CuAl2O4的加入,电池性能得到提高;当CuAl2O4含量为2%(质量分数)时,与纯TiO2薄膜光阳极相比,光电转化效率提高了39.1%.%CuAl2O4/TiO2 thin film photoanodes were prepared by doping spinel CuAl2O4 nanocrystal-line prepared by the citrate method into P25 (degussa, TiO2), and then assembled into Dye-sensitized solar cells(DSSC) and characterized the photoelectric properties. The results showed that performance of DSSC increase when doped CuAl2O4. When the doping amount is 2% (mass fraction), the photoelectric conversion efficiency was 39. 1% higher than the pure TiO2 thin film photoanodes.

  19. La tecnología cambió los escenarios: el efecto Pigmalión se hizo realidad Technology changed scene or Pygmalion came true

    Directory of Open Access Journals (Sweden)

    Julio Cabero Almenara

    2007-03-01

    Full Text Available Las diferentes tecnologías de la información y comunicación han cambiado con el paso de los años las diferentes sociedades por donde se han ido implantando. La consagración y adopción de las diferentes tecnologías ha consistido en procesos formativos mediante los cuales las creencias y expectativas que se les atribuían han hecho tal efecto que al final acaban por ser realidades y ante ella hemos de enfrentarnos. Ese trabajo refleja la invisibilidad con que las tecnologías han irrumpido en la vida diaria. This paper gives a summary of how the different information and communication technologies have changed the societies which have used them through the years. Consecration and adoption of different technologies have fulfilled beliefs and expectations that eventually have come true.

  20. Celebrado el I Encuentro Latinoamericano de Revistas Zootécnicas donde se fundó la Red Latina de Revistas de Zootecnia

    Directory of Open Access Journals (Sweden)

    Veterinaria.org

    2008-01-01

    Full Text Available ResumenSe celebró en la Universidad de Córdoba, del 12 al 14 de Diciembre de 2007, el “I Encuentro Latinoamericano de Revistas Zootécnicas”, en el cual se convocó a los responsables de la edición de las revistas más prestigiosas dentro del ámbito científico. En el cartel anunciador, figura el título y fecha del evento y debajo un arco formado por portadas de revistas del sector, entre las que está REDVET, y de fondo un mapa mundi, culminado por los logotipos institucionales de las entidades organizadoras, colaboradoras y patrocinadoras: Archivos de Zootecnia, Red Conbiand, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Universidad de Córdoba, Junta de Andalucía y Ayuntamie y Diputación de Córdoba.

  1. La guerra como respuesta a la crisis de los ingresos señoriales en el reino de Navarra durante el reinado de Carlos II (1349-1387

    Directory of Open Access Journals (Sweden)

    Jon Andoni Fernández de Larrea Rojas

    1989-01-01

    Full Text Available Más que en ningún otro período, la guerra fue uno de los mayores componentes de la vida de los hombres en los siglos finales de la Edad Media, afectando profundamente a todos los aspectos de la existencia. Es por ello una especie de atalaya desde la cual pueden observarse muchos y variados aspectos de la vida y sociedad medievales. El Reino de Navarra no fue ajeno a todo ello, es más, el particular contexto en el que se vio envuelto le llevó a sufrir en sí mismo la terrible experiencia de la guerra en numerosas ocasiones durante el reinado de Carlos II, en veinticinco de los treinta y ocho años de reinado se registra algún tipo de actividad militar.

  2. The CuInSe{sub 2}-CuGaSe{sub 2}-2CdSe system and crystal growth of the {gamma}-solid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Marushko, L.P., E-mail: marushko777@mail.r [Department of General and Inorganic Chemistry, Volyn National University, Voli Ave 13, Lutsk 43009 (Ukraine); Romanyuk, Y.E. [Swiss Federal Laboratories for Materials Testing and Research, EMPA, Uberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Piskach, L.V.; Parasyuk, O.V.; Olekseyuk, I.D. [Department of General and Inorganic Chemistry, Volyn National University, Voli Ave 13, Lutsk 43009 (Ukraine); Volkov, S.V.; Pekhnyo, V.I. [V.I. Vernadskii Institute for General and Inorganic Chemistry of the Ukrainian National Academy of Sciences, Palladina Ave 32-34, Kyiv 03680 (Ukraine)

    2010-08-27

    Phase equilibria in the CuInSe{sub 2}-CuGaSe{sub 2}-2CdSe system are studied using differential-thermal analysis and phase X-ray diffraction. An isothermal section of the system at 870 K, and phase diagrams of polythermal sections CuInSe{sub 2}-CuGaSe{sub 2} and 'CuCd{sub 2}InSe{sub 4}'-CuCd{sub 2}GaSe{sub 4} have been constructed. The 'CuCd{sub 2}InSe{sub 4}'-CuCd{sub 2}GaSe{sub 4} section is not quasi-binary and includes two solid solution regions with the wurtzite and sphalerite structure-types. Eleven crystals of the {gamma}-solid solutions with the sphalerite structure-type were grown by the Bridgman technique. The non-quasi-binary nature of the 'CuCd{sub 2}InSe{sub 4}'-CuCd{sub 2}GaSe{sub 4} section gives rise to compositional gradients for copper, cadmium, and gallium along the crystal growth direction so that the crystal tip is enriched with CdSe. Band gap of the grown crystals varies from 1.05 eV to {approx}1.30 eV.

  3. Seán MacDiarmada

    Directory of Open Access Journals (Sweden)

    Madden

    2016-12-01

    Full Text Available Seán MacDiarmada: Signatory to Proclamation – Executed after the Rising of 1916 - Leitrim to Kilmainham was written by Tom Madden to coincide with the 1916/2016 centenary commemorations. The play was first performed at the Mullagh Arts Festival in Cavan during September 2016 and provides a lively account of the background and activism of one the seven leaders of the Easter Rising of 1916. The action plays out over twelve scenes taking in MacDiarmada's journey from teacher to revolutionary activist culminating in a deeply flawed court-martial and his subsequent execution by a British Army firing squad on May 12th, 1916.

  4. Models of GexSe1-x

    Science.gov (United States)

    Malouin, Marc-André.; Mousseau, Normand

    2008-03-01

    We present numerical models of chalcogenide glasses constructed using the effective two and three body interaction potential developed by Mauro and Varshneya [1] combined with the activation-relaxation technique (ART nouveau) [2]. Structures are prepared starting from a random distribution, avoiding biases and crystalline remnants. Structural properties are studied mainly via characteristic system measurements including partial and total radial distribution functions, bond angle distributions, mean coordinations and bonds population. Results are shown for GexSe1-x for various x concentrations and compared to both experimental measurements and ab initio simulation results. [1] J.C. Mauro and A.K. Varshneya, J. Am. Ceram. Soc., 89 [7] 2323-6 (2006). [2] R. Malek and N. Mousseau, Phys. Rev. E 62, 7723 (2000).

  5. Ecuador: cuando la inestabilidad se vuelve estable

    Directory of Open Access Journals (Sweden)

    Pachano , Simón

    2005-09-01

    Full Text Available El presente artículo busca explicaciones para los derrocamientos de tres presidentes ecuatorianos, que han marcado los puntos culminantes de una década de inestabilidad. Lo hace indagando en el campo de las movilizaciones sociales que precedieron a cada uno de esos hechos, con especial referencia a su composición social y a los objetivos de sus integrantes. En la parte final se proponen algunas hipótesis acerca de la movilización en contra del gobierno de Gutiérrez. Sugiere que no son válidas las explicaciones de racismo y de temor clasista. Enlaza la explicación al surgimiento de reivindicaciones democráticas originadas tanto en los bajos rendimientos del sistema político como en el carácter dictatorial que iba tomando el último gobierno.

  6. 退火温度对异步轧制铜/铝复合板界面组织及力学性能的影响%Effect of annealing temperature on microstructure and mechanical properties of Cu/Al clad sheet fabricated by asymmetrical roll bonding

    Institute of Scientific and Technical Information of China (English)

    李小兵; 祖国胤; 王平

    2013-01-01

      研究退火温度对异步轧制法制备的铜/铝复合板界面组织及力学性能的影响,采用SEM观察界面组织形貌,结合EDX、XRD分析界面物相成分,采用显微硬度和室温拉伸实验表征复合板的力学性能。结果表明,异步轧制法制备的铜/铝复合板界面形变储能较高,退火温度为400℃时界面扩散明显;随着退火温度的升高,复合界面先后生成金属间化合物CuAl2、Cu9Al4、CuAl相,界面撕裂位置位于金属间化合物之间;界面层的显微硬度比基体的高,这是因为受到硬脆性化合物和高温软化的共同影响;退火温度越高,复合板抗拉强度越低,断裂伸长率越大。研究表明,异步轧制法制备的铜/铝复合板最佳退火温度为400℃。%The effects of annealing temperature on the interfacial microstructure and mechanical properties of Cu/Al clad sheet fabricated by asymmetrical roll bonding were investigated according to the microstructure observation by scanning electrical microscope (SEM) and the phase constituent measurement by energy dispersive X­ray detector (EDX) as well as X­ray diffractometer (XRD), in addition with the microhardness of interfacial zone and tensile test of clad sheet. The results indicate that the interfacial layer of Cu/Al clad sheet fabricated by asymmetrical roll bonding grows heavily at 400℃ due to the accumulated deform energy. The intermetallic compounds form in the order of CuAl2, Cu9Al4 and CuAl with increasing the annealing temperature, and peeling occurs between them. The interfacial microhardness is higher than that of the matrix due to the effect of annealing recovery and brittle intermetallic compound. The ultimate tensile strength decreases with rising the annealing temperature, while the elongation increases. According to the experiments, the optimal annealing temperature for Cu/Al clad sheet fabricated by asymmetrical roll bonding is 400 ℃.

  7. Absorption Spectra of CuGaSe 2 and CuInSe 2 Semiconducting Nanoclusters

    KAUST Repository

    Mokkath, Junais Habeeb

    2015-10-01

    The structural and optical properties of the chalcopyrite CunGanSe2n and CunInnSe2n nanoclusters (n = 2, 4, 6, and 8) are investigated as a function of the size using a combination of basin-hopping global optimization and time-dependent density functional theory. Although the lowest energy structures are found to show almost random geometries, the band gaps and absorption spectra still are subject to systematic blue shifts for decreasing cluster size in the case of CunGanSe2n, indicating strong electron confinement. The applicability of the nanoclusters in photovoltaics is discussed. © 2015 American Chemical Society.

  8. Photo and electroluminescence of ZnSe: Sn and ZnSe:(Sn, Pr) phosphors

    Science.gov (United States)

    Mishra, A. K.; Mishra, S. K.; Pandey, S. P.; Lakshmi Mishra, Kshama

    2016-09-01

    We have prepared ZnSe (luminescent grade) phosphor doped with Sn and (Sn,Pr) with varying concentration in an inert atmosphere in a silica tubular furnace at temperature of (780 ± 20) °C for 1 hr to obtain ZnSe:Sn and ZnSe: (Sn,Pr) phosphors. The photo luminescence (PL) and electroluminescence (EL) spectra of these phosphors have been studied at room temperature and results were discussed in the light of existing models. Dependence of EL emission on the voltage frequency has also been carried out. It is found that the plot between the integrated light intensity versus 1/√Vrms is a straight line suggesting the existence of Mott-Schottky type barrier on the metal semiconductor interface.

  9. 2-Selenouridine triphosphate synthesis and Se-RNA transcription.

    Science.gov (United States)

    Sun, Huiyan; Jiang, Sibo; Caton-Williams, Julianne; Liu, Hehua; Huang, Zhen

    2013-09-01

    2-Selenouridine ((Se)U) is one of the naturally occurring modifications of Se-tRNAs ((Se)U-RNA) at the wobble position of the anticodon loop. Its role in the RNA-RNA interaction, especially during the mRNA decoding, is elusive. To assist the research exploration, herein we report the enzymatic synthesis of the (Se)U-RNA via 2-selenouridine triphosphate ((Se)UTP) synthesis and RNA transcription. Moreover, we have demonstrated that the synthesized (Se)UTP is stable and recognizable by T7 RNA polymerase. Under the optimized conditions, the transcription yield of (Se)U-RNA can reach up to 85% of the corresponding native RNA. Furthermore, the transcribed (Se)U-hammerhead ribozyme has the similar activity as the corresponding native, which suggests usefulness of (Se)U-RNAs in function and structure studies of noncoding RNAs, including the Se-tRNAs.

  10. Determination of dispersive optical constants of nanocrystalline CdSe (nc-CdSe) thin films

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Kriti; Al-Kabbi, Alaa S.; Saini, G.S.S. [Centre of Advanced Study in Physics, Department of Physics, Panjab University, Chandigarh 160014 (India); Tripathi, S.K., E-mail: surya@pu.ac.in [Centre of Advanced Study in Physics, Department of Physics, Panjab University, Chandigarh 160014 (India)

    2012-06-15

    Highlights: ► nc-CdSe thin films are prepared by thermal vacuum evaporation technique. ► TEM analysis shows NCs are spherical in shape. ► XRD reveals the hexagonal (wurtzite) crystal structure of nc-CdSe thin films. ► The direct optical bandgap of nc-CdSe is 2.25 eV in contrast to bulk (1.7 eV). ► Dispersion of refractive index is discussed in terms of Wemple–DiDomenico single oscillator model. -- Abstract: The nanocrystalline thin films of CdSe are prepared by thermal evaporation technique at room temperature. These thin films are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). The transmission spectra are recorded in the transmission range 400–3300 nm for nc-CdSe thin films. Transmittance measurements are used to calculate the refractive index (n) and absorption coefficient (α) using Swanepoel's method. The optical band gap (E{sub g}{sup opt}) has been determined from the absorption coefficient values using Tauc's procedure. The optical constants such as extinction coefficient (k), real (ε{sub 1}) and imaginary (ε{sub 2}) dielectric constants, dielectric loss (tan δ), optical conductivity (σ{sub opt}), Urbach energy (E{sub u}) and steepness parameter (σ) are also calculated for nc-CdSe thin films. The normal dispersion of refractive index is described using Wemple–DiDomenico single-oscillator model. Refractive index dispersion is further analysed to calculate lattice dielectric constant (ε{sub L}).

  11. Optical properties of thermally annealed CdZnSe/ZnSe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Margapoti, Emanuela

    2010-07-01

    To analyse the diffusion characteristics, photoluminescence (PL) spectroscopy has been carried out in extensive detail on single, as well as, ensembles of thermally annealed (TA) CdSe/ZnSe QDs. For a series of QD-ensembles, each annealed for t{sub A} = 30 s at temperatures from T{sub A} = 300-550 C, the change in the QD-composition has been calculated from the blue-shift of the exciton ground-state PL-emission, using a concentration function based on Fick's laws of diffusion. The diffusion length (L{sub D}) and the activation energy (E{sub A}) have been determined thereof. For the studied QDs, E{sub A} has been evaluated to be 2.2 eV. Additionally, TA results also in an enhancement of the PL-intensity and reduction of the full-width-at-half maximum (FWHM) of the spectra. This point towards an increased homogeneity of the QD-size and composition, and decrease in the concentration of defects around the QDs. For single CdSe/ZnSe QDs, TA has been varied from 100-240 C, in steps for 20 C, with t{sub A} kept fixed at 30 s. Finally, the evolution of the magneto-optic response with post-growth thermal annealing has been studied for both individual QDs and QD-ensembles. An external magnetic field, applied perpendicular to the plane of the QDs (Faraday configuration), results in Zeeman spin splitting of the ground exciton state. The emissions from the Zeeman-split states are left and right circularly polarized and from the degree of circular polarization (DCP), as well as, the spectral separation of the PL-peaks, the g-factor can be estimated. For CdSe/ZnSe QD-ensembles, the g-factor has been observed to change sign with TA. (orig.).

  12. Phosphine-free synthesis of high quality ZnSe, ZnSe/ZnS, and Cu-, Mn-doped ZnSe nanocrystals.

    Science.gov (United States)

    Shen, Huaibin; Wang, Hongzhe; Li, Xiaomin; Niu, Jin Zhong; Wang, Hua; Chen, Xia; Li, Lin Song

    2009-12-21

    High quality zinc blende ZnSe and ZnSe/ZnS core/shell nanocrystals have been synthesized by two converse injection methods (i.e. zinc precursor injection or selenium precursor injection) when Se-ODE complex was chosen as the phosphine-free selenium precursor. Absorption spectroscopy, fluorescence spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM) were used to characterize the as-synthesized ZnSe and ZnSe/ZnS nanocrystals. The quality of the as-prepared ZnSe nanocrystals reached the same high level compared with the method using phosphine selenium precursors since the quantum yields were between 40 and 60% and photoluminescence (PL) full width at half-maximum (FWHM) was well controlled between 14 and 17 nm. The parameter window for the growth of high quality ZnSe nanocrystals was found to be much broader and monodisperse ZnSe nanocrystals were synthesized successfully even when the reaction temperature was set as low as 240 degrees C. As cores, such zinc blende ZnSe nanocrystals were also used to synthesize ZnSe/ZnS core/shell nanocrystals with high fluorescence quantum yields of 70%. Cu(2+) or Mn(2+) doped ZnSe nanocrystals were also synthesized by simply modifying this phosphine-free method. The emission range has been extended to 500 and 600 nm with the use of Cu(2+) and Mn(2+) dopants compared with the emission coverage of ZnSe at around 400 nm. This is the first totally "green approach" (i.e. phosphine-free synthesis) for the synthesis of high quality ZnSe, ZnSe/ZnS, and Cu(2+) or Mn(2+) doped ZnSe nanocrystals.

  13. Temperature-dependent exciton recombination in asymmetrical ZnCdSe/ZnSe double quantum wells

    CERN Document Server

    Yu Guang You; Zhang, J Y; Zheng, Z H; Yang, B J; Zhao Xiao Wei; Shen De Zhen; Kong Xiang Gui

    1999-01-01

    Temperature-dependent exciton recombination in asymmetrical ZnCdSe/ZnSe double quantum wells is studied by recording photoluminescence spectra and photoluminescence decay spectra. The exciton tunnelling from the wide well to the narrow well and the thermal dissociation of excitons are two factors that influence the exciton recombination in this structure. In the narrow well, both of the two processes decrease the emission intensity, whereas, in the wide well, these two processes have contrary influences on the exciton density. The change of the emission intensity depends on which is the stronger one. (author)

  14. In situ observation of the formation of FeSe

    DEFF Research Database (Denmark)

    Grivel, Jean-Claude; Wulff, Anders Christian; Yue, Zhao;

    2011-01-01

    The formation of the FeSe compound from a mixture of Fe and Se powders encased in a composite Cu/Nb sheath was studied in situ by means of high-energy synchrotron x-ray diffraction. Tetragonal beta-FeSe does not seem to form directly from the starting elements. Instead, a sequence of FeSe2, Fe3Se4...

  15. CdSe quantum dot in vertical ZnSe nanowire and photonic wire for efficient single-photon emission

    DEFF Research Database (Denmark)

    Cremel, Thibault; Bellet-Amalric, Edith; Cagnon, Laurent;

    as a single photon source. We have grown vertically oriented ZnSe NWs (with typical diameter of 10 nm) by molecular beam epitaxy on a ZnSe(111)B buffer layer. The growth of a ZnMgSe passivating shell increases the (otherwise weak) ZnSe near-band-edge luminescence by two orders of magnitude. This has allowed...

  16. La estructura funcional de las nominalizaciones deverbales de evento y resultado a partir de verbos de realización

    Directory of Open Access Journals (Sweden)

    Ana Clara Polakof

    2014-01-01

    Full Text Available Este trabajo pretende hacer un aporte al análisis de la estructura funcional de las nominalizaciones de evento y resultado a partir de verbos de realización desde la perspectiva de la morfología ditribuida (MD. Parte del entendido de que en cualquiera de estas estructuras debe haber una relación entre la complejidad morfológica y los nudos funcionales que son contenidos en dicha estructura, así como entiende que la existencia de estas nominalizaciones proviene de una relación entre el componente sintáctico y el conocimiento del mundo. Este trabajo tiene en cuenta los desarrollos previos que se han hecho en MD, así como sostiene la idea de que las nominalizaciones deben contener el Sv a partir del cual se forman y que este Sv tendrá distintos rasgos de v° (Harley y Noyer 2000, Harley 2006, entre otros que permiten reconocer las distintas clases aspectuales existentes y permiten explicar la relación existente entre las nominalizaciones y los verbos a partir de los cuales estas se forman

  17. El riesgo deseable: la controversia a partir de los textos que se leen en la escuela

    Directory of Open Access Journals (Sweden)

    Judith Kalman

    2006-01-01

    Full Text Available La alfabetización académica implica apropiarse de discursos y prácticas de lenguaje comunes en el trabajo intelectual con los textos. En el caso de la lectura, comportamientos lectores como la interpretación de los textos, el poder sintetizar lo que dicen, su vinculación con otros textos, la experiencia propia y el mundo circundante, la capacidad de explicar y argumentar a partir de algunos fragmentos del texto y el hablar de todo lo anterior son algunas de las prácticas que se busca arraigar en la educación formal (Heath & Mangiola, 1991. Cuando se elaboran libros de texto, la selección de lecturas es el primer momento de construcción de la alfabetización académica en la escuela, es el momento de ofrecer un primer conjunto de textos escritos sobre los cuales los maestros y los alumnos van a dialogar. El desarrollo de materiales didácticos incluye, entre otras acciones, la instrumentación de objetivos y contenidos curriculares en un entramado de actividades de aprendizaje construido a partir de la selección de textos y diversos apoyos gráficos. Esta tarea, de por sí laboriosa, se vuelve aún más compleja cuando diferentes actores intervienen en las decisiones acerca de qué deben leer o no los alumnos. La participación de múltiples voces en un proceso de selección es deseable; sin embargo un proceso de selección puede derivar rápidamente en censura, especialmente cuando los actores sociales involucrados en las decisiones están ligados al poder y limitan el acceso a los temas y a la cultura de nuestro tiempo. Mediante la narración de algunas experiencias recientes en méxico, en este artículo argumentamos que los materiales didácticos deben liberarse de cualquier compromiso que no sea educativo y buscar difundir la pluralidad de voces que hoy por hoy se escuchan en las sociedades contemporáneas. Esto nos parece especialmente importante en la elaboración de materiales para las poblaciones más marginadas, donde la

  18. Política pública de la migración en el Departamento del Valle del Cauca. ¿Cómo se está tratando el tema de la migración internacional, en el Departamento del Valle del Cauca hasta el 2009?

    Directory of Open Access Journals (Sweden)

    Lorena López López

    2011-08-01

    Full Text Available El presente documento de trabajo se basa en la tesis de grado, presentada en la Universidad Icesi de Cali, bajo el mismo título del presente artículo. El texto aborda la Política Integral Migratoria (PIM de Colombia y sus implicaciones en el departamento del Valle del Cauca. El documento está dividido en cuatro temas principales. Primero, se presenta el marco teórico, enfocado, particularmente, en el concepto de migración internacional, el cual se analiza desde distintos puntos de vista y autores. Segundo, se retoman los últimos 30 años de proceso histórico migratorio desde el departamento del Valle del Cauca al exterior. Tercero, se analiza el documento Conpes 3603, emitido por el Gobierno Nacional, en cabeza del Ministerio de Relaciones Exteriores, y se escruta sobre la influencia de este en las políticas formuladas e implementadas en el departamento. Cuarto, se enumeran algunas de las organizaciones gubernamentales, y no gubernamentales, más relevantes con las cuales trabaja el gobierno del Valle del Cauca para lograr el desarrollo de la Política Integral Migratoria (PIM en el departamento. Finalmente, el presente artículo pretende brindar algunas conclusiones, a modo de reflexión, sobre los retos que enfrenta la Política Integral Migratoria (PIM en el departamento.

  19. Improvement of dispersion stability and optical properties of CdSe/ZnSe structured quantum dots by polymer coating.

    Science.gov (United States)

    Kwon, Young-Tae; Eom, Nu Si A; Choi, Yo-Min; Kim, Bum-Sung; Kim, Taek-Soo; Lee, Chan-Gi; Lee, Kun-Jae; Choa, Yong-Ho

    2014-10-01

    In this study, CdSe core and CdSe/ZnSe core/shell quantum dots with a narrow size distribution were synthesized in a micro-reactor. A PMMA coating applied to the surface of CdSe/ZnSe core/shell QDs to prevent degradation gave improved dispersion stability compared to the CdSe core and CdSe/ZnSe core/shell. Many previous approaches to dispersion stability have not been quantitatively assessed. The dispersion stability was confirmed by multiple light scattering measurement. Additionally, the PMMA-coated CdSe/ZnSe QDs showed greatly improved optical properties with a photoluminescence quantum yield up to 80%. This structural motif is expected to prevent the degradation of QDs.

  20. Photoinduced aging and viscosity evolution in Se-rich Ge-Se glasses

    Energy Technology Data Exchange (ETDEWEB)

    Gueguen, Yann; Sangleboeuf, Jean-Christophe; Rouxel, Tanguy [LARMAUR ERL CNRS 6274, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France); King, Ellyn A.; Lucas, Pierre [Department of Materials Science and Engineering, University of Arizona, 4715 E. Fort Lowell Road, Tucson, Arizona 85712 (United States); Keryvin, Vincent [LIMATB EA 4250, Université de Bretagne Sud, Rue de Saint Maudé, 56321 Lorient Cedex (France); Bureau, Bruno [Equipe Verres et Céramiques, UMR-CNRS 6226 Sciences Chimiques de Rennes, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France)

    2013-08-21

    We propose here to investigate the non-equilibrium viscosity of Ge-Se glasses under and after light irradiation. Ge{sub 10}Se{sub 90} and Ge{sub 20}Se{sub 80} fibers have been aged in the dark and under ambient light, over months. During aging, both the relaxation of enthalpy and the viscosity have been investigated. The viscosity was measured by shear relaxation-recovery tests allowing the measurement of non-equilibrium viscosity. When Ge{sub 10}Se{sub 90} glass fibers are aged under irradiation, a relatively fast fictive temperature decrease is observed. Concomitantly, during aging under irradiation, the non-equilibrium viscosity increases and reaches an equilibrium after two months of aging. This viscosity increase is also observed in Ge{sub 20}Se{sub 80} fibers. Nevertheless, this equilibrium viscosity is far below the viscosity expected at the configurational equilibrium. As soon as the irradiation ceases, the viscosity increases almost instantaneously by about one order of magnitude. Then, if the fibers are kept in the dark, their viscosity slowly increases over months. The analysis of the shear relaxation functions shows that the aging is thermorheologically simple. On the other side, there is no simple relaxation between the shear relaxation functions measured under irradiation and those measured in the dark. These results clearly suggest that a very specific photoinduced aging process occurs under irradiation. This aging is due to photorelaxation. Nevertheless, the viscosity changes are not solely correlated to photoaging and photorelaxation. A scenario is proposed to explain all the observed viscosity evolutions under and after irradiation, on the basis of photoinduced transient defects.

  1. Phase diagram of the quasi-binary system TlInSe{sub 2}-SnSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Mozolyuk, M.Yu.; Piskach, L.V. [Department of Inorganic and Physical Chemistry, Lesya Ukrainka Volyn National University, Voli Ave 13, 43025 Lutsk (Ukraine); Fedorchuk, A.O. [Department of Inorganic and Organic Chemistry, Lviv National University of Veterinary Medicine and Biotechnologies, Pekarska St., 50, 79010 Lviv (Ukraine); Kityk, I.V. [Electrical Engineering Department, Czestochowa University of Technology, Al. Armii Krajowej 17/19, 42-200 Czestochowa (Poland); Olekseyuk, I.D. [Department of Inorganic and Physical Chemistry, Lesya Ukrainka Volyn National University, Voli Ave 13, 43025 Lutsk (Ukraine); Parasyuk, O.V., E-mail: oleg@univer.lutsk.ua [Department of Inorganic and Physical Chemistry, Lesya Ukrainka Volyn National University, Voli Ave 13, 43025 Lutsk (Ukraine)

    2011-02-10

    Research highlights: > The phase diagram of the quasi-binary system TlInSe{sub 2}-SnSe{sub 2} was investigated by X-ray powder diffraction and differential thermal analysis. > The system is of the eutectic type, with the invariant point at 63 mol.% SnSe{sub 2} and 788 K. The solid solution range of the ternary component extends to 28 mol.% SnSe{sub 2}. > The crystal structure of the solid solution alloy of 25 mol.% TlInSe{sub 2} was investigated (space group I4/mcm, a = 0.8091 nm, c = 0.6744 nm). A comparison with CuInSe{sub 2}-SnSe{sub 2} and AgInSe{sub 2}-SnSe{sub 2} systems is discussed. - Abstract: The TlInSe{sub 2}-SnSe{sub 2} quasibinary system was investigated using differential thermal and X-ray phase analysis methods. The phase diagram is of eutectic type (V type of the Rozeboom classification). The solid solution range of the ternary compound in the TlInSe{sub 2}-SnSe{sub 2} system extends to 28 mol.% SnSe{sub 2} at 670 K. The eutectic point coordinates are 63 mol.% SnSe{sub 2} and 788 K.

  2. Medikamentöse Therapie der Epilepsie

    Directory of Open Access Journals (Sweden)

    Gallmetzer P

    2009-01-01

    Full Text Available Durch neu zugelassene Antiepileptika wurde die medikamentöse Epilepsietherapie in den vergangenen Jahren entscheidend bereichert. Bei ca. 65 % der Epilepsiepatienten kann durch eine antiepileptische Therapie anhaltende Anfallsfreiheit erreicht werden, bei den übrigen 35 % entwickelt sich eine schwer behandelbare Epilepsie. Die wichtigsten Behandlungsziele sind neben der Anfallskontrolle die gute Verträglichkeit der medikamentösen Therapie, die Vermeidung chronischer Nebenwirkungen, die einfache Handhabung der Medikation für Arzt und Patient, die günstige Beeinflussung assoziierter Begleiterkrankungen sowie die Berücksichtigung der Bedürfnisse spezieller Patientengruppen. Generell sollte somit eine möglichst individualisierte Therapie erfolgen, die auf die Bedürfnisse des jeweiligen Patienten abgestimmt ist. Bei fehlender Anfallskontrolle sollte eine prächirurgische Epilepsiediagnostik erfolgen, um zu klären, ob der Patient ein Kandidat für einen epilepsiechirurgischen Eingriff ist. Mit Rufinamid, Stiripentol und Lacosamid sowie demnächst auch mit Eslicarbazepin stehen zur Behandlung schwer behandelbarer Epilepsiesyndrome neue Therapieoptionen zur Verfügung.

  3. La etnomatemática en la educación indígena: así se concibe, así se pone en práctica

    Directory of Open Access Journals (Sweden)

    Alicia Ávila

    2014-04-01

    Full Text Available En este artículo se exponen los resultados de una investigación realizada en México cuyo objetivo fue conocer cómo los profesores de las escuelas indígenas conciben la etnomatemática y la integran en sus clases de matemáticas Para reunir la información, se visitaron nueve escuelas primarias indígenas con distintas características lingüísticas, de aislamiento y de organización escolar en los estados de Chiapas, Michoacán y Puebla, los cuales tienen amplia presencia indígena. En el artículo se muestran las formas en que los profesores de las nueve escuelas visitadas conciben la etnomatemática y los saberes previos de sus alumnos y cómo esto es integrado en sus clases de matemáticas. El saber más visible a los profesores es el vinculado con las unidades y formas de medición. Las formas locales de conteo y ubicación en el espacio, si existen, no son identificadas por los docentes. La investigación se realizó en el marco de un programa de formación profesional que promueve que los profesores recuperen los saberes propios de la comunidad para enseñar, a partir de ellos, matemáticas a sus alumnos. El análisis de la información colectada permite analizar los alcances de las propuestas educativas que toman como eje la etnomatemática y discutir la formación que reciben los docentes de niños indígenas para enseñar matemáticas desde esta perspectiva

  4. La etnomatemática en la educación indígena: así se concibe, así se pone en práctica

    Directory of Open Access Journals (Sweden)

    Alicia Ávila

    2014-01-01

    Full Text Available En este artículo se exponen los resultados de una investigación realizada en México cuyo objetivo fue conocer cómo los profesores de las escuelas indígenas conciben la etnomatemática y la integran en sus clases de matemáticas Para reunir la información, se visitaron nueve escuelas primarias indígenas con distintas características lingüísticas, de aislamiento y de organización escolar en los estados de Chiapas, Michoacán y Puebla, los cuales tienen amplia presencia indígena. En el artículo se muestran las formas en que los profesores de las nueve escuelas visitadas conciben la etnomatemática y los saberes previos de sus alumnos y cómo esto es integrado en sus clases de matemáticas. El saber más visible a los profesores es el vinculado con las unidades y formas de medición. Las formas locales de conteo y ubicación en el espacio, si existen, no son identificadas por los docentes. La investigación se realizó en el marco de un programa de formación profesional que promueve que los profesores recuperen los saberes propios de la comunidad para enseñar, a partir de ellos, matemáticas a sus alumnos. El análisis de la información colectada permite analizar los alcances de las propuestas educativas que toman como eje la etnomatemática y discutir la formación que reciben los docentes de niños indígenas para enseñar matemáticas desde esta perspectiva.

  5. Direct observation of a gap opening in topological interface states of MnSe/Bi2Se3 heterostructure

    Science.gov (United States)

    Matetskiy, A. V.; Kibirev, I. A.; Hirahara, T.; Hasegawa, S.; Zotov, A. V.; Saranin, A. A.

    2015-08-01

    High-quality MnSe(111) film was bilayer-by-bilayer grown epitaxially onto the Bi2Se3(111) surface using molecular beam epitaxy. Reversal scenario with quintuple layer-by-layer growth of Bi2Se3 onto the MnSe film was also realized. Angle-resolved photoemission spectroscopy measurements of Bi2Se3 capped with two bi-layers of MnSe revealed that an energy gap of about 90 meV appears at the Dirac point of the original Bi2Se3 surface, possibly due to breaking the time-reversal symmetry on the Bi2Se3 surface by magnetic proximity effect from MnSe.

  6. Freshwater flux to Sermilik Fjord, SE Greenland

    Directory of Open Access Journals (Sweden)

    S. H. Mernild

    2010-07-01

    Full Text Available Fluctuations in terrestrial surface freshwater flux to Sermilik Fjord, SE Greenland, were simulated and analyzed. SnowModel, a state-of-the-art snow-evolution, snow and ice melt, and runoff modeling system, was used to simulate the temporal and spatial terrestrial runoff distribution to the fjord based on observed meteorological data (1999–2008 from stations located on and around the Greenland Ice Sheet (GrIS. Simulated runoff was compared and verified against independent glacier catchment runoff observations (1999–2005. Modeled runoff to Sermilik Fjord was highly variable, ranging from 2.9×109 m3 y−1 in 1999 to 5.9×109 m3 y−1 in 2005. The uneven spatial runoff distribution produced an areally-averaged annual maximum runoff at the Helheim glacier terminus of more than 3.8 m w.eq. The sub-catchment runoff of the Helheim glacier region accounted for 25% of the total runoff to Sermilik Fjord. The runoff distribution from the different sub-catchments suggested a strong influence from the spatial variation in glacier coverage. To assess the Sermilik Fjord freshwater flux, simulated terrestrial runoff and net precipitation (precipitation minus evaporation and sublimation for the fjord area were combined with satellite-derived ice discharge and subglacial geothermal and frictional melting due to basal ice motion. A terrestrial freshwater flux of ~40.4×109 m3 y−1 was found for Sermilik Fjord, with an 11% contribution originated from surface runoff. For the Helheim glacier sub-catchment only 4% of the flux originated from terrestrial surface runoff.

  7. Freshwater flux to Sermilik Fjord, SE Greenland

    Directory of Open Access Journals (Sweden)

    S. H. Mernild

    2010-10-01

    Full Text Available Terrestrial inputs of freshwater flux to Sermilik Fjord, SE Greenland, were estimated, indicating ice discharge to be the dominant source of freshwater. A freshwater flux of 40.4 ± 4.9×109 m3 y−1 was found (1999–2008, with an 85% contribution originated from ice discharge (65% alone from Helheim Glacier, 11% from terrestrial surface runoff (from melt water and rain, 3% from precipitation at the fjord surface area, and 1% from subglacial geothermal and frictional melting due to basal ice motion. The results demonstrate the dominance of ice discharge as a primary mechanism for delivering freshwater to Sermilik Fjord. Time series of ice discharge for Helheim Glacier, Midgård Glacier, and Fenris Glacier were calculated from satellite-derived average surface velocity, glacier width, and estimated ice thickness, and fluctuations in terrestrial surface freshwater runoff were simulated based on observed meteorological data. These simulations were compared and bias corrected against independent glacier catchment runoff observations. Modeled runoff to Sermilik Fjord was variable, ranging from 2.9 ± 0.4×109 m3 y−1 in 1999 to 5.9 ± 0.9×109 m3 y−1 in 2005. The sub-catchment runoff of the Helheim Glacier region accounted for 25% of the total runoff to Sermilik Fjord. The runoff distribution from the different sub-catchments suggested a strong influence from the spatial variation in glacier coverage, indicating high runoff volumes, where glacier cover was present at low elevations.

  8. Hume-Rothery electron concentration rule across a whole solid solution range in a series of gamma-brasses in Cu-Zn, Cu-Cd, Cu-Al, Cu-Ga, Ni-Zn and Co-Zn alloy systems

    Science.gov (United States)

    Mizutani, U.; Noritake, T.; Ohsuna, T.; Takeuchi, T.

    2010-05-01

    The aim of the present work is to examine if the Hume-Rothery stabilisation mechanism holds across whole solid solution ranges in a series of gamma-brasses with especial attention to the role of vacancies introduced into the large unit cell. The concentration dependence of the number of atoms in the unit cell, N, for gamma-brasses in the Cu-Zn, Cu-Cd, Cu-Al, Cu-Ga, Ni-Zn and Co-Zn alloy systems was determined by measuring the density and lattice constants at room temperature. The number of itinerant electrons in the unit cell, e/uc, is evaluated by taking a product of N and the number of itinerant electrons per atom, e/a, for the transition metal element deduced earlier from the full-potential linearised augmented plane wave (FLAPW)-Fourier analysis. The results are discussed within the rigid-band model using as a host the density of states (DOS) derived earlier from the FLAPW band calculations for the stoichiometric gamma-brasses Cu5Zn8, Cu9Al4 and TM2Zn11 (TM = Co and Ni). A solid solution range of gamma-brasses in Cu-Zn, Cu-Cd, Cu-Al, Cu-Ga and Ni-Zn alloy systems is found to fall inside the existing pseudogap at the Fermi level. This is taken as confirmation of the validity of the Hume-Rothery stability mechanism for a whole solute concentration range of these gamma-brasses. An exception to this behaviour was found in the Co-Zn gamma-brasses, where orbital hybridisation effects are claimed to play a crucial role in stabilisation.

  9. Cu2ZnSnSe4 thin-film solar cells fabricated using Cu2SnSe3 and ZnSe bilayers

    Science.gov (United States)

    Kim, Kang Min; Liao, Kuang Hsiang; Tampo, Hitoshi; Shibata, Hajime; Niki, Shigeru

    2015-04-01

    Evaporated Cu2SnSe3 (CTSe) and ZnSe bilayers are used as precursors for the fabrication of Cu2ZnSnSe4 (CZTSe) thin films. Large grains (i.e., >1 µm) in CZTSe were obtained at a relatively low annealing temperature of 500 °C. The stacking order of precursors strongly affected the chemical composition of CZTSe thin films even under identical growth conditions. Zn loss in CTSe/ZnSe/Mo precursors occurred during CTSe deposition, whereas ZnSe/CTSe/Mo precursors showed improved stability in composition. The CZTSe solar cells fabricated using ZnSe/CTSe bilayer precursors with annealing showed a conversion efficiency of over 7%.

  10. Papel de la proteína supresora de la señalización por citocinas-3 (SOCS 3 en la resistencia a la hormona de crecimiento inducida por malnutrición.

    Directory of Open Access Journals (Sweden)

    Adriana Umaña

    2003-09-01

    Full Text Available La nutrición es un regulador importante de las acciones de la hormona de crecimiento (GH. Se ha demostrado que el déficit de nutrientes induce un estado de resistencia a la hormona, en el cual están involucrados, entre otros factores, alteraciones post-receptor en la vía de señalización, pero se desconocen los mecanismos responsables. En este trabajo se investigó la participación de algunos miembros de la familia de proteínas supresoras de la señalización por citocinas (SOCS en la resistencia causada por malnutrición, que inhibe la activación de la señalización a través de Janus cinasa 2/transductor de señal y activador de la transcripción 5 (JK2/STAT5. Se estudiaron los cambios en la expresión génica del receptor de GH (RGH, IGF-I y SOCS3 en el hígado de ratas alimentadas con una dieta baja en proteína (8% y estimuladas con GH. La restricción en el consumo de proteína disminuyó significativamente (p

  11. Tailoring ZnSe-CdSe colloidal quantum dots via cation exchange: from core/shell to alloy nanocrystals.

    Science.gov (United States)

    Groeneveld, Esther; Witteman, Leon; Lefferts, Merel; Ke, Xiaoxing; Bals, Sara; Van Tendeloo, Gustaaf; Donega, Celso de Mello

    2013-09-24

    We report a study of Zn(2+) by Cd(2+) cation exchange (CE) in colloidal ZnSe nanocrystals (NCs). Our results reveal that CE in ZnSe NCs is a thermally activated isotropic process. The CE efficiency (i.e., fraction of Cd(2+) ions originally in solution, Cdsol, that is incorporated in the ZnSe NC) increases with temperature and depends also on the Cdsol/ZnSe ratio. Interestingly, the reaction temperature can be used as a sensitive parameter to tailor both the composition and the elemental distribution profile of the product (Zn,Cd)Se NCs. At 150 °C ZnSe/CdSe core/shell hetero-NCs (HNCs) are obtained, while higher temperatures (200 and 220 °C) produce (Zn1-xCdx)Se gradient alloy NCs, with increasingly smoother gradients as the temperature increases, until homogeneous alloy NCs are obtained at T ≥ 240 °C. Remarkably, sequential heating (150 °C followed by 220 °C) leads to ZnSe/CdSe core/shell HNCs with thicker shells, rather than (Zn1-xCdx)Se gradient alloy NCs. Thermal treatment at 250 °C converts the ZnSe/CdSe core/shell HNCs into (Zn1-xCdx)Se homogeneous alloy NCs, while preserving the NC shape. A mechanism for the cation exchange in ZnSe NCs is proposed, in which fast CE takes place at the NC surface, and is followed by relatively slower thermally activated solid-state cation diffusion, which is mediated by Frenkel defects. The findings presented here demonstrate that cation exchange in colloidal ZnSe NCs provides a very sensitive tool to tailor the nature and localization regime of the electron and hole wave functions and the optoelectronic properties of colloidal ZnSe-CdSe NCs.

  12. Dipole strength in 80Se for s process and nuclear transmutation of 79Se

    Science.gov (United States)

    Makinaga, A.; Massarczyk, R.; Beard, M.; Schwengner, R.; Otsu, H.; Al-Abdullah, T.; Anders, M.; Bemmerer, D.; Hannaske, R.; John, R.; Junghans, A. R.; Müller, S. E.; Röder, M.; Schmidt, K.; Wagner, A.

    2016-10-01

    The dipole strength distribution of 80Se was studied in a photon-scattering experiment by using bremsstrahlung produced with an electron beam of energy 11.5 MeV at the linear accelerator ELBE. We identified 180 γ transitions up to an energy of 9.6 MeV, and analyzed the strength in the quasicontinuum of the spectrum. Simulations of statistical γ -ray cascades were performed to estimate intensities of inelastic transitions and to correct the intensities of the ground-state transitions for their branching ratios. The photoabsorption cross section below the neutron-separation energy derived in this way was combined with the photoabsorption cross section obtained from an earlier (γ ,n ) experiment and used as an input for the calculation of 79Se(n ,γ ) reaction rates on the basis of the statistical reaction model.

  13. Mechanical properties of layered InSe and GaSe single crystals

    Science.gov (United States)

    Mosca, D. H.; Mattoso, N.; Lepienski, C. M.; Veiga, W.; Mazzaro, I.; Etgens, V. H.; Eddrief, M.

    2002-01-01

    The mechanical properties of InSe and GaSe single crystals have been studied by means of nanoindentation tests. Both bulk crystals are well ordered and present a predominant γ-type interlayer stacking sequence as determined by x-ray diffraction and transmission electron microscopy measurements. The course of plastic deformation induced in the crystals by application of a definite shear stress through the penetration of a Berkovich tip indicates that the deformation occurs predominantly by pop-in events along easy slip directions having a fairly elastic character between displacements. Hardness anisotropy along crystal axes is clearly seen and the measured elastic modulus presents a discrepancy smaller than 5% in comparison with theoretical calculations performed using previous experimental values of the elastic constants.

  14. La desaceleración económica colombiana: se cosecha lo que se siembra

    Directory of Open Access Journals (Sweden)

    Carlos Humberto Ortiz

    2009-12-01

    Full Text Available La desaceleración económica que experimenta Colombia desde 1980 se explica por el estancamiento estructural de la economía y por la escalada de violencia relacionada con la expansión del narcotráfico. Los datos disponibles no rechazan esta hipótesis. El artículo plantea que la desindustrialización y el narcotráfico se forjaron en el mismo crisol: un modelo de desarrollo que ha integrado progresivamente la economía nacional a los mercados mundiales al tiempo que ha renunciado, también progresivamente, a la opción industrialista. Además, argumenta que la explosión del narcotráfico obedece a la profundización de la guerra contra las drogas en un contexto de demanda mundial creciente e inelástica.

  15. LETTER TO THE EDITOR: Raman investigation of InSe and GaSe single-crystals oxidation

    Science.gov (United States)

    Balitskii, O. A.; Savchyn, V. P.; Yukhymchuk, V. O.

    2002-02-01

    We discuss the Raman scattering of thermally oxidized gallium selenide (GaSe) and indium selenide (InSe) single crystals. It has been established that the oxidation mechanisms of these compounds are rather different. For InSe, an increase of the oxidation temperature leads to the formation of (SeO4) complexes. For GaSe, it is characteristic that only Ga2O3 is formed as an oxygen-containing phase during the oxidation. The presence of the Me2Se3 phase (where Me is Ga or In) in its own oxide is common for both of the semiconductors.

  16. Absorption and initial metabolism of 75Se-l-selenomethionine

    DEFF Research Database (Denmark)

    Grosse Ruse, Mareile; Søndergaard, Lasse R.; Ditlevsen, Susanne

    2015-01-01

    Selenomethionine (SeMet) is an important organic nutritional source of Se, but the uptake and metabolism of SeMet are poorly characterised in humans. Dynamic gamma camera images of the abdominal region were acquired from eight healthy young men after the ingestion of radioactive 75Se-l-SeMet (75Se...... to the plasma and 0·267 h–1 from the stomach to the plasma. The delay in the liver was 0·714 h. Gamma camera imaging provides data for use in compartmental modelling of 75Se-SeMet absorption and metabolism in humans. In clinical settings, the obtained rate constants and the delay in the liver may be useful...

  17. Por uma cidade que se move e se comunica: corpo, rua e improviso

    Directory of Open Access Journals (Sweden)

    Julia Saldanha Vieira de Aguiar

    2009-06-01

    Full Text Available Este trabalho trata da relação de um lugar com suas pessoas. A reflexão acontece a partir de um estudo de caso: o Camelódromo da Praça XV. O Camelódromo foi uma grande feira, que durante 40 anos ocupou um espaço importante no centro de Porto Alegre/RS. (Auto organizado e vivido principalmente pelo povo, o fenômeno se configurava em um lugar onde improviso e estética constituiam o modo de ser e agir no cotidiano da rua. Ironicamente, no início de 2009, o Camelódromo foi transferido para dentro de um prédio. Hoje, onde se desenrolava o espetáculo do imprevisível, encontra-se um estacionamento para carros. Este trabalho foi produzido nos últimos meses do Camelódromo; em um espírito de elogio à estética do improviso e à auto-organização. Buscamos articular idéias da teoria da complexidade, do urbanismo, das artes e da comunicação, para tentar compreender um pouco essa manifestação espontânea, tão característica da urbe no século XXI.

  18. SE-BGP:一种BGP安全机制%SE-BGP: An Approach for BGP Security

    Institute of Scientific and Technical Information of China (English)

    胡湘江; 朱培栋; 龚正虎

    2008-01-01

    BGP(border gateway protocol)协议的安全是Internet路由系统安全的关键.目前已提出多种BGP安全机制,但都未能得到部署.对BGP安全机制的部署问题进行深入分析,利用AS(autonomous system)结构的Rich-Club特性,提出AS联盟的概念,设计了一种BGP安全机制:SE-BGP(security enhanced BGP).SE-BGP采用基于AS联盟的安全体系结构,使用一种具有分布式认证中心的新的信任模型--TTM(translator trust model).设计了基于TTM模型的认证算法,给出了基于现有BGP协议的扩充实现方法.与已有的安全机制相比,SE-BGP在保证安全能力的同时,所需的证书规模大约为原有机制的1%,具有良好的可扩展性.

  19. Electronic structure of the GaSe/Si(111) and InSe/Si(111) heterojunctions

    Science.gov (United States)

    Camara, M. O.; Mauger, A.; Devos, I.

    2002-05-01

    A tight-binding calculation of the electronic properties of the semiconductor GaSe/Si(111) and InSe/Si(111) heterojunctions is performed in a charge-dependent tight binding approach where the only Coulomb effect is a shift of all the pseudoatomic levels of a given atom at site i by the same quantity Ui. The fitting parameters Ui are determined in the framework of constrained optimization techniques using the conjugate gradient method. The band offsets at the interfaces are determined and found to be in quantitative agreement with recent experiments on both heterojunctions. In addition, this optimization technique allows us to give more insight in the charge transfer between atomic planes at the heterojunction. As a result of the the strain induced by the lattice mismatch of the III-VI half layer grafted to the Si(111) surface the charge distribution does not match the simple charge neutrality condition in the case of InSe/Si(111).

  20. Se evita que de vagos pasen a delincuentes”: Santafé como una ciudad peligrosa (1750-1808

    Directory of Open Access Journals (Sweden)

    Nicolás Alejandro González Quintero

    2010-11-01

    Full Text Available Este artículo analiza la discusión sobre un concepto emergente de ocio y de pobreza durante la configuración de Santafé como una ciudad peligrosa a finales del siglo xviii y comienzos del xix. A partir de la lectura de la prensa de la época y de las relaciones entre gobernantes y otros funcionarios coloniales, es explorada la formación de un espacio discursivo en el cual la peligrosidad de la ciudad estaba estrechamente ligada a una nueva lógica sobre el ocio y su regulación. Esto se evidencia en la construcción de ciertas instituciones de control y en la elaboración de la fama como eje articulador de la categorización de ciertos sujetos que no cumplían con las disposiciones imperiales, por lo que se convertían en sujetos de intervención por ser diferentes.

  1. Se evita que de vagos pasen a delincuentes”: Santafé como una ciudad peligrosa (1750-1808

    Directory of Open Access Journals (Sweden)

    Nicolás Alejandro González Quintero

    2010-07-01

    Full Text Available Este artículo analiza la discusión sobre un concepto emergente de ocio y de pobreza durante la configuración de Santafé como una ciudad peligrosa a finales del siglo xviii y comienzos del xix. A partir de la lectura de la prensa de la época y de las relaciones entre gobernantes y otros funcionarios coloniales, es explorada la formación de un espacio discursivo en el cual la peligrosidad de la ciudad estaba estrechamente ligada a una nueva lógica sobre el ocio y su regulación. Esto se evidencia en la construcción de ciertas instituciones de control y en la elaboración de la fama como eje articulador de la categorización de ciertos sujetos que no cumplían con las disposiciones imperiales, por lo que se convertían en sujetos de intervención por ser diferentes.

  2. Luminescence of nanocrystalline ZnSe:Mn2+

    NARCIS (Netherlands)

    Suyver, J.F.; Wuister, S.F.; Kelly, J.J.; Meijerink, A.

    2000-01-01

    The luminescence properties of nanocrystalline ZnSe:Mn^(2+) prepared via an inorganic chemical synthesis are described. Photoluminescence spectra show distinct ZnSe and Mn^(2+) related emissions, both of which are excited via the ZnSe host lattice. The Mn^(2+) emission wavelength and the

  3. Calculation of half-life for 79Se decay

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The half-life for 79Se decay is calculated by using the Logf1ut systematics method. Based on the data analysis and comparison with experimental data the 79Se half-life is recommended. The scheme for 79Se decay is also shown and the radiation data are calculated in the text.

  4. La teoría política de Arendt o cómo lo sólido se desvanece en el aire

    Directory of Open Access Journals (Sweden)

    Christián Matamoros Fernández

    2015-06-01

    Full Text Available En las últimas décadas, las reflexiones filosóficas de Hannah Arendt han tenido profundas influencias en la filosofía política, la sociología, la ciencia política y la teoría política. Sin embargo, a estas reflexiones les subyace un componente restrictivo que no ha sido considerado a la hora de abordar dichas influencias. Es por esto, que en el presente escrito se busca mostrar que la connotación que Arendt le asigna a la política es restrictiva, lo cual permite diferenciarla de la actividad económica y del mundo social, pero en dicha restricción se termina dejando a la actividad política sin contenido material, lo cual conlleva resituarla en el ámbito discursivo y del juicio humano, más que en el de la acción práctica. Abordaremos este objetivo mediante la revisión analítica de algunas de las principales obras de Arendt a la par que serán contrastadas con parte de la filosofía política clásica, moderna y contemporánea. De esta manera, los resultados de esta revisión analítica confirman que en el intento arendtiano por diferenciar a la política de lo social se resitúa a la primera en la abstracción carente de materialidad; en un no lugar, ajeno a los horizontes de posibilidad de la práctica colectiva concreta.

  5. Método híbrido para la identificación de fallas en máquinas eléctricas rotativas utilizando señales de vibración

    OpenAIRE

    Sanz Ramírez, Fredy Alberto

    2009-01-01

    El estudio de las vibraciones en las máquinas eléctricas rotatorias ha sido un tema de investigación que ha involucrado diversas técnicas de análisis, pasando por la modelación matemática, modelos de identificación, análisis de señales, entre otros. En los cuales se ha evidenciado que las posibles fallas que puedan aparecer en motores y generadores son susceptibles de introducir cambios en las señales de vibración que estas producen, permitiendo abrir áreas de estudio para lograr su detección...

  6. Fluorescence relaxation dynamics of CdSe and CdSe/CdS core/shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Gurvir; Kaur, Harmandeep [Centre of Advanced Study in Physics, Department of Physics, Panjab University, Chandigarh-160014 (India); Tripathi, S. K., E-mail: surya@pu.ac.in [Centre of Advanced Study in Physics, Panjab University, Chandigarh- 160014 (India)

    2014-04-24

    Time-resolved fluorescence spectra for colloidal CdSe and CdSe/CdS core/shell quantum dots have been investigated to know their electron relaxation dynamics at the maximum steady state fluorescence intensity. CdSe core and CdSe/CdS type I core-shell materials with different shell (CdS) thicknesses have been synthesized using mercaptoacetic acid as a capping agent. Steady state absorption and emission studies confirmed successful synthesis of CdSe and CdSe/CdS core-shell quantum dots. The fluorescence shows a tri-exponential decay with lifetimes 57.39, 7.82 and 0.96 ns for CdSe quantum dots. The lifetime of each recombination decreased with growth of CdS shell over the CdSe core, with maximum contribution to fluorescence by the fastest transition.

  7. Aqueous synthesis of CdSe and CdSe/CdS quantum dots with controllable introduction of Se and S sources

    Institute of Scientific and Technical Information of China (English)

    Xiao Long Rong; Qin Zhao; Guan Hong Tao

    2012-01-01

    A new and convenient route is developed to synthesize CdSe and core-shell CdSe/CdS quantum dots (QDs) in aqueous solution.The gaseous precursors,H2Se and H2S,generated on-line by reducing SeO32-with NaBH4 and the reaction between Na2S and diluted H2SO4,are used to form high-quality CdSe and CdSe/CdS QDs,respectively.The synthesized water-soluble CdSe and CdSe/CdS QDs possess high quantum yield (3% and 20%) and narrow full-width-at-half-maximum (43 nm and 38 nm).The synthesis process is easily reproducible with simple apparatus and low-toxic chemicals,and can be readily extended to the large-scale aqueous synthesis of QDs.(C) 2012 Guan Hong Tao.Published by Elsevier B.V.on behalf of Chinese Chemical Society.All rights reserved.

  8. Molecular and biochemical characterization of the selenocysteine Se-methyltransferase gene and Se-methylselenocysteine synthesis in broccoli.

    Science.gov (United States)

    Lyi, Sangbom M; Heller, Laurence I; Rutzke, Michael; Welch, Ross M; Kochian, Leon V; Li, Li

    2005-05-01

    Selenium (Se) plays an indispensable role in human nutrition and has been implicated to have important health benefits, including being a cancer preventative agent. While different forms of Se vary in their anticarcinogenic efficacy, Se-methylselenocysteine (SeMSC) has been demonstrated to be one of the most effective chemopreventative compounds. Broccoli (Brassica oleracea var. italica) is known for its ability to accumulate high levels of Se with the majority of the selenoamino acids in the form of Se-methylselenocysteine. Therefore, it serves as a good model to study the regulation of SeMSC accumulation in plants. A cDNA encoding selenocysteine Se-methyltransferase, the key enzyme responsible for SeMSC formation, was cloned from broccoli using a homocysteine S-methyltransferase gene probe from Arabidopsis (Arabidopsis thaliana). This clone, designated as BoSMT, was functionally expressed in Escherichia coli, and its identity was confirmed by its substrate specificity in the methylation of selenocysteine. The BoSMT gene represents a single copy sequence in the broccoli genome. Examination of BoSMT gene expression and SeMSC accumulation in response to selenate, selenite, and sulfate treatments showed that the BoSMT transcript and SeMSC synthesis were significantly up-regulated in plants exposed to selenate but were low in plants supplied with selenite. Simultaneous treatment of selenate with selenite significantly reduced SeMSC production. In addition, high levels of sulfate suppressed selenate uptake, resulting in a dramatic reduction of BoSMT mRNA level and SeMSC accumulation. Our results reveal that SeMSC accumulation closely correlated with the BoSMT gene expression and the total Se status in tissues and provide important information for maximizing the SeMSC production in this beneficial vegetable plant.

  9. Heterojunctions formed by annealing of GaSe and InSe layered crystals in zinc vapor

    OpenAIRE

    Kudrynskyi Z. R.; Kovalyuk Z. D.

    2012-01-01

    The article presents a method of creating heterojunc¬tions based on semiconductors with different lattice types. Substrates manufactured from GaSe and InSe layered crystals were annealed in Zn vapor. This way, n-ZnSe–p-GaSe and n-ZnSe–p-InSe heterojunctions were obtained. The obtained heterojunctions are photo¬sensitive in near and infrared spectral regions. This method opens up greate possibilities of producing heterostructures with a desired sensitivity band.

  10. Spectral anisotropy of a photoresponse from heterojunctions based on GaSe and InSe layered crystals

    Science.gov (United States)

    Katerinchuk, V. N.; Kudrynskyi, Z. R.; Kovalyuk, Z. D.

    2014-03-01

    The object of investigation is photoresponse spectra taken from the cleaved end face of heterojunctions formed by GaSe and InSe anisotropic crystals. Spectra taken from the as-prepared and chemically processed faces of the heterojunctions are compared. A modified method of growing GaSe crystals with a virgin end face is suggested, and the surface of GaSe crystals thus grown is examined by atomic force microscopy.

  11. Crystal Growth of Undoped and Doped ZnSe

    Science.gov (United States)

    Davis, Swanson L.; Chen, K.-T.; George, M. A.; Shi, D. T.; Collins, W. E.; Burger, Arnold

    1997-01-01

    The surface morphology of freshly cleaved ZnSe single crystal grown by the physical vapor transport (PVT) method was investigated by Atomic Force Microscopy (AFM) and the results were correlated with Differential Scanning Calorimetry (DSC) data. Selenium precipitates have been revealed in undoped doped ZnSe crystals having a size of about 50 nm. A transition temperature around 221 C in the DSC measurements is interpreted as the eutectic temperature of Se-saturated ZnSe. The AFM images of doped ZnSe also show that possible Cr clusters are uniformly distributed and they have an estimated size of about 6 nm.

  12. Estudio DRX en Materiales Catalizadores Cu-Ni-SiO2 para Hidrogenación de aceite de soya. Desarrollo de estructura cristalina y actividad catalítica

    Directory of Open Access Journals (Sweden)

    Gloria I. Cubillos

    2009-01-01

    Full Text Available Para buscar elementos experimentales que soporten la hipótesis según la cual se forman estructuras cristalinas Cu-Ni o eventualmente Cu-Ni-SiO2 en la síntesis de catalizadores para la hidrogenación de aceite de soya, se prepararon mezclas de estos tres materiales a partir de sales de los metales con sílice (aerosil. Se calcinaron a 270oC y se redujeron a 330oC en atmósfera de hidrógeno. En  los materiales reducidos se  estudió el difractógrama de RX en el rango 37 a 53 grados, y se comparó con el difractógrama de aleaciones Cu-Ni, en las cuales se conoce la formación  de cristales mixtos, y  con los difractógramas de los elementos puros Cu y Ni.  Los resultados muestran que se presentan señales de difracción diferentes a las señales de los componentes puros. La actividad catalítica se muestra diferente en los materiales que presentan distorsión en su estructura cristalina.  

  13. Determinación de Listeria monocytogenes en quesos frescos de producción artesanal que se expenden en los mercados del distrito de Ica, enero - marzo 2003

    Directory of Open Access Journals (Sweden)

    Ana Espinoza M

    2004-04-01

    Full Text Available Objetivo: Determinar la presencia de L. monocytogenes en quesos frescos de producción artesanal expendidos en los mercados de Ica durante el periodo enero - marzo de 2003. Material y Métodos: De la totalidad de los puestos que expenden queso fresco artesanal en los mercados Santo Domingo, Alejandro Toledo, San Antonio y Modelo, se evaluaron 74 muestras teniendo como unidad muestral 200 g según la Norma Técnica Peruana ISO 28329-1. El procesamiento, aislamiento e identificación se realizó de acuerdo con la metodología recomendada por el manual de bacteriología analítica de la Food and Drug Administration (FDA. Resultados: De las 74 muestras, 3 (4,05% presentaban L. monocytogenes, y de ellas, una muestra correspondió al mercado Alejandro Toledo y 2 muestras al mercado Modelo. Se logró aislar 28 cepas de las cuales 6 (21,4% correspondieron a L. monocytogenes, y 22 (78,6% a otros microorganismos como Lactococcus lactis ss lactis, Enterococcus spp. y Bacillus spp. No se logró aislar L. monocytogenes en los mercados Santo Domingo y San Antonio; sin embargo, en el mercado Alejandro Toledo se aisló una cepa y en el mercado Modelo, se aislaron 5 cepas, lo cual demuestra la presencia significativa de L. monocytogenes sólo en el mercado Modelo. Conclusiones: Existe L. monocytogenes en quesos frescos de producción artesanal, representando un riesgo potencial para la población consumidora.

  14. Air-Stable and Efficient PbSe Quantum-Dot Solar Cells Based upon ZnSe to PbSe Cation-Exchanged Quantum Dots

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sungwoo; Marshall, Ashley R.; Kroupa, Daniel M.; Miller, Elisa M.; Luther, Joseph M.; Jeong, Sohee; Beard, Matthew C.

    2015-08-25

    We developed a single step, cation-exchange reaction that produces air-stable PbSe quantum dots (QDs) from ZnSe QDs and PbX2 (X = Cl, Br, or I) precursors. The resulting PbSe QDs are terminated with halide anions and contain residual Zn cations. We characterized the PbSe QDs using UV–vis–NIR absorption, photoluminescence quantum yield spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Solar cells fabricated from these PbSe QDs obtained an overall best power conversion efficiency of 6.47% at one sun illumination. The solar cell performance without encapsulation remains unchanged for over 50 days in ambient conditions; and after 50 days, the National Renewable Energy Laboratory certification team certified the device at 5.9%.

  15. Atmospheric pressure chemical vapour deposition of SnSe and SnSe{sub 2} thin films on glass

    Energy Technology Data Exchange (ETDEWEB)

    Boscher, Nicolas D.; Carmalt, Claire J.; Palgrave, Robert G. [Department of Chemistry, University College London, 20 Gordon Street, London, WC1H OAJ (United Kingdom); Parkin, Ivan P. [Department of Chemistry, University College London, 20 Gordon Street, London, WC1H OAJ (United Kingdom)], E-mail: i.p.parkin@ucl.ac.uk

    2008-06-02

    Atmospheric pressure chemical vapour deposition of tin monoselenide and tin diselenide films on glass substrate was achieved by reaction of diethyl selenide with tin tetrachloride at 350-650 {sup o}C. X-ray diffraction showed that all the films were crystalline and matched the reported pattern for SnSe and/or SnSe{sub 2}. Wavelength dispersive analysis by X-rays show a variable Sn:Se ratio from 1:1 to 1:2 depending on conditions. The deposition temperature, flow rates and position on the substrate determined whether mixed SnSe-SnSe{sub 2}, pure SnSe or pure SnSe{sub 2} thin films could be obtained. SnSe films were obtained at 650 {sup o}C with a SnCl{sub 4} to Et{sub 2}Se ratio greater than 10. The SnSe films were silver-black in appearance and adhesive. SnSe{sub 2} films were obtained at 600-650 {sup o}C they had a black appearance and were composed of 10 to 80 {mu}m sized adherent crystals. Films of SnSe only 100 nm thick showed complete absorbtion at 300-1100 nm.

  16. Análisis del impacto sociocultural que se genera en las relaciones interpersonales entre la población universitaria foránea y las familias anfitrionas

    OpenAIRE

    Jaramillo Echeverri, Alina; Echeverri Duque, Sandra

    2010-01-01

    Este trabajo presenta una investigación de la prestación del servicio de alojamiento familiar en la ciudad de Medellín; la cual pretende establecer las condiciones de estandarización para el alojamiento de estudiantes foráneos. Para llevar a cabo este estudio se tomó como referencia la experiencia de otros países, que en la actualidad ofrecen servicios de calidad para el intercambio estudiantil a nivel internacional. Como es el caso de los Estados Unidos, Australia, Canadá e Inglaterra y a n...

  17. Análisis del impacto sociocultural que se genera en las relaciones interpersonales entre la población universitaria foránea y las familias anfitrionas

    OpenAIRE

    Jaramillo Echeverri, Alina; Echeverri Duque, Sandra

    2010-01-01

    Este trabajo presenta una investigación de la prestación del servicio de alojamiento familiar en la ciudad de Medellín; la cual pretende establecer las condiciones de estandarización para el alojamiento de estudiantes foráneos. Para llevar a cabo este estudio se tomó como referencia la experiencia de otros países, que en la actualidad ofrecen servicios de calidad para el intercambio estudiantil a nivel internacional. Como es el caso de los Estados Unidos, Australia, Canadá e Inglaterra y a n...

  18. Enfermedades infecciosas más frecuentes que se presentan en los recién nacidos prematuros en el Hospital Provincial Docente Ambato en el área de neonatología de enero a julio del 2014

    OpenAIRE

    Chiliquinga Sarabia, Norma Susana

    2015-01-01

    Lamentablemente no siempre ni en todos los escenarios de actuación de neonatología existen recursos disponibles que permitan establecer el diagnóstico etiológico de las infecciones que presentan los recién nacidos, por lo cual el personal responsable de atender a estos pacientes tiene que valerse de antecedentes o manifestaciones clínicas orientadoras en este sentido. El objetivo de este estudio fue analizar las enfermedades infecciosas más frecuentes que se presentan en los recién nacidos pr...

  19. Análisis del control prenatal que se brinda a las gestantes de la provincia de Heredia que tuvieron su parto en el Hospital San Vicente de Paúl

    OpenAIRE

    Alfaro Vargas, Nathalie; Campos Vargas, Grettel

    2014-01-01

    Este artículo presenta los principales resultados de una investigación cuantitativa, con un diseño no experimental de tipo descriptivo transversal, la cual tuvo por objetivo analizar el control prenatal que se brinda a las gestantes de la provincia de Heredia que tuvieron su parto en el Hospital San Vicente de Paúl durante el año 2012. La npoblación estuvo constituida por las gestantes que tuvieron su parto en dicho hospital entre los meses de diciembre 2011 a noviembre 2012 y por los profesi...

  20. La fiscalidad señorial en el Valle del Tiétar: el ejemplo de Mombeltrán

    Directory of Open Access Journals (Sweden)

    Franco Silva, Alfonso

    2004-06-01

    Full Text Available It is an essay which tries to analyze the lordly tax regulation imposed by the nobles from Mombeltrán, a small town in the province of Ávila, to their vassals: an overall view of the different methods adopted by the aristocratic treasury; its typology; the concepts they paid for; the entries in relation to the expenses; the usurpation of the Crown income and many other questions related to these problems.

    Este ensayo intenta analizar la naturaleza de la fiscalidad señorial, impuesta por los señores de la villa abulense de Mombeltrán a sus vasallos, una visión general de las diversas modalidades que adopta el fisco señorial, su tipología, los conceptos por los cuales se pagaba, los ingresos en relación con los gastos, la usurpación de las rentas procedentes de la Corona y toda una serie de cuestiones relacionadas con esta problemática.

  1. Procesos de construcción de saberes relativos a las prácticas de belleza entre mujeres de sectores populares

    Directory of Open Access Journals (Sweden)

    Claudia Gabriela Reta

    2017-01-01

    Full Text Available El propósito de este artículo es analizar los procesos de construcción de saberes de belleza y estética corporal entre mujeres en contextos de pobreza y segregación socio-espacial. Para ello se identifican y describen las prácticas realizadas por un grupo de mujeres de una villa de la Ciudad Autónoma de Buenos Aires, Argentina, en el marco de una investigación con perspectiva etnográfica. Los resultados obtenidos demuestran que dichos procesos forman parte de una dinámica a partir de la cual se construyen los estereotipos de género, clase y raza-etnia que se inscriben en y actualizan las desigualdades en las que dichas mujeres se encuentran.

  2. La Construcción Social del Enemigo

    Directory of Open Access Journals (Sweden)

    José María Tortosa Blasco

    2003-01-01

    Full Text Available En el artículo, con base en ejemplos tomados de la literatura, se parte de la constatación de que no todos los enemigos son construidos socialmente y de que forman un conjunto heterogéneo que se intenta clarificar mediante una tipología inicial. El énfasis, de todas maneras, se hace sobre los enemigos construidos; para lo cual se presentan los contextos en que es más prob a ble que tal cosa suceda y los mecanismos más usuales en dicha construcción. El artículo termina con una aplicación de la construcción del enemigo al caso del Gobierno de los Estados Unidos bajo George W. Bush, en par tic u lar a su “estrategia para combatir el terrorismo”.

  3. Synthesis of CdSe/ZnSe/ZnS Core/Shell Structure Quantum Dots by Hydrothermal Method%水热法合成CdSe/ZnSe/ZnS核壳结构量子点

    Institute of Scientific and Technical Information of China (English)

    胥燕; 王新; 翟镇德; 刘敏; 苏秀荣

    2014-01-01

    In the study, 3-mercaptopropionic acid modified CdSe/ZnSe/ZnS core/shell structure quantum dots (QDs) with high fluorescence were prepared by hydrothermal method and characterized via transmission electron microscopy (TEM). The influence factors of the fluorescence intensity and the stability of QDs have been studied. Results showed that excellent CdSe/ZnSe/ZnS QDs with uniform diameter (5-8 nm) were obtained. The prepared CdSe/ZnSe/ZnS QDs emit blue-violet light (446 nm) when excited at 372 nm with low toxicity, high fluorescence intensity and excellent stability, endowing the synthesized CdSe/ZnSe/ZnS QDs applied in biochemical analysis.%本研究采用水热法合成了3-巯基丙酸稳定的具有高荧光活性的CdSe/ZnSe/ZnS核/壳结构量子点,并通过透射电镜对量子点的形貌进行了表征。研究了影响量子点荧光强度的因素,并分析了量子点的稳定性。结果表明,水热法合成的CdSe/ZnSe/ZnS量子点,分布均匀,粒径大小均匀,约为5~8 nm。当激发波长为372 nm时CdSe/ZnSe/ZnS量子点可发射蓝紫色(446 nm)荧光,荧光活性高、荧光稳定性好,毒性低,可用于生物荧光标记、组分测定等。

  4. Three-dimensional oil spill transport and dispersion at sea by an event of blowout

    Directory of Open Access Journals (Sweden)

    Luis Otero-Díaz

    2014-01-01

    Full Text Available Las trayectorias de las gotas simuladas con el modelo 3-D de dispersión de petróleo en la plataforma del mar Caribe colombiano mostraron que las gotas con diámetro de 50 μ m , forman una pluma subsuperficial, la cual es transportada horizontalmente y puede permanecer debajo de la superficie por largo tiempo. Esta pluma podría tener un impacto muy restringido, porque la dispersión es controlada solamente por las corrientes oceánicas, las cuales a 1000 metros de profundidad, tienen baja intensidad y son poco turbulentas. En este caso, la pluma formada permanece atrapada a 1000 metros de profundidad, no poniendo en riesgo la costa Caribe. En contraste, las gotas con diámetros de 250 μ m , 1mm y 10 mm, se elevaron rápidamente a la superficie, aun con diferentes velocidades (6, 10, 20 ms-1.

  5. Kinematic field of the s-shaped nebula n119 in the lmc

    Directory of Open Access Journals (Sweden)

    P. Ambrocio-Cruz

    2008-01-01

    Full Text Available La nebulosa N119 en la Nube Mayor de Magallanes tiene una morfolog a muy peculiar, dif cil de explicar con los modelos cl asicos. El objetivo del presente art culo es proporcionar datos cinem aticos que puedan dar restricciones sobre su naturaleza, formaci on y evoluci on. La peculiar morfolog a espiral de esta nebulosa se ve re ejada en su campo de velocidades radiales, el cual muestra varias expansiones en los lamentos d ebiles, los cuales forman diferentes regiones en forma de burbujas, pero tambi en encontramos otras componentes cuyo origen no est a claro. De acuerdo con nuestros resultados, N119 parece contener 3 nebulosas en forma de burbuja formadas por los vientos estelares de estrellas O, WR y quiz as un posible remanente de una explosi on de hipernova. En el curso de este estudio hemos detectado por primera vez una burbuja alrededor de la estrella WR Br 21.

  6. Bent Polytypic ZnSe and CdSe Nanowires Probed by Photoluminescence.

    Science.gov (United States)

    Kim, Yejin; Im, Hyung Soon; Park, Kidong; Kim, Jundong; Ahn, Jae-Pyoung; Yoo, Seung Jo; Kim, Jin-Gyu; Park, Jeunghee

    2017-05-01

    Nanowires (NWs) have witnessed tremendous development over the past two decades owing to their varying potential applications. Semiconductor NWs often contain stacking faults due to the presence of coexisting phases, which frequently hampers their use. Herein, it is investigated how stacking faults affect the optical properties of bent ZnSe and CdSe NWs, which are synthesized using the vapor transport method. Polytypic zinc blende-wurtzite structures are produced for both these NWs by altering the growth conditions. The NWs are bent by the mechanical buckling of poly(dimethylsilioxane), and micro-photoluminescence (PL) spectra were then collected for individual NWs with various bending strains (0-2%). The PL measurements show peak broadening and red shifts of the near-band-edge emission as the bending strain increases, indicating that the bandgap decreases with increasing the bending strain. Remarkably, the bandgap decrease is more significant for the polytypic NWs than for the single phase NWs. This work provides insights into flexible electronic devices of 1D nanostructures by engineering the polytypic structures. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Inter-island transport in CdSe/ZnSe quantum heterostructures

    CERN Document Server

    Wachter, S; Baldauf, M; Schmidt, M; Kurtz, E; Klingshirn, C F; Kalt, H; Litvinov, D A; Gerthsen, D

    2001-01-01

    We report on localization dynamics of excitons in ensembles of self- organized CdSe islands embedded in ZnSe. The experimental methods employed are temperature-dependent, spatially resolved photoluminescence ( mu -PL), spatially integrated PL (macro-PL), as well as time-resolved PL (TRPL). We observe the well known non- monotonous shift of the PL maximum with temperature caused by redistribution of the excitons amongst the islands. The measured shift is compared with the exact shift of the bandgap deduced from mu -PL measurements and found to depend strongly on island size and distribution. These transport processes are recovered in the temporal evolution of the PL. The decaytime of the spectrally integrated PL reaches its maximum at exactly the same temperature at which the redshift of the macro-PL turns into a blueshift. In TRPL the PL- spectrum consists of two contributions. We put the emission on the high energy side down to excited states in the islands. (17 refs).

  8. Investigation of biocompatible and protein sensitive highly luminescent quantum dots/nanocrystals of CdSe, CdSe/ZnS and CdSe/CdS.

    Science.gov (United States)

    Ratnesh, R K; Mehata, Mohan Singh

    2017-02-16

    The size and shape dependent semiconductor quantum dots (0D nanoparticles) with color tunability demonstrating significant influence in a biological system and considered as ideal probes. Here, a non-coordinated colloidal approach was used for the synthesis of CdSe, CdSe/ZnS and CdSe/CdS core-shell quantum dots (QDs) of 3-4nm. The synthesized nanocrystals show a high crystallinity, examined by X-ray diffraction (XRD) and high-resolution electron microscopy (HRTEM). The core-shell semiconductor QDs exhibit stronger photoluminescence (PL) as compared to the core QDs. The strong PL with small full-width half maximum (FWHM) indicates that the prepared QDs have a nearly uniform size distribution and well dispersibility. The quantum yield (QY) of core-shell QDs increases due to the surface passivation. Further, the PL of BSA is quenched strongly by the presence of core-shell QDs and follows the well-known Stern-Volmer (S-V) relation, whereas the PL lifetime does not follow the S-V relation, demonstrating that the observed quenching is predominantly static in nature. Among CdSe core, CdSe/ZnS and CdSe/CdS core-shell QDs, the CdSe/ZnS QDs shows the least cytotoxicity and most biocompatibility. Thus, the prepared core-shell QDs are biocompatible and exhibit strong sensing ability.

  9. Resonant tunneling transport in ZnxBe1-xSe/ZnSe/ZnyBe1-ySe asymmetric quantum structures

    Science.gov (United States)

    Sirkeli, Vadim P.; Yilmazoglu, Oktay; Al-Daffaie, Shihab; Oprea, Ion; Ong, Duu Sheng; Küppers, Franko; Hartnagel, Hans L.

    2017-05-01

    II-VI compounds are promising materials for the fabrication of room-temperature terahertz devices due to their beneficial properties like as type-I conduction band alignment, high breakdown field strength ( 331 kV/cm for ZnSe vs. 80 kV/cm for GaAs), and higher values of the conduction band offset (1.5 eV for BeSe/ZnSe vs. 0.7 eV for AlAs/GaAs). In this paper we report on numerical study of the resonant tunneling transport in ZnBeSe/ZnSe/ZnBeSe symmetric and asymmetric resonant tunneling diodes (RTDs). The negative differential resistance feature is observed in the current-voltage characteristics of the ZnSe-based RTDs. It is found that the maximum of peak-to-valley ratio (PVR) of the current density is equal to 6.025 and 7.144 at 150 K, and to 1.120 and 1.105 at 300 K for the symmetric and asymmetric RTDs, respectively. The effect of barrier heights on the frequency and output power performance of RTD devices are studied and discussed.

  10. A dry method to synthesize dendritic Ag2Se nanostructures utilizing CdSe quantum dots and Ag thin films

    Science.gov (United States)

    Hu, Lian; Zhang, Bingpo; Xu, Tianning; Li, Ruifeng; Wu, Huizhen

    2015-01-01

    Dendritic Ag2Se nanostructures are synthesized in a dry environment by UV irradiating the hybrids composed of CdSe quantum dots (QDs) and silver (Ag). UV irradiation on CdSe QDs induces a photooxidation effect on the QD surface and leads to the formation of SeO2 components. Then SeO2 reacts with the Ag atoms in either Ag film or QD layer to produce the Ag2Se. The growth mechanism of Ag2Se dendrites on solid Ag films is explored and explained by a diffusion limited aggregation model in which the QD layer provides enough freedom for Ag2Se motion. Since the oxidation of the CdSe QDs is the critical step for the Ag2Se dendrites formation this dry chemical interaction between QDs and Ag film can be applied in the study of the QD surface chemical properties. With this dry synthesis method, the Ag2Se dendrites can also be facilely formed at the designed area on Ag substrates.

  11. SeP, ApoER2 and megalin as necessary factors to maintain Se homeostasis in mammals.

    Science.gov (United States)

    Krol, Magdalena Beata; Gromadzinska, Jolanta; Wasowicz, Wojciech

    2012-10-01

    Selenoprotein P (SeP) is an extracellular protein containing ten selenium atoms in the form of selenocysteine, secreted mainly from the liver. About 60% of the whole plasma selenium level is present in SeP, which makes it a useful biomarker of selenium nutritional status. The main functions of SeP are transport and storage of selenium in plasma. It is especially an important protein for the brain, testes and kidneys where the supplementation of the proper amount of Se ensures the synthesis of selenoenzymes with antioxidant properties.Recently, it has been found that SeP uptake in kidneys, testes and brain depends on the apolipoprotein receptor 2 (ApoER2) and lipoprotein megalin receptor (Lrp2). Megalin receptor represents a physiological SeP receptor in kidneys, mediating the re-uptake of secreted SeP from the primary urine. The absence of a functional megalin receptor causes a significant reduction of plasma selenium and the SeP levels as a result of Se excretion. ApoER2 is a SeP receptor in the brain and testes which uptakes Se from the extracellular fluid. Deletion of ApoER2 in mice leads to a lowered selenium level in the brain and testes, neurological dysfunction, production of abnormal spermatozoa, infertility and even death when the subjects are fed a low-selenium diet.

  12. Effect of ZnSe/GaAs interface treatment in ZnSe quality control for optoelectronic device applications

    Energy Technology Data Exchange (ETDEWEB)

    Park, Kwangwook; Beaton, Daniel; Steirer, Kenneth X.; Alberi, Kirstin

    2017-05-01

    We investigate the role of interface initiation conditions on the growth of ZnSe/GaAs heterovalent heterostructures. ZnSe epilayers were grown on a GaAs surface with various degrees of As-termination and the application of either a Zn or Se pre-treatment. Structural analysis revealed that Zn pre-treatment of an As-rich GaAs surface suppresses Ga2Se3 formation at the interface and promotes the growth of high crystal quality ZnSe. This is confirmed with low-temperature photoluminescence. However, moderation of Ga-Se bonding through a Se pre-treatment of an As-rich GaAs surface can prevent excessive intermixing at the interface and promote excitonic emission in the underlying GaAs layer. These results provide guidance on how best to prepare heterovalent interfaces for various applications.

  13. Effect of ZnSe/GaAs interface treatment in ZnSe quality control for optoelectronic device applications

    Science.gov (United States)

    Park, Kwangwook; Beaton, Daniel; Steirer, Kenneth X.; Alberi, Kirstin

    2017-05-01

    We investigate the role of interface initiation conditions on the growth of ZnSe/GaAs heterovalent heterostructures. ZnSe epilayers were grown on a GaAs surface with various degrees of As-termination and the application of either a Zn or Se pre-treatment. Structural analysis revealed that Zn pre-treatment of an As-rich GaAs surface suppresses Ga2Se3 formation at the interface and promotes the growth of high crystal quality ZnSe. This is confirmed with low-temperature photoluminescence. However, moderation of Ga-Se bonding through a Se pre-treatment of an As-rich GaAs surface can prevent excessive intermixing at the interface and promote excitonic emission in the underlying GaAs layer. These results provide guidance on how best to prepare heterovalent interfaces for various applications.

  14. Photoelectric properties of heterostructures based on thermo-oxidated GaSe and InSe crystals

    Energy Technology Data Exchange (ETDEWEB)

    Savchyn, V.P.; Kytsai, V.B. [Lviv Ivan Franko State Univ. (Ukraine). Phys. Dept.

    2000-02-21

    The thermal oxidation processes on cleaved surfaces of GaSe and InSe single crystals in the temperature ranges of 450-700 C and 300-600 C, respectively have been investigated. The photoelectric properties of the obtained heterostructures were studied. It was established that the photoconductivity peculiarities can be explained taking into consideration the nature of surface layers formed under definite conditions such as Ga{sub 2}O{sub 3} (for GaSe) and In{sub 2}(SeO{sub 4}){sub 3} or In{sub 2}O{sub 3} (for InSe) oxide phases for GaSe and InSe correspondingly. It is shown that heterostructure spectral photosensitivity can be varied in a wide range due to definite selection of treatment conditions of gallium and indium monoselenides crystals e.g. temperature and duration of oxidation in air atmosphere. (orig.)

  15. Synthesis of CdSe Quantum Dots Using Fusarium oxysporum

    Directory of Open Access Journals (Sweden)

    Takaaki Yamaguchi

    2016-10-01

    Full Text Available CdSe quantum dots are often used in industry as fluorescent materials. In this study, CdSe quantum dots were synthesized using Fusarium oxysporum. The cadmium and selenium concentration, pH, and temperature for the culture of F. oxysporum (Fusarium oxysporum were optimized for the synthesis, and the CdSe quantum dots obtained from the mycelial cells of F. oxysporum were observed by transmission electron microscopy. Ultra-thin sections of F. oxysporum showed that the CdSe quantum dots were precipitated in the intracellular space, indicating that cadmium and selenium ions were incorporated into the cell and that the quantum dots were synthesized with intracellular metabolites. To reveal differences in F. oxysporum metabolism, cell extracts of F. oxysporum, before and after CdSe synthesis, were compared using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE. The results suggested that the amount of superoxide dismutase (SOD decreased after CdSe synthesis. Fluorescence microscopy revealed that cytoplasmic superoxide increased significantly after CdSe synthesis. The accumulation of superoxide may increase the expression of various metabolites that play a role in reducing Se4+ to Se2− and inhibit the aggregation of CdSe to make nanoparticles.

  16. Effect of Sn Content in a CuSnZn Metal Precursor on Formation of MoSe2 Film during Selenization in Se+SnSe Vapor

    OpenAIRE

    Liyong Yao; Jianping Ao; Ming-Jer Jeng; Jinlian Bi; Shoushuai Gao; Guozhong Sun; Qing He; Zhiqiang Zhou; Yun Sun; Liann-Be Chang

    2016-01-01

    The preparation of Cu2ZnSnSe4 (CZTSe) thin films by the selenization of an electrodeposited copper–tin–zinc (CuSnZn) precursor with various Sn contents in low-pressure Se+SnSex vapor was studied. Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) measurements revealed that the Sn content of the precursor that is used in selenization in a low-pressure Se+SnSex vapor atmosphere only slightly affects the elemental composition of the formed CZTSe films. However, the Sn co...

  17. A method to synthesize CdSe nanocrystals

    Institute of Scientific and Technical Information of China (English)

    XIE Chuang; CHEN Wei; WANG Jingkang

    2007-01-01

    CdSe nanocrystals (NCs) have great application prospects in various fields due to their novel properties.Some high-cost and toxic materials such as tri-n-octylphosphine oxide (TOPO) are used in the popular method to synthesize CdSe NCs.Based on this,a new low-cost,environment-friendly and safe solvent was introduced in the synthesis of CdSe NCs in this paper.The prepared CdSe NCs were characterized by ultraviolet-visible spectra (UV-Vis),photoluminescence (PL),transmission electron micrograph (TEM),energy disperse X-ray spectra (EDX) and X-ray diffraction (XRD).The CdSe NCs obtained which show a good PL properry are monodisperse,size-tunable and of high crystallinity.It indicates that the new solvent A is a good substitute for the solvent used in the classic route and achieves a greener synthesis of CdSe NCs.

  18. Atomic Defects and Doping of Monolayer NbSe2.

    Science.gov (United States)

    Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J P; Lawlor, Sean; Sanchez, Ana M; Sloan, Jeremy; Gorbachev, Roman V; Grigorieva, Irina V; Krasheninnikov, Arkady V; Haigh, Sarah J

    2017-02-24

    We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.

  19. First Reported Case of Proliferative Retinopathy in Hemoglobin SE Disease

    Directory of Open Access Journals (Sweden)

    Paul Baciu

    2014-01-01

    Full Text Available We report the first case of proliferative sickle cell retinopathy in a patient with hemoglobin SE (Hb SE disease. Only a few dozen cases of Hb SE disease have been reported previously, and none had evidence of proliferative retinopathy. A 56-year-old African American man presented to our clinic for routine examination and was found to have sea-fan peripheral neovascularization bilaterally without maculopathy. Hemoglobin analysis revealed Hb SE heterozygosity. Sector laser photocoagulation to areas of nonperfusion in both eyes resulted in regression of the peripheral neovascularization over a period of 6 months. Although Hb SE disease is rare, the incidence of Hb SE disease is postulated to rise in the future. Awareness of its potential ocular complications is needed to appropriately refer these patients for screening.

  20. Timely resolved measurements on CdSe nanoparticles; Zeitaufgeloeste Messungen an CdSe Nanopartikeln

    Energy Technology Data Exchange (ETDEWEB)

    Holt, B.E. von

    2006-06-06

    By means of infrared spectroscopy the influence of the organic cover on structure and dynamics of CdSe nanoparticles was studied. First a procedure was developed, which allows to get from the static infrared spectrum informations on the quality of the organic cover and the binding behaviour of the ligands. On qualitatively high-grade and well characterized samples thereafter the dynamics of the lowest-energy electron level 1S{sub e} was time-resolvedly meausred in thew visible range. As reference served CdSe TOPO, which was supplemented by samples with the ligands octanthiole, octanic acid, octylamine, naphthoquinone, benzoquinone, and pyridine. The studied nanoparticles had a diameter of 4.86 nm. By means of the excitation-scanning or pump=probe procedure first measurements in the picosecond range were performed. The excitation wavelengths were thereby spectrally confined and so chosen that selectively the transitions 1S{sub 3/2}-1S-e and 1P{sub 3/2}-1P{sub e} but not the intermediately lyingt transition 2S{sub 3/2}-1S{sub e} were excited. The excitation energies were kept so low that the excitation of several excitons in one crystal could be avoided. The scanning wavelength in the infrared corresponded to the energy difference between the electron levels 1S{sub e} and 1P{sub e}. The transients in the picosecond range are marked by a steep increasement of the signal, on which a multi-exponential decay follows. The increasement, which reproduces the popiulation of the excited state, isa inependent on the choice of the ligands. The influence of the organic cover is first visible in the different decay times of the excited electron levels. the decay of the measurement signal of CdSe TOPO can be approximatively described by three time constants: a decay constant in the early picosecond region, a time constant around hundert picoseconds, and a time constant of some nanoseconds. At increasing scanning wavelength the decay constants become longer. By directed excitation

  1. Peculiarities of Properties of the GaSe (InSe Nanohybrids, Synthesized under Lighting

    Directory of Open Access Journals (Sweden)

    F.O. Ivashchyshyn

    2016-11-01

    Full Text Available In this paper, new technological approach to the synthesis of multilayered nanostructures was proposed. It increased sensory properties of these nanostructures and their application for highly efficient nonelectrochemical accumulation of electrical energy. In particular, it was shown, that the field of the light wave, imposed in the process of nanohybrid formation, significantly affected the changes, caused by encapsulation of thiourea, on impedance, spectrum of thermally stimulated depolarisation currents (TSD, loss tangent tg δ and dielectric constant ε. As a result, both the application of nanohybrids GaSe as highly effective photovaricap structures and accumulation of energy on the quantum level at infralowfrequency range were investigated. In addition, a huge negative photo-capacitive phenomenon and the appearance of electromotive force in a constant magnetic field («spin battery» phenomenon in nanohibryds were found.

  2. Cr:ZnSe guided wave lasers and materials

    Science.gov (United States)

    McDaniel, Sean; Lancaster, Adam; Stites, Ronald; Thorburn, Fiona; Kar, Ajoy; Cook, Gary

    2017-02-01

    We describe a variety of technological advances in the development of efficient, powerful, and continuously tunable Cr:ZnSe lasers operating in the 2.3-2.7 μm spectral region. This includes the development of compact "single chip" waveguide Cr:ZnSe lasers, waveguide mode-locked Cr:ZnSe lasers, and the creation of homogeneously broadened laser material.

  3. The synthesis and photocatalytic activity of ZnSe microspheres.

    Science.gov (United States)

    Cao, Huaqiang; Xiao, Yujiang; Zhang, Sichun

    2011-01-07

    This paper reports the synthesis of semiconductor ZnSe microspheres composed of nanoparticles via a solvothermal route between the organic molecule selenophene (C(4)H(4) Se) and ZnCl(2) without adding any surfactant. The ZnSe microspheres were characterized by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), specific surface area measurement, and photoluminescence (PL) spectra. A strong and broad blue PL emission at 443 nm in wavelength (∼2.79 eV in photon energy) is attributed to the near-band-edge (NBE) emission of ZnSe, while the 530 nm peak is a defect-related (DL) emission. The photocatalytic activity of the as-prepared ZnSe microspheres was evaluated by photodegradation of methyl orange (MO) dye under ultraviolet (UV) light and visible light irradiation. The degradations of MO reach 94% or 95.1%, close to 100%, in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 7 or 10 h under UV irradiation, respectively. Meanwhile the degradations of MO reach 94.3% or 60.6% in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 12 h, respectively. The degradation rate of ZnSe microspheres is twice that of ZnSe commercial powder under UV light irradiation, and three times under visible light irradiation. The degradation process of MO dye on ZnSe microspheres under UV or visible light is also discussed.

  4. The synthesis and photocatalytic activity of ZnSe microspheres

    Science.gov (United States)

    Cao, Huaqiang; Xiao, Yujiang; Zhang, Sichun

    2011-01-01

    This paper reports the synthesis of semiconductor ZnSe microspheres composed of nanoparticles via a solvothermal route between the organic molecule selenophene (C4H4 Se) and ZnCl2 without adding any surfactant. The ZnSe microspheres were characterized by x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), specific surface area measurement, and photoluminescence (PL) spectra. A strong and broad blue PL emission at 443 nm in wavelength (~2.79 eV in photon energy) is attributed to the near-band-edge (NBE) emission of ZnSe, while the 530 nm peak is a defect-related (DL) emission. The photocatalytic activity of the as-prepared ZnSe microspheres was evaluated by photodegradation of methyl orange (MO) dye under ultraviolet (UV) light and visible light irradiation. The degradations of MO reach 94% or 95.1%, close to 100%, in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 7 or 10 h under UV irradiation, respectively. Meanwhile the degradations of MO reach 94.3% or 60.6% in the presence of the as-synthesized ZnSe microspheres or commercial ZnSe powder after 12 h, respectively. The degradation rate of ZnSe microspheres is twice that of ZnSe commercial powder under UV light irradiation, and three times under visible light irradiation. The degradation process of MO dye on ZnSe microspheres under UV or visible light is also discussed.

  5. Crystal structures and 77Se NMR spectra of molybdenum(IV) areneselenolates having intramolecular NH...Se hydrogen bonds.

    Science.gov (United States)

    Okamura, Taka-Aki; Taniuchi, Kaku; Lee, Keonil; Yamamoto, Hitoshi; Ueyama, Norikazu; Nakamura, Akira

    2006-11-13

    Salts of the monooxomolybdenum(IV,V) areneselenolates having intramolecular NH...Se hydrogen bonds, [Mo(IV)O(Se-2-RCONHC6H4)4]2- (R = t-Bu, CH3, CF3) and [Mo(V)O(Se-2-t-BuCONHC6H4)4]-, were synthesized and characterized by 1H nuclear magnetic resonance (NMR), 77Se NMR, electron spin resonance (ESR), UV-visible spectra, X-ray analysis, and electrochemical measurements. 77Se-1H correlated spectroscopy (COSY) indicated a significant correlation between amide 1H and selenolate 77Se atoms through an NH...Se hydrogen bond with 1J(77Se-1H) = 5.4 Hz coupling. The hydrogen bonds contribute to the positive shift in the Mo(V)/Mo(IV) redox potential. In the crystal structure of (PPh4)2[Mo(IV)O(Se-2-CH3CONHC6H4)4], an NH...O=Mo hydrogen bond was found. Ab inito calculations support the presence of intramolecular NH...O=Mo and NH...Se hydrogen bonds.

  6. Ultrasonic spray pyrolysis deposition of SnSe and SnSe2 using a single spray solution

    Institute of Scientific and Technical Information of China (English)

    Jorge Sergio Narro-Rios; Manoj Ramachandran; Dalia Martínez-Escobar; Aarón Sánchez-Juárez

    2013-01-01

    Thin films of SnSe and SnSe2 have been deposited using the ultrasonic spray pyrolysis (USP) technique.To the best of our knowledge this is the first report of the deposition of SnSe and SnSe2 thin films using a single spray solution.The use of a single spray solution for obtaining both a p-type material,SnSe,and an n-type material,SnSe2,simplifies the deposition technique.The SnSe2 thin films have a bandgap of 1.1 eV and the SnSe thin films have a band gap of 0.9 eV.The Hall measurements were used to determine the resistivity of the thin films.The SnSe2 thin films show a resistivity of 36.73 Ω·cm and n-type conductivity while the SnSe thin films show a resistivity of 180 Ω·cm and p-type conductivity.

  7. Symmetry and optical anisotropy in CdSe/ZnSe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Kiessling, Tobias

    2009-10-29

    The material system of choice for the investigations performed in the frame of this Thesis were self-assembled CdSe/ZnSe QDs. The reason for this choice is twofold. First, CdSe/ZnSe QDs can be grown with excellent optical quality, which is a prerequiste for optical studies. Second, due to the polar nature of II-VI compound semiconductors, optical anisotropies induced by various asymmetries are more pronounced than in their IIIV or element IV counterparts. Unlike in the III-V materials, where the self-organization of QDs is well described by the Stranski-Krastanow growth mode, the peculiarities of the QD formation are not entirely clear in II-VI alloys. For the purposes of the current work QDs emerging from two variants of Molecular Beam Epitaxy (MBE) growth were studied. In order to establish a clear connection between the optically observed anisotropies and the growth induced asymmetries in the QDs we start out by summarizing all available structural and morphological studies that were performed on the resultant QDs, including x-ray diffraction, atomic force microscopy, high resolution transmission electron microscopy and resonant Raman scattering. Extensive investigations by Photoluminescence (PL) and Photoluminescence Excitation (PLE) spectroscopy hence detail the resultant electronic structure of excitons confined to the above QDs as well as their energy relaxation across the latter. We find that for these small-sized strongly confining QDs k-vector conservation is entirely relaxed, which enables interaction of the excitons with a continuum of phonons and explains fast and efficient exciton capture by the QDs, even for excitation conditions far above the ground state. We demonstrate how this provides an alternative fast relaxation channel to Auger-like electron-hole scattering, that may also explain fast hole relaxation and adds to the understanding of the absence of a phonon bottleneck in the energy relaxation in these type of QDs. With the above analysis as a

  8. Symmetry and optical anisotropy in CdSe/ZnSe quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Kiessling, Tobias

    2009-10-29

    The material system of choice for the investigations performed in the frame of this Thesis were self-assembled CdSe/ZnSe QDs. The reason for this choice is twofold. First, CdSe/ZnSe QDs can be grown with excellent optical quality, which is a prerequiste for optical studies. Second, due to the polar nature of II-VI compound semiconductors, optical anisotropies induced by various asymmetries are more pronounced than in their IIIV or element IV counterparts. Unlike in the III-V materials, where the self-organization of QDs is well described by the Stranski-Krastanow growth mode, the peculiarities of the QD formation are not entirely clear in II-VI alloys. For the purposes of the current work QDs emerging from two variants of Molecular Beam Epitaxy (MBE) growth were studied. In order to establish a clear connection between the optically observed anisotropies and the growth induced asymmetries in the QDs we start out by summarizing all available structural and morphological studies that were performed on the resultant QDs, including x-ray diffraction, atomic force microscopy, high resolution transmission electron microscopy and resonant Raman scattering. Extensive investigations by Photoluminescence (PL) and Photoluminescence Excitation (PLE) spectroscopy hence detail the resultant electronic structure of excitons confined to the above QDs as well as their energy relaxation across the latter. We find that for these small-sized strongly confining QDs k-vector conservation is entirely relaxed, which enables interaction of the excitons with a continuum of phonons and explains fast and efficient exciton capture by the QDs, even for excitation conditions far above the ground state. We demonstrate how this provides an alternative fast relaxation channel to Auger-like electron-hole scattering, that may also explain fast hole relaxation and adds to the understanding of the absence of a phonon bottleneck in the energy relaxation in these type of QDs. With the above analysis as a

  9. Measuring SeHCAT retention: a technical note.

    Science.gov (United States)

    Notghi, Alp; O'Brien, Joseph; Low, Chen Sheng; Thomson, William

    2011-10-01

    TauroH-23-((75)Se)selena-25-homocholic acid (SeHCAT) retention has been used for the diagnosis of bile acid malabsorption since the early 1980s. Bile acid malabsorption has been increasingly recognized as an important cause of severe chronic diarroea with subsequent increase in the number of referrals for the SeHCAT test. In this study, we review and discuss the standard techniques for the measurement of SeHCAT retention and describe a simple and modified technique using a noncollimated whole-body scanner, suitable for most modern dual-headed cameras.

  10. Properties of the Mo-CuInSe2 interface

    Science.gov (United States)

    Russell, P. E.; Jamjoum, O.; Ahrenkiel, R. K.; Kazmerski, L. L.; Mickelsen, R. A.; Chen, W. S.

    1982-06-01

    Mo has been suggested and used as an ohmic back contact for CdS/p-CuInSe2 solar cells. The Mo-p-CuInSe2 interface has been studied for both polycrystalline and single-crystal CuInSe2, using electron beam induced current and capacitance-voltage techniques. The interface is found to form a Schottky barrier, thereby limiting the attainable voltage of a solar cell with Mo back contact. Au is the only known ohmic contact to p-CuInSe2.

  11. Synthesis of CdSe Quantum Dots Using Fusarium oxysporum

    OpenAIRE

    Takaaki Yamaguchi; Yoshijiro Tsuruda; Tomohiro Furukawa; Lumi Negishi; Yuki Imura; Shohei Sakuda; Etsuro Yoshimura; Michio Suzuki

    2016-01-01

    CdSe quantum dots are often used in industry as fluorescent materials. In this study, CdSe quantum dots were synthesized using Fusarium oxysporum. The cadmium and selenium concentration, pH, and temperature for the culture of F. oxysporum (Fusarium oxysporum) were optimized for the synthesis, and the CdSe quantum dots obtained from the mycelial cells of F. oxysporum were observed by transmission electron microscopy. Ultra-thin sections of F. oxysporum showed that the CdSe quantum dots were pr...

  12. Structure of 72,74Se at high spin

    Indian Academy of Sciences (India)

    R Palit; H C Jain; P K Joshi; J A Sheikh

    2001-07-01

    Lifetimes of high spin states up to =22+ in the yrast positive parity bands have been measured to investigate the shape evolution with increasing spin in 72,74Se. The t values derived from these measurements indicate that prolate shape stabilizes for 72Se, while a triaxial shape develops for 74Se at higher spins. Comparison of the observed trend in t with spin for 72,74Se with that of the corresponding kryptones isotones emphasizes the stability provided by = 38 prolate shell gap even at high rotational frequency.

  13. Ultraviolet-blue photoluminescence of ZnSe quantum dots.

    Science.gov (United States)

    Peng, Ling Ling; Wang, Yu Hua; Li, Cheng Yan

    2010-03-01

    Zinc blende, sphericity, monodisperse, high luminescence ZnSe quantum dots (QDs) were synthesized by a one-step mild hydrothermal route with Zn and Se dissolved in aqueous NaOH as the source material. The structure and the morphology of the sample were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicated that the products were cubic blende ZnSe ranging from 3.2 to 4.5 nm in size. TEM images showed that the QDs have very good dispersibility and distribution. The characteristic features of the absorption and photoluminescence spectra of ZnSe quantum dots were studied at room temperature. Compared with the bulk ZnSe, the absorption edges and luminescent peaks of ZnSe QDs were blue shifted to higher energies due to the quantum confinement effect. Photoluminescence at ultraviolet excitation showed the strong emission at 390 nm related to the higher excitonic states. ZnSe QDs exhibiting photoluminescence line widths as narrow as 40-60 nm. Meanwhile, we simply explored the theoretical mechanism of luminescence in ZnSe QDs and analogized the relation of various point defect concentrations of ZnSe.

  14. A novel method for the deposition of nanocrystalline Bi 2Se 3, Sb 2Se 3 and Bi 2Se 3-Sb 2Se 3 thin films — SILAR

    Science.gov (United States)

    Lokhande, C. D.; Sankapal, B. R.; Sartale, S. D.; Pathan, H. M.; Giersig, M.; Ganesan, V.

    2001-10-01

    The successive ionic layer adsorption and reaction (SILAR) method is relatively new, simple and less expensive. This method is employed to deposit nanocrystalline Bi 2Se 3, Sb 2Se 3 and Bi 2Se 3-Sb 2Se 3 thin films onto amorphous glass substrates at low temperature (300 K). The preparative parameters such as concentration of precursor solutions, rinsing time, immersion cycles and immersion time are optimized to get nanocrystalline films. These films are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDAX), optical absorption and electrical measurement techniques.

  15. A reduction approach to prepare ZnSe nanocrystallites

    Institute of Scientific and Technical Information of China (English)

    JIANG Hai-qing; CHE Jun; LI Zhi-min; YAO Xi

    2006-01-01

    ZnSe nanocrystallites powders were successfully prepared by reduction method with H2SeO4 or H2SeO3 as selenium source and Zn(Ac)2·H2O as zinc source. The reaction mechanism was also discussed through XRD and DTA/TG analysis. In the process,ZnSeO4·H2O or ZnSeO3·H2O crystallites precipitated in organic solvent was prepared at first. Then the crystallites were reduced with carbon monoxide atmosphere. The XRD analysis reveals that the structure of ZnSe phase is sphalerite (cubic ZnS). The XPS results show that the atomic ratio of Se to Zn is 1-1 approximately. The TEM shows that the size of ZnSe crystallite is 30-50 nm. This method of synthesis of ZnSe nanocrystallites has the potential application in the preparation of optical composite thin films from sol-gel process.

  16. Cohort profile: Epidemiological Clinicopathological studies in Europe (EClipSE).

    Science.gov (United States)

    2009-01-01

    Epidemiological Clinicopathological Studies in Europe (EClipSE) is the harmonization of neuropathological and longitudinal clinical data from three population-based prospective longitudinal studies of aging. The EClipSE database (Version 1.0) comprises data from the first 970 people who donated their brain at death and this number will increase. EClipSE enables sociodemographic, health, cognitive, and genetic measures collected during life to be related to neuropathology at death, testing hypotheses which require more power than has been previously possible. EClipSE aims to help throw light on relationships between biological, health and psychological factors underlying ageing and the manifestation of clinical dementia.

  17. Defects and oxidation resilience in InSe

    Science.gov (United States)

    Xiao, K. J.; Carvalho, A.; Castro Neto, A. H.

    2017-08-01

    We use density functional theory to study intrinsic defects and oxygen related defects in indium selenide. We find that InSe is prone to oxidation, but however not reacting with oxygen as strongly as phosphorene. The dominant intrinsic defects in In-rich material are the In interstitial, a shallow donor, and the Se vacancy, which introduces deep traps. The latter can be passivated by oxygen, which is isoelectronic with Se. The dominant intrinsic defects in Se-rich material have comparatively higher formation energies.

  18. XAS Studies of Se Speciation in Selenite-Fed Rats

    Science.gov (United States)

    Weekley, Claire M.; Aitken, Jade B.; Witting, Paul K.; Harris, Hugh H.

    2014-01-01

    The biological activity of selenium is dependent on its chemical form. Therefore, knowledge of Se chemistry in vivo is required for efficacious use of selenium compounds in disease prevention and treatment. Using X-ray absorption spectroscopy, Se speciation in the kidney, liver, heart, spleen, testis and red blood cells of rats fed control (~0.3 ppm Se) or selenite-supplemented (1 ppm or 5 ppm Se) diets for 3 or 6 weeks, was investigated. X-ray absorption spectroscopy revealed the presence of Se–Se and Se–C species in the kidney and liver, and Se–S species in the kidney, but not the liver. X-ray absorption near edge structure (XANES) spectra showed that there was variation in speciation in the liver and kidneys, but Se speciation was much more uniform in the remaining organs. Using principal component analysis (PCA) to interpret the Se K-edge X-ray absorption spectra, we were able to directly compare the speciation of Se in two different models of selenite metabolism – human lung cancer cells and rat tissues. The effects of Se dose, tissue type and duration of diet on selenium speciation in rat tissues were investigated, and a relationship between the duration of the diet (3 weeks versus 6 weeks) and selenium speciation was observed. PMID:25363824

  19. Effect of Sn Content in a CuSnZn Metal Precursor on Formation of MoSe2 Film during Selenization in Se+SnSe Vapor

    Directory of Open Access Journals (Sweden)

    Liyong Yao

    2016-03-01

    Full Text Available The preparation of Cu2ZnSnSe4 (CZTSe thin films by the selenization of an electrodeposited copper–tin–zinc (CuSnZn precursor with various Sn contents in low-pressure Se+SnSex vapor was studied. Scanning electron microscope (SEM and energy dispersive spectroscopy (EDS measurements revealed that the Sn content of the precursor that is used in selenization in a low-pressure Se+SnSex vapor atmosphere only slightly affects the elemental composition of the formed CZTSe films. However, the Sn content of the precursor significantly affects the grain size and surface morphology of CZTSe films. A metal precursor with a very Sn-poor composition produces CZTSe films with large grains and a rough surface, while a metal precursor with a very Sn-rich composition procures CZTSe films with small grains and a compact surface. X-ray diffraction (XRD and SEM revealed that the metal precursor with a Sn-rich composition can grow a thicker MoSe2 thin film at CZTSe/Mo interface than one with a Sn-poor composition, possibly because excess Sn in the precursor may catalyze the formation of MoSe2 thin film. A CZTSe solar cell with an efficiency of 7.94%was realized by using an electrodeposited metal precursor with a Sn/Cu ratio of 0.5 in selenization in a low-pressure Se+SnSex vapor.

  20. Elucidation of two giants: challenges to thick-shell synthesis in CdSe/ZnSe and ZnSe/CdS core/shell quantum dots.

    Science.gov (United States)

    Acharya, Krishna P; Nguyen, Hue M; Paulite, Melissa; Piryatinski, Andrei; Zhang, Jun; Casson, Joanna L; Xu, Hongwu; Htoon, Han; Hollingsworth, Jennifer A

    2015-03-25

    Core/thick-shell giant quantum dots (gQDs) possessing type II electronic structures exhibit suppressed blinking and diminished nonradiative Auger recombination. We investigate CdSe/ZnSe and ZnSe/CdS as potential new gQDs. We show theoretically and experimentally that both can exhibit partial or complete spatial separation of an excited-state electron-hole pair (i.e., type II behavior). However, we reveal that thick-shell growth is challenged by competing processes: alloying and cation exchange. We demonstrate that these can be largely avoided by choice of shelling conditions (e.g., time, temperature, and QD core identity). The resulting CdSe/ZnSe gQDs exhibit unusual single-QD properties, principally emitting from dim gray states but having high two-exciton (biexciton) emission efficiencies, whereas ZnSe/CdS gQDs show characteristic gQD blinking suppression, though only if shelling is accompanied by partial cation exchange.

  1. Preparation of multiband structure with Cu2Se/Ga3Se2/In3Se2 thin films by thermal evaporation technique for maximal solar spectrum utilization

    Science.gov (United States)

    Mohan, A.; Rajesh, S.; Gopalakrishnan, M.

    2016-10-01

    The paper investigates and discusses the formation of multiband structure through the Cu2Se-Ga3Se-In3Se2 thin films for maximal solar spectrum utilization. Stacking different semiconductor materials with various band gaps were done by successive evaporation method. Based on the band gap values the layers are arranged (low to high bandgap from the substrate). The XRD results exhibits the formation of CIGS composites through this successive evaporation of Cu2Se/Ga3Se/In3Se2 and treating then with temperature. Scanning Electron Microscope images shows improved crystallinity with the reduction in the larger grain boundary scattering after annealing. Optical spectra shows the stronger absorption in an UV-Visible region and higher transmission in the infrared and near infrared region. The optical band gap values calculated for as prepared films is 2.20 eV and the band gap was split into 1.62, 1.92 eV and 2.27eV for annealed samples. This multiband structures are much needed to utilize the full solar spectrum.

  2. El futuro de la televisión pública educativa y cultural. El caso de Señal Colombia

    Directory of Open Access Journals (Sweden)

    Paula Arenas

    2015-05-01

    Full Text Available La televisión sirve de espejo y de ventana de una sociedad. Sin embargo, la televisión privada esta mediada por el filtro del interés comercial que distorsiona el reflejo del espejo y la perspectiva de la ventana, y en lugar de presentar una imagen auténtica, ofrece una imagen aspiracional del mundo. La televisión privada se convierte, entonces, en un espacio en el que las medidas aceptables son las de la reina, el cine posible es el de Hollywood y en el cual la oferta de imaginarios para sus televidentes tiene como intención venderles algo.

  3. Phase equilibria and liquid phase epitaxy growth of PbSnSeTe lattice matched to PbSe

    Science.gov (United States)

    Mccann, Patrick J.; Fonstad, Clifton G.; Fuchs, Jacob; Feit, Ze'ev

    1987-01-01

    The necessary phase diagram data for growing lattice-matched layers of PbSnSeTe on PbSe are presented. Solid compounds of Pb(1-x)Sn(x)Se(1-y)Te(y) lattice-matched to PbSe were grown from liquid melts consisting of (Pb/1-x/Sn/x/)(1-z)(Se/1-y/Te/y/)(z); phase equilibria data were determined together with liquidus data for values of x(liquid) from 0 to 40 percent and y(liquid) from 0 to 40 percent for temperatures between 450 and 540 C. It was found that relatively large amounts of Te must be added to the melt to achieve lattice matching because of its low segregation coefficient relative to Se. A significant lattice-pulling effect was discovered for the 5-percent Sn case, and a similar effect is expected for the 10- and 20-percent Sn cases.

  4. Phonon softening in the CDW Systems NbSe{sub 2} and TiSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Hott, Roland; Heid, Rolf; Bohnen, Klaus-Peter [Karlsruhe Institute of Technology, Institute of Solid State Physics, Karlsruhe (Germany); Weber, Frank [Karlsruhe Institute of Technology, Institute of Solid State Physics, Karlsruhe (Germany); Materials Science Division, Argonne National Laboratory, Argonne, Illinois (United States); Rosenkranz, Stephan; Castellan, John-Paul; Osborn, Raymond [Materials Science Division, Argonne National Laboratory, Argonne, Illinois (United States); Egami, Takeshi [Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee (United States); Said, Ayman [Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois (United States); Reznik, Dmitry [Karlsruhe Institute of Technology, Institute of Solid State Physics, Karlsruhe (Germany); Department of Physics, University of Colorado at Boulder, Boulder, Colorado (United States)

    2011-07-01

    We investigated the soft-mode behaviour of phonons in the charge density wave (CDW) systems NbSe{sub 2} and TiSe{sub 2} both theoretically in Density Functional Theory (DFT) based on ab-initio phonon calculations and experimentally by means of high resolution Inelastic X-ray Scattering (IXS). For both materials, the theoretical predictions for the phonon softening using the experimental lattice parameters coincide with the experimentally observed CDW instability behaviour. While TiSe{sub 2} shows a rather sharp phonon anomaly at T=190 K, the anomaly in NbSe{sub 2} at T=33 K is much broader than expected for a Fermi surface nesting driven CDW instability. For NbSe{sub 2}, we exclude Fermi surface nesting as main origin of the phonon softening. For TiSe{sub 2}, there is no need to go beyond DFT in order to describe the phonon softening.

  5. Phonon softening in the CDW systems NbSe{sub 2} and TiSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Hott, Roland; Heid, Rolf; Bohnen, Klaus-Peter [Karlsruhe Institute of Technology, Institute of Solid State Physics, Karlsruhe (Germany); Weber, Frank; Castellan, John-Paul [Karlsruhe Institute of Technology, Institute of Solid State Physics, Karlsruhe (Germany); Materials Science Division, Argonne National Laboratory, Argonne, IL (United States); Rosenkranz, Stephan; Osborn, Raymond [Materials Science Division, Argonne National Laboratory, Argonne, IL (United States); Egami, Takeshi [Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN (United States); Said, Ayman [Advanced Photon Source, Argonne National Laboratory, Argonne, IL (United States); Reznik, Dmitry [Karlsruhe Institute of Technology, Institute of Solid State Physics, Karlsruhe (Germany); Department of Physics, University of Colorado at Boulder, Boulder, CO (United States)

    2013-07-01

    We present new results on the soft-mode behaviour of phonons in the Charge Density Wave (CDW) systems NbSe{sub 2} and TiSe{sub 2}. Our theoretical predictions from Density Functional Theory (DFT) based on ab-initio phonon calculations coincide with the CDW instability behaviour that we observed experimentally by means of high resolution Inelastic X-ray Scattering (IXS). While TiSe{sub 2} shows a rather sharp phonon anomaly at T=190 K, the anomaly in NbSe{sub 2} at T=33 K is much broader than expected for a Fermi surface nesting driven CDW instability. For NbSe{sub 2}, we exclude Fermi surface nesting as main origin of the phonon softening. For TiSe{sub 2}, the phonon softening seems to be well described within the framework of DFT.

  6. Electronic structure and superconductivity of FeSe-related superconductors.

    Science.gov (United States)

    Liu, Xu; Zhao, Lin; He, Shaolong; He, Junfeng; Liu, Defa; Mou, Daixiang; Shen, Bing; Hu, Yong; Huang, Jianwei; Zhou, X J

    2015-05-13

    FeSe superconductors and their related systems have attracted much attention in the study of iron-based superconductors owing to their simple crystal structure and peculiar electronic and physical properties. The bulk FeSe superconductor has a superconducting transition temperature (Tc) of ~8 K and it can be dramatically enhanced to 37 K at high pressure. On the other hand, its cousin system, FeTe, possesses a unique antiferromagnetic ground state but is non-superconducting. Substitution of Se with Te in the FeSe superconductor results in an enhancement of Tc up to 14.5 K and superconductivity can persist over a large composition range in the Fe(Se,Te) system. Intercalation of the FeSe superconductor leads to the discovery of the AxFe2-ySe2 (A = K, Cs and Tl) system that exhibits a Tc higher than 30 K and a unique electronic structure of the superconducting phase. A recent report of possible high temperature superconductivity in single-layer FeSe/SrTiO3 films with a Tc above 65 K has generated much excitement in the community. This pioneering work opens a door for interface superconductivity to explore for high Tc superconductors. The distinct electronic structure and superconducting gap, layer-dependent behavior and insulator-superconductor transition of the FeSe/SrTiO3 films provide critical information in understanding the superconductivity mechanism of iron-based superconductors. In this paper, we present a brief review of the investigation of the electronic structure and superconductivity of the FeSe superconductor and related systems, with a particular focus on the FeSe films.

  7. Photoelectric Material CuInSe2%光电材料CuInSe2薄膜

    Institute of Scientific and Technical Information of China (English)

    万斌; 敖建平; 龚军

    2003-01-01

    This paper gives a review of CuInSe2 solar cells techniques and recent developments in CuInSe2 materials, it is reported that solar cells based on CuInSe2 have demonstrated efficiency of 18%. It also introduces the characteristics of CuInSe2:the extraordinarily high absorption coefficient(>105 cm-1), the use of thin layers(1~2 μm), long-term stability. The understanding of CuInSe2 will be helpful to the research of thin-film solar cells with high conversion efficiency both at home and abroad.%概述了CuInSe2太阳能电池技术,CuInSe2材料的最新发展;同时也介绍了CuInSe2薄膜的特性:非常高的光吸收系数(>105 cm-1),可以将薄膜做的很薄(1~2 μm),长期的稳定性,抗辐射性等.对CuInSe2材料的认识、了解将有助于对高效、低成本的薄膜太阳能电池的研究.

  8. Formation of ZnSe/Bi2Se3 QDs by surface cation exchange and high photothermal conversion

    Directory of Open Access Journals (Sweden)

    Guozhi Jia

    2015-08-01

    Full Text Available Water-dispersed core/shell structure ZnSe/Bi2Se3 quantum dots were synthesized by ultrasonicwave-assisted cation exchange reaction. Only surface Zn ion can be replaced by Bi ion in ZnSe quantum dots, which lead to the ultrathin Bi2Se3 shell layer formed. It is significance to find to change the crystal of QDs due to the acting of ultrasonicwave. Cation exchange mechanism and excellent photothermal conversion properties are discussed in detail.

  9. Dynamical properties and their strain-dependence of ZnSe(ZnSe:N: Zinc-blende and wurtzite

    Directory of Open Access Journals (Sweden)

    Dandan Wang

    2014-06-01

    Full Text Available The lattice dynamical properties of ZnSe and ZnSe with substitutional N incorporation(ZnSe:N are investigated in both the zinc-blend(ZB and wurtzite(WZ structures using first-principles calculations. The optical phonon modes of ZB-ZnSe at the Γ-point locate at 250 cm−1 for LO and 213 cm−1 for TO. The characteristic E2 phonon modes at about 50 cm−1 and the E1 and another E2 phonon modes around 200 cm−1 of WZ-ZnSe are suggested to be the fingerprint for distinguishing the two polytypes of ZnSe. For substitutional N incorporated ZnSe, the N incorporation introduces three new high energy modes above 500 cm−1, and the splitting of them is much larger in the WZ phase than that in ZB phase. The strain dependence of phonon frequency which could be useful for corresponding spectroscopic strain characterization are also studied. The simple linear dependence is determined for ZB-ZnSe, while the situation for WZ-ZnSe looks more complicated.

  10. Se-precipitation in ZnSe under moderate-power laser-irradiation at high-pressure

    Science.gov (United States)

    Lindberg, G. P.; Tallman, R. E.; Lauck, R.; Cardona, M.; Weinstein, B. A.

    2011-03-01

    We report evidence for the formation of Se inclusions in ZnSe under laser-irradiation during pressure-Raman experiments. Spectra of high-quality 68 Zn 76 Se crystals are recorded at 300K for pressures of 0-13GPa using 647nm excitation at powers of 10 and 100 mW (focal spot ~ 50 μ m.) For runs at the higher power a new Raman peak appears at 1.8 GPa, and shifts to lower energy at the rate --3.5 cm-1 /GPa with further increase of pressure. Its frequency, 228 cm-1 at 1.8GPa, is within 7 cm-1 of the A1 and E'' Raman peaks in trigonal Se, which both exhibit negative, strongly non-linear, pressure shifts. In particular, the pressure-shift of the new ZnSe peak gives a reasonable fit to the average dependence of the Se A1 peak over the range 2-8 GPa. No assignment to any of the ZnSe acoustic modes (one- or two- phonon) that also soften with pressure is feasible for the new peak. It is most likely related to the Se A1-mode in Se-inclusions, whose tendency to precipitate appears to increase with pressure. W. Richter, et. al., phys. stat. sol. (b) 56, 223(1993); K. Aoki, et. al., J. Phys. Soc. Japan 48, 906 (1980).

  11. Heterojunctions formed by annealing of GaSe and InSe layered crystals in zinc vapor

    Directory of Open Access Journals (Sweden)

    Kudrynskyi Z. R.

    2012-12-01

    Full Text Available The article presents a method of creating heterojunc¬tions based on semiconductors with different lattice types. Substrates manufactured from GaSe and InSe layered crystals were annealed in Zn vapor. This way, n-ZnSe–p-GaSe and n-ZnSe–p-InSe heterojunctions were obtained. The obtained heterojunctions are photo¬sensitive in near and infrared spectral regions. This method opens up greate possibilities of producing heterostructures with a desired sensitivity band.

  12. Fabrication and characterization of PbSe nanostructures on van der Waals surfaces of GaSe layered semiconductor crystals

    Science.gov (United States)

    Kudrynskyi, Z. R.; Bakhtinov, A. P.; Vodopyanov, V. N.; Kovalyuk, Z. D.; Tovarnitskii, M. V.; Lytvyn, O. S.

    2015-11-01

    The growth morphology, composition and structure of PbSe nanostructures grown on the atomically smooth, clean, nanoporous and oxidized van der Waals (0001) surfaces of GaSe layered crystals were studied by means of atomic force microscopy, x-ray diffractometry, photoelectron spectroscopy and Raman spectroscopy. Semiconductor heterostructures were grown by the hot-wall technique in vacuum. Nanoporous GaSe substrates were fabricated by the thermal annealing of layered crystals in a molecular hydrogen atmosphere. The irradiation of the GaSe(0001) surface by UV radiation was used to fabricate thin Ga2O3 layers with thickness clusters with a square or rectangular symmetry on the clean low-energy (0001) GaSe surface, and (001)-oriented growth of PbSe thin films takes place on this surface. Using this growth technique it is possible to grow PbSe nanostructures with different morphologies: continuous epitaxial layers with thickness quantum dots with a high lateral density (more than 1011 cm-2) on the oxidized van der Waals (0001) surfaces and faceted square pillar-like nanostructures with a low lateral density (˜108 cm-2) on the nanoporous GaSe substrates. We exploit the ‘vapor-liquid-solid’ growth with low-melting metal (Ga) catalyst of PbSe crystalline branched nanostructures via a surface-defect-assisted mechanism.

  13. Wittgenstein og respekten for det religiøse

    DEFF Research Database (Denmark)

    Albinus, Lars

    2006-01-01

    Fremstilling af den tidlige og den sene Wittgensteins forhold til det religiøse med særligt henblik på tabet af umiddelbarhed.......Fremstilling af den tidlige og den sene Wittgensteins forhold til det religiøse med særligt henblik på tabet af umiddelbarhed....

  14. Visualisering og modeller: Kunsten at se det usynlige

    DEFF Research Database (Denmark)

    Sønderberg Petersen, L.; Bechgaard, K.; Feidenhans'l, R. (eds.)

    2001-01-01

    Atomer kan ikke ses med det almindelige lysmikroskop. Ved udnyttelse af stråler med kortere bølgelængder end lysets, dvs. elektron-, neutron- og røntgenstråling kan man "se" ting på nanoskalaen, og med scanning tunneling mikroskopet, der udnytter densåkaldte tunnelstrømeffekt, kan man "se" enkelte...

  15. The EU assessment of the SE corporate form

    NARCIS (Netherlands)

    Cremers, Jan

    2013-01-01

    Chapter 12, authored by Jan Cremers, examines the process of revising the SE legislation. As is typical in the EU, a procedure for reviewing the impact of new legislation and deliberating on the possible need for revision was built into the SE legislation. The first go at evaluation was characterize

  16. On the Use of "Por" Plus Agent with "Se" Construction

    Science.gov (United States)

    De Mello, George

    1978-01-01

    Two explanations for the role of "se" in such constructions as "Se construyen casas" are given by grammarians; one states that it is a passive interpretation ("Houses are built"), the other advocates an impersonal interpretation ("One builds houses"). Different views are presented and analyzed. (Author/NCR)

  17. Cr:ZnSe planar waveguide mid-IR laser

    Science.gov (United States)

    Willimas, J. E.; Martyshkin, D. V.; Fedorov, V. V.; Moskalev, I. S.; Camata, R. P.; Mirov, S. B.

    2011-02-01

    Middle infrared (mid-IR) chromium-doped zinc selenide (Cr:ZnSe) bulk lasers have attracted a lot of attention due to their unique combination of optical and laser properties facilitating a wide range of potential scientific, industrial, and medical applications. Utilization of thin film waveguide geometry enabling good thermal management and control of beam quality is a viable pathway for compact chip-integrated optical laser design. Cr:ZnSe thin films are also promising as saturable absorbers and mode-lockers of the cavities of solid state lasers operating over 1.3-2.1 μm. We recently reported the first successful demonstration of mid-IR Cr:ZnSe planar waveguide lasing at 2.6 μm under gain-switched short-pulse (5 ns) 1.56 μm excitation as well as the passive Q-switching of the cavity of a fiber-pumped Er:YAG laser operating at 1645 nm using a highly doped Cr:ZnSe thin film. PLD grown Cr:ZnSe waveguide were fabricated on sapphire substrates (Cr:ZnSe/sapphire) with chromium concentration of 1018-1019 cm-3. Further development of mid-IR lasing in the Cr:ZnSe planar waveguide under continuous wave excitation were investigated. In addition, deposition of Cr:ZnSe-based thin film structures on n-type GaAs substrates were also investigated for possible mid-IR electroluminescence.

  18. Studies on electrochemically grown Cd-Fe-Se thin films

    Energy Technology Data Exchange (ETDEWEB)

    Mahalingam, T. [Alagappa Univ., Karaikudi (India). Dept. of Physics; Ajou Univ., Suwon (Korea, Republic of). Dept. of Electrical and Computer Engineering; Thanikaikarasan, S.; Raja, M.; Sanjeeviraja, C. [Alagappa Univ., Karaikudi (India). Dept. of Physics; Lee, S.; Moon, H.; Kim, Y.D. [Ajou Univ., Suwon (Korea, Republic of). Dept. of Molecular Science and Technology; Sebastian, P.J. [CIE-UNAM, Temixco, Morelos (Mexico); Chipas Polytechnical Univ., Chipas (Mexico)

    2007-01-15

    This paper presented the results of a study that investigated the electrochemical, structural, compositional, morphological and photoelectrochemical properties of cadmium ferrous selenide (Cd-Fe-Se) semiconducting thin films electrodeposited onto conducted tin oxide (SnO{sub 2}) coated glass substrates at various cadmium sulfate concentrations in the deposition bath. Experimental details were provided along with results of typical cyclic voltammograms of Cd-Fe-Se thin film cathodically deposited from an acid solution containing CdSO{sub 4}, FeSO{sub 4} and SeO{sub 2} without any additives. Variations in film thickness were determined along with compositional analysis and morphological studies. Photoelectrochemical (PEC) solar cell studies were performed in a cell consisting of photoelectrode (Cd-Fe{sub S}e), a platinum counter electrode and a saturated dalomel reference electrode. A hot probe method identified the nature of the thin film to be n-type, while the structure was found to be hexagon for CdSe, tetragonal for {alpha}-FeSe and orthorhombic for FeSe{sub 2}. According to energy dispersive analysis of X-rays (EDAX), the stoichiometric values of Cd and Se are obtained at higher concentration of CdSO{sub 4}. The maximum concentration of CD{sup 2+} ions in the solution bath yielded thin films with smooth surfaces. 18 refs., 1 tab., 6 figs.

  19. Kristeva's Thérèse: Mysticism and Modernism

    National Research Council Canada - National Science Library

    Bové, Carol Mastrangelo

    2013-01-01

    This essay focuses on Julia Kristeva’s recent volume Thérèse mon amour: Sainte Thérèse d’Avila (2008), describing and placing this blend of novel, play, psychoanalytic cultural theory, and case history in the context of her work...

  20. Effect of Se treatment on the volatile compounds in broccoli.

    Science.gov (United States)

    Lv, Jiayu; Wu, Jie; Zuo, Jinhua; Fan, Linlin; Shi, Junyan; Gao, Lipu; Li, Miao; Wang, Qing

    2017-02-01

    Broccoli contains high levels of bioactive compounds but deteriorates and senesces easily. In the present study, freshly harvested broccoli was treated with selenite and stored at two different temperatures. The effect of selenite treatment on sensory quality and postharvest physiology were analyzed. Volatile components were assessed by HS-SPME combined with GC-MS and EN. The metabolism of Se and S was also examined. Results indicated that Se treatment had a significant effect on maintaining the sensory quality, suppressing the respiration intensity and ethylene production, as well as increasing the content of Se and decreasing the content of S. In particular, significant differences in the composition of volatile compounds were present between control and Se-treated. The differences were mainly due to differences in alcohols and sulfide compounds. These results demonstrate that Se treatment can have a positive effect on maintaining quality and enhancing its sensory quality through the release of volatile compounds.

  1. Oxidation-stability studies of CuInSe2

    Science.gov (United States)

    Kazmerski, L. L.; Ireland, P. J.; Jamjoum, O.; Deb, S. K.; Sheldon, P.; Mickelsen, R. A.; Chen, W.; Bachmann, K.

    The oxidation of p-type single-crystal and thin-film polycrystalline CuInSe2 is investigated using complementary Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). The compositions of the thermally-grown oxides over the 150-300 C temperature range are found to be primarily In2O3, with some SeO2, estimated to be less than 10% by quantitative AES and XPS. The interface between the oxide and CuInSe2 is examined using AES and SIMS depth-compositional profiling in conjunction with XPS. Cu(x)Se is found to form at the interface. Angular-resolved XPS with an in-situ oxidation process is utilized to evaluate the initial oxidation of this Cu-ternary semiconductor. These studies confirm that Cu(x)Se forms during oxide growth.

  2. Initial oxidation of CuInSe2

    Science.gov (United States)

    Kazmerski, L. L.; Jamjoum, O.; Ireland, P. J.; Deb, S. K.; Mickelsen, R. A.; Chen, W.

    1981-10-01

    The oxidation of p-type single-crystal and thin-film polycrystalline CuInSe2 is investigated using complementary Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). The compositions of the thermally-grown oxides over the 150-300 C temperature range are found to be primarily In2O3, with some SeO2, estimated to be less than 10% by quantitative AES and XPS. The interface between the oxide and CuInSe2 is examined using AES and SIMS depth-compositional profiling in conjunction with XPS. Cu(x)Se is found to form at the interface. Angular-resolved XPS with an in situ oxidation process is utilized to evaluate the initial oxidation of this Cu-ternary semiconductor. These studies confirm that Cu(x)Se forms during oxide growth.

  3. NQR study of chalcogenide glasses Ge-As-Se.

    Science.gov (United States)

    Glotova, Olga; Korneva, Irina; Sinyavsky, Nikolay; Ostafin, Michal; Nogaj, Boleslaw

    2011-07-01

    A three-component Ge-As-Se system is studied by the nuclear quadrupole resonance (NQR) method on (75)As nuclei and by the nutation NQR spectroscopy. The NQR (75)As spectra of the glasses Ge(0.021) As(0.375) Se(0.604), Ge(0.043) As(0.348) Se(0.609) and Ge(0.068) As(0.318) Se(0.614) reveal broad lines with two peaks assigned to the main structural unit of As(2)Se(3). With increasing average coordination number ( ̅r), the spectrum signals are shifted towards higher frequencies. At ̅r > 2.54, the spectrum becomes complex, which is a consequence of formation of more complex molecular structures in the glasses of high content of germanium. At fixed frequencies the asymmetry parameter η of the samples studied is determined.

  4. Anisotropic Differential Reflectance Spectroscopy of Thin GeSe

    Science.gov (United States)

    Matson, Joseph; Woods, Grace; Churchill, Hugh

    2017-01-01

    Atomically thin monochalcogenides are predicted to exhibit a two-dimensional structural phase transition. This phase transition could be useful for designing new phase change memory devices. The critical temperature is dependent on the material as well as the thickness, and is predicted to occur just above room temperature for monolayer GeSe. We used differential reflectance spectroscopy on thin samples of GeSe to measure changes in the optical anisotropy with temperature as a signature of this phase transition. We constructed an apparatus for temperature-depedendent spectroscopy of micro-scale GeSe samples, and measured anisotropic optical absorption of thin GeSe. We observed a decrease in optical anisotropy of GeSe at elevated temperatures, which may be a first indication of the continuous transition from a rectangular to a square lattice in that material. This work was supported by NSF REU Grant #EEC-1359306.

  5. Shell-Controlled Photoluminescence in CdSe/CNT Nanohybrids

    Directory of Open Access Journals (Sweden)

    Si Hua-Yan

    2009-01-01

    Full Text Available Abstract A new type of nanohybrids containing carbon nanotubes (CNTs and CdSe quantum dots (QDs was prepared using an electrostatic self-assembly method. The CdSe QDs were capped by various mercaptocarboxylic acids, including thioglycolic acid (TGA, dihydrolipoic acid (DHLA and mercaptoundecanoic acid (MUA, which provide shell thicknesses of ~5.2, 10.6 and 15.2 Å, respectively. The surface-modified CdSe QDs are then self-assembled onto aridine orange-modified CNTs via electrostatic interaction to give CdSe/CNT nanohybrids. The photoluminescence (PL efficiencies of the obtained nanohybrids increase significantly with the increase of the shell thickness, which is attributed to a distance-dependent photo-induced charge-transfer mechanism. This work demonstrates a simple mean for fine tuning the PL properties of the CdSe/CNT nanohybrids and gains new insights to the photo-induced charge transfer in such nanostructures.

  6. Comunicación intergeneracional entre extraños y entre miembros de la familia

    Directory of Open Access Journals (Sweden)

    Jake Harwood

    2002-01-01

    Full Text Available Este artículo revisa investigaciones que han examinado la comunicación intergeneracional en dos áreas diferentes. En primer lugar, numerosas investigaciones han analizado la comunicación entre adultos jóvenes y mayores, extraños entre sí. Dicho trabajo se ha centrado, con frecuencia, en procesos por los cuales se forman estereotipos, así como en la "comunicación protectora", y en otras características discursivas de la interacción entre generaciones. En segundo lugar, investigaciones recientes han comenzado a examinar elementos relacionales en las conversaciones, intergeneracionales, analizando, sobre todo, la relación entre abuelos y nietos. Este trabajo se describirá dentro del contexto de modelos teóricos tales como el modelo del predicamento comunicacional en el envejecimiento y la teoría comunicacional de la acomodación.

  7. Comunicación intergeneracional entre extraños y entre miembros de la familia

    Directory of Open Access Journals (Sweden)

    Jake Harwood

    2002-01-01

    Full Text Available Este artículo revisa investigaciones que han examinado la comunicación intergeneracional en dos áreas diferentes. En primer lugar, numerosas investigaciones han analizado la comunicación entre adultos jóvenes y mayores, extraños entre sí. Dicho trabajo se ha centrado, con frecuencia, en procesos por los cuales se forman estereotipos, así como en la "comunicación protectora", y en otras características discursivas de la interacción entre generaciones. En segundo lugar, investigaciones recientes han comenzado a examinar elementos relacionales en las conversaciones, intergeneracionales, analizando, sobre todo, la relación entre abuelos y nietos. Este trabajo se describirá dentro del contexto de modelos teóricos tales como el modelo del predicamento comunicacional en el envejecimiento y la teoría comunicacional de la acomodación.

  8. Cianofitas de los sistemas fluvio-lagunares Pom-Atasta y Palizada del Este, adyacentes a la Laguna de Términos, Campeche, México

    Directory of Open Access Journals (Sweden)

    R.E. Muciño-Márquez

    2015-07-01

    Full Text Available Las cianofitas son un grupo muy diverso de microorganismos procariontes fotosintetizadores, con una amplia distribución en diferentes ambientes tanto terrestres como acuáticos. Algunas especies pueden formar florecimientos algales nocivos o tóxicos. El objetivo de este estudio consistió en identificar la composición de las especies de cianofitas en los sistemas fluvio-lagunares Pom-Atasta (PA y Palizada del Este (PE. Se recolectaron muestras de agua tanto en superficie como medio fondo para cada laguna, en febrero del 2011, en 10 sitios utilizando una botella van Dorn. Se identificaron 21 taxones, de las cuales siete especies forman florecimientos algales como: Pseudanabaena catenata, P. limnetica, Anabaenopsis circularis, A. elenkinii, Aphanizomenon cf. ovalisporum, Ap. schindleri y Dolichospermum circinalis. Además, se reportan dos nuevos registros correspondientes a Aphanizomenon cf. ovalisporum y Ap. schindleri.

  9. EL COMPONENTE INVESTIGATIVO DE LA TUTORÍA EN LAS MICROUNIVERSIDADES PEDAGÓGICAS

    Directory of Open Access Journals (Sweden)

    Ermer Efraín Merconchini Márquez

    2015-09-01

    Full Text Available El artículo aborda algunas características del modelo actual de formación de profesores y el rol del tutor en las microuniversidades pedagógicas. Se muestra cómo mejorar los resultados en la formación inicial investigativa de los profesores, a partir de las condiciones en que se desarrolla la práctica durante los últimos años de la carrera en las microuniversidades, lo cual es posible si la tutoría se sustenta en el ejemplo personal del tutor durante la práctica cotidiana común. Los resultados forman parte de la investigación y experiencia del autor en microuniversidades pedagógicas de secundaria básica en el municipio de Puerto Padre.

  10. AgSbSe{sub 2} and AgSb(S,Se){sub 2} thin films for photovoltaic applications

    Energy Technology Data Exchange (ETDEWEB)

    Garza, J.G. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Shaji, S. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Facultad de Ingenieria Mecanica y Electrica, CIIDIT - Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico); Rodriguez, A.C.; Das Roy, T.K. [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Krishnan, B., E-mail: kbindu_k@yahoo.com [Facultad de Ingenieria Mecanica y Electrica, Universidad Autonoma de Nuevo Leon, San Nicolas de los Garza, Nuevo Leon (Mexico); Facultad de Ingenieria Mecanica y Electrica, CIIDIT - Universidad Autonoma de Nuevo Leon, Apodaca, Nuevo Leon (Mexico)

    2011-10-01

    Silver antimony selenide (AgSbSe{sub 2}) thin films were prepared by heating sequentially deposited multilayers of antimony sulphide (Sb{sub 2}S{sub 3}), silver selenide (Ag{sub 2}Se), selenium (Se) and silver (Ag). Sb{sub 2}S{sub 3} thin film was prepared from a chemical bath containing SbCl{sub 3} and Na{sub 2}S{sub 2}O{sub 3}, Ag{sub 2}Se from a solution containing AgNO{sub 3} and Na{sub 2}SeSO{sub 3} and Se thin films from an acidified solution of Na{sub 2}SeSO{sub 3}, at room temperature on glass substrates. Ag thin film was deposited by thermal evaporation. The annealing temperature was 350 deg. C in vacuum (10{sup -3} Torr) for 1 h. X-ray diffraction analysis showed that the thin films formed were polycrystalline AgSbSe{sub 2} or AgSb(S,Se){sub 2} depending on selenium content in the precursor films. Morphology and elemental analysis of these films were done using scanning electron microscopy and energy dispersive X-ray spectroscopy. Optical band gap was evaluated from the UV-visible absorption spectra of these films. Electrical characterizations were done using Hall effect and photocurrent measurements. A photovoltaic structure: glass/ITO/CdS/AgSbSe{sub 2}/Al was formed, in which CdS was deposited by chemical bath deposition. J-V characteristics of this structure showed V{sub oc} = 435 mV and J{sub sc} = 0.08 mA/cm{sup 2} under illumination using a tungsten halogen lamp. Preparation of a photovoltaic structure using AgSbSe{sub 2} as an absorber material by a non-toxic selenization process is achieved.

  11. CUANDO LAS PALABRAS SE HACEN VIDA. REFLEXIONES SOBRE SER MAESTRO DE BIOLOIGÍA EN EL PAÍS DE LA DIVERSIDAD.

    Directory of Open Access Journals (Sweden)

    Laura Escárraga Torres

    2013-07-01

    Full Text Available Ser maestro es posiblemente el viaje más profundo que alguien pudiera vivir, ser maestro va más allá de una profesión y se convierte en un estado en el que vives permanentemente. Y precisamente ese el verbo que debemos prender a conjugar: vivir. Esta crónica no habla de los grandes “sabios” de la pedagogía, tampoco de las innovaciones en educación y mucho menos de las nuevas modas de la didáctica, la pedagogía y la enseñanza de la biología. Este escrito solo pretende mostrar cómo es que a vida misma es la encargada de llevarnos a despertar las voces que hay dentro de nosotros y que han sido apagadas por el sistema educativo en cual crecimos. Esta historia habla del viaje de la vida... de mi viaje... y sí, habla en primera persona, habla de pasión, de equivocación, de esas cosas que la academia en la que nos insertamos se ha encargado de sacar de nuestros discursos, porque el sentir parece que no es bien visto por el racionalismo pragmático de los ámbitos académicos. ¿Por qué no hablar de emociones, de sentires, de viajes, porque no decir que se aprende con el otro, si eso es la vida?

  12. El mercadeo de servicios en las bibliotecas públicas: ¿una herramienta que se usa? Marketing services in public libraries: a tool which is used?

    Directory of Open Access Journals (Sweden)

    Ruth Helena Vallejo Sierra

    2008-08-01

    Full Text Available Se presentan los resultados de la investigación realizada en las bibliotecas públicas de Colombia sobre el uso y la aplicación del mercadeo como filosofía de gestión. El desarrollo metodológico se abordó desde una investigación descriptiva que partió de tipificar las bibliotecas, lo cual permitió diagnosticarlas y darles un perfil para luego analizar cada uno de los elementos de la mercadotecnia de acuerdo con los resultados obtenidos. Se analizaron el sistema de información de mercadeo, los productos y servicios, los estudios de usuarios, la comunicación y el uso de la planeación estratégica de márquetin.The paper includes the results of a Colombian research on public libraries about the use and application of the marketing management philosophy. The method is based on a descriptive research which typified libraries and allowed making their diagnosis and profile in order to analyze each marketing element. Marketing information service, user studies, communication and the use of strategic marketing planning, are analyzed.

  13. Venezuela 2007: los motores del socialismo se alimentan con petróleo

    Directory of Open Access Journals (Sweden)

    Ángel E Álvarez

    2007-01-01

    Full Text Available Venezuela vive actualmente una coyuntura crítica en la que combinan cambios políticos radicales y abundancia de recursos provenientes de los altos precios internacionales del crudo. Desde la campaña electoral presidencial del año 2006, el presidente Hugo Chávez anunció la implantación de un nuevo modelo económico y político al cual bautizó como "socialismo del siglo XXI". Ahora que fue reelegido, ha anunciado el arranque de los así llamados "cinco motores" del nuevo régimen. Puede que estos "motores" sean nuevos, pero el socialismo de Chávez se está alimentando del viejo rentismo petrolero. No cabe duda que los cambios en la actual coyuntura serán radicalmente profundos. Con la nueva reforma constitucional se pretende acabar con las "desviaciones capitalistas" de la Constitución de 1999. Mientras ella se produce, el gobierno adelanta políticas "antiimperialistas", de nacionalización y regulación económica. Los "chavistas" se agrupan en el Partido Socialista Unido de Venezuela (aunque no sin cierta resistencia interna. La oposición política, dividida en dos partidos, ensaya una nueva estrategia pacífica, electoral y de largo plazo para enfrentar al gobierno. Todo parece indicar que el nuevo esquema de cambio radical en lo económico y lo político será adoptado a marcha forzada y con poca o ninguna resistencia efectiva por parte de los partidos políticos y de la sociedad civilVenezuela is currently facing a new critical juncture that combines radical political changes with an economic boom driven by high oil prices in the international market. Since the 2006 electoral campaign, President Hugo Chavez announced a new program of radical economic and instructional change: the "XXI century socialism". Once reelected, Chávez has "started" the so-called "five engines" of the new regime. These engines may be brand new ones, but they still fuelled by the old oil-based rentistic model. Nonetheless, the new wave of political and

  14. Sonochemical synthesis and mechanistic study of copper selenides Cu(2-x)Se, beta-CuSe, and Cu(3)Se(2).

    Science.gov (United States)

    Xie, Yi; Zheng, Xiuwen; Jiang, Xuchuan; Lu, Jun; Zhu, Liying

    2002-01-28

    Nanocrystallites of nonstoichiometric copper selenide (Cu(2-x)Se) and stoichiometric copper selenides (beta-CuSe and Cu(3)Se(2)) were synthesized in different solutions via sonochemical irradiation at room temperature. The influence of solvents, surfactants, and ultrasonic irradiation on the morphology and phase of products has been investigated. The morphological difference of the products was mainly affected by the solvents and surfactants, which can self-aggregate into lamellar structures or microemulsions, and then these unique structures can act as both supramolecular template and microreactor to direct the growth of copper selenides. On the other hand, it was also found that the sonochemical irradiation and solvents played an important role in the formation of different phases of copper selenides. The proposed formation mechanism of copper selenides is discussed.

  15. Synthesis and tribological properties of NbSe{sub 3} nanofibers and NbSe{sub 2} microsheets

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Hua; Li, Changsheng [School of Materials Science and Eng., Jiangsu University, Zhenjiang 212013, Jiangsu Province (China); Jiangsu Key Laboratory of Material Tribology, Jiangsu University, Zhenjiang 212013, Jiangsu Province (China); Yang, Xiaofei; Mo, Chaochao; Cao, Kesheng [School of Materials Science and Eng., Jiangsu University, Zhenjiang 212013, Jiangsu Province (China); Yan, Fengyuan [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 73000 (China)

    2011-04-15

    NbSe{sub 3} nanofibers and NbSe{sub 2} sheets were prepared by solid state reaction. The as-prepared products are characterized by powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results showed that the obtained NbSe{sub 3} nanofibers have a diameter in the range of 100-300 nm and length about 10 {mu}m, while the NbSe{sub 2} sheets have a hexagon structure. The tribological properties of the as-prepared NbSe{sub x} powders as additives in HVI500 base oil were investigated on UMT-2 multispecimen tribo-tester. The wear scars were measured by VEECO WYKO NT1100 non-contact optical profile testing instrument. It is found that the addition of both NbSe{sub x} nanofibers/sheets improves the tribological properties of base oil. Furthermore, NbSe{sub 2} sheets exhibit better friction reduction and wear resistance properties than NbSe{sub 3} nanofibers in HVI500 base oil. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Production of 82Se enriched Zinc Selenide (ZnSe) crystals for the study of neutrinoless double beta decay

    Science.gov (United States)

    Dafinei, I.; Nagorny, S.; Pirro, S.; Cardani, L.; Clemenza, M.; Ferroni, F.; Laubenstein, M.; Nisi, S.; Pattavina, L.; Schaeffner, K.; di Vacri, M. L.; Boyarintsev, A.; Breslavskii, I.; Galkin, S.; Lalayants, A.; Rybalka, I.; Zvereva, V.; Enculescu, M.

    2017-10-01

    High purity Zinc Selenide (ZnSe) crystals are produced starting from elemental Zn and Se to be used for the search of the neutrinoless double beta decay (0νDBD) of 82Se. In order to increase the number of emitting nuclides, enriched 82Se is used. Dedicated production lines for the synthesis and conditioning of the Zn82Se powder in order to make it suitable for crystal growth were assembled compliant with radio-purity constraints specific to rare event physics experiments. Besides routine check of impurities concentration, high sensitivity measurements are made for radio-isotope concentrations in raw materials, reactants, consumables, ancillaries and intermediary products used for ZnSe crystals production. Indications are given on the crystals perfection and how it is achieved. Since very expensive isotopically enriched material (82Se) is used, a special attention is given for acquiring the maximum yield in the mass balance of all production stages. Production and certification protocols are presented and resulting ready-to-use Zn82Se crystals are described.

  17. Detection of Salmonella enterica serovar Enteritidis (SE) Antibodies in Serum Using A Polystyrene Bead/SE Flagella Agglutination Assay

    Science.gov (United States)

    Serologic screening of flocks can be an important method to detect Salmonella enteritidis (SE) infections but can be labor intensive or lack specificity. Our goal was to develop a rapid agglutination assay using SE flagella adsorbed to polystyrene beads as a simple, relatively specific test to dete...

  18. Dependence of energy levels and optical transitions on layer thicknesses in InSe/GaSe superlattices

    Science.gov (United States)

    Erkoç, Şakir; Katırcıoğlu, Şenay

    1998-01-01

    We have investigated the dependence of energy levels and optical transition matrix elements in InSe/GaSe superlattices on well and/or barrier widths. Self-consistent-field calculations have been performed within the effective-mass theory approximation.

  19. Colloidal CdSe and ZnSe/Mn quantum dots: Their cytotoxicity and effects on cell morphology

    Directory of Open Access Journals (Sweden)

    Anna O. Drobintseva

    2015-10-01

    Full Text Available The CdSe and ZnSe:Mn colloidal quantum dots (QDs have been synthesized in order to use them as a contrast agent for bioimaging. The synthesis of QDs was made in the aqueous solution. These compounds are fluorescent semiconductor nanoparticles and are held to be promising fluorophores which can be used as an important research tool in biology and medicine. They can be exploited to allocate the problematic biological tissues and individual cells. Their applicability to human examination was studied. For this purpose we investigated the morphological changes in the cells by reacting with the CdSe/l-Cys and ZnSe:Mn/MPA quantum dots. The cytotoxicity of CdSe/l-Cys in the line of breast carcinoma was examined using confocal microscopy. The results can be seen as encouraging.

  20. ¿Qué se juega al jugar un juego?

    Directory of Open Access Journals (Sweden)

    Kalejman, Cecilia

    2012-06-01

    Full Text Available En el presente artículo se considera el juego en relación a la niñez. Se indaga acerca del papel que juega el juego en la niñez intentando responder a diversas preguntas, entre ellas la más importante: ¿Qué significa jugar? A lo largo de esta etapa del desarrollo en que comienza a constituirse la subjetividad del individuo el juego constituye, sin dudas, un factor central, una herramienta fundamental en el desarrollo. Juego no es sólo el juego dramático, también consideramos para nuestro análisis aquellas modalidades de juego que se transmiten de generación en generación, juegos de construcción, los dibujos, teniendo en cuenta asimismo los objetos utilizados en los juegos, los contenidos de los mismos, los espacios en los que se desarrollan. Se piensa y se interpreta al juego, como un derecho y como un modo de expresión del niño, se finaliza este desarrollo con una conclusión acera del juego y el espacio que ocupa en la vida cotidiana.